GB1039229A - Control of variable-stroke power hammers - Google Patents

Abstract

1,039,229. Power hammers. RAYMOND INTERNATIONAL Inc. Feb. 24, 1965 [April 15, 1964], No. 8038/65. Heading B3H. [Also in Division E1] An hydraulic power hammer, suitable for use in pile driving, includes a ram 21 attached to a piston 41 in a cylinder 12, and controlled by means of a cycling valve 34. After each downward working stroke of the ram the valve is reset for raising the ram by means of a water hammer effect. A vertically slidable cam 28 moves with the ram, a cam follower 29 being linked to the spool 33 of the valve. As shown, the piston and ram are moving downwardly since the fluid supplied from a source 42 to the upper part of the cylinder, through lines 44, 45, 46 and 47, acts on a greater area than that supplied at 56 to the lower part of the cylinder. When the ram strikes a pile, the sudden deceleration of the piston causes a sudden rise in pressure in the line 47, due to water hammer, this rise causing a release valve 50 to move the valve spool 33 to the right. This vents the upper end of the cylinder through lines 54, 55, and 43, thereby causing the piston to rise. Simultaneously the cam follower is rotated by the link 32 to the dotted position so that, as the piston nears the top of the cylinder, the cam 28 shifts the follower out again to reset the cycling valve to its first position. Should the ram not strike a pile, the piston passes inlet 56 and is cushioned on the volume of fluid beneath the piston, a check valve 57 preventing an excessive pressure rise in this volume. The cycling valve 34 is still actuated, however, the general rise in pressure of the system as provided by a positive displacement pump causing the valve 50 to operate. A modified but basically similar arrangement can be used where the valve 34 acts as a pilot valve, and a further, cycling, valve is provided. Figs. 7 and 8 (not shown) indicate a possible disposition of the power hammer in a cylindrical shell 80, the cylinder 53 being integral with the main housing 82 of the apparatus. A ram 86 is shown compressing a bulb pile 88 prior to filling the shell 80 with concrete.