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Diesel Hammer Operation
Figure  12-62.Trip  mechanism.

Equipment Operator Basic - Beginning construction equipment operators manual
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Figure 12-61.-Operating principles of the McKiernan-Terry diesel pile hammer. precise  moment  of  impact  for  perfect  timing.  The  fuel is atomized and splattered into the annular (ring-shaped) zone between the ram and the anvil and is ignited by the heat of compression. The  resulting  explosive  force  drives  the  ram piston upward and the pile downward and adds a push to the pile to extend the time of the total effort to drive the  pile. On the upstroke, the ram piston opens the exhaust ports (F) to permit scavenging the exhaust gases. The ram  piston  continues  freely  upward  until  arrested  by gravity. The  length  of  the  stroke  varies  with  the resistance  of  the  pile. The greater the resistance, the longer  the  stroke. Having reached the top of its stroke, the ram piston falls again, repeating the cycle. The hammer is stopped by pulling a rope (G) that disengages the fuel pump cam (D). TRIP MECHANISM.— The trip mechanism (fig. 12-62) is an off-center linkage mechanism located at the rear of the hammer, designed to lift and drop the ram for starting.    Additionally, the trip mechanism lifts and lowers the hammer in the leads. The trip mechanism is connected to a single line from the crane. Lowering the trip mechanism to the bottom of its stroke engages the lifting lever that lifts the ram. When the crane lifts the trip mechanism and ram piston past the upper stops, the finger of the trip lever is rotated clockwise around the trip lever pin, thus freeing the ram piston. The trip mechanism  is  held  in  the  upper  position  while  the hammer is in operation. The safety link in the trip mechanism is designed to break  or  bend  should  the  operator  lower  the  trip mechanism to low and engage the lifting lever while the hammer is in operation. The safety link prevents damaging the trip mechanism or ram. If the safety link is broken while the hammer is in operation, the hammer will continue to operate; however, once the hammer is shut down, the safety link must be replaced before the hammer can be restarted. 12-43







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