Vacuum pump equipped with relief valve and method for assembling the relief valve

Abstract

a pressure relief valve configured to move between a compression state and an extension state, the pressure relief valve sealing the orifice in the extension state and configured to move to a compression state in response to a pressure in the upstream stage being higher than a predetermined value, the pressure relief valve being configured to seal the orifice in the extension state and to move to a compression state in response to a pressure in the upstream stage being higher than a predetermined value, the pressure relief valve being configured to unblock the orifice in the extension state.

Description

[Technical field]

[0001] The field of the invention relates to relief valves for multi-stage pump assemblies and methods for assembling such valves into the inter-stage cavities of the pump. [Background technology]

[0002] Many systems are provided with relief or blow-off valves in pump systems to protect the pump from pressure build-up at the pump inlet. These valves can wear and require maintenance or replacement, especially in pumps configured to transport corrosive fluids. In multi-stage pumps where the valves are located in the inter-stage cavity, these valves are difficult to access. To solve the problem of valves wearing out faster than many other components of the pump, cartridge-style relief valves have been designed that are self-contained, comprised of multiple components, and can be inserted into the desired location as a working unit. Such cartridge-style relief valves suffer from the disadvantage of having a very high material content and part count. Summary of the Invention [Problem to be solved by the invention]

[0003] It would be desirable to provide a relief valve that is smaller and has fewer parts while still allowing for easy assembly and maintenance of the valve. [Means for solving the problem]

[0004] A first aspect provides a multi-stage rotary vacuum pump comprising a stator comprising a plurality of pump stages and at least one stage partition separating two adjacent pump stages, the at least one stage partition comprising two walls defining a cavity therebetween, an upstream wall bounding an upstream pump stage of the two adjacent pump stages and a downstream wall bounding a downstream pump stage of the two adjacent pump stages, the cavity comprising at least a portion of a pressure relief fluid flow passage, the pressure relief fluid flow passage extending from an outlet portion of the upstream stage to an outlet portion of the downstream stage. a pressure relief fluid flow path from the upstream stage to an inlet portion or to an exhaust portion of the upstream stage, the pressure relief fluid flow path comprising an orifice, the orifice comprising a valve seat, the multi-stage rotary vacuum pump further comprising a pressure relief valve configured to move between a compression state and an extension state, the pressure relief valve being configured to seal the orifice in the extension state and to move to the compression state such that the orifice is unblocked in response to the pressure in the upstream stage being greater than a predetermined value.

[0005] The inventors of the present invention have recognized that, although there are advantages to a cartridge-type valve assembly that allows for easy insertion and removal from a pump for replacement or maintenance, there are disadvantages to such an arrangement. In particular, these cartridges can be relatively large and have a high number of parts. The inventors of the present invention have recognized that some components of such cartridge assemblies have functions that can be performed by other parts of the machine in which they are inserted. Thus, some of the components can be omitted if the valve assembly is configured to cooperate with parts of the pump. With this in mind, there is provided a valve assembly having a compressed state and an extended state, configured to seal an orifice in the pump when in the extended state. Thus, the valve assembly can be compressed and inserted into the pump in the compressed state, and then released to the extended state in which it seals the orifice.

[0006] Thus, the valve seat is part of the pump itself and the valve, being a removable component, is the sealing and biasing means. By providing a portion of the valve in a compressed, non-sealing state, the valve can be inserted and removed from a machine, while being held in place when extended.

[0007] In some embodiments, the pressure relief valve comprises a retaining means for releasably retaining the valve in the compressed state.

[0008] The pressure relief valve may be provided with a retention means so that it can be held in a compressed state, allowing the valve to be inserted into and removed from the pump without the need to be held in a compressed state during this procedure.

[0009] In some embodiments, the outer sealing surface of the valve comprises receiving means for receiving a tool to rotate the outer sealing surface to release or engage the retaining means.

[0010] The retaining means may be releasably engaged with the cooperating means, and in some cases the method for releasing and retaining may involve relative rotation of the two parts of the valve assembly. Such relative rotation may be effected using a tool cooperating with receiving means on the outer sealing surface. The outer sealing surface is accessible when the valve is in the pump to position the valve in a compressed state to allow removal for warranty service and replacement.

[0011] In some embodiments, the retaining means comprises a hook and a retainer for retaining the hook, one of the hook and the retainer being attached to a fixed end of the valve and the other of the hook and the retainer being attached to a sealing end, the valve being configured such that rotation of the sealing end of the valve causes the hook to engage or disengage from the retainer.

[0012] The retaining means can be formed in a number of ways, but a simple and effective method is to utilize a hook and a retaining means for the hook, whereby relative rotation between the hook and the retaining means enables them to engage when in the compressed state, and reverse rotation in the compressed state enables them to disengage and return the valve assembly to the extended state.

[0013] In some embodiments, the orifice is located in one wall of the stage partition and defines the outlet of the upstream pump stage.

[0014] The orifice can be located at a number of different points in the flow path, but in some cases it is in the outer wall of the stage partition, where it is relatively easy to access and provides a convenient method of sealing the flow path from the upstream pump chamber.

[0015] In another embodiment, the cavity comprises a pump fluid flow path providing a path from the outlet portion of the upstream stage to the inlet portion of the downstream stage, the pump fluid flow path and the pressure relief fluid flow path comprising the orifice at a junction of the flow paths.

[0016] In some embodiments, a portion of the fluid flow path from the outlet portion of the upstream stage to the orifice constitutes a combined pressure relief fluid flow path and a pump fluid flow path.

[0017] In an alternative configuration that allows for efficient reuse of flow paths, the pump fluid flow path from the upstream stage to the downstream stage and the pressure relief fluid flow path from the outlet of the upstream stage share a portion of their length within the cavity. In some cases, an orifice is located at the junction of the two paths, with the pressure relief fluid flow path being blocked when the valve is closed and providing a flow path when the valve is open.

[0018] In some embodiments, the pressure relief valve is configured to extend between the two walls, with a fixed end of the valve attached to the downstream wall and a sealing end of the valve extending to the upstream wall when the valve is in the extended state.

[0019] By providing a pressure relief valve with a sealing surface adapted to seal against a valve seat that is part of the pump, the valve can be made relatively compact with a minimum of components. To ensure that the valve is held stable in place during use, in some embodiments the valve extends between two walls and a spring within the valve presses the sealing surface against the valve seat when in an extended state.

[0020] In some embodiments, the vacuum pump includes a recess for receiving a fixed end of the valve.

[0021] To stably hold the valve in this position, it may be convenient for the pump to include a recess for receiving the end of the valve remote from the sealing end and holding it in a fixed position. In embodiments where the valve extends between two walls, the downstream wall may include a recess for receiving the fixed end of the valve and thereby holding it in place. Where the valve seals an orifice between the pump fluid flow path and the pressure relief fluid flow path, the recess may be in the wall of the pressure relief fluid flow path. In either case, once the valve has been compressed with the retaining means it can be removed from the recess and removed from the pump for maintenance.

[0022] A second aspect provides a method of assembling a valve in an interstage cavity between walls separating two adjacent pump stages, the method comprising the steps of: inserting a pressure relief valve held in a compressed state by a retaining means between the walls of the interstage cavity, the pressure relief valve having a sealing end for engaging a valve seat of an orifice in a pressure relief fluid flow passage passing through the interstage cavity and connecting an outlet portion of an upstream stage to either an inlet portion or an exhaust portion of the upstream stage; disposing the valve in the fluid flow passage; and releasing the valve from the compressed state such that the valve moves to an extended state and the sealing end of the valve engages the valve seat of the orifice.

[0023] In some embodiments, the orifice is disposed in an upstream wall of the cavity; the disposing step includes disposing the opposite end of the valve in a recess in the downstream wall of the interstage cavity; and releasing the valve from the compressed state such that the valve moves to an extended state and the sealing end engages the valve seat in the upstream wall.

[0024] In another embodiment, the orifice is disposed in a wall of a pump fluid flow path in the cavity, the orifice connecting the pump fluid flow path and the pressure relief fluid flow path; the disposing step includes disposing the opposite end of the valve in a recess in a wall of the pressure relief fluid flow path; and releasing the valve from the compressed state such that the valve moves to an extended state and the sealing end engages the valve seat in the orifice.

[0025] In some embodiments, the retaining means comprises an engagement portion adapted to rotatably engage a retainer, the engagement portion being attached to one of the sealing end and the opposing end and the retainer being attached to the other of the sealing end and the opposing end, and releasing the valve from the compressed state comprises rotating the sealing end such that the retainer disengages from the engagement portion.

[0026] In some embodiments, the engagement portion comprises a hook. In some embodiments, releasing the valve from the compressed state includes engaging a tool with a receiving means on an outer surface of the sealing end and rotating the tool until the retainer disengages from the engagement portion.

[0027] Further particular and preferred aspects are set out in the dependent and dependent claims. Features from the dependent claims may be combined with features of the independent claims as appropriate, and in other combinations than those explicitly set out in the claims.

[0028] It should be understood that when features of an apparatus are described as operable to provide a certain functionality, this includes features of an apparatus that provide that functionality, or that are adapted or configured to provide that functionality. Hereinafter, embodiments of the present invention will be further described with reference to the accompanying drawings. [Brief description of the drawings]

[0029] [Figure 1] 1 shows a relief valve according to a first embodiment. [Diagram 2] 2 shows a cross section through the pump showing the location of the relief valve according to FIG. 1; [Diagram 3] 1 shows a relief valve according to a further embodiment. [Figure 4] 4 is a flow chart illustrating steps in a method for assembling a valve in a pump according to one embodiment. [Diagram 5]4 is a flow chart illustrating steps of a method for removing a valve assembly from a pump. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Before describing the embodiments in more detail, an overview will first be presented. The valve is configured to be inserted into an interstage cavity of the pump, for example in a clamshell stator. The interstage is hollow and has a wall facing the upstream stage and another wall facing the downstream stage. The valve is configured to open and close a pressure relief flow path from the outlet portion of the upstream stage back to the inlet portion of the upstream stage in the event of pressure increases at the outlet portion of the upstream stage, thereby protecting the downstream stage from these pressure increases.

[0031] The valve seat is formed in the pressure relief passage and in some embodiments is formed at one end of the passage in one of the walls, and the cavity area between the walls provides a pressure relief passage for returning gas to the inlet of the same stage. In an embodiment, the valve comprises a plunger, a spring, and a guide / support.

[0032] 1 shows a valve assembly according to a first embodiment. The valve assembly 10 is shown extended between an upstream wall 60 and a downstream wall 62 of an interstage cavity.

[0033] The valve assembly is configured so that it can be locked into a compressed state by pushing the valve plunger 30 to compress the spring 20, and once the spring 20 is compressed, the plunger 30 can be rotated with a tool in the recess 32 and the hook 40 on the end of the valve stem is held in the asymmetric slot 50 in the guide / support 47. In this state the entire assembly is small enough to slide within the cavity between the interstage walls 60, 62.

[0034] The valve assembly is moved to a position opposite a valve seat opening defining an orifice 64 in the upstream wall 60, the orifice comprising the valve seat. The support end 47 of the valve assembly is positioned in a recess in the downstream wall 62, and then, when in position, the plunger 30 can be rotated in the opposite direction to release the hook 40 from the slot 50, and the valve moves to an extended, closed position with the valve plunger 30 sealing against the valve seat in the orifice 64. In this position, the valve assembly is held in place.

[0035] A projection 45 extends from the valve support 47 and serves to stabilize the valve assembly against lateral or angular movement, helping to hold it firmly in place. When the upstream stage pressure rises above a predetermined amount, the force on the plunger 30 is sufficient to compress the spring 20, causing the plunger 30 to move away from its seat in the orifice 64, opening the pressure relief passage. When the upstream pressure falls below this critical value, the valve will again close, sealing off the pressure relief passage.

[0036] To remove the valve for maintenance or cleaning, the plunger 30 is pushed back through the seat opening 64 towards the guide / support 47 and then rotated using the recess 32 so that the hook 40 re-engages the slot 50. Once locked in compression, the valve can be simply pulled out from the interstage.

[0037] FIG. 2 shows diagrammatically the interstage walls 60, 62 of the interstage cavity with different flow paths. There is a pressure relief flow path 65 sealed by the valve assembly 10 according to the embodiment of FIG. 1. The pressure relief flow path runs from an orifice 64 at the outlet portion of the upstream pump stage to an orifice 68 at the inlet portion of the upstream pump stage. The orifice 64 constitutes the valve seat of the valve assembly 10. There is another pump flow path 67 that flows from an orifice 66 at the outlet portion of the upstream pump stage to an orifice 69 in the interstage wall 62, which allows access to the inlet portion of the downstream stage. The two flow paths 65 and 67 are separated from each other. Provided that they are bounded in some way so as to be separated from each other, they can have different forms within the cavity.

[0038] In another embodiment, not shown, the pressure relief valve is a blow-off valve rather than a recirculation pressure relief valve, in which case the pressure relief path 65 would extend to an orifice to the exhaust passage of the pump rather than to an orifice 68 in the inlet of the upstream pump stage.

[0039] 3 shows an alternative embodiment, diagrammatically, in which the pump flow passage 67 and the pressure relief flow passage 65 share the same path for the initial portion of the flow path from an orifice 66 in the outlet portion of the upstream wall. The two flow paths diverge at an orifice 64 which includes a valve seat and mates with a plunger or sealing end of the valve assembly 10. The valve assembly functions to open and close a portion of the pressure relief path 65 downstream of the orifice 64 which leads to an orifice 68 in the inlet portion of the upstream stage of the pump. The pump flow passage 67 leads to an outlet 69 which leads to the inlet portion of the downstream stage.

[0040] In this embodiment, the valve and orifice are in the fluid flow path and the valve assembly does not contact the interstage wall. Similar to the valve assembly 10 of Figures 1 and 2, this valve assembly includes a spring and retaining means (not shown) that can be compressed to hold the valve assembly in a compressed state for removal from the pump. Similarly, the valve assembly can be reinserted into the pump in a compressed state and rotating the valve plunger releases the retaining means and causes the valve to expand and engage the orifice.

[0041] In this embodiment, a recess is provided in the fluid flow passage to hold the support end of the valve assembly 10.

[0042] As with the embodiment of FIG. 2, there is an alternative arrangement (not shown) of this pressure relief valve where the valve functions as a blow-off valve, in which case the pressure relief path 65 extends to the exhaust passage of the pump rather than to the inlet portion of the upstream pump stage.

[0043] 4 shows a flow chart illustrating steps of a method of inserting a pressure relief valve into a pump according to an embodiment, in which the valve assembly is placed in a compressed state and inserted into an interstage cavity located between adjacent pump chamber walls, the support end of the valve is positioned within a recess in a downstream wall of the interstage cavity, and the sealing end of the valve is rotated to release the retaining means, causing the valve to be in an extended state and the sealing means to seal with a sealing surface over an orifice in the pump.

[0044] 5 shows a flow chart illustrating steps of a method for removing a valve assembly from an interstage cavity of a pump for valve maintenance or replacement, in which the valve assembly is compressed and a sealing end of the valve is rotated to engage a retaining means of the valve assembly and hold the valve assembly in a compressed state, such that the valve assembly can be removed from the interstage cavity.

[0045] Although exemplary embodiments of the present invention are disclosed in detail herein with reference to the accompanying drawings, it should be understood that the present invention is not limited to the detailed embodiments, and that those skilled in the art may make various changes and modifications therein without departing from the scope of the present invention as defined by the claims and their equivalents. [Explanation of symbols]

[0046] 10 Valve Assembly 20 Spring 30 Plunger 32 Depression 40 Hook 45 Protrusion 47 Support part 50 Slots 60 Step wall 62 Step wall 64 Orifice / Valve Seat 65 Pressure relief passage 67 Pump flow path 66 Orifice in wall 60 68 Orifice in wall 60 69 Orifice in wall 62

Claims

1. a stator having multiple pump stages; at least one stage divider separating two adjacent pump stages; A multi-stage rotary vacuum pump comprising: the at least one stage partition comprises two walls defining a cavity therebetween, an upstream wall bounding an upstream pump stage of the two adjacent pump stages and a downstream wall bounding a downstream pump stage of the two adjacent pump stages; the cavity comprises at least a portion of a pressure relief fluid flow passage, the pressure relief fluid flow passage providing a path from an outlet portion of the upstream pump stage towards an inlet portion or towards an exhaust portion of the upstream pump stage, the pressure relief fluid flow passage comprising an orifice, the orifice comprising a valve seat; The multi-stage rotary vacuum pump comprises: a valve assembly configured to move between a compressed state and an extended state, the valve assembly being configured to seal the orifice in the extended state and to move to the compressed state in response to the pressure in the upstream pump stage increasing above a predetermined value such that the orifice is unblocked; the valve assembly including a retaining means for releasably retaining the valve assembly in the compressed state; A multi-stage rotary vacuum pump.

2. the orifice is disposed within the upstream wall and configured to mate with the valve seat in the extended state, a fixed end of the valve assembly is disposed within the downstream wall, and an outer sealing surface of the valve assembly includes receiving means for receiving a tool to rotate the outer sealing surface to release or engage the retaining means.

2. A multi-stage rotary vacuum pump according to claim 1.

3. the retaining means comprises a hook and a slot for retaining the hook, one of the hook and the slot being attached to a fixed end of the valve assembly and the other of the hook and the slot being attached to an end of a plunger of the valve assembly opposite the slot, the valve assembly being configured such that rotation of a sealing end of the valve assembly causes the hook to engage or disengage from the slot.

3. A multi-stage rotary vacuum pump according to claim 1 or 2.

4. the orifice is located in one wall of the stage partition and defines the outlet of the upstream pump stage.

4. A multi-stage rotary vacuum pump according to claim 1.

5. the cavity includes a pump fluid flow path, the pump fluid flow path providing a path from the outlet portion of the upstream pump stage to the inlet portion of the downstream pump stage, the pump fluid flow path and the pressure relief fluid flow path including the orifice at a junction of the pump fluid flow path and the pressure relief fluid flow path.

4. A multi-stage rotary vacuum pump according to claim 1.

6. a portion of the fluid flow path from the outlet portion of the upstream pump stage to the orifice defining a combined pressure relief fluid flow path and a pump fluid flow path.

6. A multi-stage rotary vacuum pump according to claim 5.

7. the valve assembly is configured to extend between the two walls, the fixed end of the valve assembly being attached to the downstream wall and the sealing end of the valve assembly extending to the upstream wall when the valve assembly is in the extended state; 4. A multi-stage rotary vacuum pump according to claim 2 or 3.

8. the vacuum pump including a recess for receiving the fixed end of the valve assembly; 4. A multi-stage rotary vacuum pump according to claim 2 or 3.

9. a projection extending from the fixed end for retaining the valve assembly in the recess; 9. A multi-stage rotary vacuum pump according to claim 8.

10. 1. A method for assembling a valve in an interstage cavity between walls separating two adjacent pump stages, comprising the steps of: inserting a valve assembly, held in compression by a retaining means, between the walls of the interstage cavity, the valve assembly having a sealing end for engaging a valve seat of an orifice in a pressure relief fluid passageway passing through the interstage cavity and an opposite end, the pressure relief fluid passageway connecting an outlet portion of an upstream stage to either an inlet portion or an exhaust portion of the upstream stage; placing the valve assembly in the fluid flow path; and releasing the valve assembly from the compressed state such that the valve assembly moves to an extended state and the sealing end of the valve assembly engages the valve seat of the orifice. A method for assembling a valve, comprising:

11. the orifice is disposed in an upstream wall of the cavity; the positioning step includes positioning the opposite end of the valve assembly in a recess in a downstream wall of the interstage cavity; releasing the valve assembly from the compressed state such that the valve assembly moves to the extended state and the sealing edge engages the valve seat in the upstream wall. A method of assembling the valve of claim 10.

12. the orifice is disposed in a wall of a pump fluid passage within the cavity, the orifice connecting the pump fluid passage and the pressure relief fluid passage; the positioning step includes positioning the opposite end of the valve assembly within a recess in a wall of the pressure relief fluid flow passage; Releasing the valve from the compressed state so that the valve moves to an extended state and the sealing end engages the valve seat within the orifice. A method of assembling the valve of claim 10.

13. the retaining means comprises an engagement portion adapted to rotatably engage a slot, the engagement portion being attached to one of an end of a plunger of a valve assembly opposite the sealing end and the opposite end of the valve assembly, the slot being attached to the other of the end of the plunger and the opposite end of the valve assembly, and releasing the valve assembly from the compressed state includes rotating the sealing end such that the slot is disengaged from the engagement portion. A method for assembling a valve according to any one of claims 10 to 12.

14. The engagement portion comprises a hook. A method of assembling the valve of claim 13.

15. The retaining means includes an engagement portion adapted to rotatably engage a slot, and the step of releasing the valve assembly from the compressed state includes the steps of engaging a tool with a receiving means on an outer surface of the seal end and rotating the tool until the slot disengages from the engagement portion. A method of assembling the valve of claim 11.

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