Counterbalanced lift system
OwnerDouglas Waitinventor
Life of this patent
Estimating the term…
Abstract
An adjustable length counterbalance mechanism for lift doors, frequently used for cargo trailers and garages. The adjustable length torque shaft of the counterbalance mechanism is able to accommodate many different lift door widths and is simpler to install than a fixed length torque shaft. In embodiments, the adjustable torque shaft is comprised of two outer torque shafts, each with a torsion spring and cable drum and a middle torque shaft that can be assembled together. The middle torque shaft can be inserted into each of the outer torque shafts to a selected depth to determine the length of the adjustable torque shaft.
Claims16
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;
- 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, where each of the torsion springs are anchored to a mounting bracket.
A method of installing a counterbalance mechanism for a lift door, comprising:
- lifting an adjustable length torque shaft into a first and second mounting bracket, wherein the first and second mounting bracket are positioned above the lift door and at opposite sides of the lift door, and wherein the adjustable length torque shaft comprises:
- a first outer torque shaft and a second outer torque shaft connected via a middle torque shaft;
- a first torsion spring attached to the first outer torque shaft so that the first torsion spring is rotationally fixed to the first outer torque shaft;
- a second torsion spring attached to the second outer torque shaft so that the second torsion spring is rotationally fixed to the second outer torque shaft;
- and
- a first cable drum attached to the first outer torque shaft and a second cable drum attached to the second outer torque shaft;
- connecting the second end of the first torsion spring to the first mounting bracket;
- connecting the second end of the second torsion spring to the second mounting bracket;
- attaching a cable to each of the cable drums with the other end of the cable attached to the lift door;
- and
- adjusting tension on the first and second torsion springs to offset weight of the lift door.
Dependencies are inferred from the claim text.