Claims
- 1. A zero-point adjustment unit for a weighing device comprising
- a rough adjustment circuit,
- a fine adjustment circuit, and
- a central processing unit adapted to adjust the zero-point of said weighing device by receiving a no-load weight signal outputted from said weighing device and controlling the output signals from said rough and fine adjustment circuits.
- 2. The zero-point adjustment unit of claim 1 wherein said rough adjustment circuit includes a first digital-to-analog converter for rough zero-point adjustment and a first subtracter for rough zero-point adjustment, and said fine adjustment circuit includes a second digital-to-analog converter for fine zero-point adjustment and a second subtracter for fine zero-point adjustment.
- 3. The zero-point adjustment unit of claim 2 wherein said rough and fine adjustment circuits include an analog-to-digital converter, said first subtracter serves to receive an output signal from said first digital-to-analog converter and an analog no-load signal from said weighing device and to correspondingly output a first difference signal, and said second subtracter serves to receive an output signal from said second digital-to-analog converter and an output signal from said first subtracter and to correspondingly output a second difference signal to said analog-to-digital converter.
Parent Case Info
This is a division, of application Ser. No. 094,119 filed Sept. 4, 1987, U.S. Pat. No. 4,771,836 which was a division of Ser. No. 06/772,244, Sept. 3, 1985, U.S. Pat. No. 4,694,920.
This invention relates to zero-point adjustment of a weighing device and more particularly to a zero-point adjustment unit for More particularly, it relates to a combinational weighing system having at least three microcomputers in its control unit for monitoring weight data, driving the means for delivering the articles to be weighed, performing combinational computations and controlling the operation of the system.
Combinational weighing means weighing articles by a plurality of weighing devices, performing arithmetic operations for combinations of measured weight values and then selecting a combination according to a predetermined criterion. The major features of combinational weighing are great accuracy and high throughput. U.S. Pat. No. 4,398,612 issued Aug. 16, 1983 and assigned to the present assignee, for example, discloses an automatic weighing system of a combinational weighing type having a number of article batch handling units arrayed radially. Articles to be weighed are typically transported by a conveyor and dropped onto an article feeding unit which distributes them into the individual article batch handling units. Weight-measuring means associated with the individual article batch handling units are electrically connected to a control system such as a computer. The computer not only computes combinations of weight values obtained from these weight-measuring means and selects a combination according to a predetermined criterion such as the combination which gives a total weight that is within a preselected range, but also discharges the article batches from these selected article batch handling units for packaging.
Systems according to the invention disclosed in U.S. Pat. No. 4,398,612 such as Models CCW-201RLC and CCW-211RLC manufactured and sold by the assignee corporation have revealed the desirability of certain improvements. Regarding their control units, in particular, it is found desirable to generally improve the system flexibility and to introduce simpler methods of effecting zero-point and span adjustment on the weighing means. An easier input unit is also desirable by which even a relatively inexperienced user can operate the system in a variety of modes.
It is therefore an object of the present invention to provide a combinational weighing system with a control unit which is flexible and enjoys an increased degree of freedom in adjusting and controlling this system.
It is another object of the present invention to provide a combinational weighing system with a control unit which allows the user to efficiently perform zero-point and span adjustments of the weighing means in the system.
It is a further object of the present invention to provide a combinational weighing system with an input-output unit which enables even a relatively inexperienced user to efficiently perform a great variety of available functions of the system without increasing the probability of committing operational errors or necessitating the use of an operational manual.
It is a still further object of the present invention to provide an input-output unit for a combinational weighing system such that the scope of operation can be varied, depending on the qualification of the user.
In general, the present invention provides a combinational weighing system of the type having a plurality of separate article batch handling units which are adapted to receive individual article batches, to measure their weights, to output analog weight signals and to selectively discharge the measured article batches in response to a discharge signal. Its control unit includes at least three central processing units such as microcomputers individually for weight-monitoring, drive-controlling and combination computation purposes. The weight-monitoring computer is adapted to receive the weight signals and to calculate and store batch weight values indicative of the weights of the individual article batches. The drive-control computer is adapted to receive an article batch discharge signal and to cause the article batch handling units to selectively discharge article batches according to the article batch discharge signal. The combinational computation computer is not only used for combinational computation but is also adapted to control the overall operation of the system. The weight-monitoring part of the control system includes circuits for both rough and fine zero-point adjustment so that not only fine adjustment but also rough adjustment can be effected automatically. Span adjustment is also made easier by a method which provides a target output value according to which an analog-to-digital converter is adjusted.
The accompanying drawings, which re incorporated in and form a part of the specification, illustrate one embodiment of the present invention and, together with the description., serve to explain the principles of the In the drawings:
FIG. 1A-1C is a block diagram of a control unit according to on embodiment of the present invention for a combinational weighing system,
FIG. 2A-2G is a chart of the calculation computer in the control unit of FIG. 1,
FIG. 3A-3E is chart of the weight-monitoring computer in the ocntrol unit of FIG. 1,
FIG. 4A-4I is a chart of the drive-control computer in the control unit of FIG. 1,
FIG. 5 is a drawing for explaining the principle of span adjustment, and
FIG. 6 is a schematic front view of a control panel.
US Referenced Citations (4)
Divisions (2)
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Number |
Date |
Country |
| Parent |
94119 |
Sep 1987 |
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| Parent |
772244 |
Sep 1985 |
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Patent Grant
4850442
