| 摘要 |
An anvil is formed on one end of an elongated piece and the piece is driven into the ground or the like by impacting the anvil with a reciprocable ram driven by a drive mechanism that is operated by a valve which is reciprocably mounted in a normally balanced two directional fluid pressure circuit to reciprocate in the alternate directions thereof when the circuit is unbalanced in the respective directions thereof. The circuit has a pair of outlets therein which are connected with the opposing ends of the valve and disposed to slidably engage with the ram during the stroke thereof. The ram comprises an anvil impacting body having a striking surface on one end thereof and a pair of grooves in one laterally oriented face thereof which are mutually offset longitudinally the the reciprocable axis of the body on spaced parallel lines to form collateral mutually longitudinally offset lands on the lines. The grooves are adapted in axial extent, respectively, to discharge fluid from one of the outlets while the corresponding land covers the other outlet, and vice versa, to generate opposing fluid pressure differentials in the circuit across the valve and thereby unbalance the circuit in the respective directions thereof, when the body is reciprocably supported and guided in the apparatus and driven by the mechanism so that the lines of the grooves and lands intersect the outlets.
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