The two-section brake valve is designed to control the actuators of the two-circuit service brake drive
The main elements of the crane (Fig. a) are the large piston 1, the upper 2 and lower 11 valves, the follower 3 and small 9 step pistons, the elastic element 4, the lever 5, the pusher 6, the pin 7, the springs 8 and 10, the pusher small piston 12.
Conclusions I and II of the crane are connected through intermediate pneumatic devices to the brake chambers of the front and rear wheels, respectively, conclusions III and IV - to the receivers of separate service brake drive circuits.
In the initial position (the brake pedal is released), valves 2 to 11 (Fig. b) are closed under the action of their springs, output I is disconnected from output IV and output II - with output III they communicate with the atmosphere through valve 13.
When you press the brake pedal (Fig.a), the force is transmitted through the system of rods and drive levers to the lever 5 of the brake valve and then through the pusher 6 and the elastic element 4 to the follower piston 3.
Moving down, piston 3 compresses spring 8, closes the outlet window when valve 2 is touched and separates outlet II from the atmosphere, and then tears off valve 2 from the seat.
Compressed air supplied to terminal III, through the open valve 2, enters terminal II and then through the brake force regulator into the brake chambers of the rear wheels until the pressing force on lever 5 is balanced by the pressure of compressed air and spring 8 on piston 3.
In this way, the following action of the piston in the upper section of the brake valve is carried out.
Simultaneously with the increase in pressure in outlet II, compressed air passes through a channel in the valve body into the cavity above the large piston 1 of the second section of the brake valve, piston 1 moves down and acts on the small piston 9 of the second section of the brake valve.
Moving, the piston 9 compresses the spring 10, closes the outlet window of the valve 11 and separates the outlet I from the atmosphere, and then tears the valve 11 from the seat.
Compressed air supplied to terminal IV, through the open valve 11, enters terminal I and then to the brake chambers of the front wheels.
With an increase in pressure in port I, the pressure in the cavity under pistons 1 and 9 increases, which balances the force acting on piston 9 from above.
As a result, the pressure corresponding to the force on the brake valve lever is also set in output I.
In this way, the following action of the piston in the lower section of the brake valve is carried out.
If the upper section of the brake valve fails (there is no pressure in outlet II), the lower section is mechanically controlled through pin 7 and pusher 12, while maintaining its full functionality.
In this case, the follow-up action is carried out by balancing the force applied to the lever 5 from above, and the pressure of air and spring 10 on the small stepped piston 9 from below.
Failure of the lower section of the valve (no pressure in port I) does not affect the operation of the upper section.
When the force is removed from the brake pedal, the lever 5 of the brake valve returns to its original position under the action of the elastic element 4.
The follower piston 3 moves upward by the force of the compressed spring 8, valve 2 sits in the seat, and air from the receiver to outlet II stops.
As piston 3 moves upwards further, the outlet window opens and outlet II communicates with the atmosphere through valve 13.
The pressure in port II, and consequently in the cavity above the piston space of large piston 1, drops, pistons 1 and 9 move upward under the action of spring 10, valve 9 sits in the seat, and air from the receiver to port I stops.
As pistons 1 and 9 move further upwards, the outlet window opens and outlet I communicates with the atmosphere through valve 13.
Replacing a two-section brake valve
The two-section brake valve must be replaced with the following faults:
- 1. Faucet leakage. An external sign is air leakage through the atmospheric valve at the attachment points of the body sections.
- 2. Mechanical damage to the body, lever, jamming of the pistons, disrupting its normal operation.
Removing the two-section brake valve
- 1. Release the air from the air reservoirs of the brake systems of the front and rear axles
- 2. Unscrew the cap nuts securing the tips of the pneumatic pipelines to the tees and the valve adapter 14 (see figure - brake valve drive)
- 3. Unpin and remove the pin connecting the rear link fork 12 of the drive with the crane lever
- 4. Unscrew the nuts of the bolts securing the valve upper body plate to the frame brackets and remove the valve
Installation of a two-section brake valve
- 5. Install the crane on the brackets of the left side member of the frame and secure with bolts, nuts and spring washers
- 6. Attach the fork of the rear link 12 of the drive to the lever, insert the pin and cotter it
- 7. Connect the lugs of the pneumatic pipes to the tees and the valve adapter, screw on and tighten the union nuts
- 8. Start the engine and fill the pneumatic actuator of the brake systems with air. Check the tightness of the pipelines and the brake valve.
Air leakage from the atmospheric valve of the tap, both with the brake pedal released and with the brake pedal depressed, is not allowed.
Air leakage is not allowed in the connections of the pneumatic actuator pipelines.
- 9. Check and, if necessary, adjust the stroke of the brake valve lever, which should be 31.1-39.1 mm, in the following order:
- - unscrew the locknut of the medium draft fork by a few turns, unpin and remove the pin connecting the fork to the pendulum arm, remove the fork from the pendulum arm;
- - bring the intermediate lever with the first link to folding and set the required length of the middle link with the threaded fork (wrapping or unscrewing), connect it to the pendulum lever, selecting the gaps in the drive and preventing forced movement of the brake valve lever. In this case, the full pedal travel should be 100-140 mm, free play -20 - 40 mm.
The pedal should not reach the floor by 10 - 30 mm. Measure at a distance of 210-220 mm from the pedal axis, adjust if necessary with a threaded fork on the first link.