US2299234A

US2299234A - Hydraulic pump and control means therefor

Info

Publication number: US2299234A
Application number: US147178A
Authority: US
Inventors: Ira J Snader; Max A Mathys
Original assignee: Ex-Cell-O Corp
Current assignee: Ex-Cell-O Corp
Priority date: 1937-06-09
Filing date: 1937-06-09
Publication date: 1942-10-20
Anticipated expiration: 1959-10-20

Description

Oc't. 20, 1942.

1.1.1. SNADER Erm. 2,299,234

HYDRAULIC PUMP AND CONTROL MEANS THEREFOR Filed June 9, 1937 5 Sheets-Sheet 1 Oct. 2o, 1942. l, J. SNADER Erm. 2,299,234

HYDRAULIC PUMP AND CONTROL MEANS THEREFOR Filed June 9, 195'? s sheets-sheet 2 ffii@ um, f6

Oct 20, 1942.

l. J. SNADER ETAL HYDRAULC PUMP AND CONTROL MEANS THEREFOR Filed June 9, 1957 3 Sheets-Sheet 3 Patemed oct. zo, 1942 HYDRAULIC PUMP AND CNTROL MEANS THEREFOR Ira J. Snader and Max A. Mathys, Detroit, Mich., assignors to Ex-Cell-O Corporation, Detroit, Mich., a corporation of Michigan Application June 9, 1937, Serial No. 147,178

9 Claims. (Cl. 103-162) The present invention relates to improvements in hydraulic pumps and control means therefor,

\ andk particularly to a new and improved pump and control means therefor adapted for high speed and pressure operation.

An important object of the invention is to provide a pump with a novel hydraulic control for automatically varying the delivery as required within the range of volumetric capacity to maintain a predetermined delivery pressure.

A more specific object is to provide a new and improved .variable delivery pump having a volume control element adjustable by a motor under the control of a metering valve responsive to a control pressure.

Further objects and advantages will become apparent as the description proceeds.

In the accompanying drawings,

Figure 1 is an axial sectional view, taken along line I-I of Fig. 2, of a pump with control means embodying the features of our invention.

Fig. 2 is an end elevational View.

Fig. 3 is a fragmentary sectional view of the pump valve taken along line 3-3 of Fig. 1.

Fig. 4- is a fragmentary transverse sectional view taken substantially along line 4-4 of Fig. 1, and showing the face of the stationary valve member.

Fig. 5 is a fragmentary transverse sectional view taken substantially along line 5--5 of Fig. 1, and showing the face of the movable valve member.

Fig. 6 is a sectional detail view taken along line I-S of Fig. 4.

Fig. 7 is a horizontal sectional view taken substantially along line 'I--'I of Fig. l, but with the volume control valve in a different position of adjustment.

Fig. 8 is a longitudinal sectional view of a modified form of volume control valve.

Fig. 9 is a transverse sectional view taken along line 9-9 of Fig. 8.

Fig. 10 is an enlarged fragmentary sectional view of one of the pump pistons.

Fig. 11 is a diagrammatic view of one form of hydraulic circuit including the pump illustrated in Fig. 1.

Fig. 12 is a diagrammatic view of a modified form of hydraulic circuit including the pump `with the volume control valve of Fig. 8.

intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Referring more particularly to the drawings, the hydraulic pump, constituting the exemplary embodiment of the invention, comprises a closed pump housing I3 which may be of any suitable form or construction, and which in the present instance is generally rectangular in shape, and has a bottom Wall I4 adapted to be bolted or otherwise secured to a suitable support (not shown). The housing I3 also has opposite end walls I5 and I B, and is closed at the top by a.

removable cover plate II.

A suitable drive shaft I8 extends longitudinally through the housing I3, and is journaled at opposite ends in the walls I5 and I6. Integral with the wall I5 is a large external circular boss l I9 having an axial bore 20 counterbored at the inner end. A stationary valve plug 2|, in the form of a single cylindrical block, is tightly pressed into the bore 20, and is located axially by a peripheral end flange 22 seated in the counterbore. To locate the plug 2| angularly, it is formed with a longitudinal groove 23 engaging a pin 24 on the inner end of a screw 25 threaded radially into the boss I9. Formed in 4the plug 2| is an axial bore 26 which is closed at the outer end, and which is open and flared at the inner end. A bushing 21 is fitted in the bore 26, and supports one end of the shaft |8.

The opposite end wall I6 is formed with a bore 28 in axial alignment with the bushing 21. Preferably, an antifriction bearing 29 is mounted in the bore 28 to support the shaft I8 which extends therefrom externally of the housing I3 for connection to a suitable source of power (not shown). To prevent the entry of air, dust and other foreign matter through the bearing 29 into the housing I3, an oil seal 30 is mounted in the outer end of the bore 28, and is held in place by an end plate 3| bolted to the outside of the wall |6.

Secured to the shaft I8 for rotation therewith is a. cylinder block or body 32. In the present instance, the body 32 is formed with an axial bore 33 slidably receiving the shaft I8, and is located axially thereon by abutment against a shaft enlagementv34. The end of the enlargement 34 is flattened on opposite sides to define a. key 35 which interts separably with a diametrical notch 36 in the adjacent end of the body 32. Prefera'bly. the root of the notch 36 and the end face of the key 35 are arcuate in shape. i

The body 32 is in the form of a spool having a peripheral cylinder flange 31 and an axially spaced guide ange 33, and defining an intermediate spring space 39. A plurality of parallel bores 40, six in the present instance, open through the flange 31, and constitute pump cylinders annularly arranged in uniformly spaced relation about the shaft I8. Similarly, the flange 38 is formed with guide bores 4| in axial aligncured as by means of bolts 42 to the outer end face of the flange 31 andcoextensive in diameter therewith is a circular valve plate 43 which closes strokes by individual compression springs 45 located within the annular space 39. Each of the springs 45 seats at one end against a ring retainer 46 positioned against the ange 31, and at the other end against a key retainer 4l engaging a peripheral groove 48 in theassociated piston 44.

The pistons 44 are operable in uniformly timed 3 sequence, with a variable stroke as hereinafter described, by a swash or cam plate 49 which is journaled on a pin 50 for angular or rocking adjustment into different inclined positions. The pin 50 is pressed in spaced'lugs 5| in the housing I3 and is perpendicular to the axis of the shaft i8. The plate 49 has a fiat annular cam face 52 i which freely encircles the shaft enlargement 34 and which is engaged by 'oating shoes 53 operatively connected to the outer ends of the pistons 44,

Each of the shoes 53 is in the form of a disk having a flat annular bearing face 54 of ample size in sliding engagement with the cam face 52,'

and having a hollow central spherical projection 55 seating for universal movement in a comple-v mental socket 56 in the outer end of the assoin the outer end of an axial bore 58 in the piston 44, and is secured therein by a transverse lock pin or rivet 59. The retainer 51 has a semispherical head 60 which engages the interior of the projection 55 to confine the shoe 5.3 adjustably in the socket 56, and which is connected by a reduced stem 6| extending freely through a central opening 62 in the projection.

The bore 58 opens at the inner end through a small aperture 63 to the cylinder 40, and hence provides for a longitudinal pressure passage permitting the ow of lubricant to the bearing surment with the bores or cylinders 40. Rigidly seciated piston 44. A retainer 51 is loosely tted faces of the shoe 53. As one factor affectingv quietness in pump operation, the lubricant passage should be small. to drill the long bore 58 suiiciently'small in hard metal, such as the piston material, a seamless tube 64 is tightly tted therein between the retainer 51 and the aperture 63, and defines the actual pressure passage. Fluid or oil from the closed end ofthe cylinder 40. passes through the aperture 63, the tube 64 and aboutA the retainer 51v to the bearing surfaces of the socket 56 and ball projection 55. Fluid or oil also passes through the opening 62 to the bearing surfaces betwee the plate4|| and the shoe 53.

Since it is impracticable The bearing surfaces between the plate 49 and the shoe 53l and between the projection 55 and the socket 56are closely lapped to provide a hydraulic seal, and are hydraulically balanced against the mechanical reaction on the piston to the hy draulic pressure in the cylinder 40, so as to maintain at all times good bearing engagement with a proper lubricating lm. The bearing face 54 of the shoe 53 isV` relieved at the. inner edge by an annular notch 65, and is formed with a concentric drain groove 66 relieved through a plurality of drain apertures 61. 'I'he central portion of the bearing face 54, circumscribed by the inner edge of the groove 66, is under pressure, and is substantially equal in area to the pressure end of the piston 44 so as to counterbalance the outward thrust of the hydraulic pressure in the cylinder 40. The pressure area of the face 54 may be equal to the piston end area, but preferably is slightly larger to balance part of the outward pressure of the spring 45. Since the groove 66 prevents outward spreading of the pressure film, the full wearing surface of the face 54 can be much larger than the pressure balanced area without interfering at any time with good bearing contact. The effective pressure area of the socket 56 is somewhat less by reason of the opening 62 than that of the piston 44, but is sufficiently large to obtain substantially a hydraulic balance, the lubricating film being maintained under a slight excess pressure to assure good bearing contact.

The valve stator 2| and the plate 43 have annular end faces 68fand 69 in bearing engagement, and constitute a rotary end face valve for controlling the admission and discharge of fluid respectively 'to and from the pump units. Since the stator 2| is in the form of a heavy plug mounted in the large boss i9, the stationary valve face 68 is not subject to deflection under heavy pressure. f

The valve stator 2| (see Fig. 4) is provided with two arcuate suction and delivery ports 10 and 1| separated by diametrically spaced land areas 12 and 13 and arranged in concentric relation to the shaft I6. These ports are located at opposite sides of an axial plane intersecting the land areas and perpendicular to the pivotal axis of the swash plate 49. Formed in the valve face 69 of the l plate 43 are a plurality of ports 14 which open respectively to the closed ends of the pump cylinders 40, and which are annularly arranged in a circle of the same curvature as the ports 10 and 1| for movement successively across the latter upon rotation of the cylinder body 32. The ports 10, 1| and 14 are offset from the centers of the cylinders4ll, and preferably are located at' the innermost side areas thereof adjacent the shaft IB. As a result, the contacting areas of the valve faces 68 and 69 can be made small to lessen the likehood of manufacturing errors or irregularities and the chance of valve leakage, and are located closely to the center of rotation to reduce the peripheral speed. Also, any air collecting in the cylinders 40 will be separated from the liquid I by centrifugal force, and pass out with the pump delivery.4

The valve faces 68 and 69 are hydraulically balanced against-the pressure in the minimum number ofcylinders 40 ion' the pressure side of thearea, an annular concentric drain groove 15 is formed in the face |58l about the ports 10 and 1| draining from the valve facesinto the bore serves to lubricate the bushing 21. Liquid collecting in the bore 26 at opposite ends of the bushing 21 is free to pass through drain holes 16 and 11 to the locating spline groove 23, and from there into the housing I3. Liquid collecting in the housing AI3 is free to return through a passage 18 to the pump inlet. If the pump is mounted above the level of the source of liquid supply, the passage 18 may be closed, and the housing I3 may be drained through a bottom opening 19 connected to the source.

It will be evident that when the swash plate 49 is angularly disposed, rotation of the cylinder body 32 will cause the pistons 44 to be reciprocated in timed sequence and with a simple harmonic motion, and that each piston will be moving through its suctiori. and pressure strokes while4 the associated cylinder 40 is in communication respectively with the inlet and delivery ports and 1|. As the pistons 44 of each set of diametrically opposed pistons reach top and bottom dead centers respectively, the associated cylinders 48 will be closed by the land areas 12 and 13, and at these times only two cylinders will be open to either of the valve ports 10 and 1I. At all other times, three cylinders 40 will be open to each of the valve ports 10 and 1I. Consequently, the pump will discharge continuously, and the rate of discharge is substantially constant for any given setting of the swash plate 49. If the angular position of the lswash plate 49 is changed, the length of the piston stroke will be adjusted to adjust the rate and volume of pump delivery. When the plate 49 is adjusted into a plane perpendicular to the shaft I8, no reciprocation will be imparted to the pistons 44.

Preferably, the suction and delivery ports 10 and 1I are angularly advanced in relation to the top and bottom dead center positions of the pistons 44 so as to effect a pressure equalization in each cylinder 40 just before the start of both the pressure and suction strokes. Each of the cylinder ports 14 will be closed by the land area 12 during the initial part of the pressure stroke to cause the pressure therein to be built up approximately to the pump delivery pressure before free communication with the port 1I. Similarly, i

each port 14 will be closed by the land area 13 during the initial part ofthe suction stroke so that the pressure will be expanded approximately to the suction pressure effective in the port 10 before free communication therewith.

To permit such pressure equalization, the land areas 12 and 13 are somewhat wider than the ports 14 so that each cylinder 40 is closed over a predetermined degree of revolution. For fixed operating conditions and upon making proper allowance for leakage past the valve faces and pistons, the angular advance of the ports 10 and 1I .may be accurately calculated to obtain a quietly operating pump. However, the operating conditions are subject to variations, such, for example, as changes in delivery pressure, speed, displacement, temperature influences and the kind andcondition of the fluid being handled. These changes influence the pump leakage and the pressure gradients. The valve ports 10 and 'ing surface larger than the balancing pressure i 1I are therefore advanced to time the opening of the cylinder ports 14 for average or mean operating conditions.

Means may be provided for graduating even the small pressure changes which will be present when the variable pressures in the effective range deviate from the mean operating pressure. This means consists of short restricted bleed grooves 88 in the valve face 68 (see Figs. 4 and 6) opening to and constituting extensions of the ends of the arcuate por-ts 1|) and 1|. The grooves are so graduated that the cylinder ports 14 will not open abruptly to the ports 10 and 1|, thereby avoiding sudden shock even if the cylinder pressure is not equalized with that of the stationary port with which it is about to communicate.

The gradual pressure changes in passing from either to the other of the ports 10 and 1|'also have the important function of preventing the piston shoes 53 from clicking. During movement through the intake zone, each shoe 53 .is held against the cam plate 49 with a light initial pressure determined by the spring 45. In the pressure zone, the springV4 pressure is supplemented by the hydraulic pressure acting through the piston 44 so that the oil film between the cam plate 49 and the shoe 53 and between the latter and the piston is compressed under a heavy pressure. By reason of the advance of the

ports

18 and 1| and/or the provision of the bleed grooves 80, the pressure on the lm is alternately graduallyrelieved and applied, thereby placing the shoe 53 in substantial balance before each port opening. Sudden pressure surges tending to effect separation of the shoe 53 from the cam plate 49 at transition points in the operation are consequently avoided.

As noted, one of the features of the present pump is quietness in operation. The hydraulic balance of the piston shoes 53 and the

valve

58, 69 against the mechanical reaction of the hydraulic pressure contributes to this result. The elimination of pressure surges or impulses, by

reason of the angular advance of the ports 10 and 1| and the provision of the bleed grooves 18, also reduces noise in operation. As another important factor in avoiding noise, the volume of pressure liquid in the closed ends of the cylinders 48 at the end of the pressure stroke is held to a minimum. To this end, the piston clearance in the valve plate 43 is made as small as is practically convenient, and the pressure passages through ther pistons 44 are reduced in size by means of the tubes |54. Also, the pivot pin is located at a point adjacent the axis,

of each piston 44 as the latter moves into top dead center position at .the end of the pressure stroke. As a result, the inward limit of movement of the pistons 44 is substantially constant and close to the inner ends of the cylinders 40, while the outward limit of movement is variable in accordance with changes in the angular position of the swash plate 49.

The inlet port 10 may be connected in any suitable manner to the source of liquid supply, and in the present instance is in communication at the bottom or root with a plurality of longitudinal bores 8| in the valve plug 2|. The outer ends of the bores 8| are intersected by a recess 82 formed in the periphery of the plug, and,A registering with a passage 83 opening through the peripheral wall of the boss I9. A line 84 connects the passage 83 with a source of supply, such as a sump or reservoir 85. The delivery port 1I is in communication at the bottom or root with a plurality of longitudinal bores 86 formed in the plug 2|. A recess 81 in the periphery of the plug 2| intersects the bores 86, and is in registration 'with an outlet passage 68 opening through the boss I9 and connected to a pressure line 99.

The pump is adapted for various purposes, and is particularly useful as a source of power in a hydraulic transmission system or operating circuit. In Fig. 11, illustrating a hydraulic machine tool circuit, -the pressure line 89 is connected to the inlet of a reversing valve 90 for controlling the operation of a hydraulic motor 9|. The motor may be of any suitable character, and is herein shown as of the reversible rotary type having two liquid supply and

discharge lines

92 and 93. The valvel 90 also may be of any suitable type, and for purposes of illustration is herein disclosed as comprisingan outer casing 94 connected to the

lines

89, 92 and 93, and to an exhaust line 95 discharging to the sump 85. A valve member 96, of the spool type, is reciprocable in the casing 94 by means of a hand lever 91, and is adapted in one end position to connect theline89 to the line 92 and the line 93 to the line 95, in the other end position to reverse these connections, and in an intermediate position to block the

lines

09, 92 and 93.

An adjustable iiow restriction means is interposedin the line 95 to build up a low pressure controlling the operation of the motor 9|. More particularly, the speed of the'motor 9| is subject to variation by adjusting the exhaust ow restriction. This restriction may be of any suitable character, and in the present instance consists of three

parallel orices

98, 99 and |00 selectively available under the control of a valve Assuming the motor 9| to be connected to drive a reciprocatory machine tool carriage (not shown), the largest orice 98 is adapted to effect rapid traverse, the smallest oriiice'99 is adapted to effect a slow feed, and the intermediate orifice 00 is adapted to effect a relatively fast feed. v It will be understood, that each oriilcemay also be subject to individual adjustment. The selector v alve |00 may be of any suitable character, and is herein shown as comprising a casing |02 and a valve member |03 adjustable by a hand actuator |04 to connect the line 95 to the sump 85 through any one of the

orices

98, 99 and |00.

Provision is made for automatically controlling the position of the swivel plate 49'to maintain a predetermined control pressure substantially constant regardless of volume requirements. Thus, the plate 49 is automatically adjusted to reducevthe pump delivery upon an increase in the control pressure, and to increase the delivery upon a decrease in the pressure. As applied to the hydraulic circuit of Fig. 11, the pump is con'y trolled by the uid pressure in the line 95 between the motor 9| and the

selective orifices

98, 99 and 00. If the oriiice restriction is adjusted, the pressure in the line 95 will elect a corresponding variation in the pump delivery. For any selected orifice restriction, tending pressure variations in the line 95 will eiectcoxnpensatory adjustments in the pump delivery so that vthe pressure drop across the restriction regardless of motor torque will remain practically uniform. The speed of the motor 9| is vtherefore entirely under the control of the oriiice restriction.

In its preferred form, the pump adjusting means comprises a control piston |05 acting on thefree end ot the swash plate 49 in a direction to level oi the latter against the hydraulic reaction in the cylinders 40 and the action of the piston return springs 45. The control piston |05 is reciprocable in a cylinder |06 opening through the wall i6, and closed at the outer end by the cover or stop plate 3|. The cylinder |06 extends parallel to the shaft |8, (and preferably is located diametrically opposite the pin 50 and outside the circle of revolution of the cylinders 40 so that the thrust of the piston |05 against the plate 49 will have a moment arm considerably longer than that of the aggregate opposing forces resulting from the hydraulic reaction through the pistons 44. The diameter of the piston |05 and the moment arm of the force exerted thereby determine the pressure required in the cylinder |06 in relation to the pump delivery pressure to balance the cam or swash plate 49. By providing a comparatively large diameter and a relatively long moment arm as shown, the balancing pressure required in the cylinder |06 will be much lower I2 which is automatically responsive to the pres- Y sure in the line in advance of the selected orifice restriction. The valve 2 is operable to admit iluid under pressure to the closed end of the cylinder |06 or to exhaust fluid therefrom respectively upon an increase or decrease in the pressure in the line 95, whereby the speed of the hydraulic motor 9| is maintained constant re.- gardless of varying load conditions. For example. if the load is increased, which results in increased leakage, the motor 9| will tend to slow down and hence exhaust less iiuid. but the resulting drop in the pressure built up by the oriiice restriction will immediately eiect a compensatory increase in the pump delivery.

Preferably, the valve |I2 is built into the cover i'l,v and comprises a bore |I3 opening therethrough and enlarged at opposite ends to dei-lne a pressure chamber H4, a spring chamber ||5 and oppositely facing shoulders, I6 and ||1. A valve sleeve ||8 is xed in the bore ||3 against the shoulder ||5, and is formed with an axial valve passage ||9. A peripheral groove |20 opens through radial ports I 2| to,d the Ypassage H9, and is in registration with a passage |22 connecting with the closed end of the cylinder |06. The sleeve ||8 is also formed at one side of the groove |20 with a second peripheral groove |23 opening through a plurality of radial inlet ports |24 to the valve passage I9, and registering with a pressure supply passage |25 in the cover I1 and wall I5 connecting with the pump outlet passage 80. Formed in the end of the sleeve I0 at the opposite side of the groove I 20 and longitudinally` intersecting the valve passage 9 to dene exhaust ports are a plurality of bores |26 opening to the reduced intermediate section of the bore H3. Two relief passages |21 and |28 open from the bore ||3 at opposite ends of vthe sleeve ||8 through the cover I1 to the interior of the pump housing I3 from where spent uid may be discharged through the passage 18 to the pump inlet passage 83 as described.

Reciprocally disposed in the sleeve ||8 is a responsive element |33 and resilient pressure l means |34 acting in opposition. In the present vinstance, the element |33 consists of a piston in abutment with one end of the valve member |29, and reciprocable in the pressure chamber I4. A control line |35 opens from the outer end of the chamber ||4 to the interior of the reversing valve casing 94 for connection with the exhaust line 95 when the motor 9| is in operation, and with the pump discharge line 89 when the valve member 96 is in stop position.

The resilient pressure means |34 consists of a square wire coil compression spring. engaging the other end of the valve member |29 and seating against a collar |36 slidably guided in the intermediate section of the bore ||3. The collar |36 is integral with a pin |31, one end of which extends through the spring |34 into' closely spaced relation to the valve member |29, and the other end of which is guided in a screw plug |38 closing the outer end of the spring chamber ||5. ,The spring |34 is maintained under normal compression by a second spring |39 encircling the pin |31 and seating under compression at opposite ends against the collar |36 and the plug |38. The two springs |34 and |39 have different natural periods of frequency, so that any'vibrations tending to result therein from pump pulsations are out of synchronism and neutralize or oiset each other. Hence, the valve member |29 is maintained in sensitive balance without fluttering. A heavy coil compression shock spring |40 encircles the spring |39 and normally abuts at opposite ends against the shoulder ||1 and the plug |38. The inner end convolution of the spring |40 projects inwardly for engagement by the collar |36 in the event of sudden and extended movement of the valve member |29 by the piston |33.-

The valve |2 is of the graduated metering type, and when in control is normally either closed or slightly open to permit only a restricted iiow. The flow restriction in the valve l|2 results in a large pressure drop in the passage |22 when connected to the passage |25 so that the control pressure on the piston |05 is reduced and always less than the pump delivery pressure. Only small vvalve movements are required and only small pressure changes are necessary to move the valve member 29. The control is sensitive and does not reflect or develop pulsations at critical motor speeds.

In operation, when the orifice restriction in the line 95 is set for maximum opening, as by connecting the orice 98, a relatively low pressure drop is maintained, and hence the liquid or oil exhausting from the motor 9| is practically free to return Without restriction to the sump 85. Since no effective pressure will prevail in the line |35, the valve member |29 will be adjusted by the springs |34 Aand |39 into its extreme right hand position as shown in Fig. 7, forcing the piston |33 to the right, thereby fully exhausting to deliver at maximum capacity.

If the orifice restriction is now gradually increased, as by connecting the oriiice 00 for fast feed, a pressure will build up in the control line |35, and act through the piston |33 to force the valve member |29 and pin |31 to the left until the collar |36 engages the shock spring |40 as shown in Fig. 1. The valve member |29 will continue movement against the action of the spring |34 to connect the passages |22 and |25, whereupon the swash plate 49 will be adjusted to reduce the delivery of the pump to a point where the resultant pressure in the line |35 will malntain the valve 2 in closed position.

After vthe piston |05 i away fromthe stop plate 3|, the pressure inthe line |35 will be maintained substantially constant regardless of gradual changes in the size of the orifice restriction. For example, if the oriiice restriction is lstill further increased, as by connecting the smallest orifice 99, the same pressure in the line |35 will be maintained by a, corresponding reduction in the volume of pump delivery to obtain a slow feed. In general, the pressure drop across the orifice restriction will be constant for all sizes of orifices, and the volume of liquid ow therethrough will-be constant for any one size but will vary with different sizes. Hence, the speed of the motor 9| for any given orice setting will be constant regardless of varying load' conditions and resulting variations in leakage in the pressure side of the system, and will be determined entirely by the size of orifice employed. 'I'hel delivery of the pump is fully utilized at all times in doing useful work, and is varied as required without the use of relief valves and other accessories commonly employed for by-passing excess fluid.

The -leveling adjusting of the swash plate 49 is gradual by reason of the metering characteristics of the valve ||2. Howevenfif the orice restriction should be changed or closed suddenly, a pressure impulse would be transmitted through the line |35 and cause the valve member |29 acting through the pin |31 to compress the shock springl |40, thereby permitting the pressure fluid to level oil the plate 49 immediately. Conversely, if there should be a sudden pressure drop in the line |35, the spring |39 would urge the valve member |29 far to the right to effect an immediate and substantial increase in pump delivery. Upon movement of the reversing valve 90 into neutral position, the

motor lines

92, 93 will be blocked, and the control line |35 will be disconnected from the exhaust line and connected to the pump discharge line 89. Since the line 89 is also blocked, the delivery pressure of the pump will rise and effect movement of the swash plate 45| into level position to stop delivery.

The pump with the modified valve |4| is inv eluded as the source of pressure id in the hydraulic machine tool circuit shown in Fig. 12.

v Since the pump is controlled directly from the delivery pressure, this circuit does not include a control line, such as the line |35, to the exhaust side of the system, but in all other respects it is like the circuit in Fig. 11, and hence like parts are identied by the same reference numerals plus the subscript a.

In operation, when the motor torque is low and the largest orive' 98a is connected, the spring |56 will hold the valve member |52 to the right against the stop |5|, so that the pump will deliver at maximum capacity. Upon-an increase inpressure due to a load increase or a greater orice restriction, as by connecting the orice 99'* or orifice |00, thevvalve member |52 will be forced f to the left against the action of the spring |56 to supply iuid under pressure to the control cylinder |06. Thereafter, the. valve |4| will tapered surface for gradually restricting the port connection as said valve member moves into neutral position, resilient means aligned with and acting directly on one end of said valve member to urge said valve member in a direction to connect said control and exhaust ports to increase the pump delivery, and means acting on the other end of said valve member for-adjusting said valve member against said resilient means in response to the pressure in said outlet to connect said control and pressure ports to decrease the pump delivery.

2. In a variable now pump having a ypressure delivery outlet and an adjustable volume control element, in combination, a pressure chamber having an inlet passage, a pressure responsive member operatively connected to said element and movable in saidchamber to adjust said element, a valve casing having a control port open to said passage, a pressure port connected to said outlet and an exhaust port, a valve member reciprocable in said valve casing and having a land areaadapted to block said control port when said valve member is in neutral position and having metering recesses at opposite sides of said land area adapted respectively to connect the control port to said pressure port and exhaust port upon adjustment of said valve member in opposite directions out of neutral position, and resilient means tending to urge said valve member in one direction, said valve member being movable in the reverse direction inresponse to the pressure in said outlet. V

3. In a variable ilow pump having a pressure delivery outlet and an adjustable volume control `element, in combination, a pressure chamber hav- 45- valve'casing'having a control port open to said passage, a pressure port connected to said outlet, and an exhaust Port, a valve member reciprocable in said valve casing and having a land area l adaptedI to block said control port when said valve maintain a constant maximum pressure, subject to adjustment by varying the initial tension of the spring |56, and will cause the pump tosupply whatever fluid the system is able to take at this pressure.

The pump per se is disclosed and claimed in our' co-pending application Serial=No. 348,904 iled July '31, 1940. v

The hydraulic transmissions are disclosed and claimed in our co-pending application Serial No. 348,905 nled July 31, 1940.

We claim as our invention:

1. In a variable flow pump having a pressure delivery outlet and an adjustable volume control element, in combination, a pressure chamber having an inlet passage, a pressure vresponsive member in said chamber operatively connected to said element and movable to adjust said element,y

a valve casing having` a control port open to said member is in neutral position and having recesses at opposite sides of said land area adapted respectively to connect the control port to said pressure port and exhaust port upon adjustment of said valve member in opposite directions out of neutral position, a pin reciprocable in said valve casing and having a peripheral collar, a compression spring acting against said collar to urge said pin toward said valve member, a second compression spring interposed between said valve memv ber and said collar and tending to urge said valve member in a direction to connect said control and exhaust ports, a plunger operable in response to duid pressure to move said valve member in a direction to connect said control and pressure ports, and a shock spring disposed for engagement by said collar and adapted to compress upon sudden movement of said valve member by said plunger.

4. In a variable ow pump having a pressure delivery outlet and air-adjustable volume control element, in combination, a pressure chamber having an inlet passage, a pressure responsive reciprocable in said valve casing and having a* land area adapted to block said control port when said valve member is in neutral position and having metering recesses at opposite sides of said land area adapted respectively to connect the control port to said pressure port and exhaust port upon adjustment or said valve member in opposite directions out of neutral position, a compression spring acting on one end of said valve member tending to urge said valve member in one direction,and means for adjusting the normal compression of said spring, the other end of said valve member having a pressure area exposed to the pressure of the iluid from said outlet, whereby said valve member is movable againstthe resistance of said spring in response to pressure increases in said outlet.

5. In a variable flow pump having a pressure delivery outlet and an adjustable volume control element, in combination, a pressure chamber. a pressure responsive member in' said chamber and operatively, connected to said element to move the latter, a valve chamber having a uid pressure inlet and an exhaust outlet, a valve member reversibly adjustable in said valve chamber to connect said pressure chamber either ,to said inlet or to said outlet or to block said pressure chamber, two springs having different natural periods of vibration operative in series on said valve member and tending to adjust said valve member in a direction to connect said outlet to said pressure chamber, and means for directing fluid under pressure to act on said valve member in opposition to said spring means.

6. In a variable flow pump having a pressure delivery outlet and an adjustable volume control element, in combination, a pressure chamber, a pressure responsive member in said chember and operatively connected to said element to move the latter, a valve chamber having a iluid pressure inlet and an exhaust outlet, a

member moves toward and into neutral position, resilient means tending to urge said valve-mem, ber in a direction to' connect -said pressure chamber to said exhaust port, and means for directing uid under pressure to act on said valve member in opposition to said spring means and tending to urge said valve member in a direction to connect said pressure chamber to said pressure port.

8.A In a variable ilow pump having a pressure delivery outlet and en adjustable. volume control element; in combination, a pressure chamber having an inlet passage, a pressure responsive member operatively connected to said element and movable in said chamber to adjust said element, a valve casing having a bore, a valve sleeve fitted in an intermediate portionvof said bore and havinga valve bore opening therethrough to opposite ends of said first mentioned bore, said. sleeve having a control port opening to said passage, a pressure port adapted to receive uid under pressure and an exhaust port, a valve member reciprocable in said valve bore and having an intermediate peripheral land area adapted to block said control port when said valve member is in neutral position, and having recesses at opposite sides of said land area adapted respectively tov connect said control port to said pressure port or said exhaust port upon adjustment of said valve .member in opposite directions out of neutral position, resilient means in one end of said rst mentioned bore acting on said valve member to urge said valve member in one direction, and fluid pressure responsive means coacting with said valve member and slidable in the other end of said first mentioned bore, said other end of said iirst mentioned bore being adapted to receive fluid under pressure tending to urge said valve member in the revalve member reversibly adjustable in said valve chamber to connect said pressure chamber either to said inlet or to said outlet or to block said pressure chamber, spring means operative on said valve member in a-direction to connect said outlet to said pressure chamber, means for directing fluid under pressure to act on said valve member in opposition to said spring means, and a shock spring disposed in position for engagement by said valve member upon movement through a predetermined distance in response to the action of said fluid under pressure.

'1. In a variable ow pump having a pressure delivery outlet and an adjustable volume control element, in combination, a pressure chamber having an inlet passage, a pressure responsive member in said chamber operatively connected to said element and movable to adjust said element, a valve casing having a pressure port for supplying fluid under pressure and an exhaust port. a valve member reciprocable in said casing and having a land area adapted to block said pressure chamber when in neutral position and having recesses adapted upon movement of said valve member respectively in Voppositedirections to connect said pressure chamber either to said presure port or to said exhaust port, each recess having a tapered surface for gradually restricting the associated port connection as said valve verse direction against the action of said resilient means.

9. In a variable ow pump having a pressure delivery outlet and an adjustable volume control element, in combination,` a. pressure chamber having an inlet passage, a pressure responsive member operatively connected to said element and movable in said chamber to adjust said element, a valve casing having a bore, a valve Asleeve iitted in an intermediate portion of said bore andhaving a valve bore opening therethrough to opposite ends of said rst mentioned bore, said sleeve open to said passage, a pressure port and an exhaust port, a valve member reciprocable in said valve bore and having an intermediate peripheral land area adapted to block said conposition,

of said land area valve member in one direction, and adjustable resilient means in the other end of said ilrst mentioned bore and acting on said valve member to urge said valve member in the reverse direction.

IRA J. SNADEB.

MAX A. MATHYS.

having a control port