Abstract:
The self-braking wheelbarrow of the present invention comprises a wheelbarrow bin assembly mounted so as to pivot relative to an undercarriage assembly whereby the bin assembly interferes with the wheels on the undercarriage assembly causing a friction on the tread of the wheel and restricting the rotation of the wheel. In normal usage the undercarriage assembly is secured to the wheelbarrow bin assembly by securing latches. Braking is accomplished by selectively releasing securing latches, thereby permitting the wheelbarrow to pivot, and lifting the handles as if to move the wheelbarrow. The braking force applied to the tread on the wheel is proportional to the bin load thereby resulting in higher braking force with higher bin loads.

Description:
This non-provisional application filed in the United States Patent and Trademark Office claims benefit of prior U.S. provisional application Ser. No. 60/727,234, filed Oct. 17, 2005. 

   BACKGROUND OF INVENTION 
   The present invention relates to wheelbarrows and, more particularly, to a wheelbarrow with a self braking mechanism. 
   Wheelbarrows are widely used in the construction industry to transport materials on a construction site. Unloading a wheelbarrow typically involves tipping the wheelbarrow forward to dump the load contents from the front of the wheelbarrow. On level surfaces, a difficulty experienced during dumping is the forward movement of the wheelbarrow experienced as the handles of the wheelbarrow are lifted to accomplish the dumping due to the forward force vector on the wheelbarrow as the handles are lifted. The operator must restrain the wheelbarrow from rolling forward. As a result, the operator may lose control of the wheelbarrow, whereupon the wheelbarrow continues to move forward instead of tipping, risking damage to property and injury to others nearby. Additionally, once the wheelbarrow contents are dumped, the wheelbarrow may become unstable as it rests on the single axle wheel whereupon the wheelbarrow may roll backward or forward further risking injury to the operator. 
   When dumping on a forward sloping surface, the forward roll problem becomes worse. Yet more challenging is dumping the load contents on a reverse sloping surface, whereupon the wheelbarrow tends to roll towards the operator during dumping. To restrain the wheelbarrow tendency to roll forward during dumping, the operator may use a chock placed in front of the wheel such as a piece of lumber. 
   Prior art attempts to prevent or reduce the motion of the wheelbarrow during dump have been proposed including applying a brake. Previously proposed brake systems have been inadequate and have presented problems principally related to manipulating the brake activation mechanism during dumping and fouling of complex mechanisms by construction site debris. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is directed to a wheelbarrows, and, more specifically, to a wheelbarrow incorporating a self-braking feature whereby the wheel or wheels of the wheelbarrow are restricted from rotating when securing latches are selectively released and the wheelbarrow handles are lifted as in a motion to move the wheelbarrow or to dump the load contents, thereby substantially obviating one or more of the problems due to the limitations and disadvantages of the related art. 
   In its essential form, the invention is a wheelbarrow bin assembly mounted so as to pivot relative to an undercarriage assembly whereby the bin assembly interferes with wheels of the undercarriage assembly when pivoted. The wheelbarrow bin assembly comprises a wheelbarrow style bin mounted to a pair of handles with a shim wedge between the handles and the bin with an axle mounted near the end of the handles and perpendicular to the handles. The undercarriage assembly comprises a base plate supporting a front wheel axle with wheels, a support stand and clips for gripping the wheelbarrow bin assembly axle. The base plate being substantially flat, having a front, rear, top and bottom, is engineered so as to support a wheel axle at the front of the plate and clips to retain the bin assembly axle and mounted on the base plate at a position as measured from the front axle and distance slightly greater than the radius of the wheels. The wheelbarrow bin assembly further comprises securing latches mounted to each handle to engage and lock the rear of the base plate assembly against the handles when the securing latches and base plate are in the locked position. The securing latches are selectively opened by means of a connecting rod attached to each securing latch and to a respective lever handle mounted near the operator end of each handle thereby facilitating the rotation of the securing latch around a fastener mounting the securing latch to the handle. A spring is mounted to each securing latch between the latch and the handle so as to force the securing latch to the locked position when not activated. With the rear of the base plate locked and held in position against the handles by the securing latches, the wheelbarrow is used as a conventional wheelbarrow. 
   When braking is required, the wheelbarrow handles are lowered such that the support stand rests on the ground thereby relieving pressure on the latches allowing the operator to selectively release the latches. The operator lifts the handles while releasing the securing latches by means of levers conveniently mounted on the wheelbarrow handles near the end of the handle; and pivoting the wheelbarrow bin assembly forward relative to the undercarriage assembly. As the wheelbarrow pivots, pressure is applied to the tread of the wheels by the front ends of the handles thereby interfering with the rotation of the wheel. The amount of force on the applied to the wheel is proportional to the load in the bin thereby assisting the self-braking effect. High bin loads deform the wheel more as the force of the pivoting increasing and results in the front of the bin to also interfere with the tread on the wheel thereby resulting in a greater self-braking effect. The braking force applied to the wheel is therefore not dependant on the force applied by the operator to a brake lever or, as in this invention, the handle levers. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification illustrate embodiments of the invention and, together with the description, serve to explain the features, advantages, and principles of the invention. 
     In the drawings: 
       FIG. 1  is a side elevation view showing the wheelbarrow with the bin and handle assembly pivotally attached to the base plate near the wheels and locked by securing latches to the rear of the base plate according to the present invention. 
       FIG. 2  is a side elevation view of the wheelbarrow of  FIG. 1 , according to the present invention, with the bin and handle assembly pivoting forward with the securing latches released from the rear of the base plate wherein the forward end of the handles bind against the wheels so as to brake the wheel. 
       FIG. 3  is a front elevation view of the wheelbarrow of  FIG. 1 . 
       FIG. 4  is a bottom plan view of the wheelbarrow of  FIG. 2 . 
       FIG. 5  is a sectional view taken along Line  5 - 5  of  FIG. 4  showing details of the securing latch locking the rear of the base plate in position against the handles and also showing the pivot axle and pivot axle mount of the base plate. 
       FIG. 6  is a sectional view of the wheelbarrow, according to the present invention taken along Line  6 - 6  of  FIG. 4  showing details further details of the pivot axle mount and the wheel axle bracket of the base plate with the pivot axle and wheel axle in place. 
       FIG. 7  is a sectional view taken along Line  7 - 7  of  FIG. 5  illustrating the securing latch mounting bolts fastening the latches to the handles with the rear of the base plate being locked against the handles by the latches. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims. Referring now in greater detail to the various figures of the drawings wherein like reference characters refer to like parts, there is shown at  10  in  FIG. 1 , a wheelbarrow with a self braking mechanism. 
   As shown in  FIG. 1 , the wheelbarrow with self-braking mechanism of this invention is a wheelbarrow bin assembly mounted so as to pivot relative to an undercarriage assembly whereby the bin assembly interferes with wheels of the undercarriage assembly when pivoted. The wheelbarrow bin assembly comprises a pair of elongate handles  12 , having front and rear ends, mounted to the bottom of a wheelbarrow bin  14  mounted to a pair of handles  12  with a shim wedge  16  between the pair of handles  12  and the bin  14 . Mounted near the front ends of the elongated handles  12  are a pair of aligned pivot axle brackets  56  which journal a pivot axle  30  on which is mounted wheels  20 . The wheels  20  a preferably pneumatic type tires; however solid rubber or rubber-like material tires are suitable. 
   Referring to  FIG. 2 , the undercarriage assembly is shown in an unsecured position wherein the base plate  18  is attached by means of the pivot axle  30  to the wheelbarrow bin assembly at a point near the front end of the handles  12 . Note that the front end of the handles  12  extend forward from the pivot axle  30 . When the wheelbarrow bin assembly is tilted forward by lifting the handles  12  when the base plate  18  is released, the handle and bin assembly rotates forward wherein the front ends of the handles  12  interfere with the tread of the wheels  20 . The upward force applied near the rear end of the handles and the downward force of the bin and bin contents in a force applied by the ends of the handles  12  to interference point  58  along the circumference of the wheels  20 . With increasing pressure of the end of the handle  12  against the wheel  20 , the braking effect also increases thereby restricting the wheel  20  from rotating around wheel axle  22  and relative to the handle and bin assembly. Higher bin loads result in a greater forced applied by the ends of the handle to the wheel, thus further assisting the self-braking effect. The wheel  20  is compressed and deformed by the force at interference point  58 . High bin loads also provide sufficient force to deform the wheel  20  such that the front outside surface of the bin  14  contacts the wheel  20  at a second interference point  60  to provide further friction with the wheel  20 . 
   As in  FIGS. 3 , the wheels  20  are positioned on the wheel axle  22  ends such that the center of the wheel tread is aligned with the center of the front end of the corresponding handle  12 . In  FIG. 4 , cut out portions from the front of the base plate  18  permit the tread at the outside circumference of the wheels  20  to be positioned forward of the base plate  18 , handle pivot axle retainer clips  56  and handle  12  ends. The wheelbarrow bin assembly thereby may pivot relative to the undercarriage assembly at pivot axle  30  when the securing latches  40  are released. A support stand, comprising a pair of vertical legs  36  with cross members  58 , is mounted with bolt fasteners  38  to the bottom of the base plate  18  for supporting the rear of the base plate  18  and permitting the wheelbarrow to stand freely. 
   Securing latches  40 , as shown in  FIG. 5 , are fashioned from flat metal to form a semicircular element have an expansion at the front end for grasping the rear portion of the base plate  18 . The securing latch  40  is mounted by fastener  46  to the vertical side of handle  12  through a hole so as to rotate around the pivot fastener  46  at a centrally located hole in the securing latch  40 . A pin  54  fixed at the rear end for attachment to a first end of spring  42  and the distal end of connecting rod  44 . The second end of spring  42  is fixed to the handle  12  by fastener  52  forward of the securing latch pivot fastener  46  in a manner so as to provide force for the securing latch to return to position securing the base plate  18 . A pulling action on the connecting rod  44  thereby results in the securing latch to move away from the base plate  18  and release the base plate  18  to pivot around pivot axle  30 . Also illustrated in  FIG. 5  is a portion of the vertical legs  36  of the support stand and support stand fasteners  38 . 
   In  FIG. 7 , a cross sectional view taken along line  7 - 7  of  FIG. 4 , details of the mounting of the securing latches  40  to the handles  12  are shown. The securing latch pivot fasteners  46  are lag bolts in this embodiment as the handles  12  are constructed of wood. Spacer  48  is positioned between the securing latch  40  and the handle  12  to facilitate rotation and minimize wear on the handle. Although the handles  12  are constructed of wood in the preferred embodiment, other suitable materials may also be utilized. 
   Referring to  FIG. 6 , a cross sectional view taken along line  6 - 6  of  FIG. 4 , mounted on the front of the base plate  18  is wheel axle bracket  24  which journals the wheel axle  22  on which is mounted the pair of wheels  20 . In this embodiment, the base plate  18  is formed from sheet metal, however other materials may be used, such as plastic. The edges of the base plate  18 , typified at  28 , are folded downwardly for additional strength thereby also presenting a rigid element for securing the rear of the base plate by the securing latches. Also illustrated in  FIG. 6  is the stiffener element  26  welded to the bottom of the base plate  18  and positioned to run the length of the base plate  18  from front to rear. 
   Returning once again to  FIG. 1 , the handle lever  50  is fixed to handle  12  so as to rotate pulling the proximate end of the connecting rod  44  to which it is attached. In  FIG. 1 , the handle lever  50  is not activated and the base plate  18  is locked in position by the securing latches  40  adjacent to the handles  12 . In this configuration, the wheelbarrow is maneuverable as conventional wheelbarrow and shown resting on the support stand  36 . The handles  12  are fixed to the bottom of the bin  14  with a shim wedge  16  in between. On the bottom of the handles  12 , near the front end of the handles are mounted the pivot axle brackets  56  that retain the pivot axle  30  which is also held by clips on the base plate  18  as previously described. 
   Now referring again to  FIG. 2 , showing the handle levers  50  activated with the securing latches therefore releasing the base plate  18 , the wheelbarrow bin assembly rotates forward forcing the handle  12  ends into the tire tread of the wheels  20  at interference point  58 . The resulting friction between the handle  12  end and restricts the wheel  20  from rotating around wheel axle  22  thereby causing a self-braking effect. Note also that shim wedge  16  positions the front outside surface portion of bin  14  so as not to interfere with the wheel  20  tread except when the bin  14  is heavily loaded and the securing latches  40  are released so as to bind at the second interference point  60 .