Patent ID: 11859423
Assignee: nan
Field: Transport (Mechanical engineering)
Classification: CPC E  B | IPC B  E

Claim 8:
9. A counterbalance mechanism for a lift door system, comprising:
an adjustable length torque shaft positionable above a lift door, wherein length of the torque shaft is selected to extend at least proximate to a width of the lift door;
the adjustable length torque shaft including:
a first outer shaft and a second outer shaft;

the adjustable length torque shaft further including:
a middle shaft that connects the first outer shaft to the second outer shaft, wherein the middle shaft overlaps the first and second outer shafts to define a length of the adjustable length torque shaft;

two cable drums mounted proximate to opposite ends of the adjustable length torque shaft for rotation with the torque shaft, the cable drums supporting flexible cables that connect to the lift door to support at least a portion of weight of the lift door; and
two torsion springs disposed around the adjustable length shaft and operably connected to the adjustable length torque shaft, wherein the two torsion springs exert a torsional force on the adjustable length torque shaft to counterbalance at least a portion of the weight of the lift door and assist in movement of the lift door.