Conventional, user propelled wheelchairs have a seat frame, relatively large diameter rear wheels, typically from 22 inches to 26 inches, which often have a rim that the user can push to rotate the wheels and thus propel the wheelchair, and a pair of front or caster wheels that are considerably smaller in diameter than the rear or driving wheels, typically between 2 to 10 inches and more commonly 2 to 6 inches. These wheelchairs can also be pushed from behind. However, when an attempt is made to propel or manipulate such wheelchairs on rough terrain or soft terrain, where the vehicle's front wheels either encounter obstructions or sink into the terrain then movement and control of the wheelchair becomes extremely difficult and hazardous. The front wheels can unintentionally be directed in other than the desired direction of movement. Pushing a wheelchair on any surface that is not smooth is both tiring and can be enough to upset the balance of the user or pusher and result in stopping or worse, the user falls out of the wheelchair. This is particularly true for terrain such as sand, snow, ice, and mud, which require extreme strength and physical dexterity to safely propel and guide the wheelchair. Such rough terrain is often unavoidable in daily life situations for a disabled person in a wheelchair. While many of these problems can be overcome simply by increasing the diameter of the front wheels, there are substantial disadvantages to doing so. Compared to small diameter front wheels, the large diameter front wheels are more difficult to propel over normal surfaces which are essentially smooth and hard, are difficult to turn, and allow less clearance for feet positioned on foot plates.
There are known, specialized wheelchairs such as three wheeled sport wheelchairs, some of which are discussed further herein, that can help eliminate some of the above described problems in travelling over rough surfaces, however, typically these wheelchairs are expensive, bulky, and not conveniently suited for travel over smooth, everyday terrain, such as in buildings, homes or the like.
There is a need for a simple, easy to use, easy to install and remove, portable, light weight, low cost, safe, attractive, and durable attachment for wheelchairs to safely and easily negotiate difficult terrain. Such a device should improve handling and personal safety for an individual propelling such wheelchairs, occupants of such wheelchairs, and individuals in the vicinity of such wheelchairs. The device should be capable of use on snow, sand, ice, mud and other terrain, and the like, where wheels ordinarily sink into the terrain, and/or otherwise become directed in a direction other than the desired direction of travel of such wheelchairs, and make wheeled transportation otherwise difficult or impossible, and hazardous, and be easy to use. The device should be of simple construction, easy to manufacture, and easily installable as a retrofit on existing wheelchairs or in new installations during construction and fabrication of such wheelchairs, adjustable and installable for different wheel sizes and on different types of wheelchairs.
Different wheels, skids, skis and other adaptations for wheelchairs have heretofore been known, however, none of these adequately satisfies these aforementioned needs:
U.S. Pat. No. 5,116,067 (Johnson) discloses a wheelchair having a support structure that attaches to standard wheelchair wheels for providing mobility and allowing interchangeability of accessories to change the support structure for sporting events, such as water and snow skiing. The wheelchair has a frame and sockets to replace attachable wheels with water and snow skis.
U.S. Pat. No. 4,141,566 (Banes et al) discloses a sled frame for releasable attachment of a wheelchair. The sled frame has a body portion supporting a pair of laterally spaced, horizontally disposed support members which, in turn, are sized to be disposed between the wheels of a wheelchair to support the frame of the wheelchair on the sled. The support members are each provided with a plurality of locking devices which releasably engage the frame of the wheelchair to securely lock the wheelchair to the sled.
U.S. Pat. No. 5,076,390 (Haskins) discloses a wheelchair having a foldable frame with an interlinked system of parallelogram linkages which can be readily collapsed for travel and to provide access to otherwise restricted areas.
U.S. Pat. No. 5,983,452 (McGovern) discloses wheel and skid for replacement of each front wheel of a wheelchair. Each skid has a saucer-shaped base that expands the contact area of each front wheel to prevent it from sinking into the terrain, and/or otherwise become directed in a direction other than the desired direction of travel. The base has a slot, a wheel assembly having a wheel, the slot having the wheel of the wheel assembly protruding therethrough, and a fastener for fastening the wheel assembly to the wheel skid. This device is not intended to be easily installable and removable when rough terrain is encountered. Instead, it is generally permanently kept on the wheelchair which complicates folding the wheelchair and providing foot spacing on the foot support.
U.S. Pat. No. 5,427,398 (Weybrecht) discloses set of wide auxiliary wheels or wheel extensions so that the wheelchair can be much more easily used off road. An anti-tip over wheel can also be attached to the back of the wheelchair. In general, although these modifications can be added or removed to the wheelchair to adapt it to rough terrain, they generally require the assistance of an abled person, or at least they can not be conveniently added or removed by the user of the wheelchair while he or she is seated in it.
U.S. Pat. No. 4,132,423 (Chant) discloses pivoting rocker shaped struts that attach to the front of a wheelchair to enable the small front wheels of the wheelchair to negotiate side-walk curbs or the like. The struts can be either permanently attached or removably attached. However useful these devices may be for negotiating curbs or similar obstructions, they are of no great help in soft terrain or over surfaces having holes.
U.S. Pat. No. 6,869,084 (Volk) discloses a wheelchair wherein the front wheels have been replaced by skids. This adaptation is not designed to be easily installable and removable.
A recent innovation is a wheelchair adapter denoted model “Magelan MTC” (ModuleToutChemin) by the French company Magelan and marketed in the USA under the trademark “Freedom Wheel” by a Spokes-'n-Motion of Denver, Colo. This adapter comprises a Y-shaped frame that must first be attached to the front bars of a wheelchair using two grips. A nose gear wheel attached to the front of the frame is thereafter extended downward by the occupant of the wheelchair by turning a hand crank. The diameter of the nose gear wheel is large compared to the diameters of the conventional wheelchair front wheels. As the nose gear wheel is cranked downward, it tilts the wheelchair back and lifts the much smaller front wheels clear of the ground. The relatively large diameter nose gear wheel is able to roll over soft surfaces or uneven surfaces. The device can be quickly attached and detached by the wheelchair occupant, however, it is relatively large and cumbersome and requires horizontally actuated, leftside and rightside clamping devices, thus generally requiring that the wheelchair occupant have the full use of both arms to push the clamping devices closed. Further, the process of lifting the wheelchair front wheels clear of the ground is cumbersome and time consuming.
For the foregoing reasons, there is a need for a simple, easy to use, easy to install and remove, portable, light weight, low cost, safe, attractive, and durable device to facilitate maneuvering of manually propelled wheelchairs on difficult terrain. Such a device should improve handling and personal safety for an individual propelling such wheelchairs, occupants of such wheelchairs, and individuals in the vicinity of such wheelchairs.
The device should be capable of use on snow, sand, ice, mud and other uneven terrain, and the like, where wheels ordinarily sink into the terrain, and/or otherwise become directed in a direction other than the desired direction of travel of such wheelchairs, and make wheeled transportation otherwise difficult or impossible, and hazardous. The device should be of light weight, simple construction, easy and economical to manufacture, easily installable as a retrofit on existing wheelchairs of all sizes and types, and easy and safe to use.