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5-10t Internal Combustion Counterbalance Forklift Truck Operation & Maintenance Manual

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(2)Brake Working Status
A.  When  brake  pedal  is  just  pushed  down,  the  pedal  force  acts  on the control  valve  stem  1
through  lever  amplification,  and  compresses  part  3,  to  move  forward  together  with  part  5.
Through action of the feedback disc 10 and the master cylinder push rod 13, certain pressure
is  generated  inside  the  brake  master  cylinder  and  transmitted  to  the  brake  wheel  cylinder
inside the brake wheel, and at the same time, the control air valve 4 moves forward with part
5 under the action of small tapered spring 6, to get contact with the port of vacuum valve on
the control valve body 7, and close it, for the two front and rear cavities of power-assisted air
chamber  to  be  separated  from  each  other  (namely  the  rear  cavity  of  power-assisted  air
chamber is disconnected with the vacuum source.).
B. Along with the further forward movement of the control valve push rod 1, the control valve
piston  5  leaves  the  part  4,  and  the  external  atmosphere  is  filled  into  the  rear  cavity  of
power-assisted air chamber through the air filter gasket as well as the control valve cavity and
the passage B, thus most of the forward acting force caused by air pressure difference in the
two cavities of power-assisted air chamber is effected on the feedback disc, and transmitted to
the brake master cylinder, to play the power assisting function, through the control valve body
7,  except  a  small  part  of  the  action  force  used  for  balancing  the  action  force  of  the  large
tapered spring 3.
3. Brake Process Termination, and Recovery to Non-Working Status
A. In the process when  brake pedal  is pushed (namely the forward movement of the control
valve push rod), air continuously enters  into the  front and rear cavities of power-assisted air
chamber through the opened air valve port, and the control valve body keeps moving forward.
When  brake  pedal  stops  being  pushed  and  stays  at  certain  position,  the  control  valve  body
also moves forward and stops at the position where the air valve port is closed. At this point,
the vacuum valve port and the air valve port are both closed, the booster is under the balanced
status,  namely  a  balanced  status  is  maintained  among  the  three  including  the  air  pressure
difference between the  front and rear cavities of  power-assisted air chamber, the pressure of
oil  pressure  for  brake  master  cylinder,  and  the  thrust of  the  control  valve  push  rod,  and the
wheel brake is under the braked status.
B. When brake pedal is released, the control valve push rod 1 and the control valve piston 5
are  immediately  pushed  rearwards  under  the  effect  of  return  spring  14  and  large  tapered
spring 3, for the control air valve 4 to be disengaged from the vacuum pump port, and then a
braking process is completed, and it recovers to the original non-working status.
5.3.2 Method for Installation of Vacuum Booster and Brake Master Cylinder Assembly
(1)Connect  the  4-M8  bolts  for  the  booster  with  the  mounting  bracket  and  mount  it  on  the
frame  of  forklift  truck.  Connect  the  adjusting  fork  on  the  end  part  of  booster  with  the
connecting  rod  of  brake  pedal.  Then  tighten  the  4-M8  bolts,  at  a  tightening  torque  of
12N.m-18N.m.
(2)Connect the vacuum hose onto the joint of vacuum pipe for the booster, and keep it sealed.
(3)Connect  the  brake  oil  pipe  with  the  2-M10x1  thread  for  the  oil  outlet  of  brake  master
cylinder, at a tightening torque of 12 N·m-18 N·m.
(4)Open the turning  lid of  liquid  storage room, and  inject the brake  fluid (not to be blended
with dust or impurity). Exhaust the air inside the entire brake system.