US2896546A

US2896546A - Porting arrangement for hydraulic pumps and motors

Info

Publication number: US2896546A
Application number: US527356A
Authority: US
Inventors: Bruce H Lundgren; Melvin M Hann
Original assignee: Sundstrand Machine Tool Co
Current assignee: Sundstrand Machine Tool Co
Priority date: 1955-08-09
Filing date: 1955-08-09
Publication date: 1959-07-28
Anticipated expiration: 1976-07-28

Description

July 28, 1959 B. H.'LUNDGREN ETAL 2,896,546

PORTING ARRANGEMENT FOR, HYDRAULIC PUMPS AND MOTORS Filed Aug. 9, 1955 s Sheets-Sheet 1 B. H. LUNDGREN ET AL 2,396,545

PORTING ARRANGEMENT FOR HYDRAULIC PUMPS AND MOTORS Filed Aug. 9, 1955 July 28, 1959 I 3 Sheets-Sheet 2 l ifiruaemurzcyren PORTING ARRANGEMENT FOR HYDRAULIC PUMPS AND MOTORS Filed Aug. 9, 1955 July 28, 1959 B. H. LUNDGREN ET'AL 3 Sheets-Sheet 3 FIZZ '5 rates PORTING ARRANGEMENT FOR HYDRAULIC PUMPS AND MGTQRS Application August a, 1955, Serial N0. 527,356

11 Claims. (.Cl. 103-162 This invention relates to hydraulic pumps and motors and, more particularly, to a porting arrangement for hydraulic pumps and motors.

A general object of this invention is to provide a new and improved porting arrangement for hydraulic pumps and motors.

Another object of this invention is to provide a hydraulic pump wherein the intake and discharge ports are disposed in a new and improved arrangement so as to improve the performance thereof.

Another object of the invention is to provide a new and improved rotating barrel type hydraulic pump or motor wherein the intake and discharge ports are arcuately-shaped and eccentrically disposed with respect to the axis of the rotating barrel.

Another object of this invention is to provide a new and improved valving arrangement for a rotating barrel type pump or motor wherein the intake and discharge kidneys are arranged with respect to the axis of rotation of the barrel so that cylinder ports formed in the barrel are opened and closed tangentially.

Another object of this invention is to provide a new and improved porting arrangement for a hydraulic pump or motor having a rotatable cylinder block wherein the intake and discharge arcuately-shaped ports are eccentrically disposed with respect to the axis of the cylinder block so that cylinder ports formed in the cylinder block are opened to the arcuately-shaped ports tangentially.

A further object of this invention is to provide in a hydraulic pump or motor having a rotatable cylinder block provided with a plurality of cylinders and cylinder ports axially formed therein in an annular row with each cylinder having a piston reciprocable therein, a new and improved porting arrangement including an intake and a discharge port shaped and arranged relative to the axis of the cylinder block so as to open and close the cylinder ports in a manner wherein the area of the intake and discharge ports open to the cylinder ports varies directly with the rate of movement of the pistons in the cylinders for any speed of rotation of the cylinder block.

Other objects and advantages will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

Fig. 1 is a vertical sectional view of a hydraulic pump incorporating an embodiment of the invention; 6

Fig. 2 is an elevational view of the left end of Fig. 1;

Fig. 3 is a schematic view taken generally along line 33 of Fig. 1 showing one symmetrical arrangement of eccentrically disposed intake and discharge kidney ports;

Fig. 4 is a schematic view similar to Fig. 3 showing another symmetrical arrangement of intake and discharge kidney ports;

Fig. 5 is a schematic view similar to Fig. 3 showing an arrangement of intake and discharge kidney ports of different sizes; and

Fig. 6 is a schematic view similar to Fig. 3 showing another arrangement of intake and discharge kidney ports.

While the invention is herein described with reference 2,896,546 Patented July 28, 1959 ice to several embodiments, it is not intended to limit the invention to the specific forms and arrangements shown, it being contemplated that various changes may be made by those skilled in the art without departing from the spirit and scope of the invention as pointed out in the appended claims.

A hydraulic pump of the type with which this invention is well adapted to be utilized is shown in Fig. 1, and includes a casing 2, a shaft 4 rotatably mounted in

bearings

6, 8 and 10 mounted in the casing 2, and a barrel type cylinder block 12 splined to the shaft 4 at 14 so as to be rotatable therewith. The cylinder block 12 has formed therein an annular row of axial cylinders 16, each of which has a piston 18 reciprocably mounted therein constantly urged by a spring 20 against a tiltable cam plate 22. As the cylinder block 12 is rotated by the shaft 4, the pistons 18 are moved in their discharge strokes as a result of their engagement with the tilted cam plate 22, the ends of pistons 18 being rounded to form part of a ball and socket connection to slippers 23 which slidably engage the cam plate 22. The length of the stroke of the pistons 18 is determined by the angle of the cam plate 22 which may be varied by a control piston 24 slidable in a cylinder 26 formed in the casing 2, the position of the control piston 24 being determined by means including a control valve 28.

A pair of cylinder ports 30 (Figs. 1 and 3) extend be tween each cylinder 16 and a flat end face 32 of the cylinder block 12. A port plate 34 is secured to one end of the casing 2 and has a flat end face 36 in contact with the face 32 of cylinder block 12. The pump casing 2 is provided with a fluid inlet 38 and a fluid outlet 46, shown in Fig. 2.

Referring now to Fig. 3, an arcuate or crescent-shaped intake port or kidney 42 and an arcuate or crescent-shaped discharge port or kidney 44 are formed in the flat end face 36 of the port plate 34. The kidneys 42 and 44 communicate through appropriate passages (not shown) with the pump inlet 38 and the pump outlet 40, respectively. When the cylinder block 12 is rotated by the shaft 4, the cylinder ports 30 communicate alternately with the intake kidney 42 and the discharge kidney 44 so that fluid is admitted into and then discharged under pressure from the cylinders 16, thus, providing the well known fluid pumping action.

In the operation of hydraulic pumps or motors of the rotating barrel type, the fluid pressure within the cylinders changes from low to high pressure at the crossover between the two kidneys. Thus, when the device is operated as a pump, fluid under low pressure is admitted into the cylinders 16 from the intake kidney 42, but the fluid within the discharge kidney 44 is under high outlet pressure. If the fluid within the cylinders 16 is suddenly exposed to the pressures in the discharge kidney 44, noise may result, particularly where the cylinders 16 are not completely filled or where the fluid contains entrapped air. Air bubbles will be collapsed immediately upon exposure to outlet pressure, and such collapse is often accompanied by both noise and wear on the pump parts.

According to the present invention, however, the kidneys 42 and 44, particularly the discharge kidney 44, are so arranged as to provide a gradual opening of the cylinder ports 30 to the discharge kidney 44, and in the preferred embodiments, the rate of opening of the cylinder ports 30 to the discharge kidney 44 and the extent of the opening is correlated with the speed of movement of the piston 18 in the cylinder 16 so as to provide the minimum opening when piston speed is at a minimum, and a maximum opening at the point where the piston 18 is travelling at its maximum speed.

By arranging the discharge kidney 44 so that it opens to the cylinder ports 30 tangentially thereof, a smooth transition to high pressure can be achieved with the resulting elimination of noise and a quieter operation of the pump. A simple. way of achieving this tangentialopening is shown in Fig; 3/wherein the discharge kidney 44 is formed so that the outer edge 45 lies along a circle centered at the axis of rotation a of the cylinder block 12 and has a' radius equal to the distance from the axis a to the outer edge of the cylinder ports 3t), If the inner edge 47 of the discharge port 44 be so proportioned as to lie along a circle centered at point c (ie on the opposite side of the axis of rotation :1), the cylinder ports 30 will be opened to the discharge kidney 44 in the manner illustrated in Fig. 3, where the opening to the discharge kidney 44 from the cylinder ports 30 is tangential to the ports and progresses'thereacross.

Referring again to Fig. 3, it will be noted that both the intake and discharge kidneysAZ and 44haveb'een formed in the manner just described, and the leading and trailing ends 46 and 43 of the intake kidney 42 and the corresponding ends 50 a'ndSZ of the discharge kidney 44 are so formed as to terminate outside oft he circle of rotation (indicated by -b )--of the cylinder ports 30. For the purpose of describing the opening and closing of the cylinder ports by the discharge kidney 44, representative positions of the cylinder-ports 30' and Eilfof one of the cylinders 16' are indicated at A, B, C, D-andE. In the crossover position indicated at A,it' will be noted that the cylinder port 30 of one of the cylinders 16' has just left the trailing end 48 of the intake kidney 42 tangential ly to the outer periphery of the port 30' and the adjacent cylinder port 39 is just about to be opened to the leading end 50 of the discharge kidney 44 tangentially to the outer periphery of the port 30". In position A, the area of thecylinder ports 30 and'30 open to the kidneys 42 and 44 is zero and the rate of movement of the piston 18 is zero, the piston '18 having reached the end of its stroke in the cylinder 16" so that'the cylinder 16 is filled with fluid. As the cylinder block 12 is rotated to move the cylinder ports 30' and .30" from the position illustrated at A, the leading cylinder port 30' is opened to the discharge kidney 44, with such opening taking place along a line substantially tangent to the cylinder port 30". This gradual tangential opening of the cylinder port 30" continues until the outer edge 45 of the kidney 44 becomes tangent to the outer periphery of the cylinder port 39', which condition exists during a substantial portion'of the time the'cylinder port 30" is in communication with the discharge kidney 44. The trailing cylinder port St? is opened tangentially by the discharge kidney 44 in the same manner. In the position indicated at B, the area of the

cylinder ports

30 and 30" open to the discharge kidney 44 has been substantially increased and the rate of movement of the piston 18 has increased directly there.

with. In the position indicated at C, the

cylinder ports

30 and 30" are approaching the midpoint of the discharge kidney 44 where the area of the

cylinder ports

30 and 30 open to the discharge kidney 44 becomes a maximum, the inner edge 48 of the discharge kidney 44 being tangent to theinner peripheries of the

cylinder ports

30 and 30", and the rate of movement of the piston 18 in its discharge'stroke in the cylinder 16 becomes a maxi mum. In the position indicated at D, the area of the cylinder ports 30' and 30" open to the discharge kidney 44 has decreased and the rate of movement of the piston 13 in the cylinder 16' has decreased directly therewith. In the position indicated at E, the cylinder ports 30 and 30-" are approaching the trailing end 52 of the discharge kidney 44and the area of the "cylinder ports '30 and 30";open to the discharge kidney 44 has substantially decreased, the rate of movement of the piston 18 approaching the other end of its discharge stroke decreasing directly'therewith- As the cylinder ports 30' and 30" arerotated out of communication with the discharge kidney 44 and into communication with the intake kidney. 42 the --cylinder ports 30' and 30" are opened and closed tangentially to their outer peripheries in the same manner by the intake kidney 42.

Another embodiment of this invention is shown in Fig. 4 wherein an intake kidney 42a and a discharge kidney 4411 are *formed in. a port plate 34a so that the leading ends 4601 and 50a, respectively, thereof and the trailing ends 4811 and 52a, respectively, thereof are disposed within the circle of rotation (indicated by .b)' of the centers of the cylinder ports 3%. In this embodiment it will he noted that the inner edge 47a of the discharge kidney 44a lies along a circle centered at the axis of rotation a of the cylinder block 12 and having a radius equal to the distance from the axis a to the inner peripheries of the cylinder ports 34. With the outer edge 45a of the discharge kidney 44a lying on a circle having a center cl which is spaced from the axis a approximately a distance equal to the diameter of the cylinder ports 39 and toward the discharge kidney 44a, the cylinder ports 30 are opened and closed tangentially to their inner peripheries by the discharge kidney 44ain substantially the same manner as described with respect to the arrangement of Fig. 3. In this arrangement, the intake kidney 42a is formed in the same manner as is the discharge kidney 44a so that the inner edge 49:: of the intake kidney 42a is tangent to the inner peripheries of the cylinder ports 30 during a substantial portion of the period the cylinder ports 30 are in communication with the intake kidney 42a. 7 d

An embodiment of this invention wherein the two kidneys differ somewhat in size and shape is shown in Fig. 5a The discharge kidney 441) is formed substantially identical to the discharge kidney 44 of the embodiment shown in Fig. 3, the outer edge 45b lying on a circle having its center on the axis a and a radius equal to the distance between the axis a and the outer periphcries of the cylinder ports 3t) and't'ne inner edge 47]) lying on a circle having a center 02 spaced from the axis a away from the discharge kidney 44b, as with the center ,c of Fig. 3. In this arrangement, the intake kidney 42b is formed substantially identical to the intake kidney 42a of the embodiment shown in Fig. 4, an inner edge 4% of the intake kidney 42blying on a circle having its center on the axis of rotation a of the cylinder block 12 and a radius equal to the distance between the axis a and the inner peripheries of the cylinder ports 30 and an outer edge $11; lying on a circle having a center d2 spaced from-the axis a toward the intake kidney 425]. With the arrangement shown in Fig. 5 the cylinder ports 30 are opened tangentially to their peripheries by the kidneys 42b and 44b respectively substantially the same asdescribed with respect to thearrangements of Fig. 4-and Fig.3. The intake kidney 42b has the leading end] 4612 and the trailing end 43b,disposed inside the circle of rotation (indicated by b) of the centers of the cylinder ports 36, the cylinder ports 3% thus being opened and closed tangentially to their inner peripheries by the inlet kidney 421;. The discharge kidney 44b opens and closes the cylinder ports 30 tangentially/to their outer peripheries, the leading end Stib and the trailing end 52% thereof being disposed outside the circle of rotation b of the centers ofcylinder Ports30. A further embodiment of the invention is shown .in the arrangementcf Fig. 6 wherein an inlet kidney 420 andan outlet kidney 440 are arranged so that leading ends 460 and 500, respectively, thereof are disposed inside the circle of rotation (indicated byb) of the centers ofcylinder ports 30 and trailing ends 480 'and52c, respectively, thereof are disposed outside the circle of rotation (indicated by [2). The discharge kidney. 44c has an' inner edge comprising 'a leading portion 47c and a. trailingportion 47c and an outeriedge comprising-a leading-portion 45cand.a trailing portion 450. The edge portions; 47c and 45c. each define an arc havassaaie ing a center on the axis of rotation a of the cylinder block 12, the radius of the arc of the portion 470 being equal to the distance from the axis a to the inner peripheries of the cylinder ports 30 and the radius of the arc of the portion 450 being equal to the distance from the axis a to the outer peripheries of the cylinder ports 30. The inner edge portions 470' defines an arc having a center 03 spaced 'from the axis a and away from the discharge kidney 44c while the outer edge portion 45c defines an are having a center c3 spaced from the axis a andtoward the discharge kidney 440. Likewise, the intake kidney 420 has an inner edge comprising a trailing portion 49c and a leading portion 490' and an outer edge comprising a trailing portion 510 and a leading portion 51c. The edge portions 510 and 490 each define arcs having centers on the axis a and radii equal to the distances from the axis a to the outer peripheries of the cylinder ports 30 and the inner peripheries of the cylinder ports 30, respectively. The inner edge portion 490 defines an are having a center d3 spaced from axis a and away from the intake kidney 42c and the outer edge portion 510' defines an arc having a center 113' spaced from axis a approximately the diameter of the cylinder ports 30 toward the intake kidney'42c. With this arrangement, the cylinder ports 30 are opened tangen .tially to their inner peripheries by the leading ends 46c and 50c and closed tangentially to their outer peripheries by the trailing ends 480 and 52c.

As ShOWn in Figs. 4, 5 and 6, where the leading ends 46a, 46b, and 460 of the intake kidneys 42a, 42b and 42c are disposed inside the circle of rotation (indicated by b) of the centers of the cylinder ports 30, the cylinder ports 30 are opened tangentially to their inner peripheries by the leading ends of the intake kidneys so as to aid in filling the cylinders '16 inasmuch as the centrifugal force of rotation of the fluid entering the cylinder ports 30 is added to the intake pressure of the fluid.

It is noted that this invention is not limited to the embodiments of porting arrangements shown and described herein, but includes other possible arrangements of kidney ports wherein the cylinder ports are opened and closed tangentially to their peripheries by the kidney ports, and wherein the area of the kidney ports open to the cylinder ports varies directly with the rate of movement of the pistons in the cylinders without regard to the speed of the rotating cylinder block.

While an understanding of the operation of control valve 28 is not necessary to an understanding of the present invention, a description of the valve will facilitate an understanding of the pump operation as a whole. It should be understood, however, that the valve 28 is .not a necessary element in a pump utilizing the present invention, but may be omitted or replaced by other controls of the same or a different type.

In a preferred application, the control valve 28 is utilized to vary the displacement of the pump as the speed of the drive shaft varies in order that the volumetric pump output may be maintained at a constant value, for example, to drive a hydraulic motor at a constant speed. In order to attain this purpose, the cam plate 22 normally assumes a minimum displacement position (not shown) by virtue of the action of gravity on the plate and by the plurality of individual piston springs 20. When the pump is first started, the cam plate occupies such a minimum displacement position, and at that time valve 28 is effective to admit fluid under pressure to the control chamber 26 to urge the piston 24 toward the right as viewed in Fig. 1 thereby to shift the cam plate 22 toward a maximum displacement position as illustrated in Fig. 1. As the presure and flow of fluid delivered by the pump increase after operating speed is attained, valve 28 will reduce the flow of fluid to control chamber 26, or even connect the chamber to drain in order that the cam plate may return toward minimum displacement position, this 6 being desirable when the speed of the pump drive shaft increases unavoidably, if the volumetric output is to be maintained constant.

The valve 28 includes a valve bore 60 having an outer valve member 61 in the form of a sleeve slidable therein, and an inner valve member 62 slidable in valve member 61. Valve member 61 provides the displacement control referred to, while valve member 62 provides an overpressure relief control. Sleeve 61 is urged upwardly in the bore 60 by a spring 64 while the valve member 62 is urged upwardly in sleeve 61 by a spring 65 toward a snap ring 66 retained in the upper end of sleeve 61.

Control fluid under pressure is admitted to the chamber 26 through a conduit 68 adapted for connection with a port 69 in sleeve 61 when the sleeve occupies a position slightly above that illustrated in Fig. 1. When the sleeve 61 is so positioned, the port 69 therein is adapted for communication with a port 70 in valve member 62 when the latter is moved upwardly against the snap ring 66. This position, with both valve members in their uppermost positions, is the normal condition of the control valve when the pump is started. Under these conditions, the hollow interior of valve member 62 communicates through a port 71 with the valve bore 60 which in turn has a port 72 leading outwardly therefrom. a

Port 72 functions to supply control fluid to the valv bore 60 for delivery to control chamber 26, and the fluid admitted through the port 72 also acts against the lower ends of the valve members to urge both upwardly. At the upper end of the bore 60 a port 73 opens into the bore for admitting pressure fluid to act against the upper end of the valve members.

Preferably, in order to maintain a constant volumetric flow the pump outlet includes a restrictive orifice (not shown), and a conduit connects the port. 72 with the pump outlet downstream from the orifice while a sepa rate conduit connects the port 73 with the pump outlet upstream of the orifice. In this manner the pressure drop across the orifice controls the position of the valve.

In operation, when the pump is started control fluid flows to the chamber 26 through port 72, bore 60, port 71, port 70, port 69 and conduit 68 to urge the piston 24 toward the right, increasing pump displacement. As flow increases through the pump outlet, pressure rises upstream of the orifice referred to, and when the desired pump displacement is attained the pressure in port 73 and the upper end of bore 60 urges the

valve members

61 and 62 downwardly to a position wherein port 69 is blocked, substantially as illustrated in Fig. l, to hold piston 24 and cam plate 22 at the desired position.

In the event of a decrease in pump speed the pressure drop across said orifice decreases, and the valve members move upwardly to connect ports 72 and 69 and increase pump displacement. In the event of an increase in pump speed, the pressure drop across said orifice increases, the valve members move downwardly and conduit 68 is connected to drain through an outer annular groove 75 on the sleeve 61 and through a drain passage 77 leading from the bore 66, thereby to permit a reduction in the pump displacement.

Valve member 62 provides an overpressure relief control whereby, when the pressure in the pump outlet increases to an excessive value, pressure acting against the larger upper endof valve member 62 is suflicient to overcome the pressure of spring 65 and fluid acting against the smaller lower end of member 62, moving the valve member 62 downwardly from the position illustrated in Fig. l to a position wherein an outer annular groove 78 on valve member 62 connects conduit 68 and port 69 to drain through a port 80 in the valve sleeve 61, and drain passage 77.

We claim:

1. In a hydraulic pump or motor having a rotatable cylinder block provided with a plurality of cylinders formed axially therein, a cylinder port for each cylinder and opening to an end face of the cylinder block and a piston reciprocable in each of said cylinders, a porting arrangement comprising; a port plate disposed adjacent the end face of the cylinder block and having an intake kidney and a discharge kidney formed therein, said kidneys being generally crescent-shaped and positioned in said port plate to communicate alternately with the cylinder ports upon rotation of the cylinder block, the inner and outer edges of at least one of said kidneys defining arcs of circles on said port plate, one are having a center disposed on the axis of rotation of said cylinder block and a radius extending to one peripheral edge of the cylinder ports and the other are having a second center spaced from the axis of rotation of said cylinder block and a radius equal to the distance between said second center and the other peripheral edge of the cylinder ports when positioned at the midpoint of said kidney. 7

2. In a cam plate type hydraulic pump or motor having a rotatable cylinder block provided with a plurality ofcylinders formed axially therein, a cylinder port for each cylinder and opening to an end face of the cylinder block and a piston reciprocable in each of said cylinders, a porting arrangement comprising; a port plate disposed adjacent the end face of the cylinder block and having an intake kidney and a discharge kidney formed therein, said kidneys being generally crescent-shaped and positioned in said port plate to communicate alternately with the cylinder ports upon rotation of the cylinder block, the inner and outer edges of the discharge kidney defining two circular arcs having approximately equal length radii, one of the arcs having a center disposed on the axis of rotation of said cylinder block with the radius extending to one peripheral edge of the cylinder ports, the other are having a center spaced from the axis of rotation of the cylinder block a distance approximately the diameter of the cylinder ports.

3. In a hydraulic pump or motor having a rotatable cylinder block provided with a plurality of cylinders formed axially therein, a cylinder port for each cylinder and opening to an end face of the cylinder block and a piston reciprocable in each of said cylinders, a porting arrangement comprising; a port plate disposed adjacent the end face of the cylinder block and having an intake kidney and a discharge kidney formed therein, said kidneys being generally crescent-shaped and'positioned in said port plate to communicate alternately with the cylinder ports upon rotation of the cylinder block, the inner edges ofthe kidneys defining first arcs having centers disposed on the axis of rotation of the cylinder block and radii extending to the inner edges of the cylinder ports, the outer edges of the kidneys defining arcs having radii equal to the radii of said first arcs and centers spaced from the axis of rotation of the cylinder block toward the kidneys a distance approximately the diameter of the cylinder ports.

4. In a hydraulic pump or motor having a rotatable cylinder block provided with a plurality of cylinders formed axially therein, a cylinder port for each cylinder and opening to an end face of the cylinder block and a piston reciprocable in each of said cylinders, a porting arrangement comprising; a port plate disposed adjacent the end face of the cylinder block and having an intake kidney and a discharge kidney formed therein, said kidneys being generally crescent-shaped and positioned in said port plate to communicate alternately with the cylinder ports upon rotation of the cylinder block, the inner edge of the intake kidney and the outer edge of the discharge kidney defining arcs of unequal radii having centers disposed on the axis of rotation of the cylinder block, the arc defined by the inner edge of the intake kidney having a radius extending to the inner peripheries of the cylinder ports, the arc defined by the outer edge of the discharge kidney having a radius extending to the .outer peripheries of the cylinder ports, the outer edge of the intake kidney defining an are having a center spaced from the axis of rotation and toward the intake kidney and a radius such that the midpoint of the outer edge of the intake kidney is tangent to the outer peripheries of the cylinder ports, the inner edge of the discharge kidney defining an are having a center spaced from the axis of rotation and away'from the discharge kidney and a radius such that the midpoint of the inner edge of the discharge kidney is tangent to the inner peripheries of the cylinder ports.

5. In a hydraulic pump having a rotatable cylinder block provided with an annular row of cylinders formed axially therein and cylinder ports opening to an end face of the cylinder block, a porting arrangement comprising; a port plate having a face contacting the end face of the cylinder block and an intake and a discharge kidney formed in the face of the port plate and adapted to communicate alternately with the cylinder ports upon rotation of the cylinder block, said kidneys. being so arranged with respect to the axis of rotation of the cylinder block that the cylinder ports are opened and closed tangentially to the peripheries thereof, the intake kidney being arranged to open the cylinder ports tangentially to the inner peripheries thereof to add the centrifugal force of rotation to input pressure to aid in filling the cylinders with fluid.

6. The combination of claim 5, wherein the intake kidney is arranged to close the cylinder ports tangentially to the inner edges thereof.

7. The combination of claim 1, wherein the inner edge of the intake kidney defines a first are having its center disposed on the axis of rotation of the cylinder block and a radius extending to the inner edges of the cylinder ports, and wherein the outer edge of the intake kidney defines an are having a radius equal to the radius of said first arc and a center spaced from the axis of rotation of the cylinder block toward the intake kidney a distance approximately equal the diameter of the cylinder p r w 8'. In a hydraulic pump or motor having a rotatable cylinder block provided with a plurality of cylinders formed axially therein, a cylinder port for each cylinder and opening to an end face of the cylinder block and a piston reciprocable in each of said cylinders, a porting arrangement comprising; a port plate disposed adjacent the end face of the cylinder block and having an intake kidney and a discharge kidney formed therein, said kidneys being generally cresent-shaped and positioned in said port plate to communicate alternately with the cylinder ports upon rotation of the cylinder block, the inner edge of the intake kidney and the outer edge of the discharge kidney defining arcs of unequal radii having centers disposed on the axis of rotation of the cylinder block, the arc defined by the inner edge of the intake kidney having a radius extending to the inner edges of the cylinder ports, the arc defined by the outer edge of the discharge kidney having a radius extending to the outer edges of the cylinder ports the outer edge of the intake kidney defining an are having a center spaced from the axis of rotation and toward the intake kidney by an amount approximately equal the diameter of the cylinder ports and a radius such that the midpoint of the outer edge of the intake kidney is tangent to the outer edges of the cylinder ports, the inner edge of the discharge kidney defining an are having a center spaced from the axls of rotation and away from the discharge kidney and a radius such that the midpoint of the inner edge of the discharge kidney is tangent to the inner edges of the cylinder ports and the ends of the inner edge of the discharge kidney are tangent to the outer edges of the cylinder ports.

9. In a hydraulic pump or motor having a rotatable cylinder block provided with a plurality of cylinders formed axially therein, a cylinder port for each cylinder and opening to an end face of the cylinder block and a plston reciprocable in each of said cylinders, a porting arrangement comprising; a port plate disposed adjacent the end face of the cylinder block and having an intake kidney and a discharge kidney formed therein, said kidneys being generally crescent-shaped and positioned in said port plate to communicate alternately with the cylinder ports upon rotation of the cylinder block, the inner and outer edges of at least one of said kidneys defining arcs of circles on said port plate, one are being tangent to the cylinder ports at one peripheral edge thereof, and the other are having its midpoint tangent to the cylinder ports at the opposite peripheral edge thereof and its ends tangent to the cylinder ports at said one peripheral edge thereof.

10. The combination of claim 9, wherein the discharge kidney has its outer edge defining an arc tangent to the outer edges of the cylinder ports, and wherein the discharge kidney has its inner edge defining an arc tangent at its midpoint to the inner edges of the cylinder ports and 10 tangent at its ends to the outer edges of the cylinder ports. 11. The combination of claim 9, wherein each kidney has its outer edge defining an arc tangent to the outer edges of the cylinder ports, and each kidney has its inner edge defining an arc tangent to the inner edges of the cylinder ports at the midpoint of the kidney and tangent to the outer edges of the cylinder ports at the ends of the kidney.

References Cited in the file of this patent 5 UNITED STATES PATENTS Lauck et al Mar. 31, 1953