Bendix TC-7 TRAILER CONTROL BRAKE VALVE User Manual

Bendix® TC-7™ Trailer Control Brake Valve

O-RING

FRICTION

WASHER SEALING

17 15

RING

EXHAUST VALVE

BODY

INLET

VALVE

FIGURE 1

O-RING

SYSTEM

PARK

TRACTOR

PARK

TRAILER

PARK

CAM FOLLOWER

LOCKWASHER

(SPECIAL)

RETAINING RING

ADJUSTING RING

ADAPTER

CAM

GRADUATING SPRING

PISTON

9 10

O-RING

SPRING

INLET SEAT

O-RING

TRACTOR

PARK

TRUCK/TRACTOR SYSTEM

DOUBLE CHECK

STOPLIGHT SWITCH

DS-2

DC-4

BRACKET

TP-3 TRACTOR PROTECTION

SUPPLY LINE SUPPLY LINE

HANDLE

VALVE

EXTERIOR VIEW

SCREW

PARTIAL VIEW

(VALVE & HANDLE)

SD-03-824

HANDLE

BRAKE

CHAMBERS

PP-1

SYSTEM

PARK

RATIO VALVE

AIR

DRYER

COMPRESSOR

PP-8

OPTIONAL

T.M.C.

TRACTOR

PARK

LQ-4

ST-3

SAFETY

VALVE

D-2 GOVERNOR

CONTROL VALVE

SUPPLY

RESERVOIR

E-7

TRAILER

CHECK VALVE

DC-4

DOUBLE

CHECK VALVE

LP-3 LOW PRESSURE INDICATOR

REAR AXLE

SERVICE

RESERVOIR

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.

SR-1 SPRING

BRAKE VALVE

GAUGE

LP-3

FRONT AXLE

SERVICE

RESERVOIR

GAUGE

R-8 RELAY

VALVE

ANTICOMPOUND LINE

SPRING

BRAKES

R-12 RELAY

VALVE

FIGURE 2 - TYPICAL PIPING DIAGRAM

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 P ARKING. 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 T est s.

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.

REMOV AL & INST ALLA TION

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

REMOV AL

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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