Abstract: A variable displacement piston machine includes a valve plate (3) provided with high-pressure and low-pressure ports (5, 6) to supply and discharge fluid into and from piston chambers (80) in a cylinder block (2) and first and second control ports (P1, P2) disposed in opposite directions between the ports; a pivotable inclined swash plate (4) to adjust the stroke of pistons 1 in the piston chambers (80); and a feedback valve (100) having a second spool actuated by pressure of fluid introduced into an introduction passage (41) with a throttle valve (42), and a first spool (S1) slidably fitted in the second spool (S2).

Abstract: A hydraulically operated continuously variable transmission for an automobile includes a hydraulic pump coupled to an input shaft and having an outlet port, a hydraulic motor coupled to an output shaft, at least one of the hydraulic pump and the hydraulic motor being of the variable-displacement type, a closed hydraulic circuit interconnecting the hydraulic pump and the hydraulic motor, and a device for selectively making and breaking the hydraulic circuit respectively by opening and closing the outlet port. The device comprises a valve body for closing the outlet port, a valve holder for driving the valve body to selectively open and close the outlet port, and a spring for normally urging the valve body in a direction to close the outlet port, the valve body and the valve holder being held in engagement with each other for relative displacement in directions to open and close the outlet port.

Abstract: A swashplate type variable displacement hydraulic device is so constructed that a plurality of plungers are slidably received in a plurality of cylinder bores arranged annularly around an axis of rotation, a back surface of a swashplate of which a fore surface is engaged by outer ends of the plungers is supported by a swashplate holder via bearing means, and a stationary swashplate anchor supports the swashplate holder to turn about a trunnion axis which intersects the axis of rotation at right angles. Opposing surfaces of the swashplate holder and swashplate anchor are formed as spherical surfaces of which a center is located at a position where the axis of rotation intersects the trunnion axis, the swashplate holder has a pair of trunnion shafts projected from opposite ends of the swashplate holder while extending along the trunnion axis, and the trunnion anchor is formed at opposite ends thereof with recesses with which the trunnion shafts are rotatably engaged.

Abstract: A hydrostatically operated continuously variable transmission has a hydraulic pump and a hydraulic motor which are interconnected by a closed hydraulic circuit. The hydraulic pump comprises a plurality of pump plungers reciprocably disposed radially in a cylinder block, and an eccentric pump ring engaging outer ends of the pump plungers and supported eccentrically with respect to the center of rotation of a cylinder block for imparting reciprocating movement to the pump plungers in response to rotation of the cylinder block. The hydraulic motor comprises a plurality of motor plungers reciprocably disposed radially in the cylinder block, and an eccentric motor ring engaging outer ends of the motor plungers and supported eccentrically with respect to the center of rotation of the cylinder block for imparting reciprocating movement to the motor plungers in response to relative rotation between the cylinder block and an output shaft.

Abstract: A bidirectional hydraulic servomotor system includes a variable-displacement motor which may impel or brake movement of a load member that either resists or assits movement by the servomotor, respectively. The direction of load movement is under control of a directional control valve with motor displacement and function (impelling or braking) being effected automatically to achieve controlled load movemement with minimal consumption of hydraulic fluid.

Abstract: A hydraulically operated continuously variable transmission includes a hydraulic pump coupled to an input shaft, a variable-displacement hydraulic motor coupled to an output shaft, and a closed hydraulic circuit interconnecting the hydraulic pump and the hydraulic motor and including a passage connecting the inlet and outlet ports of the hydraulic pump. A servomotor makes and breaks the hydraulic circuit respectively by opening and closing the outlet port. A clutch valve continuously varies the cross-sectional area of the passage to change the amount of power transmitted between the hydraulic pump and the hydraulic motor. A control system independently controls the servomotor and the clutch valve, the control system being arranged to hold the servomotor in a position to open the outlet port when the clutch valve is opened beyond a prescribed degree.

Abstract: A hydraulically operated continuously variable transmission comprises a hydraulic motor coupled to an output shaft, a hydraulic pump coupled an input shaft, and a closed hydraulic circuit interconnecting the hydraulic motor and the hydraulic pump. The hydraulic motor has an annular array of slidable motor plungers disposed around an axis of rotation thereof and slidably disposed in respective cylinder holes defined in the motor cylinder. The hydraulic motor also has a distribution ring supported on the fixed shaft and rotatable relatively to and slidable against an end face of the motor cylinder for introducing high-pressure oil successively into the cylinder holes and discharging oil successively from the cylinder holes in response to rotation of the motor cylinder.

Abstract: The invention is vehicle propulsion system having a pump driven by an engine, a hydraulic motor driven by the pump, and a ground engaging wheel driven by the hydraulic motor. On the drive shaft connected between the engine and the pump is a flywheel whose moment of inertia is varied by radially translating weights on the flywheel. Under normal vehicle operating conditions, the weights are translated outward, whereby rotational energy is stored in the flywheel. When more power is needed then the engine can provide, the weights on the flywheel translate inwardly so that the flywheel imparts rotational energy to the pump through the drive shaft. The propulsion system has means to maintain the engine in a narrow r.p.m. range where the engine is most efficient. Vehicle speed and direction is varied by controlling the flow speed and direction from the pump, which determines the speed and direction of the hydraulic motor.

Abstract: A hydraulically operated continuously variable transmission includes a fixed shaft mounted in a transmission case, an output shaft rotatably supported in the transmission case, and a hydraulic motor coupled to the output shaft and having a motor cylinder and an annular array of slidable motor plungers disposed around an axis of rotation thereof and slidably disposed in respective cylinder holes defined in the motor cylinder. The hydraulic motor also has a distribution ring supported on the fixed shaft and rotatable relatively to and slidable against an end face of the motor cylinder for introducing high-pressure oil successively into the cylinder holes and discharging oil successively from the cylinder holes in response to rotation of the motor cylinder.

Abstract: A hydrostatically operated continuously variable transmission includes a cylinder block centrally coupled to a transmission shaft coupled to an engine, a swash-plate-type axial-piston hydraulic pump having a group of pump plungers, a hydraulic motor having a group of motor plungers, and a closed hydraulic circuit by which the hydraulic pump and the hydraulic motor are interconnected. The groups of pump and motor plungers are disposed in annular patterns in the cylinder block, and disposed concentrically such that one of the groups surrounds the other group. The plunger groups are positionally displaced in the circumferential direction of the cylinder block such that a circle inscribed in said one group passes through the other group.

Abstract: A static hydraulic continuously variable transmission includes a cylinder block which is secured to an output shaft and comprises a pump cylinder of a hydraulic pump and a motor cylinder of a hydraulic motor, these cylinders being connected to each other, wherein, a number of pump cylinder bores and a number of motor cylinder bores are annularly arranged respectively in the pump cylinder and the motor cylinder and the transferring of a working oil between the group of the pump cylinder bores and the group of the motor cylinder bores is conducted through the medium of a pair of oil chambers which are concentrically provided around the output shaft communincation between these cylinder bores is controlled by a number of first and second dispensing valves extending between both the oil chambers and adapted to be reciprocally radially moved.

Abstract: A vehicle includes at least a pair of drive wheels, each wheel being independently controlled by an integrated transmission, each transmission being powered by an input shaft operably driven by a common engine. Each transmission is of a type wherein a pump head with pistons is driven by the input shaft and conveys output fluid to a motor head which is driven thereby and rotates and output shaft. Pump head output is controlled by an operator variable swash plate. The transmission integrally includes a dampening mechanism for the swash plate, a positive neutral structure for the swash plate, an automatic parking brake with override mechanism to allow setting of the brake or release of the brake by the operator, a porting block communicating fluid flow between the pump heads and providing for overpressure relief, and a charge pump for communicating makeup fluid to the pump head and to circulate the fluid so as to cool same.

Abstract: A hydraulically operated continuously variable transmission includes a hydraulic motor coupled to an output shaft, a hydraulic pump coupled to an input shaft, and a closed hydraulic circuit interconnecting the hydraulic motor and the hydraulic pump. The hydraulic motor has an annular array of slidable motor plungers disposed around an axis of rotation thereof and slidably disposed in respective cylinder holes defined in a motor cylinder, the motor cylinder having an annular array of communication ports disposed around the axis of rotation and communicating with the cylinder holes.

Abstract: A hydrostatic machine including a casing 1 containing a rotary member 12 having radial cylinders 20 each with a piston 21 engaging a track ring 23. Both input 6 and output shafts 7 are connected either hydraulically through the transmission rotary members 12 or mechanically through a bypass shaft 10 and clutch 50 for reducing machine heat losses. Hydraulic ram 106,110 assistance for cushioning out pressure transients when transmission power returns from mechanical to hydraulic. Internal oil ducts 72,80.90 included for providing further temperature control for the main internal transmission component parts 14.24 said ducts 72,80,90 feed from a auxiliary fluid pump 8,9.

Abstract: In a hydrostatic continuously variable transmission comprising a swashplate type hydraulic pump having a pump swashplate and annularly arranged pump plungers whose suction and discharge strokes are provided by the pump swashplate, a swashplate type hydraulic motor having a motor swashplate and annularly arranged motor plungers whose expansion and shrinkage strokes are provided by the motor swashplate, and a hydraulic closed circuit formed between the hydraulic pump and motor, the middle point of a discharge region of the hydraulic pump is angularly delayed at a given angle in a direction of rotation of the hydraulic pump relative to a tilting axis of the pump swashplate, and/or the middle, point of an expansion region of the hydraulic motor is angularly advanced at a given angle in a direction of rotation of the hydraulic motor relative to a tilting axis of the motor swashplate.

Abstract: An hydraulic index drive system including a variable displacement pump closely coupled to a fixed displacement motor through an adaptor which feeds oil to and returns oil from the motor. A lever on the pump controls the position of a swash plate which determines the pump displacement. The lever is positioned by a cam which makes one revolution per cycle. The cam is designed such that for 40% of the cycle there is no pump output which is the dwell portion of the cycle and for 60% of the cycle the output rises to a set maximum and returns to zero output which is the index portion of the cycle. The pump is driven by a variable speed motor. The system is particularly suited for use with a vacuum conveyor on a bag machine line for transfer of plastic bags to a bag folder.

Abstract: A hydraulic differential having a pair of axial piston displacement units, with one being a fixed displacement unit, and the other being a variable displacement unit, and having flow-directing valve and port plates positioned therebetween. The hydraulic sealing of the components which rotate relative to each other is achieved by a floating mounting of a port plate which is urged by a block spring of the fixed displacement unit against an adjustable valve plate abutting a cylinder block of the variable displacement unit. The drive input for the hydraulic differential includes a rotatable mounting for the fixed angle wobbler of the fixed displacement unit which is drivingly connected through a connecting tubular member to the cylinder block of the variable displacement unit and with the cylinder block of the fixed displacement unit connected to a drive output shaft.

Abstract: In a swash plate type hydraulic system such as a hydraulic pump, a hydraulic motor of the like, a group of cylinder bores in which plungers engaging a swash plate are slidably received are annularly arranged in a cylinder block, and higher and lower pressure oil passages are concentrically provided in the cylinder block. Further, a group of distributor valves are provided in the cylinder block in a radially arranged configuration for controlling the connection and disconnection between the higher and lower pressure oil passages and the group of cylinder bores by radial reciprocating motion of the valves, and an eccentric wheel is provided eccentrically with respect to the center of rotation of the cylinder block to abut against the outer ends of the distributor valves so as to impart a reciprocating motion to each of the distributor valves. A shifting device is provided for changing the eccentric relationship between the eccentric wheel and the cylinder block.

Abstract: A variable displacement motor control responsive to the pressure differential across the motor, with provisions for reverse motor operation and for aiding load conditions.

Abstract: A prime-mover driven variable-rate pump of relatively great flow capacity is in delivery and return-circuit connection to an intermittently loaded hydraulic motor. A fixed-rate pump of substantially less capacity is continuously driven by the prime-mover, to charge a hydraulic accumulator, there being a safety relief to sump when a predetermined high-pressure threshold is reached. The accumulator is exclusively connected to the inlet of the variable-rate pump, being isolated by check valves from delivering any reverse flow to the fixed-rate pump and from delivering any reverse flow to the return portion of the motor-driving circuit. In said return portion, and between its check valve and the motor, a "dump" valve is operable for transient diversion of return flow to sump, thereby transiently enabling enhanced load-accelerating torque from the motor; this valve is preferably pressure-operated to "dump" position upon a load-reflecting pressure rise in the supply line from the variable-rate pump to the motor.

Abstract: A power-transmitting system provides conservation of (speed) X(torque) product between an input shaft and an output shaft. It represents the equivalent of the power being transmitted through the system. This power is transformed into the form of incompressible fluid flow at high pressure by a volumetric pump coupled to the input shaft. This fluid flow is forced at that pressure into a volumetric motor. The fluid then pushes on pistons which are constrained by a fixed enclined track. The pistons are laterally guided in a rotor and radially arranged therein. The enclined track forms a closed curved surface which surrounds these pistons and the resultant of the reactions of the track surface on the pistons results in a torque being exerted on the rotor. The structure supporting the track surface is slidable in a manner such that the piston strokes are adjustable between zero and a set maximum.

Abstract: A clutch valve system for use in a static hydraulic continuously variable transmission in which a hydraulic closed circuit is formed between a swashplate type hydraulic pump and a swashplate type hydraulic motor, wherein a first annular oil chamber and a second annular oil chamber are concentrically defined in the pump cylinder adjacent to annularly arranged cylinder bores of a pump cylinder in the hydraulic pump, the first oil chamber being adapted to be connected to the cylinder bores which are in a discharge stroke and the second oil chamber being adapted to be connected to the cylinder bores which are in a suction stroke; a plurality of clutch valves are radially arranged in the pump cylinder for providing the communication or discommunication between both the oil chambers by the radial movement thereof; and a clutch control ring engaged with the clutch valves for relative rotation therebetween so as to surround these clutch valves is pivoted on a fixing structure for pivotal movement between a clutch ON

Abstract: A static hydraulic pressure type continuously variable transmission having a hydraulic closed circuit formed between a swashplate type hydraulic pump and a swashplate type hydraulic motor, in which a high pressure oil passage is communicated through exhaust valves with a number of cylinder bores annularly disposed in a pump cylinder of the hydraulic pump, a low pressure oil passage is communicated through intake valves with the cylinder bores, and a number of distribution valves capable of being reciprocated are radially disposed so as to provide an alternate communication between a number of cylinder bores annularly disposed in a motor cylinder of the hydraulic motor and the high and low pressure oil passages. An eccentric ring for imparting reciprocation to each distribution valve is provided and a discharge side of a replenishing pump is communicated with an inner end surface of each distribution valve to hydraulically urge the distribution valve in a direction of engagement with the eccentric ring.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions and a pump system with load sensing control for supplying fluid to said actuator. A meter-in valve is provided to which the fluid from the pump is supplied and a manual or electrohydraulic controller alternately supplies fluid at pilot pressure to the meter-in valve for controlling the flow therefrom to the actuator to control direction and displacement of movement of the meter-in valve and the direction and velocity of the actuator. A pair of lines extends from the meter-in valve to the respective openings of the actuator. A meter-out valve is associated with each line to the actuator for controlling flow out of the actuator. Each meter-out valve is operated by the pilot pressure from the controller.

Abstract: The invention contemplates hydraulic-lift mechanism which employs a power integrator in the connection between a charged hydraulic accumulator and the actuator for a vertically positionable load; the power integrator, additionally, has a prime-mover connection, and the pressurized charge of the accumulator is advisedly set to fully accommodate a preselected level of average load upon the actuator. The hydraulic circuit importantly includes check valves, with a pilot-operated check valve interposed between the power integrator and the accumulator and another pilot-operated check valve interposed between the power integrator and the load actuator. The pilot-operated check valves cooperate with other check valves to assure automatic transfer of hydraulic fluid under pressure from the accumulator to the load actuator, and vice versa, as may be determined by selected control of or via the power integrator.

Abstract: A control apparatus for a hydraulic motor for use in a construction vehicle driven by hydraulic power has a hydraulic motor, a hydraulic pump serving as a pressurized fluid supply source, a manually operable directional control valve connected across supply and discharge conduits for the hydraulic motor, a brake valve section including a counterbalancing valve and a pair of relief valves all of which are connected across the conduits extending between the directional control valve and the hydraulic motor, and a selector valve for controlling the supply of control pressurized fluid introduced through a shuttle valve connected across the conduits into a displacement control cylinder contained in the hydraulic motor. The selector valve is of a pilot operated type remotely controlled by pilot pressurized fluid supplied from an external pressurized fluid supply source.

Abstract: A fluid continuously variable transmission system that includes a body forming a cylindrical chamber. A rotor with blades positioned in the chamber is connected to a power input shaft. The rotor is rotatably movable relative to the body, which in turn is connected to a power output shaft. A valve, preferably a rotary plug valve, is connected to the rim portion of the body. The valve is movable between fully open and fully closed positions, and a plurality of intermediate positions therebetween. The body forms a fluid circuit between a high pressure channel from the chamber to the valve and a low pressure channel from the valve to the chamber. The rotor pressurizes fluid in the fluid circuit against the valve in proportion to the degree of closing of the valve which action rotates the body in all valve positions except the fully closed position.

Abstract: A fluid-operated transmission device has an impeller mounted within an input chamber which is driven by a motor or other motive source. A variable-speed rotor is positioned within an output chamber, the volume of which is selectively adjustable by positioning of a baffle means so that the volume of the output chamber which forms part of the fluid flow circuit may be selectively adjusted, thereby adjusting the speed of hydraulic fluid passing through the output chamber, and thereby the speed of the output rotor at constant output power. Fluid flow direction means are provided which enable braking and/or reversing direction of rotation of the variable-speed rotor by changing the direction of flow of the fluid impinging onto the impingement surface thereof.

Abstract: A controller for maintaining a motor operation at a desired rotational speed utilizes a phase locked loop that receives input signals from a tachometer coupled to the motor shaft. Reference frequencies for the phase locked loop are generated by a voltage control oscillator in response to voltages selected in accordance with the desired motor speed. These selected voltages are coupled to the motor speed control to establish a motor speed within the lock-in range of the phase locked loop. Tachometric feedback is applied in parallel for the phase locked loop. The open loop drive provided by the selected voltage guarantees degraded open loop control of the motor should the control circuit fall.

Abstract: A rotatable hydrostatic transmission is formed by a hydraulic pump and a hydraulic motor which are coupled coaxially together. The pump and motor both have housing members and shaft members which are independently rotatable relative to a mounting structure. One member of the pump is rigidly coupled to one member of the motor, and the coupled members rotate together as a unit. The other member of the pump is an input and the other member of the motor which is not rigidly coupled is the output member. Reduction gearing is provided between the coupled members and the output member. A fluid flow control means provides an infinitely adjustable control of fluid through the pump and the motor and allows the speed of rotation of the driven output member to be varied in infinitely adjustable fashion. A direct drive can be achieved by disengaging the reduction gearing so that the shafts and housings of both the pump and motor will all turn at the same speed as if they were one single unit.

Abstract: The transmission comprises a hollow input member (1) and a coaxial output member (2) supported for rotation relative to the input member. A positive displacement pump comprises a cylinder block (12) secured to the input member and a rotor (16) which is journalled on an eccentric pin (17) and which drives the pump pistons (15). A positive displacement motor comprises a stator part (6) secured to the input member and a rotor part (5) secured to the output member. The motor cylinders (8) are supplied with hydraulic liquid from the pump through duct means (35, 37, 39) in a disc-shaped control member (22) journalled on the eccentric pin (17) and rotating together with the pump rotor (16). Return flow from the motor to the pump occurs through a space (28) which within the input member surrounds the control member (22) and which communicates with each pump cylinder (14) during the suction stroke of the associated pump piston (15).

Abstract: An axial piston-type transmission in which a group of axially displaced pump pistons, that move in a cylinder block rotated by an input shaft, slidably engage one surface of a swash plate that rotates an output shaft. A group of axially displaced motor pistons, that move in a stationary cylinder block, slidably engage an opposite surface of the swash plate so that the plate is squeezed between the two groups of pistons. The swash plate is pivotally attached to the output shaft so that the angles between the two surfaces and the axis of rotation of the swash plate can be adjusted. The pump pistons and motor pistons are hydraulically connected in pairs. A rotary valve driven by the output shaft connects half the pump cylinders together hydraulically to form an output port and the other half together to form an input port.

Abstract: A fluid control system (10) for controlling the torque of a fluid motor (22) and varying the flow to the fluid motor (22) has a mechanism (56) to control the torque and flow in proportion to the operator's input to a pilot operated control valve (16) that controls the fluid motor (22). The mechanism (56) controls the torque and flow of the fluid motor (22) during both acceleration and deceleration of the fluid motor (22). The fluid control system eliminates the need for special, complicated control valves.

Abstract: A closed loop hydrostatic transmission is disclosed which includes an improved hydraulic fluid bleed arrangement. The fluid bleed arrangement includes a variable flow bleed valve hydraulically joined with each of the closed loops of the hydrostatic transmission. Each variable bleed valve is operatively associated with the control mechanism which selectively controls the reversible flow fluid pump of the closed loop for direction of fluid under pressure in forward and reverse directions in the loop. The variable action of each bleed valve permits a relatively greater amount of hydraulic fluid to be bled from the closed loop during periods of operation when the flow of hydraulic fluid otherwise lost from the closed loops is insufficient to permit adequate replenishment of fluid in the loops with cooler charging fluid.

Abstract: A hydraulic auxiliary drive system for the normally non-driven wheels of a vehicle to assist the main wheels. The auxiliary drive comprises at least one variable displacement motor having a swash plate for driving at least one of the non-driven wheels, a variable displacement pressure compensated pump supplying the motor with a constant pressure regardless of vehicle speed, a spring for biasing each motor swash plate toward zero displacement, a servo connected to the motor swash plate for varying the displacement of the motor, and a pressure source for supplying the servo. A manually operated pressure control includes a solenoid-controlled variable orifice for controlling the pressure level supplied to the servo to vary the torque output of the normally non-driven wheels. A control valve is positioned between the pump and motor for disengaging and reversing the auxiliary drive. Another embodiment includes a second servo connected to the motor swash plate for decreasing the motor displacement.

Abstract: A hydraulic transmission operates throughout a continuous range between a neutral condition and a direct drive one to one ratio of input shaft speed to output shaft speed. The input shaft carries a rotor which provides a hydraulic pump for the input side of the transmission. Reciprocating pistons of the input pump move in camming fashion against an input side swash plate as the input shaft rotates. The fluid that is displaced in the input side pump is directed into an output side pump which is carried on the output shaft. Reciprocating pistons of the output pump are hydraulically forced against an output side swash plate to effect rotation of the output shaft. A sleeve and lever assembly controls the stroke length of the pistons of the input pump in order to vary its fluid displacement relative to that of the output pump, thereby varying the transmission ratio.

Abstract: A manual regulator for power steering devices of automobiles comprising a valve assembly equipped with a rotary plug valve having a suitable channel and passages enabling selective free or predetermined restricted flow between the hydraulic pump and the steering mechanism, thereby to regulate the effort required of the driver to effect turning of the vehicle. This militates against oversteering and manually adjusts the effort required for the steering operation suitable to the individual driver. Manual adjustment requires only the turning of the valve and subsequent locking of the valve in the adjusted position.

Abstract: A portable earth boring machine for the boring of vertically inclined shafts and the insertion of pipeline casing sections characterized by a main frame portion that supports the auger drive and casing pusher apparatus, and a detachably mounted engine frame portion that permits the transmission of power between the engine and the auger drive and casing pusher apparatus not only when the engine frame portion is positioned on the main frame portion at the boring location but also when said engine frame portion is detached and positioned at a location remote from the main frame means. The machine is further characterized by a novel control means for the auger drive apparatus that provides for remote operation and hydraulically actuated variable speed control of the boring auger.

Abstract: A portable earth boring machine for the horizontal boring of shafts and the insertion of pipeline casing sections in installations where excavation from the surface is undesirable. The machine is characterized by frame means adapted for movement along a track means, which frame means supports an engine which drives an earth boring auger as well as casing pusher apparatus for pushing casing sections into the earth fill as the boring operation progresses. The machine is further characterized by a fluid actuated pusher cylinder means for advancing the auger into the earth fill and associated automatic auger feed control means for automatically maintaining a constant fluid flow rate to said pushing cylinder means under variations in resistance to auger penetration of said earth fill during a boring operation.

Abstract: A drive mechanism for a pair of forging or stretching rollers comprising a hydraulic system including a pump, a hydraulic motor and switching means interposed between a main drive motor and the rollers.

Abstract: An apparatus with a motor driven material removing tool for cutting, drilling, milling, sawing or grinding of concrete, stone or the like. The apparatus comprises three spaced apart operational groups, namely a working group, a vacuum source and control group, and a driving group. The groups are mobile and interconnectable and disconnectable by hoses and electrical cables. The working group comprises an interchangeable tool, such as a drill, drive motor means for driving and advancing the tool, and a tool holding device mounted on the outside of a rigid suction bell. The vacuum and control group includes vacuum producing means and electrical and fluid control units. The driving group has at least one hydraulic pressure pump with motor means for generating the hydraulic power for driving and advancing the tool.

Abstract: The hydrostatic transmission includes a main pump having a plurality of reciprocating pistons projecting into and biased towards a drive chamber and has both its inlet and its drive chamber connected to a substantially constant pressure charge circuit. Displacement of the pump is controlled by controlling the fluid flowing from the charge circuit to the inlet. The pump outlet is connected to the drive chamber through a combined safety and inching valve which normally blocks fluid flow therebetween but which is responsive to excess pressure at the pump outlet to open and increase the pressure in the drive chamber. The valve is also manually operable through a pedal on the vehicle which can be used to destroke the pump in emergency situations or to provide inching control.