US Patent 7913342 Counterbalance mechanism for fold out ramp

A ramp assembly has a ramp portion configured for reciprocating motion between a stowed position, a deployed position, and a neutral position. A counterbalance is associated with the ramp portion and includes a drive element with a spring fitting. The drive element is rotatably coupled about a first axis of rotation that moves along an arcuate path. A restraint is slidably coupled to the drive element and is also rotatably coupled about a fixed axis of rotation. An end stop is associated with the restraint. A compression spring is disposed between the spring fitting and a portion of the restraint so that the compression spring provides a force to bias the ramp portion toward the neutral position.