Abstract: A hydraulic synchronizing circuit includes at least one master cylinder unit including a primary chamber, a secondary chamber, a piston and at least one piston rod, the piston having a primary effective surface and a secondary effective surface. The hydraulic synchronizing circuit further includes at least one slave cylinder unit including a primary chamber, a secondary chamber, a piston and at least one piston rod, the piston having a primary effective surface and a secondary effective surface. The master cylinder unit and the slave cylinder unit are arranged to be single-acting. The secondary effective surface of the master cylinder unit and the primary effective surface of the slave cylinder unit are substantially equal. A tank at least partially formed by the secondary chamber of the slave cylinder unit and containing a fluid is provided. A pump sucks the fluid from the tank. A first conduit operatively connects the tank to the primary chamber of the master cylinder unit via the pump.

Abstract: Three tandem drive units are provided. Outward variable volume working chambers at one end of the drive units are connected via passageways in the piston rods with inward variable volume working chambers at the opposite end of the drive units. In similar fashion, inward variable volume working chambers at the first ends of the drive units are connected to outward variable volume working chambers at the second ends of the drive units, also via passageways in the piston rods. At each end of the assembly, the piston rods pass through piston rod receiving openings in a cylinder head forming member. Each cylinder head forming member includes a manifold passageway and spool valves for controlling a sequencing movement of the drive units. The piston rods provide the spools for the spool valves.

Abstract: Three tandem drive units are provided. Outward variable volume working chambers at one end of the drive units are connected via passageways in the piston rods with inward variable volume working chambers at the opposite end of the drive units. In similar fashion, inward variable volume working chambers at the first ends of the drive units are connected to outward variable volume working chambers at the second ends of the drive units, also via passageways in the piston rods. At each end of the assembly, the piston rods pass through piston rod receiving openings in a cylinder head forming member. Each cylinder head forming member includes a manifold passageway and spool valves for controlling a sequencing movement of the drive units. The piston rods provide the spools for the spool valves.

Abstract: The identification of and compensation for changes in the dielectric properties of a hydraulic fluid in hydraulic apparatus is achieved by continuously sampling a hydraulic fluid in a resonant chamber with a central conductor that is both inductively and capacitively coupled to an oscillator. The output frequency changes of the oscillator is an indicator of changes of the dielectric properties of the hydraulic fluid and their magnitude. The invention is of particular value in hydraulic cylinder piston position determining systems.

Abstract: A short travel pneumatic cylinder device for transmitting a high force, comprising a cylinder housing having a cylindrical bore for guiding of the piston and of the piston rod, two pistons which upon generation of an overatmospheric pressure between the pistons will move in opposite direction, and further comprising a mechanical lever system with a housing cover. The first of the pistons is connected with the piston rod, and the second of the two pistons is arranged coaxially relative to the first piston, is hollow, and is movable coaxially relative to the piston rod. The first of the two pistons is connected to the lever system at the side of the interior of the cylinder opposite to the second of the two pistons. The pressure force exerted by the second piston is transmitted to the piston rod via the lever system in a direction opposite to the direction of movement of the second piston.

Abstract: In a mechanism for extending or retracting a telescopic unit, the plurality of interconnected cylinders includes an extension passage, a retraction passage and a flow-through passage interconnected to provide a flow path of a retraction signal from the first to the last cylinder and sequencing means for transmitting the retraction pressure signal sequentially from the last cylinder to the first cylinder to initiate retraction from an extended position beginning with the last cylinder. A poppet control check valve provides a position sensitive means to transmit the retraction signal to the next cylinder in the cycle. The sequence control valves and hold loading valves were formed integral to each of the cylinders. The load holding mechanism prevents unintentional extension and retraction movement under the action of the load for each of the cylinders.

Abstract: An internal check valve for use in a linear hydraulic motor in the form of a piston-cylinder unit including a cylinder body (38) reciprocally slidable on a piston component (40). The piston component (40) includes a tubular piston rod (52) and a piston head (60) defining first and second working chambers (136, 140) within the cylinder body (38). The tubular piston rod (52) includes a center tube (102) located within the piston rod (52). The center tube (102) provides a fluid passageway (134) through its center which communicates with a first working chamber (136). An annular second passageway (142) is formed by and radially between the piston rod (52) and the center tube (102). A spring biased check valve (116) is positioned within the piston rod (52, 54) and is operatively connected with one of the passageways (134, 126, 130). The check valve (116) has a valve member displaceable from a valve seat (120) by hydraulic pressure to overcome the spring bias (122, 124) and allow flow in one direction.

Abstract: The piston rods (10, 12, 14) of three linear hydraulic motors (M1, M2, M3) are stationary and include fluid pressure passageways (40, 52, 42, 54, 44, 56) which direct fluid pressure into and out from working chambers (16, 34, 18, 36, 20, 38) on opposite sides of piston heads (22, 24, 26). Movable cylinder barrels (16, 18, 20) are connected to a load, e.g. floor members (FM1, FM2, FM3) of a reciprocating floor conveyor (FIG. 18). The outer ends of the piston rods (10, 12, 14) include balls and the balls include ports (46, 58, 48, 60, 50, 62) through which fluid pressure is delivered or removed. Associated with each port is a limit valve LV1, LV2, LV3, LV4, LV5, LV6. Limit valves (LV1, LV2, LV3) are pushed into an open position by a retraction of the motors (M1, M2, M3). Limit valves (LV4, LV 5, LV6) are pulled into an open position by extension of motors (M1, M2, M3). The limit valves (LV1, LV2, LV3, LV4, LV5, LV6) includes springs biasing them into closed positions.

Abstract: A pneumatically actuatable linear drive for automatic spot welding machines includes a cylinder, a piston rod with segments and pistons and an intermediate bottom between the pistons for dividing the cylinder into pressure chambers. An axial conduit in the segments has a check valve. Radial conduits communicate between the axial conduit and the pressure chambers. Air line connections and a throttle valve lead into the pressure chambers. One piston on one segment moves toward and away from the closed end into end and terminal positions for closing and opening the radial conduits. The end and terminal positions of the one piston are determined by a cap screw of the check valve having an axially parallel conduit and by a spring on one of the segments. A connecting conduit contains the throttle valve. The intermediate bottom has a peripheral annular conduit communicating with one of the air line connections and through the connecting conduit with one of the pressure chambers.

Abstract: A dual servo actuation system is automatically equalized or rigged by electronic control circuits. A static auto rigging bias is applied to one or the other, or both, of a pair of electro hydraulic servo valves that respectively control two hydraulic actuators driving a common member, such as an aircraft control surface. An auto rigging bias, which substantially eliminates force fight, is automatically generated and stored as a fixed quantity prior to use of the system for control of the common member. With a zero commanded output of the two actuators, a difference of differential pressures at the actuators is obtained and caused to change the number in a counter as long as the difference exceeds a threshold. The counter number, while it is above the threshold, is continuously applied as a bias signal to decrease the force fight, and the number in the counter is stored as a fixed bias signal when the force fight indicated by the difference of differential pressures drops below the threshold.

Abstract: A piston assembly comprising a primary piston and a co-centric secondary piston. The pistons are received within a housing for reciprocating movement therein and relative to each other. The housing and the pistons are arranged for operating pressure to be applied to the secondary piston so as to drive both pistons within the housing. The secondary piston is provided with means enabling the operating pressure to be equalized across the secondary piston and at least one bypass passage extends through the secondary piston. The arrangement is such that upon completion of the stroke of the pistons pressure equalization occurs across the secondary piston which causes the pistons to separate. The bypass passage becomes fully operable subsequent to pressure equalization, whereby a fast return stroke is achieved.

Abstract: A telescopic pneumatic hoist has a flexible stationary hollow probe on its base arranged to unseat a check ball in the piston of the lowest intermediate stage when the piston is near the base. When such a condition exists, the probe closely interfits with the piston and has a radial port communicating with the underside of the piston. The probe connects at the bottom with a supply and exhaust passage which also communicates with the underside of the piston via a check valve controlled secondary passage.

Abstract: Hydraulic fluid under pressure is selectively supplied to multiple drive cylinders that are interconnected to one another and which have bypass lines allowing excess fluid to return to the source of hydraulic fluid as needed. Each drive cylinder receives a double acting piston and each piston is carried by and axially displaces a component pump shaft as it reciprocates within the drive cylinder under the influence of hydraulic pressure. A free end of each pump shaft carries a trip member that trips upper and lower limit switches when the piston reaches its top dead center and bottom dead center positions, respectively.

Abstract: Either a reciprocating or a stationary part in each of juxtaposed cylinder devices is provided with a scale having alternate projections and depressions which are arranged with regular pitches in a direction of reciprocation of the reciprocating part, while the other part is provided with a sensor engaging the scale for determining whether it is a projection or depression of the scale that the sensor engages at a particular point of time, and producing a pulse whenever it falls in any of the depressions. According to one preferred embodiment, the projections and the depessions of the scale of one of the cylinder devices are staggered relative to those of the scale of the other cylinder device by half a pitch. Thus, when the two cylinder devices are in synchronous operation, the sensors of the cylinder devices produce alternate pulses which do not overlap with each other in the time of occurrence.

Abstract: A carrier vehicle, for carrying at least one vehicle on a carrier bed which is slidable and tiltable relative to the carrier vehicle's frame, includes a tilt lock-out arrangement for preventing actuation of the carrier vehicle's tilt cylinders whenever the moveable carrier bed is locked in a stowed, or vehicle carrying position. The lock-out arrangement features a contactless sensor element which determines the slidable position of the movable carrier bed and inhibits hydraulic activation of the tilt cylinders to raise or lower the carrier bed unless the carrier bed has first been slid rearwardly to clear a mechanical hold-down element. Similarly, the contactless sensor element inhibits hydraulic actuation of the tilt cylinder to lower the carrier bed unless the bed has cleared the hold-down element.

Abstract: For converting a stepwise translation movement into a continuous translation movement and arrangement and a method is provided which have at least two fluid-operated cylinder-piston units with cylinders are rigidly mechanically connected with one another and pistons movable in the cylinders between end positions and having piston rods, removably arranging clamping mechanisms on the pistons of the cylinder-piston units, arranging end position sensors in the regions of the end positions of the piston of a respective one of the cylinder-piston units, arranging end position pre-signal sensors so that they are axially spaced relative to the end position sensors, connecting the sensors with electronic a control unit, and producing by the electronic control unit signals for supplying a working fluid to the cylinders of the cylinder-piston units in an alternating manner.

Abstract: A conveyorized transport apparatus has an overhead rail system for transporting articles on a suspended trolley from one location to another. A moveable rail section in the system has a pivotal connection with an adjacent rail section to pivot the moveable section from a conveying position and a diverted position in which articles are delivered closer to a work station disposed laterally of the rail system.

Abstract: An indexing mechanism comprising a member adapted to be advanced a predetermined amount and along a predetermined path, a pair of spaced drivers, and a control valve for operating the drivers in an alternative manner. The member adapted to be advanced defines a profile surface including a plurality of spaced radial segments. Each radial segment includes a crown section which is joined to an adjacent crown section by two oppositely directed ramps defining a fillet radius therebetween. The spacing between the drivers being such that when one driver is urged against a crown section the other driver acts against a fillet radius. The drivers are operated by the control valve 180.degree. out of phase relative to each other. A driver, after moving off a crown section, coacts with ramp to impart a driving force to the member. The driving force being sufficient to move the member in an indexed fashion the predetermined amount of its movement.

Abstract: An improved punch assembly (10) for a punch press comprises a main piston (13) driving a punching tool (11) and an auxiliary piston (17) which can be selectively enabled to cooperate with the main pisto1 (13) in a high force, slow speed mode or disabled to allow the main pisto1 (13) to operate alone in a low force high speed mode. The punch assembly (10) also comprises a pressure transducer (41) and position transducer (25) whose respective outputs are connected to a microprocessor controller for the punch assembly. Operation of the punch press is microprocessor controlled to reduce noise and punch cycle time. A stripper assembly (42-48) is also provided and operates in conjunction with the punching tool (11) under microprocessor control to facilitate tool stripping. The stripper assembly (42-48) can also be used for automatic measuring of work sheet thickness.

Abstract: An improved hydraulic circuit for automatically sequencing a pair of hydraulic cylinders through alternate extension and retraction cycles. A manually operated control valve initiates addition and withdrawal of fluid within the circuit and a logic valve determines which cylinder will be in communication with the control valve. The circuit uses an improved flow restrictor arrangement for creating the pressure drop which automatically shifts the logic valve. The restrictor consists of an orifice, a simple check valve and a constant pressure relief valve, all arranged in parallel. The functions of these various restrictor elements can all be performed by a single multifunction valve disclosed herein.

Abstract: A percussive tool comprising a housing (1) accommodating a movable striker (2) and connected with a power cylinder (6) in which is arranged a striker shank (4) with a gripping mechanism (14) and a drive in the form of a hydraulic cylinder (8). The percussive tool is provided with a control unit having a spool valve means (18) to control a distribution means (19). The spool valve means (18) has a casing (22) and a spool (23) taking two positions in the casing and defining two chambers (25, 26) interconnected through a throttling means (24). One chamber (25) constantly communicates with a discharge line (21), and the other chamber (26) is periodically put in communication with the space of the hydraulic cylinder (8). The spool (23) is spring-loaded with respect to the casing (22) on the side of one chamber (25) and takes in this case its first position.

Abstract: A single elongated piston rod (12) is secured by a ball and socket joint (62, 66, 68) at one end to a frame member (82). At its opposite end it is restrained against up and down and sideways movement but is not connected. A plurality of piston heads (22, 24, 26) are spaced apart along the length of the piston rod (12). A traveling cylinder (28, 30, 32) is associated with each piston head (22, 24, 26), a transverse drive beam (16, 18, 20) is connected to each traveling cylinder (28, 30, 32). Each transverse drive beam (16, 18, 20) is connected to a separate group ("1", .cent.2", "3") of the floor members (14) which make the reciprocating floor conveyor.

Abstract: A piloted rotary two-way "on-off" valve which will couple hydraulic fluid from the valve input to the valve output in the "on" position and then move to the "off" position where it will maintain the pressure on the down stream side while enabling the pressure on the upstream side to be removed.

Abstract: A fluid operable power unit which is particularly adapted for movement of a compaction head in a refuse container. However, the power unit is also useful in other types of mechanism.The power unit comprises a plurality of telescopically movable cylinders and pistons. Fluid pressure is applied for movement of the first cylinder. Then increased fluid pressure is applied for movement of the second cylinder. As the first cylinder ceases to move, fluid pressure increases and automatically operable valve means traps the fluid which has moved the first cylinder. Then increased fluid pressure moves the second piston and second cylinder. As the second piston and the second cylinder move under the influence of increased fluid pressure, the fluid which is trapped is increased in pressure.Thus, high pressure forces act to move an actuator member for compaction or for any other purpose.

Abstract: A fluid powered actuator system includes two identical fluid powered actuators operable by respective supply pressures which are controlled by respective identical valve arrangements. Operating positions of flow control elements of the valve arrangements are applied through respective couplings to a differential arrangement which operates, if these positions differ by an unacceptable amount, to apply an error indication through respective coupling to prevent the supply pressures from being applied to the respective actuators.

Abstract: A material dispensing valve finding particular application in the robotic dispensing of sealants, adhesives, etc. in a desired pattern on a workpiece. The dispensing valve comprises a unique actuating arrangement wherein back to back pancake cylinders are moveably arranged within a housing and, depending upon how the cylinders are actuated, three or four dispense rate positions can be provided. The dispense rate positions of the valve are preferably coordinated with the rate of movement of the robotic system so that the dispense rate is appropriate for the rate of movement.

Abstract: Apparatus for controlling a plurality of moving members, e.g. the flaps in an installation for heating and ventilating or for air conditioning a motor vehicle, comprises single-acting actuators (46, 48) whose piston rods (50, 52) are connected to rotate the flaps about their respective axes (12, 14), with the actuators (46, 48) being fed from a pressurized fluid distributor (32) which includes moving elements which are respectively connected to control means and to each of the piston rods (50, 52), together with fluid flow servo control means for putting the displacement of one flap under the control of the displacement of another flap.

Abstract: The casing of the jack is divided into two cylinders by a cross partition, with a first piston which moves in one of the cylinders and a second piston, forming two parts, linked by a rod which crosses the partition to its first part which moves in the first cylinder-shaped piston and its second part which moves in the second cylinder of the jack. The fluid is conveyed selectively either to the cylinder formed by the first piston or to the second cylinder which communicates with the first cylinder through holes drilled in the partition.

Abstract: Piston rods (60, 62) of three linear hydraulic motors (36, 38, 40) are connected at their outer ends (64, 68) to two spaced apart transverse frame members (10, 12). A cylinder housing (72) is driven back and forth along each pair of piston rods (60, 62). Three transverse drive beams (48, 50, 52) are provided. Each drive beam (48, 50, 52) is directly connected to an associated one of the cylinder housings (72). Three sets of floor slat members (1, 2, 3) are provided. Each set (1, 2, 3) is connected to an associated one of the transverse drive beams (48, 50, 52). The linear hydraulic motors (36, 38, 40) are operated for moving the floor slat members (1, 2, 3) in one direction, for advancing a load, and for retracting them in the opposite direction. Each cylinder housing (72) has four fluid chambers (82, 84, 86, 88). The first and third chambers (82, 86) are interconnected and the second and fourth chambers (84, 88) are interconnected.

Abstract: A pneumatically actuated tool for setting blind rivets of the type having a body, a head and breakaway pull mandrel. The tool comprises a body having a double-acting cylinder therein, a handle attached to the body, a guide body affixed to the body beneath the cylinder, a pull track in the guide body for the rivets and a bore in the body connecting the cylinder and the pull track, the cylinder, the bore, and the pull track being coaxial. The tool is provided with a rivet pickup and pull mechanism comprising a lower load piston having a downwardly depending tubular assembly slidable within the body bore and pull track and terminating in a nose piece, and an upper pull piston having a downwardly depending tubular assembly telescopicly and shiftably located within the lower load piston tubular assembly and terminating in a chuck provided with mandrel-engaging jaws. The tool has a magazine connected to the guide body and containing a strip of rivets.

Abstract: This invention relates to a valve suitable for location within a passage or bore of a piston or piston rod of a hydraulic ram assembly. The valve includes a valve body mountable in the bore or passage and a chamber provided in the valve body having a pair of fluid access ports preferably having a relatively narrow outer passage and an enlarged inner space which may function as a valve seat. There is also provided a pair of valve members wherein each valve member may co-operate with a respective valve seat to close or open same to fluid flow through the valve chamber.

Abstract: An improved mechanism is provided for controlling the relative pivoting movement of two members about a main pivot axis as effected by two hydraulic motors. Each hydraulic motor is a double-acting piston-cylinder type that is fully extended when its respective line of action intersects the main pivot axis. Each hydraulic motor has an end port at each end. Two spaced-apart intermediate ports are provided within the piston stroke length of each motor. Pilot-actuated top dead center-selector valves are provided for reversing the flow to one of the hydraulic motors in response to a pressure differential between an end port and an intermediate port of the other of the hydraulic motors. Decelerator selector valves are provided to normally direct the return flow from the hydraulic motors so as to bypass a hydraulic cushioning circuit.

Abstract: Piston rods of three linear hydraulic motors are connected at their outer ends to two spaced apart transverse frame members. A cylinder housing is driven back and forth along each pair of piston rods. Three transverse drive beams are provided. Each drive beam is directly connected to an associated one of the cylinder housings. Three sets of floor slat members are provided. Each set is connected to an associated one of the transverse drive beams. The linear hydraulic motors are operated for moving the floor slat members in one direction, for advancing a load, and for retracting them in an opposite direction. Each cylinder housing has four fluid chambers. First and third chambers are interconnected and the second and fourth chambers are interconnected. This arrangement provides adequate force producing area with a relatively small diameter cylinder housing. Fluid passageways are formed in the piston rods. Transfer valves are incorporated in end portions of some of the linear hydraulic motors.

Abstract: A hydraulic system for lifts provided with two independently supported parallel platforms comprises at least two cylinder-piston units (80, 81) for raising the platforms, a metering device (7) for feeding identical quantities of fluid to said two units, and a balancing device (74, 75) operated by means (31, 32) for measuring the height difference between the platforms and arranged to feed a quantity of supplementary fluid to that cylinder-piston unit (80) or (81) operating the lower platform by withdrawing it from that cylinder-piston unit (81) or (80) operating the higher platform.

Abstract: The invention contemplates a hydraulically operated twin-cable suspension for a clamshell or the like load-handling device. In a preferred embodiment, a charged accumulator is effectively a counterweight and is the source of all hydraulic fluid needed for the full range of actuation of two traction cylinders, one for each of the respective cables. Both cables automatically share the load, without slack, in any elevational situation, and simple hydraulic control circuitry selectively enables (a) an automated closing dig into loadable material and (b) a quick opening for load discharge. A single power integrator is interposed between the accumulator and the two traction cylinders for directionally controlling hydraulic-fluid displacement between the accumulator and the traction cylinders, as needed for all cable displacements.

Abstract: The invention contemplates a hydraulically operated twin-cable suspension for a clamshell or the like load-handling device. In a preferred embodiment, a charged accumulator is effectively a counterweight and is the source of all hydraulic fluid needed for the full range of actuation of two traction cylinders, one for each of the respective cables. Two power integrators are employed: one is interposed between the accumulator and one of the traction cylinders, and the other is interposed between the accumulator and the other traction cylinder; hydraulic control interconnections between the respective integrator circuits enable load sharing by both cables and simplified single-lever control of plural clamshell functions, including (a) an automated closing dig into loadable material and (b) a quick opening for load discharge.

Abstract: A hydraulic trim-tilt system for an outboard motor (10) utilizes a first pilot operated relief valve (48) in one trim piston (21) to limit the stroke of the trim pistons (21, 22) under load. After the trim pistons have reached the top of their stroke, under reduced load, the first pilot operated relief valve (48) is blocked and a second pilot operated relief valve (58) operates to allow a higher pressure to be supplied to the trim-tilt unit (16) to lift the outboard propulsion unit (15) in a higher shallow water drive range.

Abstract: An external combustion engine comprises an actuating cylinder in which a piston with rod is mounted for reciprocation, said piston serving as the actuating member, a valve distributor serving as the switching member, as well as a crank gear serving as the converter of the piston reciprocation to the drive shaft revolution. The piston divides the cylinder cavity into two, namely, a rod cavity and a rodless cavity. Each one of the cavities communicates with a source of working fluid via valve distributor. The piston rod is operatively connected with the drive shaft via crank gear. The engine further comprises an electric oscillator whose frequency is variable in accordance with the preset r.p.m. of the drive shaft, connected electrically with the converter in the form of a linear dynamic link, and a transducer indicating the current value of the piston position relative to its neutral position. The linear dynamic link is coupled mechanically with the distributor slide valve.

Abstract: The invention relates to a priority control means with which the actuation sequence of two servo motors can be automated. For this purpose a priority control valve is provided which on actuation of the higher priority control valve immediately blocks the lower priority servo motor. If the priority servo motor has reached a certain position the associated control valve is automatically switched back so that the actuation of the lower priority servo motor then follows automatically. Via a changeover valve the working pressure of the respective servo motor is furthermore automatically switched to the pump control of an adjustment pump or, with a constant pump, to the load-pressure-dependent pressure control so that a load-dependent regulation takes place.

Abstract: A fluid power apparatus particularly useful for an industrial robot which includes a pair of expansible chamber devices each having a pair of control chambers in fluid communication with each other to intensify the working fluid output pressure and a working chamber that expands to receive a charge of working fluid and contracts to expel working fluid therefrom. A working fluid circuit includes a first line connected with one of the working chambers and a second line connected with the other of the working chambers. A fluid actuator is connected with the circuit and has a moveable element that moves in response to flow of working fluid in the circuit to the actuator. The apparatus has a static condition in which the one working chamber is contracted with the moveable element of the actuator stationary in a first position.

Abstract: A hydraulically operated dockboard comprising a ramp which is hinged at its rear edge to the frame of the dockboard, and a lip is hinged to the forward edge of the ramp. A main hydraulic cylinder unit connects the frame and the ramp, and by operating the cylinder unit the ramp can be pivoted upwardly from a horizontal cross traffic position to an upwardly inclined position. A lip cylinder interconnects the ramp and the lip and acts to pivot the lip from a downwardly hanging pendant position to an extended position. A hydraulic line is connected to the lip cylinder, and a control valve interconnects the hydraulic line to either a supply line or a return line that is connected to the reservoir of the hydraulic system. The control valve is normally biased to a first position where the lip cylinder is connected to the return line.

Abstract: The invention relates to a device for controlling the supply of fluid under pressure to a hydraulic circuit as a function of the state of locking or unlocking of two mechanical members.The device comprises two interconnected jacks (1,2), the rods (3,4) of which are integrally fixed to mechanical members. The piston (30) of the first jack (1) separates the chamber (35) of the latter into two parts (35a,35b). The piston (31) of the second jack (2) divides the chamber (35') of the latter into three parts (35'a,35'band 35'c). The inlet chambers (35a and 35'a) are connected to pipes for supplying fluid under pressure (10a,10b), and the outlet chambers (35b and 35'c) are connected to a depressurizing pipe (20). According to the position of the pistons (30 and 31), which itself depends on the state of locking or unlocking of the rods (3,4), an interconnecting pipe (23) and a pipe (25) supplying the hydraulic circuit with fluid under pressure communicate with one chamber or another.

Abstract: A hydraulic control arrangement comprises a first hydraulic ram, a second hydraulic ram, and a hydraulic control circuit associated with the first and second hydraulic rams. Each of the hydraulic rams has a cylinder, a piston reciprocable within the cylinder, and a piston rod fixed to the piston. Each of the hydraulic rams has a cylindrical working chamber and an annular working chamber positioned on opposite sides of its piston. The piston rod of each hydraulic ram constitutes the cylinder of a respective metering ram, a respective metering piston being reciprocable within the cylinder of each metering ram to define a metering chamber therewithin. The hydraulic control circuit includes a line, which interconnects the two metering chambers, and a hydraulic valve positioned in a hydraulic fluid supply line leading to the cylindrical working chamber of the second hydraulic ram.

Abstract: An intensifier pump has a primary fluid cylinder including a primary piston and which has shaft portions received within a separate coaxial fluid chamber. A secondary fluid cylinder having a secondary piston has shaft portions reciprocally received within a separate coaxial fluid chamber. The secondary piston is of a smaller relative diameter than the primary piston. The sizing of the hydraulic pistons in the operating fluid cylinders is used to sequence the pistons in the cylinders with the largest diameter piston being stroked first followed by the second largest diameter cylinder being stroked next, followed in turn by any additional fluid cylinders in the order of the piston diameter size. When the smallest diameter cylinder has been stroked, a pressure switch signals a reverse flow pump to change the direction of circulation of the operating fluid to cycle the pistons.

Abstract: A microwave method and apparatus for detecting the position of a piston of a pneumatic cylinder. While the piston is being moved by fluid pressure a microwave signal is applied to a cavity defined by the piston and interior of the cylinder and the reflected microwave signal is detected. The reflected microwave signal is processed to determine piston position.

Abstract: A hydraulic control arrangement for providing synchronism of a return cylinder between a face conveyor and a support, has a pushing cylinder which displaces the support transverse to a face, a control valve, a control cylinder influencing loading of the pushing cylinder via the control valve, and a control column provided between the return cylinder and the control cylinder and composed of a working fluid.

Abstract: A lift truck upright having a fixed upright section, a telescopic upright section, and a load carrier mounted on the telescopic section. A pair of main lift cylinder assemblies are located adjacent opposite sides of the upright, and a second pair of relatively short free-lift cylinder assemblies are located inwardly adjacent the main lift cylinders, the pairs of lift cylinders are mounted from the fixed upright section and are hydraulically connected in parallel, and of such relative size that the free-lift cylinders and main cylinders always actuate in the proper sequence to first elevate the load carrier in free-lift and then the load carrier with the telescopic section.

Abstract: A clamping attachment with a hydraulically actuated pivoting long arm and a pivoting short arm. The hydraulic actuators are connected in parallel where both arms move simultaneously inwardly until one arm contacts a load and stops and the second arm will continue inwardly. A biasing valve insures that the long arm opens first before the short arm opens. The long arm is actuated by first and second crank links to provide maximum force at the open position. The short arm is pivotally connected closer to the center line of the frame than the long arm allowing the long arm to be positioned in the maximum force position, allows positioning of the load close to the frame center line and reduces travel of the long arm. A swivel connection in the hydraulic control system prevents operation of any arm in the down position. The frame of the clamp is asymmetrical.

Abstract: This invention relates to a pneumatically actuated stepping valve for an automatic control of inlets and outlets for a pneumatic fluid. Each stepping movement is performed in response to a feedback signal indicating that an operation controlled by the valve has been completed. A distributing disc is provided for selecting consecutive pairs of ports consisting of an inlet port and an outlet port each. The stepping valve consists mainly of plastic parts, which contain numerous bores and passages and can be made at low cost. In accordance with the invention the valve disc cooperates with a sealing piston, which in response to pressure applied to said piston establishes connections to through passages of the valve disc, whereas when the piston is pressure-relieved it will be urged by spring means to disengage the valve disc so that the latter will not be restrained by the piston during its stepping movement.

Abstract: Mining equipment for steering the cutting horizon of a mining machine cutter which is mounted on a ranging arm and which in use makes repeated traverses along the working face, comprises a boom urged into contact with the mine roof formed on a previous traverse of the machine. The boom is urged towards the mine roof by a ram hydraulically connected to a piston and cylinder device such that movement of the piston of the device is in accordance with that of the ram. Movement of the piston rod activates a flow control valve controlling operation of a ram controlling ranging of the arm.