Variable-displacement pump

Ground drive/cut off valve solenoid coil (Y143)

3258 When the electronic signal at the ground drive forward solenoid coil (Y141) is decreased, the proportional 4/2 way valve reduces the pressure to the ground drive forward/backward servo control valve (738) and the swivel angle of the ground drive variable displacement pump (211) becomes smaller. The ground drive/shut-off valve solenoid coil (Y143) is de-energised in case of a "panic braking" (pedal force >600 N) (see also Technical systems documentation - Electric system). When the ground drive/cut off valve solenoid coil (Y143) is de-energized, the magnetic needle is retracted. The ball lifts off from its seat and relieves the servo control supply pressure towards the tank. This switches the 2/2-way valves of solenoid coils (Y141 and 142) to the closed position and thus takes away the supply pressure to the proportional 4/2-way valves, so that these are set back to their initial position. Since the servo control supply pressure applied at the ground drive forward/ backward servo control valve (738) collapses, the compressed springs move this valve to its neutral position. The 4/3 way valve is moved to its centre position due to the mechanical link. Switching off the ground drive/cut off valve solenoid coil (Y143) creates a pressure drop downstream and switches the ground drive restrictor valve (738) from the unrestricted to the restricted position. This ensures smooth deceleration since the return time of the ground drive pump servo control hydraulic cylinder (313) is longer.