OIL FEED ASSEMBLY FOR A VACUUM PUMP HAVING A VENTING CONDUIT

Abstract

An oil feed assembly for a vacuum pump comprises: an oil feeder located for feeding oil to one side of a bearing of the vacuum pump; an oil sump located on the one side of the bearing and configured to receive excess oil from the oil feeder; and a venting bypass conduit fluidly coupled with the oil sump and with another side of the bearing, the venting bypass conduit having an inlet located at an elevated position above a floor of the oil sump and configured to convey gas from the oil sump to the another side of the bearing. In this way, the venting bypass conduit provides an alternative path which allows gas within the oil sump to escape during pump-down while preventing oil within the oil sump from escaping with the gas travelling through the venting bypass conduit.

Claims

1. An oil feed assembly for a vacuum pump, comprising: an oil feeder located for feeding oil to one side of a bearing of the vacuum pump; an oil sump located on said one side of said bearing and configured to receive excess oil from said oil feeder; and a venting bypass conduit fluidly coupled with said oil sump and with another side of said bearing, said venting bypass conduit having an inlet located at an elevated position above a floor of said oil sump and configured to convey gas from said oil sump to said another side of said bearing.

2. The oil feed assembly of claim 1, wherein said elevated position is higher than an expected depth of said excess oil.

3. The oil feed assembly of claim 1, wherein said inlet is elevated in at least one of an axial direction and a radial direction with respect an axis of said bearing wherein said inlet is orientated in at least one of said axial direction and said radial direction.

4. The oil feed assembly of claim 1, wherein said inlet is located at said elevated position above each floor of said oil sump.

5. The oil feed assembly of claim 1, wherein said venting bypass conduit has a sump section defining said inlet, said sump section extending from at least one floor of said oil sump.

6. The oil feed assembly of claim 1, wherein said sump section extends in at least one of an axial direction and a radial direction with respect to said bearing.

7. The oil feed assembly of claim 1, wherein said sump section is rounded to resist gathering of oil.

8. The oil feed assembly of claim 5, wherein said venting bypass conduit comprises a gallery section fluidly coupled with said sump section, extending around said oil feed cap.

9. The oil feed assembly of claim 8, wherein said gallery section comprises an annulus extending circumferentially, concentric with said bearing.

10. The oil feed assembly of claim 8, comprising a plurality of said sump sections, each defining one said inlet, each sump section being fluidly coupled with said gallery section.

11. The oil feed assembly of claim 8, wherein said venting bypass conduit comprises a coupling section fluidly coupled with said gallery section.

12. The oil feed assembly of claim 11, wherein said coupling section fluidly couples with said other side of said bearing.

13. The oil feed assembly of claim 8, wherein said sump section and one part of said gallery section are formed as a first unitary part, and said coupling section and another part of said gallery section are formed as a second unitary part.

14. The oil feed assembly of claim 1, wherein said oil sump defines at least one recess to facilitate flow of gas past said oil feeder.

15. A vacuum pump, comprising: a bearing; and said oil feed assembly of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:

[0037] FIG. 1 shows an oil feed cap according to one embodiment;

[0038] FIG. 2 shows another view of the oil feed cap of FIG. 1;

[0039] FIG. 3 is a cross-sectional view of the oil feed cap of FIG. 1;

[0040] FIG. 4 is a view similar to FIG. 2 but with the wick holders removed;

[0041] FIG. 5 is a cross-sectional view of the oil feed cap of FIG. 1;

[0042] FIGS. 6 and 7 shows the sump section within the sump region;

[0043] FIG. 8 shows an oil feed cap according to one embodiment;

[0044] FIGS. 9 and 10 show other views of the oil feed cap of FIG. 8;

[0045] FIG. 11 is a view similar to FIG. 9 but with the wick holders removed; and

[0046] FIG. 12 is a cross-sectional view of FIG. 11.

DETAILED DESCRIPTION

Overview

[0047] Before discussing the embodiments in any more detail, first an overview will be provided. Embodiments provide an oil feed assembly used to feed and recirculate oil to a bearing of a rotating machine such as a vacuum pump. Typically, the assembly is provided within a cap which is fitted to the vacuum pump. The cap has a number of wicks which extend in to a reservoir holding oil used to lubricate the bearing of the vacuum pump. As mentioned above, the oil flows up the wicks and into a series of stacked felts. The stacked felts provide oil to the bearing. When the cap is attached to the vacuum pump, a void, chamber or oil sump holding the felts is sealed by the vacuum pump. When the vacuum pump pumps down, the gas within the void is evacuated by the vacuum pump. Conventionally, such evacuation would occur through the bearing being lubricated by the oil feeder system. However, embodiments provide a bypass conduit which fluidly couples the void with the vacuum pump. This provides an alternative path for gas within the void to be evacuated. The bypass conduit is provided with an inlet within the void which is located so as to help prevent any oil within the void from being removed with the gas during pump-down. In particular, the inlet is located at a position above any face, wall or floor of the void sump on which oil may gather. It will be appreciated that the oil may gather on different faces, depending on the orientation of the vacuum pump. This helps to prevent loss of the oil, which prolongs the life of the hearing and the vacuum pump.

Oil Feed Cap—1.SUP.st .Arrangement

[0048] FIG. 1 shows an oil feed cap 10 which feeds oil to a bearing of a vacuum pump (not shown). The oil feed cap 10 has a number of wick holders 20 which extend into an oil feed reservoir within the vacuum pump.

[0049] As can be seen in FIG. 2, the wick holders 20 retain a wick 30 which conveys oil from the reservoir within the vacuum pump to a bearing aperture 40 which receives the conical surface of the nut of the bearing, thereby feeding oil to the hearing. A number of coupling section conduits 50 are formed in the oil feed cap 10, which are in fluid communication with the vacuum pump.

[0050] As can be seen in FIG. 3, the wicks 30 are received by a stack of felts 60 which are stacked within a sump region 70 within the oil feed cap 10. A gallery section 120 extends around the sump region 70.

Bypass Conduit

[0051] As can be seen in FIG. 4 (which has the wick holders 20 and associated structure removed to improve clarity), the sump region 70 contains a sump section 80 (which forms the first part of the bypass conduit) which extends radially inwards, towards the centre of the sump region 70 and which intersects the stack of felts 60. The sump section 80 defines an inlet 90. The inlet 90 is elevated above a first face 100 of the sump region 70 (defined by a circular plate), elevated above a second face (not shown—defined by an opposing circular plate supporting the wick holders 20) and elevated above a third face 110 (defined by a tubular wall extending between the first face 100 and the third face). Hence, as can be seen in FIGS. 6 and 7, should oil from the stack of felts 60 gather on the first face 100, the second face (not shown) or the third face 110, then the location of the inlet 90, which is raised off each of these faces, will impair or even prevent the flow of oil into the sump section 80. This helps to prevent loss of oil from the oil feed. The surface of the sump section 90 is rounded to help prevent the collection of oil. Also, the sump section 80 in the vicinity of the inlet 90 may be provided with drip edges to help prevent oil gathered on the sump section 80 from entering the inlet 90.

[0052] As can be seen in FIG. 5, the bypass conduit defined by the sump section 80 fluidly couples with a gallery section 120 (which forms the second part of the bypass conduit) which comprises an annular chamber which concentrically surrounds the sump region 70. The coupling section conduits 50 (which forms the third part of the bypass conduit) are fluidly coupled with the gallery section 120. Although in this embodiment one of the coupling section conduits 50 is radially aligned with the sump section 80, in other embodiments the coupling section conduit 50 is not radially aligned with the sump section 80. That is to say that the coupling section conduit 50 may be circumferentially offset from the sump section 80.

[0053] In operation, when the vacuum pump is activated, gas within the sump region 70 is evacuated and flows primarily through the inlet 90, along the sump section 80, into the gallery section 120 and through the coupling section conduits 50 into the vacuum pump. As mentioned above, even when the gas flow out of the sump region 70 is high, the location of the inlet 90 helps to prevent the flow of oil together with the evacuating gas during pump-down.

[0054] The exact positioning of the inlet 90, and in particular the depth of the end portion of the sump section 80 which defines the inlet 90, is selected based on the expected depth of any excess oil which gathers in the sump region 70. Also, the dimensioning of the inlet 90 and the sump section 80 is set to control the velocity of the gas being pumped out of the sump region 70.

Oil Feed Cap—2.SUP.nd .Arrangement

[0055] FIG. 8 shows an oil feed cap 10A which feeds oil to a bearing of a vacuum pump (not shown). The oil feed cap 10A has a number of wick holders 20A which each receive a wick 30A.

[0056] As can be seen in FIGS. 9 and 10, the wicks 30A feed a stack of felts 60A which provide oil to a bearing aperture 40A.

Bypass Conduit

[0057] As can be seen in FIG. 11 (in which the wicks 30A and the stack of felts 60A have been omitted to improve clarity), sump sections 80A (which form the first part of the bypass conduit) are provided, each of which have an inlet 90A. The inlet 90A is orientated in an axial direction with respect to a rotation axis of the bearing. The inlet 90A is located in an elevated position with respect to the first face 100A, the opposing second face (not shown) and the third face 110A.

[0058] As can be seen in FIG. 12, the sump section 80 forms an axially extending conduit section 95A which bends to form a radially extending conduit 97A. Each inlet 90A is in fluid communication with a gallery section 120A (which forms the second part of the bypass conduit) which is an annular chamber which concentrically surrounds the sump region 70A. The gallery section 120A is enclosed by a further structure (not shown) which provides the coupling section conduits (which form the third part of the bypass conduit) in a similar manner to that described above.

[0059] A series of recesses 130A are formed in the first face 100A. Recesses 140A extend axially along each side of the sump section 80A.

[0060] In operation, when pump-down occurs, gas is evacuated from the sump region 70A, assisted by flowing along the recesses 130A and 140A. The gas flows through the inlet 90A, along the axial section 95A and into the radial section 97A. The gas is then received within the gallery section 120A, flows through the coupling conduits and into the vacuum pump.

[0061] As mentioned above, even when the gas flow out of the sump region 70A is high, the location of the inlet 90A helps to prevent the flow of oil together with the evacuating gas during pump-down. It can be seen that due to the location of the inlets 90, irrespective of the orientation of the oil feed cap 10A, the inlets 90A are positioned above the likely level of any excess oil on any face within the sump region 70A, thereby helping to prevent loss of the oil during pump-down.

[0062] The exact positioning of the inlets 90A is selected based on the expected depth of any excess oil which gathers in the sump region 70A. Also, the dimensioning of the inlet 90A and the sump section 80A is set to control the velocity of the gas being pumped out of the sump region 70A.

[0063] Some embodiments provide a preferable gas path during pump down of a Turbo pump to prevent the oil in the oil sump reservoir or oil pot being drawn through the bearing and being lost into the pump. Some embodiments are functional in any orientation and not allow oil to drain out of the oil sump reservoir

[0064] Unlike in some inverted-running pumping systems where it has been found during harsh pump down some of the oil is migrating through the bearing and being loss into the pump as this is the only exit for the gas from this area of the pump this starves the reservoir of volume of oil, some embodiments create a preferential gas path to remove the gas trapped in the oil cavity during harsh venting activities. This has been achieved by connection to the gas cavity with the backing line via a complex path to avoid loss of oil for the reservoir.

[0065] One embodiment involves slotting the lower oil felt and introducing a square tunnel section into the centre of the pot. A small gas inlet slot is created in the end of the tunnel to accept gas and the end is rounded so any oil that falls on the surface runs around and away from this inlet. The inlet is then connected via an annulus to the base cap and is vented to the wire cavity which in turn is connected to the hacking-line.

[0066] Another embodiment is an integrated moulded solution that involves intricate channelling. The gas firstly passes along the slots in the base of the oil pot and reaches the inner wall where is passes up the slotted inner wall and joins any gas drawn across the top face of the upper most felt. From this point it is drawn into the four slots, equispaced around the diameter, once drawn into these it is vented to the wire cavity via an external moulded slot formed on a sliding core. This embodiment also includes moulded sealing edges against vacuum loss.

[0067] Embodiments seek to avoid the loss of oil through either being drawn directly into the outlet or oil that has pooled running directly into the outlet when stored or run in a non-inverted orientation.

[0068] Embodiments save height in the pumping system by cutting the gas exhaust path into the current oil pot constraints i.e. the pump height stays the same.

[0069] 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.

[0070] Although elements have been shown or described as separate embodiments above, portions of each embodiment may be combined with all or part of other embodiments described above.

[0071] Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are described as example forms of implementing the claims.