US Patent 7913343 Counterbalance mechanism for fold out ramp

A ramp assembly includes a ramp portion configured for reciprocating motion between a stowed position, a deployed position, and a neutral position. A counterbalance comprises a shaft and a crank fixedly coupled to the shaft. A rod is rotatably coupled to the crank with an end fitting, and an end stop is slidably coupled to the rod. A compression spring is disposed between the end fitting and the end stop, wherein the compression spring provides a force to bias the ramp portion toward the stowed position when the ramp portion is between the deployed position and the neutral position, and toward the deployed position when the ramp portion is between the stowed position and the neutral position.