Wheelchairs

Abstract

A wheelchair is disclosed which is convertible into a wheeled stretcher, wherein the chair seat will assume a comfortable angle with respect to the horizontal when the chair is in the seating position and will assume a horizontal position coplanar with the back of the chair when the chair is in the stretcher position. The chair seat and back may be locked into any relative position between a fully erect seated position and a fully reclined stretcher position. Leg support members which are connected to the chair may assume any angular position with respect to the horizontal without regard for the relative positions of the seat and back of the chair. The leg support members may have their lengths independently adjusted.

We claim: 
     
       1. A wheelchair convertible into a wheeled stretcher, comprising: a pair of wheeled support frame members horizontally spaced from one another, each having a corresponding rearwardly positioned first pivot and a forwardly positioned second pivot at substantially the same elevation;   a pair of first levers, each having a first length and pivotally mounted on a respective one of said first pivots;   a chair back support having two lateral sides each proximate to a respective one of said support frame members, each rigidly mounted to the free end of a corresponding one of said first levers;   a pair of second levers, each having substantially said first length and pivotally mounted on a respective one of said second pivots;   a pair of front arms, each rigidly mounted at an intermediate point to the free end of a respective one of said second levers;   a pair of linkages, each having a first end pivotally connected to a respective one of said front arms at a point a second length above said intermediate point and a second end pivotally connected to a corresponding one of said lateral sides of said back support at substantially said second length above said mounting point for the corresponding one of said first levers;   a pair of extendable chair seat supports, each proximate to a respective one of said support frame members, each comprising a first and second portions which slideably engage one another with the free end of said first portion pivotally connected to a corresponding one of said lateral sides of said back support at a third length below said mounting point for the corresponding one of said first levers and with the free end of said second portion pivotally connected to a corresponding one of said front arms at a fourth length below said intermediate point, said third length being greater than said fourth length;   whereby a chair seat supported by said pair of extendable seat supports, will assume a comfortable angle with respect to the horizontal when the chair is in a seating position, and will assume a horizontal position coplanar with the back of the chair when the chair is in a stretcher position.   
     
     
       2. The apparatus of claim 1, which further comprises: a first tube pivotally mounted to said pair of support frame members;   a second tube mounted in sliding engagement with said first tube, with its free end pivotally connected to said second portions of said pair of extendable seat supports;   locking means mounted on said first tube and in selective frictional engagement with said second tube;   whereby said chair seat and back may be locked in any relative position between a fully erect seated position and a fully reclined stretcher position.   
     
     
       3. The apparatus of claim 1, which further comprises: a leg support member pivotally mounted on said second portions of said pair of extendable seat supports;   a first tube pivotally mounted on said second portion of one of said pair of extendable seat supports, rearwardly of the mounting point for said leg support member;   a second tube mounted in sliding engagement with said first tube, with its free end pivotally connected to said leg support member;   locking means mounted on said first tube and in selective frictional engagement with said second tube;   whereby said leg support member can assume any angular position with respect to the horizontal without regard for the relative positions of said seat and back of the chair.   
     
     
       4. The apparatus of claim 3, wherein said leg support member further comprises: a first and second outer tubes, each pivotally mounted on said second portions of said pair of extendable seat supports;   a first and second inner tubes, each mounted in sliding engagement with a respective one of said outer tubes;   a foot rest means mounted on the free ends of said inner tubes;   a locking means mounted on one of said outer tubes and in selective frictional engagement with the corresponding one of said inner tubes;   whereby said leg support member may have its length adjusted.   
     
     
       5. The apparatus of claim 4, which further comprises two of said leg support members being so mounted on the chair, capable of independent adjustment of their relative positions. .Iadd. 6. A wheelchair convertible into a wheeled stretcher, comprising: a pair of wheeled support frame members, horizontally spaced from one another, each having a corresponding rearwardly positioned first pivot, and a forwardly positioned second pivot at substantially the same elevation;   a pair of first lever means, each having a first length and pivotally mounted on a respective one of said first pivots;   a chair back support having two lateral sides, each proximate to a respective one of said support frame members and each rigidly mounted to the free end of a corresponding one of said first lever means;   a pair of second lever means, each having substantially said first length and pivotally mounted on a respective one of said second pivots;   a pair of front arm members, each rigidly mounted at an intermediate point to the free end of a respective one of said second lever means;   a pair of linkages, each having a first end pivotally connected to one of said front arm members at a point a second length above said intermediate point and a second end pivotally connected to a corresponding one of said lateral sides of said back support at substantially said second length above said mounting point for the corresponding one of said first lever means;   a pair of seat support members, pivot means connecting one end of said pair of seat support members to said chair back support at a third length below said mounting point for the corresponding one of said first lever means, the opposite end of said pair of seat support members being supported by the lower portion of said front arm members at a fourth length below said intermediate point, said third length being greater than said fourth length to thereby position said seat support at an angle θ to the horizontal; and lost motion means operatively connected between said opposite end of said seat support members and the lower portion of said front arm members; the chair back support, the front arm members, the linkages and associated pivot points to said front arm members and said back support, the seat support members and associated pivot means on said chair back and lost motion means on said front arm members, all being substantially horizontally coplanar when the chair is folded to a stretcher position,   whereby a chair seat supported by said pair of seat support members will assume a comfortable angle with respect to the horizontal when the chair is in a seating position, and will assume a horizontal position coplanar with the back of the chair when the chair is in a stretcher position. .Iaddend. .Iadd. 7. The apparatus of claim 6 which further comprises a pair of leg support members operatively supported by said chair and being capable of independent adjustment of their relative positions. .Iaddend..Iadd. 8. The apparatus of claim 6 which further comprises:   a first tube pivotally mounted to said pair of support frame members;   a second tube mounted in sliding engagement with said first tube, with its free end pivotally connected to said pair of seat support members;   locking means mounted on said first tube and in selective frictional engagement with said second tube;   whereby said chair seat back may be locked in any relative position between a fully erect seated position and a fully reclined stretcher position. .Iaddend. .Iadd. 9. The apparatus of claim 6 which further comprises:   leg support means pivotally mounted on said pair of seat supports;   a first tube pivotally mounted on said pair of seat supports rearwardly of the mounting point for said leg support means;   a second tube mounted in sliding engagement with said first tube, with its free end pivotally connected to said leg support means; and   locking means mounted on said first tube and in selective frictional engagement with said second tube; whereby said leg support means can assume any angular position with respect to the horizontal without regard for the relative positions of said seat and back of the chair. .Iaddend..Iadd. 10. The apparatus of claim 9 wherein said leg support means further comprises:   first and second outer tubes each pivotally mounted on said pair of seat supports;   first and second inner tubes, each mounted in sliding engagement with a respective one of said outer tubes;   foot rest means mounted on the free ends of said inner tubes; and   locking means mounted on one of said outer tubes and in selective fricitional engagement with the corresponding one of said inner tubes;   whereby said leg support means may have its length adjusted. .Iaddend.