Operation - jcb JS300 Service Manual

The remote control valve is a pressure reduction valve
used to control the servo pressure operated system. Four
pressure reduction valves used to control the servo
pressure are located in the main housing. Direction of the
output servo pressure is controlled by selective movement
of the control lever. The valves and control levers are
mounted in the arm rests on both sides of the operator's
seat.
The pressure reduction unit is comprised of spools 17,
pressure control springs, return springs and spring seats
13. The spools 17 are held against the plungers 11 by the
return springs 15. When the control handle is tilted, the
plungers 11 move down, depressing the return spring
seats 13, simultaneously compressing the pressure
control springs moving the spool, allowing hydraulic oil to
flow to the designated pilot port.
The lower end of the main body contains the main inlet port
P, outlet port T to tank and the servo pressure outlet ports
1, 2, 3 and 4.
The servo pressure controls the stroke and direction of the
main control valve spools. This is achieved by providing a
spring at one end of the main control valve spools and
applying pilot pressure to the opposite end. (In some
cases, pilot pressure is applied to both ends of the control
valve spool.)
Function
Oil supplied by the hydraulic servo pump enters at port P
and the function of the spools 17 is to direct oil from the
inlet port P to the output ports 1, 2, 3 and 4 or alternatively,
to the exhaust port T to tank. The pressure control springs
act on the spools 17 to determine pressure at each port.
Plungers 11 slide in the guides to vary the compression in
the springs. The control handle, fixed to the adjusting nut
24 and circular rocker plate 25 is operated to move the
plungers 11. The control handle is able to rotate 360°
around the knuckle joint 26.
The return springs operate between the casing and the
seats 13, regardless of the outlet pilot pressure, returning
the plungers 11 to their outer positions, ensuring the
spools 17 return to their neutral (closed) positions. The
springs also provide a resistive force, giving the operator a
`tactile feel' of the controls.
E-98

Operation

TE-008
The control handles contain electrical push button and
rocker switches which are used to operate auxiliary
services.
9813/5100-1
Section E - Hydraulics
Hydraulic Control Levers
Operation
E-98