Hydraulic motor for percussion tool e.g. road drill - uses high frequency fluctuating fluid pressure opposing gas buffer to motivate piston

摘要

The hydraulic motor is for use on a percussion tool e.g. a road-drill. High frequency fluctuating oil pressures drives a primary piston (10) within a cylinder (9), and recoil pressures are provided by a cushion or buffer of compressible gas. A variable pressure feed controls the flow of hydraulic fluid, and the gas occupies a accumulator cell (16). The primary piston has an axially projecting transmission rod (53) which conveys piston motion to the tool (20), and the rod and the relevant piston face delineates an annular volume (52) within the cylindrical housing. The hydraulic fluid acts on the piston through the medium of this latter annular volume. The gas buffer (16) acts on the opposite piston (10) face, and may be confined by a tubular membrane (11).