US3189382A

US3189382A - Collapsible backrest

Info

Publication number: US3189382A
Application number: US285283A
Authority: US
Inventors: Fortier J Paul
Original assignee: Individual
Current assignee: Individual
Priority date: 1963-06-04
Filing date: 1963-06-04
Publication date: 1965-06-15
Anticipated expiration: 1982-06-15
Also published as: FR1397758A; GB1002933A; DE1239818B

Description

2 Sheets-Sheet l INVENTOR. J. PAUL FORTIER J. P. FORTIER COLLAPSIBLE BACKREST June 15, l

Filed June 4, 1963 June 15, 1965 J. P. FORTIER 3,l89,382

COLLAPSIBLE BACKREST Filed June 4, 1963 2 Sheets-Sh et 2 INVENTOR. J. PAUL FOR TIER ma; /M

ATTORNEY United States Patent Oi &189332 COLLAPEBLE BACKREST .l. Paul Fortier, Uh. i hte. 1, Foxboro, Mase. Filed filme 4, N& Ser. No. 285383 10 Claims. 31. 29'7- -351) This invention relates to backrests and more particularly to a collapsible backrest having capacity for readily and selectively erecting in support position and Collapsing into a Conveniently small, storage and hand portable bundle.

Many vacationers and sporting enthusiasts forego the convenience and enjoyrnent of chairs and backrests at beaches and other recreation areas because of the difii cuity of storing and transporting them to and from the beach or other place of use. Even the few such chairs and backrests which have been made coliapsible to reduce storage space required and to make them more portable, nevertheless are generally still too bulky, cumbersome or heavy for easy portability, or for the average individual provide too ditiicult and tedious a chore for their assembly and disassembly at the point of use.

These problems are overcome by the present invention of a eollapsible backrest which also incorporates other desirable features and advantages. Among these other desirable features and advantages are the provision of a collapsible backrest which requires only a relatively small number of parts. Another desirable feature is the provision of a collapsible backrest which provides a particularly comfortable support to the users back in that only a flexible membrane such as a plastic or fabric with its inherent shape conform ng characteristics makes contact with the back of the user. Other desirable features include extreme Simplicity of operation with very few manipulations required in erecting the backrest to support position and collapsing the backrest for ready storage and portability. Also, it may be compacted to the form of a small convenient bundle for storing or carrying with the hard metal Components being eneased in the relatively soft membrane which provides a protective padding and thereby minimizes possibility of discomfort or injury to an individual carrying the bundle. Further advantages include that of a very rugged backrest, yet one which is comprised of very simple and inexpensive Components.

A primary object of the present invention is the provision of a collapsible backrest with capacity for readily compacting into a Conveniently small, hand portable bundle.

Another object is the provision of a collapsible backrest wherein only flexible membrane makes support contact with the body of the user.

A further object is the provision of a collapsible backrest which in the compacted, hand portable bundle form inherently has its hard metal Components enveloped in comparatively soft, protective membrane wrapping.

And another object of the provision of a collapsible backrest which requires no tools of any kind and is relatively easy to erest into support portion and to Collapse into a compact, hand portable bundle.

Other objects include the provision of a collapsible backrest which is rugged, relatively simple in Construction, inexpensve to manufacture, and reliable in its operation.

These and other objects, features and advantages are achieved generally by the provision of a pair of channel members, each pivotally carrying telescoping rods in the trough of the respective channel, a fiexible membrane carried by the telescoping members, and a foldable cross bracing structure fixed to the channels for holding the channels in support position when the backrest is erected for use.

By making the flexible membrane with overlapping ice portions at its sides to form Ioops or elongated tubular formations circumscribing the telescoping rods, a simple and rugged back support arrangement of the membrane by the telescoping rods, as well as suitable Capacity for compacting in folded form is thereby achieved.

By providing a flexible strap attached at one end to the top of the membrane at substantially the fold thereof when in collapsed position, and providing fastening means at spaced intervals on the strap, a suitable locking arran gement for holding the structure in a compacted, hand portable bundle is thereby achieved, as well as an arrangement which prevents the looking strap from dragging in the dirt and sand when the backrest is in erected support position.

By making the cross bracing structure in the form of a spacer bar of two sections pivotally fixed to each other at one of their ends, and to the respective channels at the other of their ends, and an angularly disposed rigidizing member for each of the sections pivotally mounted on the respective section and the associated channel, a rugged and simple cross bracing structure, as well as one having inherent ease in erecting and collapsing to compact the structure is thereby achieved.

By providing a slot in each of the channels with an olfset notch in the upper end of each channel for guiding and locking a pin in the corresponding end of the angular rigidizing members, a simple and eective operating arrangement for the support structure is thereby achieved.

By providing openings at spaced intervals along one leg of each channel and providing an arm pivotally mounted at one end to the corresponding telescoping rod and constructed at the other end to engage a selected opening, a simple and effective arrangement for varying the angle of support of the backrest is thereby achieved.

By providing a flexible chord or strap fixed at each of its ends to the bottom ends of the channels, an elfective arrangement for both providing a suitable carrying handle for the backrest in compacted bundle form, along with a simple arrangement for retaining the upper end of the membrane in taut condition for improved comfort and support action of the overall backrest is thereby achieved.

These and other features, objects, and advantages of the invention will be better understood from the following description taken in connection with the accompanying drawings of preferred embodiments of the invention and wherein:

PIG. 1 is an elevation showing the invention in a collapsed condition forming a compact bundle for ready hand portability or storage;

FIG. 2 is a View of the FIG. 1 embodiment shown partially unfolded as a first step in its ereetion as a backrest and a next to the last step in compacting into a hand portable bundle;

FIG. 3 is a view of the unfolded back of the FIG. 1 embodiment illustrating a further unfolding stage in its erection as a backest;

FIG. 4 is a view of a portion of a channel illustrated in FiG. 3 to more clearly show Construction;

FIG. 5 is an illustration of an alternative construction of a portion of the cross bracing arrangement illustrated in FIG. 3;

FIG. 6 is a side elevation showing the completely erected backrest in support or use position;

FIG. 7 is an enlarged scale side elevation of one of the channel members of the present invention with some of the associated structures folded therein with some components only partially shown;

FIG. 8 is a cross section taken on line 8--8 of FIG. 7;

FIG. 9 is an end View of FIG. 8;

FIG. 10 is a back View of a portion of the channel member shown in FIG. 7.

areas Ref rring to the drawings in more detail, a collapsible backrest made in accordance with the present invention is designated generally by the numeral 12. The Collapsible backrest 12 has a pair of

channel members

14 and 16, preferably of suchstrong, rigid material as aluminum alloy or steel, both being of substantially similar construction. T'hus, while only the channel member 14 and its associated foldable assembly is shown in detail in FIGS. 7 through 10, it should be understood that such description also applies to the channel 16 and its associated foldable assembly.

Channel member 14 has a cross sectional shape in the form of a trough shown in FlG. 9 with a back or bottom closure 13 and substantially parallel sides or

legs

20 and 22. One end of the channel member 14 has mounted thereto, by pivot pins 24 and 26 (FIG. 8), a ground support channel member 28. The ground support channel 23 has a cross sectional configuration to fit the trough of the channel 14, and a pivotal capability of swinging outwardly from the trough of the channel member 14 so that its sides or legs enter respective slots 3@ and 32 (FlG. lO) in the back side 18 of the channel member 14 until the upper surfaces of the sicles of the ground support channel member 28 engage the ends 34 and 36 of the slots 3@ and 32 respectively so as to act as stops for the ground support channel 23. In this swung out position, the ground support channel' member 23 (FLG. 6) provides an area of contact 33 with the surface of the terrain se, which is usually soft sea. sand, and thereby prevents the end of channel member 14 from Sinking into the terrain 4@ when under load. In the event that the baclcrest 12 is to be used only on hard surfaces, the ground support channel 28 may be eliminated entirely or replaced by a small 'fixed pad at the end of the channel member 1 4 (not shown).

A flexible cord or strap 42 is also fixed to the end of the

channel members

14 and 16 carrying the pivot pins 2 4 and 26, as by a snap fastener at one end of the strap 42 and an enlarged head rivet 46 (FIGS. 2, 3) at the other end of the strap 22. Thereby, the strap 42 provides a suitable handle which enhances hand portability of the collapsible backrest 12 when in the collapsed and compacted package form shown in FIG. l. The strap also provides a highly desirablc limiter to extent of sideward separation of the lower ends of the

channel members

14 and 16 When the collapsible backrest 12 is in the erected support position shown in FIG. 6 as will be hereinafter further described.

The backs of the

channel members

14 and 16 also carry slots 48 and 5@ for slidably guiding

follower pins

52 and 54 in one end of angularly disposed rigidizing

braces

56 and 58 respectively. The rigidizing

braces

56 and 58 have

pivot pins

68 and 62 at their other ends providing pivotal mounting to each of

spacer bar sections

64 and 68 respectively at positions distal from pivot pins ?ti and 72. The pivot pins 7@ and '72 provide pivotal mourning for one of the ends of each of spacer bar sections 64 and 63 to the backs of the

channel members

14 and 16 respectively. The other end of each of the spacer bar sections 64 and &E are pivotally coupled together by a pivot pin '74.

Each of the slots 48 and Sii at their upper extremities carry an ottset looking opening such as shown at '76 in FG. 4- in position such that When the

channel members

14 and 16 are pulled outwardly away from each other to the positions shown in FIG. 3 from the collapsed position shown in FEG. 2, the

follower pins

52 and 54 will ride up slots 48 and 5@ respectively and become engaged and locked in the oifset lock-ing opening 76. Also, the spacer bar section se, adjacent the pivot pin '74, has a stop recess '77 arranged to engage a cooperating stop pin or boss '73 (FIG. 3) on the spacer bar section 64. Thereby, as the pivot pin 74 moves upwardly from the position shown in FIG. 2 to the open position shown in FIG. 3, such upward movement will come to a halt and further movement beyond the tully extended position of the spacer bar mem- Components are dimcnsioned to provide that the follower pins and 5 -3- will become locked in the looking recesses '76 when the boss or stop pin '78 firmly engages the stop rccess '77, thereby providing a rigid, seli looking and selfretaining framework. The ri gidity and self locking aspect of this framework is further enhanced by dimensioning the fiexible strap or cord 42 to be pulled taut When the

follower pins

52 and 54 fall into the looking offset openings 7 6. in some instances, to further increase the tightness of the cord 42, it may be desirable to release the snap tastener 4@ end of the cord 42 during the opening operation until the

channels

14 and 16 have been laterally separated and the follower pins and 54 lock in place in the looking oftset openings 76. hereupon the cord 42 may then be manually pulled tight and fastened in place by the snap iastener i i.

An alternative construction for rigidizing braces 56 and is shown in FIG. 5 where in place of a single member rigidizing brace as 58, two sections 5@ and 32 are pivotally mounted together by pivot pin 8% and a boss and stop arrangement which may be such as described in connection with the boss 78 and stop reeess 77. Further locking in place n the erected support position may be provided by a hole and boss arrangement in the rigidizing brace sections and 232 respectively. In this alternative Construction, pivot pin %9 does not move in a slot and is rather fixed in position in the back side of the channel 16. When it is desired to foltl the assembly to the osition shown in FIG. 2, pressure is brought to bear behind the pivot pin S i so as to push in the direction away from the pivot pin 72 to thercby cause the spacer bar section and rigidizing brace sections and i?, to told downwar `y over the channel 16 in somewhat similar manner to the folding shown in HG. 2.

Referring again to FlG. 8, in the folded position, the channel member 14 carries in its trough the ground support channel member 28 and a pair of cylindrical telescoping rods comprised of an outer and an inner telescoping rods 9@ and 92 respectively. The outer telescoping rod 96 has pivot pins 94 and 96 fastened to its upper end as by brazing, welding or other suitable means. The pivot pins 9 2'- and 96 are pivotally carried in holes in the

sides

28 and 22 respectively of the channel member 14. Spacer washers 93 and 100 may be provided to prevent undesired sideward movement in the trough of the channel member 14. The bottom end of the outer telescoping rod 9@ may Carry a closure plug 102 to prevent access of sand and dirt therein.

The inner telescoping rod 92 may have a stop button 1% protruding through a side wall opening in the inner telescoping rod 92 and carried by a spring 106 anchored by a plug 188 in the hollow of the inner telescoping rod The upper end of the inner telescoping rod 92 may also have a closure plug 110 to prevent sand and other foreign matter from entering internally thereof. It also provides a place for gripping with the fingers for eX- tendirg the inner telescoping rod 92 until the stop button 12% engages the top rim 117; of the outer telescoping rod 9-@ as shown in FIG. 6 to thereby increase the effective support length 114 of the collapsible backrest 12.

When the telescoping rods and 92 are in the shortened position shown in FlG. 8, the pressure of the plunger or stop button 194 from the spring 166 will, because of friction against the inside surface of the outer telescoping rod 90, tend to hold the inner telescoping rod 92 in place. Also, as explained above, the channel member 16 carries a similar outer telescoping rod 116 and an inner telescoping rod 115 with a similar spring pressed stop button 121 (FIG. 3). The outer telescoping rod 116 s similarly mounted to the end of channel 16 by pivot pins 117.

The outer telescoping rod 90 also carries a pivot pin 119 rigidly fixed to its outer wall as by brazing, welding &1895332 or other suitable means. The pivot pin 119 provides a fulcrum and mounting arrangement for one end of a backrest angle adjusting arm 118 having a projection 120 at its other end. The projection 120 has a configuration which fits selectively into any one of a plurality of backrest angle adjusting holes- 122, 124, 126 and 128 in the side 22 of the channel 18, the'eby permitting a selective adjustment of the angle of inclination 130 of the collapsible backrest 12. It will be noted that by making a relatively close fit at the pivot pin 119, the inherent lateral spring action of the angle adjusting arm 118 will continuously exert an outward pressure against the side 22 of the channel member 14 so as to continuously retain the projection 120 in any selected

angle adjusting hole

122, 124, 126 or 128.

A similar angle adjusting arm 130 with similar projection 132 (FIG. 3) is provided on the outer telescoping rod 116 to engage similar angle adjusting holes in the side of the channel 16 (not shown).

A thin flexible membrane 134 of a suitable plastic or woven fabric such as canvas has overlapped sides fastened as by stitching 136 or other suitable fastening means to form lower elongated

tubular formations

138 and 140 and, aligned therewith, upper elongated tubular formations 142 and 144 respectively along the sides of the flexible membrane 134.

Openings

146 and 148 are provided between the aligned, elongated lower and upper tubular formations and are preferably reinforced as by a binding 149 at the edges of the membrane 134 to provide additional strength and wear qualities.

The upper ends of the upper elongated tubular formations 142 and 144 are closed or sealed as by stitch'ng 150. Fitted inside of the lower elongated

tubular formations

138 and 140 are the

telescoping rods

90 and 116 respectively, which by means of the pivot pins 119 protruding through the membrane 134 tend to hold it in place on the telescoping rods. i

The

inner telescoping rods

92 and 115, because of the

openings

146 and 148, may be inserted into the upper elongated tubular formations 142 and 144 respectively as shown in FIGS. 3 and 6, or removed therefrom at the pleasure of the user. Thus, the

inner telescoping rods

92 and 115 will be inserted in the upper elongated tubular formations 142 and 144 to increase the support length 114 as shown in FIG. 6 when the collapsible backrest 12 is erected to the support position. The

inner telescoping rods

92 and 115 may be returned into the associated outer telescoping rods by depressing the

stop buttons

104 and 121 respectively for collapsing the collapsible backrest 12 to the hand portable packaged form shown in FIG. l.

Another strap or locking belt 152 is fastened at one end, as by stitching 154 (FIG. 3), to the top of the membrane 134 at an angle such that the strap 152 projects outwardly from the told 156 of the membrane 134 inherently formed as shown in FIG. 2 when the

channel members

14 and 16 are adjacent each other and the upper part of the membrane 134 is folded downwardly as shown in FIG. 2. In this partially folded position, the bottom portion of the membrane 134 may also be folded upwardly and back on itself as shown in FIG. 2, whereupon the so folded membrane 134 may then be wrapped around the

channels

14 and 16 and associated Components until

snap fastener members

158 and 160 on the strap 152 engage each other with the strap 152 extending about the wrap around membrane 134 to form a compact, readily hand portable packaged backrest 12 as shown in FIG. l.

It will be noted that an extension 162 of the membrane 134 is provided to form a suitable ground cover pad on which the user may sit when occupyng the erected collapsible backrest 12 as shown in FIG. 6. The ground cover extension 162 has the desirable further function and advantage, when occupied by the user, of providing an anchor for the backrest 12 from the weight of the individual sitting thereon. The eflect of this anchoring function is such that when the individual sitting on the It will also be noted that when the collapsible backi rest 12 is in the erected support position shown in FIG. 6 the strap 152 is always well above the terrain 40, thereby remaining in a position where it will inherently tend to remain clean and free of dirt at the

snap fastener components

158 and 160 to insure suitable condition for proper functioning.

Additionally it should be noted that tightening the strap 42 when the collapsible backrest 12 is in the erected support position shown in FIG. 6 helps to force the inner telescoping rods 92 and away from each other and against the outer edges of the upper elongated tubular formations 142 and 144 so as to maintain tensile loading on the top portion of the membrane 134, thereby providing a desirable firm, comfortable support for the user.

Also, it should be noted that when the backrest 12 is in the erected position shown in FIG. 6, the

spacer bar sections

64 and 68 are distal from and well out of reach of the back support membrane 134, so that at no time is there any contact of rigid metal against any portion of the human body being supported on the membrane 134. All support to the user's back comes from the flexible membrane 134 itself, thereby insuring maximum comfort and relaxation to the user.

This invention is not limited to the particular details of Construction and operation described, as equivalents will suggest themselves to those skilled in the art.

What is claimed is:

1. In a collapsible backrest, the c-ombination of a pair of channel members, each having two ends; an outer and inner telescoping rods in each `of the channel members with the outer of each of the telescoping rods mounted to pivot at one end of the respective channel member and the telescoping rods of one channel member having no direct rigid connection with the telescoping rods of the other channel member; a flexible membrane carried by the telescoping rods to form the sole direct connection between said rods .as well as the only support contact with the back of a user of said backrest; and a foldable cross 'bracing structure fixed to the channel members for holding the channel members distal from each other in support position when unfolcled and in snbstantial contact with each other when folded.

2. The combination as in claim 1 wherein the mernbrane includes a fold at each of its sides defining a tubular formation eircumscribing the respective telescoping rods with provision for receiving the inner telescoping r-od when extended axially of the outer telescoping rod, and releasable means in cooperative relation to the telescoping rods for holding the rods in extended position for theneby increasing the support length of the collapsible backrest.

3. The combination as in claim 2 having additionally a flexible strap with one end fixed to the top of membrane and fastening means on the strap for holding the backrest in a compact bundle formation in the collapsed positi on.

`4. The combination as in claim 1 wherein the cross bra cing structure includes a spacer bar comprised of two elongated sections fixed together at their extrernities to pivot with respect to each other and each section mounted at its opposite eXt-remity to pivot on the respective channel member, and an angularly disposed rigdizing member for each of the sections pivotally mounted on the respective section and the associated channel member for pro- 7 a' viding support to the spacer bar when the backrest is in the erected use position.

5. In .a collapsible backrest, the combination of a pair of elongated rigid support members, a pair of rods coupled in manner to provide extensibility of one with respect to the other, a pair of said extensible rods for each of said elongated support members pivotally mounted to the associated support member, the telescoping rods associated with one of said support members having no direct rigid connection with the telescoping rods associated with the other support member, a exible membrane having two sides fixed to the extensible rods to form the sole direct connection between said rods as well as the only support contact With the back of the user of said backrest, and a cross bracing structure fixed to the elongated .support members and having capacity 'for folding and unfolding in scissor-like action for thereby selectively holding the elongated support members and extensible rods separated the full width of the membrane in support position and in substantial contact With each other in the collapsed position.

6. The combination as in claim 5 having additionaly a ground support pad for each of the elongated support members pivotally mounted on the associated support member to ;Swing into ground supporting relation to the elongated support member When in the crected support position.

7. In a collapsible backrest, the combination of a pair of channel members, each having two ends and a guide slot; an outer and inner telescoping rods in each of the channel members with the outer of each of the telescop- :ing rods mounted to pivot at one end of the respective channel member; a fiexible mernbrane carried by the telescoping rods; and a foldable cross bracing structure fixed to the channel members for holding the channel members distal from each other in support position when untolded and in substantial contact with each other when folded, the cross bracing structure including a spacer bar comprised of two elongated sections fixed `together at gether extremities to pivot with respect to each other, each section being mounted at its opposite extremi ty to pivot on the respective channel member, an angularly disposed rigidizing member for each of the sections pivotally mounted on the respective section and having a follower slidably carried in said guide slot of the associated channel'member, and means for locking said follower in fixed position in said guide slot for providing support to the spacer 'bar when the backrest is in said untolded use position.

8. In a collapsible backrest, the combination of a pair of channel members, each having two cnds; an outer and inner telescoping rods in each of the channel members with -the outer of each of the telescoping rods mounted to pivot at one end of the respective channel member;

r a fiexible membrane carried by the telescoping rods; and

a foldable cross bracing structure fixed to the channel members for holding the channel members distal from each other in support position when untolded and in substantial contact with each other when folded, the cross bracing structure including a spacer 'bar comprised of two elongated sections fixed together at their ext remities to pivot with respect to each other, each section being mounted at its oppcsite extremity to pivot on the respective channel member, an angularly disposed rigidizing member for each of `the sections pivotally mcunt d on the respective :section and the associatecl channel member for providing support to the spacer bar when the CSI 8 backrcst is in said unfolded use position, and an elongatzed arm having two ends With one end mounted to pivot on one of the outer .telescoping rods and the other end adapted for attachment to selected positions on th corresponding channel for providing a selective angle of support for the backrest.

9. In a collapsible backrest, the combinaton of a pair of channel members, each having two ends; an outcr and inner telescoping rods in each of the channel members With the ou'ter of each of the telescoping rods mounted to pivot at one end of the respective channel member; a flexible membrane carried by the telescoping rods; and a foldable cross bracing structure fixed to the channel members for holding the channel members distal from each other in support* position when untolded and in substantial contact with each other when folded, the cross bracing structure including a spaced bar comprised of two elongated sections fixed together at their extremities to pivot with respect to each other, each section being mounted at its opposite extremity to pivot on the respective channel member, an angularly disposed rigidizing member for each of the sections pivotally mounted on the respective section and the associated channel member for providing support to the spacer bar when the backrest is in said unfolded use position; and a fiexible cord fixed to the channel members at positions distal from the spac-er bar and in opposed relation to the ends mounting the telescoping rods, and of a length tending to fulcrurn the channel members at the spacer bar to cause the extended inner telescoping rods 'to press outwardly against the membrane.

lt?. In a collapsible backrest, the combination of a pair of channel members, each having two enri s; an outer and inner telescoping rods in each of the channel members With the outer of each of the telescoping rods mounted to pivot at one end of the respective channel member; a eXible membrane carried by the telescoping rods; and a foldable cross bracing structure fixed to the channel members for holding the channel members distal from each other in support position When unfolded and in substant-ial contact With each other when folded, the cross brac ing structure including a spacer bar comprised of two elongated sections fixed together at their 'ext remities to pivot with respect to each other, each section being mounted at its opposite extrcmity to pivot on the respective channel member, an angularly disposed rigidzing member for each of the sections pivotally mounted on :the respective section and the associated channel member for providing support to the spacer bar when the backrest is in said -unfolded use position; and a second channel member pivot ally mounted to the other end of each of the first mentioned channel members with capacity to swing outwardly to provide area support on the terrain When the backrest is in the erected position and to Swing into the first mentioned channel member for compacting into the collapsed package position.

References Citcd by the Examiner UNITED STATES PATENTS %5,428 9/84 Covert 297-351 1,363,697 12/20 Vieira 297-351 FOREIGN PATENTS 80,679 3/56 Denmark.

:FRANK B. SHERRY, Pr'may Examner.

Claims

1. IN A COLLAPSIBLE BACKREST, THE COMBINATION OF A PAIR OF CHANNEL MEMBERS, EACH HAVING TWO ENDS; AN OUTER AND INNER TELESCOPIC RODS IN EACH OF THE CHANNEL MEMBERS WITH THE OUTER OF EACH OF THE TELESCOPING RODS MOUNTED TO PIVOT AT ONE END OF THE RESPECTIVE CHANNEL MEMBER AND THE TELESCOPIC RODS OF ONE CHANNEL MEMBER HAVING NO DIRECT RIGID CONNECTION WITH THE TELESCOPING RODS OF THE OTHER CHANNEL MEMBER; A FLEXIBLE MEMBRANE CARRIED BY THE TELESCOPING RODS TO FORM THE SOLE DIRECT CONNECTION BETWEEN SAID RODS AS WELL AS THE ONLY SUPPORT CONTACT WITH THE BACK OF A USER OF SAID BACKREST; AND A FOLDABLE CROSS BRACING STRUCTURE FIXED TO THE CHANNEL MEMBERS FOR HOLDING THE CHANNEL MEMBERS DISTAL FROM EACH OTHER IN