Abstract:
An underwater weighing container for measuring specific gravity, requiring relatively a small amount of reference liquids for measurement and offering wide space for mounting specimens to be measured are provided. The underwater weighing container includes a tubular body and a circular bottom plate. The tubular body has openings on both ends One end has an introvert circular rim formed thereon and the other end has a plurality of stoppers attached to the internal surface thereof. The circular bottom plate has a mesh or a porous structure and is inserted between the circular rim and the stoppers. The underwater weighing container is immersed in a reference liquid, and a solid specimen is placed on or inserted underneath the bottom plate. The underwater weighing container is hung by means of a hanging member  13  to measure the weight of the solid specimen and determine the specific gravity.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the priority benefit of Japan application serial no. JP2004-088926, filed on Mar. 25, 2004.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an underwater weighing container and an underwater weighing container unit for receiving a weight of a solid specimen immersed in a reference liquid and a buoyant force exerted thereon. The present invention also relates to an apparatus for measuring a specific gravity of the solid specimen.  
         [0004]     2. Description of the Related Art  
         [0005]     Generally, the commonly employed method for determining a specific gravity of a solid specimen without knowledge of its volume is to weigh the solid specimen in air, measure a weight of the solid specimen immersed in a reference liquid or a buoyant force exerted thereon, and use the obtained values for calculating the relevant specific gravity based on the following equation (1): 
 
Specific Gravity=Weight in Air/(Weight in Air−Weight in Liquid)=Weight in Air/Buoyant Force   Equation (1) 
 
         [0006]     As will be exemplified hereinafter, methods of weighing a solid specimen both in air and in a reference liquid, or measuring a weight of the solid specimen in air and a buoyant force produced by the solid specimen, for calculation of the relevant specific gravity have been applied to a number of conventional apparatus for measuring specific gravity. One such example is a specific gravity measuring apparatus  5 A in  FIG. 8 , wherein a solid specimen  2  is first hung and suspended in air and then placed inside a liquid bath  3  to measure its weight by means of an electronic weighing scale  7 , for determining the specific gravity. As shown in  FIG. 9 , another conventional specific gravity measuring apparatus  5 B has an underwater weighing container  1 A arranged on an electronic weighing scale  7 , allowing the underwater weighing container  1 A to mount a solid specimen  2  thereon in a liquid bath  3 B. With this configuration, after the underwater weighing container  1 A holding the solid specimen  2  is subjected to measurement, the corresponding tare weight is subtracted from the obtained weight to determine specific gravity of the solid specimen  2 . The patent literatures pertaining to these apparatuses for measuring specific gravity are Unexamined Japanese Patent Application Publication Nos. H11-230885 and 2002-243615.  
         [0007]     The aforementioned configurations are employed in the conventional specific gravity measuring apparatus and the underwater weighing containers. However, the method of hanging and suspending the solid specimen  2  as shown in  FIG. 8  is troublesome, due to the need to replace and suspend the solid specimen  2  having different shapes. In the method of providing the underwater weighing container  1 A for measuring the weight of the solid specimen  2 , as shown in  FIG. 9 , the solid specimen  2 , if its specific gravity is lower than that of a reference liquid, will be floating. As representative measures to prevent the solid specimen  2  from floating, a sinker frame  8  as shown in  FIG. 9 , or a lid (not illustrated) may be placed in a reference liquid L. If any such measure is to be implemented, users will be required to insert and remove the sinker frame  8  or to open and close the lid, whenever conducting weight measurement. This method, as illustrated in  FIG. 8 , is inconvenient for users. Depending on whether the solid specimen  2  sinks or floats in the reference liquid L, users will be required to employ a different configuration of the underwater weighing container  1 A. This can increase users&#39; work load for maintenance and management of the apparatus for measuring specific gravity. The amount of the reference liquid L used for the measurement process also increases.  
       SUMMARY OF THE INVENTION  
       [0008]     In consideration of the situation presented heretofore, the present invention is provided. An object of the present invention is to provide an underwater weighing container and a specific gravity measuring apparatus using the same, which can be applied to a solid specimen that may be heavier or lighter than the reference liquid. In addition, the underwater weighing container and the specific gravity measuring apparatus are compact and require relatively a small amount of reference liquid used for the weight measurement.  
         [0009]     In order to accomplish the aforementioned object, the present invention provides an underwater weighing container, equipped with a bottom plate movable both upwardly and downwardly within a given range. Furthermore, the bottom plate is designed to hold a solid specimen on the upper surface thereof and carry its weight thereon if the specific gravity of the solid specimen is higher than that of a reference liquid, or to place the solid specimen underneath the bottom plate for a buoyant force of the specimen to be exerted against the bottom plate if the specific gravity of the solid specimen is lower than that of the liquid.  
         [0010]     In one embodiment of the present invention, the present invention further provides an underwater weighing container unit, comprises an underwater weighing container being arranged at a lower position, a bottom plate capable of moving both upward and downward in a given range, an aerial weighing container arranged at an upper position to carry the weight of a solid specimen in air, and coupling rods to couple with the underwater weighing container and the aerial weighing container.  
         [0011]     Furthermore, apparatus for measuring specific gravity of the present invention comprises the underwater weighing container unit of the present invention, a frame supporting the underwater weighing container unit, and a weight measuring unit, the frame being placed on the weight measuring unit to determine the specific gravity of a solid specimen.  
         [0012]     An underwater weighing container, an underwater weighing container unit and apparatus for measuring specific gravity according to the present invention have the aforementioned configurations, wherein a bottom plate of the underwater weighing container are movable so as to place and hold a solid specimen inside whenever the solid specimen is subjected to measurement in a reference liquid.  
         [0013]     For this reason, they occupy a relatively small space and enable users to effectively reduce the amount of reference liquid used for the measurement process.  
         [0014]     In an underwater weighing container, an underwater weighing container unit and apparatus for measuring specific gravity according to the present invention, the underwater weighing container is equipped with a movable bottom plate. If a solid specimen is heavier than a reference liquid, the solid specimen is placed on the bottom plate and moved downward with the associated bottom plate by their gravity. If the solid specimen is lighter than the reference liquid, the solid specimen is inserted underneath the bottom plate and moved upward with the associated bottom plate by the specimen&#39;s buoyant force. Consequently the solid specimen remains inside the underwater weighing container in any case. Thus, it is possible to reduce the size of underwater weighing container, underwater weighing container unit, apparatus for measuring specific gravity, and a liquid bath used therein, and also to reduce the amount of reference liquids used for measurement. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIGS. 1A and 1B  show a configuration of an underwater weighing container  1 .  FIG. 1A  shows a front elevation view of the underwater weighing container  1 , and  FIG. 1B  shows a cross-sectional side elevation thereof.  
         [0016]      FIGS. 2A and 2B  show cross-sectional front elevation views of the underwater weighing container  1  during use.  FIG. 2A  shows a condition where a solid specimen to be measured is heavier than a reference liquid, and  FIG. 2B  shows the other condition where the solid specimen is lighter than the reference liquid.  
         [0017]      FIGS. 3A and 3B  show a configuration of an underwater weighing container unit  4 .  FIGS. 3A and 3B  are a partial cross-sectional front elevation view and a plan view of the underwater weighing container unit  4 , respectively.  
         [0018]      FIG. 4  shows a partial cross-sectional front elevation view of the underwater weighing container unit  4  during use.  
         [0019]      FIG. 5  shows a perspective view of a specimen mounting unit  6  associated with an example of the present invention.  
         [0020]      FIG. 6A and 6B  show the partial cross-sectional front elevation views of the apparatus for measuring specific gravity during use.  FIG. 6 ( a ) shows a condition where a solid specimen to be measured is heavier than a reference liquid, while  FIG. 6 ( b ) shows the other condition where the solid specimen is lighter than the reference liquid.  
         [0021]      FIG. 7  shows a block diagram of an electronic weighing scale associated with an example of the present invention.  
         [0022]      FIG. 8  is a partial cross-sectional front elevation view showing a configuration of a conventional apparatus for measuring specific gravity.  
         [0023]      FIG. 9  is a partial cross-sectional front elevation view showing a configuration of another conventional apparatus for measuring specific gravity. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     The present invention will be discussed hereinafter in detail in terms of the preferred configurations and functions of an underwater weighing container, an underwater weighing container unit and apparatus for measuring specific gravity according to the present invention with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be obvious, however, to those skilled in art that the present invention may be practiced without these specific details. In other instance, well-known configurations are not shown in detail in order to avoid unnecessary obscurity of the present invention.  
         [0025]      FIGS. 1A and 1B  show a structure of an underwater weighing container  1  according to one embodiment of the present invention.  FIG. 1A  shows a front elevation view of the underwater weighing container  1 , while  FIG. 1B  shows a cross-sectional side elevation view thereof.  
         [0026]     The underwater weighing container  1  comprises a metallic tubular body  11  having openings on both ends, wherein one end of the openings has a circular rim  11   a  produced through such processes as bending and/or welding and the other end of the opening has four stoppers  11   b  on the internal surface, wherein the four stoppers are arranged with each fixed at 90 degrees from the central axis of the tubular body  11  . The underwater weighing container  1  further comprises a circular metallic bottom plate  12  having a mesh or a porous structure and being inserted between the circular rim  11   a  and the stoppers  11   b ; and a metallic hanging member  13  being attachable to the upper part of the tubular body  11  for hanging and suspending the tubular body  11 . The bottom plate  12  is basically configured in contact with the circular rim  11   a . When a buoyant force that is greater than the weight of the bottom plate  12  is exerted to the bottom plate  12  from underneath, the bottom plate  12  can move upward until it reaches where the stoppers  11   b  are installed.  
         [0027]      FIGS. 2A and 2B  show cross-sectional front elevation views of the underwater weighing container  1  holding a solid specimen  2 .  FIG. 2A  shows a condition that the specific gravity of the solid specimen  2  is larger than that of a reference liquid L, and  FIG. 2B  shows the other condition where the specific gravity of the solid specimen  2  is smaller than that of the reference liquid L. A method of measuring specific gravity of the solid specimen  2  by using the underwater weighing container  1  is described hereinafter with reference to  FIGS. 2A and 2B .  
         [0028]     First, while the underwater weighing container  1  is submerged in a liquid bath  3 , a weighing apparatus (not shown in  FIGS. 2A and 2B ) such as a scale, together with a hanging member  13  is employed, to measure the weight (W 0 ) of the underwater weighing container  1  per se. If the solid specimen  2  is heavier than the reference liquid L, the solid specimen  2  is placed on the bottom plate  12  as shown in  FIG. 2A , and at which time the weight W 1  of the underwater weighing container  1  with the solid specimen  2  is measured. If the weight of the solid specimen  2  measured in air is Wa, the specific gravity S of the solid specimen  2  can be calculated based on the following equation (2). 
 
 S=Wa /( Wa −( W   1 − W   0 ))   Equation (2) 
 
         [0029]     If the specific gravity of the solid specimen  2  is smaller than that of the reference liquid L, the underwater weighing container  1  is lifted to insert the solid specimen  2  underneath the bottom plate  12  as shown in  FIG. 2B . Due to the buoyant force produced thereby, the solid specimen  2  is in contact with the bottom plate  12 , and moves upward together with the bottom plate  12  until the solid specimen  2  remain stationary and stable. Under this condition, the weight (W 2 ) of the underwater weighing container  1  is determined. Accordingly, the specific gravity S of the solid specimen  2  can be calculated based on the following equation (3). 
 
 S=Wa /( W   0 − W   2 )   Equation (3) 
 
         [0030]      FIGS. 3A and 3B  show a structure of an underwater weighing container unit  4  according to another embodiment of the present invention.  FIG. 3A  shows a partial cross-sectional front elevation view of the underwater weighing container unit  4 , and  FIG. 3B  shows a plan view thereof. The underwater weighing container unit  4  comprises the underwater weighing container  1  arranged in a lower position; an aerial weighing container  41  being a circular container made either of metal or resin, arranged in an upper position; coupling rods  42  coupling with the underwater weighing container  1  and the aerial weighing container  41 ; and a hanging member  43  attached to the aerial weighing container  41 . Based on this configuration, a solid specimen can be solid received in the aerial weighing container  41  to measure its weight in air, and the solid specimen can be placed on or underneath the bottom plate  12 , so that the weight of the solid specimen immersed in a reference liquid or the buoyant force exerted thereon can be weighted.  
         [0031]      FIG. 4  is a partially cross-sectional front elevation view of the underwater weighing container unit  4 , wherein solid specimens  2 A,  2 B and  2 C are received in the liquid bath  3 . The disposition of the solid specimen  2 A in  FIG. 4  represents a position designated for measuring its weight in air. The disposition of the solid specimen  2 B represents a position designated for measuring its weight in the reference liquid L, wherein the solid specimen  2 B is placed on the bottom plate  12  and submerged in the reference liquid L if the specific gravity of the solid specimen  2 B is larger than that of the reference liquid L. The disposition of the solid specimen  2 C represents a position designated for measuring its buoyant force in the reference liquid L, wherein the solid specimen  2 C is inserted underneath the bottom plate  12  and submerged in the reference liquid L if the specific gravity of the solid specimen  2 C is smaller than that of the reference liquid L. A method of measuring the specific gravities of the solid specimens  2 A,  2 B and  2 C respectively by means of the underwater weighing container unit  4  is described hereinafter with reference to  FIG. 4 .  
         [0032]     First, while only the underwater weighing container unit  4  is dipped and immersed in the liquid bath  3 , a weight measuring apparatus (not shown in  FIG. 4 ) such as a scale, together with a hanging member  43 , is employed to measure the weight W 0  of the underwater weighing container unit  4  per se. The solid specimen  2 A is arranged on the underwater weighing container unit  4 , at which time the weight W 1  of the underwater weighing container unit  4  is measured. If the solid specimen is heavier than the reference liquid L, the solid specimen is placed in the designated position as shown by the solid specimen  2 B of  FIG. 4 , and under this condition, the weight W 2  of the underwater weighing container unit  4  with the solid specimen  2 B is measured. Hence, the specific gravity S of the solid specimen  2 B can be calculated based on the following equation (4). 
 
 S =( W   1 − W   0 )/( W   1 − W   2 )   Equation (4) 
 
         [0033]     If the solid specimen is lighter than the reference liquid L, the underwater weighing container unit  4  is lifted to insert the solid specimen underneath the bottom plate  12 , as indicated by the solid specimen  2 C in  FIG. 4 . With the buoyant force produced thereby, the solid specimen  2 C floats, makes contact with the bottom plate  12 , moves upward together with the bottom plate  12  until reaching up to the locations of the stoppers  11   b . The solid specimen  2 C then remains stationary and stable. Under this condition, the weight W 3  of the underwater weighing container unit  4  with the solid specimen  2 C is measured. Therefore, the specific gravity S of the solid specimen  2 C can be calculated based on the following equation (5). 
 
 S =( W   1 − W   0 )/( W   0 − W   3 )   Equation (5) 
 
         [0034]      FIG. 5  is a perspective view of a specimen mounting unit  6  used in specific gravity measuring apparatus  5  according to another embodiment of the present invention, which will be mentioned later. The specimen mounting unit  6  comprises the underwater weighing container unit  4 ; a frame  6 A supporting the underwater weighing container unit  4 ; a liquid bath  3  containing a reference liquid to hold the underwater weighing container unit  4  completely submerged therein; a liquid bath mounting platform  6 B to place the liquid bath  3  thereon while straddling a lower frame  62  of the frame  6 A.  
         [0035]     The frame  6 A comprises an upper frame  61 ; the lower frame  62  mounted and installed on a weighing pan  71  of an electronic weighing scale  7  to be described later; coupling rods  63  and  64  and setscrews  65  connecting the upper frame  61  with the lower frame  62  at a certain height. V-shaped notched-portions  66  that are able to hold or remove the underwater weighing container unit  4  are arranged on the upper frame  61  based on a gap between the coupling rods  63  and  64 . The underwater weighing container unit  4  is supported by the frame  6 A, when the coupling rods  42  pass through the notched-portions  66 . The underwater weighing container unit  4  can be removed from the frame  6 A by lifting the aerial weighing container  41  and drawing the coupling rods  42  out of the notched-portions  66 .  
         [0036]      FIGS. 6A and 6B  show partially cross-sectional front elevation views of the specific gravity measuring apparatus  5 , wherein the specimen mounting unit  6  and the electronic weighing scale  7  are incorporated and the solid specimen  2  is held in position.  FIG. 6A  shows a condition of mounting a solid specimen  2  wherein the specific gravity of which is larger than that of the reference liquid L.  FIG. 6B  shows another condition of mounting a solid specimen  2  where the specific gravity of which is smaller than that of the reference liquid L. In these conditions, the lower frame  62  is placed on the weighing pan  71  of the electronic weighing scale  7 , and the liquid bath mounting platform  6 B is placed on a frame base  79  of the electronic weighing scale  7 .  
         [0037]      FIG. 7  shows a block diagram of the electronic weighing scale  7 . The electronic weighing scale  7  uses a load sensor  72  to convert a weight load applied to the weighing pan  71  into electrical signals. After the electrical signals are amplified by an amplifier  73 , the amplified electrical signals are converted into digital signals by an A/D converter  74 . The digital signals are input into a CPU  75  constituting a microcomputer, and are subjected to calculations according to the aforementioned Equations (4) and (5) stored in a memory device  76 . Data of specific gravity values calculated are displayed on a display device  77 . The electronic weighing scale  7  is also equipped with operation buttons  78  providing instructions for differentiating the weights measured by the weighing pan  71  as well as for the start of the calculation process.  
         [0038]     A method of measuring the specific gravity of the solid specimen  2  by means of the specific gravity measuring apparatus  5  is described hereinafter with reference to  FIGS. 6A, 6B  and  7 . First, the weight (W 0 ) of the underwater weighing container unit  4  itself, i.e., the underwater weighing container unit  4  together with the frame  6 A are measured, and the operation buttons  78  is pressed to store the data of W 0  in the memory device  76 . Then, the weight (W 1 ) of the aerial weighing container  41  holding the solid specimen  2  is measured, and the corresponding data is stored in the same manner. If the specific gravity of the solid specimen  2  is larger than that of the reference liquid L, the solid specimen  2  is placed at the position as shown in  FIG. 6A  to measure the weight W 2 , and the relevant data is recorded in the same manner. The operation buttons  78  is pressed to allow the CPU  75  to start calculating the stored data based on the aforementioned Equation (4), and then the specific gravity of the solid specimen  2  are calculated and displayed.  
         [0039]     If the specific gravity of the solid specimen  2  is smaller than that of the reference liquid L, the solid specimen  2  is inserted in the position set forth in  FIG. 6B  for measuring the weight W 3 . Subsequently, the operation buttons  78  is pressed to allows the CPU  75  to start calculating these stored data based on the aforementioned Equation (5), and then the specific gravity of the solid specimen  2  are calculated and displayed.  
         [0040]     As described heretofore, and as shown by the underwater weighing container  1  in  FIGS. 2A and 2B  and the underwater weighing container unit  4  in  FIG. 4 , the present invention is characterized in that a single and compact structure capable of weighing the solid specimen  2  immersed in the reference liquid L because the structure comprises the bottom plate  12  movable upwardly and downwardly in a given range within the tubular body  11 . Based on this configuration, the solid specimen  2  that will sink in the reference liquid L can be placed on the upper surface of the bottom plate  12  in the reference liquid L. While the solid specimen  2  that will float in the reference liquid L can be inserted underneath the bottom plate  12 . In this way, the weight of the solid specimen  2  can be measured in the reference liquid L. While several examples of the present invention are disclosed herein, the conceivable configurations according to the present invention are not limited to these embodiments. For example, the tubular body  11  can be provided with a guide that will help to prevent the bottom plate  12  from tilting during moving the bottom plate  12  upward or downward. By increasing the number of coupling rods  42 , it is possible to hang and hold the tubular body  11  more securely.  
         [0041]     While the present invention has been described with a preferred embodiment, this description is not intended to limit our invention. Various modifications of the embodiment will be apparent to those skilled in the art. It is therefore contemplated that the appended claims will cover any such modifications or embodiments as fall within the true scope of the invention.