jcb JS300 Service Manual page 716

Section E - Hydraulics
Hydraulic System
Hydraulic Operation and Schematics
Hammer Circuit
K Fig 17. ( T E-56)
For Schematic,
The hammer function only works when the hammer pedal
53 is pressed in a forward direction. In this position pilot
pressure from the foot pedal closes the hammer pressure
switch 45. The ECM then selects the pre-set hammer RPM
on the engine.
Pilot pressure from the pedal 53 selects the auxiliary spool
via port pa2.
The hammer/auxiliary solenoid B remains de-energised in
hammer mode allowing pilot pressure to select the
hammer/auxiliary changeover valve 27 to select hammer
mode.
Flow from pump 2 crosses the selected hammer spool and
exits the valve block at port A2. At the changeover valve 27
the pressure to the hammer is regulated by the hammer
ARV which is now in circuit via the selected valve 27.
Returning oil is diverted direct to tank via the hammer filter
through the changeover valve 27.
Pilot pressure from the hammer pedal 53 is also available
to the upper pilot pressure switch 52.
E-55 9813/5100-1 E-55