pump oil in the rod end of cylinder (19) cannot move the
piston because door check valve (22) stops the oil from
the head end of cylinder ( 19). When the piston can not
be moved, the pump oil pressure increases and this
increase in pressure through pilot oil line (18) opens door
check valve (22). The pump oil in the rod end of door
cylinder (19) now pushes the piston and rod, connected
to the door, to open the door. After the door opens, the
pump oil in the head end of ejector cylinder (15) moves
the piston and rod, connected to the ejector, and the
The oil pushed, by the pistons, from the rod end of
ejector cylinder (15) and from the head end of door
cylinder (19) goes through line (5), through control valve
(3) and through return oil line (13) into the filter and tank
Release the ejector control lever and a spring on the
ejector valve spool moves the valve spool to HOLD
position (B). The HOLD position stops the oil in lines (4)
and (5) and neither the ejector or door can move until the
ejector control lever is moved.
SCHEMATIC OF HYDRAULIC SYSTEM FOR ELEVATOR FAST FORWARD
1. Elevator hydraulic motor.
9. Relief valve (bowl
15. Ejector cylinder.
22. Pump (elevator).
2. Bowl cylinders (two).
16. Oil line (bowl circuit).
A. REVERSE position.
3. Control valve.
10. Oil line (to elevator
17. Oil line (for steering).
B. HOLD position.
4. Ejector valve spool.
18. Door cylinder.
C. FORWARD position.
5. Bowl valve spool.
11. Oil drain line.
19. Filter and tank.
H. HIGH SPEED position.
6. Elevator speed valve.
12. Elevator control valve.
20. Pump (bowl and
L. LOW SPEED position.
7. 8. Oil lines (for hydraulic
13. Return oil line.
14. Relief valve (elevator).
21. Door check valve.
The elevator control lever is held in FORWARD position
by the detent balls, in elevator control valve (12), that
keep the elevator valve spool in FORWARD position (C).
With the speed control lever in HI position, the valve
spool in elevator speed valve (6) is in HIGH SPEED
The oil from both sections of pump (22) goes to elevator
control valve (12). The oil from the drive end section
goes through line (10) to valve (12). Elevator relief valve
(14), with a pressure setting of approximately 2500 psi
(176 kg/cm2) (17 250 kPa), prevents high oil pressure
damage to the parts in the oil circuit from pump (22). The
oil from the cover section of pump (22) goes through