Seating system for a wheel chair

A seat assembly for a modular wheelchair comprising:

• a rectangular-shaped seat frame formed of a pair of longitudinal side members connected by at least one cross-brace member;
• each of said longitudinal side members having a rail fixed to a bottom surface of each side member and extending substantially the length of each side member, each rail having a plurality of holes for selectively positioning said seat frame on a chassis of said modular wheelchair;
• a pair of seat posts for each rail, each post having a U-shaped coupling for receiving its corresponding rail, and each post having a pin for connecting said post to its corresponding rail through the U-shaped coupling and one of said plurality of holes on the rail;
• said posts being telescopically movable within post receiving cylinders in said chassis so as to provide height and angle adjustability to said seat frame;
• a seat for supporting a user mounted on said seat frame;
• a back rest frame having a pair of back rest side members connected by a back rest cross-member, said back rest frame being pivotally connected to said seat frame by a pair of hinge plates, each of said back rest side members having a screw member threaded into a lower end of the side member such that one end of said screw member contacts a corresponding side member of the seat frame when said back rest is pivoted to the upright position, said screw member serving as a stop for further pivoting of said back rest frame, said screw member being threadably adjustable into and out of its side member according to a desired final angle of the back rest frame in the upright position relative to said seat frame;
• a back rest for supporting a user;
• means for locking said back rest frame in said upright position, said means for locking including a spring loaded block disposed on each of said seat frame side embers, each block having a flanged section for receiving and securing an end of said screw member to thereby lock said back rest frame in said upright position, each block having a ramp surface for engaging said end of said screw member as said back rest frame is pivoted to said upright position, said ramp surface being inclined such that engagement with said screw member urges said block in a direction on said seat frame side member against a spring load until said screw member is positioned within said flanged section of said block;
• and
• means for attaching a leg rest frame to said seat frame.