Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
  • F16C33/30—Parts of ball or roller bearings
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D19/00—Axial-flow pumps
  • F04D19/02—Multi-stage pumps
  • F04D19/04—Multi-stage pumps specially adapted to the production of a high vacuum, e.g. molecular pumps
  • F04D19/042—Turbomolecular vacuum pumps
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/05—Shafts or bearings, or assemblies thereof, specially adapted for elastic fluid pumps
  • F04D29/056—Bearings
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C19/00—Bearings with rolling contact, for exclusively rotary movement
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C19/00—Bearings with rolling contact, for exclusively rotary movement
  • F16C19/02—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows
  • F16C19/04—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for radial load mainly
  • F16C19/06—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for radial load mainly with a single row or balls
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
  • F16C33/30—Parts of ball or roller bearings
  • F16C33/38—Ball cages
  • F16C33/3837—Massive or moulded cages having cage pockets surrounding the balls, e.g. machined window cages
  • F16C33/3843—Massive or moulded cages having cage pockets surrounding the balls, e.g. machined window cages formed as one-piece cages, i.e. monoblock cages
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/05—Shafts or bearings, or assemblies thereof, specially adapted for elastic fluid pumps
  • F04D29/056—Bearings
  • F04D29/059—Roller bearings
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C19/00—Bearings with rolling contact, for exclusively rotary movement
  • F16C19/52—Bearings with rolling contact, for exclusively rotary movement with devices affected by abnormal or undesired conditions
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C2360/00—Engines or pumps
  • F16C2360/44—Centrifugal pumps
  • F16C2360/45—Turbo-molecular pumps
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
  • F16C33/30—Parts of ball or roller bearings
  • F16C33/38—Ball cages
  • F16C33/3806—Details of interaction of cage and race, e.g. retention, centring

Definitions

• the present invention relates to a bearing cage retainer and, in particular, a bearing cage retainer for a rolling element rotor bearing in a vacuum pump, particularly a turbomolecular pump.
• the invention further relates to a turbomolecular pump comprising such a retainer, bearing system for a turbomolecular pump, and methods for assembling turbomolecular pumps.
• Vacuum pumps typically comprise an impeller in the form of a rotor mounted on a shaft for rotation relative to a surrounding stator.
• the shaft may be supported by a bearing arrangement comprising two bearings located at or intermediate respective ends of the shaft.
• the shaft may be cantilever supported with two bearings located at or immediate to one end of the shaft.
• one or both of these bearings may be in the form of rolling element bearings.
• the upper bearing may be a magnetic bearing
• the lower bearing a rolling element bearing.
• a typical rolling bearing (1) comprises an inner race (2) fixed relative to the shaft (3) of the vacuum pump (4), an outer race (5), and a plurality of rolling elements (6), supported by a cage (7), for allowing relative rotation of the inner race (2) and the outer race (5).
• the outer race (5) is fixedly attached to a bearing support damper (8), which is in turn is fixedly attached to the housing (9) of the vacuum pump.
• the bearing support damper (8) is typically held in place by a bearing support nut (10).
• the rolling element bearing (1) is lubricated to establish a load-carrying film separating the bearing components in rolling and sliding contact in order to minimize friction and wear.
• the present invention provides a bearing cage retainer for a rolling element rotor bearing in a vacuum pump, typically a turbomolecular pump.
• the bearing may comprise an outer race, an inner race, and a plurality of separated rolling elements located within a rotatable bearing cage.
• the rolling elements are balls.
• the bearing comprises from about 6 to about 12 balls, 7 being an example.
• the bearing cage is castellated.
• the rolling elements are substantially uniformly separated.
• the bearing cage has a ring-shaped (annular) cross-section and the rolling elements are held within the ring with equidistant separation between adjacent rolling elements.
• a vacuum pump is configured to limit the longitudinal axial displacement of the bearing, in particular the outer race of the bearing.
• longitudinal axial displacement it is meant displacement in a direction parallel to the rotational axis of the bearing.
• the longitudinal axial displacement may be limited by a removable fixture coupled to the outer race, such as a retaining nut or a bearing damper retaining nut.
• the retaining nut and bearing cage retainer may be a single unitary structure.
• the bearing cage retainer may be configured to have an operational arrangement in which the retainer does not engage the bearing cage.
• the bearing cage retainer is configured to have an operational arrangement in which, at the maximum longitudinal axial displacement limit of the outer race in the direction of the retainer, the bearing cage retainer is disengaged from the bearing cage.
• the bearing cage retainer may not engage the bearing cage.
• the bearing cage retainer may be further configured to have a failure configuration in which the retainer is engaged with said bearing cage.
• a failure configuration characterised by the dislocation of the bearing cage by a longitudinal axial displacement of the bearing cage relative to the outer race in the direction of the retainer and in which the bearing cage retainer is engaged by said bearing cage.
• the bearing cage retainer enables the bearing cage to maintain the separation of the rolling elements.
• the bearing cage may remain rotatable in the failure configuration, preferably wherein the rotational axis of the bearing cage is substantially coaxial with a rotational axis of the inner race and/or a rotor shaft of the vacuum pump.
• the bearing cage and/or rolling elements remain(s) at least partially within the bearing (i.e. between the inner race and outer race) when in the failure configuration. If the turbomolecular pump is in use, the bearing cage may be rotating in an operational arrangement and remain rotating in the failure configuration.
• the bearing cage In normal operating conditions the bearing cage remains in a substantially axially fixed position relative to the outer race whilst rotating relative thereto.
• the failure configuration is characterised by an unwanted axial displacement (or dislocation) of the bearing cage relative to the outer race, typically a downward axial displacement.
• the axial displacement is relative to the position of the outer race in its normal operating configuration.
• the bearing cage may also be axially displaced relative to the inner race when in the failure configuration.
• the failure configuration provides an audible signal that the bearing is failing when the turbomolecular pump is in use. Typically, the user will hear the audible signal and stop the turbomolecular pump.
• a change in pump vibration for instance a change in amplitude or frequency, typically an increase in amplitude.
• the user may detect the change in vibration and stop the pump. Vibration detection may be by user inspection or by automated means, such as the use of accelerometers (e.g. piezo-electric transducers). The level of vibration may be compared with historical baseline values.
• accelerometers e.g. piezo-electric transducers
• the invention provides a bearing cage retainer for a vacuum pump comprising rolling element rotor bearing, the bearing comprising an outer race, an inner race, and a plurality of rolling elements located within a bearing cage, wherein the bearing cage retainer is configured to selectively engage the bearing cage only when in a failure configuration, said failure configuration being characterised by an audible signal that the bearing is failing and the bearing cage remaining rotatable.
• the retainer is configured so that the bearing cage remains at least partially within the bearing when in the failure configuration. If the turbomolecular pump is in use, the bearing cage may be rotating and remain rotating in the failure configuration.
• the failure configuration may be characterised by an axial displacement of the bearing cage relative to the outer race.
• the vacuum pump is a turbomolecular pump.
• the invention provides a bearing cage retainer for a vacuum pump comprising rolling element rotor bearing, the bearing comprising an outer race, an inner race, and a plurality of rolling elements located within a rotatable bearing cage, wherein the bearing cage retainer is configured to engage the bearing cage only when in a failure configuration, said failure configuration being characterised by an axial displacement of the bearing cage relative to the outer race and separation of the rolling elements being maintained, preferably a substantially uniform separation of the rolling elements is maintained (i.e.
• the bearing cage remains rotatable.
• bearing cage remains at least partially within the bearing when in the failure configuration. If the turbomolecular pump is in use, the bearing cage may be rotating and remain rotating.
• the failure configuration may be characterised by an axial displacement of the bearing cage relative to the outer race.
• the retainer may be configured such that when the bearing cage retainer is in a failure configuration circumferential separation of the rolling elements is maintained.
• the rolling elements remain substantially circumferentially equidistantly separated.
• the rolling elements remain at least partially retained within the bearing cage in the failure configuration.
• at least half of each rolling element remains within the bearing cage.
• the rolling elements remain engaged with the inner race and outer race.
• the rolling elements may roll in the failure configuration.
• the rolling elements are balls and in the failure configuration at least a hemisphere of each of the balls remains located between the inner and outer race of the bearing.
• a turbomolecular pump comprising a bearing cage retainer according to the invention
• the bearing cage may engage the bearing cage retainer and be maintained in a position in which the rolling elements remain within the bearing cage and substantially equally separated. Whilst the bearing will have failed, the turbomolecular pump may be shut down safely, avoiding a catastrophic failure of the pump.
• the bearing cage retainer may comprise at least one bearing cage braking surface for frictional sliding engagement with the bearing cage in the failure configuration.
• the at least one braking surface is substantially annular or part-annular (i.e. a part of an annulas). Two, three, four or five part-annular surfaces are preferred.
• the ratio of the breadth of the braking surface in a radial direction to the breadth of the bearing cage in a radial direction is from about 1 : 1 to about 1 :2, preferably from about 4:5 to about 2:3.
• the bearing cage may be configured such that, in the failure configuration, the at least one braking surface engages only the bearing cage. Preferably, the braking surface does not engage the outer race and/or the inner race when in the failure configuration.
• the at least one braking surface lies in a plane that intersects the outer race and/or inner race of the bearing, preferably the plane is substantially tangential to a rotational axis of the bearing and/or the rotational axis of the impeller.
• the braking surface is located on a bearing cage-side surface of an annular or part-annular boss forming part of the bearing cage retainer.
• the bearing cage retainer may be configured to engage and retain the bearing cage when the turbomolecular pump is running at full speed. Typically, at full speed the impeller shaft and inner race will rotate at greater than 50 000 RPM, typically at least 60 000 RPM. A bearing cage will typically rotate at approximately 1/3 the speed of the inner race, for instance 16 000 RPM or greater, or 20 000 RPM or greater, when the turbomolecular pump is running at full speed. [0033] Typically, in the operational arrangement (i.e. in normal working conditions) the bearing cage retainer does not engage the bearing cage. Additionally, or alternatively, the bearing cage retainer does not engage the bearing at all in an operational arrangement.
• the outer race is rotationally fixed whereas the inner race, bearing cage and rolling elements are rotatable substantially about an axis (i.e. they are substantially coaxial), typically they are coaxial with axis of the rotor shaft of the turbomolecular pump.
• the rolling elements rotate about their own axis and about the axis of the rotor shaft.
• the inner race is coupled to a rotor shaft of the turbomolecular pump.
• the bearing cage retainer may be rotatable relative to the outer race or fixed relative thereto.
• the bearing cage retainer may be manufactured from any suitable material, for instance an alloy, a polymer, a ceramic, or a composite.
• the material and/or geometry for the retainer will be selected to be sufficiently stiff so as to substantially limit axial deflection thereof when the retainer is engaged if a bearing failure occurs.
• the material properties may be selected so that they are appropriate for the operating temperature of the bearing, e.g. between about 90 °C and about 150 °C.
• the material may be selected so that it can be machined to the required tolerances, is thermally stable at operating and storage temperatures, and is stable when exposed to any lubricant present.
• Polymers suitable for use in the bearing cage retainers of the invention may be selected from group consisting of elastomers, thermoplastic materials or thermosets. Thermoplastic materials are preferred. Typically, the polymer is selected from the group consisting of polyolefins, such as polyethylene and polypropylene; polyvinylchloride, polyethylene terephthalate; and fluoropolymers, such as polytetrafluoroethylene, and derivatives and copolymers thereof. High performance thermoplastic materials may also be employed.
• Preferred high performance thermoplastics may be selected from the group consisting of liquid crystal polymers, including aromatic polyamides and aromatic polyesters, aromatic polyimides, polyamides, polysulpones, polyethylenimines, and polyether ether ketone (PEEK), or derivatives or copolymers thereof.
• liquid crystal polymers including aromatic polyamides and aromatic polyesters, aromatic polyimides, polyamides, polysulpones, polyethylenimines, and polyether ether ketone (PEEK), or derivatives or copolymers thereof.
• the polymers may additionally include one or more from the group consisting antistatics, antioxidants, mould release agents, flameproofing agents, lubricants, colorants, flow enhancers, fillers, including nanofillers, light stabilizers and ultraviolet light absorbers, pigments, anti-weathering agents and plasticisers.
• Suitable alloys include stainless steel, and alloys of aluminium and titanium.
• the bearing cage retainer may be self-lubricating or have a low friction surface to reduce wear. However, this is not essential in all embodiments as the portion of the pump in which the bearing and bearing cage retainer are located will typically be oiled.
• the bearing cage retainer is metallic (e.g. stainless steel) with a polymeric or inorganic (e.g. ceramic) coating, in particular to form the braking surface.
• a polymeric or inorganic (e.g. ceramic) coating in particular to form the braking surface.
• Particularly preferred coatings for forming the braking surface may be selected from the group consisting of PEEK, polyamides (e.g. nylon), polyoxymethylene, PTFE and molybdenum disulphide.
• the bearing cage retainer may comprise a thrust bearing, typically a thrust ball bearing or a thrust roller bearing.
• the thrust bearing will comprise an annular race which engages the bearing cage when in when in a failure configuration.
• the bearing cage retainer may be located on the outer race or inner race, or as part of a bearing damper, bearing retaining nut, between a felt pot and pump body, as part of a lubrication cartridge, as part of the lubrication stack, or as part of an oil delivery nut.
• the bearing cage retainer can be retrofitted to a turbomolecular pump during servicing thereof.
• the bearing cage retainer does not form part of the bearing, i.e. the bearing cage retainer is not integrally formed with the bearing itself.
• the retainer may form part of the inner race and/or outer race. Such an arrangement is advantageous because it may reduce the number of parts in the tolerance stack, and may allow the retainer to move with the damper when in use, allowing clearances between the cage and the retainer to be smaller.
• the invention further provides a bearing damper, bearing retaining nut, lubrication cartridge and/or oil delivery nut comprising a bearing cage retainer according to the invention.
• the invention further provides, a turbomolecular pump comprising a bearing cage retainer according to any other aspect or embodiment of the invention.
• the turbomolecular pump may comprise at least one rotor and at least one stator, each comprising a plurality of rotor blades or stator blades.
• the retainer is in a failure state/configuration the rotor(s) and stator(s), or blades thereof, do not contact one another.
• the invention may thus provide a turbomolecular pump comprising a bearing cage retainer and the turbomolecular pump further comprising a rolling element rotor bearing comprising an outer race, an inner race, and a plurality of rolling elements located within a rotatable bearing cage; a rotatable rotor shaft coupled to at least one substantially annular rotor array; and at least one substantially annular stator array adjacent the rotor array and operably separate therefrom; wherein the rotatable rotor shaft is coupled to the inner race of bearing, and wherein when the bearing cage retainer is in a failure configuration the rotor array and stator array remain separated.
• the invention further provides a turbomolecular pump comprising a rolling element rotor bearing comprising an outer race, an inner race and a plurality of rolling elements located within a bearing cage, the turbomolecular pump further comprising a bearing cage retainer which is configured to engage the bearing cage when the bearing cage has become axially displaced relative to the outer race by a predetermined distance in the direction of the bearing cage retainer.
• the predetermined distance is no more than half the depth of the rolling element, e.g. the half a ball depth.
• Predetermined distances of from about 50 ⁇ to about 3 mm may be used, 0.5 mm being one example.
• the turbomolecular pump comprises at least one rotor and at least one stator.
• the rotor(s) and stator(s), or blades thereof do not contact when the retainer and bearing cage are engaged.
• the invention further provides rolling element rotor bearing system for a turbomolecular pump.
• the bearing system may comprise a rolling element rotor bearing comprising an outer race, an inner race, and a plurality of rolling elements located within a rotatable bearing cage; an axial backstop configured to limit longitudinal axial displacement of the outer race of the bearing; and a bearing cage retainer located below the bearing cage and configured such that at the maximum longitudinal axial displacement limit of the outer race in the direction of the retainer the bearing cage retainer is disengaged from the bearing cage.
• the system is arranged such that in a failure configuration the bearing cage retainer engages the bearing cage and limits the axial displacement of the bearing cage relative to the outer race to an extent such that the bearing cage maintains the separation of the rolling elements.
• Said failure configuration is characterised by a dislocation of the bearing cage by the longitudinal axial displacement of the bearing cage relative to the outer race in the direction of the retainer.
• the rolling elements each remain in rolling, sliding engagement with both inner race and outer race of the bearing.
• the retainer limits the axial displacement of the bearing cage relative to the outer race to an extent such that the bearing cage and, preferably the inner race, remains rotatable, preferably wherein the rotational axis of the bearing cage remains substantially coaxial with a rotational axis of the inner race and/or a rotor shaft of the vacuum pump.
• the invention further provides a method of manufacturing a turbomolecular pump comprising installing a bearing cage retainer as disclosed elsewhere in the application.
• Fig. 1 shows a prior art bearing in situ in a turbomolecular pump.
• Fig. 2 shows a bearing cage retainer according to the invention.
• Fig. 3 shows a bearing cage retainer according to the invention.
• Fig. 4 shows a bearing cage retainer according to the invention.
• Fig. 5 shows a bearing cage retainer according to the invention.
• Fig. 6 shows a bearing cage retainer according to the invention.
• the invention provides a bearing cage retailer for a rolling element rotor bearing in a turbomolecular pump.
• the bearing cage retainer (11) is integrally formed with a bearing retaining nut (12).
• this allows the bearing cage retainer (11) to be introduced during servicing of the turbomolecular pump (4) by simply replacing the previous bearing retaining nut (10) with a bearing retaining nut (12) comprising a bearing cage retainer (11) according to the invention.
• the nut (12) is typically vented and/or castellated in order to allow oil to drain from the bearing.
• the illustrated bearing cage retainer (11) is employed to engage the bearing cage (7) in a failure configuration.
• the bearing cage retainer comprises three pads (17, 18, 19) which each comprise a braking surface (20, 21 , 22). In the failure configuration it is the braking surface (20, 21 , 22) that engages the bearing cage.
• the illustrated bearing retaining nut is a single metallic unitary structure; however, the breaking surface may be in form of a coating, e.g. a polymeric or ceramic coating.
• the breaking surface (20) lies in a plane that intersects both inner race (2) and outer race (5), and which is substantially tangential to the axis (A) of the impeller shaft.
• the rolling element rotor bearing illustrated in figure 2 is a ball bearing.
• the bearing comprises an inner race (2) which is fixedly attached to the impeller shaft (3) of the vacuum pump.
• the impeller shaft (3) rotates about an axis (A) wherein the arrow indicates an upwards direction during normal use.
• the axis of rotation of the inner race (2) and bearing cage are substantially coaxial with the axis (A).
• the illustrated bearing comprises a series of balls (6), typically from about 6 to 12, which are located within a bearing cage (7).
• the bearing cage (7) maintains the circumferentially uniform separation of the balls (6).
• maintaining the substantially uniform separation of the balls maintains the substantially coaxial alignment of the bearing cage and inner race with the axis A.
• the bearing cage (7) may for instance be a snap-fit Torlon® castellated ring.
• the illustrated ball bearing (1) and bearing retaining nut (12) with an integrally formed bearing cage retainer (1 1) form a rolling element rotor bearing system (23) for a turbomolecular pump.
• the outer race (5) is fixedly attached to the bearing support damper (8). Typically, the outer race (5) is attached to the support damper (8) using adhesive. [0059] In figure 2, the bearing cage retainer (11) is separated from the bearing cage by a sufficient axial distance that the bearing cage retainer (1 1) will not engage the bearing cage (7) unless the bearing cage (7) has become downwardly axially displaced relative to the outer race (5) (i.e. dislocated). Figure 2 shows an operational arrangement for the bearing cage retainer (11).
• the bearing retaining nut (10, 12) provides an axial backstop to the bearing support damper (8).
• the bearing retaining nut (10, 12) prevents downward axial displacements of the bearing of greater than 150 ⁇ .
• the bearing cage retainer (1 1) may be arranged such that it is separated from the bearing cage (7) at its most downward operating position by 50 ⁇ or more in an axial direction.
• the separation is from about 50 ⁇ to about 3 mm, 0.5 mm being one example.
• the separation is no more than half the depth of the rolling element, e.g. the half a ball depth.
• the bearing cage (7) may become downwardly axially displaced relative to the outer race (5) and contact the bearing cage retainer (11). This may happen because of contamination in the bearing (1) causing the bearing cage (7) to be ejected from the bearing (1).
• the bearing cage retainer (1 1) may prevent the complete ejection of the bearing cage (7) from the bearing (1) and maintain circumferential separation of the bearing balls (6), preferably circumferential ly uniform separation thereof. By maintaining the separation of the bearing balls (6), the axial alignment of the impeller shaft may be maintained, preventing the pump's rotors from contacting its stators and, thereby, avoiding a catastrophic failure.
• the vacuum pump (4) If the vacuum pump (4) is running at the time a failure configuration is attained an audible noise or change in vibration will alert the user, enabling the pump (4) to be stopped in a controlled manner.
• the bearing cage retainer (11) thereby enables the bearing (1) to fail safely.
• the bearing (1) will have failed and will need to be replaced, typically along with the bearing cage retainer (1 1); however, the vacuum pump (4) and user's instruments (not shown) may be largely unaffected by the failure.
• FIG. 3 illustrates an alternative embodiment of the invention.
• a separate bearing cage retainer (11) is located between felt pot (13) and the pump body (14).
• the bearing cage retainer (11) is axially separated from the bearing cage (7) by a sufficient distance that the bearing cage retainer (11) will not engage the bearing cage (7) unless the bearing cage (7) has become downwardly axially displaced relative to the outer race (5), e.g. in a failure configuration.
• the bearing cage retainer (11) is again preferably vented and/or castellated to enable lubricant to flow around the bearing.
• this bearing cage retainer (11) can be inserted when the felt pot (14) is replaced during a routine service of the vacuum pump (4).
• FIG. 4 illustrates a still further example of the invention in which a bearing cage retainer (1 1) forms part of the lubrication cartridge (15).
• the illustrated bearing cage retainer (11) is axially separated from the bearing cage (7) by a sufficient distance that the bearing cage retainer (1 1) will not engage the bearing cage unless the bearing cage (7) has become downwardly axially displaced relative to the outer race (5).
• this bearing cage retainer (1 1) can be installed when the lubrication cartridge (15) is replaced during a service.
• FIG. 5 illustrates a still further example of the invention in which the bearing cage retainer (1 1) is integrally formed with an oil delivery nut (16).
• the illustrated bearing cage retainer further functions as an oil thrower, which may be advantageous.
• the bearing cage retainer (11) is coupled to the impeller shaft (3). Accordingly, this bearing cage retainer (1 1) rotates about the impeller's axis (A) when the pump is in use, albeit at a different speed to the bearing cage (7).
• a moving bearing cage retainer (11) may help minimise wear on the cage (7) as it is ejected.
• the skilled person will be able to select whether a static or rotating retainer (1 1) is most advantageous for a specific bearing (1) and/or vacuum pump (4).

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Non-Positive Displacement Air Blowers (AREA)
• Rolling Contact Bearings (AREA)
• Mounting Of Bearings Or Others (AREA)

Priority Applications (4)

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Publications (1)

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• 2017
  • 2017-10-05 GB GB1716324.7A patent/GB2567202A/en not_active Withdrawn
• 2018
  • 2018-10-05 EP EP18785716.4A patent/EP3692271B1/en active Active
  • 2018-10-05 US US16/753,623 patent/US11506212B2/en active Active
  • 2018-10-05 WO PCT/GB2018/052840 patent/WO2019069086A1/en not_active Ceased
  • 2018-10-05 JP JP2020519372A patent/JP7288436B2/ja active Active
  • 2018-10-05 CN CN201880079065.6A patent/CN111417788B/zh active Active

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