Table of Contents
Advertisement
MODEL 220
HYDRAULIC
IMPACT HAMMER
V.
HYDRAULIC CIRCUITRY
A. DRIVE PUMP (CONTINUED)
After the upward movement of the ram stops, it begins to fall because the DUMP
VALVE is already open. While the ram is falling, and during the deceleration phase
of the cycle, pump flow is stored in the PRESSURE ACCUMULATOR. While the
ram is falling, the CONTROL VALVE is held in its shifted position by a pilot signal
generated by the DUMP VALVE. Oil exiting the DUMP VALVE, at high speed,
goes directly to the blind end of the CYLINDER and does not restrict the downward
movement of the ram. When the ram impacts the pile, the downward movement of
the cylinder stops, and the pilot signal is removed from the CONTROL VALVE. A
spring returns the CONTROL VALVE to its normal (lift) position, and another lift
cycle begins. The CYLINDER will continue cycling, as described above, until the
DIRECTIONAL CONTROL VALVE (V2) is de-energized by returning the
FORWARD/REVERSE switch to the NEUTRAL position. When the trip valve is
activated by the trip bar, a pilot pressure signal is sent to the CONTROL VALVE
(V3) pilot piston, shifting the CONTROL VALVE. The balance of the cycle is the
same as in the long stroke position, above.
B. STROKE CONTROL PUMP
With the diesel engine running, hydraulic oil is taken from the reservoir by the
stroke control pump (P2). The stroke control pump oil returns to the reservoir if the
clamp switch is in the NEUTRAL position. Returning oil is filtered by the return filter
(F2).
Turning the clamp switch to CLOSE retracts the variable stroke cylinder (CLY2).
Returning the switch to neutral allows the hammer to run at that stroke length.
Turning the clamp switch to OPEN momentarily, extends the variable stroke
cylinder (CLY2) Pressure is indicated by the pressure gage (GA-2). Pilot pressure
in the stroke control circuit is limited to 1500 PSI (103 Bar) by the STROKE RELIEF
valve (RV2). Adequate pressure to extend and retract the variable stroke cylinder
is insured by relief valve (RV2).
The quick-disconnect coupler (QD3 and QD4) permits de-coupling of the stroke
control hose at the power pack.
V-2
Advertisement
Table of Contents
