Mechanical counterbalance assembly

Details Mechanical counterbalance assembly Mechanical counterbalance assembly

1976-02-02

1977-09-13

Scott, Samuel

Machine element or mechanism

Mechanical movements

Rotary to or from reciprocating or oscillating

160189, 185 9, F16H 3712

Patent

active

040474410

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.

REFERENCES:
patent: 3160200 (1964-12-01), McKee et al.
patent: 3585757 (1971-06-01), Ritchie
patent: 3637004 (1972-01-01), Wardlaw
patent: 3802125 (1974-04-01), Baker

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