Patent Publication Number: US-2018045555-A1

Title: Mix weighing device

Description:
TECHNICAL FIELD 
     The present invention relates to a mix weighing device. 
     BACKGROUND ART 
     Conventionally, there have been known mix weighing devices configured so as to mix-weigh a supplied plurality of types of materials on the basis of a target weight. For example, a mix weighing device disclosed in patent literature 1 (Japanese Laid-open Patent Publication No. H 9-133573) is configured so as to mix-weigh a plurality of candies of different types on the basis of the target weight (target number) set for each type and discharge the mix-weighed candies to a bag-making packaging machine. In patent literature 1, the target weight (target number) for each type is suitably changed at a prescribed timing during operation of the device. This equalizes the total number of discharged material by each type and suppresses the possibility that a specific type of material will remain as inventory, even in cases where the inventory amounts are different according to type. 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     In the mix weighing device such as is described above, an apparent specific gravity of the supplied material could fluctuate according to the situation. For example, such fluctuation could occur when the specific gravity of sprinkle material and/or a coating material sprinkled on the material is greater than the specific gravity of the material. 
     However, in the mix weighing device in the prior art such as patent literature 1, it is conceivable that the mixing ratio, in terms of external appearance, of a plurality of types of materials after mix weighing could be different from the intended mixing ratio when such fluctuation occurs. 
     Thus, the problem of the present invention is to provide a mix weighing device which facilitates a constant mixing ratio, in terms of external appearance, of a plurality of types of materials after mix weighing. 
     Solution to Problem 
     A mix weighing device according to a first aspect of the present invention is a mix weighing device to mix-weigh a plurality of types of materials on the basis of individual weighed target weight, wherein the mix weighing device is provided with a conveying unit, a weighing unit, a storage unit, a setting unit, and a control unit. The conveying unit conveys the material. The weighing unit weighs and discharges the material conveyed from the conveying unit. The storage unit stores the apparent specific gravity of each type of the material and a mix volume proportion of each type of the material in mix weighing. The term “storage” includes temporary storage and/or permanent storage. The term “apparent specific gravity” means the mass of the material per unit volume, and is also referred to as “bulk specific gravity.” The setting unit sets individual weighed target weight for each type of the material on the basis of the apparent specific gravity and the mix volume proportion. The term “mix volume proportion” means the proportion of the volumes of the each type of the materials after mix weighing. The control unit controls the conveying unit and the weighing unit on the basis of the individual weighed target weight set by the setting unit. 
     In the mix weighing device according to the first aspect of the present invention, the setting unit sets individual weighed target weight for each type of the material on the basis of the apparent specific gravity and the mix volume proportion, and the control unit controls the conveying unit and the weighing unit on the basis of the set individual weighed target weight. A state is thereby achieved in which, after mix weighing, the plurality of types of the material are mixed at the mix volume proportion irrespective of whether the apparent specific gravity of the supplied material fluctuates. This results in facilitation of a constant mixing ratio, in terms of external appearance, of the material after mix weighing. 
     A mix weighing device according to a second aspect of the present invention is the mix weighing device according to the first aspect, wherein the storage unit further stores a post-mix-weighing total target weight. The setting unit sets the individual weighed target weight by type of the material further on the basis of the total target weight. 
     The individual weighed target weight are thereby set on the basis of the total target weight. Specifically, the individual weighed target weight can be set such that the total weight of the material after mix weighing conforms to or approximates the total target weight. As a result, the total weight after mix weighing is stabilized. 
     A mix weighing device according to a third aspect of the present invention is the mix weighing device according to the first aspect or second aspect, wherein the mix weighing device is further provided with an apparent specific gravity measurement unit. The apparent specific gravity measurement unit is disposed upstream from the weighing unit. The apparent specific gravity measurement unit measures the apparent specific gravity of each type of the material. 
     This facilitates measurement of the apparent specific gravity of the supplied material in real time during operation. As a result, the individual weighed target weight can be quickly changed in response to fluctuations in the apparent specific gravity of the supplied material. 
     A mix weighing device according to a fourth aspect of the present invention is the mix weighing device according to any one of the first to third aspects, wherein the setting unit configured and arranged to set newly the individual weighed target weight on the basis of the updated apparent specific gravity when the apparent specific gravity stored in the storage unit is updated during operation. 
     The individual weighed target weight are thereby set in real time on the basis of the updated apparent specific gravity during operation. This results in highly precise facilitation of a constant mixing ratio, in terms of external appearance, of the material after mix weighing even when variation in the apparent specific gravity of the supplied material is notable. 
     A mix weighing device according to a fifth aspect of the present invention is the mix weighing device according to the fourth aspect, wherein the setting unit sets newly the individual weighed target weight on the basis of the updated apparent specific gravity only when the apparent specific gravity of a specific type of the material is updated. 
     This makes it possible to newly set the individual weighed target weight exclusively for a specific type of the material of which the apparent specific gravity readily fluctuates. As a result, the individual weighed target weight is efficiently changed within a required minimum range. Specifically, the individual weighed target weight relating to a material of which the apparent specific gravity does not readily fluctuate may not be updated As a result, processing speed is increased because no process to calculate this individual weighed target weight is performed. 
     Advantageous Effects of Invention 
     In the mix weighing device according to the present invention, a state is achieved in which, after mix weighing, a plurality of types of the materials are mixed at a mix volume proportion irrespective of fluctuation of the apparent specific gravity of the supplied material. 
     This results in facilitation of a constant mixing ratio, in terms of external appearance, of the material after mix weighing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic configuration of a mix weighing device according to one embodiment of the present invention; 
         FIG. 2  is a schematic configuration of a mix weighing unit; 
         FIG. 3  is a schematic configuration of an apparent specific gravity measurement unit; 
         FIG. 4  is a block diagram schematically showing a control unit and units connected to the control unit; 
         FIG. 5  is a flow chart showing one example of the flow of processes in the control unit; 
         FIG. 6  is a schematic drawing showing one example of a result when mix-weighing is performed by a conventional mix weighing device; 
         FIG. 7  is a schematic drawing showing one example of a result when mix-weighing is performed by the mix weighing device according to the one embodiment of the present invention; and 
         FIG. 8  is a schematic diagram of a mix weighing device according to a modification A. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A mix weighing device  1  according to one embodiment of the present invention is described below with reference to the drawings. The embodiment described below is a specific example of the present invention, and does not in any way limit the technical scope of the present invention; modifications can be made, as appropriate, without departing from the gist of the invention. 
     (1) Overall Configuration 
       FIG. 1  is a schematic configuration of a mix weighing device  1  according to one embodiment of the present invention. In  FIG. 1 , two-dot chain-line arrows indicate a movement direction of a material (food product). 
     The mix weighing device  1  is a device to mix-weigh a supplied plurality of types of the material on the basis of individual weighed target weight Wt. There is no particular limitation as to the material mix-weighed by the mix weighing device  1 ; in the present embodiment, an example is described in which the mix weighing device  1  mix-weighs a plurality of types of the material (a food product A and a food product B). Specifically, in this example, the food product A is a material of which the apparent specific gravity (G 1 ) undergoes little fluctuation, and the food product B is a material of which the apparent specific gravity (G 2 ) fluctuates frequently according to the situation. For example, the food product A may be popcorn, and the food product B may be popcorn that is coated with chocolate (a coating material). The term “apparent specific gravity” means the mass of the material per unit volume, and is also referred to as “bulk specific gravity.” 
     The mix weighing device  1  primarily has a conveying unit  10 , a mix weighing unit  20 , an apparent specific gravity measurement unit  50 , and a control unit  60 . 
     (2) Detailed Configuration 
     (2-1) Conveying Unit  10   
     The conveying unit  10  is a unit to convey supplied material to the mix weighing unit  20 . The conveying unit  10  has a number (in the present example, two) of conveying lines equal to the number of types of supplied materials (food products). The conveying lines are, e.g., belt conveyors and/or vibrating conveyors. In the present embodiment, the conveying unit  10  includes a first conveying line  10   a  and a second conveying line  10   b.  In the present embodiment, the food product A is supplied to the first conveying line  10   a,  and the food product B is supplied to the second conveying line  10   b.    
     Each of the conveying lines has a drive unit  11  (see  FIG. 4 ) to drive the conveying line at a speed that corresponds to a control signal outputted from the control unit  60 . When the drive unit  11  is in a drive state, the material on each of the conveying lines is sent toward the mix weighing unit  20 . 
     Each of the conveying lines also has a rotation unit  12 . The rotation unit  12  includes a stepping motor for rotation, the stepping motor rotating clockwise or counterclockwise due to output of a control signal from the control unit  60 . 
     When the stepping motor for rotation rotates clockwise, the rotation unit  12  rotates downward at a prescribed angle (see dotted-line arrows in  FIG. 3 ). A state in which the rotation unit  12  has rotated downward to a prescribed angle from a horizontal surface is referred to below as an “open state” of the rotation unit  12 . When the rotation unit  12  is in the “open state,” the material that has been sent to the rotation unit  12  is dropped downward and sent to a specific gravity measurement hopper  51  (described later). 
     When the stepping motor for rotation rotates counterclockwise, the rotation unit  12  rotates upward at a prescribed angle (see dotted-line arrows in  FIG. 3 ). A state in which the rotation unit  12  has rotated upward to a prescribed angle from the open state is referred to below as a “closed state” of the rotation unit  12 . When the rotation unit  12  is in the “closed state,” the rotation unit  12  is approximately parallel to the horizontal surface, and the material that is sent to the rotation unit  12  is sent downstream from the conveying line without being dropped downward. 
     (2-2) Mix weighing unit  20   
       FIG. 2  is a schematic configuration of the mix weighing unit  20 . In  FIG. 2 , two-dot chain-line arrows indicate the movement direction of the material (food product). 
     The mix weighing unit  20  is a unit to mix-weigh the food product A and the food product B, which have been sent from the conveying unit  10 , and to discharge the food product A and the food product B which have been mix-weighed. The mix weighing unit  20  includes a number (in the present example, two) of weighing machines  30  (specifically, a first weighing machine  30   a  and a second weighing machine  30   b ) equal to the number of conveying lines, and also includes an integration chute  40  and a timing hopper  45 . 
     (2-2-1) Weighing Machines  30   
     The weighing machines  30  are mechanisms configured to weigh the material sent from a prescribed conveying line, and in the present embodiment are combination weighing machines. Specifically, the material (food product A) from the first conveying line  10   a  is sent to the first weighing machine  30   a.  The material (food product B) from the second conveying line  10   b  is sent to the second weighing machine  30   b.    
     The weighing machines  30  primarily have a dispersion unit  31 , an emission unit  32 , a plurality of pool hoppers  33 , a number of weighing hoppers  34  equal to the number of pool hoppers  33 , and a gathering chute  35 . 
     The dispersion unit  31  includes a dispersion table  311  that is circular in a plan view, and a dispersion table motor M 311  of which an output shaft is connected to the dispersion table  311 . The dispersion table motor M 311  is driven according to a control signal outputted from the control unit  60 . When the dispersion table motor M 311  is in a drive state, the dispersion table  311  rotates. 
     The emission unit  32  is a unit to convey the material (food product), which is sent from the dispersion table  311 , to the pool hoppers  33 . A plurality of emission units  32  are disposed so as to extend radially around the dispersion table  311 . The emission unit  32  primarily has an emission trough  321 , and an emission feeder  322  disposed within the emission trough  321  (not shown). Each of the emission trough  321  receives material sent from the dispersion table  311 . The emission feeder  322  includes an electromagnet and/or a leaf spring, and causes the emission trough  321  to vibrate. The material within the emission troughs  321  is thereby sent to the pool hoppers  33 . 
     The pool hoppers  33  temporarily retain the material that has been conveyed from the emission unit  32 . In the pool hoppers  33 , an opening/closing gate (not shown) provided to the lower part of each of the pool hoppers  33  is opened at a prescribed timing, thereby sending the retained material to the weighing hoppers  34 . 
     One weighing hopper  34  is provided below each of the pool hoppers  33 . Each of the weighing hoppers  34  has a hopper weight measurement part (not shown) such as a load cell or the like. The hopper weight measurement part measures the weight of the material sent from the pool hoppers  33  to the weighing hoppers  34 . The result of measuring by the hopper weight measurement part is transmitted to the control unit  60 . An opening/closing gate (not shown) is provided to the lower part of each of the weighing hoppers  34 , the opening/closing gate being opened/closed according to a control signal outputted from the control unit  60 . When the opening/closing gate is in an open state, the material within the weighing hopper  34  is discharged to the gathering chute  35 . 
     The gathering chute  35  gathers the material sent from the weighing hoppers  34  and discharges the gathered material to outside of the mix weighing unit  20 . The material discharged from the gathering chute  35  is sent to the integration chute  40  disposed below the gathering chute  35 . 
     (2-2-2) Integration Chute  40  and Timing Hopper  45   
     The integration chute  40  gathers and discharges the material (food product) sent from the weighing machines  30  (weighing hoppers  34 ). The material discharged from the integration chute  40  is sent to the timing hopper  45  disposed below the integration chute  40 . 
     The material (food product A and food product B) discharged from the weighing machines  30  and sent to the timing hopper  45  via the integration chute  40  enters a mixed state within the timing hopper  45 . An opening/closing gate (not shown) is provided to the lower part of the timing hopper  45 , the opening/closing gate being opened/closed according to a control signal outputted from the control unit  60 . When the opening/closing gate is in an open state, the material within the timing hopper  45  is discharged. The mixed material discharged from the timing hopper  45  is supplied to a process downstream from the mix weighing unit  20 . For example, the material discharged from the timing hopper  45  may be supplied to a packaging machine or the like. (not shown). 
     (2-3) Apparent Specific Gravity Measurement Unit  50   
       FIG. 3  is a schematic configuration of the apparent specific gravity measurement unit  50 . In  FIG. 3 , two-dot chain-line arrows indicate the movement direction of the material (food product), and dotted-line arrows indicate a rotation direction of the rotation unit  12 . 
     The apparent specific gravity measurement unit  50  is a unit for measuring the apparent specific gravity of the material (food product) flowing along the conveying line of the conveying unit  10 . The apparent specific gravity measurement unit  50  is disposed below the rotation units  12  of each of the conveying lines (the first conveying line  10   a  and the second conveying line  10   b ) of the conveying unit  10 . Specifically, it can also be said that apparent specific gravity measurement units  50  are disposed upstream of the mix weighing units  20 . 
     The apparent specific gravity measurement unit  50  primarily has a specific gravity measurement hopper  51  and a photoelectric sensor  52 . 
     The specific gravity measurement hopper  51  temporarily accommodates the material that has dropped from the rotation unit  12 , and measures the weight of the material. The specific gravity measurement hopper  51  has such a capacity as to be capable of accommodating a prescribed amount of the material. In the present embodiment, the specific gravity measurement hopper  51  is capable of accommodating 1000 cc of the material. A weight measurement sensor (not shown) such as a load cell or the like is disposed in the specific gravity measurement hopper  51 . The specific gravity measurement hopper  51  measures the weight of the material therein according to input of a control signal (referred to as a “measurement start signal” below) outputted from the control unit  60 , and outputs a signal (referred to as a “measured value notification signal” below) that corresponds to a measured value to the control unit  60 . 
     An opening/closing gate (not shown) is provided to the lower part of the specific gravity measurement hopper  51 , and the specific gravity measurement hopper  51  opens/closes the opening/closing gate according to a control signal outputted from the control unit  60 . When the opening/closing gate is in an open state, the material within the specific gravity measurement hopper  51  is discharged. The material discharged from the specific gravity measurement hopper  51  is sent to a recovery conveyor (not shown), and then is re-supplied to the conveying line to which the material had been supplied. More specifically, the material discharged from the specific gravity measurement hopper  51  is supplied to a location downstream from the rotation unit  12  in the conveying line. 
     The apparent specific gravity measurement unit  50  has a specific gravity measurement hopper  51 , and a photoelectric sensor  52  for detecting whether the amount of the material present within the specific gravity measurement hopper  51  has reached a prescribed first threshold value ΔTh 1 . In the present embodiment, the first threshold value ΔTh1 is set to 800 cc. When the amount of the material present within the specific gravity measurement hopper  51  has reached the prescribed first threshold value ΔTh1, the photoelectric sensor  52  outputs a signal (referred to as a “measurement preparation complete signal” below) in response to the control unit  60 . 
     (2-4) Control Unit  60   
     The control unit  60  is a functional unit to generally control the operations of the mix weighing device  1 . The control unit  60  has a microcomputer including a CPU, a memory and/or the like. In the present embodiment, the control unit  60  is disposed in the mix weighing unit  20 . The control unit  60  is electrically connected to actuators and/or sensors included in the mix weighing device  1 . Details about the control unit  60  are described later under “(4) Details about Control Unit  60 .” 
     (3) Operations of Mix Weighing Device  1   
     When running, the mix weighing device  1  operates in a process flow such as is generally described below. 
     When a prescribed material (food product) is supplied in a state in which the conveying lines ( 10   a,    10   b ) of the conveying unit  10  are being driven, the supplied material is sent downstream and reaches the rotation unit  12 . 
     When the rotation unit  12  is in a closed state, the material that has reached the rotation unit  12  passes through the rotation unit  12  and is sent to the mix weighing unit  20 . 
     When the rotation unit  12  is in an open state, the material that has reached the rotation unit 12 drops downward and is accommodated by the specific gravity measurement hopper  51  of the apparent specific gravity measurement unit  50 . After the weight of the material accommodated by the specific gravity measurement hopper  51  is measured at a prescribed timing, the material is discharged from the specific gravity measurement hopper  51  and recovered to the conveying line by the recovery conveyor. The material recovered to the conveying line is sent to the mix weighing unit  20 . 
     The material sent to the mix weighing unit  20  is sent to the corresponding weighing machines  30 . 
     After the material sent to the weighing machines  30  is dispersed in a peripheral direction due to rotation of the dispersion table  311 , the material is discharged to the emission unit  32 . The material discharged to the emission unit  32  is sent to the pool hoppers  33  due to vibration of the emission unit  32 . After the material sent to the pool hoppers  33  is temporarily retained in the pool hoppers  33 , the material is sent to the weighing hoppers  34  and is weighed. 
     Next, a combination calculation is carried out using the measured values in the plurality of weighing hoppers  34 , and a combination of weighing hoppers  34  is suitably selected so that the total weight conforms to the individual weighed target weight Wt or approximates the same within a permissible weight range. The material within the selected weighing hoppers  34  is discharged from the weighing hoppers  34  and is discharged from the weighing machines  30  via the gathering chute  35 . 
     The material discharged from the weighing machines  30  is sent to the timing hopper  45  via the integration chute  40 . After the material sent to the timing hopper  45  is mixed within the timing hopper  45  with material discharged from another weighing machine  30 , the material is discharged from the timing hopper  45  at a prescribed timing. 
     The material discharged from the timing hopper  45  is sent to a packaging machine or other downstream process. 
     (4) Details about Control Unit  60   
       FIG. 4  is a block diagram schematically showing the control unit  60  and units connected to the control unit  60 . 
     The control unit  60  is electrically connected to the first conveying line  10   a,  the second conveying line  10   b,  the first weighing machine  30   a,  the second weighing machine  30   b,  the timing hopper  45 , a first specific gravity measurement unit  50   a,  and a second specific gravity measurement unit  50   b,  as shown in  FIG. 4 . 
     The control unit  60  primarily has a storage unit  61 , an input/output unit  62 , a conveying unit control unit  63 , an apparent specific gravity calculation unit  64 , a mix weighing control unit  65 , and a weighed target weight setting unit  66 . 
     (4-1) Storage unit  61   
     The storage unit  61  includes, e.g., a RAM and/or a ROM, and a flash memory or other type of memory, and temporarily or permanently stores various information. The storage unit  61  primarily includes a program storage region  611 , a volume proportion storage region  612 , a measurement information storage region  613 , an apparent specific gravity storage region  614 , a weighed target weight storage region  615 , a total target weight storage region  616 , and a specific material storage region  617 . 
     In the program storage region  611 , there is stored a control program in which processes of the various units within the control unit  60  are defined. The control program is suitably updated. 
     In the volume proportion storage region  612 , there is stored a mix volume proportion Pv set by a user via an input device (not shown). The mix volume proportion Pv is the proportion of the volumes of the each type of the materials after mix weighing. In the present embodiment, the mix volume proportion Pv is the proportion of the volume of the food product A with respect to the volume of the food product B after mix weighing. For example, when the volume of the food product A is 500 mL and the volume of the food product B is 500 mL after mix weighing, the mix volume proportion Pv is 1:1. When the volume of the food product A is 750 mL and the volume of the food product B is 250 mL after mix weighing, the mix volume proportion Pv is 3:1. 
     In the measurement information storage region  613 , there is stored a measured value notification signal outputted from the apparent specific gravity measurement unit  50 . The measurement information storage region  613  includes a first flag F 1  and a second flag F 2  that have prescribed bit numbers. 
     The first flag F 1  and the second flag F 2  are individually set by the input/output unit  62  according to the output of a measurement preparation complete signal from the apparent specific gravity measurement unit  50 . When calculation of the apparent specific gravity by the apparent specific gravity measurement unit  50  is complete, the first flag F 1  and the second flag F 2  are individually cleared by the apparent specific gravity measurement unit  50 . 
     In the apparent specific gravity storage region  614 , there is stored the apparent specific gravity of each type of the material as calculated by the apparent specific gravity calculation unit  64 . In the present embodiment, the apparent specific gravity of each of the food product A and the food product B is individually stored in the apparent specific gravity storage region  614 . 
     In the weighed target weight storage region  615 , there are stored the individual weighed target weight Wt for each type of the material as set by the weighed target weight setting unit  66 . The individual weighed target weight Wt are target values for the weight of each type of the material in one mix weighing cycle. In the present embodiment, a first weighed target weight Wt 1  that is the individual weighed target weight Wt for the food product A and a second weighed target weight Wt 2  that is the individual weighed target weight Wt for the food product B are separately stored in the weighed target weight storage region  615 . 
     In the total target weight storage region  616 , there is stored a total target weight set by the user via an input unit (not shown). The total target weight is a target value for the total weight of the mixture of the material after mix weighing. In the present embodiment, the total target weight is suitably set according to the product use or the like. 
     The specific material storage region  617  includes a specific material distinction flag F 3  that has a prescribed bit number. The specific material distinction flag F 3  is a flag to distinguish a material (referred to as a “specific material” below) for which the individual weighed target weight Wt needs to be updated after operation of the device, and also to distinguish the apparent specific gravity measurement unit ( 50   a  or  50   b ) to which supplied the specific material. 
     The specific material is a material of which the apparent specific gravity readily fluctuates, and of which the mixing ratio, in terms of external appearance, after mix weighing could become unstable if the individual weighed target weight Wt is not appropriately updated, the material being designated by the use&#39;s decision. For example, a material on which a coating material and/or sprinkle material is sprinkled may be designated as the specific material. 
     The specific material storage region  617  includes a number of specific material distinction flags F 3  equal to the number of apparent specific gravity measurement units  50 . In the present embodiment, the specific material storage region  617  includes a first specific material distinction flag F 31  that corresponds to the first specific gravity measurement unit  50   a  (i.e., the food product A), and a second specific material distinction flag F 32  that corresponds to the second conveying line  10   b  (i.e., the food product B). 
     Each of the specific material distinction flags F 3  is individually set by the user via an input device (not shown). Specifically, a specific material distinction flag F 3  is set that corresponds to the apparent specific gravity measurement unit  50  to which the specific material is supplied. In the present embodiment, the food product B supplied to the second specific gravity measurement unit  50   b  is designated as a specific material, and the second specific material distinction flag F 32  is set in response thereto. Specifically, the food product B is stored as a specific material in the specific material storage region  617 . However, the food product A supplied to the first specific gravity measurement unit  50   a  is not designated as a specific material, and therefore the first specific material distinction flag F 31  is not set. Specifically, the food product A is not stored as a specific material in the specific material storage region  617 . 
     Individually setting each of the specific material distinction flags F 3  in this manner makes it possible for another processing unit to distinguish whether the material supplied to each of the apparent specific gravity measurement units  50  is designated as a specific material or not. In the present embodiment, the specific material distinction flag F 3  is suitably referred to by the apparent specific gravity calculation unit  64 . 
     (4-2) Input/output Unit  62   
     The input/output unit  62  is a functional unit to fulfill the role of an interface for exchanging signals with other units. When the input/output unit  62  receives a signal outputted from another unit, the input/output unit  62  stores the signal in a prescribed storage region within the storage unit  61  according to the type of signal. The input/output unit  62  also outputs prescribed signals to other units according to requests from units within the control unit  60 . 
     When the input/output unit  62  receives a measured value notification signal outputted from the apparent specific gravity measurement unit  50 , the input/output unit  62  stores information pertaining to the signal in the measurement information storage region  613 . 
     When the input/output unit  62  receives a measurement preparation complete signal outputted from (the photoelectric sensor  52  of) the first specific gravity measurement unit  50   a , the input/output unit  62  sets the first flag F 1 . When the input/output unit  62  receives a measurement preparation complete signal outputted from (the photoelectric sensor  52  of) the second specific gravity measurement unit  50   b,  the input/output unit  62  sets the second flag F 2 . 
     (4-3) Conveying Unit Control Unit  63   
     The conveying unit control unit  63  is a functional unit to control the operations of the conveying unit  10 . 
     The conveying unit control unit  63  controls the drive unit  11  of each of the conveying lines on the basis of the individual weighed target weight Wt for the supplied materials (food products). More specifically, the conveying unit control unit  63  controls the drive unit  11  such that the material (food product) is sent to the mix weighing unit  20  at a speed that corresponds to the individual weighed target weight Wt. 
     The conveying unit control unit  63  causes the rotation unit  12  of the conveying line to change from the closed state to the open state, or from the open state to the closed state, upon receiving a request from the apparent specific gravity calculation unit  64 . 
     The conveying unit control unit  63  includes a number of control units that corresponds to the number of conveying lines. In the present embodiment, the conveying unit control unit  63  includes a first conveying line control unit  631  and a second conveying line control unit  632 . The first conveying line control unit  631  controls the operations of the first conveying line  10   a.  The second conveying line control unit  632  controls the operations of the second conveying line  10   b.    
     (4-4) Apparent Specific Gravity Calculation Unit  64   
     The apparent specific gravity calculation unit  64  is a functional unit to calculate the apparent specific gravity of each type of the material. The apparent specific gravity calculation unit  64  includes a number of calculation units that corresponds to the number of apparent specific gravity measurement units  50 . In the present embodiment, the apparent specific gravity calculation unit  64  includes a first specific gravity calculation unit  641  and a second specific gravity calculation unit  642 . 
     Each of the calculation units ( 641  and  642 ) executes an apparent specific gravity calculation process. The apparent specific gravity calculation process is to calculate the apparent specific gravity of the material (food product) supplied to the corresponding apparent specific gravity measurement unit  50 . 
     When the material to be supplied to the corresponding apparent specific gravity measurement unit  50  is not designated as a specific material, the calculation units ( 641  and  642 ) execute the apparent specific gravity calculation process only during initial startup of the device. When the material to be supplied to the corresponding apparent specific gravity measurement unit  50  is designated as a specific material, the calculation units ( 641  and  642 ) execute the apparent specific gravity calculation process each time a prescribed time period t 1  elapses after the initial startup of the device. In the present embodiment, the prescribed time period t 1  is set to 30 seconds. 
     Each of the calculation units ( 641  and  642 ) refers to the specific material distinction flags F 3  (F 31  and F 32 ) of the specific material storage region  617  during startup, and determines whether the material to be supplied to the corresponding apparent specific gravity measurement unit  50  ( 50   a  or  50   b ) is designated as a specific material or not. 
     (4-4-1) First Specific Gravity Calculation Unit  641   
     The first specific gravity calculation unit  641  executes the apparent specific gravity calculation process in the manner described below. 
     The first specific gravity calculation unit  641  issues a request, at a prescribed timing, to the conveying unit control unit  63  to change the rotation unit  12  of the first conveying line  10   a  from the closed state to the open state. 
     When the first flag F 1  is set, the first specific gravity calculation unit  641  issues a request to change the rotation unit  12  of the first conveying line  10   a  from the open state to the closed state, and outputs a measurement start signal to the first specific gravity measurement unit  50   a.  The first specific gravity calculation unit  641  then clears the first flag F 1 . 
     When a measured value notification signal outputted from the first specific gravity measurement unit  50   a  is newly stored in the measurement information storage region  613 , the first specific gravity calculation unit  641  acquires and decodes this signal, and extracts a measured value Vw 1  of the first specific gravity measurement unit  50   a.  After extracting the measured value Vw 1 , the first specific gravity calculation unit  641  calculates the apparent specific gravity G 1  of the food product A on the basis of the following mathematical formula 
       G1=Vw1/C1  (Fa)
 
     G 1 : Apparent specific gravity (g/cc) of food product A
 
Vw 1 : Measured value (g) of first specific gravity measurement unit  50   a  
 
C 1 : First threshold value ΔTh 1  (cc)
 
     In the present embodiment, C 1 =first threshold value ΔTh 1 =800 (cc); therefore, when the measured value Vw 1  is 80 (g), the apparent specific gravity G 1  of the food product A is calculated to be 0.1 (g/cc). 
     The first specific gravity calculation unit  641  stores the calculated apparent specific gravity G 1  of the food product A in the apparent specific gravity storage region  614 . 
     (4-4-2) Second Specific Gravity Calculation Unit  642   
     The second specific gravity calculation unit  642  executes the apparent specific gravity calculation process in the manner described below. 
     The second specific gravity calculation unit  642  issues a request, at a prescribed timing, to the conveying unit control unit  63  to change the rotation unit  12  of the second conveying line  10   b  from the closed state to the open state. 
     When the second flag F 2  is set, the second specific gravity calculation unit  642  issues a request to change the rotation unit  12  of the second conveying line  10   b  from the open state to the closed state, and outputs a measurement start signal to the second specific gravity measurement unit  50   b.  The second specific gravity calculation unit  642  then clears the second flag F 2 . 
     When a measured value notification signal outputted from the second specific gravity measurement unit  50   b  is newly stored in the measurement information storage region  613 , the second specific gravity calculation unit  642  acquires and decodes this signal, and extracts a measured value Vw 2  of the second specific gravity measurement unit  50   b.  After extracting the measured value Vw 2 , the second specific gravity calculation unit  642  calculates the apparent specific gravity G 2  of the food product B on the basis of the following mathematical formula Fb: 
         G 2=Vw2/ C 2  (Fb)
 
     G 2 : Apparent specific gravity (g/cc) of food product B
 
Vw 2 : Measured value (g) of second specific gravity measurement unit  50   b  
 
C 2 : First threshold value ΔTh 1  (cc)
 
     In the present embodiment, C 2 =first threshold value ΔTh 1 =800 (cc); therefore, when the measured value Vw 2  is 160 (g), the apparent specific gravity G 2  of the food product B is calculated to be 0.2 (g/cc). 
     The second specific gravity calculation unit  642  stores the calculated apparent specific gravity G 2  of the food product B in the apparent specific gravity storage region  614 . 
     (4-5) Mix Weighing Unit Control Unit  65   
     The mix weighing unit control unit  65  is a functional unit to control the operations of the mix weighing unit  20 . More specifically, the mix weighing unit control unit  65  individually controls the operation of the dispersion table motor M 311 , the emission feeder  322 , the pool hoppers  33 , and the weighing hoppers  34 . The mix weighing unit control unit  65  includes a number of control units that corresponds to the number of weighing machines  30  in the mix weighing unit  20 . Specifically, the mix weighing unit control unit  65  includes a first weighing machine control unit  651  to control the operations of the first weighing machine  30   a,  and a second weighing machine control unit  652  to control the operations of the second weighing machine  30   b.  The mix weighing unit control unit  65  also includes a timing hopper control unit  653  to control the operations of the timing hopper  45 . 
     The mix weighing unit control unit  65  also includes a plurality of flags that have prescribed bit numbers. Specifically, the mix weighing unit control unit  65  includes a first weighing complete distinction flag, a second weighing complete distinction flag, and a timing hopper open flag (not shown). 
     In the present embodiment, setting the first weighing complete distinction flag makes it possible to distinguish whether the weighed material from the first weighing machine  30   a  is in a state of being discharged to the gathering chute  35 . Setting the second weighing complete distinction flag makes it possible to distinguish whether the weighed material from the second weighing machine  30   b  is in a state of being discharged to the gathering chute  35 . Setting the timing hopper open flag makes it possible to distinguish whether the timing hopper  45  is in the open state. 
     After startup, the first weighing machine control unit  651  acquires, from the weighed target weight storage region  615 , the individual weighed target weight Wt (i.e., the first weighed target weight Wt 1 ) for the material (food product A) sent from the first conveying line  10   a  each time a prescribed time period t 2  elapses. The first weighing machine control unit  651  individually controls the dispersion table motor M 311 , the emission feeder  322 , the pool hoppers  33 , and the weighing hoppers  34  such that material (food product A) at the individual weighed target weight Wt is discharged from the first weighing machine  30   a  to the gathering chute  35 . The first weighing machine control unit  651  performs the control such that the material is discharged from the first weighing machine  30   a  only when the timing hopper open flag is not set. The first weighing machine control unit  651  sets a first weighing complete flag (not shown) each time material equivalent to the individual weighed target weight Wt is discharged from the first weighing machine  30   a.    
     After startup, the second weighing machine control unit  652  acquires, from the weighed target weight storage region  615 , the individual weighed target weight Wt (i.e., the second weighed target weight Wt 2 ) for the material (food product B) sent from the second conveying line  10   b  each time the prescribed time period t 2  elapses. The second weighing machine control unit  652  individually controls the dispersion table motor M 311 , the emission feeder  322 , the pool hoppers  33 , and the weighing hoppers  34  such that material (food product B) equivalent to the individual weighed target weight Wt is discharged from the second weighing machine  30   b  to the gathering chute  35 . The second weighing machine control unit  652  performs the control such that the material is discharged from the second weighing machine  30   b  only when the timing hopper open flag is not set. The second weighing machine control unit  652  sets a second weighing complete flag (not shown) each time material equivalent to the individual weighed target weight Wt is discharged from the second weighing machine  30   b.    
     In the present embodiment, the prescribed time period t 2  is set to  30  seconds. 
     The timing hopper control unit  653  opens/closes the timing hopper  45  at a prescribed timing. When the first weighing complete flag and the second weighing complete flag are both set, the timing hopper control unit  653  opens the timing hopper  45  after the timing hopper open flag is set. After a prescribed time period has elapsed from when the timing hopper  45  was opened, the timing hopper control unit  653  closes the timing hopper  45  and clears the timing hopper open flag. 
     (4-6) Weighed Target Weight Setting Unit  66   
     The weighed target weight setting unit  66  is a functional unit to set the individual weighed target weight Wt by type of the material. 
     When the apparent specific gravity of the material is stored in the apparent specific gravity storage region  614 , the weighed target weight setting unit  66  newly sets the corresponding individual weighed target weight Wt. Specifically, when the apparent specific gravity G 1  of the food product A or the apparent specific gravity G 2  of the food product B is stored in the apparent specific gravity storage region  614 , the weighed target weight setting unit  66  executes a weighed target weight setting process. 
     In the weighed target weight setting process, the weighed target weight setting unit  66  calculates each of the individual weighed target weight Wt (in the present embodiment, the first weighed target weight Wt 1  and the second weighed target weight Wt 2 ) for each type of the material on the basis of the total target weight, the apparent specific gravity of the materials, and the mix volume proportion Pv. The weighed target weight setting unit  66  stores the calculated individual weighed target weight Wt in the weighed target weight storage region  615 . 
     Specifically, in the weighed target weight setting process, the weighed target weight setting unit  66  acquires the mix volume proportion Pv from the volume proportion storage region  612 , acquires the apparent specific gravity of each type of the material from the apparent specific gravity storage region  614 , and acquires the total target weight from the total target weight storage region  616 . 
     Next, the weighed target weight setting unit  66  calculates each of the individual target volumes Vt of each type of the material on the basis of the acquired values. The individual target volumes Vt are the target volumes for each type of the material after mix weighing. 
     For example, when the mix volume proportion Pv is set to  1 : 2 , the proportion of a first target volume Vt 1  of the food product A and a second target volume Vt 2  of the food product B is 1:2, the first target volume Vt 1  of the food product A and the second target volume Vt 2  of the food product B being as follows: 
       Vt2×2×Vt1 (g)
 
     Vt 1 : Individual target volume Vt (cc) of food product A
 
Vt 2 : Individual target volume Vt (cc) of food product B
 
     The weighed target weight setting unit  66  then calculates the individual weighed target weight Wt for each type of the material on the basis of the calculated individual target volumes Vt, the apparent specific gravity of each type of the material, and the total target weight. 
     For example, where the total target weight is set to 100 (g), the apparent specific gravity G 1  of the food product A is calculated as 0.1 (g/cc), and the apparent specific gravity G 2  of the food product B is calculated as 0.2 (g/cc), the first weighed target weight Wt 1  and the second weighed target weight Wt 2  are calculated after the individual target volumes Vt of each type of the material is calculated, as follows: 
       Wt1= G 1×Vt1=0.1×Vt1 (g)
 
       Wt2= G 2×Vt2=0.2×2×Vt1=0.4×Vt1 (g)
 
     Because total target weight is 100 (g), 
       100 (g)=Wt1+Wt2=0.1×Vt1+0.4×Vt1=0.5×Vt1
 
     Therefore, 
     Vt 1 =200 (cc) 
     Vt 2 =400 (cc) 
     Wt 1 =20 (g) 
     Wt 2 =80 (g) 
     When the apparent specific gravity of the materials fluctuates after calculation of the individual weighed target weight Wt for each type of the material, the individual weighed target weight Wt for each type of the material are calculated again on the basis of the individual target volumes Vt, the apparent specific gravity of each type of the material, and the total target weight. 
     For example, when the apparent specific gravity G 2  of the food product B designated as a specific material in the example described above fluctuates to 0.15 (g/cc), the first target volume Vt 1 , the second target volume Vt 2 , the first weighed target weight Wt 1 , and the second weighed target weight Wt 2  are calculated as follows: 
       Wt1=G1×Vt1=0.1×Vt1 (g)
 
     Wt2=G33 Vt2=0.15×2×Vt1=0.3×Vt1 (g) 
     Because total target weight is 100 (g), 
       100 (g)=Wt1+Wt2=0.1×Vt1+0.3×Vt1=0.4×Vt1
 
     Therefore, 
     Vt 1 =250 (cc) 
     Vt 2 =500 (cc) 
     Wt 1 =25 (g) 
     Wt 2 =75 (g) 
     For another example, in a case where the food product A is designated as a specific material, when the apparent specific gravity G 1  of the food product A fluctuates to 0.2 (g/cc) and the apparent specific gravity G 2  of the food product B fluctuates to 0.3 (g/cc), the first target volume Vt 1 , the second target volume Vt 2 , the first weighed target weight Wt 1 , and the second weighed target weight Wt 2  are calculated as follows: 
       Wt1=G1×Vt1=0.2×Vt1 (g)
 
       Wt2=G2×Vt2=0.3×2×Vt1=0.6×Vt1 (g)
 
     Because total target weight is 100 (g), 
       100 (g)=Wt1+Wt2 =0.2×Vt1+0.6×Vt1=0.8×Vt1
 
     Therefore, 
     Vt 1 =125 (cc) 
     Vt 2 =250 (cc) 
     Wt 1 =25 (g) 
     Wt 2 =75 (g) 
     Thus, in the weighed target weight setting process, the weighed target weight setting unit  66  calculates each of the individual target volumes Vt for each type of the material on the basis of the total target weight, the apparent specific gravity of each type of the material, and the mix volume proportion Pv, and calculates the individual weighed target weight Wt for each type of the material on the basis of the calculated individual target volumes Vt and the apparent specific gravity of each type of the material. That is, it can also be said that the individual weighed target weight Wt are calculated on the basis of the total target weight, the apparent specific gravity of each type of the material, and the mix volume proportion Pv. Specifically, the weighed target weight setting unit  66  sets the individual weighed target weight Wt for each type of the material on the basis of the total target weight such that the total weight of the mix-weighed material conforms to or approximates the total target weight. 
     In the weighed target weight setting process, there are cases where the individual weighed target weight Wt is not calculated to an integer. In such cases, the weighed target weight setting unit  66  calculates the individual weighed target weight Wt by rounding up, rounding down, or rounding to the nearest whole number. When the sum of the individual weighed target weight Wt needs to conform to the total target weight, a configuration may be adopted such that, after one of the individual weighed target weight Wt is calculated, the weighed target weight setting unit  66  calculates a value obtained by subtracting the calculated individual weighed target weight Wt from the total target weight as the other of the individual weighed target weight Wt. 
     (5) Flow of Processes of Control Unit  60   
       FIG. 5  is a flow chart showing one example of the flow of processes in the control unit  60 . 
     When electric power is supplied and an operation start command is inputted by a user, the control unit  60  executes a flow of processes such as is described below. 
     In step S 101 , the control unit  60  determines whether a total target weight has been inputted (i.e., whether a total target weight is stored in the storage unit  61 ). When the result of determination is NO (i.e., when no total target weight has been inputted), the control unit  60  repeats the determination while the operations of the other units are in a stopped state. When the result of determination is YES (i.e., when a total target weight has been inputted), the flow proceeds to step S 102 . 
     In step S 102 , the control unit  60  drives each of the conveying lines ( 10   a  and  10   b ) of the conveying unit  10  at a prescribed operation speed. The flow then proceeds to step S 103 . 
     In step S 103 , the control unit  60  sends a control signal (measurement start signal) to the apparent specific gravity measurement unit  50  at a prescribed timing and causes the apparent specific gravity measurement unit  50  to measure the weight of each type of the material supplied by each of the conveying lines. The flow then proceeds to step S 104 . 
     In step S 104 , the control unit  60  determines whether a measured value (i.e., a measured value notification signal) has been outputted from the apparent specific gravity measurement unit  50  to which the measurement start signal was transmitted. When the result of determination is NO (i.e., when no measured value has been outputted), the determination in step S 104  is repeated. When the result of determination is YES (i.e., when a measured value has been outputted), this result is stored in the storage unit  61 , and the flow proceeds to step S 105 . 
     In step S 105 , the control unit  60  calculates the apparent specific gravity of each type of the material. For materials other than specific materials, the apparent specific gravity is calculated only during startup. For specific materials, the apparent specific gravity is suitably calculated and updated not only during startup but also during operation. The control unit  60  stores the calculated apparent specific gravity in the storage unit  61 . The flow then proceeds to step S 106 . 
     In step S 106 , the control unit  60  calculates individual weighed target weight Wt for each type of the material on the basis of the apparent specific gravity of the materials, the mix volume proportion Pv, and the total target weight. The control unit  60  stores the calculated individual weighed target weight Wt in the storage unit  61 . The flow then proceeds to step S 107 . 
     In step S 107 , the control unit  60  controls driving of the weighing machines  30  on the basis of the individual weighed target weight Wt. The flow then proceeds to step S 108 . 
     In step S 108 , the control unit  60  opens/closes the timing hopper  45  at a prescribed timing (specifically, after it has been confirmed that material at the individual weighed target weight Wt is discharged from the weighing machines  30 ). The flow then returns to step S 101 . 
     (6) Function of Mix Weighing Device  1   
     In devices configured to mix-weigh, the apparent specific gravity of a supplied material could fluctuate according to the situation, depending on the type of material. In particular, in cases of the supply of a material on which sprinkle material and/or a coating material is sprinkled, such as the food product B that is coated with chocolate, the quantity of the coating material readily varies in a step for sprinkling the sprinkle material and/or coating material, and such fluctuation readily occurs. For example, such fluctuation could occur when the specific gravity of sprinkle material and/or a coating material is greater than the specific gravity of the material prior to the application of the sprinkle material and/or coating material. 
     When such fluctuation occurs, the mixing ratio, in terms of external appearance, of a plurality of types of the material after mix weighing could be different from the intended mixing ratio. Specifically, when a material B 1  that the apparent specific gravity readily fluctuates and a material Al are mix-weighed in a situation in which the mix volume proportion Pv is set to 1:1, if mix-weighing is performed without any consideration for fluctuation in the apparent specific gravity, in the manner of conventional mix weighing devices, the mix volume proportion after mix weighing will not necessarily be 1:1, and the mixing ratio, in terms of external appearance, of the material A 1  and the material B 1  could fail to be constant. For example, when the apparent specific gravity of the material A 1  fluctuates so as to double, the mix volume proportion of the material A 1  and the material B 1  becomes 2:1, as shown in  FIG. 6 . 
     However, in the mix weighing device  1 , such fluctuation is suppressed, thus facilitating a constant mixing ratio, in terms of external appearance, of a plurality of types of the material after mix weighing. Specifically, the mix weighing device  1  is configured such that the individual weighed target weight Wt for each type of the material are set in real time on the basis of the apparent specific gravity and the mix volume proportion Pv. Each type of the material is thereby mixed at the designated mix volume proportion Pv after mix weighing, irrespective of whether the apparent specific gravity of the supplied material changes. As a result, even in the example described previously, the mix volume proportion of the material A 1  and the material B 1  after mix weighing constantly remains the set mix volume proportion Pv (i.e., 1:1), as shown in  FIG. 7 . Accordingly, the mix weighing device  1  facilitates a constant mixing ratio, in terms of external appearance, of the plurality of types of the material after mix weighing. 
     Additionally, the weighed target weight setting unit  66  sets the individual weighed target weight Wt by type of the material on the basis of the total target weight stored in the storage unit  61 . The total weight of the materials after mix weighing thereby conforms to or approximates the total target weight and is stabilized. 
     (7) Characteristics 
     (7-1) 
     In the embodiment described above, the weighed target weight setting unit  66  sets the individual weighed target weight Wt for each type of the material on the basis of the apparent specific gravity and the mix volume proportion Pv, and the control unit  60  controls the conveying unit  10  and the mix weighing unit  20  on the basis of the set individual weighed target weight Wt. The plurality of types of the material are thereby mixed at the mix volume proportion Pv after mix weighing, irrespective of whether the apparent specific gravity of the supplied material changes. This results in facilitation of a constant mixing ratio, in terms of external appearance, of the plurality of types of the material after mix weighing. 
     (7-2) 
     In the embodiment described above, the weighed target weight setting unit  66  individually sets the individual weighed target weight Wt for each type of the material on the basis of the total target weight stored in the storage unit  61 . Specifically, the individual weighed target weight Wt are suitably set such that the total weight of the material after mix weighing conforms to or approximates the total target weight. As a result, the total weight after mix weighing is stabilized. 
     (7-3) 
     In the embodiment described above, the apparent specific gravity measurement unit  50  for measuring the apparent specific gravity of each type of the material is disposed upstream from the mix weighing unit  20 . This facilitates measurement of the apparent specific gravity of the supplied material in real time during operation. As a result, the individual weighed target weight Wt can be quickly changed in response to fluctuations in the apparent specific gravity of the supplied material. 
     (7-4) 
     In the embodiment described above, when the apparent specific gravity stored in the storage unit  61  is updated during operation, the individual weighed target weight Wt are newly set by the weighed target weight setting unit  66  on the basis of the updated apparent specific gravity. Specifically, the individual weighed target weight Wt are set in real time on the basis of the updated apparent specific gravity during operation. This results in highly precise facilitation of a constant mixing ratio, in terms of external appearance, of the plurality types of the material after mix weighing even when variation in the apparent specific gravity of the supplied material is notable. 
     (7-5) 
     In the embodiment described above, it is only when the apparent specific gravity of a specific type of the material designated as a specific material is updated that the individual weighed target weight Wt are newly set on the basis of the updated apparent specific gravity. Specifically, the individual weighed target weight Wt is newly set exclusively for a prescribed material of which the apparent specific gravity readily fluctuates. As a result, the individual weighed target weight Wt is efficiently changed within a required minimum range. Specifically, it is configured such that updating of the individual weighed target weight Wt relating to a material of which the apparent specific gravity does not readily fluctuate can be omitted. Accordingly, processing speed is increased. 
     (8) Modifications 
     (8-1) Modification A 
     The mix weighing device  1  indicated in the embodiment described above may be configured in the manner of a mix weighing device la as shown in  FIG. 8 .  FIG. 8  shows a mix weighing device  1   a  based on the premise of performing mix weighing of three or more types of materials (a, b, . . . n). The mix weighing device  1   a  has n number of conveying lines ( 10   a,    10   b,    10   n ), a mix weighing unit  20   a  that has n number of weighing machines  30  ( 30   a ,  30   b,    30   n ), and n number of apparent specific gravity measurement units ( 50   a,    50   b,    50   n ). 
     In such a mix weighing device  1   a , a weighed target weight setting unit  66  calculates each of an individual weighed target weight Wta for a material a, an individual weighed target weight Wtb for a material b, and an individual weighed target weigh Wtn for a material n by a weighed target weight setting process such as is described below. 
     Specifically, in the weighed target weight setting process, the weighed target weight setting unit  66  acquires a mix volume proportion Pv′ from a volume proportion storage region  612 , acquires the apparent specific gravity of each type of the material from an apparent specific gravity storage region  614 , and acquires a total target weight from a total target weight storage region  616 . The mix volume proportion Pv′ is the proportion of the volumes of the material a, the material b, . . . and the material n after mix weighing. 
     Next, the weighed target weight setting unit  66  calculates each of the individual target volumes Vt of each type of the material on the basis of the acquired each value. For example, when the mix volume proportion Pv′ is set to 1:2:3, the proportion of an individual target volume Vta of the material a, an individual target volume Vtb of the material b, and an individual target volume Vtc of a material c is 1:2:3, and the individual target volume Vta of the material a and the individual target volume Vtb of the material b being as follows: 
       Vta=Vtb+Vtc/5 
       Vtb=Vta+Vtc/ 2   
       Vtc=Vta+Vtb 
     Vta: Individual target volume Vt (cc) of material a
 
Vtb: Individual target volume Vt (cc) of material b
 
Vtc: Individual target volume Vt (cc) of material c
 
     The weighed target weight setting unit  66  then calculates the individual weighed target weight Wt for each type of the material on the basis of the individual target volumes Vt, the apparent specific gravity of each type of the materials, and the total target weight. 
     For example, In a case where the total target weight is set to 100 (g), the apparent specific gravity Ga of the material a is calculated as 0.1 (g/cc), the apparent specific gravity Gb of the material b is calculated as 0.2 (g/cc), and the apparent specific gravity Gc of the material c is calculated as 0.15 (g/cc), the individual target volumes Vt of each type of the material is calculated, and the individual weighed target weight Wta, the individual weighed target weight Wtb, and the individual weighed target weight Wtc are calculated as follows: 
       Vta=100×1/(0.1×1+0.2×2+0.15×3)=105.26≈105 (cc)
 
       Vtb=100×2/(0.1×1+0.2×2+0.15×3)=210.52≈211 (cc)
 
       Vtc=100×3/(0.1×1+0.2×2+0.15×3)=315.78≈316 (cc)
 
       Wta=0.1×105=10.5≈11 (g)
 
       Wtb=0.2×211=42.2≈42 (g)
 
       Wtc=0.15×316=47.4≈47 (g)
 
     In such a state, when the apparent specific gravity Gb of the material b designated as a specific material fluctuates to 0.15 (g/cc), the individual target volume Vta, the individual target volume Vtb, the individual target volume Vtc, the individual weighed target weight Wta, the individual weighed target weight Wtb, and the individual weighed target weight Wtc are calculated as follows: 
       Vta=100×1/(0.1×1+0.15×2+0.15×3)=117.64≈118 (cc)
 
       Vtb=100×2/(0.1×1+0.15×2+0.15×3)=235.29≈235 (cc)
 
       Vtc=100×3/(0.1×1+0.15×2+0.15×3)=352.94≈353 (cc)
 
       Wta=0.1×118=11.8≈12(g)
 
       Wtb=0.15×235=35.25≈35 (g)
 
       Wtc=0.15×353=52.95≈53 (g)
 
     In a case where all of the materials a, b, and c are designated as specific materials, when the apparent specific gravity Ga of the material a fluctuates to 0.2 (g/cc), the apparent specific gravity Gb of the material b fluctuates to 0.3 (g/cc), and the apparent specific gravity Gc of the material c fluctuates to 0.1 (g/cc), the individual target volume Vta, the individual target volume Vtb, the individual target volume Vtc, the individual weighed target weight Wta, the individual weighed target weight Wtb, and the individual weighed target weight Wtc are calculated as follows: 
       Vta=100×1/(0.2×1+0.3×2+0.1×3)=90.9≈91 (cc)
 
       Vtb=100×2/(0.2×1+0.3×2+0.1×3)=181.81≈182 (cc)
 
       Vtc=100×3/(0.2×1+0.3×2+0.1×3)=272.72≈273 (cc)
 
       Wta=0.2×91=18.2≈18 (g)
 
       Wtb=0.3×182=54.6≈55 (g)
 
       Wtc=0.1×273=27.3≈27 (g)
 
     Thus, in the mix weighing device  1   a , three or more types of materials are supplied, and individual weighed target weight Wt for each type of the materials are calculated on the basis of the apparent specific gravity of each type of the materials, the mix volume proportion Pv′, and the total target weight. Each type of the materials is thereby mixed at the mix volume proportion Pv′ even when the three or more types of the materials need to be mix-weighed. This results in facilitation of a constant mixing ratio, in terms of external appearance, of the three or more types of the materials after mix weighing. 
     The mix weighing device la can also have applied thereto the concepts set forth in the modifications described later. 
     (8-2) Modification B 
     In the embodiment described above, the weighed target weight setting unit  66  calculated each of the individual weighed target weight Wt for each type of the materials on the basis of the total target weight (g), the apparent specific gravity of each of the materials, and the mix volume proportion Pv in the weighed target weight setting process. However, modifications may instead be made such that the weighed target weight setting unit  66  calculates each of the individual weighed target weight Wt for each type of the materials on the basis of the total target volume (cc), the apparent specific gravity of each type of the materials, and the mix volume proportion Pv. In such a case, a configuration may be adopted such that the storage unit  61  is provided with a total target volume storage region in lieu of the total target weight storage region  616 , a total target volume set by a user being stored in this storage region. Moreover, a configuration may be adopted such that the weighed target weight setting unit  66  performs the weighed target weight setting process in the manner described below. 
     Specifically, the weighed target weight setting unit  66  first acquires the mix volume proportion Pv from the volume proportion storage region  612 , acquires the apparent specific gravity of each type of the materials from the apparent specific gravity storage region  614 , and acquires the total target volume from the total target volume storage region. 
     Next, the weighed target weight setting unit  66  calculates each of the individual target volumes Vt for each type of the materials on the basis of the acquired values. 
     For example, when the mix volume proportion Pv is set to 1:2, the proportion of a first target volume Vt 1  of the food product A and a second target volume Vt 2  of the food product B is 1:2, and the first target volume Vt 1  of the food product A and the second target volume Vt 2  of the food product B being as follows: 
       Vt2=2×Vt1
 
     Vt 1 : Individual target volume Vt (cc) of food product A
 
Vt 2 : Individual target volume Vt (cc) of food product B
 
     The weighed target weight setting unit  66  then calculates individual weighed target weight Wt for each type of the materials on the basis of the individual target volumes Vt, the apparent specific gravity of each type of the materials, and the total target volume. 
     For example, when the total target volume is set to 600 (cc) and the mix volume proportion Pv of the food product A and the food product B is set to 1:2, the first target volume Vt 1  and the second target volume Vt 2  are calculated as follows: 
       Vt 1 =600/(1+2)×1=200 (cc)
 
       Vt 2 =600/(1+2)×2=400 (cc)
 
     The first weighed target weight Wt 1  and the second weighed target weight Wt 2  are then calculated as follows, where the apparent specific gravity G 1  of the food product A is calculated as 0.1 (g/cc), and the apparent specific gravity G 2  of the food product B is calculated as 0.2 (g/cc): 
       Wt1=0.1×200=20 (g)
 
       Wt2=0.2×400=80 (g)
 
     In such a state, when the apparent specific gravity G 2  of the food product B fluctuates to 0.15 (g/cc), the first weighed target weight Wt 1  and the second weighed target weight Wt 2  are calculated as follows: 
       Wt1=0.1×200=20 (g)
 
       Wt2=0.15×400=60 (g)
 
     In a case where the food product A is designated as a specific material, when the apparent specific gravity G 1  of the food product A fluctuates to 0.12 (g/cc) and the apparent specific gravity G 2  of the food product B fluctuates to 0.25 (g/cc), the first weighed target weight Wt 1  and the second weighed target weight Wt 2  are calculated as follows: 
       Wt1=0.12×200=24 (g)
 
       Wt2=0.25×400=100 (g)
 
     Thus, in the present modification, the weighed target weight setting unit  66  calculates each of the individual target volumes Vt for each type of the materials on the basis of the total target volume and the mix volume proportion Pv in the weighed target weight setting process, and calculates each of the individual weighed target weight Wt for each type of the materials on the basis of the calculated individual target volumes V t  and the apparent specific gravity of each type of the materials. That is, it can also be said that the individual weighed target weight Wt are calculated on the basis of the total target volume, the apparent specific gravity of each type of the materials, and the mix volume proportion Pv. Specifically, the weighed target weight setting unit  66  sets the individual weighed target weight Wt for each type of the materials on the basis of the total target volume such that the total volume of the materials after mix weighing conforms to or approximates the total target volume. As a result, the total volume after mix weighing is stabilized. 
     (8-3) Modification C 
     In the embodiment described above, the weighed target weight setting unit  66  calculated each of the individual weighed target weight Wt for each type of the materials on the basis of the total target weight (g), the apparent specific gravity of each type of the materials, and the mix volume proportion Pv in the weighed target weight setting process. However, modifications may instead be made such that the weighed target weight setting unit  66  calculates each of the individual weighed target weight Wt for each type of the materials on the basis of only the individual volume (cc) and apparent specific gravity of each type of the materials. Specifically, when the total target weight after mix weighing is not particularly important, the individual weighed target weight Wt may be calculated without any consideration for the total target weight. 
     In such a case, a configuration may be adopted such that the storage unit  61  is provided with an individual volume storage region in lieu of the total target weight storage region  616 , and a inidividual volume for each type of the materials as set by a user is stored in this storage region. The volume proportion storage region  612  can also be omitted. Moreover, a configuration may be adopted such that the weighed target weight setting unit  66  performs the weighed target weight setting process in the manner described below. 
     Specifically, the weighed target weight setting unit  66  acquires the apparent specific gravity of each type of the materials from the apparent specific gravity storage region  614 , and acquires the individual volumes from the individual volume storage region. 
     Next, the weighed target weight setting unit  66  calculates the individual weighed target weight Wt (first weighed target weight Wt 1  and second weighed target weight Wt 2 ) for each type of the materials on the basis of the acquired values in the manner described below. 
     For example, while the individual volume V 1  of the food product A is set to 200 (cc) and the individual volume V 2  of the food product B is set to 400 (cc), when the apparent specific gravity G 1  of the food product A is calculated as 0.1 (g/cc) and the apparent specific gravity G 2  of the food product B is calculated as 0.2 (g/cc), the first weighed target weight Wt 1  and the second weighed target weight Wt 2  are calculated as follows. 
       Wt1=G1×V1=0.1×200=20 (g)
 
       Wt2=G2×V2=0.2×400=80 (g)
 
     In such a state, when the apparent specific gravity G 2  of the food product B fluctuates to 0.15 (g/cc), the first weighed target weight Wt 1  and the second weighed target weight Wt 2  are calculated as follows: 
       Wt1=0.1×200=20 (g)
 
       Wt2=0.15×400=60 (g)
 
     In a case where the food product A is designated as a specific material, when the apparent specific gravity G 1  of the food product A fluctuates to 0.12 (g/cc) and the apparent specific gravity G 2  of the food product B fluctuates to 0.25 (g/cc), the first weighed target weight Wt 1  and the second weighed target weight Wt 2  are calculated as follows: 
       Wt1=0.12×200=24 (g)
 
       Wt2=0.25×400=100 (g)
 
     Thus, in the present modification, the weighed target weight setting unit  66  calculates each of the individual weighed target weight Wt for each type of the materials on the basis of the apparent specific gravity and individual volume of each type of the materials in the weighed target weight setting process. The individual volume of each type of the materials after mix weighing is thereby stabilized. As a result, the mix volume proportion after mix weighing is stabilized. 
     (8-4) Modification D 
     In the embodiment described above, the apparent specific gravity (G 1  and G 2 ) of the material was calculated on the basis of the mathematical formulas Fa and Fb. However, the mathematical formulas for calculating the apparent specific gravity are not necessarily limited to these, but rather can be modified, as appropriate. 
     Additionally, in the embodiment described above, the apparent specific gravity of each type of the materials was calculated on the basis of a measured value from the apparent specific gravity measurement unit  50 . However, the measured value from the apparent specific gravity measurement unit  50  does not necessarily need to be considered in the calculation of the apparent specific gravity. For example, a configuration may be adopted such that the weight of the material from before the material is supplied to the conveying line is measured, and the apparent specific gravity of each type of the materials is calculated on the basis of such a measured value. In such a case, the apparent specific gravity measurement unit  50  can be omitted. 
     Additionally, the apparent specific gravity of the material does not necessarily need to be calculated by the control unit  60 ; rather, a modification may be made so that the calculated apparent specific gravity is stored in the storage unit  61 . In such a case, the apparent specific gravity measurement unit  50  can be omitted. 
     (8-5) Modification E 
     In the embodiment described above, an example was given of a case where the food product to be mix-weighed by the mix weighing device  1  was popcorn. However, the mix weighing device  1  is not limited to popcorn, but rather is capable of mix-weighing meats, snacks, rice products, dry mixtures, legumes, and any other food products. 
     Additionally, the material to be mix-weighed is not necessarily limited to food products. The mix weighing device  1  is capable of mix-weighing pharmaceuticals and other chemical products, industrial products, electronic components, metal components, and any other such products. 
     (8-6) Modification F 
     In the embodiment described above, a number (i.e., two) of conveying lines equal to the number of types of supplied material were included in the conveying unit  10 . However, the number of conveying lines included in the conveying unit  10  does not necessarily need to be equal to the number of types of the materials, but rather may be greater than the number of types of the materials (i.e., there may be three or more conveying lines). Alternatively, the number of conveying lines included in the conveying unit  10  may be less than the number of types of the materials (i.e., there may be one conveying line). In such a case, a configuration may be adopted such that the type of the materials supplied to the conveying lines is switched at each prescribed time period. 
     (8-7) Modification G 
     In the embodiment described above, a number (i.e., two) of weighing machines  30  equal to the number of types of supplied material were included in the mix weighing unit  20 . However, the number of weighing machines  30  included in the mix weighing unit  20  does not necessarily need to be equal to the number of types of the materials, but rather may be greater than the number of types of the materials (i.e., there may be three or more weighing machines  30 ). Alternatively, the number of weighing machines  30  included in the mix weighing unit  20  may be less than the number of types of the materials (i.e., there may be one weighing machine  30 ). In such a case, a configuration may be adopted such that the type of the materials supplied to the weighing machines  30  is switched at each prescribed time period. 
     (8-8) Modification H 
     In the embodiment described above, a rotation unit  12  was provided to each of the conveying lines of the conveying unit  10 . However, the rotation unit  12  is not necessarily needed, but rather can be omitted, as appropriate. In such a case, a modification may be made such that, e.g., a user suitably extracts the material supplied to the conveying line and sends the material to a prescribed apparent specific gravity measurement unit  50 . 
     Alternatively, a modification may be made such that the apparent specific gravity measurement unit  50  is omitted, and a user measures the weight of the extracted material and suitably inputs the measured value to the control unit  60 . Specifically, a user may perform the processes that would otherwise be performed by the apparent specific gravity measurement unit  50 . 
     (8-9) Modification I 
     In the embodiment described above, only a given material (food product B) from among the plurality of the materials to be mix-weighed is designated as a specific material, and the apparent specific gravity (G 2 ) of only the given material is suitably updated. 
     However, the present invention is not limited to this configuration; rather, a modification may be made such that all (types) of the materials to be mix-weighed are designated as specific materials, or such that the specific material distinction flags F 3  are omitted and the apparent specific gravity of all of the materials is suitably updated. In such a case, each of the individual weighed target weight Wt is suitably adjusted according to fluctuations in the apparent specific gravity of each type of the materials. Specifically, each of the individual weighed target weight Wt is calculated in consideration of even a minute fluctuation in the apparent specific gravity of a material of which the apparent specific gravity does not readily fluctuate. Therefore, highly precise facilitation of a constant mixing ratio, in terms of external appearance, of the material after mix weighing is realized. 
     (8-10) Modification J 
     In the embodiment described above, the control unit  60  was disposed in the mix weighing unit  20 . However, the disposition of the control unit  60  is not limited to this configuration, but rather can be modified, as appropriate. For example, all or part of the control unit  60  may be disposed in the conveying unit  10  and/or the apparent specific gravity measurement unit  50 . Alternatively, a configuration may be adopted such that all or part of the control unit  60  is disposed in a remote location, transmission/reception being made possible via a LAN and/or WAN or other network. 
     (8-11) Modification K 
     In the embodiment described above, the prescribed time periods t 1  and t 2  were set to 30 seconds. However, the prescribed time periods t 1  and t 2  can be suitably changed, according to the situation, and may be set to less than 30 seconds or to at least 31 seconds. For example, the prescribed time periods t 1  and t 2  may be set to 15 seconds, or to one minute. The prescribed time periods t 1  and t 2  do not necessarily need to be set to the same value, but rather may be set to different values. 
     (8-12) Modification L 
     In the embodiment described above, a configuration was adopted such that two types of the materials were mix-weighed. However, the number of types of materials to be mix-weighed is not necessarily limited to two, but rather may be three or more. In such a case, the number of conveying lines and weighing machines  30  may be suitably adjusted, and modifications may be suitably made to the content of the control by the control unit  60 , so as to enable mix-weighing that corresponds to the number of types of materials. 
     (8-13) Modification M 
     In the embodiment described above, the first threshold value AThl is set to 800 cc. However, the first threshold value AThl may be set to less than 800 cc or to at least over 801 cc according to the supplied material and/or design specifications. 
     (8-14) Modification N 
     In the embodiment described above, the weighing machines  30  included in the mix weighing unit  20  were combination weighing machines, but the weighing machines  30  are not limited to this configuration. The weighing machines  30  may be, e.g., automatic weighing machines for automatically weighing and discharging the material of the individual weighed target weight Wt. 
     (8-15) Modification O 
     In the embodiment described above, each of the individual weighed target weight Wt for each type of the materials was calculated on the basis of the apparent specific gravity and the mix volume proportion Pv, or on the basis of the individual volumes (cc) and apparent specific gravity of each type of the materials. However, the present invention is not necessarily limited to this configuration, but rather may be configured so as to be capable of switching between these options. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to a mix-weighing device. 
     REFERENCE SIGNS LIST 
     
         
           1 ,  1   a : Mix weighing device 
           10 : Conveying unit 
           10   a : First conveying line 
           10   b : Second conveying line 
           11 : Drive unit 
           12 : Rotation unit 
           20 ,  20   a : Mix weighing unit 
           30 : Weighing machine 
           30   a : First weighing machine 
           30   b : Second weighing machine 
           31 : Dispersion unit 
           32 : Emission unit 
           33 : Pool hopper 
           34 : Weighing hopper 
           35 : Gathering chute 
           40 : Integration chute 
           45 : Timing hopper 
           50 : Apparent specific gravity measurement unit 
           50   a : First specific gravity measurement unit 
           50   b : Second specific gravity measurement unit 
           51 : Specific gravity measurement hopper 
           52 : Photoelectric Sensor 
           60 : Control unit 
           61 : Storage unit 
           62 : Input/output unit 
           63 : Conveying unit control unit 
           64 : Apparent specific gravity calculation unit 
           65 : Mix weighing unit control unit 
           66 : Weighed target weight setting unit (setting unit) 
       
    
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Laid-open Patent Publication No. H 9-133573