Bendix TC-7 TRAILER CONTROL BRAKE VALVE User Manual

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SD-03-824

Bendix® TC-7™

Trailer Control Brake Valve

O-RING

5 CAM FOLLOWER

BRACKET

O-RING

LOCKWASHER

(SPECIAL)

RETAINING RING

HANDLE

ADJUSTING RING

VALVE

FRICTION

ADAPTER

WASHER

CAM

EXTERIOR VIEW

SEALING 15

GRADUATING SPRING

RING

EXHAUST VALVE

PISTON

14 SCREW

BODY

O-RING

SPRING

HANDLE

INLET SEAT

INLET

VALVE

O-RING

PARTIAL VIEW

(VALVE & HANDLE)

FIGURE 1

SYSTEM TRAILER

TRACTOR

PARK

TRACTOR

TRUCK/TRACTOR SYSTEM

PARK

DC-4

DS-2

TP-3 TRACTOR PROTECTION

SUPPLY LINE

DOUBLE CHECK

SUPPLY LINE

STOPLIGHT SWITCH

BRAKE

PP-1

PP-8

OPTIONAL

SR-1 SPRING

CHAMBERS

SYSTEM T . M . C .

PARK TRACTOR

BRAKE VALVE

PARK

E-7

LQ-4

RATIO VALVE

TRAILER

CONTROL VALVE

DC-4

DOUBLE

GAUGE

CHECK

ANTI-

R-12 RELAY

VALVE

LP-3

COMPOUND

R-8 RELAY

LINE

VALVE

AIR

FRONT AXLE

VALVE

DRYER

ST-3

SERVICE

SAFETY

RESERVOIR

VALVE

LP-3 LOW

SUPPLY

PRESSURE

RESERVOIR

INDICATOR

CHECK

GAUGE

VALVE

REAR AXLE

D-2 GOVERNOR

SERVICE

COMPRESSOR

RESERVOIR

SPRING

BRAKES

FIGURE 2 - TYPICAL PIPING DIAGRAM

DESCRIPTION

The TC-7™ trailer control brake valve is a hand operated control valve that provides graduated control of service brake air pressure. The most common vehicle application is the independent control of the trailer’s service brakes on a tractor trailer combination.

Typically, the TC-7™ valve is mounted either inside the steering column or clamped to the exterior of the column. The three basic components of the TC-7™ valve are available separately (valve, handle, bracket) to accommodate the appropriate mounting configuration.

Because of its use as a trailer service brake control valve, the TC-7™ valve should NOT be used in lieu of the vehicle parking brakes. The handle is marked NOT FOR PARKING. In general the TC-7™ valve should not be in use and left unattended.

OPERATION

APPLYING

When the handle or actuating lever is moved in a clockwise direction from the released position, force is exerted on the pressure graduating spring through the action of the cam and cam follower. The force of the spring on the piston causes it to move down.

The exhaust seat, which is in the center of the piston, contacts the exhaust valve and closes the exhaust passage in the piston. The continued downward movement of the piston moves the inlet valve-off its seat. Reservoir air pressure flows by the open inlet valve and out the delivery port.

HOLDING

The air pressure that flows by the open inlet valve also becomes effective on the bottom area of the piston. As the force of the air pressure beneath the piston balances the force of the depressed graduating spring above, the piston lifts slightly and the inlet valve returns to its seat. The exhaust valve remains seated so the flow of air through the valve is stopped and air pressure in the service line is held.

RELEASING

When the handle or operating lever is moved in a counterclockwise direction the force above the piston is decreased. The air pressure beneath will then lift the piston, moving it away from the exhaust valve. With the exhaust passage open, air pressure in the service line will exhaust out the exhaust port of the valve.

PREVENTIVE MAINTENANCE

Important: Review the warranty policy before performing any intrusive maintenance procedures.An extended warranty may be voided if intrusive maintenance is performed during this period.

Because no two vehicles operate under identical conditions, maintenance and maintenance intervals will vary. Experience is a valuable guide in determining the best maintenance interval for any one particular operation.

Visually check for physical damage to the brake valve such as broken air lines and broken or missing parts.

Every 3 months, 25,000 miles (40,000 km.) or 900 operating hours perform Operating and Leakage Tests.

SERVICE CHECKS

OPERATING TEST

Park the vehicle on a level surface and block the wheels.

Connect an accurate test gauge to the delivery port of the TC-7™ valve or connect the gauge to the service hose coupling of the tractor. When the gauge is connected to the service hose coupling, install a dummy hose coupling on the supply (emergency) hose coupling and place the tractor protection control in the trailer charging position. When the TC-7™ valve handle is moved to the fully applied position, the gauge should register full reservoir pressure.

NOTE: Some valves may be preset to deliver lower than reservoir pressure; however, the standard valves generally used on tractors are set to deliver full reservoir pressure. Intermediate positions should deliver proportional intermediate pressures. Upon release, the gauge should immediately register zero.

LEAKAGE TEST

Locate the exhaust port or exhaust line and apply a soap solution. (It is common practice to connect a line from the valve exhaust port to a location remote from the immediate driver’s area.) With the valve in the released position, exhaust leakage should not exceed a 1" bubble in 5 seconds (100 sccm).

With the valve fully applied, leakage at the exhaust should not exceed a 1" bubble in 3 seconds (175 sccm).

If the valve does not function as described or leakage is excessive, it is recommended that it be replaced with a new or remanufactured unit, or repaired with genuine parts available at Bendix outlets.

REMOVAL & INSTALLATION

The removal, disassembly, assembly and installation procedures are number keyed to the sectional and exterior views of the TC-7™ valve in Figure 1.

REMOVAL

1.Block the wheels or hold the vehicle on a level surface by means other than air brakes.

2.Drain all air pressure from all reservoirs.

3.Identify the air lines and connections and remove from the TC-7™ valve.

4.Consult the vehicle manual for instructions on disassembly of the steering column components.

NOTE: Some TC-7™ valve installations will be on the exterior of the steering column, in which case Step 4 can be disregarded.

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