WO2006099587A2

WO2006099587A2 - Tracked wheelchair apparatus and associated methods

Info

Publication number: WO2006099587A2
Application number: PCT/US2006/009785
Authority: WO
Inventors: Don Bloswick; Zackery Evans; Matt Greeff; Matthew Williams; Shem Peterson
Original assignee: University Of Utah Research Foundation
Priority date: 2005-03-14
Filing date: 2006-03-14
Publication date: 2006-09-21
Also published as: WO2006099587A3

Abstract

Wheelchair undercarriage attachments (10) of the present invention can include a ramp assembly (20) having at least one ramp (22) for allowing entrance of a wheelchair (12) and support thereof during use. A pair of continuous tracks (42) can be oriented in a substantially parallel relationship and operatively connected to the ramp assembly (20). A drive mechanism (70) can be operatively connected to the pair of tracks (42). The drive mechanism (70) can include a hand crank (92) oriented in an accessible position during use and configured to transfer forces to the pair of tracks (42) to cause motion. Such devices can allow for improved mobility of an attached wheelchair over a variety of terrains such as snow, sand, mud, etc.

Description

TRACKED WHEELCHAIR APPARATUS AND ASSOCIATED METHODS

FIELD OF THE INVENTION

The present invention relates to apparatuses and methods for use in connection with improving mobility of wheelchair users in a variety of terrains and conditions. More particularly, the present invention relates to devices and methods which can be used with standard wheelchairs to provide improved mobility.

BACKGROUND OF THE INVENTION It has been estimated that there are approximately 1,700,000 users of wheelchairs in the

United States. To users of traditional wheelchairs, mobility in adverse conditions such as snow, sand, mud, and the like, is greatly limited, if not impossible. Tasks that are easily and routinely accomplished in dry weather become extremely difficult as snow covers the ground. Few specialized products are commercially available to users of wheelchairs that facilitate mobility in winter or other adverse conditions. Further, most products designed for use in adverse conditions require the user to physically move to a secondary device. To users of wheelchairs, the chair becomes an extension of the body and the space around it becomes personal space. Being transferred to a secondary, snow-enabled device is both awkward and uncomfortable to most users of wheelchairs. Additionally, many of these types of devices are bulky and require a relatively large amount of space to transport. Other products which are available include various attachments which are secured, either permanently or semipermanently, to the wheelchair and which can be selectively engaged to provide additional traction or aid in overcoming specific obstacles. However, requiring assistance to switch wheelchairs, or to modify a wheelchair with various attachments, greatly diminishes independence and is impractical in many situations.

As such, devices and methods for improving mobility of wheelchair users which avoid the above-mentioned difficulties continue to be sought through on-going research and development efforts.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a wheelchair undercarriage attachment including a ramp assembly, a pair of continuous tracks, and a drive mechanism. The ramp assembly can have at least one ramp for allowing entrance of a wheelchair and which also provides support of the wheelchair on the attachment during use. A pair of continuous tracks can be oriented in a substantially parallel relationship and can be operatively connected to the ramp assembly. Further, a drive mechanism can be operatively connected to the pair of tracks to allow a user to propel the attachment having a wheelchair thereon. In one detailed aspect, the drive mechanism can be a hand crank oriented in an accessible position during use and configured to transfer forces to the pair of tracks to cause motion of the attachment and wheelchair.

In another detailed aspect of the present invention, the ramp assembly can include only two ramps each having a width sufficient to allow access of wheels of the wheelchair. Further, the ramp assembly can optionally extend the length of the pair of tracks.

In another detailed aspect of the present invention, the ramp assembly can have an access position and a motion position. The access position can allow for reverse entry of a wheelchair from the forward end. In this way, the wheelchair apparatus can be entered from the front end of the attachment while moving the wheelchair in a reverse direction which provides increased balance and reduces the chance of tipping the wheelchair backwards during access.

In yet another detailed aspect of the present invention, the wheelchair apparatus can be separable into modular components for transportability.

The present invention also provides for a method for moving a wheelchair over rugged terrain including providing a wheelchair undercarriage attachment having a pair of continuous tracks. A pair of ramps can be lowered to an access position with an end of each ramp in contact with a ground surface. Each ramp can be pivotally coupled to a corresponding track to allow the wheelchair access to the undercarriage attachment. The wheelchair can be moved onto the pair of ramps. The pair of ramps can be raised to a motion position with each ramp elevated above the ground surface and supporting the wheelchair thereon. A pair of hand cranks can be turned to move the continuous tracks and propel the undercarriage attachment with the wheelchair.

There has thus been outlined, rather broadly, the more important features of the invention so that the detailed description thereof that follows may be better understood, and so that the present contribution to the art may be better appreciated. Other features of the present invention will become clearer from the following detailed description of the invention, taken with the accompanying drawings and claims, or may be learned by the practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a wheelchair undercarriage attachment in accordance with one embodiment of the present invention, shown attached to the undercarriage of a wheelchair; FIG. 2 is a schematic side view of the undercarriage attachment of FIG. 1;

FIG. 3 is a perspective cut-away view of a continuous track and ramp assembly of the undercarriage attachment of FIG. 1, shown with the ramp in a lowered access position;

FIG. 4 is a perspective cut-away view of the continuous track and ramp assembly of FIG. 3, shown with the ramp in a raised motion position; FIG. 5 is a partial side view of a continuous track and drive mechanism of the undercarriage attachment of FIG. 1;

FIG. 6 is a perspective view of an ergonomic handle having a ratchet actuation to form a hand crank for a drive train of the undercarriage attachment of FIG. 1 in accordance with one embodiment of the present invention; FIG. 7 is a perspective view of a hand crank for a drive train of the undercarriage attachment of FIG. 1 in accordance with an alternative embodiment of the present invention;

FIG. 8 is a perspective view of the undercarriage attachment of FIG. 1 separated into three modular components in accordance with one embodiment of the present invention;

FIG. 9 is a perspective view of a wheelchair undercarriage attachment in accordance with another embodiment of the present invention; and

FIG. 10 is a schematic side view of the undercarriage attachment of FIG. 9.

The figures herein are provided merely for illustrative purposes and dimensions and relative proportions are not always to scale and may deviate from those illustrated.

DETAILED DESCRIPTION

Before the present invention is disclosed and described, it is to be understood that this invention is not limited to the particular structures, process steps, or materials disclosed herein, but is extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

It must be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a drive mechanism" includes one or more of such mechanisms, reference to "a track" includes reference to one or more of such elements, and reference to "engaging" includes reference to one or more of such steps.

Definitions

In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set forth below.

As used herein, "continuous" refers to tracks which are endless or substantially continuous. Continuous tracks can be made of a single continuous strip of material or can be assembled from one or more pieces which are then joined end-to-end to form a continuous track. As used herein, "undercarriage" refers to a supporting framework found underneath the seat of a wheelchair. An undercarriage can typically include supporting framework for the seat of the wheelchair and wheels, tracks, skis, or sleds that can facilitate movement of the wheelchair along ground surfaces.

As used herein, "wheelchair" refers to a chair with wheels that can be propelled by the occupant. A wheelchair can be a manual chair, propelled by user's own power, or a power chair, propelled by an electrical, chemical, or mechanical power supply and motor. Additionally, a wheelchair can include three wheel or four wheel chairs.

As used herein, "rugged terrain" refers to a ground surface that may pose a difficulty or hazard to a conventional wheelchair when traversing such a surface. Rugged terrain can include ground surfaces such as rough or broken pavement, hard pack, turf, gravel, snow, sand, mud, dirt, or combinations of these various ground surfaces.

As used herein, "metallic" refers to a metal, or an alloy of two or more metals. A wide variety of metallic materials is known to those skilled in the art, such as aluminum, copper, chromium, iron, steel, stainless steel, titanium, tungsten, zinc, zirconium, molybdenum, etc., including alloys and compounds thereof. Of particular interest are lightweight metals and metal alloys such as aluminum, titanium, and alloys thereof.

As used herein, with respect to an identified property or circumstance, "substantially" refers to a degree of deviation that is sufficiently small so as to not measurably detract from the identified property or circumstance. The exact degree of deviation allowable may in some cases depend on the specific context.

As used herein, "substantially free of or the like refers to the lack of an identified element or feature. Particularly, elements that are identified as being "substantially free of are either completely absent or are included only as a minor component which is insubstantial enough so as to have no measurable effect on the invention.

Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.

As used herein, a plurality of items, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. It is not the purpose of this specification to exhaustively outline every possible distinction among potentially useful components, but rather to illustrate the principles of the present invention, often with the use of such lists. Invention

The present invention provides a wheelchair undercarriage attachment which can accommodate a standard wheelchair and is useful for navigating over a variety of terrain surfaces which are not conveniently or safely traversed using an unmodified standard wheelchair. The undercarriage attachment generally includes a ramp assembly, a pair of continuous tracks, and a drive mechanism. The ramp assembly can have at least one ramp for allowing entrance of a wheelchair and which also provides support of the wheelchair on the undercarriage apparatus during use. A pair of continuous tracks can be oriented in a substantially parallel relationship and can be operatively connected to the ramp assembly. A drive mechanism can be operatively connected to the pair of tracks to allow a user to propel the attachment with a wheelchair thereon. Further, the present invention can be used in conjunction with a standard wheelchair without dismounting or leaving the wheelchair. The undercarriage apparatus can also be installed by the wheelchair user, generally without assistance, and can also be propelled by the user without assistance in order to improve and maintain the user's independence.

Thus, the present invention is an apparatus that can be attached to a standard wheelchair by the wheelchair user, and allow the wheelchair user to propel himself or herself on snow packed terrain or other adverse terrain. Further, the wheelchair undercarriage apparatus allows the traverse of inclines of various grades having surfaces covered in snow, sand, or other wheelchair unfriendly terrain. In addition, the present invention allows for modifications or installation by the wheelchair user without assistance. Each of these aspects will be discussed in more detail below.

Illustrated in FIGs. 1 and 2, a wheelchair undercarriage attachment, indicated generally at 10, is shown in accordance with an embodiment of the present invention for attachment to the undercarriage 13 of a wheelchair 12 in order to allow the wheelchair to traverse rugged terrain such as mud, snow, gravel, sand, dirt, and the like. The undercarriage attachment 10 can include a ramp assembly, indicated generally at 20, including at least one ramp 22 for allowing access to the undercarriage attachment 10 by the wheelchair 12. The at least one ramp 22 can also support the wheelchair during operation of the undercarriage attachment 10. In one aspect, the undercarriage attachment can have two ramps 22 in a spaced apart, parallel relation, and each ramp 22 can be sized and oriented to allow access of a front wheel 14 and rear wheel 16 on each side of the wheelchair.

Two channels 24 can form the ramps 22, and a frame 94 can support the ramps. Ramps 22 such as those shown can provide a combination of functionality and lightweight design. The channels 24 can be sufficiently wide to accommodate most standard wheel chairs. Additionally, sidewalls 26 can be provided to prevent wheelchairs 12 from rolling off the sides of the ramps when mounting or dismounting the undercarriage attachment 10. In another aspect, the sidewall height on the ramps and/or platforms can be adjusted or provided with smoother edges. This would reduce the chance of the wheelchair hand rims from being damaged during loading and unloading.

The ramps can generally by non-folding such that they are formed of single solid pieces of material. Alternatively, the ramps can be formed of two or more pieces which are hingedly or pivotally attached to allow folding of the ramps to increase portability.

Referring to FIGs. 3 and 4, the ramp assembly 20 can pivot between an access position with an end 30 of the ramp 22 in contact with a ground surface, as shown in FIG. 3, and a motion position with the ramp elevated above the ground surface, as shown in FIG. 4. A wheelchair can be moved onto the ramp 22 when oriented in the access position. The ramps can carry and support the wheelchair when in the motion position. The ramp can pivot between the access position and the motion position as the wheelchair is moved onto the ramp. Thus, the ramps can act as access ramps in the down, or access position, and a wheelchair platform in the up, or motion position.

The ramps 22 can have a sufficiently low slope when in the lowered access position to allow a wheel chair to easily be moved up the ramps. The slope can be any functional range; however, from about 1 :6 to about 1: 10 can be particularly useful. For example, a slope of 1:8.5 and 30" long ramps allows easy mounting of a wheelchair on the wheelchair apparatus and advantageously meets current requirements of the Americans with Disability Act for wheel chair ramp slope. Additionally, a non-skid surface treatment, such as grip tape or a non-skid coating, can be added to the ramp loading surface 28 to increase the coefficient of friction between the ramp loading surface and the wheelchair wheels. Furthermore, drainage holes (not shown) can extend through the ramp to allow drainage of water, snow and ice in order to prevent accumulation on the ramp loading surface.

Referring again to FIG. 1, as a wheelchair 12 is moved onto the ramp 22, the ramp can remain in the access position until the weight of the wheelchair is sufficiently rearward on the ramp to cause the ramp to tip to the motion position. In this way, a wheelchair user can access the undercarriage attachment 10 without assistance from another person.

The combination of ramp and platform functions provides several advantages to the present invention. For example, the pivoting ramp 22 can significantly reduce the weight of the undercarriage attachment 10 by combining two components into one. Additionally, combining the ramps and platforms into a single component also allows users to back their wheelchair up the modified ramps to a point at which the ramps pivot and rotate to become platforms, and hence, mount the undercarriage attachment without assistance.

As described above, the ramps 22 can be sized and shaped, and constructed of a lightweight material, such as aluminum, that can safely support the load of a person and the wheelchair 12. For example, 3/32" thick aluminum 6061 can be used as the material for the ramps, and provides a thin, relatively lightweight ramp with adequate strength to support a wheelchair and occupant. It will be appreciated that other lighter and stronger materials, such as titanium, carbon fiber composites, and the like, can also be used and provide the advantage of reducing overall weight of the undercarriage attachment 10. Additionally, either 1" square or 1" circular tubing can support the loads placed on the ramp assembly. Thus, in one aspect, 1" hollow round tubing can be used to form the frame 94 of the undercarriage attachment 10. Advantageously, hollow round tubing weighs less, and is generally cheaper, than square tubing and can provide a sufficiently high strength structure with relatively lower weight. Further, other size tubing or support frame materials can be used depending on the type of material and specific design of the support frame 94. Various alternatives of the undercarriage attachment frame can be made. For example, in order to improve the frame strength, 45 degree angle support bars can be added in a truss-like fashion between the axle frame bars that run along the sides of each continuous track. This can improve the track rigidity with relatively low weight increase.

Referring to FIGs. 1 through 5, FIG. 1 especially, the ramp assembly 20 can extend substantially between a front end 42 and a back end 44 of a pair of flexible, continuous tracks 40. In this way, the ramp assembly can be contained within the overall footprint, or size of the continuous tracks. The ramp assembly can also be pivotally connected to the continuous tracks so that as a wheelchair 12 is moved up the ramps, the ramps can pivot to the raised or motion position. The continuous tracks 40 can therefore provide support for carrying the wheelchair as well as a mechanism for motion across a ground surface.

The pair of continuous tracks 40 can be oriented in a spaced apart, substantially parallel relationship with one another. In one aspect, the space between the pair of continuous tracks 40 can be a distance that is wider than a distance between wheels on the wheelchair 12. Thus, when a wheelchair 12 is placed on the ramps 22, the continuous tracks 40 can provide a base to the wheelchair 12 that is larger than the wheelchair itself. Advantageously, this larger base can provide greater stability to the wheelchair 12 when the ramps 22 are in the raised motion position. Alternatively, the continuous tracks can be oriented substantially beneath the ramps. Li order to allow the ramps to move to the access position, the ramps include bearing slides, roller slides, or other similar mechanism to move the ramps forward and then down. In such embodiments the pivot point can be moved further toward the front of the wheelchair undercarriage attachment. As can be seen in FIG. 2, the front end 42 of the continuous track 40 can be slightly elevated in an effort to help the undercarriage attachment 10 climb through or over rough terrain. Referring now to FIGs. 1 and 4, drive wheels 52 can fit within the continuous track 40 and can engage the continuous track to turn the continuous track when the drive wheel is turned. Spacer wheels 54 and idler wheels 56 can also be disposed within the continuous track and along an axle frame 50. The spacer and idler wheels can tension the continuous tracks to provide continuous contact between the drive wheel 52 and the continuous track.

The pair of continuous tracks 40 can also include a ground surface engagement tread 48 that can engage the ground surface to propel the undercarriage attachment 10 over a variety of terrain. For example the ground surface engagement tread 48 can propel the undercarriage attachment and accompanying wheelchair over surfaces such as pavement, hard pack, turf, gravel, snow, sand, mud, dirt, and the like. A variety of different tread patterns can be used, depending on the intended terrains. For example, block treads as shown in FIG. 3 can be useful for rough pavement and hard pack ground, while triangular treads as shown in FIG. 1 can be more useful for snow, mud or wet conditions. Other tread patterns can also be suitable for use in the present invention such as, but not limited to, wavy tread, irregular tread, circular tread, offset protrusion tread, and the like. In yet another alternative, multiple tracks can be provided which are interchangeable. For example, the idler wheels 56 can be placed on adjustable fixtures to allow for tightening or loosening of the tracks 40. Preferably, the adjustable fixtures can be adjusted without the use of additional tools such as by a lever actuated cam or other adjustable mechanism. A non-limiting example of another suitable adjustable fixture can include a screw actuated tensioner having an integrated handle. In yet another aspect, a track tensioning device can be added. For example, an upper idler wheel can be provided for full length tracks. Increased track tension can prevent tracks from slipping during undercarriage attachment rotation.

The continuous tracks 40 can be placed on the outside of the front and rear wheelchair wheels, 14 and 16 respectively, to increase the lateral stability of the undercarriage attachment 10. Advantageously, a wider track base generates a higher moment and allows the undercarriage attachment 10 to turn more easily. Improved maneuverability and steerability can also be achieved by providing tracks 40 that run the full length of the undercarriage attachment. Full length tracks also make the undercarriage attachment capable of helping users of wheelchairs travel over different types of rugged terrain. For example, longer tracks can traverse small discontinuities in the terrain surface, and can provide a greater contact surface area with which to engage the ground and propel the vehicle on soft or mushy terrain such as snow, sand, mud and the like.

It will be appreciated that the continuous tracks 40 can be made from a variety of metallic, polymeric, or composite materials. For example, the continuous tracks can be a single loop of hardened rubber, or multiple sections of carbon fiber composite material joined together, such as those commonly used on snow blower or snowmobile tracks. In one aspect, the continuous tracks can be modified snow blower tracks, which can provide a sufficient width and weight for the present invention. In another aspect, modified snowmobile tracks can be used for the continuous tracks. The snowmobile tracks can be cut lengthwise and spliced together to fit the length of the undercarriage attachment 10. The continuous tracks can extend the full length of the undercarriage attachment, and preferably the length of the ramps 20, as shown. Alternatively, the tracks can extend partially the length of the ramps while also preserving stability, e.g. about 75% to about 95% the length of the ramp length. Referring to FIG. 1, a drive mechanism, indicated generally at 70 can be operatively connected to the pair of continuous tracks 40 on each side of the undercarriage attachment 10. The drive mechanism can operate to turn the continuous tracks which in turn propel the undercarriage attachment. The drive mechanism can include at least one hand crank 92 that can be oriented in an accessible position in relation to the wheelchair 12 during use. The hand crank can transfer forces to the pair of continuous tracks to cause motion of the undercarriage attachment and the wheelchair disposed thereon. The hand cranks can be supported by a primary support arm 74 that can extend upward from the axle frame 98. A secondary support arm 76 can also extend upward from the axle frame and can support and stabilize the primary support arm and hand crank 92. A drive chain 42 can be operatively coupled between the hand crank 92 and the drive wheel 52. The support arms 74 and 76 can maintain each drive-chain 42 in a substantially engaged position. The chains 42 can engage gears 80 that can transfer power via the chain from the hand crank to the drive wheel. In one embodiment, the gears can have a 1 to 2 gear ratio in order to achieve a propulsion speed close to a walking speed of between approximately 2 to 3 miles per hour.

Various alternative configurations of the drive mechanism can also be useful. For example, the drive mechanism can also include a gearing mechanism to easily change gears during operation. Non-limiting examples of suitable mechanisms can include typical bicycle- type gear systems or innovative planetary gear systems. Additionally, if a method of changing gears is not incorporated, the gear ratio can be optimized to facilitate easy, low-force turning that better accommodates users of wheelchairs who have low torso strength. Thus, the drive mechanism can be tailored to a specific type of user.

In another aspect, a separate braking mechanism can be provided. For example, the drive mechanism can include a hand actuated brake operatively connected to the drive chain, track, and/or one or more wheels, which can be engaged as needed.

Referring to FIGs. 1 and 6, the drive mechanism 70 can also include a pair of hand cranks 72 with each hand crank positioned and oriented in an accessible position in relation to each side of the wheelchair 12. A separate drive-chain 42 can be coupled between each hand crank and corresponding continuous track 40. Each drive chain can be engageable by the hand crank to transfer forces from the hand crank to the continuous track. Thus, the hand cranks can be turned in order to propel the undercarriage attachment 10, and consequently move the wheelchair and occupant. It will be appreciated that each of the pair of hand cranks can be independently operable to move a corresponding continuous track.

Advantageously, hand crank mechanisms tend to be more intuitive to wheelchair users. Hand crank propulsion also allows each of the continuous tracks 40 to function independently, and therefore facilitates turning of the undercarriage attachment 10. Traveling in reverse is also more intuitive using a hand crank propulsion system. In one aspect, the hand cranks 72 can be mounted on the inside of the support bars 74 and 76 to avoid interference between the support bars and the arms of a wheelchair user during operation.

Since each hand crank 72 can drive one of the continuous tracks 40, the hand cranks can become "out of sync" after turns of the hand cranks 72 are made. In one aspect, the hand cranks 72 can be double ratcheting hand cranks, such as half-inch mechanics ratchets, as shown in FIG. 6. Advantageously, a double ratcheting hand crank can allow the user to make adjustments quickly to re-synchronize the hand cranks, and also functions in both forward and reverse. Ergonomic, space-saving handles 90 can be manufactured and welded directly to the modified ratchets as shown in FIG. 6.

Referring to FIG. 7, a hand crank 92 is shown in accordance with another embodiment of the present invention. The hand crank can be a direct drive hand crank that optionally does not use a ratcheting mechanism. Instead, the direct drive hand crank simply drives the gear 80 when rotated. Thus, when the hand crank is rotated in the clockwise direction, the gear is rotated in the clockwise direction. Similarly, when the hand crank is rotated in the counterclockwise direction, the gear is rotated in the counter-clockwise direction. Consequently, rotation of the hand crank results in either forward or reverse rotation of the corresponding continuous track 40.

Advantageously, the direct drive hand cranks 92 can allow the user to turn, or change direction, without stopping to move a ratchet switch. The direct drive hand cranks can also effectively create a brake by turning the hand crank backward. It will be appreciated that a combination ratchet and direct drive hand crank can also be used in the drive mechanism 70 of the present invention to combine the advantages of each of the types of hand cranks 72 (shown in FIG. 6) and 92 (shown in FIG. 7).

Additionally, the shape of the hand cranks can have a horizontal handle 96 as shown in FIG. 7 or an angled semi-vertical handle 90 as shown in FIG. 6. Each hand crank can also be adjustable in length and position for convenience in matching size and ability or strength of different users. In one aspect, an adjustable length can either allow for increased hand displacement and decreased hand force with increasing length, or decreased hand displacement with increased hand force with decreasing length. For example, each hand crank can have an adjustable radius to allow the user to easily change the "gear ratio" of the wheelchair apparatus in order to adjust to the conditions of the terrain. This adjustable radius can provide multiple speeds or gears to the user which can be advantageous when climbing hills or traversing soft terrain such as mud or snow. The hand cranks can be positioned in a comfortable location for the occupant of the wheelchair 12. For example, as shown in FIG. 1, the hand cranks 92 can be positioned to sit slightly above and in front of the position where the user normally pushes the wheels 18 of the wheelchair. Further, the hand cranks of the present invention are oriented to improve biomechanical advantage and are positioned in a more ergonomic manner than motion required to push on conventional wheelchair wheels. In yet another aspect, the hand cranks can be adjustable in angle, position and the like to provide improved ergonomic characteristics, focusing specifically on the angles, postures and forces experienced by wrists of a user.

Ih one embodiment of the present invention, without a wheelchair 12, the only parts protruding vertically from the undercarriage attachment 10 are the hand cranks 92 and primary and secondary support arms 74 and 76, respectively. To increase portability of the undercarriage attachment, the hand cranks and support arms can be collapsible in order to lay in adjacent to the continuous tracks 40, as shown in FIG. 8. Referring back to FIG. 1, the secondary support arm 76 can improve stability of the hand crank 72 when in the upright position. The secondary support arm can be a one-piece bar that can pivot at the base 82 and can be pinned by a pin 88 at the top to the primary support arm 74. The pin can be removed so that both support arms can be collapsed to facilitate storage and transportation of the undercarriage attachment 10. Other mechanisms can also be used to secure the support arms in either or both the upright or storage positions. Suitable alternative mechanisms can include, but are not limited to, latch, pins, threads, or the like. Optional hooks 100 can be sewn onto adjustable flexible straps 102 to allow the user to securely attach the wheelchair 12 to the undercarriage attachment 10. In one aspect, one strap can be attached to the rear of the undercarriage attachment and two straps can be used attached to the front. Loops can be formed at the end of each strap to help the user tighten the straps as much as possible. Simple strap fasteners, such as hook and loop fasteners, or the like, can allow the user to easily secure each strap upon itself. Similarly, ratcheting straps (not shown) with hooks at both ends can be used to lock the wheelchair to the ramps 22. In addition the ramps can be secured in the raised or motion position using similar straps or other mechanism such as pins, latches, or the like. The center of mass of the wheelchair 12 on the ramps 22 can be positioned to ensure that the ramps do not rotate downward before the straps are locked in place.

The undercarriage attachment 10 can also include other mechanisms for securing the wheelchair to the ramps. For example, a clamping mechanism can lock the wheelchair onto the ramps by simply rolling the wheelchair into place. This can reduce attachment time and convenience. Such a mechanism can then be undamped by the user prior to dismount that would not reengage before the user could dismount. Additionally, optional vertical bars can be added to the back of the wheelchair attachment and clips can be attached to the vertical bars to attach to the rear wheelchair wheels into place. Safety can also be increased by securing the loose ends of straps once the wheelchair is attached. This can prevent the straps from dragging on the ground or getting caught in the tracks.

Referring to FIG. 8, the undercarriage attachment 10 of the present invention can be designed to be separable for break-down into separate pieces, thereby reducing the weight that any user would have to lift to use the wheelchair apparatus. Breaking down the wheelchair apparatus into separate pieces can also make the wheelchair apparatus more portable. Thus, the wheelchair apparatus can separate into two main sections 110a and 110b, with one linking piece 112 between them. Alternative, modular units can also be configured based on the description provided herein. For example, the drive mechanisms 70 or other sections can be further separable. Alternatively, one or more of the members, e.g. support arms, ramps, frame support, and wheel supports, can be foldable to allow for decreased storage size.

Main modular sections 110a and 110b can each include a continuous track 40, a drive mechanism 70, and a ramp system 20. The linking piece 112 can be a tubular frame sized and shaped to maintain a space between the main section 110a and the main section 110b while also providing sufficient mechanical support to the apparatus during use. Dividing the undercarriage attachment 10 into multiple modular pieces provides several other advantages to the present invention. For example, the linking piece 112 can be sized to accommodate different sized wheelchairs. Thus, the width of the undercarriage attachment 10 can be adjustable. In one aspect, the distance between rear wheelchair wheels can be adjusted at 0.5" increments between 19" and 23" by changing the linking piece. Additionally, as discussed above, the separate sections 110a and 110b and the linking piece 112 each weigh less than the assembled undercarriage attachment 10. Consequently, moving the sections is easier than moving the entire undercarriage attachment. Advantageously, separable sections can make it possible to move and assemble the wheelchair attachment without lifting more than 35 pounds at a time.

Although the configuration as shown and described in FIGs. 1 through 8 are currently preferred, other designs and configurations consistent with the present invention are also within the scope of the present invention. As illustrated in FIGs. 9 and 10, an undercarriage attachment 200 in accordance with another embodiment of the present invention is shown for use in propelling a wheelchair and user across rough terrain such as snow, mud, sand, or the like. The undercarriage attachment 200 can be similar in many respects to the undercarriage attachment described above.

As shown in FIG. 9, the undercarriage attachment 200 can have continuous tracks 240 that can be positioned inside the rear wheelchair wheels rather than outside. To keep the continuous tracks from interfering with the front wheels, which are generally closer together than the rear wheels, the undercarriage attachment can be mounted by backing the wheelchair onto the under carriage attachment.

The continuous tracks 240 can be placed close together and toward the back of the undercarriage attachment 200. Skis can be attached to the front corners of the undercarriage attachment to provide stability. Optionally, additional tracks, larger wheels, or other extensions which contact the ground can be attached to the front to provide stability on various surfaces. In the case where skis are used, the front edges of skis can be curved upward so as to glide across snow rather than dig into snow. Wheels can also be integrated into the skis that slightly protrude through the bottom of the ski allowing the wheelchair apparatus to be used on hard surfaces or areas where no snow is present.

The ramps 222 can be attachable to a wheelchair platform 225 to form a ramp assembly. Handles 228 can also be added to the side of each ramp to facilitate handling while attaching or detaching the ramps. Simple hooks 230 can be attached to the sides of the ramps so the ramps can easily be stowed during transit. These removable ramps can be stowed on the ramp assembly or at another convenient location.

The undercarriage attachment 200 can also have a single caster wheel 433 mounted to the frame 294 between the skis 250. The caster wheel can improve the ability to rotate the undercarriage attachment without translation on hard surfaces.

The present invention also provides a method for moving a wheelchair over rugged terrain including providing a wheelchair undercarriage attachment having a pair of continuous tracks. A pair of ramps can be lowered to an access position with an end of each ramp in contact with a ground surface. Each ramp can be pivotally coupled to a corresponding track to allow the wheelchair access to the undercarriage attachment. The wheelchair can be moved onto the pair of ramps. The pair of ramps can be raised to a motion position with each ramp elevated above the ground surface and supporting the wheelchair thereon. A pair of hand cranks can be turned to move the continuous tracks and propel the undercarriage attachment with the wheelchair.

The method of moving a wheelchair can also include securing the wheelchair to the pair of ramps. Additionally, the pair of ramps can be lowered, and the wheelchair can be moved off the pair of ramps. Moreover, the undercarriage attachment can be separated to form two separate ramp-track modular assemblies, and each of the separate ramp-track assemblies can be loaded into a vehicle for transport.

It will be appreciated that the concepts of the present invention can be found in a variety of configurations. For example, the undercarriage attachment of the present invention can also have four separate continuous tracks with two spaced-apart, parallel front tracks in line with two spaced-apart, parallel rear tracks. Alternatively, three continuous tracks can be used, for example by orienting a pair of spaced apart tracks further rearward and a third continuous track in a forward center position.

Additionally, a flat platform surface can be adjustably raised and lowered to allow access without traversing an incline. For example, using a four bar linkage, the platform can be raised to the desired position when a crank support arm is raised. This allows a combination of ramps and platforms, while maintaining the frames structural rigidity.

In yet another alternative aspect, the access ramps can also be configured to allow the user to mount the wheelchair apparatus from behind. This would allow the cranks to be closer together similar to a hand bike. Li this case, the pivot point for the ramps can be shifted further back than in the rear approach design of FIG. 1. In yet another aspect, the mechanisms and methods of positioning the support arms for the hand cranks can be simplified. Alternative mechanisms and methods can include connecting the two support arms using a locking hinge or sliding collar. Similarly, it can be beneficial to have the user position the support arm by lifting one bar, rather than two. In yet another aspect, the hand crank system of the undercarriage attachment can include an actuator, such as a thumb button on the end of the handle, which can be depressed to uncouple the cranks and drive system. This actuation allows for freewheeling and synchronizing of the hand cranks. The present invention also includes other alterations to the above-described hand cranks such as labels indicating the lever settings for forward and reverse motion, collapsible handles that prevent the user from having to remove the handles, and a hook and loop glove option to allow users with limited grip strength to maintain hand contact with the handles.

Additionally, short tracks can be used outside of the wheelchair wheels and towards the rear and one ski or track can be positioned in the front center of the undercarriage attachment. Such a triangular base can be stable, and the single ski or track can rotate to follow the direction of motion by providing an offset attachment. The front track can be shorter than the longer rear tracks, and can operate similar to a caster wheel. The turning moment created by the rear tracks can cause the front track to rotate in order to facilitate turning. The reduced length of the rear tracks can also reduce the shear forces created by turning full length tracks. Additional detailed aspects of the present invention can include functional, aesthetic, and/or convenience attributes. For example, handles can be added or handholds identified for lifting the wheelchair apparatus. An optional platform can be provided for storing personal objects. Reflectors can be oriented along the front, sides, and/or rear of the ramp assembly, drive mechanism, and/or track supports to increase safety and visibility. In yet another alternative aspect, built-in attachments points for securing the wheelchair apparatus to a conventional vehicle bicycle rack can also be included. Corrosion and wear of components can also be considered during material selection and when determining an appropriate finish. For example, frame anodizing can improve the wheelchair apparatus aesthetics as well as corrosion resistance. Using a bright red or yellow color can also improve visibility in snowy conditions. Various accessories can also be used in connection with the wheelchair apparatus such as, snowplows, sleigh hitches, trailers, and baskets to allow users to use the wheelchair apparatus for various types of recreation or even to clear snow on their driveway or sidewalks. Chain guards can also be used to increase safety. Guards can be formed of a clear plastic to eliminate corrosion and allow for visual inspection of the chains.

Of course, it is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present invention and the appended claims are intended to cover such modifications and arrangements. Thus, while the present invention has been described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred embodiments of the invention, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, variations in size, materials, shape, form, function and manner of operation, assembly and use may be made without departing from the principles and concepts set forth herein.

Claims

ClaimsWhat is claimed is:

1. A wheelchair undercarriage attachment, comprising: a) a ramp assembly including at least one ramp for allowing access to the undercarriage attachment by a wheelchair and support of the wheelchair during use; b) a pair of continuous tracks oriented in a substantially parallel relationship and operatively connected to the ramp assembly; and c) a drive mechanism operatively connected to the pair of tracks, and including a hand crank oriented in an accessible position in relation to the wheelchair during use and configured to transfer forces to the pair of tracks to cause motion.

2. The attachment of claim 1, wherein said ramp assembly includes only two ramps sized and oriented to allow access of wheels of the wheelchair.

3. The attachment of claim 1, wherein said ramp assembly extends substantially between a front end and a back end of the pair of continuous tracks.

4. The attachment of claim 1, wherein said ramp assembly pivots between an access position with an end of the ramp in contact with a ground surface, and a motion position with the ramp elevated above the ground surface, and wherein the ramp carries the wheelchair.

5. The attachment of claim 4, wherein the entry position allows for reverse entry of the wheelchair from a forward end of the undercarriage attachment.

6. The attachment of claim 4, wherein a wheelchair user can access the undercarriage attachment without assistance from another person.

7. The attachment of claim 1, wherein said pair of tracks are oriented a distance apart which is wider than a distance between wheels on the wheelchair.

8. The attachment of claim 1 , wherein each of the pair of tracks further includes a ground surface engagement tread configured to propel the undercarriage attachment on a surface terrain selected from the group consisting of pavement, hard pack, turf, gravel, snow, sand, mud, dirt, and combinations thereof.

9. The attachment of claim 1, wherein the drive mechanism includes a separate hand crank operatively connected to each track of the pair of tracks, operable to move each track independently from the other track.

10. The attachment of claim 9, wherein each hand crank is supported by a separate collapsible support frame.

11. The wheelchair attachment of claim 10, wherein each separate hand crank, collapsible support frame, and track assembly are operatively connected to form two ramp- track assemblies which can be separated from each other for transport.

12. The wheelchair attachment of claim 10, wherein each hand crank is adjustable in length and position.

13. The wheelchair attachment of claim 1, wherein the drive mechanism further comprises: a drive-chain operatively coupled between the hand crank and the continuous tracks; and a collapsible support frame supporting the hand crank and configured to maintain the drive-chain in a substantially engaged position.

14. The wheelchair attachment of claim 1, where the hand crank is configured for ratcheted motion.

15. A multi-terrain undercarriage attachable underneath a wheelchair by the wheelchair's user, comprising: a) a pair of continuous tracks oriented in a substantially parallel relationship; b) a ramp assembly operatively coupled to each of the pair of continuous tracks, and including a separate ramp operatively coupled to each of the pair of continuous tracks for allowing the wheelchair access to the undercarriage attachment and support thereof during use; c) a drive mechanism operatively connected to the pair of tracks, the drive mechanism further comprising: i) a pair of hand cranks, each hand crank oriented in an accessible position in relation to the wheelchair during use, and independently operable to move a corresponding continuous track to move the carriage and the wheelchair; ii) a separate drive-chain coupled between each hand crank and corresponding continuous track, and engageable by the hand crank to transfer forces from the hand crank to the continuous track; and iii) a separate collapsible support frame supporting each hand crank and configured to maintain each drive-chain in a substantially engaged position.

16. A method for moving a wheelchair over rugged terrain, comprising the steps of: a) providing a wheelchair undercarriage attachment having a pair of continuous tracks; b) lowering a pair of ramps to an access position with an end of each ramp in contact with a ground surface, each ramp pivotally coupled to a corresponding track to allow the wheelchair access to the undercarriage attachment; c) moving the wheelchair onto the pair of ramps; d) raising the pair of ramps to a motion position with each ramp elevated above the ground surface and supporting the wheelchair thereon; and e) turning a pair of handcranks to move said continuous tracks and propel the undercarriage attachment with the wheelchair.

17. The method of claim 16, further comprising the step of: a) securing the wheelchair to the pair of ramps.

18. The method of claim 16, wherein each step is accomplished by a wheelchair user.

19. The method of claim 16, further comprising the steps of: a) lowering the pair of ramps; and b) moving the wheelchair off the pair of ramps.

20. The method of claim 19, further comprising the steps of: a) separating the undercarriage attachment to form two separate ramp-track assemblies; and b) loading each of the separate ramp-track assemblies into a vehicle for transport.