Abstract:
A folding cart is disclosed which has a forward section, a main section, and a rear section, along with forward and rear end rails and left and right side rails. The forward and rear portions of the left and right side rails fold to a coplanar position with the main portion of each respective side rail, while the forward and rear end rails fold down to a position coplanar with the forward section and rear section, respectively. The forward and rear sections may then be rotated to a position over the main section. The forward and rear sections each have mounted to their bottom surfaces a dual wheel assembly, each dual wheel assembly having a pair of wheels which may be folded to a position parallel to their respective forward or rear section. The forward dual wheel assembly is mounted to the front section of the folding cart a rotating pivot, while the rear dual wheel assembly is mounted directly to the rear section. Finally, a folding handle is provided which is attached to the forward dual wheel assembly. The handle, when folded, extends from the midpoint of the forward dual wheel assembly over the folded wheels to the rear of the folded cart and clasps to the rear of the folded cart.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     REFERENCE TO “MICROFICHE APPENDIX” 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     This Invention relates to a folding utility cart for general use that folds into a compact shape for ease of transportation and storage. Conventional carts are made from a variety of materials, including metal, wood, and plastic, and typically have a flat bed with raised sides. Wheels are typically mounted to the underside of the bed by means of brackets, with the front wheels customarily connected to a forward extending handle and mounted for steerability. While these carts are generally sturdy and can stand up to heavy use for extended periods of time, they are large and generally difficult to transport in vehicles, particularly modern vehicles with relatively small trunks. The overall volume occupied by traditional carts can render them difficult and space consuming to store. 
     Various hand trucks, carts, wagons, creepers, and the like have been hinged in order to allow them to be folded for storage. See, e.g., Martin, U.S. Pat. No. 6,095,532; Crowell, U.S. Pat. No. 5,857,695; Miles, et al., U.S. Pat. No. 5,611,552; DeWijn, U.S. Pat. 4,398,736; Olsson, U.S. Pat. No. 3,985,372; and Hoff, U.S. Pat. No. 3,822,069. While the methods divulged in these patents have been somewhat effective for flat carts, their arrangements are not fully successful with respect to carts having side rails, and none of them are directed to such a cart. Greenberg, U.S. Pat. No. 4,957,306 discusses a two-wheeled lawn cart with sides that fold down over the bed, but the method of folding discussed in the &#39;306 patent is only partially successful in creating a compact structure; the cart discussed in the &#39;306 patent is also substantially different than the present Invention. A folding child&#39;s wagon with removable rails and wheels with a bed that folds in half is described by Shorter, U.S. Pat. No. 5,957,482. However, the folding mechanism is for the bed only, with a user forced to partially disassemble the wagon by removing the side rails and wheels in order to attain a fully compact structure. None of this prior work fully addresses the need for a fully collapsible cart, with all side and end rails as well as wheels folding into a compact package. Thus, there is a continuing need for an improved cart with side and end rails which is sturdy and which is foldable as a complete unit into a compact package for efficient storage. The present Invention answers those needs. 
     SUMMARY OF THE INVENTION 
     In accordance with the present Invention, a folding cart having both an operative position for use as well as a folded position for storage is described. The cart includes four major sets of components: the frame, which also forms the bed; the side and end rails; the wheel assemblies; and the handle, which also serves to lock the cart in its folded position. The frame is divided into forward, middle (or main), and rear frame sections. The forward and rear frame sections are defined generally as a planar structure defined by and comprising forward, rear, left, and right members with zero or more reinforcing members and a floor member attached to the upper side of the frame section. The forward and rear members of the forward and rear frame sections should be substantially parallel to each other, but do not need to be of equal lengths, such that the structure defined may be non-rectangular. The middle frame section, however, is defined generally as a planar, rectangular structure defined by and comprising forward, rear left, and right members with zero or more reinforcing members and a floor member attached to the upper side of the frame section. The reinforcing members extend across the shape defined by the forward, rear, left, and right members and are attached at their ends to any two of those members. The rear edge of the forward frame section is rotatably connected to the forward edge of the middle frame section, and the forward edge of the rear frame section is rotatably connected to the rear edge of the middle frame section. By this arrangement, in the folded position, the forward and rear frame sections fold to the top surface of the middle frame section. In the unfolded, operative position, the forward, middle, and rear frame sections form a plane. The left and right members of each frame section are hollow, forming a tube down each side of each frame section. Furthermore, manually articulable spring-loaded locking pins are present at each end of both the left and right members of the middle frame section. Each locking pin may be manually retracted and locked back into its respective frame member end, and when released, each locking pin extends from the end of its respective frame member end. In the unfolded position, the locking pins are released and extend into the respective contiguous left or right side member of the forward or rear frame section, thereby providing stability and great mechanical strength to the unfolded frame. 
     The side and end rails are also foldable. The forward end rail is rotatably connected at its lower edge to the forward edge of the forward frame section such that it folds from a raised position perpendicular to the frame into a position coplanar with the frame. Similarly, the rear end rail is rotatably connected at its lower edge to the rear edge of the rear frame section such that it too folds from a raised position perpendicular to the frame into a position coplanar with the frame. In a departure from customary practice, the left and right side rails do not fold into a position coplanar with the frame sections; rather, each side rail is divided into three sections; a forward side rail, middle side rail, and rear side rail. The rear edge of the forward side rail is rotatably connected to the forward edge of the middle side rail, and the forward edge of the rear side rail is rotatably connected to the rear edge of the middle side rail. The lower edge of the left middle side rail is non-rotatably connected to the left edge of the middle frame section such that the plane defined by the left middle side rail is substantially perpendicular to the plane defined by the middle frame section. The lower edge of the right middle side rail is non-rotatably connected in the same fashion to the right edge of the middle frame section. By this arrangement, the forward and rear side rails on each side may rotate from a position along the corresponding side edge of the corresponding forward or rear frame section into a position along the corresponding edge of the middle frame section and flush with the corresponding middle side rail. 
     The present Invention also includes two dual wheel assemblies, a forward dual wheel assembly and a rear dual wheel assembly. Each dual wheel assembly is substantially identical to the other, but the methods differ for attaching each wheel assembly to the lower surface of the frame. The rear dual wheel assembly is connected to the lower surface of the rear frame section in a fixed position; the forward dual wheel assembly, however, is rotatably connected to the lower surface of the forward frame section. This arrangement allows the forward dual wheel assembly to be used to steer the cart. Each dual wheel assembly includes a pair of wheels, each rotatably connected to a wheel bracket via a wheel axle. Each wheel bracket is rotatably connected by a pivot to one end of a dual wheel assembly bracket, which is connected to the lower frame as described. The dual wheel assembly bracket includes two wheel bracket locking pins, with one locking pin corresponding to each of the wheel brackets. By use of the locking pins, the wheels can be locked in two or more positions, including the fully folded and fully unfolded positions. 
     Finally, the present Invention includes a handle by which a user may pull the cart, which also serves to lock the Invention into the folded position. The handle is attached at one end to the forward dual wheel assembly&#39;s dual wheel assembly bracket. The manner of attachment is such that the handle is rotatable in the vertical plane, but not in the horizontal plane. The handle is divided into three segments, including a handgrip, a middle segment, and an attachment segment, with the attachment segment actually attached to the forward dual wheel assembly. The attachment segment is rotatably connected to the middle segment; both the attachment segment and middle segment comprise tubes of identical cross-section. Furthermore, a locking mechanism is set in the middle segment such that when the attachment segment and middle segment are rotated into a linear, coaxial position, the two segments are locked into this position. The locking mechanism has a manual control allowing the user to release this lock when the Invention is being folded. The handgrip is attached coaxially to the middle segment and is of smaller cross-sectional dimension than the middle segment, such that the attachment end of the handgrip extends inside the middle segment. The handgrip may slide within the middle segment, and is retained in the middle segment by means of a spring such that a user may slide the handgrip out a short distance, but may not remove the handgrip from the middle segment. This ability to slide the handgrip out a short distance is important because it allows the user to latch the handgrip around the Invention in the folded position. After passing from the middle segment, the handgrip bends to a position substantially perpendicular to the line formed by the central axis of the middle segment. The bent portion of the handgrip is of a suitable size for a person to pull on it with one hand. The terminal end of the handgrip is attached to a lip plate, which, in the folded position, holds the handgrip in place around the rear end of the folded Invention. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the cart in its fully folded position. 
     FIG. 2 is a perspective view of the partially unfolded cart. 
     FIG. 3 is a partial view from a bottom perspective of the orientation of the folded wheel, handle, and front wheel assembly swivel. 
     FIG. 4 is a perspective view of the partially unfolded cart demonstrating the manner in which the side panels unfold. 
     FIG. 5 is a view of the cart from the rear demonstrating the manner in which the wheels unfold. 
     FIG. 6 is an exploded view of one end of the dual wheel assembly. 
     FIG. 7 is a partial view of the bottom of the front end of the cart showing the front dual wheel assembly. 
     FIG. 8 is a perspective view of the fully unfolded cart. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1,  2 ,  4 , and  8  disclose the folding cart of the present Invention in a variety of positions from the fully folded position to the fully operative position. In these figures can be seen the main bed frame  100 , forward bed frame  120  and the rear bed frame  140  which, together, form the frame for the overall frame of the Invention. As shown in FIG. 2, the forward bed frame  120  and rear bed frame  140  are rotatably attached to the forward and rear edges, respectively, of the main bed frame  100  by a forward bed frame hinge  122  and a rear bed frame hinge  142 , respectively. On the top surface of the forward bed frame  120 , main bed frame  100 , and rear bed frame  140  are attached the forward bed floor  124 , main bed floor  102 , and rear bed floor  144 , respectively. In the preferred embodiment of the Invention, the perimeters of the forward bed frame  120 , main bed frame  100 , and rear bed frame  140  are formed from pieces of tubing. Set within each of the tubes forming the left and right sides of the main bed frame  100  are a pair of locking pins  110 , not shown in the drawings but each of which will be understood by those in the art as a solid pin which extends from the end of the tubing forming the left or right side of the main bed frame  100  due to tension provided by a spring. Those in the art will further understand that these spring-loaded locking pins  110  may be manually retracted entirely within the tubing. When the apparatus is unfolded and the locking pins  110  are in the unretracted position, it will be understood that each locking pin extends from the end of its respective side tube of the main bed frame  100  into the contiguous side tube of either the forward bed frame  120  or rear bed frame  140 . Those in the art will appreciate the methods and materials used to manufacture the forward bed frame  120 , main bed frame  100 , and rear bed frame  140 , and will furthermore appreciate that the forward bed floor  124 , main bed floor  102 , and rear bed floor  144  may be made out of a variety of solid or non-solid (mesh or other similar) sheet materials, such as, but not limited to, sheet steel or steel mesh or grille type materials. 
     Attached non-rotatably to the left side of the main bed frame  100  is a left side rail  200 . Similarly, a right side rail  220  is attached non-rotatably to the right side of the main bed frame  100 . At the forward edge of the left side rail, the left forward side rail  202  is rotatably attached by means of a left forward side rail hinge  204 . Also, at the rear edge of the left side rail, the left rear side rail  206  is attached to the left side rail by the left rear side rail hinge  208 . The right forward side rail  222  and right rear side rail  226  are similarly rotatably attached to the forward edge and rear edge, respectively, of the right side rail  220  by means of the right forward side rail hinge  224  and right rear side rail hinge  228 , respectively. Additionally, there is a forward end rail  130  attached to the forward edge of the forward bed frame  120  by means of a forward end rail hinge  132  and a rear end rail  150  attached to the rear edge of the rear bed frame  140  by means of a forward end hinge  152 . 
     As seen in FIG. 2, the left forward side rail  202 , left rear side rail  206 , right forward side rail  222 , and right rear side rail  226  all rotate towards the center of the Invention in its folded state and come to rest flush with the left side rail  200  and right side rail  220 . Furthermore, the combined length of the left forward side rail  202  and left rear side rail  206  is shorter than the length of the left side rail  200 , and a similar arrangement exists for the right side components. It will be observed, as in FIG. 2, that the forward end rail  130  and rear end rail  150  are planar surfaces but for a small curved portion at each end. Referring to FIG. 8, when any of the rotatable forward or rear side rails  202 ,  206 ,  222 ,  226  are moved into their unfolded positions, a slight overlap occurs with this small curved portion at the corresponding end of the forward end rail  130  or rear end rail  150 , thereby forming a full side rail around the entire perimeter of the Invention. 
     As seen in FIGS. 1,  3 ,  5 ,  6 , and  7 , a forward dual wheel assembly  500  is rotatably attached to the lower side of the forward bed frame  120 , and a rear dual wheel assembly  400  is non-rotatably attached to the lower side of the rear bed frame  150 . Each of these dual wheel assemblies are identical but for their method of attachment to the apparatus. The forward dual wheel assembly  500  includes a forward dual wheel assembly bracket  510 , which comprises an elongate U-shaped channel, with the open side of the forward dual wheel assembly bracket  510  oriented downward. The upper surface of the forward dual wheel assembly bracket  510  is attached to the forward dual wheel assembly pivot  550 , which is also attached to the forward bed frame  120 . Referring particularly to FIGS. 3,  5 ,  6 , and  7 , the forward dual wheel assembly  500  comprises the forward dual wheel assembly bracket  510  as well as a number of other components. At the ends of the forward dual wheel assembly bracket  510  are a left forward wheel bracket  522  and a right wheel forward bracket  532 . Each of these forward wheel brackets is a short U-shaped bracket which has a curved end and a squared end. Each of these forward wheel brackets is connected at its curved end to the forward dual wheel assembly bracket  510  by means of a wheel bracket pivot  540 , which passes through the forward and rear surfaces of both the forward dual wheel assembly bracket  510  and the corresponding forward wheel bracket, with the open end of the wheel bracket oriented inwards towards the centerline of the Invention. A left forward wheel  520  is mounted to the outer surface of the left forward wheel bracket  522 , and a right forward wheel  530  is mounted to the outer surface of the right forward wheel bracket  532 . Additionally, at each end of the forward dual wheel assembly bracket  510 , a forward wheel bracket locking pin  542  is mounted to each end of the rear surface of the forward dual wheel assembly bracket  510  at a distance from the corresponding forward wheel bracket pivot  540  wherein said distance is less than the radius of curvature of the curved end of either the left forward wheel bracket  522  or right forward wheel bracket  532 . Each of the forward wheel bracket locking pins  542  are mounted to the forward dual wheel assembly bracket  510  by a forward wheel bracket locking pin sleeve  546 , which includes a forward wheel bracket locking pin spring  544 , which is not pictured, but which will be understood by those familiar with the art. In its rest position, the forward wheel bracket locking pin spring  544  pulls the corresponding forward wheel bracket locking pins  542  down into the forward wheel bracket locking pin sleeve  546  such that the end of the forward wheel bracket locking pin  542  extends through the forward dual wheel assembly bracket  510 . Each of the left forward wheel bracket  522  and right forward wheel bracket  532  has two holes through its upper surface at a distance from the forward wheel bracket pivot  540  equal to the distance between the forward wheel bracket pivot  540  and the corresponding forward wheel bracket locking pin  542 . By this orientation, as seen particularly in FIG. 5, the corresponding forward wheel bracket locking pin  542  may pass through the holes on either the left forward wheel bracket  522  and the right forward wheel bracket  532 . The holes are oriented such that when a forward wheel bracket locking pin  542  extends through its corresponding wheel bracket, the wheel is locked either in the folded position or the unfolded position. Those with ordinary skill in the art will understand the method of mounting the forward wheel bracket locking pin  542 , forward wheel bracket locking pin spring  544 , and forward wheel bracket locking pin spring  546  and the placement of the holes in the left forward wheel bracket  522  and right forward wheel bracket  532  in order to effectuate this operation. 
     Similarly, the rear dual wheel assembly  400  includes a rear dual wheel assembly bracket  410 , which comprises an elongate U-shaped channel, with the open side of the rear dual wheel assembly bracket  410  oriented downward. The upper surface of the rear dual wheel assembly bracket  410  is attached directly to the lower surface of the rear bed frame  140 . Referring particularly to FIGS. 3,  5 ,  6 , and  7 , the rear dual wheel assembly  400  comprises the rear dual wheel assembly bracket  410  as well as a number of other components. At the ends of the rear dual wheel assembly bracket  410  are a left rear wheel bracket  422  and a right wheel rear bracket  432 . Each of these rear wheel brackets is a short U-shaped bracket which has a curved end and a squared end. Each of these rear wheel brackets is connected at its curved end to the rear dual wheel assembly bracket  410  by means of a wheel bracket pivot  440 , which passes through the rear and rear surfaces of both the rear dual wheel assembly bracket  410  and the corresponding rear wheel bracket, with the open end of the wheel bracket oriented inwards towards the centerline of the Invention. A left rear wheel  420  is mounted to the outer surface of the left rear wheel bracket  422 , and a right rear wheel  430  is mounted to the outer surface of the right rear wheel bracket  432 . Additionally, at each end of the rear dual wheel assembly bracket  410 , a rear wheel bracket locking pin  442  is mounted to each end of the rear surface of the rear dual wheel assembly bracket  410  at a distance from the corresponding rear wheel bracket pivot  440  wherein said distance is less than the radius of curvature of the curved end of either the left rear wheel bracket  422  or right rear wheel bracket  432 . Each of the rear wheel bracket locking pins  442  are mounted to the rear dual wheel assembly bracket  410  by a rear wheel bracket locking pin sleeve  446 , which includes a rear wheel bracket locking pin spring  444 , which is not pictured, but which will be understood by those familiar with the art. In its rest position, the rear wheel bracket locking pin spring  444  pulls the corresponding rear wheel bracket locking pins  442  down into the rear wheel bracket locking pin sleeve  446  such that the end of the rear wheel bracket locking pin  442  extends through the rear dual wheel assembly bracket  410 . Each of the left rear wheel bracket  422  and right rear wheel bracket  432  has two holes through its upper surface at a distance from the rear wheel bracket pivot  440  equal to the distance between the rear wheel bracket pivot  440  and the corresponding rear wheel bracket locking pin  442 . By this orientation, as seen particularly in FIG. 5, the corresponding rear wheel bracket locking pin  442  may pass through the holes on either the left rear wheel bracket  422  and the right rear wheel bracket  432 . The holes are oriented such that when a rear wheel bracket locking pin  442  extends through its corresponding wheel bracket, the wheel is locked either in the folded position or the unfolded position. Those with ordinary skill in the art will understand the method of mounting the rear wheel bracket locking pin  442 , rear wheel bracket locking pin spring  444 , and rear wheel bracket locking pin spring  446  and the placement of the holes in the left rear wheel bracket  422  and right rear wheel bracket  432  in order to effectuate this operation. 
     Finally, the handle  300  of the folding cart of the present invention comprises a number of components and is connected to the forward midpoint of the forward dual wheel assembly  500  by means of a handle mount  304 , which extends forward from the forward dual wheel assembly  500  and is rotatively connected to the curved main handle bar  310  by means of a handle hinge  302 . The handle hinge  302  rotates only in the vertical plane and does not rotate in any horizontal plane. This allows the user to rotate the forward dual wheel assembly  500  around the forward dual wheel assembly pivot  550  by applying lateral torque to the handle  300 . The curved main handle bar  310  is a short piece of tubing formed into a curve of an overall length substantially equal to the distance from the handle hinge  302  to the bottom of the wheels  420 ,  430 ,  520 ,  530  when they are in their retracted, locked, positions. The curve in the curved main handle bar  310  allows the handle to curve upwards from the handle hinge  302  around the forward end of the forward bed frame  120 . Attached rotatively to the curved main handle bar  310  is the straight main handle bar  320 . The straight main handle bar  320  forms the main shaft of the handle  300  and can be of any desired length suitable for providing a convenient cart handle to a user. The straight main handle bar  320  is formed from a tube with a cross-section similar to that of the curved main handle bar  310 . The rotation point for the connection between the straight main handle bar  320  and curved main handle bar  310  is provided by a main handle hinge  326 . Housed within the straight main handle bar  320  at the end connected to the curved main handle bar  310  is a main handle bar locking pin  322 , which extends from the end of the straight main handle bar  320  into the contiguous end of the curved main handle bar  310  when in the unfolded position. The main handle bar locking pin  322  is kept in the extended position by means of a main handle bar locking pin spring  324 , and may be manually retracted into the straight main handle bar  320  in order to allow rotation of the main handle hinge  326 . While these structures are not depicted in the drawings, their design and method of manufacture will be understood by those in the art. From the end of the straight handle bar  320  opposite the curved handle bar  310  extends a handle and locking clasp  330  formed from a solid piece of cross-sectional dimension equal to or smaller than the inner cross-sectional dimension of the straight handle bar  320 . One end of the handle and locking clasp extends within the tubing forming the straight handle bar  320  and is attached to a handle and locking clasp spring  332 . The handle and locking clasp spring  332  keeps the respective end of the handle and locking clasp retracted within the straight handle bar  320 , but manual force provided by a user may cause the handle to partially slide out from the straight handle bar  320 . The other end of the handle and locking clasp is curved to provide a user with a handle end, and is terminated by the locking clasp  334 . 
     While the Invention may be formed from any suitably strong material, it is understood that the preferred material is steel. Those familiar with the art will understand the components of the invention, their methods of manufacture, and the methods of connecting them to form the complete Invention. While the preferred embodiment has been described, it will furthermore be understood that various changes can be made therein without departing from the spirit and scope of the invention. 
     Catalogue of Elements 
       10  Folded cart 
       20  Unfolded cart 
       100  Main bed frame 
       102  Main bed floor 
       110  Main bed frame locking pin 
       120  Forward bed frame 
       122  Forward bed frame hinge 
       124  Forward bed floor 
       130  Forward end rail 
       132  Forward end rail hinge 
       140  Rear bed frame 
       142  Rear bed frame hinge 
       144  Rear bed floor 
       150  Rear end rail 
       152  Rear end rail hinge 
       200  Left side rail 
       202  Left forward side rail 
       204  Left forward side rail hinge 
       206  Left rear side rail 
       208  Left rear side rail hinge 
       220  Right side rail 
       222  Right forward side rail 
       224  Right forward side rail hinge 
       226  Left rear side rail 
       228  Left rear side rail hinge 
       300  Handle 
       302  Handle hinge 
       304  Handle mount 
       310  Curved main handle bar 
       320  Straight main handle bar 
       322  Main handle bar locking pin 
       324  Main handle bar locking pin spring 
       326  Main handle hinge 
       330  Handle and locking clasp 
       332  Handle and locking clasp spring 
       334  Locking clasp 
       400  Rear dual wheel assembly 
       410  Rear dual wheel assembly bracket 
       420  Left rear wheel 
       422  Left rear wheel bracket 
       430  Right rear wheel 
       432  Right rear wheel bracket 
       440  Rear wheel bracket pivot 
       442  Rear wheel bracket locking pin 
       444  Rear wheel bracket locking pin spring 
       446  Rear wheel bracket locking pin sleeve 
       500  Forward dual wheel assembly 
       510  Forward dual wheel assembly bracket 
       520  Left forward wheel 
       522  Left forward wheel bracket 
       530  Right forward wheel 
       532  Right forward wheel bracket 
       540  Forward wheel bracket pivot 
       542  Forward wheel bracket locking pin 
       544  Forward wheel bracket locking pin spring 
       546  Forward wheel bracket locking pin sleeve 
       550  Forward dual wheel assembly pivot