US2871797A - Pump - Google Patents

Description

1959 H. A. IBOURASSA ET AL 2,

PUMP

Filed March 19, 1957 2 Sheets-Sheet 1 INVENTORS nueuss A. BOURASSA BY ERIC GUNELL ATTORNEY 1959 H. BOURASSA ETAL 2,871,797

' PUMP Filed March 19, 1957 V 2 Sheets-Sheet 2 FIG. 4

I v Y INVENTORS HUGUES A. BOURASSA BY ERIC GUNELL 4 T ran/v5 r United States Patent PUMP Hugues A. Bourassa, Warreusville Heights, and Eric Guuell, Parms, Ohio Application March 19, 1957, Serial No. 647,129

4 Claims. (Cl. 103-161) This invention relates to hydraulic pumps generally and more particularly to a new and improved inclined piston pump structure.

It is an object of this invention to provide a rotary hydraulic pump having novel cylinder and valve structures wherein the centrifugal component of force on the piston automatically extends the pistons and the axial component of the reaction force insures proper sealing of the valve.

It is another important object of this invention to provide a hydraulic pump wherein inclined pistons are arranged in opposed relationship so that the unit is axially balanced.

It is still another object of this invention to provide a simplified easily manufactured hydraulic pump structure which will operate with a minimum of service or maintenance.

Further objects and advantages will be apparent in the following description and drawings, wherein:

Figure l is an end view of a preferred embodiment of a hydraulic pump according to this invention; a

Figure 2 is a side elevation partially in longitudinal section;

Figure 3 is an end view with the end bell removed showing the internal structure, and;

Figure 4 is a section taken along 44 of Figure 2 showing one of the porting surfaces.

Conventional multi-cylinder hydraulic pumps normally utilize pistons that are either radial or axial relative to the axis of rotation. In the case of a radial pump, difficulty is encountered since the valving ports are in concentric surfaces which tend to wear and produce leakage. In the axial type pump, means must be provided to extend the pistons since centrifugal forces are not available for this purpose. In a pump according to this invention, we utilize inclined cylinders and pistons wherein a radial component of force is available to extend the pistons during the intake stroke and the axial component of the force reaction is available to insure proper sealing of the port surfaces. 7

Referring to the drawings, the pump includes a main housing 10 formed with two opposed ports 11 and 12, one of which is the inlet and the other the exhaust. The direction of rotation of the pump determines which of the ports 11 or 12 is the inlet and which is the exhaust as will be understood from the following description. One of these ports is connected to the hydraulic fluid reservoir and the other to the pressure side of the system. The housing 10 can be provided with suitable base lugs 13 for mounting the pump on the associated equipment.

Referring to Figure 2, the housing 10 is formed with a circular pump cavity 14, open at a radial face 16 on one end of the housing. An end member 17 is secured to the housing 10 against the radial face 16 and in cooperation with the housing forms a pump chamber 18. Suitable bolt fasteners 19 may be used to secure the end ice member 17 to the housing 10. A drive shaft 22, adapted to be connected to a suitable source of rotary power, extends through the end of the housing 10 and through the pump chamber 18 and is rotatably journaled on antifriction bearings 23 and 24 on either side of the pump chamber 18. A bearing end plate 26 is bolted to the housing 10 to hold the outer race of the bearing 23 and may be provided with a seal ring 27 to prevent leakage out along the drive shaft 22. Similarly an end plate 28 is bolted on the end of the end member 17 to secure the outer race of the bearing 24 in its position and close the right end of the unit.

Keyed t0 the drive shaft 22 are a pair of similar cylinder rings 29 and 31 which are radially located by the shaft and rotationally fixed relative thereto by keys 32. In Figure 2 the keys 32 for the cylinder ring 29 are not shown but could be located at a point spaced 'along the periphery of the section line. Preferably, the drive shaft 22 is provided with a shoulder 33 radially within each cylinder ring 29 and 31 which is formed with a spherical outer surface so that the associated cylinder ring will be radially located but free to align itself with the porting surface about to be described. For the same reason the pivot key 32 should be formed with a cylindrical outer surface. The housing 11) is formed with a radial porting surface 34 against which mating port surface 36 formed on the cylinder ring 29 is seated. Even though its two porting surfaces 34 and 36 are accurately manufactured, imperfections of manufacture will often cause the surfaces to be slightly inclined relative to the main axis and it is for this reason that the self-aligning structure of the shoulder 33 and of the keys 32 are utilized to insure that the two surfaces properly engage and seal.

The cylinder ring 31 and the end member 17 are also formed with port surfaces 37 and 33 which are similar to the port surfaces 34 and 36. A spring 40 extends between the 'two cylinder rings 29 and 31 and resiliently maintains the associated port surfaces in initial engagement. Substantially equally spaced around each of the cylinder rings 29 and 31 are a plurality of cylinder bores 39 each containing a piston 41 which is inclined relative to the axis of the drive shaft 22. The cylinder rings 29 and31 are imilar and opposed so the pistons 41 of each of the cylinder rings 29 and 31 form banks of cylinders which are symmetrical and opposed relative to each other.

Mounted in the housing 16 is a piston radial thrust bearing having a non-rotating outer race 42 and a rotating inner race or thrust ring 43 supported on the outer race by ball bearings 44 for rotation around an eccentric axis 45. The pistons 41 engage the inner race or piston thrust ring 43 and cause by friction rotation of the thrust ring when the cylinders and pistons are rotated by the drive shaft 22; The outer race 42 is radially located within the housing between two slide blocks 46, best seen in Figure 3, and vertically located by a stroke adjusting mechanism 47, seen in Figure 2. The stroke adjusting mechanism determines the concentricity or eccentricity of the thrust ring 43 and provides adjustment of the eccentricity which in turn determines the stroke of the pistons 41. To provide this adjustment we have utilized a gland nut 48 mounted on the housing 10 through which extends an adjusting screw 49 which can be rotated by a handle 51. The adjusting screw 49 is threaded into the gland nut 48 and rotation causes it to move radially relative to the housing. Since the end of the adjusting screw 49 engages the outer race 42, it is capable of moving the outer race vertically relative to the housing to adjust the stroke of the pistons 41 by moving the eccentric axis 45 relative to the axis of the drive shaft 22. A spring 50, shown in Figure 3, holds a cup shaped plunger 55 against the lower side of the outer race 42 and operates to hold the outer race 42 against the adjusting screw 49. When the adjusting screw 49 is threaded out along the gland nut 48, the outer race 42 moves to a position of greater eccentricity relative to the drive shaft 22 and in turn greater eccentricity relative to the cylinder rings 29 and 31. Those skilled in the art will recognize that the volumetric capacity per revolution of the pump is determined by the eccentricity of the piston thrust ring 43 which determines the stroke of the pistons 41.

The pair of port surfaces 34 and 36 are similar to the pair 37 and 38 so only the pair of surfaces 37 and 38 will be discussed in detail with the understanding that the described structure applies equally to pair 34 and 36. A pair of similar opposed arcuate slots 52 and 53 are formed on either side of the surface 37 wherein the slot 52 opens to a passage system 54 and the slot $3 opens to a passage system 56. The passage systems 54 and 56 connect corresponding slots on the port surface 34 an are connected to the ports 11 and 12 respectively, as shown in Figure 1. The mating port surface 38 on the cylinder ring 31 is formed with an axial port 57 connected to each of the cylinder bores 39. The ports 57 are arranged to progressively move into registry with the arcuate slots 52 and 53 as the cylinder ring 31 rotates to bring the associated cylinder bores 39 into communication with the ports 11 and 12 as the case may be. Therefore, as a given piston 41 is rotated from the bottom position around to the top position, its cylinder bore is brought into communication with the arcuate slot connected to the reservoir. During this travel the piston moves from the bottom dead center position to the top dead center position and draws liquid into the cylinder bore. As the given piston 41 continues to rotate from the top dead center position back to the bottom dead center position, its port is brought into communication with the other arcuate slot and discharges the liquid to the pressure or exhaust port. Because the pistons in each of the rings are equally spaced around its surface, there is always one group of pistons in the intake or extension cycle and another in the compression or exhaust cycle.

In order to insure that there will be a proper sealing pressure between the two porting surfaces and automatic compensation for wear, the inclined type piston is used. As the liquid is pressurized by the piston, a hydraulic reaction force is developed on the cylinder ring 31 which is opposite to the reaction force of the pressure of the liquid on the pistons 41 in which liquid is being pressurized. This cylinder ring reaction force has an axial component urging the cylinder ring 31 in a direction toward the porting surface 37. This axial component of force is a function of the cylinder ring reaction force and the angle of inclination of the pistons 41. Since the reaction force is a function of the pressure developed, the axial force urging the surface 38 against the surface 37 will be a function of the pressure developed so a higher force is available when high pressures are encountered.

This axial component of force urging the two surfaces 37 and 38 together is opposed by the axial forces developed at the two surfaces urging them apart. These opposing forces operate over two areas. Assuming that the direction of rotation is such that the arcuate slot 52 is the exhaust slot there is a hydraulic reaction force which is equal to the area of this slot times the pressure of the hydraulic fiuid which tends to separate the engaging port surfaces 37 and 38. In addition there is a pressure gradient or film pressure across the area of engagement producing sealing. This pressure gradient reaches the pressure in the slot 52 immediately adjacent thereto and is equal to the pressure within the chamber 18 adjacent to the chamber. The force reaction of this pressure gradient may be resolved and is equal to the average pressure between the surfaces of sealing engagement times the area of sealing engagement. These tWo separating reaction forces are both a function of the exhaust pressure and combine to oppose the axial component of reaction force acting on the cylinder ring.

To insure that the sum of all the forces act to provide proper sealing, it is necessary to proportion the various elements so that the axial component of the reaction force is greater than the two opposing forces. This can be done in several ways and any of them may be chosen so long as the desired end result is produced. The total axial component of the reaction force is determined by the area of all the cylinders containing pressure fluid and the angle of inclination of the pistons 41 relative to the drive shaft 22. Therefore, if larger or more cylinders and pistons are used, a greater reaction force will be developed. Also as the angle of inclination of the pistons 41 relative to the drive shaft 22 is decreased, so that the axis of the pistons 41 more nearly approaches a parallel relationship relative to the axis of the drive shaft 22, the axial component of the reaction force increases. It should be kept in mind that sufficient inclination must be provided to produce a large enough centrifugal force to extend the pistons 41 and maintain them in engagement with the radial thrust ring 43. Still another approach is to reduce the magnitude of the opposing forces by reducing the area of the slot 52 and or reducing the area of sealing engagement between the surfaces 37 and 38. To reduce the size of the sealing area, we provide relief grooves 53 in the port surface 37 which are open to the pump chamber 13. This in effect reduces the sealing area to a size equal to the area between the grooves 58 around the slot 52. In the disclosed structure the axial component of the reaction force acting on the cylinder rings is greater than the opposing forces created by the pressure in the exhaust slot 52 and the pressure gradient, so proper sealing results regardless of the fluid pressure developed.

Because two similar cylinder rings 29 and 31 are provided, the axial components of force on the thrust ring 43 created by one group of pistons 41 is balanced by the axial components of force created by the opposed group of pistons 41. Therefore, the only resulting force on the thrust ring is radial which can adequately be carried by the ball bearings 44. For the same reason the force of engagement between the associated port surfaces 34 and 36 is equal and opposite to the force of engagement between the associated port surfaces 37 and 38, so the entire pump is axially balanced and it is not necessary to provide large axial thrust bearings. Those skilled in the art will recognize that the use of the described structure provides a unit which has the advantages of both a radial pump and an axial pump without the disadvantages of either. Also the preferred structure results in a balanced pump and eliminates the need of heavy axial thrust bearings and the like.

Although a preferred embodiment of this invention is illustrated, it will be realized that various modifications of the structural details may be made without departing from the mode of operation and the essence of the invention. Therefore, except insofar as they are claimed. in the appended claims, structural details may be varied widely without modifying the mode of operation. Accordingly, the appended claims and not the aforesaid detailed description are determinative of the scope of the invention.

We claim:

1. A hydraulic pump comprising a housing formed with first and second opposed radially extending porting surfaces each formed with a first arcuate slot adapted to be connected to a hydraulic source of fluid and a second arcuate slot adapted to be connected to a hydraulic pressure system, a rotatable shaft extending through said housing, first and second opposed cylinder rings rotatably fixed relative to said shaft each formed with radial porting surfaces engaging the cooperating porting surface in said housing, each cylindrical ring being formed with a plurality of cylinder bores substantially equally spaced around and inclined relative to the axis of said shaft, an axially extending port for each cylinder bore proportioned to progressively move into registry with said slots as said shaft and rings rotate, and a piston thrust ring carried by said housing eccentrically relative to said shaft engaged by said pistons, the centrifugal force on said pistons produced by rotation thereof maintaining them in engagement with said thrust ring, the sum of axial components of force transmitted to said thrust ring by the pistons of one cylinder ring being opposed by the axial components of force transmitted thereto by the piston of the other cylinder ring and the axial components of the hydraulic forces acting on said cylinder rings urging the associated porting surfaces into engagement with a force which is a direct function of the hydraulic pressure produced by said pump.

2. A hydraulic pump comprising a housing formed with first and second opposed radially extending porting surfaces each formed with a first arcuate slot adapted to be connected to a hydraulic source of fluid and a second arouate slot adapted to be connected to a hydraulic pressure system, relief grooves in said porting surface on either side of said slots open to the interior of said housing, a rotatable shaft extending through said housing, first and second opposed cylinder rings rotatably fixed relative to said shaft each formed with radial porting surfaces engaging the cooperating porting surface in said housing, each cylindrical ring being formed with a plurality of cylinder bores substantially equally spaced around and inclined relative to the axis of said shaft, an axially extending port for each cylinder bore proportioned to progressively move into registry with said slots as said shaft and rings rotate, and a piston thrust ring carried by said housing eccentrically relative to said shaft engaged. by said pistons, the centrifugal force on said pistons produced by rotation thereof maintaining them in engagement with said thrust ring, the sum of axial components of force transmitted to said thrust ring by said piston being zero and the axial components of the hydraulic forces acting on said cylinder rings urging the associated porting surfaces into engagement with a force which is a direct function of the hydraulic pressure produced by said pump.

3. A hydraulic pump comprising a housing formed with first and second opposed radially extending porting surfaces each formed with a first arcuate slot adapted to be connected to a hydraulic source of fluid and a second arcuate slot adapted to be connected to a hydraulic pressure system, relief grooves in said porting surface on either side of said slots open to the interior of said housing, a rotatable shaft extending through said housing, first and second opposed cylinder rings rotatably fixed relative to said shaft each formed with radial porting surfaces engaging the cooperating porting surface in said housing, a spring extending between said cylinder rings urging said cooperating porting surfaces into initial engagement, each cylindrical ring being formed with a plurality of cylinder bores substantially equally spaced around and inclined relative to the axis of said shaft, an axially extending port for each cylinder bore proportioned to progressively move into registry with said slots as said shaft and rings rotate, and a piston thrust ring carried by said housing eccentrically relative to said shaft engaged by said pistons, the centrifugal force on said pistons produced by rotation thereof maintaining them in engagement with said thrust ring, the sum of axial components of force transmitted to said thrust ring by said piston being zero and the axial components of the hydraulic forces acting on said cylinder rings urging the associated porting surfaces into engagement with a force which is a direct function of the hydraulic pressure produced by said pump.

4. A hydraulic pump comprising a housing formed with first and second opposed radially extending porting surfaces each formed with a first arcuate slot adapted to be connected to a hydraulic source of fluid under pressure and a second arcuate slot adapted to be connected to a hydraulic pressure system, a rotatable shaft extending through said housing, first and second opposed cylinder rings rotatably fixed relative to said shaft each formed with a radial porting surface engaging the cooperating porting surface in said housing, each cylinder ring being formed with a plurality of cylinder bores symmetrically around and inclined relative to the axis of said shaft, an axially extending port for each cylinder bore proportioned to progressively move into registry with said slots as said shaft and rings rotate, a rotatable piston thrust ring carried by said housing eccentrically relative to said shaft engaged by said piston, the centrifugal force on said pistons produced by rotation thereof maintaining them in engagement with said thrust ring, means on said housing operable to adjust the amount of eccentricity of said thrust ring and in turn the stroke of said pistons, the sum of axial components of force transmitted to said thrust ring by said piston being zero and the axial components of the hydraulic forces acting on said cylinder rings urging the associated porting surface into engagement with a force which is a function of the hydraulic pressure in said cylinder. 7

References Cited in the file of this patent UNITED STATES PATENTS 2,105,454 Ferris -a Jan. 11, 1938 2,273,468 Ferris Feb. 17, 1942 2,406,138 Ferris et al Aug. 20, 1946

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