Abstract: A platform lift mountable to a vehicle, which includes a platform that can remain horizontal while lifting and can tilt to faciltate loading and unloading of the platform. The lift includes a linkage pivotally mounted to the base frame, and the linkage includes a base leg, a platform leg, a lift arm, and a reference arm. In a lift/lower mode the legs and the arms form a parallelogram system that will maintain the platform in a level horizontal arrangement. In a tilt mode, the upper arm is extensible in order to change the geometry from a parallelogram to a quadrilateral with equal legs and unequal arms.

Abstract: A truck lift gate has a platform which is raised and lowered on runners to which it is attached, and which are guided in vertical rails. The runners are lifted by flexible members such as chains or cables, and are lowered by their own weight when the flexible members are slacked off. An equalizer is carried by each runner which overhangs and contacts the top of the platform at an elevation relative to the horizontal which is respective to the platform when it is horizontal. Then the platform cannot tilt sidewise when it is lowered.

Abstract: A controlled-folding and controlled-unfolding multiple section platform assembly for a structural entry. A platform assembly includes an inner and an outer platform section which are pivotally joined together for folding and unfolding. Fold control means comprises a pair of pivotally jointed rigid supports and a rigid co-ordinating member extending between the inner platform section and the outermost of the rigid supports. Tilting of the inner platform section is accompanied by a folding action of the outer platform section, there being a unique included angle between the two platform sections for every unique angle of tilt of the inner platform section.

Abstract: Actuator and control circuits for tailgate lifts of the type which lift and lower loads in a lifting mode and which fold in a folding (closing) mode. Control circuitry is provided which minimizes the risk of inadvertent folding of the gate when loaded. The circuitry can also be adapted to limit the lifting capacity of the actuator to the lifting of a safe load.

Abstract: For use with a vehicle tailgate lift that has a platform which when substantially level moves in an up and down movement, and which near and at its upper limit can also be moved in a folding mode, a circuit which enables the platform to be moved up, down or folded but which frustrates inadvertent folding of the platform by the provision of a safety circuit.

Abstract: A platform lift mountable to structures such as trucks or loading docks, which lift includes a platform that can be raised and lowered while horizontal and can be tipped to an upright raised position. The platform is carried by a compound hinge that includes parallelogram means which in one parallelogram configuration raises and lowers the platform in a horizontal alignment, and which when it encounters selective restraint means, assumes a different parallelogram configuration in which the platform is raised to an erect alignment.

Abstract: To prevent rapid collapse of a hydraulic lift mechanism in event of the failure of the hydraulic mechanism (e.g. as by rupture of a pressurized hydraulic line) a rate of flow responsive check valve is provided, either in a separate backup cylinder or at the inlet-outlet port of the lift cylinder, to close off the return flow path of the hydraulic line in the event of sudden depressurization of the hydraulic feed line or other pressure failure in the hydraulic liquid. In normal operation, the check valve does not oppose the return flow since the rate of such flow is insufficient to activate the valve.