US2373723A - Fluid pump or motor - Google Patents

Description

April 17, 1945.

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April 17, 1945. G. A. WAHLMARK FLUID PUMP 0R MOTOR '3 Filed March 2. 1942 6 Sheets-Sheet 2 I v INVENTOR. GwmarQz MahZmar/a V I r April 17-, 1945. G. A. WAHLMARK I 2,373,723

FLUID PUMP 0R MOTOR 6 Sheets-Sheet 3 Filed March 2, 1942 April 17 1945. G A. WAHLMARK 2,373,723

v FLUID PUMP 0R MOTOR Filed March 2, 1942 6 Sheets-Sheet 4 '3 v v INVENIOR. I L Gunnar @ZUaMmar/Q April 17, 1945. s. A. WAHLMARK 2,373,723

' FLUID PUMP on MOTOR Filed March 2. 1942 e Sheets-Sheet s INVENTOR. BYGMIZO/T Q [flaidmar/a b j u N N Nmw P 1 G. A. WAHLMARK 2,373,723

FLUID PUMP on MOTOR Filed March 2. 19 42 6 Sheeis-Sheet 6 MahZmar/a W Why 1, SM .J 18, V .mmw 55 m Q T/nbw b Q m hm. mi-mm 4 5y 3 a B .a w v I? J NI the line 2-2 of Fig. -1'. Fig. 3 is a fragmentary central longitudinal section along the line 3-3 of Fig.2, with certain Patented Apr. 17,1945

um'rso STATES PATENT OFFICE FLUID rum on. Moron sauna A. Walllmark, Rockford, 111. 7

Application MarchZ, 1942, Serial No. 432,917

23 Claims. (Cl. 103-113) It is the general object of the invention to provide a new and improved pump or motor. More particularly itis an object to provide a new and improved .piston type pump or motor embodying servo control means for adjusting the stroke of the pistons.

Another object is to provide a reversible Wobbler type mechanism with a new and improved control means for adjusting the stroke of the pistons, and the position of the wobbler on both sides of neutral as well as to its neutral or no-stroke position.

' It is another object to provide such a mochanism with a unitary Wobbler reversing and stroke adjusting control of the servo type, and more particularly to provide a unitary control of this .kind of extremely small size, light weight and high sensitivity.

Another object is to provide a piston type fluid pump or motor with an improved gyratory valve mechanism for controlling the flow of fluid to and from the cylinders.

Another object is it provide a compact and light weight motor driven unit embodying two pumps 1having stroke adjusting and fluid reversing control incorporated therein, and capable of producing large quantities of fluid at high pressures.

Another object is to provide a Wobbler type pump with-improved means for holding the parts thereof together so as to withstand high fluid pressures without leakage. A more particular object is to provide a motor driven pumping unit with two independently controllable pumps driven from a single motor, each pump being capable of absorbing the full output of the motor, and'having built-in and manually adjustable servo controls, and a reservoir for containing the necessary fluid to operate two fluid motors. 1

Another object is to provide a pumpin'gdevice neutral or no-stroke position. There is illustrated in the drawings and hereof the invention and is not intended to limit the 7 of the wobbler type with fluid actuated stroke '1 from the following description, taken inconnection with the accompanying drawings, in which:

Fig. 1 is a front elevational view, .partly in sec-.

tion along the line li of Fig. 2, form of my invention.

Fig. '2 is an end view,

of a preferred partly in section, along parts at the right hande'nd turned 90 about the' shaft Fig. 4 is a fragmentarysection along the line 4-lofFig.3.

Fig. 5 is a fragmentary view along theline 5-5 of Fig. 3.

Fig. 6 isa top plan view of the preferred form of the invention Fig. 7 is a vertical section'along the line'l-l of Fig. 3. 1

Fig. 8 is a horizontal section along the line 88 of Fig. 7. i

9 is a. horizontal section alongthe line 9-4 of Fig. 7.

Fig. 10- is a diagrammatic representation of the hydraulic circuit for one piston pump device with its servo control valves and the Wobbler adjusted to their neutral or no-stroke'position.

' Fig. 11 is a. similar circuit diagram with the servo control valves moved to their neutral position, the Wobbler still remainingin the maximum. stroke position of Fig. 11.

Fig. 14 is a similar circuit diagram, with the pump Wobbler in its no-stroke position and a modified form of servo control adjusted to its inafter described in detail, a preferred form of' the invention, together with a modiflcationthereof, with the understanding that the disclosure is intended as an exempliflcation of the principles invention to the forms shown. The scope of the invention will be'pointed out in the appended claims. a

In the form selected for purposes of disclosure and as illustrated in Figs. lxto 13; the invention comprises generally a three-quarter horsepower 6000 R. P. M. direct current motor M, two twelve cylinder wobbler type piston pumps P and P with self-contained servo, controls 0 and C',' respectively, a gear type Dump GP for furnishing a fluid (such as oil), for control and make-up purposes, reductlongearing G connecting the motor shaft M to a pump shafts (which is common to both of the pumps P and P), high pressure safety valves V and V for the pumps Pand P, re-

spectively, and a casing or housing H which env closes and connects certain of the parts to procylinder bores therein,

2 u vide a unitary structure. It is contemplated that theinlet and outlet ports for each pump willbe lower portion of the housing H. The motor shaft M extends through an opening in the adjacent housing wall 23, through a mechanical seal 24 (which is shown as of the type disclosed and claimed in my Patent No. 2,216,218, dated October 1, 1940) and into abore 25 in a pinion '25. This pinion, is formed integrally witha shaft 26 which issupported in a bushing-21 carried in a bracketlike extension 28 on the housing wall 23. The fit of the motor shaft M' in the bore 25' is such that.v the end of the motonshaft is supported in the pinion. A driving connection is provided by a cross key 29 which extends through a diametric'al slot in the shaft M and into registering longitudinal slots (not shown) in the pinion 25.

The gear pump GP (Fig. 1) comprises a pin-- ion 30 pinned on the end of shaft 26 and'a meshing pinion 3|, rotatably mounted on a pin' 22. A chamber for the gears is formed by a recess in mounted on the drive shaft 8' by means of a pin ll. The wobble plate is thus adlustable an larly about the'pin I from the neutral or nostroke position shown in Fig's. 3 and 10 toward the full stroke positions shown in Figs. 11 and 12 an extension 34 on the bushing 21, and a suitable cover plate 33.

The gearing G (Figs. land 3)' for driving the pumps P and P includes the drive pinion 25, an idler gear 35. and a gear 26 (Fig. 3) formed integrally with a cylindrical pump drive member 31 which is rotatably mounted in the upper portion ofthehousing H by means of a ball beard ing as.

. As illustrated herein the pumps Panel P (and their associated servo controls C and'C') are sub.- stantially alike in construction and operation, so that a detailed description of pump P will suiflce. The corresponding parts of pump P will be given the same numerals thereto. i g 1 The shaft S for the pumps extends in opp ite directions from the drive member; 21' (Fig. 3) and has acentral enlarged portion "which is fitted "intoza central bore in the member 31. A

plurality of pins ll extend radially inward through bores in the drive member 31 and into registeringsockets-fl-in the shaft S to form a driving connection therebetween, a pair of bands 43 being provided to hold the pinsl,l in their bores and sockets. i

The pumps, as mentioned. hereinbefore, are

-45 with a "prime"- added A disk-like member; or valve plate 0 is positioned in the pump casing against the flanged end of the cylinder block, and a cap member 81 is positioned against the cute surface of the valve plate II. The cylinder b ock, valve plate and cap member are eflective'l clamped in place in the casing bya ring 02 which has external screw threads ensasins corresponding threads on the casing 21, and a plurality of screw devices 83-, herein twelve in number,;which are threaded through the ring 62'and against the cap member ii to tighten the parts in place. This type of clamping means for the ports has the advantage of the full tensile strength of the casing as distinguished from prior constructions wherein bolts under tension were u'sed, the screws 62 herein being under compression.

The flow of fluid to and from the pump cylinders BI is controlledby means of a wheel-like valve 85, which is positioned in a cylindrical valve chamber 86 formed in the cylinder block 50, and

is driven by the shaft 8 through an eccentric pin 61 thereon so as to have a gyratory motion.

This type of valve is disclosed and claimed in my Patent No.; 2,190,812, dated February 20, .1940. Briefly, it includes arim ll which covers and uncovers the adjacent ends of the cylinders 5i and alternately connects them to the valve chamber j 68 outwardly of the rim 6. and inwardly of the rim. The outer portion of the valve chamber connects through an annular series of ports 89 (in the valve platefll), with an annular port I0 in the cap member II, this annular port communicating in turn with a first pump port ll (Fig. 2). A second pump port 12 connects with a recess 13 (Fig. 3) in the cap member 68, and through a plurality of ports 14 in the valve plate communicates with the gyratory valve inwardly of the rim 08. Since the rim of the valve is connected to its hub 15 by spokes Ii communication is established periodically between the ports 14 and the cylinders ll. a

.When the invention is usedfor pumping fluid at relatively high pressures, the valve 65 is pref erably made relatively thin, as shown. The peripheral portion of the valve plate 60, and the portion just inwardly of the ports 89 are backed up rigidly by the cap member 8i as is evident from Fig. 3. To reinforce the center of the valve plate when the ports 14 are pressure or outlet ports, thechamber 13 is arranged 'so that the of the wobbler type and have twelve cylinders each; Preferably they are of the type disclosed and claimed in my prior application Serial No. 305,690, filed November 22, 1939, now issued as Patent "No. 2,280,875, dated April as, 1942. As illustrated, the pump P comprises a casing' 2|, generally cylindrical in form as shown best in Fig. '1, and secured at one end to the casing 2| of the pumpP'.

and has an external flange 52 positioned against an annular shoulder 53 within the casing 2|. Pistons N are reciprocably mounted in the cylinders SI and extend therefrom and into engagement with an outer member 55 of a wobbler device. An inner an.-

- nular member 56 is connected to the outer member 55 by a ball bearing 51, and is pivotally I by A cylinder block .50 has twelve fluid underhigh pressure can act against the adjacent central portion of the valve Plate and keep it in efilcient sealing contact with the valve 65. I

. As illustrated herein, the shaft 8' is supported at its ends by bushings 18 and I. which are mounted in the cylinder blocks 50 and; I0 and have outwardly extending flanges which are clamped against shoulders in the cylinder blocks by means of threaded ring 12 and I9. Preferably the bushings and rings are then secured against rotation in the cylinder blocks by pins as indicated at With the exemplary form of the invention it is contemplated that the pump shaft 8 will be driven continuously by the motor M and that the output of the pumps P and P and the direction of flow of the fluid therefrom, will be controlled adjustment of the wobble plates of the pumps from neutral to forward and reverse positions. The means for adjusting the wobble plates will now be described.

IAS illustrated in the drawings the adjustin means for each pump comprises a control sleeve 05 (Fig. 3) control pistons 80 and 8I (Figs. 3 and '7) and means including the servo control C for controlling the fluid acting on the control sleeve and control pistons. The control sleeve 85 is slidably supported on the cylinder block 50 and is provided with an internal annular shoulder 80 which functions as a piston. An annular chamber 80 surrounds the cylinder block between the shoulder piston and an opposed shoulder 00. on the block 50. As more fully described hereinafter, the chamber 09 is supplied with fluid from the gear pump GP to move the control sleeve towards the Wobbler of the associated pump and thereby determine the angular position of the Wobbler. In Fig. 3, the control sleeve has moved the Wobbler 50, 50 to a neutral or no-stroke position wherein the right hand end 9| of the control sleeve engages the outer member 55 of the Wobbler throughout its periphery and holds it in exact neutral.

The control pistons 0t and 81"(Fig. 7) are herein arranged in pairs, the pistons 80 operating through piston rods 90 (Figs. 3 and '7) to move the Wobbler in one direction from its neutral position (against the action of fluid on the control sleeve piston 08), and the pistons 01 operating through piston rods W to move the Wobbler in an opposite direction from neutral. Each pair of piston rods 90 is formed as the legs of a U-shaped member, thebight 90 of which is pivoted in a lug 99 formed integrally with the inner wobbler member 50. Cylinders I00 for the piston 'iit and I cylinders IIJI for the pistons 81 are bored through the drive member 37 and are then closed at one end by means of plugs I02 and I03, respectively, the plugs being held in place by the pins 4 I. The control pistons 00 and 8! may properly be referred to as "forward and reverse pistons since their function, primarily, is to reverse the direction of fluid flow through the pump P. It i believed readily apparent that the control sleeve 00 acts todetermine the stroke or the pump pistons regardless of the direction of fluid flow through the pump. This characteristic of the control sleeve is utilized in a unique manner in connection with the servo control C. the construction and operation of which will now be described.

The servo control designated generally by the letter C is associated with the pump P and includes a cylindrical reversing valve RV and a pair" of servo valves SVF and SVR. (Figs. 3, 7 and 9). The reversing valve RV is rotatably mounted in a bushing 01' casing I supported in a vertical position in a plate I00 secured to the top of the pump casing N. This valve is herein provided with a stem I01 for the attachment 'of an operating arm I00 and is adapted to be rotated out of the neutral position of Figs. 1 to 3 and 6 to 10 to the forward and reverse positions of Figs. 11 and 12, respectively. As shown most clearly in Figs. 3, '7 and 8. control fluid under pressure supplied through a port 0 in the .casing' I05 enters a chamber III in the casing formed by a cutaway portion on. the valve RV. By rotating the valve counterclockwise (Fig. 8) this fluid can be directed out through a valve port M2 to a passage H0 which leads ultimately to the control cylinders I00. When in this position, fluid from the control cylinders I M is exhaustedthrough a passage or port I I4, through a port I I5 in the casing I05, a port H0 in the valve RV and an axial passage III in the valve which discharges at its lower end into the casing 2| of the pump P. Rotation of the valve RV in a clockwise direction from the position of Fig. 8 directs control fluid through a port I I0 in casing I05 into port I I0 and on to control cylinders IIII while at the same time fluid from the control cylinder IIlII exhausts through a passage H3, a, port H0 in casing I05,

' RV has been moved to its reverse position as in Fig. 12. As shown in Figs. 3, '7 and 9. the valve RV is formed with a flange I on its lower end and carries diametrically opposite-downwardly extending pins I2I and. I22 to which links I23 and I24 are anchored. The other ends of these links are connected. by pins I25 and I26, to the valves SVR and SVF respectively. The servo valves are cylindrical in form and slide in parallel bores I29 and I30 in a block or casing I3I which is mounted fixedly on the control sleeve 80 and is secured thereto by screw devices I32 so that the casing for the servo valves moves with the control sleeve 85 whose movement the servo valves control.

Although a more complete disclosure of the fluid circuits for the pumps and controls will be found in the circuit diagrams of Figs. 10 to 13, some of the passages are illustrated in Figs. 3; 4, 7 and 8. In these figures the passage H3 includes (Fig.3) connecting bores in the plate I00, connecting bores in the casing 2i, connecting bores in the cylinder block 50, a port through bushing I8, an annular groove 'in the shaft S, a short radial port, a longitudinal bore (Fig. 4) and an oblique bore in the shaft, and a recess (Fig. 7) in the member 31 which connects the outer end of the oblique bore with the two control cyle inders I00. A. corresponding series of bores, ports and recesses form the passage I It.

The high pressure relief valves V and V are alike so a description of valve V in connection with Fig. 2 will sufiice. The pump ports II and I2 are connected by a by-passport I45. A valve I40 is arranged to control the by-passing of fluid through this port and is operable in this capacity when port II is the outlet port of the pump and also when the port I2 is alternatively the outlet port. Valve I00 has a cylindrical portion I4I which is slidably mounted in a bore in the valve casing I48 and is engaged by a coiled spring I 69 which serves to urge thevalve I40 constantly towards its closed position as shown. The cylindrical portion I61 is made to have a cross sectional area approximately twice the cross sectional area of the port Itii where it forms a seat for the valve I40. When the port I2 is the pump outlet port the fluid discharged by the pump acts against the left hand end of valve I40, and when the pressure rises above the value for which the spring I49 is adjusted, valve I40 opens and bypasses fluid back to the port II which is then the inlet port for the pump. When the Wobbler is reversed so that port II is the pump outlet port the fluid acts on the exposed surfaces of the valve I40 which are within the port II. These surfaces include the exposed end of the cylindrical portion I" and part of both sides 01 the valve I46. The parts are so proportioned that the areas acted upon by the fluid to urge the valve I46 to its open position exceed the area acted upon by the fluid to seat the valve by an amount equal to the cross sectional area of port I45.

Thus the valve I46 opens to by-pass fluid at the same pre-adjusted pressure for both directions of pump discharge. I

Reference is now made more particularly to Figs. 10 to 13. In these figures there is illustrated the hydraulic circuit for the pump P and since the circuits for the two pumps are identical a description of one will suflice. In Fig. 10, the control C and the pump P are adjusted to their neutral or no-stroke position. The pump ports II and K2 are shown connected to a suitable fluid motor FM by means of conduits I50 and II. Fluid from the reservoir R is conducted to the gear pump GP by a conduit I52 and is conducted away from the gear pump by a conduit I53 which leads to the port Hill" of the reversing valve RV. A by-pass valve E56 is provided to maintain constant pressure in the conduit I53 and to permit excess fluid to pass back to the reservoir. A conduit I55 leads from the conduit I53 to the casing I56 of a pressure reducing valve PRV. .Fluid which passes the valve 'PRV is conducted by a conduit I5? to the chamber 89 wherein it acts on the piston 86' formed on the control sleeve 85. The valve PRV' has a reduced cylindrical portion I58, which normally lies opposite valve ports I59 in the casing I55 so as to restrict the passage of fluid over the valve. The valve is urged into this position by a spring I60, a stem I 6| on the valve engaging a perforated disk I62 to limit the movement of the valve by the spring. The fluid in chamber 88 moves the control sleeve 85 towards the left (Fig. to the no-stroke position shown since the pistons 86' and 81. are then inactive.

The pressure of the fluid in chamber 59 is herein controlled by the servo valves SVF and SVR' by regulating the exhaust of fluid from said chamber through an exhaust passage I65. This passage leads to a port I66 which communicates with bores I61 and I68 in which the valves SW and SVR. are slidable. Preferably the port I 55 is sopositioned that when the servo valves are in the positions shownin Fig. 10, there is a slight discharge of fluid into the bores I51 and I55. this fluid then returning to the reservoir R by gravity. The discharge under these conditions is so small that it does not affect materially the pressure in the chamber 86' but it does mean that the exhaust passage I65- is slightly open and that upon any movement of the valves SVF and SVR' the exhaust of fluid from passage I65 increases instantaneouslyj Movement of the reversing valve RV in either I53, through port H0, port H2 and passage H3 to cylinders IOI to act on pistons 51. Si.- multaneously the servo valve SVR is pulled towards the right from the position shown in Fig. 10 was to at first uncover the lower end of exhaust port I66 and thereby reduce the pressure in the annular control sleeve chamber 86, the exhaust of fluid through passage I65 then being greater than the fluid suppliedthrough the ports I59 of the reducing valve PRV due to the restriction caused by the port I58 of that valve. The pistons 81' then exert a force on the wobbler which overcomes the efiect of the control sleeve Piston 88 and the control sleeve is moved towards the right from the position of Fig. 10 towards the position of Fig. 11. Since the casing ISI for the servo valves is carried on and moves with the control sleeve 85, the casing I M follows the servo valve SVR' to its right hand position (as in Fig. 11) and until the port I66 is again just slightly uncovered by the end of the servo valve and the exhaust of fluid through passage I65 is reduced to a, slight discharge. The pressure in chamber 89 is then built up t the full value required to counter balance the effect of the pistons 61. Since the servo valve SVR is mechanically coupled to the flange I26 of the valveRV the position of the valve member SVR is determined by the angle through which the valve RV is shifted, and this position of the member SVR' will determine the extent of the movement of the casing I3I as it follows the servo valve SVR just far enough to cause the port E66 to be covered by the end of the valve member SVR. The control sleeve 85', being rigidly connected to the casing I3I, is thus arrested at any selected position corresponding to the angle through which the valve RV is shifted. The Wobbler vis thus adjusted t whatever position is selected for the-servo valve SVR, which may be anywhere between neutral and maximum stroke. Thus the direction of movement ofthe valve RV from neutral determines the direction of flow of the fluid from the pump GP and the distance the valve RV is moved from neutral determines the volumetric output of the pump.

In Fig. 12 the reversing valve RV is shown in its "forward position, the servo valve SVF then functioning to determine the volumetric output the reversing valve RV and the servo valves SVF and SVR' aremoved quickly from their reverse positions of Fig. 11 to their neutral" or no-stroke positions of Fig. 10 and before the control sleeve 85 has had time'to move to neutral in response thereto. The exhaust port I 66 is, therefore, entirely closed, preventing even the slight leakage which normally passes therethrough when the parts have reached equilibrium. This condition causes an increase in the pressure of the control fluid in chamber 89, and

also in the right hand end of the casing I56 of the pressure reducing valve PRV' with the result that this valve is shifted to the left as shown in Fig. 13 and permits increased flow of fluid through the ports I59. This causes a fast movement of the Wobbler to its neutral position and provides for a rapid deceleration of the associated motor FM.

Fig. 14 illustrates a form of the invention embodying a modification of the servo control. In this form, a single servo valve SVX is used This valve, is connected by a link I15 and pivot pins I15 and IT! to a flange IIBwon the reversing valve RV. The parts are arranged as shown so that with the Wobbler and the reversing valve in their neutral positions, the link I15 is in a "dead center position. Thus regardless of the direction of movement of the reversing valve from neutral, the servo valve SVX moves towards the right and opens the exhaust or relief port I86.

' trol fluid passes from the port through port H8 and passage Ill to cylinders I00 and actuof Fig. 14, control fluid from the port l 60' passes through port H2 and passage H3 to the cylinders NH and actuates the pistons 81 towards the right, thus swinging the wobbler in a counterclockwise direction fromthe position shown. This also causes the control sleeve 85' to move towards the right and to follow" the servo valve to its new position.

Preferably the plate I06 which supports the reversing valve RV and the associated servo valves SVF and SVR, is mounted so that it may be adjusted on the casing 2i longitudinally of the axis of the casing so as to permit of slight adjustment of the servo valves with respect to the exhaust port I66. Although no particular means for this adjustment is shown, in practice the adjustment is obtained by enlarging or elongating the holes in I06 through which the clampingscrews pass so that by loosening the screws the plate can be shifted toa slight extent.

I claim:

1'. In a fluid pump or motor, incombination, a plurality of piston and cylinder devices, a shaft, a, wobbler device pivoted with respect to the shaft and engaging the pistons, and means for control ling the angularity of the wobbler device comprising an annular member, one end of which forms a runway for a part of the wobbler device,

movable from a neutral position, wherein the piston comprising a pair of servo valves and a casing for the servo valves carried on said member and movable therewith as a unit, a reversing valve for controlling said reversible means, and means connecting the servo valves to the reversing valve so that one servo valve operates in each direction of fluid output.

2. In a fluid pump or motor, in combination, a plurality of piston'and cylinder devices, a shaft, a wobbler device pivoted with respect to the shaft and engaging the pistons, and means for controlling the angularity of the wobbler device comprising an annular member, one end of which forms a runway for a part of the wobbler device, movable from a, neutral position, wherein the wobbler is held perpendicular to the shaft, to stroke,

parallel to said shaft, means forming a control piston operable to move said member toward its neutral position, meansfor' supplying fluid under pressure continuously to said piston to move said member toward its neutral position, and a servo control mechanism ror controlling the pressure or the hold acting on the control piston comprising a, servo valve, a casing ior said servo valve carried on said member and movable therewith as a unit, a revers ng valve-zor controlling said reversible means, and means connecting the servo valve to the reversing valve so that the servo valve operates in each direction or nuid output.

3. In a fluid pump or motor, in combination, a plurality of piston and cylinder devices, a shaft, a pivoted wobbler device pivoted with respect to theshaft and engaging the pistons, and means for controlling the angularity oi the wobbler device comprising a member, one end of which has portions engageable with the wobbler device on opposite sides of its pivot axis, movable froma neutral position, wherein the wobbler is held perpendicular to the shaft, to stroke positions wherein the wobbler is at another angle to the shalt, reversible means for moving the wobbler device out of its neutral position, means supporting said member for movement parallel to said shait, means forming a piston operable to move said member toward its neutral position, means ior supplying limited quantities of nuid under pressure continuously to said piston to move said member toward its neutral position', a servo control mechanism for controlling the exhaust or the fluid acting on the control piston comprising a pair of servo valves and a casing for the servo valves carried on said member and movable therewith as a unit, and a reversing valve {or controlling said reversible means.

4. In a fluid pump or motor, in combination, a plurality of piston and cylinder devices, a sh'ait, a wobbler device pivoted with respect to the shalt and engaging the pistons, and means for controlling the angularity of the wobbler device com-- prising an annular member, one end of which forms a runway for a part of the wobbler device, movable from a neutral position, wherein the wobbler is held perpendicular to the shaft, to stroke positions wherein the wobbler is at another angle to the shaft, reversible'means for moving the wobbler device out of its neutral position, mean supporting said annular member forv movement parallel to said shaft, means forming a control piston operable to move said member toward its neutral position, means for supplying fluid under pressure continuously to said piston to move said member toward its neutral position, a servocontrol mechanism for controlling the pressure of the fluid acting on the control piston comprising a pair of servo valves and a casing for the servo valves carried on said member and movable therewith as a unit, a rotary reversing valve, and means connecting the servo valves to opposite sides of the reversing valve.

5. In a fluid pump or motor, in combination, a

plurality of piston and cylinder devices, a shaft,

a wobbler device pivoted with respect to the shaft and engaging the pistons. and means for controlling the, angularity of the wobbler device comprising an annular member, one end of ,which forms a runway for a part of the wobbler device,

\ movable from a neutral position, wherein the wobbler is held perpendicular to the shaft, to stroke positions wherein the wobbler is at another, angle to the shaft, reversible means for movin the wobbler device out of its neutral position,

means supporting said annular member for movement parallel to said shaft, means forming a control piston operable to move said member toward its neutral position, means for supplying fluid under pressure continuously to said piston to move said member toward its neutral position, and a servo control mechanism for controlling the pressure of the fluid acting on the control piston comprising a servo valve, a casing for said servo valve carried on said member and movable therewith as a unit, a rotary reversing valve, and means connecting the servo valve to a dead center position on the reversing valve.

6. In a Wobbler type pump or motor, a fluid operated means for moving the Wobbler out of its no-stroke position to forward and reverse stroke positions, a fluid operated device opposing the movement of the Wobbler from its no-stroke PO51- tion and movable from a no-stroke position wherein the device engages the Wobbler on both sides of its pivot; axis to stroke positions wherein it engages the wobbler on one side of its pivot or the other, and effective to determine the wobbler position for both forward and reverse stroke adjustment, means for supplying fluid under pressure to said fluid operated means and said device, a reversing valve movable in opposite directions from a neutral position for controlling the fluid supplied to said fluid operated means, a servo control valve for controlling the pressure of the fluid operating on said device and having a casing carried on said device, and a link connecting said device, a rotary reversing valve movable in opposite directions from a. neutral position for controlling the fluid supplied to said fluid oper-' ated means, a servo control valve for controlling the pressure of the fluid operating on said device and having a casing carried on said device, and a link connecting said servo valve to the reversing valve and in a dead center position when the reversing valve is in neutral,

9. In a Wobbler type pump or motor, a fluid operated means for moving the wobbler out of said servo valve to the reversing valve and in a dead center position when the reversing valve is in neutral.

7. In a Wobbler type pump or motor, a fluid operated means for moving the Wobbler out of its no-stroke position to forward and reverse stroke positions, a fluid operated device opposing the movement of the wobbler from its no-stroke position and movable from a no-stroke position wherein the device engages the Wobbler on both sides of its pivot axis tostroke positions wherein it engages thewobbler on one side of its pivot or the other, and efiective to determine the Wobbler position for both forward and reverse stroke adjustment, means for supplying fluid under pressure to said fluid operated means and said device, a reversing valve movable in opposite directions from a neutral position for controlling the .fiuid supplied to said fluid operated means, and

means for controlling-the fluid acting on said device comprising a pair of servo valves, a casing for said valves movable with said devicei 1;, fluid e to said device, and a re e pas- 235 acting on said device controlled by said servovalves and a pressure operable valve normally restricting the flow of fluid throughsaid supply passage, and operable when the relief passage is closed to increase the pressure of fluid on said device.

8. In a Wobbler type pump or motor, a. fluid.

operated means for moving the Wobbler out of its no-stroke position to forward and reverse stroke positions, a fluid operated device opposing the movement of the wobbler from its nostroke position and movable from a. no-stroke position, wherein the device engages the wobble: on both sides of its pivot axis, to stroke positions wherein it engages the wobubler on one side of its pivot or the other, and effective to determine the wobbler position for both forward and reverse stroke adjustment, means for supplying fluid under pressure to'said fluid operated means and its no-stroke position to forward and reverse stroke positions, a fluid operated device opposing the movement of the Wobbler from its nostroke position and movable from a no-stroke position, wherein the device engages the Wobbler on both sides of its pivot axis, to stroke positions wherein it engages the Wobbler on one side of its pivot or the other, and effective to determine the Wobbler position for both forward and reverse stroke adjustment, means for supplying fluid under pressure to said fluid operated means and said device, a rotary reversing valve movable in opposite directions from a. neutral position for controlling the fluid supplied to said fluid operated means, and means for controlling the fluid acting on said device comprising a servo valve, acasing for said valve movable with said device, a supply fluid passage to said device, and a. relief passage for fluid acting on said device controlled by said servo valve, and a pressure operable valve normally restricting the flow of fluid through said supply passage and operable when said relief passage is closed to increase the pressure of fluid on said device.

10. In a piston type pump or motor having an elementwith a neutral position and movable varying amounts to either side of neutral to determine the operation of the pump or motor, a fluid operated means for moving said element out of its neutral position to positions on either side of neutral, a fluid operated deviceopposing the movement of said element from its neutral position, means for supplying fluid-under pressure to said fluid operated means and said device, a reversing valve movable from and to a neutral position for controlling the fluid supplied to said fluid operated means, a pair of servo control valves for controlling the pressure of the fluid operating on said device and having a casing carried on said device, and means connecting said the movement of said element from its neutral position, means forsupplying fluid under pressure to said fluid operated means and said device, a reversing valve movable from and to a, neutral position for controlling the fluid supplied to said fluid operated means, and means for controlling said device controlled by said servo'valv'es, and a pressure operable valve normally restricting the flow of fluid through saidsupply passage. and

operable when the relief passage is closed to increase the pressure of fluid on said device.

' 12. A motor driven multiple pump device comprising a first pump having a casing and a pump shaft extending outwardly from one end thereof,

a driving member for the shaft rotatably supported at the end of the casing from whichthe shaft projects and having gear teeth on its periphery, a second pump associated with and driven by the extending portion of said shaft with .an idler gear which also engages the gear teeth on said. drive member, means in the downwardly extending portion of said casing forming a housing'for said gearing and supporting a control fluid pump; a shaft extending from said pinion to drive said control fluidf pump and a unitary fluid direction and volume control device for said first and second pumps mounted within the pump casings and embodying servo control means for determining pump displacement,

13. A motor driven multiple pump device comprising a first pump having a casing and a pump shaft extending outwardly from one end thereof, a driving member for the shaft rotatably supported at the end of the casing from which'the shaft projects, a second pump associated with and driven by the extending portion of said shaft and havinga casing secured to the casing of the first pump, said first pump casing having a downwardly extending portion forming a fluid reservoir, a motor positioned under said second pump and mounted'on said downwardly extending casing portion and having a motor'shaft extending thereinto, means connecting said motor shaft drivingly to, said drive member, a control fluid pump in the downwardly extending portion of said casing, means connecting said motor-shaft 'drivingly to said control fluid pump and a fluid direction and volume. control means for said first and second pumps mounted within the pump casings and utilizing fluid from said control fluid l4. Amotor driven multiple pump device com prising a first piston type pump having a casing.

a second piston type pump having a casing secured to the casing of the first pump, said first pump casing having a downwardly extending portion forming afluid reservoir, a motor mounted on said downwardly extending casing portion and having ashaft extending thereinto, means for driving said pumps from said motor. shaft, and,

' a unitary fluid direction and volume control device for each pump mounted within the pump casing and embcdy fl servo control means for determining pump displacement.

15. Incombination with a reversible flow pump having a pair of pump ports, a by-pass port connecting said pump ports, a valveclosing one end of said by-pass port and extending through the adjacent pump port, a; spring urging said valve to seated position, and a diflerential piston means on the portion of said valve in said pump port having a net effective area subject to the fluid passing out of-said pump port equal substantially to thearea of said valve subjected to the fluid in said by-pass port and faced in the same direction as said area and against the action of ,saidsprina.

16'. In combination with a reversible flow pump having a pair of pump ports, a by-pass port connecting said pump ports, ,a valve closing one end. of said by-pass port and extendingthrough the adjacent pump port. a spring urging said valveto seated position, and a difierential piston means on the portion of said valve in said pump'port having a net effective area subject to the fluid passing out of said pump port equal substantially to the area of said valve subjected to the fluid insaid by-pass port.

17. In a wobbler type pump or motor, in combination, a tubular casing formed with an internal shoulder, a cylinder block having a flange around one end positioned against said shoulder, a valve plate positioned against the flanged end of the cylinder block and cooperating therewith to form a cylindrical valve chamber, a gyratory wheel-like valve operable in said chamber, a cap member positioned within the casing and against said valve plate, a ring member screw threaded into the casing and overlying an annular portion along the outer'edge of said cap member, and a plurality of screw devices spaced annularly around and extending in threaded engagement through said ring member and into engagement with said cap member to clamp the cap member, valve plate and cylinder block together and the cylinder block against said shoulder. 18. In a Wobbler type pump or motor, in combination, a tubular casing formed with an vinternal shoulder, a cylinder block having a flange around one end positioned against said shoulder, a valve plate positioned against the' flanged end of the cylinder block and cooperating therewith to form a valve chamber, a valve operable in said chamber, a cap member positioned within the casing and against said valve plate, a ring member screw threaded into the casing and overlying 40 an annular portion along the outer edge of said cap member, and a plurality. ofscrew devices spaced annularly around and extending in threaded engagement through-said ring member and into engagement with said cap member to clamp the cap member, valve plate and, cylin -der block together and the cylinder block against I said shoulder.

19. In a device of the character described, a casing comprising a cylinder block having a'pl'urality of annularLv arranged parallel cylinders formed therein and sport opening through one face of the block to each of the cylinders, said ports being annularly arranged, a plate having fluid supply and exhaust passages formed therein, an annular flange on said cylinder block cooperating with the face of the blockiand said plate to form acylindrical valve chamber; one of said passages communicating with said valve chamber inwardly of said ports and radiallyoutwardlyv of the center of the chamber, and the other of said es communicating with said chamber adjacent the periphery of the chamber, a whee1- like valve comprising a rim, a hub and connecting spokes, said rim and hub each having a fluid-tight sliding flt in said valve chamber with both and cylinder block "and said plate, said said valve with a fluidmotion whereby the valve sue rality of annularly arranged parallel cylinders formed thereinand a port opening through one face of the block to each of the cylinders, said. ports being annularly arranged, a plate having :fluid supply and exhaust passages formed therein and means forming an annular spacer interposed between said plateand the face of the block cooperating therewith to form a cylindrical valve chamber, one of said passages communicating with said valve chamber inwardly of said ports and radially outwardly of the center of the,

chamber, and the other of said passages communicating with said chamber adjacent the periphery of the chamber,- a wheel-like valve in said valve chamber, means for imparting to said valve an eccentric motion whereby the valve successively connects the ports alternately to the supply and exhaust passages, and means forming a chamber adjacent said plate on the side,opposite said valve chamber and in communication with the passage from the inner portion of the valve chamber so as to subjectj the outer face of said plate to the pressure of the fluid in saidchamber andmaintain the plate in eflicient sealing contact with the valve..

21. In a piston type fluid device operable as a pump or as a motor and having an element determinative by its position of the direction and rate of discharge of fluid when the device is operating as a pump and the direction and rate of operation when operating as a motor, a first fluidpressure actuated means for moving said element in opposite directionsirom a neutral position, a member movable in one direction from a neutral position and operable to control the position of said-element on both sides of its neutral position, a second fluid pressure actuated means operable of operation when operating as a motor, a first rate of discharge of fluid when the device is operating as a pump and the direction and rate fluid pressure actuated means for moving said element in opposite directions from a neutral position, a member movable in one direction from a neutral position and operable to control the position of said element on both sides 01 its neutral position, a second fluid pressure actuated means' operable to move'said member toward its neutral position,'m'eans ior supplying fluid under pressure to said first fluid pressure actuated means and continuously supplying fluid to said second fluid pressure actuated means to urge said member toward its neutral position, arotary reversing valve movable from and to a neutral position for controlling the fluid supplied to said first fluid pressure actuated means, a pair of servo control valves for controlling the pressure of the fluid operating on .said second fluid pressure actuated means and having a casing movable with said member, and means connecting said servo valves to the reversing valve at points on oppositesides thereof when the reversing valve is in neutral so as to move in opposite dinections as said re'versing valve is moved in either direction from neutral.

23. In a piston type 'fluid device operable as a pump'or as a motor and having an element determinative by its position of the direction and rate -of discharge of fluid when the device is op erating as a pump and the direction and rate of operation when operating as a motor, a first fluid .pressure actuated means for moving said element in opposite directions from a neutral position, a member movable in one direction from a neutral position and operable to control the position of said element on both sides of its neutral position, a second fluid pressure actuated means operable to move said member toward its neutral position, means for supplying fluid under pressure to said flr'st'fluid pressure actuated means and continuously supplying fluid to said second fluid pressure actuated means to urge said memto move said member toward its neutral position, means for supplying fluid under pressure to said first fluid pressure actuated means and continuously supplying fluid to said second fluid port, a reversing valve for controllin the supply of fluid to said first fluid pressure actuated means,

' and means connecting said servo valve to operate v with said reversing valve.

22. In a piston type fluid device, operable as a pump or-as a motor, and having an elementdeterminative by its position of the direction and reversing valve to determine the extent 0! movement of said element in the direction determined by said reversing valve, and a pressure operable valve normally restricting the flow of fluid through said supply passage'and operable when said port is closed to increase the pressure of the fluid supplied to' said second fluid pressure actuated means,

GUNNAR A, WAI-ILMARK.

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