Vibrator
856,238. Earth-excavating equipment; boring earth. INDUSTRIKOMPANIET A.B. June 29, 1959 [July 1, 1958], No. 22195/59. Classes 68(1) and 85. [Also in Group XXIX] A liquid-pressure engine for excavating, drilling rock &c., comprises a piston 42 reciprocatable in a cylinder 31 and connected by an element 37 and a spring system 44, 44a to a valve 36, 38, which is moved in accordance with the movements of the piston to connect the cylinder to a source of liquid 60 or to an outlet 63, the spring system being in a chamber 43b connected by at least one passage 55 to an outlet 64 for discharging liquid from the chamber to prevent pressure therein affecting operation of the engine. The lower surface of the piston is permanently connected to the source 60, and the upper surface alternately connected to the source and the outlet 63 by the valve which is connected to the piston by the element 37 in the form of a spindle and the springs 44, 44a engaging an abutment 43.in the chamber 43b formed in the piston rod, piston, valve chamber or valve casing, the valve thus being moved with a time-lag in accordance with the movements of the piston which are of high frequency, e.g. 6000 strokes/min. The valve chamber 43b is connected to the outlet by passages 55 in an extension of the piston or by a passage in the spindle 37. A single spring may be used. The frequency and amplitude of the movement of the piston may be varied by modifying the dimensions of the springs or by controlling the pressure of the supply of liquid. Specifications 814,240, 856,239 and 856,240 are referred to.