GB2079554A - Automatic combination weighing machine - Google Patents

Abstract

An automatic weighing machine for arranging samples of a product into groups each having a total weight within a preset range includes a single weighing device for weighing the samples sequentially the samples being supplied to respective retaining hoppers, the measured weights being stored in respective memories 54, the contents of different combinations of these memories are summed up and the sum is compared 68,70 with the preset range, and, when the sum is within said range the contents of the hoppers corresponding to the memories of the particular combination are discharged and collected together. <IMAGE>

Description

SPECIFICATION Automatic combination weighing machine This invention relates to an automatic combi nation weighing machine, for use in instances wherein a plurality of articles or samples of a product are packed together with each pack having nearly constant weight.

A weighing device which is generally re ferred to as a "combination balance" or "combination weighing device" is used for separating articles, such as cakes, fishes and vegetables, having relatively large variations in their weights, and collecting selected arti cles together into a group having a total weight which is nearly equal to a predeter mined intended weight. A typical example of such a device is disclosed in United States Patent No. 3,939,928, and another example which is improved over this U.S. Patent in arithmetic arrangement is described in the pending patent application No. 7942517 filed December 10, 1979.In these devices, a plurality of articles are weighed individually by the same number of weighing balances at the same time, all mathematical combinations of the respective weights are summed respec tively and the respective sums are subtracted ) from the intended weight to obtain corre sponding deviations. Thus, the combination providing the least deviation is selected. How ever, these devices must be provided with a plurality of weighing balances whose number is equal to the number of the articles con tained in each pack. Therefore, they are ex pensive and become more expensive as the number of articles in each pack increases.

According to the present invention there is provided an automatic combination weighing machine, comprising a single weighing device for weighing samples of a product and pro ducing an output indicative of the weight of a sample being weighed, a plurality of retaining hoppers for holding samples delivered thereto and each arranged to discharge the sample held therein in response to a gating signal, delivery means for delivering weighed product samples to the hoppers, means for feeding samples in turn first to the weighing device to be weighed thereby and then to the delivery means, a plurality of memories associated with respective hoppers and coupled to the weighing device for each memory to receive an input indicative of the weight of a sample when that sample is delivered to the hopper associated with said memory, the memories having outputs respectively connected through normally open switches to arithmetic means arranged to sum the inputs supplied thereto and provide an output signal when the input sum is within a preset range, control means for closing said switches in accordance with difference combinations and providing an output indicative of the particular combination, a temporary memory for storing the output from the control means and responsive to an output signal from the arithmetic means to reset the memories associated with the switches closed at that time and to supply gating signals to the hoppers associated with said memories for said hoppers to discharge the contents thereof.

It should be understood that each product sample may be a separate article, a group of articles or an amount of material.

Such a machine needs only one weighing device regardless of the number of samples in each pack, and can operate continuously and efficiently in automatic fashion.

A better understanding of this invention will be had from the following detailed description given with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of an embodiment of the automatic combination weighing machine according to this invention, representing an arrangement of its structural components; Figure 2 is a schematic plan view representing an arrangement of the retaining hoppers of the embodiment of Fig. 1; Figure 3 is a block circuit diagram of the control system of the embodiment of Figs. 1 and 2; and Figure 4 is a schematic side view representing another embodiment of the article feeding mechanism applicable to the system of this invention.

Throughout the drawings, same reference symbols are given to corresponding structural components.

Referring to Fig. 1, the machine includes a weighing device 10 having a weighing cradle 1 2 for weighing articles 14 transferred one by one from an adjoining receptacle 1 6 by a wavy transferring arm 1 8 which is circularly moved by a pair of wheels 20 rotating synchronously in the same direction as shown.

The articles 14, having generally a substantial variance in their weights, are fed sequentially onto the receptacle 1 6 by a backet conveyor 22 and then transferred in turn by the arm 18 through the cradle 1 2 and a ramp 24 into a shoot 26. The weighing device 10 produces successively electric signals (W) indicative of the weights of articles and sends them to a control system 28. The wheels 20 and the conveyor 22 are driven synchronously by a driving mechanism 30 which is controlled by a control signal (D) from the control system 28.

In Figs. 1 and 2, the shoot 26 is fixed centrally to a large toothed wheel 32 which meshes with a pinion 34 driven by a reversible motor 36, so that it can be rotationally driven under control of a control signal (M) supplied from the control system 28 to the motor 36 around its central axis 38. The shoot 26 has a lower outlet 40 angularly deviating from the central axis 38 and facing to eight retaining hoppers 42-1, 42-2, 42-3, ... 42-8 which are arranged circularly at equal intervals under the shoot 26. The each hopper 42 has a normally closed gate 44 at the bottom (shown as opened) and a sensing and control unit 46 adapted thereto.

The unit 46 includes a load sensing element, such as load cell, and supplies a sensing signal (S) to the control system 28 when the article 14 exists in the hopper. The unit 46 also includes a gate control device, such as electromagnet, actuated by a gating signal (G) from the control system 28 to open the gate 42 for a preset short period of time to exhaust the article in the hopper. The gates 44 of the all hoppers 42 open in a common collecting shoot 48 and the articles from the hoppers are collected therein together and exhausted downwards for packing. Corresponding to the eight retaining hoppers 42, eight microswitches 50-1, 50-2, 50-3, .. 50-8 are arranged circularly so that their contacts can touch with a moving contact 52 which is fixed to the toothed wheel 32 to be moved with the shoot 26, and can produce a signal (H) indicative of the hopper 41 faced at that time by the outlet 40 of the shoot 26, to the control system 28.

Referring to Fig. 3 representing a main portion of the control system 28, the weight signals W1, W2, W3, ... W8 produced sequentially by the weighing device 10 are supplied through a switching device (not shown), such as rotary switch, to memories 54-1, 54-2, 54-3, ... 54-8, sequentially.

The memories 54-1, 54-2, 54-3, ... 54-8 are arranged to produce control signals Al, A2, A3, ... A8, respectively, when they received their contents, which are applied to an AND gate 56. The AND gate 56 produces an output to actuate a combination generator 58 when the all memories 54 are filled. The combination generator 58 has eight outputs respectively coupled to the control inputs of eight normally open switches 60-1, 60-2, 60-3, ... 60-8 which couple respectively the outputs of the memories 54-1, 54-2, 54-3, ... 54-8 to an adder and subtractor 62.

The combination generator 58 is a device for successively producing all mathematical combinations of the outputs, whose number should be 2"-1 in total if the number of outputs is n, therefore 28-1 = 255 in this example, to close the switches 60 in accordance with these combinations. Although various circuit configurations can be considered by those skilled in the art for the combination generator 58, an example which is relatively simple is an orbit (8-bit, in this embodiment) binary counter which is driven by a suitable clock generator (not shown).When the parallel outputs derived from the respective bits of the counter are coupled respectively to the control inputs of the switches 60 and the switches are arranged to close in response to binary "1" inputs for example, the switches 60 will encounter the all combinations of actuation during progression of count from zero to the greatest or full count. The outputs of the combination generator 58 are also applied successively to a combination memory - 64 and stored temporarily therein.

The contents of the memories 54 supplied through the actuated switches 60 to the adder and subtractor 62 are summed up and then subtracted from the present content of a reference weight register 66 to obtain a plus or minus deviation from a predetermined reference weight in the adder and subtractor 62.

The deviation output of the adder and subtractor 62 is applied to a pair of comparators 68 and 70 and compared with allowable upper and lower deviations which are respectively preset in upper and lower limit registers 72 and 74. The comparators 68 and 70 are arranged to produce signals when the input deviations are within the preset limits. When the both comparators 68 and 70 produce outputs at the same time, an AND gate 76 receives them and produces an output. This output is coupled to the trigger input of the combination memory 64 to cause it to exhaust its content as corresponding gating signals (G) which are in turn applied to the control units 46 (Fig. 1) of the corresponding retaining hoppers 42 to open their gates 44.

Thus, a set of hoppers 42 specified by the allowable combination exhaust their contents into the collecting shoot 48 for packing. The gating signals (G) are also applied to reset inputs of the corresponding memories 54 to reset their contents.

When the retaining hoppers 42 exhaust their contents, their sensing units 46 supply vacancy signals to a drive control unit 78.

Then, the drive control unit 78 supplies a motor control signal M to the motor 34 to drive the shoot 26 so that its outlet 40 is sequentially directed to the vacant hoppers 42, in co-operation with the microswitches 50 which supply outlet position signals (S) to the control unit 78. At the same time, the drive control unit 78 supplies a drive signal D to the driving mechanism 30 to drive the conveyer 22 and the transferring arm 1 8 so that additional articles 14 are successively weighed by the weighing device 10 and then thrown into the vacant hoppers 42, respectively. When the vacant hoppers 42 and also the reset memories 54 corresponding thereto are thus filled again, the AND gate 56 produces an output to disable the drive control unit 78 and again actuate the combination generator 58. Thus, a new cycle of operation is initiated and the same procedure as aforementioned is repeated. As the such pattern of drive control is often used in various technical fields and the circuit configuration of the drive control unit 78 can be designed arbitrarily by those skilled in the art, no more detailed description will be done about the unit 78.

If there was no combination of articles in the hoppers 42 the total weight of which came in the predetermined range, no output is produced from the AND gate 76. Therefore, a NAND gate 80 whose inputs are respectively coupled to the outputs of the AND gates 76 and 56 produces an output and applies it to an alarm unit 82, such as lamp or buzzer, to actuate the same. In this case, the operator may stop the machine, remove the articles manually from the all hoppers and then resume the operation similarly. It is also understood that the alarm unit 82 is also actuated when no output is produced from the AND gate 56 due to any vacancy existing among the memories 54.

Although, in this embodiment, eight (8) retaining hoppers 42 and corresponding memories 54 and other components are used, it should be noted that this number is only for an illustrative purpose and can be selected optionally as occasion demands. Though the embodiment of Fig. 1 has been shown and described as the articles are weighed one by one and the each hopper retains a single article, this invention is also applicable to such a case where the articles to be packed are relatively small-sized, particulate or powdered and weighed and retained group by group.

Fig. 4 shows an example of article feeding mechanism which can be used in the such case. As shown in the drawing, particulate articles 1 4 are transferred by a belt conveyor 84 and a vibration conveyer 86 to a rotary feeder 88, which divides the articles 14 into groups successively and throws the each group in a hopper-like cradle 1 2 of the weighing device 1 0. The cradle 1 2 has a controlled gate 90 which is opened periodically to send the content to the shoot 26. Other part of operation is same as that of the embodiment of Fig. 1. Furthermore, instead of the alarm unit 82 in the embodiment of Fig. 3, logic means may be provided for searching a combination which gives a total weight which is outside but nearest the allowable range and opening the corresponding gates of the hoppers, so that the operation is continued automatically without interruption.

Claims (8)

1. An automatic combination weighing machine, comprising a single weighing device for weighing samples of a product and producing an output indicative of the weight of a sample being weighed, a plurality of retaining hoppers for holding samples delivered thereto and each arranged to discharge the sample held therein in response to a gating signal, delivery means for delivering weighed product samples to the hoppers, means for feeding samples in turn first to the weighing device to be weighed thereby and then to the delivery means, a plurality of memories associated with respective hoppers and coupled to the weighing device for each memory to receive an input indicative of the weight of a sample when that sample is delivered to the hopper associated with said memory, the memories having outputs respectively connected through normally open switches to arithmetic means arranged to sum the inputs supplied thereto and provide an output signal when the input sum is within a preset range, control means for closing said switches in accordance with different combinations and providing an output indicative of the particular combination, a temporary memory for storing the output from the control means and responsive to an output signal from the arithmetic means to reset the memories associated with the switches closed at that time and to supply gating signals to the hoppers associated with said memories for said hoppers to discharge the contents thereof.

2. A machine as claimed in claim 1, wherein each of the hoppers comprises a discharge opening normally closed by a gate, the gate being arranged to be opened in response to a gating signal from the temporary memory.

3. A machine according to claim 1 or 2, wherein the hoppers are arranged around a circle, and the delivery means comprises a chute mounted for rotation about the axis of the circle, and means for controlling the position of the chute about said axis to deliver a weighed sample into a selected hopper.

4. A machine according to claim 1, 2 or 3, wherein said switch control means comprises a binary counter having bit outputs coupled respectively to control inputs of said normally open switches, and a clock pulse generator coupled to the input of said counter.

5. A machine according to any one of claims 1 to 4, wherein said memories are arranged to produce respective pilot outputs when weight signals are stored therein, and AND circuit has respective inputs coupled to said pilot outputs of said memories, and said switch control means is arranged to commence operation in response to an output from said AND circuit indicating that all the hoppers contain samples.

6. A machine according to claim 5, wherein a NAND circuit has respective inputs coupled to the outputs of said AND circuit and said arithmetic means, and an alarm means is arranged to be actuated by an output from said NAND circuit.

7. A machine according to any one of claims 1 to 6, wherein means is provided for detecting a lack of contents in the retaining hoppers to produce vacancy signals, the delivery means is controlled in response to said vacancy signals for delivering weighed samples to the empty hoppers.

8. An automatic combination weighing machine substantially as herein described with reference to the accompanying drawings.