CA1299484C

CA1299484C - Ambulatory wheelstand

Info

Publication number: CA1299484C
Application number: CA000594283A
Authority: CA
Inventors: Daniel W. Davis
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-03-21
Filing date: 1989-03-21
Publication date: 1992-04-28
Anticipated expiration: 2009-04-28
Also published as: GB9020669D0; GB2234915B; WO1989009158A1; US4927167A; GB2234915A

Abstract

ABSTRACT
An ambulatory wheelstand includes a user support structure pivotably attached to a wheeled frame. The frame includes a pair of large diameter drive wheels and a pair of front castor wheels. The user support structure includes hinge pins which are entrained in elongated horizontal slots in the frame.
A pivot arm also connects the support structure to the frame so that the structure can pivot between an upright and a prone position. As the support structure is lowered to a prone position, the hinge pin slides rearwardly in the elongated slot to prevent the center of gravity from shifting too far forward. Conversely, when in the upright position, the hinge pin slides to the forward end of the slot, maintaining the center of gravity in substantially the same position.

Description

~2~18~

AM8ULATO~Y WHEELSTAMD
Background of the ~nvention I. Field of the Invention This invention relates to ambulatory c~evices for physically handicapped individuals and, in particular, to an ambulatory wheelstand having multiple angular positions in ~hich the center of gravity of the user remains centrally disposed above a particular location on the wheelstand frame.
10 II. Description of the Prior Art Ambulatory devices have been used to enable a non-ambulatory person, such as a paraplegic or a quadraplegic, to move about more or less on his own.
Typical wheelchairs were the first types of ambulatory 15 devices, but required the user to remain in one position, thus causing atrophy of the muscles.
Wheelstands first resembled a cross between a wheelchair and a gurney and employed a foldable or a pivotable stretcher portion which could pivot between a 20 horizontal and an upright position. Examples of these earlier wheelstands can be found in U.S. Patent Nos.

2,295,006 to Philips and 2,986,200 to Nobile. Each of these patents discloses a device having a large central driving wheel rotatably attached to a frame stabilized 25 by castor wheels at the front and the rear of the device. The patient support is pivotably secured to the frame and includes either a straight stretcher or a somewhat chair-shaped platEorm to support the user.
The support is pivotable between an upright position 30 and a horizontal position. Because of the relatively high pivoting point of the support structure of these ~2~

devices, the center of gravity of the dev;Lces i~ quite high, rendering the device somewhat unstable. The front and rear castor wheels are required to improve stability.
An improved ambulatory wheelstand is disclosed in U.S. Patent No. 4,620,714 to Davis and a modification of this wheelstand is shown in Fig. 1.
In this wheelstand, the pivot point (1) is lowered so that, when the support structure (2) is moved to a 10 horizontal position, the center of gravity of the device is likewise lowered. However, as the center of gravity is lower, it also shifts forwardly, thus causing undue stress on the castor wheels (3) at the front of the device. The Davis device can be operated 15 individually by a paraplegic (4) who is able to reach the drive wheel (5) regardless of the position of the user support structure (2). A locking bar (6) secures the support structure (2) to the frame (7) at a particular angle.
U.S. Patent 4,310,167 to McLaurin disclosed what the inventor calls a center of gravity wheelchair with an articulated chassis. This wheelchair also has a large drive wheel centrally located and both front and rear castor wheels. The chassis is articulated so 25 that the user can shift the center of gravity of the device forward by operation of a lever which extends the chassis frame and the front castor wheel, thus elongating the frame and improving the stability. This device is particularly useful for negotiating curbs, 30 hills or the like. However, McLaurin still employs front and rear castors and requires the user to assume a sitting position only.

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Summary of the_Inve"ntion This lnvention is an amhulatory wheels-tand haviny a ~enter of gravi~y. The frame of the wheelstand has a longitudinal axis, a pair of elongated, spaced lateral supports and at leas~ one cross support between them. There are two large diameter drive wheels attached to the lateral suppoxts near ~he rear of the frame. At least one castor-type wheel is attached to the front of the frame. This construction allows the wheels to support the frame above the ground surface. A
user support structure is pivotally secured to the frame and it is movable between an upright position where the support is vertical and a prone position where the support is in a horizontal position. Means are provided for the structure so that regardless o~ its position the center of gravity of the user remains at a single point with respect to the frame.
Pivoting means which include a pivot memher interconnecting the frame and the user support structure. The pivot means also include an elongated groove in the frame member which ls disposed substantially longitudinally and there is a hinge pln in the groove which connects the structure to the frame.
The user support structure preferably comprises a pair of elongated rails spanned at one end by a chest plate, and at the other end by a foot plate. The user support structure may also include a thlgh plate and a leg wedge and all of the support plates may ~e padded for user comfort.
The novelty of the present inventlon lies in its improved pivoting mechanism which greatly enhances the stability of khe device. The stability of a wheelstand of this type depends on the posltion of the center of gravi~y of the device combined with its user. The center of gravity is ideally located as close to the ground as possible and~ with ..

6~572--334 respect to the front and the rear of the frame, ~hou].cl he locatecl between the drive wheels ancl the castor wheele;, but c~loser to the clrive wheels than to the c~astor wheels. In the 3a 3,';;~, ~2~9~

previously known wheelstands, when the user support was shifted from the upright to the prone position, the center of gravity was shifted from the rearward position over the drive wheels Eorward to a position 5much closer to the front castor wheels, thus putting undue stress on the castor wheels rendering the wheelstand unstable.
In the present invention, however, the center of gravity does not move forward to the same extent as 10in previous devices when the user support is shifted from the upright to the prone position. Instead, the center of gravity remains distributed over sub-stantially the same location of the frame regardless of the position of the user support. This is accomplished 15by sliding the user support structure rearwardly as it is pivoted from the upright to the prone position. An elongated slot is provided for this purpose in each of the lateral supports, preferably formed in a block portion spaced above the lateral support. Hinge pins 20secured to the elongated rails of the user support structure are slidably entrained in the slots. A pivot arm is secured at a first end to an intermediate cross support forward of the elongated slot, and at a second end is pivotably secured to the user support structure.
25In the upright position of the user support structure, the hinge pin is disposed in the forward en~ of the elongated slot. As the support structure pivots to the prone position~ the hinge pin slides rearwardly to the .~
rear end of the slot and the pivot arm pivots at the 30cross support from an upright position to a more rearward, more horizontal position.

1~99~

Brief Descri tion of the Drawinas P ~
The present invention will be more ~ully understood by reference to the following detailed description, when read in conjunction with the 5 accompanying drawings in which like reference characters refer to like parts throughout the several views and in which:
FIG. l is a perspective view of a wheelstand of the prior art;
~IG. 2 is a perspective view of a wheelstand according to the present invention;
FIG. 3 is a side view of the user support pivot mechanism, enlarged for clarity;
FIG. 4 is a side plan view showing user 15 support structure in an upriyht position with portions removed for clarity;
FIG. 5 is a side plan view showîng the user support structure in a prone position, with portions removed for clarity;
FIG. 6 is an alternate embodiment of the user support structure in an upright position with portions removed for clarity FIG. 7 i9 a perspective view of optional foot supports for the wheelstand of the present invention;
25 and FIG. ~ is a perspective view of an alternate embodiment of a wheelstand according to the present invention detailing the mechanism for lowering the user support structure.
Detailed Description of the Preferred Embodiment Referring first to Figure 2, a wheelstand lO

according to the present invention is thereshown. The 4~

wheelstand 10 comprises a frame 12 wh.Lch may be of tubular or sol.id construction and includes a pair of e.longated lateral supports 14 arranged in spaced~
parallel relationship. The Erame 12 furthe.r includes 5 at least one cross support 16 extending between the lateral supports 14 at the front end 1~ of -the frame 12. Preferably, an intermediate cross support 20 extends between the lateral supports 14 between the front end 18 and the rear end 22 of the frame 12. At 10 the rear end 22 the lateral supports 14 include an enlarged block portion 24 which extends the frame 12 upwardly and rearwardly from the lateral. support 14.
The enlarged block portion 24 provides a place for the rotatable attachment o two large diameter drive wheels 15 26 which preEerably are lightwei~ht, spoked wheels.
Alternatively, the wheels may be disks to prevent fingers from being caught (not shown), or may be spoked with peripheral finger protection in the form of a cover over the endmost portions of the spokes (not 20 shown). The enlarged block portion 24 also includes an elongated slot 28 for a purpose to be subsequently described.
At the front end 18 of the frame 12 a pair of castor wheels 30 extend rom the lateral support 14.
25 The castor wheels 30 and the drive wheels 26 are attached to the frame 12 so that the lateral supports 14 are substantially parallel to a ground surface (not shown) which supports the wheels of the wheelstand 10.
The castor wheels 30 are pivotably secured to the 30 lateral supports 14 so as to permit turning of the wheelstand 10.

129948~

Referring now to Figures 2, 3 and 4, the wheelstand lO further comprises a user support structure 32 having a pair of elongated rails 34 in spaced parallel relationship. At the head end of the 5 user support structure 32 a chest plate 36 extends between the elongated rails 34. At the foot end of the user support structure 32 a foot support 38, including two foot plates 40, extends between the elongated rails 34. Intermediate the head and foot ends leg or thigh 10 plates 42 extend between the elongated rails 34. The chest or torso plate 36 and the thigh plate 42 may each be padded as shown in the drawing to enhance user comfort. Moreover, a wedge shaped leg pad 44 may be disposed centrally between the elongated rails 34 in a 15 position to extend between the legs of a user of the wheelstand lO. Additionally, a pair of adjustable adductor pads 43 may be included to provide hip support. A strap or belt (not shown) preferably is used to secure the user to the user support structure 20 32.
As best shown in Figure 3, each of the elongated rails 34 includes a hinge pin 46 extending outwardly from the user support structure 32. The hinge pins 46 are coaxial and are dimensioned to fit in 25 the elongated slots 28 of the block portion 24. The spacing between the enlarged block portions 24 and the elongated rails 34 is such that the hinge pins 46 are entrained within the elongated slots 28. A pivot arm 48 has a first end secured at a pivot point 50 to thé
30 frame 12 and preferably to the intermediate cross support 20. A second end o the pivot arm 48 is qL8~

pivotably attached at p.ivot point 52 to the elonsated rail 34 of the user support strwcture 32. In the preferred embodiment, two such pivot arms 48 are employed, one associated with each elongated rail 3~
sand extending to the intermediate cross support 20 at each side near the lateral supports 14. The user support structure 32 pivots from the upright position (shown in Figure 4 and in solid line in Figure 3) to the prone position (shown in Figure 5 and in phantom in Figure 3). As it does so, the hinge pin 4~ slides from the forward end of the elongated slot 28 to the rearward end as indicated by the arrow A in Figure 3, while the pivot arm 48 moves in the direction of arrow B. Adjustment bar 21 selectively locks the support structure in a variety of positions.
By shifting the user support structure 32 rearwardly as shown by the arrow A in Figure 3, the tendency of the center of gravity to shift forward upon lowering of the support structure 32 is counteractedO
20Accordingly, instead of an unstable wheelstand haviny undue stress placed on its forward castor wheels, the wheelstand 10 of the present invention remains stable due to its ability to maintain the center of gravity distributed over substantially the same location 25regardless of the positiorl of the user support structure 32.
For example, referring to Figure 4 and assuming that the center of gravity is located approximately at the tip of the wedge pad 44, it is 30disposed over the front edge of the enlarged block portion 24. If the user support structure 32 were 8~

simply hinged, as in the prior art structures, lowering the support structure to the horizontal position would place the same center oE gravity forward of the intermediate cross support 20. However, referring to 5 Figure 5, the center of gravi~y at the tip of the wedge 44 is still located above the forward edge of the enlarged block portion 24 when the user support structure 32 is in the horizontal or prone position.
By selecting appropriate lengths for the 10 elongated slot 28 and the pivot arm 48, as well as appropriate pivot points 50 and 52, it is possible to achieve the ideal situation where the center of gravity of the combined user and wheelstand remains always over the ideal location between the front castor wheel 30 15 and the drive wheel 26, preferably towards the latter.
Practically, it does not matter if the center of gravity varies slightly from this ideal location so long as it remains substantially over this preferred location. For this reason, the position of the front 20 castor wheels 30 may be adjustable as shown in phantom in Figure 4.
Referring back to Figure 4, the wheelstand of the present invention may be further fitted with options necessary to meet the personal needs of the 25 user, thus underscoring the versatility of design.
For convenience of the user's assistant, the support structure 32 may be removably detachable from the frame 12 by releasing the str~cture 32 from a pair of lateral support sub-structures 51. Conventional 30 quick-release fasteners 49 are provided to allow removal.

On the side of the support structure 32 approximately opposite the chest plate 36 may be provlded a pair of accessory brackets 66. Each of the brackets 66 is provided to accommodate a variety of 5 user accessories, including handles 64 to allow the user to stabilize his upper torso and to allow the user to draw himself toward the wheelstand when mounting the same. Other accessories may include a tray 80 (shown in Figure 6) for use as a classroom aid and an exercise 10 pad (not shown). The selected accessory may be selectively released from the brackets 66 by means of an accessory release 68 fitted to each of the brackets 66.
In addition, one or more trunk pads 70 may be 15 provided to offer trunk or torso support to the user.
Referring back to Figure 5, the above-described proper balance of the wheelstand notwithstanding, a pair of adjustable, spring-loaded, telescoping antitippers 60 may be provided. The 20 antitippers, each fitted with one or two antitipper wheels 62, provide added security for the user, particularly when negotiating steps or inclines. The spring-loading of the antitippers 60 also allow the user to accomplish "wheelies", thereby allowing the 25 climbing of curbs. In addition, this characteristic makes the wheelstand more fun, and therefore more desirable to use in various environments by young people.
With reference to Figure 6, an additional 30 option is shown to provide the user with back support without the need for assistance from others. According h~99~

to the prior art described above, a belt or the like is reguired to hold the user against the support structure 32. However, such a device is not likely convenient to or workable by the user, thus re~uiring assistance from 5 others. To provide independence to the user, a back support is provided which may be emplaced by the user.
A back support pad 76 is provided at an end of a back support pad shaft 7~. The pad shaft 74 is pivotally attached to the support structure 32 and is drawn 10 toward the user by a spring loaded piston 75. A remote back support pad release 78 is provided convenient to the hands of the user. ~hen not in use, the back support pad shaft 74 locks in an open position (not shown). Once the user has mounted himself onto the 15 wheelstand, he operates the release 78 and the pad 76 gently springs into place to urge the user against the structure 32 into the closed position as illustrated.
Referring to Figure 7, yet a further option is shown relating to the user's feet and legs.
To accommodate legs of different lengths, each adjustable foot plate 80 may be adjusted up or down relative to a user in position on the wheelstand. Such movement is accomplished by a telescoping leg support bar 86 which may be telescoped within a telescoping leg 25support bar housing 88. The bar 86 may be selectively locked into place within housing 88 by means of a conventional tightener 90.
To accommodate feet of different sizes, each adjustable foot plate 80 may be provided with a pair of 30paddedl adjustable lateral supports 82 slidable along adjustable lateral support slots 92. To secure the ~g~

user's toes, each p]ate 30 may be Eurther provided with a toe cup 84.
Because the user's feet may be contorted in a variety of positions, the Eoot plate 80 may be adjusted 5back and forth relative to the user by slidlng the plate 80 along a pair of adjustment slots 93.
Furthermore, to more fully accommodate the variable positions of the user's feet, each of the plates 80 may be angled relative to the leg support bar 86 according 10to adjustment accomplished by altering a foot rest pivotable adjustment mechanism 85.
Referring finally to Figure 8, other options are shown to provide added comfort and convenience to the user. In lieu of the chest plate 36 shown in, for example, Figure 2, a conventional rest 108 may be used and adjustment of the rest 108 is accomplished by the raising or lowering of the rest 108 by adjusting a rest bar 110.
While the adjustment bar 21 of Figure 2 allows 20Operation by the assistant, a means is shown and hereafter detailed by which to allow the user structure 32 to be lowered by the user at his selection. This is accomplished by the provision of a spring-loaded piston 100 pivotally attached to the cross support 20 by a 2sframe bracket 102. A piston rod 101 is pivotally attached to structure 32 by a structure bracket 104. A
remote piston release valve 106 is provided convenient to the user, and is fluidly attached to the piston 100 by a remote piston release line 112.

In use, the user, in place on the wheelstand, may selectively wish to lower the structure 32 to a ~L2~

prone position. By operating the valve 106, air is released from the piston 100 and the user may stop the downward motion at any one of an inEinite number of positions. To prevent abrupt halting of the structure 32 at the position selected by the user, the piston is spring loaded.
The foregoing detailed description of the structure and operation of the present invention has been given for clearness of understanding only and no unnecessary limitations should be understood therefrom.
Some modifications will be obvious to those skilled in the art to which the invention pertains, without deviation from the spirit of the invention as defined by the scope of the appended claims.
I claim:

Claims

1. An ambulatory wheelstand for a user having a center of gravity, said wheelstand comprising:
a frame having a pair of elongated, spaced lateral supports and at least one cross support extending between said lateral supports at a front end of said frame;
two large diameter drive wheels rotatably attached to said lateral supports towards a rear end of said frame;
at least one castor wheel attached to said frame towards the front end, said wheels being adapted to support said frame above a ground surface;
a user support structure pivotably secured to said frame and movable between at least an upright position, in which said structure is substantially vertical, and a prone position, in which said support is substantially horizontal; and means for pivoting said user support structure so that, regardless of its position, the center of gravity of the user supported by the support structure remains above substantially a single point with respect to said frame.

2. The wheelstand as defined in claim 1 wherein said user support comprises a pair of spaced elongated rails, said rails being spanned at one end by a chest plate, at another end by a foot support and intermediate said ends, by a thigh plate.

3. The wheelstand as defined in claim 2 wherein said user support structure further comprises a leg pad arranged in a V-shape pointing away from said foot support.

4. The wheelstand as defined in claim 2 wherein said foot support includes a foot plate disposed substantially perpendicularly to a plane defined by said elongated rails.

5. The wheelstand as defined in claim 1 wherein said frame is rectangular and said at least one castor wheel comprises two castor wheels disposed one each at the front end of said lateral supports.

6. The wheelstand as defined in claim 1 and comprising a brake mechanism to selectively prevent rotation of said drive wheels.

7. The wheelstand as defined in claim 1 wherein said single point is located between said drive wheels and said at least one castor wheel.

8. The wheelstand as defined in claim 1 wherein said means for pivoting comprises:
a portion of each of said lateral supports defining an elongated slot therethrough, each slot extending substantially parallel to said lateral supports;
a pair of hinge pins secured coaxially to said user support structure, one of said hinge pins being slidably entrained in each of said slots and movable between at least a front end and a rear end of said slot;
at least one pivot arm having a first end pivotably secured to said frame in front of said slots and a second end pivotably secured to said user support structure toward the chest plate end from said hinge pin, wherein said hinge pin is disposed at the front end of said slot when the user support structure is in the upright position and at the rear end of said slot when the user support structure is in said prone position.

9. The wheelstand as defined in claim 8 and comprising locking means for selectively locking said user support structure with respect to said frame against further pivoting.

10. The wheelstand as defined in claim 8 wherein said elongated slot is disposed in a block portion at the rear end of said lateral supports so that the elongated slot is disposed above a point where said first end of said pivot arm is secured to said frame.

11. The wheelstand as defined in claim 8 wherein said first end of said pivot arm is secured to said frame at a cross support intermediate said front and rear ends of said frame.

12. The wheelstand as defined in claim 8 and comprising a spring-loaded piston means, said means including:
at least one spring-loaded piston body having a first and a second end pivotally secured to said frame;
a shaft having two ends provided for each of said at least one piston body slidably insertable into said body at said shaft's second end and pivotally secured to said support structure;
one or more fluid lines fluidly attached to each of said at least one piston body; and at least one user control valve provided within reach of said user on said wheelstand and fluidly attached to said one or more fluid lines.

13. The wheelstand as defined in claim 1 wherein said foot support comprises:
a foot plate for each foot pivotally attached to an attachment shaft, said shaft being slidably disposed within said rail;
a means for locking said shaft within said rail;
said plate including a toe cup means for accommodating and securing the toes of the feet of said user;
said plate having adjustable lateral supports;
and said plates being adjustable forward or backward relative to said support structure.

14. The wheelstand as defined in claim 5 and further including at least one cantilevered antitipper bar secured to said frame substantially opposite each of said two castor wheels.

15. The wheelstand as defined in claim 14 wherein each of said antitippers includes means for adjusting the length thereof.

16. The wheelstand as defined in claim 2 wherein said chest plate is provided with fittings for removably receiving pull-bars having hand grips.

17. The wheelstand as defined in claim l wherein said user support structure is releasably attachable to said frame.

18. The wheelstand as defined in claim 3 wherein said user support structure further comprises one or more axially provided hip adductor pads.

19. The wheelstand as defined in claim 2 wherein said user support structure further includes a back support means for urging said user substantially against said user support frame.

20. The wheelstand as defined in claim 19 wherein said back support means comprises:
a curved shaft having a first end and a second end;
one or more back support pads fixed to said first end of said shaft;

said second end of said shaft being pivotally attached to said frame;
a spring loaded piston having a first end and a second end, said first end of said piston being pivotally attached to said shaft; and said second end of said piston being pivotally attached to said frame.