| 摘要 |
<p>A hydraulically-operated road breaker comprises a casing with a tool mounting and housing an oscillatory piston/striker and cylinder arrangement. A sequence valve mounted in the casing controls pressurisation and exhausting of the piston to produce power and return strokes of the piston. Pilot port means positioned in the cylinder of the device are uncovered, at the end of each return stroke of the piston, to allow a valveactuating flow of hydraulic fluid through the port means to change over the sequence valve and thereby cause stroke reversal of the piston. Manually-operable stroke selection means provide for adjustment of the position of the piston in the cylinder at which the valve-actuating flow occurs, whereby to vary the piston stroke.</p> |
