Abstract:
An adjustable wheel suspension assembly for a wheeled walker providing both lateral and longitudinal stability under load. With a calibrated spring preload adjustment, the wheel suspension assembly provides lateral stability for any particular user body weight and a wheel deflection working stroke sufficient to absorb wheel shocks over irregular terrain. The wheel suspension assembly is particularly advantageous for upright wheeled walkers.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is filed under 35 U.S.C. 111(a) pursuant to 37 C.F.R. 1.53(b) and claims the benefit under 35 U.S.C. §119(e) of U.S. Patent Application No. 62/215,656 filed on Sep. 8, 2015 and entirely incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention: 
         [0003]    This invention relates generally to a wheel suspension assembly for wheeled mobility-assistance devices and more particularly to an adjustable wheel suspension for wheeled walkers 
         [0004]    2. Description of the Related Art 
         [0005]    The wheeled walker (also denominated rollator) is well-known in the art as an improvement to the earlier walker and cane mobility aids and is a popular mobility assistance vehicle for the mobility impaired. The advantages of the wheeled walker are known to include smother and more comfortable movement along even surfaces without obliging the user to lift or slide the aid along. But adding wheels to the mobility aid introduces the new disadvantages of instability and user safety. For example, in U.S. Pat. No. 8,936,033, Velarde suggests adding wheels to only two of the four walker supports to ease movement while controlling instability. 
         [0006]    Many practitioners suggest further improvements to mitigate these added disadvantages. For example, in U.S. Pat. No. 4,907,794, Rose discloses a foldable rolling walker having a high crossbar for easier walking convenience, height adjustable handles centered over offset wheels for greater stability, lockable pivoting front wheels and reversible brakes. Other similar improvements made to wheeled walkers include folding mechanisms, user-controlled wheel brakes and larger wheel sizes to improve stability and user safety. For example, in U.S. Pat. No. 7,001,313, Crnkovich discloses a rollator that includes four large pneumatic tires, with rear tires larger than the front tires, to facilitate safer movement over rough terrain. As another example, in U.S. Pat. No. 9,173,802, Willis discloses a collapsible wheeled walker with large wheels and a folding mechanism for convenient storage. 
         [0007]    Some practitioners propose improving the walker mobility aid by adding upper body support means for supporting the user&#39;s forearms, hands or shoulders, to improve user comfort and posture. For example, in U.S. Pat. No. 5,657,783, Sisko et al. disclose accessory forearm rests that may be mounted to any conventional invalid walker, preferably disposed above the normal hand-grips to provide added upper body support. 
         [0008]    Such an upright wheeled walker may provide enough upper body support to permit the user to walk upright. For example, in U.S. Pat. No. 8,540,256, Simpson discloses a walker with a forearm support frame to permit an upright user to step forward with the walker footprint. Similarly, in U.S. Pat. No. 8,740,242, Stomp discloses a foldable posterior walker with an anteriorly open frame that permits an upright user to step forward within the walker footprint. 
         [0009]    But adding upright support to the wheeled walker introduces the new disadvantages of lateral and longitudinal instability and user safety. Any wheeled walker has longitudinal stability problems when rolling on slopes and over irregular terrain, which may imperil user safety by causing falls during use. This longitudinal instability problem is exacerbated by adding upright support to a wheeled walker because of the increased wheel loads imposed by user upper body weight, which not only increases unwanted longitudinal instability but introduces a new lateral instability arising from the alternating wheel load fluctuations created by user stepping. 
         [0010]    Several practitioners suggest improvements to mitigate the wheeled walker longitudinal stability problem with braking system improvements. For example, in U.S. Pat. No. 8,998,223, Chang discloses a wheel braking system for a rollator with a “dead-man brake” whereby the wheels are halted upon the release of the user&#39;s hands from the handles, improving user safety on slopes. Similarly, in U.S. Pat. No. 9,221,433, Dunlap discloses a safety braking system for a rollator that includes a park mode, a walk mode and a brake mode with a handlebar control mechanism. 
         [0011]    Several practitioners suggest improvements to mitigate the wheeled walker longitudinal stability problem with wheel suspension improvements. A rolling walker may include a spring suspension at each wheel to absorb shocks from rough terrain, thereby improving longitudinal stability. But in an upright wheeled walker, the wheel spring suspension exacerbates the lateral instability arising from the alternating wheel load fluctuations created by user stepping. Hardening or eliminating the suspension springs can reduce lateral instability but only at the expense of increasing longitudinal instability over irregular terrain. 
         [0012]    Several practitioners suggest improvements to mitigate lateral or longitudinal rollator stability to increase user safety and prevent falls. For example, in U.S. Pat. No. 8,100,415, Kindberg et al. disclose a wheel suspension for a rollator that facilitates curb climbing. Similarly, in U.S. Pat. No. 5,636,651, Einbinder discloses an adjustable walker controller for stabilizing a wheeled walker by selectively shifting between a mobile and a stable state. But there remains a long-felt unmet need in the art for a suspension that provides both longitudinal and lateral stability in an upright wheeled walker in all states. 
         [0013]    These unresolved problems and deficiencies are clearly felt in the art and are solved by this invention in the manner described below. 
       SUMMARY OF THE INVENTION 
       [0014]    This invention solves the upright wheeled walker stability problem by providing a wheel suspension assembly that, for the first time, suppresses lateral motion from fluctuating wheel load fluctuations created by user stepping while also dampening wheel shocks from irregular terrain. Through a calibrated spring preload adjustment, the wheel suspension assembly of this invention provides lateral stability for any particular user body weight and a wheel deflection working stroke sufficient to absorb wheel shocks over irregular terrain, This wheel suspension assembly is particularly advantageous for upright wheeled walkers. 
         [0015]    It is an advantage of the wheel suspension assembly of this invention that a preload adjustment may be made to facilitate customization for any user. 
         [0016]    It is a purpose of the wheel suspension assembly of this invention to provide a wheel suspension for wheeled walkers that stabilizes the walker both laterally during user stepping and longitudinally over irregular surfaces when bearing some user body weight. 
         [0017]    In one aspect, the invention is a wheel suspension assembly coupled between one of the plurality of wheels and the frame in a wheeled walker having a frame supported above a surface by a plurality of wheels, comprising a preloaded spring restrained by a preload force and disposed to resist displacement of the frame toward the surface and a compressor for changing the preload force. 
         [0018]    In another aspect, the invention is a mobility assistance vehicle adapted to support at least some user weight, comprising a frame having a supporting structure adapted to support the user, a plurality of wheels connected to the frame and a shock absorber having a shock absorbing element pre-loaded to a predetermined load limit and disposed between two ends, one shock absorber end being coupled to the frame and the other shock absorber end being coupled to one of the plurality of wheels. 
         [0019]    In a preferred embodiment, the invention is an upright wheeled walker comprising a frame and a plurality of wheel assemblies coupled to the frame and disposed to support the frame above a surface; each comprising a wheel and a wheel suspension assembly coupled between the wheel and the frame including a preloaded spring restrained by a preload force and disposed to resist displacement of the frame toward the surface and a compressor for changing the preload force. 
         [0020]    The foregoing, together with other objects, features and advantages of this invention, can be better appreciated with reference to the following specification, claims and the accompanying drawing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    For a more complete understanding of this invention, reference is now made to the following detailed description of the embodiments as illustrated in the accompanying drawing, in which like reference designations represent like features throughout the several views and wherein: 
           [0022]      FIG. 1  is an oblique view of an exemplary upright wheeled walker embodiment with four wheel assemblies illustrating an exemplary embodiments of this invention; 
           [0023]      FIG. 2  is a close-up oblique view of the left front wheel assembly embodiment of  FIG. 1 , 
           [0024]      FIG. 3  is a close-up cutaway side view of portion of the wheel assembly embodiment of  FIG. 2  illustrating the wheel fork assembly hinge structure; 
           [0025]      FIG. 4  is an oblique view of the wheel suspension assembly embodiment of  FIG. 2 ; 
           [0026]      FIG. 5  is a side cross-sectional view of the wheel suspension assembly embodiment of  FIG. 4 ; 
           [0027]      FIG. 6  is an oblique view of an exemplary (spring) shock absorber embodiment suitable for use with the wheel suspension assembly of this invention; 
           [0028]      FIG. 7  is a side cross-sectional view of the shock absorber element embodiment of  FIG. 6 ; 
           [0029]      FIG. 8  is an exploded view of the shock absorber embodiment of  FIG. 6 , 
           [0030]      FIG. 9  is a side view of an exemplary embodiment of a preload force setting tool and indicator embodiment suitable for use with the wheel suspension assembly of this invention; 
           [0031]      FIG. 10  is a chart illustrating the force vs. displacement characteristic of the shock absorber embodiment of  FIG. 6 ; 
           [0032]      FIG. 11  view of an alternative (gas) shock absorber embodiment suitable for use with the wheel suspension assembly embodiment of this invention; 
           [0033]      FIG. 12  is a chart illustrating the force vs. displacement characteristic of the shock absorber embodiment of  FIGS. 11 ; and 
           [0034]      FIG. 13  is an oblique view of a user standing in a partially supported position with the upright wheeled walker embodiment of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0035]      FIG. 1  shows an upright wheeled walker  100  with a frame  102  supported above a surface  104  on four wheel assemblies exemplified by a wheel assembly  106  at the left front corner and with an upper body support assembly  108 . Wheel assembly  106  includes a wheel  110  and a wheel suspension assembly  112 , which is fixed to frame  102  at a junction  114 . 
         [0036]    During use, a user (not shown) stands between the two frame elements  116 A- 13  and grasps each of the upper handles  118 A-B with a hand (not shown) while resting a forearm (not shown) in each of the armrest gutters  120 A-B, thereby resting at least some weight on upright wheeled walker  100  and surface  104  The user may then walk forward in the direction shown by the arrow  122  as upright wheeled walker  100  rolls over surface  104  while supporting at least some weight, thereby assisting the user to walk over surface  104 . 
         [0037]      FIG. 1  also illustrates an X-folder element  124  and an upper folder element  126  that are useful for collapsing upright wheeled walker  100  for convenient storage and transportation. The elevation adjusters  128 A-B are useful for adjusting the elevation of upper body support assembly  108  above surface  104  for a particular user height and each of the angle adjusters  130 A-B are useful for adjusting the angle of the respective upper handle  118 A-B. The lower handles  132 A-B are useful for several purposes such as providing user support when arising from a seated position (not shown), for example. 
         [0038]      FIG. 2  shows wheel assembly  106  in more detail. A wheel fork assembly  134  is rotatably coupled to wheel  110  at an axle  136  and to wheel suspension assembly  112  at a hinge  138  thereby permitting displacement of frame  102  with respect to surface  104  responsive to any rotation of wheel fork assembly  134  at hinge  138  and axle  136 . Any rotation of wheel fork assembly  134  changes the elevation  140  of frame  102  above axle  136  as can be appreciated with reference to the arrows  142  and  144  in  FIG. 2 . Wheel suspension assembly  112  is also in contact with wheel fork assembly  134  at the support  146  and controls elevation  140  responsive to the downward force  148  imposed on wheel assembly  106  in the manner that is described below in connection with  FIGS. 5-12 . 
         [0039]      FIG. 3  shows a cutaway side view of wheel assembly  106  illustrating the wheel fork assembly hinge  138  and the lower portion of wheel suspension assembly  112  with the shock absorber  150  ( FIGS. 6-7 ) removed (dotted lines) for clarity. The absent lower pin  152  (dotted lines) of shock absorber  150  ( FIGS. 6-7 ) normally rests against a cavity  154  in wheel fork assembly  134  substantially as illustrated. A snubbing spacer  156  of any suitable material known in the art is shown disposed to limit the rotation about hinge  138  and avoid metal-on-metal contact from larger shocks. 
         [0040]    Wheel suspension assembly  112  is shown in  FIG. 4  in an oblique view and in  FIG. 5  as a cross-sectional side view showing lower pin  152  and hinge  138 .  FIG. 6  shows shock absorber  150  in an oblique view as it appears when removed from wheel suspension assembly  112 .  FIG. 7  shows shock absorber  150  in a cross-sectional side view, which is now described. 
         [0041]    In  FIG. 7 , shock absorber  150  includes the outer housing  158  that houses a preloaded spring  160  embodiment that contains the coil spring  162 , which is compressed and restrained by the preload force created between lower pin  152  and the upper pin  164  when the spring compressor  166  embodied as a cap screw is threaded into outer housing  158 . Coil spring  162  may be embodied as, for example, a constant pitch column spring characterized by a constant spring coefficient or as a conical spring, or an hourglass spring, or a barrel-shaped spring, or any useful spring providing a variable spring coefficient over a varying suppression distance, for example. In shock absorber  150  the preload force can be changed by threading spring compressor  166  along inside outer housing  158  to adjust the distance  168 , which may be measured with a calibrated preload force setting indicator such as the scaled hex wrench embodiment  170  illustrated in  FIG. 9 , for example, to determine the preload force imposed on preloaded spring  160 . 
         [0042]      FIG. 8  shows an exploded view of the elements of shock absorber  150  to illustrate more clearly the relationship among outer housing  158 , lower pin  152 , coil spring  162 , upper pin  164 , and spring compressor  166 . Coil spring  162  is selected with the length and spring constant necessary for imposing the preload force desired when assembled. According to the teachings of this invention, this preload force must be selected to simultaneously absorb wheel shocks while rolling over uneven terrain and support the user body weight resting on the wheeled walker wheels without reducing elevation  140  ( FIG. 2 ) of frame  102  beyond a predetermined amount. Wheel suspension assembly  106  accomplishes this with shock absorber  150  in the manner that may be appreciated with reference to  FIG. 10 . 
         [0043]      FIG. 10  is a curve  172  illustrating the relationship between the displacement (along the vertical axis  174 ) of frame elevation  140  ( FIG. 2 ) and the force imposed on wheel suspension assembly  106  (along the horizontal axis  176 ) for shock absorber  150  of  FIG. 7 .  FIG. 10  is not to scale and certain regions are emphasized to better illustrate the features of this invention. Curve  172  has three regions demarked with dotted lines and labeled as a stability region  178 , a shock absorbing region  180  and a snubbing region  182 . Within stability region  178 , upright wheeled walker  100  ( FIG. 1 ) will remain at a fixed elevation above surface  104  ( FIGS. 1-2 ) for any imposed downward force between zero and a predetermined adjustable force  184 , which may be adjusted by adjusting compressor  166  ( FIGS. 7-8 ) using, for example, scaled hex wrench  170  ( FIG. 9 ) as a calibrated preload force indicator. Within shock absorbing region  180 , which is a linear region for the constant pitch column spring embodiment of coil spring  162  illustrated in  FIGS. 7-8  (force rises linearly with displacement), shock absorber  150  operates to absorb wheel shocks while rolling over uneven terrain. In snubbing region  182 , wheel suspension assembly  112  ( FIG. 3 ) has bottomed out against snubbing spacer  156  ( FIG. 3 ) at a maximum design displacement  186  and no additional displacement is possible. 
         [0044]    In a preferred embodiment, when a user rests on wheeled walker  100  with her arms on armrest gutters  120 A-B, wheeled walker  100  carries some user weight and gives her support for better mobility. Preferably coil spring  162  is preloaded by compressor  166  according to the user&#39;s weight and her support preference, in such a manner that the user&#39;s supported weight alone permits shock absorber  150  to operate in stability region  178 . This means that the amount of force exerted on shock absorber  150  by the supported user through armrest gutters  120 A-B is less than the spring preload force created by compressor  166 . Accordingly, there is no walker elevation change under the supported weight and the user enjoys a stable ride. 
         [0045]    However, when wheel  110  encounters and rolls over uneven terrain, such as a rock or an edge, for example, a shock force is received by wheel  110  transferred to shock absorber  150  through wheel fork  134  and lower pin  152 . According to the purpose of this invention, the spring preload force is predetermined to be less than the shock force magnitude created by rolling over uneven terrain. Accordingly, when shock absorber  150  operates in shock absorbing region  180 , any shock force exceeding the predetermined preload force is absorbed by compression of coil spring  162 , thereby maintaining longitudinal stability and cushioning the user from unpleasant bumps and jars when rolling over uneven terrain. The predetermined spring preload force is preferably established according to the user&#39;s weight, which creates a known correlation between the distance  168  ( FIG. 7 ) and the user&#39;s weight. Thus, hex wrench embodiment  170  may be, for example, scaled with various user weights in pounds as shown in  FIG. 9 , for convenient calibration of the preload force established in shock absorber  150  according the user&#39;s weight. 
         [0046]      FIG. 11  shows an alternative shock absorber embodiment  188  suitable for use with the wheel suspension assembly of this invention. Shock absorber  188  includes an outer housing  190  containing a gas pressure chamber  192  that embodies a preloaded spring.. The upper valve core  194  embodies a compressor means to change the gas pressure in chamber  192 , thereby providing an adjustable preload force on the lower pin  196 , which is slidably engaged with gas pressure chamber  192  and sealed with a gas seal  198  to prevent loss of preloaded chamber pressure. Any useful gas pressure gage (not shown) may be used as a preload force setting indicator to measure gas pressure in chamber  192  whereby the preload force restraining lower pin  196  can be adjusted by varying the gas pressure in chamber  192  to a desired value. Shock absorber  188  is suitable for use with the wheel suspension assembly of this invention as may be appreciated with reference to  FIG. 12 . 
         [0047]      FIG. 12  is a curve  200  illustrating the relationship between the displacement (along the vertical axis  174 ) of frame elevation  140  ( FIG. 2 ) and the force imposed on wheel suspension assembly  106  (along the horizontal axis  176 ).  FIG. 12  is not to scale and certain regions are emphasized to better illustrate the features of this invention. Curve  200  has three regions demarked with dotted lines and labeled as a stability region  202 , a shock absorbing region  204  and a snubbing region  206 . Within stability region  202 , upright wheeled walker  100  ( FIG. 1 ) will remain at a fixed elevation above surface  104  ( FIGS. 1-2 ) for any imposed downward force between zero and a predetermined adjustable force  208 , which may be adjusted by adding or releasing gas from gas pressure chamber  192  through the upper valve core  194  ( FIG. 11 ) using, for example, any useful gas compressor and pressure gage known in the art (not shown) as a calibrated preload force indicator. Within shock absorbing region  204 , which is an inverse region (force rises linearly with pressure which rises as the reciprocal of volume), shock absorber  188  operates to absorb wheel shocks while rolling over uneven terrain. In snubbing region  206 , wheel suspension assembly  112  ( FIG. 3 ) has bottomed out against snubbing spacer  156  ( FIG. 3 ) at a maximum design displacement  186  and no additional displacement is possible. Unlike coil spring  152  ( FIGS. 7-8 ), gas pressure chamber  192  will not “bottom out” internally. 
         [0048]      FIG. 13  illustrates a user  300  standing with upright wheeled walker  100  and illustrates the proper disposition of user forearms and hands when using upright wheeled walker  100  for support while walking along a surface substantially as described above. 
         [0049]    Clearly, other embodiments and modifications of this invention may occur readily to those of ordinary skill in the art in view of these teachings. Therefore, this invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawing.