| 摘要 |
A power driver and method of pile driving. The invention encompasses a pile driver having a ram, cylinder and piston arrangement mounted in a framework, such arrangement being typical of those power drivers of the prior art. A compressible fluid, such as air or steam, enters into the cylinder through an intake port and leaves through an exhaust port. Both ports are controlled by a common valve. Expansion of the steam within the cylinder acts against the piston causing the piston rod to rise thus raising the ram and an associated slide bar. As the slide bar rises, it triggers the valve to move into a position effecting closure of both intake and exhaust ports. Further rising of the piston effects movement of the valve into a position wherein the intake port remains closed and the exhaust port is opened, thus exhausting the excess steam. Movement of the valve by elevation of the slide bar at each stage of movement is effected through triggering of cam followers or trips by cams on the slide bar. At the end of the power stroke, the valve is returned to the first position which opens the intake port and closes the exhaust port and the steps are repeated. Thus, during a significant portion of the total distance of travel of the piston, fluid is neither entering nor leaving the cylinder but is expanding and performing work on the piston, thereby providing an energy savings in operation of the driver of ten to fifty percent over devices of the prior art.
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