Automatic door operator

A universally configurable door operator for driving any of various swing-mounted doors regardless of the directions of normal opening and panic swing of such door, said operator including a prime mover and a main housing and comprising within said main housing a door driving shaft, means mounting said door driving shaft for rotation about a vertical axis, said shaft being connectable to said door for closing and opening of said door by either clockwise or counterclockwise rotation of said door driving shaft, transmission means interconnecting said prime mover and said door driving shaft for producing rotation of said shaft in either a clockwise or counterclockwise direction for normal opening of said door pursuant to selective delivery of power by said prime mover, a pinion interconnected with said shaft for corresponding rotation with said shaft, and a rack gear meshing with said pinion for shifting movement in either of opposite directions about a longitudinal axis transverse to the rotational axis of said shaft in response to clockwise or counterclockwise rotation of said shaft, said main housing including an opening for access to one end of said rack gear, the improvement comprising a single changeable modular assembly including an assembly housing for selective attachment to said main housing and an operating rod within said assembly housing and including a portion extending through said opening into said main housing for selective interengagement with said one end of said rack gear, said assembly housing including a single coiled compression spring maintained therein in a state of pretension by said operating rod, said assembly housing orienting said spring for compression on an axis aligned with the longitudinal axis of transverse shifting movement of said rack gear, said spring having an inner end oriented toward said rack gear and an outer end oriented remote from said rack gear, said operating rod providing further tensioning of said spring by compression of said spring from said inner end or the outer end thereof in response to shifting of said rack gear in a predetermined direction corresponding to the direction of normal opening swing of said door for storing energy, said spring returning to its original state of pretension for transferring said stored energy to said rack gear via said operating rod to close said door upon cessation of delivery of power by said prime mover, and means within said assembly housing for limiting movement of said operating rod to establish the permissible extremes of shifting of said rack gear thereby to determine the permissible extremes of normal opening and panic swing of said door, said modular assembly being changeable for changing the normal opening and panic swing directions of said door.