Abstract:
A weighing scale having a display and processor for determining and identifying the optimal position coordinates for a load placed on the weighing scale includes a platform and a plurality of support assemblies, each containing a load cell for receiving the weight of the load. The display includes a meter or other graphical display that identifies position coordinates along with the determined numerical weight. Individual outputs from each of the plurality (e.g. 4) of load cells are received by a processor configured to compute x,y vector coordinates associated with the weight parameters for each load cell. The determined current or actual load position relative to an optimal position is calculated and displayed along with the weight.

Description:
[0001]    This application claims the benefit under 35 USC 119(e) of U.S. Provisional Patent Application Serial No. 60/426,142, filed Nov. 14, 2002, the entirety of which is hereby incorporated by reference. 
     
    
     
       FIELD OF INVENTION  
         [0002]    The present invention relates to weight measurement devices. More particularly, the present invention relates to a weighing scale having a processor that is programmed to determine the position of a load being weighed thereon and a display for graphically indicating the load&#39;s position relative to an optimal weighing position, so that the load can be repositioned to the optimal weighing position.  
         BACKGROUND OF THE INVENTION  
         [0003]    There are many different types of electronic weighing scales in use today. One popular type of electronic weighing scale is constructed with a platform for receiving the load to be weighed and a set of levers, pivots, flexures, and torque tubes to mechanically combine the forces applied to the platform by the load, thereby enabling the measurement of these forces with a single electronic load cell, which operates as a force transducer. The load cell is typically constructed with a mechanically-deformable sensor plate with one or more sensor elements bonded thereto. When a load is applied to the load cell, the sensor plate mechanically bends and the sensor elements bonded thereto produce an electrical output signal, the magnitude of which is commensurate with the load applied to the load cell.  
           [0004]    Another popular type of electronic weighing scale is constructed with a platform for receiving the load to be weighed, and a plurality of electronic load cells disposed at the corners of the platform, or more or less evenly spaced along the periphery or marginal periphery of the platform, for supporting the platform. Each of the load cells produces an electrical output signal indicative of the load sensed thereby. The electrical output signals of the load cells are averaged by processing circuitry associated with the scale to enable the load to be measured over a large area of the platform.  
           [0005]    One problem associated with the multi-load cell scale described immediately above is that when the load is unevenly positioned on the platform, the load or force sensed by each of the load cells is not the same, with a disproportionate amount of the load or force being sensed by certain ones of the load cells. Consequently, the associated processing circuitry arrives at a weight calculation that is offset from the load&#39;s “true weight” determined when the load is centrally or optimally positioned on the scale.  
           [0006]    Accordingly, a weighing scale is needed, which is capable of determining the position of a load being weighed thereon, and displaying the load&#39;s position relative to an optimal weighing position, so that the load can be repositioned to the optimal weighing position.  
         SUMMARY OF THE INVENTION  
         [0007]    A weighing scale having a display and processor for determining and identifying the optimal position coordinates for a load placed on the weighing scale comprises a platform and a plurality of support assemblies, each containing a load cell for receiving the weight of the load. The display includes a meter or other graphical display that identifies position coordinates along with the determined numerical weight. Individual outputs from each of the plurality (e.g. 4) of load cells are received by a processor configured to compute x,y vector coordinates associated with the weight parameters for each load cell. The determined current or actual load position relative to an optimal position is calculated and displayed along with the weight. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a perspective view of an exemplary embodiment of a weighing scale according to the present invention.  
         [0009]    [0009]FIG. 2 is a plan view of the weighing scale platform.  
         [0010]    [0010]FIG. 3 is a block diagram depicting the major functional components of the weighing scale of the present invention.  
         [0011]    [0011]FIG. 4 is a flow chart depicting the operation of the weighing scale according to an exemplary embodiment of the present invention.  
         [0012]    [0012]FIG. 5A is block diagram depicting an embodiment of a method for calculating the weight of the load, the actual position of the load on the platform, and how the actual position of the load on the platform deviates from the optimal position, according to the present invention.  
         [0013]    [0013]FIG. 5B is block diagram depicting another embodiment of a method for calculating the weight of the load, the actual position of the load on the platform, and how the actual position of the load on the platform deviates from the optimal position, according to the present invention.  
         [0014]    [0014]FIG. 6 is a plan view of an exemplary embodiment of a display assembly according to the present invention.  
         [0015]    [0015]FIG. 7A is an exemplary embodiment of a circuit diagram of the processor and load cell circuitry of the weighing scale for implementing the embodiment of the method of FIG. 5A.  
         [0016]    [0016]FIG. 7B an exemplary embodiment of a circuit diagram of the processor and load cell circuitry of the weighing scale for implementing the embodiment of the method of FIG. 5B. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    [0017]FIG. 1 shows an exemplary embodiment of a weighing scale  10  according to the present invention. The scale  10  comprises a base or platform  20  having a top surface  22  and a bottom surface  24 . A plurality of supports  40  are provided for supporting the platform  20 .  
         [0018]    The supports  40  are attached to the platform  20  in a symmetrical or evenly-spaced arrangement so as to support the platform  20  above a ground, floor, table, or like surface in a stable and safe manner. In the shown embodiment, the platform  20  has a square or rectangular configuration with four supports  40  attached to the corners thereof. Although not shown, platforms having circular, elliptical, oval, triangular, octagonal, etc. configurations are also contemplated.  
         [0019]    Each of the above mentioned supports  40  has integrated therein a load cell LC 1 -LC 4 , which is positioned such that it can sense a portion of a load (e.g. a person, animal or other object or article to be weighed) positioned on the platform  20  to be weighed. The load cells LC 1 -LC 4  are typically located below the bottom surface  24  of the platform  20 . Each of the load cells LC 1 -LC 4  outputs an electrical signal in response to a portion of the load placed on the top surface  22  of the platform  20 . Electrical conductors  30  or other means electrically connect each of the load cells LC 1 -LC 4  to a processor  90 , which electrically communicates with a display assembly  50  (the processor  90  may be contained within the display assembly  50  as shown in this embodiment) attached to, or integrated with the top surface of the platform  20 . For additional information regarding the operation of the load cells and weighing scales employing load cells for weighing purposes, reference can be made to commonly assigned U.S. Pat. No. 5,929,391 entitled “Load Cell for an Electrical Weighing Scale”, U.S. Pat. No. 6,417,466 entitled “Load cell with Bossed Sensor Plate for an Electrical Weighing Scale”, and U.S. Pat. No. 5,886,302 entitled “Electrical Weighing Scale”.  
         [0020]    As shown in FIG. 2, the platform  20  of the scale  10  is arranged in symmetrical quadrants Q 1 , Q 2 , Q 3 , and Q 4  (shown with broken lines). Quadrant Q 1  represents the top left quadrant of the platform  20 , which is supported by load cell LC 1 ; quadrant Q 2  represents the top right quadrant of the platform  20 , which is supported by load cell LC 2 ; quadrant Q 3  represents the bottom right quadrant of the platform  20 , which is supported by load cell LC 3 ; and quadrant Q 4  represents the bottom left quadrant of the platform  20 , which is supported by load cell LC 4 .  
         [0021]    [0021]FIG. 3 is a block diagram depicting the major functional components of the scale  10 . As shown, the scale includes the components earlier described platform  20 , platform supports  40  with LC 1 -LC 4 , and display assembly  50  containing the processor  90 . The scale  10  also includes analog electronic circuitry (e.g. for resistance calibration)  70 , an analog-to-digital converter  80 , a memory  95  for storing data processed by the processor  90 , a digital weight display  52 , and a graphics position offset display  60 , all of which may be contained in the display assembly  50 .  
         [0022]    [0022]FIG. 4 is a flow chart depicting the operation of the scale  10 . The scale  10  may operate in a tare mode, the steps of which are represented by blocks  200 - 230 , and a weight measuring and optimal positioning mode, the steps of which are represented by blocks  240 - 290 . The tare mode is performed before a load to be weighed, is placed on the scale  10 , and commences in block  200  with an analog-to-digital conversion process, wherein the analog signal output of a selected one of the load cells LC 1 -LC 4  is converted by the A/D converter in block  210  to a digital signal. In blocks  220 , the processor uses the digital signal to tare the selected load cell. In block  230 , the processor determines whether all the load cells LC 1 -LC 4  have been tared. If the answer is no, the steps of blocks  210  through  230  are repeated.  
         [0023]    If the answer in block  230  is yes, the weight measurement and optimal positioning mode may be commenced in block  240  with the placement of the load to be weighed onto the top surface of the scale platform in a predetermined position corresponding to x and y load position coordinates. The resulting analog signal output of a selected one of the load cells LC 1 -LC 4  is converted in block  250  to a digital signal by the A/D converter. In block  260 , the processor reads an A/D counter and in block  270  determines whether the analog signal outputs of all the load cells LC 1 -LC 4  have been converted to digital signals. If the answer is no, the steps of blocks  250  through  270  are repeated. If the answer is yes, the actual position of the load on the platform, and how the actual position of the load on the platform deviates from the optimal position are calculated by the processor (using the digital information obtained in blocks  250  and  260 ) in block  280 . The actual position of the load (and the weight of the load) may be communicated to the display assembly at this stage of the optimal positioning mode also. The optimal positioning process may end here or as depicted in block  290 , a determination may be made as to whether a predetermined time period has run out. If the predetermined time period has run out (timeout), the optimal positioning mode ends (even if the optimal position has not been achieved) and the scale reverts to a conventional weighing mode. If the predetermined time period has not run out, steps  250 - 290  are repeated (the scale stays in the optimal positioning mode), thus allowing relocation of the load to the optimal position.  
         [0024]    [0024]FIG. 5A is a block diagram depicting an embodiment of a method for calculating the weight of the load, the actual position of the load on the platform, and how the actual position of the load on the platform deviates from the optimal position (block  280  of FIG. 4), according to the present invention. In block  300 , partial weight W1 applied to platform quadrant Q 1  is obtained from LC 1  A/D; partial weight W2 applied to platform quadrant Q 2  is obtained from LC 2  A/D; partial weight W3 applied to platform quadrant Q 3  is obtained from LC 3  A/D; partial weight W4 applied to platform quadrant Q 4  is obtained from LC 4  A/D; and total weight W is obtained by summing the partial weights W1, W2, W3, W4 obtained from LC 1  A/D, LC 2  A/D, LC 3  A/D, and LC 4  A/D. If the load is optimally positioned on the platform of the scale (e.g. typically at the very center X c , Y c  of the platform  20  shown in FIG. 2), then the partial weights will be equal to one another (W1=W2=W3=W4), and the total weight will equal the sum of the partial weights (W=W1+W2+W3+W4).  
         [0025]    In block  310 , the portion of the load&#39;s weight distributed on the left side of the scale (quadrants Q 1  and Q 4  associated with axis segment x 1 -x c  shown in FIG. 2), the right side of the scale (quadrants Q 2  and Q 3  associated with axis segment X 2 -x c  shown in FIG. 2), the top side of the scale (quadrants Q 1  and Q 2  associated with axis segment y 2 -y c  shown in FIG. 2), and the bottom side of the scale (quadrants Q 4  and Q 3  associated with axis segment y 1 -y c  shown in FIG. 2), is calculated. The portion of the load&#39;s weight distributed on left side of the scale is calculated by summing partial weight W1 and partial weight W4; the portion of the load&#39;s weight distributed on right side of the scale is calculate by summing partial weight W2 and partial weight W3; the portion of the load&#39;s weight distributed on top side of the scale is calculated by summing partial weight W1 and partial weight W2; and the portion of the load&#39;s weight distributed on bottom side of the scale is calculated by summing partial weight W4 and partial weight W3. The above calculations are carried out by the processor  90  and stored in the memory  95 .  
         [0026]    In block  320 , the half weight of the load is calculated by summing the partial weights W1, W2, W3, and W4 and dividing this sum by two (2). The above calculations are carried out by the processor  90  and stored in the memory  95 .  
         [0027]    In block  330 , x-axis and y-axis load position offsets are calculated wherein the x-axis offset is the distance the weight of the load is offset, either left or right, from the center position x c  of the x 1 -x 2  axis of the platform (FIG. 2) and the y-axis offset is the distance the weight of the load is offset, either top or bottom, from the center position y c  of the y 2 -y 1  axis of the platform (FIG. 2). The x-axis offset may be calculated by dividing either the sum of the partial weights W1 and W4 for the left side of the scale, or the sum of the partial weights W2 and W3 for the right side of the scale, by the half weight. The y-axis offset may be calculated by dividing either the sum of the partial weights W1 and W2 for the top side of the scale, or the sum of the partial weight W4 and W3 for the bottom side of the scale, by the half weight. Each of these calculations is carried by the processor  90  and the result stored in the memory  95 .  
         [0028]    In block  340 , the processor  90  compares the x-axis and y-axis offsets with a predetermined threshold value (e.g. zero) to determine whether a disproportionate quantity of the load&#39;s weight is on the left, right, top or bottom sides of the scale platform. For example, if the x-axis offset was calculated using the left side partial weights, and the value of this x-axis offset is greater than zero (x-axis offset&gt;0), then a disproportionate amount of weight is on the left side of the scale platform and the corresponding percentage value of the x-axis offset indicates the relative vector offset from the optimal position x c . If the value of the x-axis offset is less than zero (x-axis offset&lt;0), then a disproportionate amount of weight is on the right side of the scale platform and the corresponding percentage value of the x-axis offset indicates the relative vector offset from the optimal position x c . If the value of the x-axis offset is equal to zero (x-axis offset=0), then the weight on the left and right sides of the platform scale are substantially equal and optimally positioned at x c  of the x 1 -x 2  axis.  
         [0029]    Similarly, if for example, the y-axis offset was calculated using the top side partial weights, and the value of this y-axis offset is greater than zero (y-axis offset&gt;0), then a disproportionate amount of weight is on the top side of the scale platform and the corresponding percentage value of the y-axis offset indicates the relative vector offset from the optimal position y c . If the value of the y-axis offset is less than zero (y-axis offset&lt;0), then a disproportionate amount of weight is on the bottom side of the scale platform and the corresponding percentage value of the y-axis offset indicates the relative vector offset from the optimal position y c . If the value of the y offset is equal to zero (y-axis offset=0), then the weight on the top and bottom sides of the platform scale are equal and optimally positioned at y c  of the y 2 -y 1  axis.  
         [0030]    In block  350 , the processor communicates the values of x-axis and y-axis offsets (e.g. percentage values) to the display assembly  50  for display to the user, along with the determined weight. In this manner, the user obtains a visual indication of both the measured load weight as well as an indication of the load&#39;s relative position on the scale relative to the optimal position. In an alternative embodiment, the processor may activate some type of light and/or sound indicator when the load is located in or relocated to the optimal position instead of, or in addition to, communicating the x- and y-axis offsets to the display assembly  50 . In such an embodiment, the determined weight may still be communicated to the display assembly  50  for display to the user.  
         [0031]    In another embodiment, as shown in the block diagram of FIG. 5B, only the distance the weight of the load is offset, either left or right, from the center position x c  of the x 1 -x 2  axis of the platform is determined. Thus, the processor calculates only the x-axis load position in block  330 ′, compares the x-axis offset with the predetermined threshold value to determine whether a disproportionate quantity of the load&#39;s weight is on the left or right sides of the scale platform in block  340 ′ and communicates the result to the indicator and/or the display assembly in block  350 ′.  
         [0032]    [0032]FIG. 6 shows an exemplary embodiment of the display assembly of the present invention. The display assembly  50  comprises a display window  52  for displaying a numerical indication of the total measured weight W of the load. The display assembly further comprises a meter or graphics position offset display  60  including a first scale  62  for indicating the load position along the x 1 -x 2  (left-right) axis relative to an optimal center position x c  (the percentage value of the x-axis offset) and a bi-directionally movable position indicator  64 , and a second scale  66  for indicating the load position along the y 2 -y 1  (front-back) axis relative to an optimal center position y c  (the percentage value of the y-axis offset) and a bi-directionally movable position indicator  68 . The first and second scales  62 ,  66  provide a graphical representation to the user of relative x and y offsets. In the embodiment where only the x-axis offset is utilized (FIG. 5B), the movable position indicator  64  would not be provided. Further, the meter or graphics position offset display  60  (with both x- and y-axis indicators or just x-axis indicator) may be omitted altogether and replaced with or combined with the visual and/or sound indicator mentioned earlier, which activates only if the load is in the optimal position. The visual indicator may be some type of a light generating device, such as an LED. The sound indicator may be a sound generating device that generates a ringing or buzzing sound. The visual and/or sound indicator may be separate from the display assembly or integrated therewith.  
         [0033]    [0033]FIG. 7A shows an exemplary embodiment of processor and load cell circuitry that is capable of calculating x- and y-axis offsets and comparing the x- and y-offsets to threshold values. FIG. 7B shows an exemplary embodiment of processor and load cell circuitry that is capable of calculating an x-axis offset and comparing the x-offset to a threshold value.  
         [0034]    It is to be understood that one skilled in the art may make many variations and modifications to that described herein. All such variations are intended to be within the scope of the invention as defined in the appended claims.