Abstract:
A wheelchair has a seat, a reclining backrest and anti-tip legs movable between a retracted position and an extended ground contacting position in response to movement of the backrest between an upright and a reclining condition. The inclination of the backrest can be conveniently adjusted by a person seated in the wheelchair by latching a pair of detent arms in one of several slots spaced under the chair&#39;s armrests. The anti-tip legs extend to support the wheelchair against tipping backwards when the backrest is reclined and retract out of the way when the backrest is brought upright.

Description:
[0001]     This is a Continuation-in-part of Ser. No. 10/692,830 filed Apr. 3, 2003 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention pertains generally to the field of seats and chairs with reclining backs and in particular to reclining backs with anti-tip protection for wheelchairs.  
         [0004]     2. State of the Prior Art  
         [0005]     Wheelchairs have been equipped with reclining backs in the past, and it is known to provide restraints against rearward tipping of the chair. The previous reclining backs and anti-tipping restraints were not operable by the wheelchair occupant. What is needed is a reclining backrest operable by a user seated in the wheelchair with anti tipping restraints automatically deployed in response to movement of the backrest.  
       SUMMARY OF THE INVENTION  
       [0006]     A wheelchair having a wheelchair frame including a seat supported on the frame has a backrest which is pivotable on the frame between an upright position and a reclined position. A pair of rear wheels are journaled to the frame for rotation about a rear wheel axis, and a pair of anti-tip legs are attached to the frame and movable between a retracted position and an extended position for contacting a ground surface behind the rear wheel axis in response to pivoting movement of the backrest.  
         [0007]     The wheelchair frame may have a pair of armrests and a detent plate is provided along one of the armrests, the detent plate having a slot including a plurality of detent notches open to the slot. A detent arm can be attached to the backrest, the detent arm having a forward end captive for displacement along the slot and engageable in any one of the detent notches for detaining the backrest at one or more positions intermediate to the upright position and the reclined position. Preferably, a handgrip is provided on the forward end of the detent arm.  
         [0008]     The backrest, the legs and the detent arm may be spring biased towards the upright position, the retracted position and a forwardmost position, respectively. For example, the anti-tip legs can be spring loaded towards their retracted position such that the spring force acting on the detent arm and on the anti tip legs tends to return the backrest to its upright position when the detent arm is released from the detent notch.  
         [0009]     In a presently preferred form of the invention a pair of linkage arms are pivoted to the wheelchair frame, the backrest being supported on the linkage arms for pivotal movement therewith relative to the wheelchair frame, and the linkage arms are connected for moving the legs between the retracted position and extended position responsive to pivoting movement of the backrest. A mounting plate may be fastened to each side of the wheelchair frame, and a linkage arm pivoted to each mounting plate.  
         [0010]     In a particular embodiment of the invention the anti tip legs are mounted for generally vertical movement on the wheelchair frame and the backrest has linkage arms connected for urging the legs downwardly into ground contacting position responsive to rearward pivoting of the backrest. The legs may be vertically slidable through leg holders fastened to the wheelchair frame. The leg holders may be removably fastened to the wheelchair frame on a pair of bottom tubes of the wheelchair frame terminating in rear ends behind the rear wheel axis. The leg holders may be in the form of holder sleeves fitted to the rear ends of the bottom tubes provided with sleeve fasteners for releaseably securing the holder sleeves to the rear ends.  
         [0011]     The reclining backrest can be removably attached to the wheelchair frame to allow folding of the wheelchair frame or replacement of the reclining backrest with a non-reclining backrest.  
         [0012]     These and other improvements, features and advantages will be better understood by reference to the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a left side view of a wheelchair provided with a reclining backrest with anti-tip protection according to this invention, showing the backrest in upright position and the anti-tip legs in retracted position;  
         [0014]      FIG. 2  is a side view as in  FIG. 1  but showing the backrest in reclined position and the anti-tip legs in ground contacting extended position;  
         [0015]      FIG. 3  is a detail perspective view of the wheelchair of  FIG. 1  showing the left side mounting of the backrest on a pivoting linkage arm, the attachment of the linkage arm for actuating the left anti-tip leg and the rear end of the detent arm connected to the backrest;  
         [0016]      FIG. 4  is a side view of the detent plate mounted under the left arm rest and showing forward end of the detent arm captive in the slot of the detent plate with a spring connected between the detent arm and the detent plate for urging the detent arm into engagement with the detent notches along the slot;  
         [0017]      FIG. 5  is a detail cross-sectional view taken along line  5 - 5  in  FIG. 4  illustrating the handgrip on the captive forward end of the detent arm; and  
         [0018]      FIG. 6  is a detail view showing how the left linkage arm is pivoted to the left side mounting plate and how the removable backrest is supported on the linkage arm. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]     With reference to the drawings wherein like elements are designated by like numerals,  FIG. 1  shows a wheelchair generally designated by numeral  10  having a wheelchair frame  12  which generally consists of a tubular framework including a pair of front legs  14 , a pair of rear legs  16 , left and right side arm rests  15  supported on side arm tubes  18  connecting the top ends of the front and rear legs  14 ,  16 , a pair of seat carrier tubes  20  on each side of the wheelchair frame  12  connecting the front and rear legs  14 ,  16  at a mid height level, and a bottom tube  22  which connects the lower ends of each front leg  14  and the corresponding rear leg  16 . The wheelchair also has a pair of front caster wheels  24  mounted to the lower ends of the front legs  14 , and a pair of larger rear wheels  26  journaled to the wheel chair frame  12  for rotation about a rear wheel axis  28 . A wheelchair seat  30  is supported between the left and right seat supports  20 .  
         [0020]     A reclining backrest generally designated by numeral  30  has a seat back  32  which may have a padded or cushioned front  34  and is fastened to a frame consisting of left and right posts  36  and a cross rail  38  which extends across the lower end of the seat back  32 , as best seen in  FIG. 3 . The upper ends of the vertical posts  36  are connected by a handle bar  42 .  
         [0021]     The backrest  32  is supported on linkage arms  40 , in a manner which will be explained in greater detail below, and which in turn are pivoted to mounting plates  44  fastened to the rear legs  16 . Each linkage arm  40  has a short upright arm portion  46  into which is cut a receiving slot  48 . One linkage arm  40  is mounted on each of the left and right rear legs  16  of the arm chair  12 , and while  FIG. 3  shows only the left side linkage arm and corresponding mounting plate  42 , the right hand side arrangement of linkage arm  40  and anti-tip leg  50  not shown in  FIG. 3  is essentially a mirror image of the illustrated left side.  
         [0022]     An anti-tip leg  50  is suspended from the rear end  41  of each linkage arm  40  in generally vertical position and approximately parallel to the rear leg  16  of the wheelchair frame by a pivotal connection  52  between the upper end of the leg  50  and the rear end  41  of linkage arm  40 . The lower portion of leg  50  slides through a guide ring portion  54  of leg holder  56 , which is a tubular sleeve fitted onto the rear end of bottom tube  22  of the wheelchair frame, and is fastened in place by a set screw  58 . A rubber tip  60  may be fitted onto the bottom end of the leg  50 . The leg  50  is biased upwardly towards a retracted position by coil spring  62  compressed between guide ring  54  and a washer  64  fixed on leg  50 .  
         [0023]      FIG. 3  shows part of a detent arm  66  which has a rear end  68  pivotably attached to vertical post  36  of the backrest by a retractable pin  70 . Turning to  FIG. 4 , a detent plate  74  is mounted along the underside of armrest tube  18  and has a horizontal slot  76  with a number of detent notches  78  open to the slot  76 , and detent arm  66  has a forward end  72  captive for movement within slot  76 .  
         [0024]      FIG. 5  shows how the detent arm  66  is retained to the plate  74 . As seen in  FIG. 5 , detent plate  74  is a side wall of a detent tube  80  of rectangular cross section. A pin  82  is secured to detent arm  66  as by welding at  84 , and carries a spacer ring  86  and a retaining disc  88  The disc  88  has a disc diameter greater than the width of slot  76  except at an enlarged end opening  92  provided at the forward end of slot  76 . The enlarged opening  92  admits the retaining disc  88  into the detent tube  80  and permits engagement of the pin  82  for sliding displacement along slot  76 . The diameter of pin  82  within slot  76  is admitted into any one of detent notches  78  so as to detain the forward end  72  of arm  66  at a selected detent notch  78  against displacement along slot  76 . A detent spring  94  is stretched between pin  82  and anchor hole  96  in the detent tube  80  and applies a spring bias urging detent arm  66  into engagement with any of the detent notches  78  underlying pin  82  of the forward end of detent arm  66 . A guide plate  67  is welded to leg  16  under side arm tube  18 , and detent arm  66  passes through guide slot  69  cut in plate  67 , as seen in  FIGS. 3 and 4 . Slot  69  helps keep the detent arm  66  in slot  76 .  
         [0025]     A handgrip  90  is fastened as by welding at  98  to the forward end of detent arm  66 . The handgrip may be a short cylindrical section closed at its free end by cap  102 , and is located so as to be conveniently within grasp of a person seated in the wheelchair, well forward of the backrest  32 .  
         [0026]      FIG. 6  shows how the backrest  32  is supported on linkage arm  40  for pivotal movement relative to the wheelchair frame  12 . A mounting tab  100  extends from each end of the cross rail  38 , as best seen in  FIG. 3 , and is received in slot  48  of linkage arm  40 . The linkage arm  40  is mounted on pivot pin  102  to mounting plate  44 . The linkage arm  40  pivots in a vertical plane relative to wheelchair frame  12  as indicated by arrow A in  FIG. 3 , thereby causing backrest  32  to pivot between an upright position illustrated in  FIG. 1  and a reclined position shown in  FIG. 2 , as suggested by arrow B in  FIG. 3  and arrow C in  FIGS. 2 and 3 . Pivotal movement of the linkage arm  40  also moves the anti tip leg  50  up and down as suggested by arrow D in  FIGS. 2 and 3  between an elevated or retracted position of the leg  50  shown in  FIG. 1  and a ground contacting extended position seen in  FIG. 2 . The length of leg  50  is such that in the retracted position of  FIG. 1 , the tip  60  is retracted to a position within the envelope of rear wheel  26  such that the tip of the leg does not interfere with displacement of the wheelchair, for example, while descending a step. In  FIG. 2 , the tip  60  rests upon a ground surface G under rear wheel  26  and makes contact with ground surface G at a location behind the rear wheel axis  28  so as to provide support against rearward tipping of wheelchair  10  which might result from loading of the reclined seat back  32 . The length of leg  50  can be made adjustable by providing a rod  50   a  threaded into leg tube  50   b . Rod  50   a  is fixed against rotation about its long axis to linkage arm  40 , while tube  50   b  can be turned about its long axis such that it is displaced up or down along rod  50   a , thereby adjusting the height of tip  60  above ground surface G.  
         [0027]     A lockdown screw  104  is threaded in linkage arm  40  transversely to tab  100  and can be manually turned into an advanced position for closing the receiving slot  48  so as to capture tab  100  and secure the backrest  32  to the linkage arm  40 . In the case where the wheelchair has a folding frame  12  the frame can be folded after removing the backrest  30 . The screw  104  when retracted as in  FIG. 6  frees the tab  100  for withdrawal from slot  48  as suggested by arrow E, and pin  70  is withdrawn to free the backrest from detent arms  66 . Folding of the wheelchair frame  12  does not require removal of the linkage arm  40  or the anti-tip leg  50  on each side of the wheelchair frame.  
         [0028]     The leg spring  62 , in biasing the leg  50  towards its elevated, retracted position also operates to urge linkage arm  40  to an elevated position corresponding to an upright position of the backrest  30 . In this manner, leg springs  62  on the two legs  50  operate to return the backrest  30  to an upright position, the detent arm  66  to a forwardmost position, and the legs  50  to a retracted condition.  
         [0029]     A person sitting in wheelchair  10  can operate the reclining backrest  30  by grasping the handle  90  under the left arm rest  15  of the wheelchair, lifting the handle slightly to free the detent pin  82  from detent notch  78 , and pushing against the seat back  32  sufficiently to overcome the bias of springs  62  until the backrest is angled to a desired reclining position, and then lowering the detent pin  82  into a detent notch  78  most closely corresponding to the desired angle of backrest  32 . Elevation of the seat back is accomplished by freeing the detent arm from the detent notches  78  and allowing the springs  62  to raise the backrest  30  to its upright position of  FIG. 1 .  
         [0030]     The reclining backrest with anti-tip protection of this invention can be retrofitted onto existing wheelchair frames without permanent modification to the wheelchair. The detent tube  80  can be attached to arm rest tube  88  of an existing wheelchair frame using screws normally provided through armrest tube  88  for fastening the armrest pad  15  to tube  18 . Such screws have screw heads underneath tube  18  and thread upwardly into the bottom of the armrest pad  15 . The detent tube  80  can be provided with screw holes (not shown) in its upper side  81  and aligned openings (not shown) in its bottom side  82  so as to allow insertion of a screwdriver into tube  80  for tightening of screws through side  81  and through armrest tube  18  into armrest pad  15 . The mounting plate  44  may be one of a pair of such plates parallel to each other and tightened by means of bolts  45  so as to capture between them the T-joint of frame tubes  16  and  20 .  
         [0031]     In the presently preferred form of the invention a single detent arm  66  with one corresponding handle  90  is provided, so that the seat back position can be adjusted with one hand by the wheelchair occupant. It is also contemplated, however, that the seat back reclining mechanism of this invention could be provided with a pair of left and right detent arms  66 , one detent arm along each arm rest, each with a corresponding detent plate  74 , the two detent arms and detent plates being essentially mirror images of each other.  
         [0032]     While a particular embodiment of the invention has been described and illustrated for purposes of clarity and example, many changes, substitutions and modifications to the described embodiment will be apparent to those having only ordinary skill in the art without thereby departing from the scope of this invention, which is defined by the following claims.