Land vehicles – Wheeled – Extensible
Reexamination Certificate
1999-11-16
2001-10-16
Johnson, Brian L. (Department: 3618)
Land vehicles
Wheeled
Extensible
C280S250100, C280S650000
Reexamination Certificate
active
06302429
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to wheelchairs and, more specifically, to convertible wheelchairs. All frame components are designed to accept parts for both the folding and rigid frame wheelchairs. Tubular components are designed to be easily attached to other members with the special connector fittings allowing for further conversion to other desirable designs.
2. Description of the Prior Art
Two different methods have been used in the design and production of manual wheelchairs. The most common is the folding cross brace wheelchair. This design utilizes a welded cross brace mechanism, allowing the wheelchair to fold similar to a director's chair (from side to side). The main advantage of this method is that the wheelchair can be easily folded by most users. The disadvantage of this design is low energy efficiency due to its loose construction since a part of the energy used to propel the wheelchair is transferred to the frame rather than the wheels.
A second popular design is the rigid frame wheelchair. In this design the cross brace mechanism is replaced with tubular crossbars welded to the side frames of the wheelchair. The advantage of this design is its energy efficiency. However, this wheelchair does not fold as compactly as the cross brace chair for easy travel, storage or transportation.
The above-described designs have a problem in common—welded construction. The welded construction makes it extremely difficult, if not impossible, to adapt the wheelchair to the end user's changing needs and environment. Conversion from rigid frame to folding wheelchair is virtually impossible. In addition, welding creates a heat-affected zone weakening the frame tube around the welded joint, which is a main cause for structural failure in wheelchairs.
For the majority of wheelchair users it is necessary to have both wheelchairs—the rigid frame and the folding one. The folding wheelchair is more convenient for travel and indoor use, whereas the chair must be folded and stored. The rigid wheelchair is better suited for outdoors and a more active lifestyle. Unfortunately, it is not economically feasible for most users to own both wheelchairs.
Some wheelchair manufacturers build both folding and rigid frame chairs. There is a number of folding wheelchairs that use the conventional crossbrace design. Rigid chairs exist that are of a modular design and can change the width of the wheelchair with little difficulty. There is a design that converts from a user propelled to an assistant propelled wheelchair (U.S. Pat. No. 5,294,141). There is also a wheelchair that converts the riding position from the standard seating position to a recumbent position (U.S. Pat. No. 5,011,175). There is a weld-free folding wheelchair which folds in a non-conventional manner but is not convertible (U.S. Pat. No. 4,682,783). Another wheelchair design appears to be of a weld-free design that allows the wheelchair to adjust to different needs by use of special shaped bars and plates but is not a convertible wheelchair (U.S. Pat. No. 5,743,545). There are several U.S. patents that claim the chair to be modular, allowing for different components to be used to build the chair to the user's needs. Among these is a rigid frame wheelchair (U.S. Pat. No. 5,421,598), but again this wheelchair does not convert to folding. There are no wheelchairs known to exist at this time that can fully convert from a rigid frame to folding frame.
In U.S. Pat. No. 5,253,888, issued to the assignee of the subject invention, a rigid frame weld-free wheelchair is disclosed that utilizes a series of special clamping members for clamping tubes to each other. However, such weld-free construction had some disadvantages. A series of specially designed clamps had to be utilized which were not universal to all designs, making further conversion and design changes virtually impossible. Also, by virtue of the clamp designs, numerous bolts were required that were clearly visible and detracted from the appearance of the wheelchair.
It is possible for one wheelchair to have all of the advantages of both the folding and the rigid chairs while eliminating the disadvantages of each.
SUMMARY OF THE INVENTION
An object of this invention is to provide a convertible wheelchair that does not have the disadvantages inherent in prior art wheelchairs.
It is an object to provide a convertible wheelchair utilizing standard [???] components which can be used for both folding and rigid frame wheelchair design.
It is another object of this invention to provide a durable, lightweight and economical wheelchair that can be quickly and easily converted by a layman from a folding frame to a rigid frame and vice versa.
It is still another object of the invention to provide a wheelchair that can be easily converted to a sport type wheelchair.
It is yet another object of the invention to provide a wheelchair that can be easily converted to a companion chair.
It is a further object of the invention to provide a wheelchair that can be easily converted to a front wheel drive wheelchair.
It is still a further object of the invention to provide a wheelchair that can be easily converted to a pediatric wheelchair.
It is yet a further object of the invention to provide a wheelchair that can be easily converted to a hand cycle with optional attachment.
It is an additional object of the invention to provide a wheelchair that can be easily converted to a lever driven wheelchair with optional attachment.
It is still an additional object to provide convertible wheelchairs that can be converted with the use of simple tools.
In order to achieve the above objects of this invention, as well as others that will become apparent hereinafter, the convertible wheelchair of the present invention has a pair of like side frame assemblies spaced from each other and each including a generally horizontal seat tube and a generally horizontal bottom tube below said seat tube. Each of these seat and bottom tubes has front and rear ends. A generally vertical backrest tube has a lower end proximate to said rear ends of said seat and bottom tubes and an upper end extending upwardly of said set tube and forming handgrips.
A caster assembly for each side frame assembly carries a caster wheel and has a generally upwardly extending shaft portion. Connecting means is provided for rigidly clamping respective rear ends of the seat and bottom tubes and the lower ends of the backrest tubes, for rigidly clamping the respective front ends of the seat and bottom tubes and caster assembly shaft portion, and for rigidly connecting said conversion means to frame assemblies. A footrest means is secured to the seat tube, and a conversion means selectively converts the connection between the side frame assemblies to convert the wheelchair from a folding wheelchair to a rigid wheelchair and vice versa.
Conversion means may include pivotally connected elongate means having ends pivotably connectable to the side frame assemblies for selectively replacing the transverse tube means and for permitting the side frame assemblies to move from the width position of the wheelchair to proximate positions in the collapse condition of the wheelchair, or a kit consisting of at least two transverse members including at least two elongate rigid tubes having a length substantially corresponding to the normal operative width of the wheelchair and at least one set of pivotably connected members that can pivot relative to each other.
The convertible wheelchair frame is made up of left and right side frame assemblies, two push handle assemblies, upholstery and removable folding or rigid crossbars (all assemblies are weld-free). Specially designed fittings are used to provide for a secure fastening internally between mating tubes. These fittings are used throughout all assemblies where two or more tubes mate up. These fittings shall be referred to as connector fittings throughout this text. Each side frame assembly is provided with mounting holes to as
DA International, LTD
Johnson Brian L.
Lackenbach Siegel
Luby Matt
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