Land vehicles – Wheeled – Occupant propelled type
Reexamination Certificate
1999-02-26
2001-02-20
Mai, Lanna (Department: 3619)
Land vehicles
Wheeled
Occupant propelled type
C280S304100, C403S205000, C016S019000, C016S029000, C016S030000
Reexamination Certificate
active
06189906
ABSTRACT:
SUMMARY OF THE INVENTION
1. Field of the Invention
The invention relates to a wheelchair having side frames, more particularly, to a wheel chair having side frames that include tube sections, which have a bearing housing screwed onto the front bottom end of each via a screw mounting. The bearing housing has an approximately vertical bearing bore for accommodating an upwardly directed axle pin of a steering fork for holding a caster. The wheelchair also has an adjustment device, which is integrated in the screw mounting, for adjusting the bearing housing with respect to the side frame so that the bearing bore can be aligned perpendicular to the ground.
2. Description of Related Art
One known embodiment is illustrated in
FIGS. 1
a
and
1
b
. These wheelchairs, which are usually hand-operated, usually have front casters. A trailing action in a steering fork, which holds the caster, ensures stable and straight movement in a forward direction. Each steering fork is mounted in a bearing housing, which is screwed to the wheelchair side frame. An axle pin, which is connected to the steering fork and is directed vertically upward, is guided in two deep-groove ball bearings of the bearing housing, which are spaced apart from one another.
With this wheelchair, it is very important for the axle pin always to be aligned vertically with respect to the; ground to ensure wobble-free forward movement and to ensure that the wheelchair will turn without difficulty. To accomplish this, each steering-fork bearing housing is usually designed in such a manner that they can be rotated on the side frame at their attachment points irrespective of a seat tilt (the incline of the wheelchair frame to the rear by means of an appropriate height offset from rear wheels to front wheels).
One of these known solutions is illustrated in
FIGS. 1
a
and
1
b
in which the steering-fork bearing housing is attached to the front vertical tube section of the side frame and can be pivoted about a horizontal axis of rotation with respect to the side frame. This rotation with respect to the side frame is effected by displacing eccentric sliding blocks (not illustrated). Then, when the bearing housing is in the desired position, the steering-fork bearing housing is fixed by tightening the clamping screws.
There are additional known ways of attaching the steering-fork bearing housings to the bottom horizontal tube section of the side frame, which comprise displacing eccentric sliding blocks or rotating an eccentric disk.
The following difficulties are encountered in all of the aforementioned known devices. First, each wheelchair has a load lever which corresponds to the distance between the contact point of the caster and the pivot axis for the bearing adjustment. The side frame and steering-fork bearing housing are subjected to considerable loads near the attachment points by an additional torque. As a result, the screw connections have to be produced with a high tightening torque. In order to prevent plastic deformation, it is necessary in turn for the frame tubes—at least in the case of an aluminum structure—to be reinforced in this area by thick-walled tube sections which are pushed in. This is complex and costintensive and increases the weight.
As a result of the aforementioned loads, the steering-fork bearing housings are usually made from extruded aluminum sections. Relatively expensive machining is required to cut these sections to the correct length and to produce the bores, bearing seats and screw threads. It is not possible to produce the sections from plastic because of the. aforementioned high load levels.
For the bearing housings to be attached in a correctly functioning manner, it is necessary for the front bottom region of each wheelchair side to be constructed, as much as possible, at a right-angle. This is usually achieved by welding two straight tube sections together at a right angle. Welding, however, is the most expensive process in producing a wheelchair.
It is not possible to use a tube-bend part for at least two reasons. First, the steering-fork bearing housing would have to be attached above the tube bend, which is too high and would result in the steering fork and tube bend colliding with one another. Second, the steering-fork bearing housing would have to be attached to the bottom horizontal tube section, behind the tube bend, which would result in the caster being positioned too far to the rear. As a result, there is a risk that the wheelchair would tip forward or the caster and the rear wheel would interfere with each other.
The difficulties suggested in the preceding are not intended to be exhaustive, but are among many which tend to reduce the effectiveness of wheelchairs. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that such methods and apparatuses appearing in the past will admit to worthwhile improvement.
SUMMARY OF THE INVENTION
Accordingly, it is therefore a general object of the invention to provide a wheelchair which will obviate or minimize difficulties of the type previously described.
It is a specific object of the invention to provide a wheelchair that has a tube-bend assembly at the bottom front end of each of its side frames.
It is another object of the invention to provide a steering-fork mounting that is adjustable in such a manner as to avoid the drawbacks cited above.
It is still another object of the invention to reduce the load levers acting on the side frames of a wheelchair having greatly reduced load levers.
It is a further object of the invention to provide a side frame for a wheelchair that eliminates the need to weld the front bottom end.
It is yet a further object of the invention to provide a lighter side frame for a wheelchair.
It is still a further object of the invention to reduce the cost of producing a wheelchair.
A preferred embodiment of the invention which is intended to accomplish at least some of the foregoing objects includes a front vertical tube and a bottom horizontal tube connected by a tube-bend portion; a bearing housing mounted to the tube-bend portion; and a fastener for fastening the bearing housing to the tube-bend portion.
Additional objects and advantages of the invention will be set forth in the following description and, in part, will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
REFERENCES:
patent: 4405142 (1983-09-01), Whetstine
patent: 4721321 (1988-01-01), Haury et al.
patent: 4981305 (1991-01-01), Lockard et al.
patent: 5409247 (1995-04-01), Robertson et al.
patent: 5560627 (1996-10-01), Zatulovsky et al.
patent: 5590893 (1997-01-01), Robinson et al.
patent: 5593173 (1997-01-01), Williamson
patent: 5871286 (1999-02-01), Kern et al.
Foley & Lardner
Ilan Ruth
Mai Lanna
Otto Bock Orthopaedische Industrie Besitz-und Verwaltungs-Komman
LandOfFree
Wheelchair having a single tube bend does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Wheelchair having a single tube bend, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wheelchair having a single tube bend will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2583593