Spring operated counterbalance hinge assembly for aircraft doors

Abstract

A compact, spring operated, two-way counterbalance system is disclosed for the hinge assembly of an inwardly/outwardly moveable plug-type aircraft passenger door of the type adapted to pivot about an inwardly canted hinge axis whereby a first convolute clock-type spring member is wound during the final stages of downward door-closing movement to provide an outward biasing force for assisting on-board flight attendants in opening the door during that portion of door movement when it must move in an upward direction; and, a second convolute clock-type spring member is provided which is wound during the latter stages of door opening movement when the door is moving in a downward direction, with the second convolute spring member thus providing a biasing force for assisting the on-board flight attendant in pulling the door upwardly and away from the fuselage during upslope door-closing movement. In the exemplary form of the invention disclosed, this is achieved by providing a pair of compact, coaxial, convolute, clock-type spring members which are oppositely wound and which have their free outer ends secured to the fuselage body structure with the inner ends thereof being separably engageable with radially projecting shoulder defining means formed on the inwardly canted body-mounted torque tube. The compact nature of the spring biasing arrangement of the present invention readily permits the incorporation of more extensive bearing support surfaces for the torque tube and the necessary snubber mechanisms and the like which serve to brake or retard movement of the relatively heavy door during the downward portions of movement when the door is being closed or opened.