Foldable bow spring with center support for bridge or ramp comprises two-part spring as clamped and fixed one end and clamped at far end to form transition join for raised or lowered bridge.

摘要

The two identical parts (1,2) of the spring joined by a hinge crosspiece (3) are clamped (4,5) at their ends to the bridge or boom structure. The spring is supported on the crosspiece by a supporting mechanism (6-9). One clamp is fixed as against the second clamp which is slidably joined to the bridge etc for length adjustment. When the bridge etc rises (angle alpha ) the crosspiece (3) acts as a freely movable joint as opposed to the downwards movement of bridge when the (angle alpha ) crosspiece (3) forms a rigid connection. When extended, the longitudinal axis of the spring parts (1,2) passes through the bridge etc pivot point so the hinge point of the crosspiece (3) registers with this bridge pivot point and the clamps (4,5) lie along the spring axis as specified. The hinge and leverage conditions are so selected that the supports (6-9) underpin the spring in the correct position, i.e. that adopted by the unsupported spring bow.