jcb JS300, Service Manual

Page: 47 / 51

03 - Attachments, Couplings and Load Handling
10 - Excavator Arm Quickhitch
06 - Hydraulic Quickhitch
03 - 9 9813/7500-2 03 - 9
Operation
The quickhitch latch electrical control system allows
operation of the quickhitch hydraulic latch when
the boom and dipper are in the correct position. A
solenoid valve diverts oil pressure to the quickhitch
latch ram.
The quickhitch latch control system is controlled by
the HECU (Hydraulics Electronic Control Unit).
There are three ground inputs to the HECU:
• When the dipper position sensor recognises
that the dipper is in a safe position
(perpendicular or closer to the cab) it sends a
ground signal to the HECU J2 pin 29.
• When the boom position sensor recognises that
the boom is in a safe position (parallel to the
ground or lower) it sends a ground signal to
HECU J2 pin 34.
• When the bucket crowd service operates the
quickhitch pressure switch sends a ground
signal to J2 pin 35.
When the quickhitch momentary switch is pressed
a ground signal is seen at J2 pin 3. If the operator
has pressed the switch by mistake the switch can be
selected in the opposite direction and an input is sent
to pin 15 to cancel the request.
When the HECU receives the input from the switch
it will inform the DECU (Display Electronic Control
Unit) via the CAN (Controller Area Network)bus of
a quickhitch unlock request. The DECU will then
display the boom/dipper/ padlock symbol. As the
boom and dipper position sensors connect the HECU
to ground, the applicable symbol will change to green
to show that either boom or dipper are in the correct
position to allow operation of the quickhitch. The LED
(Light Emitting Diode) lights on the boom will also
flash to act as a warning to others that the attachment
can release from the dipper.
With the dipper and boom now in a safe position
and bucket crowd pilot switch closed, the operator
can select the quickhitch button (C095 - X2) on the
right hand controller. This will send a ground signal
to HECU J2 pin 16 and the HECU energises the
quickhitch solenoid. The quichhitch hydraulic latch
opens.
When the quickhitch is in the unlock position the
DECU will display the padlock unlocked symbol and
activate the warning buzzer. The LED on the boom
comes ON to warn personnel that the quickhitch latch
is open.
The button on the right hand controller must remain
pressed throughout the operation. If the button is
released before the procedure is complete the unlock
procedure must be repeated from the start.