IL31184A - Radial piston pump and motor device - Google Patents

Description

RADIAL PI STON PUMP ANO MOTOR DSVtOS n Vto-n mia a >ya yna¾ rrarog PBD Title: RADIAL PISTON PUMP AND MOTOR DEVICE ■■·.

Abstract of the Disclosure A radial piston pump or motor including a pintle shaft, a cylinder block rotatable about the pintle shaft, and a reaction ring chassis shiftable transversely of the pintle shaft, a ring assembly rotatably mounted on the chassis, and a series of piston-reaction ring segments carried by said ring assembly to be movable relative to each other and the ring assembly, said segments including piston members extending radially into the bores of the block, the piston members including parti-spherical piston heads to permit a relative tilting of the pistons within the bores.

Background of the Invention Field of the invention This invention is in the field of radial piston pumps and motors.

The Prior Art Radial piston pumps and motors typically comprise a pintle shaft, a cylinder block rotatable about the shaft, including a series of radially directed bores, the bores being connected to the discharge areas of the pintle shaft during rotation. by radially directed fluid passages. Pistons are mounted within the bores for radial shifting movement, the distal ends of the pistons being engaged against a surrounding reaction ring, the axis of which reaction ring may be displaced from the axis of rotation of the block. The outer ends of the pistons, in certain constructions, are not directly engaged by the reaction ring, the pistons in such instances being provided with pivotal connections to piston shoes, the block and induces an inward and outward movement of the pistons. Where the device is used as a motor, fluid under pressure is introduced to the supply area of the pintle shaft and is taken from the discharge area, inducing rotation of the block. Where the . device is used as a pump, the block is rotated, causing fluid under pressure to be expressed through the discharge area of the pintle shaft.

In most of the units heretofore known, the piston heads are cylindrical, the length of the cylindrical piston portions in slidable engagement with the cylinder walls varying with the requirements of the particular pump or motor.

The use of a short length piston has been found undesirable since there is always a tilting force exerted against the pistons by reason of the outward pressure of the outer end of the pistons against the reaction ring which is angularly related to the piston axis at all but two positions during the rotative cycle. In a short piston section, the effect of this torque is magnified by the relatively high leverage factor and communicated to the walls of the cylinder bores, drastically shortening the life of the piston and the cylinder.

In certain devices, elongated cylindrical pistons have been employed but ths use of these devices involves other drawbacks. Specifically, where an elongated piston is employed, lubrication throughout '· the length of the piston becomes a problem since normal leakage about the periphery of the piston is effective to lubricate a portion only of the length of the piston.

Similarly,, the use of an elongated piston will obviously increase the over-all size of the radial piston device of a given dis spherical head portions. Such parti-spherical piston heads provide the advantages of short contact length of the cylinders, thus reducing piston-cylinder lubrication problems. Also, the problem of undue wear of the cylinder bores is avoided, since the pistons are free to tilt within a limited range. These advantages are theoretically available without unduly enlarging the over-all diameter of the pump or motor. Heretofore, however, despite the apparent advantages, no device employing the spherical piston head configuration has achieved significant commercial success. Such failure is engendered by the ancillary disadvantages of complex piston-reaction ring connections required by prior constructions, the failure of such devices to exert the torque generating forces at the exact desired vectoral directions, difficulties in replacing one or more of the pistons in case of failure, and like problems .

A particular problem unsolved by any prior pump or motor is the high friction losses at the piston-reaction ring junction. Lubrication in this area is often provided by controlled leakages through passages in the pistons and piston slippers, which introduce a film of oil between the piston slippers and the reaction ring. While the losses which inhere in utilizing such controlled lubrication are individually relatively small, they ar.e collectively significant since efficiency loss is measured as a multiple of the losses of each component of the system. In many instances, such lubrication is effected through minute passages formed in the length of the pistons and piston slippers, which passages communicate with fluid in the cylinder- ro er. In addition to the difficult of conductin oil th passages, to reduce or eliminate the flow of lubricant. In this connection it should be appreciated the lubricant must be admitted to the area between the piston and the reaction ring under high pressure since the considerable centrifugal force exerted by the piston against the reaction ring constantly tends to drive the lubricant out from between the noted parts.

Summary of the Invention A radial piston pump or motor comprising a pintle shaft having fluid supply and discharge areas, a cylinder block having radially directed cylinder bores, passages communicating the bores with the supply and discharge areas sequentially during rotation, a reaction ring chassis shiftable transversely of the pintle shaft, including a ring assembly rotatable relative to the chassis, the device being particularly characterized by a series of piston-reaction ring segments movable relative to each other and mounted on the ring for angular or arcuate movement about the axis of the rings, the segments including piston members affixed thereto and terminating in parti-spherical piston heads disposed in sealing relation of the cylinder bores.

The segments may be individually mounted and dismounted, and may move toward and away from each other in a plane perpendicular to the axis of the pintle shaft in the course of rotation, while at all times maintaining the pistons perpendicular to the axis of rotation of the rings, whereby the force vectors of the pistons are at all times aligned for optimum, efficiency.

It is therefore an object of the invention to provide an improved radial piston pump or motor having segmented piston-reaction ring segments employing parti-spherical piston heads. duced outside diameter as compared with comparable displacement pumps and motors heretofore known.

A further object of the invention is the provision of a device of the class described which may be readily manufactured and assembled and wherein replacement of individual piston-reaction ring segments may be effected without disassembly of the entire device.

A further object of the invention is the provision of a device of the class described wherein forces exerted by or against the pistons are at all times aligned in a direction to operate with utmost efficiency.

It is a further object of the invention to provide a pump-motor of the type described wherein the friction between the pistons and cylinders is greatly reduced.

Still a further object of the invention is the elimination of the difficult lubrication problems resulting from the requirement of conducting lubricant under high pressure to the area between the piston head or piston slipper and the reaction ring, a position which, in all prior known devices of this sort, is a considerable , radial distance from the pintle shaft.

To attain these objects and such further objects as may appear herein or be hereinafter pointed out, reference is made to the accompanying drawings, forming a part hereof, in which: Figure 1 is a vertical sectional view through a hydraulic pump or motor in accordance with the invention, certain details of the apparatus being depicted in simplified form to facilitate an understanding of the invention; Figure 2 is a discontinuous section taken on the line In accordance with the invention, 10 is a pintle shaft having fluid input and output conduits 11, 12, which may be connected either to a source of fluid under pressure and a reservoir, where the device is used as a motor, or to a hydraulic motor, where the device is used as a pump.

The pintle shaft is provided with laterally open discharge and supply areas 13, 14, separated by diametrically opposed lands 15, 16 in a well known manner. The pintle shaft in the illustrated embodiment is provided with a continuous cylindrical portion 17 at its innermost end for defining a seal. A cylinder block assembly 18 is mounted for rotation on the pintle shaft.

In the device of the illustrated embodiment, the block 18 is disclosed to comprise a ho bw shell, for purposes of lightness, it being recognized that the conventional solid casting having radially directed cylinder bores may be substituted for the shell, where lightness is not a consideration.

The block 18 is provided with seal areas 19, 20 engaged against solid peripheral areas of the pintle shaft axially displaced from , the fluid supply-discharge areas, which seal areas may incorporate any usual form of rotary seal 20'.

The block includes an end wall 21 connected to an output or input shaft 22, as by a pair of machine screws 23 (one only being illustrated) displaced from the center of the shaft.

A series of radially directed cylinder bores 24, (seven in the illustrated embodiment) , are formed in the block. In the usual manner, fluid in the discharge and supply areas 13 or 14 is communicated to the bores 24 through flow passages 25 extending between the cylindrical bores and the supply and discharge areas secure the other advantages which are enumerated in my United States Patent No. 3345,916 of October 10, 1967, the supply passages 25 are configurated in the manner set forth in said patent, i.e. they are elongated in the direction of the axis of the pintle. shaft and foreshortened in the angular direction at the pintle shaft, and grow progressively shorter and wider and merge smoothly with the cylinder bores at the area radially outwardly spaced from the pintle shaft.

A reaction ring chassis 26 is supported on the frame of the device (not shown) in a manner to permit lateral movement of the chassis with respect to the pintle shaft within the limits permitted by the eccentricity slots 27, 28 formed at the opposed ends of the chassis. It will be understood that lateral movement may be applied to the chassis by any suitable manual or automatic means. For purposes of illustration, the apparatus for imparting lateral movement is depicted as an adjustment lever 29 mounted on a fixed fulcrum pin 30. The lower end of the lever 29 carries a bifurcated yoke 31 which surrounds drive pin 32 on the chassis, it being understood that pivotal movement of the lever about the pin 30 will cause a side-to-side adjustment of the chassis.

The chassis is provided with a spaced pair of rings 33, 34, separated from the circular periphery of walls 35, 36 forming the chassis 26 by roller bearing assemblies 37, 38.

The apparatus, to the extent heretofore described, is essentially conventional in most of its details.

To the rings 33, 34 are anchored a series of piston-reaction ring segments 39 which are generally U-shaped in vertical section (see Figure 2) , the U-shaped elements being defined by 41, at their innermost radial ends 43, are arcuate, to conform to the radius of curvature of the outer periphery of the rings 33 and 34.

The ends 43 are enlarged in the direction of the axis of the pintle shaft in comparison to the thickness of the major por¬ tion of the legs 40, 41, defining radially outwardly directed arcuate shoulders 44, 45.

The legs of the piston-reaction ring segments are main¬ tained in juxtaposition to the outer periphery of the rings 33, 34 by inner and outer arcuate attachment fixtures 46, 47. The attach¬ ment fixtures are generally L-shaped in section, including inwardly directed, arcuate overlap shoulders 48, 49, respectively, dis¬ posed in mating complemental relation to the outwardly directed shoulders 44, 45, respectively, defined by the enlargement por¬ tion 43 at the inner ends of the legs. The radii of curvature of the inturned portions 48, 49 and the shoulders 44, 45 are the same, so as to provide a smooth mating alignment to these parts.

The legs 40, 41 of the piston-reaction ring segments are secured to the rings 33, 34 against relative radial outward 50 movement by cross pins ^hich pass through aligned apertures in the inner and outer fixtures 46, 47 and in the rings 33, 34.

The cross pins 50 have thus an enlarged head 51 lying against the inner and outer segments 46, 47, the shank 52 of the pins extend¬ ing through the aligned apertures in the inner segment 46, ring 34, outer segment 47, and a washer 53. Cotter pins 54 or like securing members may be passed through apertures formed in the outer ends of the pins 50 to maintain the pins in the desired position. As will be best observed from Figure 1, preferably at From the foregoing description, it will be observed that the arcuate enlargement 43 at the innermost ends of the legs ^ 40, 41 prevent the legs from moving radially inwardly by engagement with the outer periphery of the rings 33, 34, and from moving radially outwardly by the overlying arcuate shoulders 48, 49 of the fixtures 46, 47 secured to said rings.

It will further be observed that the segments 39 may be moved angularly relatively to the rings by the above noted arrangement so that adjacent piston-reaction ring segments 39 are enabled to approach and retreat from each other in the course of rotary movement, such approach and retreat travel being confined within a plane perpendicular to the axis of rotation of the rings 33, 34.

It will be understood that the leg portions of all of the piston-reaction ring segments are secured to the rings in a similar fashion.

It will be further appreciated that while a specific form of attachment connection between the piston-reaction ring segments and rings has been illustrated, enabling angular relative movement while preventing radial relative movement of the noted, parts, various other forms of connections for accomplishing this end will occur to the skilled artisan. For instance, and without limitation, it will be appreciated that, rather than providing separate fixtures, a single annular disk providing a trackway engaging the enlargements of the legs will be effective for the intended purpose.

As a further variation, one or more roller bearings may be interposed between the piston-reaction ring segments and reaction ring segments may be provided with roller bearing conv^ ponents which engage against the inwardly directed surfaces of the flanges, the above structure being mentioned by way of example only.

From the bridging portions 42 of the piston-reaction ring segments there extend radially inwardly directed tubular . piston rods 55. It will be understood that while the piston rods 55 have been shown as integral with the bridging portion 42, it is altogether feasible to provide a replaceable connection wherein the rod is removably secured to the bridging element.

The radial innermost ends of the rods 55 are provided with piston heads 56, the peripheries of which heads are parti-spherical in section. The parti-spherical piston heads permit relative tilting movement of the pistons within the bores 24, the parti-spherical nature of the heads assuring a sealed condition of the bores throughout all tilted positions.

The operation of the device will be evident from the foregoing description. Assuming that the unit is to be used as a pump, the shaft 22 is connected to a source of rotative power, thus to drive the cylinder block 18 about the pintle shaft. The rotation of the block will cause a concomitant rotation of the rings 33, 34 and the reaction ring segments 39.

When the adjustment lever 29 is arranged so that the axis of rotation of the rings 33, 34 is in alignment with the axis of the pintle shaft, no inward or outward movement of the pistons relative to the cylinder bores will be experienced and no pumping action will take place. Also, in such condition the segments 39 will be equally spaced from each other throughout the entire rotation of adjustment lever 29 so as to displace the axis of the rings to:, one or the other side of the axis of the pintle shaft, an inward and outward sequential movement of the pistons will result, due to the eccentricity of the rings relative to the pintle shaft. The inward and outward movement of the pistons will create a discharge area of one or the other of the areas 13 or 14 selectively, according to which side of the axis of the pintle shaft the chassis has been shifted.

When the device is used as a motor, as will be readily understood, fluid under pressure is admitted to one of the areas 13 or 14, incuding an outward movement of the pistons which is translated to a rotary movement of the block and drive shaft 22, the direction of rotation being a function of which of the areas 13 or 14 is connected to the pressure conduit and the direction of eccentricity.

As best understood from Figure 3, it will be appreciated that the axes of the pistons are maintained at all times in radial alignment with the center C or axis of rotation of the rings 33, 34 As will be further appreciated from Figure 3, when an eccentricity is applied to the rings, the axes of the pistons are displaced from the axes of the cylinder bores (except at two points during the rotation of the device, i.e. when the axes of the pistons and cylinders are in alignment with a line L—L extending through the axis of the pintle shaft C* and the axis of relation C of the rings), such displacement or tilting movement being permitted by the parti-spherical interfit of the piston heads 56 and the cylinder bores 24.

In the course of such tilting movement, the piston-rets will move toward and awa from each other the — from the direction of displacement of the center C from the center ^ C1, and vice versa.

The amount of eccentricity permitted, should be calculated to prevent interference between the sides of the piston rods 55 and the bores 24 of the block, it being appreciated that the greater the eccentricity, the greater the separation and approach of the piston-reaction ring segments and, hence, the greater the tilting of the pistons in the cylinders.

From the foregoing, it will be evident that there is described an improved radial piston pump or motor having multiple advantages over radial piston pumps or motors heretofore known.

The unit may be readily assembled and disassembled for replacement of an individual reaction ring-piston segment, for instance, without the necessity for disassembling the remaining segments. By reason of the fact that the conventional circumferential reaction ring is not employed, the over-all diameter of the unit will be reduced by a considerable factor and the unit will be lighter in weight.

Further, since no circumferential reaction ring in the conventional sense is employed, the centrifugal forces developed within the unit will be reduced.

Also, lubrication is, facilitated by avoiding the necessity of transporting lubricating fluid under pressure into the space between the outermost ends of the pistons and the reaction rings, as is required in all prior known radial piston devices.

Since, as noted previously, the piston axis must always be precisely aligned with the center of the rotating rings 33, 34, the force vector affecting the pistons will always be aligned and the typical radial piston device, the axes of the pistons are radially directed with respect to the axis of the cylinder block. This requires that the* end of the piston or the piston shoe engage against the reaction ring at an angle with respect to the reaction ring, rather than perpendicular to the engaged portions of the reaction ring. Such angular relation of the parts induces a tilting moment in the pistons, with the result that a purely radial force is not applied.

As previously explained, the tilting moment results in increased wear on the sides of the pistons and cylinder bores as well as at the area of engagement between the piston heads and the reaction ring.

While in the illustrated embodiment the piston-reaction ring segments are shown as essentially integral components comprising integral leg portions 40 and 41 and bridging portion 42, it will be evident that these elements may be comprised of separate parts, subsequently integrated by machine screws, cross pins, etc.

It will be further evident that variations in structure may be made in the noted device without departing from the spirit of the invention and, accordingly, the invention is to be broadly construed within the scope of the appended claims.

Claims (7)

WHAT IS CLAIMED IS:

1 - In a radial piston pump or motor comprising a pintle shaft having fluid supply and discharge areas, a cylinder block rotatably mounted on said shaft having radially directed cylinder bores and passages connecting said bores with said areas, and a chassis surrounding said pintle shaft and movable transversely with respect thereto, the improvement which comprises a spaced pair of rings at opposite sides of said block mounted on said chassis for rotation about a common axis, a series of generally U-shaped piston assemblies, in number corresponding to the number of said bores, mounted on said rings, each said assembly comprising a spaced pair of legs, a leg of each said assembly being movably connected to a different one of said rings for angular movement about the axis of rotation of said rings, a bridging member joining the ends of said legs remote from said rings spaced radially outwardly of said block and a piston member rigidly fixed to and extending radially from said bridging member into a bore of said block, said piston member including a parti-spherical piston head disposed in sealing relation of said bore and tiltable relative to said bore.

2 - A device in accordance with claim 1 wherein said rings and the legs of said piston assemblies include complemental arcuate bearing surfaces.

3 - A device in accordance with claim 2 and including fastener means for linking together said piston assemblies and rings against relative radial movement, while permitting angular

4 - A device in accordance with claim 3 wherein each said leg3 portion includes an outwardly directed arcuate surface concentric with the axis of said rings, said fastener means comprising arcuate segments removably secured to said rings and having inwardly directed arcuate bearing surfaces in outwardly lapping, slidable engagement with the outwardly directed arcuate surfaces of. said leg portions.

5 - In a radial piston pump or motor comprising a pintle shaft having fluid supply and discharge areas, a cylinder block rotatably mounted on said shaft and having radially directed cylinder bores and passages connecting said bores with said areas, a ring chassis surrounding said pintle shaft and movable transversely with respect thereto, the improvement which comprises a bearing ring assembly rotatably mounted on and surrounding said chassis, said ring assembly being rotatable relative to said chassis about an axis parallel with the axis of said shaft./ a plurality of reaction ring segments, mounting means connecting said segments to said ring assembly to permit relative angular movement of said segments and ring assembly about the axis of rotation of said ring assembly while limiting relative radial movement of said parts, a piston member fixed to each of said segments against angular movement and extending radially inwardly toward the axis of said ring, the inner ends of said piston members being defined by parti-spherical piston heads disposed in sealing relation of said bores and tiltable relative to said bores.

6 - A device in accordance with claim 5 wherein said mounting means comprises complemental arcuate bearing portions on said ring assembly and said segments.

7 - A device in accordance with claim 6 wherein said mount assembly and having an inwardly directed arcuate surface in outwar lapping engagement of a complemental, outwardly directed bearing surface formed on said reaction ring segment. Atterneys for Applicant