Background of the Invention
[0001] Special needs of wheelchair users dictate an unending variety of alterations to a
basic wheelchair structure. Unfortunately, virtually all improvements for making
a wheelchair more adaptable are limited to just one or two components. For example,
U.S. Patent No.s 3,815,586 and 4,073,537 describe universally adjustable body support
pads. The pads are connected to a fixed non-adjustable wheelchair framework. U.S.
Patent No. 4,592,570 describes a seat frame which is adjustably attached to a fixed
main frame. The frame itself cannot be altered. U.S. Patent No. 4,595,212 sets forth
a fixed side frame having means for adjustable connection with wheel assemblies. Again,
adjustment of the sideframe is not possible.
[0002] Adding to the difficulty of providing adjustability to wheelchair components, is
the desire to make the chair collapsible. This entails more complicated mechanisms,
more cost and more weight. It severely limits the overall adaptability of present
day wheelchairs.
Summary of the Invention
[0003] A wheelchair is provided having a framework comprising opposing sideframe structures
which can be geometrically varied as desired. The sideframes may be adjustably spaced-apart
by a folding assembly. The sideframes comprise individual frame sections having track
means that is utilized in forming a wide variety of structrural and supplemental connections.
Link and attachment means are used to adjustably interconnect the frame sections
to create a stable lightweight framework.
Brief Description of the Drawings
[0004]
Fig. 1 is a perspective view of a wheelchair constructed in accordance with the present
invention with the seat, backrest and drive wheels shown in phantom.
Fig. 2 is a side elevational view of the wheelchair shown in Fig. 1.
Fig. 3 is a front elevational view taken along lines 3-3 of Fig. 2.
Fig. 4 is an enlarged fragmentary cross-sectional view taken along lines 4-4 of Fig.
2.
Fig. 5 is an enlarged fragmentary cross-sectional view taken along lines 5-5 of Fig.
2.
Fig. 6 is an enlarged fragmentary cross-sectional view taken along lines 6-6 of Fig.
2.
Fig. 7 is an enlarged fragmentary cross-sectional view taken along lines 7-7 of Fig.
2.
Fig. 8 is an enlarged fragmentary cross-sectional view taken along lines 8-8 of Fig.
2.
Fig. 9 is an enlarged fragmentary cross-sectional view taken along lines 9-9 of Fig.
2.
Fig. 10 is an enlarged fragmentary cross-sectional view taken along lines 10-10 of
Fig. 2.
Fig. 11 is an enlarged fragmentary cross-sectional view taken along lines 11-11 of
Fig. 2.
Fig. 12 is a side elevational view showing the side-frame of Fig. 1 without auxiliary
attachments.
Fig. 13 is a side elevational view showing the side-frame of Fig. 12 in a different
configuration and without the lower frame section.
Fig. 14 is a side elevational view showing the side-frame of Fig. 13 in an open configuration.
Description of the Preferred Embodiments
[0005] With reference to Figs. 1-3 of the drawings, a comprehensive wheelchair design is
shown incorporating the unique features of the present invention. The basic wheelchair
framework comprises two generally parallel spaced-apart sideframes 12,14 which are
usually configured to be mirror-images of each other. Although the sideframes may
be fixed in a spaced-apart relationship by conventional cross-pieces (not shown),
they are preferably movable together by a folding assembly 16.
[0006] With particular reference to Figs. 12-14, each side-frame comprises a base section
20 and at least three discrete frame bar sections shown as upright section 21, upper
section 22 and front section 23. The bar sections consist of linear structural elements
preferably of lightweight extruded aluminum, aluminum alloy or composite plastic.
Each section includes a track means which, as shown, comprises an undercut slot 24
extending laterally along at least one, and preferably two opposing bar section sides.
[0007] Most conveniently, the slots extend throughout the length of the inner face 38 and
outer face 39 of each bar section. Each slot has a cross-sectional shape corresponding
to the outline of a slidable fastener 25 which is retained therein. As best shown
in Figs. 4-8, the slots have a T-shaped cross-section and the slidable fasteners comprise
a conventional nut having a threaded accessible through said slot.
[0008] As will be hereinafter apparent, the number of slidable fasteners contained in each
track means will be dictated by bar section connections and the requirements of supplemental
engagement means. Further, it will be appreciated that track means may include slotted
strips or sliding bolt means and the like, secured to one or more of the bar section
faces.
[0009] Base section 20 comprises an elongated part 28 secured to a transversly extending
leg part 29. Each part has an outer end that includes attachment for connection with
a frame bar section. The attachment means comprises an outer bar opening 30 at the
outer end of elongated part 28 including upper opening 31 and lower opening 32 at
the opposing ends of leg part 29. An end of a frame bar section is inserted into
a selected opening and adjusted longitudinally as desired. End fasteners 33 extend
transversly through the outer end walls and engage corresponding fasteners 25 in
the bar section slots to secure the bar sections in place.
[0010] Preferably, the base section comprises straight hollow structural parts having quadrilateral
cross-sections corresponding to, and slightly larger than, the quadrilateral cross-sectional
shape of the frame bar sections. In this way, the bar sections can telescope into
the base section openings and be readily adjusted longitudinally. It is also preferred
to have leg part 29 extend about perpendicularly across the back end of the elongated
part. In this manner, a fixed angular corner A will be formed to provide a strong
foundation for the overall sideframe structure.
[0011] In the Figs. 1-12 embodiment of the sideframes, upright section 21 extends upwardly
from opening 31 and a lower bar section 26 extends downwardly from the lower bar opening
32. The longitudinal axis of both sections and the leg part are coextensive forming
a straight backside to the sideframe. Note that the upright and lower sections have
identical cross-sectional shapes and, in fact, the lower section 26 may simply be
a continuation of upright section 21 that extends through leg part 29. Be aware also
that use of the lower section is optional and it functions primarily to secure the
lower end of a brace means in a manner to be hereinafter described.
[0012] Telescoping out from bar opening 30 is optional bottom frame bar section 27. This
bar section serves as a linearly adjustable extension of elongated part 28. Its'
construction is the same as the lower and front bar sections. It includes slots 24
and slidable fasteners 25 which serve to adjustably secure it to opening 30 with end
fasteners 33.
[0013] The outer end of the bottom section is joined to front section 23 by a link means
35. Although various types of H brackets, yoke bars, clamps and braces could be used
for the link means, the preferred means is shown as connector elements 36 with link
fasteners 37. The connector elements are flat generally rectangular plates having
spaced-apart orifices through which the link fasteners extend. The link fasteners
preferably comprise bolts which are threaded to engage the female threads of the slidable
fasteners. Of course, other types of link fasteners could be used as dictated by the
particular link means and track means being utilized such that the invention should
not be limited by any specific fastening system.
[0014] The link fastener orifices are arranged to include at least two at a securement end
portion of each connector element and one at an opposing pivot end portion thereof.
As so arranged, link fasteners extending through the securement end orifices into
engagement with the respective slidable fasteners, will serve mainly to firmly fix
the element to the end of a bar section. However, the link fastener extending through
the pivot end orifice into engagement with a slidable fastener on the adjacent connecting
bar section, will function as a pivot until tightened. Thus, an angularly adjustable
joint is formed between the connecting bar sections. Further, the joint will be longitudinally
adjustable as a result of the slidable fastener on the adjacent bar section. Still
further, the connector elements can be reversed for allowing either bar section to
be pivotable.
[0015] With reference back to the connection of bottom section 27 to front section 23, a
connector element is secured to the bottom section outer end with two securement end
link fasteners 37. A pivot end fastener 37′ extends through the pivot end orifice
and engages a slide fastener from front section 23. Before the fasteners are tightened,
the angle B between the bottom and front sections can be varied as desired. Also,
the front section can be moved longitudinally relative to the bottom section outer
end. Clearly, this allows for unlimited variety in size and geometric arrangement
of each sideframe structure. Further, note that to strengthen the joints, the link
means may be used, as shown, on both the inner and outer bar section faces.
[0016] In a similar fashion, angular and longitudinal adjustable link fastener joints can
be formed with upper section 22 at the upper ends of front section 23 and upright
section 21. As shown, the securement portion of each connector element is secured
to the bar section upper ends. The pivot link fasteners 37′ engage respective slidable
fasteners at opposing ends of the upper bar section. Angle C between the front and
upper bar sections and angle D between the upright and upper bar sections can be varied
in the same manner as angle B. All three angles will also vary in accordance with
the desired spacing between joints on the upper section and front section and, per
the amount the bottom section and upright sections extend from the base section parts.
[0017] In the Fig. 13 embodiment, lower section 26 and bottom section 27 are omitted. The
front section 23 is rotated inwardly forming an acute angle C and is attached to
the elongated part 28. As shown, the securement portion of the connector elements
are fixed to the outer end of part 28 and to the upper end of front section 23. This
permits securement anywhere along the longitudinal extent of the front section. The
sideframe configuration of Fig. 13 may be appropriate where leg support is not required
or where obstructions at the wheelchair front must be minimized for desk or counter
work.
[0018] Fig. 14 illustrates the basic sideframe construction of Fig. 13 in an open configuration.
Here, the front section inclines outwardly from its' upper end forming an obtuse
angle C without connection to elongated part 28. This embodiment provides an ultra
lightweight structure suitable for use by children or in sport applications.
[0019] It should be noted that upper bar sections 22 have a greater cross-sectional area
than the front, bottom, upright and lower bar sections which, otherwise preferably
have identical cross-sections. The increased area allows for the addition of a set
keyway 34 on inner faces 38. The seat keyway extends throughout the length of the
upper bar section and includes an enlarged inner area 84. The enlarged area provides
a means for retaining the expanded side edges 87 of seat 85.
[0020] With reference to Figs. 5 and 6, seat 85 preferably comprises a durable pliable material
that spans the area between opposing upper bar sections. A seat engagement means is
provided whereby the material is folded 180° to form the opposing edges 87, 87 and,
retainer rods 86 are inserted between the folds to expand the edges. The edges are
then guided simultaneously into respective open ends of the seat keyways on each upper
bar section. Free ends of the edge folds (not shown) may be secured by hemming or
be drawn together by lacing or the like.
[0021] Since the seat material is pliable, such as with canvas, leather or reinforced Nylon
fabric, it will flex and crease along its' midportion when the sideframes are drawn
together into a wheelchair closed position. It will be appreciated, however, that
if the wheelchair is non-collapsing, a rigid seat with engagement edges could be
used in place of the pliable seat material.
[0022] For heavy duty wheelchair applications, it may be desirable to strengthen the sideframe
structures with brace means 40 as shown in the Figs. 1-12 embodiment. The brace means
may comprise an elongated member that connects upper section 22 with base section
20 or lower section 26. Most basically, it may simply consist of a shaft conventionally
secured to the aforesaid sections. However, it is preferable that the brace means
include means to accomodate the variable geometry of the sideframe. To this end,
universal joint means are used to connect the brace to the frame sections at varying
angular adjustments. Longitudinal adjustment means may also be used to vary the brace
length and facilitate attachment along the length of a frame bar section.
[0023] With particular reference to Figs. 2, 3, 6, 8 and 11, the brace means includes an
elongated hollow brace member 41 having opposing upper and lower open ends. The lower
end is provided with a stationary plug 42 which is secured therein by pin 43. Attached
to the outer end of the plug is a lower universal joint assembly 44. This includes
a ball fastener 45 having a ball end and a shaft end which is threadably engaged to
the plug end. Surrounding the ball end and forming a universal joint therewith is
annular joint fastener 46. The joint fastener includes a threaded portion that extends
through base section orifices and engages corresponding threads in a lower bar section
slidable fastener. A set nut and washer assembly 47 inhibits loosening of the fasteners.
[0024] The upper open end of brace member 41 contains longitudinal adjustment means which,
as shown, comprises sliding shaft 50. The shaft includes orifices 51 that are axially
spaced-apart and correspond to brace member orifices 52. A releasable pin 53 engages
selected aligned orifices of the shaft and brace member in accordance with the desired
axial extent of the plug (and overall brace length).
[0025] In the same manner as with stationary plug 44, an upper universal joint assembly
54 is attached to the end of sliding shaft 50. The upper assembly includes a ball
fastener 45 secured to the end of shaft 50. A joint fastener 46 forms a universal
joint with the ball fastener. However, the threaded end of the joint fastener is secured
to a joint block 56. The block facilitates a strong connection with upper section
22 and includes upper fasteners 57. The upper fasteners engage upper section slidable
fasteners to secure the upper end of the brace means to the desired position along
the upper section slot 24.
[0026] In some wheelchair applications, it may be desirable to move the upper assembly forward.
Alternately, the sideframe height or width may be increased which, in turn, alters
the variable corner angles B, C and D. In all of the above cases, simple adjustment
of the brace means length will be all that is needed for disposing the brace means
in the most suitable alignment. This is because the universal joint connections permit
automatic angular movement at the point of connection. Consequently, the sideframe
of the invention is provided with an effective strengthening means which does not
at all detract from the sideframe's ability to change configuration.
[0027] The folding assembly 16 of the invention is most conveniently attached to opposing
sideframes via the above-described brace means. This eliminates additional multiple
connections to the appropriate frame sections, saves cost, minimizes weight and prevents
interference with sideframe adjustability. The assembly includes at least one pair
of hinged spacer bars having lateral adjustment means for varying the distance between
sideframes.
[0028] With reference to Figs. 1-3, 10 and 11, an illustrative folding assembly is shown
comprising a pair of upper spacer bars 60,61 and lower spacer bars 62,63. Each pair
includes overlapping inner end portions having aligned openings through which a pivot
shaft 64 extends. The shaft is secured by nut 65. The outer ends of each bar are
secured to respective opposing brace members 41. The bar connections to each brace
member preferably occur adjacent to the ends of the member. In this way, greater leverage
occurs to pivot the assembly and move the sideframes in and out. Also, as a result
of the bars being connected at spaced-apart locations on the brace member, a stronger
more stable alignment occurs between the opposing sideframes.
[0029] The pivot shaft openings 66 are located at the inner end of outer bars 60,62 and
at a location inwardly offset from the end of inner bars 61,63. The offset portions
of the inner bars from locking arms 68. The arms swing beneath overlapping inner end
portions of outer bars 60,62 when the bars are in straight alignment corresponding
to a wheelchair open position. To secure the bars in straight alignment, the locking
arms are provided with a lock pin 67 which is biased outwardly by spring 71 into corresponding
lock openings 72 on the inner faces of outer bars 60,62. Lock ring 70 is pulled to
withdraw the lock pin and permit the bars to pivot toward each other. This action
results in the sideframes being drawn toward each other and disposes the wheelchair
in a closed inoperative position.
[0030] The folding assembly lateral adjustment means comprises corresponding openings 66
which are spaced-apart at predetermined locations along the length of each bar. The
desired spacing between sideframes can thereby be varied by inserting pivot shaft
64 through openings aligned in correspondence to the desired spacing. In such case,
the amount of bar overlap will vary accordingly. Therefore, equally spaced-apart lock
openings will be required to allow entry of the lock pin to secure the bars in straight
alignment.
[0031] To enhance lateral stability of the wheelchair when in an open position, the folding
assembly can include strut means to interconnect a spacer bar to an opposing sideframe.
In Figs. 1-3 and 10, crossing strut members 75,76 are shown connecting upper spacer
bars with respective sideframe base sections. Ball joint means are used for end connections
to allow unrestricted angular movement of the strut members with the spacer bars.
[0032] With particular reference to Figs. 3,10 and 11, the upper end of strut member 75
is connected to upper spacer bar 61 by upper ball joint means 77. The ball joint means
includes a round head and ball fastener 78 that threadably engages strut opening 79
of the spacer bar. Ball ring 80 conformally engages the round head and includes a
ring fastener 81 that extends axially by threaded engagement into the outer end of
the strut member.
[0033] The lower end of strut member 75 is shown as connected with the outer end of elongated
part 28 on the sideframe which is opposite of spacer bar 61. If desired, the lower
connection could be to the adjacent bottom section 27. In the lower connection, the
ball joint means is the same as in the upper connection. However, ball fastener 78
engages a strut block 82. The strut block, in turn, includes strut fasteners 83 which
engage the slidable fasteners contained in bottom section 27.
[0034] Use of the strut block provides a stronger connection and allows movement of the
lower connection onto and along the bottom frame section. In this regard, the upper
spacer bars include additional strut openings 79 and, the strut member length can
be varied by rotation of the threaded ring fasteners. It will be further appreciated
that all of the above discussion applies equally to strut member 76. The only exception
is that the upper end of strut member 76 is attached to spacer bar 60 and the lower
end is connected to part 28 on the sideframe opposite spacer bar 60.
[0035] The wheelchair backrest means will now be described which demonstrates some of the
unique advantages of the novel sideframe structure. The backrest means includes a
pair of upstanding backrest frame bars 90,91 each joined to a respective upper bar
section 22 by backrest link means. The cross-sectional shape of the backrest frame
bars and upper bar sections are substantially identical. Therefore, the backrest link
means can include connector elements 36 with link fasteners 37 and pivot end fasteners
37′.
[0036] As best shown in Figs. 1 and 2, connector elements 36 are positioned at opposing
sides of the lower end of each backrest frame bar. Link fasteners 37 engage corresponding
slidable fasteners contained within slots 24 in the same manner as with the sideframe
bar sections. The pivot portion of each connector element extends beyond the end of
the backrest bar and overlies respective inner and outer faces of the upper bar section.
Pivot link fasteners are then used to engage corresponding slidable fasteners in the
upper bar section slots.
[0037] To strengthen the backrest joints, the backrest link means may include an angle bar
93. The upper end of each angle bar is positioned to overlie the upper end of an outer
face connector element. It is then secured, along with the connector element by a
link fastener common to both. The angle bar lower end includes a pivot fastener 37′
that engages a corresponding slidable fastener in the upper bar section slot. With
the above arrangement, it can be seen that the backrest bars may be readily moved
longitudinally along the upper bar sections. They can also be tilted as desired to
vary angle E with the upper section.
[0038] To provide upper backrest support, a pair of hinged support arms 95,96 are used to
interconnect with opposing upper portions of the backrest bars. The arms are hinged
at inner ends by support pin 97. The arms include a lock means to releasably maintain
an open colinear position. The lock means comprises hook 98 at an extended portion
of arm 95 that engages a hook pin 99 projecting from arm 96 when the arms are in longitudinal
alignment.
[0039] The opposing outer end of each support arm is hinged to a respective arm block 101,102.
Each block is provided with arm fasteners 103 that engage slidable fasteners in the
backrest bars. This connection allows adjustment and movement of the support arms
up and down the backrest bars.
[0040] In the same same way as with the upper bar section seat keyways, the backrest bars
include backrest keyways 104. A back support structure 105, shown in phantom in Figs.
1 and 3, includes enlarged opposing side edges which slide into the keyways at the
open end of each backrest bar. The back support structure can be rigid as with a non-collapsing
wheelchair, or it can be flexible such as with the seat material.
[0041] Conventional wheelchair drive wheels 107 (depicted in phantom in Figs. 1 and 3) are
secured to the elongated part 28 of respective opposing base sections. The extended
axle 109 of each drive wheel extends through an opening 110 in axle plate 111 and
is fixed thereto by axle nut 112. Plate fasteners 113, that extend through clamp plate
114 and threadably engage the axle plate, draw the plates against opposing sides of
the elongated part. This clamping action secures the wheels in place. It also permits
adjustment of wheel location anywhere along the length of the elongated part.
[0042] To exemplify the advantages of the invention, it will be appreciated that attachment
of adjunct wheelchair assemblies (such as footrests, casters, armrests, handles and
body support pads), can all be accomplished with supplemental connector means in
conjunction with the slidable fasteners of the novel frame bar sections. Use of the
above, in cooperating relation with frame bar track means, allows all supplemental
connections to be semi-permanent and adjustable. This feature together with the infinitely
variable sideframe geometry, makes it possible for a single wheelchair to be adaptable
for an endless variety of special needs and uses.
[0043] To illustrate the above, note conventional caster assemblies 114 which are secured
to the forward portion of bottom bar section 27 by a caster block means. Such means
provides a supplemental connector junction whereby a caster assembly is connected
to castor block 115. The block, in turn, includes block fasteners 116 which engage
slidable fasteners in the bottom bar section. The combined assembly can be moved,
as desired, anywhere along lateral slot 24.
[0044] Similarly, handles 118 are joined to the upper portion of respective backrest bars
by supplemental means comprising a handle connector block 119. The block is split
to frictionally engage the tubular handle base. Threaded handle fasteners 120 tighten
the block to the handle. The fasteners also engage corresponding slidable fasteners
in the backrest bars.
[0045] In a similar fashion, supplemental connector means, shown as footrest block 122 with
fasteners 123, interconnect footrest plates 124 to slidable fasteners in front bar
section 23. Even more simply, a toggle brake assembly 126 includes brake fasteners
127 which pivotally connect brake arms directly to the upper bar section via engagement
with corresponding slidable fasteners.
[0046] In more detailed manner, armrests 130 are joined by a supplemental armrest mounting
means to respective backrest bars 90,91. The mounting means includes a split block
131 securing a transverse shaft 132. The shaft rotatably supports the handle by engagement
with housing 133 at the handle base. Peg 134 extends from the shaft into the slot
and impinges the slot end to limit, in a predetermined manner, up and down rotation
of the handle. The split block 131 includes armrest fasteners 135 which engage corresponding
slidable fasteners in the backrest bars.
[0047] While the invention has been described with respect to preferred embodiments, it
will be apparent to those skilled in the art that various modifications and improvements
may be made without departing from the scope and spirit of the invention. Accordingly,
it is to be understood that the invention is not to be limited by the specific illustrative
embodiments, but only by the scope of the appended claims.
1. A wheelchair having a seat, backrest and wheels, and characterized by:
opposing adjustable sideframes supporting said seat, backrest and wheels, each sideframe
comprising a base section having an elongated part with an outwardly extending leg
part; and.
frame bars adjustably connected to each other by link means and to said parts to form
a support structure, said frame bars having slots which contain slidable bar fasteners.
2. The wheelchair of claim 1 wherein said link means comprises connector elements
with link fasteners for engagement with said bar fasteners.
3. The wheelchair of claims 1 or 2 including attachment means for connecting a frame
bar to each base section part.
4. The wheelchair of claim 2 wherein said frame bars have a quadrilateral cross-sectional
shape and said slots extend longitudinally along opposing sides of said bars.
5. The wheelchair of any one of the preceding claims wherein said frame bars include
an upright section, an upper section, a front section and a bottom section; said upright
section extending upwardly from said leg part to the upper section, said upper section
extending from said upright section to the front section, said front section extending
from said upper section to the bottom section, said bottom section extending from
said front section to the elongated part.
6. The wheelchair of claim 5 wherein said frame bars include a lower section extending
downwardly from said leg part and including a brace means connecting said upper section
to said base section or said lower section.
7. The wheelchair of any one of the preceding claims wherein said opposing sideframes
are interconnected by a folding assembly.
8. The wheelchair of claim 5 wherein said folding assembly includes lateral adjustment
means for varying the spacing between opposing sideframes.
9. The wheelchair of claim 7 including brace means interconnecting at least two of
said frame bars on a sideframe.
10. The wheelchair of claim 9 wherein said folding assembly includes pivoted spacer
bars having opposing outer ends secured to a respective sideframe brace means.
11. The wheelchair of claim 10 wherein said folding assembly includes strut means
connecting a sideframe to a spacer bar.
12. The wheelchair of claims 10 or 11 wherein said upper section is provided with
a seat keyway and said seat has opposing side edge seat engagement means for retention
by said seat keyway.
13. The wheelchair of claims 10 or 11 wherein said backrest comprises a pair of backrest
frame bars each having a backrest keyway and each being connected to a respective
sideframe upper section and, a back support structure having opposing side edge back
engagement means for retention by said backrest keyway.
14. The wheelchair of claim 13 wherein said backrest frame bars include lateral slots
which contain slidable bar fasteners and each of said backrest frame bars are connected
to a respective sideframe upper section by backrest link means that include link fasteners
that engage said slidable bar fasteners.
15. A wheelchair having a seat, backrest and wheels supported by a framework, and
characterised by:
opposing spaced-apart sideframes constructed of a base section and frame bar sections,
said sections assembled to form at least a three-cornered structure having a fixed
angular corner with at least two angularly adjustable corners and including at least
three longitudinally adjustable sides.
16. A framework for a wheelchair, the framework supporting a seat, backrest and wheels
and characterized by:
opposing sideframes each comprising at least three discrete linear frame bar sections
adjustably joined together in a selected angular and longitudinal orientation and,
a base section having an elongated part and a leg part connected to at least one of
said frame bar sections.
17. The framework for a wheelchair of claim 16 wherein said frame bar sections include
track means having slidable fasteners; and, link means jointing together said frame
bar sections having link fasteners for engagement with said slidable fasteners.
18. A wheelchair framework constructed in part by an assembly of discrete linear frame
bar sections interconnected by longitudinal and angular adjustable joints.
19. The framework of claim 18 wherein said frame bar sections include track means
having slidable fasteners.
20. The framework of claim 19 wherein said joints are formed with link means having
link fasteners that engage corresponding slidable fasteners in said track means.