Abstract:
Cargo cart  10  can be used independently or attached to a conventional walker  101 . Cooperative attach means  40  connect cart  10  in front of walker  101  through roll leader  44 , which propels and steers cart  10  in response to user&#39;s control of walker  101 . In attached mode, rear wheels  34  of cart  10  are suspended above travel surface to allow cart  10  to be steered easily and predictably by roll leader  44 . Cart  10  is attached and detached with one hand without tools. Handle  50  and optional cargo basket  29  fold flat for storage. Slots in peripheral rails  24  retain cargo that is wider than cargo support  28.

Description:
FIELD OF THE INVENTION 
     This invention relates to carts propelled and controlled by a user, and more specifically to cargo carts that can be attached to a mobility device. 
     BACKGROUND OF THE INVENTION 
     Many people who have balance problems or weak muscles use some type of mobility device, such as an electric scooter or walker frame. These mobility devices typically require the user to use both hands to operate the device. The user steers the mobility device and either pushes the device with both hands or uses the hands to operate mechanical throttle and brake controls. 
     Because the user does not have a hand free for carrying any objects, such mobility aids frequently have some article carrier attached to it. Scooters often have a bicycle type basket mounted between the handlebars. Walker frames may have a tray, basket, or pouch attached to the frame. Users of walker frames with seats often place articles on the seat for transport. 
     Such article carrying containers are limited in size and lend themselves to transport of articles of only certain shapes and sizes. The carrying containers are typically attached to the upper part of the mobility device such that carrying heavy items can make the mobility device easier to overturn and harder to steer. Articles placed on a seat often fall off. 
     Thus, there is a need for a cart that users of mobility devices can use to safely carry larger and more awkwardly shaped articles than can be carried in conventional baskets, trays, or pouches. 
     Various attempts to create carts for use with wheelchairs have been made. One of the more practical-appearing examples is U.S. Pat. No. 4,484,755 of Houston. One embodiment of Houston&#39;s cart is included in the drawings herein as  FIG. 1 , labeled “Prior Art.” 
     Houston&#39;s cart  200  is supported by four wheels  210  and is attached to the front of a wheelchair  300  or walker frame (not shown). The axles of all four wheels  210  of cart  200  and the front pair of wheels  310  of wheelchair  300  are offset from the attachment points of wheels  210 , 310  such that all three pairs of wheels  210 , 310  are freely pivoting. This arrangement will likely result in unpredictable steering of the cart and wheelchair combination. 
     Houston does not describe the detailed means by which the user of wheelchair  300  steers cart  200 .  FIG. 1  shows that the cart and wheelchair combination includes three pairs of pivoting casters  210 ,  310  in series. The user of wheelchair  300  may need to use “opposite” steering, such as used by the driver of an auto with attached trailer to back up. Actually, the steering is likely to be far more unpredictable than simple opposite steering and the wheelchair/cart combination may tend to lock up during a complicated maneuver, such as a three-point turn in a grocery store aisle. 
     If Houston&#39;s cart  200  were attached to a walker frame with pivoting front wheels, the situation would be the same. Either the cart would swing unpredictably in response to steering of the walker, or the user would need to apply opposite steering and initially move in the direction opposite the turn. 
     Houston also discloses an embodiment of the cart attached to a walker frame without wheels (not shown). It appears the user of the walker would have to lift the walker and use the elevated walker frame to steer the Houston cart. This would potentially require more muscle power and agility than a typical user of a mobility aid device has, as well as putting the user off-balance with each change of direction. 
     The Houston cart  200  of  FIG. 1  elevates the basket portion well above the castered chassis. The Houston cart  200  clearly has a very high center of gravity; when loaded with articles it could be dangerously top heavy. 
     Other cargo-carrying carts for use in combination with wheelchairs have been patented. Most of them would not be feasible to use with a walker frame or scooter. None appear to be capable of being steered safely and intuitively by a person using a walker frame. 
     Thus, there is a need for a safe, convenient cart that can be attached to a mobility aid device, including an electric scooter, a wheelchair, or a walking frame. There is a need for a cart that can be propelled and steered easily by a fragile or even easily-confused person using a mobility device. There is a need for a cart that has a low center of gravity whether empty or heavily loaded and that will not tip. There is a need for a cart that can securely carry a variety of large or oddly-shaped articles. There is a need for a cargo cart that can be easily detached from the mobility device when not needed, that can be stored conveniently, and that can even be used independently of the mobility device. 
     SUMMARY OF THE INVENTION 
     The present invention is a cargo cart that can be attached to a mobility device, in particular a walker frame with wheels, often simply called “a walker.”. The cart can be attached and detached from the walker by the user, using one hand and without bending over. When detached from the walker, the cart can be used as a conventional hand truck or folded for storage. 
     The cart includes a cargo platform that is supported close to the floor by a pair of freely swiveling casters in front and a pair of non-swiveling wheels in back. A handle extends upwardly from the back end of the cart. 
     The back end of the cart can be attached to a walker so that the walker propels and controls the movement of the cart. The attachment means is adapted to support the back wheels of the cart slightly above the floor so that they do not interfere with the steering of the cart supported on the casters. 
     The user pushes and steers the walker in the accustomed manner. This movement and steering is transferred through the attachment to the cart so as to steer the cart in the same direction as the walker. 
     When the cart is not attached to a walker, it may be used as a hand truck, such as by pulling the cart by the handle. Thus, the cart can be used by others in the household of the user of the walker frame for various tasks. In this mode of use, the cart steers better if it is pulled so that the non-swiveling wheels precede the casters. 
     The cargo platform may be adapted so that it can accept many shapes of articles. For example, the platform is preferably surrounded by a rail to retain small articles. The rail preferably includes slots or protrusions to aid in holding items that are wider than the platform. Specialized article holders may be added, such as an optional tall basket for holding laundry or an insert with deep wells to hold pitchers and glasses of beverage. 
     The handle of the cart is adapted for folding flat for storage of the cart under a bed or hanging on a wall. The optional tall basket is adapted for folding flat along with the handle. 
     The features and advantages of the invention will be readily understood when the detailed description thereof is read in conjunction with the drawings wherein like reference numerals refer to like parts throughout. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a prior art shopping cart and wheelchair combination from the patent of Houston. 
         FIG. 2  is a left front perspective view of the cart of the present invention. 
         FIG. 3  is a front perspective view of the cart of  FIG. 2  attached to a conventional mobility device. 
         FIG. 4  is a left side elevation view of the cart and mobility device combination of  FIG. 3 , the right side being a mirror image. 
         FIG. 5  is a left front perspective view of a preferred embodiment of attachment means for the cart of  FIG. 2 . 
         FIG. 6  is a left front perspective view of the attachment means of  FIG. 5  mounted on an alternative conventional wheeled walker. 
         FIG. 7  is a front exploded perspective view of an alternative preferred embodiment of attachment means for the cart of  FIG. 2 , in combination with an alternative conventional wheeled walker. 
         FIG. 8  is a left front perspective view of an alternative embodiment of the cart of the present invention, including a tall basket for holding cargo. 
         FIG. 9  is a left front perspective view of the cart of  FIG. 8 , shown in a folded position. 
         FIG. 10  is a left front perspective view of the cart and walker frame combination of  FIG. 3 , showing a conventional folding chair carried as cargo. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 2  is a left front perspective view of the cart  10  of the present invention.  FIG. 3  is a front perspective view of cart  10  of  FIG. 2  attached to a conventional mobility device  100  such as a walker frame  101 , such as two-wheeled walker  101 A.  FIG. 4  is a left side elevation view of cart  10  and walker  101 A combination of  FIG. 3 . 
     Cart  10  generally includes a first end  14  defining a first direction of travel, a second end  16  defining a second direction of travel, cargo portion  20  between first end  14  and second end  16 , wheels  30 , attachment means  40  for attaching cart  10  to walker  101 , and a handle  50  attached to first end  14 . 
     First end  14  and second end  16  define a longitudinal axis x of the cart  10  stretching between them. Cart  10  has a first and a second direction of travel, as shown in  FIG. 4 . 
     Cargo portion  20  includes frame  22  with peripheral rails  24  and cargo support area  28  enclosed within rails  24 . Frame  22  is generally rectangular and includes rails  24  on all four edges. Rails  24  add strength to frame  22  and prevent cargo from rolling or sliding off of cargo support  24 . 
     Wheels  30  are attached to frame  22  of cargo portion  20 . Wheels  30  typically include a pair of non-pivoting wheels  34  attached to opposing sides of frame  22  near first end  14  such that the axis of rotation of each wheel  34  is perpendicular to longitudinal axis x. 
     Wheels  30  further include one or more casters  32  attached to frame  22  near second end  16 . Caster  32  is a conventional pivoting roller including an offset bracket  33 A and rolling member  33 B. Offset bracket  33 A is free to pivot at least 180° about a vertical axis. Rolling member  33 B is rotatably mounted in offset bracket  33 A with a horizontal axis of rotation. Because the pivot axis and rotation axis of caster  32  are offset, rolling member  33 B has many degrees of freedom for traveling upon travel surface  150 . 
     Preferably, one caster  32  is attached to each of the opposing sides of frame  22  to which a non-pivoting wheel  34  is attached. If cart  10  has four wheels  30  attached at four corners of a generally rectangular frame  22 , the carrying capacity of cart  10  is maximized and cart  10  will not easily tip over when loaded. 
     Handle  50  is attached to frame  22  near first end  14 . Handle extends upwardly from frame  22  to a height that is convenient for a user to grasp. Handle  50  may be a U-shaped frame as depicted in the drawings, a single upright shaft, or any other convenient arrangement. Handle  50  is preferably narrow in side profile so as to not interfere with walker  101  when cart  10  is attached. 
     The preferred embodiment of handle  50 , attached near first end  14 , as shown in the drawings, provides a secondary benefit of acting as a safety screen to help stabilize loaded cargo and prevent items being carried on cart  10  from falling through the frame of walker  101  and striking or tripping a user. 
     Handle  50  is used to pull and steer cart  10 , preferably in the first direction of travel, when cart  10  is unattached to walker frame  101 . Preferably, handle  50  can be shortened for storage of cart  10  when not in use. Handle  50  may be adapted to fold flat over cargo portion  20 , telescope downward to a low height, or even be removed from frame  22 . 
       FIGS. 3 and 4  illustrate cart  10  attached to a walker  101 A that includes left side  120 , right side  122 , and center section  124  connecting right and left sides  120 , 122 . 
     Cart  10  is selectively attachable to any walker  101  with cooperative attachment means  40 . Attachment means  40  typically includes two cooperating components: cart attachment means, which is typically an integral part of frame  22 , such as hook means such as hooks  42 , and walker attachment means  43 . 
     Walker attachment means  43  typically includes a horizontal roll leader  44  that engages with hooks  42 . As seen in  FIG. 3 , center section  124  of walker  101 A includes a lower crossbar  126 . Lower crossbar  126  is in the desired range of 5⅜ to 5⅝ inches above travel surface  150 , so crossbar  126  is well adapted for use as roll leader  44 . 
     Cart  10  is attached to walker  101 A by positioning hooks  42  close to roll leader  44  and pulling upward on handle  50 , preferably with no cargo loaded in cart  10 . Handle  50  is manipulated to engage hooks  42  with roll leader  44 . This operation may be performed with only one hand, so that one hand can remain on walker  101 A for support or balance. The user does not need to bend over to see or manipulate small fittings. 
     As best seen in  FIG. 4 , when hooks  42  are engaged with roll leader  44 , first end  14  of cart  10  is attached to walker frame  101 A and non-pivoting wheels  34  are supported about 0.5 inch above travel surface  150 . Supporting non-pivoting wheels  34  above travel surface  150  simplifies steering of the combination of cart  10  with walker  101 , as will be explained below. 
     To use cart  10  with a walker  101  that does not have an appropriate existing feature to use as roll leader  44 , an adaptor bracket  47  is removably mounted upon walker  101  to adapt it for attachment to hooks  42 . 
       FIGS. 6 and 7  depict alternative walker frames  101 .  FIG. 6  shows a walker frame  101 B with two front wheels  104  and two rear wheels  105 . 
     Walker frame  101 A of  FIGS. 3 ,  4 , and  10  and walker frame  101 B of  FIG. 6  are controlled by gripping control means  110  of walker frame  101 , such as the uppermost portions of left and right sides  120 , 122  of walker frame  101 A or walker frame  101 B. Walker frame  101 C of  FIG. 7  is controlled by handlebars  110 B. 
     The user propels walker frame  101  by pushing or pulling control means  110  and steers by applying differential pressure to left and right control means  110 . The differential pressure causes the pair of front wheels  104  to turn toward the desired direction. The rear wheels  105  of walker frame  101 B respond, as do casters  32  of cart  10 . Both the propulsion and the steering are directly transferred from control means  110  through roll leader  44  to cart  10 . 
     If non-pivoting wheels  34  were left in contact with travel surface  150  when cart  10  is attached to walker  101 , the multiple pairs of wheels would confuse the direction of steering. In some cases, the user might need to steer walker  101  in the opposite direction from the direction desired in order to steer cart  10  in the direction desired. In some cases, non-pivoting wheels  34  might get into an orientation that would require forward-and-backward shuffling of walker  101  to get straightened out, or might require excessive force from the user to overcome. 
     Because the cargo cart  10  of the present invention supports non-pivoting wheels  34  above travel surface  150  when attached to walker  101 , casters  32  follow front wheels  104  of walker frame  101  easily and predictably. 
       FIG. 5  is a front perspective view of an alternative preferred embodiment of walker attachment means  43 , adapter bracket  47  such as drop bracket  46 . Drop bracket  46  is for adapting walker  101 B to cooperate with hooks  42 . Drop bracket  46  includes roll leader  44  and mount means to mount drop bracket  46  on walker  101 B, such as plurality of hooks  49 .  FIG. 6  is a front perspective view of drop bracket  46  of  FIG. 5  mounted on walker  101 B. 
     Roll leader  44  is a preferred height above travel surface  150 . Hooks  42  can then be dropped onto roll leader  44  as described above. 
       FIG. 7  is a front perspective, exploded view of an alternative preferred embodiment of adapter bracket  47 , such as crosstie  48 , for adapting conventional walker  101 C for attachment to cart  10 . Crosstie  48  includes roll leader  44  and mounting means such as clamps  45 . Clamps  45  are used to mount crosstie  48  on walker  101 C at a desired height for engaging with hooks  42 . 
     It can be seen that many designs of walker  101  can be adapted for use with cart  10  by mounting an appropriate adaptor bracket  47 . Preferred features of a appropriate walker adaptor bracket  47  are that it provide an attachment point such as roll leader  44  that will support non-pivoting wheels  34  at the preferred height when attached, that adaptor bracket  47  is easy to mount on walker  101 , that cart  10  is easy to attach to adaptor bracket  47  with one hand and without bending, and that adaptor bracket  47  does not impede the normal use of walker  101 , such that it will not be necessary to remove adaptor bracket  47  after every use of cart  10 . 
     Cooperative attachment means  40  has been described and illustrated herein as comprising a pair of hooks  42  for mounting upon a horizontal crossbar  126  or roll leader  44 . It will be apparent that many forms of mechanical attachment as are well known are feasible for use as cooperative attachment means  40 . 
     For example, hooks  42  may alternatively comprise a single half tube attached to first end  14  and opening downwardly, that engages roll leader  44 . 
     Roll leader  44  may include centering means, such as protrusions  49  on roll leader  44 , as shown in  FIG. 3 .  FIG. 3  shows cart  10  attached to a walker  101 A that has an appropriate existing feature (crossbar  126 ) that functions as roll leader  44 . Protrusions  49  are preferably thick flexible rings that can be mounted on roll leader  44  or may be simply bands of friction tape wrapped around roll leader  44 . 
     Cargo cart  10 , as shown in  FIGS. 2 ,  3 , and  4 , includes exemplary adaptations for supporting large cargo such as features  26 , various recesses or protrusions of rails  24 . Features  26  may be used for retaining a variety of cargoes, and may also be specially adapted for certain frequently carried items.  FIG. 10  shows cart  10  supporting a folding chair  400 . Although folding chair  400  is wider than cargo support  28 , features  26  hold the frame of folding chair  400  securely. 
     Other adaptations for retaining cargo are also possible.  FIGS. 8 and 9  show cargo cart  10  with a tall basket  29 , such as could hold laundry or long-handled household cleaning tools. Basket  29  folds flat for storage, as seen in  FIG. 9 . An alternative preferred embodiment, not shown, includes a closeable removable case adapted to fit snugly within rails  24 . 
     An alternative embodiment, envisioned but not illustrated, has handle  50  attached to second end  16  of cart  10 . This embodiment would have the potential advantage of making cart  10  easier to use as a pushed handcart in the unattached mode, instead of a pulled cart. This embodiment would have the potential disadvantage of limiting the size of cargo able to be carried by cart  10 . 
     Although particular embodiments of the invention have been illustrated and described, various changes may be made in the form, composition, construction, and arrangement of the parts herein without sacrificing any of its advantages. Therefore, it is to be understood that all matter herein is to be interpreted as illustrative and not in any limiting sense, and it is intended to cover in the appended claims such modifications as come within the true spirit and scope of the invention. 
     For example, the invention has been mainly described and illustrated herein as being for attachment to a wheeled walker  101 . Cart  10  is easily adapted for use with other sorts of mobility device, such as wheelchairs or electric scooters.