Land vehicles – Wheeled – Occupant propelled type
Reexamination Certificate
2002-04-08
2004-05-25
Hurley, Kevin (Department: 3611)
Land vehicles
Wheeled
Occupant propelled type
C188S005000
Reexamination Certificate
active
06739610
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to wheelchair brakes for preventing unwanted rearward movement of a wheelchair during an occupant's transitional ingress and egress, and more particularly to a wheelchair having a brake apparatus that automatically releases when a patient is properly seated.
Using a wheelchair enables patients suffering from various physical and mental disabilities to engage in some level of activity without experiencing the pain or limitations ordinarily placed upon them, and many patients who use wheelchairs are not permanently confined thereto. For these patients, the wheelchair is a convenient tool to facilitate mobility that is not possible otherwise. But often, getting in and out of the wheelchair can pose a problem for such users, in that the chair may roll backward unexpectedly as the patient transitions from standing to sitting, and vice versa. It is especially important that the wheelchair remains stationary during this period, since the natural motion associated with transitioning from sitting to standing, and vice versa, tends to transmit a rearward force on the wheelchair. Further, because only a minimal force is required to move the wheelchair backwards rather rapidly, the patient is extremely vulnerable to falling injuries.
In the past, various attempts to prevent such unwanted movement involved installing a braking mechanism on the wheelchair. In fact, most wheelchairs incorporate some type of brake which stabilizes the wheelchair in a stationary position by preventing rotation of the rear wheels. Conventional wheelchairs which are foldable for storage are invariably fitted with hand-operated brakes. These brakes engage the main drive wheels of the wheelchair, and are applied by the user, or an assistant, to stabilize the wheelchair before the user is seated. Once seated, the user releases the brakes by hand to again permit wheelchair mobility, and when the user wishes to leave the wheelchair, the brakes are re-applied. Brakes of this conventional type are adequate when the user is not seriously physically handicapped and when the user is in substantial control of his mental faculties. However, when the user is severely handicapped or otherwise unable to operate the hand brake, manual brakes are quite inadequate. An unaided user attempting to get into, or out of, a wheelchair which is not locked into a stationary position is faced with a difficult and dangerous task. Further, an unbraked wheelchair used as a temporary support to assist walking also presents a serious hazard to the user.
One of the most widely used devices for stopping and securing the wheelchair is a brake similar to that shown in U.S. Pat. No. 4,570,756 to Minnebraker et al., in which a lever arm is provided to urge a braking member into contact with the tread of the wheelchair tire. However, despite its popularity, this brake causes unnecessary wear to the tire tread, lacks substantial holding efficiency on sloped surfaces, and becomes almost unusable when the tire is wet. Since the device is only applied to one wheel, applying stopping action on both wheels of the wheelchair requires installation of two devices that must be engaged using two hands, which may not be an available option for a particular patient.
Similar wheelchair brakes are also disclosed in U.S. Pat. No. 3,529,700 to Marshall; U.S. Pat. No. 2,426,451 to Hammack; U.S. Pat. No. 4,384,732 to Wierwille; U.S. Pat. No. 4,852,697 to Kulik; and U.S. Pat. No. 4,350,227 to Knoche. All of these disclose braking devices for wheelchairs wherein braking pressure is applied directly to the tire rather than to the wheel rim.
Because of the above problems typically associated with prior wheelchair brakes, attempts have been made to provide an alternative brake system which automatically remains braked while the wheelchair is unoccupied, and which releases automatically under the weight of the user when properly seated.
For example, U.S. Pat. No. 4,623,043 to Babilas discloses an automatic wheelchair brake that automatically locks both wheels when a patient attempts to rise from the wheelchair. While seated, the patient can manually operate a three-way lever brake having a manual-locked, a manual-unlocked and an automatic position. If the patient attempts to rise while the brake lever is in the manually unlocked position, the lever automatically returns to the automatic position and both wheels still lock automatically. After the patient has exited, the wheelchair may only be moved by shifting the operating lever to the manual unlock position. However, the threat of rollback remains after the wheelchair is freely repositioned, especially if an unaided patient forgets to re-engage the manual-lock before sitting, or another unaware patient attempts to sit in the unbraked wheelchair. Thus, despite the automatic engagement feature, the manual nature of this brake is not generally desirable for seriously impaired patients.
Another wheelchair having an automatically engaging braking system is disclosed in U.S. Pat. No. 3,529,700 to Marshall, and uses chains or rod linkages connected between a set of rigid actuating bars attached to the seat panel to operate a pair of transverse brake levers which engage the main wheels. U.S. Pat. No. 4,320,818 to Knoche discloses a wheelchair brake assembly for use with a conventional foldable wheelchair which provides a pair of rearwardly extending brake arms connected to adjacent side frames underneath the seat. Each brake arm includes a transverse forward portion pivoted to the side frame and having a brake shoe biasing into engagement with a drive wheel. The rearward portion of each brake arm is provided with a post engageable by the wheelchair seat to pivot the brake shoe out of engagement with the wheel when the seat is depressed and moved downwardly by the weight of an occupant. The wheelchair side frames are connected by a tension spring to ensure that the brake is engaged when the wheelchair is unoccupied.
Yet another prior art wheelchair brake is the anti-rollback assembly of U.S. Pat. No. 6,092,824 to Ritchie. The one-way brake assembly is shown in
FIGS. 1 and 2
as an example of a prior art wheelchair brake that automatically immobilizes the wheelchair against rearward movement when the occupant attempts to rise.
More specifically,
FIG. 1
shows a wheelchair
1
having a frame
2
and an anti-rollback assembly. The anti-rollback assembly includes fastening devices
3
A and
3
B attached to opposing portions
2
A and
2
B of the frame
2
above the point where the opposing axles
4
A and
4
B intersect the frame
2
. The fastening devices
3
A and
3
B include a large number of individual components as shown in
FIG. 2
, but the rotatable connection members
3
a
and
3
b
are most noteworthy for purposes of this discussion. A rigid crossbar
6
A is rotatably attached to and interposed between the rotatable connection members
3
a
and
3
b
such that the rigid crossbar
6
A transversely connects the fastening members
3
A and
3
B over the horizontal distance spanning between the two opposing sides
2
A and
2
B of the frame
2
. The rigid cross bar
6
A includes an arm
6
B having a first portion
6
a
perpendicularly extending from the horizontal rigid crossbar
6
A and joining with a second portion
6
b
at an elbow. The second portion
6
b
extends vertically upward from the elbow such that a third portion
6
c
is positioned under the wheelchair seat
7
. A pair of brake arms
5
A and
5
B are rigidly attached to the rotatable connection members
3
a
and
3
b
and positioned to contact the rear wheels
20
A and
20
B such that the rear wheels are not moveable. When a patient sits on the wheelchair seat
7
, the third portion
6
c
of the arm
6
B is pressed downward, causing the rigid crossbar
6
A to rotate in a rearward direction. The brake arms
5
A and
5
B lift upward in co-rotation with the rigid crossbar
6
A and out of contact with the rear wheels
20
A and
20
B which are then freely moveable.
Another prior art wheelchair brake assembly is
Connors James B.
Famulare Frank
Iles Edward
Air Movement Technologies, Inc.
Burr & Brown
Hurley Kevin
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