Patent ID: 7798489

Claim:
A media handling system for an image forming machine, comprising: a stationary frame; a platform for supporting a stack of media sheets thereon; a bin movable relative to the stationary frame, the bin supporting said platform and in turn supported on said stationary frame, the bin undergoing movement relative to said stationary frame between a first position in which said bin locates said platform below and aligned with a sheet feeding position and movable relative to said bin toward and away from said sheet feeding position and a second position in which said bin displaces said platform away from and out of alignment with said sheet feeding position; and a motion transmitting assembly coupled between said stationary frame, platform and bin and operable to convert movement of said bin between said first and second positions relative to said stationary frame into movement of said platform relative to said bin toward and away from said sheet feeding position, said motion transmitting assemble including a spring mechanism being windable and unwindable to maintain a wound condition biased toward unwinding and tailored to counterbalance the position and weight of said platform and any stack thereon relative to said bin and the position of said bin relative to said stationary frame such that said spring mechanism in maintaining said counterbalance converts movement of said bin relative to said stationary frame between said first and second positions into movement of said platform relative to said bin toward and away from said sheet feeding position, said spring mechanism including: a hoist drum defining a central axis and having: a first part rotatably mounted about said central axis to an end of said bin and having a gear section formed thereon concentric about said central axis, and a second part having a reel on an opposite side of said drum from said end of said bin and rotatably mounted to said first part so as to be rotatable relative thereto and define an annular cavity therebetween and concentric about said central axis; and a spring device disposed in said annular cavity and having opposite ends respectively connected to said first and second parts of the hoist drum, said spring device being resiliently yieldable so as to be windable and unwindable to maintain the wound condition biased toward unwinding and tailored to said counterbalance, the spring device comprising a spiral leaf spring having opposite ends respectively connected to the first and second parts of the hoist drum.