Overview; Brake Master Cylinder; Wheel Brake - Yale A7S1 Service Manual

8000 YRM 2199

OVERVIEW

Brake system is in a front double-wheel brake type,
and it is composed of brake master cylinder, Dry
Brakes (Drum and Shoes), and brake pedal.

BRAKE MASTER CYLINDER

The brake master cylinder contains a valve seat, one-
way valve, return spring, primary cup, piston, and
secondary cup. It is held together using a thrust
washer and snap ring. The external part is protected
through a rubber dust cap. The master cylinder piston
moves with a push rod that is operated by the brake
pedal. When brake pedal is activated, the push rod
pushes the piston forward, and the brake fluid in the
cylinder body flows back to oil tank through return oil
port, until the primary packing cup blocks the return oil
hole. After primary packing cup blocked the return oil
port, the brake fluid in front cavity of master cylinder is
1. TO OIL RESERVOIR
2. TO WHEEL SPEED REDUCER

WHEEL BRAKE

The wheel brake is a internal expansion, hydraulic
type, composed of brake shoes, spring, wheel cylinder,
adjuster, and bottom plate. The two brake shoes are
mounted on the two ends of the front axle. One end of
brake shoe is connected with support pin, while the
compressed and opens the one-way valve. This allows
oil to flow to the wheel cylinder through the bypass
pipeline. The pistons of the wheel cylinders extend
outwards. This causes friction plate of brake shoes
and the brake drum to contact each other, allowing the
forklift truck to deceleration and brake. The rear cavity
of piston is supplied with the brake fluid from return oil
port and oil inlet port. When brake pedal is released,
the piston is retracted by the return spring. Brake
cylinders are likewise compressed by return spring of
brake shoes, causing the brake fluid to return to the
master cylinder (the front cavity of piston) through a
one-way valve. The piston returns, and the brake fluid
in master cylinder flows back to oil tank through return
oil port. The pressure of the one-way valve adjusts to
to the remaining pressure in brake cylinders. This
causes the secondary packing cup of wheel cylinder to
be correctly placed to prevent oil leaks, and to
eliminate air in the brake system.
3. PRIMARY PACKING CUP
4. SECONDARY PACKING CUP
Figure 24. Brake Master Cylinder
other end is connected to the brake adjuster, and
presses onto the bottom plate by spring and pull rod.
The brake is mounted on primary brake shoe, while
adjustment pull rod for automatic clearance adjuster is
on secondary brake shoe. See Figure 25 and
Figure 26.
Brake System
27