US2806430A - Positive displacement variable volume delivery pump and associated control system - Google Patents

Description

SePt- 17 1957 L. E. osBoRNE 2,806,430

POSITIVE DISPLACEMENT VARIABLE VOLUME DELIVERY PUMP AND ASSOCIATED CONTROL SYSTEM 2 Sheets-Sheet l Filed March 22. 1952 Sept. 17, 1957 L. E, OSBORNE 2,806,430

' POSITIVE DISPLACEMENT VARIAB VOLUME DELIVERY PUMP AND ASSOCIATED CO OL'SYSTEM Filed llarch 22, 1952 2 Sheets-Sheet 2 l-Illl 42 m "j 45 5J 1N V EN TOR.

2,805,430 Patented Sept. 17, 1957 ein POSITIVE DISPLACEMENT VARIABLE VOLUME DELIVERY PUMP AND ASSOCIATED CONTROL SYSTEM Lyle E. Osborne, South Bend, Ind., assistanttn Bendix Aviation Corporation, South Bend, Ind.` corporation of Delaware Application March 22, 1952, Serial No. 27 8.61m

11 Claims. (Cl. 10S- 37) This invention is concerned with pumping systems ci that type utilizing a positive displacement pump having means for varying the output or pump delivery at constant stroke, thus avoiding the problems which arise in connection with pumps wherein delivery is varied, for example, by varying the effective angle of a wobble plate.

An object of the invention is to provide a pumping system of the type specified having the advantages of relative simplicity in construction and reliability in operation.

Another object is to provide a combined positive displacement and by-pass pump and associated control for fuel supply systems for engines, particularly gas turbine or jet engines, wherein a wide range oi metering pressures is available or may be selected and maintained with a minimum amount of fuel by-passed back to the low presa sure side of the pump.

Another object is to provide a positive displacement pump and associated control system wherein a relatively wide range ot' delivery pressures are available with n minimum of temperature rise created in the pumped fluid due to heat energy absorbed by the iiuid.

Another object is to provide a system of the` type specified having a quick time response to changes in demands on the system.

Another object is to provide in a pumpingy system of thc type specified means for avoiding surge when the pump responds to a change in demand from an engine t'ucl control or analogous device.

Another object is to provide a combined check valve and control valve arrangement for reciprocating plunger or like positive displacement pumps which permits varying of the pump output at constant stroke and at the same time tends toward simplicity in construction and operation.

A further object is to provide an improved fue! pressurizing and control system particularly gas turbine engines.

A still further object is to provide in a wobble plate, reciprocating plunger type pump improved means for avoiding side thrust on the plungcrs.

The foregoing and other objects and advantages will become apparent in view of the ioilowing description taken in conjunction with the drawings wherein:

Figure l is a view in sectional schematic of a pump and associated control system in accordance with the invention;

Figure 2 is an enlarged view in section of one of th.: check valves and adjacent parts; and

Figure 3 is a cross section view taken substantially' on the line 3 3 of the Figure l.

Referring to the drawings, a main exterior pump body or housing is generally indicated at 161; it consists of a hollow cylindrical member' l0', defining a pump chamber 11 and having a bolting-on liange l2 at one end thereof, to which is attached another cylindrical section 13, the latter in turn having a bolting-on flange 14 for attachment of end plate 15.

The section 13 is provided with a series of bores 16, arranged in annular formation, and in each ot said bores iS Secured a plunger bushing i7. A series of pumping adapted fer i plungers 18 are mounted to reciprocate in the bushings 17; they are shown as being of hollow cylindrical form, each having a tappet or bearing shoe 19 secured in the outer open end thereof.

The chamber 11 receives the lluid to bc pumped, fuel in the present instance, which is conducted thereto by way of a conduit 2l) and entrance passage 20 formed in a hollow boss 21 and retainer 22. A pumping chamber 23 is defined in cach hollow bushing 17 at the inner end of cach plunger, and when the plunger is retracted, fuel flows to thc chamber 23 by way of passages or ports 24, formed in the annular walls 25 defining the bores 16 and in the bushing itself, note lower right-hand portieri of Figure l where one of the plungers is shown in retracted position. Springs 26 are provided to retract the plungers, said springs at their outer ends engaging retainers 27 and at their inner ends abutting the annular walls or bushing sockets 25.

A series of check valves, one for each plunger 1S and pumping chamber 23, are indicated at 28; they are each mounted to slide in guide bushings 29, the latter being located in a series of bores 30, formed in the housing section 13, and held in place by hollow cnd nuts 3l. The inner or left-hand end of each bushing 29 defines thc adjacent end wall of thc pumping chamber 23, and it also defines a seat 32 for the said valve; and when the lutter is unscatcd, fuel may pass through discharge port 33, chamber 34, ports 34', annular chamber 35 and thence by way of ports 36 to a common central chamber or manifold 37, the latter being in communication with outlet passage 38 and delivery conduit 39.

Each check valve 28 is hollow, defining chamber 40 for mounting a spring 41, which exerts a force on the valve tending to seat the same. ln order to provide a controllable fuel differential across each valve. the latter is mounted to permit a certain leakage ot fuel from the high pressure side to the low pressure side thereof, or from the chamber 34 to chamber 40. This may be done by a predetermined clearance or tolerance between the valvc and its bushing, or by a series of calibrated vent holes provided in the wall of the valve, as at 42, or by a suitable bleed (not shown) between common central chamber 37 and manifold 44. This leakage or pump control fuel in chamber 4l) flows through ports 43 in the end nuts 31 to annular chamber or manifold 44, common to all the checit valve chambers 4t), from which it may flow by way of passage and conduit 46 to a control unit to be described.

A wobble plate assembly is generally indicated at 47; it comprises a wobble plate proper 47', having a hub which is keyed or splined to a drive shaft 48, said plate being formed with bearing surfaces 49 and 49'. A socalled torque block is indicated at 50; it is formed with an inner convex clearance surface, which permits a wobbling or rocking motion with respect to the shaft 48. Two opposite sides of this block are inserted between the fingers 51, 5l of a yoke which projects rearwardly from thc hub of a thrust plate 52, which at its outer edge is formed with a flange 52'. A bearing ring S2 is secured to the thrust plate and is contoured to engage the bearing surfaces 49 and 49 of the wobble plate 47. The block 53 and consequently the thrust plate 52 are held against rotation by the opposed fingers 53, 53 of a yoke which projects forwardly from the rear end section 13 of the pump body 10 `and spans the two opposite sides of the block which lie at right tangles to the sides spanned by the fingers 51, 51', see Figure 3. To facilitate assembly, screws 53 may be threaded through the fingers 53, 53' into openings formed in the adjacent sides of the block 50, to hold the latter in place between said lingers. 0bviously, once the block is engaged between all four of the yoke lingers, a connection is established between the thrust plate S2 and the pump housing which holds the thrust plate against rotation while permitting nutation or a wobbling motion thereof.

The outer edge portion of the thrust plate 52 has threaded therein a series of plunger-engaging shoes or contact members S4, one for each plunger 18, each of the shoes S4 being provided with a cone-shaped bearing sur face 54. The purpose of the particular bearing surface arrangement of the shoes 54 is to provide `a straight line thrust on the plungers at all positions of the wobble plate 47' or to avoid side thrust effects on the plungers.

It will be seen that when the drive shaft 48 is rotated, it in turn imparts rotation to the wobble plate 47. The rotary' action of the wobble plate 47 is converted into axial or reciprocating motion as it Cams on the bearing ring 52", to thereby effect reciprocation of the plungers 18. Since the bearing surfaces 54' of the shoes El are tapered or relieved in planes which are always normal to the line of thrust between the cam plate 47' land the plungers 18 irrespective of wobble plate position, the effective thrust on said plungers will always be in an axial direction.

When the pump is in operation, the reaction of the plungers tends to turn the thrust plate 52. This would throw the conical bearing surfaces 54 out of alignment with the plunger heads or ends were it not for the torque block 50, which constitutes a hub for the thrust plate and holds the latter against rotation while permitting universal movement about the drive shaft.

To minimize agitation of the fuel flowing into the chamber 1l. a shield 55 is attached to the outer exposed surface of the wobble plate 47.

The outer end of the drive shaft 48 is formed with an enlarged hollow annular portion which is journaled in a wobble plate hearing assembly 56, 56 and 56"; and beyond this the said shaft is formed with a relieved portion which rotates in an outer removable sealing assembly 57. A stub shaft 48 is inserted in and keyed to the hollow outer extremity of shaft 48 and has a drive spline 4S on the outer end thereof.

The bearing assembly for the wobble plate is self-align ing. viz., it will automatically provide a flush thrust bearing or surface for the wobble plate even though there muy be some misnlignment between thc shaft 48 and bearing and wobble plate assembly. This is due to the eoncavo-convex bearing surfaces provided by the dish-shaped bushing 56 and the interitting convex or sphericalashaped floating member 56', which may be made of suitable wearresistsnt metal or other material and has a certain amount of peripheral clearance to facilitate aligning movement. Between the member 56' and the adjacent surface of the wobble plate is a thrust ring 56".

ln the installation as illustrated in the present instance, the improved pumping and control system is used to supply fuel under pressure to a gas turbine or jet engine, the rate of fuel feed being controlled by a suitable fuel control device, illustrated diagrammatically at 53, rand the high pressure delivery conduit 39 leads to the input sido of the said fuel control. The conduit 59 leading from the fue] control device 58 represents a flow passage for metered fuel on the way to the burner discharge nozzles.

in order to regulate the pressure of the fuel in response to demands of the fuel control 53, a regulator valve 60 is provided and is connected to a diaphragm 61, which forms a movable wall between a pair of metered and unmetered fuel chambers 62 and 63. A spring 64 is located in chamber 63 and normally urges the valve 60 to closed position. Chamber 64 is vented to metered fue] pressure by way of passage 65, while chamber 62 is vented to pump discharge or unmetered fuel pressure by way of passage 66: hence the differential across the diaphragm 6l is proportional to the pressure drop across the fuel control unit, and any variation in said drop will result in proportional repositioning of valve 60.

The passage 46, which receives pump control pressure fuel from the annular chamber or manifold 44, leads to the inlet side of a valve port or orifice 67, controlled by valve 60, and fuel flowing across this port 67 passes into a passage 68, thence to chamber 69, across valve ports or openings 7l), into passage 7l and thence to the low pressurc side of the pump l0, or the conduit 20. The valve ports 70 are formed in a hollow sliding dashpot valve member 72, secured to the adjacent side of a diaphragm 73, which forms a. movable wall between the chamber nl? and a chamber 74, the latter being vented to leakage or ditlcrential fuel pressure by way of passage and passage 46. A calibrated restriction 75 is located in passage 75. A spring 76 tends to move the valve 72 toward open position in opposition to the pressure of the furl in chamber 74. The spring rate of spring 76 is preferably such as to produce a substantially constant pressure drop across valve 60 during equilibrium operation. 'l he purpose of valve 72 is to prevent too sudden in ow of fluid past valve 60 in response to quick changes in position of said valve, and which sudden changes in ow would cause surging of the delivery pressure. This action will be more fully explained in the following description oiA operation.

Operation lt will be obvious that when shaft 4S is rotated, it in turn effects rotation of the wobble plate 47", and this in turn effects reciprocation of the plungers i8 through the non-rotatable but rockable bearing ring 52, thrust plate S2 and Contact members 5:3. When used in a fuel system as in the example illustrated. the drive shaft 48 will have a driving connection with the engine through the drive spline 4S.

@n the upper side of Figure l` the wobble plate 47 ha:V moved one of the plungers 18 to a substantially full discharge position. At the lower side of said gure, one the plungers 18 is in its retracted position, at which point fuel is free to flow into the plunger chamber 23 from the pump chamber 1l by way of ports 24. The liow produced in the fuel discharge conduit 39, when the plungers 18 move to close the ports 24 and expel fuel from chambers 23 outwardly through ports 34 and 36 into chamber 37, depends on the period of time the check .'z'ilvcs remain open during the return or retraction stroke of the plungers, while the pressure generated in said com duit depends upon such period of time and the restriction to flow due to the setting of the fuel control device 58. For exan'iple, when the plungers lt; move back or are retracted, should the check valves 28 close instantly` all the fue] taken into chambers 23 will be low pressure fuel from the pump chamber ll, whereas should the check vulves be held open during part of the retracting stroke of the plungers, then the chambers 23 will ll partly with high pressure fuel from chamber 37 and partly with low pressure fuel from pump chamber 1]. The period of time the check valves 28 remain open is controllable as a function of, or in relation to the drop between the pressure of the fuel in discharge passage 39, which may be considered unmetered fuel pressure. and the pressure of the fuel in the passage 59, which may be considered as metered fuel pressure.

Let it be assumed that the pilot opens the throttle of the engine fuel control device 58 and there is a momentary drop in pressure in passage 39. This will immediately effect a reduction in the differential across the check valves 28 tending to move the latter towards close position, so that when the plungers 18 retract, the said check valves will immediately close and substantially all of the fuel expelled from chambers 23 will come from the pump chamber 11. The differential across the check valve is reduced due to the pressure in passage 39 being communicated by way of passage 66 to diaphragm charnber 62, reducing the differential across the diaphragm 6l, so that the valve 60 will close the port 67. Closure of the port 67 means that the pressure in back of the check valves 28, viz., the pressure in passage 46, annular chamber 44 and check valve chambers 40, will immediately build up and reduce anti finally stop leakage of fuel past said valves.

When the metered fuel pressure attains the desired or selected value as determined by the setting of the pilots control lever, the pressure of the fuel in conduit 39 will have attained a value such that the differential across the diaphragm 6l will open valve 60 sufficiently to pass enough fuel to the low pressure side of the pump by way of port 67, passage 68, chamber 69 and passage 71 to maintain an equilibrium condition.

There may be times when the pump would tend to surge were it not for the valve 72. To illustrate, let it be assumed that the system is operating at some idle or intermediate setting of the fuel control 58 and the pilot suddenly opens the throttle for maximum delivery of fuel to the burner nozzles. Momentarily, there would be a drop in pressure in conduit 39 which would be communicated to diaphragm chamber 62, and substantially simultaneously there would be an increase in pressure in conduit S9 which would be communicated to diaphragm chamber 63. The fuel differential across diaphragm 6l would quickly decrease and spring 64 would tend to close valve 60. immediately pump delivery pressure increases in conduit 39, however, and the fuel differential across diaphragm 61 starts to build up to equilibrium; but before this condition occurs the valve 60 may have overshot, or moved beyond equilibrium. This would throw the valve 60 out of phase with the response of the pump, with resultant surging. However, the valve 72 opens more or less gradually and prevents or damps sudden changes in flow across valve 60, bringing the response of the pump in harmony with that of the valve 60. Another advantage is that the valve 60 may be contoured for less travel, thereby facilitating the use of a spring 64 having a constant spring rate.

It will be seen that the fuel in chamber 37 not used to partially fill one set of plunger chambers 23 when the plungers 18 are retracted is utilized to fill another set of said chambers, viz., it is free to flow from chamber 37 back past any of the check valves 28, depending upon the degree of closing movement of the latter. Thus the only displaced or expelled fuel which is by-passed is that used for regulation, which is relatively small and remains small even though much less fuel is consumed by the cngine at high altitudes. By utilizing the differential across the check valve as a controlling medium in the manner heretofore described, a relatively simple arrangement is pro-vided for varying the volume delivery of a pump of the constant stroke reciprocating plunger type. Less power is required to drive a pump of the hereindisclosed type for a given over-all range or average of pump discharge pressures than is required for fixed displacement type pumps. This results from the assist to wobble plate rotation caused by the high pressure fuel return through the check valve ports Whenever the fuel requirements are tess than maximum volume discharge which reduces the effective torque required to drive the pump. As a consequence, there is less fluid temperature rise across the pump,

Although only one embodiment of the invention has been illustrated and described, the disclosure is amply sufficient to teach those skilled in the art to adapt the invention to various installations other than that shown.

I claim:

l. In a system for pressurizing fluid, a pump having a plurality of pumping elements, means for imparting constant pumping strokes to said elements, means providing individual pumping chambers in which said elements move to expel fluid and from which said elements retract to permit inflow of fluid, said chambers having inlet ports for low pressure till fluid and discharge ports through which fluid is expelled, check valves for ysaid discharge ports, an outlet for pressurized fluid common to said outlet ports, a device for variably controlling the pressure in said outlet, means resiliently urging said check valves to seated position, a portion formed on the seating side of said valves for subjection to the fluid in said outlet, means permitting the passage of fluid from said portion of the seating sides of said valves to the opposite sides thereof to establish a pump control fluid differential pressure across said valves, a receiving chamber for fluid passed to the opposite sides of said check valves common to all of said valves, a passage through which fluid from said receiving chamber may flow to the low pressure side of the pump, and means in said latter passage for variably regulating the pressure in said receiving chamber as a function of the pressure drop across said control device.

2. A system as claimed in claim l, wherein the means for variably regulating the pressure in said receiving chamber comprising a regulator valve and means responsive to the pressure drop across said control device is provided for variably positioning said regulator valve.

3. A system as claimed in claim l, wherein the means for variably regulating the pressure in said receiving chamber comprises a regulator valve and means responsive to the drop in pressure across said control device is provided for variably positioning said valve, and in addition there is another valve responsive to the drop across said regulator valve for damping the response of the pump to the action of the regulator valve.

4. In a system for pressurizing fuel to an engine, a pump having a plurality of pumping elements, means for imparting constant pumping strokes to said elements, means providing individual pumping chambers in which said elements move to expel fuel and from which said elements retract to prevent inflow of fuel, said chambers having inlet ports for low pressure ll fuel and discharge ports through which fuel is expelled, means providing a chamber for expelled fuel common to said discharge ports, a passage for conducting fuel from said latter chamber to the engine, a fuel regulating device in said passage, check valves controlling said discharge ports, means permitting passage of a limited quantity of fuel from the one side of said check valves to the opposite sides thereof to establish a pump control fuel differential pressure across said valves, a receiving chamber for such last named fuel common to all of said valves, a passage for conducting fuel from said receiving chamber to the low pressure side of' the pump, a valve for regulating flow through said latter passage to thereby regulate the differential across said check valves, and means for variably positioning said regulating valve in response to changes in the demands of the engine as determined by the rate of llc-w of fuel to the engine.

5. In a fuel supply system for an engine, a fuel pump having a pumping chamber' provided with a fuel inlet port and a fuel discharge port, an outlet conduit connected to said discharge port, a pumping member having a substantially constant pumping stroke, a che-ck valve controlling said fuel discharge port, means for establishing a pump control fuel differential pressure across said check valve to control the seating of said valve and regulate the flow from said outlet to said chamber, means for by-passing at least a portieri of the fuel utilized in creating such differential pressure to a low pressure source, and means for variably regulating the pressure of the by-passed fuel.

6. in `a system for pressurizing fuel to an engine, a pump having a plurality of reciprocating pumping plungers, a constant-angle wobble plate for actuating said plungers, means for effecting rotation of said wobble plate, means providing individual pumping chambers for said plungers, said chambers having inlet ports for low pressure ll fue] and discharge ports through which fuel is expelled, a passage for conducting fuel to the engine having an inlet common to said discharge ports, a fuel regulating device in said passage, check valves controlling said discharge ports, means permitting leakage of fuel from one side of said check valves to the opposite side thereof to establish a pump control fuel differential pressure across said valves, a receiving chamber for leakage fuel common to all of said valves, a passage for conducting leakage fuel back to the low pressure side of the pump, a regulating valve in said passage, and means responsive to variations in the drop in pressure across said device for variably positioning said regulating valve.

7. ln a system for pressurizing fluids, a pump having a plurality of pumping elements, means for imparting constant pumping strokes to said elements, means providing individual pumping chambers into which said elements move to expel uid and from which said elements retract to permit inow of fluid, said chambers having inlet ports for low pressure fill fluid and discharge ports through which iluid is expelled, means providing a chamber for expelled fluid common to said discharge ports, check valves controlling said discharge ports, means for continuously subjecting at least a portion of one side of said check valves to the fluid in said last mentioned chamber, means for subjecting a portion of said one side of said check valves to the lluid in said pumping chambers, means providing for leakage of fuel from said one side of said check valves to the opposite side thereof to establish a pump control fluid differential pressure across said valves, and means for variably regulating the pressure exerted by said leakage fuel tending to seat said valves.

8. In a system for pressurizing fluids, a pump having a plurality of pumping elements, means for imparting constant pumping strokes to said elements, means providing individual pumping chambers into which said elements move to expel fluid and from which said elements retract to permit inow of uid, said chambers having inlet ports for low pressure lill fluid and discharge ports through which iluid is expelled, means providing a chamber for expelled fluid common to said discharge ports, a 7

pump discharge conduit leading from said latter chamber, means for continuously subjecting a portion of one side of said check valves to the fluid in said last mentioned chamber, means for subjecting another portion of said one side of said check valves to the fluid in said pumping chambers, means providing for the passage of fluid from one side of said check valves to the opposite side thereof to establish a pump control uid differential pressure across said valves, a chamber for said last mentioned iluid common to all of said valves, and means for variably controlling the pressure in said latter chamber as a function of the pressure in said conduit.

9. In a system for pressurizing fluid, a pump having a plurality of pumping elements, means for imparting constant pumping strokes to said elements, means providing individual pumping chambers in which said elements move to expel uid and from which said elements retract to permit inow of fluid, said chambers having inlet ports for low pressure fill fluid and discharge ports through which uid is expelled, check valves for said discharge ports, an outlet for pressurized fluid common to said outlet ports, means continuously subjecting a portion of one side of said check valves to the fluid in said outlet, means for subjecting another portion of said one side of said check valves to the fluid in said pumping chambers, means resiliently urging said check valves to seated position, means permitting passage of uid from the rst mentioned portion of said one side of said valves to the opposite side thereof to establish a pump control Huid differential pressure across said valves, a receiving chamber for fluid passed to the opposite sides of the check valve common to all of said valves, a passage through which fluid from said receiving chamber may ow to the low pressure side of the pump, and means for variably regulating the fluid pressure in said latter passage ns a function of the pressure in said outlet.

l0. A system as claimed in claim 9 wherein the means for regulating the pressure of fluid in said passage to the low pressure side of the pump comprises a regulator valve responsive to variations in pump discharge pressure.

ll. A system as claimed in claim 9 wherein the means for regulating the pressure of fluid in said passage to the low pressure side of the pump comprises a valve responsive to variations in pump discharge pressure, and means are provided for damping the action of said regulator valve.

References Cited in the tile of this patent UNITED STATES PATENTS 1,010,206 Wainwright Nov. 28, 1911 1,690,097 Ackermann Nov. 6, 1928 2,018,119 Brouse Oct. 22, 1935 2,268,000 Treer Dec. 30, 1941` 2,381,528 Trich Aug. 7, 1945 2,395,964 Fodor Mar. 5, 1.946 2,433,220 Huber Dec. 23, 1947 2,506,162 Metzgar May 2, 1950 2,549,711 Ruben Apr. 17, 1951 2,575,677 Neu Nov. 20, 1951 2,582,535 Drouot Jan. 15, 1952 2,636,438 Roustan Apr. 28, 1953 2,682,227 Burris June 29, 1954 FOREIGN PATENTS 48,535 Denmark Mar. 9, 1934

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