Abstract: An apparatus for reducing harmonic distortion and causing a more linear response in a hydraulic vibrator apparatus which generates a seismic signal into the surface of the earth is disclosed. The force developed in the actuator of a hydraulic vibrator is directly related to pressure applied to the hydraulic piston. Conventional vibrators use flow control type servovalves to develop this pressure. Changes in loading due to earth surface conditions reflect back as changes in pressure across the hydraulic piston. Pressure can be better controlled in the actuator such that it varies only as a function of the input signal, and the natural response of a vibrator can be made more linear, and the harmonic distortion can be reduced by using a pressure control type servovalve.

Abstract: A gas venting device serves to automatically closing and opening vent holes of a foam mold so that air and reaction product gases are sufficiently exhausted and a foamed product is effectively prevented from extending through the vent holes. The gas venting device includes valves for closing and opening the vent holes, valve driving cylinders for driving the valves, a pilot operated two-position change-over valve, pressure tanks connected through the pilot operated two-position change-over valve to the valve driving cylinders, and mechanical change-over valves connected to the pilot operated two-position change-over valve for changing over it by dogs provided on a passage of the foam mold. The device further includes an air timer for delaying closing the vent holes by the valves.

Abstract: An apparatus for controlling operating reaction of winch comprising a reaction device whose output is variable for applying the output as an operating reaction to an operating lever of a winch, load detection means for detecting a lifting load of the winch, lever operating amount detection means for detecting an operating amount of said operating lever, and a controller for indicating an output having a value corresponding to the lifting load and the lever operating amount to said reaction device on the basis of the detection amount by said load detection means and said lever operating amount detection means.

Abstract: An energy regenerative circuit in a hydraulic apparatus wherein when a direction control valve is at the actuator unloaded-side chamber acting position, the discharge fluid line of a variable displacement pump is connected to a fluid tank via the direction control valve, by-pass fluid line change-over valve and by-pass fluid line that has a signal orifice. The by-pass fluid line is connected to a capacity control mechanism of the variable displacement pump via a signal fluid line on the upstream side of the signal orifice. The loaded-side chamber of the actuator is so connected that the pressurized fluid thereof is partly added through the direction control valve to the fluid line through which the pressurized fluid discharged from the variable displacement pump is fed to the loaded-side chamber.

Abstract: A metering valve adapted to operate a seat on a side of an actuator port by means of a poppet section of a main poppet arranged in a valve casing to selectively communicate the actuator port to a tank passage. The main poppet is formed with a pressure chamber on a side thereof opposite to the poppet section. The pressure chamber has a pressure receiving area substantially equal to that of the seat. Also, the main poppet is formed with a through-hole constantly communicated to the actuator port and a pilot chamber to which pilot pressure for moving the main poppet in a direction of opening the seat is applied. Thus, the metering valve is capable of stably accomplishing its control irrespective of a variation of pressure on the side of the actuator port.

Abstract: Described is a control circuit for a hydraulic power lift driven by a displacement pump which has a check valve releasable at least for lowering movements of the power lift, a actuation means switching the check valve off and on to control the flow from a pump line into an operating line leading to the power lift and vice-versa, and a load-sensing line carrying the load pressure and connected to the operating line, by which the variable-displacement pump is capable of being activated. The actuating means has an actuating unit switching the check valve off and on and a servo valve, activated simultaneously and controlling the flow to and from the power lift, with at least three switch positions. In the starting position of the actuating means, the latter connects the load-sensing line and the operating line, by way of the servo valve, with the tank and, after passage through a central position, the operating line with the pump line.

Abstract: Device in a hydraulic power system connected to load driving hydraulic motor (18; 32), comprising a pilot controlled flow regulating directional valve (1; 29) for alternative connection of the service ports of the motor (18; 32) to a pressure medium source and a tank. The directional valve (1; 29) comprises two opposite and by a pilot pressure activatable activating means (3, 4), and a pilot pressure means (84) is arranged to pressurize and activate the activating means (3, 4), alternatively, and drain one of the activating means to the tank through a flow restriction (6, 7) at activation of the other activating means (3, 4).

Abstract: A drive for a steam servo valve (2), including a control valve arrangement for regulating the actuating pressure of a servo drive (1), whereby the drive can always be actuated reliably and quickly even with comparatively high oil pressure. This is achieved by the control valve arrangement having at least two regulatable control valves (17, 21) which are pressure-actuated via at least one pilot regulating valve (proportional pressure valve 29, 34).

Abstract: A multiplexed hydraulic control system which avoids the use of a rotary multiplexer and thereby allows for random selection of the multiplexed outlet ports and variable dwell times for the respective ports. A single hydraulic input is multiplexed among a plurality of hydraulic outputs. A control system provides two types of signals: (1) modulation signals selected from a plurality of multiplexed input signals for producing a modulating hydraulic flow, and (2) selector signals for operating on the multiplexer means to route the modulated signal to the appropriately selected channel.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving an element of the actuator in opposite directions, a pump for supplying fluid to the actuator. A meter-in valve individual to each opening is provided to which fluid from the pump is supplied and a pair of lines extending from the respective meter-in valves to the respective openings of the actuator. A controller alternately supplies pressure to the respective meter-in valves for controlling the direction of movement of the load. A second pair of lines extends from the first pair of lines to tank and a variable pressure relief valve is positioned in each line of the second pair of lines.

Abstract: A proportional directional control valve in combination with a pressure compensator flow rate control valve opening towards a reservoir and a pressure unloading valve in the load- pressure- carrying control line for the compensator valve are provided to actuate the telescopic cylinder of a tipper truck. The valve device is connected to a pump of constant displacement. The operating speed of the telescopic cylinder is independent from the load to be lifted and the driving speed of the pump. Upon reaching a predetermined load pressure the pressure unloading valve is activated and the load pressure engaging the compensator valve towards closing direction is reduced via the reservoir such that the compensator valve opens and the pump displacement volume returns to the reservoir.

Abstract: A pneumatic percussion tool includes a head valve device including first and second head valves disposed in the body and movable in response to the pressure variation in the head valve chamber. The first and second head valves are positioned at a first position for preventing communication between the main air chamber and the percussion piston chamber while permitting communication between the percussion piston chamber and the outside of the body and preventing communication between the head valve chamber and the outside of the body when the compressed air is introduced into the head valve chamber through the change-over valve.

Abstract: A directional control valve for a pneumatic cylinder in which a piston of the cylinder can be lowered and elevated in a high speed with a minimum air consumption and the lowering/rising speed of the piston can be controlled before it reaches the upper/lower end portions to prevent bounding of the piston.

Abstract: A hydraulic control valve is controlled and changed over by a hydraulic pressure output from a remote control valve. A change-over valve is provided between an output port of the remote control valve and a pilot port of the hydraulic control valve. The change-over valve connects the output port of the remote control valve to the pilot port of the hydraulic control valve when the remote control valve is operated, and it connects the pilot port of the hydraulic control valve to a tank when the remote control valve is set to the neutral position. The change-over valve comprises a hydraulic change-over valve capable of establishing the above states of connection by the hydraulic pressure output from the remote control valve, or an electromagnetic change-over valve capable of establishing the above states of connection by electrically detecting the operation of the remote control valve.

Abstract: For the relief of a highly pressurized hydraulic liquid in a working chamber of pilot controlled 2/2 poppet valve is used. The working chamber is further connected to a pressure relief valve, the output of which is connected to a control conduit extending between a control chamber of the 2/2 poppet valve and the pilot valve. The apparatus of the invention requires a shorter period of time for the pressure relief without the danger of relief noise.

Abstract: A pneumatically powered point driver utilizes a valve mechanism having a core that is operated by air conducted therethrough from the supply source. The valve core is preferably provided with an enlarged head, to enhance the rapidity and firmness of the action produced.

Abstract: A directional control valve for a penumatic cylinder in which a piston of the cylinder can be lowered and elevated in a high speed with a minimum air consumption and the lowering/rising speed of the piston can be controlled before it reaches the upper/lower end portions to prevent bounding of the piston.

Abstract: A hydraulic circuit suitable for use in a hydraulic operating circuit of a power shovel includes a hydraulic cylinder for driving a working component and a hydraulic change-over valve for selectively supplying the cylinder with a discharge oil pressure of a hydraulic pump driven from an engine. The hydraulic circuit prevents cavitation in an oil chamber of the cylinder and includes a pair of first signal receiving portions provided in the hydraulic change-over valve for moving the spool thereof in the forward and reverse directions away from a netural position, respectively, and a second signal receiving portion for pulling back the spool toward said neutral position.

Abstract: An articulated arm employs a controller to generate .delta.r, .delta..THETA. and .delta.z signals for controlling the movement of the arm in r, .THETA. and z directions to product movement of an end point from an initial location along a desired path toward a desired location. The actual location is determined by sensing the relationships between the arm segments and determining the actual location of the end point. The actual location is continuously compared with the desired location represented by the r, .THETA. and z signals and, if the difference between the actual location and desired location exceeds preselected limits, the .delta.r, .delta..THETA. and .delta.z are scaled down thereby redefining the desired location to ensure that the actual arm movement does not lag an unacceptable amount relative to the desired location.

Abstract: A hydraulic drive system for a civil engineering and construction machine of the present invention comprises a hydraulic pump (11, 11A), a plurality of actuators (4-6) driven by a hydraulic fluid supplied from the hydraulic pump and including an arm cylinder (5) and a boom cylinder (4), a plurality of flow control valves (12, 14, 16) for controlling flows of the hydraulic fluid supplied to the respective actuators and including an arm directional control valve (14) and a boom directional control valve (12) and a plurality of distribution compensating valves (13, 15, 17; 13A, 15A, 17A) for controlling differential pressures across the respective flow control valves, the distribution compensating valves each having a first device (13d,15d, 17d; 13e, 13f, 15e, 15f, 17e, 17f) to set a target value of the differential pressure across the associated flow control valve.

Abstract: Pilot control circuits are useful, for example, for controlling the actuation of main control valves of load sensing hydraulic systems. Using the main supply pump as the source of pressurized pilot fluid sometimes results in inadequate pilot pressure for maintaining the main control valves in an actuated position under some operating conditions. The subject pilot control system includes an accumulator to store pressurized fluid received from the main supply pump for use by the pilot control circuit when the pressure level of the main hydraulic system momentarily drops below a level for proper pilot control operation. Thus, the main control valves are maintained in their actuated position irregardless of the pressure level of the fluid in the main supply system.

Abstract: An electrohydraulic control arrangement for controlling a hydraulic cylinder having a double-acting working piston. At least one control valve having a control slide unit that is spring-loaded at one end and can be shifted by a servomotor against the spring force is provided. A valve housing having at least one section is provided with at least one control valve for alliance with each of the pressure chambers of the hydraulic cylinder, with the control slide units of the control valves being spaced from one another and being coaxially disposed in a mirror symmetrical manner relative to one another. A common control element of the servomotor is disposed between the inner ends of the control slide units for moving the same in the same direction.

Abstract: In a pilot operated control valve system provided with a plurality of valves for controlling a plurality of hydraulic devices such as hydraulic cylinders, there is employed a plurality of valves each of which does not interfere with each other in operation and requires a minimum mounting space in the system to enable the system to be a small system having a construction easily adapted to control a plurality of hydraulic devices and also adapted to simultaneously supply the pressure oil to the hydraulic devices from a pair of hydraulic pumps through the same hydraulic circuit as needs require.

Abstract: A control device for a cylinder including a spool type valve which includes a spool and is formed therein with a cylinder port. In the spool type valve is arranged an operation check valve for permitting only flowing of fluid to the cylinder. An orifice is formed so as to communicate a pilot chamber of the operation check valve and the cylinder port with each other. The spool is formed with a first control port and a second control port for selectively carrying out communication between the pilot chamber and the return passage. Thus, when the spool is moved to communicate the first control port with the pilot port, the pilot chamber is communicated with the return passage. This causes fluid to flow through the orifice to lead to a difference in pressure between both sides of the orifice, resulting in a poppet of the operation check valve being opened.

Abstract: A multiplexed hydraulic control system in which high force margins for the multiplexer are achieved by employing hydraulic oscillators as the multiplexer driving means. The multiplexer is typically in the form of a hydraulic cylinder having an input port and a plurality of output ports, with an operator in the cylinder for individually connecting the input port to the output ports. The hydraulic oscillator is mechanically coupled to the multiplexer operator, and oscillation of the former causes oscillation of the latter to sequentially connect the input to each of the outputs. Various means are taught for initiating reversal of the oscillator and controlling the oscillation speed.

Abstract: An energy regenerative circuit in a hydraulic apparatus wherein when a direction control valve is at the actuator unloaded-side chamber acting position, the discharge fluid line of a variable displacement pump is connected to a fluid tank via the direction control valve, by-pass fluid line change-over valve and by-pass fluid line that has a signal orifice. The by-pass fluid line is connected to a capacity control mechanism of the variable displacement pump via a signal fluid line on the upstream side of the signal orifice. The loaded-side chamber of the actuator is so connected that the pressurized fluid thereof is partly added through the direction control valve to the fluid line through which the pressurized fluid discharged from the variable displacement pump is fed to the loaded-side chamber.

Abstract: A hydraulic lift is raised by hydraulic fluid which passes through a servo valve and is lowered when the servo valve exhausts the hydraulic lift to a reservoir. The hydraulic fluid travels to and from the lift through a service line in which a blocking valve is disposed. A control unit opens the blocking valve against a spring bias in response to the application of a control pressure to a control element disposed on one side of the control unit. The control pressure is supplied via a control line which also actuates the servo valve. A branch control line branches from the control line and applies pressure to another control element which acts counter to the first-mentioned control element. The branch control line includes tow throttles between which a discharge line is connected and communicates with the reservoir.

Abstract: An improved pneumatic control valve apparatus which uses poppet valves as the primary valve components. The poppets are in a pair of poppet valve assemblies, each assembly containing a pair of spaced poppets on a shiftable shaft biased in one direction to cause the poppets to close respective valve seats and to open the valve seats when the shaft moves in the opposite direction. A roller diaphragm is used to couple the shaft to an adjacent support of the assembly. As the shaft moves in the opposite direction against a bias force, the roller diaphragms of each assembly flex in a rolling action to coordinate the movements of the poppets and the shaft. The poppets will simutaneously open their respective valve seats so that the same amount of fluid will flow through the valve seats and thereby assure precision movements of the shiftable parts of the work-producing device with which the poppet valve assemblies are coupled.

Abstract: The invention is directed to a hydraulic control mechanism for a work vehicle. The work vehicle is provided with a work implement that is operated by a hydraulic actuator. The positioning of the work actuator is controlled by a pilot control system that supplies a pilot control signal to the end caps of a main hydraulic control valve. The mechanism comprises two pressure sensing valves which control the flow of hydraulic fluid from a fixed displacement pump to move the hydraulic actuator, and the flow of hydraulic fluid from a variable displacement pump to hold the hydraulic actuator.

Abstract: A remote control modification (11) for a hydraulic steering system (13) of the type used to steer underground loaders and the like is disclosed. The remote control modification comprises a bidirectional, spring-loaded remote control valve (51) connected in parallel with the bidirectional, spring-loaded control valve (19) that normally responds to steering inputs created by the manual movement of a steering arm (25). The remote control valve (51) has outlet ports (75 and 77) that are smaller than the outlet ports (39 and 41) of the manual control valve (19). Movement of the piston of the remote control valve (51) is controlled by a slave hydraulic actuator (53). The flow of hydraulic fluid to the slave hydraulic actuator (53) is controlled by a solenoid-actuated valve (59). The solenoid (61) of the solenoid-operated valve (59), in turn, is controlled by a receiver (63) that responds to radio frequency control signals (105) generated by a remotely located transmitter (65).

Abstract: Device in a hydraulic power system connected to a load driving hydraulic motor (18; 32), comprising a pilot controlled flow regulating directional valve (1; 29) for alternative connection of the service ports of the motor (18; 32) to a pressure medium source and a tank. The directional valve (1; 29) comprises two opposite and by a pilot pressure activatable activating means (3, 4), and a pilot pressure means (84) is arranged to pressurize and activate the activating means (3, 4), alternatively, and drain one of the activating means to the tank through a flow restriction (5, 7) at activation of the other activating means (3, 4).

Abstract: A hydraulic circuit suitable for use in a hydraulic operating circuit of a power shovel includes a hydraulic cylinder for driving a working component and a hydraulic change-over valve for selectively supplying the cylinder with a discharge oil pressure of a hydraulic pump driven from an engine.

Abstract: A main poppet body of a logic valve receives inlet pressure at first and second ends. A flow-restricting orifice between the first and second ends produces a differential pressure between the two ends when inlet fluid is permitted to flow from the second end. The main poppet body is normally resiliently seated against a seat. A pilot poppet body, movable in the main poppet body, seats against a seat in the main poppet body. The pilot poppet body, when sealed to its seat, seals the fluid at the second end of the main poppet body from flowing. Thus, equal pressures exist at opposed ends of the main poppet body, and the main poppet body remains in its sealing position. An external source of controllable pilot pressure acts on the pilot poppet body to unseal it from its seat. This permits a flow of inlet fluid from the second end of the main poppet body, and produces a pressure reduction at the second end.

Abstract: A pneumatic gun having an improved firing valve is disclosed wherein the firing valve is sealingly secured to the housing of the gun by a pair of rolling diaphragm seals. On the underside of the firing valve, there is a deflector having a downwardly curled outer edge operative to direct air flow into the top of the cylinder upon opening of the firing valve. The firing valve is so configured that exposure of multiple differential areas of the valve to a common high pressure results in the valve being biased toward a sealed position relative to the cylinder of the gun while in the unfired position.

Abstract: A control circuit for a hydraulic actuator which allows the hydraulic actuator to be operated readily without much skill and at a suitable speed in accordance with a load applied thereto. The control circuit includes a change-over valve provided intermediately of a pilot pipe line communicating with a pilot oil chamber of a hydraulic change-over valve which belongs to one of a pair of hydraulic change-over valve sets of a hydraulic operating circuit for the hydraulic actuator. The change-over valve is normally urged to a position wherein the pilot oil chamber of the hydraulic change-over valve is communicated with a tank, but is changed over, when a hydraulic pressure higher than a predetermined value acts upon a pilot oil chamber of the change-over valve, to another position in which the pilot oil chamber of the hydraulic change-over valve is communicated with the pilot pipe line.

Abstract: A pilot control circuit including a pilot pressure pump and a float center connected directional control pilot valve is provided with a warm up circuit for warming up the hydraulic fluid in the pilot circuit. The warm up circuit includes a pair of branch conduits commonly connected to the high pressure side of the pilot pressure pump and respectively connected via flow restriction to the pilots of a primary directional control valve. Fluid can flow from the branch conduits through the pilots and then through the centered pilot valve to the low pressure side of the pilot pump, allowing a warm up circulation of fluid through the entire pilot circuit while its control valve remains centered.

Abstract: A relay valve unit having a control pressure communication line for the relay valve equipped with a reducer unit so that when activating the relay valve, any delay is either non-existent or negligibly larger than would be required for the complete opening of the relay valve.

Abstract: A control system for a hydraulic lift driven by a variable displacement pump is disclosed. It is comprised of a blocking valve which may be opened at least for lowering movement of the hydraulic lift. A control device is provided for opening and closing the blocking valve and for regulating the volumetric flow from a pump line to an operating line leading to the hydraulic lift, and the flow from the hydraulic lift to a tank line leading to a tank. In addition, a load indicating line is provided which transmits the load pressure. The control device is comprised of a servo valve with three valve positions, and is further comprised of an actuator unit which opens and closes the blocking valve. The servo valve regulates the volumetric flow to and from the hydraulic lift. The load registering line is connected to the operating line, and in the initial position of the control device the load registering line is connected via the servo valve to the tank.

Abstract: A spool type directional control valve switches flow of oil discharged from an oil hydraulic pump to a hydraulic actuator, and decreases internal leak of a cylinder. Two sets of separated cylinder passages are formed on a valve body provided with a main spool, and a nonleak valve is provided across them. The nonleak valve is equipped with a main passage switching puppet having a throttle on the nose, a spring for energizing it to a close side, a pilot poppet for controlling pressure of a spring chamber in which the spring is enclosed, and a piston for operating the poppet.

Abstract: A hydraulic circuit suitable for use on power shovel or other construction machines, more specifically a hydraulic circuit for a cylinder in a hydraulic power transmission, of the type which is adapted to control pressurized oil flows to and from two oil chambers in the cylinder by switching the position of a directional control valve in communication with a pressurized oil source. The hydraulic circuit includes a logic valve provided between the directional control valve and a load-holding oil chamber in the cylinder. The logic circuit has first and second ports connected to the directional control valve and said load-holding oil chamber, respectively.

Abstract: A drive control system for a hydraulic construction machine, comprises a prime mover driven by a hydraulic pump, at least one hydraulic actuator driven by hydraulic fluid discharge from the hydraulic pump, first rotational speed setting arrangement including a first operating arrangement for setting rotational speed of the prime mover, and a second operating arranngement for controlling operation of the hydraulic actuator (3).

Abstract: A 3/2 proportional control valve is provided with an actuating piston which is subjected to the control pressure set in a pilot valve. The area relationships of the actuating piston are so chosen that at the actuating piston a high pressure gradient obtains and the adjustment dynamics of the regulating piston are increased.

Abstract: The invention concerns a valve structure comprising a valve body, a chamber space disposed within the valve body, two running spindles and seats disposed to cooperate and placed within the chamber space, each running spindle enabling the aperture in the respective seat to be controlled. The valve structure comprises an input duct, a return duct and a working duct, the ducts being connected to the chamber space, a pressurized fluid being supplied through the input duct in the chamber space and the fluid being conducted through the controllable apertures with the aid of the running spindles either through the return duct out from the valve means to a tank or equivalent, or through the working duct to at least one power cylinder or equivalent, and the position of the running spindles and the size of the apertures being controlled with the aid of pilot valves.

Abstract: In a servo steering system for motor boats comprising a steering wheel which mechanically acts on the position of a hydraulic control valve, and a rubber cylinder connected to a hydraulic power unit by way of the control valve, the control valve comprises an additional adjustment unit which is connected to an autopilot unit and is controllable by this latter. In this way both normal servo-assisted hand-steering and autopilot steering are made possible in a simple manner.

Abstract: A directionally controllable air cylinder has a set of circumferentially disposed air passages formed at each end of a closed tube. A sleeve manifold surrounds the tube and is pneumatically sealed thereto by means of a plurality of O-rings. The O-rings are positioned such that they selectively expose the sets of air passages to the manifold for receiving compressed air and to the atmosphere for venting. The direction of piston movement is determined by the set of passages exposed to compressed air. A pilot piston moves the manifold in response to a pilot air signal in one embodiment and an electrically operated solenoid moves it in another version. The manifold may also be manually or mechanically moved to operate the air cylinder. Hydraulic cylinders utilizing fluids, other than air, are also disclosed.

Abstract: A turning gear is used to rotate a turbine rotor under conditions where it is heating up or cooling down without sufficient motive fluid to cause it to rotate. The turning gear avoid the occurence of a thermal bow. A hydraulic turning gear is disclosed for application in confined areas where a substantial force is required to provide rotation to the rotor. A booster cylinder is used to elevate low pressure fluid for use in a reduced diameter hydraulic cylinder. A ratchet wheel and pawl mechanism uses an adjustable friction force to withhold the pawl from the ratchet wheel after initial contact and further employs a stationary guide rail to reset the pawl for the next contact.

Abstract: Control valve means for a driving tool operated with compressed air for the driving of fasteners into workpieces. Through a specific design of the main and the auxiliary valve and through a connection to the piston return chamber the control of the valves are brought into synchronization with the movement of the working piston. By this, high repetition frequencies can be achieved. Further, in the mode "automatic operation" also single shot operation is possible.

Abstract: Impact rippers are useful in fracturing rocks, concrete, etc. which cannot be fractured by ripping alone. Operating the impactor of the impact ripper without sufficient loading applied to the ripper tip is detrimental to the life of the impact ripper. The subject control system includes a pilot operated selector valve which blocks pressurized fluid from the impactor in the absence of pilot fluid thereto and is shifted by pressurized pilot fluid to a position to direct pressurized fluid to the impactor. A pressure switch is rendered conductive when the fluid pressure generated in a hydraulic cylinder exceeds a predetermined value due to loading on the ripper tip. This actuates a solenoid valve to direct pressurized pilot fluid to the selector valve. Thus the impactor is activated only when the loading on the ripper tip is above a preselected threshold and is automatically deactivated when the loading on the ripper tip drops below the preselected threshold.

Abstract: The invention relates to a method and a device for reducing the piston speed in a piston and cylinder assembly (1), as the piston approaches the end position. The piston end position is sensed, and a signal is generated for starting the end position dampening. Dampening is effected in two steps. In the first step (14), a time delay is provided and in the next step (15), the actual braking (retardation) of the piston is effected.The invention also comprises an electronic braking device comprising a dampening activation unit (13) which is connected to transducers (6), a braking delay unit (14) connected to the unit (13) and also to the control lever (5) at issue and a reference signal source, as well as a braking unit (15) connected to the delay unit (14) and adapted, upon activation, to provide a signal (U) to a setting system (3) for controlling the supply of pressure fluid to the piston and cylinder assembly (1).

Abstract: A control system for controlling a double-acting cylinder includes four pilot-operated, proportional-type poppet valves for controlling fluid flow between the cylinder, a pump and a reservoir. Four solenoid-controlled pilot valves operate the poppet valves in response to error signals generated by a control circuit. The control circuit receives a cylinder position feedback signal and an operator-generated command signal. The control circuit provides for float, shutdown, variable deadband and pressure adjustment operation.