Abstract:
A wheeled carrier device is provided which includes a plurality of foldable walls supported on a base member and movable between an erected state wherein the walls define a carrier space and a collapsed state wherein the walls are folded on top of the base member. The carrier device has at least two wheels and a wheel mounting assembly pivotably mounts the wheels on the device on opposite sides thereof such that the wheels are movable through 270° from a first, operative position wherein the wheels support the carrier device and a second, inoperative position wherein the wheels are folded over on top of the folded walls in the collapsed state thereof. A handle is affixed to the carrier device and is movable between an operative state wherein the handle can be used to pull the carrier device and an inoperative state wherein the handle is stowed in substantially flush relation with the remainder of the carrier in the collapsed state of the walls.

Description:
FIELD OF THE INVENTION 
     The present invention relates to wheeled carts, wagons and like carrier devices and, more particularly, to a collapsible wheeled carrier device which folds or collapses down to a very thin profile. 
     BACKGROUND OF THE INVENTION 
     Consumers have increasingly placed a premium on compact yet durable, space saving devices which move cargo, a fact that is easily demonstrated by the exponential growth in wheeled luggage devices using recessing, telescoping handles, as well as the ever expanding number of utility carts and four wheel wagons providing folding or recessing handles. It is often the stated object of many of these latter mentioned cart or wagon devices to provide for a simple design which includes a folding or recessing handle structure, thereby allowing for easier transport of devices, e.g., in a car trunk, or to allow for compact display or storage. However, in actuality, there is little that is compact or space-saving in most of these devices which characteristically incorporate a fixed or one piece cargo area or “well,” and set of two or four wheels which are affixed to an axle, and which provide no method for any of the wheels to fold or recess in a space saving manner. In general, merely recessing or folding a handle structure alone goes a very little way in creating a truly space-saving cart or wagon device. 
     Over many years, countless designs have been proposed for folding or collapsing rolling carts and wagons. Most suffer from a number of problems, including those relating to difficulty of manufacture, the need for many detachable parts, or difficulty in use, i.e., the requirement for non-intuitive actions by a consumer in order to determine how to collapse or set-up the cart or wagon. For example, see U.S. Pat. No. 4,109,926 (Lane), U.S. Pat. No. 4,856,810 (Smith), U.S. Pat. No. 4,765,643 (Pappanikolaou). Previous patents have also generally disclosed folding side, front and rear walls which fold or collapse in various fashions (see, e.g., U.S. Pat. No. 4,887,836 (Simjian)). 
     Further, numerous patents have described methods to fold or nest cart or wagon handles using various methods, including articulating joints, detachable handles, or pivoting handle structures. For example, see U.S. Pat. No. 2,350,062 (Mosier), U.S. Pat. No. 2,984,499 (Humphrey), U.S. Pat. No. 4,889,360 (Havlovitz) and U.S. Pat. No. 5,692,761 (Havlovitz). The devices of the Havlovitz patents are notable for the simplicity of their design and both include a folding handle. The primary deficiency of the devices of the Havlovitz Patents, despite their simplicity, is that the devices are not truly compact designs. Moreover, in the latter patent, it is quite awkward for the consumer to fold the handle down, since this requires lifting of the entire cart off the ground to achieve the recess handle position. The prior art also discloses wheel support arms which pivot through, in general, 90° along an axis adjacent to the base or underside of the wheeled device, but, in general, such wheels support arms must be folded out from the underside of the device and generally require some other interfitting device or part to cooperate with the wheel support arms to “lock” or resiliently retain the pivoting wheel structure in place. 
     In general, the invention overcomes a large number of deficiencies and disadvantages in the prior art carts and wagons. It is believed that these deficiencies and disadvantages have prevented the manufacture of a truly compact, space saving wheeled device having a very thin profile. The invention also provides a folding cart or wagon which is simple to assemble and manufacture, which sets up in seconds, which includes a minimum number of separate parts, which has no part which normally detaches, which is very simple to operate properly, and which does not require a consumer to occupy an awkward position to set up. 
     Objects of the invention include the following: to provide a unique 270° pivoting wheel and wheel support structure which may be used with several different types of support arm structures, including the provision of retention means between the support arm structure and the base and/or walls of the various two or four-wheel devices described hereinbelow; to provide a unique ultra-flat, compact and space saving construction which involves recessing of a generally “U” shaped handle (or two straight handles) into the profile of such a device, as well as in the provision of cooperating sleeves constructed as a part of the folding side walls, to provide that the handle, whether generally “U” shaped or in the form of two straight handles, telescopes and engages the outer portion of the cart base along a slide path, is provided with detents so that the handle may recess directly inside a sleeve or cylinder around which a pivoting wheel support structure pivots; to provide several alternative embodiments for a simple kickstand or other underside support for the device; to provide for cooperation and interlocking between the walls of the cart in the movement thereof between their folded raised position, to further provide a four-wheel wagon or cart embodiment which includes a center pull handle which folds and nests flat into the base or bed of the wagon, and provide for a zippered carry bag made of a mesh, or other suitable material, which is capable of being rolled up and stored in a storage cavity provided in either end of the base of the cart, as well as a shoulder strap for transporting the collapsed cart, and to provide for a fold-down drink and/or implement holder as a part of a wall of the wagon or cart, to provide for a number of alternative wheel structures and support arm structures, and to provide a number of base underside strengthening and support embodiments, as well as other important improvements as further described hereinafter. 
     According to one aspect of the invention, a wheeled carrier device is provided which comprises a base member; a plurality of foldable walls supported on the base member and movable between an erected state wherein the walls define a carrier space and a collapsed state wherein the walls are folded on top of the base member; at least two wheels; and wheel mounting means for pivotably mounting the at least two wheels on the device on opposite sides thereof such that the at least two wheels are movable through 270° from a first, operative position wherein the wheels support the carrier device and a second, inoperative position wherein the wheels are folded over on top of the folded walls in the collapsed state of the latter. 
     Preferably, the wheeled carrier device further comprises a handle affixed to the carrier device and movable between an operative state wherein the handle can be used to pull the carrier device and an inoperative state wherein the handle is stowed in substantially flush relation with the remainder of the carrier in the collapsed state of the walls. 
     In one preferred embodiment of the handle, the handle comprises a substantially U-shaped handle member including parallel arms pivotably connected to the carrier device. The foldable walls include side walls and these side walls preferably each include handle receiving means for supporting the parallel arms in the operative state of the handle. The parallel arms of said U-shaped handle member advantageously comprise telescoping arm elements which telescope between an extended position in the operative state of the handle and a retracted position in the inoperative state of the handle. The handle member further comprises releasable means for retaining the telescoping arm elements in the retracted state thereof. 
     In a further preferred embodiment thereof, the handle preferably comprises an elongate handle member pivotably connected to one end of the carrier device and movable to a folded down storage position wherein the handle extends longitudinally of the carrier device in the collapsed state of the walls. 
     In an advantageous embodiment, the walls comprise first and second spaced, parallel walls and third and fourth spaced, parallel walls extending orthogonally to the first and second walls, the first and second walls each having and inwardly facing surface including at least one curved channel therein at each end thereof extending between side and bottom edges thereof, and the third and fourth walls including projecting elements received in the channels for enabling a downward folding movement of the third and fourth walls to collapsed positions wherein the third and fourth walls fold down on the base member. 
     The wheel mounting means preferably includes a wheel support member including oppositely extending mounting elements and the base member of the carrier device preferably includes spaced, opposed cavities therein in which the mounting elements are pivotably received. The wheel mounting means preferably includes manually operable releasable means for, when engaged, serving to retain the at least two wheels in the operative position thereof. 
     In an embodiment wherein the carrier device has two wheels the carrier device further comprises an erectable support element affixed to the carrier device in spaced relation to the two wheels for, when erected, supporting the base member of the carrier device in a substantially horizontal position. In a preferred implementation, the erectable support element comprises a U-shaped support member including support arms pivotably connected to the base member and pivotably to a nested position with respect to the base member. 
     Advantageously, the wheeled carrier device further comprises an erectable tray element for, when erected, providing a support surface. 
     The wheeled carrier device preferably further comprises means defining an elongate storage space at one end of the device, and a rollable carrier bag stowable in said storage space. 
     In an embodiment wherein the cart has four wheels, two of the wheels, in the operative state thereof, are rotatable through 360° beneath the base member. 
     According to a further aspect of the invention, a wheeled carrier device is provided which comprises a base member; a plurality of foldable end walls and side walls supported on said base member and movable between an erected state wherein said walls define a carrier space and a collapsed state wherein the walls are folded on top of said base member; at least two wheels; and a handle affixed to the carrier device and movable between an operative state wherein the handle can be used to pull the carrier device and an inoperative state wherein the handle is stowed in substantially flush relation with the remainder of the carrier in the collapsed state of said walls, the handle including handle arms disposed on opposite sides of the side walls, and the side walls each including handle arm receiving means for supporting the handle arms in the operative state of said handle. 
     As set forth above, the handle advantageously comprises a substantially U-shaped handle member and the handle arms comprise parallel arms of the U-shaped handle member pivotably connected to the carrier device. As in the first aspect of the invention, the walls preferably comprise first and second spaced, parallel walls and third and fourth spaced, parallel walls extending orthogonally to the first and second walls, said first and second walls each having an inwardly facing surface including at least one curved channel therein at each end thereof extending between side and bottom edges thereof, and the third and fourth walls including projecting elements received in the channels for enabling a downward folding movement of the third and fourth walls to collapsed positions wherein said third and fourth walls fold down on the base member. 
     Similar to the first aspect of the invention, each wheel mounting means includes a wheel support member including oppositely extending mounting elements and the base member of the carrier device includes spaced, opposed cavities therein in which the mounting elements are pivotably received. 
     In accordance with a third aspect of the invention, a wheeled carrier device is provided which comprises: a base member; a plurality of foldable end walls and side walls supported on said base member and movable between an erected state wherein said walls define a carrier space and a collapsed state wherein the walls are folded on top of said base member; at least two wheels; and a handle affixed to the carrier device and movable between an operative state wherein the handle can be used to pull the carrier device and an inoperative state wherein the handle is stowed in substantially flush relation with the remainder of the carrier in the collapsed state of said walls, the handle comprising an elongate handle member pivotably connected to the carrier device at one end thereof centrally of said one end and being pivoted back, in said operative state, to a folded down position between the folded side walls in the collapsed state of the side walls. 
     Further features and advantages of the present invention will be set forth in, or apparent from, the detailed description of preferred embodiments thereof which follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view, partially in section and partially broken away, of a first preferred embodiment of the collapsible cart of the invention; 
     FIG. 2 is a front elevational view of a portion of the cart of FIG. 1; 
     FIG. 3 is a side elevational view, partially in section and partially broken away, of a further preferred embodiment of the cart of the invention; 
     FIGS. 3A to  3 F show details and alternative embodiments of parts of the cart of FIG. 3; 
     FIG. 4 is a side elevational view, partially broken away and partially in section, of a further preferred embodiment of the cart of the invention; 
     FIGS. 4A,  4 B and  4 C show details of the cart of FIG. 4; 
     FIG. 5 is a side elevational view, partially in section, of a further embodiment of the invention; 
     FIG. 6 is a side elevational view, partially in section, of yet another embodiment of the invention. 
     FIG. 7 is an exploded perspective view of a wheel support structure in accordance with a preferred embodiment; 
     FIG. 7A is an alternative embodiment of the wheel support arm; 
     FIG. 8 is a schematic top plan view showing folding of the wheels; 
     FIGS. 9A and 9B are side elevational views of an alternative wheel support arrangement; 
     FIG. 10 is an end elevation, partially in section, showing folding of a wheel; 
     FIG. 11 is an end elevation, partially in section, showing folding of two wheels; 
     FIG. 12 is a plan view of an alternative cart base construction; 
     FIGS. 12A and 12B show alternative embodiments of details of FIG. 12; 
     FIG. 13 is a side elevational view, partially broken away, of one embodiment of the wheel support structure; 
     FIG. 14 is a perspective view of the wheel support structure, showing a step in the disconnection thereof from the cart; 
     FIGS. 15A,  15 B,  15 C and  15 D show details of the wheel support structure; 
     FIG. 16 is a top plan view of a further embodiment of the two-wheeled cart; 
     FIGS. 17A,  17 B,  17 C,  17 D,  17 E,  17 F and  17 G show components of a further embodiment of the invention; 
     FIG. 18 is an end elevation view, partially in cross section, showing the folded wheels; 
     FIG. 19 is an end elevation view, partially in cross section, showing details of the side wall construction; 
     FIG. 20 is a fragmentary side elevational view showing folding of the end walls; 
     FIGS. 20A and 20B show details of the end walls; 
     FIG. 21 is a top plan view of another cart embodiment; 
     FIGS. 22A,  22 B and  22 C show details of a further kickstand embodiment; 
     FIG. 23 is a perspective view showing details of a wheel support construction; 
     FIGS. 24 and 25 are end and side elevation views, respectively, of a wheel support construction; 
     FIG. 26 is a perspective view of a kickstand embodiment; 
     FIGS. 27 and 28 show details of the embodiment of FIG. 26; 
     FIGS. 29A and 20B are a perspective view and cross sectional view, respectively, showing details of a cover plate construction; 
     FIG. 30 is a side elevation view, partially broken away, of a further four wheel cart embodiment; 
     FIG. 31 is a top plan view showing details of one handle embodiment; 
     FIG. 32 is an end elevation view of the embodiment of FIG. 31, showing the handle nested and walls folded; 
     FIG. 33 is a top plan view of the embodiment of FIG. 31, showing further details; 
     FIGS. 34 and 35 show embodiments of the rotatable wheel construction; 
     FIG. 36 is a side elevational view of an alternative frame construction; 
     FIGS. 36A,  36 B and  36 C show details of the alternative frame construction of FIG. 36; 
     FIG. 37 is a top plan view of the embodiment of FIG. 36; 
     FIG. 38 shows a further embodiment of FIG. 36; 
     FIG. 39 shows further details of the embodiment of FIG. 38; 
     FIG. 40 is an exploded side elevational view showing further details; 
     FIG. 41 is a schematic representation of a stored cart; and 
     FIG. 42 is a schematic representation of an alternative method of cart storage. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, FIG. 1 shows a two-wheeled cart, generally denoted CA, in a completely assembled or set-up state. The same cart CA, when folded, in the preferred embodiment, has a thickness of about the length of a credit card, and includes two side walls (one of which, denoted  1 , is shown in FIG. 1) and front and rear walls  2  and  3 . A base  4  has slightly elevated exterior base perimeter walls. A generally “U” shaped telescoping handle  5 , constructed of extruded aluminum, another metal or any suitable plastic, is shown in solid lines in FIG. 1 in a final, upwardly secured, operative position of the handle  5  wherein handle  5  resiliently fits snugly into one or more sleeves or support sockets  6  molded into each side wall  1  of the cart. In operation, when the recessed, nested handle  5  (shown in dashed lines at  5 -A) is pulled forward so that the handle  5  telescopes until it reaches a telescoped locked position, shown in dashed lines at  5 -B, handle  5  is further lifted, as shown in dashed lines at  5 -C, and is ultimately secured into support sockets  6  provided on the side walls in the position shown in solid lines. This allows the “U” shaped handle  5  to serve as a lifting element for raising the cart up off of a kickstand  17 , and thus enables the cart CA to be propelled forward on two wheels  9  and  10 , mounted on cart CA in a manner described below. 
     Referring further to FIG. 1, which shows one of the two side wall sleeves or sockets  6  which resiliently secure the handle  5  in place in the telescoped state thereof, the sleeves  6  being preferably molded and incorporated into the side wall construction. It is contemplated that matching recesses, grooves or other matching structures (not shown) between the handle  5  and sleeves  6  will be used to further resiliently hold the handle  5  and sleeves  6  together. An end point  7 , where the two telescoping handle sections of handle  5  meet when both are recessed, is secured into a recess  8  in the cart base wall  4 . Protrusions or projections  23  provided in spaced relation along the outer edge of the front wall  2  and the outer edge of back wall  3  cooperate with cooperating curved grooves or recesses  24  in the cart side walls  1 . After dropping each of the wheels  9  and  10  to the lowered, operative positions (as shown), the side walls  2  are raised, when then allows the nested front and rear walls,  2  and  3 , to slide up along grooves  24  into raised positions through cooperation with both side walls  1 , as is discussed in further detail in connection with other figures. The above-mentioned kickstand  17  is secured to both sides of the cart base  4  under the control of a handle  18 . The structure of the kickstand  17  is designed to recess into the honeycomb wall structure of the cart base  4  so that it adds no further depth to the cart CA when folded, as indicated in dashed lines. The user may operate the kickstand  17  with the foot, or with a combination of the foot and hand. Other figures described below provide some additional detail as to cooperating structures built as part of the turn handle  18 , which allow handle  18  to resiliently hold the kickstand  17  in the “down” position. 
     Two wheels  9  and  10  are connected to the cart base  4  via arm-like structures or support elements  11 . The wheel support elements  11  can pivot 270° between a lowered, in use, position shown in FIG. 1, and a nested storage position shown in other figures. The wheels  9  and  10  and the associated support structures  11  can be secured to the cart base wall  4 , through a variety of methods described hereinbelow in more detail. One side of the support portion of the wheel support element  11  is indicated in dashed lines at  11   a,  with this support portion  11   a  fitting into matching cavities  12  accessed through the interior wall of the cart base  4  as described below. A cavity or holder  13  extends along the rear wall  3 , or base  4 , of the cart CA with sufficient space to hold a tightly rolled mesh zippered bag (not shown), as well as a shoulder strap (not shown). In this preferred embodiment, the walls  1 ,  2 ,  3 , and the cart base  4  are preferably made of a honeycomb plastic, as indicated at  14 , but can also be made, for example, of any similar molded material construction which provides durability, but is lightweight. 
     A carry handle  15  is tapered and molded into the base side wall  4 . Additionally, a gap  16  is molded into each side wall  1  so that, when the side walls are folded closed, gap  16  mates with a similar gap through the base structure  4 , thereby providing a handlehold to enable carrying of the cart CA when folded closed. 
     A plurality of support arms  19  serve to retain the handle  5  in its recessed nested position. A side wall lifting/moving handle  20  is provided on each side wall  1 . As explained in more detail below, the exterior of each wheel support element  11  has a longitudinal protrusion  21  which interfits with a corresponding recess  22  in each of the side walls  1  allowing the wheel support element  11  to resiliently nest into the side walls  1  when the cart CA is folded closed. 
     This wheel support elements  11  lock resiliently to the lower cart wall base  4  via two resilient finger like structures (not shown) although a separable insert element is indicated at  25  which houses same and is incorporated into the underside of the wheel support elements  11 , which interfit into corresponding sockets (not shown) molded into the cart base  4 , as described below. Finger hole openings  26  allow the consumer to release each of the finger-like structures to free the wheel support from the cart base wall  4  at such time as a consumer decides to fold the cart CA for storage. 
     Referring to FIG. 3, there is shown a four wheel wagon or cart CB, with numerous attributes discussed elsewhere shared with the two wheeled cart design of FIG.  1 . This four wheel wagon/cart embodiment uses a different handle structure than the two wheel cart, although either method may be employed in either embodiment. In the embodiment of FIG. 3 there is no external handle nested around the exterior base of the cart CB and instead there is a center pull handle  27  shown, in solid lines, in the operative position and shown, in dashed lines, nested into the cart base  4 . Handle  27  cannot reach the nested position shown unless the front, rear and side walls are folded down. The handle  27  is resiliently maintained in the rested or stored position by a fit with projections (not shown) which are molded into either the inner aspect of the rear cart base wall  3 , and/or protrusions or recesses  2   a  and  3   a  molded into the centermost portion of the front and rear folded walls  2  and  3 .  2  and  3 . Further detail of the arrangement whereby the handle connects to the front cart base wall support structure is shown in FIG.  3 A. In FIG. 3A, the cart handle is provided with two protrusions  27   a  which are molded to interfit into grooves  3   a  in the front base wall  3  of the cart CB. This allows the handle  27  to pivot for use or storage as shown in FIG.  3 . 
     In FIG. 3, the side walls (one of which, denoted  1 , shown), front and rear walls  2  and  3 , fold down into the base  4  as previously discussed. A swing out door  28 , which is formed from a portion of the entire side wall  1 , is provided on one or both sides of the cart. Door  28  is hinged to a portion of the side wall, and any one of a number of conventional and well-known latch structures, indicated at  29 , can be used to latch door  28 . Front and rear walls  2  and  3  have projecting or protruding members  23  at each outer edge which fit into curved side wall slide paths or recesses as shown in dashed lines at  24 . In the embodiments shown in FIGS. 3B,  3 C and  3 D, for front wall  2 , the front and rear walls  2  and  3  are thicker along the uppermost portion of the walls than at the lower end of the walls, as shown, so as to provide an interfit into a raised portion  4   a  of the base wall  4 . As shown in FIG. 3B wall  2  may include a hinged latch  2 L, as shown, preferably made of plastic. Any alternate interfit arrangement with no latch is shown in FIG.  3 C. In FIG. 3D another alternative resilient arrangement is used to secure the foldable or collapsible wall  2  to the fixed cart base wall  4 , where the wall  2  is pressed down, once raised, to assist in providing the resilient interfit. Alternatively, a split wall and base construction may be employed as discussed below in connection with FIG.  6 . 
     A thin, yet supportive cart base “seat” (not shown) or front or rear wall “pad” (not shown), can be provided which would attach to the base  4  or the walls  1 ,  2  or  3  with straps which interlace through the preferred honeycomb wall structure and would be secured around the outer facing of such walls or base with velcro or snaps. These pad(s) would add comfort if children are seated in the wagon CB. 
     As indicated above for FIG. 1, a rolled up mesh bag  13  may be recessed along either a front or rear cavity in the base  4  in any suitable manner. 
     A “rotating” wheel structure support  16  is provided for a rotating wheel  30  which also allows a 270° pivot action that is facilitated through arms  12 . Arms  12  are identical to these on the non-rotating wheel support structures of the rearmost wheel  9  described above in connection with FIG.  1 . The front two wheels of the four wheel cart CB (one of which is shown at  30 ) can also be of a caster wheel type shown in FIG.  3 E. It will be appreciated that each of the two rear wheels (one shown at  9 ) can be supported by structures surrounding the wheel  30  on both sides, i.e., a two-sided construction, or can be supported by a single sided arm support as shown in FIG.  3 F. Again, rotating wheel  30  may rotate 360 degrees by virtue of a metal arm  33  which extends longitudinally up into a wheel arm support  31  mounted in base  4 . A washer  32  is resiliently held at the bottom of the wheel support,  31 , by a crimped or widened portion  33   a  below the washer  32 , and the upper part of the metal arm  33  extends through the center of the wheel arm support  31  to a grooved out and recessed area at the top of the wheel arm support  31  where support  31  is secured by an end cap or bolt  34 . It is noted that an alternative securing arrangement is shown in FIGS. 24 and 25 described below. 
     The construction of FIG. 3 does not prevent the consumer from utilizing the finger holes or recesses, shown at  26 , which allow release of the wheel structure  16  from the cart base  4 . Arms  12 , in cooperation with cavities shown in dashed lines, hold the entire wheel structure  16  in the cart base side wall  4   a,  while for wheels  9  portion, a central retention insert box portion  25 , of the wheel arm structure  11  on the underside, includes two finger-like projections  25   a,  which resiliently interfit into matching areas in the cart base  4 . An alternative embodiment of the four wheel cart is shown in FIG. 30 described below. 
     Referring to FIG. 4, further details of the telescoping U-shaped handle structure  5  of FIG. 1 are shown, particularly with respect to the manner of securement of same to the two wheel cart base  4 . With handle  5  in the fully raised, fully telescoped out position shown in solid lines in FIG. 4 handle  5  is secured in side wall sleeve  6 , which includes a spring maintained detent button  35 . Detent button  35  is shown in more detail in FIG. 4A, which shows the detent button  35  and associated spring  35   a  as well as the innermost portion of the telescoping handles portions  5 , and the outermost handle portion  5 A. It will, of course, be understood that the portion of the telescoping handle which is the outermost sleeve may be reversed from that shown in FIG.  5 A. The detent button  35  may either simply recess or retract in response to forceful contact, or, alternatively, may require the user to press firmly down on button  35  or even turn a hand dial (not shown) in order to inwardly telescope the handle structure  5 . Also shown in FIG. 4 are the kickstand turn handle  18  described above as well as the cart handle support arms  19 . 
     FIG. 4A also shows the end pin member  37  of the tubular handle  5  where the handles are secured through an opening to the cart base  4  or to side wall  1 . A screw hole  55  extends completely through the handle  5  and pin  37  extends through the cart base wall  4  where a head  38  on the pin  37  screws or fits onto the pin. Alternatively, the pin structure may interfit through the cart base  4 , through the handle  5  and then resiliently snap and hold the handle  5  through the holes just described. The pin  37  and associated head  38  may be designed to further interfit into a recessed, grooved out portion of base wall  4  indicated at  39  to fix the pin  37  or to otherwise retain the pin  37  in an immobile position. 
     Referring again to FIG. 4, an alternative embodiment is shown wherein a slide path  40   a  is provided by slide element  40  (depending upon the size of the cart and nature of the handle  5 . This slide path is shown in more detail in FIG.  4 C. The pin structure  36  which travels through holes in the end of handle  5  are secured into the slide path defined by element  40 . In FIG. 4C, handle  5  is shown as being affixed or secured in the slide  40  and, in dashed lines, shown as moving along the slide path with the pin structure  36  moving in the path. As illustrated, both ends of the slide path  40   a  are configured, i.e., are narrowed or necked down, so as to resiliently hold the handle  5  in the desired position. 
     Referring to FIG. 5, there is shown an alternative embodiment of the two wheel cart of FIG. 1, which utilizes a different securing arrangement for the cart handle  5  to the base. In this embodiment, the handle  5  is not telescoping, but rather travels into a recessed position completely through the hollow circular structure  4  of a wheel arm support  11 , by using spring maintained detents  42  at the end of the handle  5 . At a point indicated by the circle at  43 , the handle  5  travels along a slide path to a termination point, where the handle  5  is then raised. Not shown is a slide path sleeve which would travel along the entire cart base wall, on both sides of the wheel arm support  11 . This sleeve is partly open at the top to allow the handle  5  to be raised for use. 
     An opening  44  is molded in the cart base wall  4  to allow a suitable flexible cord  44   a  (such as a “Bungie” cord) to be tied-off and secured to the cart base wall  4 . A series of open grooves  44   b  are provided to resiliently secure the cord  44   a  in place when the latter is stretched from the opposing side. It will be appreciated that a multiplicity of such areas may be molded into the cart base  4 . 
     Referring to FIG. 6, there is shown another alternative wheel cart side wall embodiment. In this embodiment, the side wall is constructed of a honeycomb molded material and hinged to cart base  4  by a series of hinges, one of which is shown at  1   h.  The hinged structure  1   h  may include male protrusions molded into side wall  1  which resiliently fit into corresponding female recesses in the cart base  4  (not shown in FIG.  6 ), rather than an actual hinge traveling through the lower most edge of the side wall  1 . Further, as shown at  44 , the side wall  1  is molded so when raised it provides a flush single side wall profile  1   p  immediately above the wheel arm structure  11 , as well as with other portions of the base wall  4 . When side wall  1  is raised, the lower edge may also interfit resiliently with the uppermost facing edge of the base wall  4 , in one of several alternative embodiments, as described below in connection with other figures. 
     Referring to FIG. 7, there is shown, in an exploded perspective view, an embodiment which provides an especially durable cart base and wheel arm support structure, formed from a series of separate wheel arm and housing parts, in contrast to the more unitary molded wheel support element  11  and an associated housing construction disclosed in the figures discussed above. Alternatively in other figures. A non-unitary wheel support  45  and associated fixed wheel  9  shown adjacent to a base and wheel structure shows the support member  47 . A support sleeve  46   a,  which fits through spaced cylindrical holes or openings  47   a  formed by bracket arms  47   b.  Wheel support element  45  includes an upper cylindrical portion  45   a  which fits between bracket arms  47   a  so that the opening in cylindrical portion  45   a  aligns with openings  47   a.  Cylinder fits through the openings  47   a  in bracket arms  47   b,  and the hollow cylindrical portion  45   a  of wheel support  45 . Hollow end caps  48  fit over cylindrical and help secure the wheel structure in place. Alternatively, end caps  48  may be elongated and have enlarged end structures which interfit into corresponding cavities molded within the cart base walls as disclosed below in connection with other figures. 
     When the wheel structure  45  is in place, and is folded down into the operable position, a “retention” element or recess  45   b  interfits resiliently with a corresponding projecting base and wheel support structure element  47   c.  Of course, the two may be reversed wherein a female recess (not shown) is provided at  47  and a male element (not shown) is provided at  45   b.  FIG. 7 shows, on the other side of the base support  47 , the entire wheel support structure  45  and associated wheel  9  in a first, lowered position in dashed lines, and a further, stored position, also in dashed lines, wherein the wheel is disposed in its storage position atop base and wheel support member  47 . Essentially, the wheel pivots 270° between its operative and storage portions. 
     For purposes of further illustration in FIG. 7, the two sides of the U-shaped handle  5  are shown and  7 , and, as illustrated, detent is provided at  49  which is held on through an end cap  50 . This allows the entire handle structure  5  to travel through the hollow sections of cylinder  46 , opening  45   a,  openings  47   a  and openings (not shown) in end caps  48 . In the latter regard, end caps  48  have a hollowed out central section or opening to allow for interior passage of the cart handle  5 . Referring to FIG. 7A, an alternative wheel support  51 , is shown for wheel  9  wherein the lowermost axle portion  51   a  passes through only one side of the central rim or hub of the wheel  9 . 
     FIG. 8 illustrates, in a schematic manner, the wheel and support structure  11  (both (1) in the stored position, as shown to the left, and (2) in the pivoting position, as shown to the right, with the folded down side walls  2  being indicated in dashed lines. 
     Referring to FIGS. 9A and 9B, an alternative embodiment of the wheel support structures is shown. The embodiment is a 90° wheel support structure rather than a 270° pivoting structure as described above. The wheel  9  is mounted to the underside edge of the cart base  4  with a hinged member  52  and an associated hinged or articulating arm  53  with a central hinge. The wheel structure may be folded up under the cart (as shown in FIG.  9 B), with the wheel  9  folded under the base  4  and hinge of arm  53  folded up as illustrated in FIG.  9 B. Thus, although the 270° pivoting embodiment is preferred, an alternative embodiment of the cart or wagon of the invention could include some or all other elements of the cart/wagon disclosed herein, but use the type 90° folding wheel rather than the pivoting wheel structure disclosed elsewhere. Hinge  53  can incorporate a suitable “locking” hinge, which releases via forceful pressure or via pressure on a release button (not shown). 
     FIG. 10 shows further detail of the wheel construction described with male and female retention arrangements to allow for support or stabilization of the construction in its operable, folded down position. The wheel  9  and support structure  11  are shown nested atop the cart base  4  (side and front walls are omitted for purposes of clarity view), and the same wheel  9  and support structure  11  in the lowered, operable position. Longitudinal protrusions  21  are provided along the exterior of the wheel structure  11  which are designed to loosely, yet resiliently interfit with corresponding grooves (not shown) molded into the side wall when nested (side wall not shown). The wheel  9  pivots 270° as shown and cooperating male finger-like protrusions,  25 A, on the wheel support  11  are designed to resiliently hold the wheel support structure in the lowered, operable position, via an interfit with grooves or other receptors  54  the cart base wall wheel structure receiving area of base  4 . 
     FIG. 11 simply shows both wheel wheels  9  and associated structures  11  nested above the cart base  4  and in the operable positions thereof. As indicated above, the cart walls (not shown) must be folded down to allow the pivoting wheel structures  11  to nest. 
     Referring to FIG. 12, an embodiment is shown wherein the cart base and wheel structure support  47  is made of single or multiple cross members or “joists”  55 , constructed of a suitable metal or plastic. Cross members  55  interfit with one or more corresponding grooves  56 , thereby providing resiliently interfitting with the members  55 . Members  55  are molded through a passthrough slot in the bottom of the cart base  4  as indicated in FIG. 12 or, alternatively, as shown in FIG. 12A, comprise members which, resiliently snap in from under the base  4  and resiliently interfit into grooves that correspond with the base support  47 . In this embodiments, ridges or protrusions  56  are molded into the underside of the cart base  4 . FIG. 12A shows a side view of such a resilient base and wheel support  47  fit with the cart base  4  where underside support  47  snaps under the base  4 , and detachable supports  56  each extend upwardly from each end of the base  4 , to form a support structure for the wheels  9  and  10 . The cylindrical support members  56  may thus either be manufactured as a unitary structure with the support base and wheel structure  47 , or may be resiliently interfitted onto the base support member  47 , depending upon desired strength for the base of the structure and for the wheels themselves. The wheel support arms  57  are constructed in a “U” shape, rather than cylindrical manner, allowing a unitary wheel support structure to mount thereon, and be retained into cart base wall cavities described below which are designed to hold the wheel support arm and allow the same to pivot 270°. 
     FIG. 13 shows one arrangement for providing the retention of the pivoting wheel support structure  11 . FIG. 13 shows a portion of the exterior side of the base wall  4  as will the exterior lower portion of the upright side wall  1  and part of the wheel support  11 . Base wall cavities  12  are shown which support the cylindrical ends of one arm of the unitary wheel support structure arms  11 A. These ends are each held in the corresponding cavity  12  which is molded into the base wall  4 , but accessed through the interior side of the base wall as disclosed in other figures. The uppermost portions  57  of the optional “U” shaped arms of the wheel structure support members  11 , which support arms  11 A and may be unitarily constructed as a part of the cart base wall  4 , as a stand-alone structure which resiliently attaches to a separate cart base support  47  (shown in FIG.  12 ), or as a structure which is constructed as part of a separable base support member. User finger holes  26  allow detachment of the wheel structure  11  from the cart base side wall  4  in order to release and nest the wheel structure  11  and associated wheels  9  as described in more detail below. Any suitable alternative quick connect or resilient “button release” arrangement may be employed (e.g. in central retention section  25 ) to provide quick release and/or for automatic resilient interfit of the wheel structure to the cart base. 
     FIG. 14 shows a preferred arrangement whereby the wheel support structure  11  resiliently interfits into the cart base  4 . In this arrangement, the user places the fingers into recesses  26  on each side of central retention section  25 , and presses inward on resiliently movable finger-like elements or structures  25 A which, as shown in FIG. 14, are then freed from slots  58  which are molded as a part of the overall cart base,  4 . The finger-like structures  25 A are constructed with outwardly facing clip like portions, which extend or “secure” past the corresponding openings  58  in cart base  4 . Once the structures  25 A are freed from cart base  4  by being squeezed inward, the wheel support structure  11  can be pivoted 270° to ultimately nest the associated wheel  9 . Further multiple retention means can also be employed. Secondary male attachment elements  59  are molded into the wheel support structure  11  closest to the cart base  4  on either side of the central retention section  25 , and these affix or attach to secondary female cart base attachment recesses or grooves  60  which interfit resiliently element  59 , but this attachment can be readily overcome when the user detaches the central section  25  and its finger-like projections  25 A by a finger squeeze on the latter and pulls forcefully on the wheel structure  11  in a direction away from the cart base  4 . Of course, any of male and female connectors can be reversed. In addition, male connector elements or protrusions  61  are incorporated in the inwardly attaching central insert section  25 , which mate with female connector elements or recesses  62  formed in molded portions of base  4 . In addition a series of matching female recesses  64  are also molded into the side walls of the cart base  4  to interfit with male protrusions  63  on each side of the wheel support structure  11 . In general, the retention for wheel support structure is chosen to provide firm holding but should be releasable when finger-like control elements are depressed and released. 
     FIGS. 15A,  15 B,  15 C and  15 D shown in more detail the central wheel structure retention section  25  described above in connection with FIG.  14 . In FIG. 15A, a view is provided from the outwardly facing external side of the wheel support  11 , and the central retention member  25  is shown as resiliently interfit into the wheel support, with the recesses for finger access shown again at  26 . FIG. 15B shows the central support member  25  as including a perimeter exterior lip  65  which provides a resilient interfit with an opening (not shown) on the wheel support structure  11 . The finger-like members  25 A are shown in FIG. 15B as well as FIG. 15D which shows a side view of one preferred finger configuration. In FIG. 15B, further male resilient attachment elements, shown in dashed lines at  61 , are adapted to mate with recesses  62 , shown in FIG. 15C which are molded into the cart base wall  4 . FIG. 15C also shows the open receiving areas  58  molded into the cart base wall  4 , which, as described above capture and return the finger-like structures  25 A shown in FIG.  15 B. FIG. 15C also shows another view of the adjacent secondary retention recess  60  in the cart base side wall  4 , which, as described above, is adapted to receive a secondary male retention element  59  of the wheel support structure  11  (not shown in FIG.  15 C). 
     FIG. 16 is a top plan view of the two wheel cart “CA” with all parts completely folded and nested. In this view, the side walls  1  lie atop the rear and front walls  2  and  3  which are shown in dashed lines, with the base  5  therebeneath and the generally “U” shaped handle  5  nested shown. While this U-shape for handle  5  is preferred, two straight handles (not shown) may be employed which would extend along the sides of both side walls  1 , although, among other advantages the “U” shaped handle  5  provides more inherent support to the side walls  1  when the latter are raised. Recessed cavities  66  are molded into the cart base wall  4  to receive any suitable arrangement for mounting a shoulder strap  67 . Strap  67  includes suitable hooks  67   a  which are retained at  66  so as to enable carrying of the device when nested and closed. The cavity  13  for holding the plastic or mesh bag described above, is located at one end of the cart CA, and can be used when the cart CA is nested and fully closed. The cavity may zip or use velcro, for example. The two wheels  9  and  10  are shown in their nested, stored position, and as described above these wheels may be retained in this nested position by one or more ore means. For example, as described in connection with FIG. 1, wheels  9  and  10  can be resiliently held in corresponding side wall grooves  22  which interfit with corresponding protrusions  21  (see FIG. 1) molded as part of the exterior wall of the wheel structure, or alternatively, or in addition, the upper section of the inner cart base wall can be provided with a ledge, indicated schematically at  68 , which resiliently interfits with a corresponding male/female protrusion, recess or groove (not shown) molded as a part of either wheel support structure  11 . 
     As indicated above, an opening,  16 , may be molded all the way through side walls  1  as well as the cart base  4  itself to present a handhold for the user to lift the closed, folded cart from either side. In addition, exterior molded handles  15  may be made as part of the exterior side wall of the base  4 . 
     FIG. 16 also shows the kickstand handle structure  18 , and a plurality of support arms  19  for the cart handle  5 . 
     Molded elements  69  on the inner base walls  4  are used to resiliently hold each of the side walls  1  when they are folded and nested as discussed above. Sleeves  6  are molded as a part of the side walls  1  and receive the handle  5  when the latter is raised up. In this embodiment, the handle  5  is shown extending through the cylindrical wheel support  11  as described above. In the alternative embodiment described above, a telescoping handle  5  such as shown in FIG. 1, can be secured to the base wall  4 . 
     FIG. 17A shows separated parts of the two wheel cart CA and includes a top plan view of the base  4 , as well as the wheel structure support parts described above in connection with FIG.  7 . It is noted that most of these of which are optional since many of these structures may be instead molded into a unitary wheel structure  11  as indicated in FIG.  17 C. FIG. 17B shows details of the “kick stand” unit  17  which was generally described above and which can be constructed of metal, extruded aluminum or suitable plastic and includes outwardly protruding kickstand elements  60  which clear the exterior perimeter of the cart base wall  4  to serve as the kickstand. Two detachable turn handles  18  are employed which interfit into each of two handle arms  71  through holes (not shown) in the exterior walls of the cart base  4 . As indicated in dashed lines each end of the kickstand arm structures can alternatively be connected by a connection element  72  extending under the cart base  4 , and the turn handles  71  may extend through another hole through corresponding underside cross members  79 , also shown in dashed lines, on either end of the base underside, thereby securing the kickstand  17  and the turn handles  18  by resilient fit between the end of a turn handle arm  71  and corresponding cross member  79 . 
     FIGS. 17C and 17D show two alternative wheel structures, wherein structure  45  of FIG. 17C requires a separate cylindrical sleeve (not shown), and wherein structure  11  of FIG. 17D is a more unitary wheel support structure incorporating arms  11 A which interfit in matching cavities (not shown) in the cart base wall. 
     FIG. 17E shows some details of the side walls  1 , rear wall  2 , front wall  3 , particularly as to how the various walls actually interfit. Integrated hinges  74  are built into the base of the side walls  1  which are designed to interfit with portions of the base wall  4  itself, or with lowest edge of the interior side of the base wall  4 . When front and rear walls  2  and  3  are completely lowered, the protruding members  23  that fit into the side walls are released somewhat from the bottom of each of the side walls  1  because the side walls  1  are tiered slightly higher on the base  4  than the front and rear walls  2  and  3 . the front and rear walls  2  and  3 , which are supported at a slightly lower tier on the cart base  4  are hinged by hinges  73  on each end to the cart base  4 . FIG. 1F shows one alternative interfit design between the front and rear walls  2  and  3 , protrusions  23 , and the side wall slide paths  24  wherein protrusions  23  and slide path  24  are replaced by alternative shaped protrusions  75  molded to the end walls  2  and  3  and alternative matching protrusions and recesses  76  are molded in side walls  1 . As shown in FIG. 17E the rear wall  3  (or the front or side walls) may include a drop-down hinged member  77 , shown further in FIG. 17G, which serves as a tray to hold implements, or to hold beverage containers. a “stop”  78  is molded into the wall or drop down portion. 
     FIGS. 18,  19  and  20  show further details of the two wheel cart wall structure CA. FIG. 18 shows, in solid lines, the cart walls completely folded down and with the wheels  9  and  10  stowed away, i.e., in the nested, inoperable position. The optional wheel support arms  47  are also shown in dashed lines. A resilient interfit is provided, as indicated at  21 , between each wheel in its nested position and a portion of the nested left and right side walls  1 . The wheels  9  and  10  in the nested position thereof, may resiliently interfit into a fixed base wall ledge  68  as indicated schematically. 
     FIG. 19 shows details of the left and right exterior side walls  1  including, molded therein, the handle sleeve  6  for the handle  5  which as is also shown, then is lifted to the position shown in dashed lines so as to resiliently snap into the corresponding receptacle sleeves  6 . 
     FIG. 20 shows the movement of the front and rear walls  2  and  3  relative to a side wall  1 , shown in dashed lines, wherein protrusions  23  formed along the side edges of the front and rear walls  2  and  3  fit into a respective slide path  24  along each of the side walls as described above. The walls  2  and  3  are shown in dashed lines in their upright wall positions. The front and rear walls  2  and  3  may be pressed or pushed down in front and rear floor channels  80  in the floor of base  4  via sloping terminating grooves  81  at the path upper end points of the slide paths  24 . There is a channel and recess  80  along the front and rear of the base  4  of the cart to receive and to allow the front and rear walls  2  and  3  to be pressed down slightly into a locked down position, and all the walls are further retained and stabilized due to the protrusions  23  being pressed into the sloping slide path end points  81 . FIGS. 20A and 20B also show alternative methods of supporting the front wall  2  (which is equally applicable to any of the side walls, whether front, rear or side) and although what is shown is for the two wheel cart, these approaches are equally applicable to the four wheel cart. FIG. 20 shows that each front and rear wall  2  or  3  (or the side walls  1 ) include protrusions  82  which provide a resilient interfit with corresponding recesses molded into the cart base wall  4 . 
     FIG. 21 is a top rear view of the upright rear and front walls  2  and  3 , respectively, upright side walls  1 , two of the multiple protrusions  23  shown in the upright position in solid lines, and nested down in dashed lines. The handle  5  is shown nested to the exterior of the front and rear walls  2 ,  3  and side walls  7 , and, in this embodiment, extends through a cylindrical sleeve  46  which also supports the wheel support structure  11 . 
     FIGS. 22A,  22 B and  22 C show details of the underside of the cart base  4  and the kickstand unit  17 . (The directional relationship of the kickstand unit to the cart underside may be reversed from that shown here.) In FIG. 22B the kickstand structure  17  includes outwardly projecting protrusions  70  which clear the base wall  4  of the cart, and arm structures  83  (one of which is shown) are provided at the point where a hollow section receives the turn handle arm  18  which extends through an opening (not shown) in the exterior base wall  4 . 
     As shown in FIG. 22A the cart CA has cross members or joints  79  which include respective recesses that enable the kickstand  17  to nest into the underside of base  4 . The turn handle  18  has ridges  18   a  to allow a positive hand grip. FIG. 22C shows an underside cross member  79  (or, alternatively, the outermost wall portion of the base), with a hole  84  that allows the handle arm  71  to extend through the hole  84  to secure the kickstand arm, and to extend further through another “joist” structure  79  where it resiliently holds the kickstand  17  between the underside of support members or joints  79 . In FIG. 22C, one cart base underside “joist” member,  79  is shown which includes a number of protrusions or recesses  85  (one of which is shown). The latter correspond with protrusions or recesses in either the underside of the handle  18  and/or via a claw-like portion  86  of the turn handle arm  71  furthest from the handle itself, as more is fully shown in FIGS. 26 and 27. In an alternative embodiment, element  72  shown in dashed lines in FIG. 22A is a portion of kickstand  17  which extends across the underside of the cart base  4  between the kickstand handle portions. 
     FIG. 23 is a perspective side view from the exterior of the cart base  4  of the wheel support structure  11 , and illustrates an embodiment wherein a wheel structure support arm  87  extends through the central upper portion of the wheel support structure  11 . Support arm  87  can be molded into the cart base wall  4  or be a part of a separate structure, which extends down and interfits with the cart base  4 . The wheel structure  11  itself would be constructed with a gap or groove  87   a  to allow the support arm  82  to pass through the center of the structure. In addition, a plurality  4  of male/female resilient contact points  63  and  64  are provided between the wheel support structure  11  and the cart base wall  4 . 
     FIGS. 24 and 25 show alternative embodiments of the wheel support construction of the invention which include a 360° rotating wheel  30  a wheel support structure  31 , a retaining washer  32  and a support arm  33 . Referring to FIG. 24 the central longitudinal metal support arm or shaft  33  can extend all the way through structure  31  to be capped by a cap indicated on dashed lines at  34  or the wheel can alternately be constructed with a pass through gap or groove from front to rear and an end cap  88  provided for the longitudinal portion of the wheel support arm  33 . FIG. 25 shows the view of the same wheel structure from the side, including a screw and bolt assembly  89  which passes through the wheel support  31 , through a pass through in support  31 , and which also passes through an eye or opening  90  in the distal end portion of wheel support arm  33 . The screw and bolt assembly  89  serves to fixate support arm or shaft  33  so as to prevent the 360° rotation of wheel  30  about the axis formed by arm  33 . 
     FIG. 26 shows some details of the kickstand gripping handle  18  described above. Protrusions  93  (and/or recesses) extending from the underside of the handle  18  cooperate with matching recesses  93   a  (and/or protrusions) molded into the exterior cart base wall  85 . Each of the two kickstand arms  17  has a hole  17   h  through which a handle portion  71  extends. The distal kickstand handle arm end or “claw” end, i.e., the end most distant from the turn handle  18  resiliently clips or holds onto a support member joint  79  molded into the underside of base  4  and also engages matching grooves  85  (or protrusions) in the underside wall joist  79 . This kickstand may be alternatively designed with a support member  72  that extends all the way through between the handles. Protrusions or grooves  91  on the free end or “head” of the kickstand arm  17  interfit into corresponding molded areas in the underside of cart base  4  at the point where the arm is in its lowered position (with the “head” portion  91  face up) to further support the kickstand  17  from movement while it is in such recess, locked position. 
     FIG. 27 shows an alternative kickstand turn handle  18  including arms  92 . 
     FIG. 28 is another view of the kickstand assembly of FIG. 26 including the kickstand arm  17  and the gripping handle  18  which resiliently attaches to the gripping handle arm  71 . The latter extends through the kickstand arm  17  and terminates at the claw area  86 . As described above, the arm  71  extends through a base underside support joist  79  then resiliently attaches to the same support joint  79 , which is molded as part of the underside of the cart base  4 . One of the two kickstand arms is shown at  17  and this arm is molded with a slot  94  therethrough. Slot  94  is cylindrical at its center, but may have four cross members as shown, so that when the handle arm  71  is passed therethrough, the slot  94  allows the kickstand arm  17  to be turned to a lowered or raised position. As indicated above, connector  72 , shown in dashed lines, is used in the alternative embodiment wherein the kickstand arm  17  extends between the two sides of the cart. 
     FIG. 29A is a view looking down from inside the well of the cart base  4  toward the space where the wheel support structure interfits into each of the cart base wall cavities  12 . This view is a cut-away view of the base wall  95  (indicated by arrows), and for purposes of illustration, omits a portion of the cart base wall in the area extending from the base floor, up to just below the cavity openings  12 . The cavities  12  which hold the wheel support structure  11  (shown in dashed lines), have shaped openings  12 A which permit the wheel structure arms  11 A to be received in the cavity  12  only from the interior side of the cart base wall  4 . However, once placed in the cavities  12 , the wheel structure  11  is constructed such that the wheel support structure  11  can still then pivot 270° through this opening between the cart walls to a lowered, operable position, as described above. Another phantom view of the wheel structure  11  is shown at the upper right as pivoting outwardly and the central retention insert box  25  is shown in solid lines so as to indicate that when the corresponding wheel  9  is lowered and operable, the central retention insert box  25  interfits resiliently with an engaging means shown at  54  provided in the base wall wheel structure receiving area which is actually just below the cart base area shown. When the wheel support structure  11  is in the lowered and in the “locked” position, the structure  11  forms a flush profile in the base wall  4  between cavities  12 . As indicated above, protrusions or recesses  64  can be provided along the side of each cart base wall  4 , which interfit and further resiliently hold the wheel support structure  11  in the lowered position. 
     In the areas of the cart base wall (or along the omitted cart wall between the cavities  12 ), just beside each cavity opening, a stop element in the form of a molded ledge or protrusion  68  is provided which serves to resiliently connect to a corresponding protrusion or molded portion of the wheel support structure  11  so that when the wheel structure  11  is nested into the cart base  4 , the wheel structure  11  cannot move or close further. Thus, element  68  serves as a stop, and also resiliently holds the nested wheel structure  11  in place. 
     Two resiliently interfitting small wheel arm cavity covers  96  are employed and include protrusions  97  for securing each of the covers  596  into each cavity  12 . The covers  96  slide into slide grooves  99  and the protrusion  96  retains the wheel structure arms  11 A inside each cavity  12  in the base wall  4 . 
     Alternatively, rather than the two separate covers  96 , there can be a single unitary access cover  98  as shown in FIG. 29B which slides in the grooved openings  99  (or resiliently snaps therein) formed in the cart base walls  4  at a low enough profile on the base wall so as to allow the required pivoting of wheel support structure  11 , i.e., so that structure  11  can still pivot 270° above same. 
     FIG. 29B shows another embodiment cavity cover, wherein  11 A is the wheel support arm and an access cover  98 A, shown in dashed lines and including an inner shaped portion  986  and outwardly extending, flexible locking legs  98 C is placed as shown in solid lines, into the base wall area surrounding the cavity  12 . The preferred embodiment shown in FIG. 29B avoids the use of screws but it will however, be appreciated that metal screws, or suitable resiliently held “pins”, may be used to secure any cavity cover components in place. 
     FIG. 30 is a side elevation view of an alternative embodiment of the four-wheel folding cart construction wherein the generally “U” shaped handle  5  is employed rather than a center pull handle. The telescoping handle  5 , which is shown in the raised position in solid lines and in an even higher position in dashed lines recessed to the exterior of the cart base as shown in the lowest dashed lines, retained by the support arms  19 . The telescoping handle is attached at point  8  to the cart base and/or wall by a pin  36  or small arm traveling through the handle to the cart base. The front wheel  9  furthest from the handle is provided with a 360° turning caster wheel structure  100 . While this embodiment of the handle and base structure has advantageous features that the handle folds and nests into a relatively flush and thin profile, the U-shaped handle  5  must be raised higher than in the other embodiments in order to allow the rear wheels  9  to pivot 270° back up and onto the cart base  4 . 
     FIG. 31 is a top plan view of the four wheel cart CB and shows center pull handle  27  and all four wheel structures, i.e., the two rotating front wheels  30  and the two rear fixed wheels  9  and  10 , extending laterally. Recesses  22  provide a loose interfit with the wheels in their nested position, as shown in the lower right in dashed lines. The handle  27  is shown in dashed lines in the recessed position thereof where the handle  27  is resiliently affixed to a portion  69  of the base at the point closest to the outer edge of the handle  27 . The swing out side door  28  is also shown. FIG. 31A shows one embodiment of the handle  27  wherein protrusions  27 A are provided to resiliently hold the handle in matching recesses of the front cart base wall. 
     FIG. 32 shows the closed, nested position of a four wheel cart CB and the manner in which the parts are opened out. The center pull handle  27  shown nested between side walls  1  above the front or rear wall  2  or  3  which is the last part folded upward. 
     FIG. 33 is a top plan view of the components of the four wheel cart CB in the folded, closed position or state. Grooves  22  provide resilient fit with the respect rotating I support structure  31  and wheels  30  and further grooves  22  provide a similar fit with wheels  9 ,  10  and corresponding wheel support structures  11 . When the user lifts side doors  1  from the base  4  of the cart CB, all four wheels automatically break out of their loose resilient fit with grooves  22 , and the user then pivots them and “snaps” them into their stable operable (retained) position as indicated above. An opening  16  through the side wall (and base) provides a hand hold for the user. Gaps  20  extend through the side walls  1  and serve as hand pulls while cart base wall protrusions  69  hold the nested handle  27  (as well as the side walls  1 ),  2 A and  3 A are protrusions (or recesses) on the nested front and rear walls which cooperate with corresponding structures on the handle  27  to resiliently hold the handle  27  in its nested position. The swing out door  28  hinged onto one of the side walls  1  is also shown. 
     FIGS. 34 and 35 show two embodiments of the front wheel support structure for the four wheel cart, which allow 360° turning of the respective wheels  30 . FIG. 34 shows a construction where a non-unitary wheel support structure is employed, and an end cap  34  is secured after placement of a washer (not shown) in a recessed area  45   a  of the top of the wheel support  45  and a longitudinal metal wheel support arm or support shaft  33  extends down to a further washer  32 . End caps  48  close off the support sleeve or cylinder  46  which extends through the hollow upper area of the non-unitary wheel support structure  45  as described above. As was also described previously, the entire wheel support structure interfits into a matching cavity  12  molded out of the base wall itself and indicated in dashed lines The wheel support arms  57  are shown in dashed lines and as described above can be constructed in several ways as indicated previously using elements  47 A or elements  56  which were described above, and which are not shown here. The separate wheel support arm structures  46  and  48  can be eliminated entirely, if desired, in an alternative unitary, one piece embodiment of the wheel support arm structure shown in FIG.  35 . 
     FIG. 36 shows an alternative two wheel cart embodiment, commonly referred to as a hand cart and denoted DC. The embodiment shown includes a tubular (or similar) “lower” frame structure made of aluminum, or other suitable metal or plastic generally indicated at  101 . Wheel support arms  102  include uppermost spaced elements  102   a  which are hollow and cylindrical and which slide on to the “upper” frame at  103 . Elements  102   a  are preferably retained in position by suitable sleeves (not shown) which are held in place with pin screws (not shown) which extend into the frame  103 . Multiple protrusions or clamp like extensions  104  on the wheel support arms  102  extend inwardly toward the frame structure  101  and provide a retention means between the wheel support arms  102  and the lower section of the frame  101  at such time as the wheel is pivoted 270° from the axis point along upper frame  103  to the lowered, operable position. 
     FIG. 36A shows the wheel structure arm pivot point or pivot axis  105 , as well as the lower frame structure  101 , and the retention clamps  104 . The cart wheel structure may employ either a two sided support for the wheel  9 , as shown in FIG. 36A, or a single sided support for the wheel (see FIG. 3F above), with the single sided support either closest to the frame or cart side of the wheel or vice-versa. 
     FIG. 36 also shows the generally “U” shaped handle  5  which nests inside of the lower portion of the frame section  101 . The handle  5  may be telescoped or extended out to the dashed line position shown. A cargo tray  106  of the hand cart HC, is adapted to pivot and nest down into the lower section of the frame  101 , as indicated in dashed lines. The cargo tray  106   a  pivots along an axis  107 . As shown in FIG. 36B, the cargo carrier or tray  106  meets a stop  108  which is formed by a portion of the lower frame member  101 . Alternatively, stop  108  can be separate part  109  retained in place on the frame via a screw pin,  10  or as shown in FIG.  36 C. 
     FIG. 37 is a top plan view which shows the cargo carrier or tray  106  in the nested state, the 270° pivoting wheel supports  102  in their nested position, and the handle  5  also nested as shown in solid lines with the extended handle shown in dashed lines. The handle  5  actually nests inside the tubular (or similar) lower frame structure  101 . 
     FIG. 38 shows the nested position of a wheel  9 , the foot of tray  106 , and of the handle  5 . In dashed lines, the wheel structure  102  is shown pivoting from the operative position of the wheel structure. FIG. 38 also indicates the retention means for securing the wheel support structure  102  to the lower frame  101 . 
     FIG. 39 is a top plan view showing the cargo carrier or tray  106  which includes a cylindrical or hollow portion  106 A, to allow a lower frame cross member or arm  101 A to extend through the tray cylinder  106 A, as well as through two pass-through openings  101 B in the lower frame  101 , whereby end caps or screw-in pieces  111  close off the cross members  101 A. The wheel support structures are indicated at  102  wherein, for illustration purposes, the wheels are omitted. 
     FIG. 40 shows the wheel structures  102  are mounted on one upper frame arm  103 A and the manner of assembly of some components. The wheel structure  102  is slid on to upper frame arm  103 A before the same is recessed into an upper frame socket  112  and after these parts are secured, an end cap  113  is inserted in position in the end arm  103 A. In this embodiment suitable stability sleeves  114  are placed on either side of the wheel structure  102  in order to retain the pivoting when structure  102  in place should a tubular frame be used. As indicated in dashed lines, the cross member  103 A around which the foot or tray sleeve (not shown) is slid and is then secured in place with any suitable end cap configuration indicated by end caps  111 . The preferred hand cart embodiment described above uses a frame-like upper and lower structure, although each “side” of the frame may alternatively be constructed of solid plastic or metallic materials without any separate upper and lower frame structure, yet still provide the same basic two wheeled hand cart construction compatible with the basic features disclosed herein. 
     FIGS. 41 and 42 show storage methods or techniques for the folding cart. FIG. 41 shows one of numerous potential wall storage methods using a hook H mounted on a wall W with another implement indicated at  1 . FIG. 42 shows the cart CA (or any of the other carts discussed above) retained in the underside of an open vehicle trunk lid  115  of a vehicle V wherein a series of retaining arms or elements  116  hold the corners of the carts CA, and one of the tapered carry handles  15  is resiliently held to the lid via resilient cooperation with any portion of the trunk lid  115 . Given that one of the main objects of this invention is to create a thin profile folding cart, it is apparent that any of the folded, nested carts described above can be fitted to be stored and nested along any flat surface, such as a vehicle trunk lid, hatch or door, whether similar or different to that disclosed in FIG. 42, or even inside a custom created slot or groove manufactured inside the vehicle lid or door or other accessible structure. 
     Although the invention has been described above in relation to preferred embodiments thereof, it will be understood by those skilled in the art that variations and modifications can be effected in these preferred embodiments without departing from the scope and spirit of the invention.