GB1253538A - A transducer for converting liquid pressure oscillations into mechanical oscillations - Google Patents

Abstract

1,253,538. Liquid actuated rock drill. A. F. HYDRAULICS Ltd. 17 June, 1969 [2 July, 1968], No. 31606/68. Heading B4C. [Also in Division F1] In a transducer for reciprocating a rock drill bit 19, Fig. 1, wherein a piston 11 is oscillated in a cylinder 12 by pressure pulsations applied to at least one of the chambers 13, 14 on opposite sides 21, 22 of the piston, excessive movement of the piston to one side thereof e.g. to the right displaces an axially movable valve 27, Fig. 3, whereby pressure fluid within a storage container 28 is passed to cylinder chamber 14 thereby returning the piston to its central position; the container 28 being maintained at a pressure greater than the algebraic mean pressure in chamber 13 by means of a flow regulator valve 26. As shown both chambers 13, 14 are subjected to pressure pulses of opposite phase and the piston 11 comprises large and small area lands 21, 22. A shoulder 39 on land 21 abuts a flange 37 of valve 27 and serves to displace the valve against a spring 39a until a valve land 32 becomes unseated from the fixed valve body 30 resulting in oil container 28 being connected through a port 35 to chamber 14. On further movement of the valve 27 a second land 36 becomes unseated from the valve body 30 and chambers 13, 14 become directly connected and piston reciprocation ceases. Pist on lands 21, 22 are formed on a sleeve 16 slidable on an inner rod like piston member 17 carrying a heavy mass 18 at one end and having at its other end a counterbore engaged by a relatively slidable plunger 60, Fig. 5, rigid with the outer end of sleeve 16 and forming an act filled dash pot device 54. The mass 18 slides within a sleeve 45 spaced radially inwardly of the end of cylinder 12 to provide an oil-filled space 46 provided with a damping valve whereby should the piston move excessively to the right e.g. due to the tool 18 breaking through soft material, the sleeve 45 yields to the mass 18. The outer end of piston sleeve 16 is supported by a bearing 80 which may be of the resilient type. In a modification the piston 11, Fig. 8, is in one tubular piece and is slidably connected at one end 98 by a tubular spigot 96 held on a spherical seat 100 of the cylinder end by a split clamp ring 102. Oil leakage is passed through a return line 104 and the piston interior is vented to atmosphere through a filter 108.