Patent Description:
Weighing apparatus are known which convey an article and measure the weight of the article as it is being conveyed. In such weighing apparatus, sometimes error arises between the actual weight of the article and the weight of the article that is measured due to the article being lifted up by an air flow or the like during conveyance.

To address this, patent document <NUM> (<CIT>) discloses collecting a preset number (a number of tests recommended by the manufacturer) of weighing results (dynamic weighing values) obtained by weighing, while conveying, a sample article whose weight is already known and then calculating a correction value using the collected weighing results. Obtaining a weight value of an article by using the calculated correction value to correct the dynamic measurement value when actually weighing the article is also disclosed.

<CIT> discloses a weighing method for weighing containers having various forms, for example vials, bottles, capsules, containing various substances in the inside thereof, for example liquids, which are more or less viscous, powders, granules, tablets or similar, in particular in the pharmaceutical, medical or food sector, where there is a great need for weighing precision, accuracy and repeatability.

In this connection, the extent to which the weighing results (dynamic weighing values) vary in a weighing apparatus also differs depending on, for example, the environment where the weighing apparatus is installed. For that reason, how many sample article weighing results are necessary to obtain an appropriate correction value differs depending on the weighing apparatus. In other words, the proper value for the number of tests in patent document <NUM> (<CIT>) differs depending on the weighing apparatus.

If, in calculating the correction value, the set number of tests is fewer compared to the proper value, there is a potential that the calculated correction value is not an appropriate value. If the number of tests is set to a sufficiently large number, the potential that the calculated correction value is not an appropriate value can be reduced. However, in this case, there is a potential that an excessive number of tests are performed, which runs the risk of unnecessarily increasing the operating time needed to calculate the correction value.

It is an object of the present invention to provide a weighing apparatus that weighs an article while conveying the article, the weighing apparatus being able to calculate a proper correction value for correcting the weight measured by a measurement unit and the actual weight of the article while reducing the operating time of the weighing apparatus needed for calculating the correction value.

A weighing apparatus of a first aspect includes a conveyance unit, a detection unit, and a control unit. The conveyance unit receive and convey an article. The detection unit detect a weight of the conveyance unit or, in a case where the conveyance unit is conveying the article, a weight of the conveyance unit and a weight of the article on the conveyance unit and output a weigh signal. The control unit calculates a correction value for correcting the weight of the article detected by the detection unit, based on the weigh signals output by the detection unit when a reference sample is conveyed by the conveyance unit for a predetermined number of times. The control unit calculates the predetermined number of times based on the weigh signals output by the detection unit when the control unit drives the conveyance unit.

In the weighing apparatus of the first aspect, the number of times the reference sample should be run when calculating the correction value is calculated based on the weigh signals output by the detection unit when the conveyance unit has been driven, so the occurrence of a situation where the number of weighings of the reference sample is too few for calculating an appropriate correction value or conversely where the number of weighings of the reference sample is too many can be reduced. As a result, in the weighing apparatus of the first aspect, an appropriate correction value can be calculated while reducing the operating time of the weighing apparatus needed to calculate the correction value (the amount of time needed to calculate the correction value).

A weighing apparatus of a second aspect is the weighing apparatus of the first aspect, wherein the control unit calculates the predetermined number of times based on the weigh signals output by the detection unit when the control unit drives the conveyance unit and conveys the article.

In the weighing apparatus of the second aspect, the predetermined number of times is calculated based on the weigh signals output by the detection unit when the article is being conveyed, so an appropriate predetermined number of times for calculating the correction value can be calculated based on the effects of article conveyance in addition to the characteristics of the weighing apparatus itself and the effects of the installation environment.

A weighing apparatus of a third aspect is the weighing apparatus of the second aspect, wherein the control unit calculates the predetermined number of times based on the weigh signals output by the detection unit when the control unit drives the conveyance unit and conveys the reference sample.

In the weighing apparatus of the third aspect, the predetermined number of times is calculated based on the weigh signals output by the detection unit when the reference sample used to calculate the correction value is being conveyed, so an appropriate predetermined number of times for calculating the correction value can be calculated based also on the characteristics of the reference sample that the weighing apparatus actually weighs.

A weighing apparatus of a fourth aspect is the weighing apparatus of the first aspect, wherein the control unit calculates the predetermined number of times based on the weigh signals output by the detection unit when the conveyance unit is driven without conveying the article.

In the weighing apparatus of the fourth aspect, an appropriate predetermined number of times for calculating the correction value can be calculated in a short amount of time without conveying the article by the conveyance unit.

A weighing apparatus of a fifth aspect is the weighing apparatus of any of the first aspect to the fourth aspect, further includes an output unit that outputs the predetermined number of times calculated by the control unit.

In the weighing apparatus of the fifth aspect, the calculated predetermined number of times is output, so an operator or the like operating the weighing apparatus can check whether the number of times that has been calculated is an appropriate value.

A weighing apparatus of a sixth aspect is the weighing apparatus of any of the first aspect to the fifth aspect, further includes a storage unit that stores the predetermined number of times. The control unit stores the calculated predetermined number of times in the storage unit. The control unit calculates the correction value for correcting the weight of the article detected by the detection unit, based on the weigh signals output by the detection unit when the reference sample is conveyed by the conveyance unit the predetermined number of times stored in the storage unit.

In the weighing apparatus of the sixth aspect, the predetermined number of times that has been calculated is automatically set by the weighing apparatus, so the workforce of the operator for manually setting the predetermined number of times can be reduced.

The weighing apparatus of the present invention calculates the number of times the reference sample should be run when calculating the correction value based on the weigh signals output by the detection unit when the conveyance unit has been driven, so the occurrence of a situation where the number of weighings of the reference sample is too few for calculating an appropriate correction value or conversely the number of times of reference sample weighings is too many can be reduced.

An embodiment of the weighing apparatus of the invention will be described with reference to the drawings.

A weighing apparatus <NUM> pertaining to the embodiment of the weighing apparatus of the invention will be described with reference to <FIG>. <FIG> is a schematic front view of the weighing apparatus <NUM> seen from the front. <FIG> is a block diagram of the weighing apparatus <NUM>. <FIG> is a schematic plan view of main parts of the weighing apparatus <NUM> seen from above.

The weighing apparatus <NUM> is a weighing apparatus that weighs a weighing object P while conveying the weighing object P.

As shown in <FIG>, the weighing apparatus <NUM> mainly has a conveyance device <NUM> and a detection device <NUM>. As shown in <FIG>, the weighing apparatus <NUM> also has a control device <NUM> that controls the operations of the conveyance device <NUM> and the detection device <NUM>.

The conveyance device <NUM> receives and conveys the weighing object P, which is supplied from an upstream process not shown in the drawings (e.g., a process to manufacture the weighing object P). Specifically, the conveyance device <NUM> conveys the weighing object P to a place where its weight is detected by the detection device <NUM>.

The detection device <NUM> detects the weight of the weighing object P conveyed by the conveyance device <NUM> and outputs a weigh signal corresponding to the weight the detection device <NUM> has detected to the control device <NUM>. The control device <NUM> calculates a weight W of the weighing object P based on the weigh signal that is output when the detection device <NUM> detects the weight of the weighing object P. Moreover, the control device <NUM> judges whether or not the calculated weight W of the weighing object P is within an allowable weight range. The phrase "the weight W of the weighing object P being within an allowable weight range" means that the weight of the weighing object P is equal to or greater than an allowable minimum weight and equal to or less than an allowable maximum weight.

For example, a sorting device not shown in the drawings is disposed downstream of the weighing apparatus <NUM>. The sorting device sorts the weighing object P based on the weight W of the weighing object P calculated by the control device <NUM>. For example, in a case where the weight W of the weighing object P is outside the allowable weight range, the sorting device removes the weighing object P from the conveyance line of the weighing object P.

The weighing apparatus <NUM> will be described in detail below.

It will be noted that in the following description expressions such as "front", "rear", "upper", "lower", "right", and "left" may be used to describe directions and positional relationships, but these expressions are used for convenience of explanation.

Expressions such as "front", "rear", "upper", "lower", "right", and "left" follow the directions indicated by the arrows in the drawings unless otherwise specified.

The conveyance device <NUM> conveys the weighing object P along a conveyance direction A (see <FIG> and <FIG>).

The conveyance device <NUM> includes a first conveyor <NUM> and a second conveyor <NUM> as well as a first drive unit 18a and a second drive unit 18b. The first drive unit 18a and the second drive unit 18b are, for example, motors.

In the conveyance device <NUM>, as shown in <FIG> and <FIG>, the first conveyor <NUM> and the second conveyor <NUM> are arranged in this order from upstream in the conveyance direction A of the weighing object P.

As shown in <FIG>, among the first conveyor <NUM> and the second conveyor <NUM>, the first conveyor <NUM> is disposed upstream in the conveyance direction A. The first conveyor <NUM> functions as an intake conveyor that introduces to the weighing apparatus <NUM> the weighing object P conveyed from the process upstream of the weighing apparatus <NUM>. The first conveyor <NUM> conveys the weighing object P in the conveyance direction A and passes the weighing object P to the second conveyor <NUM>.

The first conveyor <NUM> includes a first conveyor belt 12a (see <FIG>). The first conveyor belt 12a is entrained about a drive roller 122a and a follower roller 122b, and the first conveyor <NUM> conveys the weighing object P on the first conveyor belt 12a in the conveyance direction A as a result of the first drive unit 18a driving the drive roller 122a.

As shown in <FIG>, among the first conveyor <NUM> and the second conveyor <NUM>, the second conveyor <NUM> is disposed downstream in the conveyance direction A. The second conveyor <NUM> receives and conveys the weighing object P conveyed by the first conveyor <NUM>. The detection device <NUM> detects the weight of the weighing object P which is conveyed by the second conveyor <NUM> and outputs the weigh signal. The second conveyor <NUM> conveys the weighing object P in the conveyance direction A and passes the weighing object P to a process downstream of the weighing apparatus <NUM> (e.g., the sorting device not shown in the drawings).

The second conveyor <NUM> includes a second conveyor belt 14a (see <FIG>). The second conveyor belt 14a is entrained about rollers 144a and 144b, and the second conveyor <NUM> conveys the weighing object P on the second conveyor belt 14a in the conveyance direction A as a result of the second drive unit 18b driving the roller (drive roller) 144a.

The detection device <NUM> will be described with further reference to <FIG> is a schematic configuration diagram of the second conveyor <NUM> of the conveyance device <NUM> and the detection device <NUM>.

As shown in <FIG> and <FIG>, the detection device <NUM> mainly has a sensor <NUM> and a load cell <NUM> serving as an example of a detection unit.

The sensor <NUM> detects that the weighing object P conveyed by the first conveyor <NUM> has reached the second conveyor <NUM>. The sensor <NUM> is, for example, a photoelectric sensor. However, the type of the sensor <NUM> is not limited to a photoelectric sensor and may be any type as long as it is a sensor that can detect the arrival of the weighing object P to the second conveyor <NUM>.

The control device <NUM> detects the timing when the entire weighing object P is on the second conveyor belt 14a based on the detection result of the sensor <NUM>, a conveyance speed V of the conveyance device <NUM>, and a length L1 of the weighing object P in the conveyance direction A. The control device <NUM> calculates the weight W of the weighing object P based on a weigh signal output by the load cell <NUM> while the entire weighing object P is on the second conveyor belt 14a.

The load cell <NUM> includes a spring element 28a that becomes deformed in proportion to force acting thereon and a strain gauge (not shown in the drawings) that is adhered to the spring element 28a, converts strain into an electrical signal (this signal is called a weigh signal), and outputs the electrical signal. In short, the load cell <NUM> sends a weigh signal corresponding to the force acting thereon. The load cell <NUM> is housed inside a case <NUM> disposed under the second conveyor <NUM> (see <FIG>).

Weight detection by the load cell <NUM> will be described. Before describing weight detection by the load cell <NUM>, details about the structure of the second conveyor <NUM> of the conveyance device <NUM> will first be described.

The second conveyor <NUM> mainly has, in addition to the second conveyor belt 14a, a frame <NUM>, a drive roller 144a and a follower roller 144b (see <FIG>).

The frame <NUM> of the second conveyor <NUM> is supported by brackets <NUM> that extend upward from the case <NUM>. The case <NUM>, as shown in <FIG>, is secured to a frame <NUM> of the weighing apparatus <NUM>.

As shown in <FIG>, the drive roller 144a and the follower roller 144b are provided on both ends of the frame <NUM>. The drive roller 144a and the follower roller 144b are supported by the frame <NUM> so as to be freely rotatable. The second conveyor belt 14a is entrained about the drive roller 144a and the follower roller 144b. The second drive unit 18b drives the drive roller 144a, whereby the second conveyor belt 14a rotates and the second conveyor <NUM> conveys the weighing object P on the second conveyor belt 14a in the conveyance direction A.

Due to the above structure, when the weighing object P is not on the second conveyor belt 14a, the load cell <NUM> detects the weight of the second conveyor <NUM> serving as a conveyance unit (the force that the second conveyor <NUM> exerts on the load cell <NUM>) and outputs a weigh signal. It will be noted that, here, the weight of the second conveyor <NUM> is generally the total weight of the frame <NUM>, the drive roller 144a and the follower roller 144b, and the second conveyor belt 14a. Furthermore, when the second conveyor belt 14a is conveying the weighing object P, the load cell <NUM> detects the weight of the second conveyor <NUM> and the weight of the weighing object P on the second conveyor <NUM> and outputs a weigh signal.

The control device <NUM> controls the operations of each part of the weighing apparatus <NUM>. Furthermore, the control device <NUM> performs a process to calculate the weight W of the weighing object P based on the weigh signal sent by the detection device <NUM>.

The control device <NUM> of this embodiment mainly includes a CPU, a memory comprising a ROM, a RAM, and/or an auxiliary storage device (e.g., flash memory), and various electronic circuits. The control device <NUM> controls the operations of each part of the weighing apparatus <NUM> and performs various processes as a result of the CPU reading and executing programs stored in the memory.

It will be noted that the configuration of the control device <NUM> described here is merely an example configuration of the control device <NUM>, and the same functions as those of the control device <NUM> of this embodiment may be realized by hardware such as a logic circuit or may be realized by a combination of hardware and software. Furthermore, the control device <NUM> may be realized by one device or may be realized by plural devices.

The control device <NUM> is electrically connected to the first drive unit 18a and the second drive unit 18b of the conveyance device <NUM> and the sensor <NUM> and the load cell <NUM> of the detection device <NUM>.

The control device <NUM> is also electrically connected to an input device <NUM> and an output device <NUM> (see <FIG>). The input device <NUM> receives various types of commands input by an operator of the weighing apparatus <NUM> and various types of information input by the operator. For example, the input device <NUM> is a touch panel display. The information input to the input device <NUM> includes, for example, a prescribed weight Wt of the weighing object P, the length L1 of the weighing object P, and the conveyance speed V at which the weighing object P is conveyed by the conveyance device <NUM>. The commands and information input to the input device <NUM> are sent to the control device <NUM>. The output device <NUM> is controlled by the control device <NUM> and outputs various types of information. For example, the output device <NUM> is a display that displays various types of information. In other words, in this embodiment, a touch panel display functions as the input device <NUM> and the output device <NUM>.

It will be noted that the input device and the output device are not limited to the above device. For example, the input device may be a communication unit <NUM> that receives commands and information sent from an external device <NUM> (e.g., a mobile device operated by the operator or the like of the weighing apparatus <NUM>, or a central control unit higher than the weighing apparatus <NUM>). Furthermore, the output device may, for example, be a communication unit <NUM> that outputs (sends) various types of information to an external device <NUM> (e.g., a mobile device carried by the operator or the like of the weighing apparatus <NUM>, or a central control unit higher than the weighing apparatus <NUM>). In <FIG>, the external device <NUM> and the communication unit <NUM> are indicated by dashed lines.

The memory of the control device <NUM> includes a storage unit <NUM> that stores various types of information. Examples of the information stored in the storage unit <NUM> will be described later.

The CPU of the control device <NUM> functions as a control unit <NUM> by reading and executing programs stored in the memory.

The control unit <NUM> controls the operations of the weighing apparatus <NUM> based on the commands input to the input device <NUM> and the information input to the input device <NUM>, such as the prescribed weight Wt of the weighing object P, the length L1 of the weighing object P in the conveyance direction A of the weighing object P conveyed in the conveyance direction A by the conveyance device <NUM>, and the conveyance speed V at which the weighing object P is conveyed by the conveyance device <NUM>.

For example, when an operation command is input to the input device <NUM>, the control unit <NUM> controls the operations of the first drive unit 18a and the second drive unit 18b so that the speed at which the weighing object P is conveyed by the first conveyor <NUM> and the second conveyor <NUM> becomes the conveyance speed V.

Furthermore, for example, the control unit <NUM> calculates the weight W of a given weighing object P based on the weigh signal output by the load cell <NUM> when that weighing object P is being conveyed by the second conveyor <NUM>. Specifically, the control unit <NUM> detects the timing when the entire weighing object P is on the second conveyor belt 14a based on the detection result of the sensor <NUM>, the conveyance speed V, and the length L1 of the weighing object P. The control unit <NUM> calculates the weight W of the weighing object P based on the weigh signal output by the load cell <NUM> while the entire weighing object P is on the second conveyor belt 14a. The calculation of the weight W of the weighing object P by the control unit <NUM> will be described later.

Furthermore, for example, the control unit <NUM> judges whether the calculated weight of the weighing object P is within the allowable weight range. For example, the control unit <NUM> judges whether the calculated weight W of the weighing object P is a value between the allowable minimum weight (prescribed weight Wt of article - α) and the allowable maximum weight (prescribed weight Wt of article + β) (α and β are set numerical values). The control unit <NUM> judges that the weighing object P is an accepted article if the calculated weight W of the weighing object P is within the allowable weight range and judges that the weighing object P is a rejected article if the calculated weight W of the weighing object P is outside the allowable weight range.

The process by which the control unit <NUM> calculates the weight W of the weighing object P will be described. First, a configuration of the control device <NUM> for the weight calculation process will be described with reference to <FIG> is a block diagram of a configuration of the control device <NUM> for the weight calculation process.

The control device <NUM> includes an amp <NUM>, an analog filter <NUM>, and an A/D converter <NUM>. Furthermore, the control unit <NUM> includes a signal processing unit <NUM> as a functional unit for the process for calculating the weight of the weighing object P.

The amp <NUM> amplifies the weigh signal input from the load cell <NUM> and outputs the amplified signal to the analog filter <NUM>. The analog filter <NUM> removes unnecessary highfrequency components from the amplified signal and outputs an analog signal. The A/D converter <NUM> converts the analog signal output from the analog filter <NUM> to a digital signal and outputs the digital signal to the signal processing unit <NUM>. The signal processing unit <NUM> filters the digital signal using a predetermined finite impulse response (FIR) filter (hereinafter simply called a filter), although this should not be construed as limiting the filter type. In short, the signal processing unit <NUM> uses the predetermined filter to filter the weigh signal that has been preprocessed by the amp <NUM>, the analog filter <NUM>, and the A/D converter <NUM> (hereinafter the weigh signal after being preprocessed will be called the weigh signal of the load cell <NUM>). The control unit <NUM> calculates the weight W of the weighing object P based on the weigh signal of the load cell <NUM> filtered by the signal processing unit <NUM>. Specifically, the control unit <NUM> calculates the dynamic weight of the weighing object P based on the weigh signal of the load cell <NUM> filtered by the signal processing unit <NUM>. The control unit <NUM> calculates the weight W of the weighing object P by multiplying the dynamic weight by a correction value. The dynamic weight and the correction value will be described later.

It will be noted that, as mentioned above, in a case where the second conveyor belt 14a is conveying the weighing object P, the load cell <NUM> detects the weight of the second conveyor <NUM> and the weight of the weighing object P on the second conveyor <NUM> and outputs a weigh signal. For that reason, in a case where the second conveyor belt 14a is conveying the weighing object P, if the control unit <NUM> calculates the weight as is based on the weigh signal from the load cell <NUM>, the control unit <NUM> calculates the total weight of the second conveyor <NUM> and the weighing object P. Therefore, the control unit <NUM>, before it actually starts measuring the weight of the weighing object P, implements a process to derive a zero point based on the weigh signal output by the load cell <NUM> in a state in which the weighing object P is not on the second conveyor belt 14a. In other words, the control unit <NUM>, before it actually starts measuring the weight of the weighing object P, implements in advance a process to derive the weight of the second conveyor <NUM> that should be subtracted from the total weight of the second conveyor <NUM> and the weighing object P on the second conveyor <NUM>.

It will be noted that the reason the signal processing unit <NUM> filters the weigh signal of the load cell <NUM> is the weigh signal of the load cell <NUM> includes noise caused by the natural vibration of the weighing apparatus <NUM> and rotational vibration of the motors (e.g., the motor used as the second drive unit 18b) and the rollers (e.g., the drive roller 144a and the follower roller 144b of the second conveyor <NUM>) used in the weighing apparatus <NUM>.

Referring to <FIG>, the weigh signal of the load cell <NUM> is a signal that includes a vibration component with a relatively large amplitude (noise) as indicated by the dashed line in <FIG>. The weight of the weighing object P cannot be accurately calculated from the weigh signal that includes this vibration component. Therefore, the signal processing unit <NUM> uses the predetermined filter to filter (reduce the noise in) the weigh signal of the load cell <NUM> to extract a signal with little noise (generally, a signal showing just the force the weighing object P exerts on the load cell <NUM>) such as indicated by the solid line in <FIG>.

The control unit <NUM> calculates the dynamic weight of the weighing object P based on the value of the difference between the weigh signal after being filtered (in which noise has been reduced) by the signal processing unit <NUM> and the zero point. Specifically, the control unit <NUM> calculates the dynamic weight of the weighing object P based on the value of the difference (the value indicated by DW in <FIG>) between the weigh signal in the period in which the entire weighing object P is on the second conveyor belt 14a (the weigh signal in the plateau portion of the solid line in <FIG>) and the weigh signal in the period in which the weighing object P is not on the second conveyor belt 14a.

When measuring the weight of an article as it is being conveyed, sometimes the article being conveyed experiences phenomena such as the article being lifted up by air resistance. For that reason, there is a potential that the dynamic weight of the weighing object P that the control unit <NUM> calculates based on the weigh signal of the load cell <NUM> filtered by the signal processing unit <NUM> differs from the actual weight of the article. Therefore, the control unit <NUM> calculates the weight W of the weighing object P by multiplying the dynamic weight by the correction value so that the dynamic weight is converted to the actual weight of the article.

An example of a method of calculating the correction value will be described with reference to the example of the flowchart of a correction value calculation process of <FIG>. It will be noted that the calculation method described here is merely an example and should not be construed as limiting the calculation method. For example, the order of processes in the flowchart may be appropriately changed where not contradictory.

As a premise for calculating the correction value, it will be assumed that a reference sample S, whose accurate weight is known, exists when calculating the correction value. The reference sample S is not limited, but preferably it is the same type of article as the weighing object P that the weighing apparatus <NUM> will actually weigh.

It will be noted that the accurate weight of the reference sample S is, for example, a weight (static weight) SW calculated based on the weigh signal output by the load cell <NUM> when the reference sample S has been placed on the second conveyor belt 14a in a state in which the conveyance device <NUM> is stopped. It will be noted that in a state in which the conveyance device <NUM> is stopped, since the detection of the weight of the reference sample S is not affected by air resistance, the correction value is unnecessary to calculate the weight SW of the reference sample S. It will be noted that the weight SW of the reference sample S may also be measured in a weighing apparatus different from the weighing apparatus <NUM>.

Assuming the reference sample S exists, the operator attempting to calculate the correction value, for example, operates the input device <NUM> to cause the weighing apparatus <NUM> to operate in a correction value calculation mode (step S <NUM>).

It will be noted that when causing the weighing apparatus <NUM> to operate in the correction value calculation mode, the operator also inputs the value of the weight SW of the reference sample S as information to the input device <NUM>. The weight SW of the reference sample S input to the input device <NUM> is stored in the storage unit <NUM>. It will be noted that in a case where the weight of the reference sample S is measured by the weighing apparatus <NUM>, rather than the weight SW of the reference sample S being input to the input device <NUM> by the operator, the weight calculated by the control unit <NUM> may be stored as is as the weight SW in the storage unit <NUM>.

In the correction value calculation mode, the control device <NUM> causes the conveyance device <NUM> and the detection device <NUM> to operate. Preferably, in the correction value calculation mode, the control device <NUM> controls the operation of the conveyance device <NUM> so that the reference sample S is conveyed at the conveyance speed (the conveyance speed V) used when the weighing apparatus <NUM> actually weighs the weighing object P (the article that is actually weighed). In this state, the reference sample S is placed on the first conveyor <NUM> of the conveyance device <NUM>, the first conveyor <NUM> thereby conveys the reference sample S to the second conveyor <NUM>, and the control unit <NUM> calculates the dynamic weight based on the weigh signal output by the load cell <NUM> of the detection device <NUM> when the reference sample S is being conveyed by the second conveyor <NUM> (step S2). The control unit <NUM> stores the dynamic weight it has calculated in the storage unit <NUM> (step S3). It will be noted that the control device <NUM> continues to operate the conveyance device <NUM> and the detection device <NUM> until the data count of dynamic weights stored in the storage unit <NUM> reaches a predetermined number (a later-described number of times of reference sample weighings N) (step S4). In other words, the operator attempting to calculate the correction value places the reference sample S on the first conveyor <NUM> of the conveyance device <NUM> a number of times equal to the number of times of reference sample weighings N to thereby have the control unit <NUM> calculate the dynamic weight of the reference sample S a number of times equal to the number of times of reference sample weighings N.

When a number of dynamic weights DW<NUM>, DW<NUM>,. , DWN accumulate in the storage unit <NUM> reaches to the number of times of reference sample weighings N, the control unit <NUM> stops the operation of the conveyance device <NUM> (step S5).

Then, the control unit <NUM> uses the following formula <NUM> to calculate a correction value k (step S6).

The control unit <NUM>, when it actually calculates the weight W of the weighing object P, calculates the weight W by multiplying, by the correction value k, the dynamic weight of the weighing object P calculated based on the weigh signal of the load cell <NUM> filtered by the signal processing unit <NUM>. In short, the control unit <NUM> calculates the correction value k for correcting the weight of the weighing object P detected by the load cell <NUM> based on the weigh signals output by the load cell <NUM> when the reference sample S is conveyed by the second conveyor <NUM> a number of times equal to the predetermined number of times of reference sample weighings N.

It will be noted that variations in the value of the dynamic weight calculated by the control unit <NUM> (in other words, the effect of noise remaining in the weigh signal after being filtered) differ depending on, for example, the characteristics of the weighing apparatus <NUM> itself and the environment of the site where the weighing apparatus <NUM> is installed. For example, in a case where there is a device that vibrates in the vicinity of the place where the weighing apparatus <NUM> is installed, and/or the place where the weighing apparatus <NUM> is installed is a place susceptible to the effects of air flows generated by an air conditioning system, variations in the value of the dynamic weight calculated by the control unit <NUM> tend to be large.

If the number of times of reference sample weighings N is set to a fixed value and the number of times of reference sample weighings N is set to a small number, there is a potential that the correction value k calculated for the weighing apparatus <NUM> installed in such an environment is not an appropriate value. Conversely, if the number of times of reference sample weighings N is set to a large number considering the potential for the weighing apparatus <NUM> is installed in such an environment, the possibility that the calculated correction value k is not an appropriate value can be reduced. However, in this case, there is a potential that an excessive number of tests are performed and the operating time needed to calculate the correction value increase unnecessarily.

Therefore, the control unit <NUM> uses a method such as those exemplified below to calculate the number of times of reference sample weighings N suitable for each weighing apparatus <NUM> based on the weigh signals output by the load cell <NUM> when the conveyance device <NUM> (particularly the second conveyor <NUM>) is driven.

A first example of a process for calculating the number of times of reference sample weighings N for the correction value calculation process will be described with reference to the flowchart of <FIG>.

In the first example, the control unit <NUM> calculates the number of times of reference sample weighings N based on the weigh signals output by the load cell <NUM> when the control unit <NUM> drives the conveyance device <NUM> to convey an article. It will be noted that the article the conveyance device <NUM> conveys when calculating the number of times of reference sample weighings N may be arbitrarily selected, but preferably it is the reference sample S. Here, description will be given assuming that the article the conveyance device <NUM> conveys when calculating the number of times of reference sample weighings N is the reference sample S whose weight is already known.

The operator attempting to calculate the number of times of reference sample weighings N, for example, operates the input device <NUM> to cause the weighing apparatus <NUM> to operate in a number-of-weighings calculation mode (step S11).

It will be noted that when causing the weighing apparatus <NUM> to operate in the number-of-weighings calculation mode, the operator also inputs as information the value of the weight SW of the reference sample S to the input device <NUM>. The weight SW of the reference sample S input to the input device <NUM> is stored in the storage unit <NUM>. It will be noted that in a case where the weight of the reference sample S is measured by the weighing apparatus <NUM>, rather than the weight SW of the reference sample S being input to the input device <NUM> by the operator, the weight calculated by the control unit <NUM> may be automatically stored as the weight SW in the storage unit <NUM>.

In the number-of-weighings calculation mode, the control device <NUM> causes the conveyance device <NUM> and the detection device <NUM> to operate in the same way as in the correction value calculation mode. Preferably, in the number-of-weighings calculation mode, the control device <NUM> controls the operation of the conveyance device <NUM> so that the reference sample S is conveyed at the conveyance speed (the conveyance speed V) used when the weighing apparatus <NUM> actually weighs the weighing object P (the article that is actually weighed). In this state, the reference sample S is placed on the first conveyor <NUM> of the conveyance device <NUM>, the first conveyor <NUM> thereby conveys the reference sample S to the second conveyor <NUM>, and the control unit <NUM> calculates the dynamic weight based on the weigh signal output by the load cell <NUM> of the detection device <NUM> when the reference sample S is being conveyed by the second conveyor <NUM> (step S12). The control unit <NUM> stores the calculated dynamic weight in the storage unit <NUM> (step S13). The control device <NUM> continues to operate the conveyance device <NUM> and the detection device <NUM> until the data count of dynamic weights stored in the storage unit <NUM> reaches a predetermined number B (e.g., five) (step S14). In other words, the operator attempting to calculate the number of times of reference sample weighings places the reference sample S on the first conveyor <NUM> of the conveyance device <NUM> a number of times equal to B to thereby have the control unit <NUM> calculate the dynamic weight of the reference sample S a number of times equal to B. It will be noted that for the value of B, a number with which the dispersion of the dynamic weights can be calculated in step S16 and which is as small a value as possible is selected.

When a number of dynamic weights DW<NUM>, DW<NUM>,. , DWB accumulate in the storage unit <NUM> reaches to B, the control unit <NUM> stops the operation of the conveyance device <NUM> (step S15).

The control unit <NUM> uses the following formula to calculate dispersion <MAT> caused by noise (step S16).

It will be noted that the sample mean x when the number of times of reference sample weighings is M follows the normal distribution given by formula <NUM> and formula <NUM> if the dispersion <MAT> caused by noise is already known. <MAT> <MAT>.

Consequently, in a case where, for example, µ is to be kept within a scale interval of ±e in a <NUM>% confidence interval, performing interval estimation using the standard normal distribution yields formula <NUM>.

Thus, by determining M so as to satisfy formula <NUM>, the correction value k can be accurately calculated.

Therefore, the control unit <NUM> determines the smallest whole number greater than the value of M calculated using formula <NUM> to be the number of times of reference sample weighings N (step S <NUM>).

It will be noted that the control unit <NUM> may also output to the output device <NUM> the number of times of reference sample weighings N calculated by the control unit <NUM> (step S18). Specifically, for example, the control unit <NUM> displays the number of times of reference sample weighings N on a display serving as an example of the output device <NUM>.

Moreover, although it is not shown in the flowchart of <FIG>, for example, the control unit <NUM> may have a display serving as an example of the output device <NUM> display an indication prompting an input to the input device <NUM> as to whether or not the number of times of reference sample weighings N is to be employed. Then, in a case where there is an input to the input device <NUM> indicating that the number of times of reference sample weighings N is to be employed, the process may proceed to step S19, and in a case where there is an input to the input device <NUM> indicating that the number of times of reference sample weighings N is not to be employed, the control unit <NUM> may reimplement the series of processes starting from the step S11. By configuring the control unit <NUM> in this way, if, for example, the number of times of reference sample weighings N is for some reason a numerical value that is clearly abnormal, the occurrence of a situation where that value is utilized as the number of times of reference sample weighings N can be inhibited.

It will be noted that the process of step S18, the step of prompting, on the output device <NUM>, the operator to input whether or not to employ the number of times of reference sample weighings N to the input device <NUM>, and the step of inputting to the input device <NUM> an indication that the number of times of reference sample weighings N is to be employed may be omitted.

Next, the control unit <NUM> stores the calculated number of times of reference sample weighings N in the storage unit <NUM> (step S19). The control unit <NUM>, when calculating the correction value k based on the flowchart shown in <FIG>, calculates the correction value k for correcting the dynamic weight of the weighing object P detected by the load cell <NUM> based on the weigh signals output by the load cell <NUM> when the reference sample S is conveyed by the second conveyor <NUM> a number of times equal to the number of times of reference sample weighings N stored in the storage unit <NUM>.

It will be noted that the dynamic weights DW<NUM>, DW<NUM>,. , DWB of the reference sample S obtained when calculating the number of times of reference sample weighings N may also be used for the dynamic weight data of the reference sample S for calculating the correction value k. By using the dynamic weights DW<NUM>, DW<NUM>,. , DWB of the reference sample S obtained when calculating the number of times of reference sample weighings N as the dynamic weight data of the reference sample S for calculating the correction value k, the amount of time needed to calculate the correction value k can be shortened.

A second example of a process for calculating the number of times of reference sample weighings in the correction value calculation process will be described with reference to the flowchart of <FIG>.

In the second example, the control unit <NUM> calculates the number of times of reference sample weighings N based on the weigh signals output by the load cell <NUM> when the conveyance device <NUM> is being driven and the second conveyor <NUM> is not conveying an article (is not conveying anything).

Here, an article such as the reference sample S is not necessary to calculate the number of times of reference sample weighings N.

The operator attempting to calculate the number of times of reference sample weighings N, for example, operates the input device <NUM> to cause the weighing apparatus <NUM> to operate in the number-of-weighings calculation mode (step S11a).

In the number-of-weighings calculation mode of the second example, the control device <NUM> causes the conveyance device <NUM> and the detection device <NUM> to operate in the same way as in the first example. Preferably, in the number-of-weighings calculation mode, the control device <NUM> controls the rotational speed of the motors of the first drive unit 18a and the second drive unit 18b to a rotational speed with which the conveyance speed V is realized when the weighing apparatus <NUM> actually weighs the weighing object P (the article that is actually weighed). In this state, the control unit <NUM> acquires the weighs signal output by the load cell <NUM> while the second conveyor <NUM> is operated (step S12a) and stores the weigh signals in the storage unit <NUM> (step S13a). The control device <NUM> continues to operate the conveyance device <NUM> and the detection device <NUM> and continues to acquire the weigh signals output by the load cell <NUM> and store the weigh signals in the storage unit <NUM> until a predetermined amount of time elapses (step S14a).

When the predetermined amount of time's worth of weigh signals are stored in the storage unit <NUM>, the control unit <NUM> stops the operation of the conveyance device <NUM> (step S15a).

Then, the control unit <NUM> calculates the dispersion <MAT> caused by noise in the weigh signals stored in the storage unit <NUM> (step S16a).

The processes of step S17 to step S19 are the same as the processes of step S17 to step S19 of the first example, so description thereof will be omitted here.

(<NUM>-<NUM>) The weighing apparatus <NUM> pertaining to an example of the weighing apparatus includes the second conveyor <NUM> serving as an example of a conveyance unit, the load cell <NUM> serving as an example of a detection unit, and the control unit <NUM>. The second conveyor <NUM> receives and conveys an article. The load cell <NUM> detects the weight of the second conveyor <NUM> or, in a case where the second conveyor <NUM> is conveying the article, the weight of the second conveyor <NUM> and the weight of the article on the second conveyor <NUM> and outputs a weigh signal. The control unit <NUM> calculates the correction value k for correcting the weight (dynamic weight) of the article detected by the load cell <NUM>, based on the weigh signals output by the load cell <NUM> when the reference sample S is conveyed by the second conveyor <NUM> for a number of times equal to the number of times of reference sample weighings N. The control unit <NUM> calculates the number of times of reference sample weighings N based on the weigh signals output by the load cell <NUM> when the control unit <NUM> drives the second conveyor <NUM>.

In the weighing apparatus <NUM>, the number of times the reference sample S should be run when calculating the correction value k is calculated based on the weigh signals output by the load cell <NUM> when the second conveyor <NUM> has been driven, so the occurrence of a situation where the number of weighings of the reference sample S is too few for calculating an appropriate correction value k or conversely where the number of weighings of the reference sample S is too many can be reduced. As a result, in the weighing apparatus <NUM>, an appropriate correction value k can be calculated while reducing the operating time of the weighing apparatus <NUM> needed to calculate the correction value k (the amount of time needed to calculate the correction value k).

(<NUM>-<NUM>) In the first example, the control unit <NUM> calculates the number of times of reference sample weighings N based on the weigh signals output by the load cell <NUM> when the control unit <NUM> drives the second conveyor <NUM> and conveys the article.

Here, the number of times of reference sample weighings N is calculated based on the weigh signals output by the load cell <NUM> when the article is being conveyed, so an appropriate number of times of reference sample weighings N for calculating the correction value k can be calculated based on the effects of article conveyance in addition to the characteristics of the weighing apparatus <NUM> itself and the effects of the installation environment.

Preferably, the control unit <NUM> calculates the number of times of reference sample weighings N based on the weigh signals output by the load cell <NUM> when the control unit <NUM> drives the second conveyor <NUM> and conveys the reference sample S.

In this weighing apparatus <NUM>, the number of times of reference sample weighings N is calculated based on the weigh signals output by the load cell <NUM> when the reference sample S used to calculate the correction value k is being conveyed, so an appropriate number of times of reference sample weighings N for calculating the correction value k can be calculated based also on the characteristics of the reference sample S that the weighing apparatus <NUM> actually weighs.

(<NUM>-<NUM>) In the second example, the control unit <NUM> calculates the number of times of reference sample weighings N based on the weigh signals output by the load cell <NUM> when the second conveyor <NUM> is being driven without conveying the article.

Here, an appropriate number of times of reference sample weighings N for calculating the correction value k can be calculated in a short amount of time without the article conveying the article by the second conveyor <NUM>.

(<NUM>-<NUM>) The weighing apparatus <NUM> preferably includes the output device <NUM> that outputs the number of times of reference sample weighings N calculated by the control unit <NUM>.

In the weighing apparatus <NUM>, the calculated number of times of reference sample weighings N is output, so an operator or the like operating the weighing apparatus <NUM> can check whether the number of times that has been calculated is an appropriate value (whether it is a value that is clearly too small or a value that is clearly too large technically).

(<NUM>-<NUM>) The weighing apparatus <NUM> includes the storage unit <NUM> that stores the number of times of reference sample weighings N. The control unit <NUM> stores the calculated number of times of reference sample weighings N in the storage unit <NUM>. The control unit <NUM> calculates the correction value k for correcting the weight (dynamic weight) of the article detected by the load cell <NUM>, based on the weigh signals output by the load cell <NUM> when the reference sample is conveyed by the second conveyor <NUM> the number of times of reference sample weighings N stored in the storage unit <NUM>.

In the weighing apparatus <NUM>, the number of times of reference sample weighings N that has been calculated is automatically set by the weighing apparatus <NUM>, so the workforce of the operator for manually setting the number of times of reference sample weighings N can be reduced.

However, the weighing apparatus <NUM> should not be construed as being limited to this, and the operator may also manually input, via the input device <NUM>, the number of times of reference sample weighings N that has been calculated (e.g., the number of times of reference sample weighings N output by the output device <NUM>).

Example modifications of the embodiment will be described below. It will be noted that the example modifications described below may also be appropriately combined where they are not mutually contradictory.

The weighing apparatus <NUM> includes the conveyance device <NUM>, the detection device <NUM>, and the control device <NUM>, but the weighing apparatus <NUM> may also be an apparatus having configurations other than these. For example, in the above embodiment, an example is described where a sorting device separate from the weighing apparatus <NUM> is disposed downstream of the weighing apparatus <NUM>, but the weighing apparatus <NUM> may also have a sorting mechanism that sorts the weighing object P based on the weighing results of the weighing object P.

The present invention can be widely applied to weighing apparatus that weigh an article while conveying the article, and is therefore useful.

Claim 1:
A weighing apparatus (<NUM>) comprising:
a conveyance unit (<NUM>) configured to receive and convey an article (P);
a detection unit (<NUM>) configured to detect a weight of the conveyance unit or, in a case where the conveyance unit is conveying the article, a weight of the conveyance unit and a weight of the article on the conveyance unit and output a weigh signal; and
a control unit (<NUM>) configured to calculate a correction value for correcting the weight of the article detected by the detection unit, based on the weigh signals output by the detection unit when a reference sample (S) is conveyed by the conveyance unit for a predetermined number of times,
wherein the control unit is configured to calculate the predetermined number of times based on the weigh signals output by the detection unit when the control unit drives the conveyance unit.