 | |
| Illustration 1 | g00720867 |
Manifold (trailer) (13) | |
Note: For additional information on the location of other callouts, refer to the schematic in Systems Operation, "General Information".
The manifold provides control of the maximum pressure for the rod end of ejector cylinder (5). The manifold controls tailgate cylinders (19). The manifold also acts as a connection to the head end of ejector cylinder (5) .
The manifold contains the following components: relief valve (14), counterbalance valve (27), check valve, control orifice and manually operated valve. During maintenance work on the machine, the valve is used to lower the tailgate manually without interactions with the hydraulic system. To lower the tailgate, a hex head bolt (28) is located on the manifold. Loosen the locknut on the hex head bolt and turn the hex head bolt on the manifold counterclockwise. Turn approximately two turns.
To ensure for proper operation of the ejector cylinder, the relief valve for the rod end of ejector cylinder (5) is set to crack at 22753 kPa (3300 psi). This keeps high pressure on the rod end high during the eject cycle. The check valve for the tailgate prevents the backflow of pressure from head end of tailgate cylinder (19). This effectively gives control of the pressure of the head end to the counterbalance valve. The orifice control for the tailgate slows the return speed of the tailgate.
Counterbalance valve (27) controls the opening of the tailgate by keeping high pressure in the head end of the tailgate cylinders high until the appropriate pilot pressure is applied. The counterbalance valve is set to crack at 20685 kPa (3000 psi) and the counterbalance valve has a pilot ratio of three to one. When the truck body is empty, 6895 kPa (1000 psi) of pressure in the head end of the ejector cylinder will convert to 20685 kPa (3000 psi) in the counterbalance valve and this will cause the tailgate to open. When the pressure reaches, the counterbalance valve senses both head pressure of ejector cylinder (5) and head pressure of tailgate cylinders (19). The combined pressure 20685 kPa (3000 psi) of these cylinders will cause the tailgate to open. The counterbalance valve also acts as a safety or thermal relief for the tailgate.