Abstract:
As a weighing device which can not only make water and dust less likely to reach the sensor unit, but also simply discharge water having reached that position if any, and which further can improve the maintenance workability of water-washing of the sensor unit, an electronic balance includes a weighing pan, a load cell that measures a load of a measuring object placed on the weighing pan, and a scale main body case that supports the load cell. The load cell is disposed outside and over the scale main body case, a cylindrical transparent cover that covers the whole side face of the load cell is integrally provided for the weighing pan, and the lower end of the transparent cover is disposed with a clearance over an upper face of the scale main body case.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a weighing device excellent particularly in drainability and maintainability. 
       BACKGROUND ART 
       [0002]    Electronic balances are widely known as weighing devices. The electronic balances are devices that convert loads applied to weighing pans into electrical signals by sensor units such as load cells, and display the same as load values on display units, and have been used in various fields such as the food industry and the manufacturing industry. This type of electronic balance, commonly, has a sensor unit stored in the interior of a scale main body case and has a weighing pan disposed outside and over the scale main body case. Moreover, the weighing pan and sensor unit are coupled via an opening formed in an upper face of the scale main body case. Therefore, in such electronic balances, water and dust may enter from the opening in the upper face of the scale main body case. 
         [0003]    To cope with such problems, as solutions thereto, Patent Literature 1 proposes a weighing device in which a diaphragm is provided for the opening in the upper face of the scale main body case and which prevents water and dust from entering into the scale main body case by the diaphragm, and Patent Literature 2 proposes a weighing device in which circular cylindrical drainers are provided on a lower side of the weighing pan and which prevents water from entering into the scale main body case by the drainers. 
       CITATION LIST 
     Patent Literature 
       [0004]    Patent Literature 1: Japanese Published Unexamined Patent Application No. 2005-291765 
         [0005]    Patent Literature 2: Japanese Published Examined Utility Model Application No. S61-36897 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    However, in the above-described weighing devices, for both of which waterproofing and/or dustproofing is performed for a scale main body case after a sensor unit is stored in the interior of the scale main body case, when water and/or dust once enter into the scale main body case and reach the position of the sensor unit, discharge of the same cannot be easily performed. 
         [0007]    Also, in the above-described weighing devices, the sensor unit is stored in the scale main body case, and the sensor unit cannot simply be externally exposed. Therefore, the situation is not favorable in terms of maintenance workability such as water-washing of the sensor unit. 
         [0008]    The present invention has been made in view of such circumstances, and an object thereof is to provide a weighing device which can not only make water and dust less likely to reach the sensor unit, but even if water reaches the position of the sensor unit, can also simply discharge the water, and which further can improve the maintenance workability of water-washing and the like of the sensor unit. 
       Solution to Problem 
       [0009]    In order to achieve the above-mentioned object, a first aspect of the invention is a weighing device including a weighing pan on which a measuring object is placed, a sensor unit that measures a load applied to the weighing pan, and a scale main body case that supports the sensor unit, in which the sensor unit is disposed outside as well as over the scale main body case, for the weighing pan, a cylindrical cover that covers a whole side face of the sensor unit is integrally provided, and a lower end of the cover is separated upward with respect to an upper face of the scale main body case. 
         [0010]    According to the present invention, covering the periphery of the sensor unit with a cylindrical cover allows the cover to serve a windproofing role, while even if water reaches the position of the sensor unit, because the lower end of the cover is separated upward with respect to the upper face of the scale main body case, allows draining the water through a section between the lower end of the cover and the upper face of the scale main body case by causing the same to run on the upper face of the scale main body case. 
         [0011]    Also, according to the present invention, because the sensor unit is disposed outside the scale main body case, water-washing of the sensor unit can be performed. 
         [0012]    A second aspect of the invention is the first aspect of the invention, in which on the upper face of the scale main body case, a drain guide face using an upper face outer edge of said scale main body case as a downstream end is formed, and the drain guide face is inclined so as to become higher toward an upstream side than at the downstream side. According to the present invention, drainability on the upper face of the scale main body case can be further improved by use of the inclination of the drain guide face. 
         [0013]    A third aspect of the invention is the first or second aspect of the invention, in which on the upper face of the scale main body case, a plurality of projecting portions that project upward are provided outside of the cover, and the respective projecting portions have their respective upper ends disposed opposite to the weighing pan, and make contact with said weighing pan to serve as stoppers when an overload is applied to said weighing pan. According to the present invention, the scale main body case is provided with a plurality of projecting portions, and the respective projecting portions act as anti-overloading stoppers. Because the respective projecting portions are disposed outside of the cover, blocking of drainage by the projecting portion as in the case where the projecting portion is disposed in the interior of the cover does not occur, and drainability can be maintained while overloading can be prevented. 
         [0014]    A fourth aspect of the invention is the third aspect of the invention, in which at least one of the plurality of projecting portions is a display unit that displays a weighed value. According to the present invention, the display unit can be used as an anti-overloading stopper. 
         [0015]    A fifth aspect of the invention is the third or fourth aspect of the invention, in which at least one of the plurality of projecting portions is disposed in a rear face corner portion of the scale main body case. 
         [0016]    A sixth aspect of the invention is any one of the first to fifth aspects of the invention, in which on the upper face of the scale main body case, at a position to attach the sensor unit, an upwardly projecting base is provided, and the sensor unit is attached on the base. According to the present invention, because a base is provided on the upper face of the scale main body case and a sensor unit is attached to the base, the sensor unit can be disposed at a position raised further than the upper face of the scale main body case. Thus, even when wind enters from the section between the upper face of the scale main body case and the lower end of the cover, the wind can be made less likely to directly hit the sensor unit, so that adhesion of water and dust to the sensor unit can be further suppressed. Also, according to the present invention, because the sensor unit is disposed at a position raised further than the upper face of the scale main body case, water having reached the position of the sensor unit flows down onto the upper face of the scale main body case from the high positon, and retention of water in the position of the sensor unit can be prevented. 
       Advantageous Effects of Invention 
       [0017]    According to the present invention, the cover can be made to serve a windproofing role, while even if water reaches the position of the sensor unit, the water can be drained through a section between the lower end of the cover and the upper face of the scale main body case, and therefore, not only can water and dust be made less likely to reach the sensor unit, but even if water reaches the position of the sensor unit, the water can also be simply discharged. 
         [0018]    Also, according to the present invention, because the sensor unit can be washed with water, the maintenance workability can be improved. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0019]      FIG. 1  is a front perspective view showing an electronic balance according to a first embodiment of the present invention. 
           [0020]      FIG. 2  is a rear perspective view of the same electronic balance. 
           [0021]      FIG. 3  is a longitudinal sectional view of the same electronic balance (a sectional view taken along a line III-III shown in  FIG. 1 ). 
           [0022]      FIG. 4  is a longitudinal sectional view of the same electronic balance (a sectional view taken along a line IV-IV shown in  FIG. 3 ). 
           [0023]      FIG. 5  is a cross-sectional view of the same electronic balance (a sectional view taken along a line V-V shown in  FIG. 1 ). 
           [0024]      FIG. 6  is a longitudinal sectional view showing an electronic balance according to a second embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0025]    Hereinafter, embodiments of the present invention will be described based on the drawings. 
         [0026]      FIG. 1  to  FIG. 5  show an electronic balance  10 A according to a first embodiment of the present invention. 
         [0027]    The electronic balance  10 A, as shown in  FIG. 1  to  FIG. 5 , includes a display unit  50  at its front face side (front side). The display unit  50  is disposed standing with a hollow longitudinal wall form, and a liquid crystal screen  50   a  is provided on a front face of the display unit  50 . In the display unit  50 , an electronic circuit board  40  that arithmetically processes an output detected in a load cell  20  to be described later and controls data to be displayed on the liquid crystal screen  50   a  is disposed at a back side of the liquid crystal display  50   a.    
         [0028]    At a rear face of the above-mentioned display unit  50 , as shown in  FIG. 1  to  FIG. 5 , to its lower region, a synthetic resin-made scale main body case  12  formed in a substantially rectangular shape in a plan view is integrally connected. The scale main body case  12  maintains a horizontal width that is identical to the horizontal width of the display unit  50  while extending rearward, and its interior continues into the display unit  50 . 
         [0029]    The scale main body case  12  has an upper face  12   a . The scale main body case upper face  12   a  is curved so as to be the highest at a substantially central portion and become lower further to the outside (outer edge) than the substantially central portion, and the whole face of the scale main body case upper face  12   a  ranging from its substantially central portion to an outer peripheral edge portion centered on its substantially central portion constitutes an inclined drain guide face  12 A. Therefore, even if water exists on the upper face  12   a  of the scale main body case  12 , the water naturally flows to the outer edge side of the scale main body case upper face  12   a  to be drained to the outside of the scale main body case  12 . Furthermore, in the present embodiment, an inclined face  12 Aa is formed in laterally opposite peripheral edge portions and a rear peripheral edge portion of the scale main body case  12  in order to enhance the above-described draining function, and its inclination angle is greater than that of other parts. 
         [0030]    On the upper face  12   a  of the scale main body case  12 , as shown in  FIG. 1 ,  FIG. 2 ,  FIG. 4 , and  FIG. 5 , hollow projecting portions  56  are formed in right and left corner portions at a rear side (rear face side) of the scale main body case  12 , respectively. The hollow projecting portions  56  are formed such that their upper ends are identical in height to the upper end of the display unit  50 , and over the upper face  12   a  of the scale main body case  12 , a load cell housing chamber S surrounded by the hollow display unit  50  and the pair of right and left hollow projecting portions  56  and  56  is formed. Outside faces of the hollow projecting portions  56  are formed to be flush with outside faces of the scale main body case  12 , so that unification in the appearance design from side and behind of the electronic balance  10 A is achieved. 
         [0031]    In the scale main body case  12 , as shown in  FIG. 3 , a battery housing chamber  17  that houses dry cell batteries  18  serving as a power supply is defined. The battery housing chamber  17  is opened at a bottom face side of the case  12 , and by removing a cover  17   a  assembled on its opening portion, replacement of the dry cell batteries  18  can be performed. 
         [0032]    On the upper face  12   a  of the above-described scale main body case  12 , as shown in  FIG. 2  to  FIG. 5 , a load cell  20  is disposed. The load cell  20  is fixed at its fixed-side end portion  20   a  to the upper face  12   a  of the scale main body case  12  by use of fixing screws  27   a  and  27   b , and accordingly, the load cell  20  horizontally extends in the lateral direction (in  FIG. 3 , in the right and left direction) with a cantilevered form. 
         [0033]    The load cell  20  includes a metallic rectangular block-like elastic body  22  provided with a spectacle-shaped side face through-hole  23  that define elastic portions. Strain gauges  24  are stuck on an upper face of upper elastic portions  22   a  of the elastic body  22 , and on an upper face of the elastic body  22 , a flexible printed circuit board  24   a  that is electrically connected with the strain gauge  24  to constitute a bridge circuit such as a resistor for output compensation is stuck. In the fixed-side end portion  20   a  of the load cell  20 , a vertical through-hole  26  is formed (refer to  FIG. 3  and  FIG. 4 ). The vertical through-hole  26  communicates with the interior of the case  12  via a vertical through-hole  14  provided in an upper face wall of the scale main body case  12 , and through the vertical through-holes  26  and  14 , an electrical wiring  25  that is led out of the above-described flexible printed circuit board  24   a  is inserted. The electrical wiring  25 , after being led into the scale main body case  12  in a manner penetrating through the vertical through-holes  26  and  14 , is connected to the electronic circuit board  40  in the above-mentioned display unit  50  via a relay circuit board  16  (refer to  FIG. 4 ) in the case  12 . 
         [0034]    For such an elastic body  22 , a silicone insulating coating  28   a  is provided at its upper face side, and in the vertical through-hole  26 , a silicone material  28   b  serving as a sealing means is filled. The silicone insulating coating  28   a  covers the electrical components (strain gauges  24  and flexible printed circuit board  24   a ) and the electrical wiring  25  to ensure insulation and waterproofing in conductive portions of the electrical components, and the silicone material  28 b reliably seals the interior of the scale main body case  12 . 
         [0035]    In the present embodiment, because the vertical through-hole  26  for inserting the electrical wiring  25  therethrough is opened at the upper face side of the elastic body  22  on which the electrical components such as the strain gauges  24  are mounted, the electrical wiring  25  that connects (the electrical components mounted on) the load cell  20  and the electronic circuit board  40  disposed in the scale main body case  12  fits in without sticking out to the right and left from the upper face of the elastic body  22 . Therefore, it becomes easy to form the insulating coating  28   a  for waterproofing on the conductive portions of the electrical components exposed on the upper face of the elastic body  22 , and also, when carrying the load cell  20  or assembling as an electronic balance, there is no longer a possibility that the insulating coating  28   a  is stripped by the electrical wiring  25  being caught on something. 
         [0036]    To a movable-side end portion  20   b  of the above-mentioned load cell  20 , as shown in  FIG. 3  and  FIG. 4 , a weighingpan  30  on which a measuring object is placed is coupled. The weighing pan  30  is composed of a transparent synthetic resin-made pan main body  32  to be coupled to the movable-side end portion  20   b  of the load cell  20  and a synthetic resin-made pan cover  34  to cover an upper face side of the pan main body  32 . 
         [0037]    The pan main body  32  is formed by integrally molding a substantially rectangular-shaped top panel portion  35  and a cylindrical-shaped transparent cover  36 . The top panel portion  35  is coupled using a fixing screw  31 C to a coupling plate  29  that is fixed to an upper face of the movable-side end portion  20   b  of the load cell  20  by use of fixing screws  31   a  and  31   b . The top panel portion  35  is formed in substantially the same shape as the pan cover  34 , and the pan cover  34  is freely attatchably and detachably fitted onto the top panel portion  35 . 
         [0038]    The transparent cover  36  is, as shown in  FIG. 2  to  FIG. 5 , extended downward from a lower face of the top panel portion  35 . The transparent cover  36 , in a plan view, occupies a smaller proportion than that of the top panel portion  35 , and is formed in a convex shape as a whole. Therefore, the top panel portion  35  is in a state of sticking out to the outside, with respect to the transparent cover  36 , at one side of its near side and both corner portions of its rear face side (rear side), and in a region under this part, the above-mentioned display unit  50  and the above-mentioned hollow projecting portions  56  are disposed (refer to  FIG. 5 ). The display portion  50  and the hollow projecting portions  56  are disposed outside of the transparent cover  36 , and their respective upper ends are disposed opposite to the top panel portion  35  and with a predetermined clearance in the vertical direction. Thus, when an overload is applied to the weighing pan  30 , the upper end of the display unit  50  and the upper ends of the hollow projecting portions  56  come into contact with the top panel portion  35  of the pan main body  32 , so that the overload is prevented from acting on the load cell  20 . 
         [0039]    The transparent cover  36 , as shown in  FIG. 2  to  FIG. 5 , surrounds with a clearance the periphery of the load cell  20  arranged in a load cell arrangement space S. The lower end of the transparent cover  36  is, over the scale main body case upper face  12   a , disposed with a predetermined clearance  51  with respect to the upper face  12   a  of the scale main body case  12 , and the clearance  51  is formed slightly greater than a clearance between the foregoing display unit  50  and the top panel portion  35  and the clearance between the upper end of the hollow projecting portion  56  and the top panel portion  35 . Therefore, at the time of overloading, the lower end of the transparent cover  36  and the upper face of the scale main body case  12  do not contact, and as described above, the upper end of the display unit  50  and/or the upper ends of the hollow projecting portions  56  come into contact with the top panel portion  35  of the pan main body  32 . 
         [0040]    Next, the operation of the electronic balance  10 A configured as above will be described. 
         [0041]    In the above-described electronic balance  10 A, because the load cell  20  is disposed outside as well as over the scale main body case  12  and the clearance  51  is provided between the transparent cover  36  and the upper face  12   a  of the scale main body case  12 , when a liquid enters the load cell arrangement space S, the liquid flows on the scale main body case upper face  12   a , and is externally drained through the clearance  51  between the transparent cover  36  and the scale main body case upper face  12   a.    
         [0042]    Also, because the upper face  12   a  of the scale main body case  12  is inclined constituting the drain guide face  12 A, even if water exists on the upper face  12   a  of the scale main body case  12 , the water is naturally externally drained. 
         [0043]    Further, because the display unit  50  and the hollow projecting portions  56  are disposed outside of the transparent cover  36 , obstruction in drainage in the interior of the transparent cover  36  as in the case where the display unit  50  and the hollow projecting portions  56  are disposed in the interior of the transparent cover  36  does not occur, and drainage is reliably performed. Therefore, in the electronic balance  10 A, water having entered the load cell arrangement space S can be externally smoothly drained without causing retention in the interior. 
         [0044]    Also, in the electronic balance  10 A, because the cylindrical transparent cover  36  is disposed so as to cover the whole side face of the load cell  20 , the transparent cover  36  acts as windproofing, which enables high-precision weighing. Further, because dust and dirt, etc., can be kept out of the load cell arrangement space S by the transparent cover  36 , contamination of the load cell arrangement space S (peripheral region of the load cell  20 ) can be suppressed. 
         [0045]    Further, in the electronic balance  10 A, because the cylindrical transparent cover  36  is integrally provided for the weighing pan  30 , the transparent cover  36  is removed by only removing the weighing pan  30 , so that the load cell  20  is exposed. Specifically, by removing the pan cover  34  of the weighing pan  30  from the pan main body  32  and removing the fixing screw  31   c  to remove the pan main body  32  integrally with the transparent cover  36 , the load cell arrangement space S as a whole is opened. Because the load cell  20  can thus be simply exposed, in the present embodiment, maintenance such as washing can be easily performed. Furthermore, in the present embodiment, the degree of contamination of the peripheral region of the load cell  20  can be externally visually checked through the transparent cover  36 , and the weighing pan  30  can be removed according to necessity to wash the contamination of the peripheral region of the load cell  20 . 
         [0046]    In the present embodiment, the fixed-side end portion  20   a  of the load cell  20  is fixed at the height position of the upper face  12   a  of the scale main body case  12 , but the present invention is not limited thereto. For example, as shown in  FIG. 6 , a base  13  may be provided on the upper face of the scale main body case  12  to fix the fixed-side end portion  20   a  of the load cell  20  to the base  13 . The base  13  shown in the same figure is formed to be substantially horizontal at the highest position, and the load cell  20  is fixed to this position. Also, an inclined portion  13 A is provided around the base  13 , and the surface of the inclined portion  13 A is provided as an inclined face  13   a  that is lower at the outside than at the inside. When such a base  13  is provided, the load cell  20  becomes hardly visible through the clearance  51  between the transparent cover  36  and the scale main body case upper face  12   a , which allows preventing wind having entered from the clearance  51  from directly hitting the load cell  20 . Also, because the load cell  20  is disposed at the raised position, water in the position of the load cell  20  is reliably drained. 
         [0047]    Although embodiments have been described above, the present invention includes the following modes.
   (1) The shape of the scale main body case upper face  12   a  that constitutes the drain guide face  12 A is not limited to the shape according to the embodiment described above, but suffices with a shape having such an inclined face that water on the scale main body case upper face  12   a  flows to the outside. For example, the whole of the scale main body case upper face  12   a  may be provided as an inclined face that is lowered from the right side to the left side in  FIG. 3 , and may be provided as an inclined face that is the highest at the position to fix the load cell  20  and is gradually lowered toward the outside. Further, the scale main body case  12  may be included only in part, without inclining the whole thereof (the drain guide face  12 A may be formed in a part of the scale main body case upper face  12   a ).   (2) As the load cell  20 , a variety of load cells can be used.   
 
       REFERENCE SIGNS LIST 
       [0050]      10 A Electronic balance (weighing device) 
         [0051]      12  Scale main body case 
         [0052]      12   a  Scale main body case upper face 
         [0053]      12 A Drain guide face 
         [0054]      13  Base 
         [0055]      13 A Base inclined portion 
         [0056]      13   a  Base inclined face 
         [0057]      20  Load cell (sensor unit) 
         [0058]      30  Weighing pan 
         [0059]      32  Pan main body 
         [0060]      34  Pan cover 
         [0061]      36  Transparent cover (cover) 
         [0062]      50  Hollow standing wall-like display unit 
         [0063]      51  Clearance 
         [0064]      56 ,  56 A Hollow projecting portion