HYDRAULIC PUMP - TM-10-3930-623-120017

TM 10-3930-623-12

1-16. The distributor times the occurrence of the ignition

output to both the power steering system and the control

spark in relation to the engine by a set of breaker points

valve assembly inlet port. A relief valve in the flow

operated by an engine-driven cam. Variations in timing

divider valve limits hydraulic pressure in the power

under changing speed are accomplished through a

steering system. This relief valve cracks open at 700 psi

centrifugally operated spark advance mechanism in the

and is fully open at 1050 psi.

distributor. The timed high voltage impulses are fed

through the center terminal of the distributor cap to the

1-20. The control valve assembly is a two-spool fluid

rotor inside. The rotor then directs the high voltage to

control valve with a control handle for each spool. The

each spark plug wire (arranged from cap to spark plugs

inboard control handle and spool control the raising and

in proper engine firing order) in sequence, to spark each

lowering of the forks by applying or releasing hydraulic

spark plug at the proper time.

pressure to the hoist cylinder. The outboard control

handle and spool control tilting of the upright carriage.

1-17. HYDRAULIC PUMP. Hydraulic pressure for

Each control handle has two actuating positions with a

steering, hoisting, and tilting of the uprights is supplied

center neutral position. A pilot operated relief valve

by an engine-driven hydraulic pump. This pump is

limits system pressure to 1500 psi. The hoist cylinder is

mounted at the left rear side of the engine, driven by a

a two-stage single-acting unit, raised by applying fluid

gear which engages the camshaft timing gear. The

pressure, and lowered by releasing pressure to permit

pump is a gear type positive displacement pump.

gravity return of the elevated parts. The tilt cylinders are

double-acting cylinders.

1-18. UPRIGHT CARRIAGE AND FORK ASSEMBLY

HYDRAULIC SYSTEM (See figure 1-4). Using pressure

1-21. POWER STEERING GEAR. The power steering

from the engine-driven hydraulic pump, this system

gear unit is basically a Saginaw recirculating ball

controls raising of the forks and fore and aft tilting of the

steering gear to which has been added a torque

uprights.

The control valve assembly permits the

sensitive valving arrangement, and in which the ball nut

operator to direct pressure to the hoist cylinder for

has been redesigned to act as a hydraulic piston. The

raising the forks, or to the tilt cylinders to adjust the

valve (see figure 1-6) is an open-center rotary three-way

angle of the uprights and forks.

valve, with a grooved spool to

1-19. The flow divider (priority) valve directs the pump

Figure 1-5. Steering System Arrangement

1-5