Abstract: The hydraulic circuit of the invention includes first and second directional control valves 13, 15, each shiftable between three positions. Hydraulic circuit extending from the second directional control valve 15 and a second cylinder 7 to a first cylinder 11 is so configured that, when the second directional control valve 15 is shifted to the first position, with the first directional control valve 13 being assigned to the N-position, hydraulic oil from the second cylinder 7 is directed to the first cylinder 11, so as to cause the attachment 9 to be tilted in the forward direction, and when the second directional control valve 15 is shifted to the second position, hydraulic oil expelled from the second cylinder 7 is directed to the first cylinder 11, so as to cause the attachment 9 to be tilted in the rearward direction.

Abstract: In a self-sealing coupling with a bypass for a hydraulic circuit designed to connect a hydraulic sub-circuit to a midway portion of a main circuit of a hydraulic device, there is provided a coupling body with an input passage, an output passage, an input passage side and an output passage side self-closing valves and a bypass valve. The bypass valve is provided with a cylindrical valve element which is reciprocatively slidable within either one of said input passage and said output passage so as to open and close that one passage relative to a bypass provided therebetween. The cylindrical valve element is adapted to be moved together with the self-closing valve element provided in the one passage, to be shifted to a bypass valve opening position where the bypass is opened by the cylindrical valve element valve closed condition.

Abstract: A speedup device or valve means comprises a check-valve disposed in an oil passage connected with the rod-end chamber of a double-acting cylinder for preventing working oil from returning toward a tank only, a circulation valve provided in the upstream of said check valve, said circulation valve being usually urged by a spring to block communication between the oil passages connected with the rod-end and the piston-end chambers, respectively, said circulation valve being designed to move against the spring so as to connect the oil passages with each other in response to the pressure rise in the return oil from the rod-end chamber when said double-acting cylinder is in its rod-extending motion, causing the return oil from the rod-end chamber to shift into the piston-end chamber through a variable restriction, and a circuit set up in a portion of said circulation valve for allowing a portion of the return oil from the rod-end chamber to return to the tank through a variable restriction and a restriction passage

Abstract: A lockable pin comprises a ring-like locking element which is cut at a place on the circumference to provide free ends at which it is pivotally attached to the pin body.In use, the pin is inserted in a throughgoing hole formed in a shaft end and the locking element is brought into engagement with a recess formed in the front end of the pin body or with an annular groove formed in the shaft end. The locking element is firmly held in the recess or groove by the elasticity of the locking element itself or by an upward elastic force acting on the pin body.

Abstract: A speedup device for reciprocating cylinders which make use of fluid pressure such as hydraulic pressure or pneumatic pressure. The speedup device incorporates a poppet valve adapted to be moved for valving upon application of fluid pressure and is installed in a pipe line connecting a control valve to the front and rear chambers of a cylinder, the arrangement being such that when the rod of the reciprocating cylinder is to be extended, all the return from the front cylinder chamber flows into the rear chamber, thereby speeding up the extension of the rod of the reciprocating cylinder.

Abstract: An apparatus for controlling the hydraulic system of hydraulic actuators, such as hydraulic cylinders. The apparatus is constituted only by a combination of two kinds of control valves in that normally opened and normally closed, solenoid-operated, spring-returned type control valves are serially connected together through a common port formed in each control valve.