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.
1. A ramp assembly, comprising:
(a) a ramp portion configured for reciprocating motion between a stowed position, a deployed position, and a neutral position; and
(b) a counterbalance associated with the ramp portion, comprising:
(i) a drive element comprising a spring fitting, wherein the drive element is rotatably coupled about a first axis of rotation, the first axis of rotation moving along an arcuate path when the ramp portion reciprocates between the stowed position and the deployed position;
(ii) a restraint slidably coupled to the drive element and coupled for rotational movement about a second axis of rotation, wherein the second axis of rotation has a fixed location relative to the neutral position of the ramp portion; and
(iii) a compression spring disposed between the spring fitting and a portion of the restraint, wherein the compression spring provides a force to bias the ramp portion (1) toward the stowed position when the ramp portion is between the deployed position and the neutral position, and (2) toward the deployed position when the ramp portion is between the stowed position and the neutral position.
2. The ramp assembly of claim 1 , wherein the spring fitting engages a first end of the compression spring to move the first end of the compression spring toward a second end of the compression spring when the ramp portion moves from the neutral position toward the stowed position.
3. The ramp assembly of claim 2 , wherein the spring fitting engages the first end of the compression spring to move the first end of the compression spring toward the second end of the compression spring when the ramp portion moves from the neutral position toward the deployed position.
4. The ramp assembly of claim 1 , wherein the force provided by the compression spring does not bias the ramp portion when the ramp portion is in the neutral position.
5. The ramp assembly of claim 1 , further comprising a crank associated with the ramp portion to rotate (1) in a first direction when the ramp portion moves toward the stowed position, and (2) in a second direction opposite the first direction when the ramp portion moves toward the deployed position, wherein the drive element is rotatably coupled to the crank about the first axis of rotation.
6. The ramp assembly of claim 1 , wherein the drive element is a rod concentrically disposed within the compression spring.
7. The ramp assembly of claim 1 , wherein the restraint is a rod concentrically disposed within the compression spring.
8. The ramp assembly of claim 1 , wherein the drive element further comprises a second spring fitting, and wherein the restraint comprises first and second end stops, the counterbalance further comprising a second compression spring disposed between the second compression spring fitting and the second end stop, wherein the second compression spring provides a force to bias the ramp portion (1) toward the stowed position when the ramp portion is between the deployed position and the neutral position, and (2) toward the deployed position when the ramp portion is between the stowed position and the neutral position.
9. The ramp assembly of claim 8 , wherein the drive element is a rod concentrically disposed within the first and second compression springs.
10. The ramp assembly of claim 8 , wherein the restraint is a rod concentrically disposed within the first and second compression springs.