Abstract:
Novel self-leveling wheelbarrows are described and illustrated herein. Exemplary embodiments include novel locking mechanisms for maintaining the wheelbarrow at a horizontally level position relative to the underlying terrain.

Description:
[0001]     This application claims the benefit of the filing of co-pending U.S. provisional application Ser. No. 60/633,516, filed Dec. 6, 2004, and which is incorporated by reference herein in its entirety. This application is also a continuation-in-part of U.S. Ser. No. 10/769,989, filed Feb. 2, 2004, which in turn claims the benefit of Ser. No. 60/443,961, filed Jan. 31, 2003, all of which are incorporated by reference herein in their entireties. 
     
    
     BACKGROUND AND SUMMARY OF THE INVENTION  
       [0002]     The present invention is directed to improvements of a product innovation referred to as a “self-leveling wheelbarrow,” and which are also described in the inventors&#39; pending patent application, U.S. Ser. Nos. 10/769,989 and 60/443,961. The wheelbarrow incorporates self-adjusting legs which conform to the terrain and lock into place when at rest on the ground. The self-leveling feature offers added stability and provides a significant advantage over conventional wheelbarrows when used on sloping or uneven terrain.  
         [0003]     Conventional wheelbarrows are well suited for use on smooth, level surfaces. Their ease of use, excellent mobility, and low cost have made them the material handling equipment of choice for moving small loads in the construction and landscaping industries. As a result of the great success of the conventional wheelbarrow, their basic design has remained essentially unchanged for many years.  
         [0004]     However, due to its high center of gravity, fixed leg assembly, and the inherent instability of a tripod-style base, the use of a conventional wheelbarrow on uneven or sloped terrain is somewhat restricted. These factors result in a tendency to overturn if the legs are not resting on a level surface. When level ground cannot be found in close proximity to the working area the worker may be forced to park the wheelbarrow some distance away. The additional walking between the wheelbarrow and the working area during loading or unloading reduces worker productivity. When parked on uneven or sloping terrain, extra care must be taken to avoid overturning and potential injury to the user. Often a wedge or block is placed beneath one leg in order to provide additional stability and prevent overturning. These common problems associated with conventional wheelbarrows are illustrated in  FIG. 1 .  
         [0005]     A simple solution has been devised which greatly improves the stability of a wheelbarrow on sloping or uneven ground and eliminates its tendency to overturn. A self-adjusting mechanism has been added to the leg assembly, allowing the legs to conform to the terrain as the wheelbarrow is lowered and locked into position when both legs are in contact with the resting surface. The self-leveling action increases stability and maintains the wheelbarrow in a level position. The center of gravity remains very nearly centered above the midpoint of the legs, thus the weight is more evenly distributed between the legs, and the tendency to overturn is diminished.  
         [0006]     The present invention is directed to a self-leveling wheelbarrow comprising (a) a basin having a front end, a rear end, a left side and a right side; (b) a wheel disposed beneath the basin near said front end; (c) a handle assembly secured to the basin; and (d) a rear mounting bracket secured near the rear end of the basin, the mounting bracket having a top end secured beneath the basin. In certain aspects, the present invention further includes (a) a leg assembly comprising a pair of legs secured to one another by a centrally disposed plate, such that one of the pair of legs is positioned beneath the right side of the basin and the other one of the pair of legs is positioned beneath the left side of the basin, the plate further having a centrally disposed, arcuate top edge and a set of teeth arranged along the top edge; (b) a means for movably securing the leg assembly plate to the rear mounting bracket, such that the leg assembly may rotate in a counterclockwise or clockwise direction and in a vertical direction relative to the rear mounting bracket; and (c) a locking component secured beneath the basin and positioned above the top edge of the leg assembly plate, wherein the locking component is a C-channel member having a pair of adjacent side walls extending downward, each of the side walls further having a tapered edge; and whereby as the leg assembly contacts the underlying ground as the wheelbarrow is parked, the leg assembly rotates about the rear mounting bracket to accommodate the contour angle of the ground, sliding the top edge of the plate within the locking component to thereby engage the tapered edges of said locking component within adjacent teeth of the top edge of the leg assembly plate, thereby further locking the plate therein to prevent the leg assembly from rotating further, either in a clockwise direction of travel or a counterclockwise direction of travel. In certain embodiments, the locking component may be secured to the rear mounting bracket. In addition, each of the side walls of the locking component may include a notch, each notch further including the tapered edge for engagement between adjacent teeth of the top edge of the leg assembly plate when the locking component is engaged with the top edge of the leg assembly plate.  
         [0007]     In addition to the basin, wheel, handle assembly, rear mounting bracket, and means for movably securing the leg assembly plate to the rear mounting bracket described above, other aspects of the present invention include (a) a first locking component secured to the leg assembly, the first locking component comprising an elongated inverted U-shaped member having two opposing ends, each of the ends secured to one of the rear legs, and a central portion disposed between the opposing ends; and (b) a second locking component secured beneath the basin and above the central portion of the first locking member, the second locking component comprising a first bar having a slot configured to engage therein the central portion of the first locking component. In operation, as the leg assembly contacts the underlying ground as the wheelbarrow is parked, the leg assembly rotates about the rear mounting bracket to accommodate the contour angle of the ground, sliding the central portion of the first locking component within the slot of the second locking component, thereby locking the central portion of the first locking component therein to prevent the leg assembly from rotating further, either in a clockwise direction of travel or a counterclockwise direction of travel. In other aspects of this embodiment, the second locking component may further include a second bar adjacent the first bar, the second bar having a slot configured to engage therein the central portion of the first locking component, with the slots of the first and second bars being in registration with one another. In addition, the second locking component may secured to the rear mounting bracket.  
         [0008]     In addition to the basin, wheel, handle assembly, rear mounting bracket, and means for movably securing the leg assembly plate to the rear mounting bracket described above, other aspects of the present invention also include (a) a first locking component secured to the leg assembly, the first locking component comprising an inverted elongated U-shaped member having two opposing ends, each of the ends secured to one of the rear legs, and a central portion disposed between the opposing ends, the first locking component further including a series of holes penetrating through the first locking component; and (b) a second locking component secured beneath the basin above the first locking component, the second locking component comprising a locking pin configured for engagement within one of the holes of the first locking component. In operation, as the leg assembly contacts the underlying ground as the wheelbarrow is parked, the leg assembly rotates against the rear mounting bracket to accommodate the contour angle of the ground, sliding the central portion of the first locking component upwards for engagement of the locking pin within one of the holes, thereby locking the central portion of the first locking component therein to prevent the leg assembly from rotating, either in a clockwise direction of travel or a counterclockwise direction of travel. In other aspects of the present invention, the holes of the first locking component may be a series of rectangular shaped notches penetrating an outer edge of the first locking component, and wherein the locking pin is a rectangular tab configured for locking engagement within one of the notches. In this embodiment, as in the embodiments described above, the second locking component may be secured to the rear mounting bracket.  
         [0009]     The means for movably securing the leg assembly plate to the rear mounting bracket may include a vertical slot provided in the rear mounting bracket and a pin extending from the leg assembly plate, the pin slidably engaged within the vertical slot to allow the leg assembly to move vertically within the slot and to rotate in a clockwise and counterclockwise direction about the pin. Alternatively, the means for movably securing the leg assembly plate to the rear mounting bracket may include a vertical slot provided in the leg assembly plate and a pin extending from the rear mounting bracket, the pin also engaged within the vertical slot of the leg assembly plate to allow for similar vertical and rotational movement of the leg assembly plate against the rear mounting bracket.  
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0010]      FIG. 1  is a schematic illustration of a conventional wheelbarrow parked on sloping terrain.  
         [0011]      FIGS. 2-7  are rear views of one embodiment of the wheelbarrow design comprising features of the wheelbarrow design of the present invention.  
         [0012]      FIG. 8  illustrates exemplary locking teeth designs for the central plate of the rear leg assembly of the embodiment illustrated in  FIGS. 2-7 .  
         [0013]      FIG. 9  illustrates a replacement plate comprising one of the locking teeth designs of  FIG. 8 , the replacement plate designed to be secured to the central plate of the rear leg assembly.  
         [0014]      FIG. 10  illustrates one design of the locking component secured to the rear mounting bracket of the wheelbarrow, the locking component designed to engage the locking teeth of the leg assembly plate.  
         [0015]      FIG. 11  is second embodiment of the locking component secured to the rear mounting bracket of the wheelbarrow for engagement of the locking teeth of the leg plate assembly.  
         [0016]      FIG. 12  is a third embodiment of the locking component secured to the rear mounting bracket of the wheelbarrow for engagement of the locking teeth of the leg plate assembly.  
         [0017]      FIG. 13  is a rear view of another embodiment of the inventive wheelbarrow, showing an inverted U-shaped locking member for engagement with a second locking component secured beneath the basin of the wheelbarrow.  
         [0018]      FIG. 14  is a side view of the embodiment shown in  FIG. 13  showing one embodiment of the second locking component.  
         [0019]      FIG. 15  is a bottom view of a wheelbarrow of  FIG. 13 , illustrating a second embodiment of the second locking component.  
         [0020]      FIG. 16  is an enlarged view of the wheelbarrow shown in  FIG. 15 .  
         [0021]      FIG. 17  is a rear view an embodiment similar to that shown in  FIG. 13 , wherein the rear mounting bracket is T-shaped.  
         [0022]      FIG. 18  is a side view of third embodiment of the wheelbarrow shown in  FIG. 13 , wherein the U-shaped locking member comprises a series of holes, and the second locking component is a pin designed for engagement within one of the holes of the U-shaped locking member.  
         [0023]      FIG. 19  is an enlarged view of the locking mechanism shown in  FIG. 18 .  
         [0024]      FIGS. 20   a - 20   d  are modifications of the U-shaped locking member shown in  FIG. 18 .  
         [0025]      FIG. 21  is an enlarged side view of a fourth embodiment of the wheelbarrow shown in  FIG. 13 , wherein the U-shaped locking member comprises a series of notches as shown in  FIG. 20   d,  and the second locking component is a rectangular tab.  
         [0026]      FIG. 22  is a modification of the second locking component shown in  FIG. 21 .  
         [0027]      FIG. 23  is a side view of the embodiment shown in  FIG. 13 .  
         [0028]      FIG. 24  illustrates top and rear views of the leg assembly in combination with the rear mounting bracket and front mounting bracket, wherein the front mounting bracket is smaller in size than the rear mounting bracket.  
         [0029]      FIG. 25  illustrates exemplary front mounting bracket designs.  
         [0030]      FIG. 26  illustrates the front mounting bracket and the rear mounting bracket oriented between the front and rear legs of the leg assembly, as opposed to being positioned outside of the legs. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]     Several embodiments are described herein; however, the general operation of each embodiment is similar and described in co-pending application Ser. No. 10/769,989. In summary, mounting brackets are affixed beneath the wheelbarrow basin B, preferably to the handle assembly H. A lower leg assembly  4  is attached to the mounting brackets in a manner such that it is free to pivot relative to the mounting brackets, wheelbarrow handles, and body. This allows the leg assembly to rotate to match the contour of the ground. When the wheelbarrow is in its final resting position, a locking device is either manually or automatically engaged to prevent rotation of the legs relative to the wheelbarrow body and the desired position is maintained.  
         [0032]     The self-adjusting leg assembly allows the user to park the wheelbarrow W in a much wider range of terrain conditions. The need to use a wedge or block beneath a leg or to park the wheelbarrow a great distance from the working area is eliminated ( FIG. 1 ). When parked on uneven terrain, the weight is more evenly distributed between the legs, resulting in greater stability and reduced tendency to overturn. As a result, worker productivity and safety are substantially improved.  
         [0033]     One embodiment of the present invention utilizes a vertical slot  20  in the rear mounting bracket  2 , a set of locking teeth  10  on the rotating leg assembly  4 , and a means to engage the corresponding teeth on the mounting bracket  2 . This embodiment is presented here to form the baseline for other embodiments described later, and is illustrated in  FIGS. 2-7 . It comprises of a lower leg assembly  4  (i.e. set of legs  4   a  joined by a plate  6 ) which is free to pivot via a pin  8  extending from the leg plate  6  and through a vertical slot  20  in the rear mounting bracket  2 . [Alternatively, the vertical slot  20  may be provided in the leg assembly plate  2  and the pin  8  extending from the rear mounting bracket  2 . For ease of explanation, however, the figures illustrate the former design.] This allows the leg assembly to rotate until the legs  4   a  match the contour of the ground G. The top edge of the leg plate  6  has a set of teeth  10  forming an arc with its center at the pivot point. The rear mounting bracket  2  has a matching set of one or more locking teeth  5  positioned a small distance above those of the leg plate  6 . (Note in  FIG. 2  that the teeth on the rear mounting bracket and the upper edge of the leg plate are positioned behind the rear mounting bracket. These features, however, are only visible in  FIG. 2  for ease of illustration). This matched set of locking teeth may be formed within or integral with the rear mounting bracket  2 , or they may be a part of a separate locking component that is fastened separately to the mounting bracket prior to use. Alternatively, as shown in  FIG. 10 , this separate locking component may simply comprise a C-channel member  15  having adjacent side walls  16  with edges  17  sufficiently ground down (i.e. tapered edge) to engage the teeth  10  of the leg plate  6 .  
         [0034]     As the leg assembly  4  rotates, the gap between the two sets of teeth (or locking components) remains constant. When both legs are in contact with the ground G, the rotation of the leg assembly stops. As the wheelbarrow continues to be lowered, the leg assembly moves up in the slot  20 . This engages the two sets of teeth and locks the assembly into position, as shown in  FIG. 3 . The number of teeth and the spacing between teeth establish a finite number of positions which can be achieved.  FIG. 8  illustrates various tooth designs  10 ,  100 ,  200 ,  300  that may be employed. A practical design must consider the resolution desired between positions, the loads to be carried, and the physical properties of the materials in order to establish an appropriate tooth size and spacing. When the handle assembly H (not shown in  FIGS. 2-7  for ease of illustration) is lifted and the legs lose ground contact, the weight of the leg assembly causes it to move down in the slot and disengage the teeth. The leg assembly then rotates back to a free-hanging position. This embodiment and its operation are illustrated in  FIGS. 4-7 .  
         [0035]     Improvements to the design illustrated in  FIGS. 2-7  include the provision of a separate replacement plate  11  comprising a series of locking teeth  12 , as illustrated in  FIG. 9 . This feature is desireable when the original locking teeth of the leg plate  6  begin to wear down over time, thereby failing to lock the leg assembly in place when the wheelbarrow is parked. In one embodiment, the replacement plate  11  may be secured to the leg assembly plate by any conventional means, including screws, clamps, clips, bolts, and the like.  FIG. 9  illustrates one embodiment of the replacement locking plate comprising holes  13  through which a screw (not shown), for example, may be engaged. It is recommended, however, that the teeth of the leg plate  6 , regardless of configuration (i.e.  10 ,  12 ,  100 ,  200 ,  300 ) be formed of a harder material than the teeth  5  on the rear mounting bracket to prevent premature wear.  
         [0036]      FIG. 11  illustrates an improvement to the design illustrated in  FIG. 10 . Here, the separate locking component that is secured to the rear mounting bracket  2  is very similar to that illustrated in  FIG. 10  in that it is essentially a C-channel member  150  having adjacent side walls  160 . The embodiment illustrated in  FIG. 11 , however, differs in that each side wall further includes a notch  180 . Each notch  180  has an upper edge  170  that is tapered to engage the teeth  10  of the leg assembly plate  6 , similar to the edges  17  of the locking component illustrated in  FIG. 12 . The provision of the notches  180  prevents front-to-back movement of the locking teeth  10 , once engaged therein.  
         [0037]      FIG. 12  illustrates another embodiment of the locking component of the rear mounting bracket  2 , wherein the upper edge  21  comprises two teeth  40  having edges ground down to engage the teeth  10  of the leg plate  6 .  
         [0038]      FIGS. 13-22  illustrate another improvement to the design illustrated in  FIGS. 2-7  as well as those embodiments illustrated and described in co-pending U.S. Ser. No. 10/769,989.  FIG. 13  is schematic rear view of this embodiment wherein the leg assembly  4  is secured to an inverted U-shaped locking member  40 . Each end  41  of the locking member is secured to a corresponding rear leg  4   a  of the leg assembly  4 , each of the legs also secured to a leg assembly plate  60  similar to the leg plate  6  illustrated in  FIGS. 2-7 . Like the leg assembly plate  6  as illustrated in  FIGS. 2-7 , a pin  8  extends therefrom for engagement within a slot  20  of the rear mounting bracket  2  (note that the rear mounting bracket shown in  FIG. 17  is modified to include a top horizontal segment  2   b  and a lower vertical segment  2   a,  arranged in a T-formation). Alternatively, as discussed above, the pin  8  may extend from the rear mounting bracket  2  for engagement within a vertical slot provided in the leg assembly plate  60  (not shown).  
         [0039]     The leg plate  60  in this second embodiment, however, differs from that shown in  FIGS. 2-7  in that the top edge  61  of the leg plate  60  is not configured to engage the locking component of the rear mounting bracket  2 , for example. Instead, the central portion  42  of the U-shaped locking member  40  is configured to engage a slot  62  provided in the locking component of the rear mounting bracket  2 . As better shown in  FIGS. 13-14 , this locking component may be a locking bar  63  comprising a slot or channel  62  that must be sufficiently large to allow clearance for the central portion  42  of the locking member (to move up and down, yet be sufficiently narrow to lock when in a fully seated position (i.e. when the wheelbarrow is parked). The locking bar  63  is pivotally secured (relatively loosely) to the rear mounting bracket  2  through a slot  66  provided in the rear mounting bracket  2 . The locking component may be single locking bar or consist of two adjacent bars or plates  64 , each with a notch  65  in registration within one another to form the slot or channel for engagement of the locking member  40  therein, as best illustrated in the photographs of  FIGS. 15-16 . [As used herein in the present description and claims, the terms “bar” and “plate” are synonymous] The end of each plate  64  is engaged within a corresponding slot  65  provided in the rear mounting bracket, as described above, such that the plates  64  may move slightly left or right (in the direction of arrows A in  FIG. 15 ) as the curved locking member  40  moves clockwise or counterclockwise, thereby acting as a self-locking friction brake. The more the leg assembly  4  rotates in either direction, the greater the locking force.  FIG. 17  is a rear view the embodiments shown in  FIGS. 15-16 .  
         [0040]      FIGS. 18-20  illustrate an alternate design to that shown in  FIGS. 13-17 . As discussed above, the inverted U-shaped locking member  40  is maintained within the locking bar  63  or plates  64  via friction only. In the embodiments illustrated in  FIGS. 18-20 , however, the U-shaped locking member  40  is provided with a series of holes  71  through which a locking pin  80 , extending downward from the locking component, may be engaged when the wheelbarrow is parked.  FIG. 18  is a side view of this embodiment, and  FIG. 19  is an enlarged view of this locking feature. Thus, instead of providing a pair of locking plates  64  (or single locking bar  63 ), each forming an arcuate slot for engaging the complementarily curved portion  42  of the locking member  40  for friction engagement therein, this second embodiment comprises a simple pin  80  that extends downward from the wheelbarrow basin B, or as shown in  FIGS. 18-19 , a portion of the rear mounting bracket  2  secured to the bottom of the basin B. As the leg assembly  4  of the wheelbarrow rotates, the locking member  40  also rotates freely beneath the pin  80 . When the wheelbarrow is parked, the central portion  42  of the locking member  40  moves upward to engage the pin  80 .  
         [0041]     It will be appreciated by the skill artisan that the size, spacing, and configuration of the holes  71  provided in the locking member  40  may be modified. In addition, the angle of the arc and the configuration of the locking member may be modified if desired.  FIGS. 20   a - 20   b  each show locking members  40  having a tubular shape, although  FIG. 20   a  is a rounded tube while  FIG. 20   b  is square.  FIGS. 20   c - 20   d  illustrate the use of a somewhat L-shaped angle member having a side wall  44  and a top wall  45 . In  FIGS. 20   a - 20   c,  the locking members all comprise centrally positioned holes  83 ; while  FIG. 20   d  illustrates a series of notches  81  that penetrate the outer edge and extend toward the center of the top wall of the angle member.  
         [0042]      FIGS. 21-22  illustrate the design of the locking feature of the rear mounting bracket  2  when the locking member of  FIG. 20   d  is employed (i.e. angle member). Here, instead of employing a pin, as shown in  FIGS. 18-19 , a substantially rectangular tab  82  is employed that extends downward from the rear mounting bracket  2 , as shown, similar to the locking pin  80  embodiments shown in  FIG. 18-19 . Preferably, the tab  82  is sufficiently small (i.e width and length) to easily engage the corresponding notches to thereby lock the wheelbarrow leg. However, the tab  82  should be large enough such that engagement is relatively tight to minimize minor rotation of the legs while the wheelbarrow is parked. It should be further noted that the tab  82  may be cylindrical, like pin  80  or of another configuration, to engage complementary-shaped notches of the locking member.  
         [0043]     The figures illustrate locking components  15 ,  150 ,  63 ,  64  as being secured to the rear mounting bracket  2 ; however, it will be readily appreciated by those of ordinary skill in the art that these locking components could, instead, be secured directly to the bottom of the wheelbarrow basin B or to another structure that in turn is secured to the bottom of the basin B (not shown). Likewise, the second locking component  80 ,  82  illustrated in  FIGS. 18-19  and  21  may also be secured directly to the basin B or to a separate component secured to the basin (not shown).  
         [0044]     It is important to note that the front and rear pivot points provided in the front  7  and rear mounting brackets  2 , respectively, must lie on a line that is substantially perpendicular to the plane of the curved member. Such orientation ensures that the U-shaped locking member  40  (or angle member ( FIG. 20   d )) will rotate in a plane, and that regardless of the degree of rotation, the holes  71 , 83  (or notches  81 ) will always line up with the pin  80  (or tab) or locking bar  63  (or plates  65 ) (see  FIG. 23 ). If the axis of rotation is not perpendicular to the plane of the curved member, the holes or notches will be increasingly misaligned with the pin (or tab) with increasing rotation of the legs.  
         [0045]     Other modifications of the inventive wheelbarrow design are also illustrated  FIGS. 24-26 .  FIG. 24  includes top and rear views of the leg assembly in combination with the rear mounting bracket  2  and front mounting bracket  7 . In  FIG. 24 , the front mounting bracket  7  is smaller in size than the rear mounting bracket  2 .  
         [0046]      FIG. 25  illustrates exemplary front mounting bracket designs  7 ,  700 .  
         [0047]     Finally,  FIG. 26  illustrates the front mounting bracket  7  and the rear mounting bracket  2  oriented between the front and rear legs of the leg assembly, as opposed to being positioned outside of the leg assembly.