Abstract:
A wheeled walker convertible to a transport chair. The walker has a strap-type backrest that is pivotally attached to the upper end of the handlebars. The backrest can be placed in a forward position when the apparatus is used as a walker and the user wishes to rest in a rearward facing sitting position and in a rearward position when the apparatus is used as a transport chair and the user sits in a forward facing position and is propelled by a care-giver. A novel braking system locates the brake actuating linkage inside the leg and handlebar members and provides accommodates extension height adjustment of the handlebars. A brake lever system providing a linear pull non-cable brake actuation is also disclosed.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to a wheeled walker that can be used as a transport chair for the disabled and to a novel braking system for wheeled apparatus.  
           [0002]    Many persons, by reason of age or disability have difficulty in walking without a walking aid. Wheeled walkers are widely used by many such persons to assist in mobility. A wheeled walker typically has a frame mounted on four wheels and a pair of rearwardly extending handle bars which the user can grip for support while walking. The user positions himself between the handle bars behind the walker and pushes the walker forward. The wheels permit the user to roll the walker smoothly over the ground thereby avoiding the laborious action of picking up and moving a non-wheeled walker in step-by-step fashion. The handle bars can be fitted with brake levers that when squeezed by the user, actuate some form of wheel braking mechanism.  
           [0003]    Wheeled walkers are routinely equipped with a seating surface that permits the user to rest in the sitting position. The seating surface is usually positioned transversely between the handle bars within the wheel base of the walker to offer a stable platform for sitting. In order to use the seating surface, the user must turn around and sit down in the rearward facing direction, opposite to the normal direction of travel, with his feet resting on the ground. The braking mechanism can be fitted with a locking mechanism to maintain braking engagement with the wheels to prevent the walker from rolling while the user is sitting.  
           [0004]    While the provision of a seat to permit the user to rest is a useful feature, it often occurs that the user is too tired to continue walking and requires the assistance of a care-giver continue travel. Conventional wheeled walkers are not adapted to support a seated user and be pushed by a care-giver. In particular, because the user is seated in a rearward facing position between the handlebars, there is very little space between the user and the care-giver, making it difficult for the care-giver to take walking steps without interfering with the feet of the user. Moreover, there is no dedicated means on conventional walkers to support the feet of the user while in the sitting position with the result that the feet are usually dragged across the ground or propped up on a frame member in an unnatural position.  
           [0005]    There have been a number of attempts to provide a wheeled apparatus that is useful as a self-propelled walker and also as a care-giver propelled transport chair.  
           [0006]    U.S. Pat. No. 5,451,193 discloses a combined wheelchair and walker. In the normal walking position, the seating surface is pivoted up rearwardly toward the seat back to provide space between the handlebars for the user to walk. The user walks in a forward direction pulling the walker behind him. When the user wishes to sit, the seating surface can be flipped down. There is no provision to permit the walker to be pushed by a care-giver. Indeed, the patent discloses that a third party must pull the seated user backwards by pulling on the seat back.  
           [0007]    U.S. Pat. No. 5,451,193 discloses a combination wheelchair and walker. While the user or the care-giver can push the apparatus from behind as a conventional walker or transport chair, in order to assume the seated position, the user must walk around to the front of the apparatus, which manoeuvre can be difficult for a physically challenged person.  
           [0008]    U.S. Pat. No. 5,605,345 discloses a wheeled apparatus for use both as a walker and a wheelchair. The design has rearward facing handle bars to permit the apparatus to be used as a wheeled walker. The design also has a bidirectional seating arrangement. When the seat is placed in the rearward facing position, it permits the person using the device as a walker to rest in a seated position by turning around and sitting down in the rearward facing direction with his feet resting on the ground. When the seat is placed in the forward facing position, the apparatus can be used as a conventional wheelchair. The wheelchair design is conventional in that it has large rear wheels with hand-rings that permit the wheelchair to be propelled by the occupant or rearward facing handles to permit the wheelchair to be pushed by a care-giver.  
           [0009]    While the design disclosed in U.S. Pat. No. 5,605,345 offers significant advantages, it is not well adapted for use as a walker. Because it is based on a conventional wheelchair design, it is heavy and bulky, making it difficult to manoeuvre in confined locations. Furthermore, the bi-directional seating arrangement uses a frame mounted link arrangement which cannot be practicably adapted to a light walker design. Because the seat back is pivoted to the seat base, the vertical rise of the seat back is limited and accordingly offers only lower back support. Furthermore, when positioned in the walker mode, the seat back obscures the user&#39;s view of the ground directly in front of the walker.  
           [0010]    Conventional walkers have been equipped with handle bar mounted braking system actuators that permit the user to manually apply braking force when walking or to lock the brakes to permit the user to safely assume a seated position. For example, one such system is disclosed in U.S. Pat. No. 5,279,180 and relates to a cable braking system. The actuating mechanism uses a connecting lever to pull the cable when the brake lever is raised to a braking position or depressed to a locked position.  
           [0011]    Thus, there remains a need for a walking aid that offers all of the functionality of a conventional wheeled walker and can be readily converted for use as a transport chair.  
           [0012]    Cable type braking systems are commonly used on walkers which have height adjustable handle bars. In such a case, the flexible cable accommodates the variable length between the brake handle actuator and the wheel mounted braking element. However, cable type braking mechanisms have a number of deficiencies. In particular, the cables require rather precise and periodic adjustment to maintain effective braking action. Moreover, because the cables are routed from the brake handle actuator to the wheels outside of the frame and require some slack to accommodate height adjustability, the resulting loop or bight in the cable is prone to catching or snagging on other objects, a deficiency which is particularly problematic in the case of a folding style walker that is transported in the trunk of a car.  
           [0013]    Thus, there remains a need for a brake actuating system which avoids the problems associated with cable based systems.  
         SUMMARY OF THE INVENTION  
         [0014]    The present invention provides a wheeled walking aid that functions as a conventional walker, but is adapted to also be used as a transport chair. The present invention also provides for a novel braking system in which the brake actuating linkage is internal of structural members, and is length adjustable.  
           [0015]    In accordance with the present invention, there is provided a convertible walker/transport chair apparatus, comprising a frame having a longitudinal axis in the forward and rearward directions, a pair of front wheels evenly spaced on either side of said longitudinal axis along a front transverse axis and rotatably mounted at the lower ends of a pair of upwardly extending front leg members, a pair of rear wheels evenly spaced on either side of said longitudinal axis along a rear transverse axis and rotatably mounted at the lower ends of a pair of upwardly extending rear leg members, a horizontal seating surface transversely disposed at the upper ends of said front and rear leg members, a pair of handle bar members slidably received for telescopic movement within the upper ends of said rear leg members and projecting upwardly and rearwardly of said seating surface, a pair of push handle assemblies, each of said assemblies disposed at the upper end of said handle bar member, a backrest connection member projecting forwardly from the upper end of each said handle bar members, a generally arcuate shaped backrest disposed transversely between said backrest connection members, pivotal attachment means disposed substantially in vertical alignment over the longitudinal mid-point of said seating surface for connecting said backrest to said connection members, said pivotal attachment means permitting said backrest to be pivoted between a first position in which said backrest extends in a generally horizontal forward projecting position adapted to support a rearward facing seated user&#39;s back when in the walker configuration and a second position in which said backrest extends in a generally horizontal rearward projecting position adapted to support a forward facing seated user&#39;s back when in the transport chair configuration, and stop means for selectively retaining said backrest in said first or second position. The backrest connection members are preferably connected to said push handle assemblies and is a strap formed of a flexible plastic material with said attachment means integrally moulded at the ends thereof. In a preferred embodiment, the walker/transport chair includes a cross-bar member extending transversely between the lower ends of said front leg members, the cross-bar member having a central portion thereof that is disposed substantially in vertical alignment with the front edge of the seating surface. The cross-bar may include integrally moulded end fittings extending forward of the lower end of said forward leg members, and wherein each of said front wheels is rotatably mounted in a caster type fork assembly having a vertically disposed mounting shaft, said mounting shaft being rotatably received in said end fitting.  
           [0016]    In a preferred embodiment, the walker/transport chair may include a footrest member mounted for pivotal movement between a stowed position transversely disposed between said front leg members and a deployed position projecting forward of the lower ends of said front leg members for supporting a forward facing seated user&#39;s feet when in the transport chair configuration.  
           [0017]    In accordance with another aspect of the invention, there is provided an apparatus for actuating a brake of a wheeled vehicle comprising a housing, a brake lever having a forward end retained in said housing and a handle projecting from the rear of said housing, and manually operable between a neutral position, a raised brake actuating position and a depressed brake locking position, said brake lever having a first pivot means and a first abutment surface located near the forward end of said brake lever, and a second pivot means and a second abutment surface located intermediate the forward end and the handle of said brake lever; whereby when said handle is raised from said neutral position to said brake actuating position said brake lever pivots about said first pivot means and said second abutment surface is moved to a raised position and when said handle is depressed from said neutral position to said brake locking position said brake lever pivots about said second pivot means and said first abutment surface is moved to a raised position, a brake actuating slide member retained in said housing having a third abutment surface in opposed relation with said first abutment surface whereby said upward movement thereof moves said slide upward along said axis and having a fourth abutment surface in opposed relation with said second abutment surface whereby said upward movement thereof moves said slide upward along said axis. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is a front right perspective view of the walker/transport chair of the present invention with the back rest in the walker position;  
         [0019]    [0019]FIG. 2 is a right side view of the walker/transport chair of the present invention with the back rest in the walker position;  
         [0020]    [0020]FIG. 3 is a plan view of the walker/transport chair of the present invention with the back rest in the walker position;  
         [0021]    [0021]FIG. 4 is a right side view of the walker/transport chair of the present invention with the back rest in the transport chair position;  
         [0022]    [0022]FIG. 5 is a plan view of the walker/transport chair of the present invention with the back rest in the transport chair position;  
         [0023]    [0023]FIG. 6 is a right side view of the back rest extension arm;  
         [0024]    [0024]FIG. 7 is a left side view the back rest extension arm;  
         [0025]    [0025]FIG. 8 is a perspective view showing the manner in which the backrest is connected to the extension arms;  
         [0026]    [0026]FIG. 9 is a front view of the cross-bar member;  
         [0027]    [0027]FIG. 10 is a top plan view of the cross-bar member;  
         [0028]    [0028]FIG. 11 is a right side view in partial section of the cross-bar member connection details;  
         [0029]    [0029]FIG. 12 is a side view of the inside of the right brake housing half;  
         [0030]    [0030]FIG. 13 is a side view of the inside of the left brake housing half;  
         [0031]    [0031]FIG. 14 is a left side view of the brake actuator slide;  
         [0032]    [0032]FIG. 15 is a rear view of the brake actuator slide;  
         [0033]    [0033]FIG. 16 is a right side view of the brake actuator slide;  
         [0034]    [0034]FIG. 17 is a side view of the inside of the right brake housing half showing the position of the brake actuator slide;  
         [0035]    [0035]FIG. 18 is a left side view of the brake lever;  
         [0036]    [0036]FIG. 19 is a right side view of the brake lever;  
         [0037]    [0037]FIG. 20 is a side view of the inside of the left brake housing half showing the brake lever in the neutral position;  
         [0038]    [0038]FIG. 21 is a side view of the inside of the left brake housing half showing the brake lever in the depressed brake locking position;  
         [0039]    [0039]FIG. 22 is a side view of the inside of the left brake housing half showing the brake lever and the brake actuator slide in the neutral position;  
         [0040]    [0040]FIG. 23 is a side view of the inside of the left brake housing half showing the brake lever and the brake actuator slide in the raised brake actuating position;  
         [0041]    [0041]FIG. 24 is a side view of the inside of the left brake housing half showing the brake lever in the depressed brake locking position;  
         [0042]    [0042]FIG. 25 is a right side view in partial section of the internal brake actuating mechanism of the present invention;  
         [0043]    [0043]FIG. 26 is a perspective view of the brake wire clamp;  
         [0044]    [0044]FIG. 27 is a right side view, in partial section showing the brake shoe connection details;  
         [0045]    [0045]FIG. 28 is a perspective view of the brake shoe;  
         [0046]    [0046]FIG. 29 is a side view of the brake shoe showing the position of the friction member;  
         [0047]    [0047]FIG. 30 is a perspective view of the friction member. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0048]    Referring to FIGS.  1  to  3 , there is shown a perspective view of walker/transport chair  10  in the walker configuration. Walker/transport chair  10  has a pair of forward leg members  12 , a pair or rearward leg members  16 , and a U-shaped transverse seat support member  20 . Front leg members  12  are fixedly secured at their upper ends to front leg brackets  22  and rear leg members  16  are fixedly attached at their upper ends to rear leg brackets  26 . Front leg brackets  22  are pivotally attached to rear leg brackets  26  at pivot pins  30 . In the open or operative position shown in FIGS.  1  to  3 , abutment surfaces  32  at the upper ends of front leg brackets  22  engage the forward lower edge of seat support member  20  when forward leg members  12  are in the open and weight bearing position. Front leg brackets  22  permit the front leg members  12  to be folded toward rear leg members  16  in order to collapse walker/transport chair  10  into a more compact configuration, for example for placement in the trunk of a car.  
         [0049]    Walker/transport chair  10  is locked in the open position by means of lock rod  73  which engages projections  75  on front leg brackets  22 . Handle  77  is rotatably mounted about transverse seat support member  20  for moving lock rod  73  out of engagement with projections  75 . Handle opening  36  is provided in seating surface  34  to provide easy access to handle  77 .  
         [0050]    Seating surface  34  is horizontally supported at its forward edge  90  by transverse seat support member  20  and provides a stable seating platform. Seating surface  34  is pivotally attached to transverse seat support member  20  such that it can be flipped to a vertical position by pulling up on rear edge  71 . This position is particularly useful when the user wishes to move as far forward as possible, for example when reaching ahead of the walker/transport chair to remove objects from a cupboard.  
         [0051]    Front leg members  12  are stabilized by cross-bar member  68  which extends horizontally between front leg members  12  and is fixedly secured to the bottom ends of front leg members  12  at end fittings  40 . Front wheels  38  are mounted on front fork assemblies having a vertical axle shaft carried in a bearing assembly (not shown) in each end fitting  46  for rotation about the vertical axis to permit front wheels  38  to caster for ease of steering walker/transport chair  10 .  
         [0052]    Rear wheels  42  are carried at the lower ends of rear leg members  16  on rear fork assemblies  44 . Rear fork assemblies  44  are fixedly connected to the lower ends of rear leg members  16 .  
         [0053]    Push handle assemblies  50  are fixedly attached to the upper ends of telescopic tubes  52  which are slidably received in rear leg members  16 . The height of push handle assemblies  50  can be adjusted by extending or retracting telescopic tubes  52  in rear leg members  16 . Telescopic tubes  52  have a series of through holes at uniform spacings along their length through which thumb screws  54  can be selectively inserted to fix push handle assemblies  50  at the desired height.  
         [0054]    Push handle assemblies  50  comprise handgrips  60 , handle housings  62  and brake levers  64 . Brake levers  64  are operatively connected to brake shoes  66  by length adjustable rod assemblies housed within telescopic tubes  52  and rear leg members  16 . Movement of brake levers  64  will cause brake shoes  66  to move into braking engagement with the tread of rear wheels  42  thereby arresting rolling motion.  
         [0055]    When walker/transport chair  10  is in the walker configuration as shown in FIGS.  1  to  3 , the user positions himself behind walker/transport chair  10 , and between push handle assemblies  50  facing the forward direction. In order to function as an effective walker, it is desirable that the geometry of the walker be such that the user can position himself far enough forward that his centre of gravity is vertically aligned over handgrips  60 . This will permit the user to support a substantial portion of his weight on handgrips  60  when desirable to reduce the weight on the feet. In order to ensure stability of the walker when a substantial vertical load is placed on handgrips  60 , the handgrips must be positioned forward of the point of ground contact of rear wheels  42 . Moreover, in order to facilitate walking, there must be sufficient room in front of the user to permit him to extend his feet forward in a natural walking gait without interfering with tile walker structure, and in particular with the seating surface. Accordingly, the position of seating surface  34  is biased to the front of walker/transport chair  10  such that its rear edge  71  is forward of handgrips  60 . In addition, seating surface  34  can be flipped to a vertical position about transverse seat support member  20  as described above. This will provide the user with additional space to move forward between push handle assemblies  50  if desired.  
         [0056]    When the user wishes to rest, he simply turns around between push handle assemblies  50 , using liandgrips  60  for support if required, and sits down on seating surface  34 , with his feet on the ground. Backrest  70  is provided to support the user&#39;s back while seated on walker/transport chair  10 . Backrest  70  is attached to extension arms  72  which are fixed at their rearward ends to push handle assemblies  50 .  
         [0057]    [0057]FIGS. 6, 7 and  8  show the details of extension arms  72  and the manner in which backrest  70  is attached to extension arms  72 . Extension arms  72  each have an inward facing partannular recess  96  with a central cylindrical bore  98  formed therethrough. Backrest  70  has formed therein two mounting points  100  and  102  for attachment to extension arm  72 . Mounting point  100  can be used as the point of attachment for a larger user whereas mounting point  102  effectively shortens the length of backrest  72  for a smaller user. The configuration of mounting points  100  and  102  is identical and will be described with reference to point  102  which is visible in FIG. 8.  
         [0058]    Backrest  70  is formed of a flexible plastic material and at each end has a connection piece  80 . Backrest  70  and connection piece  80  can be unitarily moulded of a suitable plastic material that has sufficient flexibility in the central back-supporting area to conform to and support a user&#39;s back and sufficient mechanical strength to function as a connection piece. In the alternative, backrest  70  and connection piece  80  can be separate components joined together. Moreover, backrest  70  can be formed of a rigid material such as aluminum if a non-flexible backstrap type backrest is desired. Connection piece  80  has all outwardly projecting key type lug  82  and a central bore  84  formed therethrough. Part-annular recess  96  in extension arm  72  is sized to fit over and closely receive key type lug  82  on backrest  70  with the cylindrical bores  84  and  98  axially aligned. A suitable bolt (not shown) with a smooth shank passes through cylindrical bores  84  and  98  and is fastened with a captive nut (not shown) located in hex-head recess  86  in connection piece  80 . In this manner, backrest  70  is pivotally connected to extension arms  72 .  
         [0059]    Stop lug  104  projects inwardly of recess  96  in extension arm  72 . Abutment surface  106  on stop lug  104  limits forward rotation of backrest  70  by contacting key type lug  82  in connection piece  80  and maintains backrest  70  in the forward facing horizontal position. Similarly, abutment surface  108  limits rotation of backrest  70  by contacting key type lug  82  in connection piece  80  and maintains backrest  70  in the rearward facing horizontal position. This arrangement permits backrest  70  to be manually flipped from the forwardly extending position shown in FIGS.  1  to  3  for use in the walker mode, to the rearwardly facing position, shown in FIGS. 4 and 5 for use in the transport chair mode.  
         [0060]    When walker/transport chair  10  is in the transport chair configuration, the user or a care-giver flips backrest  70  to the rearward extending position as shown in FIGS. 4 and 5. The user positions himself in front of and facing away from walker/transport chair  10  and sits down on seating surface  34  with his back against backrest  70 . Footrest  72  is then folded from the stowed position shown in FIGS. 2 and 3 to the deployed position shown in FIGS. 4 and 5. The user rests his heels on footrest tray  76  and in that position can be comfortably propelled by the care-giver in the transport chair mode. (Footrest  72  has been omitted from FIG. 1 to show greater detail of cross-bar  68 ). The forward facing seated position is not only useful when the apparatus is being propelled by a care-giver in the transport chair mode, but also permits the apparatus to be positioned close to a table, for example when eating a meal. Conventional walkers in which the user is seated in the rearward facing position are not well suited to this application because the rearward projecting handgrips and the rear wheels limit how close the walker can be placed, while the seating surface is typically positioned far forward of the hangrips.  
         [0061]    Conventional walkers usually require a cross-bar between the front leg members to strengthen the frame against collapse when the walker is bearing substantial weight, for example, when the user is seated. A front cross-bar is particularly required where the front leg members are pivotally attached to the frame to permit folding, which pivotal attachment provides little resistance to outward splaying of the legs under load.  
         [0062]    For conventional walkers, the presence of a cross-bar between the front legs of the walker typically does not interfere with the user&#39;s movements, as the user is positioned behind the walker in both the walking and sitting positions. However, the front cross-bar on a conventional walker interferes with its use as a transport chair. In particular, in order to assume the forward facing sitting position in the transport chair mode, a user must be able to position his heels very close to a point on the ground directly under the front edge of the seating surface. If the user is positioned too far forwards, he tends to lose balance when attempting to assume the seated position, falling backward in an uncontrolled manner onto the seating surface. This can cause the walker to upset resulting in serious injury to the user. Conventional cross-bars are usually positioned well forward of the front edge of the seating surface and accordingly tend to prevent a user from positioning his heels close to a point on the ground directly under the front edge of seating surface.  
         [0063]    The walker/transport chair design of the present invention is configured to overcome the limitations of conventional walker frame design. First, as seen in FIG. 1 front leg members  12  are positioned at an angle closer to vertical than are most conventional walkers. This minimizes the extent to which the lower ends of front leg members  12 , and consequently cross-bar  72 , project forward of the forward edge  90  of seating surface  34 . However, this has the undesirable effect of shortening the wheelbase and lessening stability. In order to provide for a lengthened wheelbase, the front fork assemblies  48  are not secured axially inside the lower end of front legs  12  as is conventional practice in walker design. Instead, front fork assemblies  48  are secured in end fittings  40  which project forwardly from the lower end of leg members  12 , effectively lengthening the wheelbase.  
         [0064]    Another feature of the present invention that enhances its use as a transport chair is the design of cross-bar  68 . As best shown in FIGS. 4 and 5, cross-bar  68  attaches to front leg members  12  at their lower ends, which point is forward of the forward edge  90  of seating surface  34 . In order to permit the user to more safely assume the forward-facing seated transport chair position, cross-bar  68  is rearwardly curved such that its central portion is located substantially under the forward edge  90  of seating surface  34 . This curved cross-bar arrangement permits the user to place his heels close to a point on the ground directly under the front edge of seating surface, and thereby. While a curved geometry is shown in the drawings, other configurations could be used so long as the cross-bar is configured such that its central portion is located substantially under or behind the forward edge  90  of seating surface  34 .  
         [0065]    Construction details of cross-bar  68  and end fittings  40  can be seen in FIGS.  9  to  11 . Cross-bar  68  and end fittings  40  are unitarily moulded or cast from a material of suitable strength. For example cross-bar  68  can advantageously be formed of cast aluminum. Cylindrical bores  120  are provided in cross-bar  68  to receive connector piece  122  which is bolted into the lower ends of forward leg member  12 . Front fork shaft  124  is vertically received in bore  126  and is rotatable retained by upper and lower bearings  128  fitted in bore  126 .  
         [0066]    As noted above, the front fork assemblies of conventional walkers are typically inserted directly into the hollow ends of the leg members. The fork mounting shaft is usually carried in a single bearing which is press-fitted into the bottom end of the leg member. This arrangement is prone to failure. In particular, repetitive striking of the wheels into curbs and other obstacles and impact over rough road surfaces has a tendency to deform and widen the lower end of the leg members into which the bearing is pressed. This can cause the bearing, and the entire fork/wheel assembly to fall out of the bottom of the leg member. By mounting the front fork assemblies  48  to end fittings  40  fitted with two bearings, rather than directly into a single bearing in the bottom end of the leg, the ability of the fork assemblies and the lower leg mounting hardware to absorb shock, without failure is greatly improved.  
         [0067]    The design of the walker/transport chair  10  permits the use of a novel and effective braking system. Conventional walkers use Bowden cables which extend from the hand grip mounted brake levers to the braking wheels. Bowden cables are relatively inexpensive and because they are flexible, can be installed with excess length in a free standing loop or bight to accommodate changes in length occasioned by the adjustment of handgrip height. However, the use of a Bowden cable arrangement has a number of disadvantages. The same free standing loop or bight that permits handgrip height adjustability is prone to being caught or hooked on various obstructions, particularly when the walker is loaded into, or unloaded from the trunk of a car. In addition, Bowden cables must be accurately adjusted and even a slight lack of adjustment can cause unsatisfactory braking action.  
         [0068]    The design of the present invention permits the use of an internal brake actuating mechanism. Referring to FIGS. 12 and 13, handle housing  62  comprises right side housing shell  200  and left side housing shell  202  which are bolted at their lower ends to telescopic tube  52 . Hand grip  60  is bolted between right side housing shell  200  and left side housing shell  202  at their upper ends. Brake lever  64  is retained between right side housing shell  200  and left side housing shell  202  in the manner described below.  
         [0069]    Referring to FIG. 12, the inside face of right side housing shell  200  is shown. Raised wall  204  forms an elongated groove  206  on the inside face with a longitudinal axis that is parallel to telescopic lube  52 . Semicircular bearing surfaces  208  are formed in the lower portion of the inside face.  
         [0070]    Referring to FIGS.  14  to  16 , brake actuator  210  has raised tongue portion  212  which is sized to be slidably retained in elongated groove  206  of right side housing shell  200  and cylindrical portion  214  which is sized to be slidably retained in semicircular bearing surfaces  208  of right side housing shell  200 .  
         [0071]    [0071]FIG. 17 shows the position of brake actuator  210  when it is slidably received in right side housing shell  200 . Bias spring  218  is carried between retaining lug  216  formed at the upper end of brake actuator  210  and stop wall  220  formed at the upper end of groove  206  and biases brake actuator  210  in the downward direction. Brake actuator  210  has elongated aperture  215  formed through cylindrical portion  214 . This elongated aperture  215  permits cylindrical portion  214  to extend down into telescopic tube  52  and allow bolts to pass through bolt holes  217  in right side housing shell  200 , telescopic tube  52 , elongated aperture  215 , telescopic tube  52  and bolt holes  217  in left side housing shell without interfering with the vertical sliding motion of brake actuator  210 . Such a through-bolting arrangement greatly improves the mechanical strength of the attachment of push handle assemblies  50  to telescopic tubes  52 .  
         [0072]    Referring to FIGS. 18 and 19, brake lever  64  comprises upper arm  220  and lower arm  222  joined at their rear extremities by ball shaped gripping projection  224 . Brake lever  64  is shaped such that braking action, as more completely described below, can be effected by placing the hands on handle grips  50 , inserting fingers through opening  226  and pulling up on upper arm  220  with inward gripping action. Downward pressure on lower arm  222  will move brake lever  64  downward into a locked or “parked” position, also as more completely described below. Ball shaped gripping projection  224  assists in moving brake lever in a downward direction by enabling the user to hook a thumb over the projection to apply downward force. This is particularly useful for a user with strength or mobility limitations in the hands.  
         [0073]    Pivot pin  228  projects from the left side of brake lever  64  at its forward end and is sized to be received in slot  230  formed in the inside surface of left side housing shell  202 . Brake actuating lug  232  projects from the right side of brake lever  64  and its upper surface engages downward facing abutment surface  234  formed in brake actuator  210 . Camming lug  236  projects from the left side of brake lever  64 . Brake lock actuating lug  238  projects from the right side of brake lever  64  at its forward end opposite pivot pin  228 .  
         [0074]    Referring to FIGS. 20 and 22, brake lever  64  is shown in the neutral position when no manual braking action is applied. In this position, the brake lever  64  projects rearwardly in a direction slightly below horizontal. Pivot pin  228  rests at the bottom of slot  230  in left side housing shell  202  and camming lug  236  (shown in phantom lines) rests on upward facing abutment surface  240  formed on the inside surface of left side housing shell  202 . Brake lever  64  is retained in this position by the downward pressure of bias spring  218  acting on brake actuator  210 , as can be seen with reference to FIG. 17.  
         [0075]    Downward facing abutment surface  242  (shown in phantom lines) formed in brake actuator  210  abuts the upper surface of brake lock actuating lug  238  (shown in phantom lines) formed in brake lever  64  and the downward action of bias spring  218  on brake actuator  210  urges pivot pin  228  to the bottom of slot  230 . Similarly, downward facing abutment surface  234  (shown in phantom lines) formed in brake actuator  210  abuts the upper surface of brake actuating lug  232  (shown in phantom lines) formed in brake lever  64  and the downward action of bias spring  218  on brake actuator  210  urges camming lug  236  into engagement with upward facing abutment surface  240 .  
         [0076]    Thus in the neutral position as shown in FIGS. 20 and 22, brake lever  64  rests with pivot pin  228  at the bottom of slot  230  and camming lug  236  resting on upward facing abutment surface  240 . Brake actuator  210  is urged downwardly by bias spring  218  and rests with downward facing abutment surface  242  resting on brake lock actuating lug  238  and downward facing abutment surface  234  resting on brake actuating lug  232 .  
         [0077]    Referring to FIG. 23, brake lever  64  is shown in the braking position when manual braking action is applied. In this position, the brake lever  64  has been pivoted about pivot pin  228  in the bottom of slot  230  until the upper arm  220  of brake lever  64  is substantially horizontal. This pivoting action causes brake actuating lug  232  (shown in phantom lines) to raise brake actuator  210  by engagement with downward facing abutment surface  234  (shown in phantom lines). By manually releasing brake lever  64 , bias spring  218  will urge brake actuator  210  back to the neutral position shown in FIG. 13. The upward motion of brake actuator  210  between the neutral and braking positions is transmitted to rear wheel brake shoes  66  in a manner described below.  
         [0078]    Referring to FIGS. 21 and 24, brake lever  64  is shown in the locked or “park” position. In this position, brake lever  64  has been pivoted down about camming lug  236  (shown in FIG. 21 in phantom lines). This pivoting motion causes pivot pin  228  to move upward in slot  230  and draws camming lug  236  forward over upward facing abutment surface  240  onto lower abutment surface  246 .  
         [0079]    As can be seen with reference to FIG. 24, this pivoting motion causes brake lock actuating lug  238  (shown in phantom lines) to raise brake actuator  210  by engagement with downward facing abutment surface  242  (shown in phantom lines). Brake lever  64  is retained in this locked or “park” position by the downward pressure of bias spring  218  acting on brake actuator  210  which urges camming lug  236  backwards into engagement with forward facing abutment surface  248 . Downward bias is also provided by spring  290  (see FIG. 27). By applying manual pressure to raise brake lever  64 , camming lug  236  is raised over forward facing abutment surface  248  and returns to the neutral position shown in FIG. 22. Thus, the sliding movement of camming lug  236  over forward facing abutment surface  248  provides an overcentre action to lock and unlock brake lever  64 . The upward motion of brake actuator  210  between the neutral and lock or “park” positions is transmitted to rear wheel brake shoes  66 , as described below.  
         [0080]    As is evident from the foregoing description, the user can apply and release a braking force to the walker by pulling up and releasing brake lever  64 , and can apply a constant braking force by pushing brake lever  64  down into the locked or “park” position.  
         [0081]    Referring now to FIG. 25, the manner in which the upward motion of brake actuator  210  is transmitted to rear wheel brake shoe  66  is shown. Brake actuator  210  is bolted in the upper end of telescopic tube  52  as described above. Telescopic tube  52  is slidably received inside rear leg member  16 . Rear leg member  16  is fixedly attached to fixed rear leg bracket  26  in a manner that leaves the inside volume of rear leg member  16  open to permit telescopic tube  52  to slide therein. For example, bosses having threaded sockets can be provided on the outer surface of rear leg member  16  and corresponding keyway can be formed in fixed rear leg bracket  26  to receive such bosses. Leg  16  and bracket  26  can then be secured by bolting through an aperture in the keyway into the threaded sockets.  
         [0082]    Telescopic tube  52  is provided with a series of evenly spaced holes  254  along a portion of its length. Fixed rear leg bracket  26  has a transverse bore  256  formed in each side, with the inner bore being internally threaded to receive the threaded end of thumb screw  54  (see FIG. 1). Handgrip assembly  50  may be fixed at the desired height by aligning a selected hole  254  in telescopic tube  52  with bore  256  in bracket  26 . Thumb screw  54  is inserted into the outer bore  256  of bracket  26 , through the selected hole  254  in telescopic tube  52 , and is screwed into the threaded inner bore  256  on the opposite side of bracket  26 .  
         [0083]    This arrangement provides for a secure manner of adjustably attaching handgrip assembly  50  to the fixed rear leg bracket  26  of the walker. The use of thumb screw  54  which passes entirely through telescopic tube  52  and is threaded into the opposite side of bracket  26  distributes the load applied by the user on handgrip assemblies  50  evenly across bracket  26 . This is a far more durable means of attachment than that one which merely secures the telescopic tube by a thumbscrew which passes through one wall of the bracket and squeezes against the outer surface of the telescopic tube. A solid attachment between the telescopic tube  52  and bracket  26  is extremely important not only for reasons of durability and safety, but also because of the sense of security imparted to the user. Users are far less willing to accept a walker if the handgrip assemblies feel loose or flimsily mounted. While the through-bolt arrangement of thumbscrew  54  does offer enhanced durability, it does requires a special arrangement to permit brake actuation internally within telescopic tube  52 .  
         [0084]    Referring to FIG. 25, brake wire  250  is formed in an inverted “U” shape with its bight at its upper end being retained in groove  252  formed in the cylindrical portion  214  of actuator  210 . Downwardly extending legs  258  and  260  of brake wire  250  are attached to brake rod  262  by means of clamp  264 . Brake rod  262  is an elongated “U” shaped channel member.  
         [0085]    Referring to FIG. 26, clamp  264  has back surface  268  and side surfaces  270  which are sized to be closely received in the “U” channel of brake rod  262 . Recesses  272  are provided to accommodate downwardly extending legs  258  and  260  of brake wire  250  and teeth  274  are formed in recesses  272  to grip brake wire  250 . Clamp  264  is drawn tight against the upper end of brake rod  262  by means of Allen screw  266  and teeth  274  trap and secure brake wire  250  to brake rod  262 . Allen screw  266  is axially aligned with the first hole  254  in telescopic tube  52  above bracket  26  permitting a wrench or key to be inserted therethrough for the purpose of loosening or tightening clamp  264 . Brake wire  250  can advantageously be formed of wound steel piano wire (e.g. 0.09 inch diameter) as the ridged surface thereof can be securely gripped by teeth  274 .  
         [0086]    Elongated slot  276  is formed in the centre web of brake rod  262 . Thumbscrew  54  which is threaded into transverse bore  256  passes through slot  276 . Slot  276  is sized as to permit brake rod  262  to be displaced longitudinally by the upward and downward movement of brake actuator  210  without contacting thumbscrew  54 .  
         [0087]    In order to adjust the height of handgrip assemblies  50 , a key or wrench is inserted through hole  254  above bracket  26  and Allen screw  266  is loosened to permit relative longitudinal movement between brake wire  250  and brake rod  262 . Thumb screw  54  is then unscrewed and withdrawn from transverse bore  256 . Telescopic tube is then raised or lowered until the desired hole  254  is axially aligned with transverse bore  256  and thumbscrew  54  is reinserted and tightened to secure telescopic tube  52  in bracket  26 . Finally, Allen screw  266  is tightened to secure brake wire  250  to brake rod  262 .  
         [0088]    Referring to FIG. 27, rear fork assembly  44  comprises inner and outer fork housings  280  (only one of which is shown in FIG. 20) between which rear wheel  42  is mounted for rotation about axle  282 . Rear fork assembly  44  is attached to rear leg member  16  by means of through-bolts (not shown) which pass through holes  283  in the fork housings and rear leg member  16 . Brake shoe  66  is pivotally mounted on shaft  284  which is transversely secured between fork housings  280 . Brake rod  262  is connected at its bottom end to brake shoe  66  at pivot point  286 . Elongated slot  288  is provided in the centre web of brake rod  262  to permit the through-bolts to pass therethrough and is sized to permit brake rod  262  to be displaced longitudinally by the upward and downward movement of brake actuator  210  without contacting the through-bolts. Spring  290  is retained between lug  292  and housing  280  and biases brake shoe out of engagement with rear wheel  42 .  
         [0089]    Referring to FIGS.  28  to  30 , the details of brake shoe  66  can be more readily seen. Brake shoe  66  has a horizontally disposed upper surface  294  an vertical sidewalls  296  which together bound a downwardly open cavity. Friction member  294  is carried within said cavity and is attached thereto at point  300 . Friction member  294  has downwardly protruding tang  302  at its rearward end. Adjusting screw  304  is threaded through the upper surface  294  of brake shoe  66  and contacts the upper surface of friction member  294 . The extent to which tang  302  protrudes below brake shoe  66  can be varied by turning adjusting screw  304  in or out. This adjustability permits fine tuning of the braking action and compensates for tire wear.  
         [0090]    When brake rod  262  is moved upwardly by the operation of brake lever  64 , brake shoe  66  is caused to pivot about shaft  284  forcing tang  302  downward into frictional engagement with rear wheel  42 . When brake lever  64  is released and returns to its neutral position, brake rod  262  moves downwardly and brake shoe  66  pivots out of frictional engagement with rear wheel  42 . In this manner, braking action is transmitted from brake lever  64  to brake shoe  66  internally of telescopic tube  52  and rear leg member  16 .  
         [0091]    While the present invention has been described with reference to the embodiments disclosed in the Figures, it will be understood that variations and modifications may be made without necessarily departing from the scope of the invention. Accordingly, the scope of the invention is to be determined in accordance with the claims appended hereto.