Chapter 10. HYDRAULIC SYSTEM REPAIR INSTRUCTIONS

TM 10-3930-621-34

CHAPTER 10

HYDRAULIC SYSTEM REPAIR INSTRUCTIONS

Section I. HYDRAULIC SYSTEM

forward, hydraulic oil pressure is released and the

10-1. Description

carriage and masts are lowered by their own weight.

The hydraulic system is comprised of a hydraulic

c. Tilt Control.

reservoir, a hydraulic pump, control valve, three section

mast assembly, tilt cylinders, and associated hydraulic

(1) When the tilt control handle is

hoses and hose connections. Refer to figure 10-1.

pushed forward, hydraulic oil pressure is applied through

the control valve to the rear of the tilt cylinders. The

10-2.

Operation

cylinder plunger rods move forward and tilt the masts

forward. At the same time, hydraulic oil in the front of the

a. Pump Action. The hydraulic pump draws

tilt cylinders is recirculated through the control valve.

oil from the hydraulic reservoir and supplies oil under

pressure to the control valve.

(2) When the tilt control handle is

centered, hydraulic oil pressure is equalized in both sides

b. Lift control.

of the tilt cylinders and the masts remain in the desired

tilt.

(1) When the -lift control handle is

pulled back, hydraulic oil is delivered through the control

(3) When the tilt control handle is pulled

valve to the two outer cylinders on the cylinder cluster

back, hydraulic oil pressure is applied through the control

(12, fig.10-3). Oil pressure forces the two outer cylinder

valve to the front of the tilt cylinders. The cylinder

rams upward, raising the chains and lifting the carriage

plunger rods move backward, resulting in a backward tilt

up the mast. Continued raising actuates the center

of the masts. At the same time, hydraulic oil in the rear

cylinder of the cluster and the single lift cylinder.

of the tilt cylinders is recirculated through the control

valve.

(2) When the lift control handle is

released to neutral, hydraulic oil pressure will hold the

carriage stationary.

(3) When the lift control handle is pushed

10-1