Abstract:
The handcart has various embodiments, each embodiment having a pair of larger wheels at the back of the load-carrying platform and a rear axle located above the plane of at least the forward portion of the platform. Smaller caster wheels are mounted on arms extending forward and outward from the forward corners of the platform. The outward ends of the arms are displaced upwardly to place the platform bottom only very slightly higher than the bottoms of the forward casters, thus increasing stability by lowering the center of gravity of the cart and contents, and facilitating loading and unloading of the cart due to the very low platform. The cart need not be tilted rearward to lift the platform from the floor, but may be pushed over the underlying surface with the load-carrying platform remaining level and with all four wheels rolling over the underlying surface.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to carts, and more specifically, to a handcart having forward casters that are longitudinally and laterally offset outwardly from the forward corners of the platform for greater stability, and are further vertically offset upward to allow the platform to be as low as possible above the underlying surface. 
     2. Description of the Related Art 
     Handcarts, hand trucks, and similar manually operated conveyances have been known and used for a considerable period of time to facilitate the transport of limited loads over limited distances and terrain. Examples of such usage are the movement and positioning of heavy articles of furniture and appliances from a motorized truck to a home or office, the delivery of heavy paper goods (copier supplies, books, etc.) to home or office, etc. 
     Such carts are also often specialized for use in the storage and transport of cylinders of compressed gas, e.g., oxygen and acetylene cylinders for oxyacetylene welding, etc. Such carts conventionally have a pair of relatively large diameter, non-steerable wheels at the rear of their load platforms, with the axle raised to allow the load-carrying platform to rest on the surface when the platform is horizontal and the cart and contents are upright. This greatly facilitates the movement of cylinders (or other articles) on and off the platform, but requires that the cart be tilted rearward to raise the platform above the surface for movement by means of the rear wheels. A person moving the cart must not only provide the energy required for moving the cart, but must also maintain the angle of the cart in order to at least approximately balance the load on the rear wheels. This can be tricky when the cart must be moved over rough or uneven surfaces, and a wheel catches momentarily on some discontinuity in the surface. 
     As a result, a number of handcarts have been constructed with a smaller caster wheel beneath each of the front corners of the platform. The installation of the caster wheels beneath the platform obviously raises the platform above the supporting surface to a height at least slightly greater than the diameters of the casters. While the casters are usually of relatively small diameter, i.e., only a very few inches, this positioning of the platform some distance above the underlying surface can make it quite difficult to load or unload a very heavy object onto or from the platform. 
     An example of such is found in Japanese Patent No. 2001-180,496 published on Jul. 3, 2001. This reference describes (according to the drawings and English abstract) a folding cart. The drawings show relatively large, rearwardly disposed main wheels with their axles below the bottom of the cart, and smaller diameter caster wheels located beneath the forward corners of the cart. 
     Additionally, Japanese Patent No. 2009-005,702 published on Jan. 15, 2009, describes (according to the drawings and English abstract) a handcart for use in watering plants. The cart includes a pair of relatively large wheels at the rear of the cart and below the floor of the platform, with a pair of smaller diameter casters beneath the front corners of the platform. 
     None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus, a handcart solving the aforementioned problems is desired. 
     SUMMARY OF THE INVENTION 
     The handcart comprises a series of different configurations, differing primarily in their upper structures. In each configuration or embodiment, the lower portion of the structure comprises a platform having a pair of large diameter rearwardly disposed wheels having their axle located above at least the lowermost portion of the load-carrying platform. A smaller diameter caster wheel is mounted on an arm that extends forwardly and outwardly from each forward corner of the platform. The outboard ends of the arms are displaced upwardly from the plane of the load-carrying platform, thus placing the bottom of the load-carrying platform barely above the bottoms of the wheels. This configuration allows articles to be loaded onto and unloaded from the platform without undue effort, and also allows the cart to be moved without needing to tilt the cart back and balance the load on the rear wheels. The outward and forward placement of the smaller casters also greatly increases stability in comparison to such smaller wheels located beneath the platform, as in many other carts. Brakes may be provided on the casters, if so desired. 
     These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a first embodiment of a handcart according to the present invention, shown from the right front and illustrating various details thereof. 
         FIG. 2  is a perspective view of a second embodiment of a handcart according to the present invention, shown from the right front and illustrating various details thereof. 
         FIG. 3  is a perspective view of a third embodiment of a handcart according to the present invention, shown from the right front and illustrating various details thereof. 
         FIG. 4  is a perspective view of a fourth embodiment of a handcart according to the present invention, shown from the right front and illustrating various details thereof. 
         FIG. 5  is a partial right side elevation view of the handcart of  FIG. 1 , illustrating the low platform level provided by the wheel configuration of the various handcart embodiments. 
     
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The handcart described herein comprises various embodiments of a four-wheeled handcart having a lower, load-carrying platform positioned between the wheels in order to place the platform only a very slight distance above the underlying surface. This allows various bulky and/or heavy articles, e.g., pressurized cylinders of oxygen and acetylene for welding, etc., to be placed upon and removed from the cart without requiring them to be lifted to any great degree. Moreover, the cart may be moved without need to tilt it rearward, as is the case with conventional carts, wherein the platform rests directly upon the underlying surface when the cart is upright. 
       FIG. 1  of the drawings provides a perspective view of a first embodiment of the handcart  110 . The handcart or cart  110  is adapted or configured particularly for the carriage of pressurized cylinders thereon, e.g., welding cylinders, but it will be understood that the cart  110  may be readily adapted for the carriage of other articles or objects as well, if desired. The cart  110  includes a flat, planar load-carrying platform  112  formed of a relatively thin and unbroken sheet of metal or other suitable material. The platform  112  includes a rear portion  114 , an opposite forward portion  116 , a left front corner  118   a , and a right front corner  118   b . The periphery of the platform includes a downwardly bent lower flange or edge  120  serving to stiffen the platform structure. 
     A superstructure  122  extends upwardly from the platform  112 . In the case of the handcart  110  of  FIG. 1 , the superstructure  122  includes forwardly disposed left and right members  122   a  and  122   b  that extend upwardly and rearward from the forward corners  118   a ,  118   b  of the platform  112 , with a rearwardly disposed handle  122   c  joining the upper ends of the two members  122   a ,  122   b . Similarly configured (but shorter) left and right rear members, respectively  122   d  and  122   e , extend upwardly from the rear corners of the platform  112  and are joined by a crossmember  122   f  that extends generally medially across the two forward members  122   a ,  122   b . The various components  122   a  through  122   f  may be formed of tubular steel material, or may alternatively be formed of other structural material as desired. Additional structure may be provided, e.g., cylinder retaining chains  124 , an accessory tray  126  for holding a striker, different welding tips and/or tip cleaning tools, etc., as desired. 
     A rear axle  128  extends laterally across the two rear members  122   d  and  122   e  of the superstructure  122 . Large diameter left and right rear wheels, respectively  130   a  and  130   b , extend from the respective ends of the axle  128  and immediately outboard the sides of the platform  112 . The two rear wheels  130   a ,  130   b  are directionally fixed, i.e., they are not steerable relative to the remainder of the structure of the handcart  110 . The rear axle  128  is located somewhat above the plane of the load-carrying platform  112 , or at least the forward portion  116  thereof (a stepped platform embodiment with a higher rear portion is illustrated in  FIG. 4  and discussed in detail further below). The rear axle  128  is located vertically so as to position the platform  112 , or more specifically the lowermost edges of the downwardly folded lower flange  120  thereof, very close to the underlying surface when the rear wheels  130   a ,  130   b  and the smaller diameter forward casters (discussed further below) are resting upon that surface. 
     Left and right caster wheel arms, respectively  132   a  and  132   b , extend forwardly and laterally outwardly from the respective left and right front corners  118   a  and  118   b  of the platform  112 . The two arms  132   a ,  132   b  preferably extend essentially diagonally from their respective corners  118   a  and  118   b , i.e., defining essentially equal angles of substantially 135 degrees between the axes of the arms and the edges  120  of the platform  112 . However, these angles may be adjusted as desired to provide greater lateral or forward offset. Each of the arms  132   a ,  132   b  includes an upwardly offset distal end, respectively  134   a  and  134   b , providing for the attachment of a small diameter caster wheel thereto. 
     Small diameter left and right caster wheels, respectively  136   a  and  136   b , depend from the upwardly offset distal end  134   a ,  134   b  of each arm  132   a  and  132   b . The upwardly offset distal ends  134   a ,  134   b  have sufficient vertical offset as to be located above the upper surface plane of the platform  112 , as shown clearly in the side elevation view of the lower portion of the handcart in  FIG. 5 . The configuration illustrated in  FIG. 5  for the lower portion of the handcart may be considered to be applicable to all of the handcart embodiments described herein, as well. 
     Even though the caster wheels are of relatively small diameter, i.e., considerably smaller than the larger diameter rear wheels, it will be seen that their diameter is greater than the height of the depending lower edge  120  of the platform  112 . Accordingly, the vertical offset of the two caster arms  132   a ,  132   b  is sufficient to position the axle, e.g., axle  138   b  of the caster  136   b  shown in  FIG. 5 , above the lowermost edge of the depending lower edge  120  of the platform  112 . Along with the raised rear axle  128 , this results in a clearance C between the lowermost edge of the lower flange  120  of the platform  112  of only a small fraction of an inch, more or less. The vertical location of the rear axle  128  in combination with the vertical offsets of the two caster wheel arms  132   a  and  132   b , results in the platform  112  being substantially parallel to the underlying surface when all four wheels  130   a ,  130   b ,  136   a , and  136   b  are resting on the underlying surface, as shown in  FIG. 5 . 
     As the platform  112 , or more specifically its depending lower flange  120 , is spaced above the underlying surface by means of the support provided by the four wheels  130   a ,  130   b ,  136   a , and  136   b , there is no friction between the underside of the platform and the underlying surface to hold or maintain the position of the cart. Accordingly, the two casters  136   a  and  136   b  are preferably provided with selectively operable brakes to keep the cart from rolling inadvertently. The brakes are preferably conventional axially disposed, toe-operated toggle levers  140 , as illustrated in the drawing Figs., although other brake types or principles may be incorporated if so desired. 
       FIG. 2  of the drawings illustrates a perspective view of a second embodiment of the handcart, designated as handcart or cart  210 . The lower portion of the cart  210  is essentially identical to that of the cart  110  of  FIG. 1 , with only the superstructure  222  being different. The superstructure  222  is preferably formed of tubular steel and comprises forwardly disposed left and right members  222   a  and  222   b  that extend upwardly from the forward corners  118   a ,  118   b  of the platform  112 , with their upper ends bent to extend rearward to connect to the upwardly extending left and right rear members  222   d  and  222   e . The left and right rear members  222   d  and  222   e  may be formed as a single component, with the central portion comprising a rearwardly disposed handle  222   c . Additional bracing may be provided by a crossmember  222   f  extending between the two rear uprights  222   d  and  222   e , at the points of connection with the rearward extending ends of the forward members  222   a  and  222   b . Additional structure may be provided, e.g., a cylinder retaining bracket  224  extending forwardly from the rear crossmember  222   f , an accessory tray  226  for holding a striker, different welding tips and/or tip cleaning tools, etc., as desired. 
     The lower portion of the handcart  210  of  FIG. 2  is essentially identical to the corresponding portion of the handcart  110  of  FIG. 1 , comprising a load-carrying platform  112  having rearward and forward portions  114  and  116 , left and right forward corners  118   a  and  118   b , and a depending lower edge or flange  120 . The rear axle  128  extends across the lower portions of the two rear uprights  222   d  and  222   e , and is located sufficiently far above the platform  112  to position the lower edge of the depending edge or flange  120  very close to the underlying surface when supported thereon by the large diameter wheels  130   a  and  130   b.    
     Caster wheel arms  132   a  and  132   b  extend forwardly and laterally outwardly from their respective platform forward corners  118   a  and  118   b , with the arms  132   a ,  132   b  having distal ends  134   a ,  134   b  with small diameter caster wheels  136   a ,  136   b  depending respectively therefrom. The wheels  136   a ,  136   b  may be equipped with conventional toggle lever type brakes  140 . The arms  132   a ,  132   b  have essentially the same configuration as those components of  FIG. 1 , i.e., an upward offset to place the lowermost edge of the depending flange or edge  120  of the platform as low as possible above the underlying surface when all four wheels  130   a ,  130   b ,  136   a , and  136   b  of the cart  210  are resting thereon. 
       FIG. 3  of the drawings illustrates a perspective view of a third embodiment of the handcart, designated as handcart or cart  310 . The lower portion of the cart  310  is essentially identical to that of the carts  110  of  FIGS. 1 and 210  of  FIG. 2 , with only the superstructure  322  being different. The superstructure  322  is preferably formed of tubular steel and comprises forwardly disposed left and right members  322   a  and  322   b  that extend upwardly and rearward from the forward corners  118   a ,  118   b  of the platform  112 , with a rearwardly disposed handle  322   c  joining the upper ends of the two members  322   a ,  322   b . Similarly configured (but shorter) left and right rear members, respectively  322   d  and  322   e , extend upwardly from the rear corners of the platform  112  and are joined by a crossmember  322   f  that extends generally medially across the two forward members  322   a ,  322   b.    
     In addition, a lifting arm  322   g  extends upwardly from the rear edge of the platform  112 , and is joined directly to the crossmember  322   f  and indirectly to the handle  322   c  by a connecting member. The upper end of the lifting arm  322   g  is forwardly offset to position it essentially over the center of the load-carrying platform  112 . In this manner the lifting arm  322   g  may be used to hoist or lift the cart  310  and its contents with the cart and contents remaining substantially balanced below the lift point. Alternatively, the lifting arm  322   g  may be used to tow the cart  310  on its larger diameter rear wheels  130   a ,  130   b.    
     The various components  322   a  through  322   g  may be formed of tubular steel material, or may alternatively be formed of other structural material as desired. Additional structure may be provided, e.g., upper and lower cylinder retaining brackets  324   a  and  324   b  extending forwardly from the lifting arm  322   g , an accessory tray  326  for holding a striker, different welding tips and/or tip cleaning tools, etc., as desired. The accessory tray  326  of the handcart  310  of  FIG. 3  is also equipped with a lid, which feature may be provided for any of the other embodiments of the handcart as well. 
     The lower portion of the handcart  310  of  FIG. 3  is essentially identical to the corresponding portions of the handcart  110  of  FIGS. 1 and 210  of  FIG. 2 , comprising a load-carrying platform  112  having rearward and forward portions  114  and  116 , left and right forward corners  118   a  and  118   b , and a depending lower edge or flange  120 . The rear axle  128  extends across the lower portions of the two rear uprights  322   d  and  322   e , and is located sufficiently far above the platform  112  to position the lower edge of the depending edge or flange  120  very close to the underlying surface when supported thereon by the large diameter wheels  130   a  and  130   b.    
     Caster wheel arms  132   a  and  132   b  extend forwardly and laterally outwardly from their respective platform forward corners  118   a  and  118   b , with the arms  132   a ,  132   b  having distal ends  134   a ,  134   b  with small diameter caster wheels  136   a ,  136   b  depending respectively therefrom. The wheels  136   a ,  136   b  may be equipped with conventional toggle lever type brakes  140 . The arms  132   a ,  132   b  have essentially the same configuration as those components of  FIGS. 1 and 2 , i.e., an upward offset to place the lowermost edge of the depending flange or edge  120  of the platform as low as possible above the underlying surface when all four wheels  130   a ,  130   b ,  136   a , and  136   b  of the cart  310  are resting thereon. 
       FIG. 4  of the drawings illustrates a perspective view of a fourth embodiment of the handcart, designated as handcart or cart  410 . Much of the lower portion of the cart  410  is essentially identical to that of the carts  110 ,  210 , and  310 , but the handcart  410  is significantly narrower than the carts  110 ,  210 , and  310  due to its configuration for carrying two cylinders in tandem on its stepped platform  412 , discussed in detail further below. 
     The superstructure  422  is also different, resembling a narrower configuration of the superstructure  222  of the cart  210  of  FIG. 2 . The superstructure  422  is preferably formed of tubular steel and comprises forwardly disposed left and right members  422   a  and  422   b  that extend upwardly from the forward corners  118   a ,  118   b  of the lower forward portion  416  of the platform  412 , with their upper ends bent to extend rearward to connect to the upwardly extending left and right rear members  422   d  and  422   e . The left and right rear members  422   d  and  422   e  have rearwardly angled upper extremities that serve as handles for the cart  410 , although the upper extremities of the rear members  422   d  and  422   e  may be connected to provide a generally lateral handlebar, if so desired. 
     Additional bracing may be provided by a left side lower longitudinal member  422   f  extending between the left side members  422   a  and  422   d , and a laterally opposed right side lower longitudinal member  422   g  extending between the right side members  422   b  and  422   e . These two lower members  422   f  and  422   g  are connected medially by a lower lateral member  422   h , with a corresponding upper lateral member  422   i  extending between the upper horizontal portions of the left and right forward members  422   a  and  422   b . The two lateral members  422   h  and  422   i  are positioned essentially vertically above the center of the platform  412 , and serve to separate two cylinders placed in tandem on the cart  410 . Additional structure may be provided, e.g., forward and rearward cylinder restraints  424   a  and  424   b  extending respectively between the forward members  422   a  and  422   b  and between the rearward members  422   d  and  422   e . It will be noted that while no accessory tray is shown for the handcart  410  of  FIG. 4 , such a tray may be provided therewith as in the other embodiments discussed further above. 
     The load-carrying platform  412  also differs from the platforms  112 ,  212 , and  312  of the carts of  FIGS. 1 ,  2 , and  3 . The platform  412  is stepped, with its rearward portion  414  being somewhat higher than its forward portion  416 . A generally vertical medial section defines a step between the two portions  414  and  416 , with the medial section being located essentially directly beneath the two lateral members  422   h  and  422   i . This configuration provides for the carriage of two cylinders in tandem on the cart  410 , with one cylinder being carried on the lower forward portion  416  of the stepped platform  412  and the second cylinder being carried on the raised rearward portion  414  of the platform. 
     The wheel structure of the handcart  410  of  FIG. 4  is essentially identical to the corresponding portions of the handcarts  110 ,  210  and  310  of  FIGS. 1 ,  2 , and  3 . The rear axle  128  is essentially the same as the rear axle of the other cart embodiments, but is shown in broken lines in  FIG. 4  due to its concealment by the rearward edge of the raised rear portion  414  of the platform  412 . The rear axle  128  extends across the lower portions of the two rear uprights  422   d  and  422   e , and is located to position the forward portion of the lower edge of the depending edge or flange  420  of the platform  412  very close to the underlying surface when supported thereon by the large diameter wheels  130   a  and  130   b.    
     Caster wheel arms  132   a  and  132   b  extend forwardly and laterally outwardly from their respective platform forward corners  118   a  and  118   b , with the arms  132   a ,  132   b  having distal ends  134   a ,  134   b  with small diameter caster wheels  136   a ,  136   b  depending respectively therefrom. The wheels  136   a ,  136   b  may be equipped with conventional toggle lever type brakes  140 . The arms  132   a ,  132   b  have essentially the same configuration as those components of  FIGS. 1 through 3 , i.e., an upward offset to place the lowermost edge of the depending flange or edge  420  of the forward portion  416  of the platform  412  as low as possible above the underlying surface when all four wheels  130   a ,  130   b ,  136   a , and  136   b  of the cart  310  are resting thereon. 
     Each of the carts  110  through  410  has a wheel configuration essentially similar to that illustrated in the side elevation view of  FIG. 5 , i.e., the lowermost edge of the depending flange  120  (or the forward portion of the flange  420 , in the case of the stepped platform  412  of the cart  410  of  FIG. 4 ) is spaced above the underlying surface by some small fraction of an inch, more or less, when all four wheels  130   a ,  130   b ,  136   a , and  136   b  are resting upon that surface. 
     Thus, a person using any of the carts described herein need not lift a cylinder (or other object) significantly to load it onto the cart, or at least the forward portion of the platform of the cart in the case of the stepped platform cart  410  of  FIG. 4 . The round base of conventional cylinders of pressurized gas may be rolled easily onto the platform, or the lowermost portion of the platform, without undue difficulty. 
     Any of the carts described herein may be moved or rolled on their wheels with their platforms remaining clear of the underlying surface. There is no need to tilt the cart rearward and balance the cart and load thereon to move the cart and its contents, as is the case with most conventional carts. 
     In addition, the very low platform (or forward portion thereof for the cart of  FIG. 4 ) provides the lowest possible center of gravity for the cart and its contents, thereby greatly increasing stability. Stability is further enhanced by the outwardly disposed caster wheels extending from the forward corners of the platform. Accordingly, the handcart in any of its various embodiments provides greatly enhanced safety and security for the user of the cart, particularly when it is used to carry potentially hazardous objects such as cylinders of pressurized gas for welding or other purposes. 
     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.