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2. Summary
The brake system is the front two-wheel braking type consisting of a master cylinder, brakes
and brake pedal.
2.1 master cylinder
The 2t-3.5t master cylinder contains a valve seat, check valve, return spring,
primary cup, piston and secondary cup, which are kept in place with stop washer and
stop wire. The exterior of the cylinder is protected from dust by means of a rubber dust
cover. The piston is actuated through the push rod by operation of the brake pedal.
First, as the brake pedal, the push rod pushes the piston forwards. The brake fluid in
the cylinder flows back to the reserve tank through the return port until the primary cup
blocks up the return port. After the primary cup passes the return port, the brake fluid
in the cylinder is pressurized and opens the check valve, flowing through the brake
lines to the wheel cylinder. Thus, each wheel cylinder piston is forced outwards. This
brings the brake shoes into contact with the wheel drum and slows or stops the lift
truck.. Meanwhile, the cavity caused behind the piston is filled with brake fluid led
through the return port and inlet port to lubricate the piston. When the brake pedal is
released, the piston is forced back by the return spring. At the same time, the brake
fluid in each wheel cylinder is pressurized by the force of the brake shoe return spring,
thus returning into the master through the check valve. With the piston in its original
position, the fluid in the cylinder flows into the reserve tank through the return port.
The brake fluid in the brake lines and wheel cylinders has a residual pressure
proportioned(about 0.04MPa) to the set pressure of the check valve, which makes
each wheel cylinder piston cup securely seated to prevent oil leakage and eliminates
of vapor lock developing when the lift truck is sharply braked.
Brake principle of brake master cylinder of 1t-1.8t forklift is similar.
1. Lock nut 2. Rod 3. Duct cover 4. Light spring 5. Gasket ring 6. Piston
7. Primary cup
8. Spring
9. Raffinate valve 10. Valve seat 11. Cylinder body
Fig. 6-1 Master cylinder