GB1424494A - Exhaust means for percussion tool motors - Google Patents

Abstract

1424494 Boring earth &c HUGHES TOOL CO 16 May 1974 [25 June 1973] 21840/74 Heading E1F The drill bit 17 of a fluid operated, percussion drilling apparatus is retained in its housing 13 when the bit is suspended above the bottom of a borehole by a shoulder 25 on the bit 17 engaging a split-type stop ring 29 which has fluid passage means to permit the by-pass of fluid past the exterior of the bit. the ring and the housing to cause cessation of piston hammer 11 reciprocation. As described the stop ring 29 consists of two body portions 31, 33 held together by a flexible retainer in a peripheral groove 36 and having oblique ends 51 which form a groove for the by-pass of fluid. The stop ring 29 is fixed in the housing 13 between a shoulder 49 on the housing 13 and a surface 41 formed on the end of a splined driver sub 57 screwed into the housing 13. When the bit 17 is suspended above the bottom of the borehole a shoulder 25 on the bit 17 engages the stop ring 29 as shown in Fig. 1, and fluid in the working chamber 23 can escape, as indicated by the arows, through the grooves 51 in the stop ring 29 and between the bit 17 and sub 57 to cause cessation of the piston-hammer 11 reciprication.