Impact Hammer - Hammer Trip System Operation (Refer To Figure K-7.)
There are four stages of operation for the hammer trip system. The hammer trip assembly, moving
along the hammer trip track rails and controlled by the hammer line (main hoist) of the crane, is used to
start the impact hammer by raising and automatically releasing the piston at a predetermined height
The predetermined height is determined by the position of the trip disengage lug on the impact
hammer. To start the impact hammer with the hammer trip assembly, the weight of the impact hammer
must be fully on a pile, allowing the following sequence to occur:
With the trip safety lever cord (attached to the trip safety lever) pulled and held in place
by ground personnel, the trip engage lug is engaged. The hammer trip assembly is then
lowered by the crane operator, via the hammer line (main hoist) of the crane, along the
hammer trip track rails. The lifting pawl is in the vertical disengaged position.
As the hammer trip assembly is lowered, the cam attached to the lever and shaft
encounters the trip engage lug mounted at the bottom of the upper cylinder. The trip
engage lug pushes the cam (and lever and shaft) upward, rotating the lifting pawl
towards the horizontal, engaged position via the connecting links.
The hammer trip assembly is raised by the hammer line (main hoist). The lifting pawl is
in the horizontal engaged position. The connecting links have passed "over-center" and
rest against the stop pin. The leaf spring assists in rotating the connecting links over-
center and retaining them in position. As the lifting pawl engages the lifting collar on the
piston, the piston is lifted and the connecting links bear against the stop pin.
The crane operator continues raising the hammer trip assembly, via the hammer line
(main hoist), until the lever and shaft encounters the trip disengage lug. The connecting
links will rotate away from the over-center position and the stop pin, causing the lifting
pawl to rotate to the vertical disengaged position. The piston falls freely.
The crane operator must cease hoisting the hammer trip assembly as
soon as the piston falls.
The normal position of the trip safety lever is used to lock out the hammer trip assembly in order to use
the hammer line (main hoist) to raise and lower the entire impact hammer. The trip safety lever is held
in its normal position by a spring (when the trip safety lever cord is not pulled) and maintains the trip
engage lug in the disengaged position. The trip disengage lug is out of alignment with the hammer trip
assembly and will not engage with the cam attached to the lever and shaft.
The trip safety lever is used to engage the trip engage lug to allow the hammer line (main hoist) to raise
the hammer trip assembly (and piston) in order to start the impact hammer. This is accomplished by
pulling and holding the trip safety lever cord attached to the trip safety lever. This will rotate the trip
engage lug into position in order to engage with the cam attached to the lever and shaft of the hammer
trip assembly when lowered.
Rotating the lever and shaft with a wrench can manually disengage the hammer trip assembly.