Abstract: A hand crusher with a main body, which consists of a cylinder unit having a built-in oblong hydraulic cylinder and a parallel plate unit bonded on the periphery of said cylinder unit. Crushing arms are pivotally supported on the lower portion of the parallel plate unit, and the crushing are opened or closed in linkage with a piston rod, which extends from the hydraulic cylinder and makes reciprocal movement along the center line. Slide keys located at the tip of the piston rod engage in guide grooves on the parallel plate unit. A ring-like handle member is rotatably mounted on the rotating unit at the upper end of the cylinder unit, and a left grip and a right grip are connected on both ends of the handle member. On the inner periphery of the rotating unit of the handle member, balls are movably embedded at symmetrical positions, and catching recesses to catch the balls are furnished at every predetermined angle on the outer periphery of the rotating unit.

Abstract: A crusher for concrete structures, having a head carried by a traveling carrier, a rotating base supported by the head concentrically therewith for rotation relative thereto, a pair of hydraulic cylinders pivotally supported at ends by the rotating base and symmetrically disposed, a pair of jaw members pivotally supported by the rotating base and symmetrically disposed, and click-stop means provided between the head and the rotating base, the hydraulic cylinders being drivingly coupled to the respective jaw members. The rotating base and the head are coupled to each other by a rotative coupling arrangement comprising first and second disc members disposed in face-to-face engagement with each other, synthetic resin-made bearing members, and stopper means for preventing disengagement of the second disc member from the first disc member.