US 4,047,441 A · Mechanical counterbalance assembly

Abstract

A mechanical counterbalance assembly for an overhead, track mounted, aircraft door includes a frame, a shaft mounted for rotation in the frame, and a torsion spring interconnected between the shaft and the frame. As the shaft is turned in a first direction, the spring is wound so that a torque is applied to the shaft in the direction opposite to rotation. The spring rate of the torsional spring is selected so the spring torsional force slightly exceeds the component of the door weight acting along the path of motion of the door throughout the door travel. A cable drum is mounted for rotation on the shaft and is releasably affixed thereto. A cable is wrapped about the drum and has its free end connected to the overhead sliding door. A planetary gear train has its low speed input shaft coupled to the shaft and its high speed output shaft operatively coupled to a centrifugal brake and to a manually rotatable drive wheel. When the door is lowered from its open position to its closed position, cable is unwound from the drum, rotating the shaft to store energy in the spring. When the door is opened, a torque is imparted to the shaft by the spring to counterbalance the door and assist in raising it to an open position. Should the cable break or the door be lightened for any reason, the rotational speed of the shaft as urged by the spring is limited by a centrifugal brake coupled to the high speed output of the planetary gear train. Similarly, should the torsional spring break, the lowering rate of the door is limited by the action of the centrifugal brake.

Claims10

Dependent claims

A torsional counterbalance assembly for counterbalancing the weight of an object mounted for movement in a vertical direction comprising:

a first rotatable member having a rotational axis and frame means mounting said rotatable member for rotation about its axis,
spring means associated with said first rotatable member for imparting torque to said first rotatable member to rotate said first rotatable member in a first direction and to resist rotation of said first rotatable member in the opposite direction,
a second rotatable member associated with said first rotatable member and mounted for rotation relative thereto, and means associated with said second rotatable member for translating the rotational motion thereof into motion corresponding to the movement of said object,
manually actuated connection means associated with said first and second rotatable members for releasably interconnecting said first rotatable member and said second rotatable member in mutually driving relationship, so that said first rotatable member can rotate independently from said second rotatable member when released from said second rotatable member.
manually actuated locking means associated with said frame means for selectively preventing said second rotatable member from rotating, and
drive means associated with said first rotatable member for manually rotating said first member.

3 more elements

Dependencies are inferred from the claim text.

Mechanical counterbalance assembly

Life of this patent

Mechanical counterbalance assembly

Life of this patent

Abstract

Claims10