Abstract:
A load cell assembly is used with a scale having a weighing platform, in order to provide a very low clearance above a surface on which the scale is positioned. The load cell assembly has a load cell with first and second arms. A bridge portion of the load cell connects the arms, maintaining them in a substantially parallel relationship, with at least a portion of the second arm having a height that is larger than a height of the first arm and the bridge portion. A fastener attaches the load cell to the weighing platform, on the second arm portion with a larger height. A foot device, attached to the first arm, spaces the load cell above the surface on which the scale is positioned.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from International Patent Application No. PCT/US2009/044144 filed on May 15, 2009 and having a priority date of May 15, 2008. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The disclosed embodiments of the present invention relate to a platform scale that utilizes a plurality of slot block load cells. 
       BACKGROUND OF THE INVENTION 
       [0003]    In the known prior art, many platform scales are known, but these tend to have a relatively high profile to them, due to the weighing mechanism deployed therein. As a result, either the weighing level is positioned above the surrounding floor, or, in the alternative, a depression has to be provided in the floor to permit a flat entrance onto the platform. 
         [0004]    Torsional sensing load cells are known in the prior art, and several patents, including commonly-owned U.S. Pat. Nos. 5,714,695, 5,872,319, 5,925,832, 6,293,585, 6,499,360 and 6,672,176 are based upon this concept. 
         [0005]    It is an unmet object of the prior art to provide a platform scale that has a sufficiently low profile to allow it to be placed on a surface and still provide a weighing surface that is within an inch or less of the surface on which it is placed. It is a further unmet object to provide a load cell that can be arranged with a platform to provide the desired low profile. 
       SUMMARY OF THE INVENTION 
       [0006]    This and other unmet advantages are provided by a load cell assembly for use with a scale having a weighing platform with a low clearance above a surface. The load cell assembly comprises a load cell, means for fastening the load cell to the weighing platform, and means for spacing the load cell above the surface. The load cell itself has a first and a second arm. A bridge portion connects the respective arms, maintaining them in a substantially parallel relationship. At least a portion of the second arm has a height that is larger than a height of the first arm and the bridge portion. The fastening means is on the second arm portion with a larger height. The spacing means is on the first arm. 
         [0007]    In some embodiments, the load cell is formed from a monolithic block piece of a metal, with the first and second arms being defined by a longitudinal slot cut into the block from one end of the block and terminating short of the opposite end of the block, which defines the bridge portion. In such an embodiment, the longitudinal slot may terminate internal to the monolithic block in an enlarged, rounded end. 
         [0008]    In some of the embodiments, the load cell assembly also comprises a means for limiting relative displacement of the ends of the first and second arms, opposite the bridge portion. In some of these embodiments, the displacement-limiting means comprises a bore, passing transverse to a longitudinal axis of each of the arms near the ends opposite the bridge portion, and a pin, positioned in the bore of each of the arms. 
         [0009]    In some embodiments, the weighing platform fastening means comprises at least one bore into the second arm portion having a larger height, and a fastener corresponding to each bore, sized to be threadingly received in the bore to which it corresponds. 
         [0010]    In some embodiments, the surface spacing means comprises at least one bore into the first arm, and a foot, sized to be threadingly received in the bore to which it corresponds. 
         [0011]    Other objects of the invention are achieved by a scale having a weighing surface less than one inch above the surface on which the scale is positioned. Such a scale comprises a weighting platform, an upper surface of which defines the weighing surface; and a plurality of the load cell assemblies described above, each load cell assembly arranged around a periphery of the weighing platform. 
         [0012]    In some of the scales, the weighting platform will be a rigid planar sheet having a trapezoidal profile, and three load cell assemblies are used, with two placed near the corners of the longer of the two parallel sides of the trapezoidal platform and the third placed near a midpoint of the shorter of the parallel sides. 
         [0013]    In another embodiment of the scale, the weighting platform comprises a rigid planar sheet having a rectangular profile, and four load cell assemblies are used, all of the load cell assemblies placed near the corners of the rectangular platform. 
         [0014]    In a third embodiment of the scale, the weighing platform comprises a rectangular platform, defining an upper surface on which an object to be weighed is placed and an opposing lower surface and a first and a second channel, one of the channels formed along each of a pair of opposing sides of the rectangular platform, each channel being open towards the lower surface of the platform, each channel having a height selected to allow placement of a load cell assembly therein while positioning the platform lower surface in close proximity to the surface on which the scale is used. In such a case four load cell assemblies will be used with the weighing platform, all of the load cell assemblies placed inside the channels near the corners of the rectangular platform. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    A better understanding of the disclosed embodiments will be obtained from a reading of the following detailed description and the accompanying drawings wherein identical reference characters refer to identical parts and in which: 
           [0016]      FIG. 1  is a partial section view of an embodiment of a platform scale; 
           [0017]      FIG. 2  is an enlarged view of a slot block load cell as used in the  FIG. 1  embodiment; 
           [0018]      FIG. 3  is a top plan view of an exemplary wiring arrangement for a platform scale using the  FIG. 2  load cell; 
           [0019]      FIG. 4  is a side sectional view of the  FIG. 3  embodiment; and 
           [0020]      FIG. 5  is a perspective view of a platform for an alternate embodiment of the platform scale. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]      FIG. 1  shows an exemplary embodiment of the platform scale device  10 . The device  10  has a platform  12  which is preferably rigid and planar, and also preferably rather thin in thickness while retaining its rigid nature. The platform  12  is trapezoidal. There are three torsional load cell assemblies  14 , further details of which are disclosed below, deployed about the periphery of the platform  12 . Of the three load cell assemblies  14 , two are placed near the corners of the longer of the two parallel sides and the third assembly is placed at a midpoint along the shorter of the parallel sides. In the case of two of the load cell assemblies  14 , the assemblies are positioned below the platform  12  in a manner that largely obstructs these assemblies from view, but, in the lower left corner of  FIG. 1 , a portion of the platform  12  is sectioned away so that the load cell assembly  14 , including load cell  20  and its attachment to the platform with screws  30  is more clearly viewable. 
         [0022]      FIG. 2  shows an exemplary load cell assembly  14 , comprising a torsional load cell  20 , means  30  for fastening the load cell beneath a lower surface of the platform (not shown in  FIG. 2 ) and a means  40  for spacing the load cell above an underlying surface S ( FIG. 4 ). Load cell  20  has first and second arms  22 ,  24 , the respective arms intersecting at a bridge portion  26 , which serves not only to connect the arms  22 ,  24 , but maintains them in a parallel relationship to each other. A portion  28  of the second arm  24 , and, specifically, the portion of the second arm that is furthest from bridge portion  26 , has a height that is higher, by an amount H, than a height of the remainder of the second arm  24 , the first arm  22  or the bridge  26 , all of which have a substantially identical height. The means  30  for fastening the load cell beneath the platform is provided by a pair of screws, which are threadingly received in holes  21 ,  23  in higher portion  28 . Other means  30  for fastening will be known and useful to those skilled in art, so long as the object is achieved, that is, allowing the lower surface of the platform to rest upon, and pass the gravitational force bearing thereupon solely onto, the higher portion  28 . 
         [0023]    The means  40  for spacing the load cell  20  above the underlying surface is exemplified in the illustrated embodiment by a foot  40  that is threadingly received in a hole  25  in a lower surface of the first arm  22 . This sets up the torsional capability of the load cell  20 . In the illustrated embodiment, the threaded shafts of screws  30  and foot  40  are arranged in parallel relationship. Further, the center of hole  25  and a midpoint between the centers of holes  21 ,  23  are, in the disclosed embodiment, at the same distance along their respective arms  22 ,  24 , when measured from the bridge portion  26 . 
         [0024]    At the opposite end of the arms  22 ,  24 , a limit pin  50  can be received in a hole  27  provided at the end of each of the arms (only the hole  27  in arm  22  is visible in  FIG. 2 ), opposite the bridge portion  26 . This limit pin  50  provides overload protection to the load cell. The pin  50  has a threaded portion which engages threads in the hole  27  in the arm  22 . A remainder of the pin  50  is preferably unthreaded and resides in a hole in the arm  24  aligned with the hole  27  substantially colinearly. Clearance between the hole in the arm  24  and the unthreaded portions of the pin  50  can be selected to provide the amount of overload protection desired. Pin size and pin material can also be selected to provide the desired overload protection. 
         [0025]    A further feature which may be noted in  FIG. 2  is that load cell  20  can be formed by removing material from a monolithic block of a material, especially a metal such as aluminum or steel. In particular, arms  22 ,  24  may be formed by cutting a longitudinal slot  52  through a block of the material, the slot terminating at the bridge portion  26 . In some embodiments, as illustrated, it is preferred to terminate slot  52  in a somewhat larger, rounded “keyhole” end  54 , as seen in  FIG. 2 . It may also be useful to enhance the flexibility of the load cell by the use of one or more mass relief holes  56 , one of which is visible in arm  22 . 
         [0026]      FIGS. 3 and 4  show, in respective top plan and side sectional views, a wiring arrangement for an embodiment of the platform scale device  110  having a generally triangular platform  112 . Three torsional load cell assemblies  14  are deployed near the vertices of the platform  112  and standard wiring for each torsional load cell coupled to known prior art rotational displacement transducers associated with each load cell is directed to a central box  60 , from which a signal output may be directed to an external electronics module through a wiring conduit  70 . While  FIG. 3  depicts an exemplary length from the central box  60  through the conduit  70 , other lengths and specific wiring bundle details could be provided. It is noted that  FIG. 4  also provides a clear depiction of how the bottom surface of platform  112  can be placed with 25 mm or so of the surface S on which the device  110  is being used. 
         [0027]      FIG. 5  shows a perspective view of an alternate platform  114  upon which a low ground clearance platform can be built, using a load cell assembly of the type taught in  FIG. 2 . This rectangular platform  114  is characterized by a pair of channels  116  having an “inverted-U” profile that are formed along a pair of the opposing sides. Rather than providing a rigid, planar platform (as is shown in  FIG. 1 ), this alternate platform  114  uses the channels  116  to provide a raised area, with one of  FIG. 2  load cell assemblies positioned inside the channel, an inside surface of one of the channels bearing directly on the load-receiving arm  24  of the  FIG. 2  load cell assembly. Holes  168  in the corners of the platform  114  show the position where fastening means  30  would be used. In the illustrated embodiment, a planar weight-receiving surface  118  is provided and an upstanding support wall  119 , along one of the remaining two sides, is one way in which the rigidity of the surface  118  can be maintained. In this way, even the upper surface of the weight-receiving surface  118  can be very close to the base surface S ( FIG. 4 ) upon which the device is used. Such an arrangement allows easy loading and unloading of items onto the scale. 
         [0028]    Applications of the embodiment described herein will be recognized by one of ordinary skill in this art. However, for exemplary purposes, several such applications are set forth with specificity. 
         [0029]    In a first application, the device will be used to provide real time inventory control on a product stored in a keg or other cylindrical container. A particular example would involve a scale for a beer keg. Because of the low profile, even a full keg could be easily placed on the platform, which would typically have a circular profile when viewed from above, with three or more load cells distributed around the circumference of the platform. 
         [0030]    In another application, the device will be used as a veterinarian scale for weighing animals. In this application, the platform is more likely to have a roughly rectangular profile, but a circular profile may be more appropriate in some circumstances. Depending upon the particular size of the animal being weighed, three or four load cells would be deployed about the periphery of the platform. With four cells, they would typically be deployed at corners. In a large animal application, it may be necessary to use from six to eight load cells. 
         [0031]    In a third application, the device will be used as a scale for weighing a patient in a wheelchair. The low profile of the device allows the wheelchair to be easily rolled onto and off of the platform, which is likely to have a roughly rectangular profile. Three or four load cells would be deployed about the periphery of the platform. With four cells, they would typically be deployed at corners. This type of embodiment would also be useful as a bariatric scale. 
         [0032]    In a particular variation on the wheelchair scale application, it may be useful in some situations to use two spaced-apart platform scales, which may be electrically interfaced with each other, to weigh a patient who is confined to a bed, particularly a gurney or other wheeled bed. In such as case, the bed could be rolled so that the front legs of the bed would be placed on the first of the devices and the rear legs of the bed would be rolled onto the second of the devices. In a particularly useful embodiment for this variation, each platform would be separately useful with a signal output that could be, in a single application, directed to an electronics module and, in a dual application, ganged with a signal output from the second platform to be directed to an electronics module. Similarly, a pair of spaced-apart platforms could also be used in many other applications to weigh products on wheeled trucks such as those used to move items around in a warehouse. 
         [0033]    This disclosure is provided to reveal a preferred embodiment of the invention and a best mode for practicing the invention. Having thus described the invention in this way, it should be apparent that various different modifications can be made to the preferred embodiment without departing from the scope and spirit of this disclosure. When structures are identified as a means to perform a function, the identification is intended to include all structures which can perform the function specified.