| 摘要 |
<p>A 'down-the-hole' hammer operated by a supply of compressed air, comprising a backhead assembly (11) and an air distributor (41) secured to an outer cylinder (6), an inner cylinder (47) mounted adjacent the outer cylinder for defining a porting arrangement (14), the air distributor extending within the inner cylinder, a piston (4) slidably mounted with respect to the inner and outer cylinders and adapted to reciprocate therein so as to repeatedly strike a bit (5) mounted in a chuck at the forward end of the outer cylinder, wherein the rear end of the piston, the air distributor and the inner cylinder together define a rear pressure chamber (2), which when fully pressurized drives the piston towards the bit, and wherein the forward end of the piston, the bit and the outer cylinder together define a forward lift chamber (1), which when pressurized lifts the piston away from the bit after it has struck the bit, wherein a sliding valve member (42, 60) is provided within the rear pressure chamber (2) adapted to vary the effective pressurizable volume of the rear chamber during the cycle of operations which causes a piston to reciprocate within the hammer.</p> |
