Abstract: A piston hydraulic device comprises a cylinder block having a plurality of cylinder assemblies and is rotatable about a first rotation axis. Each cylinder assembly comprises a cylinder and a piston. A port plate has a first port and a second port that are angularly spaced relative to the first rotation axis. A plurality of first conduits connect respective cylinders alternately to the first port or the second port. At least one second conduit is connected to a fluid reservoir. At least one directional control valve is positioned in the first conduit and fluidly connects to the second conduit. The at least one directional control valve connects the cylinder to the port plate in a first position and to the fluid reservoir in a second position. A controller is operatively associated with the directional control valve for switching between the first and the second positions.

Abstract: Methods and systems for a bent axis motor are described. In one example, a bent axis motor includes a valve plate coupled to at least one piston of a cylinder block, the valve plate comprising a first plurality of grooves spaced about openings of the valve plate on a first side of the valve plate facing the cylinder block, the valve plate further comprising a second plurality of grooves arranged on a second side of the valve plate facing away from the cylinder block.

Abstract: The present disclosure relates to an axial piston machine, such as a pump or motor. The axial piston machine, in on example, includes a pivotable displacement adjustment plate, the displacement adjustment plate having a first side supported by a first hydrostatic support arrangement and a second side supported by a second hydrostatic support arrangement. Further, in the axial piston machine one or both of the hydrostatic support arrangements include a large area support and a small area support which can be fluidly separated from each other.

Abstract: A hydrostatic axial piston machine includes a cylinder drum that rotates during operation and has a plurality of cylinder bores in which displacement pistons are arranged, each of which opens out in a control opening in one end face of the cylinder drum, and having a control part against which the cylinder drum bears with the end face and on which two kidney-shaped control ports in the form of circular arcs are provided. Between the two kidney-shaped control ports, a first changeover web and a second changeover web are formed, wherein two sets of compensating openings that are able to be overlapped by control openings are located in the changeover webs with one compensating opening of each set located in each changeover web, and the compensating openings in the two sets of compensating openings are connected together via respective compensating fluid paths.

Abstract: A blade rotation system including an hydraulic gear motor and a spindle shaft. The hydraulic gear motor has a drive shaft, and the drive shaft is configured with one or more first permanent magnets coupled thereto. The spindle shaft is adapted for connection to a blade, and the spindle shaft is configured with one or more second permanent magnets coupled thereto. The one or more first permanent magnets are configured to magnetically engage the one or more second permanent magnets so that rotation of the drive shaft by the hydraulic gear motor translates into rotation of the spindle shaft to impart motion to the blade.

Abstract: Example hydraulic brake actuators and related methods are disclosed herein. An example hydraulic brake actuator includes a rotary valve disposed in a bore of a housing. The rotary valve includes a shaft rotatably disposed within a sleeve. The sleeve and the shaft have ports that align at certain rotational positions to create a flow path between the bore and an inner chamber of the shaft. The example hydraulic brake actuator also includes a pump coupled to the shaft to increase and decrease a pressure within the inner chamber of the shaft.

Abstract: A port plate for a swashplate type axial piston pump is described herein. The port plate includes an inlet port, a discharge port, and a first metering notch in fluidic communication via a first passage with a metering notch area adjustment valve configured to adjust the effective area of the metering notch. The first metering notch is disposed at a leading edge of one of the inlet port or the discharge port.

Abstract: A hydrostatic radial piston machine is useable inversely. The hydrostatic radial piston machine has a distributor in which a flushing valve, a pressure-maintaining valve connected downstream of the flushing valve, and two nonreturn valves are arranged.

Abstract: Disclosed is hydraulic rotating equipment provided with a rotating shaft, a cylinder block including a plurality of cylinders, a like plurality of pistons accommodated in the cylinders, respectively, and a valve plate maintained in slide contact with a rear end surface of the cylinder block. The valve plate includes a low-pressure port communicable with the cylinders, a high-pressure port formed in an arcuate shape over a predetermined angle along a circumferential direction of the rotating shaft and communicable with the cylinders, a seal land maintained in slide contact with the rear end surface, and a sliding contact member arranged on a periphery of the seal land in a range of the predetermined angle along the circumferential direction of the rotating shaft and maintained in slide contact with the rear end surface. A working machine provided with the hydraulic rotating equipment is also disclosed.

Abstract: The present invention relates to a subassembly for forming a hydraulic motor after assembly onto an assembly including a shaft, said subassembly including a cover forming a housing element, a multilobe cam, a cylinder block opposite the cam, pistons guided so as to slide radially within the respective cylinders of the cylinder block and bearing on the lobes of the cam, and a valve intended to apply pressurized fluid to said pistons in series, wherein said subassembly includes means for temporarily attaching the cylinder block to the cover and means for accessing an element of the valve through the cover in order to enable, during installation, the angular positioning of said element with respect to the shaft, followed by the attachment thereof to the shaft. The present invention also relates to a method for assembling such a hydrobase.

Abstract: A machine and method for a hydrostatic axial sliding bearing that has bearing and sealing functions and is capable of exhibiting reduced power losses. The hydrostatic axial sliding bearing of the machine is defined by axial sliding bearing surfaces that are separated by a fluid film and adapted for movement relative to each other during operation of the machine. The machine has first and second elements that define a first and a second of the axial sliding bearing surfaces. In combination, the first and second axial sliding bearing surfaces function as bearing and sealing surfaces for the hydrostatic axial sliding bearing. The machine is adapted so that the first and second axial sliding bearing surfaces move relative to each other in a first direction of motion, and at least the second axial sliding bearing surface has a surface profile with an oscillatory waveform in the first direction of motion.

Abstract: A spindle body defining a central axis and having a hydraulic motor assembly operably mounted thereon. At least a portion of the hydraulic motor assembly is rotatable relative to the spindle body about the central axis. A plurality of hydraulic passages extend within the spindle body. Each of the passages includes axial and lateral sections. The axial sections are in fluid communication with the hydraulic motor assembly and define a first centerline extending substantially parallel with the central axis. Each of the lateral sections are in fluid communication with one of the axial sections and form a port on an outer surface of the spindle body. The lateral sections also each define a second centerline wherein the second centerlines are positioned in mutually parallel planes and each of the first centerlines and the central axis are substantially parallel with each of the mutually parallel planes. A method of manufacture is also disclosed.

Abstract: The invention relates to a piston engine comprising a rotatably mounted cylindrical drum (2) provided with a plurality of cylindrical boreholes distributed over the circumference thereof and containing displaceable pistons. Said cylindrical boreholes (3,4) comprise cylindrical openings (35.1, 35.2, . . . 35.9) on one side, which are temporarily connected to one of two control nodules (9, 10) according to the angle of rotation of the cylindrical drum (2), said control nodes being respectively connected to a working line (27, 28). A reversing region (30, 31) is respectively embodied between the control nodules (9, 10), a first end (32) of a pressure compensation line (33) ending in one of the reversing regions (30, 31).

Abstract: An articulate vehicle comprises a first frame disposed at one of front and rear portions of the vehicle and a second frame disposed at the other of front and rear portions of the vehicle. The first frame supports a first transaxle apparatus supporting a first axle. The second frame supports a second transaxle apparatus supporting a second axle. Proximal ends of the frames with respect to the vehicle are coupled to each other through a coupling part so that the first and second frames are rotatable relative to each other around a vertical axis according to steering operation. An engine is mounted on the first frame. A first hydraulic motor is integrally assembled in the first transaxle apparatus so as to drive the first axle. A working vehicle is equipped at a distal side of the second frame with respect to the vehicle. A second hydraulic motor is integrally assembled in the second transaxle apparatus so as to drive the second axle.

Abstract: An articulated vehicle with a working device has a first frame having a prime mover mounted thereon and supporting a first transaxle apparatus. The first transaxle apparatus includes an input shalt receiving power from the prime mover, a pair of first axles, and a hydrostatic transmission. The hydrostatic transmission comprises a variable hydraulic pump, a first hydraulic motor fluidly connected to the hydraulic pump via a fluid passage, and a housing with a port fluidly connected to the fluid passage. The second transaxle apparatus includes a pair of second axles having different lengths and a second hydraulic motor. The second hydraulic motor is fluidly connected to the port. Proximal ends of the first and second frames with respect to the vehicle are coupled to each other so that the first and second flames are rotatable around a vertical axis relative to each other when steered.

Abstract: This invention relates to a device to reduce pulsations on a hydrostatic positive displacement unit, such as an axial piston machine or a radial piston machine which can be used both as a pump and as a motor. The direction of rotation of the positive displacement unit is reversible and at least one piston is mounted so that it can move longitudinally in a cylinder bore forming a cylinder chamber. The device has a buffer element which can be brought into communication with the cylinder chamber by a connecting channel.

Abstract: This invention relates to a device to reduce pulsations on a hydrostatic positive displacement units, such as an axial or radial piston machine working both as a pump and as a motor with a reversible direction of rotation. In the displacement units, at least one piston is mounted so that it can move longitudinally in a cylinder bore which forms a cylinder chamber. The device has a buffer element which is in communication with the high-pressure side and can be brought into connection with the cylinder chamber. The device reduces pulsations on hydrostatic positive displacement units by which the reversing actions of the cylinder chambers are optimized and the pulsations are effectively minimized in a broad bandwidth of operating conditions. A switchable valve, in particular a non-return valve which opens toward the cylinder chamber is located in a connecting channel between the buffer element and the cylinder chamber.

Abstract: A hydraulic piston pump 1 includes a distributing valve 11 having a pair of arcuate or circular ports 11a and 11b formed through it. The arcuate port 11b is shorter circumferentially than the arcuate port 11a to reduce, by a predetermined amount, the amount of pressure oil to be discharged from and sucked into the pump through it. The valve 11 also has a pair of tank ports 11c and 11d formed through it circumferentially on both sides of the shorter port 11b. The circumferential dimensions of the tank ports 11c and 11d correspond to the predetermined amount of oil.

Abstract: A hydraulic axial pump/motor comprises a plurality of revolving as well as reciprocating pistons, operatively associated with a stationary port plate. The port plate comprises at least a first, elongated, arcuate suction port and at least a second elongated, arcuate discharge port, divided by a bringing portion extending between the downstream side of the suction port and the upstream side of the discharge port. A tortuous passage of a non-uniform cross-section is formed in the bridging portion, allowing the by-passing of the fluid first in a direction towards the downstream side of the suction port and then towards and into the upstream side of the discharge port.

Abstract: Each cylinder of a hydrostatic hydraulic machine of the displacement type is preliminarily pressurized after the inlet port of the cylinder has been exposed to the low pressure side of the machine and before the inlet port of the cylinder is exposed to the high pressure side of the machine. The preliminary pressurization is effected by use of a separate pressure chamber containing a pressurized fluid that is rapidly discharged into the inlet port of each cylinder before the cylinder inlet port is exposed to the high pressure side of the machine. The separate pressure chamber is recharged from the high pressure side of the machine at a rate that is slower than the rate at which pressurized fluid is discharged from the chamber into the inlet port of a cylinder.

Abstract: The rotary machine of the invention includes a series of cylindrical chambers swept by pistons in hydraulic liquid admission-and-discharge cycles and alternately connected to high pressure openings and to low pressure openings during each revolution of the machine, wherein said machine it includes a pre-discharge opening disposed between the high pressure opening and the low pressure opening in that order relative to a direction of rotation of the machine, and wherein the pre-discharge opening is connected by a connecting duct to rotary support devices to cause hydraulic fluid to pass through the rotary support devices.

Abstract: An axial piston type motor for a hydrostatic transmission, wherein the motor is arranged to generate an output torque at the drive flange uses a Rzeppa joint (32) to couple the drive flange (10) with the cylinder barrel (16). The center of the Rzeppa joint (32) is located in the tilting point (60) between the axes of the drive flange (10) and of the cylinder barrel (16). The number of balls (42) of the Rzeppa joint (32) is equal to the number of pistons (24). The outer joint member of the Rzeppa joint (32) is formed by the drive flange (10). The balls (42) and grooves (40) of the Rzeppa joint (32) are angularly offset with respect to the ball-and-socket joints (28,30) of the pistons (24) by half the angular spacing of the ball-and-socket joints and extend up to the space between the ball-and-socket joints.

Abstract: An axial piston type motor for a hydrostatic transmission, wherein the motor is arranged to generate an output torque at the drive flange uses a Rzeppa joint (32) to couple the drive flange (10) with the cylinder barrel (16). The center of the Rzeppa joint (32) is located in the tilting point (60) between the axes of the drive flange (10) and of the cylinder barrel (16). The number of balls (42) of the Rzeppa joint (32) is equal to the number of pistons (24). The outer joint member of the Rzeppa joint (32) is formed by the drive flange (10). The balls (42) and grooves (40) of the Rzeppa joint (32) are angularly offset with respect to the ball-and-socket joints (28,30) of the pistons (24) by half the angular spacing of the ball-and-socket joints and extend up to the space between the ball-and-socket joints.

Abstract: A piston machine, particularly a radial piston machine which includes a pintle supporting a rotor which has a plurality of radially extending bores in which radial pistons are guided. These bores are in communication with control chambers formed in the pintle. One of the chambers is a high-pressure chamber and the other is a low-pressure chamber. Pre-control grooves and additional passages are provided at the control chambers to prevent, during the operation of the radial piston machine the occurrence of pressure shocks at the inner and outer dead centers.

Abstract: A gas compressor has a cup-like casing. A driving shaft is rotatably carried by a bottom of the casing and has a rotary plate secured thereto. A driven shaft is disposed in the casing at an inclination angle of 20.degree. against the driving shaft, supported by a bearing provided on an end of the driving shaft, and driven by the driving shaft. A cylinder block is fixed to the driven shaft and has a cylinder bores receiving pistons coupled with the rotary plate so that the pistons reciprocate in the cylinder bores upon rotation of the driving shaft. A side plate is secured to an open end of said casing and has a bore receiving a bearing for supporting one end of the driven shaft. The bore is formed in the inside the side plate which projects outside, so that a distance between the bearing of the driving shaft and the bearing in the bore is extended and stable.

Abstract: The hydraulic apparatus may either be a quiet hydrostatic drive with an axial piston pump and an axial piston motor or may be a quiet pump unit formed by two axial piston pumps. In either case, the apparatus includes two rotatable cylinder blocks disposed on opposite sides of a rotationally stationary valve block and tied together by a rod which transmits forces between the two cylinder blocks so that any force tending to unseat one cylinder block from the valve block tends to seat the other cylinder block against the valve block. A resiliently yieldable sealing ring on one end portion of the rod defines a pressure chamber which receives oil at working pressure to automatically increase and decrease the axial clearance between the cylinder blocks and the valve block as the working pressure increases and decreases, respectively.

Abstract: New type of piston machine operating as a piston pump or piston engine, preferably called a diagonal engine, which, with the aid of hydrostatic bearings, is constructed with the cylinder through-bores having an area free throughout from any construction points. Due to the considerable angle at which the cylinder bores are disposed, a very long stroke can be obtained for the piston compared with the stroke-length possible with other hydrostatic piston pumps and piston engines.

Abstract: An axial-piston pump includes a rotatable cylinder barrel having pistons extending from cylinder bores formed at one end thereof. A swashplate is positioned adjacent the cylinder barrel and includes an inclined surface for engaging and reciprocating the pistons upon rotation of the cylinder barrel relative thereto. The cylinder barrel is rotatably supported by a bearing spaced from the swashplate in a direction toward the cylinder barrel. The location and orientation of the bearing results in the development of bearing forces which operate on the same equivalent force point as the contact forces developed between the pistons and swashplate. Since the forces thus developed all operate on the same equivalent force point, pitching or cocking moments on the cylinder barrel are substantially eliminated.

Abstract: An axial plunger pump or motor of the type such that a valve plate having a suction port and a discharge port drilled therein is fixed to a casing in which a rotary shaft is mounted. A cylinder block having one end surface opposed to the valve plate is coupled to the rotary shaft. A plurality of bores whose one ends can be communicated with the suction port and the discharge port are drilled in the cylinder block in parallel to the rotary shaft. A plurality of plungers, which can reciprocate within the respective bores in accordance with rotation of the rotary shaft are slidably fitted in the bores on the side of the other ends. A seal plate positioned between the valve plate and the cylinder block and making slide contact with the valve plate is coupled to the rotary shaft.

Abstract: An improved fluid pressure energy translating device of the axial piston type including a cylinder barrel mounted on a drive shaft. The cylinder barrel is centered on the drive shaft by a crowned bearing on the drive shaft and coupled through a splined connection which includes crowned male splines on the drive shaft. The crowned bearing and the crowned male splines on the drive shaft have centers located to either side to the center of bending of the drive shaft under load so as to eliminate tilting of the barrel.

Abstract: Improved energy translation devices, such as fluid motors or pumps of the type including an orbiter member operatively coupled between a stator and a rotor, are disclosed which include an individually pressure compensated valving arrangement, telescopically interfitted piston elements having spherical, pressure loaded sealing ends, and a unique counterbalancing mechanism. The valving arrangement has a pair of intercommunicated, freely laterally movable valve bodies adjacent each fluid displacement piston assembly and respectively on opposite sides of the orbiter; each body includes especially designed, opposed fluid chambers therein for receiving pressurized fluid and individually urging each pair of bodies toward the central orbiter to establish a sliding seal with the orbiter and a desired amount of lubricating leakage of fluid adjacent the valve bodies.

Abstract: In a number of patents my former art of control bodies which have centric and eccentric portions are disclosed for the passing and control of flow of fluid into and out of working chambers in fluid handling devices, such as fluid pumps, motors, compressors, transmissions.The invention discovers, that those control bodies of the former art under certain circumstances tend to rotate slightly by a few degrees under friction in the control mirror and then stick very strongly their seats whereby they lose their ability to adjust themselves axially and for good seal under small friction along the stationary control face of the rotor.The invention overcomes this problem by providing a retainer on a stationary portion in the device to prevent the control body from any rotation around one of its axes. The smooth operation of the control body is thereby assured and the former sticking and loss of ability to operate perfectly is overcome.

Abstract: The invention relates to a fluid mechanism supplied with pressurized fluid by means of a "dis-engageable" valve-seat. Such mechanism further comprises a controlled and independent device for re-engaging the said valve-seat. The invention finds an application in the production of a hydraulic relief engine for use on a trailer pulled by a tractor.

Abstract: There is disclosed a hydrostatic motor provided with radially arranged hydraulic cylinders provided with radial pistons composed of pairs of pistons with different diameters fitted one into the other. The motor is selectively operable in either of two operating conditions, in a first of which the large and small pistons move as a unit in a heavy duty operation, and in a second of which only the small pistons move in a low duty operation. The motor includes a rotor and a stator, duct means arranged in the stator for the supply of pressure fluid to the pistons, a change-over unit within the motor, and a fluid distributor unit housed in the stator. The motor of the invention employs virtually the same distributing circuits during its operation in both its heavy duty and its low duty modes of operation.

Abstract: The engine comprises a base having a spool fastened thereon, the spool including a hub symmetrical about a first axis and having a pair of side plates normal to and having inside faces spaced apart along the first axis. There are plate ports in the inside faces. A cylinder rotor includes a second hub rotatable on the first hub about the first axis and includes a pair of side discs normal to the first axis and having outside faces spaced apart axially between said side plates to establish first and second axial clearances between the side plates and the adjacent side discs. There are cylinders mounted radially on the cylinder rotor with ducts extending from the cylinders to the disc ports in the outside faces radially opposite the plate ports. A driven shaft symmetrical about a second axis is eccentrically journalled in and extends through the hub. A rotor is fast on the driven shaft and carries pivot pins.

Abstract: A transfer tube and seal structure for a hydraulic unit for connecting a pair of flow passages in a housing to flow passages in a valve plate which is floatingly mounted and engageable against a cylinder block in an axial piston hydraulic unit with ports in the valve plate communicating with axially-extending bores in the cylinder block, each of which carries a piston movably mounted therein. A transfer tube is loosely positioned in coaxial flow passages to span the gap between the valve plate and the housing and maintain a sealed flow relation therebetween while permitting movement of the valve plate relative to the housing. The transfer tubes each have an outwardly-opening groove adjacent each end thereof mounting a metallic seal ring and with the outer face of the seal ring being of substantially reduced width for a limited area of sealing contact with the walls of the flow passages.

Abstract: The invention relates to a radial piston pump of the type in which a piston carrier, together with an end slide plate within a track carrier, produces one piston stroke per revolution. The piston carrier is rotatably disposed between two parallel housing surfaces and has distributing passsages opening at the end and cooperating with distributing apertures at the pressure and suction sides in at least one housing surface. At least one pressure surface, which is bounded by sealing rings, is in communication with the pressure side to force the piston carrier and slide plate apart. An annularly shaped corrugated spring is provided for aiding and supplementing the pressurized fluid in also pressing the piston carrier and slide plate apart.

Abstract: A rotary valve coupled to a radial cylinder motor sequentially provides pressure fluid to the cylinders of the motor and drains the cylinders through discharge openings in the valve casing. The rotary distributor of the valve and the valve casing have each two radial face portions directed in opposite axial directions and defining two throttling gaps connected by a chamber in the casing and respectively communicating with intake and return openings in the casing so that a pressure intermediate the intake and return pressures of a fluid prevails in the chamber and axially biases the distributor outward of the chamber while the substantially full hydraulic fluid pressure biases the distributor inward of the chamber. Recesses in the distributor alternatively connect discharge openings with the intake opening and the return opening of the valve casing. The distributor floats axially in the valve casing under the opposed biasing pressures.

Abstract: An axial piston machine of the swash plate type includes a valve plate provided in a front face thereof with control openings which communicate at opposite ends through bores with the rear face of the valve plate. A plurality of shallow pockets, respectively forming hydrostatic bearings, are also provided in said front face, which communicate through connecting bores respectively with throttle bores, which in turn communicate at inner ends with respective control openings, and in which spring loaded throttle pins are arranged with small clearance for oscillating movement.

Abstract: A hydraulic fluid pressure energy translating device comprising an axial multi-piston pump including an axially and laterally constrained barrel and a floatingly disposed port plate responsive to hydrostatic forces within the pump. The port plate includes hydrostatic pressure balancing means which tend to balance hydrostatic forces acting on the port plate during operation of the pump to maintain an optimum bearing clearance between the port plate and barrel, thereby controlling fluid leakage and maintaining adequate lubrication and support at this interface.

Abstract: In a hydraulic axial piston machine, which may be a pump or hydraulic motor, whose cylinders are located on a larger circle than the cylinder ports and the stationary high pressure and low pressure ports of a stationary body, a tilting moment is exerted on the cylinder block which is compensated by radial pressure exerted on the cylinder block by positioning cylinder and piston members operated either directly by high pressure fluid from the high pressure conduit of the stationary body, or indirectly under the control of a valve operated by leakage fluid obtained from a recess in the control face of the stationary body.

Abstract: A hydraulic pump of the axial piston type comprising check valves each of which is adapted to open and allow the associated cylinder to discharge fluid when the pressure inside the cylinder has been raised above the discharge pressure of the pump by the piston on its compression stroke, passage means for communicating each of the cylinders with the low-pressure system including a pump suction pipe or drain tank during the period in which the piston on the compression stroke moves from a point at least short of the top dead center to a point past the center and where the cylinder communicates with the suction port, and pressure-reducing means disposed in the passage means.

Abstract: A hydraulic fluid pressure energy translating machine is provided with hydrostatic pressure-balancing means which communicate with the primary port to balance hydrostatic forces acting on the barrel during operation of the machine to maintain an optimum bearing clearance between the head and barrel, thereby controlling fluid leakage and maintaining adequate lubrication and support at this interface.

Abstract: A pressure responsive control body in the housing of a fluid handling device has a control face which abuts against the control face at one axial end of a rotor which is provided with working chambers for the inflow and expulsion of a fluid. A portion of the control body extends into a pressure chamber of the housing and the control body is movable axially of the housing. The control body seals a portion of the pressure chamber by means of an eccentrically located cylindrical shoulder a portion of which extends radially beyond the control face. This insures that the position of the pressure center of the eccentric shoulder relative to the axis of the rotor is the same as the position of the pressure center between the control faces.

Abstract: In order to reduce noise and erosion within a hydrostatic translating unit having a reversible mode of operation, preferably a pump, of the type having a cylinder barrel defining a plurality of piston bores with the cylinder barrel being rotatable relative to a cylinder head for periodically communicating the piston bores with first and second pressure ports or passages, a restrictive orifice and shuttle valve are arranged in parallel communication between each pressure port and an intermediate port positioned for communication with each cylinder bore prior to communication of the cylinder bore with the respective pressure port.

Abstract: A hydraulic device which is primarily intended for use as a motor, includes an annular stator having an internal cam surface consisting of a plurality of outwardly and inwardly extending reaction surfaces, and a rotor disposed within said stator having a plurality of open-ended fluid pressure chambers with a rolling element therein engaging the outwardly and inwardly extending reaction surfaces and extending the width of the rotor. The rotor is mounted on a shaft and when operating as a motor is rotated by the rolling elements reacting on the outwardly extending reaction surfaces to rotate the shaft. Fluid inlet and outlet passages are disposed in a port plate disposed along the side of the rotor and communicate with the fluid pressure chambers through one of their open ends.