Abstract:
A wheelchair seatback assembly suitable for detachable mounting to the back-supporting posts of a wheelchair. The back assembly includes a relatively rigid shell member carrying post-engaging pins and a plurality of mounting clips attachable to wheelchair posts. At least selected ones of the mounting clips are further formed to releasably engage the post-engaging pins. The mounting units are also formed for single-handed automatic unlocking and release of the pair of hooks from the mounting units and posts upon rotation of the shell member forwardly over the wheelchair seat by an amount in excess of any displacement occurring during normal use of the wheelchair.

Description:
This application is a continuation-in-part of PCT/US01/45850 filed Nov. 1, 2001 which claims benefit from U.S. provisional application Ser. No. 60/245,074 filed Nov. 1, 2000. 

   FIELD OF THE INVENTION 
   The present invention relates to the fields of furnishings and cushions, and more particularly to the field of wheelchair seatbacks. The invention is particularly suited for use with collapsible wheelchairs wherein a rigid, yet easily removable seatback is desired. 
   BACKGROUND OF THE INVENTION 
   Many of the problems faced by wheelchair users are related to the positioning and ultimate posture of the seated user. Typical problems include progressive spinal deformations such as kyphosis, lordosis, and scoliosis. Poor posture and permanent spinal deformations can cause reduced function and mobility, fatigue, impaired respiration, impaired swallowing, and increased risk of sacreal, coccygeal, lumbar or thoracic tissue break down. Thus, it is very important for any wheelchair seatback system to provide for proper back angle adjustment and support because different users usually require a specifically tailored seat to back angle in order to optimize their own function and mobility. 
   An advantage of using rigid seatbacks as opposed to sling-type arrangements is that posture control is greatly enhanced. Thus, rigid seatbacks are generally preferred over sling-type seatbacks so that the user may achieve the most appropriate support for a given condition. Moreover, a rigid arrangement increases structural rigidity to the wheelchair, and provides a more effective force transmission element for active wheelchair users. 
   Another important object to any wheelchair seatback system not using a sling-type arrangement is that it be convenient to remove and install. Disabled users must frequently remove and install the wheelchair back and wheelchair cushion from the wheelchair in order to collapse the wheelchair for storage or transportation, and put it back together for use. This procedure, when performed independently by a user with impaired mobility, is often accomplished from the driver&#39;s side seat or passenger&#39;s side seat of an automobile. To collapse the wheelchair, the user must first reach out and remove the back. The wheelchair may then be collapsed and be placed in the desired location, such as the rear seat of the automobile. To re-assemble the wheelchair, the user will typically pull the collapsed chair from the rear seat of the car and unfold the chair at ground level next to the car. Once the frame is unfolded, the user must then reach out and attach the seatback onto the wheelchair. Both disassembly and assembly are usually accomplished mostly with one hand because the disabled user must maintain support with the other hand, normally by grasping the steering wheel. 
   The maneuver of reaching out from the car to attach or detach the wheelchair back can be difficult, particularly since most wheelchair users, especially quadriplegics, have impaired upper extremity function and compromised dexterity in their hands and, therefore, may experience great difficulties in manipulating heavy objects in a precise manner. Because of this, the degree of manipulation required of a particular wheelchair component, such as a seatback, will often determine whether or not it can even be used by a disabled individual. 
   Besides having the seatback system as simple and easy as possible to attach and detach, it is also beneficial to have it attachable and detachable by a user from in the front of the wheelchair. This is because a user having just transferred out of the wheelchair, or about to transfer into the wheelchair, will usually be positioned generally in front of the wheelchair. Accordingly, a simplified seatback mounting mechanism that enables the wheelchair user to swiftly attach or detach the back system to or from the wheelchair, especially from a position in front of the wheelchair, would greatly expand the usability of the seatback system to the disabled population. 
   Another problem facing wheelchair back systems has been the variability of each type of commercially available wheelchair. In particular, the vertical upright posts or canes often differ in configuration from one wheelchair to another. The nominal diameter of the posts may vary from ½″ to 1¼″. The center to center distances of the posts may vary ±½″ despite the typical designation by the wheelchair manufacturer that the chair is a nominal width to the nearest inch (i.e., an 18″ wide wheelchair may actually measure 17.6″ wide). These vertical posts may also not be parallel and indeed are designed to taper outward from bottom to top. All of these variations along with the metric size requirements offered by foreign wheelchair manufacturers demand either a custom made seatback system or a custom fit off-the-shelf seatback system with considerable adjustability through the available size ranges of wheelchairs. 
   Many prior art systems have dealt with the post (cane) dimension variability by maintaining a maximum and minimum width capability, which inherently results in a loose fit at the narrow end of the width limit. The loose fit may cause the seatback to shift from side to side or, in some cases, the outer margins of the seatback system overhang the width of the wheelchair and interfere with armrests and other peripheral features on the wheelchair. 
   Numerous attempts have been made to replace the conventional wheelchair upholstery sling back with a comfortable, sturdy, adjustable, supportive, pressure relieving, easy to use seatback system. However, prior art systems have generally failed to provide a suitable degree of adjustability, without loss of seat depth, in conjunction with a system that is easily attached or detached from the wheelchair and that is also capable of seatback angle adjustment with no loss of seat depth while the user is occupying the wheelchair. Available systems known to date have also failed to incorporate both the capability to adjust the seatback angle while the user is in the wheelchair and a removably attachable mounting system that does not alter the adjusted seatback angle each time the back system is removed from the wheelchair. Furthermore, the prior art seatback systems have generally failed to address the related problems of maintaining pelvic alignment while the back system is adjusted to the optimum seat to seatback angle. 
   SUMMARY OF THE INVENTION 
   The invention is directed to an adjustable and removable seatback system for use with any chair having four seatback mounting locations, but particularly with respect to such a seatback for use with a wheelchair having two vertical posts or canes. The present invention permits convenient, single-handed attachment or detachment of the seatback to and from a wheelchair without pre-release or actuation of latches or safety hooks. The invention also provides a seatback mounting system that securely self locks, but unlocks easily with a simple positive action by the user to release the back system from the wheelchair. In a preferred embodiment, the seatback can be conveniently released from its mountings by a simple forward rotational motion through a prescribed angle in conjunction with a lifting action. 
   Because of the high level of adjustibility inherent in a preferred embodiment, the invention permits a user to quickly modify the seatback tilt, anterior-posterior location, and height while the user is seated in the back system. Moreover, once established, the seatback position is maintained regardless of removal and reinstallation onto a wheelchair. 
   Further attributes of the invention include a high level of adaptability for use with various wheelchairs, vibration resistance, lightweight, modular design, and safety. 
   The seatback system comprises, in part, a rigid shell seatback having mounted thereto a first pair of laterally extending pin assemblies and a second pair of laterally extending pin assemblies where each pin assembly has an extending pin portion. The system also comprises a first pair of mounting clips and a second pair of mounting clips. The first pair of mounting clips selectively retains the first pair of pins while the second pair of mounting clips temporarily retains the second pair of pins so long as the first pair of extending pins is secured by the first pair of mounting clips. Alternatively, the second pair of mounting clips can be generally identical to the first pair of mounting clips, although ease of use of the invention may be compromised since user manipulation of the second pair of mounting clips would be necessary in addition to the first pair. 
   In a preferred embodiment, each laterally extending pin assembly comprises a pin bar having a bar and an orthogonally attached pin, as well as an “L” bracket wherein the “L” bracket is adjustably mounted (laterally) to the rigid shell seatback so that the invention can be used in conjunction with various wheelchair post spacings. Moreover, the pin bar is translationally mounted to the “L” bracket so that the anterior-posterior location of the seatback can be easily modified. Because a preferred embodiment uses asymmetrical pin bars (the pin is located at one end of the bar), it is further possible to reverse the orientation of the pin bar on the “L” bracket to further increase the adjustability of the seatback position. 
   The first pair of mounting clips are preferably self-locking and manually releasing, and are mounted to an upper portion of the wheelchair&#39;s vertical posts or canes. The second pair of mounting clips are preferably “U” shaped members mounted to a lower portion of a wheelchair&#39;s vertical posts or canes wherein the web portion of the “U” receives the pin. Alternatively, the location of the first pair and second pair of clips can be reversed without adverse effect to the operation of the invention. Moreover, an alternative arrangement reverses the mounting locations of the laterally extending pins and the mounting clips: the pins can be mounted either fixedly or adjustably to the posts or canes while the mounting clips (of either disclosed variety) can be mounted either fixedly or adjustably to the seatback. 
   A preferred embodiment also includes a cushion removably attached to the rigid shell seatback wherein the cushion preferably is of the self-inflating type and resides in a cover having one part of a two part mounting means affixed thereto. By affixing a second part of a two part mounting means to the rigid shell seatback, positive location and retention of the cushion to the seatback can be achieved. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view of the seatback system of the present invention; 
       FIG. 2  is a front elevation view of the shell that comprises a part of the seatback system; 
       FIG. 3  is a front elevation view of the cushion assembly wherein the cover is shown in partial cut-away; 
       FIG. 4  is a cross section view taken substantially along the line  4 — 4  of  FIG. 3  showing the relationship between the cushion core, bonded cover, and breathable outer cover; 
       FIG. 5  is a partial perspective view illustrating the “L” bracket of the seatback system; 
       FIG. 6  is a partial perspective view illustrating the “L” bracket of the seatback system from a different perspective; 
       FIG. 7  is a partial perspective view illustrating the “L” bracket of the seatback system from a different perspective; 
       FIG. 8  is a diagramatic matrix illustrating the various seatback configurations that are possible when manipulating the pin bar assembly on the “L” bracket; 
       FIG. 9  is a perspective view, in partial section, of the upper and lower mounting clips installed on a wheelchair post; 
       FIG. 10  is a cross section elevation of the upper mounting clip shown installed on a wheelchair post and in an “open” position; 
       FIG. 11  is similar to  FIG. 10 , except that the clip is shown in a “closed” position; 
       FIG. 12  is a perspective view of the seatback system as the seatback is being installed onto a wheelchair equipped with upper and lower mounting clips; 
       FIG. 13  is a perspective view of the seatback system as the seatback is being removed from a wheelchair equipped with upper and lower mounting clips; and 
       FIG. 14  is a perspective view of a mounting clip and resilient shim being installed on a post having a diameter less than the nominal diameter less than that of the mounting clip. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring then to the several Figures wherein like numerals indicate like parts, and more particularly to  FIGS. 1 ,  2  and  5 , the general components of the invention are shown. Seatback system  20  is intended to be mounted to a conventional wheelchair having a pair of vertical posts or canes  24   a  and  24   b.  Seatback system  20  comprises shell  30  to which are mounted L-brackets with pin bar assemblies  70   a,    70   b,    70   c,  and  70   d  (generally referred to as pin bar assemblies  70  unless otherwise indicated, as each assembly consists of identical components); upper mounting clips  90   a  and  90   b;  lower clips  140   c  and  140   d;  and cushion assembly  50 . All structural components are preferably manufactured from lightweight metals such as aluminum or alloys such as aluminum-magnesium, or high strength polymers such as acrylic-butadiene-styrene (ABS) resin. The composition of cushion assembly  50  will be described in detail below. 
   Beginning first with shell  30 , it is preferably a hard rigid matrix, which extends between wheelchair posts  24   a  and  24   b,  and provides mechanical support for seatback system  20 . In the preferred embodiment, shell  30  is formed from an aluminum alloy having a sectional thickness of about 50 to 100 mils. The overall width of shell  30  should not extend beyond the internal minimum width of posts  24   a  and  24   b  for the size range of wheelchairs that the particular seatback size is designed. It is desirable that the maximum width of shell  30  clear the inside of posts  24   a  and  24   b  so that shell  30  may be reclined there through. The preferred embodiment has five sections across the horizontal of the part: central portion  40 , first lateral portions  42   a  and  42   b,  and second lateral portions  44   a  and  44   b.  Central portion  40  may have a slight anterior concave curvature depending upon the intended application and design considerations. 
   First lateral portions  42   a  and  42   b  of shell  30  extend anteriorly and laterally to form an approximately 45 degree angle with central portion  40 . The profile of shell  30  is designed to fit either conventional folding wheelchairs, which typically have two or three upwardly extending tubular posts, or to fit a rigid non-folding wheelchair, which differs from the folding type in that a formed tubular structure (not shown) extends between the vertical posts for added stability. 
   First lateral portions  42   a  and  42   b  are generally flat and provide an excellent surface to mount pin bar assemblies  70 , as well as to provide support for cushion  52 . Lower mounting slots  32   c  and  32   d  are punched, milled or fabricated in first lateral portions  42   a  and  42   b  of shell  30  (about 10–40% from the bottom of the shell), as best shown in  FIG. 2 . This distance corresponds to a level equivalent to a seated user&#39;s preferred pelvic alignment control points (posterior iliac crests). Upper mounting slots  32   a  and  32   b  are punched in first lateral portions  42   a  and  42   b  of shell  30  (about 50–80% from the bottom of the shell). This distance provides sufficient structural support and balance to seatback system  20 . As will be described in more detail below, upper and lower pin bar assemblies  70  are semi-permanently, but adjustably, attached in their respective locations to shell  30  at these locations. Slots  32   a–d  allow for selected lateral placement and indexing of the pin bar assemblies along the range of the slotted holes. 
   Hand grip cut-out  34  is provided at the upper central portion of shell  30  to facilitate handling of seatback system  20  during removal or installation procedures. In addition, cut-out  34  provides a means whereby flap  48  of cover  62  may more securely engage shell  30  as will be described in more detail below. 
   Also present on the anterior surface of shell  30  are a plurality of fastening means for securely, but removably, attaching cushion assembly  50  to shell  30 . In this embodiment, a two part hook and loop fastening system is used. Thus, for example, sections of self-adhesive hook material  38  are disposed on shell  30  substantially as shown in  FIG. 2 . As will be seen, complementary loop material is fixedly attached to the posterior portion of cushion assembly  50  whereby the position of cushion assembly  50  is relatively fixed to shell  30  upon engagement of the hook and loop sections. 
   Finally, potentially exposed peripheral edges of shell  30  are preferably fitted with a rubber-like polymer material piping  36  (with internal metal pieces offering reinforcement). 
   Cushion assembly  50 , which is best illustrated in  FIGS. 3 and 4 , comprises self-inflating cushion  52  and cover  62 . Cushion assembly  50  provides the wheelchair user increased positioning control because of the contour which partially envelopes a seated user&#39;s back. Cushion assembly  50 &#39;s contour is rigidly supported by all anterior portions of shell  30  (central portion  40 , first lateral portions  42   a  and  42   b,  and second lateral portions  44   a  and  44   b ), although a certain level of self-contour is inherent in cushion  52 . 
   Cushion  52  is preferably fabricated according to the methods disclosed in U.S. Pat. No. 5,282,286, the disclosure of which is incorporated herein by reference. The height of cushion  52  may be approximately the same as shell  30 , with a small extension to provide overlap of the shell perimeter. The posterior of cushion  52  has essentially the same profile as shell  30 , except that it preferably extends laterally beyond second lateral portions  44   a  and  44   b  so as to minimize user contact with the shell perimeter. The anterior face of cushion  52  is specifically contoured to provide a suitable level of positioning and support to a seated user. In the present embodiment, the anterior surface has several vertically spaced segments generally corresponding to the anterior portions of shell  30  that are defined in part by vertical grooves  56 . 
   A feature of cushion  52  is that it has a pre-established curvature. This curvature approximates the curvature of shell  30  and is accomplished by creating a curved foam core blank to which the coated fabric is bonded. Moreover, while both the anterior and posterior fabric panels are of generally equal area and the two panels are bonded together at their common perimeter, the anterior fabric must occupy vertical grooves  56  of cushion  52 . Consequently, when the anterior panel is bonded to the foam core, the perimeter portions thereof are urged towards a point central and above the anterior surface, thereby creating an anteriorly concave profile in cushion  52 . 
   Cover  62  is constructed from a breathable fabric material and removably envelops cushion  52 . In addition to protecting cushion  52  from the elements and user damage, cover  62  has attached thereto loop material  68 , which permits location of cushion assembly  50  on shell  30 . Flap  48 , which also has a portion of loop material  68  thereon, is insertable from the posterior side of shell  30  through hole  34 , over and above the upper perimeter portion of shell  30 . It engages hook material  38  on the posterior surface of shell  30  to provided for a secure fastening means that will prevent vertical movement of cushion assembly  50  on shell  30 . 
   On the anterior surface of cover  62  is highly breathable fabric panel  64 . The location of panel  64  generally corresponds to the location of a user&#39;s back when engaging seatback system  20 . Because this is a high moisture area during use, the interior surface of panel  64  has bonded thereto a reticulated foam section that provides mechanical support of cover  62  from cushion  52  while ensuring sufficient ventilation properties. Moreover, because the reticulated foam is formed from expanded polymer resin, it also operates as a flame retardant barrier, thus providing greater flame resistance to cushion  52 , which preferably is constructed in major part from urethane foam, a flammable material. 
   Turning now to  FIGS. 1 ,  2  and  5 – 10 , the wheelchair engaging components of seatback system  20  will now be presented. As previously described, shell  30  has four slots  32   a–d  formed therein for receiving pin bar assemblies  70 . Pin bar assemblies  70  each comprise pin bars  72  and “L” bracket  82 . While all pin bars  72  and brackets  82  are identical to each other, each pin bar assembly  70  is arranged to have a mirror image of each other viz a viz the sagittal plane with assembled on shell  30 . Screws  84  and collar nuts  86  function to secure each bracket  82  to shell  30 , and screws  88  function to secure each pin bar  72  to bracket  82 . Brackets  82  function to permit lateral adjustment of pin bars  72  to accommodate variations in the distance between posts  24   a  and  24   b,  while slot  76  of each pin bar  72  functions to permit anterior-posterior adjustment of shell  30  relative to the wheelchair as shown in  FIGS. 5–8 . Moreover, by rotating any pin bar  72  180°, further shell adjustment can be achieved as again specifically shown in  FIG. 8 . Detents  78  in each slot  76  function to positively index a position of pin bar  72  relative to bracket  82  so that symmetry between each pin bar assembly pair and/or between pairs is easily maintained. In all instances, screws  84  and  88  include a thread locking device or compound to resist unintentional disengagement due to vibration and the like. 
   Each pin bar  72  as previously described has bar portion  74  and extending pin portion  80 . Bar portion defines slot  76  and pin portion  80  extends orthogonally from bar portion  74 . Because pin portion  80  is located at one end of bar portion  74 , inherent asymmetry permits a great latitude of mounting possibilities on bracket  82  as best shown again in  FIG. 8 . 
   Pin portion  80  is sized to fit within the confines of either mounting clip  90  or mounting clip  140 . As illustrated in FIGS.  9 , 10  and  11 , mounting clip  90  includes vertical post clamp portion  92 , bracket portion  94 , rotatable cam body  102 , and pawl  116 . Other components include spring  132 , retainer  100 , ball extension  130 , and shafts  134 . Cam body  102  defines major recess  106 , minor recess  108 , groove  110 , and includes peripheral surface  112  as well as portion  114 . Pawl  116  has exposed portion  118 , fork portion  120 , which includes a fork-like structure having major finger  122  and minor finger  124 , spring locator  128 , and ball extension  130 . 
   Mounting clip  90  functions to releasably hold pin portion  80  therein when inserted into slot  98  of bracket portion  94  and major recess  106  of cam body  102  as is best shown in  FIG. 10 . Prior to insertion, major finger  122  rests in groove  110 . The light pressure created by spring  132  on pawl  116  prevents unintended rotation of cam  102  due to the position of major finger  132 . Upon insertion of pin bar  72  into slot  98  and major recess  106 , cam body  102  rotates until major finger  122  engages minor recess  108  of cam body  102 . Spring  132  again operates to create light pressure of fork portion  120  on cam body  102 , thereby preventing rotation of cam body  102 . Upon pressing exposed portion  118  of pawl  116  towards post  24 , major finger  122  disengages from minor recess  108 . 
   So as to eliminate constant user pressure on exposed portion  118  to overcome the extension bias of spring  132 , ball extension  130  engages receiver  100  when exposed portion  118  is fully depressed (not shown). However, this state is not conducive to permitting major finger  122  to locate in groove  110 . Therefore, when cycling from the engaged state shown in  FIG. 11  to the receiving state shown in  FIG. 10 , extension  114  of cam body  102  momentarily contacts minor finger  124 . This causes dislocation of ball extension  130  from receiver  100  at a point during cam rotation that is after dislocation of major finger  122  from minor recess  108 . From that point until the completion of pin removal, major finger  122  rides peripheral surface  112  until locating in groove  110  (see  FIG. 10 ). 
   In contrast to the active engagement of mounting clip  90 , mounting clip  140  functions to provide a captive perch for pin portion  80 , as best shown in  FIGS. 12  and  13 . Pin portion  80  is restrained from anterior and posterior movement by way of post  24  and extension  46 , and is restrained from downward movement by recess  148 . Upward movement of pin portion  80  is restrained only when pin bar  72  is positively retained in mounting clip  90 . Otherwise, as illustrated in  FIGS. 12 and 13 , a pin bar assembly is free to move upwardly and thus release shell  30  from the wheelchair. 
   In order to accommodate the attachment of mounting clips  90  and  140  to posts of varying diameters, shims  150  are provided. Referencing  FIG. 14 , each shim  150  is preferably formed from a compliant polymer resin material, and is insertable between clamp portion  92  or  142  and a post  24 . Either with or without shims  150 , each mounting clip  90  and  140  is compressively retained to a post. A thread locking device or compound is preferably used so as to prevent unintentional loosening of a mounting clip.