Training Material of Loader Brake System

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Training Material of Loader Brake System

• Shandong Lingong
• Import and Export Corp. Training Room
• 2011

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Contents

• Section I Overview
• Section II Working Principles of Brake System
• Section III Main Components of Service Brake
  system
• Section IV Main Components of Emergency and
  Parking Brake System
• Section V Use, Replacement and Notes of Brake
  Fluid
• Section VI Trouble Shooting of Brake System

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Section I Overview

• I. Concept of Pneumatic Transmission
• Pneumatic Transmission refers to the process of
  taking the compressed air as power source and an
  actuating medium to achieve energy transmission,
  signal transmission and process control.
• 1.Advantages Simple structure, low cost, easy to
  achieve stepless speed regulating
• 2.DisadvantagesThe working pressure is low, so
  it only adapts to low-power transmission. Since
  the air is compressible, the stability of the
  pneumatic device is poor and the working speed
  often changes with the external load.

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• II. Requirements of Pneumatic Transmission on
  Actuating Medium
• 1.The compressed air is required to have enough
  pressure and flow
• 1)Without enough pressure, neither the executive
  mechanism can generate sufficient thrust, nor can
  the control mechanism act correctly
• 2)The action speed and procedural requirements of
  the executive mechanism cannot be guaranteed
  without enough flow.

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• 2.The compressed air is required to have a
  certain degree of cleanliness and dryness
• 1)Cleanliness is the degree on the content of
  oil, dust and impurity in the air
• 2)Dryness is the amount of moisture in the
  compressed air (the water content in the air of
  the pneumatic device is required to as little as
  possible)

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• III. Concept of Brake
• Brake means a sufficient large brake torque is
  produced through the brake system to consume the
  saved kinetic energy generated during the moving
  of the machine in brake to force it to slow down
  and even stop within a certain distance. The more
  frequently used method in the brake system is to
  consume the kinetic energy of the moving vehicles
  to produce the brake force by using mechanical
  friction.
• IV. Classification of Brake System
• It can be divided into service brake and parking
  brake according to the role or function of the
  brake.

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• V. Composition of Brake System
• An energy supplying device, a control device, a
  transmission device, an actuating device and
  auxiliaries
• 1. Energy supplying device Compressor
• 2. Control device Oil-water separator, air brake
  valve, brake solenoid valve, hand brake valve,
  etc.
• 3. Transmission device Booster pump, parking
  brake chamber, etc.
• 4. Actuating device Brake caliper, parking
  brake, etc.
• 5. Auxiliaries Gas tank, pipeline, etc.

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Section II. Working Principles of Brake System

• I. Service Brake System
• It is used to lower the speed and park during the
  moving of the vehicles, which is controlled by a
  driver through a brake pedal.
• 1.According to the brake circuit It can be
  divided into single-circuit system and
  Dual-circuit system
• 2. According to the different mediums of the
  brake shoes It can be divided into dry brake and
  wet brake
• The caliper disc brake is dry brake, and the ZF
  drive axle brake is wet brake.

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• (1)Single Circuit Brake System
• 1)Composition An air compressor, a oil-water
  separator, a booster pump (front and rear), a
  pneumatic brake valve, a brake caliper, an air
  storage tank, pipelines, etc.
• 2)Type Gas cap oil four-wheel forceps disc brake

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Bake pedal
Bake
Disc brakes (fixed with axle pipe
Brake valve
To off valve
Afterburner cans
Bake master pump
Rear
Leather cup
Oil-water separator
Adjusting valve
Leather collar
Air
Air compressor
Tire charging
Air tank
1type seal ring
Filled oil Pressure air Charging air
Air
Front
Rear axle
Brake
Brake
Front axle
Air bleeding
Tire charging
Structure Chart of Single-circuit Service Brake
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Bake
Afterburner pump
Oil-water separator
Air brake valve
Brake caliper
Air tank
Layout Diagram of Single-circuit Service Brake
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Afterburner pump of front drive
Afterburner pump of rear drive
Schematic Diagram of Single-circuit Service Brake
1. Air Booster Pump 2. Foot Brake Valve 3. Gas
Tank 4. Oil-water Separator Combination Valve 5.
Air Compressor
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• (2)Dual-circuit Service Brake System
• 1)Composition Air compressor, oil-water
  separator, booster pump (front and rear),
  pneumatic brake valve (left and right), brake
  caliper (or wet brake), air storage tank,
  pipeline, etc.
• 2)Type Gas cap oil four-wheel forceps disc (or
  wet) brake

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Brake caliper
Bake
Oil-water separator
Air brake valve
Front afterburner pump
Rear afterburner pump
Air tank
Layout Diagram of Dual-circuit Service Brake
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Schematic Diagram of Dual-circuit Brake System
1.Air Booster Pump2.Shuttle Valve3.Pneumatic
Brake Valve4.Gas Tank 5.Oil-water Separator
Combination Valve 6.Brake Solenoid Valve7.Parking
Brake Chamber
Brake pump of front drive
Brake pump of rear drive
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• (3)Wet Brake
• ?The ZF drive axle uses a wet brake, whose
  structure is similar to that of the gear clutch
  of the gearbox. The high-pressure brake fluid
  runs into the piston chamber during a brake,
  presses the friction plate tight by pushing the
  piston to move in order to achieve brake. Run a
  return spring to release the brake.
• ?The structure and working principles of the
  brake are completely different from those of the
  dry brake. The requirements of brake fluid and
  brake fluid displacement in respect of the
  sealing elements of the both are also different.
• ?Now, the ZF drive axle uses single
  (Dual)-circuit gas cap oil brake system. The
  difference lies in that the booster pump used is
  a special booster pump with low-voltage large
  displacement. The storage cup of the booster pump
  is changed into a storage drum, which is
  arranged separately on the back outside the
  driving cab and connected with a inlet of a brake
  master cylinder through an oil pipe. The brake
  fluid is SAE10 universal oil, Mobil Delvac 1310
  is recommended. (Main configuration 959?969)

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• II. Parking Brake System
• It is used to brake in case of an emergency
  during the operation of the loader, and keep the
  loader at the original location after parking in
  order not to move due to the road slope or other
  external forces.
• Brake position The brakes of the parking brake
  system are always installed on the front output
  shaft of the gearbox on the loader. Through
  manual control or chamber control, the brake
  shoes expand or clap (clap-type) the brake disc
  to achieve parking brake.

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• 1. Classification According to Brake Form
• Manual parking brake, electric air-controlled
  parking brake, manual air-controlled parking
  brake.
• 2. Divide according to the brake type
• Caliper disc type and internal expanding shoe type

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(1)Manual Caliper Disc Type Parking Brake
Mainly composed of ?Control Lever ?Control
Flexible Shaft ?Caliper Disc Parking Brake,
etc. 933?953?952, etc.
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• (2)Electric Air-controlled Parking Brake
• 1)Composition A caliper disc type (or drum type)
  brake, a parking brake chamber, a brake solenoid
  valve, a pressure switch, a brake knob, an air
  storage tank, pipeline, etc. (936?958?959, etc.)
• ?Brake off rotate the operation button
• ?Emergency or parking brake press the operation
  button
• ?Automatic protection control the pressure
  switch automatically switch off the power supply
  to the brake valve when the air pressure is lower
  than 0.4Mpa

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1. Air Pressure Signal Lamp Switch 5. Brake
Solenoid Valve 8. Parking Brake Chamber 14.
Hand Brake 17. Pressure Switch 19. Pressure
Sensor
Structure Chart of Electric Air-controlled
Caliper Disc Type Brake System
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Schematic Circuit Diagram of Electric
Air-controlled Brake System
Pressure switch
Brake knob
Brake magnetic valve
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• (3)Manual Air-controlled Caliper Disc Type Brake
• 1)Composition A caliper disc brake, a parking
  brake chamber, a hand brake valve, an air storage
  tank, pipelines, etc. (mainly used in 956?956L)
• 2)Working principles The brake principles of the
  manual air control and electric air control are
  basically the same, and the difference lies in
  that the hand brake valve is used instead of the
  3/2 way solenoid valves. As for the operation of
  the hand brake valve, press the button down to
  brake off and lift up the button to connect.
• 3)Automatic protection When the brake pressure
  is lower than 0.28Mpa,the manual button will
  pop-up automatically and cut off the air supply.

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Parking brake indicator switch connector
Schematic Diagram of Manual Air-controlled Brake
System 1. Parking Brake Chamber 2. Hand Brake
Valve 3. Oil-water Separator Combination Valve
4. Air Compressor 5. Air Storage Tank 6. Foot
Brake Valve 7.Air Booster Pump
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Friendly Reminder

• Since there is no rigid connection between the
  loader engine and the output shaft of the torque
  converter, its suggested that the driver should
  not only use the parking brake, but also put
  blocks under the wheels or compact the ground
  with a bucket to prevent the vehicle from sliding
  when the vehicle is stopped at the slope (uphill
  or downhill) and the driver intends to leave.

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Section III Main Components of brake System

• I. Air Compressor
• The air compressor is installed in the front of
  the injection pump shaft coupling in the same
  axis with the injection pump camshaft and driven
  by the drive gear of the injection pump inside
  the gear room.
• Lubrication the press oil is led in by the
  engine oil passage through the oil pipe fixed on
  the cylinder into the air compressor to lubricate
  bearings and then cylinder sleeves by splashing
  before returning to the oil pan via the timing
  gear chamber.

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• Air source the air intake must pass through an
  air filter before entering the air pipe in front
  of the turbocharger connected to the air inlet of
  the air compressor.
• Cooling use the same water circulating cooling
  system with the engine.
• 1.Function to provide compressed air to the
  brake system.

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Structure of Air Compressor
1 Inlet Pipe 2 Exhaust Pipe 3 Piston Pin 4
Cylinder 5 Crankcase 6 Crankshaft 7 Crankshaft
Oil Seal 8 Oil Pan 9 Return Pipe Joint 10 Drive
Joint 11 Piston Ring Set 12 Cylinder Head 13
Intake Valve 14 Exhaust Valve 15 Piston 16
Connecting Rod
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• 2. Working Process
• (1) Air intake
• (2)Air compressing
• Potential causes of faults excessive abrasion of
  cylinder, piston and piston ring, incomplete
  closure of intake and exhaust valves, etc.

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• II. Oil-water Separator Combination Valve
• The oil-water separator combination valve is a
  valve composed of an oil-water separator and an
  air pressure regulator.
• 1. Functions
• (1)Separte oil, water and other foreign matters
  in the compressed air
• (2)Automatically regulate the working pressure of
  the brake systems air source (exhaust at
  0.784Mpa supply air at 0.686Mpa)
• (3)Ensure the safety of the brake system
  (protection at 0.882Mpa)
• (4)Inflate tyres.

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2. Structure Composition It mainly consists of
mid-body, upper cover, lower shell, internally
separated oil-water separation chamber, filter
element, check valve and safety valve assembly,
air pressure regulating components and air liquid
release valve, etc.
Structure Chart of Oil-water Separator
Combination Valve
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1.Upper Cover2.Mid-body3.Lower Shell4.Pressure
Regulating Spring5.Control Piston
Assembly6.Return Spring Of Check
Valve7.Regulating Stem8.Regulating Valve9.Air
Release Piston Assembly10.Air Release
Valve11.Air Release Piston12.Return
Spring13.Air Filter
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Notes for Oil-water Separator Combination Valve

• The air pressure control screws, safety valve
  assembly and other key parts have been adjusted
  by the manufacturer before leaving the factory
  and shall not be adjusted arbitrarily in general
  conditions so as to avoid potential damages on
  the brake system for safety concerns. If the
  adjustment is necessary, then adjust the Safety
  Valve Assembly 9 first and then the Pressure
  Regulating Valve 7 to avoid an excessive increase
  of the pressure in the system.

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Common Faults of Oil-water Separator

• 1. When the seal ring of the air release valve in
  the lower part of the exhaust piston is damaged
  or stuck with foreign matters, air leakage will
  occur for incomplete closure of the valve.
• 2. When the return spring of the air release
  piston fails or the piston is stuck, air leakage
  will occur for incomplete closure of the valve.
• 3. When the air hole to the atmosphere of the
  upper shell is blocked, the air release piston
  can not return effectively and air leakage will
  occur for incomplete closure of the vale.

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Common Faults of Oil-water Separator

• 4.When the tympanic membrane ruptures, the
  pressure will become lower and the compressed air
  will leak from the air hole in the upper cover.
• 5.When the elasticity of the regulating spring
  decrease for the long-time working, the system
  pressure will become lower.
• 6.When the throttle orifice from chamber C to
  chamber D is blocked, the pressure regulating
  spring and the piston assembly are stuck, parts
  of the air pressure regulating functions fail
  and the air pressure exceed 0.882Mpa,the
  compressed air acts on the safety valve, breaks
  through the valve and enters into the atmosphere.

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• III. Air Storage Tank
• 1. Functions
• (1)It stores the compressed air for the brake
  system. When the air compressor is not working,
  the air needed for certain number of brakes is
  ensured.
• (2) It is equipped with a safety valve, a
  pressure sensor, an inflation valve, a drain
  valve and a pressure switch.

Structure Chart of Air Tank
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Foreign matters like water and rust may enter the
booster pump via the pipelines if the air storage
tank hasn't discharged water for a long time.
Pollution too dirty
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• IV. Air Brake Valve
• The brake valve is a control device controlled by
  the brake pedal for wheel brake or brake release.
• 1. Functions
• In the brake state, it controls the amount of
  the compressed air into the air chamber of the
  booster pump, i.e., control the air pressure of
  the booster pump for different brake effects. It
  makes the driver able to feel the brake degree
  from the pedal stroke and the size of operating
  force.

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2. Structure Composition It consists of a pedal,
a upper cover, a lower valve body and a carrier
rod, an assembly consisting of a piston, a
balance spring, an air intake valve inside the
vale body and a return valve, etc.
Structure Chart of Air Brake Valve
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• 3. Working Process
• (1)Brake
• (2)Release of brake
• (3)Funcions of balance spring

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1.Upper Cover2.Valve Body3.Carrier
Rod4.Balance Spring Assembly5.Piston 6.Return
Spring7.Retainer Ring8.Valve Core
Assembly9.Return Spring10.Air Intake
Valve11.Valve Assembly (Spring Seat)
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Notes for Brake of Loader Driving on Ramp

• According to the working principle of the brake
  valve, in the brake state, the brake pedal
  applies some pressure on the balance spring which
  exerts force on the piston to push the air intake
  valve core open and close the passage for the
  compressed air in the brake valve entering into
  the atmosphere. For example, by frequent
  triggering of the brake, the passage to the
  atmosphere between the piston and the top of the
  air intake valve keeps opening and closing,
  causing the constant exhaust of the compressed
  air via the duct in the middle of the air intake
  valve if the air exhausted exceeds the supply of
  the air compressor, the air in the air tank will
  decrease rapidly, and when the air pressure is
  lower than 0.4Mpa, the brake effects decrease.

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• Current operation when driving downwards, keep
  the foot on the pedal and press properly
  according to the road conditions for different
  brake effects and pay attention to the change in
  brake pressure and do not frequently trigger the
  brake.
• During the the brake test on 953,the consecutive
  trigger of brake for about 10 times will decrease
  the air pressure from 0.7Mpa to below 0.4Mpa.

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Common Faults of Air Brake Valve
1.Limit screw it is used to adjust the free
stroke of foot brake valve by turning clockwise
to increase the free stroke and turning
anti-clockwise to decrease when it is turned
anti-clockwise to a certain degree, the exhaust
port will close and open the air intake valve
core. 2.Air intake valve core if it is stuck in
the air intake state, when the foot brake pedal
returns, the air in the air storage tank will
enter the atmosphere via the inner hole of the
air intake valve.
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Common Faults of Air Brake Valve

• 3.When the seal ring on top of the air intake
  valve or there are foreign matters, in the brake
  state, some air in the air storage tank leaks at
  the damaged position, thus decreasing the brake
• 4.If the brake piston is stuck in the brake
  state, when the foot brake pedal is released, the
  lower part of the brake piston contacts the
  exhaust port and the air returning from the
  booster pump can not be exhausted or exhausted
  rapidly form the exhaust port, causing brake
  dragging and unclear classification of the faults.

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• V. Power Cut Switch (fit for 956L only)
• 1.Function
• Connect or disconnect the passage for the
  compressed air to the air cut valve of the speed
  change valve for the cut-off or normal passing of
  the power oil.
• 2. Advantage
• The use of the power cut-off makes the loaders
  transmission system terminate the power
  transmission in the brake state, decreases the
  fault rate of the transmission system, increases
  the safety effects of the brake and makes it
  possible to apply all the power on the working
  devices when the loader shovels.

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• 3.Disadvantages
• In some working conditions, such as ramp
  construction, the switch shall be turned to the
  cut-off position to avoid the sliding of the
  loader for gravity at the moment of reintegration
  of the gear clutch when restarting after
  releasing the brake.

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• VI. Air Booster Pump
• 1.Function
• Use the compressed air from the air brake valve
  to pressurize the brake fluid in the brake master
  pump to promote the working of the brake caliper
  piston.
• 2. Working Process
• 1) Brake state
• 2)State of releasing brake

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3.Main Structure It mainly consists of a booster
cylinder, a brake pump, a air chamber piston, a
oil pressure piston, a push rod, a push rod seat,
a end cover, a return spring, a oil storage cup,
seals, etc.
Structure Chart of Air Booster Pump
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1.Brake Pump2.Booster Cylinder3.Repirator4.End
Cover (Booster Pump Body)5.Air Chamber
Piston6.Oil Pressure Piston7.Push Rod8.Return
Spring7.Push Rod Seat Assembly8.Oil Intake
Valve9.Central Seal Ring10.Master Pump
Cup11.Booster Cylinder Apron
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Common Faults of Air Booster Pump

• 1.When the apron of the air chamber piston is
  damaged, the compressed air enters the
  low-pressure chamber from the high-pressure
  chamber and is exhausted from the breathing hole,
  and the brake force decreases.
• 2?When the guiding seal ring of the push rod is
  damaged, the oil in the oil storage cup leaks
  from the damaged position and the brake liquid
  leaks from the breathing hole of the booster
  chamber or the joint between the cylinder and the
  end cover.
• 3?When the piston cup of the brake pump is
  damaged, when boosting, the high-pressure brake
  liquid returns to the oil storage cup from the
  damaged cup, resulting in upward leakage of the
  brake liquid and brake weakness.
• 4?When the seal ring at the compensation hole
  between the push rod seat and the brake pump
  piston are damaged, the upward leakage of the
  brake liquid and brake weakness also occur.

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Common Faults of Air Booster Pump

• 5.When the seal ring at the joint of the brake
  master pump and the end cover is damaged, the
  leakage of the brake liquid will occur.
• 6.When the seal ring in the joint of the oil
  storage cup and the end cover is damaged, the
  leakage of the brake liquid will occur.
• 7.When the respirator in the booster is blocked,
  the brake force will become inadequate or the air
  chamber piston can not return in time, resulting
  in delay of brake release.
• 8.When the return spring in the air chamber
  breaks, the brake force will become inadequate or
  drag.

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Leakage inside Brake Master Pump
Brake fluid ejective
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Rupture of Booster Pump Spring
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• VII. Caliper Disc Brake
• 1.Function
• The pressurized brake liquid acts on the brake
  caliper piston to facilitate the brake friction
  slice to clamp the rotating brake disk to brake.

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2.Main Structure It mainly consists of a
caliper, a brake piston, a friction slice and
rectangular seal rings.
Structure chart of Caliper-type Brake
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1.Inner caliper2.Outer caliper3.Seal
ring4.Piston5.Rectangualr seal ring6.Dust cover
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Functions of Rectangular Seal Ring 1.Seal of the
brake liquid inside the brake caliper 2.Automatic
return of the brake caliper piston 3.Automatic
adjustment of brake clearance after the wear of
the brake pad
(a) (b) Working Conditions of
Rectangular Seal Ring 1 Rectangular Seal Ring 2
Brake Caliper 3 Piston
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• 3. Working Process
• (1)While braking
• (2)After brake releasing
• (3)Automatic compensation of the friction slice
  clearance

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?Abnormal wear of the brake disc and brake
pad?After identification, the material quality
and hardness of the brake disc and the brake pad
are within the scope of the requirements, and the
wear is caused by sands and stones spraying on
the space between the brake pad and brake disc.
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Common Faults of Brake Caliper

• 1.When the seal ring between the outer caliper
  and inner caliper is damaged, the leakage of the
  brake liquid will occur.
• 2.The rusting of the brake caliper piston will
  cause malfunction of the piston.
• 3.The air in the brake pipeline will cause
  inadequate brake force or delay of brake release.
• 4.When the rectangular seal ring is damaged, the
  leakage of the brake liquid, inadequate brake
  force and incomplete piston return will occur.

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Section IV Main Components of Emergency and
Parking Brake Systems

• I. Air inlet of the hand brake valve is connected
  with the air storage tank, and air outlet
  connected with the parking brake air chamber and
  exhaust port directly to the atmosphere.
• 1.Air Pressure Protection
• Automatic protection at pressure below 0.28Mpa.
• 2.Working Process

Air inlet
Air outlet
Exhaust port
Figure 3.5-11 Emergency and Parking Brake
Systems 1 Control Button 2 Carrier Rod 3 Seal
Ring 4 Spring 5 Valve Body 6 Valve Assembly 7
Seal Ring 8 Bottom Cover
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1.Brake Button2.Air Inlet3.Air Outlet4.Exhaust
Port
P. Connected with the air tankA. Connected with
the brake air chamberT. Connected with the
atmosphere
Picture of Hand Brake Valve
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• II .Brake Solenoid Valve
• Brake solenoid valve has the similar operation
  principle as the hand control valve, but the
  valve is controlled by electrical signal instead
  of hand.
• 1. After pulling out of the control knob, connect
  the power of the solenoid valve, the solenoid
  valve core pull in and open the air passage to
  the parking brake air chamber, the air pressure
  overcomes the elastic force of spring in air
  chamber, then the parking brake is released.
• 2. When the control knob is pushed or brake air
  pressure is below 0.4 MPa, the brake solenoid
  valve is power off, the valve core cuts off the
  air passage to the brake air chamber and open the
  passage of the brake air chamber to the
  atmosphere, thus connecting the brake.

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Common Failures1. Line failure 2. Solenoid
valve coil failure 3. poor seal of Reversing
valve
P. Connected with air storage tank A. Connected
with brake air chamberT. Connected with the
atmosphere
Picture of Brake Solenoid Valve
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• III .Parking Brake Air Chamber
• 1. Function when the air pressure overcomes the
  elastic force of the spring in air chamber,
  parking brake is released when the source is cut
  off or the brake pressure is less than the
  specified value, the spring of the air chamber
  returns thus connecting the brake.

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2. Main Structure
Mainly consist of an end cover, a push rod, a
outer cylinder, pistons, springs, seals, etc.
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1. Cylinder Body 2. End Cover3. Piston 4. Air
Chamber Apron 5. Push Rod 6. Return Spring
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• 3. Cautions
• If the compressive elasticity of brake spring in
  the parking brake air chamber is too great, the
  dismantling shall not made. In case of a failure,
  please replace an assembly to prevent safety
  accident.
• For the machine equipped with the parking brake
  air chamber, if it needs to be moved by a trailer
  due to a breakdown or other reasons, the air
  chamber push rod and handle of the brake shall
  be loosened before pulling so as to avoid the
  damage of the machine.

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• IV Hand Brake
• 1.FunctionIn the brake state, the handle is
  lifted and the friction slices (caliper disc) act
  on the brake disc and brakes the loader in the
  state of brake released, the handle is loosened
  and the friction slices on the both sides
  automatically expand under the effect of the
  spring force, and then the brake is released.

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2. Main Structure Mainly consist of a handle, a
spring, friction slices, adjuster bolts, holders
and so on.
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Section V Use, Replacement and Cautions for Brake
Fluid

• I .Categories of Brake Fluid
• Three major types alcohol-based, mineral oil and
  synthetic. Among them, alcohol-based and mineral
  oil brake fluid are not commonly used, and the
  synthetic brake fluid is mostly used now.
• 1. Synthetic Brake Fluid
• The kind of brake fluid is made based on the
  synthetic fluid with the various additives.

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• 2. Labeling
• Taking HZY3 as an example, where H, Z and Y
  respectively represents the first letter of
  synthetic, brake and fluid in Chinese, the number
  3 is a mark for distinguishing each standards
  of this series without any specific meaning.
• Our service brake system uses HZY3(DOT3)
  synthetic brake fluid. (wet brake usually uses
  Mobil Delvac 1310)

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• II Use of Brake Fluid
• 1.Brake fluids of different brands shall not be
  mixed so as to avoid the layering which may
  result in the brake failure
• 2.Container of the brake fluid shall be dedicated
  so as to avoid the mixing of other oils which may
  result in reacting and the brake failure.
• 3.The container of the brake fluid shall be clean
  and tightly covered so as to prevent the entrance
  of mechanical admixture and moisture. During the
  use, dust and foreign materials found on the
  surface of the brake fluid shall be cleared and a
  mixing is prohibited use a clean special tool to
  fill the brake fluid.

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• III .Replacement of Brake Fluid
• 1. When the brake fluid is mixed with mineral
  oils, such as gasoline, diesel and so on
• 2. When the vehicle is under normal driving but
  the brake keeps an anomalistic changing
• 3. When the brake fluid in the system becomes
  less for some reasons or the vehicle with a
  liquid level alarm gives an alarm
• 4. When checking the brake fluid and finding the
  color of oil turns to turbid or contains
  impurities and sediments.

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• IV .Cautions for Replacement of Brake Fluid
• 1.Use the brake fluid specified by the Company
• 2.When replacing the brake fluid, clean the
  raffinate in the brake system and examine new
  brake fluid
• 3.When replacing the brake fluid, reduce the time
  for the brake contacting with the air so as to
  prevent the brake fluid absorbing moisture, thus
  lowering the performance of the brake fluid
• 4.Before replacing the brake fluid, it could be
  better if the brake system is washed with alcohol.

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• V .Exhaust of Brake System
• Air entering into the brake pipeline will affect
  the brake,and the brake failure will occur if the
  case is serious. So after the replacement of the
  parts, clean the system and replace the brake
  fluid, the system shall exhaust and the steps to
  exhaust are as followed
• 1. Fill the oil storage cup of the booster pump
  with the brake fluid
• 2. Loosen the screw at the relief port of the
  booster pump until a stream of the fluid flows
  out, and then tighten the bleed screw

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• 3. Start the engine, and after the air pressure
  rises to the specified value(0.68MPa), step on
  the brake valve pedal for several times to make
  the brake pipeline and brake caliper filled with
  the brake fluid in the state that the brake
  pedal is stepped down, loosen the bleed screw of
  the brake caliper to discharge the air, and
  tighten the bleed screw quickly, repeat the steps
  above until no bubble appears in the brake
  caliper and a stream of the brake fluid flows
  out, and then stop discharging the air and
  tighten the bleed screw.

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• 4.During the process of discharging, continuously
  supply the oil cup of the brake with the brake
  fluid in order to prevent the entering of the
  air.
• 5. After completing the air discharge, fill the
  oil storage cup with the brake fluid until the
  liquid level of the brake fluid is above
  two-thirds and then tighten the cap of the oil
  cup.

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Section VI Typical Failure Removal for Brake
System

• Case 1
• Failures
• The reason why there is a brake drag in the
  loader?
• Definition of brake drag when brake is released,
  the brake caliper has separating problems so that
  the part of brake moment is still transmitted by
  the brake caliper under the state of non-brake
  state.
• Thread of Judgment
• ?Air enters into the brake system
• ?Examine whether the front and rear axle are
  jammed
• ?Failure in brake caliper
• ?Failure in brake valve
• ?Failure in booster pump.

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• Case 2
• Failures
• The reason why the booster pump leaks the brake
  fluid?
• Thread of Judgment
• ? First, observe where the brake leaks and
  distinguish whether it is internal leakage or
  external leakage
• ? Leak from the breather of the booster cylinder
  or the joint, the guiding seal ring of the push
  rod is damaged and an internal leakage occurs
• ? At the joint of the pump body and end cover,
  the seal ring is damaged and an external leakage
  occurs
• ? At the joint of the oil storage cup and end
  cover, the seal ring is damaged and an external
  leakage occurs
• ? The oil leakage occurs at the mouth of the oil
  storage cup and the oil seal of the brake pump is
  damaged the brake fluid in the high-pressure
  chamber returns to the low-pressure chamber
• ? Damage of push rod and seal sockets can also
  cause the oil leakage of the oil storage cup.

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• Case 3
• Failures
• The reason why the brake produces squeal during
  braking along with the brake heated?
• Thread of Judgment
• ? First, observe which part of the brake caliper
  makes the sound
• ? The connecting bolt between the brake caliper
  and drive axle is loosened crash or abrasion are
  incurred from the friction
• ? Hard object is between the brake lining and
  brake disc
• ? Material quality of brake lining and brake disc.

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• Case 4
• Failures
• The reason why the loader pulls to one side
  during brake ?
• Thread of Judgment
• ?The direct reason of pulling to one side is that
  the brake moments of left and right wheels are
  not equal.
• ?The brake caliper on the side of the wheel is
  jammed and difficult to get away during
  running, which is usually caused by the damage of
  the rectangle seal ring which plays the return
  function in the brake caliper.
• ?When stepping on the foot brake pedal, the brake
  caliper on one side brakes, but due to the
  internal leakage, the oil-way is jammed or piston
  of the brake caliper is corroded on the other
  side, the brake fluid cannot enter into the brake
  caliper, causing the brake moment inequality
  which results in pulling to one side.

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• Case 5
• Failures
• Why the no brake occurs during the running of
  the loader? How to take the emergency measures?
• Thread of Judgment
• ?If a no brake suddenly occurs for the air
  pressure in the air storage tank and oil storage
  in the oil cup of the brake master cylinder
  within the prescribed limit, examine the reasons
  below
• ?Air chamber apron in the booster pump suddenly
  anti-lips or tears, the compressed air rushes
  into the low-pressure chamber through the seals
• ?Packing cup of the brake master cylinder
  suddenly anti-lips or tears, the brake fluid in
  the high-pressure chamber rushes into the
  low-pressure chamber
• ?Air brake valve piston assembly is suddenly
  blocked, and cannot effectively push the intake
  valve core down to open the air inlet
• ?In an emergency, when no brake occurs
  suddenly, lay the basket flat on the ground, and
  brakes with force downward or reverse gear.

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Case 6 Failures The brake pressure cannot be
increased, why? Thread of Judgment ?Pipeline
failure ?Oil-water separator failure ?Brake
valve failure ?Air compressor failure.
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• THE END

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