Hydraulic hammer

摘要

A hydraulic hammer for driving a pile into soil in which an impact weight is arranged for being driven with reciprocating motion along guideways in a casing by a double-acting hydraulic cylinder. A pump having a drain line and a pressure line is connected to drive a piston in the hydraulic cylinder. Two two-position valves connect a piston cavity of the hydraulic cylinder with the pressure line or the drain line of the pump. Each valve has a valving element whose front axial end bears against a seat along an annular contact surface when the valve is closed. The valves carry at their rear axial ends control pistons, each of which has a diameter smaller than the diameter of the contact surface of the valving element with the seat. The two valves are coaxially arranged in opposition to one another and control communication between the hydraulic cylinder and the pressure or drain lines of the pump. Each valving element is in the form of a cylinder sealingly accommodated in a valve body along its outer diameter, the size of which is close to the diameter of the contact surface of the valving element. A cavity located at the front axial end of one valving element is communicated with a cavity located at the rear axial end of the other valving element.