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 anoil 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.
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
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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.
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 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 that
consumes less power.
It is an objective of the present invention to provide a dry screw vacuum pump with an
extended service life.
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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 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 driver rotor and driven rotor are having an open machined balancing
pocket on their 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
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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 driver rotor and driven rotor are having an open machined balancing
pocket on their front and rear surface, 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.
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 driver rotor and driven rotor are having an open machined balancing
pocket on their 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 Vshaped 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,
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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.
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.
Detailed Description of the Invention
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
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.
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
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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
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.
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The above combination of barrier seal 18, the piston ring seal (19 and 20) and theinverted 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.
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 (1) connected to a motor (7), wherein the casing (1) comprises of:
an inlet suction port;
a discharge port;
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 (3
and 6) is having a front surface (31 and 32) and a rear surface (33 and 34);
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 (28 and 30) and driven rotor shaft (27 and 29) extending from
the rear surface (33 and 34) of the driver (3) and driven rotor (6) is on the inlet suction port
side;
a composite sealer (14) encompassing the above-mentioned shafts on the inlet suction port
side and discharge side; and
wherein, saiddriver rotor (3) and driven rotor (6) are having an open machined balancing
pocket (23-26) on its front (31 and 32) and rear surface (33 and 34).
2. The Dry Screw Vacuum Pump as claimed in claim 1, wherein said rear surface (33 and
34) is situated on the inlet suction port side and said front surface (31 and 32) is situated on
the discharge port side.
3. The Dry Screw Vacuum Pump as claimed in claim 1, wherein, said rotors (3 and 6) and
shafts (27-30) on the inlet suction side and discharge side are fixedly mounted on a pedestal
(8) forming the bottom part of the casing (1).
4. The Dry Screw Vacuum Pump as claimed in claim 1, wherein said open machined
balancing pockets (23-26) are engraved during casting followed by machining of the rotors
(3 and 6) for counterbalancing of the dynamic and static imbalance produced in the rotors (3
and 6) 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 (23-26) are designed to partially form the front (31 and 32) and rear
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surface (33 and 34) of the rotors (3 and 6) and are completely open to the inner surrounding
of the casing (1).
6. The Dry Screw Vacuum Pump as claimed in claim 1, wherein each of the said rotor (3 and
6) is having variable screw pitch, wherein, said pitch of the rotors (3 and 6) may or may not
be the same.
7. The Dry Screw Vacuum Pump as claimed in claim 1, wherein composite sealer (14)
comprising 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
shaftsextending from the rear surface (33 and 34) of the said rotors (3 and 6) and a piston
ring seal (19 and 20) sequentially spaced between the barrier seal (18) and the inverted Vshaped seal (21).
8. The Dry Screw Vacuum Pump as claimed in claim 7, wherein said barrier seal (18), piston
ring seal (19 and 20) and the inverted V-shaped seal (21) that are sequentially arranged on
the suction side to prevent fluid leakage at the junction point of the rotor (3 and 6) and shaft,
and contamination from the atmosphere.
9. The Dry Screw Vacuum Pump as claimed in claim 7, wherein said composite sealer (14)
is having a hollow space (22) between the barrier seal (18) and the piston seal (19 and 20)
enabling a significant amount of pressure drop between the process side of the rotors (3 and
6) and rotor shaft (29 and 30).
10. The Dry Screw Vacuum Pump as claimed in claim 7, wherein said 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 of the Dry Screw
Vacuum Pump.
11. A Rotor (3 or 6) of Dry Screw Vacuum Pump comprises:
a front surface (31 and 32) and a rear surface (33 and 34), each specially designed to
secure an open machined balancing pocket (23 - 26);
a screw main body having helically designed conveyor grooves with variable pitch;
wherein said open machined balancing pockets (23-26) that are engraved during casting
followed by machining of the rotors (3 and 6) for counterbalancing of the dynamic and static
imbalance produced in the rotors (3 and 6) while the dry screw vacuum pump is operational.
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12. The Rotor (3 or 6) as claimed in claim 11, wherein, said rotor (3 or 6) serves as a driver
(3) or driven rotor (6) or both on the inlet suction side and discharge side and is fixedly
mounted on a pedestal (8) forming the bottom part of the Dry Screw vacuum Pump.