ES403891A1 - Hydraulic repeating hammer - Google Patents

Abstract

A hydraulic repeating hammer has a hydraulically actuated striking piston mounted on bushings for longitudinal movement in a cylinder. A piston ring flange about the middle of the elongated cylindrical piston body subdivides the annular space between the piston and the cylinder, which space is terminated longitudinally by the bushings, into two cavities each of which is adapted to be filled or emptied through one or more ports connected to the hydraulic system. The hydraulic system includes a pump with a storage tank on its intake side, a valve unit and lines interconnecting the pump, storage tank, valve unit and cylinder ports. The connection between the cylinder ports and the rest of the hydraulic system is preferably by flexible hose for isolation of mechanical shock generated by the striking piston. The portions of the piston on either side of the piston ring flange have different diameters, so that the hydraulic chambers have different radial dimensions and hence different rates of change of volume with respect to piston displacement. This feature makes it possible to connect the chamber with the smaller rate of change of volume continuously to the pressure side of the pump, so that only one port per chamber and two on-off valves are needed. An electronic system electromagnetically controls the operation preferably by digital logic, and provides for independent control of the stroke repetition rate, stroke length, dwell period and stroke start position. The piston may have an axial bore through which a pull rod with an end cap or flange may pass. The pull rod may be screwed on to the tool chuck in order that the hammer may be used to pull out a tool as well as to drive a tool into the work. Proximity switches in the cylinder ends are interconnected with the control system to protect the cylinder and its associated structure from unnecessary shock.