Inventors:
Kjell I. Erlandsson - Milwaukee WI
William B. Weishar - Brookfield WI
Assignee:
Kelley Company, Inc. - Milwaukee WI
International Classification:
E01D 100
Abstract:
An improved counterbalancing mechanism for the ramp of a dockboard. The ramp is hinged at its rear edge to the frame of the dockboard and is adapted to be pivoted between a generally downwardly inclined position and an upward inclined position by a counterbalancing spring assembly. The counterbalancing spring assembly includes a first link pivotally connected to the underside of the ramp and a second link pivotally connected to the frame. The two links are connected together and are disposed in an acute angle relationship when the ramp is in the downwardly inclined position. One end of an extension spring is connected to the frame, while the opposite end of the spring is connected to one of the links. When the ramp is in the maximum downwardly inclined position, the spring is in a fully tensioned condition and when the holddown mechanism of the dockboard is released, the force of the spring will move the links toward an in-line position. The links are arranged so that the counterbalancing moment will slightly exceed the moment of the ramp as the ramp is pivoted, and at the elevated position of the ramp, the spring will be fully relaxed.