Abstract:
The present invention concerns a cart with a flat cargo platform adapted to travel in the horizontal direction via foldable wheels mounted respectively via one wheel fork, and with a vertically pivotable pole handle.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is based upon German Patent Application No. 102 40 895.5, filed Sep. 4, 2002, from which priority is claimed. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention concerns a cart with foldable wheels. 
   2. Description of the Related Art 
   A cart of this type is known from WO 00/73122. It includes a perpendicularly somewhat diagonally upwardly projecting frame element for pushing the cart. The projecting frame is collapsible into the cargo platform. Further, wheels foldable about horizontal axis are provided on the bottom side of the cargo platform, wherein the front wheels besides this are pivotable about a vertical axis. This known cart is not very easy to operate, since is includes relatively complex mechanisms for locking the push element and wheels into place in the assembled condition as well as the folded together condition. Besides this, it is difficult to keep the cart moving in the desired direction, since the pivotable front wheels do not easily follow any movement and may even prevent sideways movement. Finally, the manufacture thereof is complicated to the extent that different wheels must be manufactured and assembled to the front and the back ends of the cart. This increases the difficulty in the blocking of the front wheels. The pivotable front wheels, so-called swivel or steering wheels, must have an axial bearing, in order to be able to accept the load pressure of the transport cart, while at the same time, be easily rotatable. These steering wheels are broad or thick, particularly in the area of the bearings, and in the folded-in condition, are relatively thick, which increases the overall thickness of the folded-together cart. Besides this, the steering wheeels can get directed to a wrong direction on contact with even small impediments (cables, cross-grates, edges of carpets, etc.), making it necessary, while pushing the cart, to repeatedly force the cart back onto the desired direction. The complicated design of this known cart, in particular due to the many necessary construction components, is characterized by a high intrinsic weight, which is of disadvantage when folding and unfolding the cart, as well as during the transport thereof. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, a high capacity cart with horizontal cargo platform and large undercarriage wheels is to be provided, which is easy to manufacture and operate, which is comprised of lighter-weight components than conventional carts, and which can be quickly and easily folded together to present an extremely flat shape which can be easily stored, particularly in a vehicle trunk. Thereby the weight of the transport cart is to be very low, and in particular the cart should be stably guided in a desired direction without being influenced by an uneven ground. 
   This task is inventively solved in a cart according to the present invention. 
   Preferred embodiments of the invention are set forth herein. 
   The securing of the handle to the swiveling mount makes possible the unproblematic movement of the cart in any desired direction without any impediment. This swiveling mount can also be pivoted 180° relative to the loading platform even when the handle is not in the folded-in position. Thereby the grip of the handle can project beyond the rear end of the cargo platform, and the cart can be carried via this handle grip or, in the case that the folded over wheels project beyond the edges of the cart, as is easily possible by appropriate shaping of the cargo platform, be easily transported upon one of the foldable wheels. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     On the basis of the figures, a preferred embodiment of the invention will be described in greater detail. There is shown: 
       FIG. 1  a schematic side view of the inventive cart with foldable wheels located in the operating position, wherein the front part of the handle is broken away, 
       FIG. 2  a bottom view of the cart shown in  FIG. 1  with foldable wheels in the folded position, 
       FIG. 3  an enlarged partial view of the cart wheel platform and a folded-in foldable wheel with the associated locking device, seen parallel to the longitudinal center line of the cart in the direction of travel towards the front, 
       FIG. 4  a partial sectional enlarged partial view of a folding device with the associated bearing and locking device thereof, 
       FIG. 5  a partial view corresponding to  FIG. 4 , which in comparison to  FIG. 4  is rotated by 90°, 
       FIG. 6  an enlarged view of a locking element for the foldable wheels, 
       FIG. 7  a schematic representation of the cart in folded condition during transport by a user, 
       FIG. 8  a longitudinal section through the handle with hand grip, 
       FIG. 9  a partial view of a foldable wheel corresponding to  FIG. 4  in an other embodiment of the associated bearing and locking device thereof, and 
       FIG. 10  an axial section of the upper end of the carrier fork shown in  FIG. 9 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In the representation according to  FIG. 1 , the various foldable wheels  2 ,  2 ′ are in an operating position projecting perpendicular from the cargo platform  1 . The thin walled, essentially planar cargo platform is carried by two front foldable wheels  2 ′ and two rear foldable wheels  2 , of which in  FIG. 1  respectively only one is to be seen. Each foldable wheel  2 ,  2 ′ is rotatably mounted within a carrier or wheel fork  3 ,  3 ′. Each wheel fork is foldable in and out about a wheel fork rotation axle  4 ,  4 ′ extending parallel to the longitudinal centerline  50  ( FIG. 2 ) of the cart  1  between (a) an operating position of the foldable wheels  2 ,  2 ′ shown in  FIG. 1  and (b) a folded-in position (rear foldable wheels  2 ) or, as the case may be, folded-out (front foldable wheels  2 ′) shown in  FIG. 2 . In  FIG. 2  additionally each of the front foldable wheels  2 ′ is also shown in the operating position  2 ″, in order to illustrate the folding process. 
   As can be seen from  FIGS. 3 through 5 , each wheel fork  3 ,  3 ′ exhibits a substantially U-shaped recess  22  ( FIG. 5 ) between its fork shanks  22 ′, in which a detent element  6  of the foldable wheel locking mechanism can move almost free-of-play, and in which therebelow respectively one foldable wheel  2 ,  2 ′ is received. Each foldable wheel  2 ,  2 ′ is mounted rotatably about a wheel axis  51  in the fork shanks  22 ′. 
   Each wheel fork  3 ,  3 ′ is associated with a bearing or mounting bore  46  extending perpendicular to the wheel axis  51 , which slidingly encompasses a wheel carrier fork rotation axle  4 ,  4 ′ extending parallel to the carrier platform  1 . The end of the wheel fork-rotation axle  4 ,  4 ′ projecting out of the bearing bore  46  is tightly encompassed by a U-shaped segment of a securing element  5 ,  5 ′ and is secured thereto. The end segment of the securing element  5 ,  5 ′ extending parallel to the cargo platform  1  includes screw holes  8 , through which threaded bolts  48  extend anchored in the cargo platform  1  and secured by nuts  49 . Between the securing elements  5  and the cargo platform  1  distancing disks  40 ′ are inserted for a purpose discussed in greater detail below, which likewise are penetrated-through by the threaded bolts  48 . The securing element  5 ,  5 ′ of the wheel fork-rotation axle  4 ,  4 ′ can also be differently designed, for example, as a cylindrical mounting block with quadratic, square or other cross-section, and with a central hollow cylindrical recess for receiving one of the tubular shaped cantilevered or self-supporting carrier fork rotation-axles per interference-fit. The securing screws (threaded bolts  48 ,  FIG. 5 ) are then screwed into the internal threading of the cylindrical securing block. The wheel fork rotation axle  4  need not absolutely be designed self supporting or cantilevered, but could be secured on both sides. 
   Close to the free carrying-end of the wheel fork rotation-axle  4 ,  4 ′, which in this embodiment is tubular, there is on the outer side of the rotation axle secured, for example by welding, a wheel fork blocking element  7 ,  7 ′ shown in greater detail in  FIG. 6 . In similar manner the opposite tube end can be secured in the U-shaped recess of the securing element  5 ,  5 ′ by welding. The blocking element  7 ,  7 ′ exhibits on its circumference three respective indentations  23 ,  24 ,  25  in angular separations of 90°. Curve tracks  26 ,  27  are provided between the indentations  23 ,  24 ,  25 . On a thickening or reinforcement  41  of the wheel fork  3 ,  3 ′, which lies within the U-shaped recess  22 , the end of a detent element spring  6  is tensioned or clamped in via a threaded bolt  21  and a thereupon seated nut  42 , of which the opposite free end carries a finger protection cap  45 . The detent element can engage in any of the indentations  23 ,  24 ,  25 , since it is pretensioned against the circumference of the blocking element  7 ,  7 ′ in such a manner that during rotation of the wheel fork  3 ,  3 ′ it automatically engages in the next adjacent indentation  23 ,  24 ,  25  in the direction of the arrow C ( FIG. 4 ). By lifting the finger protection cap  45  in the direction of the arrow D, detent element  6  can be lifted out of the respective indentation and slide over an adjacent curve track  26  or  27 , until it snaps into the next indentation  23 ,  24 ,  25 . In each of the indentations  23 ,  24 ,  25  the detent element  6 ,  6 ′ of the associated wheel fork  3 ,  3 ′ is fixed on both sides of the operating position in the operating position  2 ″ or, as the case may be, in a folded position. In each of the folded positions, which differ by 180° about the wheel fork rotation axle  4 ,  4 ′, the respective wheel fork  3 ,  3 ′ lies very close to the bottom side  12  of the cargo platform  1 , so that the total thickness of the collapsed cart is extraordinarily narrow. 
   Preferably the foldable wheels  2 ,  2 ′ inclusive of the wheel forks  3 ,  3 ′ and the associated folding mechanism in the inventive cart are of the identical construction and can be positioned at any location on the bottom side  12  of the platform  1  depending upon intended use. This means that it is possible, without any particular change in construction techniques, and using the same principle and using essentially the same components, to produce long, short, wide or narrow carts. At the rear end of the cart, it is possible to provide four or more foldable wheels  2 ,  2 ′ in a row next to each other, whereby the load bearing capacity of the cart can be greatly increased. Thereby, likewise, no change in the components of the construction is necessary. 
   While the cart discussed in the introductory part of the specification is relatively heavy due to the large number of parts, the inventive cart, in comparison having the same load bearing surface, is extraordinarily light weight. Thereby it&#39;s operation and transport is particularly facilitated. 
   On the sides set off from the curve tracks  26 ,  27  the diametrically oppositely lying indentations  24  and  25  are provided with a higher side wall  43  or as the case may be  44 , so that the detent element  6 ,  6 ′ cannot leave the indentation in this direction. Therewith an extraordinarily reliable securing of the foldable wheels  2 ,  2 ′ is possible in the operating position according to  FIG. 1  or, as the case may be, the collapsed position according to  FIG. 2 . As can be seen in particular from  FIG. 2 , the wheel fork-axle  4  of the rear foldable wheels  2  are secured close to the outer edge  33  of the cargo platform  1 , so that the two associated foldable wheels  2  can be folded inwards towards the longitudinal centerline  50 , while the wheel fork rotation-axle  4 ′ of the front foldable wheels  2 ′ is positioned close to the longitudinal center line  50 , so that the two foldable wheels  2 ′ come to rest projecting from the side edges  33  of the cargo platform  1 . This is made possible by the special design of the cargo platform  1 . This design is defined by a slightly bowed-out rear edge  31 , two parallel straight longitudinal sidewalls  33 , which transition to the rear edge  31  respectively by curvature  32 , two side edges  34  merging towards each other towards the front, thus narrowing the front part of the cargo platform  1  and a front edge  36  running perpendicular and connecting the sidewalls  34 . By the narrowing of the cargo platform  1  in the front area, that is, in the area of the sidewalls  34 , the outwardly folded front foldable wheels  2 ′ shown in  FIG. 2  in the collapsed position can project sideways beyond the side edges  34 , so that the cart situated in the folded together condition, as can be seen in  FIG. 7 , can run with one of its front foldable wheels  2 ′ on the ground  52 . Thereby, the oppositely lying rear end is held in the hand  53  of the user or, as the case may be, pulled along. For facilitating this holding, an oval through-hole  18  is provided in the cargo platform  1  close to the rear edge  31 . The through-hole serves as grip and is preferably beveled at its edges. Two further substantially similar through-holes  17  and  17 ′ close to the longitudinal edges  33  can likewise serve as grips, in this case for carrying the cart. The side edges  34  likewise transition via curvature  35  to the front edge  36 . During rolling of the collapsed cart on one of its front foldable wheels  2 ′, according to  FIG. 7 , this can be either pulled in the direction of arrow A or pushed in the direction of arrow B. 
   The narrowed side-wheels  34  of the cargo platform  1  are very beneficial even during the pulling of the cart by means of the folded-out handle  11 . If, namely, a significant change in direction is to be accomplished during pulling of the cart, for example deviating from the previous direction of travel by up to 90°, the front end of the swivel mount  9  must extend so far beyond the front of the cargo platform  1 , that during turning of the swivel mount  9  by up to 90°, it would have to be able to project beyond the rim of the cargo platform  1  for any position. Otherwise, the cargo platform would prevent a slanted positioning of the handle  11 , which would be the natural position when being pulled by the pulling hand of the user, and a free rotation of the swivel mount  9  would not be possible. As a result of the narrowed side edges  34 , the front of the swivel mount  9  projects beyond the circumference of the cargo platform  1  in any direction of rotation. Therewith, a change in direction of the transport cart of 90° is possible due to the suitable shape of the cargo platform  1  and even beyond this. Thereby the swivel mount  9  can be significantly shortened in the longitudinal direction of the cart and therewith the total length of the cart can be substantially reduced. 
   From the front side of the cargo platform  1 , there project, barely noticeably, parallel longitudinally-running anti-skid strips  30  for goods being transported on the cargo platform (not shown). From the bottom side  12  of the cargo platform  1  there slightly project reinforcement ribs  13  and  16 , which in each case are lower than the running wheels  2 ,  2 ′ and their wheel forks  3 ,  3 ′ when in the folded position according to  FIG. 2 . For further reinforcement, there is also a box  37  slightly projecting on the bottom side  12 , which is provided essentially parallel to the cargo platform  1  and serves, besides reinforcement, also for storage of cargo straps, elastic bands with hooks, and the like. The box  37  has, as in the case of reinforcing ribs  13 ,  16 , maximally the height of the wheel forks  3 ,  3 ′ below the bottom side  12  of the cargo platform  1 . It is also possible to provide a multiplicity of such boxes  37  on the bottom side  12 . In the area of the narrowing front part of the cargo platform  1  there is provided, on the bottom side  12 , a swivel mount  9  rotatable on the cargo platform about an axis of rotation  19 , which includes recess  10  projecting from the front edge  36  of the cargo platform and slanted downwards, as can be seen from  FIGS. 1 and 2 . The thickness of the swivel mount  9  corresponds thereby to the thickness of the spacer disk  40 ′, so that the securing elements  5  and  5 ′ of the rear or, as the case may be, front foldable wheels  2 ,  2 ′ lie in the same separation below the bottom side  12  of the cargo platform  1 . Thereby an essentially horizontal position of the cargo platform is guaranteed. The slanted recess  10  of the swivel mount  9  is shaped as a fork and receives flush or level a handle block  38  suited at the lower end of the handle  11 , which includes a transverse extending, cylindrical, through-going opening  39  and a threaded bolt extending through this opening  39  and screwed tight to the recess  10 . Thereby, the handle  11  is pivotable in the vertical direction and can, on the other hand, be pivoted in the horizontal direction about the rotation axis  19  together with the swivel mount  9  for steering the cart. 
   When the front foldable wheels  2 ′ are in the outer folded position shown in  FIG. 2 , the mounted handle  11  can be folded between the two wheel forks  3 ′ parallel and close the bottom side  12  of the cargo platform  1  towards the back, so that it can be folded from the position indicated with dashed lines on the right end of  FIG. 2  into the rearward directed folded-in position lying almost against the bottom side  12  according to  FIG. 2 . In this position, it can snap into a fork-like or approximately U-shaped holder clamp  14 , so that it is held securely on the bottom side  12 . The outer end of the handle  11  is in the form of a flat hand grip  15 , which widens for comfortable guidance by one hand and includes an appropriate oval opening  15 ′. It can be seen from  FIG. 8  that the hand grip  15  with its opening  15 ′ was slightly offset to the side or double-curved relative to the longitudinal axis  11 ′ of the handle  11 , so that when in its position in  FIG. 2  it lies on the outer side of the folded-in outer foldable wheels  2  outside of the wheel forks  3 . The total thickness between the upper side cargo platform  1  and bottom side of the collapsed handle hand grip  15  is not larger than that between the upper side and the wheel forks  3 ,  3 ′. Therewith, there results, overall, an extraordinarily slender and lightweight construction of the cart, which is easily transported, steered and, in the folded together condition, is easily stored. 
   So that the wheel forks  3 ′ of the front foldable wheels  2 ′ are not impeded by the swivel mount  9  during sideways folding-in into the folded position according to  FIG. 2 , there are on both sides of the swivel mount  9 , seen in the vertical direction, U-shaped recesses  28  and  29 , in which respectively one side shank of each wheel fork  3 ′ can extend into when in the folded position. 
   Since all four foldable wheel components are completely identical, there results a great advantage for the mass-production of the inventive cart. Each foldable wheel can, as illustrated, as desired, be pivoted into any of three positions, that is, an operating position and two opposite folded positions, and can be locked in each of these positions. Thus, it would also be possible in the framework of the invention, for example, for the design of a higher capacity cart, to provide at the back four of these identical foldable wheel units in a row, side-by-side, wherein in the folded position of the cart, the two inner foldable wheels can be pivoted in a simple manner towards the centerline  50  and the two outer foldable wheels towards outwards. 
   Between each wheel fork  3 ,  3 ′ and the securing element  5 ,  5 ′ of the respective foldable units, there is a round spacer disk  40 , which ensures a problem-free rotation and at the same time axial mounting or holding of the wheel forks  3 ,  3 ′ (see  FIG. 4 ). On the other axial end each wheel fork  3 ,  3 ′ is respectively held by the wheel fork locking element  7 ,  7 ′ lying with play against the wheel fork. 
   At the left end of  FIG. 1 , a further alternative embodiment of the cargo platform is indicated, with a laminated-on upper surface  54 , which is connected with the cargo platform  1  in such a manner, that a conventional, somewhat stronger or reinforced cargo surface is formed. 
   Another embodiment of the foldable wheel locking mechanism is shown in  FIGS. 9 and 10 . Instead of the carrier fork blocking element  7 ,  7 ′ as shown in  FIGS. 4 and 6 , in this embodiment on the wheel fork rotation-axle  4 ,  4 ′ a guide element  55  encompassing this is provided, which radially outside of the wheel fork-rotation axle  4 ,  4 ′ has at least one hollow cylindrical recess  56  for the sliding reception of a securing bolt  57 , of which the tip section  58  is insertable in a hollow cylindrical recess  59  of the respective carrier fork  3 ,  3 ′ by axial sliding of the securing bolt  57 . Thereby, a securing of the foldable wheel  2 ,  2 ′ or, as the case may be, the wheel fork  3 ,  3 ′ in a running position. Since, however, in the illustration three cylindrical recesses  59  respectively offset by 90° are provided in the wheel fork  3 ,  3 ′, the tip segment  58  of the securing bolt  57  allows itself to be selectively inserted into one of the two cylindrical recesses  59 , so that a securing is possible in two opposing folded positions of the foldable wheel  2 ,  2 ′. This reception of the tip segment  58  in the cylindrical recess  59  can, in contrast to the exaggerated illustrated representation in  FIGS. 9 and 10 , for easier understanding, occur nearly free of play. 
   The guidance of the securing bolt  57  within the recess  56  of the guide element  55  can likewise occur free of play. For biasing in the securing position, the securing bolt  57  exhibits within the cylindrical recess  56  a thrust collar  60 , which is based in the direction towards the tip segment  58  via a pressure spring  61 , so that the tip segment  58  can be extracted out of the cylindrical recess  59  only by operation of a hand grip  62  widening out of the guide element  55 . 
   In a further alternative embodiment the carrier fork  3 ,  3 ′ does not exhibit three hollow cylindrical recesses  59  set-off respectively by 90° as shown in  FIGS. 9 and 10 , but rather only one single, namely, the central of the three cylindrical recesses  59 , while in the guide element  55  respectively three cylindrical recesses  56  set off by 90° are provided. The securing bolt  57  can be selectively received in these cylindrical recesses  56 . In this case, the thrust collar  60  must, of course be omitted, since otherwise the securing bolt  57  cannot be pulled out of the recess  56 . In many applications this simplified method of securing is adequate. 
   
     
       
             
           
             
             
             
           
         
             
                 
             
             
               Reference Number List 
             
           
        
         
             
                 
               Pos. 
               Description 
             
             
                 
                 
             
             
                 
               1 
               cargo platform 
             
             
                 
               2, 2′ 
               foldable wheels 
             
             
                 
               3, 3′ 
               wheel fork 
             
             
                 
               4, 4′ 
               wheel fork-rotation axle 
             
             
                 
               5, 5′ 
               securing element 
             
             
                 
               6, 6′ 
               detent element 
             
             
                 
               7, 7′ 
               wheel fork block element 
             
             
                 
               8 
               screw holes 
             
             
                 
               9 
               swivel mount 
             
             
                 
               10 
               swivel mount recess 
             
             
                 
               11 
               handle 
             
             
                 
               11′ 
               handle longitudinal axis 
             
             
                 
               12 
               bottom side 
             
             
                 
               13 
               reinforcing ribs 
             
             
                 
               14 
               securing clamp 
             
             
                 
               15 
               handle grip 
             
             
                 
               15′ 
               opening 
             
             
                 
               16 
               reinforcing ribs 
             
             
                 
               17, 17′ 
               through hole as hand grip 
             
             
                 
               18 
               through hole as grip 
             
             
                 
               19 
               rotation axis 
             
             
                 
               20 
               through holes 
             
             
                 
               21 
               threaded bolts 
             
             
                 
               22 
               U-shaped recess 
             
             
                 
               22′ 
               fork shanks 
             
             
                 
               23 
               indentation 
             
             
                 
               24 
               indentation 
             
             
                 
               25 
               indentation 
             
             
                 
               26, 27 
               curve track 
             
             
                 
               28, 29 
               U-shaped recesses 
             
             
                 
               30 
               anti-skid strips 
             
             
                 
               31 
               back edge 
             
             
                 
               32 
               curvature 
             
             
                 
               33 
               longitudinal side edges 
             
             
                 
               34 
               side edges 
             
             
                 
               35 
               curvature 
             
             
                 
               36 
               front edge 
             
             
                 
               37 
               box 
             
             
                 
               38 
               handle block 
             
             
                 
               39 
               cylindrical through hole 
             
             
                 
               40, 40′ 
               spacer disks 
             
             
                 
               41 
               thickening 
             
             
                 
               42 
               nut 
             
             
                 
               43, 44 
               higher side wall 
             
             
                 
               45 
               finger protection cap 
             
             
                 
               46 
               mounting bore 
             
             
                 
               47 
               screw holes 
             
             
                 
               48 
               threaded bolts 
             
             
                 
               49 
               nut 
             
             
                 
               50 
               longitudinal center line 
             
             
                 
               51 
               rail axis 
             
             
                 
               52 
               floor 
             
             
                 
               53 
               hand 
             
             
                 
               54 
               cover layer 
             
             
                 
               55 
               guide element 
             
             
                 
               56 
               hollow cylindrical recess 
             
             
                 
               57 
               securing bolt 
             
             
                 
               58 
               tip segment 
             
             
                 
               59 
               hollow cylindrical recess 
             
             
                 
               60 
               thrust collar 
             
             
                 
               61 
               helical spring 
             
             
                 
               62 
               hand grip