US 4,447,026 A · Cam operated counterbalance assembly for aircraft doors

Abstract

A compact, cam operated, counterbalance system (30) is provided for the torque tube assembly (25) associated with a moveable hinged structural member (20) of the type hingedly connected to a fixed structural member and adapted to pivot about an inclined hinge axis in which the counterbalance system includes: (i) a cylindrical cam (31) surrounding a torque tube (38) and defining an axially presented continuous cylindrical cam surface (32) formed by a plurality of axially presented curved ramps (32a, 32b); (ii) cam follower means (34, 35, 36) mounted concentrically about the torque tube (38); (iii) a compression spring (42) mounted concentrically about the torque tube (38) for continuously biasing one of the cylindrical cam (31) or the cam follower means (34, 35, 36) axially towards the other; (iv) one of the cylindrical cam (31) and the cam follower means (34, 35, 36) being rigidly mounted on the fixed structural member (22); (v) the other of the cylindrical cam (31) and the cam follower means (34, 35, 36) being nonrotatably mounted on the torque tube (38) with freedom for axial movement therealong under the forces exerted axially thereon by the compression spring (42); and (vi), wherein the cylindrical cam ramps (32a, 32b) are profiled such that the spring (42) is fully compressed axially when the movable structural member (20) is in a first position so that when the movable structural member (20) is shifted between first and second positions and the torque tube (38) is rotated about its axis so that the energy stored in the compression spring (42) when the movable structural member (20) is in the first position imparts a rotational torque to the torque tube (38) as the spring (42) is extended for reducing the amount of torque that must be manually applied when attempting to push the first structural member (20) upslope about the inclined hinge axis from the first to the second position and so that the spring (42) is compressed during movement of the movable structural member (20) from the second position to the first position.

Apparatus for reducing the torque required to manually rotate a movable structural member about a canted hinge axis comprising, in combination:

(a) a fixed structural member;
(b) a torque tube mounted on said fixed structural member, said torque tube lying in a plane defining an acute included angle .alpha. with the vertical and defining an inclined hinge axis;
(c) a movable structural member;
(d) hinge means for coupling said movable structural member to said torque tube for permitting rotation of said movable structural member and said torque tube about said inclined hinge axis with said movable structural member rotating between first and second positions and wherein said movable structural member is constrained for movement in an upslope direction about said inclined hinge axis during at least a portion of rotation thereof from said first to said second position and for movement in a downslope direction during at least a portion of rotation thereof from said second to said first position;
(e) cylindrical cam means mounted concentrically about said torque tube and co-axial therewith, said cylindrical cam means defining an axially presented cylindrical ramp-like cam face;
(f) cam follower means mounted concentrically about said torque tube and co-axial therewith;
said cam follower means including a plurality of cam rollers engaged with said cylindrical ramp-like cam face;
(g) one of said cylindrical cam means and said cam follower means being fixedly mounted on said fixed structural member;
(h) the other of said cylindrical cam means and said cam follower means being nonrotatably mounted on said torque tube with freedom for axial movement therealong;
(i) axially compressible and expandable spring means mounted concentrically about said torque tube and having one end thereof restrained from axial movement relative to said torque tube and the other end thereof bottomed on said other of said cylindrical cam means and said cam follower means for normally biasing said other of said cylindrical cam means and said cam follower means into engagement with said one of said cylindrical cam means and said cam follower means;
and,
(j) said cylindrical cam means being profiled so that said spring means is fully compressed when said movable structural member is in said first position so that when said movable structural member is rotated from said first position towards said second position about said inclined hinge axis, said spring means is permitted to expand axially as said movable structural member moves in an upslope direction and said torque tube rotates to cause said cam follower means to relatively traverse said ramp-like cam face whereby the other of said cylindrical cam means and said cam follower means imparts rotational torque to said torque tube as said spring means expands axially to thereby reduce the manual exertion required to rotate said movable structural member in an upslope direction about said inclined hinge axis during movement thereof from said first position to said second position.

9 more elements

Cam operated counterbalance assembly for aircraft doors

Life of this patent

Cam operated counterbalance assembly for aircraft doors

Life of this patent

Abstract

Claims22