Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H39/00—Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution
  • F16H39/04—Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution with liquid motor and pump combined in one unit
  • F16H39/06—Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution with liquid motor and pump combined in one unit pump and motor being of the same type
  • F16H39/08—Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution with liquid motor and pump combined in one unit pump and motor being of the same type each with one main shaft and provided with pistons reciprocating in cylinders
  • F16H39/10—Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution with liquid motor and pump combined in one unit pump and motor being of the same type each with one main shaft and provided with pistons reciprocating in cylinders with cylinders arranged around, and parallel or approximately parallel to the main axis of the gearing
  • F16H39/14—Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution with liquid motor and pump combined in one unit pump and motor being of the same type each with one main shaft and provided with pistons reciprocating in cylinders with cylinders arranged around, and parallel or approximately parallel to the main axis of the gearing with cylinders carried in rotary cylinder blocks or cylinder-bearing members

Definitions

• This invention relates to an improved hydrostaticall augmented mechanical drive unit which has excellent operating efficiency and torque multiplication character ⁇ istics, and which can be embodied in compact, light weight designs.
• hydrostatic transmissions provide the important advantage of a continuously variable " ratio between the speed of the input shaft and that of the output shaft.
• One commonly used type of hydrostatic transmission provides a hydraulic pump which is driven by an input shaft and is hydraulicall coupled to a hydraulic motor which in turn drives an output shaft.
• the only means for transferring power from the pump to the motor is by means of pressurized hydraulic fluid.
• this arrangement provides the disadvantage that high speeds for the output shaft are obtained through high volume operation of the pump. Therefore, pumping losses tend to be high when the output shaft is rotating at or near the speed of the input shaft.
• a second type of hydrostatic transmission of the prior art differs from the first in that both mechan ⁇ ical and hydraulic means are provided for transmitting torque and power from the pump to the motor.
• the trans- missions disclosed in U.S. Patents 2,679,139 to Posson, 2,633,710 to Jarmann and 3,698,189 to Reimer are examples of this second type.
• These transmissions can provide the advantage of near zero hydraulic pumping activity when operating at 1:1 ratio between the input and output shaft speeds.
• All three utilize an opposed piston design in which the valving apparatus is situated in a relatively inaccessable position between the motor and the pump, and the length of the transmission is therefore greater than the sum of the individual lengths of the pump and motor.
• variable angle pump cam plates and. therefore variable displacement pumps which are capable of generat ⁇ ing extremely high hydraulic pressures when the pump cam plates are oriented at small angles with respect to the input shafts.
• extremely high pressures are often undesirable, for they may require the use of safety valves which pose a potential reliability problem and which can only operate to reduce - the operating efficiency of the transmission.
• Additional examples of hydrostatic transmission of this second type include those disclosed in U.S. Patent 2,141,166 to Bischof, U.S. Patent 2,186,556 to Robbins, " U.S. Patent 2,571,561 -to Genety, U.S. Patent 3,313,108 to Allgaier, and British Patent 10,108 to Renault.
• a drive unit which to a large extent overcomes the aforemen ⁇ tioned disadvantages.
• a drive unit which includes a first axial face cam mounted to a first shaft and first and second cylinder blocks mounted to a second shaft.
• a second axial face cam is mounted to provide a reaction point with respect to the cylinder blocks, and first and second pistons are slide- ably mounted in cylinder bores defined by the first and second cylinder blocks such that differential rotation between the first cam and the first cylinder block actuates the first pistons and differential rotation between the second cylinder block and the second cam actuates the second pistons.
• Valve means are provided for conducting hydraulic fluid between the first and second cylinder blocks to transmit power hydraulically between the first and second pistons.
• the drive unit of this invention has been optimized for efficient operation at a mechanical ratio of 1:1, the ratio at which many drive units operate for the great majority of time.
• Additive torque is trans- mitted mechanically from the input shaft to the output shaft by means of reaction torques on the first pistons and the first cylinder block.
• the first pistons are hydraulically locked in place in the first cylinder block, the input and output shafts rotate together, coaxially, and in unison, without pumping activity or pumping losses. In effect, the input and output shafts have been locked together, so they rotate as a unit, without gearing or pumping losses.
• the first pistons are allowed to pump fluid to the second cylinder block, the second cylinder block, second pistons and second cam operate as a variable displacement hydrostatic motor which hydraulically augments the torque on the output shaft.
• the first shaft is coupled to a prime mover such as a heat engine or an electric motor
• the second shaft is mounted coaxially with the first shaft and is connected to a load such that all torque on the first shaft is transmitted directly to the second shaft via the first cam, pistons and cylinder block, without relative movemen between the cylinder blocks and the second shaft.
• the second cam, pistons and cylinder block When hydraulic fluid is allowed to pass from the first to the second cylinder blocks, the second cam, pistons and cylinder block then serve to provide additional torque in ' the forward reduction mode which adds directly to the torque transmitted to the output shaft via the first cam, pistons and cylinder block.
• the first cam is mounted at a fixed tilt angle. This arrangement provides the addi ⁇ tional advantage of low peak hydraulic pressures within the transmission.
• the first and second cylinder blocks are nested, one within the other, such that one of the two sets of pistons is situated within the perimeter defined by the other set of pistons.
• This geometry significantly reduces the axial length of the drive unit and it allows both cams to be placed on one side of the cylinder blocks and all necessary valving to be placed on. the o er side of the cylinder blocks, where the valves can readily be serviced if necessary and can readily be structurally reinforced in an adequate manner.
• the first cylinder block is held in place by a tension member, which passes through the first cylinder block, and a valve head, which is attached to the tension member and serves to control the axial position of the first cylinder block.
• valve head defines the ports and passage ⁇ ways needed to conduct fluid to and from the first pistons.
• Another aspect of this invention relates to a motor activation valve which selectively interrupts the flow of high pressure fluid from the first to the second cylinder blocks in order simultaneously (1) to reduce hydraulic pressure on the second pistons, and (2) to hydraulically lock at least some of the first pistons in place in the first cylinder block.
• This valve is in- tended for use when the transmission is in the 1:1 mode in order to reduce unnecessary wear and friction associ ⁇ ated with unnecessary hydraulic pressure on the second pistons.
• a further advantageous feature of this inven- tion relates to a soft-start valve which, when actuated, allows hydraulic fluid to recirculate within the cylin ⁇ ders of the first cylinder block, bypassing the cylinders of the second cylinder block.
• This soft-start valve provides a true neutral, hydraulically disengaging the first and second shafts. Furthermore, this valve allows the second shaft to be gradually engaged with the first shaft by gradually closing the soft-start valve.
• FIG. 1 is a cross sectional view of the presently preferred embodiment of the drive unit of this invention.
• FIG. la is a cross sectional view taken along line la-la of FIG. 1.
• FIG. 2 is a cross sectional view taken along line 2-2 of FIG. la.
• FIG. 3 is a cross sectional view taken along line 3-3 of FIG. la.
• FIG. 4 is a perspective view of the valve head 100 of the embodiment of FIG. 1.
• FIG. 5 is a cross sectional view taken along ' line 5-5 of FIG. 4.
• FIG. 6 is a cross sectional view taken along line 5-6 of FIG. 4.
• FIG- 7 is a cross sectional view taken along line 7-7 of FIG. 4.
• FIG. 8 is a cross sectional view taken along line 8-8 of FIG. 4.
• FIGS. 1 and la show two cross-sectional views of the presently preferred embodiment of the drive unit of this invention.
• the reference numeral 10 is used to refer gen ⁇ erally to this drive unit.
• the drive unit 10 includes an output shaft 20 which defines a circular array of aperture 22 and a central recess 24.
• the output or driven shaft 20 would be coupled to a load, such as to the driving wheels of a land vehicle for example.
• the drive unit 10 also includes a cylinder block 40 which is provided with an annular skirt 42 extending- from one and.
• the cylinder block 40 defines a central bore 44 extending completely therethrough and a central recess 46 surrounded by the skirt 42.
• a plurality of threaded apertures 48 are formed in the extreme end portion of the skirt 42, and are positioned to mate with the circular array of apertures 22 in the output shaft 20,
• a plurality of threaded fasteners 50 are positioned in the apertures 48,22 to secure the output shaft 20 rigidly to the cylinder block 40 such that the two rotate as a unit.
• the skirt 42 defines a first array of radial openings 52 which extend roughly in a circle around the periphery of the skirt 42.
• the skirt 42 defines a second array of radial openings 54, which also extend around the periphery of the skirt 42.
• adjacent openings in each array are staggered with respect to one another in order to maximize the strength of the skirt 42.
• the cylinder block 40 defines an inner array of cylinder bores 56, each of which extends in the axial direction, and each of which terminates in a respective fluid port 58.
• the cylinder block 40 also defines an outer array of cylinder bores 60, each of which terminates in a narrowed respective fluid port 62.
• each of the arrays of cylinder bores 56,60 comprises a plurality of individual cylinder bores, each of which is spaced at a predetermined radial distance from the center of the central bore 44.
• a respective inner piston 64 is slidingly and sealingly received in each . of the cylinder bores included in the inner array of cylinder bores 56.
• Each of these inner pistons 64 terminates at one end with a spherical head 66.
• an actuating shoe 68 is pivotably mounted on the respective spherical head 66 such that each actuating shoe 68 is free to articulate with respect to the respective inner piston 64.
• a respective outer piston 70 is slidingly and sealingly received in each of the outer array of cylinder bores 60.
• Each of the outer pistons 70 defines a ' respective spherica head 72 which serves as a pivoting mount for a respective actuating shoe 74.
• the drive unit 10 also includes an input or driving shaft 90 which in use would be coupled to a prime mover such as a heat engine or an electric motor.
• This input shaft 90 defines a fixed-angle, axial face, inner cam 92, which preferably is integrally formed with the input shaft 90 such that the cam 92 rotates in unison with the input shaft 90.
• the input shaft 90 also in- eludes an axially extending tension member 94 which terminates in a threaded end portion 96. As shown in FIG. 1, the tension member 94 extends through the central bore 44 in the cylinder block 40.
• the inner array of pistons 64 is positioned such that the actuating shoes 68 of the inner pistons 64 bear on the inner cam 92.
• a valve head 100 is mounted to the tension member 94 within the skirt 42 of the cylinder block 40.
• This valve head 100 defines a central bore 102 sized to receive the threaded end portion 96 of the " tension member 94.
• a nut 98 threadedly engages the threaded end portion 96 of the tension member 94 in order to securely hold the valve head 100 in place on the .tension member 94.
• a key 103 and keyway 105 are provided to ensure that the angular orientation of the valve head 100 on the tension member 94 remains constant.
• a constant force spring washer 99 is positioned within the recess 24 to bear on the nut 98 in order to bias the valve head 100 toward the cylinder block 40.
• the valve head 100 defines a number of cham- bers, ports and passageways.
• certain elements of the valve head 100 will be defined as either high pressure or low pressure elements. It is to be understood that the terms high pressure and low pressure have been selected merely to facilitate an understanding of this embodiment, and that they designate the relative pressures customarily found in these elements during normal operation of the drive unit 10 in the forward reduction mode when power is being transmitted from the input shaft to drive a load attached to the output shaft. It should be understood that in other modes of operation the relative pressures in the elements of the valve head 100 may be reversed.
• the valve head 100 defines an annular high pressure chamber 104 and a spaced annular low pressure chamber 106, both of which extend completely around the periphery of the valve head 100. As shown in FIG. la, when the valve head 100 is assembled within the skirt 42 of the cylinder block 40, the high pressure chamber 104 is positioned adjacent the first array of radial open- ings 52, and the low pressure chamber 106 is positioned adj cent the second array of radial openings 54.
• the valve head 100 also defines an arcuate high pressure port 108 and an arcuate low pressure port 110. As best shown in FJG. 3, each of the arcuate ports 108,110 extends over somewhat less than a 180° at a fixed radius from the center of rotation of the valve head 100.
• valve head 100 Internal passageways 112,114 are provided within the valve head 100 to interconnect the high pressure port 108 with the high pressure chamber 104 and the low pressure port 110 with the low pressure chamber 106, respectively.
• a valve plate 116 is pinned to the valve head 100 so as to prevent relative movement therebetween.
• This valve plate 116 defines two arcuate cutouts 118,120 which correspond in shape and orientation to the high pressure port 108 and the low pressure port 110, respectively.
• the valve plate 116 is positioned between the cylinder block 40 and the valve head 100 to provide a low friction sliding joint therebetween.
• the drive unit 10 also includes a housing 130 which is provided with two tapered roller bearings 132,134 which serve to position the input shaft 90 with respect to the housing 130 while allowing rotary motion of the input shaft 90.
• a gear pump 136 is mounted to the housing 130. This gear pump 136 is provided with a pump inlet 138 and a pump outlet 140 and is driven by the input shaft 90.
• the gear pump 136 functions as a replen ⁇ ishing pump, as will be explained in detail below.
• the housing 130 also defines a cylindrical support bearing 142 which serves to support a non- rotating, axial face, outer cam 143.
• This outer cam 143 is an annular cam positioned around the inner cam 92 such that the shoes 74 of the outer pistons 70 slide on the outer cam 143, and reciprocation of the outer pistons 70 in the outer cylinder bores 60 causes the cylinder block 40 to rotate with respect to the outer cam 143 and the housing 130.
• the outer cam 143 is supported by an outer cam support member 144 which defines " a cylindrical support surface 146.
• This cylindrical support surface 146 is provided with a radius of curvature matching that of the cylindrical support bearing 142 defined by the housing 130.
• the outer cam support member 144 cooperates with the cylindrical support bearing 142 to prevent rotary motion of the outer cam 143 about the axis of the input shaft 90.
• the outer cam support member 144 is provided with a central opening 148 through which the input shaft 90 and the inner cam 92 pass.
• An actuator 150 is mounted between the housing 130 and the outer cam support member 144.
• the axial length of the actuator 150 can be changed in order to adjust the relative position of the outer cam support member 144 with respect to the housing 130, and therefore the tilt angle of the outer cam 143 with respect to the input shaft 90.
• the housing 130 is also provided with a fill plug 152 and a drain plug 154. In normal use the interior of the housing 130 is substantially filled with an incompressible hydraulic fluid.
• a valve block 160 is secured to the housing 130 by means of a plurality of fasteners 162 such that the valve block 160 serves to seal off the interior of the housing 130.
• the valve block 160 cooperates with the valve head 100 in order to control the flow of hydraulic fluid between the inner and outer arrays of cylinder bores 56,60.
• the valve block 160 defines an annular high pressure reservoir 164 positioned adjacent the first array of radial openings 52 and the high pressure chamber 104, and an annular low pressure reservoir 166 positioned adjacent the second array of radial openings 54 and the low pressure chamber 106.
• the radial openings 52,54 ensure constant fluid communication between the high pressure chamber 104 and the high pressure reservoir 164, and the low pressure chamber 106 and the low pressure reservoir 166, respectively.
• a valve plate 168 is secured to the valve block 160 by pins such that the " valve plate 168 is prevented from rotating with respect to the valve block
• This valve plate 168 which is shown in FIG. 3, defines an arcuate high pressure port 170 and an arcuate
• both the high pressure port 170 and the low pressure port 172 are somewhat less than 180° in angular extent, and each is situated at a constant radius from the center of rotation of the cylinder block 40.
• standard engineering principles are used to create hydraulic thrust bearings between the cylinder block 40 and the valve plates 116 and 168 and between the shoes 68,74 and the respective cams 92, 143.
• this can be accomplished by providing a shallow recess on the sliding surface of each shoe 68,74 which is in fluid communication with the cylinder bore of the -respective piston 64,70, and by properly balancing the areas of the recesses and the areas of the cutouts 118,120, and the ports, 108,110, 170,172 such that hydraulic forces reduce frictional forces to the desired level.
• a high pressure passageway 174a,174b extends between the high pressure reservoir 164 and the high pressure port 170.
• a motor activation valve 176 is mounted in the valve block 160 in order to selectively pass fluid from the high pressure passageway 174a to the high pressure passageway 174b.
• This valve 176 comprises a bore 178 defined by the valve block 160.
• a valve rod 180 is dimensioned to slide within the bore 178 in a sealing manner. -The position of the valve rod 180 within the bore 178 is controlled by an actuator 182.
• the valve rod 180 defines a region of reduced diameter 184 which is long enough to extend between the points at which the high pressure passageways 174a,174b communicate with the bore 178.
• the high pressure passageways 174a,174b are interconnected by means of the bore 178, and hydraulic fluid is thus free to flow from the high pressure reservoir 164 via the high pressure passageways 174a, 174b and the bore 178, to the high pressure port 170.
• the actuator 182 is positioned to cause the valve rod 180 to move to the left as shown in FIG. la, the valve rod 180 completely obstruct the high pressure passageway 174a, thereby completely interrupting the flow of fluid through the high pressure passageway 174a.
• the valve block 160 also defines a low pressure passageway 186 which interconnects the low pressure reservoir 166 with the low pressure port 172.
• the low pressure passageway 186 also communicates via a soft- start valve 190 with the high pressure reservoir 164.
• This soft-start valve 190 includes a bore 192 defined by the valve block 160.
• a valve rod 194 having a reduced diameter portion 196 is dimensioned to slide within the bore 192 in a sealing manner.
• the position of the valve rod 194 in the bore 192 is controlled by an actuator 198.
• a passageway 200 extends between the bore 192 and the low pressure reservoir 166, and a passageway 202 extends between the bore 192 and the high pressure reservoir 164.
• the bore 192 serves to interconnect the passageways 200,202 such that fluid is freely passed directly between the high pressure reservoir 164 and the low pressure reservoir 166 without passing into the cylinder block 40.
• the actuator 198 is used to move the valve rod 194 to the left as shown in FIG. la, the valve rod 194 obstructs the passageways 200,202, thereby preventing the free circula ⁇ tion of fluid from the high pressure reservoir 164 to the low pressure reservoir 166 via passageways 200,202.
• the valve block 160 also includes two check valves 210,212 each of which is connected to a respective one of the two passageways 200,202.
• the check valves 210,212 are in fluid communication with the gear pump outlet 140 by a conduit.
• the gear pump 136 serves to ' pump hydraulic fluid at relatively low pressure from the interior of the housing 130 to the check valves 210,212.
• the drive unit 10 is designed to operate with maximum efficiency at a 1:1 mechanical ratio and in the forward reduction mode to rotate the output shaft 20 at a speed in the range between the speed- of the input shaf 90 and one-quarter the speed of the input shaft 90.
• mechanical ratio will be used to refer to the ratio between the speeds of the input and output shafts.
• a mechanical ratio of 2:1 corresponds to the input shaft turning in the same direction as and with twice the speed of the output shaft.
• The. valve plate 116 rotates in unison with the inner cam 92 at an appropriate phase angle to ensure that the inner pistons 64 operate as a pump to pump fluid from the low pressure reservoir 166 to the high pressure reservoir 164.
• the inner pistons 64 operate to pump 10 cubic inches of fluid from the low pressure reservoir 166 to the high pressure reservoir 164.
• the outer pistons 70 cooperate with the adjust ⁇ able, outer cam 143 to form a variable displacement motor, wherein the displacement of the motor is a func ⁇ tion of the tilt angle of the outer cam 143.
• the tilt angle is defined as the angle between the plane of the outer cam 143 and a plane perpendicular to the axis of rotation of the input shaft 90.
• the tilt angle when the tilt angle is set equal to zero, the displacement of the motor goes to zero, thereby preventing the flow of fluid out of the high pressure reservoir -164 and hydraulically locking the inner pistons 64 in place in the cylinder block 40. In that the inner pistons 64 are locked in place, relative
• a tilt angle of 0° therefore corresponds to a mechanical ratio of 1:1 and a torque on the output shaft 20 which is equal to that on the input shaft 90.
• the drive unit 10 is capable of operating at mechanical ratios between 1:1 and 4:1 in a stepless manner while providing efficient torque multiplication.
• Considerable axial forces are developed by the inner pistons 64 as a result of their pumping action.
• the tension member 94 and the valve head 100 have been designed to cooperate with the inner cam S2 to bear these axial forces simply and efficiently, - -
• the motor activation valve 176 operates further to reduce wear and frictional losses when the drive unit 10 is being used, at a mechanical ratio of 1:1.
• a mechanical ratio of 1:1 corresponds to a tilt angle of 0° and therefore a zero stroke for the outer pistons 70.
• the outer pistons 70 do not contribute torque to the output shaft 20, and they can therefore be isolated from the high pressure reservoir 168 without interfering with the operation of the drive unit 10.
• the motor activation valve 176 performs just this function by interrupting the flow of hydraulic fluid from the high pressure reservoir 164 to the outer pistons 70.
• valve 176 simultaneously prevents the flow of fluid out of the high pressure reservoir 164 via the high pressure passageway 174a, the inner pistons 64 are still hydraulically locked in place and the drive unit operates at a mechanical ratio of 1:1, even though the outer pistons 70 are not subjected to high pressure fluid.
• the valve 176 provides the significant advan ⁇ tage that it allows an important reduction in wear and friction by isolating the outer pistons 70 from high
• the soft-start valve 190 acts to provide a true neutral mode of operation which is effective for all angular positions of the output shaft 20.
• the valve rod 194 When the valve rod 194 is in the position shown in FIG. la, high pressure fluid is free to flow directly from the high pressure reservoir 164 to the low pressure reservoir 166 via the passageways 200,202, thereby bypassing the outer pistons 70 completely. In this way the inner pistons 64 are hydraulically disconnected from the outer pistons 70 and hydraulic power transmission is interrupted.
• the bypass passageways By gradually moving the valve rod 194 from the position of FIG. la to the left as seen in FIG. la, the bypass passageways
• 200,202 can be gradually disconnected, thereby gradually applying more and more hydraulic power to the outer pistons 70.
• the drive unit 10 described above provides a number of important advantages. First, this transmission operates to provide efficient torque multiplication and speed reduction with a minimum of pumping losses. At a mechanical ratio of 1:1, substantially all pumping and frictional losses are eliminated. Because the input shaft 90 reacts directly against the cylinder block 40 (which is in a sense an extension of the output shaft 20) torque is efficiently and directly transmitted from the input shaft 90 to the output shaft 20 at all mechanical ratios from 1:1 to 4:1, or even lower, if so designed.
• this drive unit operates the pump comprising the inner pistons 64 at a low speed, always less than the speed of the input shaft 90 when the drive unit is operating in the forward reduction mode.
• the pump speed is only 75% of the input shaft speed at a 4:1 mechanical ratio and is actually zero at a 1:1 mechanical ratio.
• the sum of the pump speed and the motor speed is always equal to the input shaft speed.
• the tilt angle of the inner cam 92 is fixed, the drive unit 10 provides the further advantage that, for a given maximum torque on the input shaft, the maximum hydraulic pressure generated by the input shaft 90 in the drive unit is a known, fixed value. This is in marked contrast to conventional, variable tilt angle pumps which can generate extremely high hydraulic pressures ⁇ at small tilt angles.
• the drive unit 10 eliminates such high hydraulic pressures and provides a simple, reliable design which does not rely heavily on pressure relief valves when operating in the forward reduction mode.
• the nested configuration of the cylinder block 40 in which the- inner pistons 64 are positioned within the circle_ defined by the outer pistons 70, results in a compact design-which is extremely short in the axial direction. Furthermore, this nested configuration allows all valving means to be placed conveniently on one side of the cylinder block 40, thereby facilitating the placement and structural reinforcement of the necessary valving means.
• the enlarged valve head 100 and the tension member 94 further contribute to the efficient operation of the drive unit 10 by providing a direct means for properly positioning the cylinder block 40 against the cams 92,143, which entirely eliminates the need for peripheral thrust bearings around the cylinder block 40 and which minimizes unnecessary relative movement.
• the drive unit is operating at a mechanical ratio of 1:1, all differential movement between the cylinder block 40 and the thrust bearing valve plate 116 is eliminated.
• the use of the thrust member 94 and valve head 100 is not limited to drive units of the type described above. A similar construction can be used to hold either a motor cylinder block or a pump cylinder block against a shaft mounted cam and to accept axial forces developed during the operation of the motor or pump.
• I invention can be embodied in forms which utilize the standard sequential position for the motor and pump rather than the nested configuration described above.
• the motor activation and soft-start valves can be used with other types of drive units, including some of those discussed above.
• the specific angles, displacements and dimensions of the drive unit can readily be altered to fit individual applications. It is therefore intended that the foregoing description be regarded as illustrative of the presently preferred embodiment rather than as limiting the scope of the invention. It is the following claims, including all equivalents which are intended to define the scope of this invention.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Reciprocating Pumps (AREA)
• Hydraulic Motors (AREA)

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• 1982
  • 1982-09-07 EP EP19820902952 patent/EP0088794A4/fr not_active Withdrawn
  • 1982-09-07 WO PCT/US1982/001202 patent/WO1983001096A1/fr not_active Application Discontinuation

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