Hydraulic percussion tool with gas cell energy accumulator - has double piston and controls frequency and magnitude of applied force

摘要

The percussion unit for bush hammering etc. is operated by hydraulic, and includes a gas-cell (19) energy-accumulator. The unit provides for the adjustment of both the frequency and the magnitude of the applied force. The unit has a compression piston (21) and a hammer-piston (14) within a cylindrical casing (11). A pressurised fluid feed system (1-9) which can vary the fluid pressure in the least one feed line, supplies hydraulic fluid to the casing (11). The gas-cell (19) between the compression piston and the rear of the hammer piston (14), may be formed by a tubular membrane (18), and compressed as the compression hammer (21) advances. A retaining mechanism holds the hammer piston (14), to release it when the gas is compressed, and thus, obtains the abrust projection of the hammer piston. The membrane (18) may be fixed to the rear of the hammer pistn and may locate within the bore of the casing and within an annular volume of oil (11c).