E - Fixed Constructions – 21 – B
Patent
E - Fixed Constructions
21
B
255/13
E21B 4/14 (2006.01) E21B 21/12 (2006.01)
Patent
CA 1295604
ABSTRACT OF THE DISCLOSURE: A pneumatic percussion hammer for rock drilling has a tubular casing (10) with a top sub (23) for connection to the outer tube of a double tube drill stem, an air feed pipe (19) from the top sub (3) extend- ing co-axially into the casing and co-axially about an air outflow pipe (21) for connection to the inner tube of the drill stem, its lower end being slidable in an air passage (38) through a bit (31) of which the shank (32) is slidable, a driver sub (33) at the lower casing and is topped by an anvil (35), this passage (43) having ducts (39) being to the exterior of the bit, the air outflow pipe having ducts (44) to the bottom of the bit (31). A tubular piston (27) slidable in the casing (10) and about the air outflow pipe (21) slidably engages, when brought down onto the anvil (35), a sliding seal tube (37) rising from the air passage (38) through the bit, shank and anvil. Annular chambers (11, 12, 13) are formed within the casing (10) and the axial passage of the piston is divided into upper and lower passages (29, 30). The piston (27) is so formed with ports (45, 46, 47, 48) as to act as a valve for effecting reciprocating movement, impacting the anvil (35) on its downstrokes, but if the casing (10) is raised to lift the bit (31) from its work face, the anvil (35) and piston (27) so descend that the hammer is in a state of balance and automatically ceases operation.
550225
Lister William
Robic
LandOfFree
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