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EP-4739915-A1 - CLAW BOOSTER PUMP

EP4739915A1EP 4739915 A1EP4739915 A1EP 4739915A1EP-4739915-A1

Abstract

A claw booster pump (104) comprising: a pair of parallel shafts (202, 204) arranged to rotate in opposite directions to each other; a pair of rotors (206, 208) secured to the pair of shafts (202, 204), respectively, the pair of rotors (206, 208) including a first rotor (206) having a claw portion (220) projecting in a radial direction and a second rotor (208) having a recess (228) into which the claw portion (220) enters in use; a pump chamber (210) accommodating the pair of rotors (206, 208); an inlet (114) formed in the pump chamber (210) on one side of a plane (232) containing axes of the pair of shafts (202, 204); and an outlet (116) formed in the pump chamber (210) on another side of the plane (232); wherein a maximum capacity of the claw booster pump (104) is less than or equal to 40m 3 /hr.

Inventors

  • SCHOFIELD, NIGEL PAUL
  • HOLBROOK, ALAN ERNEST KINNAIRD
  • BEDWELL, DAVID

Assignees

  • Edwards Limited

Dates

Publication Date
20260513
Application Date
20240605

Claims (18)

  1. 1. A claw booster pump comprising: a pair of parallel shafts arranged to rotate in opposite directions to each other; a pair of rotors secured to the pair of shafts, respectively, the pair of rotors including a first rotor having a claw portion projecting in a radial direction and a second rotor having a recess into which the claw portion enters in use; a pump chamber accommodating the pair of rotors; an inlet formed in the pump chamber on one side of a plane containing axes of the pair of shafts; and an outlet formed in the pump chamber on another side of the plane; wherein a maximum capacity of the claw booster pump is less than or equal to 40m 3 /hr.
  2. 2. The claw booster pump of claim 1 , wherein the claw booster pump is a double claw pump.
  3. 3. The claw booster pump of claim 1 or 2, wherein the maximum capacity of the claw booster pump is less than or equal to 30m 3 /hr.
  4. 4. The claw booster pump of claim 3, wherein the maximum capacity of the claw booster pump is between 10m 3 /hr and 30m 3 /hr.
  5. 5. The claw booster pump of any preceding claim, wherein at least one rotor of the pair of rotors is formed from a polymer, and wherein the polymer is preferably selected from a group of polymers consisting of polyether ether ketone, PEEK; polyphenylene sulphide, PPS; a fibre-reinforced polymer; fibre-reinforced PPS; glass fibre-reinforced PPS.
  6. 6. The claw booster pump of any preceding claim, wherein a distance between the pair of parallel shafts in the radial direction is less than or equal to 50mm, preferably less than or equal to 40mm.
  7. 7. The claw booster pump of any preceding claim, further comprising a housing defining the pump chamber, the housing having one or more dimensions selected from a group of dimensions consisting of: a length of less than or equal to 250mm, the length being in a direction parallel to the axes of the pair of shafts width height; a width of less than or equal to 150mm, the width being in a radial direction between the pair of shafts; and a height of less than or equal to 100mm, the height being in a radial direction that is perpendicular to the width.
  8. 8. The claw booster pump of any preceding claim, wherein the claw booster pump is a multi-stage pump having at least a first pumping stage and a second pumping stage, wherein a maximum capacity of the first pumping stage is less than or equal to 40m 3 /hr, and a maximum capacity of the second pumping stage is less than that of the first pumping stage.
  9. 9. The claw booster pump of any preceding claim further comprising: a module comprising a motor, gears, and bearings, for mounting and driving the pair of parallel shafts, the pair of parallel shafts extending out of said module into the pump chamber portion.
  10. 10. The claw booster pump of any preceding claim, wherein the pair of rotors are each formed of multiple rotor slices mounted on and fixed to the respective shafts.
  11. 11 . The claw booster pump according to claim 10 when dependent on claim 8, wherein the multiple stages comprise rotor sections with different numbers of rotor slices.
  12. 12. The claw booster pump of claim 10 or 11 , wherein the rotor slices are aligned and fixed to the respective shafts with cross pins.
  13. 13. The claw booster pump of claim 9 or claims 10 to 12 when dependent on claim 9, wherein an output shaft power of the motor in typical continuous use is less than or equal to 150W, preferably less than or equal to 100W.
  14. 14. A method of manufacture of a claw booster pump according to any one of claims 10 to 12 when dependent upon claim 9, comprising mounting a pair of shafts within and extending out of a drive module comprising a motor, gears and bearings; mounting at least one slice of a claw rotor onto each of said pair of shafts; fixing said slices of rotor in place; and arranging a pump chamber housing around said rotor.
  15. 15. The method of manufacture of claim 14, further comprising initial steps of: determining a capacity of said claw booster pump; and selecting a number of rotor slices to mount on said pair of shafts.
  16. 16. The method of manufacture of claim 15, comprising a further initial step of selecting a length of said pair of shafts in dependence upon said determined capacity.
  17. 17. The method of manufacture according to claim 15 or 16 wherein the determined capacity lies between 6 and 40 m 3 /hr, preferably between 10 and 40 m 3 /hr.
  18. 18. A pumping system comprising: a claw booster pump, the claw booster pump being in accordance with any of claims 1 to 13; and a primary pump, wherein the outlet of the claw booster pump is fluidly coupled to an inlet of the primary pump.

Description

CLAW BOOSTER PUMP FIELD OF THE INVENTION The present invention relates to a claw pump for use as a booster pump at the inlet of a primary pump in a pumping system. BACKGROUND A roughing pump, or backing pump, is a vacuum pump (typically, a dry vacuum pump) that is used to initially evacuate a vacuum system. This may be done as a first stage towards achieving high vacuum in the vacuum system. The roughing or backing pump may be referred to as a “primary pump”. Once a “rough vacuum” is achieved in the vacuum system by the roughing or backing pump (i.e., the primary pump), a “secondary pump” may operate so as to establish the high vacuum in the vacuum system. Roughing or backing pumps (i.e., the primary pump) are typically those that work efficiently at atmospheric pressure. Many vacuum pumps, for example primary pumps used in semiconductor fabrication facilities, operate at low inlet pressures, e.g. of less than about 5mbar, for most of the time. In such cases, booster pumps (such as Roots blowers) are used at the inlet to the primary pump to give a higher pumping speed at typical process pressures. This allows for the primary pump to be much smaller, which tends to save substantial cost and power consumption. SUMMARY OF THE INVENTION For small primary pump applications (i.e., applications in which the primary pump has a maximum capacity of, or pumps less than or equal to, 30m3/hr of gas, e.g. less than or equal to 20m3/hr of gas, or less than or equal to 15m3/hr of gas, or less than or equal to 10m3/hr of gas), the inlet pressures at the primary pump can be similar to those of larger applications, such as semiconductor fabrication applications. For example, the inlet pressures at the primary pump may be O.l mbar to 5mbar. An example of a small primary pump application includes, but is not limited to, the pumping of gas from the exhaust of a turbo pump used in for example a mass spectrometer. In these small primary pump applications, a booster pump may be used to reduce the size and power of the primary pump. However, conventionally, the use of booster pumps in small primary pump applications has been avoided due to the increased cost and complexity of such a system, and due to the poor compression ratio (for example, due to the high clearance leakage relative to the swept volume) of booster pumps, e.g. when scaled down. Aspects provided herein provide a booster pump which tends to have a high compression ratio, low cost, and tends to enable significant net power saving. In an aspect, there is provided a claw booster pump comprising: a pair of parallel shafts arranged to rotate in opposite directions to each other; a pair of rotors secured to the pair of shafts, respectively, the pair of rotors including a first rotor having a claw portion projecting in a radial direction and a second rotor having a recess into which the claw portion enters in use; a pump chamber accommodating the pair of rotors; an inlet formed in the pump chamber on one side of a plane containing axes of the pair of shafts; and an outlet formed in the pump chamber on another side of the plane; wherein a maximum capacity of the claw booster pump is less than or equal to 40m3/hr. The claw booster pump may be a double claw pump. The maximum capacity of the claw booster pump may be less than or equal to 30m3/hr. The maximum capacity of the claw booster pump may be between 10m3/hr and 30m3/hr. At least one rotor of the pair of rotors may be formed from a polymer. The polymer may be selected from a group of polymers consisting of polyether ether ketone, PEEK; polyphenylene sulphide, PPS; a fibre-reinforced polymer; fibre-reinforced PPS; glass fibre-reinforced PPS. A distance between the pair of parallel shafts in the radial direction may be less than or equal to 50mm. A distance between the pair of parallel shafts in the radial direction may be less than or equal to 40mm. A distance between the pair of parallel shafts in the radial direction may be about 32mm. The claw booster pump may further comprise a housing defining the pump chamber. The housing may have one or more dimensions selected from a group of dimensions consisting of: a length of less than or equal to 250mm, the length being in a direction parallel to the axes of the pair of shafts width height; a width of less than or equal to 150mm, the width being in a radial direction between the pair of shafts; and a height of less than or equal to 100mm, the height being in a radial direction that is perpendicular to the width. The claw booster pump may be a multi-stage pump having at least a first pumping stage and a second pumping stage. A maximum capacity of the first pumping stage may be less than or equal to 40m3/hr. A maximum capacity of the second pumping stage may be less than that of the first pumping stage. The claw booster pump may further comprise a motor arranged to drive one or more of the shafts, wherein an output shaft power of the motor in typical continuous use is less t