Abstract: A hydraulic by-pass control system is provided in the hydraulically operated lift assembly of a loader which uses double-acting hydraulic cylinders. The by-pass control system provides a low-resistance alternative pathway between the lowering circuit of the lift assembly and the hydraulic fluid tank. Accurate weighing measurement of the load on the lifting arms of the loader may be achieved by temporarily opening the alternative low-resistance pathway, thereby effectively converting the hydraulic circuit to a single-acting configuration during the taking of load cell signal measurements of back-pressure in the lift circuit.

Abstract: A monitoring system for a fork lift truck or other load handling vehicle comprises a plurality of transducers each assigned to detect a particular condition of vehicle usage; means for deriving from the transducers a plurality of binary signals each representative of the condition detected by a respective one of said transducers; and binary processing means including means for selectively gating the binary signals thereby to produce a plurality of sets of data each corresponding to a mode of vehicle usage represented by a respective combination of said signals. The sets of data are accumulated thereby to derive a count representative of the duration of each said mode of vehicle usage. The data read-out may be transmitted to a remove receive over an optical link.

Abstract: In a vehicle such as a tractor or a trailer having fluid-operated spring brakes to which fluid is supplied under pressure for releasing the brakes from a locked condition, security means are provided to prevent unauthorized release of the brakes. The security means comprises a bistable solenoid valve for controlling the supply of fluid to the brakes, energizing circuit means for operating the valve, and limited access switching means operable to set the solenoid valve selectively in an open or a closed condition.

Abstract: The invention provides an electric monitoring system for use in association with a load handling vehicle, such as a fork lift truck. The system provides a number of transducers and switches operable in response to operating conditions of the vehicle such as whether it is loaded or unloaded, and whether it is stationary or being driven, and gating circuitry interconnects these transducers and switches with a variety of timers and counters which record the various modes of use of the vehicle during a working shift.