GB2590430A

GB2590430A - Lubricant delivery within a vacuum pump

Info

Publication number: GB2590430A
Application number: GB1918636.0A
Authority: GB
Inventors: Percival-Alwyn Richard
Original assignee: Edwards Ltd
Current assignee: Edwards Ltd
Priority date: 2019-12-17
Filing date: 2019-12-17
Publication date: 2021-06-30
Also published as: GB201918636D0

Abstract

A vacuum pump 5 comprises a coolant system configured to provide a flow of coolant fluid to cool said vacuum pump, a lubricant delivery system 40 for delivering lubricant to portions of said vacuum pump and a pumping mechanism 20 configured to be driven by the coolant fluid and operable to drive the lubricant within the lubricant delivery system. The pumping mechanism may comprise a driving portion 42 configured to be driven by the coolant fluid flow, a driven portion 12 configured to drive the lubricant and a sealing means 30. The driven and driving portions being isolated from each other by the sealing means. The pumping mechanism is preferably a diaphragm pump where the diaphragm is the sealing means. The driving and driven portions may comprise positive displacement rotors. The coolant fluid may comprise water. The positive displacement rotor may comprise a water turbine. The lubricant delivery system may comprise a lubricant collecting vessel 44 and a lubricant supply reservoir 46. A method of supplying lubricant to portions of a vacuum pump is also claimed.

Description

LUBRICANT DELIVERY WITHIN A VACUUM PUMP

FIELD OF THE INVENTION

The field of the invention relates to vacuum pumps and to delivering one or more lubricants to the different parts of a pump.

BACKGROUND

Vacuum pumps have parts which rotate at high speed and many such pumps require both cooling and lubricating. Conventionally, lubricating of a vacuum io pump may involve "splash" lubrication which uses an oil thrower mounted on an end of a rotating shaft and which dips into an oil sump when rotating. The oil thrower throws the oil from the sump towards other parts of the pump as it rotates with the shaft. The other parts of the vacuum pump may include the parts requiring lubrication and in some cases may include an oil supply reservoir from which oil may be gravity fed to parts to be lubricated. Other conventional lubrication systems include the use of a gerotor mounted on a shaft and pumping the oil from a sump to a supply reservoir.

A drawback of these two methods is that oil throwers do not provide a very targeted oil supply for much of the lubricant that is thrown and the incorporation of a gerotor adds complexity.

It would be desirable to provide an alternative lubricant supply mechanism.

SUMMARY

A first aspect provides vacuum pump comprising: a coolant system for cooling said vacuum pump, said coolant system being configured to provide a flow of coolant fluid through said coolant system to cool said vacuum pump; a lubricant delivery system for delivering lubricant to portions of said vacuum pump; a pumping mechanism configured to be driven by a flow of said coolant fluid and operable to drive said lubricant within said lubricant delivery system. -2 -

The inventor of the present invention recognised that in many vacuum pumps there is a supply of coolant fluid to the vacuum pump that is there to provide the required cooing. He also recognised that the required flow rate of lubricant to portions of the vacuum pump such as the bearings and other moving parts is relatively low in comparison to the required coolant flow rates. As such he determined that it should be possible to use a flow of coolant fluid and to take some of the kinetic energy from that flow to drive a lubricant delivery system.

Thus, a pumping mechanism is provided that is driven by a flow of coolant fluid that is available at the pump for cooling purposes and which in turn drives the lubricant within the lubricant delivery system.

In some embodiments, said pumping mechanism comprises: a driving portion configured to be driven by said coolant fluid flow; a driven portion configured to drive said lubricant within said lubricant delivery system; and a sealing means, said driven and driving portions being isolated from each other by said sealing means.

Embodiments make use of a flow of coolant fluid which is generally available at a considerably higher flow rate than the flow of lubricant required, to drive a pumping mechanism, which in turn drives lubricant flow. One potential problem with such an arrangement is the potential for contamination between the lubricant and coolant fluid. This is addressed in embodiments by providing the pumping mechanism with a sealing means between the driven and driving portions such that they are separated from each other by a means that is resistant to fluid flow.

Although, the pumping mechanism may have a number of forms, in some embodiments, said pumping mechanism comprises a diaphragm pump, said diaphragm of said diaphragm pump comprising said sealing means.

A diaphragm pump is an effective, low maintenance and relatively inexpensive pump which by its nature already has a sealing means between the pumping and -3 -pumped fluids in the form of the diaphragm. Thus, this makes an effective pumping mechanism for driving lubricant flow using a coolant flow as the driving force.

In other embodiments, said driving portion of said pumping mechanism comprises a rotatable shaft comprising a positive displacement rotor configured to extend into and be driven by said flow of coolant fluid; and said driven portion of said pumping mechanism comprises a positive displacement rotor configured to extend into and be driven by said lubricant flow; wherein said rotatable shaft is io configured on rotation to convey torque to and thereby drive said positive displacement rotor extending into said lubricant flow.

An alternative to having a diaphragm pump may be to have a rotatable shaft that comprises a positive displacement rotor that is driven by the flow of coolant fluid.

This rotatable shaft may be configured on rotation to convey torque to and drive a further positive displacement rotor that extends into the lubricant flow. In this regard, the rotatable shaft may mount both a positive displacement rotor in the coolant flow and one in the lubricant flow and have a sealing means in the form of a shaft sealing means between them. In other embodiments, the shaft may not extend into the lubricant flow but may be used drive the positive displacement rotor via an intermediate element such as gearing.

Although the coolant fluid may comprise different things, in some embodiments the coolant fluid comprises water.

Water is readily available and has a high heat capacity and as such makes a convenient coolant fluid. The water used may be simple mains water, or it may be water that has been treated in some way, perhaps to reduce corrosion.

Although the positive displacement rotor may have a number of forms, in some embodiments it comprises a water turbine. -4 -

Although the pumping mechanism may deliver lubricant directly to different portions of the vacuum pump that require the lubricant either to lubricate the elements and/or to cool them, in some embodiments the lubricant delivery system comprises a lubricant collecting vessel and a lubricant supply reservoir, said pumping mechanism being configured to pump lubricant from said lubricant collecting vessel towards said lubricant supply reservoir.

In many vacuum pumps the vacuum pump may have a lubricant supply reservoir and a lubricant collecting vessel generally in the form of a sump to collect oil that has flowed from the supply vessel down through the parts to be lubricated. In some embodiments the lubricant delivery system uses the pumping mechanism to pump lubricant from the collecting vessel to the supply reservoir. The oil is then distributed to the different parts of the pump where it is required from the lubricant supply reservoir.

In some embodiments, said lubricant collecting vessel is located in operation at a lower point than said lubricant supply reservoir, such that said lubricant supply reservoir provides a head of pressure for flow of said lubricant.

The lubricant supply reservoir may be located above the lubricant collecting vessel and in some cases above the components of the vacuum pump that it is to deliver lubricant to. This allows the delivery of lubricant to occur using gravity and the pumping mechanism is simply used to move the oil from the lower sump to the higher lubricant supply reservoir. The delivery of lubricant may be targeted to particular parts of the vacuum pump using felts and/or conduits. Where felts are used capillary action may allow the lubricant supply reservoir to be located below at least some of the components that it is supplying lubricant to.

In some embodiments, said coolant fluid flow that said pumping mechanism is configured to be driven by, is within said coolant system. -5 -

The coolant fluid flow that drives the pumping mechanism may be within the cooling system itself. The cooling system will comprise a coolant flow that flows around the system and is in thermal contact with portions of the vacuum pump that require cooling. Thus, the coolant fluid will be warmed by contact with the vacuum pump and will remove the heat as it exits the coolant system. The fluid flow in a coolant system is generally quite high and thus, the flow rate is sufficient to drive a pumping mechanism to pump a lubricant, where the fluid flow requirements are generally much lower, without causing issues in terms of flow restriction and pressure drop in the coolant system.

In some embodiments, however the coolant fluid flow that is used to drive the pumping mechanism may be a separate coolant fluid flow to that in the coolant system. In this regard, it may be that it is more convenient to locate the pumping mechanism away from the coolant system and as there is a supply of coolant fluid to the pump for the coolant system, this supply can be used to provide a flow of coolant fluid to drive the pumping mechanism. In this regard, the coolant fluid may be water and the coolant fluid supply may be mains water or it may be water, perhaps treated water that is suppled from a header tank.

Having a separate coolant fluid flow system for driving the pumping mechanism may have advantages where, for example, the coolant system is temperature controlled. The supply of lubricant should be continual during operation and thus, if the flow of coolant in the system is stopped intermittently this may cause problems. Having a separate coolant fluid flow system mitigates against this and may provide a continuous steady flow of lubricant. However, in embodiments that use a lubricant supply reservoir rather than directly feeding the lubricant to the pump parts, it may be that some intermittent operation of the pumping mechanism is acceptable.

A second aspect provides a method of supplying lubricant to portions of a vacuum pump comprising: cooling said vacuum pump using a flow of coolant fluid; driving a pumping mechanism using a flow of said coolant fluid such that -6 -said pumping mechanism pumps lubricant to supply lubricant to portions of a vacuum pump In some embodiments, said flow of coolant fluid driving said pumping mechanism is within a coolant system cooling said vacuum pump.

In some embodiments, said pumping mechanism pumps lubricant from a lubricant collecting vessel to a lubricant supply vessel.

In some embodiments, the method comprises a further step of lubricant flowing from said lubricant supply vessel to said lubricant collecting vessel via said portions of said vacuum pump.

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

Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which: Figure 1 shows a pumping mechanism for supplying lubricant to a vacuum pump according to an embodiment; Figure 2 shows a flow diagram illustrating steps in a method according to an embodiment; and Figure 3 shows a vacuum pump according to an embodiment. -7 -

DESCRIPTION OF THE EMBODIMENTS

Before discussing the embodiments in any more detail, first an overview will be provided.

An embodiment provides a mechanism for pumping lubricant that is powered by a flow of coolant fluid. The pumping mechanism provides delivery of the lubricant to the different parts of the vacuum pump requiring lubricating and/or cooling. In some embodiments, the coolant fluid is water, the lubricant is oil and the parts of the vacuum pump include the bearings. The system is particularly effective for io delivering low pressure oil to parts of a vacuum pump using a higher pressure cooling water flow. As the lubricant is pumped by the flow of coolant fluid it doesn't need to be driven from one of the vacuum pumps shafts or by a separate motor.

In some embodiments a seal is provided to protect from contamination of the lubricant and cooling fluid by any mixing of the two.

In some embodiments, the coolant flow is within the coolant system, while in others it may be a separate flow. A separate flow requires additional conduits, but may be preferable as the flow can be maintained at a steady state whatever the operation of the vacuum pump, and thus, any interruption of the coolant flow which may occur where there is for example, a temperature controlled valve in the coolant system, will not affect the flow of lubricant.

Figure 1 shows one example of a lubricant pumping mechanism 20 according to an embodiment. In this embodiment impeller 17 is mounted on a rotatable shaft 32. The rotatable shaft 32 also mounts a water turbine 17. Flow of coolant fluid from a coolant fluid inlet 10 towards a coolant fluid outlet/return 11 drives the water turbine, which in turn rotates shaft 32, which in turn drives impeller 47.

The two fluid flows are isolated from each other by a shaft seal 30 which impedes any contamination between the lubricant and the coolant fluid. -8 -

Rotation of impeller 47 drives lubricant, in this case oil, within the lubrication system. The oil is picked up from a collection reservoir of sump at conduit 43 is pumped by impeller 47 upwards through conduit 40 towards the parts to be lubricated. In some embodiments there may be a lubricant supply reservoir connected to conduit 40 from which the lubricant feeds to the parts to be lubricated, in other embodiments there may be direct feeding of the lubricant to the parts with no supply reservoir.

The flow of coolant fluid to drive turbine 17 may be within a coolant system for cooling the vacuum pump. Alternatively, the coolant fluid supply for the coolant system may be used to provide coolant fluid to a separate system which contains the water turbine and is configured to provide a constant flow of coolant fluid to provide a constant flow of lubricant.

Figure 2 shows a flow diagram illustrating steps in a method according to an embodiment. In this method a flow of coolant fluid drives a pumping mechanism at step S10. This in turn drives a flow of lubricant at step S20, the lubricant being supplied to different parts of the pump at step S30.

Figure 3 shows a vacuum pump according to an embodiment for supplying lubricant to a vacuum pump 5. In this embodiment, the coolant system supplies coolant from a coolant supply inlet 10 to a coolant supply return 11. The coolant passes through a coolant driven pump 20 and a cooling plate/ heat exchanger 15 for cooling the vacuum pump 5. The coolant driven pump 20 in this embodiment comprises a coolant-powered drive side 12 for receiving coolant fluid and an oil-driven side 42 for receiving lubricant, which in this embodiment is oil. The two sides are separated by a sealing means 30, which were this to be a diaphragm pump would be the diaphragm of the diaphragm pump.

Flow of the coolant fluid through side 12 of the pump causes flow of lubricant through side 42 of the pump. -9 -

In this lubricant delivery system there is an oil collecting vessel or sump 44 for collecting oil which has passed through the vacuum pump 5. Diaphragm pump 20 pulls oil from the sump 44 though conduit 43 into the oil pump side 42 and then pumps the oil via the oil delivery system 40 to oil supply reservoir 46 from where it is conveyed to the parts where it is required, this may be the gears, bearings, seals or any parts that require lubricating and/or cooling. Although in this embodiment there is an oil supply reservoir 46 that is fed by the oil delivery system 40 and from which oil is led via gravity feeding to the different parts of the vacuum pump, in other embodiments, the oil delivery system 40 may deliver the oil directly to the different parts requiring lubricating and/or cooling by the oil.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

-10 -

REFERENCE SIGNS

vacuum pump coolant supply in 11 coolant supply return 12 coolant flow cavity of diaphragm pump heat exchanger 17 water turbine pumping mechanism sealing means io 32 rotatable shaft oil delivery system 43 oil pick conduit 44 oil collecting vessel 46 oil supply vessel 47 oil impeller

Claims

CLAIMS1. A vacuum pump comprising: a coolant system for cooling said vacuum pump, said coolant system being configured to provide a flow of coolant fluid through said coolant system to cool said vacuum pump; a lubricant delivery system for delivering lubricant to portions of said vacuum pump; a pumping mechanism configured to be driven by a flow of said coolant fluid and operable to drive said lubricant within said lubricant delivery system.
2. A vacuum pump according to claim 1, wherein said pumping mechanism comprises: a driving portion configured to be driven by said coolant fluid flow; a driven portion configured to drive said lubricant within said lubricant delivery system; and a sealing means, said driven and driving portions being isolated from each other by said sealing means.
3. A vacuum pump according to claim 2, wherein said pumping mechanism comprises a diaphragm pump, said diaphragm of said diaphragm pump comprising said sealing means.
4. A vacuum pump according to claim 2, wherein said driving portion of said pumping mechanism comprises a rotatable shaft comprising a positive displacement rotor configured to extend into and be driven by said flow of coolant fluid; and said driven portion of said pumping mechanism comprises a positive displacement rotor configured to extend into and be driven by said lubricant flow; 30 wherein said rotatable shaft is configured on rotation to convey torque to and thereby drive said positive displacement rotor extending into said lubricant flow.
-12 - 5. A vacuum pump according to claim 4, wherein said rotatable shaft is configured to mount both said positive displacement rotor configured to extend into said coolant flow and said positive displacement rotor configured to extend into said lubricant flow; and said sealing means comprises a shaft sealing means mounted on said rotatable shaft.
6. A vacuum pump according to any preceding claim, wherein said coolant io fluid comprises water.
7. A vacuum pump according to claims 6 when dependent on any one of claims 4 orb, wherein said positive displacement rotor in said coolant system comprises a water turbine.
8. A vacuum pump according to any preceding claim, said lubricant delivery system comprising a lubricant collecting vessel and a lubricant supply reservoir, said pumping mechanism being configured to pump lubricant from said lubricant collecting vessel towards said lubricant supply reservoir.
9. A vacuum pump according to claim 8, wherein said lubricant collecting vessel is located in operation at a lower point than said lubricant supply reservoir, such that said lubricant supply reservoir provides a head of pressure for flow of said lubricant.
10. A vacuum pump according to any preceding claim, wherein said coolant fluid flow that said pumping mechanism is configured to be driven by, is within said coolant system.
11. A vacuum pump according to any one of claims 1 to 9, wherein said coolant fluid flow that said pumping mechanism is configured to be driven by, is separate from said coolant system.
-13 - 12. A method of supplying lubricant to portions of a vacuum pump comprising: cooling said vacuum pump using a flow of coolant fluid; driving a pumping mechanism using a flow of said coolant fluid such that said pumping mechanism pumps lubricant to supply lubricant to portions of a vacuum pump.
13. A method according to claim 12, wherein said flow of coolant fluid driving said pumping mechanism is within a coolant system cooling said vacuum pump.
14. A method according to claim 12 or 13, wherein said pumping mechanism pumps lubricant from a lubricant collecting vessel to a lubricant supply vessel.
15. A method according to claim 14, comprising a further step of lubricant flowing from said lubricant supply vessel to said lubricant collecting vessel via said portions of said vacuum pump.