EP0055084A1 - Compresseurs du type à palettes coulissantes et rotor disposé excentriquement - Google Patents

Compresseurs du type à palettes coulissantes et rotor disposé excentriquement Download PDF

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Publication number
EP0055084A1
EP0055084A1 EP19810305927 EP81305927A EP0055084A1 EP 0055084 A1 EP0055084 A1 EP 0055084A1 EP 19810305927 EP19810305927 EP 19810305927 EP 81305927 A EP81305927 A EP 81305927A EP 0055084 A1 EP0055084 A1 EP 0055084A1
Authority
EP
European Patent Office
Prior art keywords
compressor
stator
vacuum relief
rotor
passage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP19810305927
Other languages
German (de)
English (en)
Inventor
Richard John Gray
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hydrovane Compressor Co Ltd
Original Assignee
Hydrovane Compressor Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hydrovane Compressor Co Ltd filed Critical Hydrovane Compressor Co Ltd
Publication of EP0055084A1 publication Critical patent/EP0055084A1/fr
Ceased legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
    • F04C28/06—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids specially adapted for stopping, starting, idling or no-load operation

Definitions

  • the present invention relates to rotary compressors of the sliding vane eccentric rotor type.
  • Such compressors include a stator within which a rotor is eccentrically mounted for rotation, the rotor and stator together defining a crescent shaped working space.
  • a plurality of equispaced radial slots are formed in the rotor and these accommodate freely movable vanes which divide the working space into a number of cells.
  • the stator is provided with appropriately positioned inlet and outlet ports and-as the rotor is rotated each cell gradually increases in volume thereby drawing in air through the inlet and thereafter decreases in volume until its volume is virtually zero at which point it communicates with the outlet port or ports through which the air which has been compressed within the cell is discharged.
  • Such compressors are generally "oil sealed”, that is to say oil is circulated within the compressor by differential pressures within it and injected into the compression cells to ensure an adequate seal between the vanes and the stator and the end plates by which the stator is closed.
  • the oil is entrained in the compressed air in the form of droplets and is subsequently removed, generally by two oil separation stages, and returned to the compressor sump.
  • Compressors of this type conventionally incorporate an unloader valve arranged to restrict or close the compressor inlet and controlled by a servo valve which is responsive to the compressor delivery pressure. If the demand for compressed air should fall substantially or stop altogether the compressor delivery pressure rises above its normal working value and the unloader valve restricts or closes the inlet so that a reduced amount of air, or no air at all, is compressed so that the compressor pressure stops rising and the power consumption of the compressor drops. In this unloaded condition not only is the compressor pressure higher than usual but the pressure at the inlet drops to below atmospheric pressure.
  • compressors are provided with a vacuum relief valve responsive to the compressor inlet pressure which bleeds high pressure air from.the compressor casing or secondary oil separation unit to the compressor inlet when the compressor is off- loaded.
  • This air is drawn into the rotor stator unit through the normal inlet so that when even totally off- loaded the compressor is continually compressing a small volume of air.
  • This constant circulation of-air around the compressor when it is offloaded improves the force - distribution acting on the vanes and largely overcomes the problem of their instability.
  • the amount of air circulated is relatively small it does have the effect of increasing the power consumed by the compressor when it is running off-load.
  • Compressors of this type are commonly used for powering tools and machines of various kinds, such as pneumatic drills, and generally have a rated output pressure of about 7 bar (100 psi).
  • the volume of air that must be circulated when the compressor is offloaded to avoid blade chatter leads to an increase in power consumption.
  • compressors having a higher output pressure of e.g. 10 bar (150 psi) With such compressors the volume of air that must be circulated using.a conventional vacuum relief valve to prevent blade chatter when the compressor is offloaded is considerably greater and the power consumption of such higher pressure compressors when offloaded can be. unacceptably high.
  • a rotary compressor of sliding vane eccentric rotor type including a stator, a rotor eccentrically mounted for rotation within the stator and defining together with the stator a crescent shaped working space, a plurality of vanes slidably received in radial slots in the rotor and, in use, contacting the stator thereby dividing the crescent shaped working space into a plurality of compression cells, an unloader valve arranged to restrict or close the compressor inlet when the compressor pressure rises above its normal working value, a vacuum relief valve responsive to the unloaded condition of the compressor and a vacuum relief passage controlled by the vacuum relief valve, communicating with a space which, in use, is substantially at the compressor delivery pressure, and passing through the stator and communicating with the crescent shaped working space whereby, in use, when the compressor enters the unloaded condition high pressure air is bled directly into one of the compression cells.
  • the vacuum relief valve may be responsive to the change in either of these pressures. However in the preferred embodiment the vacuum relief valve is acted on by the inlet pressure opposed by atmospheric pressure.
  • the vacuum relief passage communicates with the space between the stator and the compressor casing.
  • the compressor rotor rotates at a relatively high speed, and it is therefore desirable that the vacuum relief passage communicates with the crescent shaped working space at two or more - points along its length.
  • the vacuum relief passage includes a passage extending along the length of the stator wall communicating with the crescent shaped working space through a plurality of spaced transverse passages.
  • the vacuum relief valve bleeds high pressure air to the point in the rotor stator unit where it is most needed rather than into the inlet passage as before. This has the result that the volume of bleed air which is required to produce the desired result is considerably less than previously and the power consumed by the compressor when it is offloaded is therefore also considerably less.
  • the vacuum relief passage preferably communicates with the crescent shaped working space at a point or points positioned between 35 0 and 100° from the outlet in the stator in the direction of rotation of the rotor and more preferably immediately downstream of the point where the compressor inlet begins to communicate with the crescent shaped space, i.e. at that point at which the blades start to move out of their slots.
  • the inlet passage generally communicates with the crescent shaped working space via a generally kidney-shaped recess formed in one of the compressor end plates. This recess extends around the end plate for about 135°, that is to say for as many degrees as each compression cell expands in volume before it starts to contract again thereby compressing the air.
  • a preferred embodiment of the present invention includes a further passage arranged to bleed high pressure air into each radial slot during at least a part of each revolution of the rotor.
  • the further passage extends transverse to the rotor axis through one of the compressor end plates and communicates both with the vacuum relief passage and with the space within the stator at a point which will communicate with the space behind each blade sequentially as the rotor rotates. It is found experimentally that the blades tend to reach their position of maximum instability at 25° to 65 0 , especially 45° before the outlet in the stator and thus in the preferred embodiment the further passage communicates with the space within the stator at a point spaced between 25° and 65° before the outlet in the stator in the direction of rotation of the stator. Thus, just as each blade is reaching its point of maximum instability high pressure air is briefly bled into the space behind it which reduces the force tending to pull it out of contact with the stator or even produces a force urging it against the stator.'
  • a stator 2 includes an eccentric bore within which is a rotor 4 mounted on a shaft 6 which is sup-- ported in bearings in two end plates 8 and 10 at respective ends of the stator.
  • the rotor 4 has eight equispaced radial slots 12 formed in it each of which contains a freely movable vane 14.
  • the rotor and stator together define a crescent shaped working space which is divided into compression cells by the vanes 14.
  • the shaft 6 is coupled via a drive coupling, generally designated 16, to a drive motor (not shown).
  • the end plate 8 remote from the drive end is provided with a generally kidney shaped recess (not shown) extending on its inner surface over about 135 0 which communicates with an inlet passage 18.
  • the inlet passage 18 is controlled by an unloader piston 20 forming part of an unloader valve 22 which is actuated by a servo valve 23 which is- responsive to the compressor supply pressure.
  • the stator is provided with a plurality of outlet ports 24 extending along its length, and extending around the stator is an impingement shield 26 connected to the drive end plate 10.
  • the rotor In use, the rotor is rotated clockwise, as seen in Figure 2, and the vanes are maintained in contact with the inner wall of the stator by virtue of centrifugal force. As each compression cell passes the inlet it is increasing in volume and thus draws air in. Subsequently its volume decreases to nearly zero thereby compressing the air which is discharged through the ports 24. Oil is injected into the compression cells by means which are not shown to lubricate the vanes and ensure an adequate seal between them and the stator and the end plates and the compres-- sed air is therefore charged with oil droplets.
  • the compressed air impinges with high velocity against the impingement shield and the majority of the oil droplets coalesce against it and drop down to the bottom of the outer compressor casing 28 which constitutes a sump and from which oil is withdrawn and reinjected into the stator under the action of pressure differentials within the compressor as is conventional.
  • the compressed air flows to the left, as seen in Figure 1, between the impingement shield and the stator and then to the right and thence through a passageway 30 connecting the compressor casing 28 with a secondary separator casing 32 secured to it.
  • the air then passes through a tubular secondary separation element 34 made of _e.g: ceramic material and thence out of the compressor to its point of use. Any remaining oil droplets are coalesced and removed from the air by the element 34 and drip down to the bottom of the casing 32 whence it is returned to the compressor inlet by a passageway, not shown, under the action of the pressure differential.
  • the normal working pressure of the compressor is 10 bar. If the demand for compressed air should drop substantially the compressor pressure, i.e. the delivery pressure which is substantially equal to the pressure within the casings 28 and 32, will rise and this increase in pressure is sensed by the servo valve which progressively closes the unloader valve which restricts the inlet 18 and therefore reduces the volume of air being compressed.
  • the servo valve and unloader valve are so arranged that when the demand for compressed air falls to substantially zero the unloader valve completely closes the inlet 18.
  • a vacuum relief valve which is responsive to the reduced pressure which occurs in the inlet 18 when the compressor is on no-load to bleed a small volume of high pressure air back into the compressor.
  • the vacuum relief valve comprises a valve member 38 carrying an 0 ring 40 and connected to a piston 42 which is acted on by a return spring 44 and on one side (the right hand side as seen in Figure 1) by compressor inlet pressure via a passage 46 which communicates with the inlet 18 and on the other side by atmospheric pressure via a passage 48 which communicates with the atmosphere.
  • the 0 ring 40 In its normal position, that is to say the position shown in Figure 1 with the compressor in normal operation, the 0 ring 40 completely seals a longitudinal bore 50 in the end plate 8.
  • the bore 50 communicates with a transverse bore 52 which communicates with a further transverse bore 54 which in turn communicates with a bore .56 extending along the length of the stator wall.
  • the bore 56 communicates with the interior of the stator at a point immediately downstream of the upstream end of the inlet recess through a plurality of transverse bores 58 spaced along the length of the stator.
  • transverse bore 60 which terminates adjacent the side of the-valve member 38 and which communicates with a longitudinal bore 62 which communicates with a longitudinal bore 64 in the stator which in turn communicates with a transverse bore 66 in the stator which terminates at the surface of the stator.
  • the passage 52 in the end plate 8 communicates with a single longitudinal bore 70 which communicates with the working space at a point about 45 0 upstream of the outlets 24 in the direction of rotation of the rotor and radially positioned that it communicates with the interior of each slot 12 behind the blades as they pass. It is found that it is approximately at this 45 0 position that maximum instability of the blades occurs when the compressor is off-loaded.
  • the vacuum relief valve when passing air through the bores 58 a brief pulse of air at substantially delivery pressure will be injected behind each blade through the bore 70 thus reducing the vacuum in this space or even producing a superatmospheric pressure and thereby reducing the force which tends to pull the blade out of contact with the stator.
  • the provision of the bore 70 may reduce the volume of air that needs to be passed through the bores 58 to eliminate blade rattle and therefore also further reduce the power consumed when the compressor is offloaded.
EP19810305927 1980-12-23 1981-12-17 Compresseurs du type à palettes coulissantes et rotor disposé excentriquement Ceased EP0055084A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8041245 1980-12-23
GB8041245A GB2089891B (en) 1980-12-23 1980-12-23 Rotary positive-displacement fluidmachines

Publications (1)

Publication Number Publication Date
EP0055084A1 true EP0055084A1 (fr) 1982-06-30

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ID=10518203

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19810305927 Ceased EP0055084A1 (fr) 1980-12-23 1981-12-17 Compresseurs du type à palettes coulissantes et rotor disposé excentriquement

Country Status (2)

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EP (1) EP0055084A1 (fr)
GB (1) GB2089891B (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2602833A1 (fr) * 1986-08-12 1988-02-19 Eagle Ind Co Ltd Pompe a palettes
CN113586450A (zh) * 2021-07-05 2021-11-02 王丽娜 一种真空泵

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH152328A (de) * 1930-09-25 1932-01-31 Sulzer Ag Rotationskompressor.
US3399826A (en) * 1966-08-26 1968-09-03 Cenco Instr Corp Pump with auxiliary vacuum pumping stage
GB2020363A (en) * 1978-03-13 1979-11-14 Imi Fluidair Ltd Rotary compressor
US4295804A (en) * 1978-11-07 1981-10-20 Adriano Pezzot Intermediately cooled air vacuum pump with balancing of the pressures

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH152328A (de) * 1930-09-25 1932-01-31 Sulzer Ag Rotationskompressor.
US3399826A (en) * 1966-08-26 1968-09-03 Cenco Instr Corp Pump with auxiliary vacuum pumping stage
GB2020363A (en) * 1978-03-13 1979-11-14 Imi Fluidair Ltd Rotary compressor
US4295804A (en) * 1978-11-07 1981-10-20 Adriano Pezzot Intermediately cooled air vacuum pump with balancing of the pressures

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2602833A1 (fr) * 1986-08-12 1988-02-19 Eagle Ind Co Ltd Pompe a palettes
CN113586450A (zh) * 2021-07-05 2021-11-02 王丽娜 一种真空泵
CN113586450B (zh) * 2021-07-05 2022-12-09 厦门微能电子科技有限公司 一种真空泵

Also Published As

Publication number Publication date
GB2089891B (en) 1984-04-26
GB2089891A (en) 1982-06-30

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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Effective date: 19821221

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Effective date: 19850721

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Inventor name: GRAY, RICHARD JOHN