US3238884A

US3238884A - Variable positive displacement pump with rising pressure curve

Info

Publication number: US3238884A
Application number: US208473A
Authority: US
Inventors: George W Wright
Original assignee: Tokheim Corp
Current assignee: Tokheim Corp
Priority date: 1962-07-09
Filing date: 1962-07-09
Publication date: 1966-03-08
Anticipated expiration: 1983-03-08

Description

March 8, 1966 G. w. WRIGHT 3,238,834

VARIABLE POSITIVE DISPLACEMENT PUMP WITH RISING PRESSURE CURVE Filed July 9, 1962 6 Sheets-Sheet 1 INVENTOR.

GEORGE W. WEIGHT 3 a 9 398 ATTORNEY March 8, 1966 c. w. WRIGHT 3,238,884

VARIABLE POSITIVE DISPLACEMENT PUMP WITH RISING PRESSURE CURVE Filed July 9, 1962 6 Sheets-Sheet 2 I l k 0 I I I l l I I I /A/IIO l I fi I: Q /oa g I06 I03 I04 I ()1 I Q) l K 430 17/16 7 l2?. l \H4L L30 Il8 I 6 Isa l j me; L\\\ 946a A NI m 1 4 -|44 l l *f' :4s 1 I 14a 7:; 41 1 17 i l x T I 3 INVENTOR.

Gamma W. WRIGHT HTTORNEY March 8, 1966 wm 3,238,884

VARIABLE POSITIVE DISPLACEMENT PUMP WITH RISING PRESSURE CURVE Filed July 9, 1962 6 Sheets-Sheet 5 5 I Fig.4

. I84- |66 Eli.

23 I I aaa A 220 F 134 j a O I36 3 we I26 &4- I68 I68 2,8? I74 176 L 2 Fla/Ia 6 glam--75 A i l 2fl9- INVENTOR. Gamma W. WRIGHT Arvoawzv MWIM March 8, 1966 G. w. WRIGHT VARIABLE POSITIVE DISPLACEMENT PUMP WITH RISING PRESSURE CURVE 6 Sheets-Sheet 4 Filed July 9, 1962 INVENTOR. QEORGEW WRIGHT BY Q 4 4 fi'rromzv Fig.7

March 8, 1966 G. w. WRIGHT 3,238,884

VARIABLE POSITIVE DISPLACEMENT PUMP WITH RISING PRESSURE CURVE Filed July 9, 1962 6 Sheets-Sheet O 2.0 4-0 5 7O 8O G. P. H. i i P151. F I 9. 9 10 r l PCLOSED Pasron FULL Fouc'roilz Hcnfim. 8 Qmncz \N PISTON Fuu. EDUCTOR HcTmN I 6 a NEEDLE V LvE CITOSED- -Monu=|En [Dug/TOR FICTION NEED -EVALVE 3 OPEN. 4- 1 FREssuRE CONTROL PISTON Removes.

0 1o 20 '30 4-0 50 so 70 a0 so 100 G.P.H.

INVENTOR. GEoRaE W. Wanam- T'TORNEY March 8, 1966 G. w. WRIGHT 3,238,334

VARIABLE POSITIVE DISPLACEMENT PUMP WITH RISING PRESSURE CURVE Filed July 9, 1962 6 Sheets-Sheet 6 44 IIIIIIIIIIIII ZIII! I I I [PRESSURE CONTROL PIST?N REVIIOVED 10 4M 10 6'0 0 .90 Jfid INVENTOR. (250m: W WRIGHT ATTORNEY nited States Patent VARIABLE PUSiTlWE DISPLACEMENT PUMP WITH RISING PRESSURE QURVE George W. Wright, Yoder, ind, assigncr to Tokheim Corporation, Fort Wayne, End, a corporation of Indiana Filed July 9, 1962, Ser. No. 208,473

22 Claims. (Cl. HIS-12d) This invention relates to a variable positive displacement pump in which the Output pressure rises with the rate of delivery flow, and especially to an automotive fuel pump which at low delivery flows provides fuel at relatively low pressure and at high delivery flows provides fuel at relatively higher pressure.

In an automotive fuel system, for example on trucks and other heavy duty automotive equipment, and in various other pumping systems, the pump output is delivered through a line of considerable length to a remote point of use at which the how may necessarily be restricted, as by the valve port of a control valve, such as the float valve in a carburetor. At low flow rates, such line and restriction exert little back pressure, and substantially full pump pressure must be controlled by the valve. At high flow rates, on the other hand, the line and restriction exert high back pressure and reduce flow. In a conventional variable positive displacement pump, the output pressure of the pump drops as the delivery rate and volume increases. Accordingly, in a remote delivery system as described, the pump delivery pressure drops as the back pressure rises, and the net result is a serious loss of delivery pressure and volume at the point of use. In an automotive fuel system, this loss produces starvation of the carburetor, which results in a lean fuel mixture and loss of power and may cause damage to the engine. If a pump is used which has sufiicient high-flow pressure to avoid these difficulties, its even greater pressure at low.

flow causes control difliculties, such as leakage at the valve and flooding of the carburetor.

The falling pressure curve of a conventional variable displacement pump produces similar disadvantages in other situations. In a gasoline dispensing system, for example, the relatively high pressure produced at low flow causes difiiculties of control of the dispensing nozzle, and the progressively lower pressure at high flow reduces delivery and etficiency.

It is the object of the present invention to produce a variable positive displacement pump having a rising pressure output curve, that is, a pump which produces relatively low pressure at low flow or cut-off and progressively higher pressure at higher rates and volumes of flow. It is an especial object of the invention to provide a fuel pump and fuel pump system in which the delivery pressure at the point of use can be held constant at varying flow rates and can be made to rise with increasing flow rates, so that for increasing fuel demand, the system provides increasing flow at prograssively increasing pressure.

The invention may be applied to a variable-delivery positive-displacement pump provided with a movable displacement element, such as a sliding ring, which is movable between maximum and minimum displacement positions and which is urged toward its maximum displace ment or delivery position by a biasing means such as a spring. Such a pump also has displacement control meansdisplacement reducing means-responsive to pump output pressure for opposing the spring bias and moving the movable element toward its minimum displacement position in response to increasing output pressure.

The variable displacement element, the displacement- "ice increasing biasing means, and the displacement-reducing means may take various forms, in accordance with conventional practice. For example, the variable displacement element may be a sliding ring which moves in a translatory movement as in Hankel et al. Patent No. 2,922,376, or may be a pivoted ring as in De Lancey et al. Patent No. 2,669,189. The displacement reducing means may be provided by the ring itself and its arrangement relative to the suction and pressure areas of the pump, and may be responsive to pressure operating either internally as shown in Patent No. 2,669,189 or externally as shown in Patent No. 2,922,376. The displacement control means, alternatively, may be in the form of a hydraulic motor element such as a piston or diaphragm, which is exposed to delivery pressure, as in Lane Patent No. 2,142,275. Further, the displacement reducing means may be a one-stage arrangement in which the control is directly and continuously responsive to the output pressure of the pump, or maybe a two-stage arrangement, in which the actuating pressure is controlled by a pressure responsive valve, as in De Lancey Patent No. 2,635,551.

In accordance with the present invention, the pump also includes a pressure raising means which is responsive to pump output how and which, in response to such flow, tends to move the variable displacement element toward its maximum delivery position. The pressure raising means thus acts in opposition to the action of the displacement reducing means, and in support of or to increase the displacement-increasing effect of the biasing means.

The net result of the combination is to raise, progressively with increasing flow, the output pressure required to move the variable displacement element against the biasing means toward its minimum delivery position, and thus to raise the output pressure progressively with increasing flow.

In a preferred arrangement, the pressure raising means may consist of a piston or other hydraulic motor element which is responsive to the difference between the output pressure of the pump and a lower pressure produced by delivery flow, for example, by an eductor actuated by the delivery flow. Similar results may also be obtained by a motor responsive to reduced pressure produced by the eductor alone, or by a motor responsive to a pressure differential across a restriction in the output line. In any case, the pressure raising means is connected to act in oppposition to the displacement reducing means, so that the displacement reducing means has its maximum effect at minimum flow rates, and the pressure raising means has its maximum effect at maximum flow rates.

The accompanying drawings illustrates the invention. In such drawings:

FIG. 1 is a diagrammatic view of an automotive fuel system in which a pump embodying the invention is placed in the line between the tank and the carburetor of the system;

FIG. 2 is a diagrammatic view of a preferred embodiment of the invention, for purposes of showing its general operation;

FIG. 3 is a vertical section of the automotive fuel pump shown in FIG. 1;

FIG. 4 is a section taken on line 4-4 of FIG. 3 and looking upward;

FIG. 4a is a partial section similar to FIG. 4 showing a modification;

FIG. 5 is a section taken on the line 55 of FIG. 4;

FIG. 6 is a section taken on the line 66 of FIG. 3;

FIG. 7 is a section taken on the line 7-7 of FIG. 6;

FIG. 8 is a section taken on the line 3-8 of FIG. 6;

FIG. 9 is a graph showing pressure curves produced by a pump of the type shown in FIG. 3 to 8 with full eductor pressure-raising action and with modified pressure-raising action, and a comparative pressure curve produced by the same pump with a pressure raising piston removed so that it operated as a conventional prior art P p;

FIG. is a graph of pressure curves showing the character of changes produced by operating the same fuel pump unit at lower and higher voltages than its 12-volt design voltage;

FIG. 11 is a sectional view similar to that of FIG. 4 but showing a modified pump in which the flow-responsive pressure raising means in accordance with the invention is a piston responsive to pressure drop across an orifice in the pump delivery passage;

FIG. 12 is a graph showing a curve obtained with a pump like that of FIG. 11, and a comparative curve obtained with the same pump with its pressure control piston removed so that it operated as a conventional prior art pump; and

FIG. 13 is a somewhat diagrammatic view of a modification in which the flow-responsive pressure raising means acts on a valve which in turn controls the position of the sliding displacement element.

In the system shown in FIG. 1, a motor pump unit. 10 is connected in the fuel line between a fuel supply tank 12 and a carburetor 14, so that it receives fuel through a suction line 16 and delivers the same to the float chamber 20 of the carburetor 14 through a pressure line 18 and a float-valve port 22 controlled by a float valve 24. As is known, line losses will occur in the line 18 and the restricted port 22, and such line losses and back pressure will increase progressively with the rate of flow.

The pump shown in FIG. 2 is generally similar to that of Patent No. 2,922,376. It comprises a pump body 32 mounted in a casing 33 which together provide end and circumferential walls defining a chamber which receives a sliding pump ring 34. Such pump ring 34 surrounds a rotor 36 provide with pumping vanes 38 and driven clockwise by a central shaft 40. The pump ring 34 has two opposite chordally-directed

projections

42 and 44 which slidably received in guideways formed in the pump body 32. The projections and guideways permit the ring 34 to slide radially to the right in FIG. 2 from the eccentric position shown to a position concentric with the shaft and the rotor 36. A biasing spring 48 urges the ing 34 to its eccentric position shown. In this eccentric position of the ring, the pump has maximum displacement, while with the ring concentric with the rotor, the pump has minimum or zero displacement.

The

chordal projections

42 and 44 are offset from the diametric plane of eccentric movement of the ring 34 and divide the external space within the pump body 32 into an inlet chamber 50 and an outlet chamber 52 which are unsymmetrical with respect to that plane of eccentric movement.

The pump has an inlet passage 54 in the boss at the bottom of FIG. 2, which connects to an inlet port 56 in communication with the inlet chamber 50 externally of the ring 34 and with the expanding suction chambers 58 between the rotor vanes 38 internally of the ring 34. An outlet port 60 communicates with the outlet chamber 52 externally of the ring 34 and with the contracting pressure chambers 62 between the vanes 38 internally of the ring 34.

The operation of the pump as so far described is in accordance with the disclosure of Patent No. 2,922,376. The inlet and

outlet ports

56 and 60 and the

internal pumping chambers

58 and 62 are substantially symmetrical with respect to the plane of eccentric movement of the ring 34, so that the pressures internally of the ring 34 will produce forces thereon which are normal to such plane of movement and will be taken by the

projections

42 and 44 and their guideways. In the unsymmetrical external inlet chamber 50 and outlet chamber 52, however, pressure differences will act on the external surface of the ring 34 to produce force tending to move the ring from its eccentric position of maximum displacement toward its centric position of minimum displacement.

The pump ring 34 is normally held eccentric by the spring 48. As operation of the pump produces pressure differences in the inlet and

outlet chambers

50 and 52, and when the resulting force on the ring exceeds that of the spring 48, the ring 34 is forced from its eccentric position toward a centric position, to reduce the pump displacement and reduce its output flow. The eccentricity of the ring 34 and the resulting displacement of the pump will vary with delivery flow, and output pressure will be generally that determined by the force of the spring 48 at its existing state of compression. The greatest spring force will exist at minimum flow and displacement, and less spring force at greater How and greater displacement. For this reason and others, there will be a progressive falling off of delivery pressure as displacement and flow rates increase.

In accordance with the present invention, the ring 34 is connected by a rod 70 to a piston 72 in a cylinder 74. The piston may be urged outward by its own bias spring 73. The inner end of the cylinder 74 communicates with the outlet chamber 52 through a free passage 76. The outer end of the cylinder 74 is closed by an end Wall 78 which defines between itself and the piston 72 a motor chamber 80. The piston 72 may contain a restricted orifice 82 by which output liquid from the outlet chamber 52 of the pump may flow to the motor chamber 80.

The motor chamber is also connected by a line 84 to the suction inlet 86 of an eductor 88 whose actuating nozzle 90 is connected by a line 92 to the pump outlet port 60, so that the entire delivery flow from the pump (except that through the orifices 82 and line 84) is through such line 92 and the eductor nozzle 90. The eductor nozzle 90 discharges through a venturi passage 98 to a delivery line 99 containing a valve 100 which may be considered equivalent to the carburetor valve 24. A bypass line 94 containing a needle valve 96 connects the delivery line, ahead of the eductor nozzle, with the suction chamber 86, and adjustment of the needle valve 96 controls the suction produced by the eductor.

In the operation of this FIG. 2 device, if it is assumed that the valve 100 is closed to cut off all outlet flow from the pump, the output and suction pressures in the

chambers

52 and 50 externally of the sliding ring 34 will act on such ring to move it from its eccentric position shown to or toward its centric position, in accordance with the conventional action in a sliding-ring pump. Under such no-flow conditions, the pressures on opposite sides of the piston 72 will be equalized through the passage 76 to the inner side of the piston and through the line 92, nozzle 90, and line 84 to the outer side of the piston, and also through the orifice 82 if such an orifice is present. Under such equalized pressures, the piston 72 will have no modifying effect on the conventional operation, and the ring 34 will be driven to centric position by the pump pressures as explained above. Thus, under no-flow conditions, the output pressure of the pump will be the same as in conventional operation, and will depend wholly on the bias produced by the main biasing spring 48 and any supplemental spring 73.

Under flow conditions, however, a modified action will occur, and the output pressure will be progressively raised. The main outlet flow from the pump is throughthe line 92 and the eductor 88, and such flow will actuate the eductor to produce a reduced pressure or suction in the eductor suction chamber 86, which will be transmitted through the line 84 to the motor chamber 80 of the cylinder 74. While this reduced pressure may be partially satisfied by flow through the restricted orifice 82, it will not be entirely satisfied, and a pressure differential will be created across the piston 72, with high pump output pressure on the right-hand side of the piston 72 and a lower eductor-created pressure on the left-hand side of the piston, depending upon the rate of pump outlet flow through the eductor. Such pressure differential will act on the piston 72 to exert a force to the left, which will urge the pump ring 34 to the leftin the same direction as it is urged by the spring 48 and in opposition to the centering force exerted by the pressures in the outlet chamber 52 and the suction chamber 50.

The net result will be that as the valve is opened to permit greater outlet flow from the pump, this will produce greater suction in the suction chamber 86 of the eductor 88, which will in turn produce a greater pressure drop across the piston 72 of the pressure regulating means of the pump, and such increased pressure drop across the piston 72 will have the effect of increasing the pressure which the pump must create in the outlet chamber 52 in order to drive the ring 34 toward its centric position. Accordingly, the pump output pressure will rise progressively with an increase in the discharge fiow permitted by the control valve 100. The pump will have a rising pressure curve as illustrated by the three upper curves in FIG. 9.

The motor pump unit 10 shown in FIG. 3 comprises a motor drive assembly 102 like that shown in Patent No. 3,074,347 issued January 22, 1963. This contains a motor (not shown) and the driving half of a magnetic coupling all housed within a hermetically sealed housing 105. The drive assembly 102 is carried by a mounting body 108 supported by a resilient cushion 110 in a mounting bracket 112. The body 108 has a depending central sleeve 114 within which an output shaft 116 is mounted in bearings 118. The shaft carries the driven half 120 of the magnetic coupling co-axially with the driving half 104, but on the opposite side of the imperforate end wall 106 of the housing 105. As a result, the sealed motor shaft 103 is magnetically coupled to the external output shaft 116.

At its lower end, the mounting body 108 has a counter bore 122 for the reception of an axial flange 124 on a pump casing 126. The joint is sealed by an intervening gasket 128. The upper end of the pump casing 126 defines a cavity which is closed by the lower end of the mounting body 108, to form an outlet chamber 130 for the pump. Leakage from this chamber 130 along the shaft 116 is prevented by a rotary seal 132 on the shaft. A drain tube 134 connects the cavity containing the driven clutch element 120 to the inlet side of the pump.

The lower portion of the pump casing 126 comprises an outer wall 1.36 defining a generally cylindrical cavity to house a pumping assembly. This is closed at its lower end by a body 138 containing an inlet valve and having an axial flange 140 which is telescopically received within the wall 136 and which defines an inlet chamber 142. The lower end of the body 138 carries a depending threaded sleeve 144 which combines with a cup shaped cover 146 to define a filter cavity 148. A filter element 150 is mounted within such cavity and is centrally sealed by a gasket 151 to a depending nipple 152 which defines an inlet passage to the inlet chamber 142. The upper end of such inlet passage is closed by a check valve 154 opening toward the inlet chamber 142.

The pump assembly contained within the pump casing wall 136 comprises an upper end plate 160, an intermediate body plate 162, and a lower end member 164. These are relatively located and held against rotation by a pair of dowel pins 166 mounted in the casing 126 and engaged in notches in the three plates.

As seen in FIGS. 4 and 5, a slidable pump ring 168 mounted within the body plate 162 and between the end plates and 164, defines a pumping chamber which contains a rotor 170 having four radial slots 172 provided with pumping vanes 174. The rotor 170 is driven by the lower reduced end of the shaft 116, by a pair of splines 176.

The pump ring 168 is slidable between the

end plates

160 and 164, and is guided by a pair of chordally-directed projections and 182 slidably received in

guideways

184 and 186 formed in the body plate 162, which limits the ring to movement in the direction of the diametric plane of its eccenticitycorresponding to the section line 3 3 in FIG. 4 The projections extend the full distance between the

end plates

160 and 162, and separate the external space surrounding the ring 168 into an inlet space cavity 188 and an outlet space cavity 190. Since the

guides

180 and 182 are respectively offset upwardly and downwardly (FIG. 4) from the diametric plane of eccentricity, the inlet and

outlet cavities

188 and 190 are unsymmetrical with respect to that plane, so that pressure differences therein will produce ring-driving force.

The upper end wall 160 has a large central opening 192 to pass the drive shaft 116 and to feed outlet pressure to the inner ends of the vane slots 172 of the rotor 170.

The plate 160 also has an eccentric generally reactangular outlet port 104 which communicates through an outlet opening 106 (FIGS. 4 and 5) with the outlet chamber 130 defined between the pump casing and the mounting body 108. At a diametrically opposite point from the port 194, the upper end plate 160 has on its lower surface a shallow inlet channel 198 which bridges the ring 168 and interconnects the inlet space 188 with the pumping space between the ring 168 and the rotor 170.

The lower end plate 164 has a central depression of the same diameter as the central opening 192 of the upper plate, and may carry a central thrust bearing 200 for the shaft 116. The lower plate 164 has an inlet port 202 of the same general rectangular configuration as the cavity 198 shown in FIG. 4, which connects with the inlet chamber 142 formed below the plate 164. Such port 202, like the cavity 198, bridges the ring 168 and communicates both with the inlet space 188 outside the ring and with the pumping space between the ring and the rotor. At a diametrically opposite point, the lower plate 164 has a shallow outlet channel 204 opposite to and of the same configuration as the outlet port 194 in the upper plate 160.

The inlet connection passage for the pump is shown in FIG. 5. This comprises a threaded bore 206 in the pump body 126, leading to a downward bore 208 which opens to a sloping passage 210 in the body 138 leading to the filter chamber 148.

The sliding pump ring 168 is biased to its essentric position-the left in FIG. 4by a biasing spring 212 supported by an adjusting screw 214 and housed within the projection 180 and the guideway 184.

At the opposite guide 182, the ring 168 is connected by a rod 216 to a piston 218 in a cylinder 22. The piston may be biased to the left by a supplemental biasing spring 220. The inner end of the cylinder 222 is connected by a passage 223 to the outlet space 190 between the ring 168 and the guide member 162. As shown in FIG 3, the outer end of the cylinder 222 is connected by an upward extending channel 224 to a transfer passage 226 leading to the eductor shown in FIG. 6. The eductor comprises a venturi passage 230 formed in the pump casing 126 and connected at its outer end with a threaded outlet bore 232 adapted to receive the discharge line from the pump. At the inner end of the venturi passage 230, a counterbore is formed to receive an eductor nozzle 234 and to form a suction chamber 236. The mouth of the eductor nozzle 234 is in open communication with the outlet chamber 130- so that liquid under pressure in such chamber will be discharged from the nozzle 234 through the eductor passage 230, to produce reduced pressure in the suction chamber 236. Such reduced pressure will be communicated through the passage 226 and the channel 224 to the outer end of the piston cylinder 222.

For the purpose of controlling the section produced in the cylinder, an adjustable bypass is formed as shown in FIGS. 6 and 8. A bore 240 in the pump body 126 connects the suction chamber of the eductor to a transfer passage 246 (FIG. 8) communicating with the outlet chamber 130. A needle valve 242 mounted in the bore 240 and seating on a seat 244 control the bypass. By opening the needle valve 242, liquid from the outlet chamber 130 is bled into the suction chamber 236, to partially or wholly satisfy the suction produced therein, and thus modify or destory the suction applied to the piston cylinder 222.

Operation of the pump of FIGS. 38 is similar to that of FIG. 2. Inlet liquid entering through the connection 296 flows down the passages S and 210 to the filter chamber 148, thence through the filter and up through the central nipple 152, past the check valve 154, to the inlet chamber 142. From here it is drawn into the expanding pumping chambers communicating with the inlet port openings 262 and 198 (FIGS. 4-5), is carried clockwise by the rotor 1'70, and is discharged as the pumping chambers contract in communication with the

outlet port areas

194 and 204. From these the liquid flows upward to the pressure chamber 136, and from there through the eductor (FIG. 6), by way of the nozzle 234 and venturi 230, to the outlet connection 232.

The discharge pressure is also communicated through the passage 223 to the inner end of the cylinder 222 and against the inner face of the piston 218.

With unrestricted outlet fiow, the ring 168 is biased to its eccentric position, to the left and as shown in FIG. 4, by the springs 212 and 221 and by the action of the piston 218. The outer face of such piston is subjected to reduced pressure communicated through the passage 226 and channel 224 from the suction chamber of the eductor. Under full flow conditions, maximum suction will be produced by the eductor and a maximum pressure difference will exist across the piston 218, to create a force acting through the rod 216 to pull the ring 168 to the left.

If outlet flow is restricted, as by the carburetor valve 24 in the arrangement of FIG. 1, the suction produced by the eductor will be less, and the pressure difference across the piston 218 will be reduced, and this will reduce the flow-responsive force urging the ring 168 eccentric. Further, with the outlet flow restricted, the pump outlet pressure in the pressure space 190 externally of the ring 168 will act on the ring tending to force it toward centric position.

The ring will therefore seek a position in which the variable displacement of the pump produces that output pressure in the space 190 which will create on the ring 168 a centering force equal to the combined spring and piston forces urging the ring toward eccentric position. This position will vary with the rate of pump delivery flow permitted by the downstream restriction. Further, the outlet pressure will rise with increasing flow, since in creasing flow will produce greater suction in the venturi and this in turn will act on the piston 216 to increase the force tending to move the ring 168 eccentric and opposing the centering force created by outlet pressure in the space 190.

If outlet fiow is frilly cut off by a downstream valve, the eductor will produce no suction and full outlet pressure will be transmitted through the suction passages to the outer face of the piston 218. Pressures across the piston will then be equalized, and will create no force to pull ring 168 toward eccentric position. The pump delivery pressure will then depend solely on the bias of the

springs

212 and 220.

A rising pressure curve produced by the operation just described is shown in dotted lines in FIG. 9, in which delivery pressure is plotted against delivery flow. With full eductor action, the pressure rises with increasing delivery fiow, at a sharply increasing rate, until the design capacity of the pump is reached at about 40 g.p.h.

For comparison, the chain-line bottom curve in FIG. 9 shows the pressure output of the same pump with the piston 218 removed, and the suction passage blocked, so that the eccentricity of the ring is controlled entirely by the bias of the

springs

212 and 220 and the pressure differential in the intake and

output spaces

188 and 190. As will be seen, without the pressure regulating of this invention, the pressure progressively drops with increasing flow.

FIG. 4a shows a modification which reduces the sharp rise shown by the top curve in FIG. 9. The piston 218a corresponding to that in FIG. 4, is provided with a restricted orifice 219 which bleeds pressure (and delivery flow) from the pump outlet space 190 to the suction side of the piston. This partially satisfies the suction produced at high flows by the eductor, and lowers the peak of the pressure curve while increasing somewhat the outlet capacity of the pump.

The dotted line curve in FIG. 9 shows the operation of the same pump with an orifice 219 in the piston. The pressure again rises with fiow, still at a progressively increasing rate, but not as sharply as without the orifice.

The by-pass needle valve 242 also adjusts the amount of pressure rise obtained. Thus, with the needle valve opened part way, the same pump, with the orifice 219, gave the pressure curve shown in full lines in FIG. 9. Again, the pressure rose with increasing flow, but to a lesser degree and in a more uniform relationship. A substantially similar curve was obtained without the orifice 219 in the piston, by similar adjustment of the needle valve 242.

In automotive applications where the battery power supply voltage may vary widely, the pump must nevertheless produce adequate delivery and pressure at low voltages, and avoid excessive low-floor pressures at high voltages. FIG. 10 shows that the pump of FIGS. 3-8 meets these requirements. The pump motor was designed for 12 volts. When operated at 9 volts, it produced full low-flow pressures, and a rising pressure curve over a wide delivery range which would fully meet operating requirements under conditions-of low speed and low battery charging ratein which a low supply voltage would be likely to exist. On the other hand, when operated at 15 volts, the pump gave substantially higher delivery rates with higher pressures at high flow rates, but the low-flow pressures were not much higher than normal and would create no problem of control by a carburetor valve capable of handling the normal pressures.

The modification of FIG. 11 is the same as the pump of FIG. 4, except that it contains no eductor, and the entire delivery flow is through an orifice which produces a pressure drop across the piston.

In the structure of FIG. 11, the only outlet from the pump 168470 is by way of the outlet space 190 externally of the ring, to the cylinder 322 containing a piston 318 connected to the rod 216 attached to the pump ring 168. The piston contains an orifice 319, and the pump discharge outlet is provided by a passage 332 in the end wall of the cylinder. A by-pass 340 containing a needle valve 342 connects the opposite ends of the cylinder 322.

Operation of this modification is similar to that of the pump of FIG. 4. At cut-off or no-flow condition, pressures across the piston will be equalized and the pressure-responsive position of the sliding ring 168 will depend wholly on the bias of the

springs

212 and 220. With progressively increasing delivery, the flow through the orifice 319 will cause a progressively higher pressure drop across the piston 318, and this will produce an increasing force urging the pump ring 168 toward a more eccentric position, and augment the spring bias in this direction. This will produce a rising pressure curve, as shown in full lines in FIG. 12. Output of .the same pump with the piston removed is represented by the dotted line curve. It will be noted that the restriction of discharge flow produced by the orifice reduces slightly .the maximum delivery capacity of the pump, but this occurs beyond the normal operating range of the pump. Within the normal range, the piston and orifice produce an in- 9. creased pressure, which rises with delivery rate up to the design capacity of about 45 g.p.h.

In the modification of FIG. 13, a pressure regulating eductor acts on a control valve which in turn controls the pressure response of the sliding ring; The sliding ring 368 is mounted in a rectangular cavity ina casing 350, and surrounds a rotor 370 having vanes 374. An inlet 352 is connected by a passage 353 to an inlet port 354 formed in the back wall of the casing 350. An oppositely disposed outlet port 355 is connected by. a discharge passage 356 to the nozzle passage 357 of an eductor 358 leading to an outlet359.

The ring 368- is slidable from the maximum-displacement eccentric position shown, upward to a centric position in which its central opening is concentric with the rotor 370 and the pump has minimum or zero displacement. A clearance space 388 at the top houses a light biasing spring 387 and is connected by a bleed groove 366 to the inlet port 354. A pressure space 390 below the ring 368 forms a motor chamber in which pump output pressure may act to force the'ring fromeccentric to centric position.

Such chamber 390 is connected through a port 391, a spool valve chamber 392, and a pressure passage 393 to the outlet passage 356. The chamber 390-is also connected by a suction passage 394 to the suction inlet of the eductor 358. A spool valve in the chamber has a pressure piston 398 normally blocking flow from the pressure passage 393 to port 391, and has a regulating piston 396 between the openings of the pressure passage 393 and the suction passage 394. A pressure-regulating spring 400 biases the spool valve to the left, and the spring chamber is connected by a bleed passage 402 to the inlet port 354-.

In operation, if pump discharge flow is cut off or restricted and output pressure rises to a predetermined value, such pressure will displace the valve piston 398 to the right to uncover the port 391; this will deliver pressure to the motor chamber 390, where it will force the sliding ring 368 toward centric position to reduce the displacement to an amount just sui'ficient to maintain the valve-displacement position. At full cut-off or no-fiow condition, the force opposing such displacement of the valve will be that of thespring 400 alone, for. with no flow the eductor will have no effect and pressures on opposite sides of the control piston will be. equalized. Under flow conditions, however, the eductor will reduce the pressure at the left of the control piston 396, and the pressure differential across such piston will urge the spool valve to the left, and augment the force of the spring 400. The augmenting force will increase progressively with flow, and will progressively raise the pressure which the pump will need to generate to displace the spool valve to the right.

Accordingly, in this modification as in the others, the pump will have a rising pressure curve, but in this case the regulating action of the eductor-or equivalent elementwill act to vary the bias on a control valve rather than that on the sliding ring itself.

I claim as my invention:

ll. In a variable displacement pump having (a) a pump rotor and a variable displacement element,

such as a sliding ring, movable with respect to the rotor to vary the displacement of the pump by varying the eccentrically of the displacement element relative to the axis of rotation of the rotor, and

(b) control means for normally positioning the displacement element in eccentric position and for de creasing the eccentrically of said displacement element in response to pressure developed by the pump,

(c) said control means including pressure-responsive means and an opposed resilient element which is stressed by the pressure-responsive means in response to pressure developed by the pump, and the reaction force of which resilient element determines the presit) sure required to be developed by the pump to produce movement of the displacement element in a displacement-reducing direction, the improvement which comprises the combination therewith of (d) means responsive to flow of pumped liquid and operative, in response to increased flow, to augment the force exerted by said resilient element in opposition to the pressure-responsive means,

whereby, in response to flow, the pressure required to be developed by the pump to cause displacement-reducing movement of the displacement element is increased beyond that determined by the resilient element.

2. The invention defined in claim 1 in which (a) said resilient element acts to normally bias said displacement element to maximum displacement position, and

(b) said pressure-responsive means acts to urge said displacement element in a displacement-reducing direction,

whereby the position of the displacement element is directly determined by the force exerted by said pressure responsive means against the bias of said resilient element and the augmenting force of said flow responsive means.

3. The invention defined in claim 1 in which (a) said control means includes hydraulic motor means for moving said displacement element in a displacement-reducing direction, and

(b) a valve controlling said motor means and normallyheld in closed position by said resilient element and urged to open position in response to pump-pressure.

4. The invention defined in claim 1 in which said flow-response means comprises (a) an eductor having an operating flow passage and a suction inlet,

(b) said flow passage being connected in series with the pump whereby the eductor is actuated by flow of pumped liquid, and

(c) a pressure motor device connected for actuation by suction developed in said eductor and operatively connected to apply force on said pressure-responsive means in the same direction as said resilient element.

5. The invention defined in claim 4 with the addition of (a) a variable bypass interconnecting the pressure inlet and suction inlet of said eductor to regulate the suction produced therein by the flow of pumped liquid.

6. The invention defined in claim 1 in which the flowresponsive means comprises (a) a flow passage having a restriction therein and connected in series with the pump, to produce a pressure drop across the restriction in response to and varying with flow of pumped liquid,

(b) and a pressure motor device responsive to the pressure drop produced by said restriction and operatively connected to urge said pressure-responsive means in the same direction as said resilient element.

7. The invention defined in claim 1 in which (a) said resilient element biases the displacement element in a displacement-increasing direction,

(b) said pressure-responsive means urges said displacement element against said bias and in a displacementreducing direction, and

(c) said flow-responsive means comprises means for producing a flow-responsive pressure lower than pump-developed pressure, and

(d) a pressure motor device having a piston or the like the opposite sides of which are exposed to pumpdeveloped pressure and said flow-responsive pressure,

(e) said motor device being operatively connected to urge said displacement element in a displacementincreasing direction in response to the pressure differential on the opposite sides of the piston.

8. A variable positive displacement pump comprising,

(a) a pump rotor,

(b) a variable displacement element movable with respect to the rotor to vary the displacement of the pump by varying the relationship of the displacement element to the axis of rotation of the pump rotor,

(c) biasing means to bias said displacement element to maximum displacement position,

((1) said pump including means responsive to pressure developed by the pump and arranged to move said displacement element against said biasing means in a displacement-reducing direction, whereby said biasing means controls the pressure developed by the P p,

(e) flow-responsive means responsive to flow of pumped liquid for producing a pressure which varies with flow, and

(f) a pressure motor responsive to said flow-produced pressure and connected to exert a force on said displacement element which in response to increased flow, progressively augments the force of said biasing means and urges the displacement element in a displacement-increasing direction, whereby in response to flow the pressure developed by the pump is increased over that determined by the biasing means.

9. A variable positive displacement pump as defined in claim 8 in which (a) said flow responsive means is an eductor having a suction intake,

(b) and said pressure motor is connected to the suction intake of said eductor.

10. A variable positive displacement pump as defined in claim 8 in which (a) discharge flow from the pump is passed through a restricted orifice,

(b) and said pressure motor comprises a piston or the like exposed on one side to the pressure on the down stream side of said orifice.

11. A variable positive displacement pump as defined in claim 9 which includes (a) a variable bypass for regulating pressure applied to the pressure motor.

12. A variable positive displacement pump as defined in claim 10 which includes (a) a variable bypass for regulating pressure applied to the pressure motor.

13. A variable positive displacement pump as defined in claim 8 in which (a) said pressure motor comprises a piston or the like responsive to the pressure differential between pumpgenerated pressure and a lower pressure which is produced by said flow-responsive means and which decreases with flow of pumped liquid.

14. A variable displacement pump, comprising (a) a pump shaft mounted for rotation on an axis,

(b) a pair of end walls having radially-disposed, axiallyspaced inner faces for defining a pumping chamber,

(c) a variable-displacement ring slidably disposed between said end walls,

(d) a rotor operatively connected to said shaft and rotatable between said end walls within said ring and having sliding vanes defining with said ring and end walls a plurality of of pumping spaces of variable displacement depending on the eccentricity of said ring relative to the axis of said shaft and rotor,

(e) an inlet port in one of said end walls,

(f) casing means defining an outlet chamber on the opposite side of one of said end end walls from said pumping chambers,

(g) an outlet port for delivering fluid under pressure from said pumping chambers to said outlet chamber,

(h) an eductor having its pressure inlet in communication with said outlet chamber and extending transversely within the axially projected area of said end walls,

(i) pressure motor means for urging said displacement ring toward eccentric position, and

(j) said eductor having a suction inlet connected to actuate said motor means in displacement increasing direction in response to flow from said outlet chamber through said eductor.

15. A variable displacement pump as defined in claim 14, further comprising (a) an outlet connection at the outer end of said eductor at one side of said pump and substantially radially disposed relative to said pump, and

(b) an inlet connection communicating with said inlet port and disposed substantially parallel with and on the opposite side of the pump from said outlet connection.

16. A variable displacement pump as defined in claim 14, further comprising (a) casing means defining an inlet chamber on the axially opposite side of said pumping chamber walls from said outlet chamber and in communication with said inlet port, and

(b) said inlet chamber, pumping chamber and outlet chamber lying substantially within the same axially projected area.

17. A variable displacement pump as defined in claim 16, further comprising (a) casing means defining a filter chamber axially beyond the inlet chamber, and

(b) a check valve between said filter chamber and inlet chamber.

18. A variable displacement pump, comprising (a) a first casing having a radial wall and an axial flange wall defining a cavity,

(b) a pair of end plates received in said cavity and defining end faces of a pumping chamber,

(c) a ring guide between said end faces,

(d) a variable displacement ring slidably disposed between the plates within said ring guide,

(e) a rotor rotatable on an axis between said plates and having sliding vanes defining with said ring and end faces a plurality of pumping spaces of variable displacement depending on the eccentricity of the ring relative to the rotor axis,

(f) a second casing in closing relation with the cavity of the first casing and retaining said end plates therein,

(g) said second casing coacting with the adjacent end plate to define a fluid chamber and such end plate having a port therein for connecting said pumping spaces with said fluid chamber, and

(h) pressure motor means for urging said displacement ring toward eccentric position in response to to increased flow of fluid pumped by said pump.

19. A variable displacement pump as defined in claim 18, further comprising (a) a fluid motor chamber formed in said first casing and having its inner end openly connected for exposure to pump-generated pressure,

(b) a motor element in said chamber mechanically connected to said displacement ring and defining a control chamber at the outer end of said motor chamber, and

(0) means to create in said control chamber, in response to flow of pumped fluid, a pressure lower than said pump-generated pressure, and thereby create a pressure diflerential across said motor element to urge said displacement ring toward eccentric position.

20. A variable displacement pump as defined in claim 19, in which (a) said means to create a lower pressure comprises an eductor housed in said first casing, having a pressure inlet connected to the presside side of said pump, and having a suction inlet connected to said control chamber.

21. A variable displacement pump, as defined in claim 19, in which (a) said means to create a lower pressure comprises a restriction in the delivery passage of the pump, said inner end of the motor chamber being connected to the pump upstream of said restriction and the control chamber being connected to the pump downstream of the restriction.

22. A variable displacement pump as defined in claim 18, further comprising (a) a third casing mounted at the opposite end of the first casing and defining therewith a second fluid chamber communicating with a port in the other end plate, and

(b) a drive means mounted to said third casing and having a drive shaft connected to said rotor.

References Cited by the Examiner UNITED STATES PATENTS 2,502,546 4/1950 Adams.

2,562,615 7/1951 Huber 103--1 2,600,632 6/1952 French 103l20 2,600,633 6/1952 French 103120 2,799,995 7/ 1957 Hallsman.

2,894,458 7/ 1959 Hallman.

2,922,376 1/1960 Hankel et a1 103120 2,944,488 7/1960 Meyer 103-21 3,067,693 12/1962 Lambeck 1031 DONLEY I. STOCKING, Primary Examiner.

LAURENCE V. EFNER, JOSEPH H. BRANSON, 1a.,

Examiners.

Claims

1. IN A VARIABLE DISPLACEMENT PUMP HAVING (A) A PUMP ROTOR AND A VARIABLE DISPLACEMENT ELEMENT, SUCH AS A SLIDING RING, MOVABLE WITH RESPECT TO THE ROTOR TO VARY THE DISPLACEMENT OF THE PUMP BY VARYING THE ECCENTRICALLY OF THE DISPLACEMENT ELEMENT RELATIVE TO THE AXIS OF ROTATION OF THE ROTOR, AND (B) CONTROL MEANS FOR NORMALLY POSITIONING THE DISPLACEMENT ELEMENT IN ECCENTRIC POSITION AND FOR DECREASING THE ECCENTRICALLY OF SAID DISPLACEMENT ELEMENT IN RESPONSE TO PRESSURE DEVELOPED BY THE PUMP, (C) SAID CONTROL MEANS INCLUDING PRESSURE-RESPONSIVE MEANS AND AN OPPOSED RESILIENT ELEMENT WHICH IS STRESSED BY THE PRESSURE-RESPONSIVE MEANS IN RESPONSE TO PRESSURE DEVELOPED BY THE PUMP, AND THE REACTION FORCE OF WHICH RESILIENT ELEMENT DETERMINES THE PRESSURE REQUIRED TO BE DEVELOPED BY THE PUMP TO PRODUCE MOVEMENT OF THE DISPLACEMENT ELEMENT IN A DISPLACEMENT-REDUCING DIRECTION, THE IMPROVEMENT WHICH COMPRISES THE COMBINATION THEREWITH OF (D) MEANS RESPONSIVE TO FLOW OF PUMPED LIQUID AND OPERATIVE, IN RESPONSE TO INCREASED FLOW, TO AUGMENT THE FORCE EXERTED BY SAID RESILIENT ELEMENT IN OPPOSITION TO THE PRESSURE-RESPONSIVE MEANS, WHEREBY, IN RESPONSE TO FLOW, THE PRESSURE REQUIRED TO BE DEVELOPED BY THE PUMP TO CAUSE DISPLACEMENT-REDUCING MOVEMENT OF THE DISPLACEMENT ELEMENT IS INCREASED BEYOND THAT DETERMINED BY THE RESILIENT ELEMENT.