Air supply unit and method for applying an air supply unit-
Description
Technical Field
The invention relates to an air supply unit with a main body comprising at least
one inlet connectable to a compressed air source, an outlet connectable to a
blowing device, a main duct for supplying air at a first pressure from the at least
one inlet to the outlet, a secondary duct for supplying air at a second pressure
from the at least one inlet to the outlet, with a first air flow control valve provided
in the main duct and arranged to control the supply of compressed air through
the main duct to the outlet, and with a second air flow control valve provided in
the secondary duct, wherein the second air flow control valve is a throttle valve
and arranged to throttle compressed air in the secondary duct.
Prior Art
US 6,062,273 discloses a apparatus for supplying compressed air to a main
blowing device of an airjet weaving machine for weft thread insertions with a
integrated air supply unit including an inlet opening or inlet directly connected to
the compressed air supply, an outlet connected to the main blowing device and
air flow control valves with valve drives. Main ducts and bypass ducts provide
communication between the inlet and the outlet with the airflow control valves
controlling the supply of air to the outlet of the air supply unit. The air flow control
valves include a shut-off valve arranged to control in an on/off manner the
supply of compressed air from the main duct to the outlet; a first adjustable
throttling valve arranged to throttle compressed air supplied to the outlet during
weft thread insertions when the shut-off valve is open and a second adjustable
throttling valve arranged to throttle compressed air supplied to the outlet between
weft thread insertions when the shut-off valve is closed.
US 6,305,433 discloses an air supply unit with a main body or air supply block
with a substantially straight parallelepiped housing. The air supply block in
cludes ducts and switched and/or adjusted valves driven by valve drives arranged
between inlets and outlets. The air supply block provides two outlets at
one longitudinal side of the housing, each outlet being associated with its own
valves. Three sides of the housing are free of valve drives or other elements for
allowing several blocks to be connected to each other via these sides.
It is known from US 5,970,996 to provide a pneumatic system, wherein two
main blowing devices are each connected by a first branch to a compressed-air
source supplying high-pressure compressed air for purposes of weft thread in
sertion. The main valve is opened by a control unit to insert a weft thread and
thereafter is closed again. Each of the main blowing devices is connected
through a secondary branch to the compressed-air source to supply lowpressure
compressed air to the main blowing devices. The two secondary
branches comprise a common pressure regulator and one throttling valve each.
A control unit is provided for adjusting the throttling valve to different throttling
gaps. The control unit may adjust the throttling valve so that, immediately after
closing the main valve compressed air of higher pressure shall be supplied
through the secondary branch, the pressure of the compressed air thereafter
being reduced by adjusting the throttling valve. The pressure then will be raised
again in timely manner before the next insertion of a weft thread. A non-return
valve may be provided in each secondary branch downstream of the throttling
valve for precluding the pressure, when released by the main valve, from entering
the secondary branch. After closing the main valve the pressure at the blow
ing devices will drop only very slowly. This effect is further assisted as a length
of a pneumatic line between the throttling valve and the non-return valve is
comparatively long and an air volume of the compressed air in the secondary
duct before opening the non-return valve is high.
Summary of the Invention
It is the object of the invention to provide an air supply unit for supplying air to a
blowing device of an airjet weaving machine and a method for applying an air
supply unit for supplying air to a blowing device of an airjet weaving machine,
wherein a fast and reliable transition from an air supply at a first pressure to an
air supply at a second pressure and vice versa is achieved.
This object is solved by an air supply unit for supplying air to a blowing device of
an airjet weaving machine and a method for applying an air supply unit for sup
plying air to a blowing device of an airjet 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 an air supply unit for supplying air
to a blowing device of an airjet weaving machine with a main body comprising
at least one inlet connectable to a compressed air source, an outlet connectable
to the blowing device, a main duct for supplying air at a first pressure from the
at least one inlet to the outlet, a secondary duct for supplying air at a second
pressure from the at least one inlet to the outlet, with a first air flow control valve
provided in the main duct and arranged to control the supply of compressed air
through the main duct to the outlet, and with a second air flow control valve provided
in the secondary duct, wherein the second air flow control valve is a throt
tle valve and arranged to throttle air in the secondary duct, wherein the secon
dary duct ends into the main duct downstream of the first air flow control valve,
and wherein a non-return valve is provided in the secondary duct downstream
of the second air flow control valve. The main duct is also named the first duct.
The non-return valve is arranged in the secondary duct near to the place where
the secondary duct ends into the main duct.
Generally, the first pressure, also referred to as weaving pressure, is sufficiently
high for allowing a weft thread insertion. Appropriate first air pressures are for
example in the range of about 2 bar to about 7 bar. The second pressure, also
referred to as holding pressure, is generally lower than the first pressure. Using
a second pressure in the range of about 0,1 bar has been successful for reliably
holding a weft thread in the blowing device when the weft thread not inserted.
The non-return valve opens or closes due to pressure differences upstream and
downstream of the non-return valve. No actuator is required for the non-return
valve. By providing the non-return valve downstream of the second air flow con
trol valve in the secondary duct of a main body, a compact structure of the air
supply unit is given, wherein an air volume between the non-return valve and
the second air flow control valve and/or between the non-return valve and the
first air flow control valve may be kept small. This allows prevailing pressures
upstream or downstream of the non-return valve to be quickly adapted to
changes in the conditions due to an opening or closing of the first air flow co n
trol valve and a subsequent closing or opening of the non-return valve. Thereby,
the non-return valve opens or closes quickly in response to a closing or opening
of the first air flow control valve for a fast and reliable transition from an air sup
ply at a first pressure to an air supply at a second pressure and vice versa.
The object is also solved by a method for applying an air supply unit for supply
ing air to a blowing device of an airjet weaving machine for inserting a weft
thread, wherein the air supply unit comprises a main body, the main body comprises
at least one inlet connected to a compressed air source, an outlet con
nected to the blowing device, a main duct for supplying air at a first pressure
from the at least one inlet to the outlet, a secondary duct for supplying air at a
second pressure from the at least one inlet to the outlet, wherein the air supply
unit further comprises a first air flow control valve provided in the main duct and
arranged to control the supply of compressed air through the main duct to the
outlet and a second air flow control valve provided in the secondary duct,
wherein the second air flow control valve is a throttle valve and arranged to
throttle air in the secondary duct, wherein the secondary duct ends into the
main duct downstream of the first air flow control valve, and wherein a nonreturn
valve is provided in the secondary duct downstream of the second air
flow control valve, wherein the method comprising the following steps of: sup
plying air at a second pressure via the secondary duct while the first air flow
control valve is closed, opening the first control valve and supplying air at a first
pressure via the main duct for a weft thread insertion of a weft thread, wherein
the first pressure is higher than the second pressure, and subsequently closing
the first air control valve.
When closing the first air flow control valve, the pressure in the main duct
downstream of the first air flow control valve will drop. When the pressure at the
outlet is below a pressure in the secondary duct upstream of the non-return
valve, the non-return valve opens and air is supplied at the second pressure.
While no air flow is present through the second air flow control valve, the sec
ond air flow control valve has no throttling effect and the pressure upstream and
downstream of the second air flow control is essentially equal. Therefore, a
higher pressure will act on the non-return valve for opening the non-return valve
than after the non-return valve has opened and air flows through the second air
flow control valve. Therefore, a fast opening of the non-return valve is achieved.
For example, the pressure prevailing before the opening of the non-return valve
may be chosen to 1.5 bar, whereas the pressure supplied via the secondary
duct after the non-return valve has opened is throttled to 0,1 bar. Due to the fast
opening of the non-return valve and the small volumes of the secondary duct, a
pressure drop at the outlet to a pressure below the desirable holding pressure is
successfully avoided.
According to an embodiment, an essentially linear passageway is provided in
the main body for the formation of the secondary duct, wherein the second air
flow control valve and the non-return valve are arranged in line in the passage
way. Preferably, essentially linear passageways are provided in the main body
for the formation of both the main duct and the secondary duct. The passage
ways are manufactured for example as boreholes. For a simple manufacturing,
the passageways extend preferably at least partially in parallel. The volume of
the secondary duct downstream of the second air flow control valve is prefera
bly minimized. The volume is kept sufficiently large to meet constraints of de
sign and mechanical strength of the valves provided in the duct and the value of
the second pressure. In one embodiment, the respective passageway is formed
in the main body for the secondary duct, wherein tubular or sleeve-type ele
ments are provided in order to minimize the air volume in the secondary duct.
After closing the first air flow control valve, it is advantageous that the pressure
downstream of the first air flow control valve drops rapidly. By minimising the
volume of air downstream of the first air flow control valve, in particularly by
closing the non-return valve arranged between the main duct and the secondary
duct, a fast dropping of the pressure is achieved after closing the first air flow
control valve. This allows to define precisely the moment at which a main blow
ing device is no longer blowing on the weft thread at the end of the weft thread
insertion, what prevents too much blowing on a weft thread which is braked or
already halted, so that a damaging of the weft thread is avoided. This is advan
tageous to brake and/or hold a weft thread as desired at the end of the weft
thread insertion.
In another embodiment the valve seat of the second air flow control valve is
mounted on or formed integrally with an inlet of the non-return valve. In pre
ferred embodiments, a sleeve-type element with a central through-opening is
provided in a passageway of the main body, wherein the central throughopening
functions as the inlet of the non-return valve and the valve seat of the
second air flow control valve is provided in the entry region of central throughopening
at a first face of the sleeve-type element. According to an embodiment
the sleeve-type elements with a central through-opening are provided in a passageway
of the main body, wherein the non-return valve is arranged between
the sleeve-type elements and wherein a valve seat of the second air flow co n
trol valve is provided at the entry region of central through-opening at the
sleeve-type element arranged upstream of the other sleeve-type element. The
passageway, in particular a borehole, may be dimensioned sufficiently large for
allowing a simple manufacturing of the main body. The diameter of the throughopening
may be chosen to be substantially smaller than the diameter of the
passageway provided in the main body in order to minimize the volume of the
secondary duct. In addition, the conjoint embodiment of the valve seat and the
inlet of the non-return valve as a sleeve-type element allows for a compact de
sign.
Preferably, the sleeve-type element is fixedly secured in the secondary duct, in
particular via a screw connection. The sleeve-type element may easily be replaced.
For example in order to alter a throttling action of the second air flow
control valve or to provide another non-return valve.
In one embodiment, the second air flow control valve comprises a stationary
valve seat with an essentially circular-cylindrical inside surface and a plunger
with a conical outer surface. The conicity of the plunger preferably is between 3 °
and 30°. In a preferred embodiment, the position of the plunger is adjustable
with respect to the valve seat for adjusting a throttling gap.
In another embodiment, the second air flow control valve comprises an actuator
for adjusting the throttling gap, in particular an electrically controlled actuator.
The actuator preferably is coupled with a screw-thread device for transforming a
rotational movement of the actuator into an axial movement of the plunger hav
ing a conical outer surface. The second air flow control valve can be set to a
desired throttling gap.
In one embodiment, the plunger for example is guided upon movement by
sidewalls of the passageway. According to still another embodiment, the second
air flow control valve comprises a support structure sealingly arranged in the
secondary duct, wherein the plunger, in particular a plunger skirt, is slideably
supported in the support structure. The non-return valve, the second air flow
control valve, the support structure and the actuator for the second air flow co n
trol valve are inserted in the passageway formed in the main body. The support
structure is sealingly arranged in the passageway in order to avoid air losses. In
one embodiment, the plunger comprises a plunger skirt and a plunger head,
which are secured to each other to form a uniform element. In other embodi
ments, the plunger skirt and the plunger head are formed integrally. With integral
is meant self existing. The support structure allows dimensioning the d i
ameter of the plunger smaller than the diameter of the passageway of the main
body.
In a preferred embodiment, a diameter of the plunger is smaller than a crosssection
of the second duct part of the secondary duct upstream of the valve
seat of the second air flow control valve. This allows to minimize the force re
quired for moving the plunger.
In another embodiment, the first air flow control valve is a shut-off valve arranged
to control in an on/off manner the supply of compressed air through the
main duct to the outlet. The first air flow valve comprises in preferred embodi
ments a closure element and an actuator, in particular an electro-magnetic ac
tuator. In a preferred embodiment, the main duct comprises two main duct parts
extending essentially perpendicular to one another, wherein the closure element
of first air flow control valve is arranged in the transition region between the two
main duct parts for closing an air supply to the second main duct part of the
main duct. This allows a simple manufacturing of the main duct and the corre
sponding first air flow control valve. The actuator is preferably arranged at a
side wall of the main body and connected to the closure element via a shaft. In
one embodiment, the closure element is held in a closing contact with a valve
seat by a return spring and moved by the actuator against the force of the return
spring.
According to another embodiment, the non-return valve comprises a valve element
arranged axially moveable in the secondary duct. The moving direction of
the non-return valve coincides with the moving direction of the second air flow
control valve. Preferably, the passageway for the secondary duct is arranged at
least partially in parallel to the first main duct part of the main duct allowing a
simple manufacturing.
In another embodiment, the main body has an essentially straight parallelepiped
housing, wherein an actuator for the first air flow control valve and the at least
one inlet for the main duct are arranged at a first wall, an actuator for the sec
ond air flow control valve is arranged at a second wall, perpendicular to the first
wall, and the outlet is arranged at a third wall parallel to the first wall, and
wherein three remaining walls of the housing are formed as free surfaces. With
such a structure, no elements or units extending to the outside of the housing
are provided on the free surfaces. This allows to place several air supply units
next to each other.
In one embodiment, one inlet is provided on the main body for the supplying of
air via the main duct and the secondary duct, wherein the pressure of the air
supplied to the secondary duct preferably is reduced using a pressure regulat
ing valve. According to a preferred embodiment, two inlets are provided on the
main body, wherein air is supplied at a first pressure from a first inlet to the out
let via the main duct and air is supplied at a second pressure from the second
inlet to the outlet via the secondary duct. A common compressed air source
may be provided, wherein outside the main body a pressure regulating valve is
provided for reducing the pressure to be supplied via the secondary duct. The
pressure of the air supplied to the secondary duct can be adjusted independ
ently on the pressure supplied to the main duct.
In a preferred embodiment, a supply duct extending transversely through the
main body is provided, wherein air is supplied to the secondary duct via this
transversely extending supply duct. Several air supply units may be arranged
next to one another, wherein air is supplied to the secondary ducts via the supply
duct. This allows a compact structure of the air supply unit and requires only
a limited number of additional supply ducts at the main body.
In preferred embodiments, the air supply unit is fitted with at least one electrical
connector connecting an actuator or drive unit for the first air flow control valve
and/or an actuator or drive unit for the second air flow control valve with a co n
trol unit, in particular a control unit of the weaving machine.
Further advantages and features of the invention will emerge from the following
description of the embodiments illustrated in the drawings.
Brief Description of the Drawings
In the following, embodiments of the invention will be described in detail based
on several schematic drawings in which
Fig. 1 shows a schematic cross-sectional view of an air supply unit according to
a first embodiment;
Fig. 2 shows a schematic side view of the air supply unit of Fig. 1;
Fig. 3 shows a schematic view of a valve element of a non-return valve of the
air supply unit of Figs. 1 and 2;
Fig. 4 shows a graph representing the pressure course over time at an outlet of
the air supply unit;
Fig. 5 shows a front view of a number of air supply units according to the inven
tion arranged next to one another; and
Fig.6 shows a schematic cross-sectional view of an air supply unit of a second
embodiment similar to Fig. 1.
Detailed Description of Preferred Embodiments
In the following, embodiments of the invention will be described in detail with
reference to the drawings. Throughout the drawings, the same or similar ele
ments will be denoted by the same reference numerals.
Fig. 1 and 2 show a first embodiment of an air supply unit 1 with a main body 2
for supplying air to a blowing device 3 (schematically shown) of an airjet weav
ing machine in a schematic cross-sectional view and a side view, respectively.
The main body 2 further comprises a main duct 4 with a first main duct part 5
and a second main duct part 6 for supplying air at a first pressure from the first
inlet 7 to the outlet 8 and a secondary duct 9 with a first duct part 10 , a second
duct part 11 and a third duct part 12 for supplying air at a second pressure from
the second inlet 13 to the outlet 8. The first inlet 7 is connectable to a first com
pressed air source (not shown), the second inlet 13 is connectable to a second
compresses air source (not shown) and the outlet 8 is connectable to the blow
ing device 3 of the airjet weaving machine.
A first air flow control valve 14 is provided in the main duct 4 and is arranged to
control the supply of compressed air through the main duct 4 to the outlet 8.
The shown first air flow control valve 14 is a shut-off valve that is arranged to
control in an on/off manner the supply of compressed air through the main duct
4. The air flow control valve 14 comprises a closure element 15 and an actuator
16 , in particular an electro-magnetic actuator or any other suitable drive unit.
The main duct 4 comprises two main duct parts 5 and 6 extending essentially
perpendicular to one another, wherein the closure element 15 is arranged in the
transition region between the two main duct parts 5 and 6 for closing the supply
of air to the second main duct part 6 of the main duct 4. The actuator 16 is a r
ranged at a side wall 35 of the main body 2 at which also the first inlet 7 is pro
vided. The actuator 16 is connected to the closure element 15 via a shaft 17.
The closure element 15 is held in a closing contact with a valve seat 19 pro
vided at the second main duct part 6 by a return spring 18 and is moved by the
actuator 16 against the force of the return spring 18.
In the secondary duct 9 a second air flow control valve 20 is provided, wherein
the second air flow control valve 20 is a throttle valve and is arranged to throttle
the air flow through the secondary duct 9. The secondary duct 9 ends into the
main duct part 6 of the main duct 4 downstream of the first air flow control valve
14.
Further, a non-return valve 2 1 is provided in the secondary duct 9 downstream
of the second air flow control valve 20. Fig. 3 shows in more detail the nonreturn
valve 2 1 of the air supply unit 1. The second air flow control valve 20 and
the non-return valve 2 1 divide the secondary duct 9 in three duct parts 10, 11
and 12, a first duct part 10 upstream of the second air flow control valve 20, a
second duct part 11 between the second air flow control valve 20 and the non
return valve 2 1, and third duct part 12 downstream of the non-return valve 2 1.
For a weft thread insertion a first pressure or weaving pressure is provided
which is sufficiently high for allowing a reliable weft thread insertion. Appropriate
first air pressures that are provided at the first inlet 7 are for example in the
range of about 2 bar to about 7 bar. The second pressure or holding pressure is
lower than the first pressure. Using a second pressure in the range of about
0,1 bar has been successful for reliably holding a weft thread in the blowing device
when not inserted. Suitable second pressures that are provided at the sec
ond inlet 13 of the air supply unit 1 are for example in the range of 1,5 bar.
The non-return valve 2 1 opens or closes due to pressure differences in the
compressed air between the second main duct part 6 of the main duct 4 and the
second duct part 11 of the secondary duct 9. No actuator is required for the
non-return valve 2 1.
Fig. 4 shows an example of a graph that shows the pressure over time at the
outlet 8 of the air supply unit 1. During weaving, when no weft thread is inserted,
air at the second pressure is supplied via the secondary duct 9 while the
first air flow control valve 14 is closed. For a weft thread insertion, the first air
flow control valve 14 is opened at an instant T 1 and air at a first pressure is
supplied to the outlet 8 via the main duct 4. After the weft thread insertion, the
first air flow control valve 14 is closed at an instant T2. As can be seen in Fig. 4,
a fast transition between the two pressure levels is achieved. The non-return
valve 2 1 is closed at an instant T3, shortly after the first air flow control valve 14
has been opened. After the first air flow control valve 14 is closed again, the
non-return valve 2 1 is opened again at an instant T4.
The function of the air supply unit 1 will be explained with reference to Figs. 1 to
4. When closing the first air flow control valve 14, the pressure in the second
main duct part 6 of the main duct 4 downstream of the first air flow control valve
14 will drop. The pressure in the third duct part 12 of the secondary duct 9 is
substantially equal to the pressure in the second main duct part 6. When the
pressure in this third duct part 12 of the secondary duct 9 is below a pressure in
the second duct part 11 of the secondary duct 9 upstream of the non-return
valve 2 1, the non-return valve 2 1 opens and air can be supplied at the second
pressure to the outlet 8.
As long as no air flows through the opened second air flow control valve 20, the
pressure upstream and downstream of the second air flow control valve 20 is
essentially the same. Therefore, a pressure that is provided at the second inlet
13 will act via the second duct part 11 on the non-return valve 2 1 for opening
the non-return valve 2 1. This pressure is higher than when an air stream is
throttled by the second air flow control valve 20 after the non-return valve 2 1
has opened and air flows through the second air flow control valve 20. For example,
the pressure supplied via the second inlet 13 and prevailing in static
conditions, i.e. before the opening of the non-return valve 2 1, may be chosen to
1,5 bar, whereas the pressure supplied via the secondary duct 9 after the non
return valve 2 1 has opened due to the throttling drops to 0,1 bar. This way on
one hand after closing the first air flow control valve 14 a fast opening of the
non-return valve 2 1 is achieved and on the other hand after the opening of the
first air flow control valve 14 a fast closing of the non-return valve 2 1 is
achieved.
Further, by providing the non-return valve 2 1 downstream of the second air flow
control valve 20 in the secondary duct 9 of the main body 2, a compact st ruc
ture of the air supply unit 1 is given, wherein an air volume between the no n
return valve 2 1 and the second air flow control valve 20 and between the no n
return valve 2 1 and the first air flow control valve 14 is kept small. This allows
prevailing pressures upstream and/or downstream of the non-return valve 2 1 to
quickly adapt to changes in the conditions due to an opening or closure of the
first air flow control valve 14 and the non-return valve 2 1. In particularly a fast
decreasing of the pressure in the second main duct part 6 of the main duct 4
and in the third main duct part 12 of the secondary duct 9 is achieved after the
closing of the first air flow control valve 14. This allows to define precisely the
moment at which a weft thread during a weft thread insertion is no longer pro
pelled by a blowing device 3 receiving air from an air supply unit 1 according to
the invention. This way e.g. a braking and/or a clamping of the weft thread at
the end of the weft thread insertion may be done without a risk of damaging the
weft thread because of the blowing device 3 blows too hard.
Due to the higher pressure acting on the non-return valve 2 1 under static condi
tions and the small volumes of the duct parts 11 and 12 of the secondary duct 9
downstream of the second air flow control valve 20, the non-return valve 2 1
opens or closes quickly in response to a closing or opening of the first air flow
control valve 14 for a fast and reliable transition from an air supply at a first
pressure to an air supply at a second pressure and vice versa. In addition,
pressure drops at the outlet 8 to a pressure below the expected holding pres
sure are successfully avoided.
The main duct parts 5, 6 and the duct part 10 are implemented as bore-holes in
the main body 2 which allows a simple manufacturing. The duct part 10 of the
secondary duct 9 is essentially in parallel to the first main duct part 5 of the
main duct 4. The non-return valve 2 1 is placed in the passageway 22 of which
the duct part 10 makes part. In the shown embodiment, the non-return valve 2 1
comprises two sleeve-type elements 23, 24 with a central through-opening
48, 49 and a valve element 25 of the non-return valve 2 1 arranged slidingly in
the sleeve-type elements 23, 24. The valve element 25 is preferably executed
as light as possible in order to allow a fast movement. The central thoughopening
48 of the sleeve-type element 23 forms the duct part 11, while the cen
tral through-opening 49 of the sleeve-type element 24 forms the duct part 12.
The two sleeve-type elements 23, 24 are fixedly secured to each other and
sealingly arranged in the passageway 22. Further, a fastening element 26 is
provided for fastening the sleeve-type elements 23, 24 in the passageway 22
that for example comprises a screw element. The sleeve-type elements 23, 24
may easily be replaced. The passageway 22 is dimensioned sufficiently large
for allowing a simple manufacturing of the main body 2. The diameter of the
central through-openings 48, 49 of the two sleeve-type elements 23, 24, which
central through-openings 48, 49 form the duct parts 11 and 12 respectively, is
chosen substantially smaller than the diameter of the passageway 22 for mini
mizing the air volume in the second and third duct part 11 and 12 of the secondary
duct 9. In order to achieve an airtight closure by the non-return valve 2 1,
the non-return valve 2 1 comprises a closure ring 5 1. The closure ring 5 1 is a r
ranged between the sleeve-type elements 23 and 24.
The second air flow control valve 20 comprises a stationary valve seat 27 with
an essentially circular-cylindrical inside surface and a plunger 28 with a conical
outer surface. The conicity of the plunger 28 preferably is between 3 ° and 30°.
In the embodiment shown, the valve seat 27 is formed at the entry region 47 of
the central through-opening 48 of the duct part 11 that is part of the sleeve-type
element 23. To close the second air flow control valve 20 airtight, the plunger 28
comprises a closure ring 52 which can cooperate with the recess 53 of the
sleeve-type element 23. Further the plunger 28 comprises a plunger skirt 43
which can be moved to contact the surface 54 of the sleeve-type element 23.
This contact allows to perform an unambiguous positioning of the plunger 28 so
that a controlling of the actuator 29 of the second air flow control valve 20 may
be done precisely. In this case the closure ring 52 is pressed into the recess 53.
The position of the plunger 28 is adjustable with respect to the valve seat 27 for
adjusting a throttling gap. For this purpose, the second air flow control valve 2 1
comprises an actuator 29, in particular a stepper motor or any other suitable
drive unit. The actuator 29 is coupled with a screw-thread device for transform
ing a rotational movement of the actuator 29 into an axial movement of the
plunger 28. The second air flow control valve 20 can be set to a desired throt
tling for throttling suitable and adapted to the weaving conditions the air flow
through the second duct 9. The plunger 28 is arranged at a slider element 30
and can be moved with the slider element 30 in the axial direction of the pas
sageway 22.
As schematically shown in Fig. 2, the air supply unit 1 is further fitted with at
least one electrical connector 3 1, 32 connecting the actuator 16 for the first air
flow control valve 14 and connecting the actuator 29 for the second air flow co n
trol valve 20 with a control unit 33, in particular a control unit of the weaving
machine.
The main body 2 has an essentially straight parallelepiped housing 34, wherein
the actuator 16 for the first air flow control valve 14 and the first inlet 7 are a r
ranged at a first wall 35, the actuator 29 for the second air flow control valve 20
is arranged at a second wall 36, perpendicular to the first wall 35, and the outlet
8 is arranged at a third wall 37 parallel to the first wall 35, and the remaining
three walls 38, 39, 40 of the housing 34 are formed as free surfaces, as sche
matically shown in Fig. 5. With such a structure, no elements or units extending
to the outside of the housing 34 are provided on the free surfaces. This allows
placing several air supply units 1 next to each other.
As shown in Figs. 1, 2 and 5 a supply duct 4 1 (shown in broken lies) extending
transversely through the main body 2 is provided, wherein the first duct part 10
of the secondary duct 9 coincides with the supply duct 4 1 and air is supplied to
the secondary duct 9 via the supply duct 4 1. When arranging several air supply
units 1 next to one another, for example as shown in Fig. 5, the supply ducts 4 1
of a number of air supply units 1 are coupled and air is supplied to the secondary
ducts 9 via the supply ducts 4 1. In this case the second inlet 13 is located
near the supply duct 4 1 of a first air supply unit 1 that is arranged at one side
and the supply duct 4 1 of an last air supply unit 1 that is arranged at the oppo
site side is sealed with a cover 50. This allows a compact structure of the air
supply unit 1 with a limited number of additional air ducts at the main body 2. As
shown in Fig. 5 compresses air can be supplied to the air supply unit 1 accord
ing to the invention via several air ducts 55 and air ducts (not shown) to an inlet
7.
In the embodiment shown in Figs. 1 and 3, the plunger 28 comprises a plunger
head 42 and a plunger skirt 43 and the second air flow control valve 20 com
prises a support structure 44 arranged in the passageway 22 for the secondary
duct 9 , wherein the plunger 28 is slideably supported in the support structure
44. The non-return valve 2 1, the second air flow control valve 20, the support
structure 44 and the actuator 29 for the second air flow valve 20 are inserted in
the passageway 22. With a sealing ring 45 as shown in Fig. 1, the support
structure 44 is sealingly arranged in the passageway 22 in order to avoid air
losses. The support structure 44 allows to dimension the diameter of the
plunger 28 smaller than the diameter of the passageway 22. The sliding element
30 of the plunger 28 is also sealingly arranged with a sealing ring 46 in the
support structure 44. Due to the small diameter of the sealing ring 46 also the
force required for moving the plunger 28 is minimized, for example against the
force of a pressure prevailing in the first duct part 10 of the second duct 9.
Fig. 6 is a schematic cross-sectional view of an air supply unit 1 according to a
second embodiment of the invention. In the embodiment shown in Fig. 6 , the
plunger 28 is formed as an integral unit slidingly arranged in the passageway
22, wherein the plunger 28 is guided by the sidewalls of the passageway 22.
Also a closure ring 56 is provided between the plunger 28 and the actuator 29.
In this embodiment, the first duct part 11 of the secondary duct 9 is vanishingly
small. The plunger 28 can co-operate with a valve seat 27 that is provided at
the entry region 47 of the central through-opening of the sleeve-type element
23, more particularly the entry region 47 downstream of the valve seat 27 of the
second air flow control valve 2 1. In this case the first inlet 7 and the second inlet
13 are arranged next to one another at the wall 35. Each inlet 7 and each inlet
13 can be connected via an own air duct to a compressed air source.
An air supply unit and a method according to the invention are obviously not
limited to the exemplary embodiments which have been illustrated and de
scribed, but can also include variations and combinations thereof which fall u n
der the claims. An air supply unit according to one of the claims is particularly
suitable for applying a method according to one of the claims.
Claims
A air supply unit for supplying air to a blowing device (3) of an airjet
weaving machine, wherein the air supply unit (1) comprises a main body
(2), the main body (2) comprises at least one inlet (7, 13) for air, an outlet
(8) for air, a main duct (4) for supplying air at a first pressure from an in
let (7) to the outlet (8), a secondary duct (9) for supplying air at a second
pressure from an inlet (13) to the outlet (8), with a first air flow control
valve (14) provided in the main duct (4) and arranged to control the sup
ply of compressed air through the main duct (4) to the outlet (8), and with
a second air flow control valve (20) provided in the secondary duct (9),
wherein the second air flow control valve (20) is a throttle valve and a r
ranged to throttle the air in the secondary duct (9), and wherein the sec
ondary duct (9) ends into the main duct (4) downstream of the first air
flow control valve (14), characterized in that a non-return valve (21 ) is
provided in the secondary duct (9) downstream of the second air flow
control valve (20).
The air supply unit according to claim 1, characterized in that an essen
tially linear passageway (22) is provided in the main body (2) for the fo r
mation of the secondary duct (9), wherein the second air flow control
valve (20) and the non-return valve (21) are arranged in line in the pas
sageway (22).
The air supply unit according to claim 1 or 2 , characterized in that
sleeve-type elements (23, 24) with a central through-opening (48, 49) are
provided in a passageway (22) of the main body (2), wherein the no n
return valve (21 ) is arranged between the sleeve-type elements (23, 24)
and wherein a valve seat (27) of the second air flow control valve (20) is
provided at the entry region (47) of central through-opening (48) at the
sleeve-type element (23) arranged upstream of the other sleeve-type e l
ement (24).
The air supply unit according to claim 3, characterized in that the sleevetype
element (23, 24) is fixedly secured in the passageway (22) of the
main body (2), in particular using a fastening element (26).
5. The air supply unit according to any one of claims 1 to 4, characterized in
that the second air flow control valve (20) comprises a stationary valve
seat (27) with an essentially circular-cylindrical inside surface and a
plunger (28) with a conical outer surface.
6. The air supply unit according any one of claims 1 to 5, characterized in
that the second air flow control valve (20) comprises an actuator (29) for
adjusting the throttling gap, in particular an electrically controlled actuator.
7. The air supply unit according to claim 5 or 6, characterized in that the
second air flow control valve (20) comprises a support structure (44)
sealingly arranged in the secondary duct (9), wherein the plunger (28) is
slideably supported in the support structure (44).
8. The air supply unit according to claim 7, characterized in that a diameter
of the plunger (28) is smaller than a cross-section of the second duct part
( 1 1) of the secondary duct (9) upstream of the valve seat (27) of the second
air flow control valve (20).
9. The air supply unit according to any of claims 1 to 8, characterized in that
the first air flow control valve (14) comprises a closure element (15) and
an actuator ( 1 6), in particular an electro-magnetic actuator, arranged to
control in an on/off manner the supply of compressed air through the
main duct (4) to the outlet (8).
10. The air supply unit according to any one of claims 1 to 9, characterized in
that the non-return valve (21 ) comprises a slider element (25) arranged
axially moveable in the secondary duct (9).
11. The air supply unit according to any one of claims 1 to 10, characterized
in that the main body (2) has an essentially straight parallelepiped hous
ing (34), wherein an actuator ( 16) for the first air flow control valve (14)
and an inlet (7) for the main duct (4) are arranged at a first wall (35), an
actuator (29) for the second air flow control valve (20) is arranged at a
second wall (36), perpendicular to the first wall (35), and the outlet (8) is
arranged at a third wall (37) parallel to the first wall (35), and wherein
three remaining walls (38, 39, 40) of the housing (34) are formed as free
surfaces.
12. The air supply unit according to any one of claims 1 to 11, characterized
in that two inlets (7, 13) are provided on the main body (2), wherein air is
supplied at a first pressure from a first inlet (7) to the outlet (8) via the
main duct (4) and air is supplied at a second pressure from the second
inlet (13) to the outlet (8) via the secondary duct (9).
13. The air supply unit according to claim 12, characterized in that a supply
duct (41 ) extending transversely through the main body (2) is provided,
wherein air is supplied to the secondary duct (9) via this supply duct (41 )
extending transversely.
14. The air supply unit according to any one of claims 1 to 13, characterized
in that the non-return valve (21) is arranged in the secondary duct (9)
near to the place where the secondary duct (9) ends into the main duct
(4).
15. Method for applying an air supply unit (1) for supplying air to a blowing
device (3) of an airjet weaving machine for inserting a weft thread,
wherein the air supply unit ( 1 ) comprises a main body (2), the main body
(2) comprises at least one inlet (7, 13) for air, an outlet (8) for air, a main
duct (4) for supplying air at a first pressure from an inlet (7) to the outlet
(8), a secondary duct (9) for supplying air at a second pressure from an
inlet (13) to the outlet (8), wherein the air supply unit (1) further com
prises a first air flow control valve (14) provided in the main duct (4) and
arranged to control the supply of compressed air through the main duct
(4) to the outlet (8) and comprises a second air flow control valve (20)
provided in the secondary duct (9), wherein the second air flow control
valve (20) is a throttle valve and arranged to throttle the air in the secon
dary duct (9), wherein the secondary duct (9) ends into the main duct (4)
downstream of the first air flow control valve (14), and wherein a no n
return valve (21 ) is provided in the secondary duct (9) downstream of the
second air flow control valve (20), wherein the method comprises the
steps of: supplying air at a second pressure via the secondary duct (9)
while the first air flow control valve (14) is closed, opening the first control
valve (14) and supplying air at a first pressure via the main duct (4) for a
weft thread insertion of a weft thread, wherein the first pressure is higher
than the second pressure, and subsequently closing the first air flow co n
trol valve (14).