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
  • F04C14/00—Control of, monitoring of, or safety arrangements for, machines, pumps or pumping installations
  • F04C14/10—Control of, monitoring of, or safety arrangements for, machines, pumps or pumping installations characterised by changing the positions of the inlet or outlet openings with respect to the working chamber
  • F04C14/12—Control of, monitoring of, or safety arrangements for, machines, pumps or pumping installations characterised by changing the positions of the inlet or outlet openings with respect to the working chamber using sliding valves
• • 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
  • F04C14/00—Control of, monitoring of, or safety arrangements for, machines, pumps or pumping installations
  • F04C14/24—Control of, monitoring of, or safety arrangements for, machines, pumps or pumping installations characterised by using valves controlling pressure or flow rate, e.g. discharge valves or unloading valves
  • F04C14/26—Control of, monitoring of, or safety arrangements for, machines, pumps or pumping installations characterised by using valves controlling pressure or flow rate, e.g. discharge valves or unloading valves using bypass channels

Definitions

• This invention relates to gerotor pumps for pumping incompressible fluids, and in particular relates to pumps having a feedback sensing device and more than one outlet port.
• the feedback sensing device is used to reduce outlet flow as outlet back pressure increases, facilitating a reduction of input power requirements at non-critical operating conditions.
• Gerotor pumps have been known for many years.
• a machined lobate, eccentrically mounted rotor element interacts with a mating machined, lobate driven member and a chamber having a circular cross section.
• the eccentrically mounted rotor element having n lobes cooperates with a surrounding lobate ring gear having n+1 lobes, itself contained within a close fitting cylindrical enclosure.
• Such constant displacement pumps are often used with non- compressible fluids, such as water or hydraulic oil.
• the design point for these pumps is usually determined by the flow rate and pressure developed at an idle speed under maximum temperature conditions.
• the pump may be driven directly from the main drive shaft, and will have an operating speed the same as, or directly proportional to, the engine generally. In these circumstances idle may correspond to a speed in the range of 1000 r.p.m. or less, and average speed may be in the 3000 to 4000 r.p.m. range.
• the same pump operating at very high speed, perhaps 7000 to 8000 r.p.m., will pump far more oil than is required, and may be capable of producing far greater pressures than necessary. In that case the majority of the oil will be directed back to the inlet.
• Traditionally a pressure relief valve is used to 'dump' the excess back to a sump.
• U.S. 3,175,800 to Dormer et al. discloses a pressure responsive spool multistage spool valve, but does not alter the fluid supplied to the system.
• U.S. 2,446,730 to Wemp discloses a gerotor pump which works in co- operation with a spool valve to provide pressure relief on a pressure schedule varying with ambient temperamre, but the relief valve otherwise operates in the conventional manner.
• U.S. 3,224,662 to Oldenburg presents a two phase, or vapour cycle air conditioning system in which a radially sliding vane pump is used to compress gas emanating from a low pressure evaporator. Implicity, Oldenburg prevents liquid phase refrigerant from entering the compressor, and thereby causing damage, by providing an input pressure sensing signal to a reciprocating spool valve, causing the compressor to unload, or idle, when full cooling demand is not present.
• U.S. 5,338,161 to Eley discloses a two lobed pump with sliding spool valve which may alternately direct hydraulic fluid to a load or to the pump inlet through an internal bypass passage, but the use of me spool valve is controlled by an operator and is intended to operate as an 'On'-'Off control, in effect.
• None of tiiese earlier inventions provides a constant displacement pump which is self regulating in response to discharge pressure as in the present invention.
• the present invention concerns a positive displacement pump for pumping a fluid from an intake condition to a discharge condition, mat pump comprising a rotor, stator, and follower set having at least one inlet and at least two outlets; a valve controlling at least one of those outlets, that valve sequentially movable among at least (a) a full flow position, (b) a partial flow position, and (c) a pressure relief position; and that valve being responsive to the discharge condition.
• the pump outlets include at least a first outlet and a last outlet;
• the pump comprises an intake, a discharge and a bypass passage;
• the bypass passage, intake, and inlet are in mutual fluid communication;
• the last outlet is in fluid communication with the discharge;
• the first outlet gives onto the valve;
• the valve comprises at least two exhaust ports, a first of them communicating with the discharge and a second one communicating with the bypass passage, and the bypass passage being in fluid communication with the intake; in a full flow position of the valve the first exhaust port being open and the second exhaust port being closed; and in partial flow and pressure relief positions of the valve the first exhaust port being closed and the second exhaust port being open.
• the valve comprises a pressure relief valve having a pressure relief port in fluid communication with the bypass passage; the last outlet is in fluid communication with the pressure relief valve and with the discharge; the pressure relief port is closed in the full and partial flow positions, and open in the pressure relief position, whereby in the pressure relief position the pressure relief port permits fluid to flow from the last outlet to the bypass passage.
• the stator comprises a cavity having a cylmdrical wall for containing the rotor and follower; the rotor is mounted eccentrically relative to the cylindrical wall; and the outlets are radial outlets disposed in the cylindrical wall whereby fluid departing the rotor, stator and follower set traverses that wall.
• a gerotor pump in which the rotor is an inner gerotor; the follower is an outer gerotor having a number of lobate teeth that is one greater than the number of lobate teeth of the inner gerotor, the follower having an equal number of tooth roots therebetween; those inner and outer gerotors engage to create a series of variable geometry chambers therebetween;
• the stator comprises a cylindrical surface for containing the rotor and follower, the cylindrical surface comprising at least two outlets;
• the follower has a mating cylindrical surface for sliding engagement within the cylindrical surface of the stator;
• the follower comprises radial ports, one disposed in each root, whereby during rotation of the follower within the stator the radial ports periodically and sequentially communicate with the outlets;
• the pump has an operating cycle comprising an intake cycle and an exhaust cycle; in the exhaust cycle fluid is expelled from each of the chambers in succession through those radial ports;
• the exhaust cycle comprises a pressurizing portion; in the full flow position the pressurizing portion
• the gerotor pump may be constructed in an embodiment in which the rotor, stator, and follower set has at least three outlets; the valve controls at least two outlets; and the valve is movable among (a) a first, fully open position (b) a second, high reduced flow position (c) a third, low reduced flow position and (d) a fourth, pressure relief position.
• Figure 1 is an horizontal cross section of the gerotor pump of the present invention, and comprises four sequential Figures la, lb, lc, and Id.
• Figure 2 is an horizontal cross section of the gerotor pump of the present invention taken in a plane parallel to and above that of Figure 1 showing the geometry of the intake port and internal bypass flow passages.
• Figure 3 is a partial vertical cross section showing the relationship of the cross sections shown in Figures 1 and 2.
• Figure 1 is taken on section 'X- X' and
• Figure 2 is taken on section 'Y-Y'
• Figure 4 shows a longimdinal section of a spool valve of the gerotor pump of Figure 2 taken on section 'Z-Z' and includes four sequential Figures 4a, 4b, 4c, and 4d corresponding to Figures la, lb, lc, and Id.
• a gerotor pump is shown generally as 2.
• This gerotor pump is one example, or species, of constant displacement, rotating pump having variable geometry chambers.
• the cross section of Figure 1 is taken in a plane perpendicular to the axis of a drive shaft 3 by which the pump is driven.
• Drive shaft 3 transmits torque by a keyway or any mechanical equivalent to a keyway, and might include flats, as shown in Figure 1, or splines.
• Pump 2 comprises a main inlet 4, a stator, or casing 6, an ira ⁇ er gerotor, or keyed lobate rotor 8, a correspondingly lobate outer gerotor or follower ring 10, a bypass passage, or return passage 12 cast into casing 6, a spool valve 14, a discharge 16 and an intake 18.
• rotor 8 comprises eight lobate teeth 20 disposed for co-operation with the nine inwardly oriented lobate teeth 22 of follower ring 10, as is well known in the art.
• Casing 6 comprises a circular cylindrical surface 24 for close tolerance, sliding engagement with a mating external cylindrical face 26 of follower ring 10, and a perpendicularly planar face 28 upon which follower ring 10 may slide and rotate.
• Cylindrical surface 24 is eccentrically disposed relative to shaft 3 to which rotor 8 is mounted.
• a rotor, stator, and follower set of eight and nine teeth generally comprise a first gear of a number of teeth 'n', and a second gear of one more teeth, 'n-t- , and which maintain line contact between the lobes of the rotor and follower.
• the minimum number of teeth will be determined by the number of outlets chosen. Due to the eccentric nature of the mounting a series of chambers 30 is formed between the opposed faces, the lobate surfaces of rotor 8 and the lobate surfaces of follower ring 10.
• Casing 6 also comprises an inlet 36 and exhaust outlets 37, 38, and 39. Each of these outlets is disposed to align periodically with radial ports 34 such that fluid may exit corresponding chambers 30. Outlets 37 and 38 are separated by a first land 40 and outlets 38 and 39 are separated by a second land 41. Radial ports 34 will be blocked during that period of each cycle when sweeping past closed portion 42 of surface 24 between outlet 39 and inlet 36 and again when sweeping past portion 43 between inlet 36 and outlet 37.
• Gerotor pumps, or rotating vane pumps with variable geometry chambers have an operating cycle that may be divided into an intake cycle and an exhaust cycle.
• the intake cycle commences when chamber 30 passes the aphelial point of the eccentric, at which chamber 30 has its minimum volume, approaching nil.
• chamber 30 expands, drawing in fluid through intake port 35.
• the intake cycle ends when the trailing edge of chamber 30 loses contact with intake port 35. Chamber 30 is at its maximum volume.
• the exhaust cycle commences just as the leading edge of radial port 34 exposes the first edge of outlet 37, and continues until the trailing edge of radial port 34 clears the last edge of outlet 39, at which time chamber 30 is again reduced to its minimum, nearly nil, volume at the aphelion.
• the exhaust cycle may variously include both a first, bypass portion, and a second, pressurizing portion. If valve 14 is in the full flow position there will be no bypass portion and the pressurizing portion will occupy the entire exhaust cycle. In that case any diminution in the size of chamber 30 will expel the full flow of working fluid against the prevailing discharge pressure.
• the first portion of the exhaust cycle will expel fluid from chamber 30 through radial port 34, then through an outlet, such as outlet 37, to valve 14, manifold 92 and passage 12 whence it returns to intake 18.
• This bypass portion is followed by a pressurizing portion corresponding to that part of the exhaust cycle in which chamber 30 expels fluid through the balance of outlets, such as outlet 39, which are in fluid communication with discharge 16, and hence sensible to that higher discharge pressure.
• spool valve 14 comprises a hollow cylinder 48 machined into casing 6 and a multi-chamber bobbin 50 disposed for close fitting slidable motion therealong.
• bobbin 50 has two waists, 52 and 54, although the present invention could be practised with a larger number of waists as may be found convenient.
• spool valves of this kind have square shouldered waists, or rebates, although they need not have, provided a flow passageway is created between the cylinder wall and the hollowed out waist portion of the bobbin.
• bobbin 50 has three pistons, indicated in figure 4a as 60a, 60b, and 60c.
• Bobbin 50 is hollow.
• a return spring 62 has a first end disposed within bobbin 50 and a second end captured by end cap 64, which also serves to close off and seal the otherwise open end of cylinder 48.
• a hollow abutting shoulder 66 limits travel of bobbin 50 away from end cap 64 and ensures that face 68 of piston 60c is exposed to the static pressure prevailing in that portion of casing 6 contiguous with a passage 70 leading from throat 47. Face 68 is thus sensible to the prevailing discharge pressure.
• face 68 performs the functions of both a position control sensing device responsive to the discharge condition of the fluid, in this case responsive to the discharge pressure, and as transducer which converts that sensed pressure into a mechanical signal, or mechanical motion to move the spool valve 14 away from its fully opened position as pressure increases. Any number of electromechanical or hydraulic devices and linkages would serve this purpose.
• use of the last piston 60c in this way permits the sensing and transducing functions to be performed with a very small number of parts - a piston and piston face - which are directly connected, are directly in line with, and form an inseparable part of, bobbin 50 of spool valve 14.
• return passage 12 has been formed in casing 6 for carrying fluid from a passage, or manifold 92, generally disposed above cylinder 48, to the intake side of the pump generally, and to the vicinity of inlet 36 in particular.
• cylinder 48 intersects, and is in fluid communication with throat 45 and throat 46.
• Cylinder 48 also intersects apertures 82, and 84 dirough which fluid may under certain conditions flow to discharge 16.
• cylinder 48 intersects three bypass ports 86, 88, and 90, which give onto manifold 92.
• Antechamber 80 of valve 14 adjacent cap 64 is vented to passage 92 as well to prevent oil from being trapped behind bobbin 50.
• Figure la illustrates a first, full flow position in which the pressure at discharge 16 is relatively low, either because the motor driving the pump is only mrning slowly, or because there is little downstream flow resistance. Under these conditions the full flow of fluid expelled from any chamber 30 is directed to discharge 16 and none is directed to passage 12. For example, this may be any condition up to a given discharge pressure, perhaps 50 psig.
• Piston 60c remains seated against hollow shoulder 66. Throats 45 and 46 are open to cylinder 48 and ports 82 and 84 permit fluid to flow across me space provided by waists 52 and 54 and exit to discharge 16. Passage 70 is in unimpeded fluid communication with discharge 16. Ports 86, 88 and 90 are closed off by pistons 60a, 60b and 60c.
• first bypass return port 90 opens, permitting fluid to flow upwardly into, and along manifold 92 in fluid communication with bypass or return passage 12.
• the pressure of the fluid discharged along this path is only greater than the pump inlet pressure, or relative vacuum, by an amount determined by the fluid resistance in those passages. This amount is small relative to load pressures.
• Land 40 serves to segregate this unpressurized flow from the higher pressure required to. force hydraulic fluid out discharge 16. For example, if the first discharge pressure were as above, the exit port 82 would close at 50 psig.
• FIG. Id there is a pressure relief position in which the discharge pressure is so high that bobbin 50 has been displaced far enough for piston 60c to uncover port 90, which is, in effect, a high pressure relief valve.
• Port 90 is only partially uncovered leaving a slit, or orifice, such that die pressure drop across the orifice corresponds to some pressure greater than the relief pressure. Consistently with the above example, this pressure relief might occur at 70 psig.
• These example values are arbitrarily chosen, and are merely intended to illustrate that at each stage the discharge pressure is increasing. In the pressure relief mode the work done to compress the fluid to the relief pressure is lost, but this amount is less than the full flow by the amount vented through ports 86 and 88.
• the present invention may be extended to a variable geometry chamber, constant displacement pump having a plurality of outlets giving sequentially onto a suitable valve. Of those outlets at least one, the last, corresponding to outlet 39, is in fluid communication with discharge 16.
• outlet 37 corresponds to a first exhaust port, aperture 82, which leads to discharge 16, and a second exhaust port, bypass port 86, which leads to the bypass, or return passage 12.
• outlet 38 corresponds to aperture 84 and bypass port 88.
• the valve 14, and more particularly bobbin 50 reciprocates sequentially between the full flow and pressure relief positions as pressure increases or decreases, traversing intermediate positions in order.
• spool valve 14 is self actuating, responding to load conditions at the outlet.
• flow through the pump may increase in absolute terms as the motor driving the pump turns more quickly, the flow displaced per revolution decreases. In this sense the flow is reduced relative to the fully open flow that would otherwise occur at that rate of revolution.
• the spool valve cuts back the flow as the outlet pressure increases, that is to say, as the pump becomes more heavily loaded or as it is driven more rapidly by, for example, an accelerating motor. It permits maximum flow per revolution when the pump is unloaded, or if the rotor is being driven at a lower speed, such as idle.
• the principles of the present invention may be practised, with suitable modifications, with a gerotor pump of any chosen number of lobes which satisfy the condition that the spool have at least three regimes, the first being a fully open flow, the second a partially open flow, and the third a pressure relief flow.
• the principles of the present invention may also be practised with reciprocating vane pumps, the efficacy thereof depending on the quality of the seals.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Details And Applications Of Rotary Liquid Pumps (AREA)
• Rotary Pumps (AREA)
• Multiple-Way Valves (AREA)

Priority Applications (7)

Applications Claiming Priority (1)

Publications (1)

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ID=4173104

Family Applications (1)

Country Status (7)

Cited By (3)

Families Citing this family (4)

Citations (6)

• 1995
  • 1995-08-14 JP JP9508763A patent/JPH11510871A/ja active Pending
  • 1995-08-14 WO PCT/CA1995/000481 patent/WO1997007337A1/en active IP Right Grant
  • 1995-08-14 AT AT95927609T patent/ATE197729T1/de not_active IP Right Cessation
  • 1995-08-14 EP EP95927609A patent/EP0845080B1/de not_active Expired - Lifetime
  • 1995-08-14 DE DE69519482T patent/DE69519482D1/de not_active Expired - Lifetime
  • 1995-08-14 AU AU31597/95A patent/AU3159795A/en not_active Abandoned
  • 1995-08-14 CA CA002229056A patent/CA2229056C/en not_active Expired - Lifetime

Patent Citations (6)

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