US2833225A - Hydraulic pump structure - Google Patents

Description

May 6, 1958 F. A. SHERMAN 2,333,225

HYDRAULIC PUMP STRUCTURE Filed Aug. 25, 1954 4 Sheets-Sheet 1 IN V EN TOR;

F1. am 4 SHE/may 4 TTOFNHS May 6,1958

F. A. SHERMAN HYDRAULIC PUMP STRUCTURE 4 Shee ts- Sheet' 2 Filed Aug. 25, 1954 1 N V EN TOR.

FL 0 r0 4 Sum/4N y 6, 1958. F. A. SHERMAN HYDRAULIC PUMP STRUCTURE 4 Sheets-Sheet 3 Filed Aug. 25, 1954 JNVENTOR. FLOYD ,4 Syn/v4 [BY 1 ATTOAME'VS M y 1953 F. A. SHERMAN 2,833,225

HYDRAULIC PUMP STRUCTURE Filed Aug. 25, p54 .4 Sheets-Sheet 4 I1E=E| J o M r r, /70 M Z1 Z2 U INVENTOR. Ham 4 jymm/v A TTOP/VEVS United States atent HYDRAULIC PUMP STRUCTURE Floyd A. Sherman, Birmingham, Mich, assignor to Motor Products Corporation, Detroit, Mich, a corporation of New York Application August 25, 1954, Serial No. 452,169 Claims. Cl. 103-161) This invention relates generally to pump assemblies and refers more particularly to improvements in hydraulic variable displacement types of pump assemblies.

It is an object of this invention to provide a pump structure rendering it possible to deliver fluid at a subs-tam tially constant predetermined pressure regardless of variations in the speed of rotation of the pump.

It isanother object of this invention to provide a pump structure of the above type'which is compact in size and is composed of a relatively few simple parts capable of being inexpensively manufactured and assembled.

The foregoing as well as other objects will be made more apparent as this description proceeds especially when considered in connection with the accompanying drawings, wherein:

Figure 1 is a longitudinal sectional view through a pump embodying the features of this invention;

Figure 2 is a sectional view taken on the line 2-2 of Figure l;

Figure 3 is a sectional view taken on the line 3-3 of Figure 2;

Figure 4 is a sectional view taken on the line 44 of Figure 1;

Figure 5 is a sectional view taken on the line 55 of Figure 1; and

Figure 6 is a fragmentary sectional view showing a modified form of pump assembly.

The pump assembly selected herein for the purpose of illustration has a body 10 provided with a rear wall 11 having an axially extending annular flange 12 extending forwardly from the periphery thereof and form ing a chamber 13 which may be and preferably is connected to a reservoir (not shown) for hydraulic fluid. The front side of the chamber 13 is closed by a cap 14 having the peripheral portion clamped to the front end of the flange 12 by studs (not shown) and having a centrally disposed hub section 16 axially bored to receive a drive shaft 17. Therear end of the drive shaft 17 is reduced in diameter to provide a shoulder 18 and is journaled in a bearing 19 supported within a blind bore 20 formed in the wall 11. The shaft 17 is also journaled in the hub section 16 of the cap 14 by a pair of ball bearings 21 supported in side by side relationship within the hub section 16. The rear bearing 21 abuts apart 22 secured to the shaft 17 within the chamber 13 and the front bearing 21 abuts a shoulder 23 formed by reducing the bore in the hub section 16.

The part 22 is fixed on the shaft 17 adjacent the shoulder 18 and is formed with a rearwardly extending annular flange 24 concentric with the axis of the shaft 17 and having a bearing engagement with the wall 11 of the body 10. In cases where the wall 11 is formed of a relatively soft material, a plate or disc 25o-f wear re sisting material is inserted in the front face of the wall 11 to provide a bearing surface for the rear side of the flange'24. The disc 25 is centrally 'apertured to receive the bearing 19 and. for practical purposes is considered apart of the front'wall 11 of the body 18. The flange 24 Patented May 6, 1958 is fashioned to provide a plurality of circumferentially spaced cylinders 26 which extend radially through the flange 24 and are rectangular in cross section. The rear sides of the cylinders are open and are closed by the front surface of the disc 25 or wall 11 of the body 10, as shown in Figure 5 of the drawings.

Supported in each cylinder 26 for sliding movement radially with respect to the axis of the shaft 17 is a piston 27 which is also rectangular in cross section. The rear sides of the pistons 27 form in effect continuations of the rear end of the flange 24 and have a sliding bearing engagement with the disc 25 or wall 11 of the body 10..

The above structure is particularly advantageous from the standpoint of economy in manufacture since it facilitates and simplifies the forming operations.

The rear end of the flange 24 on the part 22 and the rear walls of the pistons are maintained in bearing engagement with the disc 25 or rear wall 11 of the body 10 by an adjusting nut 28 threadably supported in the front end of the hub 16 and centrally apertured to receive the shaft 17. The rear end of the nut 28 engages an enlargement 29 on the shaft 17 and cooperates with the latter to provide an adjustment whereby the rear surfaces of the flange 24 and pistons 27 are held in contact with the disc 25 regardless of wear. A lock nut 30 is threadably mounted on the nut 28 in a position to engage the front end of the hub and thereby prevent accidental rotation of the nut 28.

Surrounding the outer ends-of the pistons 27 within the shaft 17 against the shoulder 18. An annular flange 36.

extends rearwardly from the periphery of the part 35 to the disc 25 and serves to close the radially inner ends of the cylinders 26. The inner surface of the annular flange 36 is recessed at the rear end of the flange to receive a closure disc 37 which is secured to the flange 36 and cooperates with the part 35 to provide a closed annular space 38 around the shaft 17. A ring 39 surrounds the shaft 17 within the space 38 and the opposite ends of the ring respectively slidably engage the part 35 and disc 37. The internal and external diameters of the ring 39 are determined to enable floating of the ring radially within the space 38 throughout a distance approximating the stroke of the pistons 27 within the cylinders 26. The ring 39 is operatively connected to the pistons 27 by pins 40 which are respectively slidably supported within circumferentially spaced openings extending radially through the flange 36. The openings are so positioned that the inner the outer ends respectively bear against the inner ends of the pistons 27. The construction is such that the pins 40 cooperate with the floating ring 39 and the cam ring 31 to move the pistons 27 inwardly and outwardly in their respective cylinders 36 without the use of springs or equivalent means. Thus, the pistons are positively moved in 'both directions with a minimum amount of friction and reliable operation of the pump is assured throughout the life of the latter. 1

Formed in the front surface of the disc 25 are two arcuate passages 41 and 42 concentric with the axis of the shaft 17 and positioned to register with the radially inner ends of the cylinders 26 as the latter are rotated by the shaft 17. The passage 41 is an intake for fluid and n3 communicates with the reservoir or with a supply of hydraulic fluid through a port 43 formed in the wallll. The intake passage 41 is so located with respect to the cam ring 31 that it registers with the cylinders 26 when the pistons 27 in the cylinders move radially outwardly. As a result fluid is drawn into the inner ends of the cylinders 26 as the latter travel along the arcuate intake pas sage 41. The passage 42 is a discharge passage and communicates with the point or points of demand for high pressure fluid through a port 44 formed in the wall 11.

The passage 42 is so located with respect to the cam ring 31 that it registers with the radially inner ends of the cylinders 26 when the pistons 27 are moved radially inwardly by the cam ring 31. The arrangement is such that the fluid admitted into theinner ends of the cylinders 26 through the inlet passage 41 during outward movement of the pistons 27 is subsequently discharged under pressure through the outlet passage 42 by inward movement of the pistons 27;.

Due to the surface to surface contact provided between the disc and adjacent surfaces of the pistons 27 and flange 24 a seal is provided which reduces the escape of fluid into the chamber 13 to a minimum. The escape of fluid along the shaft 17 is prevented by a seal 45 surrounding the shaft 17 at the front side of the forwardmost ball bearing 21 and engageable with a shoulder 46 formed by reducing the bore extending through the hub section 16.

As shown in Figure 3 of the drawings, diameterically opposite sides of the cam ring 31 are seated in recesses 47 formed in the body 10 and are provided with flats 48 which slidably engage adjacent side walls of the recesses 47. Suitable retaining plates 49 are fastened to the body at opposite sides of the cam ring 31 and overlie the adjacent sides of the cam ring to maintain the latter in sliding engagement with the walls of the recesses. The above construction enables sliding movement of the cam ring 31 relative to the body 10 in a plane perpendicular to the axis of the shaft 17. As a result of this sliding movement of the cam ring 31, the degree of eccentricity of the inner surface of the cam rim may be varied to alter the stroke of the pistons 27 in the cylinders 26 and thereby vary the pressure of the fluid displaced from thecylinders 26 through the discharge port 44.

In the present instance, it is desired to maintain the pressure of the fluid at the pump discharge port 44 substantially uniform regardless of variations in the speed of rotation of the drive shaft 17, and this is accomplished herein by automatically adjusting the cam ring 31 relative to the body 10. As shown in Figure 1 of the drawings, the flange 12 is formed with a pair of radially extending bores 50 diameterically opposed with respect to the cam ring 31 and having the outer ends closed by plugs 51. A plunger 52 is slidably supported in each bore 50 in a manner such that the inner ends of the plungers respectively engage flats formed on the outer surface of the cam ring 31 in diametrically opposed relationship. The spaces in the bores'50 radially outwardly of the plungers 52 respectively communicate with fluid ports 53 and 54.

The flow of fluid to the bores 50 is controlled by a sleeve valve 55 having a casing 56 formed with an axially extending chamber 57 and having a spool 58 slidably mounted in the chamber 57. One end of the casing 56 has a port 59 connected to the pressure outlet port 44 of the pump so that the pressure of the fluid discharged from the outletport 44 acts on the outer end of the spool 58 tending to move the'latter inwardly in the chamber 57. This movement of the spool 58 is resisted by a coil spring 60 housed within the chamber. 57' at the inner end of the spool with one end engaging the spool and with the other end engaging a part 61 mounted on the casing 56. The force exerted on the spool 58 by the spring 60 is variable by adjusting the part 61- and for this purpose an adjusting screw 611 s provided. In practice, the spring 60 opposes inward movement of the spool tit) 58 with a force corresponding to a predetermined or specified pump outlet pressure.

The casing 56 also has a pair of ports 63 and 64 which communicate with the chamber 57 and which are spaced from one another longitudinally of the spool 58. The port 63 has a fluid connection with the port 53, and the port 64 has a fluid connection with the port 54. In addition, the casing 56 has a drain port 65 which is connected to the reservoir (not shown) and communicates with the chamber 57 at points spaced from one another longitudinally of the chamber'57. A passage 66 is formed in the casing 56 to one side of the chamber 57 and communicates at its outer end with the interior of the chamber 56 adjacent the pressure inlet port 59. The inner end of the passage 66 communicates with the interior of the chamber 56 through a port 67 located in opposed relationship to the ports 63 and 64 between the latter. A

The valve spool 58 has three enlargements 68 spaced equal distances from one another lengthwise of the spool 58 for controlling the flow of fluid under pressure through the valve 55. The arrangement of the enlargements 68 and the relationship of the various ports to the enlargements are such that when a predetermined pressure exists at the pump discharge port 44, the valve spool 58 is held by the spring 60 in an intermediate position wherein the pressure port 67 is closed by the center enlargement 68 on the spool 58. When the valve 55 is in the inoperative position thereof noted above, the cam ring 31 is in the position thereof shown in Figures 1 and 2 of the drawings or, in other words, is in a position to aflord maximum eccentricity and, hence, imparts the maximum stroke to the pistons 27. However, should the pressure at the Outlet port 44 of the pump become greater than the predetermined desired pressure determined by the spring 60, the valve spool 58 moves inwardly against the action of the spring 60 to connect the high pressure port 59 to the port 64 and to connect the drain port 65 to the port 63. Since the port 64 in the valve casing 56 communicates with the port 54 in the body 10 of the pump assembly, and since the port 63 in the valve casing 56 communicates with the port 53 in the pump body 10, the plunger 52 engaging the bottom side of the cam ring 31 (Fig. 1) moves inwardly toward the drive shaft 17 and the opposed plunger moves. outwardly. Thus, the cam ring 31 is shifted relative tothe pump body 10 in a direction to reduce the degree of eccentricity relative to the. axis of the drive shaft 17. As a result, the. displacement of the pistons 27 in the cylinders 26 is reduced and the pressure of the fluid at the outlet port 44 is lowered. It will be apparent that if the pressure drops below the desired value, the valve spool 58 is moved outwardly by the spring 60 to close communication between the ports 64 and 67, and open communication between the port 67 and the port 63. Also, the port 64 is connected to the drain 65 so that the cam ring 31 is moved by the top plunger 52 in Figure 1 in a direction to increase the. degree of eccentricity.

During normal operation of. the. pump, the valve spool 58 is in the position thereof shown in Figure 1 of the drawings wherein the center enlargement 68 is positioned between the ports 63 and 64 in closing relationship to the. port 67. Thus, relatively slight movements of the valve spool 58 in either direction efiects an adjustment of the cam ring 31, and hence, a substantially constant pressure may be obtained .at the pump outlet port 44 regardless of variations in the speed of rotation of the shaft 17. e

The embodiment, of the invention shownin Figure 6 of the drawings diflersfrom the above-construction in that the cam ring 31 is fixed and, hence, the, adjusting means for this cam are omitted. However, provision is made for preventing the pressure of the fluid at the outlet port 44 from exceeding apredetermined value and this is accomplished by introducing a leaf spring 70 between the adjusting nut 28 and the abutment 29 on the shaft 17. The arrangement-is such that-should the pressure of the fluid in the respective cylinders 26 exceed a predetermined value determined by the strength ofthe spring 70, the drive shaft 17 along with the parts 22 and 35 moves axially forwardly to provide a clearance between the front surface of the disc 25 and the rear walls of thepistons 27. Thus, fluid may escape from the cylinders 26 into the chamber 13 and the pump outlet pressure is correspondingly reduced. In this connection, attention is called to the fact that the outer races of the bearings 21 have a sliding fit with the bore extending through the hub 16 and the inner races have a pressed fit on the shaft 17. Hence, the end thrusts are transmitted to the shaft 17 through the ball bearings 21 during axial adjustment.

What I claim as my invention is:

l. A pump assembly comprising a body, a part supported for rotation relative to the body and having circumferentially spaced radially extending cylinders of rectangular section closed at the radially inner ends and open at the radially outer ends, said part providing radial walls for three sides of said respective cylinders, pistons of rectangular section respectively slidably supported in the cylinders and coacting therewith in defining pumping chambers radially inwardly of the pistons, said body having a bearing surface which constitutes a fourth side wall of said respective cylinders, being slidably engaged flatwise by an adjacent side of said respective pistons, a cam ring encircling the radially outer ends of the cylinders beyond the pistons, means for holding the radially outer ends of the pistons into engagement with the inner surface of the cam, said holding means comprising pins respectively slidably supported in circumferentially spaced bores extending radially through the inner walls of the cylinders and having the outer ends respectively engageable with the inner ends of the pistons, a ring surrounding the axis of rotation of the rotatable part in a position to engage the radially inner ends of the pins and supported by said part for floating movement radially with respect to the axis of rotation of said part, the inner surface of the cam ring being contoured to effect successive movement of the pistons inwardly andoutwardly in response to rotation of said part, thereby to discharge and draw in fluid, respectively, in relation to said pumping chambers, an inlet passage positioned within the body to introduce fluid into the cylinders upon outward movement of the pistons and an outlet passage in the body for'receiving fluid under pressure from the cylinders upon inward movement of the pistons, and means maintaining said part in end sealed engagement with said bearing surface.

2. A pump assembly comprising a body, a part supported for rotation relative to the body and having circumferentially spaced radially extending cylinders of rectangular section closed at the radially inner ends and open at the radially outer ends, said part providing radial walls for three sides of said respective cylinders, pistons of rectangular section respectively slidably supported in the cylinders and coacting therewith in defining pumping chambers radially inwardly of the pistons, said body having a bearing surface which constitutes a fourth side wall of said respective cylinders, being slidably engaged flatwise by an adjacent side of said respective pistons, a cam ring encircling the radially outer ends of the cylinders beyond the pistons, means adjustably supporting said cam ring for shift in a plane perpendicular to the axis of rotation of said part, means for holding the radially outer ends of the pistons into engagement with the inner surface of the cam, said holding means comprising pins respectively slidably supported in circumferentially spaced bores extending radially through the inner walls of the cylinders and having the outer ends respectively engageable with the inner ends of the pistons, 21 ring surrounding the axis of rotation of the rotatable part in a position to engage the radially inner ends of the pins and sup ported by said part for floating movement radially with respect to the axis of rotation of said part, the inner surface of the cam ring being contoured to effect successive movement of the pistons inwardly and outwardly in response to rotation of said part, thereby to discharge and draw in fluid, respectively, in relation to said pumping chambers, an inlet passage positioned within the body to introduce fluid into the cylinders upon outward movement of the pistons and an outlet passage in the body for receiving fluid under pressure from the cylinders upon inward movement of the pistons, and means maintaining said part in end sealed engagement with said bearing surface.

3. A pump assembly in accordance with claim 2, in which said adjustable cam ring supporting means comprises pressure responsive plungers mounted for radial movement on said body in engagement with said cam ring, and spring biased valve means controlling the application of fluid pressure from said outlet passage to said respective plungers to actuate the same in response to .variation in pressure in said outlet passage.

4. A pump assembly comprising a body, a part supported for rotation relative to the body and having circumferentially spaced, radially extending cylinders of rectangular section closed at the radially inner ends and open at the radially outer ends, said part providing radial walls for three sides of said respective cylinders, pistons of rectangular section respectively slidably supported in the cylinders and coacting therewith in defining pumping chambers radially inwardly of the pistons, said body having a bearing surface which constitutes a fourth side wall of said respective cylinders, being slidably engaged flatwise by an adjacent side of said respective pistons, a cam ring encircling the radially outer ends of the cylinders beyond the pistons, said cam ring being fixedly supported by the body, means for holding the radially outer ends of the pistons into engagement with the inner surface of the cam, said holding means comprising pins respectively slidably supported in circumferentially spaced bores extending radially through the inner walls of the cylinders and having the outer ends respectively engageable with the inner ends of the pistons, a ring surrounding the axis of rotation of the rotatable part in a position to engage the radially inner ends of the pins and supported by said part for floating movement radially with respect to the axis of rotation of said part, the inner surface of the cam ring being contoured to effect successive movement of the pistons inwardly and outwardly in response to rotation of said part, thereby to discharge and draw in fluid, respectively, in relation to said pumping chambers, an inlet passage positioned within the body to introduce fluid into the cylinders upon outward movement of the pistons and an outlet passage in the body for receiving fluid under pressure from the cylinders upon inward movement of the pistons, and means maintaining said part in end sealed engagement with said hearing surface.

5. A pump assembly in accordance with claim 4, in i which said last named means comprises a spring yieldably urging said part against said bearing surface.

References Cited in the file of this patent UNITED STATES PATENTS 732,109 Patterson June 30, 1903 1,666,466 Peters Apr. 17, 1928 1,729,764 Dinesen Oct. 1, 1929 2,179,071 Wiedmann Nov. 7, 1939 2,192,660 Johnson Mar. 5, 1940 2,195,812 Czarnecki Apr. 2, 1940 2,214,552 Ferris Sept. 10, 1940 2,287,369 Anderson ..a June 23, 1942 2,311,162 Du Bois Feb. 16, 1943 2,354,076 Tucker et al July 18, 1944 (Other references on following page) UNITED STATES PATENTS Rauch Nov. 9, 1948 Adams Apr. 4, 1950 Harrington Sept. 15, 1953 De Lancey et a1 Feb. 16, 1954 OConnor et al Nov. 22, 1955 OConnor et al Apr. 24, 1956 FOREIGN PATENTS

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