Abstract: An input apparatus capable of concurrently accommodating itself to any external signal from a different hydraulic control system or the like. The apparatus includes electrical load sensors each arranged on a push rod or block for detecting the amount of operation of a control lever to generate an electrical signal corresponding to the amount of operation of the control lever. Also, an input apparatus which is capable of concurrently responding to both a signal generated by itself and an external signal fed thereto is provided. The apparatus includes a pilot section for exerting force which permits a shuttle to be moved against coiled compression springs. The pilot section is fed with a signal from an external hydraulic control system.

Abstract: An input apparatus capable of concurrently accommodating itself to any external signal from a different hydraulic control system or the like. The apparatus includes electrical load sensors each arranged on a push rod or block for detecting the amount of operation of a control lever to generate an electrical signal corresponding to the amount of operation of the control lever. Also, an input apparatus which is capable of concurrently responding to both a signal generated by itself and an external signal fed thereto is provided. The apparatus includes a pilot section for exerting force which permits a shuttle to be moved against coiled compression springs. The pilot section is fed with a signal from an external hydraulic control system.

Abstract: A device for controlling multiple hydraulic actuators to protect a system from an overpressure caused by increasing the load on an individual actuator. By controlling the supply of hydraulic fluid to a pair of cylinders each associated with a pilot valve so that each cylinder always has enough fluid pressure to operate, the device of the present invention prevents the shutdown of the device caused by too much fluid going to the actuator operating at the maximum pressure. Thus all actuators continue to operate even if one is overpressured.

Abstract: An input apparatus capable of concurrently accommodating itself to any external signal from a different hydraulic control system or the like. The apparatus includes electrical load sensors each arranged on a push rod or block for detecting the amount of operation of a control lever to generate an electrical signal corresponding to the amount of operation of the control lever. Also, an input apparatus which is capable of concurrently responding to both a signal generated by itself and an external signal fed thereto is provided. The apparatus includes a pilot section for exerting force which permits a shuttle to be moved against coiled compression springs. The pilot section is fed with a signal from an external hydraulic control system.

Abstract: A flow control valve has a first variable restrictor to control a flow rate of a hydraulic fluid supplied from a hydraulic fluid supply line to a hydraulic actuator and a second variable restrictor to control a flow rate of the hydraulic fluid discharged from the hydraulic actuator to a hydraulic fluid return line. A pressure compensating valve holds constant a differential pressure across the first variable restrictor, and a recovery circuit having a recovery line has a check valve that allows flow of the hydraulic fluid only toward the supply line. The recovery circuit receives at least part of the hydraulic fluid discharged from the hydraulic actuator and returns it to the supply line at a portion between the pressure compensating valve and the first variable restrictor through the recovery line upon controlling of the discharged flow rate by the second variable restrictor to thereby recover the discharged hydraulic fluid.

Abstract: A control valve for construction equipment adapted to operate a control mechanism in which a central by-pass passage is provided with a pilot pressure generating mechanism such as an orifice or the like and which is adapted to generate a pilot pressure due to pressure loss of fluid passed through the pilot pressure generating mechanism when a valve connected to the central by-pass passage is set at an open position, resulting the pilot pressure acting to control a discharge rate of a variable discharge pump. The control valve includes a valve body, in which a first spool and a second spool are arranged in series in such a manner that inner ends of the first and second spools are opposite to each other. An outer end of the second spool faces a second pilot chamber. A centering spring is arranged so as to act on an outer end of the first spool, so that the inner ends of both spools may be abutted against each other and received in a first pilot chamber when the spools are at their normal position.

Abstract: A pilot poppet (44) is unseated when a pressure in a back pressure chamber (39) exceeds a spring (47) preload force to communicate the back pressure chamber (39) with a relief port (33). The pressure in a pressure port (32) is communicated to the back pressure chamber (39) through a radial clearance between a piston poppet (61) which extends through a relief poppet (31) and the relief poppet (31). A spring (62) maintains the piston poppet (61) engaged with the pilot poppet (44). Alternatively, the piston poppet and pilot poppet may be integral (66). The relief poppet (31) is unseated by a pressure difference between the back pressure chamber (39) and the pressure port (32) to communicate the pressure port (32) with the relief port (33) since communication of the back pressure chamber (39) with the relief port (33) causes the pressure in the back pressure chamber (39) to drop. The relief poppet (31 ) seats when the pressure in the pressure port (32) drops below the pressure in the back pressure chamber (39).

Abstract: A pilot poppet (44) is unseated when a pressure in a back pressure chamber (39) exceeds a spring (47) preload force to communicate the back pressure chamber (39) with a relief port (33). The pressure in a pressure port (32) is communicated to the back pressure chamber (39) through a tubular piston poppet (37) which extends through a relief poppet (31). The relief poppet (31) is unseated by a pressure difference between the back pressure chamber (39) and the pressure port (32) to communicate the pressure port (32) with the relief port (33) since communication of the back pressure chamber (39) with the relief port (33) causes the pressure in the back pressure chamber (39) to drop. The piston poppet (37) is moved to engage the pilot poppet (44) and block communication between the pressure port (32) and the back pressure chamber (39), thereby causing the pressure in the back pressure chamber (39) to drop further.