Abstract: A piston for a striker is displaceable in a cylinder and forms compartments on opposite sides which can selectively be connected by hydraulically controlled valve elements to a pump and to an accumulator. A hydraulic controller for the valve elements initially connects a compartment on one side of the piston to contribute the pressure from a respective compartment to the accumulator during a lifting operation, cuts off the valve element affording this pressure accumulation to brake the piston, and other such valve elements enable the accumulator to be charged with the piston in its raised position so that, upon triggering by the controller of the valve elements, the pressure which drives the ram is equal to the total pressure delivered by the accumulator and the pump to the piston.

Abstract: The invention refers to a step adjustable monoaxial vibrator intended to be used on the vibrating rollers or similar machines.In order to adjust the peak value of the excitation at various levels, it has three rotary balls (rollers) rolling along the pendular frame rolling path while being driven by a dynamic balanced fork as a rotor.Across the rotor axle there is an obturating rod in order to locate the central ball either in the same compartment or in the opposite one versus the remaining two balls.This allows the steady frequency excitation to be set up either at the maximum peak value or at a value three times lower. By removing the central ball, a medium size excitation is obtained.