Abstract:
A load cell assembly, including an adapter adapted to receive a vertical load, and having loaded and unloaded dispositions; a load cell body including a spring element having a first cutout window defined by a top beam and a bottom beam, the window transversely disposed through the body, the spring element adapted such that responsive to a downward force exerted on a top face of the adapter, the beams assume a primary double-bending configuration; a strain-sensing gage, attached to the spring element, the strain-sensing gage for measuring strain in the spring element; and an at least two-dimensional flexural member having a second cutout window, the second cutout window being transversely disposed through the body; the adapter disposed in mechanical relation to the flexural member such that, in the loaded disposition of the adapter, the flexural member assumes a secondary, substantially double-bending configuration.

Description:
[0001]    This invention claims priority from Great Britain Application Number 1413735.0, filed Aug. 3, 2014, which application is incorporated by reference for all purposes as if fully set forth herein. 
       FIELD AND BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to weight measurement devices, and more particularly, to weighing devices employing load cell assemblies having integral flexures. 
         [0003]    Load cells are employed extensively in weighing scales because of their accuracy in measuring weights. Such load cells, or transducers, may have a metallic body having a generally rectangular perimeter. Opposing surfaces of the perimeter may carry surface-mounted, resistor strain gauges, interconnected to form an electrical bridge. The central portion of the body may have a rigidly-designed opening beneath the strain gauges to define a desired bending curve in the body of the load cell. The body of the load cell is adapted and disposed to provide cantilevered support for the weighing platform. Thus, when a weight is applied to the weighing platform, temporary deformations in the load cell body are translated into electrical signals that are accurately and reproducibly responsive to the weight. When the weight on the platform is removed, the metallic load cell body is designed to return to an original, unstressed condition. 
         [0004]    The inventor has determined the need for improved accuracy in low-profile load cell assemblies. 
       SUMMARY 
       [0005]    According to the teachings of the present invention there is provided a load cell assembly, including: (a) a load cell body including a spring element having a first cutout window at least partially defined by a top beam on a top side of the load cell body and a bottom beam, the window transversely disposed through a long dimension of the body; (b) an adapter adapted to receive a vertical load, the adapter disposed on the top side of the load cell body, the adapter having a first end, distal to the spring element, and a second end, opposite the first end, proximal to the spring element, the adapter having an unloaded disposition and a loaded, depressed disposition, in which, optionally, the second end is depressed with respect to the first end; (c) at least one strain-sensing gage, bonded to the spring element, the strain-sensing gage adapted to measure a strain in the spring element; and (d) an at least two-dimensional flexural member having at least a second cutout window, the second cutout window being transversely disposed through the long dimension of the body, the flexural member being mechanically associated with the spring element, the flexural member disposed along a flexural longitudinal section of the load cell body that is defined by a length of the second cutout window along the long dimension, the flexural member being distally disposed, with respect to the spring element, distally along the long dimension of the body; the spring element adapted such that responsive to a downward force exerted on the adapter, the beams assume a primary double-bending configuration having an at least partial double-bending behavior; the adapter disposed in mechanical relation to the flexural member such that, in the loaded disposition of the adapter, the flexural member assumes a secondary double-bending configuration, having an at least partial double-bending behavior; wherein optionally, the load receiving position of the adapter is longitudinally positioned within the flexural longitudinal section of the load cell body; and wherein optionally, the adapter has an anchored end distal to the flexural member, and an adaptive end proximal to the flexural member. 
         [0006]    According to yet another aspect of the present invention there is provided a load cell assembly, including: (a) an adapter adapted to receive a vertical load, and having an unloaded disposition and a loaded disposition; (b) a load cell body including a spring element having a first cutout window at least partially defined by a top beam and a bottom beam, the window transversely disposed through the body, the spring element adapted such that responsive to a downward force exerted on a top face of the adapter, the beams assume a primary double-bending configuration having an at least partial double-bending behavior; (c) at least one strain-sensing gage, bonded to the spring element, the strain-sensing gage adapted to measure a strain in the spring element; (d) an at least two-dimensional flexural member having at least a second cutout window, at least a portion of the second cutout window being transversely disposed through the body; (e) a weighing platform; and (f) a base; the load cell body disposed between the platform and the base, the body secured to the platform at a first position along a length of the body, and secured to the base at a second position along the length. 
         [0007]    According to further features in the described preferred embodiments, the adapter has an unloaded disposition and a loaded, depressed disposition, in which the second end is depressed with respect to the first end. 
         [0008]    According to still further features in the described preferred embodiments, the load receiving position of the adapter is longitudinally positioned within the flexural longitudinal section of the load cell body. 
         [0009]    According to still further features in the described preferred embodiments, the adapter has an anchored end distal to the flexural member, and an adaptive end proximal to the flexural member. 
         [0010]    According to still further features in the described preferred embodiments, the adapter and the flexural member are integral with the load cell body. 
         [0011]    According to still further features in the described preferred embodiments, the load cell body is a monolithic load cell body integrally including the spring element and the flexural member, and optionally, the adapter. 
         [0012]    According to still further features in the described preferred embodiments, the load cell body has, along a longitudinal axis thereof, a first adaptive end and an anchored region, the spring element being longitudinally disposed distal to the region, towards the adaptive end; and the flexural member being disposed between the spring element and the adaptive end. 
         [0013]    According to still further features in the described preferred embodiments, a height of the load cell body or the double load cell body is at most 30 mm, at most 25 mm, at most 20 mm, at most 15 mm, at most 14 mm, at most 13 mm, or at most 12.5 mm. 
         [0014]    According to still further features in the described preferred embodiments, a top surface of adapter, in the unloaded disposition, is at most 6 mm, at most 5 mm, at most 4 mm, at most 3 mm, at most 2 mm, or at most 1 mm above a top surface of the flexural member mechanically associated with the adapter. 
         [0015]    According to still further features in the described preferred embodiments, the secondary double-bending configuration improves the partial double-bending behavior of the spring element. 
         [0016]    According to still further features in the described preferred embodiments, the secondary double-bending configuration at least partially compensates for a parasitic mode of the primary double bending configuration. 
         [0017]    According to still further features in the described preferred embodiments, the adapter has a longitudinal length La between the first and second ends of the adapter, and the load receiving position is disposed on an inner half of La. 
         [0018]    According to still further features in the described preferred embodiments, the load receiving position is disposed on an inner third or on an inner quarter of the longitudinal length La. 
         [0019]    According to still further features in the described preferred embodiments, the load receiving position is disposed on an inner half of the length of the second cutout window. 
         [0020]    According to still further features in the described preferred embodiments, the load receiving position is disposed on an inner third or on an inner quarter of the length of the second cutout window. 
         [0021]    According to still further features in the described preferred embodiments, the load receiving element is disposed within an area defined by a projection from a top side of the load cell body on the flexural member. 
         [0022]    According to still further features in the described preferred embodiments, wherein, in the loaded disposition, the load receiving element is disposed or at least partially disposed within a hollow volume of the flexural member. 
         [0023]    According to still further features in the described preferred embodiments, the adapter disposed with respect to the flexural member such that in the loaded disposition, a top plane or face of the adapter is depressed with respect to a top plane or face of the flexure member. 
         [0024]    According to still further features in the described preferred embodiments, the second cutout window includes a plurality of windows, the windows optionally disposed one on top of another. 
         [0025]    According to still further features in the described preferred embodiments, the plurality of windows has an average length L avg , a maximum dimensionless length deviation of any of the windows from L avg , being defined by: 
         [0000]      |L i −L avg |/L avg ,
 
         [0000]    L i  being a particular length of any of the windows; the maximum dimensionless length deviation being less than 0.2, less than 0.15, less than 0.10, less than 0.07, less than 0.05, less than 0.03, less than 0.02, less than 0.015, less than 0.01, or less than 0.005. 
         [0026]    According to still further features in the described preferred embodiments, the load cell body is a monolithic double load cell body integrally including the spring element and the flexural member of each of the assemblies. 
         [0027]    According to still further features in the described preferred embodiments, the monolithic double load cell body integrally includes the adapter of each of the assemblies. 
         [0028]    According to still further features in the described preferred embodiments, the assembly further includes a weighing platform disposed on a top face of the load cell body or the double load cell body, and a base disposed underneath the load cell body or the double load cell body. 
         [0029]    According to still further features in the described preferred embodiments, a total height of the platform, the load cell body or the double load cell body, and the base, in an assembled configuration, is at most 40 mm, at most 35 mm, at most 30 mm, at most 25 mm, at most 22 mm, or at most 20 mm. 
         [0030]    According to still further features in the described preferred embodiments, a total height of the platform, the load cell body or the double load cell body, and the base, in an assembled configuration, is at most 5 mm, at most 7.5 mm, at most 10 mm, at most 12 mm, at most 15 mm, at most 18 mm, or at most 20 mm more than a height of the load cell body or the double load cell body. 
         [0031]    According to still further features in the described preferred embodiments, the assembly is adapted to weigh, in a single weighing, at least one item having a total weight of up to 40 kg, up to 35 kg, up to 30 kg, up to 25 kg, up to 20 kg, or up to 15 kg. 
         [0032]    According to still further features in the described preferred embodiments, the assembly provides a weighing accuracy of at least 1/3000 divisions for weighing items having a weight within a range of 50 grams to 15,000 grams. 
         [0033]    According to still further features in the described preferred embodiments, the double load cell body is centrally anchored to the base. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Throughout the drawings, like-referenced characters are used to designate like elements. 
           [0035]    In the drawings: 
           [0036]      FIG. 1A  is a simplified perspective view of a prior art load cell assembly; 
           [0037]      FIG. 1B  is a schematic side view of the load cell assembly of  FIG. 1A , with a partial cross-sectional view at the left end of the assembly; 
           [0038]      FIG. 1C  is a transverse cross-sectional view of the load cell assembly of  FIG. 1A , taken along the A-A plane shown in  FIG. 1B ; 
           [0039]      FIG. 1D  is a transverse cross-sectional view of the load cell assembly of  FIG. 1A , taken along the B-B plane shown in  FIG. 1B ; 
           [0040]      FIG. 1E  is a schematic top view of the load cell assembly of  FIG. 1A ;  FIG. 1F  is a conventional schematic diagram of the strain gage electronics; 
           [0041]      FIG. 2A  is a perspective view of a double ended bending beam having an adapter disposed generally within an integral two-dimensional flexure, according to an embodiment of the present invention; 
           [0042]      FIG. 2B  is an exemplary static nodal stress plot showing a vertical deflection of the flexure arrangement and the load cell arrangement in one embodiment of the load cell assembly of the present invention; 
           [0043]      FIG. 2C  is an exemplary static nodal stress plot showing a horizontal deflection of the flexure arrangement and the load cell arrangement in one embodiment of the load cell assembly of the present invention; 
           [0044]      FIG. 2D  is a block diagram of a weighing scale or load cell assembly, according to one embodiment of the present invention; and 
           [0045]      FIG. 3  is an exploded view of a low-profile load cell assembly, according to one embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0046]    The principles and operation of the low-profile load cell assembly according to the present invention may be better understood with reference to the drawings and the accompanying description. 
         [0047]    Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. 
         [0048]    Load cells with low profiles may have a small signal and therefore limitations in the total weight to be measured and due to the inherent sensitivity of load cells, there may be noise and an unacceptable settling time in the use of such devices. The current invention resolves or appreciably reduces parasitic noise issues with low profile load cells and enables measurements with high accuracy. 
         [0049]    As used herein in the specification and in the claims section that follows, the term “spring element”, and the like, refers to a spring unit having one or more strain gages associated therewith. As shown in the figures and described herein, the spring element is disposed along a longitudinal section of the load cell body that is defined by a length of the cutout window of the spring element along the long dimension of the load cell body. The at least one strain gage associated with the spring element is longitudinally positioned within this longitudinal section of the load cell body. 
         [0050]    As used herein in the specification and in the claims section that follows, the term “flexural member”, “flexure”, and the like, refers to a spring element that is completely devoid of strain gages. Referring now to the drawings,  FIG. 1A  is a simplified perspective view of a load cell and flexure assembly  100  (also termed load cell assembly) according to my previous patent publication no. WO/2013/164675, assigned to Shekel Scales (2008) Ltd.  FIG. 1B  provides a schematic side view of the load cell assembly of  FIG. 1A , with a partial cross-sectional view at the left end of the assembly. Transverse cross-sectional views are provided in  FIG. 1C  (along the A-A line) and  FIG. 1D  (along the B-B line). 
         [0051]    A load cell body  125  may be made from a block of load cell quality metal or alloy. Referring collectively to  FIGS. 1A-1D , at least one transverse cutout or cutout window  110  is disposed in a side of load cell body  125 , to form bending beams above and below the cutout. These beams and cutout  110  form a spring element  107  of load cell body  125 . The beams are held in fixed parallel relationship by end blocks  112 ,  114  on both ends of load cell body  125 . Load cell arrangement  105  may include strain-sensing gages  120  adapted and positioned to measure the strains caused by a force applied to the top of the (“free” or “adaptive” side of) load cell body  125 . When a vertical load acts on a free end (i.e., an end unsupported by the base, as shown in  FIG. 2 )  130  of load cell body  125 , the load cell body undergoes a slight deflection or distortion, with the bending beams assuming a double-bending configuration having an at least partial, and typically primarily or substantially, double-bending behavior. The distortion is measurably sensed by strain gages  120 . 
         [0052]    The load cell body may also have a hole, threaded hole, or receiving element (not shown) for receiving or connecting to a base or base element of the weighing system. Towards free end  130  of the load cell body, an adapter  102  disposed on a top face of load cell body  125  may have one or more hole, threaded hole, or receiving element  104  for receiving or connecting to a platform of the weighing system. 
         [0053]    Load cell and flexure assembly  100  may also have at least one transverse cutout or cutout “window”  150  formed in the side of the load cell body, in lateral position with respect to the transverse cutout(s) associated with the strain gages  120 . In  FIGS. 1A, 1B, and 1D  are shown three such windows, disposed one on top of the other. The windows may be of a substantially rectangular profile. The ends of the windows may have a rounded or hemi-circular profile, substantially as shown. 
         [0054]    Windows  150  may advantageously provide additional flexibility to the load cell body, and absorb excessive impact delivered to the body. Thus, windows  150  may form or partially form a flexure or shock-absorbing arrangement  175 . Thus, flexure or shock-absorbing arrangement  175  is integral with load cell body  125  (e.g., both are disposed within a monolithic load cell body such as a monolithic block of alloy, aluminum metal, or aluminum-containing alloy suitable for use as a load cell body), within load cell and flexure assembly  100 . 
         [0055]    Windows  150  may be disposed in the proximal side of the load cell body, with respect to the free end  130  of the load cell body. In other words, windows  150  may be disposed longitudinally in-between transverse cutout  110  and free end  130 . 
         [0056]      FIG. 1E  provides a schematic top view of the load cell assembly of  FIG. 1A , showing two strain sensing gages  120  disposed on a top surface of the load cell body. 
         [0057]      FIG. 1F  provides a conventional schematic diagram of the strain gage electronics, which may be used in, or with, the load cell assemblies and weighing modules of the present invention. The load cell system may further include a processing unit, such as a central processing unit (CPU). The processing unit may be configured to receive the load or strain signals (e.g., from 4 strain gages SG1-SG4) from each particular load cell and to produce a weight indication based on the load signals, as is known to those of ordinary skill in the art. 
         [0058]      FIG. 2A  is a perspective view showing a top and side of a double ended bending beam load cell assembly  500 , including first and second spring elements  505 , (at least) first and second integral two-dimensional flexures (or flexural members)  510 A and  510 B, and first and second adapters  520 A and  520 B, according to an exemplary embodiment of the present invention. Load cell assembly  500  includes, along a longitudinal axis thereof, two adaptive ends and a central anchored region, with first and second spring elements  505  being longitudinally disposed distal to the anchored region, towards each of the adaptive ends; and first and second flexural members  510 A and  510 B being disposed between respective spring elements and respective adaptive ends. Two-dimensional flexures (or flexural members)  510 A and  510 B, each have at least one cutout window transversely disposed through a load cell body  550 . 
         [0059]    A flexural longitudinal section of the load cell body may be defined, for each flexural member  510 A and  510 B, by a length (i.e., maximum length) of the at least one cutout window. It must be emphasized that load cell assembly  500  may be constructed as a single ended bending beam, or as a pair of single ended bending beams. In the case of a single ended beam structure, the load cell body may have, along a longitudinal axis thereof, an adaptive end and an anchored region, with a spring element being longitudinally disposed distal to the anchored region, towards the adaptive end, and the flexural member being disposed between the spring element and the adaptive end. 
         [0060]    Adapter  520 A, which, in similar fashion to other load cell body adapters described hereinabove, may be adapted to receive vertical (and optionally, horizontal forces) from a weighing platform. In the exemplary embodiment provided in  FIG. 2A , adapter  520 A is largely disposed within the hollow volume of flexure  510 A. Significantly, the load receiving element (such as hole or screw hole  524 ) through which adapter  520 A receives forces from a weight or from weighing platform (see  FIG. 3  and the associated description), may be disposed within the top profile of flexure  510 A (or within an area defined by a projection from a top side of load cell assembly  500  on flexure  510 A), and in the direction of the longitudinal center of load cell body  550 . In the exemplary embodiment provided in  FIG. 2A , adapter  520 A has a longitudinal length La between a first end of adapter  520 A (a first end  562  of load cell body  550 ) and the opposite end  564  of that adapter, and screw hole  524  is disposed on the inner half of length La. In some cases, screw hole  524  is disposed on the inner third of length La, or on the inner quarter of length La. In some embodiments, the load receiving element or position is disposed on an inner half, inner third or inner quarter of the length of the at least one cutout window. 
         [0061]    The second dimension of the integral two-dimensional flexure  510 , including top-oriented cutout  525  around adapter  520 , is adapted to serve as a horizontal shock-absorbing mechanism for the relatively delicate load cell spring element  505 . 
         [0062]      FIG. 2B  is an exemplary static nodal stress plot showing a vertical deflection of the flexure arrangement and the load cell arrangement in one embodiment of the load cell assembly of the present invention. The vertical displacement of adapter  520  relative to the flexure  510 A is shown. 
         [0063]      FIG. 2C  is an exemplary static nodal stress plot showing a horizontal deflection of the flexure arrangement and the load cell arrangement in one embodiment of the load cell assembly of the present invention. The horizontal displacement of adapter  520  relative to the flexure  510 A is shown. 
         [0064]    One of ordinary skill in the art will readily appreciate that the responses to vertical and horizontal forces depicted in  FIGS. 2B and 2C , respectively, also apply to single ended bending beams of the present invention. In these responses, the bending beams assume a double-bending configuration having an at least partial, and typically primarily or substantially solely, double-bending behavior. 
         [0065]      FIG. 2D  is a block diagram of a weighing scale or load cell assembly. An object to be weighed is placed on the top plate of a weighing scale. During operation, vertical forces applied to the top plate are transferred via adapters (e.g., adapter  520 ) to load cell bodies (e.g., load cell body  550 ) configured to measure vertical forces. Electrical signals from the load cell strain gages are transmitted to a processor. The processor processes the signals to produce weight information, and may then transmit the weight information to a display device. A processor port may also be available for maintenance, calibration or firmware updates. 
         [0066]      FIG. 3  is an exploded view of an exemplary weighing scale or load cell assembly  300 , according to one embodiment of the present invention. Weighing scale  300  may be a low-profile weighing scale, substantially as shown. Weighing scale  300  may include at least one load cell assembly such as double ended bending beam load cell assembly  305 , and a solid top plate  320  disposed above double ended bending beam load cell assembly  305 , and connected thereto via adapters  330 . A base  310 , typically having a broad, flat bottom adapted to rest flush against a flooring, supports top plate  320  and load cell assembly  305 , and anchors load cell assembly  305  via intervening shims  325  (to base  310 ) using bolts  360 . 
         [0067]    Exemplary low-profile weighing scale  300  may advantageously employ two double ended bending beam load cell assemblies  305 . 
         [0068]    Double ended bending beam load cell assemblies  305  may be similar or substantially identical to double ended bending beam load cell assembly  500 , provided in  FIG. 2A , and described hereinabove. 
         [0069]    Load cell assemblies  305  may have monolithic double load cell bodies integrally including two spring elements and two at least two-dimensional flexural members. At each end of each of the load cell bodies, adapters  330  may be disposed at a top face of the load cell bodies, and are adapted to receive a vertical load transmitted from top plate  320 . Washers  390  may be placed between adapters  330  and top plate  320  to ensure that the weight is transferred solely to adapters  330 , and not to other locations on the load cell body. 
         [0070]    In the exemplary embodiment provided in  FIG. 3 , overhanging vertical walls  340  of top plate  320  may fit over generally upright walls  350  of base  310 . 
         [0071]    In one embodiment, the adapter may be machined to an unloaded equilibrium height above the top surface of the flexural member or top of the load cell body. Typically, the adapter may protrude above the top surface of the flexural member by at most 6 mm, at most 5 mm, at most 4 mm, at most 3 mm, at most 2 mm, or at most 1 mm. 
         [0072]    The overall height of weighing scale  300 , in an assembled configuration (including top plate  320  and base  310 ), may be at most 5 mm, at most 7.5 mm, at most 10 mm, at most 12 mm, at most 15 mm, at most 18 mm, or at most 20 mm more than the height of the load cell body or load cell assembly  305 . 
         [0073]    The height of the load cell body or load cell assembly  305  may be the dominant contributor to the height of weighing scale  300 . The height of the load cell body or load cell assembly  305  may be at most 30 mm, at most 25 mm, at most 20 mm, at most 15 mm, or at most 12.5 mm. The total height of weighing scale  300 , in assembled form, may accordingly be at most 40 mm, at most 35 mm, at most 30 mm, at most 25 mm, at most 22 mm, at most 20 mm, or at most 17.5 mm. 
         [0074]    The height of the load cell assembly  305  may be at least 6 mm or at least 7 mm, and more typically, at least 8 mm, at least 9 mm, or at least 10 mm. 
         [0075]    Weighing scales employing load cell assemblies having vertical dimensions as described above may weigh, in a single weighing, at least one item having a total weight of up to 40 kg, up to 35 kg, up to 30 kg, up to 25 kg, up to 20 kg, or up to 15 kg. The weighing accuracy may be at least 1/3000 divisions, corresponding to a deviation of 0.03% from the actual weight for weighing items having a weight within a range of 50 grams to 15,000 grams. 
         [0076]    Referring back to  FIG. 1B , the height of transverse cutout  110  is defined as H 3 . The height of flexure arrangement  175  extending above the top of transverse cutout  110  is defined as H 1 , and the height of flexure arrangement  175  extending below the bottom of transverse cutout  110  is defined as H 2 . The minimum value of each of H 1  and H 2  is zero (i.e., H 1  and H 2  do not assume negative values). 
         [0077]    With regard to the load cell assemblies of the present invention, the inventor has found that it may be highly advantageous for the heights H 1 , H 2 , and H 3  to satisfy the relationship: 
         [0000]      ( H   1   +H   2 )/ H   3 &lt;0.50. 
         [0000]    It may be of further advantage for (H 1 +H 2 )/H 3  to be less than 0.40, less than 0.30, less than 0.25, less than 0.20, less than 0.15, less than 0.10, or less than 0.05. In some cases it may be of further advantage for (H 1 +H 2 )/H 3  to be substantially zero. This structural relationship may enable various low-profile scale modules, and may also enable facile retrofitting of the inventive load cell arrangement in existing weighing scales and weighing scale designs. 
         [0078]    Referring back to  FIGS. 2A , side windows or cutouts  511 ,  512  of flexural members  510 A and  510 B, may have an average length L avg . A maximum dimensionless length deviation from L avg , of any of windows  511 ,  512 , may be defined by: 
         [0000]      |L i −L avg |/L avg ,
 
         [0000]    where L i  is a particular length of any of windows  511 ,  512 . The maximum dimensionless length deviation may be less than 0.2, less than 0.15, less than 0.10, less than 0.07, less than 0.05, less than 0.03, less than 0.02, less than 0.015, less than 0.01, or less than 0.005. 
         [0079]    In the embodiment provided in  FIGS. 2A-2C , load cell assembly  500  may be adapted, when secured within a weighing module as described in  FIG. 3 , such that a vertical impact (e.g., an object that is slammed down with great force onto the weighing platform) acts upon one-dimensional flexures  510 A,  510 B, while load cell spring elements  505  remain largely or substantially completely unaffected. Thus, flexures  510 A,  510 B may serve as a vertical shock-protection mechanism for the relatively delicate load cell spring elements  505 . Flexures  510 A,  510 B may be designed and adapted to exhibit, at a maximum load capacity for the load cell, a vertical deflection that is at most 3 times, at most 2 times, at most 1.5 times, at most 1.0 times, or at most 0.8 times, the vertical deflection exhibited by the load cell itself (without the flexure), at that maximum capacity. 
         [0080]    It will be appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. 
         [0081]    Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.