Abstract: A linear actuator system has a rotary spool valve configuration having a spool, a piston, and a cylinder. The spool and piston have return apertures so positioned, configured and angled to direct return flow towards the center of a spool central return port and spool pressure ports to direct pressurized flow into upper or lower chambers. Rotation of the spool synchronizes and aligns ports and apertures to reverse flows and effect upward and downward translation of the cylinder to vibrationally drive an implement to perform work. The positioned and angled apertures direct the fluid to a region demarcated by a total length of 1.5 times the interior diameter of the spool central return port centered about a piston shoulder. A base plug member having a bull-nose tip, baffles and cavities is disposed within the spool central return port to reduce or eliminate cavitation.

Abstract: A servo valve includes a fluid transfer valve assembly comprising a supply port and a control port; a valve spool arranged to regulate flow of fluid from the supply port to the control port in response to a control signal; and a drive means configured to move the valve spool relative to the fluid transfer assembly in response to the control signal to regulate the fluid flow. The drive means is arranged to rotate the spool relative to the fluid transfer assembly, the spool provided with openings arranged to selectively align with or block flow channels in the fluid transfer assembly according to the direction and degree of rotation of the spool.

Abstract: A hydraulic vibration generation device is provided. The device includes a manifold member having an inner volume, a fluid inlet orifice and a fluid outlet orifice. The device further includes a vibration generating member having a channel grooved drive and an off-center weight, and bearing retaining plates. The inner volume receives the vibration generating member within the inner volume. The bearing retaining plate that retain bearings operate to retain the vibration generating member within the inner volume in response to coupling the bearing retaining plate to the manifold member wherein two bearings on opposing ends of the vibration generating member are retained within recesses of the bearing retaining plates. The vibration generating member rotates and generates vibration in response to hydraulic fluid flowing into the manifold member through the inlet orifice and out of the manifold member through the outlet orifice.

Abstract: Hammering device functioning with pressure fluid of a hydraulic arrangement which hammering device comprises a body (16), (19) which can be attached to a working machine on which machine a hammering mass (3) is adjusted to be resting and to be moving which hammering mass is moved into a hammering position with the help of hydraulic pressure by directing the pressurized fluid into the ring-shaped, first chamber space (6) wherein the hammering mass (3) when it is moving into a hammering position compresses gas in the chamber space (K1) located at the first side of the hammering mass (3) and in order to perform the hammering movement with the hammering mass (3) to the hammering element (5), (27) the flow of hydraulic pressure is blocked to the first chamber space (6) and the access for pressure fluid is allowed away from the first chamber space (6) with the help of the valve (2).

Abstract: An analyzer with a combustion furnace includes a flow path of byproducts of combustion coupled to a bidirectional ballast chamber by valves which are sequentially actuated for alternately filling and exhausting byproducts of combustion from opposite sides of the chamber during combustion. Alternately, a plurality of low volume ballast chambers are employed. A method of determining the concentration of elements in a sample includes the steps of combusting a sample; and alternately collecting and exhausting the byproduct gases of combustion in opposite sides of a bidirectional ballast. The bidirectional ballast chamber has an outer wall defining a chamber with sealed enclosures at opposite ends of the wall, a movable piston positioned within the chamber, and gas ports associated with the chamber on opposite sides of the piston.

Abstract: A compressed fluid motor comprising at least one solenoid valve, motor timing sensor, and controller for operating the motor.

Abstract: A pneumatic impact tool and method includes a cylinder pipe or housing closed with a cover, as well as an impact piston that forms a first pressure chamber between an impact plate and the impact piston, and a second pressure chamber between the cover and the impact piston. The cover is provided with at least one opening, the surface of which is smaller than the piston surface, whereby the impact piston seals the opening when it is in its fully retracted position.

Abstract: A high-pressure valve assembly having a valve body that defines a preferably cylindrical valve cavity, a fluid inlet, a fluid outlet and a plurality of valve ports; and a fluid pressure intensifier assembly having a plurality of piston-plunger assemblies and utilizing the high-pressure valve assembly to distribute the working fluid. The valve assemblies have a valve rotor rotatably mounted within the valve cavity. In one embodiment, the valve rotor divides the valve cavity into a high-pressure region in communication with the fluid inlet and a low-pressure region in communication with the fluid outlet. As the valve rotor rotates, at least one and preferably three or more valve ports communicate with the power chamber and at least one and preferably three or more valve ports communicate with the discharge chamber.

Abstract: A multicylinder, double acting improved mud pump is disclosed. The preferred embodiment incorporates a hydraulic powered piston in a cylinder which connects with a piston rod which, in turn, drives a second piston in a cylinder adapted to pump fluid mud. The first piston is driven by hydraulic oil delivered under pressure to intake manifolds through an independently driven valving apparatus which times the delivery of the hydraulic fluid for the main power stroke and further times the discharge of the hydraulic fluid for the return secondary power stroke, the system being controlled independently of piston action in timing of multiple pistons in multiple cylinders by the valve system. Additionally an intake valve delivers fluid mud at lower pressure on the intake side of the mud compression piston, and an outlet valve transverses with the piston rod to direct the outlet mud flow.

Abstract: A rotary servo valve includes a valve body having a longitudinal bore therethrough. A sleeve fits into the bore. The wall of the sleeve is perforated by two groups of port openings, each group includes a plurality of sets of radially-disposed ports. In each group, the central longitudinal axis of one set of ports is radially displaced from the central longitudinal axis of one other set of ports by a preselected angular displacement. At least a third set of ports in one group is in continuous fluid communication with a source of pressurized fluid; at least a third set of ports in the other group in continuous fluid communication with a return sump. A hollow rotary control member consists of two internal chambers. Each chamber includes a number of sets of apertures that are radially disposed around the walls of the chambers, spaced-apart by a preselected angular separation.

Abstract: A pneumatic cushion for a wheel chair and the like is disclosed which comprises an air plenum box, a plurality of air openings in the air plenum box, and a plurality of air channels communicating with an air supply. The air channels communicate with the air openings to deflate and inflate individual air sacks carried over the air openings. The air sacks are unattached so that they act individually. An air distribution manifold includes a rotating blocking member to periodically block air distribution to the air sacks allowing them to deflate. The air sacks are constructed from a fabric having a low air permeability. The blocked air sacks thus allow air to escape through the sacks for deflation which cools the portion of the occupant seated on the cushion while allowing temporary pressure relief during deflation. The air sack inflation system is open so that, in addition, pressure may be relieved by a backward flow of air through the system.

Abstract: A vibration generator including an inertial body and a housing which are relatively movable and where hydraulic fluid is directed into the inertial body through a control valve mounted in the inertial body, the fluid being directed alternately into one or another working chamber which causes oscillation of the housing and any attached load. A wave form shape of pressure or flow rate of the hydraulic fluid flow is detected and used to control the frequency at which the vibration generator oscillates so that the frequency is maintained at a resonant frequency. The device has particular application in a frequency range of 20 Hertz to 1000 Hertz.

Abstract: A compactor includes a longitudinally extending ground supported frame having an open end and a closed end. A cylinder and piston assembly is positioned within the frame and extends longitudinally therealong and a ram is secured to the piston for transferring waste through the open end. The cylinder has fluid ports at opposite ends thereof. An hydraulic fluid supply assembly introduces pressurized fluid to said ports for causing selective movement of the piston relative to the cylinder. An hydraulic spool valve is carried by the piston for permitting fluid to flow between the ports and for thereby preventing displacement of the piston when the dwell assembly engages one of the ends.

Abstract: The present invention provides a pump assembly which is used to control the amount of extension and flexion of an inflatable pouch which is used to exercise the fingers, hand, or other limb of a patient. A diaphragm pump is provided together with a rotatable cycling valve and a metering control valve to supply air to the diaphragm pump and to cyclically inflate and deflate the pouch upon which a patient's hand is positioned. Manual overrides are provided to inflate and deflate the pouch to a desired degree, dependent upon the position of the hand of the patient as well as the amount of flexion and extension desired and which the patient is capable of. A method of cyclically inflating and deflating the pouch is also provided.

Abstract: An impact tool for linearly accelerating a mass such as in a jack hammer. The tool includes first and second members respectively mounted in sealing relationships in first and second outlets of a chamber. The chamber is initially pressurized with a first quantity of gas which remains constant during the normal operation of the tool. To begin a cycle, the first member is moved toward the second member to sealingly engage the end portions thereof and entrap a first volume of gas therebetween. The volume of the entrapped gas is then reduced by continuing to move the first member. This raises the pressure of the entrapped gas and opens a one-way check valve to place the entrapped gas in fluid communication with the gas in the surrounding chamber. Forward movement of the first member is then stopped which again seats the check valve wherein movement of the first member is reversed so that it moves away from the second member.

Abstract: An oscillator is proposed which comprises a pair of cylinders having a common, circular-cylindrical outer wall (100) and two sealingly guided pistons (120, 122) each having one piston rod (121, 123), which are likewise guided in a sealing manner to the outside through the closure walls of the cylinder. The cylinder is divided by the pistons (120, 122) into outer chambers (124, 125) and inner chambers combined into one common chamber (126). The chamber (126) is filled with fluid. The outer chambers (124, 125) have two openings (102, 103) offset from one another by 180.degree.. A control cylinder (101) having axially offset, oppositely disposed holes (104, 105, 106, 107) connects the outer chambers in alternation with an annular high-pressure chamber (113, 115) and an equalization chamber (114) whenever the control cylinder (101) is rotated. The two pistons (120, 122) thereby execute movements in common toward the left or right, respectively.

Abstract: A multicylinder, hydraulic driven, dual arranged mud pump is disclosed. The preferred embodiment consist of dual mud pumping units arranged to be selectively operated as individual pumps, as two pumps whose output flow is in parallel, or as two pumps whose output flow is in series. Each mud pumping unit is comprised of plural pumping assemblies with each assembly consisting of a pair of separate end to end cylinders, one cylinder being arranged to be driven by a second cylinder with the one cylinder further being arranged to pump mud and the second cylinder being arranged to be reciprocally driven in a sequential manner by pressurized hydraulic fluid.

Abstract: This invention pertains to a hydraulic reciprocating device having a housing and a piston in the housing. The piston has a first and second surface, and a means for intermittently communicating the first surface of the piston with a hydraulic pressure source. Also provided is a means for continuously communicating the second surface of the piston with pressurized fluid such as pneumatic fluid. The piston moves in a first direction when the hydraulic pressure source communicates with the first surface of the piston and the piston moves in a second direction when the hydraulic pressure source does not communicate with the first surface of the piston.

Abstract: A rotor (23) is mounted for rotation in a housing (10) having a pressure chamber (31) and an exhaust chamber (33) formed about the rotor. The rotor is provided with slots (36 and 37) which are moved sequentially in pairs into alignment with plungers (48 and 68). When a plunger (48) partially overlays a slot (36), pressurized air passes from chamber (32), through an exposed portion of a slot (36), through plungers openings (49, 44, and 43) to one end of an air cylinder (12) while exhaust atmospheric pressure is presented from chamber (33), through an exposed portion of a slot (37), through a plunger openings (71, 67, 64, and 63) to the opposite end of the air cylinder (12) to permit movement of a piston (83) to drive some external mechanism.

Abstract: A multicylinder, double acting improved mud pump is disclosed, the preferred embodiment incorporates a hydraulic powered piston in a cylinder which connects with a piston rod which, in turn, drives a second piston in a cylinder adopted to pump fluid mud. The first piston is driven by hydraulic oil delivered under pressure to intake manifolds through an independently driven valving apparatus which times the delivery of the hydraulic fluid for the main power stroke and further times the discharge of the hydraulic fluid for the return secondary power stroke, the system being controlled independently of piston action in timing of multiple pistons in multiple cylinders by the valve system. Additionally an intake valve delivers fluid mud at lower pressure on the intake side of the mud compression piston, and an outlet valve traverses with the piston rod to direct the outlet mud flow.

Abstract: A method of controlling the revolution of the drive shaft of an external combustion engine comprises shaping a control signal for a switching member and converting said signal to mechanical movement of an actuating member. The control signal is shaped in the form of symmetric, periodic sustained vibrations of variable sign, the time intervals of positive and negative values of said vibrations being of equal duration, and the frequency of said vibrations is set equal to a preset number of drive shaft revolutions. The variation of said movement corresponds in time to variation of the control signal, an instantaneous value of the control signal is varied in proportion to the variation of load on the drive shaft, and the actuating member movement is converted to revolution of the engine drive shaft.

Abstract: A control system for a superhigh pressure generation circuit includes a hydraulic pump having a usual range of delivery pressure. An electrohydraulic servo valve controls the flow rate of pressurized fluid from the pump and supplies it to a primary side of a boost cylinder. A stepped piston slidably received in the boost cylinder strokes in response to the input fluid to generate a fluid pressure elevated in accordance with an effective sectional area ratio of the stepped piston in a secondary side of the boost cylinder. The fluid pressure in the secondary side is caused to coincide accurately with a reference pressure level on the basis of a feedback control.

Abstract: An electronically controlled apparatus for controllably positioning pneumatic actuators includes, in a first embodiment, first means for selectively flowing compressed fluid to the actuator and valve means for selectively exhausting compressed fluid from the actuator. An electronic control panel is adapted to receive digital command signals from a computerized controller and is coupled to the first means and to the valve means for actuation thereof in response to the command signals. Means are included for isolating electrical switching transients from the controller.In a second preferred embodiment, the positioner also includes transducer means for generating a feedback signal representative of the position of the actuator piston assembly. A third preferred embodiment is similar to that of the second embodiment and incorporates a control adapted to receive analog rather than digital command signals. An optional high limit pressure switch may be used with any embodiment.

Abstract: A power stage servo valve for a seismic vibrator includes a stationary orifice plate defining a plurality of valve ports having a first shape. A rotary orifice plate, abutting the stationary orifice plate, defines a like plurality of valve ports that have a shape different from the valve ports in the stationary orifice plate. The configuration and shape of the rotary valve ports is such that the valve opens more quickly than it shuts off when the plate is rotating continuously in one direction at a desired angular velocity.

Abstract: An apparatus for converting pressure into motion includes a housing having a plurality of ports formed therein. Movably disposed within the housing is a piston having a first plurality of apertures communicating with a first chamber and a second plurality of apertures communicating with a second chamber therein. The piston is positioned within the housing so that the apertures can register with consecutive ones of the ports as the piston is moved in either of two directions within the housing. The movable member is moved by a pressurizing substance applied to a selectable one of the ports through an appropriate valve circuit. The valve circuit is operated by excitation signals from a control member. By operating the valve circuit in an appropriate sequence, the pressurizing substance is sequentially applied to consecutive ones of the ports to move the piston longitudinally through the housing.

Abstract: Apparatus for the continuous adjustment of the stroke amplitude of the piston of a jack, the latter having a control member of which at least part is in the form of a rod, which is movable in rotation and in translation and cooperates with the said piston, wherein said rod has an extension in the form of a differential piston which is movable in translation and in rotation within a cylinder and defining also in the latter a chamber with a large cross-section and a chamber with a small cross-section, the latter being permanently connected to a pressurized fluid source, said differential piston having an inner cavity in which is located a second rod immobilized in translation and which can be angularly oriented, said second rod being provided with a cam having two opposite edges which can cyclically uncover and cover, during the rotation of the differential piston, at least two openings respectively connected to the two chambers.

Abstract: Apparatus for incremental cylinder length control in hydraulic seismic vibrators having increased frequency range. The vibrator apparatus (10) of the type having a reaction mass (38) and axial cylinder bore (42) utilizes hydraulically movable end sleeves (86 and 96) in each end of the cylinder bore (42) so that the end sleeves (86 and 96) can be controllably positioned thereby to alter the cylinder volume and adjust the hydraulic drive system (18) for maximum efficiency relative to operating frequency.

Abstract: An improvement in a reciprocating engine used in an energy recovery system wherein the inlet valves to the cylinders of the engine are operated by independently time adjustable actuating means.The system for recovering energy from a pressured reactor comprising a reactor, a reciprocating engine connected to the reactor to receive reaction effluent from said reactor thereby driving the pistons of the reciprocating engine by expansion of the effluent and recovery apparatus downstream of the engine for recovering products from the effluent.The expanding reactor effluent is used to drive the pistons which are especially valved in conjunction with the effluent inlet port in the cylinder to facilitate handling the effluents to adjust the flow into an expansion chamber to obtain maximum recovery, the pistons in turn operate a crankshaft through a crosshead which may power compressors or operate a generator to produce electricity.

Abstract: A pumping unit pumps two wells, simultaneously, to save energy and space, weight of one rod string offsetting weight of the other string.

Abstract: A hydraulic cylinder for generating vibrations which comprises: a cylinder body; a hollow piston rotatably mounted in said cylinder body; and a valve rotor rotatably engaged within said hollow piston, said valve rotor having a change-over valve portion adapted to be rotated for applying hydraulic loads to said piston alternately in axially opposite directions.

Abstract: A hydraulic vibrator for moving a ramming or drawing body or the like has a hydraulic working cylinder, a double-acting working piston axially movable in the hydraulic working cylinder, and a device for supplying a working medium into the hydraulic working cylinder, alternately at both axial sides of the working piston so that the working piston vibrates with selectively variable frequency and displaces the ramming and drawing body or the like.

Abstract: Two fluid passages are connected through flow restrictors to a fluid supply. Downstream of the restrictors the fluid supply has a drooping pressure-load characteristic. Venting means for the fluid passages comprises vent openings therein downstream of the restrictors and variable position obstructor means cooperating with vent openings to vary venting and thereby vary fluid pressures in the fluid passages.Fluid conduits connect these pressure outputs to a double acting piston moving in a cylinder whose opposite ends are connected to the fluid conduits. The piston and cylinder form the responder of the system.A receiver is formed by a piston and cylinder or other fluidic motor remotely fluidically connected to the responder, the motor driving a load.A feedback means controlled by the position of the responder piston and/or the load varies pressure in the fluid conduits by variably venting same.

Abstract: A control device is designed for center pivot irrigation units of the type having an elongate water carrying pipe with a plurality of support vehicles spaced therealong, and wherein each of the vehicles includes a double acting hydraulic cylinder mounted thereon for moving the vehicle and the water pipe over the ground. The irrigation unit includes a device for aligning the vehicles, a hydraulic pump with pressure and return lines, and power and retract manifolds respectively interconnecting power and retract sides of the cylinders. The control device includes a hydraulic valve with three positions which communicate the pressure line with the power manifold, the retract manifold, and the pump return line respectively.

Abstract: A synchronizer is provided for synchronizing the movements of two hydraulic actuators. The synchronizer consists of a two-piston pump which supplies hydraulic fluid to both actuators. The two pistons are mechanically connected so as to move simultaneously through equal distances, and on each complete stroke of the pump, each actuator receives fluid from both cylinders of the pump, so that both actuators receive precisely equal amounts of fluid.

Abstract: A hydraulically operated vibration exciter for a vibrating compactor of the kind comprising a piston in a cylinder, the piston and cylinder being arranged to move to and fro relative to each other, a source of liquid under pressure, a pressure line connecting the source to the cylinder and means for causing the liquid to move to and fro between the source and the cylinder to bring about the relative movement between the piston and cylinder is cooled by a method in which, during the relative movement, a quantity of the liquid is withdrawn from the cylinder and this quantity is not returned to the cylinder in the subsequent stroke, but is replaced by a fresh quantity of liquid at a lower temperature.

Abstract: A vibration motor comprising a rotor arranged within a cylindrical chamber having opposed radially arranged reciprocating pistons within cylinders opening into the chamber. Circumferential grooves formed in the rotor surface sequentially open the cylinders to a pressurized fluid outlet passageway, to move each piston outwardly, and to a fluid exit passageway to drain the cylinders for inward movement of the pistons. The pistons are axially aligned with and coupled to each other for producing rapid, low amplitude beam vibration. This is a division of application Ser. No. 898,905, filed Apr. 24, 1978, now U.S. Pat. No. 4,154,641.

Abstract: An apparatus providing for the generation, control and application of power to a cyclic functioning machine, using fluids under pressure to transmit and control energy by means of a rotary, segmented cam wheel. The cam wheel provides a plurality of interchangeable segments formed into a rim portion with axially spaced complementary counteracting cam faces formed about opposite rim ends. An individual cam follower, carried on a piston rod of a related hydraulic cylinder, coacts with each of the cam faces to accurately regulate the flow of hydraulic fluid to and from a working cylinder of a machine to provide timed and synchronized machine functions through the control movement of the working cylinder. The contoured configuration of the cam faces are arranged to provide for a desired acceleration and retardation of machine motions. Further, variable speed drive means, employed to drive the cam wheel, provides a timing adjustment between machine cycles.

Abstract: A system for porting of hydraulic fluid in a hydraulically driven seismic energy vibrator of the reciprocating mass type. A mass is reciprocated relative to an earth contacting frame which includes at least two hydraulic piston rods coacting with internal cylinders within the mass. The piston rods, of the type having double rod ends, each include a single axial bore therethrough in communication with respective opposite sides of the piston ring assemblies, and cross porting is effected between opposite ends of the mass cylinders.

Abstract: A hydro-mechanically operated reciprocating spindle for a machine tool is disclosed in the environment of a vertical gear shaper. The spindle comprises a piston which is slidable in a cylinder and which carries a cutting tool at its bottom end. The spindle-piston has two faces of different area to which hydraulic fluid under pressure is directed, the larger area face being used to drive the spindle downwardly in the cutting stroke, and the smaller area face being used to drive the spindle upwardly in the return stroke. Further, the spindle-piston has an axial bore which receives a vertically reciprocable valve. The valve is reciprocated by linkages driven by a rotating shaft, and the arrangement is such as to drive the valve downwardly and thus to move the spindle downwardly at a controlled velocity and under a controlled hydraulic force, and then as the valve is moved upwardly the spindle is moved upwardly on the return stroke at preferably a higher velocity.

Abstract: Device for a hydraulically driven percussion hammer for activating a tool, comprising a differential piston with corresponding cylinder, where the piston's largest surface is closest to the percussion tool, and where the smallest working surface is in direct hydraulic connection with an air tank. The largest working surface is above a multiple valve in connection with a hydraulic pressure medium. The valve is adjustable from an admission position with closed return duct to a position where the admission is blocked and the return duct is open. The piston chamber above the piston's small working surface has a feed duct with back pressure valve for a hydraulic pressure medium.

Abstract: Apparatus is presented for the precision control of an output signal in accordance with an input signal. The output signal is the output of a hydraulic motor, the output of which is compared to an electrical input signal in a geared differential comparator, the output of the comparator operating a distributor supplying the hydraulic motor.

Abstract: Opposed pivotally mounted tamper arms are oscillated by respective single-acting hyraulic piston assemblies controlled by separate hydraulic duplex rotary distributing valves. Fluid supply and return lines for each piston assembly are connected to a source of pressurized hydraulic fluid via the respective rotary valve. Each valve has a stationary ported shell which receives a rotary cylindrical spool having a pair of axially displaced supply and return throughports which alternately register with supply and return line ports in the shell to open and close the connections between the respective piston assembly and the supply and return lines. While the rotary valves are preferably driven by a common drive unit, the relative phase of the oscillations of the arms can be determined by rotationally offsetting one of the spools with respect to the other by the desired phase angle.

Abstract: A springless impact device including a piston-cylinder mechanism having at least one preselected coacting port and passageway operatively connected to a valve pressurized fluid control apparatus which selectively feeds and exhausts pressurized fluid to and from the device in a predetermined manner. There is an area differential between the top and bottom ends of the piston head. The device includes an inverted "U"-shaped seal ring on the piston head which functions as a one-way check valve to effect piston reciprocation in coaction with the area differential on the piston head.

Abstract: This disclosure relates to an improved electro-hydraulic pulse motor wherein safety valves are arranged in hydraulic circuits provided for the hydraulic motor part of an electro-hydraulic pulse motor so as to release abnormal high pressure produced in the circuits due to sudden interruption of the operation of an electric pulse motor part of the electro-hydraulic pulse motor. As a result, breakage of the circuits or four way pilot valve part of the electro-hydraulic pulse motor can be avoided.

Abstract: A gun of the kind in which liquid propellant is burned in the firing chamber to fire a projectile from the gun is constructed so that a number of gun modules can be combined in a modular gun. Each gun module is cam controlled, and a common cam is used to control each gun module in the modular gun. The cam can be a flexible cam having a belt configuration to permit the gun modules to be arranged in both circular groupings and in non-circular groupings, such as side by side. The modular gun includes fixed, non-rotating gun modules to eliminate the need for tangential velocity correction factors in the fire control and the need to accelerate the mass of the barrel assembly to operational speed. The individual gun module includes propellant injection mechanism for injecting propellant at high pressure when a non-hypergolic bi-propellant is used as the propellant. One or more hydraulic actuators are used to develop the high injection pressures and to operate other components of the gun, such as the bolt.

Abstract: What follows is a description of a hydraulically powered actuator for producing a reciprocating output and a method which produces a reciprocating output in response to the controlled flow of a hydraulic fluid. The hydraulic actuator includes, in one embodiment, a cylinder within which a piston assembly is reciprocated, the cylinder being itself displaceably mounted within a housing so that it can periodically introduce a unique flow passage through which a rapid fluid flow occurs, the provision of the passage reduces the hydraulic power lost during reciprocating movement of the piston assembly and ensures a high energy output.

Abstract: Apparatus for incremental cylinder length control in hydraulic seismic vibrators having increased frequency range. The vibrator apparatus (10) of the type having a reaction mass (38) and axial cylinder bore (42) utilizes hydraulically movable end sleeves (86 and 96) in each end of the cylinder bore (42) so that the end sleeves (86 and 96) can be controllably positioned thereby to alter the cylinder volume and adjust the hydraulic drive system (18) for maximum efficiency relative to operating frequency.