A pressure regulator device
Technical Field
The invention relates to a pressure regulator device for an air supply system for an airjet
weaving machine. The invention further relates to an air supply system for supplying
compressed air to a blowing device of an airjet weaving machine, wherein the pressure
regulator device is arranged downstream of a compressed air source.
Prior Art
In airjet weaving machines, it is known to regulate the flow of compressed air coming
from a compressed air source, such as a compressor or an airtank, and supplied to a
blowing device for inserting a weft thread using a pressure regulator to match the actual
flow of compressed air to the demand for compressed air. The actual flow of com
pressed air is regulated by the pressure regulator in such way, that an output pressure
of the pressure regulator is kept substantially constant in order to achieve a reliable
weft thread insertion within the time interval that a weaving shed, formed by warp
threads, is open. Generally, the output pressure is regulated so that the inserted weft
thread arrives at the opposite side of the shed before the shed closes. In particular, the
output pressure is regulated so that the weft thread moves with a sufficient speed in
order to arrive at the opposite side of the shed and to arrive on the expected arrival
moment. The output pressure can be set in advance, for example depending on the
kind of weft thread to be inserted, or can be adapted during weaving, for example depending
on the moment of arrival of weft threads at the opposite side of the shed.
An air supply system for supplying compressed air to a blowing device of an airjet
weaving machine is known for example from US 5,970,996. According to US 5,970,996
two main blowing devices are each connected by a first branch to a compressed-air
source feeding high-pressure compressed air for purposes of a weft thread insertion,
wherein compressed air coming from the compressed-air source is fed via a pressure
regulator to a buffer airtank.
JP 2931080 B2 describes a pressure regulator device for weaving machines arranged
between a main tank and a buffer airtank arranged downstream of the main tank,
wherein the pressure regulator device comprises a motor controlled pressure regulator
having a diaphragm actuator with a diaphragm loaded by a pressure regulating spring.
A force of the pressure regulating spring is set using a motor. For adjusting an output
pressure the setting of the pressure regulating spring is adapted. In order to compensate
the influences due to the compressed airflow through the pressure regulator on
the output pressure of the pressure regulator at a setting of the pressure regulating
spring, a feed-back control using pressure sensors is provided, wherein the pressure
sensors measure the pressure at the buffer airtank arranged downstream of the outlet
of the pressure regulator and wherein the setting of the pressure regulating spring is
adjusted accordingly in order to obtain the desired output pressure.
JP 7-100898 B2 discloses the use of a pilot pressure regulator in an air supply system
for a weaving machine. The pilot controlled pressure regulator comprises a bypass at
an inlet and a diaphragm actuator that is loaded by a feed pressure, which feed
pressure is balanced by an output pressure. In weaving machines the feed pressure
can however vary within limits. Such variations in the feed pressure can lead to a
disturbance of the pilot pressure regulator.
From technical fields not analogous to the technical field of the invention, fluid
amplifier are known. For example US 4,653,523 shows a fluid amplifier, which
is used in a pneumatic transducer to provide an output pressure in response to
a pilot pressure provided as a function of a current signal. The fluid amplifier
includes a pressure chamber connected to an outlet duct with an inlet port and
an exhaust passageway. In the pressure chamber a valve is provided that
opens a pressure source to the inlet port and also controls pressure feeding
through the exhaust passageway. The amplifier valve is provided with a nega
tive feedback arrangement using the exhaust back pressure to stabilize the op
eration.
EP 0 112 145 A2 discloses a weft transfer control system for controlling the
supply pressure to a nozzle of an airjet weaving machine comprising a pilot
controlled pressure regulator, wherein the supply pressure inside a tank is ad
justed by connecting the tank to a pressured air source via the regulator. The
control pressure or pilot pressure of the pilot controlled pressure regulator is set
using an electromagnetic air pressure valve, which electromagnetic air pres
sure valve is receiving a predetermined control signal from a control box.
Summary of the Invention
It is the object of the invention to provide a pressure regulator device for an air
supply system for an airjet weaving machine and an air supply system for an
airjet weaving machine, wherein a feedback control of the pressure regulator
device can be avoided.
This object is solved by the pressure regulator device for an air supply system
for an air-jet weaving machine and the air supply system for an air-jet weaving
machine with the features of claims 1 and 15. Preferred embodiments are defined
in the dependent claims.
It is the basic idea of the invention to provide a pressure regulator device for an
air supply system for an airjet weaving machine, wherein the pressure regulator
device comprises a pilot controlled first pressure regulator, which first pressure
regulator is loaded by a settable pilot pressure, and wherein a second pressure
regulator is provided for regulating the settable pilot pressure of the pilot con
trolled first pressure regulator.
In a pilot controlled pressure regulator, a valve element is arranged for reciprocal
movement by an actuator, for example a diaphragm actuator, which actua
tor is loaded by a load by a control pressure, also referred to as pilot pressure,
against the load by the output pressure. In the context of this invention, the
term "feed pressure" is defined as the pressure prevailing in the feed line to the
pressure regulator, and the term "output pressure" is defined as the pressure
prevailing at the outlet of the pressure regulator. The term "load" means in the
context of this invention a force exerted due to a pressure. The load generally
depends of the effective surface on which the pressure acts.
The output pressure of the pressure regulator remains essentially constant for a chosen
or set pilot pressure, irrespective of the actual airflow through the pilot controlled
pressure regulator. Further, a force element, for example a spring may be provided for
keeping the pressure regulator closed in case no airflow flows through the pressure
regulator or no pilot pressure is applied. The force of the force element may be chosen
small and suspensions may be kept to a minimum in order to avoid non-linearities, so
that forces applied by the spring are substantially constant. In case of an increased
airflow, in other words an increased demand for air, an output pressure at the outlet of
the pressure regulator decreases, in response to which the valve element is moved
until the output pressure at the outlet of the pressure regulator reaches again a desired
value. As in contrast to pressure regulators which are set using a pressure regulating
spring, in which a movement of the valve element corresponds to a change in length of
the pressure regulating spring and results in a changed load by the pressure regulating
spring, the moving of the valve element of a pilot-controlled pressure regulator does not
influence the load by the control pressure or pilot pressure. Therefore, an output pres
sure at the outlet of the pressure regulator is essentially independent from the quantity
of air flowing through the pressure regulator. This is very advantageous in weaving ma
chines, in particular in case of the changing of the airflow through the pressure regula
tor due to changes in the control times of valves or due to transitions between periods
wherein valves are or are not controlled, for example transitions between periods
wherein weft thread is inserted and periods wherein no weft thread is inserted
As a result, a feed-back control for an actuator of the pressure regulator using pressure
sensors downstream of the pressure regulator can be avoided.
Further, a regulation of the airflow through the pressure regulator is independent of a
regulation of the set pilot pressure. This allows to weave at any speed and with any
weft insertion pattern for weft threads.
According to the invention, next to the pilot controlled first pressure regulator, a second
pressure regulator is provided for regulating the pilot pressure of the pilot controlled first
pressure regulator.
In one embodiment, the pilot controlled first pressure regulator is connectable to a
compressed air source supplying a feed pressure, wherein the second pressure regula
tor is adapted for regulating the pilot pressure in order to provide an output pressure,
which output pressure is independent of variations in the feed pressure. The second
pressure regulator may also be connected to the feed pressure, either directly or via
additional elements. In weaving mills the pressure fed to the weaving machines may
vary in time, for example due to pressure changes within limits at a compressor used
as a compressed air source caused by an ON/OFF control of the compressor, due to
variations in the number of active compressors, in case that several compressors are
used in parallel as a compressed air source, due to pressure losses in supply ducts
such as distribution ducts that are dependent on an airflow there through, due to
changes in the number of active weaving machines, for example caused by weaving
machines that have been stopped because of an error or for another reason, such as
maintenance, due to electric voltage changes in an electric feed line to the compressor,
due to airfilters that become dirty resulting in a lower airflow there through, or due to
other reasons. For example, in a weaving mill variations in the feed pressure between
5,8 bar and 5,3 bar may occur. In order to avoid that pressure variations in the feed
pressure result in a variation of the pilot pressure and therefore in a setting of the ac
tuator, the pilot pressure is regulated by the second pressure regulator.
The output pressure of the pilot controlled first pressure regulator can equal the
feed pressure of the pilot controlled first pressure regulator. In one embodi
ment, the pilot pressure is set lower than the feed pressure of the pilot con
trolled first pressure regulator and lower than the output pressure of the pilot
controlled first pressure regulator. In this case, the output pressure of the pilot
controlled first pressure regulator at any feed pressure can equal the feed
pressure of the pilot controlled first pressure regulator. Also in this case using
the lower pilot pressure the valve element can always be brought into a fully
open position at any feed pressure.
In preferred embodiments, the second pressure regulator is adapted to regulate the
pilot pressure to the pilot controlled first pressure regulator to a pressure lower than the
feed pressure, for example the minimum expected feed pressure, for example in the
aforementioned example to a pressure lower than 5,3 bar, and preferably substantially
lower than this minimal expected feed pressure, for example in the aforementioned
example to a pressure between 2,5 bar and 3,5 bar. In this case the pilot pressure is
substantially lower than the feed pressure of the pilot controlled first pressure regulator.
Hence it is avoided that pressure variations in the feed pressure result in variations of
the pilot pressure while the output pressure of the pilot controlled first pressure regulator
can be equal to the feed pressure of the pilot controlled first pressure regulator. In
other words, by providing a second pressure regulator that is adapted for regulating the
pilot pressure of the pilot controlled first pressure regulator to a pressure lower than the
minimal expected feed pressure for the pilot controlled first pressure regulator, the pilot
pressure to the pilot controlled first pressure regulator is regulated such that the output
pressure, that depends on the pilot pressure, is independent of variations in the feed
pressure.
The pilot pressure regulated to a desired value may simultaneously or subsequently be
adjusted for setting the pilot pressure to match the weaving conditions. In one embodi
ment, an adjustment to the weaving conditions is carried out in the second pressure
regulator. Hereby a feedback control for an actuator of the pressure regulator using
pressure sensors downstream of the pressure regulator can be avoided.
Preferably, the pilot controlled pressure regulator of the pressure regulator device, in
particular the pilot controlled first pressure regulator comprises a diaphragm actuator
with at least one a first diaphragm loaded by a settable pilot pressure and a valve element
mounted for reciprocal movement by the actuator. In the context of this invention
the term "diaphragm" means a dividing element forming a moveable dividing wall for
compressed air between two chambers. In the context of this invention the "diaphragm"
can consist of a dividing wall in the form of a bellows-like element, a plate-like element
or any other suchlike element. According to one embodiment, the pilot controlled first
pressure regulator comprises at least a first pressure chamber set under pilot pressure
that is delimited by the first diaphragm, wherein the at least one first pressure chamber
has an opening that allows a leak air flow from the first pressure chamber to the env i
ronment. In use, the first pressure chamber is set under pilot pressure. The opening
allows a small leak air flow from the first pressure chamber to the environment. For this
purpose, the first pressure chamber in one embodiment is communicated with the env i
ronment directly via the opening. In other embodiments, the opening leads to one or
more further chambers and from this chamber or these chambers via further openings
to the environment. In case pilot pressure is fed to the first pressure chamber, this
small leak air flow is advantageous to avoid a hysteresis when a change of pilot pressure
is required. This ensures a fast pressure control. In case no pilot pressure is fed to
the first pressure chamber, for example in idle times, the pressure in the first pressure
chamber will eventually equal the environment pressure.
Such a pressure regulator can act very fast because the moving parts can be designed
lightweight. The pressure prevailing at an outlet, also referred to as output pressure,
acts in opposite direction to the pilot pressure on the diaphragm actuator. Hence, the
valve element is moved in response to a pressure load difference between the load by
the pilot pressure and the load by the output pressure and, if present, the force load by
a spring, for increasing or decreasing a valve gap opening in order to adjust the output
pressure of the pressure regulator in dependence of the set pilot pressure. In particular,
in case of an increased airflow or increased demand for air, the output pressure of the
pressure regulator decreases, in response to which the valve element is moved to increase
a valve gap until the output pressure at the outlet reaches again a desired
value.
In one embodiment, the second pressure regulator for regulating the control pressure
or pilot pressure is a motor controlled pressure regulator. The second pressure regula
tor is preferably small in dimension and an airflow through the second pressure regula
tor is comparatively low, so that a fast regulating is possible and influences for example
due to a changing airflow through the second pressure regulator are negligible. The
motor controlled second pressure regulator comprises in one embodiment a throttle
valve, wherein a throttling gap of the throttle valve is set by a motor, in particular a
stepper motor. In another embodiment, as second pressure regulator a motor con
trolled second pressure regulator as described in US 4,627,459 is used, wherein the
content of US 4,627,459 is herewith incorporated by reference. In this case, the motor
can be a steppermotor. In addition, or as an alternative, the motor controlled second
pressure regulator comprises a transmission mechanism with a lever for a transmission
of a movement of a motor shaft to a setting element of the second pressure regulator.
This allows the motor to be kept small in size.
In another embodiment, the second pressure regulator is also a pilot controlled pressure
regulator. The second pressure regulator is preferably smaller in dimension than
the first pilot controlled first pressure regulator.
In one embodiment, the feed pressure for the second pressure regulator comes directly
from the compressed air source. In other words, the feed pressure for the second pressure
regulator is defined by the pressure coming from the compressed air source. In
another preferred embodiment, a third pressure regulator is provided for regulating or
stabilising a feed pressure for the second pressure regulator. Variations of the feed
pressure of the second pressure regulator indeed result in small variations on the pilot
pressure to the pilot controlled first pressure regulator, if the second pressure regulator
for example is a spring type pressure regulator. Using the third pressure regulator, the
feed pressure for the second pressure regulator may be reduced. For example the feed
pressure that is fed by the third pressure regulator to the second pressure regulator
about 4 bar. In case a motor controlled pressure regulator is used as a second pres
sure regulator, such a decrease is also advantageous since the forces on the second
pressure regulator are relatively low and a smaller motor can be used. The second
pressure regulator can also be embodied as a pilot controlled pressure regulator ac
cording to an embodiment. In an example, an adjustment to the weaving conditions of
the feed pressure to the second pressure regulator can be carried out using the third
pressure regulator.
According to one embodiment, the third pressure regulator is a manually settable pressure
regulator. The airflow through the third pressure regulator is relatively low and a l
most constant. Therefore, a manually settable, in particular a manually settable spring
type third pressure regulator can be used.
In another embodiment the second pressure regulator comprises a housing having an
inlet for throttling air, an outlet and an air volume there between, wherein a loaded
pressure relief valve is provided on the housing, comprising a settable biasing force.
Herein a spring loaded pressure relief valve can be provided on which a motor settable
pre-set force can be provided. According to this embodiment, air is fed to the housing
via the inlet. As the inlet is small, there is a pressure decrease due to a throttling effect.
If the pressure in the air volume reaches a preset value, then the pressure relief valve,
for example a ball valve, opens and air can escape until the pressure is decreased to
the preset value and the pressure relief valve closes. In balance, an airflow flows a l
most permanently into the air volume with a low flow, therewith making a pressure drop
across the inlet, and an airflow having an equal flow flows via the pressure relief valve
out of the air volume. Preferably, the pressure relief valve is loaded using a spring e le
ment, which is controllable manually and/or by a motor. This system is operable to pro
vide a set pressure to be subsequently used as pilot pressure accurately. Because
such a second pressure regulator is little sensitive to variations in the feed pressure, no
third pressure regulator is necessary.
According to another preferred embodiment, the second pressure regulator is provided
integrally with a pressure chamber of the pilot controlled first pressure regulator. Pref
erably, the second pressure regulator is integrated in a top of a pressure chamber of
the pilot controlled first pressure regulator, in other words arranged directly above a
diaphragm of the pilot controlled first pressure regulator. In this case, a throttling valve
is for example provided at the inlet of the second pressure regulator.
According to another preferred embodiment, a force enlarging device is provided, so
that a load by the pilot pressure on the diaphragm actuator of the pilot controlled first
pressure regulator is enlarged and that this pilot pressure is substantially lower than the
output pressure of the pilot controlled first pressure regulator. The resulting load is ba l
anced by the output pressure and if applicable a spring. Therefore, the output pressure
of the pilot controlled first pressure regulator is higher than the pilot pressure of the pilot
controlled first pressure regulator. In particular, when a low control pressure or pilot
pressure is used, such a force enlarging device is advantageous. The force enlarging
device allows an output pressure which is as high as the feed pressure, with a pilot
pressure which is relatively low and lower than the feed pressure, irrespective of variations
in the feed pressure coming from a compressed air source, which feed pressure
for example varies for example between 5,3 bar and 5,8 bar.
In one embodiment, the force enlarging device is at least partially an integral compo
nent of the diaphragm actuator of the first pilot controlled pressure regulator. In the context
of this invention the expression "partially an integral component" means that two
devices have at least one common component. Providing a load enlarging device that
is at least partially an integral component of the diaphragm actuator allows for a pres
sure regulator small in size. This allows to arrange several pressure regulators adjacent
to each other in a small place.
In a preferred embodiment, at least one second diaphragm loaded by the pilot pressure
is provided, wherein the load on the second diaphragm is applied to the first d ia
phragm, and the resulting load on the first diaphragm is balanced by the output pres
sure. The pilot pressure is fed to all diaphragms, for example as well to the first diaphragm
as to each second diaphragm. Each second diaphragm is coupled to the first
diaphragm for a transmission of the load, for example by a rod, wherein the effective
surface loaded by the pilot pressure is substantially higher than the effective surface
loaded by the output pressure. The output pressure, i.e. the pressure of the airstream
leaving the pilot controlled first pressure regulator, is only in contact with the first diaphragm,
so that the resulting output pressure is higher than the pilot pressure. In an
embodiment, several second diaphragms may be provided in a stacked assembly. This
embodiment has as advantage that the diameter of the first and the second diaphragm
can be chosen small, allowing several pressure regulators of this type to be arranged
next to one another in a small space. This is also advantageous to reduce losses in
ducts to the pressure regulators.
Alternatively, a diaphragm actuator is provided comprising a first diaphragm loaded by
the pilot pressure and a third diaphragm loaded by the output pressure which are cou
pled for a transmission of the movement, wherein the effective surface of the third diaphragm
is smaller than the effective surface of the first diaphragm. In other words, the
first diaphragm and the third diaphragm are moved conjointly, wherein the load of the
output pressure acting on the third diaphragm is balanced by the load of the pilot pres
sure acting on the first diaphragm. The first diaphragm has a larger effective surface
than the third diaphragm. Hence, the output pressure for balancing the pilot pressure is
higher than the pilot pressure.
According to another embodiment, at least one pressure sensor is arranged upstream
of the first, second and/or third pressure regulator for measuring a feed pressure of the
compressed air source, wherein an open-loop control unit is provided which is arranged
for regulating a control variable, for example the pilot pressure, of the first pressure
regulator, for example in dependence of the measured feed pressure.
By fitting a pressure sensor for measuring the pressure in the feed duct upstream of the
pressure regulator, the pressure regulator may be adapted when the feed pressure
changes or when the feed pressure drops below a boundary value for pressure which
is for example related to a desired output pressure of the pressure regulator.
In particular, according to the preferred embodiment, it is avoided that the late arrival
due to a drop in the feed pressure leads to a control which results in an unrealisable
increase of the desired output pressure or at least such an increase is kept small.
Therefore, when the feed pressure subsequently increases, the desired output
pressure at the pressure regulator still almost matches the weaving conditions.
The advantages are a simple control device and method, in particular when the feed
pressure of the compressed air source drops to a value lower than a desired value for
the output pressure, this for example means a desired pressure in a buffer airtank.
According to a preferred embodiment further an apparatus for determining an airflow
through the pressure regulator is provided, wherein the open-loop control unit is a r
ranged for regulating the control variable of the pressure regulator in dependence of
the measured feed pressure and the airflow determined. In case of an increased a ir
flow, an output pressure at the outlet of the first pressure regulator decreases, in response
to which the valve element of the first pressure regulator is moved until the out
put pressure at the outlet of the first pressure regulator reaches again a desired value.
By considering the airflow through the pressure regulator with a device for determining
an airflow, every unwanted decrease of an output pressure due to an increased airflow
can be compensated.
In accordance with other embodiments, the apparatus for determining an airflow
through the first pressure regulator comprises a calculation unit for calculating the a ir
flow in function of measured parameters, in particular in function of the opening times
of the valve systems to the blowing devices, of the pressure fed to the blowing devices,
of the kind of nozzles of the blowing devices and of the number of blowing devices that
are used. For each blowing device, a value for an airflow can be determined approxi
mate in advance, for example based on previous measurements or based on formulae
of airflow dynamics. The total airflow can be calculated based on these values.
The object is also solved by an air supply system for an airjet weaving machine com
prising at least one blowing device and a compressed air source, wherein compressed
air from the compressed air source is supplied via the air supply system to the at least
one blowing device, wherein the air supply system comprises a pressure regulator de
vice with at least one pilot controlled first pressure regulator arranged between the
compressed air source and a buffer airtank, the at least one pilot controlled first pres
sure regulator is arranged for regulating the pressure in the buffer airtank, which buffer
airtank is arranged between the pressure regulator device and the blowing device.
In preferred embodiments, a group of pilot controlled pressure regulator devices is pro
vided, which are arranged next to one another. The pilot controlled pressure regulator
devices may be at least partially formed as integral components. An arrangement of the
pilot controlled pressure regulator devices according to the invention next to one another
allows an arrangement that is small in size. Further, the length of supply ducts
and pressure losses in the supply ducts may be reduced.
Brief Description of the Drawings
Fig. 1 is a schematic view of an air supply system for an airjet weaving machine
comprising a pilot controlled first pressure regulator, a motor controlled
second pressure regulator and a manually adjustable third pressure regu
lator;
Fig 2 is a schematic view of a cross section of an embodiment of a pilot con
trolled first pressure regulator;
Fig 3 is a schematic view of a cross section of a variant of the pilot controlled
first pressure regulator from fig. 2;
Fig 4 is a schematic view of a cross section of yet a further variant of the pilot
controlled first pressure regulator from fig. 2;
Fig 5 is a schematic view of a cross section of a motor controlled second pres
sure regulator;
Fig 6 is a schematic view of a cross section of a variant of the motor controlled
second pressure regulator from fig. 5;
Fig. 7 is a schematic view of a cross section of an embodiment of a pilot con
trolled first pressure regulator into which a motor controlled second pres
sure regulator is integrated;
Fig. 8 is a schematic view of a cross section of yet a further variant of the pilot
controlled first pressure regulator of fig. 2;
Fig. 9 is a schematic view of a cross section of a variant of the pilot controlled
first pressure regulator from fig. 8;
Fig. 10 is a schematic view of an open-loop control of an air supply system, and;
Fig. 11 is a schematic view of an air supply system according to the inven
tion for an airjet weaving machine.
Detailed Description of Preferred Embodiments
Fig. 1 shows a schematic view of an air supply system 1 for an airjet weaving machine
comprising a first pressure regulator 2, a second pressure regulator 3 and a third pres
sure regulator 4, in particular a pilot controlled first pressure regulator 2, a motor con
trolled second pressure regulator 3 and a manually adjustable third pressure regulator
4. The air supply system 1 is intended for supplying compressed air from a compressed
air source 5 via an air filter 6, a feed line 7, the first pressure regulator 2, a buffer airtank
8 and a valve system 9 to a blowing device 10. The pilot controlled first pressure
regulator 2 is provided upstream of the buffer airtank 8 and is intended for regulating an
airflow through the pressure regulator 2 so that air with a desired output pressure is
supplied via a duct 12 from the outlet 11 of the pressure regulator 2 to the buffer airtank
8. The first pressure regulator 2 is arranged between the compressed air source 5 and
the buffer airtank 8 and is intended for regulating the pressure in the buffer airtank 8.
The buffer airtank 8 is arranged between the first pressure regulator 2 and the blowing
device 10.
The first pressure regulator 2, in particular the pilot controlled first pressure regulator 2,
is regulated by a pilot pressure supplied to the first pressure regulator 2. The pilot
pressure for the first pressure regulator 2 is regulated using the second pressure
regulator 3, in particular the motor controlled second pressure regulator 3, in order to
supply compressed air at a pilot pressure via a duct 13 to the first pressure regulator 2.
To the second pressure regulator 3 compressed air is fed via the third pressure
regulator 4, in particular the manually adjustable third pressure regulator 4, and a duct
14. The air supply system 1 comprises a pressure sensor 15 arranged upstream of the
first pressure regulator 2 for measuring a feed pressure in the feed line 7 between the
compressed air source 5 and the first pressure regulator 2. The pressure sensor 15 is
also arranged upstream of the second pressure regulator 3 and of the third pressure
regulator 4. Further, the air supply system 1 comprises an apparatus 30 for determining
an airflow through the first pressure regulator 2, in particular an airflow measuring
device 16, which airflow measuring device 16 is arranged upstream of the first pressure
regulator 2 in the feed line 7. The airflow measured by the airflow measuring device 16
is mainly defined by the airflow through the first pressure regulator 2, since the airflow
through the second pressure regulator 3 and the third pressure regulator 4 is negligibly
small. An airflow measuring device is described for example in WO 2010/046092, the
content of which is herewith incorporated by reference. According to the invention a
pressure regulator device 17 comprises at least the pilot controlled first pressure
regulator 2. In the embodiment shown the pressure regulator device 17 comprises the
pilot controlled first pressure regulator 2, the motor controlled second pressure
regulator 3 and the manually adjustable third pressure regulator 4. The pressure
regulator device 17 is arranged downstream of the compressed air source 5.
The first pressure regulator 2 is controlled with a settable pilot pressure as control
variable. In a pilot controlled first pressure regulator 2 a valve element 18 is arranged
for reciprocal movement by an actuator 19, which actuator 19 is loaded by the load
applied by the pilot pressure from the second pressure regulator 3, against the load
applied by the output pressure at the outlet 11. Further, a force element 20 such as a
spring may be provided for forcing the pressure regulator 2 in closed state, which force
element 20 can exert a small and almost constant force. The force element 20 acts in
opposition to the pilot pressure on the valve element 18. The force element 20 is
intended for keeping the first pressure regulator 2 closed, this means keeping the valve
element 18 in closed position when no pilot pressure is applied or when no flow is
demanded.
In this pilot controlled first pressure regulator 2 the valve element 18 is forced to an
open position by the force exerted by the pilot pressure on the actuator 19 and to a
closed position by the force exerted by the output pressure on the actuator 19. By
choosing the pilot pressure sufficiently high the valve element 18 can in this case be
kept in a full open position. The force element 20 forces in this case the valve element
18 to a closed position, whereby the force exerted by the force element 20 in normal
use is substantially smaller than the force exerted by the pilot pressure or the force
exerted by the output pressure.
The second pressure regulator 3 is motor controlled and is provided for regulating the
settable pilot pressure of the pilot controlled first pressure regulator 2. As will be
explained further on, the pilot pressure is preferably chosen lower than a feed pressure
of the compressed air source 5 to the pilot controlled first pressure regulator 2. It is
known that in weaving mills the feed pressure is normally chosen between 5 bar and
7 bar, for example 5,5 bar, and that the feed pressure may vary randomly over time. In
weaving mills, for example, when a feed pressure of 5,5 bar is chosen, random
variations in feed pressure between 5,3 bar and 5,8 bar may occur. In order to avoid
that pressure variations in the feed pressure result in a variation of the pilot pressure,
the pilot pressure is regulated by the second pressure regulator 3 to a pressure lower
than the minimum expected feed pressure of the compressed air source 5, in an
embodiment to a pressure between 2,5 bar and 3,5 bar.
In fig. 1, also a third pressure regulator 4 is provided for regulating a feed pressure for
the second pressure regulator 3. According to an embodiment, the third pressure
regulator 4 is a manually adjustable pressure regulator. The feed pressure for the
second pressure regulator 3 is in this case set lower than the feed pressure of the
compressed air source 5 and set higher than the desired pilot pressure to the first
pressure regulator 2, for example set at about 4 bar. In case a motor controlled
pressure regulator is used as second pressure regulator 3, such a reduction is also
advantageous as due to this the forces on the second pressure regulator 3 are
relatively low, and a smaller motor can be used. In other embodiments the third
pressure regulator 4 is omitted, so that the feed pressure of the second pressure
regulator 3 corresponds to the feed pressure of the compressed air source 5.
In fig. 1 a control unit 2 1, more particularly an open-loop control unit 2 1 is shown which
is arranged for controlling or regulating a control variable of the first pressure regulator
2, in this embodiment the pilot pressure for the first pressure regulator 2, by controlling
the second pressure regulator 3 in dependence of, for example, the measured feed
pressure of the compressed air source 5, a determined airflow through the feed line 7,
the desired output pressure p_w and/or an insertion parameter such as an arrival
moment of a weft thread at a thread detector 22 which, for example, is arranged along
an insertion path of the weft thread. In the context of the invention, with an "open-loop
control unit" a control unit is meant for controlling the output pressure of a pressure
regulator wherein the output pressure of the pressure regulator is not measured and
not used as a feedback for controlling the output pressure, but wherein the output
pressure however may be controlled in dependence of other parameters than the
output pressure, parameters such as for example the abovementioned feed pressure,
the desired output pressure, the abovementioned airflow, the abovementioned arrival
moment and/or other suchlike parameters. With "open-loop" is so meant that no
feedback of the actual output pressure exists, but that the desired value for the output
pressure may be regulated based on other parameters. If the blowing device 10
comprises a main blower, the output pressure is adapted to measured parameters for
the inserted weft thread, while if the blowing device 10 comprises a relay nozzle, the
output pressure is usually kept constant or changed sporadically. The control unit 2 1
can cooperate with the apparatus 30, in particular with the airflow measuring device 16
of the apparatus 30. Preferably a feedback control of the pressure regulator device 17
based on the output pressure at the outlet 11 or the pressure in the buffer airtank 8 is
avoided, so that no pressure sensor has to be provided downstream of the outlet 11 of
the first pressure regulator 2, for example at the buffer airtank 8. Further the apparatus
30 comprises instead of or in addition to the airflow measuring device 16, for example,
a calculating unit 23 for calculating an airflow through the first pressure regulator 2.
According to another possibility, the calculating unit 23 is part of the control unit 2 1. The
calculating unit 23 can calculate the airflow, for example as a sum of values determined
in function of parameters such as the opening times of the valve systems 9 to the
blowing devices 10, the pressure fed to the blowing devices 10, the kind of nozzles of
the blowing devices 10, the number of blowing devices 10 that are used and other
parameters. This calculation can be based on previous measurements or on formulae
of airflow dynamics.
As shown in fig. 2, the actuator 19 of the first pressure regulator 2 is formed by a
diaphragm actuator 24 with a first diaphragm 25 loaded at one side by a pilot pressure
from the second pressure regulator 3 and at the other side by the output pressure of
the first pressure regulator 2. The first pressure regulator 2 further comprises a valve
element 18 mounted for reciprocal movement by the actuator 19.
In the embodiment shown in fig. 2 also a second diaphragm 26 loaded by the pilot
pressure from the second pressure regulator 3 is provided. The second diaphragm 26
is coupled for force transmission to the first diaphragm 25 by a rod 27, so that the
second diaphragm 26 can press on the first diaphragm 25. The load on the second
diaphragm 26 is applied to the first diaphragm 25, and the resulting load on the first
diaphragm 25 is balanced by the output pressure of the first pressure regulator 2. The
output pressure is only in contact with the first diaphragm 25. The effective surface of
the first diaphragm 25 on which acts the pilot pressure is somewhat decreased by the
rod 27. However this decrease is generally negligible and the effective surface loaded
by the pilot pressure is essentially equal to the joint surface of the first and the second
diaphragm 25, 26. Therefore the effective surface loaded by the pilot pressure is
substantially higher than the effective surface loaded by the output pressure. The
output pressure is in this case approximately double of the pilot pressure, for example
1,9 times the pilot pressure. Due to this a compact pilot controlled pressure regulator 2
is obtained.
In this embodiment, a first pressure chamber 3 1 set under pilot pressure, also referred
to as first pressure chamber for pilot pressure, is provided that is delimited by the first
diaphragm 25. Further, a second pressure chamber 32 for pilot pressure is provided
that is delimited by the second diaphragm 26. The pressure chambers 3 1 and 32 are
stacked and mutually connected by an intermediate chamber 33. The first pressure
chamber 3 1 is further delimited by a cover 34. The intermediate chamber 33
communicates with the environment via an opening 35, so that the environment
pressure prevails in the intermediate chamber 33. The intermediate chamber 33 is
delimited by the second diaphragm 26 and the cover 34. The outlet 11 communicates
with the pressure chamber 7 1 via an opening 72.
The cover 34 that delimits the first pressure chamber 3 1 is provided with a through
opening 36 through which the rod 27 moves. Between the rod 27 and the opening 36 a
sealing, for example a sealing ring, may be provided. The cover 34 comprises a small
opening 79 that allows that a small leak air flow can flow from the first pressure
chamber 3 1 via the openings 35 and 79 to the environment. In use, the first pressure
chamber 3 1 is set under pilot pressure, i.e. a pilot pressure is fed to the first pressure
chamber 3 1. The small leak air flow is advantageous to avoid a hysteresis when a
change of pilot pressure is required. Thereby, a fast pressure control is ensured. In
case no pilot pressure is fed to the first pressure chamber 3 1, for example in idle times,
the pressure in the first pressure chamber 3 1 will eventually equal the environment
pressure.
This leak air flow also flows through the second pressure regulator 3 (see fig. 1) , which
offers the advantage that the second pressure regulator 3 by this leak air flow is less
sensitive to so-called hysteresis. In the context of this invention "hysteresis" means that
the pilot pressure to the pilot controlled first pressure regulator 2 remains almost
constant in case of a certain change of position of the stepper motor of the second
pressure regulator 3, both if this stepper motor moves toward a certain position with a
movement in the one direction and with a movement in the opposite direction.
Hysteresis may arise because of the friction and the deformations in case of absence
of an airflow through the second pressure regulator 3. Because of the leak air flow the
pilot pressure can decrease when desired.
The rod 27 also comprises an axial air duct 37 that allows that compressed air flows
between the first pressure chamber 3 1 and the second pressure chamber 32. The air
duct 37 ends with openings 28. The leak air flow also flows through the duct 13, the
pressure chamber 32, the axial air duct 37 with opening 28 and the pressure chamber
3 1. The air duct 37 offers the advantage that the pilot pressure can be supplied as well
to the first pressure chamber 3 1 as to the second pressure chamber 32 via only one
duct 13. If no seal is provided between the rod 27 and the opening 36 the function of
the opening 79 may be replaced by providing a limited play defined beforehand
between the rod 27 and the opening 36.
Fig. 3 shows a first pressure regulator 2 with a diaphragm actuator 24 alike to fig. 2.
The diaphragm actuator 24 of the first pressure regulator 2 shown in fig. 3 comprises
next to the first diaphragm 25 and a first second diaphragm 26 as shown in fig. 2, also
an additional or second second diaphragm 38 loaded by the pilot pressure that is
provided in a stacked arrangement. The additional or second second diaphragm 38 is
arranged in a corresponding third pressure chamber 39 and the load applied to the
additional or second second diaphragm 38 is transmitted to the first second diaphragm
26 via a rod 40 in a way similar as the rod 27 shown in fig. 2 can provide in a force
transmission between the second diaphragm 26 and the first diaphragm 25 in fig. 2.
Also an intermediate chamber 4 1 is provided between the pressure chambers 32 and
39. The intermediate chamber 4 1 is alike to the intermediate chamber 33 and may also
be provided with an opening 73 to the environment alike to the opening 35. The fluid at
pilot pressure is fed to the third pressure chamber 39 via the duct 13. The rod 40
comprises an axial air duct 37 with a first aperture 28 ending in the second pressure
chamber 3 1 and with a second opening 29 ending in the second pressure chamber 32.
According to still another variant, more than three diaphragms with a corresponding
pressure chamber for pilot pressure may be provided in a stacked arrangement, with
for example corresponding intermediate chambers between adjacent pressure
chambers for pilot pressure and corresponding rods.
As shown in fig. 4, another variant embodiment of a first pressure regulator 2 with a
diaphragm actuator 24 is shown that comprises a first diaphragm 43 loaded by the pilot
pressure via the duct 13 and a third diaphragm 42 loaded by the output pressure via
the opening 72, wherein the effective surface of a third diaphragm 42 is substantially
smaller than the effective surface of the first diaphragm 43. The pilot pressure is
present in the pressure chamber 74 delimited by the first diaphragm 43, while the
output pressure is present in the pressure chamber 75. The third diaphragm 42 and the
first diaphragm 43 are in this embodiment coupled by a rod 44, for example a ring
shaped rod 44, and move conjointly, wherein the load of the pilot pressure acting on
the first diaphragm 43 is balanced by the load of the output pressure acting on the third
diaphragm 42. Hence, the output pressure for balancing the pilot pressure is
substantially higher than the pilot pressure. An opening 35 for a leak airflow is provided
in the pressure chamber 74 under pilot pressure. By providing an opening 80 the
intermediate chamber 76 between the first and the third diaphragm 42, 43 can be kept
at environment pressure.
A diaphragm actuator 24 as shown in figs. 2 to 4 forms in any case a force enlarging
device 45, so that a load exerted by the pilot pressure on the diaphragm actuator 24 is
enlarged or amplified. The force enlarging device 45 forms in this case an integral
component of the compact diaphragm actuator 24. By applying a force enlarging device
45 a load by the pilot pressure exerted on the diaphragm actuator 24 is enlarged, so
that a desired output pressure can be set by a pilot pressure that is chosen lower than
the output pressure or chosen lower than the minimally expected value of the feed
pressure of the compressed air source 5 (shown in fig. 1) .
The load by the pilot pressure is in this case balanced by the load by the output
pressure and the force element 20. The force enlarging device 45 allows a relative high
output pressure with a pilot pressure which is relatively low and is independent from the
feed pressure coming from a compressed air source 5. A force enlarging device 45
allows to set an output pressure which is as high as the feed pressure, so that the feed
pressure can be used fully for inserting weft threads.
In the embodiment of figs. 1 to 3 the diaphragms 25, 26, 38 are formed by a dividing
element that forms a moveable dividing wall for compressed air between two
chambers. The diaphragms 25, 26, 38 comprise in this embodiment a bellows-like
element of which the edges are clamped. In the embodiment of fig. 4, the diaphragms
42, 43 are formed by a plate-like element, preferable a relatively elastic plate-like
element, such as a membrane. The diaphragms 42, 43 form a moveable dividing wall
between two chambers and their edges are clamped.
Fig. 5 shows an embodiment of a second pressure regulator 3. The second pressure
regulator 3 shown in fig. 5 for regulating the pilot pressure is a motor controlled
pressure regulator. The second pressure regulator 3 comprises a motor 46, for
example a stepper motor, and a transmission mechanism 47 with a lever 48 for a
transmission of a movement of a motor shaft 49 of the motor 46 to a setting element 50
of the second pressure regulator 3. In an embodiment the motor shaft 49 does not
perform a turning movement but a linear axial movement when driving the motor 46.
The force applied by the lever 48 on the setting element 50 defines the preload of the
spring 5 1 which acts on the diaphragm actuator 52. The diaphragm 53 of the second
pressure regulator 3 is loaded on one hand by the spring 5 1 and on the other hand by
the pilot pressure supplied to the first pressure regulator 2 via the duct 13 and a force
element 54 to move the valve element 55 of the second pressure regulator 3. Such a
pressure regulator 3 is known from US 4,627,459.
Compressed air is supplied to the second pressure regulator via duct 14. To the
second pressure regulator 3 compressed air may be supplied at a lower pressure than
the feed pressure, for example from the third pressure regulator 4. If this lower
pressure is chosen low enough below the feed pressure, for example at 4 bar in case
of a feed pressure of 5,5 bar, the second pressure regulator 3 is not submitted to
undesired variations in the feed pressure, so that a precise regulating of the pilot
controlled first pressure regulator 2 becomes possible easily.
According to an embodiment, at a calibration of the air supply system 1, for example
during an assembly of the air supply system 1, factors which influence the pilot
pressure undesirably are eliminated, such as dimension tolerances of amongst others
the lever 48, the spring 5 1, the setting element 50 or the force element 54 of the
second pressure regulator 3. The simplifies the providing of an open loop control unit
2 1 for the output pressure of the first pressure regulator 2 without a feedback control for
the output pressure of the first pressure regulator 2.
In fig. 6 an embodiment of the second pressure regulator 3 is shown having a housing
56 with an inlet 57 allowing to throttle compressed air, an outlet 58 to a duct 13 to the
first pressure regulator 2 shown in figs. 1 to 4 and an air volume 59 there between,
wherein a loaded pressure relief valve 60 is provided on the housing 56, which
pressure relief valve 60 is loaded by a settable force. According to this embodiment, air
is fed to the air volume 59 of the housing 56 via the inlet 57. As the inlet 57 is small,
there is a pressure decrease due to a throttling effect. If the pressure in the air volume
59 reaches a preset value, then the pressure relief valve 60, for example a ball valve
with a spring element 6 1 and a ball 62, opens and air can escape until the pressure is
decreased to the preset value and the pressure relief valve 60 closes again. Preferably,
the spring element 6 1 of the pressure relief valve 60 is loaded using a plunger 63,
which is controlled manually and/or by a motor 64. The motor 64 can be controlled by
the control unit 2 1 shown in fig. 1. The motor 64 of the second pressure regulator 3 is
operable to provide a set pressure to be subsequently used as pilot pressure
accurately. The inlet 57 is connected to the duct 14, as shown in fig. 1. Due to the
throttling at the small inlet 57 in this embodiment a third pressure regulator 4 is not
necessarily needed, as for example is shown in fig. 1 and the inlet 57 may be
connected directly with the feed line 7 as shown in fig 1. According to a variant not
shown the pressure relief valve comprises a closing element that is driven by a motor
formed as an actuator, for example a linear actuator, such as a magnetic or solenoid
actuator.
According to a variant shown in fig. 7, the second pressure regulator 3 is provided
integrally with a second pressure chamber 32 of the pilot controlled first pressure
regulator 2. In this case, the second pressure regulator 3 is integrated in a top of a
second pressure chamber 32 of the pilot controlled first pressure regulator 2, in other
words arranged directly above the second diaphragm 26 of the pilot controlled first
pressure regulator 2. In this embodiment, a throttling valve 65 is provided at the inlet 57
of the second pressure regulator 3, which is directly connected to the feed line 7.
According to a variant not shown, the inlet 57 may as well be connected to the duct 14
as shown in fig. 1. The throttling valve 65 allows to set suitably the throttling at the inlet
57. The throttling gap of the throttle valve 65 is set by a motor 66, in particular a
stepper motor or any other actuator such as an electromagnetic actuator, so that a
sufficient airflow flows through the throttling valve 65 in order to allow to increase or
decrease the pilot pressure. In this embodiment the pilot pressure in the pressure
chamber 32 at the outlet 58 is set by controlling the motor 64 of the pressure relief
valve 60 in a way as described for fig. 6. The second pressure chamber 32 has the
same function as the air volume 59 as described in fig. 6.
In fig. 8 another variant embodiment of a first pressure regulator 2 is shown having a
diaphragm actuator 24 comprising a diaphragm 8 1 that is loaded by the output
pressure via the opening 72 and by the pilot pressure via the duct 13. The diaphragm
8 1 is a dividing element with a moveable dividing wall for compressed air between a
first pressure chamber 3 1 under pilot pressure and pressure chamber 7 1 under output
pressure. The diaphragm 8 1 is in this case a disc or plate-like element that is provided
at its edges with a sealing 82 and that may be moved up and down in the housing 83.
The diaphragm 8 1 is connected to the valve element 18 via a rod 84, wherein the valve
element 18 is moveable in a cavity 85 which is connected with the environment via an
opening 102. The first pressure chamber 3 1 is fed via a duct 13 with a pilot pressure
from a second pressure regulator 3, so that the pilot pressure prevails in the first
pressure chamber 3 1. The pressure chamber 3 1 comprises an opening 35 to allow a
leak air flow through the pressure chamber 3 1. The first pressure chamber 3 1 is also
provided with a manually settable pressure relief valve 87. This pressure relief valve 87
comprises a plunger 86, a closing element 88, a spring element 89 and a setting button
90. The pressure relief valve 87 is for example set to a maximal pressure allowed in the
pressure chamber 3 1, for example to a pressure of 3,8 bar if in normal conditions the
pilot pressure is allowed to vary between 2,5 bar and 3,5 bar. This offers the advantage
that when the pilot pressure would force the valve element 18 into fully open condition,
the pressure prevailing in the pressure chamber 3 1 never can become higher than the
set maximal value, even if the pilot pressure from the second pressure regulator 3
would be higher. As the effective surface of the diaphragm 8 1 under pilot pressure is
larger than the effective surface of the diaphragm 8 1 under output pressure, the
diaphragm acts as a force enlarging device 45. .
In fig. 9 a variant is given of the pilot controlled pressure regulator 2 as shown in fig. 8
wherein the force enlarging device 45 comprises a couple of levers 93, 94, a hinge
element 95 and a connecting part 96. The diaphragm 9 1 forms a dividing element for
compressed air between the pressure chambers 3 1 and 99 and is in this case,
comparable to the diaphragm 8 1 from fig. 8, moveable up and down in the housing
100. The diaphragm 9 1 is provided with a sealing 101 at its edges and is loaded by the
pilot pressure via the duct 13 and by the environment pressure via the opening 98. The
levers 93 and 94 are hinged connected to each other by the hinge element 95 and are
slidably hinged connected to the diaphragm 9 1 and to the housing 100. The connecting
part 96 is connected to the hinge element 95 and to the diaphragm 92 so that by an up
and down movement of the diaphragm 9 1 the connecting part 96 is moved up and
down and provides in a transmission of the load by the pilot pressure on the diaphragm
9 1 to the diaphragm 92. The diaphragm 92 is provided with a sealing 97 at its edges
and is loaded by the output pressure via the opening 72 and by the environment
pressure via the opening 98. The load by the output pressure on the diaphragm 92 is
balanced by the load by the pilot pressure on the diaphragm 9 1 enlarged by the force
enlarging device 45. The rod 84 is connected to the diaphragm 92 for moving the valve
element 18. In this way a force enlarging device 45 is conceived wherein the
diaphragm 9 1 is always making a larger movement than the diaphragm 92, so that with
a pilot pressure lower than the output pressure the valve element 18 always may be
brought in fully opened position.
Embodiments of methods for supplying compressed air to a blowing device 10 of an
airjet weaving machine with an air supply system 1 comprising a pilot controlled first
pressure regulator 2 as shown in fig. 1 will be explained hereafter in detail.
In case the airflow through the first pressure regulator 2 and/or the output pressure at
the outlet 11 of the first pressure regulator 2 changes, the valve element 18 of the first
pressure regulator 2 is moved until the output pressure at the outlet 11 of the first
pressure regulator 2 reaches again a desired value.
In this case the pilot pressure is also adjusted in function of the weaving conditions. In
this case, an adjustment to the weaving conditions is carried out using the second
pressure regulator 3 that determines the pilot pressure.
Fig. 10 shows a schematic view of a control for the air supply system 1 of figure 1 using
an open-loop control unit 2 1 according to the invention. The control unit 2 1 comprises a
setting device 67 for setting a desired output pressure in dependence of the weaving
conditions, such as weft thread properties, the weaving speed, the weaving pattern,
measurement values for a weft thread insertion, such as an average value for an arrival
moment of a weft thread at a thread detector 22 and other parameters. In order to
obtain that an arrival moment of a weft thread lies within predefined limits, it is
advantageous to regulate the output pressure at the first pressure regulator 2. As long
as an arrival moment is within the predefined limits, an exact knowledge of the output
pressure at the first pressure regulator 2 or of the feed pressure of the compressed air
source 5 is irrelevant for regulating the open-loop controlled output pressure. The
setting device 67 can according to a variant be an external setting device which is
connected by wire or wirelessly for data communication with the control unit 2 1, in
particular with the open-loop control unit 2 1. In this case weaving conditions are
determined and a desired output pressure is matched to the weaving conditions.
If weft threads arrive too late at a thread detector 22 the control unit 2 1 controls a
control parameter for the pilot pressure for the pilot controlled first pressure regulator 2
so that this pilot pressure increases and in this way the output pressure of the pilot
controlled first pressure regulator 2 increases, while if weft threads arrive too early at a
thread detector 22 the control unit 2 1 controls a control parameter for the pilot pressure
for the pilot controlled first pressure regulator 2 so that this pilot pressure decreases
and in this way the output pressure decreases. According to another possibility, for
example, in case a bobbin change is detected, the pilot pressure for the pilot controlled
first pressure regulator 2 can be increased temporarily in order to avoid the influence of
an expected slow weft thread coming from the beginning of the bobbin.
In order to be able to apply an open-loop control, prior to the start of the weaving
machine, thus prior to the weaving a calibration of the air supply system 1 is carried
out. At calibrating a number of values are determined for an output pressure in
dependence of a number of feed pressures, a number of airflows and/or a number of
control variables to the first pressure regulator 2. These values are stored as calibration
data. The calibration data is used for determining a control variable to the first pressure
regulator 2 in dependence of the measured feed pressure and/or a determined airflow,
so that a desired output pressure is achieved.
This means that, at the calibrating, data is collected for an output pressure in
dependence of a number of control variables, also named control parameters or input
parameters, to the first pressure regulator 2, for a number of airflows through the first
pressure regulator 2 and/or for a number of feed pressures to the first pressure
regulator 2. These measurements are referred to as calibration and the collected data
is referred to as calibration data. Using the calibration data it is in return possible to
determine a control variable for a measured feed pressure, a determined airflow, and a
desired output pressure.
To collect such calibration data for a certain type of first pressure regulator 2 together
with a certain type of second pressure regulator 3 in a lab for example following
measurements are done. For different positions of for example the stepper motor of the
second pressure regulator 3, different flows of air through the first pressure regulator 2
and different feed pressures of the compressed air source 5, the output pressure at the
first pressure regulator 2 is determined. This may be done each time for a number of
first pressure regulators 2 of a certain construction and a number of second pressure
regulators 3 of a certain construction.
The open-loop control unit 2 1 comprises a storage element 68 in which the collected
calibration data is stored. Also a mathematical model for those calibration data may be
stored and used by an operator unit 69, which for example defines average values for
each type of pressure regulator. When using an individual first pressure regulator 2 and
an individual second pressure regulator 3, in a certain weaving machine a number of
the abovementioned measurements may be repeated to bring the influence of
individual tolerances, such as for example dimension tolerances, into account. For
example additional measurements by at least two output pressures, one flow and one
feed pressure are carried out to apply individual corrections based on the mathematical
model via the operator unit 69 to for example the average values of the mathematical
model for the actually used first pressure regulator 2 and the actually used second
pressure regulator 3. Those additional measurements may be done at the
manufacturer, at the assembly of the weaving machine, or at a weaving machine in the
weaving mill.
The open-loop control unit 2 1 is arranged for regulating a control variable x of the first
pressure regulator 2, for example in dependence of a measured feed pressure p_in, a
determined airflow Q, a desired output pressure p_w and/or signals of a thread detector
22 and the calibration data stored in the storage element 68. The calibration data
allows an efficient open-loop control for controlling an output pressure p_out in case no
unexpected disturbances occur, such as defects in a feed line 7 upstream of the first
pressure regulator 2 or in the duct 12 downstream of the first pressure regulator 2. The
storage element 68 may be an integral part of the open-loop control unit 2 1. In other
embodiments, an external storage element is provided which is connected with the
open-loop control unit 2 1 by wire or wirelessly for data communication. The actual
output pressure p_out is in this case not supplied to the control unit 2 1.
The control unit 2 1 preferably cooperates with a pressure sensor 15 for measuring the
feed pressure pjn in the feed line 7 upstream of the first pressure regulator 2. For
example, the control unit 2 1 also cooperates with an apparatus 30 for determining
and/or calculating an airflow Q through the first pressure regulator 2. The control unit
2 1 can adjust the output pressure p_out of the first pressure regulator 2 when the feed
pressure pjn changes or when the feed pressure pjn drops below a boundary value
for this feed pressure p_in that is for example related to a desired output pressure p_w
of the first pressure regulator 2. The output pressure p_out mainly corresponds to the
pressure in the buffer airtank 8. In this way the first pressure regulator 2 also allows to
compensate random variations in the feed pressure of the compressed air source 5.
The control unit 2 1 uses calibration data to determine a control variable x for adjusting
the first pressure regulator 2 in dependence of the measured feed pressure p_in in the
feed line 7, the determined airflow Q through the feed line 7, the desired output
pressure p_w and the calibration data, so that at an outlet 11 of the first pressure
regulator 2 an actual output pressure p_out is achieved equal to a desired output
pressure p_w. A control variable for the motor controlled second pressure regulator 3 is
adjusted in dependence of amongst others the above parameters. By considering the
airflow Q through the first pressure regulator 2 with an apparatus 30 for determining an
airflow, every unwanted decrease of an output pressure p_out due to an increased
airflow Q can easily be avoided.
The open-loop control unit 2 1 is arranged for determining of a control variable x for
adjusting the first pressure regulator 2 in dependence of the measured feed pressure
pjn, the airflow Q through the pressure regulator 2 and the desired output pressure
p_w. In the embodiment shown, the control variable x is a control command to a motor
46, 64, 66 of the second pressure regulator 3. The control of the motor 46, 64, 66
allows to set the position of the motor 46, 64, 66 and also to set the pilot pressure to
the first pressure regulator 2. In the embodiment shown the pilot pressure is mainly
influenced by suitably controlling the motor 46 or 64, more particularly by controlling the
motor to a defined position.
The setting device 67 for example also comprises a relational operator unit 69 for
comparing a measured feed pressure pjn with the set desired output pressure p_w
and for detecting a decrease of the feed pressure p_in below a minimal value for the
set desired output pressure p_w.The setting device 67 is arranged to adapt a method
for controlling the desired output pressure p_w of the air supply system 1 if a decrease
of the feed pressure pjn below a minimal value for the desired output pressure p_w is
detected, so that the pilot pressure for the desired output pressure p_w at the first
pressure regulator 2 is no longer adapted or is adapted only between limits. This
increases a stability of the air supply system 1. The minimal value for the desired
output pressure p_w may be defined as the minimal value of the measured feed
pressure p_in during weaving under normal conditions and may be stored.
The air supply system 1 according to the invention with a pressure sensor 15 is
particularly suitable to be applied in case the feed pressure of the compressed air
source 5 drops below a set value that is function of the desired output pressure at the
first pressure regulator 2. Hereby a control variable to the pressure regulator 2 can be
adjusted in dependence of the measured feed pressure of the compressed air source
5. If the feed pressure decreases below a certain value, this may be displayed or
signalled by a displaying unit of the weaving machine.
A drop of the feed pressure can result in that an inserted weft thread arrives later at a
thread detector 22. If the late arrival is due to a too low feed pressure, an increase of
the desired output pressure at the pressure regulator 2 to compensate the late arrival is
in most cases not possible. In these circumstances a late arrival of the weft thread
could be compensated by an increase of the pilot pressure at the first pressure
regulator 2. As the low output pressure is due to a too low feed pressure, such an
adaptation of the pilot pressure does not result in an increase of the output pressure, as
the pilot controlled pressure regulator 2 in this case is already fully open. In this case
the feed pressure in the feed line is fully used as the valve element 18 is in full open
position. If such an increase of the pilot pressure would be carried out, in case the feed
pressure would increase again, the output pressure at the pressure regulator 2 would
become undesirable high, which also could lead to weaving errors. Due to this in case
of a too low feed pressure, more particularly if the measured feed pressure is dropped
below a set feed pressure, the pilot pressure for a desired output pressure is not
adapted any more or is only adapted within limits. This means that the pilot pressure for
the pilot controlled first pressure regulator 2 is not adapted any more or is only adapted
within limits. The motor controlled second pressure regulator 3 is provided for adjusting
the pilot pressure for the first pressure regulator 2. A control variable for the motor
controlled second pressure regulator 3 is in this case adjusted at least in dependence
of the measured feed pressure. In this case it is obtained that when the feed pressure
increases subsequently again, the output pressure at the first pressure regulator 2 still
approximately corresponds to the weaving conditions.
In a method the first pressure regulator 2 is set to a maximum opening for allowing a
maximum flow in order to allow a maximum airflow. This allows to weave as fast as
possible. This is also used in case the feed pressure in the feed line 7 is lower than a
pre-set minimal value. In this case the pilot pressure is set sufficiently high in order to
achieve that the valve element 18 is fully opened independently of the output pressure
of the first pressure regulator 2 and independently of the force of the force element 20.
This is possible because a force enlarging device 45 for the pilot pressure is present, in
other words because this pilot pressure can always increase sufficiently in order to be
able to fully open the valve element 18 at any output pressure of the first pressure
regulator 2.
As shown in fig. 11 a group of pressure regulator devices 17 is provided, each of which
comprise at least a pilot controlled first pressure regulator 2 to which compressed air is
fed at feed pressure via a common feed line 7. The first pressure regulators 2 are
arranged adjacent or next to each other and may be at least partially formed as integral
components. An arrangement of the pilot controlled pressure regulators 2 of the
pressure regulator devices 17 next to one another allows an arrangement that is small
in size. Further, the length of feed lines 7 and losses in the feed lines 7 may be reduced
due to the small sized pilot controlled first pressure regulators 2. An air filter 6 may be
arranged close to the pressure regulator devices 17.
In this embodiment also several buffer airtanks 8 with associated blowing devices 10
are supplied with compressed air from a common compressed air source 5 via
respective first pressure regulators 2. In this case one common pressure sensor 15 for
measuring the feed pressure upstream of all first pressure regulators 2 is sufficient,
instead of several pressure sensors each associated to each buffer airtank 8.
Consequently, in preferred embodiments, no pressure sensors are provided at the
buffer airtanks 8.
The open-loop control unit 2 1 as described above allows for example that an operator
of weaving machines is able to compare the weaving pressures, this means the
pressures at which a weft thread is inserted, of different blowing devices 10 and of
different weaving machines easily without using pressure sensors in the various buffer
airtanks 8. The different pressures in the pressure regulator devices 17 and/or the
pressures in each buffer airtank 8 may be determined by the control unit 2 1 (shown in
fig. 1) using calibration data and may be displayed on a display unit of the weaving
machine. Herein the displayed output pressures are equal to the output pressures
controlled or desired by the open-loop control unit 2 1 and approximately equal to the
actual output pressures at the pressure regulator 2.
If several weaving machines are coupled to a central control unit that can cooperate
with the control unit 2 1 of each weaving machine, by means of different pressure
measurements with a pressure sensor 15 at a feed line 7 of each weaving machine,
pressure differences in several supply ducts 70 to a respective weaving machine,
which are fed with compressed air from a compressed air source 5 via a distribution
system 77 to a respective feed line 7 of a weaving machine can be determined. The
feed line 70 is herein connected to the inlet of the air filter 6 arranged upstream of the
feed line 7. This allows to determine when the supply pressure in a supply duct 70 to a
certain feed line 7 of a weaving machine is different, in particular is substantially lower
than to another weaving machine, so that malfunctions in one of the supply ducts 70 or
in one of the ducts 78 of the distribution system 77 for compressed air from a
compressed air source 5 to one of the several weaving machines can be determined.
Since a decrease of the feed pressure also may be caused by an air filter 6 that is dirty,
this method is also suitable to define when an air filter 6 is dirty.
According to a variant not shown, the second pressure regulator 3 is as the first
pressure regulator 2 executed as a pilot controlled pressure regulator, whereby the pilot
controlled second pressure regulator 3 can be smaller in dimension than the pilot
controlled first pressure regulator 2.
The apparatus 30 for determining an airflow through the pressure regulator 2 is not
limited to the shown airflow measuring device 16 and/or calculating unit 23, but can
also be formed by any other device that is capable to determine the amount of air
through the pressure regulator 2.
A pilot controlled pressure regulator 2 with a diaphragm actuator 24 can act very fast
because the moving parts can be designed lightweight. As the output pressure acts in
opposite direction to the pilot pressure on a diaphragm actuator 24 the valve element
18 is moved in response to a load difference between the load by the pilot pressure
and the load by the output pressure. By moving of the valve element 18 the valve
opening is increasing or decreased. Due to this the regulation is influenced by the load
difference and the regulation is almost not influenced by the absolute value of the set
pilot pressure. This is advantageous for weaving with a desired speed and weft
insertion pattern. A diaphragm actuator 24 with a force enlarging device 45 allows to
form a pressure regulator 2 small in size, so that several pressure regulators 2 can be
arranged adjacent to each other in a small place.
In the context of the invention, with the term "motor controlled pressure regulator" a
pressure regulator is meant which is controlled by a motor, for example by a rotating
stepper motor, a linear stepper motor, a controllable DC motor, a servo motor, an
electromagnet with a magnet core and/or permanent magnet, an actuator such as a
linear actuator, a rotating actuator, a voice coil actuator or a moving spool actuator, or
any other motor which is electrically controllable.
The pressure regulators, the pressure regulator devices, the air supply systems and the
methods according to the invention are not limited to the embodiments shown and
described as example, but may also comprise variants and combinations of these
embodiments that fall under the claims.
Claims
1. A pressure regulator device for an air supply system for an airjet weaving
machine comprising a pilot controlled first pressure regulator (2), which first
pressure regulator (2) is loaded by a settable pilot pressure, characterised in
that a second pressure regulator (3) is provided for regulating the settable
pilot pressure of the pilot controlled first pressure regulator (2).
2. The pressure regulator device according to claim 1, characterized in that the
pilot controlled first pressure regulator (2) is connectable to a compressed
air source supplying a feed pressure, wherein the second pressure regulator
(3) is adapted for regulating the pilot pressure in order to provide an output
pressure, which output pressure is independent of variations in the feed
pressure.
3. The pressure regulator device according to claim 1 or 2, characterized in
that the pilot pressure is set lower than the feed pressure for the pilot con
trolled first pressure regulator (2) and is set lower than the output pressure
of the pilot controlled first pressure regulator (2).
4. The pressure regulator device according to claim 2 or 3, characterized in
that the second pressure regulator (3) is adapted for regulating the pilot
pressure of the pilot controlled first pressure regulator (2) to a pressure
lower than the minimal expected feed pressure for the pilot controlled first
pressure regulator (2).
5. The pressure regulator device according to claims 1 to 4, characterized in
that the pilot controlled first pressure regulator (2) comprises a diaphragm
actuator (24) having at least one first diaphragm (25, 26, 38, 43, 8 1, 9 1, 92)
which is loaded by a settable pilot pressure, and a valve element (18) a r
ranged for reciprocal movement by the diaphragm actuator (24).
The pressure regulator device according to one of claims 1 to 5, character
ized in that the second pressure regulator (3) is a motor controlled pressure
regulator.
The pressure regulator device according to one of claims 1 to 5, character
ized in that the second pressure regulator (3) is a pilot controlled pressure
regulator.
The pressure regulator device according to one of claims 1 to 7, character
ized in that a third pressure regulator (4) is provided for regulating a feed
pressure to the second pressure regulator (3), the third pressure regulator
(4) preferably being a manually settable pressure regulator.
The pressure regulator device according to one of claims 1 to 8, character
ized in that the second pressure regulator (3) comprises a housing (56) hav
ing an inlet (57), an outlet (58) and an air volume (59) there between,
wherein a loaded pressure relief valve (60) is provided on the housing (56),
having a settable biasing force, in particular wherein the pressure relief
valve (60) is loaded using a spring (61 ) , which is manually and/or motor
controlled.
The pressure regulator device according to claim 9, characterized in that the
second pressure regulator (3) is provided integrally with the pressure cham
ber (32) of the pilot controlled first pressure regulator (2).
The pressure regulator device according to any of claims 3 to 10, character
ized in that a force enlarging device (45) is provided, so that a load applied
by the pilot pressure on the diaphragm actuator (24) of the pilot controlled
first pressure regulator (2) is enlarged.
The pressure regulator device according to claim 11, characterized in that
the force enlarging device (45) is at least partially an integral component of
the diaphragm actuator (24) of the pilot controlled first pressure regulator
(2).
The pressure regulator device according to claim 12, characterized in that at
least one second diaphragm (26) loaded by the pilot pressure is provided,
wherein the load on the second diaphragm (26) is applied to the first d ia
phragm (25), and the resulting load on the first diaphragm (25) is balanced
by the output pressure.
14. The pressure regulator device according to claim 12, characterized in that
the at least one first diaphragm (43) loaded by the pilot pressure and at
least one third diaphragm (42) loaded by the output pressure are provided
which are coupled for a transmission of the movement, wherein the effective
surface of the third diaphragm (42) is smaller than the effective surface of
the first diaphragm (43).
15. An air supply system for an air jet weaving machine comprising at least one
blowing device (10) and a compressed air source (5), wherein air from the
at least one air source (5) is supplied via the air supply system ( 1) to the at
least one blowing device (10), and wherein the air supply system ( 1) com
prises at least one pressure regulator device (17) according to any of claims
1 to 14 arranged between the at least one air source (5) and a buffer air tank
(8) for regulating the pressure in the buffer air tank (8).
16. The air supply system according to claim 15, characterized in that a group
of pressure regulator devices (17) are provided, which are arranged adjacent to each other.