Abstract:
A portable, detachable desk or table extension is disclosed for use by a person in a wheelchair that may be vertically and angularly adjusted to an optimum height and position for use. The extension has a portable work surface or platform that extends out, away from, and above the surface of the desk or table to which it is attached, so that a user in a wheel chair may pull up to and under it and not be blocked or hindered by the table or desk underneath. The elevation as well as the angle of tilt of the platform may be adjusted for optimum positioning so that the user in a wheelchair may pull up close to and under it. The extension clamps to the table via a pair of vertical supports that collapse down onto the platform for storage.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of copending application Ser. No. 11/221,465, filed on Sep. 7, 2005, incorporated herein by reference in its entirety, which claims priority from U.S. provisional application Ser. No. 60/609,061 filed on Sep. 9, 2004, incorporated herein by reference in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     Not Applicable 
     NOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTION 
     A portion of the material in this patent document is subject to copyright protection under the copyright laws of the United States and of other countries. The owner of the copyright rights has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office publicly available file or records, but otherwise reserves all copyright rights whatsoever. The copyright owner does not hereby waive any of its rights to have this patent document maintained in secrecy, including without limitation its rights pursuant to 37 C.F.R. §1.14. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains generally to portable work surfaces, and more particularly to portable work surfaces for use by physically impaired persons. 
     2. Description of Related Art 
     Many persons having physical impairments spend much of their time in wheelchairs. Unfortunately, even with modem advances in wheelchair technology, many wheelchairs are still large, cumbersome and bulky. The height of a typical table or desk is ordinarily too low to allow a wheelchair to fit under it. As a result, it is often difficult for a person in a wheelchair to comfortably pull up to and under the table or desk in order to make good use of it. Thus, it is desirable to provide a desk or table extension to make the desk or table more usable by persons in wheelchairs. 
     One such table extension is disclosed in U.S. Pat. No. 4,384,532. This patent describes an extension that is permanently affixed underneath a table so that the extension may be pulled out and brought up to the same height as the table. Unfortunately, this unit is not portable, and if the table it is attached to is not sufficiently tall to allow a user in a wheelchair to pull up to and under it in the first place, this extension is of little help. 
     It is therefore desirable to provide a portable, detachable desk or table extension for use by a person in a wheelchair that may be adjusted to a usable height regardless of the height of the desk or table to which it is attached. In particular, it is desirable that the extension extend out a sufficient distance away from the desk or table so that the user in a wheelchair may comfortably pull up to and under it during use. It is also desirable that the extension be pivotally mounted so that it is angularly adjustable (tiltable) to allow a physically impaired user to adjust it to an optimum position for use. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is an adjustable extension for temporary attachment to a table or desk designed for use by physically impaired (handicapped) persons. 
     The present invention is a portable, detachable desk or table extension for use by a person in a wheelchair that may be vertically and angularly adjusted to an optimum height and position for use. The extension has a portable work surface or platform that extends out, away from, and above the surface of the desk or table to which it is attached, so that a user in a wheel chair may pull up to and under it and not be blocked or hindered by the table or desk underneath. The elevation as well as the angle of tilt of the platform may be adjusted for optimum positioning so that the user in a wheelchair may pull up close to and under it. The extension clamps to the table via a pair of vertical supports that collapse down onto the platform for storage. 
     An aspect of the invention is a portable work surface for attachment to a stationary structure having a stationary work surface. The stationary structure generally comprises a desk, table, or like structure. The portable work surface has a platform having a planar work surface, and a pair of spaced apart support members coupled to the platform, wherein the support members are configured to support the platform at an elevation above the stationary work surface. The support members are configured to abut at least partially against a side edge of the stationary structure. At least one bracing member is coupled to the support elements. The bracing member is configured to contact the stationary work surface. Furthermore, at least one clamping member is coupled to the support elements. The clamping member contacts a lower surface of the stationary structure to releasably secure the support members to the stationary structure. 
     In one embodiment of the current aspect, the platform is coupled to the support members so that the platform is capable of translating with respect to the support members to alter the elevation of the platform with respect to the stationary work surface. 
     The platform may also be rotatably coupled to the support members so that the platform is capable of rotating with respect to the support elements to alter the angle of the platform with respect to the stationary work surface. 
     In another embodiment, the support members are configured collapse into a stowed orientation by folding horizontally against a bottom surface of the platform. 
     Generally, the support members are configured to support the platform at a location in front of the side edge of the stationary work surface. 
     In another embodiment, a biasing element is disposed between the support member and the platform, wherein the biasing element unloads at least a portion of the platform&#39;s weight to facilitate translation of the platform with respect to the stationary work surface. 
     In one mode, a pair of elevation members coupled to the platform, wherein the support members house the elevation members to facilitate linear translation of the platform in a direction normal to the stationary work surface. Generally, the support members are configured to be secured at an orientation normal to the stationary work surface. In a preferred variation, the elevation members are spring loaded to ease translation of the platform to varying elevations. 
     A locking mechanism may also be coupled to the support members to lock translation of the elevation members. 
     Another aspect of the invention is a portable work surface having a platform with a planar work surface. The portable work surface comprises a means for releasably securing the platform to the stationary work surface; and a means for adjusting the elevation and angular orientation of the platform with respect to the stationary work surface so that the platform may be positioned at a location in front of and above the level of the stationary work surface. 
     In one embodiment of the current aspect, the means for means for releasably securing the platform comprises a pair of adjustable supports that are configured to fold underneath the platform other for storage. 
     A means for locking and unlocking the elevation and angular orientation of the platform with respect to the stationary work surface may also be included. 
     In yet another embodiment, a biasing means is coupled to the platform, wherein the biasing means at least partially unloads the weight of the platform when the elevation is unlocked. The biasing means may comprise a spring disposed between the platform and the securing means. 
     A further aspect is a method of extending a stationary work surface of a stationary object. The method includes the steps of releasably securing a support member to the stationary object, wherein the support member is coupled to a platform having a planar work surface, and positioning the platform at a location forward of and above the stationary work surface. 
     The method may further include slideably adjusting the elevation of the platform above the stationary work surface, and locking the elevation of the platform with respect to the first and second support members. In addition, at least a portion of the weight of the platform may be unloaded such that application of a force smaller than the weight of the platform adjusts the elevation of the platform. 
     Furthermore, the method includes detaching the support member and platform from the stationary object, and folding the support member to rest on a bottom surface of the platform. 
     Further aspects of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only: 
         FIG. 1  is a side view of a portable work surface attached to a desk or table in accordance with the present invention. 
         FIG. 2  is a side view of the portable work surface of  FIG. 1  with the platform at different elevation levels. 
         FIG. 3  illustrates the portable work surface of  FIG. 1  with the platform oriented at an angle with respect to the table. 
         FIG. 4  shows a perspective view of the portable work surface of  FIG. 1  with one clamping assembly in a stowed position, and the other clamping assembly positioned for attachment to a table or desk. 
         FIG. 5  illustrates the footprint of the clamping assemblies (with platform assembly removed), attached to a circular or oval table. 
         FIG. 6  illustrates the footprint of the clamping assemblies (with platform assembly removed), attached to a rectangular table or desk. 
         FIG. 7  illustrates a front view of a clamping assembly in accordance with the present invention. 
         FIG. 8  illustrates a perspective exploded view of the clamping assembly of  FIG. 7 . 
         FIG. 9  shows a perspective view of an alternative portable work surface attached to a table in accordance with the present invention. 
         FIG. 10  shows the portable work surface of  FIG. 9  in a collapsed configuration. 
         FIG. 11  shows another alternative portable work surface attached to a table in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring more specifically to the drawings, for illustrative purposes the present invention is embodied in the apparatus generally shown in  FIG. 1  through  FIG. 11 . It will be appreciated that the apparatus may vary as to configuration and as to details of the parts, and that the method may vary as to the specific steps and sequence, without departing from the basic concepts as disclosed herein. 
     Referring now to  FIG. 1 , a portable work surface  20  in accordance with the present in is illustrated attached to a fixed work surface  10 , such as a desk, table or the like. The portable work surface  20  provides a platform  40  that raises the effective work surface  12  of the table  10  upward and outward. This change in the effective work surface allows more flexibility for those in wheelchairs, or even users who desire to change the effective work surface for anatomical or other reasons (e.g. the upward disposition of the platform may allow the user to access a keyboard, mouse or other device at a more comfortable anatomical orientation, relieving stress on wrists, shoulders, back, etc.) 
     Platform  20  generally comprises a flat, planar surface  42 . As shown in  FIG. 4 , the platform is preferably rectangular in shape (although any number of shapes are contemplated), having a thickness sufficient enough to support the expected loading (e.g. keyboard, weight of user&#39;s arms while resting, etc.). The platform is preferably constructed of lightweight yet rigid material, e.g. a hard plastic). The platform may also be weight relieved on the bottom surface  54 , and may comprise other light-but-rigid constructions (such as a honeycomb core). 
     Work surface  20  comprises a pair of clamping assemblies  52  (see also  FIG. 2 ) that are configured to releasably attach to the desk  10 . Each clamping assembly comprises a vertical support  26  that houses an arm  24  and brace  22 . Arm  24  is configured to clamp to the underside  14  of table  10 , while brace  22  spans generally horizontally away from support  26  to contact the upper surface  12  of the table  10  to hold the work surface  20  locked in place. 
     Arm  24  is generally L-shaped so that it may clamp to the table  10  even in the presence of a flashing  16  or other protrusion emanating from the underside  14  of the table  10 . Arm  20  is coupled to the vertical support  26  via a knob  28  that allows rotational and vertical (e.g. via clockwise or counter-clockwise tightening) manipulation of the arm  24  to tighten it against tables or desks of varying thickness. The braces  22  provide resistance to the clamping pressure imparted by arms  20  when knobs  28  are tightened. 
     A brace  22 , which generally comprises a flat plate, extends horizontally from the upper end of the vertical support  26  to engage the upper surface  12  of the table or desk  10 . Once the arm  24  is properly positioned to contact the underside  14  of the table  10 , knob  28  is tightened to lock the portable work surface  20  on to the table  10  and maintain its position with respect to the table, even in the presence of external loading on the portable work surface  20 . 
       FIGS. 5 and 6  show top views of the clamping assemblies  52  (with platform assembly  80  hidden) mounted on a circular or oval table  82  ( FIG. 5 ) and rectangular table  84  ( FIG. 6 ). The spaced apart orientation of the clamping assemblies  52  allow the platform  20  to be mounted on a variety of different desk/table configurations, and allow the vertical supports  26  to abut the edge of the table so that the platform  20  does not unduly extend laterally from the table or desk. 
     Referring back to  FIGS. 1-4 , each vertical support  26  is coupled to the platform  40  via a support member  50  and elevation rod  34 , which is fixedly coupled to the support member  50 . The elevation rod  34  is slideably housed in bore  32  that runs vertically down a portion of the length of the vertical support  26 . The bore  32  is sized to match (or be slightly larger than) the diameter of the elevation rod  34  so that the rod may move freely within the bore  34  in a vertical and linear fashion. Each rod  34  is retained vertically by a locking member  30 , such as a cam lever, or similar quick release mechanism known in the art. 
     As shown in  FIG. 2 , by releasing the cam levers  30  (shown as an upward orientation in  FIG. 2 ), the elevation rod  34  is free to move upward or downward in bore  32 , which corresponds to an upward or downward translation of the platform  40 . In a preferred embodiment, a biasing spring  36  is coupled between the support member  50  and the vertical support  26  to aid the user in adjusting the elevation of the platform  40 . As shown in  FIG. 2  the biasing spring  36  is located exterior to the elevation rod  34  and is capped at its upper and lower extremities via counter bores  86  and  88  in the vertical support  26  and support member  50 . Thus the spring generates an axial force against collapse of the support member  50  (and platform assembly  80 ) toward the vertical support  26 . 
     Hence, the user merely needs to apply a slight upward force on the platform  40  to effect an upward translation of the platform, and a slight downward force on the platform  40  to effect an downward translation of the platform (both shown in phantom in  FIG. 2 ). Thus, adjustment of the platform  40  elevation may be achieved with one hand, while the other hand is use to unlock/lock the locking members  30 . 
     Spring  36  may be sprung such that the platform, under its own weight, rests at a nominal or intermediate position along its range of travel (e.g. spring resistance at half of compression distance being substantially equal to the weight of the platform assembly  80 ). 
     Alternatively, the spring  36  may be under-sprung so that the platform naturally rests at the bottom of its travel (e.g. the support member  50  touching the vertical member  26 ). In this case, the user simply applies a slight upward force to mover the platform to a higher elevation. 
     In a further alternative, the spring  36  may be over-sprung so that the platform naturally rests at the top of its travel (e.g. the elevation rod  34  fully extended). In this case, the user simply applies a slight downward force to mover the platform to a lower elevation. 
     Referring now to  FIG. 3 , the platform assembly  80  is preferably configured such that the platform  40  may be angularly adjusted with respect to the stationary work surface  12 . When the platform is oriented at a level or horizontal orientation (as shown in  FIGS. 1 and 2 ), the bottom surface  54  of the platform  40  generally rests on the contact surface  72  of the support member  50  (see  FIGS. 7 and 8 ). Each support member  50  may also have a flange  76  on the outside edge for retaining the sides of the platform. 
     The support member  50  is also coupled to the platform via a u-shaped hinge  56 . The hinge  56  is rotatably coupled to the platform  40  via a housing  58  that is fixed to the bottom surface  54 . The hinge  56  runs through the length of the housing  58  substantially parallel to the front edge  66  and back edge  68  of the platform. The hinge  56  protrudes from each side of the housing  58 , wherein it curves roughly 90 degrees toward the back edge  68  of the platform  40  to interface with each of the support members  50  (see  FIG. 4 ). 
     Buy rotation of the inclination knob  44 , a gear mechanism  46  drives the platform  40  to rotate about the central axis  60  of the hinge, therefore tilting the back edge  68  of the platform  40  upward so that the platform  40  forms an angle θ with respect to horizontal. Counter-clockwise or clockwise rotation of knob  44  allows for fine adjustment of the angle θ as desired by the user. The Back edge  68  of the platform is supported by strut  38  which is mounted to the bottom surface  54  of the platform  40  by bracket  92 . 
     Referring now to  FIG. 4 , both of the clamping assemblies  52  are configured to be folded down when the portable platform  20  is not in use. The hinge  56  is rotatably coupled to each of the support members  50  via a bushing  94  so that the support member  50  (and clamping assembly  52 ) can be rotated about the hinge  56  and collapsed inward toward the center of the bottom surface  54  of the platform. As seen in  FIGS. 7 and 8 , the inner edge  74  of the support members are curved to allow the support member to rotate 90 degrees such that the inner edge rests parallel to the platform lower surface  54 . 
     Referring now to  FIG. 9 , an alternative embodiment of a portable work surface  100  is illustrated. The portable work surface  100  comprises a clamping assembly  110  having a pair of spaced apart vertical support members  102  that are configured to abut against an edge  11  of table or desk  10 . The vertical supports have a pair of braces  106  at their upper extremities for restraint against the upper surface of the table  10 . The supports further house a pair of clamp arms  104  that are configured to be tightened to the bottom surface of the table  12 . Knobs  122  may be loosened or tightened accordingly to effect adjustment of the arms and corresponding tightening to lock the clamping assembly  110  steadfast to the table  10 . 
     The vertical supports  102  house a pair of elevation members  108  that are vertically oriented inside a bore (see  FIG. 1 ). Knobs  118  allow the elevation members  108  to be locked into position when tightened, and correspondingly allow vertical translation V of the elevation members  108  when loosened. The elevations members  108  are coupled to the platform  120  via a frame  114  and swivel members  112 . The frame  114  and swivel members are generally horizontally oriented (e.g. parallel to the upper surface of the table  10  when the portable work surface  100  is installed). 
     The frame  114  is hingedly coupled to the platform via hinge bracket  116 , such that the platform  120  may be rotated upward angle θ with respect to the frame  114  and table  10 . Knobs (e.g. or similar to knobs  118 ,  102 ), or similar devices known in the art may be used to effect rotation of the platform  120 , and tighten it when in the desired orientation. 
       FIG. 10  illustrates the portable work surface  100  in a stowed orientation. The platform  120  is ideally retracted to a horizontal or parallel position with the frame  114  such that the lower surface of the table  124  is in contact with the frame  112  and or swivel base. With the claming assemblies  110  detached from the desk  10 , the swivel bases are allowed to rotate inward (e.g. via hinge, pin  132  or other rotational joint available in the art) toward the bottom surface  124  of the platform  120  to essentially collapse level with the platform  120 . This allows the portable work surface  100  to be easily transported or stowed. 
     As shown in  FIG. 10 , platform  120  may optionally have an upper surface  126  with raised edges or flanges  128  to retain contents placed on the work surface, and prevent objects from sliding off the panel when it is tilted away from horizontal. 
     Referring to  FIG. 11 , another embodiment of a portable work surface  150  is illustrated having a clamping mechanism  160  for attachment to the edge  11  of a desk or table  10 . This clamping mechanism  160  includes a pair of clamping arms  152  that are pivotally attached to a support frame  154  at pivots  156 . One end  158  of each arm  152  is bent at an upward angle, and an optional end piece (such as a rubber footing, felt, or a plastic cap)  160  may also be provided. 
     The opposite end of each arm  152  is provided with a generally orthogonally positioned member  162  through which an adjustable tightening mechanism  164  is attached. Mechanism  164  is preferably provided in the form of a knob attached to a screw member  166  which may be threaded through an opening (not shown) in orthogonal member  162 . Each knob may be turned in one direction (e.g., clockwise) to extend screw member  166 , thereby causing arm  152  to rotate at pivot (lever)  156 , pressing end  158  (and cap  160 , if supplied) against the underside  14  of the table  10 , thereby tightening the clamping mechanism  160  and securing frame  154  to table  10 . Rotating each knob in the opposite direction loosens arm end  158  from the underside of table  10  allowing for removal. The arms  152  of the clamping mechanism  160 , and frame  154 , should be sufficiently wide so as to allow a wheelchair to pull directly into and between the clamps, so that neither the wheels of the chair nor the knees of the user bump into the clamps or supports. 
     Support frame  154  includes a pair of generally vertically oriented members  166 , to which each of arms  152  is pivotally attached. A pair of generally horizontally oriented upper arms or braces  168  extend out from each vertical support member  166 . Each arm  168  extends generally parallel to the top surface of the table  10 , and is configured to be positioned and rest on top of the table  10 . Thus, arms  166  provide resistance to the clamping pressure imparted by arms  21  when knobs  29  are tightened. 
     A telescoping member  170  is housed in each of the vertical members  166 . The position of each member  170  may be slideably translated along the vertical axis to effect the elevation of the platform  174 , and then be fixed by tightening knob  180  attached to member  166 . Members  170  support upper frame  172 , which is generally rectangular in shape and parallel to surface  12  of the table  10 . 
     Frame  172  provides support the table extension of platform  174 . Thus, by loosening knobs  180 , telescoping members  170  may be raised or lowered to correspondingly raise or lower upper frame  172  and attached platform  174 . This allows platform  174  to be adjusted to a desired height. 
     One end of panel  174  is hingedly attached to frame  172  so that it may also be tilted at an angle relative to frame  172 . In the illustrated embodiment, rotating knob  176  operates a gear mechanism (not shown) that raises or lowers strut  178 , thereby raising or lowering platform  174 . However, other suitable raising and lowering devices may alternatively be employed. Platform  174  is shown in raised position in  FIG. 11 . Platform  174  (much like previous embodiments shown in  FIGS. 1-10 , may be titled at an angle of up to 90 degrees from horizontal (i.e. vertical), but ordinarily will not be raised more than about 45 degrees. 
     Optional features include a rim  180  extending around all or part of the perimeter of the platform  174 . Holders for beverages, writing implements, paper and desk items may also be provided either attached to panel  174 , frame  154 . The platform  40 ,  120 ,  174  may be made of a variety of materials, and may also comprise a laminate structure, e.g. with a layer of an erasable white board for use with colored markers. 
     Alternatively, platform  40 ,  120 ,  174  may be provided with a clear cover that can be written on with an erasable marker. The clear cover may be fitted between the raised outside ridges or flanges  180 , and allows for paper to be placed under the clear plastic. This feature is beneficial for persons with severe disabilities (sight, fine motor, etc.) who cannot use a traditional pencil and paper, and allows such persons to grasp a larger writing utensil and write on the large surface that can be color coded to enhance usability and performance. Paper may also be placed under the clear plastic if the user is unable to hold the paper on the tabletop extension. Such paper may be blank, or it may be provided with lines or staffs so that it may be followed, or with other objects to be or traced. 
     Clamp assemblies  52 ,  110 , and  160 , and their respective members as well as frames, and their respective members may be made of plastic, metal, wood, other suitable materials known in the art. Any of the securing mechanisms  28 ,  30 ,  118 ,  122 ,  164 , or  176  may be replaced by cranks, handles or other suitable structures for easier grasping and rotation by a physically impaired person. 
     As an alternative to the securing mechanisms  30 ,  118 , and  180 , a series of openings may be provided along vertically oriented support members  26 ,  102 ,  166 , and elevation/telescoping members  34 ,  108 ,  170  may be provided with depressible spring biased buttons that pop-out and lock into one of said openings to hold each of telescoping members in place. It is also appreciated that the present invention may comprise any combination of individual elements of the embodiments disclosed in  FIGS. 1-11 . 
     Although the description above contains many details, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”