This invention relates to the technical field of Dry Screw Vacuum Pumps. More Particularly,
the invention relates to the Dry Screw Vacuum Pump having rotors uniquely designed to
minimize premature bearing failure and a combination of sealing arrangement to avoid
leakage in order to enhance the performance of pump.
Background of the Invention
In general, Dry Screw Vacuum Pumps are known for generating vacuum in any industry where
the requirement of clean vacuum exists, as the name suggests there are no lubricating/sealing
fluid in the working chamber and no contact between the parts even with tight clearances
within the pump, thus producing an oil free dry pumping unique characteristic to this type of
pumping technology. In order to create an effective vacuum for pumping within the pump, the
Dry pump needs to run at high speeds and for this the rotors should be mechanically balanced
to minimize vibration while the pump is operational so as to enable the smooth running of the
pump. A number of such rotors for Dry Screw Vacuum Pump have been developed in the past
to avoid the mechanical imbalance produced during the rotation. Some of them casted closed
cavities in the rotor or internal cavities through the rotor profile for smooth balancing of the
rotors. The cavity rotors formed in the conventional pump were either by drilling or through
mass removal during the casting stage itself, the later has been observed to face a high
rejection rate due to defects in casting and also required specially skilled manpower for
casting. There is also a possibility that sand gets deposited in the casted deep cavity, leading
to the creation of imbalance within the pump during its operation and sand may act as an
unwanted particulate responsible for intense pump vibration, scratches and internal damages
of the pump on its way out through discharge, thereby, causing a major internal premature
mechanical failure of the pump.
As we know, dry screw vacuum pumps are meant to create high to low pressure vacuum, such
dry pumps operate at high differential pressure to create ultimate vacuum thus making it
necessary for the sealing to ensure the minimum amount of leakage to get the desired result
in the pumping chamber. In the conventional pumps, there have been multiple kind of seals
employed along with grease lubrication, such seals were lip seals, labyrinth seals, piston ring
seals, mechanical seals, etc. because of which a major internal sealing failure and a high
operating temperature have been observed on suction side of the pump which is untraceable
in grease lubricant causing drop down in the ultimate vacuum affecting performance of the
pump and which ultimately led to the component failure resulting in shortening the life span of
the pump.
3
US6139297A discloses a double worm system, wherein, it is possible, by varying the angle of
contact of the worm and any balance hollows and/or by altering the contour of the worms in
the medium engagement region, to reduce the size of the balance hollows, sometimes to
"zero", and with the possible use of additional masses. Besides the advantage of simple raw
component manufacture, worms balanced in this way also permit the use of special materials
and extreme worm geometries for fitting in pumps used in the chemical, medical and food
sectors.
The above disclosed double worm system may or may not have inner balancing hollows on
the ends of the screw rotor, this system will create problems in balancing the screw rotors as
there will be deposition of contaminants in the inner balancing hollows, which will lead to the
intense vibration and ultimately to premature system failure, the above problem has been
solved in the present invention by employing an open machined pocket on the ends of the
screw rotor for avoiding mechanical imbalance during the operation of the pump. Besides, one
of the main objectives of the double worm system is to create a possibility of using special
materials for casting which is not possible in the prior arts, whereas, the objective of the
present invention is entirely different.
US20180340535A1 discloses a dry vacuum pump, wherein a sealing device is arranged
between the high-vacuum-side bearing and at least one suction chamber adjacent to the highvacuum-side bearing. The cut-out is connected, by means of a first channel, to a region of
the dry vacuum pump in which there is a higher pressure than in at least one suction chamber
adjacent to the high-vacuum-side bearing, wherein, the sealing device comprises of at least
two lip seals and an intermediate chamber between the at least two lip seals.
The two lip seals disclosed above are directed in the same direction, there will be a problem
as it will prevent only one way leakage, i.e. either from the process side to the atmosphere or
from the atmosphere to the process side. The above problem is solved by the present
invention by providing two oppositely directed flaps with unique serration/grooves acting as a
sealant for fluids between the process and the atmosphere side, thereby preventing two-way
leakage.
KR1020190017111B1 discloses a dry screw vacuum pump having a drain chamber and a
groove and a mechanical seal, main and driven screw within a casing, wherein, a Gas Purge
Seal provided on the inner circumferential surface of the casing inside the fluid exhaust portion
of the main and driven screw rotors and provided on the main and driven shafts, wherein, a
double lip seal provided outside the gas purge Seal, a Mechanical Seal provided on the side
of the fluid exhaust portion and an Oil Seal provided on the inner circumference of the end
casing at the end of the fluid exhaust part.
4
CN111188770 discloses a dry oilless seal screw vacuum pump having a combined sealing
device on the exhaust shaft end, wherein the combined sealing device includes a lip seal and
a mechanical seal, the lip seal and the mechanical seal are arranged in sequence on the
exhaust shaft end.
CN205714762 discloses a screw vacuum pump with piston ring seal and mechanical seal
structure, comprising a pump body, a suction port is provided on the pump body, and active
rotor and passive rotor are arranged side by side in the pump body, wherein, the front end
cover of the active rotor and the passive rotor are equipped with an exhaust end sealing
structure and there is also a suction end sealing structure is provided between the active and
passive rotor.
CN105649987 discloses a composite seal for a vacuum pump, characterized in that it
comprises a piston ring seal, a sealing ring, a nitrogen seal, a labyrinth seal and an exhaust
chamber, the cavity of the vacuum pump and an exhaust cavity is provided between the oil
tank filled with lubricating oil, and the rotor shaft of the vacuum pump passes through the
cavity and passes through the exhaust cavity. And inserted into the oil tank; the part of the
rotor shaft located in the exhaust chamber is respectively sleeved with a piston ring seal and
a labyrinth seal, the piston ring seals are provided between both ends of the piston ring seal
and the rotor shaft. The medium in the cavity is sealed with the sealing ring on this side through
the piston ring seal, so the lubricating oil or oil gas in the oil tank is sealed by the sealing ring
and the labyrinth seal on this side; in the exhaust cavity, located between the two ends of the
piston ring seal.
The placement of composite sealings, sealing device or any other sealing structure in
KR1020190017111B1, CN111188770, CN205714762 and CN105649987 is focused mainly
on the discharge side of the pump, no patent has paid heed for a sealing arrangement on the
suction side of the pump, there is a suction end sealing structure provided in CN205714762,
but that too between the screw rotors, which will not solve the problem of leakage from the
inside of the pump to the outside or a contamination from outside.
It would be desirable, therefore, to develop an improved Dry Screw Vacuum Pump, which is
capable of balancing the rotor mechanically without the need of forming an inner or enclosed
cavity in the rotor or by means of drilling external holes, avoiding internal leakage or
contamination from outside or the suction chamber (grease/oil) on the suction side of the pump
for creating an ultimate vacuum, balancing the high differential pressure, reducing the overall
operating temperature on the suction side of the pump, thus, ensuring low level of vibrations
and no contamination /consumption of oil in the suction chamber of the pump for enhancing
5
the service life of the pump, and obviates to the challenges that exist in the prior arts leading
to premature failure of the pump as cited in the arts above.
Summary of the Invention
The various objectives and embodiments of present invention as presented herein are
understood to be illustrative and not restrictive and are non-limiting with respect to the scope
of the invention.
It is an objective of the present invention to provide a dry screw vacuum pump capable of
avoiding intense vibration leading to premature component failure.
It is an objective of the present invention to provide a dry screw vacuum pump having rotors
with no internal closed cavity by avoiding drilling or cavity casting in rotor, therefore, eliminating
the need of closed sand cavity and specially skilled manpower for casting.
It is an objective of the present invention to provide a dry screw vacuum pump capable of
protecting the internals of the pump from scratches and other damages on its way out through
pump discharge.
It is an objective of the present invention to provide a dry screw vacuum pump capable of
preventing leakage from and contamination in the pump thus ensuring high volumetric
efficiency for the creation of high ultimate vacuum within the pump.
It is an objective of the present invention to provide a dry screw vacuum pump that consumes
less power.
It is an objective of the present invention to provide a dry screw vacuum pump with an
extended service life.
It is an objective of the present invention to provide a dry screw vacuum pump which is
maintenance friendly and allows convenient replacement in the pump.
A term “open machined balancing pocket” for rotors has been used below in various
embodiments and other paragraphs, it means rotors of a particular design are casted followed
by machining to create “open pockets” on their front and rear surfaces. Open pockets refer to
the mass removal from the front and rear surfaces of the rotors, and the resultant surfaces are
open to the internal surrounding of the casing of the dry screw vacuum pump, therefore, not
causing any internal particles deposition.
A term “barrier seal” has been used below in various embodiments and other paragraphs
which is a part of the composite sealer on the inlet suction side, barrier seal is vertically placed
at the junction point of the rotor and rotor shaft, it is having protrusions affixing into the grooves
6
of the junction point of the rotor and rotor shaft, because of its placement, structure and
functionality, it acts as a barrier to prevent leakage from rotor side to the atmosphere side,
hence the name, barrier seal.
A term “inverted V-shaped seal” has been used below in various embodiments and other
paragraphs which is a part of the composite sealer, that comprises of two oppositely directed
flaps capable of preventing two-way synchronous leakage and contamination, i.e. from the
rotor to the shaft and from the atmosphere to the rotor, because of its shape, orientation and
functionality, hence the name inverted V-shaped seal.
In accordance with one embodiment of the present invention, there is provided a dry screw
vacuum pump comprising of a casing connected to a motor, wherein the casing comprises of
an inlet suction port, a discharge port, a driver rotor and a driven rotor parallelly embedded
within the casing with a certain clearance between them to avoid direct contact, a pair of driver
rotor shafts extending from the front and rear surface of the driver rotor and a pair of driven
rotor shafts extending from the front and rear surface of the driven rotor, a composite sealer
encompassing the above-mentioned shafts on the inlet suction side and discharge side,
wherein, said each driver rotor and driven rotor is having an open machined balancing pocket
on its front and rear surface.
In accordance with above embodiment of the present invention, wherein, each of the said rotor
is having a front surface and a rear surface and wherein, the driver rotor shaft and the driven
rotor shaft extending from the front surface of the driver and driven rotor is on the discharge
port side, wherein, the driver rotor shaft and driven rotor shaft extending from the rear surface
of the driver and driven rotor is on the inlet suction port side, wherein said rear surface is
situated on the inlet suction port side and said front surface is situated on the discharge port
side, wherein, said rotors and shafts on the inlet suction side and discharge side are fixedly
mounted on a pedestal forming bottom part of the casing.
In accordance with one embodiment of the present invention, there is provided a dry screw
vacuum pump comprising of a casing connected to a motor, wherein the casing comprises of
an inlet suction port, a discharge port, a driver rotor and a driven rotor parallelly embedded
within the casing with a certain clearance between them to avoid direct contact, a pair of driver
rotor shafts extending from the front and rear surface of the driver rotor and a pair of driven
rotor shafts extending from the front and rear surface of the driven rotor, a composite sealer
encompassing the above-mentioned shafts on the inlet suction side and discharge side,
wherein, said each driver rotor and driven rotor is having an open machined balancing pocket
on its front and rear surface, wherein said open machined balancing pockets are engraved
7
during casting followed by machining of the rotors for counterbalancing of the dynamic and
static imbalance produced in the rotors while the dry screw vacuum pump is operational.
In accordance with above embodiment of the present invention, wherein said open machined
balancing pockets are designed to partially form the front and rear surface of the rotors and
are completely open to the inner surrounding of the casing, wherein each of the said rotor is
having variable screw pitch, wherein, said pitch of the rotors may or may not be the same.
In accordance with one embodiment of the present invention, there is provided a dry screw
vacuum pump comprising of a casing connected to a motor, wherein the casing comprises of
an inlet suction port, a discharge port, a driver rotor and a driven rotor parallelly embedded
within the casing with a certain clearance between them to avoid direct contact, a pair of driver
rotor shafts extending from the front and rear surface of the driver rotor and a pair of driven
rotor shafts extending from the front and rear surface of the driven rotor, a composite sealer
encompassing the above-mentioned shafts on the inlet suction side and discharge side,
wherein, said each driver rotor and driven rotor is having an open machined balancing pocket
on its front and rear surface, wherein said composite sealer comprises of a barrier seal affixed
onto the rear surface of the driver rotor and driven rotor, an inverted V-shaped seal towards
the end of the rotor shafts extending from the rear surface of the said rotors and a piston ring
seal sequentially spaced between the barrier seal and the inverted V-shaped seal.
In accordance with just above embodiment of the present invention, wherein composite sealer
is having a hollow space between the barrier seal and the piston seal enabling a significant
amount of pressure drop between the process side of the rotors and rotor shaft, said barrier
seal, piston ring seal and the inverted V-shaped seal that are sequentially arranged on the
suction side to prevent fluid leakage at the junction point of the rotors and shafts, and
contamination from the atmosphere.
In accordance with above embodiment of the present invention, wherein said V-shaped seal
comprises of two oppositely directed flaps capable of preventing two-way synchronous
leakage and contamination, i.e. from the rotor to the shaft and from the atmosphere to the
rotor on the suction side enabling reduction in the operating temperature of the Dry Screw
Vacuum Pump.
In accordance with another embodiment of the present invention, there is provided a rotor of
dry screw vacuum pump comprising a front surface and a rear surface, each specially
designed to secure an open machined balancing pocket, a screw main body having helically
designed conveyor grooves with variable pitch, wherein said open machined balancing
pockets that are engraved during casting followed by machining of the rotors for
8
counterbalancing of the dynamic and static imbalance produced in the rotors while the dry
screw vacuum pump is operational.
In accordance with just above embodiment of the present invention, said rotor serves as a
driver or driven rotor or both on the inlet suction side and discharge side and is fixedly mounted
on a pedestal forming the bottom part of the Dry Screw vacuum Pump.
Brief Description of Drawings
Figure 1a shows the top view of the dry screw vacuum pump along with joining of its internal
and external components.
Figure 1b shows the rotors, rotor shafts and open machined balancing pockets of rotors within
the casing of the dry screw vacuum pump.
Figure 1c shows the positioning of the inlet suction port and discharge port along with the
pedestal, transmission gear and the motor.
Figure 2a shows a driver rotor and a driven rotor intermeshing with each other pair, wherein,
each of said rotor is having an open machined balancing pocket on its front and rear surface.
Figure 2b and 2c shows the front and rear profile of the rotors with engagements of the open
machined balancing pockets with each other.
Figure 3 shows a dry vacuum pump having a composite sealer encompassed around the
rotor shaft on the inlet suction side and discharge side.
Figure 4a shows the composite sealer on the suction inlet side.
Figure 4b shows the composite sealer on the discharge side.
Detailed Description of the Invention
In accordance with one embodiment of the present invention, there is provided a dry screw
vacuum pump comprising a casing connected to a motor, wherein the casing comprises of an
inlet suction port, a discharge port, a driver rotor and a driven rotor parallelly embedded within
the casing with a certain clearance between them to avoid direct contact, a pair of driver rotor
shafts extending from the front and rear surface of the driver rotor and a pair of driven rotor
shafts extending from the front and rear surface of the driven rotor and a composite sealer
encompassing the above-mentioned shafts on the inlet suction port side and discharge side,
wherein said composite sealer comprises of a barrier seal affixed onto the rear surface of the
driver rotor and driven rotor, an inverted V-shaped seal towards the end of the shafts extending
from the rear surface of the said rotors and a piston ring seal sequentially spaced between the
barrier seal and the inverted V-shaped seal.
9
In accordance with above embodiment of the present invention, said composite sealer is
having a hollow space between the barrier seal and the piston seal enabling a significant
amount of pressure drop between the process side of the rotors and rotor shaft, wherein said
barrier seal, piston ring seal and the inverted V-shaped seal that are sequentially arranged on
the suction side to prevent fluid leakage at the junction point of the rotor and shaft, and
contamination from the atmosphere.
In accordance with just above embodiment of the present invention, wherein said V-shaped
seal comprises of two oppositely directed flaps capable of preventing two-way synchronous
leakage and contamination, i.e. from the rotor to the shaft and from the atmosphere to the
rotor on the suction side enabling reduction in the operating temperature of the Dry Screw
Vacuum Pump.
In accordance with one of the above embodiment of the present invention, wherein, the driver
rotor shaft and the driven rotor shaft extending from the front surface of the driver and driven
rotor is on the discharge port side, wherein, the driver rotor shaft and driven rotor shaft
extending from the rear surface of the driver and driven rotor is on the inlet suction port side,
wherein each of the said rotor is having a front surface and a rear surface, wherein said rotors
are having an open machined balancing pocket on their front and rear surface.
In accordance with just above embodiment of the present invention, wherein said open
machined balancing pockets are engraved during casting followed by machining of the rotors
for counterbalancing of the dynamic and static imbalance produced in the rotors while the dry
screw vacuum pump is operational, wherein said open machined balancing pockets are
designed to partially form the front and rear surface of the rotors and are completely open to
the inner surrounding of the casing.
In accordance with one embodiment of the present invention, there is provided a composite
sealer of dry screw vacuum pump that comprises of a barrier seal affixed onto the rear surface
of a driver rotor and a driven rotor, an inverted V-shaped seal towards the end of rotor shafts
extending from the rear surface of the said rotors and a piston ring seal sequentially spaced
between the barrier seal and the inverted V-shaped seal.
In accordance with just above embodiment of the present invention, wherein said composite
sealer encompasses the rotor shafts on the inlet suction port side and discharge side of the
dry screw vacuum pump and said barrier seal, piston ring seal and the inverted V-shaped seal
are sequentially arranged on the suction side to prevent fluid leakage at the junction point of
the rotors and shafts, and contamination from the atmosphere.
10
In accordance with just above embodiment of the present invention, wherein said V-shaped
seal comprises of two oppositely directed flaps capable of preventing two-way synchronous
leakage and contamination, i.e. from the rotor to the shaft and from the atmosphere to the
rotor on the suction side enabling reduction in the operating temperature of the Dry Screw
Vacuum Pump.
In accordance with one of the above embodiment of the present invention, said composite
sealer is having a hollow space between the barrier seal and the piston seal enabling a
significant amount of pressure drop between the process side of the rotors and rotor shaft,
wherein, said rotors and rotor shafts are as per any of the above embodiments.
Referring to the Figure 1a that shows a Dry Screw Vacuum Pump having a casing 1 connected
to a motor bracket 4, wherein the casing 1 comprises of a driver rotor 3 and a driven rotor 6
parallelly embedded within the casing 1 with a certain clearance between them to avoid direct
contact, wherein, each of the said rotor is having a front surface (31 and 32) with open
machined balancing pockets (25 and 26) and a rear surface (33 and 34) with open machined
balancing pockets (23 and 24), a pair of driver rotor shafts (28 and 30) extending from the
front (31 and 32) and rear surface (33 and 34) of the driver rotor 3 and a pair of driven rotor
shafts (27 and 29) extending from the front (31 and 32) and rear surface (33 and 34) of the
driven rotor 6, wherein, the driver rotor shaft (28 and 30) and the driven rotor shaft (27 and
29) extending from the front surface (31 and 32) of the driver 3 and driven rotor 6 is on the
discharge port side, wherein, the driver rotor shaft (27 and 29) and driven rotor shaft (28 and
30) extending from the rear surface (33 and 34) of the driver 3 and driven rotor 6 is on the inlet
suction port side, wherein the driver rotor shaft (27 and 29) extending from the front surface
(31 and 32) of the driver rotor 3 on the discharge side is fixedly connected to the motor 7 via
a gear box 10 and the driver rotor shaft (27 and 29) is enabling to rotate both the driver rotor
3 and driven rotor 6 in opposite direction with the help of intermeshing engagements between
the transmission gears 9 within the gear box 10, wherein, said rotors (3 and 6) and shafts (27,
28, 29 and 30) on the inlet suction side and discharge side are fixedly mounted on a pedestal
8 forming bottom part of the casing 1, wherein a composite sealer (13 and 14) is encompassed
on the shafts (27, 28, 29 and 30) on the inlet suction side and discharge side. Refer Figure 1c
for the position of the inlet suction port, discharge port, transmission gear 9 and pedestal 8
with respect to other components of the dry screw vacuum pump as mentioned above.
Referring to Figure 1b and 2a that shows a pair of rotors of dry screw vacuum pump
intermeshing with each other with a certain clearance to avoid direct contact between them,
wherein, said rotors are driver rotor 3 having open machined balancing pockets (26 and 24)
on its front surface 32 and the rear surface 34, and the driven rotor 6 having open machined
11
balancing pockets (23 and 25) on its front surface 31 and the rear surface 33, wherein a
composite sealer (13 and 14) is encompassed on the shafts (27, 28, 29 and 30) on the inlet
suction side and discharge side. Such open machined balancing pockets (23, 24, 25 and 25)
are engraved during casting followed by machining of the rotors for counterbalancing of the
dynamic and static imbalance produced in the rotors (3 and 6) while the dry screw vacuum
pump is operational. Also, open machined balancing pockets are designed to partially form
the front (31 and 32) and the rear surface (33 and 34) of the rotors (3 and 6) and are completely
open to the inner surrounding of the casing (1), wherein, said rotors (3 and 6) are having
variable screw pitch, wherein, said pitch of the rotors may or may not be the same.
Referring to Figure 2b and 2c that shows the front and rear profiles of the rotor having open
machined balancing pockets while they are intermeshing with each other.
Referring to Figure 3 that shows a dry screw vacuum pump focusing on the composite sealer
13 on the discharge port side and the composite sealer 14 on the inlet suction port side,
wherein, composite sealer 13 on the discharge port side comprises of Angular ball bearing 12,
bearing housing 35, Mechanical seal 36 and an inverted V-shaped seal 17, wherein,
composite sealer 14 on the inlet suction port side comprises of a barrier seal 18 affixed onto
the rear surface (33 and 34) of the driver rotor 3 and driven rotor 6, an inverted V-shaped seal
21 towards the end of the rotor shafts (29 and 30) extending from the rear surface of the driver
rotor 3 and driven rotor 6, a piston ring seal (19 and 20) sequentially spaced between the
barrier seal 18 and the inverted V-shaped seal 21 and a hollow space 22 between the barrier
seal 18 and the piston ring seal (19 and 20).
Referring to Figure 4a that shows a composite sealer 13 encompassed on the driver 3 or
driven shaft 6 on the discharge port side, which comprises of an Angular ball bearing 12,
bearing housing 35, Mechanical seal 36 and an inverted V-shaped seal 17, wherein, said
inverted V-shaped seal 21 and the mechanical seal 36 are sequentially arranged on the shafts
(27 and 28) on the discharge end of the dry screw vacuum pump, inverted V-shaped seal 17
is used to reduce and maintain the operating temperature at the discharge side end, therefore,
high temperature is prevented from being transmitted into the mechanical seal and the internal
components of the pump or bearings (12 and 35). This cooling effect greatly enhances the
service life of the seal.
Referring to Figure 4b that shows a composite sealer 14 encompassed on the driver 3 or
driven shaft 6 on the suction inlet port side, which comprises of a barrier seal 18, a piston ring
seal (19 and 20) and an inverted V-shaped seal 21 that are sequentially arranged on the
suction side to prevent fluid leakage from the inside to outside at the junction point of the rotors
(3 and 6) and shafts (29 and 30), and contamination from the atmosphere, wherein, a hollow
12
space 22 is provided between the barrier seal 18 and the piston ring seal (19 and 20) for
enabling a significant amount of pressure drop between the process side of the rotors (3 and
6) and rotor shaft (29 and 30), wherein, said barrier seal 18 is vertically placed with a protrusion
18a affixing onto the groove of shaft surface, hence making the path of leakage more long and
complex to prevent leakage and preventing leaking of high-pressure fluid to the atmosphere
and minimizing internal leakage, reducing contaminant ingression not only by restricting the
clearance through which the process particles enter but also by creating areas of complex flow
to exclude contaminants. Thus, as a combination with piston ring seal (19 and 20) and the
inverted V-shaped seal 21, barrier seal 18 provides a more reliable sealing arrangement,
wherein, said inverted V-shaped seal 21 comprises of two oppositely directed flaps capable
of preventing two-way synchronous leakage and contamination, i.e. from the rotor to the shaft
and from the atmosphere to the rotor on the suction side enabling reduction in the operating
temperature and permitting higher surface speeds. This specially designed inverted V-shaped
seal 21 can be used to replace standard elastomeric rotary shaft seals having limited
application range with respect to temperature, surface speed, media compatibility, pressure
or a combination of all above due to the inherent limitations of many elastomer grades. Also,
the material with which the inverted V-shaped seal 21 is made offers low friction, hence stick
and slip free running, thereby, reducing temperature generation and permitting higher surface
speeds, wherein, said piston ring seal 19 comprises of a pair of rings 20 parallelly affixed onto
the piston grooves serving as a sealing surface to prevent leakage of process fluid from inside
to outside and contaminants from outside to protect the internal components of the dry screw
vacuum pump.
The above combination of barrier seal 18, the piston ring seal (19 and 20) and the inverted Vshaped seal 21 to form the composite sealer 14 on the inlet suction port side helps to reduce
the amount of leakage which ultimately help to achieve the high level of ultimate vacuum and
enhance the dry screw pump life.
While the invention is amenable to various modifications and alternative forms, some
embodiments have been illustrated by way of example in the drawings and are described in
detail above. The intention, however, is not to limit the invention by those examples and the
invention is intended to cover all modifications, equivalents, and alternatives to the
embodiments described in this specification.
The embodiments in the specification are described in a progressive manner and focus of
description in each embodiment is the difference from other embodiments. For the same or
similar parts of each embodiment, reference may be made to each other.
13
It will be appreciated by those skilled in the art that the above description was in respect of
preferred embodiments and that various alterations and modifications are possible within the
broad scope of the appended claims without departing from the spirit of the invention with the
necessary modifications.
Based on the description of disclosed embodiments, persons skilled in the art can implement
or apply the present disclosure. Various modifications of the embodiments are apparent to
persons skilled in the art, and general principles defined in the specification can be
implemented in other embodiments without departing from the spirit or scope of the present
disclosure. Therefore, the present disclosure is not limited to the embodiments in the
specification but intends to cover the most extensive scope consistent with the principle and
the novel features disclosed in the specification.

We Claim:
1. A Dry Screw Vacuum Pump comprises:
a casing connected to a motor, wherein the casing comprises of:
an inlet suction port;
a discharge port;
a driver rotor and a driven rotor parallelly embedded within the casing with a certain clearance
between them to avoid direct contact, wherein, each of the said rotor is having a front surface
and a rear surface
a pair of driver rotor shafts extending from the front and rear surface of the driver rotor and a
pair of driven rotor shafts extending from the front and rear surface of the driven rotor, wherein,
the driver rotor shaft and the driven rotor shaft extending from the front surface of the driver
and driven rotor is on the discharge port side, wherein, the driver rotor shaft and driven rotor
shaft extending from the rear surface of the driver and driven rotor is on the inlet suction port
side,
a composite sealer encompassing the above-mentioned shafts on the inlet suction side and
discharge side; and
wherein, said each driver rotor and driven rotor is having an open machined balancing pocket
on its front and rear surface,
2. The Dry Screw Vacuum Pump as claimed in claim 1, wherein said rear surface is situated
on the inlet suction port side and said front surface is situated on the discharge port side.
3. The Dry Screw Vacuum Pump as claimed in claim 1, wherein, said rotors and shafts on the
inlet suction side and discharge side are fixedly mounted on a pedestal forming the bottom
part of the casing.
4. The Dry Screw Vacuum Pump as claimed in claim 1, wherein said open machined balancing
pockets are engraved during casting followed by machining of the rotors for counterbalancing
of the dynamic and static imbalance produced in the rotors while the dry screw vacuum pump
is operational.
5. The Dry Screw Vacuum Pump as claimed in claim 1, wherein said open machined balancing
pockets are designed to partially form the front and rear surface of the rotors and are
completely open to the inner surrounding of the casing.
15
6. The Dry Screw Vacuum Pump as claimed in claim 1, wherein each of the said rotor is having
variable screw pitch, wherein, said pitch of the rotors may or may not be the same.
7. The Dry Screw Vacuum Pump as claimed in claim 1, wherein said composite sealer
comprises of a barrier seal affixed onto the rear surface of the driver rotor and driven rotor, an
inverted V-shaped seal towards the end of the rotor shafts extending from the rear surface of
the said rotors and a piston ring seal sequentially spaced between the barrier seal and the
inverted V-shaped seal.
8. The Dry Screw Vacuum Pump as claimed in claim 7, said barrier seal, piston ring seal and
the inverted V-shaped seal that are sequentially arranged on the suction side to prevent fluid
leakage at the junction point of the rotors and shafts, and contamination from the atmosphere.
9. The Dry Screw Vacuum Pump as claimed in claim 7, wherein composite sealer is having a
hollow space between the barrier seal and the piston seal enabling a significant amount of
pressure drop between the process side of the rotors and rotor shaft.
10. The Dry Screw Vacuum Pump as claimed in claim 7, wherein said V-shaped seal
comprises of two oppositely directed flaps capable of preventing two-way synchronous
leakage and contamination, i.e. from the rotor to the shaft and from the atmosphere to the
rotor on the suction side enabling reduction in the operating temperature of the Dry Screw
Vacuum Pump.
11. A Rotor of Dry Screw Vacuum Pump comprises:
a front surface and a rear surface, each specially designed to secure an open machined
balancing pocket;
a screw main body having helically designed conveyor grooves with variable pitch;
wherein said open machined balancing pockets that are engraved during casting followed by
machining of the rotors for counterbalancing of the dynamic and static imbalance produced in
the rotors while the dry screw vacuum pump is operational.
12. The Rotor as claimed in claim 11, wherein, said rotor serves as a driver or driven rotor or
both on the inlet suction side and discharge side and is fixedly mounted on a pedestal forming
the bottom part of the Dry Screw vacuum Pump.
13. A Dry Screw Vacuum Pump comprises:
a casing connected to a motor, wherein the casing comprises of:
an inlet suction port;
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a discharge port;
a driver rotor and a driven rotor parallelly embedded within the casing with a certain clearance
between them to avoid direct contact, wherein, each of the said rotor is having a front surface
and a rear surface;
a pair of driver rotor shafts extending from the front and rear surface of the driver rotor and a
pair of driven rotor shafts extending from the front and rear surface of the driven rotor, wherein,
the driver rotor shaft and the driven rotor shaft extending from the front surface of the driver
and driven rotor is on the discharge port side, wherein, the driver rotor shaft and driven rotor
shaft extending from the rear surface of the driver and driven rotor is on the inlet suction port
side;
a composite sealer encompassing the above-mentioned shafts on the inlet suction port side
and discharge side; and
wherein, said composite sealer comprises of a barrier seal affixed onto the rear surface of the
driver rotor and driven rotor, an inverted V-shaped seal towards the end of the shafts extending
from the rear surface of the said rotors and a piston ring seal sequentially spaced between the
barrier seal and the inverted V-shaped seal.
14. The Dry Screw Vacuum Pump as claimed in claim 14, wherein said barrier seal, piston
ring seal and the inverted V-shaped seal that are sequentially arranged on the suction side to
prevent fluid leakage at the junction point of the rotor and shaft, and contamination from the
atmosphere.
15. The Dry Screw Vacuum Pump as claimed in claim 14, wherein said composite sealer is
having a hollow space between the barrier seal and the piston seal enabling a significant
amount of pressure drop between the process side of the rotors and rotor shaft.
16. The Dry Screw Vacuum Pump as claimed in claim 14, wherein said V-shaped seal
comprises of two oppositely directed flaps capable of preventing two-way synchronous
leakage and contamination, i.e. from the rotor to the shaft and from the atmosphere to the
rotor on the suction side enabling reduction in the operating temperature of the Dry Screw
Vacuum Pump.
17. The Dry Screw Vacuum Pump as claimed in claim 14, wherein said rotors are having an
open machined balancing pocket on their front and rear surface.
18. The Dry Screw Vacuum Pump as claimed in claim 17, wherein said open machined
balancing pockets are engraved during casting followed by machining of the rotors for
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counterbalancing of the dynamic and static imbalance produced in the rotors while the dry
screw vacuum pump is operational.
19. The Dry Screw Vacuum Pump as claimed in claim 17, wherein said open machined
balancing pockets are designed to partially form the front and rear surface of the rotors and
are completely open to the inner surrounding of the casing.
20. A composite sealer of Dry Screw vacuum Pump comprises of:
a barrier seal affixed onto the rear surface of a driver rotor and a driven rotor;
an inverted V-shaped seal towards the end of rotor shafts extending from the rear surface of
the said rotors; and
a piston ring seal sequentially spaced between the barrier seal and the inverted V-shaped
seal.
21. The composite sealer as claimed in claim 21, wherein said composite sealer encompasses
the rotor shafts on the inlet suction port side and discharge side of the dry screw vacuum
pump.
22. The composite sealer as claimed in claim 21, wherein said barrier seal, piston ring seal
and the inverted V-shaped seal are sequentially arranged on the suction side to prevent fluid
leakage at the junction point of the rotors and shafts, and contamination from the atmosphere.
23. The composite sealer as claimed in claim 21, wherein, composite sealer is having a hollow
space between the barrier seal and the piston seal enabling a significant amount of pressure
drop between the process side of the rotors and rotor shaft.
24. The composite sealer as claimed in claim 21, wherein, said V-shaped seal comprises of
two oppositely directed flaps capable of preventing two-way synchronous leakage and
contamination, i.e. from the rotor to the shaft and from the atmosphere to the rotor on the
suction side enabling reduction in the operating temperature of the Dry Screw Vacuum Pump.
25. The composite sealer as claimed in claim 21, wherein, said rotors and rotor shafts are as
claimed in claim 1.