To miniaturize the whole of a device by employing a cylinder expanding and contracting elastically under hydraulic pressure as a spring for recovery and installing a mechanism of a rack and a pinion interlocked with a plunger of the cylinder between the cylinder and a link.

A storage body 2 is installed through the intermediary of the rotary links 4, 4 in a manner such as to be able to move forward and downward. The links 4, 4 are mounted in a manner such as to be able to rotate within the range of prescribed angles on the internal surfaces of right and left side plates 1a, 1a of a frame 1. The cylinder 5, which is provided with the plunger 5a protruding elastically under the hydraulic pressure, is mounted in an attitude such as to steer its extendable and contractible direction vertically on either of the side plates 1a, 1a. A rack 5b is mounted on the side surface of the plunger 5a, and the pinion 6 engaging with the rack 5b is mounted coaxially on a rotary shaft 4a on the side of the side plate 1a of any of the links 4, 4 and integrally on the link 4.