Fluid operated vehicle body level control system

In a fluid operated levelling system of a vehicle body having a source of fluid under pressure connected to a fluid reservoir, the combination comprising:

• adjustors operative to raise and lower the vehicle body relative to ground;
• levelling valves communicating with the source and the reservoir and being responsive to the tilt of the vehicle body with respect to road surface and operative to communicate the adjustors with the source and the reservoir to move the vehicle body to a level substantially parallel to the road surface;
• first electrically controlled normally open valve means connected between the source and inlets of the levelling valves;
• second electrically controlled normally open valve means connected between the reservoir and outlets of the levelling valves;
• sensing means for sensing the tilt of the vehicle body relative to road surface and generating an electrical tilt representing signal in response to said sensed tilt;
• a delay unit connected to the sensing means and including integrating means for integrating said electrical tilt representing signal with respect to time;
• and
• a solenoid control unit connected between the delay unit and the first and second valve means, said solenoid control unit including a level detector responsive to the output of the delay unit and operative to feed said electrical tilt representing signal to the electrically controlled valve means when the integrated level of said electrical tilt representing signal is above a predetermined value for thereby closing said electrically controlled valve means to block fluid communication between the source and the reservoir and the levelling valves.