US1965937A

US1965937A - Variable displacement pump

Info

Publication number: US1965937A
Application number: US551818A
Authority: US
Inventors: Ferris Walter
Original assignee: Oilgear Co
Current assignee: Oilgear Co
Priority date: 1931-07-20
Filing date: 1931-07-20
Publication date: 1934-07-10
Anticipated expiration: 1951-07-10

Description

'July'lo 1934- W. FERRIS VARIABLE DISPLACEMENT PUMP Filed Jully 20, 1931 4 Sheets-Shea?I l gwumntoz WALTER FERRIS.

' July 10, 1934. w. f-ERRIS 1,965,937

VARIABLE DI S PLACEMENT PUMP Filed July 2o. 1931 4 sheets-Sheet 2 31m/vento@ WALTER FEFQRIS.

dbbozmq 4 Sheets-Sheet 3 nO W d 31a/vento@ July 10, 1934. w. FERRIS VARIABLE DISPLACEMENT PUMP Filed July 20, 1931 July 1o, 1934. l

Filed July 20; 1951 4 Sheets-Sheet 4 Fig. 5.

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Patented `.Iu,ly 1o,v1934 A 1,965,937 VARIABLE DISPLACEMENT PUMP walter Ferris, Muwaukee, wis., signor to The Oilgear Company, Milwaukee, Wis., a corporation of Wisconsiny Application July 20. 1931, Serial No. 551,818

14 Claims.

This invention relates to variable displacement pumps.

The pump to which the ,invention applies in particular has itsl pistons and cylinders arrangedv eccentricity between the axes-thereof and thereby vary pump displacement, such as the pumpdisclosed in Patent No. 1,901,501 whichy issued,

March 14, 1933 upon my copending application, Serial No. 549,664 filed July 9, 1931 of which this application is' a continuation as to matters common to both applications.

The driver should be rigidly heldin its ad.- justed position in order to withstand the high internal forces which are created 'within' the pump whenever it is delivering liquid under high pressure.

` One object of this invention is to provide means within the pump itself for holding the driver against being moved 'or deflected from its adjusted position 'by internal pump forces.

Another object is to provide means for easily and accurately adjusting the stroke of the pump. Another object is-to`provide a pump of Athis character to which the prime mover may be easily and readily connected.

Other objects and advantages will appear hereinafter.

According to the invention in a general as-A 40 pect, a pump of the above type has its driver carried yby a cradle which has projections orf' pistons arranged upon diametrically opposite sides thereof and projecting` therefromparallel tothe plane of the cylinders into'sockets or cylinders which are carried lby the pump casing vto support the cradle and allow it to be moved in a straight line transverse to the pintle axis to thereby vary pump displacement.

According to the invention in another aspect'.

the pump is provided with afdriver'which is supported by pistons and cylinders arrangedvupon diametrically opposite sides thereof and which is adjustedto vary pump displacement and rer. tained in adjusted positionsby liquid delivered "D to the supporting cylinders.

(CI. 10a- 161) According to the A`invention in another aspect. the pump casing has one of its sides substantially closed by a. slide or sliding head which carries an electric motor, and the motor shaft is inserted into the driverto drive it direct from the motor and to move the motor and its support with the driver when the driver is adjusted to vary pump displacement.

' The invention is embodied in the pump illustrated in the accompanying drawings in which the views are as follows:

Fig. 1 is a central vertical section through the Dunn-, K

is a. sectional plan view taken on. the une 2--2 or Fig. 1. 7

Fig. 3 is a sectional plan 'view taken on the line 3--3 of Fig. 1.

Fig. 4. is a sectionalrplan view taken on the line 4-4 of Fig. 1.

Fig. '5 is a sectional planview taken on the line 5-5 of' Fig. 1.v

Fig. 6 is a vertical sectiontaken on the line Fig. 'T is a. diagram, oi' the hydraulic circuit.

'I'he pump has its mechanism arranged within a casingl whicheonstitutes s. reservoir 2 for the working liquid, such ascii, and has its top closed by a slidable head or'cap 3. f

The casing 1 has a central boss or support i rigidlysecured vtol-or formed integral with its bottom wall and provided with anarm 5 which Y- A is connected to or, formed integral with one of its sidewalls. n

- 'I'he support 4 has rigidly secured therein the lower end of avertical pintlel which has two axial' passageways 'l and mior'rned therein and communicatingrespectively, at the lower ends ,thereof with two passageways' 9 and 10 formed in the support4 andin; the arm 5. I

vThe upper ends voffthe 'passageways 'I and 844 95 comn'ninicate,v respectively, with twol segmental ports 11 and v12-whichv are formed in opposite sides of the-pintle 6.6

The upper part .of the pintle Btapers slightly. for instance .005" per inch of -length, and has a cylinder barrel 13 fitted thereon-and .provided with a number of cylinders 14, -forinstance five cylinders, each of which has a port v15 formed in its inner end to communicate alternately with the ports 11 and 12. as the cylinder barrel 13 rotates. `f l Each cylinder 14has a piston 13 tted therein and provided-upon its'outer end with a crosshead 11 by means oi' which it is 'reciprocated The cylinder bari-e118 is rotated upon the pim tle 6 and. the pistons 16 are reciprocated in the cylinders 14 by a circular driver 18 which is suymorted within a cradle or carrier 19 and rodrivcr 1S has a. vertical inner flange 20 which provided with a number of straight bearing faces 2l each of which is arranged at a right angle to the axis of a cylinder 14 and provided its center with an opening 22 through which the stem of the piston 16 extends.

The crossheads 17 are held in contact with the faces 21 by roller bearings 23 arranged between the same and an equal number of segmental i'langes 24 which are carried by the driver 18 at the periphery thereof and have suitable roller plates inserted in their inner faces and arranged parallel to the corresponding faces 2l.

When the driver 18 is rotated, the cylinder barrel 13 will be rotated and, if its axis is offset from the axis of the pintle 6, each piston 16 will be drawn outwardly during one-half of a revolution by its crosshead 17 riding upon the face 21 and will be forced inwardly during the other half of the revolution by its crosshead177 bearing against the bearing 23 which is 'supported by the flange 24.

If the driver 18 is offset as shown in Fig. 2 and is rotating in a clockwise direction, each piston will be drawn outwardly and draw liquid into its cylinder 14 during the time that its port 15 is in communication with the pintle port 12 and will be forced inwardly and expel liquid from its cylinder during the time that its port l5 is in communication with the pintle port 11.-

The pump thus draws liquid into its cylinders through the passageways 8 and 10 and exhausts liquid through the passageways 7 and 9. If the driver 18 is rotated in the opposite direction or if the axis of the driver 18 is moved to the opposite side of the axis of the pintle, the pump will deliver liquid in the opposite direction. The pump is capable of delivering liquid at high working pressures, for instance 2500# per square inch, and high lateral forces are created upon the discharge side of the pump which would move the driver relatively to the pintle unlessthe driver and the pintle are positively held against lateral movement.

The pintle is held against movement by being embedded in the support 4 and the driver is held against lateral movement relatively to the head 3 by being journaledA and supported within the cradle 19 by two anti-friction bearings 25 and 26. The bearing 25 has its inner ring fitted upon the hub of the driver 18 and its outer ring fitted within the upper end of the cradle 19. The bearing 26 has its outer ring tted within the bottom of the driver 18 and its inner ring tted within an annular ange 27 which is fixed to the bottom of the cradle 19.

The cradle 19 is supported by two projections or

pistons

28 and 29 which are xed thereto diametrically opposite each other and tted, respectively, insockets or

cylinders

30 and 31 carried by the front and rear walls of the casing 1.

The

pistons

28 and 29 allow the cradle 19 to be moved longitudinally of the casing 1 to vary pump displacement but hold it against any lateral movement. The cradle 19 is prevented from rocking upon the

pistons

28 and 29 by a guide 32 which extends through one side wall of the casing 1 and has its inner end fitted in a longitudinal slot 33 formed in the cradle 19.

The cradle 19 and the driver 18 are moved transversely of the casing l to vary pump displacement by the

pistons

28 and 29 which are actuated by pressure fluid delivered to the

cylinders

30 and 31 through a control valve 34 which is ordinarily carried by the casing 1, as by means of a bracket 35.

The control valve 34 has a port 36 which is connected by a pipe 37 to the cylinder 30, a port 38`which is connected by a pipe 39 to the cylinder 3l, and an admission port 40 which is arranged between the

ports

36 and 38 and open at all times to fiuid pressure. Both ends of the valve casing are connected to a drain pipe 41 which discharges into the reservoir 2.

The control valve 34 has a plunger 42 which controls the

ports

36 and 38 and is hydraulically balanced so that it moves easily in the Valve casmg.

The plunger 42 has its stem pivoted to one end of a lever 43 which is pivoted intermediate its ends to a rod 44 and has its other end connected by a link 45 to a hand lever 46 intermediate the ends thereof.

The rod 44 is rigidly secured to the piston 28 and extends through a packing 47 carried by the cap ofthe cylinder 30 so that the rod 44 moves with the piston 28 and the packing 47 prevents loss of pressure in the cylinder 30.

The hand lever 46 has its inner end pivoted to a bracket 48 which iscarried by the casing l and has an arcuate rib 49 provided along its outer edge.

The rib 49 is engaged by a friction block 50 which is secured upon a rod 51 having the ends thereof slidable through two

lugs

52 and 5 3 carried by the lever 46.

The rod 51 between the lug 53 and the friction block 50 is encircled by a helical compression spring 54 which urges the friction block 50 against the rib 49 and thereby frictionally holds the lever 46 against movement.

If the hand lever 46 is moved toward the outer end of the rib 49, the lever 43 will pivot upon the rod 44 and move the valve plunger 42 inwardly, thereby opening the port 36 to the drain pipe 41 and opening the port 38 to the admission port 40.

The pressure fluid entering the valve cylinder through the admission port 40 will now ow through the port 38 and the pipe 39 to the cylinder 31 and force the piston 28 inwardly, thereby varying the distance between the axis of the driver 18 and the axis of the pintle 6.

As the piston 29 moves inwardly, the piston 28 moves outwardly and working fluid is expelled from the outer end of the cylinder 30 through the pipe 37, the Valve 34 and the drain pipe 41.

As the piston 28 moves outwardly, the rod 44 also moves outwardly and, as the friction plate 50 holds the hand lever 46 against movement, the lever 43 pivots upon the end of the rod 44 and returns the plunger 42 to its initial position to close the

ports

36 and 38.

The driver 18 is thus moved a distance which is exactly proportional to the distance through which the hand lever 46 is moved and, when the plunger 42 closes the

ports

36 and 38, the working fluid is trapped in the

cylinders

30 and 31 and holds the cradle 19 and the driver 18 rigidly in adjusted position.

If the hand lever 46 is moved in the opposite direction, or toward the inner endl of the rib 49, the valve plunger 42 will be drawn outwardly and pressure uid will flow to the cylinder 30 and move the piston 28 inwardly until the movement thereof is sufficient to return the plunger 42 to its initial position. k-

The driver 18 is rotated by an electric motor 55 which is supported upon the casing head 3 and has its shaft 56 tted in the hub of the driver 18 and xed for rotation therewith, as by means of a key 57.

When the cradle 19 and the driver 18 are moved longitudinally of the casing 1 to change pump displacement, the head 3 and the motor 5 5 are moved therewith and the head 3 is held to a straight line movement andprevented from rotating by two tap bolts 58 one of which is shown in Fig. 3 andthe other of which is arranged diametrically opposite thereto.

Each bolt 58 is threaded into the flange of the casing l and fitted n a slot 59 which is formed in the flange of the head 3 and has sufficient length to allow the axis of the driver 18 to be moved from its extreme. position upon one side of the axis of the pintle 6 to its extremeposition upon the other side thereof.

The

pistons

28 and 29 are actuated by liquid supplied by a gear pump 60 which has its housing 61 arranged within the head 3 upon the flangev of the casing land held in position thereon by bolts 62.

The pump housing 61 has a pump chamber 63 formed therein which contains two intermeshing 'gears 64 and 65 arranged, respectively, upon shafts 66 and 67 and drivenby a. gear 68 fixed to the shaft 66.

The gear 68 meshes with an idler gear 69 which is arranged upon a shaft 70 carried by the gear pump housing 61, and the gear 69 meshes with a driving gear 7l which is fixed to the hub of the driver 18. y

The gear pump 60 is thus driven in unison with the driver 18, and the movement of the driver 18 longitudinally of the casing 1 isso slight relatively to the distance between the centers of the gears 69 and 71 that the meshing of these gears is .substantially unaffected by the movement of the driver 18. y

When the

gears

64 and 65 are rotated, liquid is drawn into the chamber 63 from the reservoir 2 through an intake passageway 72 which commuricates with the chamber 63 at one side of the

gears

64 and 65 and extends through the housing 6l and downwardly into thereservoir 2 through a rib 73 formed upon the side wall of the casing 1. v

Thegear pump 60 discharges its output into a discharge passageway 74 which extends downwardly from the pump chamber 63 at the other side of the gears 64 andr 65 and communicates with a horizontal passageway 75formed in the housing 61. One end of the passageway 75 communicates with a relief valve 76 which is also arranged in the housing 61 and limits the pressure created by the gear pump 60. The other end of the passageway 75 communicates with a passageway 77 which is formed in the rib 73 and connected to a low pressure supply pipe 78 intermediate the ends thereof, as best shown in Figs.

2 and 4.

The ends of the supply pipe 78 arev connected through two

check valves

79 and 80 to opposite ends'of a valve block 81 which is attached to the wall of the casing l and provided with two transverse passageways which' form continuations of the

passageways

9 and 10. The check valves 79 Y and 80 allow liq'uid to flow from the pipe 78 into the

passageways

9 and 10 but prevent it from owing inthe opposite direction'.

The

passageways

9 and 10 extend through the valve block 8l and communicate, respectively, with two

pipes

82 and 83 which are attached to the valve block 81 by means of two

pipe fittings

84 and 85. 80

The valve block 81 also contains a high pressure relief valve 86, which has its inlet connected to the passageway 9 and its outlet connected to the passageway 10 to limit the pressure developed by the pump vwhen vit is discharging through the 85 passageway 9, and a high pressure relief valve 8'7 whichhas its inlet connected to the passageway 10 'and its outlet connected to the passage way 9 to limit the pressures developed by the pump when it is discharging through the passageway 10.

Liquid for

actuating'the pistons

28 and 29 is delivered to the valve 34 'through a pipe 88 which has one of its ends connected to the supply pipe 78 intermediate the ends thereof and its other 95 end connected,l to the admission port 40 in the valve 34. The` pipe 78 or the pasageway 77 may also have a supply pipe 89 connected thereto, as shown diagrammati'cally in Fig. 7, through which the gear pump vmay deliver liquid for other auxiliary purposes.

With the axis of the driver 18 eccentric to the axis of the pintle 6 in the direction shown in Fig. 2 and with the driver rotating in a clockwise direction, the gear pump 60 will deliver liquid through the check valve 79, the passageways 10 and 8 and the port l2 to each cylinder 14'during nearly one-half revolution of the driver 18, and each piston 16 will be forced inwardly by the driver 18 during substantially the other half 'rev- 110 olution thereof and expel the liquid from its cylinder through the port 11 and the passageways 7 and 9 into the hydraulic circuit through the pipe 82, the check valve 80 preventing the liquid from entering the gear pump circuit.

The liquid returning from the hydraulic circuit ows to the cylinders 14 through the pipe 83, the passageways 10 and 8 and the port 12. At the same time, the gear pump is tending to deliver liquid into the pipe 83 through the check 120 valve 79 and is thus keeping the return side of the hydraulic circuit ooded with liquid and supercharging the variable delivery pump at a pressure determined by the adjustment of the relief valve 76 through which is exhausted the 125 liquid delivered by the gear pump in excess of requirements.

The invention herein set forth is susceptible of various modifications without departing from the scope thereof as hereafter claimed.

The invention is hereby claimed as follows:

1. A variable displacement pump, comprising a casing, a pintle fastened at only one of its ends to said casing in a fixed position within the same and provided with intake and exhaust ports and passageways, a cylinder barrel 'tted upon said pintle to rotate thereon and having cylinders communicating with said pintle ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a driver for rotating said cylin- +40 der barrel upon said pintle and adapted to reA ciprocate'said pistons in said cylinders whenever its axis is eccentric to the axis of said pintle, means for rotating said driver, a cradle for rotatn ably supporting said driver and for holding the same against radial movement relatively thereto and adjustable transversely of said casing to vary the distance between the axes offsaid' driver and said'pintle to thereby vary pump displacement,

sockets carried by said casing upon opposite sides 15@ foffsiatidpintle, and projections'xed upon opposite sides of ysaid cradle and bearing in said flacasing, a pintle fastened at only one of its ends to said casing in a fixed position within the same and provided with intake and exhaust ports and passageways, a cylinder barrel fitted upon said pintle to rotate thereon and having cylinders communicating with said, pintle ports alternately as said'cylinder barrel rotates, pistons arranged in said'cylinders, a driver for rotating said cylinder barrel upon said pintle and adapted to reciprocate said pistons in said cylinders Whenever its axis is eccentric to the axis of said pintle, means for rotating said driver, a cradle `for rotatably supporting said driver and for holding'the same against radial movement relatively thereto and adjustable transversely of said casing to vary the distance between the axes of said driver and said pintle to thereby vary pump displacement, cylinders carried by said casing upon opposite sides of said pintle, cylindrical projections iixed upon opposite sides of said cradle and bearing in said cylinders to slide therein and thereby support said cradle in said'casing and allow it to move transversely thereof to vary pump displacement and a guide carried by said casing and engaging said cradle to preventfit from rotating upon the axes of said projections.

3. A variable displacement pump, comprising a casing, a pintle fastened at only one of its ends to said casing in a fixed position Within the same and provided with intake and exhaustports and passageways, a cylinder barrel fitted upon said pintle to rotate thereon and having .cylinders communicating with said pintle ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a driver for rotating said cylinder barrel upon said pintle and adapted to reciprocate said pistons in said cylinders whenever its axis is eccentric to the axis of said pintle, means for rotating said driver, pistons and cylinders for supporting said driver, and means for delivering pressure iiuid to said supporting cylinders to actuate said pistons and move said driver and thereby vary pump displacement.

4. A variable displacement pump, comprising a casing, a pintle carried by said casing and fixed at only one of its ends in a stationary position with` in the same and provided with intake and exhaust ports and passageways, a cylinder barrel tted upon said pintle to rotate thereon and having cylinders communicating with said pintle ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a driver for rotating said cylinder barrel upon said pintle and adapted to reciprocate said pistons in said cylinders whenever its axis is eccentric to the axis of said pintle, meansior rotating said driver, pistons and cylinders for supporting said driver, hydraulic means for delivering pressure fluid to said supporting cylinders to actuate said pistons and move said driver and thereby varypump displacement, and means for controlling the' delivery of liquid to said hydraulic means and responsive to the operation thereof to discontinue said delivery of liquid.

5. A variable displacement pump, comprising a casing, a pintle carried by said casing and xed at only one of its ends in a stationary position Within the same and provided with intake and exhaust ports and passageways, a cylinder barrel tted upon said pintle to rotate thereonand having cylinders communicating with said pintle ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a driver for rotating said cylinder barrel upon said pintle and adapted to reciprocate said pistons in said cylinders whenever its axis is eccentric to the axis of said pintle, means for rotating said driver, pistons and cylinders for supporting said driver, an auxiliary pump lfor delivering pressure fluid ,to said supporting cylinders to actuate said pisv tons and move said Ydriver and thereby varypump displacement, a valve for controlling the delivery of liquid from said pumpto said supporting cylinders, and means for operating said valve to direct liquid to said supporting cylinders and responsive to the movement of said supporting pistons to close said valve after said pistons have moved a predetermined distance.

- 6. A variable displacement pump, comprising a casing, a pintle fastened at only one of its ends to said casing in a xed position within the same and provided with intake and exhaust ports and passageways, a cylinder barrel tted upon said pintle to rotate thereon and having -cylinders communicating with said pintle ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a driver for rotating said cylinder barrel upon said pintle and adapted to reciprocate said pistons in said cylinders Whenever its axis is'eccentric to the axis of said pintle, means for rotating said driver, a cradle. arranged Within said casing, means for rotatably supporting said driver in said cradle and for holding the same against radial movement relatively thereto, pistons and cylinders for supporting said cradle, and means for delivering pressure fluid to said supporting cylinders to actuate said pistons and'move said cradle and thereby vary pump displacement.

7. A variable displacement pump, comprising Qa casing, a pintle fastened at only one of its ends to said casing in a fixed position within the same and provided with intake and exhaust ports and passageways, a cylinder barrel iitted upon said pintle to rotate thereon and having cylinders communicating with said pintle ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a driver for rotating said cylinder barrel upon said pintle and adapted to reciprocate said pistons in said cylinders Whenever its axisv is eccentric to the axis ofsaid pintle, means for rotating said driver, a cradlearranged within said casing, means for rotatably .supporting said driver in said cradle and for holding the same against radial movement relatively thereto, pistons and cylinders for supporting s aid cradle, hydraulic means for delivering pressure uid to said supporting cylinders to actuate said pistons and move said cradle and therebyvary pump displacement, and means for controlling the delivery of liquid to said hydraulic means and rerel fitted upon said pintle to rotate thereon and having cylinders communicating with said'pintle ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a driver for rotating said cylinder barrel upon said pintle and adapted to reciprocate said pistons in said cylinders whenever its axis is eccentric to the ders Whenever axs of said pintle, means for rotating said driver, a cradle arranged within said casing, two bearings arranged upon opposite sides of the plane of said pistons for rotatably supporting said driver in said cradle and for holding the same against radial movement relatively thereto,.pistons and cylinders for supporting said cradle, and means for delivering pressure fluid to said supporting cylindersk to actuate said supporting pistons and move said cradle and thereby vary pump displacement. 1 n

9. A variable displacement pump, comprising a casing having a slidable head, a pintle carried by said casing in a fixed position within the same and provided with intake and exhaust ports and passageways, a cylinder barrel tted upon said pintle to rotate thereon and having cylinders communicating with said pintle ports alternately as 'said cylinder barrel'rotates, pistons arranged in said cylinders,d a driver for rotating said cylinder barrel upon said pintle and adapted to reciprocate said pistons in said cylinders whenever its axis is eccentric to the axis of said pintle, an electric motor carried by said casing head and having its shaft connected to said driver for rotating the same, a cradle arranged within said casing, means for rotatably supporting said driver in said'cradle and for holding the same against radial movement relatively thereto, /pistons and cylinders for supporting said cradle Within said casing, and means for delivering pressure fluid to said supporting cylinders to actuate said pistons and move said cradle to thereby vary .pump displacement'. l

10. A variable displacementpump, comprising a casing having a slidable head, a pintle carried by said casing in a fixed position within the same and provided with intake and exhaust ports and passageways, aicylinder barrel fitted upon said pintle to rotate thereon yand `having cylinders communicating with said pintle ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a' driver for'rotating said cylinder barrel upon said pintle and adapted to reciprocate said pistons in said cylinders whenever its axis is eccentric to the axis of said pintle, an electric motor carried by said casing head and having its shaft connected t'o said driver for ro- Jtating the same, a cradle arranged within said casing, means for rotatably supporting said driver in said cradle and for holding the same- 4against radial movement relativelythereto, pistons and cylinders for supporting said cradle within said casing, means for delivering pressure fluid to said supporting cylinders to actuate said pistons and move said cradle to vary pump displacement, and means for controlling the delivery of said fluid and responsive to the operation of said pistons to discontinue said delivery-of fluid. y

11. A variable displacement pump, comprising a casing, a pintle fastened at only one of its endsV to said casing in a xed position within the same and provided with intake and exhaust ports and passageways, a cylinder barrel fitted upon said pintle to rotate thereon and having cylinders communicating with said pintle ports alternately as said cylinder barrelrotates, pistons arranged in said cylinders, a driver for rotating said cylinder barrel upon said pintle and adapted to reciprocate said pistons in said cylini'ts axis is eccentric to the axis of said pintle, means for rotating said driver, a cradle arranged within said casing, means for rotatably supporting said driver in said cradle and for holding thesame'agqainst radial movement;

relatively thereto, pistons and cylinders for supporting said cradle, an auxiliary pump carried by said cas-ing in a stationary position and driven by said'driverV in all positions thereof for ,delivering pressure fluid to said supporting cylinders to actuate said supporting pistons kand move said cradle and'thereby vary pump displacement, a valve for controlling the delivery of liquid from said pump to said 'supporting cylinders, and means for operating said valve to direct liquid to said supporting cylinders and responsive to the movement of said supporting pistons to close said valve after said pistons have moved a predetermined distance.

12. A variable displacement pump, comprising a casing having an opening in one side thereof and a slidable head substantially closing said opening,.an electric motor carried by said head to slide therewith and having its shaft extending therethrough, a pintle secured at only one of its ends in a fixed position within saidcasng in approximate alinement with said motor shaft and provided with intake and exhaust ports and passageways, a cylinder barrelfitted upon said pintle to rotate thereonand having radial cylinders communicating with said ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a driver keyed to said motor shaft to :rotate said cylinder barrel upon said pintle as said .shaft rotates and to reciprocate said pistons in said cylinders whenever its axis is eccentric to the axis of said pintle, a cradle arranged around said driver and provided with an antifriction bearing upon each side of the plane of said cylinders'to support said driver within said cradle and to restrain it from radial or axial displacement, means for supporting said cradle in said casing and allowing it to move in a straight line transverse to said pintle to change pump displacement but restraining it from moving transverse to that line, and means for moving said cradle along said line to move saiddriver transverse to said pintle and to thereby move said motor and said slidable head.

13. A variable displacement pump, comprising a casing having an opening in one side thereof and a slidable head substantially closing said opening, an electric motor carried by said head to slide therewith and having its shaft extending therethrough, a pintle-secured at only one of its ends in a fixed'position within said casing in approximate alinement with said motor shaft and provided with intake and exhaust ports and passageways, a cylinder barrel fitted upon said pintle to rotate thereonv and having radial cylinders communicating with said ports alternately as said cylinderbarrel rotates, pistons arranged in said cylinders, a driver keyed to said motor shaft to rotate said cylinder barrel upon said pintle as said shaft rotates and to reciprocate said pistons in said cylinders Whenever its axis is eccentric to the axis of said pintle, a cradle arranged around said driver and provided with an antifriction bearing upon each sidev of the plane of said cylinders yto support said driver within said cradle and to restrain it from radial or axial displacement, means including pistons and cylinders for supporting said'cradle in said casing and allowing it to move in a straight line transverse to said pintle to change pump displacement but restraining it from moving transverse to that line, and means for moving said cradle along said line to move said driver transverse to said pintle and to thereby move said motor and said slidable head.

14. A variable displacement pump, comprising a casing having an opening in one side thereof and a. slidable head substantially closing `said opening, an electric motor carried by said head to slide therewith and having its shaft extending therethrough, a pintle secured at only one of its ends in a xed position within said casing in approximate alinement with said motor shaft and provided with intake and exhaust ports and passageways, a cylinder barrel tted upon said pintle to rotate thereon and having radial cylinders communicating with said ports alternately as said cylinder barrel rotates, pistons arranged in said cylinders, a driver keyed to said motor shaft to rotate said cylinder barrel upon said pintle as said shaft rotates and to reciprocate said pistons' in said cylinders whenever its axis is eccentric to the axis of said pintle, a cradle arranged around said driver and provided with an antifriction bearing upon each side of the plane of said cylinders to support said driver within said cradle and .to restrain it from radial or axial displacement, sockets carried by said casing upon opposite sides of said pintle, and projections fixed upon opposite sides of said cradle and extending into said sockets to slide therein whereby said cradle is supported in said casing and allowed to move in a straight line transversely thereof to change pump displacement but is restrained from moving transverse to that line, and means for moving said cradle axially of said sockets to move said driver' and thereby move said motor and said slidable head.

WALTER FERRIS.`