Abstract: An object of the present invention is to provide a two dimensional drive system driven by fluid pressure. The drive system of the present invention comprises: a pair of X-guides; a pair of Y-guides; an X-rod whose each end is slidably attached to each Y-guide; a Y-rod whose each end is slidably attached to each X-guide; an X-piston section being provided at the midway of the X-rod; a Y-piston section being provided at the midway of the Y-rod; and a moving body having an X-chamber through which the X-rod is pierced and a Y-chamber through which the Y-rod is pierced, the X-chamber being divided into two subchambers by the X-piston section, the Y-chamber being divided into two subchambers by the Y-piston section. With this structure, the moving body is capable of moving in a plane by selectively supplying fluid to each subchamber.

Abstract: A method and an apparatus for conducting predetermined operations in the interior of a pipe with a cutter, in which the cutter is shifted so that a rotary axis of the cutter is angularly displaced about an axis extending along the pipe and is displaced in the axial direction of the pipe while the cutter is rotated about an axis extending in the axial direction of the pipe or about an axis extending in the radial direction of the pipe.

Abstract: An arrangement for converting linear motion from a power source to rotary motion, where the power source is intended to coact with a cam in a manner to produce rotary motion, this rotary motion being carried out by a shaft. The invention is characterized by a first member which comprises a rod-unit (4) or a corresponding element intended to move reciprocatingly, and the cam (2) which is attached to one end of the rod-unit, this cam having curve-shaped parts (20, 21) on solely the surface thereof remote from the rod-unit. A second member includes two mutually opposing wing-shaped parts (6, 7) which project outwardly away from the shaft and which are rigidly connected to the shaft (3). A roller (8, 9) or corresponding element is rotatably mounted on the outer part of each wing (6, 7). The rollers are intended to roll on the cam (2), therewith converting linear motion to rotary motion.

Abstract: A compact lightweight piston/cylinder assembly having a body provided with a plurality of adjacent chambers, each chamber having a piston reciprocally mounted therein. Each piston is secured to a piston guide member which reciprocally moves in the body with each of the pistons. One of the pistons serves as an output piston and is provided with a piston rod extending therefrom.

Abstract: An air-operated diaphragm spring brake (10) is provided with a mounting means (16) which permits adjustment of the position of the pneumatic ports (30, 32) on the brake with respect to the vehicle. The mounting means (16) comprises a plate (84) mounted to an end section (88) of a housing (82) overlying a central aperture (90). A pair of threaded mounting studs (96) are fixedly secured to the plate (84) for mounting the plate to the vehicle.

Abstract: Located in a stationary frame is a cylinder-piston unit, the piston of which is adapted to displace the bearing housing of a roll in a paper-making machine at right angles to the longitudinal axis thereof. The bearing housing is guided in the frame with the aid of linear guide-elements. The radial play between the piston and the cylinder-bore is greater than the transverse play between the said linear guide-elements. Furthermore, the axial length of the piston is less than the depth of the cylinder-bore. Whenever the cylinder-piston unit is relieved of its load, and the cylinder thus returns to its position of rest, it is centered in the cylinder-bore by means of a centering device.

Abstract: A device designed to actuate the positive clutches of gearbox sliding gears following synchronization of the respective pairs of gears. A cylinder mechanism is provided on each sliding plate of the gearbox, as well as solenoid valves which are controlled by an electronic calculator to select and actuate the cylinders. Each cylinder mechanism includes two oppositely acting pistons, each connected to the sliding plate, and each sliding in its own cylinder which also includes a return spring which operates against each piston and which practically eliminates the clearance above the piston as the piston is about to be acutated.

Abstract: A mechanism for converting linear displacement of a piston to angular displacement of a shaft by positioning a cam in a recess of a unitary piston which is adapted for positioning by differential fluid forces applied to opposite ends of the piston. To provide a linear displacement drive for a shaft positioned to rotate about an axis perpendicular to the axis of the piston, a cam profile consisting of two symmetrical, opposite and identical involutes is employed.

Abstract: A connecting rod for an internal-combustion, steam or the like, engine, having hydraulic means for converting the reciprocating motion of engine piston to the rotating motion of crankshaft. While producing the same torque on crankshaft, the hydraulic connecting rod enables the crankshaft throw to be shorter and, therefore, enables a decrease of the centrifugal force and inertia load produced by crankshaft rotating motion. Futhermore, the present invention enables a significant decrease of piston-ring friction and significantly reduces total engine friction. The present invention also yields significant decreases of centrifugal, inertia and friction loads resulting in a significant increase of total engine efficiency and power output.

Abstract: A steam engine, which comprises a crankcase frame (1) arranged so as to rest on a foundation, a steam cylinder (25) supported by the crankcase frame, a cylinder bore (28) in the steam cylinder, a reciprocating piston (45) in the cylinder bore (1), a connecting rod (50), connected at one end with the piston by means of a piston rod (46), steam valves on the cylinder, a crankshaft (56) with crank webs (57, 65) supporting a crank pin (63), for the other end of the connecting rod a crank pin (63), and in the crankcase a plurality of crankshaft bearings (8) allowing rotation of the crankshaft.

Abstract: A hydraulic cylinder comprising a hollow sleeve, having inserted in it, a hollow piston rod. The hollow sleeve further contains an opening allowing hydraulic fluid to pass therethrough and into the hollow piston rod. At the end remote to the opening, a mounting mechanism is contained. On the end proximate the mounting mechanism, a fluid outlet is contained. In use, hydraulic fluid passes through the opening of the hollow sleeve, into the piston rod, and out of the piston rod proximate the mounting mechanism.

Abstract: A linear hydraulic motor includes a piston rod of conventional steel carrying a fragible piston head movable in a cylinder, the head being designed to break away in the event the cylinder wall is punctured and deformed such that a portion of the cylinder wall becomes an obstacle in the path of the piston. Two or more such motors are frequently connected redundantly to one control surface such that if one motor is damaged, the other can continue to perform its function. The piston head is of a brittle metallic matrix material and includes a conventional seal groove formed on its cylindrical surface.

Abstract: The device has primary and secondary frame members interconnected by extensible and retractable positioning members connected by fluid circuits that cause extension of the member at either end of a circuit in response to retraction of the member at the other end of the circuit. Relative movements of the positioning members occur in response to the imposition of forces and moments at the projected center of compliance upon a pin or the like supported by the secondary frame member, and so adjust the position of the secondary frame member as to cause translatory and rotative movement of the supported pin.

Abstract: Device at such pneumatic cylinders where the piston is provided with a lateral carrier means (2) extending through a slot in the cylinder wall, said slot being sealed by means of a sealing band (3). On the outside of the cylinder (1) there is provided at least one undercut groove (4) extending along the cylinder and in parallel with its axis. A strip (6) corresponding to the length of the cylinder is further arranged to comprise at least two profiles (8) lying in a common plane, turned in opposite directions and having a cross-sectional form corresponding to that of the undercut groove (4).

Abstract: Disclosed herein is a slide cylinder basically consisting of a cylinder block internally defining a plural number of intercommunicating cylinder bores in parallel relation with each other, a piston and a piston rod fitted in each cylinder bore, and plate-like cross members integrally connecting the respective piston rods at the opposite ends thereof. The drive chambers defined by the pistons are communicated with fluid supply/discharge ports at the opposite ends of one of the piston rods and one of fluid supply/discharge ports provided in the cylinder block, permitting a diversity of piping modes by selective use of these ports. When installed upside down, it is possible to move either the cylinder block or cross plates whichever is desired. The slide cylinder can transfer loads accurately without involving rotational motion. Fixing of a piston against a piston rod is by means of caulking the ends of cylindrical portion of a piston at fixing grooves of a piston rod.

Abstract: A servoactuator unit to operate flight-control mechanisms, in particular for control of the position of the oscillating plate which adjusts the cyclic pitch and collective pitch of helicopter rotors, in which two pairs of hydraulic actuators are used, connected together in parallel, arranged with their axes parallel and close together like the diagonals of a quadrilateral, their rods connected together at their end and acting on the said oscillating plate and the cylinders also being connected together at the back. Each pair of actuators is powered, through a servovalve, by an independent hydraulic circuit so as to enable operation even in the event of one of the pairs breaking down, with symmetrical stress being placed on the pair of actuators during operation.

Abstract: A variable height column having a base, a midsection and an upper section. The base includes at least one upwardly extending guide shaft and the upper section includes at least one downwardly extending guide shaft. The midsection includes guide paths and bearings dimensioned for sliding engagement with the guide shaft. Hydraulic actuating means are provided to move the midsection vertically relative to the base and to move the upper section vertically relative to the midsection at the same rate to permit the uniform straightline extension and retraction of the column.

Abstract: A free piston machine comprising a mounting, an inner movable mechanism comprising a central cross-member and guided in translation so as to be able to move with an alternating motion along the axis of the mounting and an outer movable mechanism comprising two outer cross-members connected by at least one tie-rod. The mounting includes a base (10) and a header (11) connected by at least one central one-piece structure. The inner movable mechanism comprises four inner drive pistons movable along drive cylinders (15a-15b) arranged at the corners of a rectangle and two compressor pistons sliding in compressor cylinders (17a-17b) whose axles pass outside of said rectangle.

Abstract: Table couplings for coupling hydraulic actuators to large shaking tables, such as earthquake simulator tables are preloaded under gaseous pressure to permit the couplings to be nontension carrying couplings, which in turn permits use of hydrostatic slip bearings between the side surfaces and the bottom surface of the table and the actuators. The hydrostatic bearings in turn reduce the need for swivels, links and yokes that carry both tension and compression. The use of compression only loading such as that permitted with the present device, also reduces the problem of making a satisfactory table foundation, because only compression loads are carried to the foundation rather than alternating tension-compression loads.

Abstract: A pressure cylinder with a piston arranged in an inner chamber of a tubular casing has a second, also cylindrical inner chamber parallel to the first inner chamber and in which is slidingly guided an auxiliary piston. An extension of the auxiliary piston and an extension of the first piston in each case pass through the elongated slot in the casing wall, the two extensions of the two pistons being rigidly interconnected, preferably with the aid of a joint plate.

Abstract: A motor mount having first and second mounting surfaces with at least three mounting elements fixed therebetween is used to absorb motor vibration and shock impulses which are produced primarily parallel with the plane of the mounting surfaces. Two of the three mounting elements are dampers which flexibly connect the first mounting surface in a parallel relation with the second mounting surface. The third mounting element maintains a preferred range of distance separation between the mounting surfaces to that a damping flexion potential of the dampers is maintained.

Abstract: A porting and ducting arrangement for a pair of adjacent hollow cylinders includes respective pluralities of passages extending longitudinally in the walls of the cylinders. Each passage is provided with a port in communication with the interior of the associated cylinder. Plural recesses in the end of the cylinders or in a cover are each in communication with a separate passage or group of passages when the cover is applied to the cylinders. There are a pair of such recesses thereby associated with each cylinder and at least one recess of each pair is in communication with a recess of the other pair via duct means in the cover. Gasket means is retained between the cylinders and the cover to seal each recess of each pair of recesses with respect to the other recess of the pair.

Abstract: A force transmitting fluid actuator for use with a control device wherein an actuator member, movable within an actuator housing, actuates the control device due to the urging force of a plurality of pistons which can be selectively pressurized in unitary increments. The plurality of pistons are disposed within pressure chambers formed in the actuator housing in a symmetrical ring-shaped arrangement concentric to a single pressure chamber disposed on the vertical axis of the housing. A number of passageways interconnect the plurality of pressure chambers to form groupings of pressure chambers which act simultaneously in response to operation of a solenoid valve associated with each passageway. In addition to the symmetrical arrangement of the pressure chambers, the valve and passageway arrangement provide for a symmetric pressurization of the pressure chambers thereby resulting in a balanced force being exerted on the actuator.

Abstract: A ram-type valve assembly for well blowout prevention applications and the like. Opposing ram assemblies disposed in ram guideways transverse to the valve bore are each provided with two pistons extending outward of the valve housing having internal passages communicating with respective passages internal of the housing terminating in respective closing and opening ports. A cylinder assembly with interconnected cylindrical chambers is slidably disposed about respective pistons. Pressurizing the closing or opening ports transmits pressure through the pistons to the chambers, effecting cylinder assembly movement along the pistons inward toward and outward from the bore, respectively. Each cylinder assembly is interconnected to its respective ram, transmitting cylinder movement to the ram. The hydraulic circuits are isolated from the bore preventing hydraulic circuit contamination and accidental ram opening from bore pressure leaks into the hydraulics.

Abstract: A tandem brake master cylinder which includes a single inlet union having two inlet union portions which are connected to each other as a single, unitary body via a connecting portion, the connecting portion having at approximately a central portion thereof a mounting portion which projects toward a cylinder body and which has an insertion hole formed therein. The distance between each inlet union and a common mounting screw may be double that as compared with the distance between the inlet union and its associated mounting screw in conventional master cylinders and therefore the play of the inlet union portions may be greatly reduced.

Abstract: A multi-cylinder engine for a motor vehicle comprises at least two cylinders mounted in mutually displaced relationship with respect to longitudinal and transverse directions of the vehicle. The crankshaft for one of the cylinders is located at a higher level than the crankshaft for the other cylinder. A crankcase assembly of the engine is vertically divided into pieces by a plurality of planes extending perpendicular to the crankshafts and each plane passing through each center of the cylinders. The engine provides first and second gears mounted on the primary shaft, a crank gear for one of the crankshaft, a crank gear for the other crankshaft, and an idle gear. The first gear is in meshing engagement with the crank gear for one of the crankshaft, while the second gear is connected to the other crank gear through the idle gear.

Abstract: An improved jam-proof control including a cylinder-piston assembly in which the piston is controllably positioned within the cylinder to perform the control function and in which the cylinder snugly envelopes a deformable sleeve so that when the cylinder is deformed by sharp impact, the piston is permitted to continue to reciprocate within the cylinder due to the deformation, either due to frangibility or softness, of the sleeve.

Abstract: The safety device includes a self-closing cylindrical gate which, in closed position, blocks the hydraulic conduit surrounding the hydraulic turbomachine; the gate is housed, in the open position, in a chamber including two components near the hydraulic conduit defining wth the gate two orifices situated upstream and downstream with respect to the gate; pressure on top of the gate takes an intermediate value between the upstream and downstream pressures, and is determined by the ratio of the product of the discharge coefficient with the passage cross-section upstream orifice over the product of the discharge coefficient with the passage cross-section downstream orifice, so that a pressure is exerted on the upper edge of the gate, resulting in a force which tends to move the gate to close the hydraulic conduit.

Abstract: A forging manipulator has a mobile truck on which a gripper support is suspended by articulated linkages. To move the gripper support relative to the truck, and to provide cushioning of the gripper support, the gripper support is coupled to the truck by hydraulic cylinder assemblies. Each cylinder assembly includes three cylinders placed one above another with the piston of a middle cylinder connected to the truck and with the pistons of the outer cylinders connected to each other and to the gripper support.

Abstract: An opposed free piston tandem machine includes at least two drive piston-cylinder groups A and B and compressor cylinders and movable parts of this machine constitute two trains.The compressor cylinders of the outer movable train are arranged outside cross-pieces (23, 24) on which the drive pistons and outer compressors (3, 6, 15, 16, 17, 18) are fixed and which are joined together by linking rods (25, 26). The machine can include several drive units and several compressor units, and constitute an autogenerator of gas.

Abstract: A receptacle lift apparatus for a cotton harvester or other dumping vehicle including a linear hydraulic motor including a first rod and piston assembly attached to the receptacle and a second rod and piston assembly attached to the chassis and a floating cylindrical housing receiving the first piston in one end and the second piston in the other end being independent of the chassis and receptacle for axially unrestrained movement relative thereto.

Abstract: A percussive device for creating impact impulses, which device comprises a housing accommodating a striker. The striker has a tail portion located in a power cylinder which is joined to the housing and is filled with a fluid medium under pressure, said fluid medium operating the striker. Provision is made of an arresting mechanism which is kinematically connected to a drive designed to engage the striker for effecting its backward stroke in the process of which the fluid medium under pressure is compressed, storing potential energy. According to the invention, the striker backward stroke drive is constructed in the form of several hydraulic cylinders equidistantly spaced round the periphery of the housing. The rod of each of the hydraulic cylinders is connected to the striker arresting mechanism.

Abstract: An elevator lift system in which at least two connected hydraulic piston cylinder devices for controlling the vertical displacement of the lift platform above a lower level. One hydraulic cylinder includes a case connected to a second case and a piston slidably mounted within each case and movable in opposite directions. One of the hydraulic cylinders has a lift platform attached to its top end and the other hydraulic cylinder has its bottom end fixed to a base plate at a lower level. The hydraulic cylinders are connected to each other by the use of a housing which also encloses a control system which allows the rate of ascent or descent of both hydraulic cylinders to be equal. Multiple pairs of hydraulic cylinders are connectable to each other by way of a frame to reach additional heights and still allow the system to be lowered that the tops of all the cylinders are substantially flush.

Abstract: A basket lift apparatus for a cotton harvester including a pair of linear hydraulic motors having floating axially unrestrained housings is provided with a variable length guide tube assembly pivotally connected between the respective cylinder housings to prevent rotation thereof.

Abstract: A valve, comprising: a cylindrical casing, closed at its ends by covers, and having axially aligned inlet and outlet chambers midway of its length disposed at right angles to the axis of the casing. Communication between said chambers is controlled by a ported, fluid pressure operated, movable valve plate assembly, including parallel cylinders, each containing a stationary piston connected to the inner end of a pair of axially aligned rods, or guides, fixed at their outer end to the covers. Each rod has a passageway communicating at its inner end with one end of its associated cylinder for supplying operating fluid thereto to bodily reciprocate the valve plate assembly on said rods within the casing. An adjustable collar positions a fixed wear plate in sealing engagement with one side of the valve plate assembly, and a fluid pressure actuated loading ring urges a floating wear plate into contact with the other side of said valve plate assembly.

Abstract: A hydraulic manifold assembly includes a body (20) having an end face (28). Bolts (26) and a flange (22) are employed to mount the body (20) within a sealed chamber (14) in nominally aligned relation with an enlarged opening (30) from the chamber (14). External threads (50) adjacent the end face (28) extend through the opening (30) and a fluid conduit (32) terminates in a port (36) in the end face (28). A nut (52) is sized to cover the opening (30) for any position of nominal alignment of the body (20) to the opening (30) and is disposed on the threads (50) such that a side (64) of the nut covers the opening. A seal (62) is carried by the nut for sealing the interface of the nut (52) and a side (10) of the chamber (14).

Abstract: A system for damping abrupt movement of a punch press ram at the moment of cut-breakthrough with the use of at least two damping pistons disposed within cylinders and arranged to engage the press ram before and during cut-breakthrough. The cylinders within which the damping pistons are carried are connected to a hydraulic control system which permits the pistons to yield with the ram until the instant of cut-breakthrough, whereupon the damping pistons act as rigid bodies and prevent abrupt breakthrough movement of the ram.

Abstract: A ballistic tolerant control actuator of the hydraulic cylinder-piston type and having a hybrid housing comprising a structural outer wall of selected characteristics and wall thickness "t", a central sleeve snuggly fitted within the outer wall and being of selected characteristics and selected wall thickness so that when the outer wall is impacted and/or penetrated by a projectile of diameter D, impact induced stress waves from the outer wall pass into the central sleeve with sufficient intensity to locally disintegrate and clear the central sleeve in the vicinity of the projectile impact, and so that the petals formed in the outer wall will not project farther radially inwardly than the petals which would be formed in the most critical case by a projectile whose diameter D produced the ratio t/D=1/3.

Abstract: An oil well pump which uses a pair of vertical hydraulic pistons to raise a cross beam. The polish rod is secured to the cross beam. At the top of the stroke automatic limit switches reverse the hydraulic fluid flow to allow the polish rod to descend and complete the pumping cycle.

Abstract: An improved jam-proof control including a cylinder-piston assembly in which the piston is controllably positioned within the cylinder to perform the control function and in which the piston rod which extends through the cylinder wall is enveloped by a deformable sleeve so that when the piston rod is deformed by sharp impact, the piston rod is permitted to continue to reciprocate within the housing due to the deformation, either due to frangibility or softness, of the piston rod sleeve.

Abstract: A hot gas engine of the Stirling type having a cylinder and associated piston, piston rod and cross-head, wherein the seals for the cylinder and piston rod are carried in a seal assembly unit clamped between separable engine housing parts. The seal assembly unit includes a guide for the cross-head.

Abstract: A large mobile self-propelled excavator machine comprises an upper section on which a plurality of movable components, such as a boom, stick, and shovel, are mounted. A plurality of self-contained independently operable electrohydraulic power units are provided, one for each movable component, and each power unit comprises a housing, a pair of hydraulic rams mounted on the housing, means for pivotally connecting the housing and the ram piston rods to their associated components, a fluid reservoir in the housing, a reversible main pump in the reservoir for supplying the rams, auxiliary pumps on the housing, an electric motor on the housing for driving the pumps, and solenoid valve control means on the main pump. Each power unit is supplied with electric power for its electric motor by a cable from a generator on the upper section of the excavator machine.

Abstract: A control and actuator system for a press brake having a frame, a bed, a ram, and a pair of hydraulic cylinders for reciprocating the ram, utilizes a jackscrew arrangement in conjunction with positive mechanical stops on the ram pistons to support the ram beneath the cylinders to enable the bottom travel limit of the ram to be preset. The top travel limit of the ram is preset by means of vertically adjustable actuator rods on the ram, which engage actuator stems on valves associated with each cylinder to stop upward travel and hold the ram in position. Tilt compensation is provided at the top and bottom ram limits by independent adjustment of the jackscrews and actuator rods, obviating the need for a complex tape and pulley driven differential valve arrangement. The novel hydraulic circuit provided for powering the cylinders utilizes pilot-driven control valves, and provides for direct venting of the system high-volume hydraulic pump when not in use to maximize system efficiency.

Abstract: A pressure fluid operated feed drive system for a movable member, and particularly for a slide of a machine tool, the system having a source of fluid pressure feeding a pair of interconnected piston and cylinder units connected between the member and a fixed support. The piston rod side areas of the pistons are arranged in effective opposition and valve means are provided to permit pressure fluid to be supplied selectively to the units to enable the member to be moved alternatively by a force derived from differing piston areas.

Abstract: A device for controlling hydraulic motors as in an aircraft "fly-by-wire" system wherein redundant hydraulic motors and controls are required to protect against failure of portions of the system or device. The device includes two master valves for controlling flow of fluid to and from the motors, one controlled by electrical signals from a command station and the other controlled mechanically through manual or automatic operation. There is a transfer valve for selecting which of the master valves is to be operable and to provide for smooth transition of control from the electrically controlled valve to the mechanically controlled valve.

Abstract: An actuator, and a system employing the same, which will continue to operate after deformation of a portion thereof which deformation would normally restrict movement between the piston and cylinder of the actuator. The piston or gland of the actuator is constructed so as to include segmented flanges which will fracture responsive to forces applied to them upon engagement of the deformation. Slots defining the segments are filled with a rubber-like material which is bonded to the piston or gland thus providing a solid structure to enable appropriate sealing while not interfering with the fracturability of the segments.

Abstract: A two-axis positioning servoactuator includes a support, a movable member arranged adjacent the support for independent pivotal movement relative thereto about each of two perpendicular intersecting axes, a pair of differential piston and cylinder actuators operatively interposed between the support and movable member for effecting such angular movement about each of the axes, an electrohydraulic servovalve for each of the actuators and operatively associated therewith to control the same, and means providing a position feedback signal to the corresponding servovalve for effecting controlled movement of the member about each of the axes.

Abstract: A working cylinder for pneumatic or hydraulic pressure media has a piston reciprocable in a cylinder chamber closed at one end. The cylinder and the piston have polygonal cross-sections. The end of the cylinder may be closed by a cylinder cap secured in place by bolts passing through it and threaded in the ends of the cylinder. Polygonal seals are provided between the cylinder caps and the piston and the interior walls of the cylinder. Two opposed walls of the cylinder may be thicker than the outer walls, and provided with through holes for attachment means.

Abstract: A machine drive mechanism between a power unit and an energy absorbing unit, such as a compressor unit. The power unit may be connected to a crosshead carrying a pair of spaced and inwardly facing racks or to a double rack member and the compressor unit may be connected to one end of a piston-like guide and seal member which, in turn, is pivotally connected to one end of the double rack or the pair of spaced racks. The double rack extends between a pair of pinion gears mounted on fixed shafts and operably engaging the spaced racks and the double rack. When the power unit is directly connected to the energy absorbing device, the spaced racks merely serve as counterbalancing means. The power unit may also be connected by a relatively long unpivoted shaft to the energy absorbing unit either directly or through the racks by a connection providing transverse flexing movement between the double rack and the shaft.

Abstract: An improved structural arrangement for mechanically and hydraulically interconnecting a cluster of three hydraulic cylinders of the hydraulic jacks associated with the load carriage elevating and mast structure elevating functions of a forklift truck. The clustered cylinders include a centrally located "secondary" cylinder and two oppositely disposed "primary" cylinders symmetrically positioned contiguous to the centrally located secondary cylinder. Each cylinder has a corresponding attachment block rigidly secured thereto, each attachment block being provided with a hydraulic passage therethrough which communicates with an aligned hydraulic passage through the wall of its corresponding cylinder.