JPS60249691A - Rotary piston vacuum pump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates generally to rotary piston vacuum pumps, and more particularly to pumps with anti-suck back features that stop the flow of lubricant from a stopped pump to a low pressure working chamber.

In mechanical rotary vacuum pumps, the flow of oil around its working elements serves to lubricate these working elements and provide a gap seal between the elements. In such rotary pumps without forced circulation of oil, the flow rate of oil from the sump to the internal pumping mechanism is primarily a function of the differential pressure between these two regions. Maximum oil flow circulation occurs when the sump is at its normal atmospheric pressure and the pump is operating at the lowest absolute pressure at its pump inlet. At higher suction pressures, the oil flow is reduced; in fact, in the inlet pressure range above Iga (500 mm) there is no oil flow to the pump mechanism.

Thus, in this pressure range the operating time must be limited. Prolonged operation without oil flow can result in insufficient lubrication, heat loss, and pump failure.

To solve this problem and provide for long operating times over a wide pressure range, it is advantageous to attach an oil pump to the oil circuit of the mechanical vacuum pump, which produces a forced oil flow over the entire operating pressure range of the vacuum pump.

In dual-stage (two-stage) mechanical vacuum pumps, the oil pump is typically attached to the oil circuit of the second or roughing stage;
Oil flow in the first or high vacuum stage is caused by a small pressure differential and gravity. Additionally, the intermediate stage degassed oil is typically recirculated through the first stage pump chamber in a separate, independent oil circuit.

This is because oil at atmospheric pressure often contains air which, if discharged into the first stage, would significantly reduce the effective pump capacity.

When a vacuum pump stops operating, each pump chamber within the pump has a different pressure. For example, in a two-stage rotary piston pump, the first stage communicates with a working chamber, or low pressure chamber, which is evacuated at the pump inlet, and the second stage communicates with the pump outlet through a discharge separator. The pressure is relatively low compared to the pressure. When this differential pressure exists between the pump chambers, lubricating and sealing oil often leaks or flows back into the first pump chamber from between the actuating elements. In vacuum pumps using separate oil circuits, this leakage or backflow typically contaminates the first pump chamber as well as the supply degassed oil. Also, if oil flows back through the pump inlet, it contaminates the working chamber.

Furthermore, even if the pressure difference between the letters is not large enough to cause oil flow between the chambers, if the pump is stopped at a low pressure in the pump chamber,
The oil in the lubrication circuit for the pump chamber returns to the pump chamber. This also often causes flooding of the pump chamber and contamination of the working chamber.

Prior art vacuum pumps were equipped with a device to stop the flow of oil to the pump chamber or pump stage when it was shut off under vacuum or low pressure conditions within the pump chamber. These devices avoid an overflow of the pump chamber and a backflow of oil through the pump inlet device and also avoid contaminating the working chamber attached thereto. By preventing oil flooding of the pump, problems associated with starting a flooded pump are also eliminated. Methods and/or devices that prevent the flow of oil back into the inlet device are typically referred to as "anti-suck back" devices. Previous oil backflow prevention d=devices had solenoid valves or centrifugally actuated mechanisms, these valves or mechanisms having, for example, resilient elastomer plunger seals that stopped the flow of oil to a stopped pump. . However, these devices are relatively expensive and lack high responsiveness to sudden changes during pump operation. These so-called anti-suction devices are usually incorporated into oil-sealed rotary vane vacuum pumps.

Another technique to prevent oil siphoning back into the vacuum system has been the use of inlet line isolation valves in combination with atmospheric vents.

This valve is closed before the vacuum pump is stopped; when the pump is stopped, a small solenoid valve positioned on the pump suction side of the isolation valve and electrically connected to the pump motor opens the atmospheric vent to Or, if necessary, air/
The exhaust gas from the oil separator housing is introduced into the pump. However, this method does not completely prevent flaring of the pump cylinder, and some type of oil line isolation device is still desirable. Also, it is difficult to achieve a perfect sealing effect at very low inlet line pressures. Typical seals that are strong enough to withstand repeated use are usually not flexible enough to seal securely at low pressures. Thus, it is often necessary to provide sophisticated sealing arrangements to prevent air leakage along this inlet line when the isolation valve is closed.

In some applications, these previous anti-suck back techniques function adequately even if some small amount of oil leaks. However, when manufacturing semiconductor chips and microprocessor devices, very low pressures (0.5-1.5 mmHga
Vacuum pumps are often required to achieve this and to be completely uncontaminated by the return flow of oil from the vacuum pump population to the semiconductor working chamber. Thus, there has been a need for an inexpensive, highly reliable anti-suck back device.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an inexpensive and highly reliable vacuum pump sump prevention device.

Another object is to provide an improved anti-suckback system for a rotating piston having a hydraulically actuated control valve that simultaneously controls lubricant flow and pump chamber pressure relief.

It is a still further object to provide an improved hydraulically controlled vacuum back prevention device for a dual or multi-stage vacuum pump having an inlet line shut-off valve seal sufficient to prevent leakage through the inlet line shut-off valve at low pressures. It is.

Still another object is to provide a device for achieving pressure equalization in the pump chamber after stopping the vacuum pump and further preventing backflow of lubricant into the working chamber by means of a highly responsive shutoff valve in the working fluid inlet flow path. It is to be.

These and other objects of the invention are accomplished by providing a shaft lip seal as an inlet shut-off valve seal in the working fluid inlet conduit of a rotary piston pump between the first pump chamber of the vacuum pump and the inlet to the working chamber. achieved. With axially inclined radial surfaces, even under low pressure
A piston valve is provided for engaging this seal and shutting off flow between the first pump chamber and the supply to the working chamber. The vacuum pump stops working and the pressure relief head
When connected to the pump chamber, the piston valve is actuated into sealing engagement with the shaft lip seal. (When the vacuum pump is stopped, the structure connecting the pressure relief head to the first pump chamber is the oil pump of the lubricating oil circuit, the pressure relief head connected to the pump chamber from the higher pressure source, and the oil pump and oil circuit. The pressure relief and pressure relief circuits are connected between the vent and the first pump chamber, respectively, and are made by actuated valves to control oil flow and pressure.The oil pump pumps the oil in the oil lubrication circuit into a vacuum pump operated This valve is responsive to the oil pressure created by the oil pump.This valve operates when the vacuum pump is operating to maintain a free flow of oil from the oil pump to the oil circuit. When the vacuum pump is shut down, energization of the valve stops the flow of oil through the oil circuit and opens the connection between the pressure relief head and the first pump chamber, increasing the pressure in the first pump chamber and causing the lubricating oil to stop flowing through the oil circuit. This increased pressure from the pressure relief vent actuates the inlet shut-off valve to isolate the first pressure chamber from the working chamber.

In multi-stage rotary vacuum pumps with several independent oil circuits, the valve structure of the present invention can control oil flow in several of these oil circuits simultaneously.

Pressurized oil from a single oil circuit creates the control signal and actuates the valve structure. Thus, only that oil circuit requires an oil pump. A pressure relief vent is also coupled to at least the first pump chamber and controlled by the valving structure. The valve structure may include a single slide valve interconnecting each oil circuit and pressure relief passage to the pump chamber, or multiple slide valves each interconnecting one or more oil circuits and/or pressure relief passages. It is good to have either one. When the vacuum pump stops, the valve structure provides a control signal in response to a drop in oil pressure in the oil circuit to prevent oil flow to at least the first pump chamber and provide pressure relief to that pump chamber. .

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention in conjunction with the accompanying drawings.

FIG. 1 shows a preferred embodiment of the invention, showing a partial cross-section of a two-stage rotary vacuum pump 10, which has a housing 15 in which a first pump chamber 2o and a second Pump chambers 25 are provided respectively. The drive shaft 3o connects the first and second pump chambers 20.2
5 and supported by housing 15.

The first and second pump chambers 20.25 are each provided with independent oil circuits for lubricating the working elements within the chamber and for sealing gaps between relatively moving members. For the first pump chamber, the oil circuit uses degassed oil from the reservoir 35. Degassed oil is passed from reservoir 35 through conduit 37 to valve member 50 (shown in FIGS. 2 and 3).
(described in detail below). From there, the shin oil flows directly to the first pump chamber 2o via a line 41 or via a line 39 in the drive shaft 30 to the first pump chamber 20.
Continue to exit boat 43 inside. As the piston pump (not shown) in the first pump chamber rotates and reciprocates, the flow of degassed gas returns to the reservoir 35.

The oil circuit of the second pump chamber 25 has an oil reservoir portion 45 . From this reservoir the oil flows through line 47 and then to valve 50 in section A. Oil flow returns from valve 50 through line 49 to drive shaft 30 at bearing 32. The oil flows along the drive shaft 3o into the second pumping chamber 25 and is transferred by the pumping action in this chamber to the sump 45 and via the conduit 81 to the discharge separator 80. Discharge separator 8
0 passes the vacuum pump working fluid, typically air, to the vacuum pump's atmospheric outlet (not shown) and returns the transferred oil to the sump 45 through conduit 81. The exhaust separator 80 also includes a pressure relief vent line 82 for returning the flow of working fluid to the valve 50.

Briefly stated, the present invention provides that when the vacuum pump stops,
A device is provided to prevent excess oil from flowing into the pump chamber. This is accomplished by a hydraulically responsive valve structure that shuts off the oil circuit and equalizes the pressure within the pump chamber when the vacuum pump shuts down. More specifically, in the exemplary two-stage vacuum pump 1° of FIG. 1, when the hydraulic control signal to valve 50 indicates that the vacuum pump has stopped, both reservoirs 35.4
5 from flowing into the first and second pump chambers 20°25. At the same time, the discharge working fluid is allowed to flow from the valve 5i to the first pump chamber 20 through the conduit 82 to relieve pressure. Thus, when the vacuum pump stops, valve 5
o, the pressures in the first pump chamber 20 and the second pump chamber 25 are made equal. The hydraulic control signal applied to valve 50 is generated by pressurizing oil from reservoir 45 alone by oil pump 7o. The oil pump 7o operates in response to the operation of the vacuum pump 10.

At the same time, the circulation of oil in both ground circuits is stopped and the pump chamber 20.
By equalizing the pressure in 25, the vacuum pump 1
When stopping the operation of the pump, oil is prevented from flowing into these chambers from both the oil supply of each pump chamber and the oil supply of an adjacent pump chamber. By using hydraulic pressure to provide the hydraulic control signal of the present invention, the vacuum pump 10
The response of the valve 50 to actuation of the valve 50 is quick and accurate.

FIG. 2 shows an enlarged partial cross-sectional view of the portion of FIG. 1 indicated by A. The position of valve 50 in FIG. 2 is shown for when vacuum pump 10 is operating.

This view can be compared with a cross-sectional view similar to FIG. 3 showing the position of valve 50 when the vacuum pump is turned off.

As shown in FIG. 2, valve 50 is movable along bore 56 and is, for example, a slide valve biased upwardly by spring 52. As shown in FIG. Valve 50 is actuated downwardly by hydraulic pressure within the bore chamber against the spring bias of spring 52. The oil pump 70 is provided, for example, as a gear pump driven by an extension 72 of the drive shaft 30 past the sealing device 34 and having a gear member 74 . Oil from sump 45 entering in line 47 is pressurized by the pumping action of the oil pump and then passes through line 76 to seal line 78 and inlet line 62 when vacuum pump 10 is in operation. It then flows into the bore chamber 54 of the valve 50.

Degassed oil from reservoir 35 flows through line 37 to valve 50 but is not pressurized by the pump. This degassed oil flows through the degassed oil circuit by gravity and pressure differential only. Degassed oil entering in line 37 passes through line 58 and through control valve 50 when vacuum pump 10 is operating. Degassed oil from line 58 exits bore 56 and enters inlet boat 36 of drive shaft 30. This oil then passes through line 39 in drive shaft 30 to outlet boat 43 or to line 41.
through which it flows directly to the first pump chamber 20.

Pressure relief vent line 82 from discharge separator 86 is connected to line 6
4 to reach valve 50. Line 68 communicates with pump chamber 20.During operation of vacuum pump 10, valve 50 blocks communication between lines 64,68. Pressurized oil from line 78 forms an oil seal at recess 60 of valve 50 between lines 64, 68 and is transferred from pressure relief line 82 to first pump chamber 20.
prevent leakage.

When the vacuum pump 10 is operating, the drive shaft 30
drives the oil pump 70 to pressurize the oil in the oil circuit of the second pump chamber 25. When vacuum pump 10 is not operating, oil pump 70 is not operating and does not pressurize its oil, thus the oil pressure within chamber 54 does not overcome the spring bias of spring 52. Valve 50 then moves upwardly into bore chamber 54 as shown in FIG.

When valve 50 moves upwardly past the inlet of conduit 49,
The flow of oil from the reservoir 45 and line 62 back to the second pump chamber 25 via line 49 will be restricted and stopped. At the same time ~ the inlet of line 58 moves upwards past the outlet of line 37 and the flow of oil from sump 35 and line 37 back to first pump chamber 20 via line 39.41 is restricted and It will be stopped. This same upward movement of valve 50 aligns the outlet of line 64 with the inlet of line 66 and aligns the outlet of line 66 with the inlet of line 68 to remove relief pressure from exhaust separator 80 to the first It flows into the pump chamber 20. Thus, the valve 50 is connected to the pump chamber 20
．． Stopping the flow of oil in both oil circuits to 25 opens the pressure relief flow to increase the pressure in the first pump chamber 20 and equalize the pressure between the pump chambers 20.25. This structure prevents backflow or leakage of oil from either or both oil circuits into either of the pump chambers when the vacuum pump 10 is not operating.

When the vacuum pump 10 starts operating again, the oil pump 70 also starts operating again, pressurizing the oil in the chamber 54 again. This causes the valve 50 to move downwardly from the bore chamber 54 against the bias of the spring 52. Thereby, from line 62.49 to second pump chamber 25 and line 37.58.39.41
Oil flows from there to the first pump chamber 20. At the same time, the line 64.66.68 from the discharge separator 80 to the first pump chamber 20
communication between them is restricted and stopped. Similarly, conduit 7
High pressure oil communication from 8 is resumed with recess 60, thus
When the vacuum pump JO starts operating again, line 64.6
The oil seal between 8 and 8 is reestablished.

4 and 5 illustrate partial cross-sectional views of another rotary piston vacuum pump 110 having another embodiment of the present invention. FIG. 4 shows the position of various anti-suction elements of the present invention when vacuum pump 110 is in operation. FIG. 5 shows the position of the same elements when the vacuum pump 110 is stopped.

In comparison to FIGS. 1, 2, and 3, FIGS. 4 and 5 are cross-sectional views taken along a plane generally perpendicular to the views of FIGS. 1, 2, and 3.

Also, vacuum pump 110 is preferably a two-chamber pump with separate oil circuits for each chamber, and is similar to vacuum pump 10 in all other respects except as shown and described with respect to FIGS. The same is true.

As shown in FIGS. 4 and 5, vacuum pump 110 includes a housing 115, a discharge separator 180, and first and second pump chambers (not shown). Each pump chamber has an oil circuit associated with it as in the embodiment of FIG. Each oil circuit has an oil sump and an oil conduit extending to and from the suckback prevention section of the present invention shown in FIGS. 4 and 5.

This embodiment also has anti-suck back performance.

Instead of controlling oil circuit flow to both pump chambers and pressure relief and balancing between the pump chambers by a single valve, vacuum pump 110 has multiple valves.

Valve 250 limits pressure relief to the first pump chamber and pressure equalization between the pump chambers. This valve also controls the flow of control signal oil to valve 150, which controls the flow of lubricant in both independent lubricant circuits. These valves are also hydraulically actuated by oil pressure from an oil pump in response to actuation of vacuum pump 110.

Valves 150,250 are each biased, for example by a spring 152,252, and are slidably disposed within a bore 156,256. Valve 150 opposite spring 152.252
．． Bore chambers 154 and 254 are provided at the ends of 250, respectively. Thus, the pressurized oil supplied to the bore chambers 154,254 can overcome the biasing action of the springs 152,252, respectively, and actuate the valves 150,250.

Oil from the second pump chamber flows through line 147 to oil pump 170 having pump gear 174 .

Oil pump 170 pumps pressurized oil through line 176 to valve 250.
is supplied to the bore chamber 254. Valve 250 is biased downwardly toward bore chamber 254 by spring 252 . As shown in FIG. 4, when the vacuum pump 110 is operating,
Oil pump 170 applies hydraulic pressure to bore chamber 254, which exceeds the force of spring 252 and forces valve 250 into bore chamber 15.
4 to allow oil to flow into line 162 and then into bore chamber 154.

Valve 250 has a valve element 255 at the end opposite bore chamber 254.
has. Bore 256 has a valve seat 257 around the outlet of conduit 164 to valve 250 . Also, bore 256
has an exit boat 258 through its side wall. valve 2
50 is shown, for example, in the case where the valve element 255 has a hollow portion inside. Line 164 receives pressure relief from exhaust separator 180 through pressure relief vent 182 . As shown in FIG. 4, when valve 250 is hydraulically pushed up from bore chamber 254, valve element 255 covers the outlet of conduit 164 and seats in valve seat 257, causing conduit 164
64, past valve element 255 and through outlet port 258 to conduit 168 and into the first pump chamber. The pressure relief path to the first pump chamber passes through a portion of the bore 254 and then to the outlet boat 25.
8 and extends via conduit 168 to inlet shutoff valve 220 . The pressure relief path continues past the valve 220 into the first pump chamber port 240. However, when the vacuum pump 110 is operating, the inlet shut-off valve 22.0 rests on the stop 222 to at least partially close off this relief pressure path.

When the valve 250 is moved from the bore chamber 254 by hydraulic pressure,
Communication with line 9162 is opened and oil flows through line 162 to bore chamber 154 of valve 150. Valve 150 is spring 1
52 upwardly towards the bore chamber 154. Valve 15, as in valve 50 of FIGS.
0 has a central deaerated oil line 158, which line 13
7.161, the degassed oil is passed from the degassed oil sump of the first pump chamber (not shown) through these lines and through the internal line 139 of the drive shaft (not shown) to the first pump. Flow into the room. This alignment is achieved when the vacuum pump 110 is operating and the bore chamber 1 from conduit 176, bore 254 and conduit 162.
This occurs when hydraulic pressure in 54 overcomes the bias of spring 152 and slides valve 150 downwardly into bore 156, as shown in FIG. At the same time, valve 1'50 opens communication with line 149 leading to a second pump chamber (not shown) so that oil from line 162 passes through bore chamber 154 to line 149 and the second pump chamber. Let it flow.

Thus, when the vacuum pump 110 is in operation, the oil pump 170 continues to supply pressurized oil to the bore chamber 254, 154 and subsequently into the oil circuit of the second pump chamber. This hydraulic pressure causes valve 250 to close line 164 by closing valve element 255 against valve seat 257 and opening inlet shutoff valve 220.
while blocking pressure relief to the first pump chamber. Similarly, hydraulically, valve 150 allows oil to flow into lines 139, 149 leading to the first and second pump chambers.

Further, the hydraulic pressure of only a single oil circuit (the oil circuit of the second pump chamber) is used to provide a hydraulic pressure control signal to operate the valve 150 to control the flow of oil through the multiple oil circuits.

When the vacuum pump stops operating as shown in FIG.
does not provide a flow of pressurized oil that overcomes the spring bias of spring 252 to . Valve 250 then slides downward into bore chamber 254. Valve element 255 thus disengages from valve seat 257 and pressure relief flow passes from exhaust separator 180 through pressure relief vent line 182 and line 164 to bore 256 of valve 250 and to line 168 and then to the inlet. Proceed to shutoff valve 220.

The pressure from the exhaust separator 180 is typically higher than the pressure within the first pump chamber. Thus, as the air flow continues from valve 250 through conduit 168 to inlet shutoff valve 220 , the pressure differential causes shutoff valve 220 to rise and away from stopper 222 and cause valve face 225 of inlet shutoff valve 220 to rise.
is seated on the large mouth valve seal 230. This restricts the flow of pressure relief through the inlet filter 210 and vacuum pump inlet 200 back to the working chamber (not shown).

When the inlet shut-off valve 220 is so actuated, the flow of relief pressure follows the working fluid path of the vacuum pump 110 to the first
Pass through the pump room entrance and proceed to the first pump room. As a result,
The pressure within this pump chamber increases, causing a pressure equalization between the first and second pump chambers.

When vacuum pump 110 is not operating, valve 250 stops the flow of oil from line 147.176 to line 162 and bore chamber 154. Thus, pressurized oil is not effective in acting on valve 150 to overcome the bias of spring 152.

The valve 150 then slides inwardly into the bore chamber 154 between the bore chamber 154 and line 149 towards the second pump chamber, as well as lines 137, 158, 139 towards the first pump chamber.
Restrict and stop the flow of oil between. Thus, either the low pressure or the differential pressure limits the supply of oil drawn into the pump chamber. In combination with pressure relief to eliminate low pressure and differential pressure conditions, no significant backflow or oil overflow occurs.

When the vacuum pump 110 is not operating, it effectively prevents oil backflow and flaring of the pump chamber, thereby significantly reducing the pollution of the working environment of the working vacuum chamber. Furthermore, due to the operation of the inlet shut-off valve 220, such contamination does not occur from the lubricating oil within the vacuum pump 110. vacuum pump 110
starts operating again, the oil pump also starts operating again and repressurizes the oil flow so that valve 250 closes the inlet shut-off valve 220.
Relieve pressure to stop flow. When the pressure in the first pump chamber decreases, the valve face 225 of the inlet shutoff valve 220 moves toward the valve seat 230.
, and descends to stopper 222 to begin flowing working fluid from the working vacuum chamber to pump 110 .

FIG. 6 is an enlarged view of the portion of FIG. 4 showing the inlet shutoff valve structure of the present invention due to the presence of a flow conduit for the flow of working fluid into the first pump chamber past the artificial shutoff valve 220 shown in FIG. A partial cross section is shown. The artificial shutoff valve 220 is, for example, a support 22
It is a cylindrical piston-like valve that can slide within 4 and is centered on a centerline axis 300. The inlet shutoff valve 220 has an annular flange 227 extending radially therefrom about the centerline axis 300. The support 224 has a stopper 222 which, by engagement with one side of the flange 227, opens the inlet 240 of the first pump chamber.
The downward movement of the inlet shutoff valve 200 toward the is restricted. A valve surface 225 is formed on the flange 227 as an axially inclined surface on a radial surface.

When the inlet shutoff valve 220 is actuated as shown in FIG.
Valve face 225 is forced upwardly into sealing engagement with valve seal 230 by the flow of relief pressure through line 168 into the first pump chamber. This sealing engagement is then maintained by the differential pressure between the working chamber and the first pump chamber as long as the vacuum pump 110 is not operating. Valve seal 230 consists of a shaft-pushing element commonly used to seal rotary drive shirts against the flow of grease or oil or working fluid. The shaft lip seal itself is a standard commercial product. As conventionally used, the shaft lip seal is continuously radially compressed by a rotating shaft extending therethrough. however,
In the present invention, a shaft lip seal is used to create an axially resilient diametrical seal against the valve face plate.

The exemplary shaft lip seal provided on the valve seal 230 has a cantilevered seal 232 formed of, for example, Viton elastomer, extending in the direction of the centerline axis 300 and supported by a spring ring 234. Tauchi lip 23
6 is formed. The apex of the inner tube 236 is significantly thinner than the remainder of the cantilevered seal 232. Spring ring 234 is made of stainless steel, for example. Examples of commercially available shaft lip seals suitable for use with the present invention include:
Chicago Rawhide Par) (Chicago Ra1u)
hide part) No. 9982. inner lip 2
The surface of the valve face 225 that seals against the valve face 36 may be formed of, for example, polished steel.

When the valve face 225 and valve seal 230 are engaged by actuation of the inlet shut-off valve 220, the unique construction of the shirt door seal provides a fluid-tight seal over a wide range of pressures, including very low pressures within the working chamber. This fluid-tight seal action is achieved by a cantilevered seal 232 on the inner knob 236.
an inner lip 236 that provides significantly greater flexibility than the rest of the
arises from the relative thinness of This flexibility allows the valve surface 225
The use of hard Viton elastomers provides a stronger valve seal and longer operating life. Since valve seal 230 is formed from readily available commercial components, no specially modified and expensive valve seals are required. The valve shut-off seal structure of the present invention provides significant improvements over conventional flat elastomeric seals in terms of durability and leak protection for both working fluids and lubricants.

The present invention combines the advantages of hard and soft elastomeric seats in a single unique and inexpensive construction.

Although the invention has been described with respect to oil flow and air pressure relief, it should be clearly understood that these embodiments are merely exemplary. The present invention includes the use of any other suitable lubricant in addition to oil to hydraulically actuate the valve structure to control lubricant flow and pressure relief. In addition to air, any other suitable fluid, such as a chemically inert gas or liquid, may be used to relieve pressure to the pump chamber when the vacuum pump is not operating. Also, there is no need to connect a pressure relief vent to the exhaust separator. In some applications, the pressure relief vent may be in communication with other pressure sources. This other pressure source may be, for example, an air vent to atmospheric pressure. In some applications of the invention, different fluids besides the evacuation working fluid may be used for pressure relief.

Additionally, the pressure relief to the first pump chamber may not be exactly equal to the pressure in the second pump chamber. It is only necessary that this pressure relief be at least substantial.

This should be at least sufficient to reduce the differential pressure in combination with a pressure relief or restriction of the flow of lubricant to prevent the flow of lubricant between the pump chambers, especially into the first pump chamber. It means that.

From the foregoing description of the preferred embodiments, it is clear that the objects of the invention are achieved and the invention has been described and shown in detail by way of illustration and not as a limitation. should be clearly understood. The spirit and scope of the invention should be limited only by the claims appended hereto.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view along the drive shaft of a vacuum pump embodying the invention; FIG. 2 shows certain essential parts of the anti-suction device according to the invention when the vacuum pump is in operation; An enlarged partial cross-sectional view of this section in the same plane as the section of FIG. 1; FIG. 3 is a partial cross-sectional view of the same section shown in FIG. 2 when the vacuum pump is stopped; FIG. A partial cross-sectional view of another vacuum pump showing another embodiment of the invention when in operation; FIG. 5 is a section of the same part of the pump shown in FIG. 4 when the vacuum pump is deactivated; Cross Sections (For purposes of comparison, it should be noted that the cross sections of FIGS. 4 and 5 are in a plane generally perpendicular to the plane of the cross sections of FIGS. 1, 2, and 3. be)
FIG. 6 is a partial cross-sectional view of an enlarged portion of FIG. 4 detailing the inlet shutoff valve structure of the present invention without a flow conduit past the inlet shutoff valve 220; 10... rotary vacuum pump, 20... first pump chamber,
25... Second pump chamber, 30... Drive shaft, 3
5.45... Reservoir, 37.39.41.47.49
...Pipe line, 43...Outlet boat, 50...Valve, 7
0...Oil pump, 80...Discharge separator, 81...
Conduit, 220... Inlet shutoff valve, 222... Stopper, 225... Valve surface, 227... Flange ~ 230
...Valve seal, 232...Cantilever seal, 234...
・Spring ring, 236...-inner ring. Fi6; G

Claims (1)

[Scope of Claims] (1) A rotary piston vacuum pump having a housing having a vacuum port and at least one first pump chamber, the rotary piston vacuum pump communicating with the first pump chamber and applying pressure to the pump in response to the vacuum pump; a pressure relief device supplying the chamber, the pressure relief device being operable only when the vacuum pump is actuated; coupled in communication with the pressure relief device, the pressure relief device is adapted to operate only when the vacuum pump is actuated; an inlet shutoff valve arrangement for preventing the flow of relief pressure through the vacuum inlet when not in use, the inlet shutoff valve arrangement having a valve face and a valve portion actuated by relief pressure from the pressure relief arrangement; and a valve sealing device having a shaft lip sealing device, the valve sealing device forming a fluid-tight seal over a wide range of pressures, including low pressures, when the inlet shut-off valve is actuated;
A rotary piston vacuum pump 62 characterized in that it can be engaged with said valve face, said vacuum pump further comprising a lubricant circuit for lubricating its working elements and a fluid lubricant in said lubricant circuit, said vacuum pump having said shaft lip. a sealing device prevents the flow of lubricant as well as the relief pressure through the vacuum inlet when the vacuum pump is stopped, and when the valve member is actuated by the pressure relief;
The rotary piston vacuum pump according to claim 1, wherein the rotary piston vacuum pump is engaged with the valve surface. 3. The valve member has a radially extending flange;
2. A rotary piston vacuum pump according to claim 1, wherein said valve face is formed from an axially inclined radial surface of said radially extending flange. 4. The shaft lip seal device has an internally extending cantilevered sealing element, the lip portion of which is more flexible than the sealing element, and the inlet shut-off valve is actuated to reduce relief pressure through the vacuum inlet. A rotary piston vacuum pump according to claim 1, characterized in that it has an area that engages and mates with a surface of said valve face when preventing flow.