US 3198534 A
Description (OCR text may contain errors)
Aug. 3, 1965 T. R. PORTER 3,198,534
STAIR CLIMBING WHEEL CHAIR Filed Oct. 18, 1963 5 Sheets-Sheet 1 Aug- 3, 1965 r. R. PORTER 3,198,534
STAIR CLIMBING WHEEL CHAIR Aug. 3, 1965 T. R. PORTER 3,198,534
STAIR CLIMBING WHEEL CHAIR Filed Oct. 18, 1965 5 Sheets-Sheet 5 United States Patent() sns/asse STAIR CLE/ING WVHEEL CHIR Than Robinson Porter, 329 E. l3th St., Apt. A, New York, NSY. Filed Get. 16, 1963, Ser. No. 326,233.3 1S Claims. (Cl. Mtl-5.22)
This invention pertains to an improved type of invalid ychair which enables the occupant under his own power to propel himself over obstacles such as curbs and stairs and which chair can still 'be operated by lthe occupant on a flat, level surface yas -an ordinary hand operated, folding wheel chair without undue sacrifice of qualities such as collapsibility, maneuverab-ility without damage to oo-rs or stairs, compactness, lightness, and economy.
Although there have been many proposals in the past for stair climbing invalid chairs, they have been mostly very heavy, expensive, non-collapsible devices which are too large to negotiate narrow steps and doorways. Furthermore, previous attempts at obstacle-climbing invalid chairs which employ endless tr-ack devices either provide no means at .all for supporting the straight, ground engaging part of the tracks or provide for a very complicated Iand expensive battery of small wheels.
The object of this invention, therefore, is to overcome these defects by providing an invalid chair which:
(l) :can be propelled by .the occupant on a level, fiat surface without marring floors, r-ugs, or other surfaces;
(2) is capable by means of endless track type tires of negotiating street curbings Iand `any stairs with 'average height risers and depth lof tread as found in oce buildings and homes, including spiral staircases, even .in the presence of at least 'as much litter and moisture `as would not unduly hinder a person walking up the stairs, without damaging the stairs, without necessitating undue time in shifting from the stair climbing function to ordinary operation and vice vers-a, and without the installation of any ramps, electrical outlets .or any other devices not integr-al parts 4of the chai-r;
(3) has a simple means of supporting the above-mentioned endless tracks evenly all along the straight, ground engaging part of said tracks;
(4) is so compact that it can be turned on a stair landing that is no larger than three by three feet, can be folded and stored in a standard automobile or taxicab, is no wider than its own seat when in operation, and can even be made narrower for negotiating tight places;
(5) can accomplish the foregoing without the necessity of unreasonable force applied by the occupant and without the sacrifice of comfort, safety, or extra devices such as adjustable foot rests, means for allowing the occupant to get on and off from the side, and the like. y
The following is a brief gener-al description of the means by which this invention accomplishes the foregoing objects.
On each side of the chair are two endless belt type tracks, one toward the front and one toward the back of the chair and articulated by means of two coaxial, laterally spaced cog wheels and which have exible rubber tires which roll on and are supported by metal rims each of which has a straight lower. section and approximately semicircular end sections and which are adjustable by means of hydraulic jacking devices and/ or springs so that either the straight parts of the said tires form a ground engaging track for mounting obstacles or the semicircular end sections are in contact with the floor with the floor tangent to the tires near the rear of the chair thus enabling the tires to function like ordinary circular tires supporting the rear of the chair. A single caster type wheel supports the front of the chair.
FIG. l is a side elevational view showing the chair in the normal operating position for rolling on a flat, level surface.
FIG. 2, viewed from above, is an enlarged detail of the means for supporting the front caster type wheel.
FIG. 2A, viewed from above, is an enlarged detail of the front wheel support showing the method by which the -front wheel is to be folded when the chair is collapsed.
FIG. 3 shows the chair in successive stages of starting up the sta-irs.
FIG. 4 shows two side elevational views of the chair. The main position, shown entirely by solid lines, shows the chair entirely on the stairs. The `alternate position with a few parts shown by phantom lines, shows the chair at the top of the stairs as it is about to be converted back to an ordinary wheel chair.
FIG. 5 is a side view detail of the rim and tire and a cog wheel to drive it.
FIG. 6 shows an alternative method of making the tire roll on a fixed rim.
FIG. 7 shows a pendulum type automatic leveling device.
FIG. 8 shows a detailed cross section of a tire and rim with a cog wheel to drive it and a set screw type brake.
FIG. 9 is a front elevation of the left handfside of the chair showing the lateral placement of the tires, hand rim, and various other parts in planes A through E, which planes are perpendicular to the plane of the drawing. The footrests, for simplicity, are not shown in this gure.
FIG. l0 shows a cross section of FIG. 6.
FIG. l1 shows a side elevation of the chair in the position to begin mounting stairs.
FIG. l2 shows a detail of the stair climbing drive mechanism.
FIG. 13 shows a detail of the lower right corner of FIGS.
FIG. 14 shows a cross section of the upper part of FIG. 12.
FIG. l5 shows a detail of the Very small gear shown in FIG. l2.
The operation and construction of this'invention will become more clear from the following detailed description.
As this invention is laterally symmetrical, with the exception of part 32 to be described later, only one side is shown and described.
The chair unit, except for the wheels and accompanying hydraulic adjustment mechanisms may be a conventional wheel chair with a tubular frame, hand grips for propulsion by an attendant, a back and seat of flexible material such as cloth or leather, and footrests. As there is no mechanism above the seat and in front of the back, a skirt shield such as is on most 'conventional wheel chairs is not really necessary, although the chair of this invention could be equipped with one.V
This chair is folded in the conventional manner by raising the seat frame Il thus folding the X braces 13 together so that they are vertical. The chair of this invention has a curved frame member 26 instead of the usual rectangular frame member so as not to interfere with the stairs, as is evident from FIG. 4. The X braces are situated slightly forward of their position on a conventional wheel chair so as not to interfere with the frame member 26. The frame member 2l) is an arc of a circle with center at 9.
The front of this chair is supported by a small caster type wheel 48 (FIGS. 1, 2 and 4) which is supported by two rods 37a and 37b (FIGS. l and 2) which are pivotally connected by pins 36a and 35h underneath frame member 33, said rods being pivotally connected to each other by rod 38 which is connected to the wheel. The non-pivoted ends of rods 37a and 37b are not fastened to frame member 33 but are underneath and slide along frame member 33 when the chair is folded. The caster is very small since the stair climbing feature makes it unnecessary to provide a large wheel for great facility in rolling over small obstacles.
The rear of the chair of this invention is supported by the tires 17 and 51 (FG. 1) which are mounted on rims d3 and 45, which are cross-sectionally outwardly concave as is shown by FIG. 8. The tires 17 and 51 are made of exible rubber with notched tread 46 (FIG. 1). The tires have attached to them by small pins two rows of small ball bearings 63 (FIGS. 5 and 8) which enable the tires to roll around on the rims while the rims remain xed with relation to the chair. There is also either a thin band of very tiexible spring steel or several fine wires on the inside of each tire with metal pockets 62 which t the teeth of the cog wheels 155, 1*; and 44 (FIG. l) which engage the tires through slots in the rims i3 and 4S. This exible band of spring steel or the wires prevent the tire from stretching and the metal pockets prevent the teeth from damaging the rubber.
. The rims 43 and 45 are adjustably supported at three places, the front, middle, and rear as canbe seen in FIG. 1. The front of rim 43 is pivotally attached by means of pin 39 to a bar 27 which articulates with and slides upon or in another bar 14 by some means such as a set of two pins on bar 27 that tit into a slot in bar 14 or by bar 14 being tubular with bar Z7 fitting inside it like a telescope or by any other simple means. For the middle support, a light flange 50a for mounting wheels 44, is attached to rim 43 thus bearing axle 49 to which the two cog wheels 44a and 4411 are fixed and are laterally spaced so that one cog wheel engages tire 17 and the other, tire 51 with tire 51, as is shown by FIG. 9, being on the outside. Looking back to FlG. 1, the axle 49 is supported by a tubes-1 which iits very accurately into the tubular frame member 16. Rim 45 is similarly attached to bar 41. For the rear support, rim 45 is pivotally attached at pin 34 to another tube 22, which tits into tube 15, which in turn ts into tube S which is mounted by means of a hollow pin 2 to a hydraulic pump 1, which has a plunger 3, which is operated by a lever 4 pivoting at 5, lever 4 being also an armrest. Armi-est 4 is made with a shoulder 6 that prevents it from going down any fartherV than its horizontal position. Furthermore, it has a slight curve near the pivot point so that it can be raised to a vertical position without interfering with frame member-10.
A cog wheel 19 is a ring gear supported by the small cog wheel 26 and the small dummy cog wheels 26a and 26h, the axles of which are mounted iny ange Stic (FIG. 12).
The wheel 19, having a diameter of about five or six inches, has large teeth on the outer side of its periphery and very small, ne teeth on the inside of its periphery, said small teeth engaging with small teeth on cog wheel 26 which has a diameter of only about one half inch. The wheels 26a and 2eb are dummy wheels for supporting wheel 19. T he axles of all the wheels 26 are supported by frange 56C. Coaxial with wheeliti is a hand rim 21 connected to wheel 26 by means of a light sheet metal ange 7h (FG. 9) or by spokes or other convenient means. A small handle like the wheel spinner on an automobile steering wheel is attached to the hand rim, said spinner being capable of being folded upV or pulled out to be used as a crank handle to turn the hand rim continuously in one direction if desired byv the occupant.
To prevent wheels 13 and l@ and adjacent mechanism from falling away from the chair, a pin on the inside of ange Stic at about the center of wheel 19 its into a slot in small, light, liat bars 24a and Zlb which are welded to the frame at 29 and other points at the ends of bars 24a and 24h.
Wheel 18, having a diameter of about two inches, is mounted to rim 43 and engages tire 17 in a manner similar to that of wheel 19. Attached coaxially with wheel 18 is a knob 18a (FIGS. 1 and 9) which is shaped like a doorknob having approximately the same diameter as cog wheel 13.
The occupant propels the chair by turning tire 17 by either of two alternative methods thus turning cog wheel 44a which turnsV cog wheel 44h, which is rigidly mounted on the same axle as 44a, thus turning tire 51. The two alternative methods of turning tire 17 are by turning knob 18a, which turns cog wheel 18 which engages with tire 17, or by turning hand rim 21, which turns wheel 26, which turns wheel 19, which engages with and turns tire 17.
The tire 17 is raised to the position of FIG. 1 for normal operation or lowered to the position of FIG. 11 for mounting obstacles simply by being pushed down or pulled up by the occupant. A small catch 25 (FIG. l), consisting either of a set screw in part 14 that screws down against part 27 or a pin on a spring which pin slips into notches on part 27 or some other simple type of easily releasable catch, holds tire 17 in-either the position of FIG. l or FIG. 11 or any other position desired. For mounting small obstacles in a forward direction, tire 17 is put into a position slightly higher than the position of FIG. 1l but not higher than the footrests 47.
The chair mounts stairs backwards beginning with the position of FIG. 11. As the tire 51 turns, the notches 46 engage the edge of the step and the back of the chair begins to rise.
As the rear of the chair rises, the seat will tend to be tilted forward. Valves 2 and 7 are opened to allow fluid to How out of tube 16, through frame members 12 and Y10, and out'of tube 8 to allow rods 22 and 41 to retract. Either the occupant operates these valves or there is a small pendulum 69 (FIG. 7) which opens and closes the valves to keep the chair level automatically. As the pendulum 69 swings to the right, the opening 67 is uncovered while the opening 66 remains covered; and similarly when pendulum 69 swings to the left, opening 65 is uncovered. There is a set knob at the pivot point 63 `for iixing the valve in any position at the will of the occupant. Also, the pendulum can be bent at point 63 so as to make it hang vertically with the chair .tilted if desired. For the valve in the hollow pin 2, the bar covering openings 66 and 67 is in the form of a cylinder inside the hollow pin, but the principle is the same. To prevent any tilting forward at all, the chair can be tilted slightly back at the beginning by adjusting the bar of the pendulum.
FGS. 1 and l2 show springs 15a and 16a, which hold up most of the weight on the middle and 'rear supports thus greatly reducing the necessary pressure in the hydraulic fluid.
As the chair mounts the stairs, the tires 17 and 51 gradually come to a more nearly straight line as is shown by FIG. 3 until the chair is entirely on the stairs as is shown by FIG. 4 with the tires in Contact with several steps like 57, 58 and 59. There is no reason that the angie of elevation of the liat parts of tires 17 and 51 need be the same for the two sides of the chair. Hence this chair can negotiate triangular steps and spiral staircases and other irregular obstacles.
When the chair nearly reaches the top of the stairs and tire 51 is up in the air entirely oif the stairs, it falls down on the stair landing as in the atlernate position of FIG. 4, the valve 2 (FIG. 1) having been turned some time previously to the position allowing uid to flow into, but not out of, tube 8. Tire 51 continues to fall down until the plane 53 through the center of gravity of the chair is to the right of 59 and the back of the chair is supported by tire S1. As the front of the chair continues to go up, the chair leans back. The occupant can either let it lean back, or he can jack himself up with the hydraulic jack. When point 30 is above and to the right of point 59 in FIG. 4, tire 17 will tend to rotate clockwise about point 39 while tire 51 will tend to rotate counterclockwise, both of which rotations will cause the wheel 44 to come down to the floor.
It the chair has not been jacked to an upright position by means of tire 51, a little more jacking of tube 41 is necessary to right the chair. If the hydraulic fluid is compressible or if there is a compression spring in reservoir 1, the occupant can pump the jacks at his convenience.
When the chair is at the top of the stairs in an upright position, the occupant simply pulls the tire S1 up to the position of FIG. 1. If no more stairs are to be mounted, the ltire 17 is also pulled up. If the chair has reached a landing and more stairs are to be mounted, the tire -17 can be left down. The chair must skid a little to turn with the tire 17 down because the t-ire 17 is in contact with the lloor along a straight line in the down position, and a straight line cannot possibly it on a circle. Hence if the landing has an expensive rug or easily scratched surface, .the tire 17 must be raised anyw-ay so as not to damage the floor by skidding. It can be raised just slightly to the intermediate position, as herein before described, as a safety factor so that in case caster wheel 48 should accidentally slip olf the landing, the chair would still be caught by the tire v1'7.
For descending stairs, the procedure for ascending is simply reversed.
The common center of the arcs of 14, 24h and 27 (FIG. 1) is axle 49. The center of the arcs of lo, 24a, and 41 is the pin 3@ when in the position of PEG. 11. Either axle d pivots about point Sil in the position of FIG. 1 or point Si@ pivots about point di), but not both. Thus in the position of FiG. 1, bar41 cannot retract even if the hydraulic fluid leaks out because point 39 is not at the center of the arc of bar 41. Therefore for normal operation the chair is not supported by the hydraulic fluid.
When 41 is fully retracted into 15 (FIG. 4), the axle 49 is above the end of tube 16. To accommodate this axle, -there is a slot 28 which, as can be seen in FIG. 1, does not extend far enough to `.allow any lluid to escape. As frame member 2@ is Welded to tube 16, there is considerably rigidityrso that slot 23 does not unduly weaken the frame.
The center of the arc of the part of tire 17 between wheel 19 and wheel te is point 42 as shown by FIG. l. The center of the arc of the part of tire 17 between wheel 19 and the front of tire 17 is point 52 as shown by FIG. l. it is important for tire 17 to have approximately the size and shape shown in order for it .to fit well on the steps, giving good balance, and still allow for accessibility of hand rim 21 and knob 13a and still allow the hat bars 24 to be of such a length and position that they will not project out beyond the frame members of the chair and snag or gouge things.
Since, with the front wheel turned back, there is no part of this chair, exclusive of footrests, which projects forward beyond the front frame member of the chair, this chair can be driven up against a bureau or sink or the like. Also, with the arm rests in the vertical position, it can be driven under a table or desk.
Referring to FIG. 1 and the lettered planes A through E perpendicular to the plane of the paper of FIG. 9, in plane A are tube 16, bar 41, and frame member 20. Parts 1d and 27 and bars 24.1 are in plane B. As parts 14 and 27 may be made at, there is room in plane B for 1d and 24a to cross each other las is shown in FGS. l and 9. in plane C are tire 17 and tubes 8 and 15 with `bar Z2. Because the rims do not rotate as on an ordinary wheel chair, there neednt be much clearance between pianes B and C thus allowing for maximum compactness. ln plane D are the hand rim Z1, knob 13a, frame member 1e (except where it curves over to meet frame member 2d), seat frame member 11, frame member 12, and rear .tire 51. The footrest support 35 is 'also in plane D although the bottom horizontal part of the footrest support 31 is bent in to plane Ato meet frame member 33.
If greater longitudinal Ycompactness is desired, hand rim 21 may be in plane E so that tire 51 and hand rim 21 will not be in the same plane, thus 'allowing tire 51 to be drawn up higher toward frame member 20. In the position of FG. 11, the tire 51 can be drawn up all the way anyway since the hand rim 21 is far enough forward not to interfere. If minimum width is not desired, knob 13a and hand rim 21 may be in plane E merely to make them slightly more accessible to the occupant. But if minimum width is desired, nothing need be in plane E so that the entire chair is no wider than the seat.
The point 5d `at which the tires touch the oor in normal operation is directly under rear frame member 10 as is the case for a conventional rear drive Wheel chair, thus giving stability with compactness.
To prevent the chair from plunging down the stairs if the hand rim is released, there is a ratchet having means for being released at the will of the occupant for descending stairs, which releasing means must be consciously held to be released, with a spring to return it to its engaged position so that the occupant must hold it in its released position all the way down the stairs. If the occupant becomes incapacitated for some reason such as fainting, the ratchet will automatically engage and stop the chair. The ratchet operates on any of the wheels 1S, 19 or 44 but might most conveniently be installed on the axle of hand rim 21 with a small cable coming out of the axle of hand rim 21 with a ring on the end of the cable, which ring when pulled with one finger releases the ratchet thus allowing the rest of the hand to be used to hold the hand rim. For normal operation, when the ratchet is not being used,'the cable may be hooked onto the wheel spinner on the hand rim or any other convenient place. v
For a brake, screw 6@ is screwed into a small bracket 61 which isr welded to rim 43 at any convenient place.
When screw 6o is `screwed down against tire 17, the tire is clamped to the rim and cant r-oll, thus preventing the chair from moving.
As an alternative method of enabling the tires to roll around the rims,V 64a and 64b are flat plates in FIG. 6 joining a series of cylindrical rollers 65a, b, 65C thus forming a chain similar to a bicycle chain, which is imbedded in the rubber of the tire. As on a bicycle chain,
45 the spaces between'the rollers receive the teeth of the cog Wheels 1S, 19 and de. The plates 64 areslightly narrower than the diameter of the cylindrical rollers 65 so that only Kthe rollers 65 are in contact with the rim 43 thus allowing the tire to roll freely around the rim. The tire in this case need not even be continuous but can be in the form of little blocks of rubber spaced a small distance apart so as to allow for greater ilexibility.
The following may be Iattached to this chair as optional access-Orres.
A small crank 32 (FIG. 9) connected by a flexible means such as a chain or cable 71 to the opposite side of the chair can be turned to shorten the length of the chain thus partially folding the chair to make it temporarily narrower for going through tight places.
There may be a small crank handle imbedded in knob 18a so that it can be hinged in flush with the knob to be out of the way or can be hinged out to be used to turn knob 18a continuously in one direction instead of turning a little and then get-ting another grip to turn again.
For operation by a person having only one hand, there can be a exible drive shaft connecting the axle of wheel 18 or 26 to its mate on the other side Vof the chair, said flexible drive shaft being passed through the chair between the two X braces.
For rapid opera-tion, on a city street for instance, there can be a small cog wheel that replaces knob 18a and which is connected by a chain drive to a large crank which is up near the arm rests. This crank would be similar to the pedals and, sprocket on a bicycle.
The foot rests can be made adjustable just as they are on many conventional wheel chairs so that for more compactness resulting in smaller turning radius, they can be pulled in under the seat of the chair on each side of wheel 48 or turned out or any other Way that adjustable footrests normally turn.
Axle 49 may be made in two parts 49a and 4% as shown by FIG. 13, with 49h having a keyed shaft connected to cog wheel 44!) and fitted into a hole in the other shaft 49a connected to cog wheel 44a so that for sustained operation as an ordinary Wheel chair without the stair climbing feature, tire 51 may be disengaged by simply pulling the axle out. A small catch holds the two parts of the axle together.
The tire 51 can be either hooked up somewhere on the chair, on flange 56a for instance, or, by means of a wing nut on the pin 2, tire 51 and its accompanying hydraulic adjusting mechanism can be removed altogether.
For -added rigidity there can be spokes for the rims 43 and 45. For the iiat parts of these rims, there can be a wire spoke 40 (FIGS. 1 and l2) stretched over` a small spacing block 39.
As an additional safety device, there can be a small rod 38a which can be either folded up out of the way as is shown by FIG. 1 or let down against the step as in FIG. 4 to prevent the chair from skidding down the stairs if there is insuiiicient traction.
Having set forth a description of this invention, I claim:
1. An improved type of stair climbing wheel chair comprising a pair of metal supported, closed curve tracks on each side of said chair, the tracks in each pair having a straight ground engaging section and each pair of tracks being adjustablevvertically at three places to vary the angle between said straight sections, closed curve rims which are cross sectionally approximately semicircular and concave outward, one of said rims being positioned with its front end approximately at the front of the chair and its rear end at the rear of the chair, the other one of said rims having its front end slightly forward of the rear of the chair, thus longitudinally lapping and being laterally spaced slightly from the that described rim, with the rear end of the second described rim projecting rearwardly from the back of the chair, said iirst described rim having an arcuate upper section, a longitudinally straight, ground engaging lower section, and substantially semicircular end sections, the second described rim having longitudinally straight upper and lower sections and substantially semicircular end sect-ions, said front semicircular end section of the second described rim having the same center and radius as the rear semicircular end section of the rst described rim.
2. An invalid chair as in claim 1 having, on each side, two flexible, closed curve, tread bearing tracks continuously supported by the rims with means for said tracks to roll freely around said rims while said rims remain fixed with relation to the chair, said tracks having metal lined notches for receiving and engaging with cog wheel teeth on the inner side and having means imbedded in said tracks for preventing stretching of said tracks.
3. An invalid chair as in claim 2 with means of articulating both said two rims and the two tracks, said articulating means consisting of av pair of coaxial, laterally spaced wheels having a supporting axle positioned at the common center of the front semicircular section of the rear rim and the rear lsemicircular section of the front rim, said laterally spaced wheels having teeth such that the teeth of the inner one of said wheels engage the front track through a slotin the front rim and the teeth of the outer one of said wheels engage the rear track through a slot in the rear rim, the axleV being supported on the Vrims by a ange on each side of said rims.
4. An invalid chair as in claim 3 with, on each side, -a hydraulically extendable' and retractable support which consists of a rod that iits into a tube like a telescope, both of which rod and tube are in the shape of an arc of a o circle which hydraulic support vertically positions said axle the center of the arc of said hydraulic support being near the floor and approximately under the front frame member of the chair.
5. An invalid chair as in claim 4 having, on each side, a hydraulically extendable support for the rear end of the aforementioned rear rim, said hydraulically extendable and retractable support being pivotable both at its point of connection with the aforementioned rear rims with said hydraulic support being attached to the chair behind the back of said chair.
6. An invalid chair as in claim 5 having, inside of the hydraulic supports, a coil spring for holding up most of the weight on the hydraulic supports.
7. An invalid chair as in claim 6 having, on each side, a hydraulic pump withk a handle for pumping hydraulic fluid into the hydraulic mechanisms, said handle serving as an arm rest attached pivotally to the frame of the chair of this invention in such a way that it may be rotated to a vertical position to permit free side access to the chair.
S. An invalid chair as in claim 7 having, on each side, an extendable and retractable support in the shape of an arc of a circle for the front end of the front rim the center'of the arc of said support being the wheel supporting axle when said hydraulic support is fully extended for normal operation, the support of this claim being pivotally attached to said front rim at the center of the arc of the hydraulic support, the length o'f this extendable and retractable support being xable where desired by the occupant by means of a small adjustable catch.
9. An invalid chair as in claim 8 having, on each side, a driving means consisting of a small knob or crank or both connected coaxially with a cog wheel of approximately the same diameter as said knob or crank, the teeth of said cog wheel engaging with the front track through a slot in the front rim.
10. An invalid chair as in claim 9 having, on each side, a driving means consisting of -a hand rim or crank or both about tive or six inches in diameter coaxially connected with Va small cog wheel about a half inch in diameter, which small cog wheel has small teeth that engage with teeth on the inside of the periphery of another wheel of much larger diameter, said larger wheel having teeth which engage with and drive the front tracks.
11. An invalid chair as ink claim 10 having a flexible drive shaft connecting the axle of said driving means with its mate on the other side of the chair to provide for operation by one-armed occupant.
12. An invalid chair as in claim 11 having on each side, a means for removing the rear rim along with its accompanying track and the hydraulic support, said means consisting of a means of removing the pin on which the support is connected to the frame of the chair together with `a keyed axle for the one of the wheels which engages the aforementioned rear track, which axle fits into a similarly shaped keyed hole in the axle of the one of the Wheels that engages the front track with a snap ball catch holding the above-mentioned axles together so that they operate as one axle while allowing them to be pulled apart laterally.
13. An invalid chair as in claim 12, having, on each side, a means of hooking the rear rims and accompanying tracks in an inoperable position with the two sections of the axle disengaged from each other.
14. An invalid chair as in claim 13 having a single small caster type wheel positioned laterally in the middle of said chair and under the front of said chair, said Wheel being supported by two rods in a horizontal plane just underneath the lowest side frame members of said chair, said rodsrbeing centrally pivoted forming an X and pivotally connected at the front end to the side frame members of the chair, the other ends of said rods being positioned underneath, but not connected to, the side frame members of the chair so that said nonconnected ends can slide from front to back of the chair as the said rods pivot on each other so yas to allow the side frame members to come closer together to fold up the chair.
15. An invalid chair as in claim 14 having a means for temporarily narrowing said chair by partially folding it up with the occupant seated in said chair, said folding being accomplished by the occupant himself by means of a small crank mounted on the side frame member of the chair on one side only, said crank being connected to and capable of shortening a chain or other exible tie means connecting the side frame members, said shortening causing the Width of the chair to be decreased with a corresponding raising `of the seat.
16. An invalid chair as in claim 15 having, on each side, a ratchet safety device which unless consciously held disengaged will engage :and prevent the chair from rolling down the stairs, said ratchet device being connected to the axle of one of the Wheels, said ratchet being provided with a means for hooking it in the disengaged position when the stair climbing mechanism is not being used.
f 17. An invalid chair as in claim 16 having, on each side, a brake consisting of a small U clamp at any convenient place on said rim with a set screw screwed into said U clamp which set screw clamps a track to its supporting rim thus preventing said track from rolling.
18, An invalid chair as in claim 17 having, for the valve of yeach hydraulically extendable and retractable support, a pendulum leveling device for changing the valves to the three positions inflow, outow, and stop.
References Cited by the Examiner UNITED STATES PATENTS 6/56 McLaughlin ISU-9.24 3/64 Greub 280-'5.2Z