Tadano TR-800XXL4, Service Manual

Page: 288 / 402

T - 4 T - 4
Booster (Brake)
23
W404-0012E
When the inside pressure in chamber B reaches
the signal pressure level (same level as pressure
in chamber A), the body seat comes in contact
with valve assy 33s, shutting off the passage
between chamber D and chamber B. Therefore,
the pressure in chamber B does not increase.
When the signal pressure becomes higher, the
above sequence is repeated, increasing the outlet
pressure proportionately with the increase in
signal pressure. In this manner, the pressure in
chamber A is constantly balanced with that in
chamber B during operation.
3. Booster in operation when releasing brakes
When the brake pedal is released slightly, the
pressure in chamber A becomes lower than that in
chamber B, causing piston 33n to be moved up.
As a result, the piston clears from valve assy 33s,
and the compressed air in chamber B is
discharged to the atmosphere through path C,
thereby decreasing pressure in the air cylinder.
When the compressed air is discharged until the
pressure in chamber A becomes equal to that in
chamber B, piston 33n comes in contact with
valve assy 33s again.
In this manner, the pressure in chamber A is
constantly balanced with that in chamber B also
when the air is discharged.
4. Brakes completely released
When the brake pedal is released completely, the
signal pressure becomes zero. The compressed
air having been supplied to the air cylinder is
discharged from chamber B to atmosphere
through path C.
The relay valve is now in the booster
non-operation state.
Pressure in balance
When brakes are released