Foldable wheelchair frame

A wheelchair that upon folding can become more compact for transporting and storage by enabling the vertical side frames of the wheelchair to move towards each other through the use of a sliding mechanism.

BACKGROUND

A wheelchair with the ability to become narrower for transportation and storage has several benefits. It allows the wheelchair to fit into a vehicle easier without the need to remove components, such as wheels. It takes less room to store when not in use. When folded it will fit through narrow passageways. However, traditional folding wheelchairs suffer from several problems.

As non-limiting examples, a typical folding wheelchair with an X-frame style frame, as can be seen in U.S. Pat. Nos. 2,379,566 and 5,328,183, folds very compactly but at the expense of functionality and durability. Other designs fold the frame vertically, as can be seen in U.S. Pat. No. 5,593,173, or laterally, as can be seen in U.S. Pat. Nos. 4,863,181; 6,572,133 and 4,595,212. All of the folding methods require many additional components adding substantial weight and complexity. The added weight makes it much more difficult to self propel and to lift into a vehicle for transport. Due to the many joints and pivots, they also have reduced durability for daily use requiring frequent maintenance. The additional components also increase the cost of manufacture.

SUMMARY

A foldable frame for a wheelchair is provided. The foldable frame includes first and second side frames and a frame structure connecting the first side frame to the second side frame. The frame structure permitting the first side frame and the second frame to selectively move toward each other and away from each other.

DETAILED DESCRIPTION

A foldable wheelchair constructed, in accordance with one embodiment of the present disclosure, may be best understood by referring toFIGS. 1-10. The foldable wheelchair includes a set of large rear wheels5, a set of front smaller wheels or casters6. The wheels are connected to two generally vertical side frames10,20between which extends interconnecting frame structures8connecting the forward ends of the side frames10,20and9connecting the aft ends of the side frames10,20. The seating and backrest fabric3and4respectively are attached to the side frames. Footrest assemblies7are inserted into the side frames10,20and can be fixed at a variety of heights depending on the size of the user.

As may be best seen by referring toFIG. 2, the interconnecting structures include sliding joints. In its preferred form, it would include two telescopic cross tubes. The telescopic tubes include an outer sleeve tube13fixed to side frame10and a slidable inner sleeve tube23fixed to side frame20. When the side frames10and20are pulled away from one another such that the seating and backrest fabric3,4are pulled tight, the inner and outer tubes can be locked together to form a rigid frame in the open position with the use of a locking mechanism40.

Referring toFIGS. 2-3, when the locking mechanism40is in its unlocked position the side frames10,20can slide toward each other which slides the inner sleeve tube23further inside the outer sleeve tube13until the outer sleeve tube13touches the side frame20which represents the wheelchair in its folded position.

As may best be seen by referring toFIGS. 1-2, side frames10and20are substantially mirror images of each other and will be described together with the few exceptions highlighted. The side frame components are made from hollow structural steel tubing. The side frames are composed of side rails11,21which support the mostly horizontally positioned seat fabric3and are then bent downward near their midpoint to align with the footrest assembly7. Near the forward ends of the side frames11,21the castor connects tubes15,25are welded to both the side rails11,21and the vertically oriented castor tubes30. The mostly vertical backrest support frames12,22are welded to the aft end of side rails11,21. Additionally, the backrest support frames have the substantially horizontal axle mount tubes33, passing through them and welded near their lower ends. The axle bolts of the rear wheels5pass through the axle mounts33and are locked in place. The backrest canes31slide into the upper end of the backrest support frames12,22and are locked into position. The armrest support tubes14,24are welded at their aft ends to the backrest support frames12,22they follow a substantially horizontal position on which the armrests2are bolted, they then bend downward near their midpoint and continue to the side rails11,21where they are welded.

The interconnecting tube assemblies include the two outer sleeve tubes13. The forward tube passes through and is welded to side frame11and the second passes through and is welded to backrest support tube12. Additionally, there are two inner sleeve tubes23. The forward inner sleeve tube23passes through and is welded to side frame21and the second passes through and is welded to backrest support tube22. The inner sleeve tube is of proper outside diameter to fit inside the outer sleeve tube13with sufficient clearance to not bind up, but similar enough to allow the outer sleeve tube13to be securely clamped around it using clamping assembly40.

As may be best seen by referring toFIG. 4-10, the clamping assembly40includes the binding tube45which is oriented perpendicular the outer sleeve tube13and mitered to match the outer diameter of outer sleeve tube13and then welded to the under side of it near its end, the barrel lock bolt43which passes through the binding tube45and adjustment nut44which is threaded onto the barrel lock bolt43. The cam lock lever41is attached to the barrel lock bolt with the cam pin42. The barrel lock bolt43is mitered near its mid section to match the outer diameter of the inner sleeve tube23. This allows the inner sleeve tube23to pass through the binding tube45and barrel lock bolt43without interference. Near the end of the inner sleeve tube23there is an inner sleeve tube miter46oriented perpendicular to its length and the same diameter as the barrel lock bolt43. The inner sleeve tube miter46is located such that when lined up with binding tube45, a bolt the diameter of the barrel lock bolt43could pass through the inner sleeve tube23without interference.

The clamping assembly works in two ways to lock the inner sleeve tube23to the outer sleeve tube13when the wheelchair is in its open position. The first way the inner and outer sleeve tubes23,13are locked together is with a barrel lock. The barrel lock has an open and a locked position. When the barrel lock is in the open position (FIGS. 4-6) the barrel lock bolt43is rotated so its mitered section matches the contour of the inner sleeve tube23, thus allowing it to pass through the barrel lock bolt43. To place the barrel lock in its locked position (FIGS. 7-9) the inner sleeve tube miter46is lined up with binding tube45and the barrel lock bolt43is rotated one hundred eighty degrees, moving its unmitered side into the inner sleeve tube miter46, thus preventing the inner sleeve tube23from sliding in or out of outer sleeve tube13or rotating relative to outer sleeve tube13.

Referring toFIGS. 4-10, the second clamping mechanism includes a cam lock. The cam lock utilizes several additional features built into the binding tube45, cam lever41, adjustment nut44and outer sleeve tube13. A miter that matches the shape of the cam lever profile when the cam lever41is substantially vertically oriented is cut into the end of binding tube45. The hole that allows the cam pin42to pass through cam lever41is slightly offset horizontally relative to the location of the center of the cam lever profile when the cam lever41is positioned substantially vertical. Additionally, a slot47(FIG. 10) has been cut through the underside the outer sleeve tube13and the binding tube45. The cam lock has an open and locked position. In the open position (FIGS. 4-6) the cam lever41is oriented such that cam lever profile edge with the shortest distance relative to cam pin42is along the side of the mitered profile of the binding tube45. To place the cam lock in its locked position (FIGS. 7-10) the cam lever41is rotated approximately 180 degrees about the cam pin42. When the cam lever41is rotated, the cam lever profile edge will be the longest distance relative to the cam pin42is moved along the side of the mitered profile of the binding tube45thus pulling the barrel lock bolt43and adjustment nut44in the direction of the cam lever41. As the barrel lock bolt43and adjustment nut44are pulled toward the cam lever41the adjustment nut pushes against the unmitered end of the binding tube45and the cam lever41pushes against the mitered end of binding tube45partially collapsing the slot47and compressing the outer sleeve tube13onto the inner sleeve tube23. With the addition of the cam lock, any space between the inside of the outer sleeve tube13and inner sleeve tube23is removed providing a firmly locked joint when used in combination with the barrel lock.

A foldable wheelchair of the present disclosure includes a set of large rear wheels, a set of front smaller wheels or casters. The wheels are connected to two generally vertical side frames between which extends interconnecting frame structures connecting the two side frames together. The interconnecting frame structures connect the first side frame to the second side frame in a manner permitting the first frame member and the second frame member to be selectively moved toward and away from each other, thereby, permitting the collapse of the wheelchair for storage or transport. The interconnecting structure includes a sliding joint. In its preferred form, it would have two telescopic cross tubes. One telescopic tube connects the forward end of the side frames and the second connects the aft end of the side frames. The telescopic tubes include an outer tube fixed to one side frame and a slidable inner tube fixed to the other side frame. The inner and outer tubes can be locked together to form a rigid frame. The locking mechanism can be readily changed from the locked open wheelchair position to an unlocked position that allows the wheelchair to be folded.

The sliding interconnecting structure provides a robust and simple folding mechanism. With fewer components and no pivoting joints the system provides a durable, lightweight and lower cost folding system.