FR2486235A1 - Automatic combination weighing machine - uses single weighing device for weighing samples supplied to respective retaining hoppers - Google Patents

Abstract

The 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 are 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. 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. Pref 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 combination memory.

Description

 This invention relates to an automatic weighing machine that can be used, for example, in applications where a plurality of objects are wrapped together, each package of objects having an almost constant weight.

 Such a weighing machine which is generally called "combined balance or" combined weighing device "is used to extract and collect a plurality of objects from a group of objects, such as for example cakes, fish or vegetables whose respective weights have relatively large variations so that the group extracted has a weight which is practically equal to a predetermined value. A typical example of such a device is described in US Pat. No. 3,939,928 and another example, which constitutes an improvement of this prior device in an arithmetic arrangement is described in French patent n o 79 30299 filed on December 11, 1979. In these prior devices, a plurality of objects are weighed individually and at the same time. using an equal number of weighing scales, the sum of all the mathematical combinations of the respective weights is respectively performed and the respective sums are subt weights of the desired weight so as to obtain the corresponding deviations. The combination providing the smallest deviation or deviation is thus chosen. However, such devices must be provided with a plurality of weigh scales, the number of which is equal to that of the articles contained in each package. As a result, these devices become more and more expensive with the increase in the number of objects.

 Therefore, an object of this invention is to provide an automatic weighing device which requires only a weighing scale regardless of the number of objects in each package.

 Another object of this invention is to provide an automatic weighing machine which can perform such grouping, efficiently, continuously and automatically.

 An automatic weighing machine according to the invention comprises a unique weighing device designed to weigh an object or a group of objects and generate a signal representative of the weight and a plurality of memories for storing the signals representative of the weight, delivered successively by the weighing device. This weighing device comprises means for delivering the objects one by one or group by group to the weighing device. A plurality of storage hoppers are arranged respectively in correspondence with the memories and means are provided for successively transferring the objects from the device. weighed in the respective hoppers. Each hopper has a normally closed gate, placed at its lower part, this gate temporarily opening in response to a gate signal from a combination memory. The outputs of the respective memories are coupled, via respective normally open switches, to an arithmetic unit which is designed to sum its inputs, subtract this sum from a predetermined value and produce a output when the difference is within a predetermined range. A switching control device is provided for closing some of the normally open switches, chosen according to a plurality of predetermined combinations. The combination outputs for controlling the switches are also successively delivered to the combination memory where they are temporarily stored, this memory producing a combination of gate signals from the hoppers, in response to the output of the arithmetic unit.

Other characteristics and advantages of this invention will emerge from the description given below with reference to the accompanying drawings which illustrate various examples of non-limiting embodiments.
- Figure 1 is a schematic side elevation view
of an embodiment of an automatic weighing machine
according to this invention, this figure illustrating the arrangement
structural components of the machine,
- Figure 2 is a schematic plan view showing
the detail of the storage hopper system of the real mode
sation shown in Figure 1
- Figure 3 is a block diagram of the control system
of the embodiment shown in Figures 1 and 2 and,
- Figure 4 is a schematic side elevation view
representing another exemplary embodiment of the mechanism
feeding objects, applicable to the machine according to the
vention.

 In all the figures, the components of corresponding structure have been given the same reference symbols.

 Referring to FIG. 1, it can be seen that the automatic weighing machine according to the invention comprises a weighing device 10 comprising a platform 12 for weighing objects 14 delivered one by one, from a neighboring receptacle 16, by a bent transfer arm 18 which is circularly mobile under the action of a pair of wheels 20 driven in rotation in synchronism in the same direction, as indicated in the drawing. The objects 14, the respective weights of which generally have substantial differences in weight, are brought sequentially to the receptacle 16 by a bucket conveyor 22 and then they are transferred in turn by the arm 18 to the plate 12 then in a chute 26 by means of an inclined plane 24. The weighing device 10 successively produces electrical signals (W) representing the weights of the objects and it delivers them to a control system 28. The wheels 20 and the conveyor 22 are driven in synchronism by a drive mechanism 30 which is controlled by a control signal (D) coming from the control system 28.

 In the exemplary embodiments illustrated in FIGS. 1 and 2, the chute 26 is fixed by its central part on a large diameter toothed wheel 32 which meshes with a pinion 34 driven by a reversible motor 36 so that it can be moved rotating around its axis 38 under the control of a signal (M) delivered by the control system 28 of the motor 36.

The chute 36 has a lower outlet orifice 40, angularly offset with respect to the central axis 38 and disposed opposite eight storage hoppers 42-1, 42-2, 42-3 ... 42-8, which are circularly arranged at regular intervals, under the chute 26. Each hopper 42 has at its lower part a normally closed grid 44 (shown open in the drawing) and a detection and control unit 46 adapted to the grid. The unit 46 comprises a load sensing element, such as for example a load cell, and it delivers a detection signal (S) to the control system 28, when an object 14 is present in the hopper. 46 also comprises a gate control device, for example an electromagnet, actuated by a gate signal (G), coming from the control system 28, to open the gate 42 for a short predetermined period so as to cause the object of the hopper. The grids 44 of all the hoppers 42 open into a common collecting chute 48 and the objects coming from the hoppers are collected together in this chute from where they are extracted down for packaging. Eight micro-switches 50-1, 50 -2, 50-3 ... 50-8, corresponding to the eight storage hoppers 42, are arranged in a circle so that their contacts can touch a movable contact 52 which is fixed to the toothed wheel 32 to be moved with the chute 26, the micro-switches being able to produce a signal (H) indicating which is the hopper 42 which, at this instant, is arranged opposite the outlet orifice 40 of the chute 26, this signal being delivered to the control system 28.

Reference is now made to FIG. 3 which represents an essential part of the control system 28. The weight signals W1, W2, W3 ... W8, produced sequentially by the weighing device 10, are delivered by the via a switching device (not shown), for example a rotary switch, to memories 54-1, 54-2 54-3 ... 54-8, sequentially. The memories 54-1 ... 54-8 are designed and produced so as to produce control signals AI, A2, A3
A8, respectively, when they receive their contents, these signals A1, ... A8 being applied to an AND gate 56. This gate 56 produces an output for actuating a combination generator 58 when all of the memories 54 are filled. The 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 respectively couple the outputs of the memories 54-1, 54-2, 54 -3 ... 54-8 to an adder subtractor 62.

 The combination generator 58 is a device designed to successively reproduce all the mathematical combinations of the outputs, the number of which will be 2n - 1 in total if the number of outputs is equal to n, therefore 28 - 1 = 255 in this example, to close the switches 60 according to these combinations. A certain number of circuit configurations can be envisaged by a person skilled in the art as regards the design and production of the combination generator 58.

A relatively simple example is constituted by a binary counter with n - binary digits (8 in this exemplary embodiment) which is driven by a suitable clock generator (not shown). When the parallel outputs derived from the respective binary digits of the counter are respectively coupled to the control inputs of the switches 60 and the latter are designed and arranged so as to be closed in response to the binary inputs "1" for example, the switches 60 meet all the operating combinations during the counting progression from zero to the largest digit or Until the counting ends. The outputs of the combination generator 58 are also applied successively to a combination memory 64 and they are temporarily stored.

 The contents of the memories 54 delivered, via the actuated switches 60, to the adder-subtractor 62, are added and then subtracted from the predetermined content (setpoint) of a reference weight register 66, in order to obtaining a positive or negative deviation from a predetermined reference weight in the adductor-subtractor 62. The deviation or deviation output of the additivist-subtractor 62 is applied to a pair of comparators 68 and 70 and it is compared to permissible upper and lower deviations or deviations which are respectively predetermined in the upper and lower registers 72 and 74. The comparators 68 and 70 are designed and produced so as to produce signals when the input deviations are between pre-established limits.

When the two comparators 68 and 70 simultaneously produce outputs, these are received by an AND gate 76 which produces an output. This output is coupled to the trigger input of the combination memory 64 in order to cause the latter to extract its content in the form of corresponding grid signals (G) which are in turn applied to the control units 46 ( FIG. 1) corresponding storage hoppers 42, in order to open their grids 44. Consequently, a set of hoppers 42, specified by the admissible combination, release their content which is collected in the collecting chute 48 to then carry out the packaging . The gate signals (G) are also applied to restore the inputs of the corresponding memories 54 so as to restore their content.

 When the storage hoppers 42 release their contents, their detection units 46 deliver vacancy signals to a drive control unit 78. Then, the drive control unit 78 delivers a motor control signal M to the motor 34 for driving the chute 26 so that its outlet 40 is directed sequentially towards the vacant hoppers 42, in co-operation with the micro-switches 50 which deliver to the control unit 78 position signals (S) supply outlet port. At the same time, the drive control unit 78 delivers a drive signal (D) to the drive mechanism 30 in order to start the conveyor 22 and the transfer arm 18 so that additional objects 14 are successively weighed by the weighing device 10 and then introduced respectively into the vacant hoppers 42. When the vacant hoppers 42 and also the corresponding memories 54 denied at zero are at n When the door is filled, the ET grid 56 produces an output to deactivate the drive control unit 78 and connects to the combination generator 58. Thus a new operating cycle is initiated and the same process as described above takes place again. given that such a drive control configuration is often used in various technical fields and that the circuit configuration of the drive control unit 78 can be designed and implemented arbitrarily by those skilled in the art art, we will not give here a description of this unit 78.

 If there is no combination of objects in the hoppers es2 whose total weight falls in the predetermined range, no output is produced from the AND grid 76. Consequently, a NON-AND grid 80 whose inputs are respectively coupled to the outputs of ET gates 76 and 56, produces an output and applies this to an alarm unit 82, for example a lamp or a buzzer, to excite this unit. In this case, the operator can stop the machine, manually remove the objects from all the hoppers and then repeat the operations in the same way. We understand that the alarm unit 82 is also actuated when no output is not produced from the AND grid 56 due to any vacancy existing among the memories 54.

 Although in the embodiment which has just been described, eight storage hoppers 42 and eight corresponding memories 54 have been used, as well as the same number of other components, it will be noted that this figure is only an example not limiting since it can be chosen according to needs.

 Although the example of embodiment shown in FIG. 1 has been represented and described with reference to objects weighed one by one and each hopper holding a single object, it remains to be understood that this invention also applies to the examples of application in which the objects to be packaged are relatively small, or powdery objects, in particles, weighed and retained group by group.

 FIG. 4 shows an exemplary embodiment of an object feeding mechanism which can be used in this case. As can be seen in the drawing, the particulate objects 14 are transferred by a belt conveyor 84 and a vibrating conveyor 86, to a rotary feeding system 88 which divides the objects 14 successively into groups and which releases each group of objects thus formed on the hopper-shaped tray 12 of the weighing device 10. The tray 12 comprises a controlled grid 90 which is opened periodically so as to deliver this content from the tray to the chute 26. The rest of the device is identical to that described with reference to FIG. 1.

 Instead of the alarm unit 82, in the exemplary embodiment illustrated by FIG. 3, it is possible to provide logical means for searching for a combination which gives a total weight which is outside but very close to the domain admissible and to open the corresponding grids of the hoppers so that the operation takes place continuously automatically without interruption.

 it remains to be understood that this invention is not limited to the various embodiments described and shown but that it encompasses all the variants thereof.

Claims (5)

REVi2iDICATIONS  1.- Automatic weighing machine characterized in that it comprises  - A plurality of storage hoppers (42A, 42-2 ... 42-8) arranged in a circle, each of said hoppers being provided at its lower part with a normally closed grid (44) which temporarily opens in response to a gate signal  - a chute (26) rotatably mounted about the axis of said circle so that the outlet orifice (40) of this chute can be placed facing the entry of any of the storage hoppers  - Means (32 - 34 - M) for intermittently rotating said spout so as to bring its outlet orifice sequentially opposite the inputs of said storage hoppers  - a unique weighing device (10) for weighing an object (14) and producing a weight output signal indicating the value of the weight of the object  - Means (16 - 24) for delivering a plurality of objects to be weighed sequentially one by one or group by group and for then bringing them into said chute in synchronism with the rotation of the latter  - a plurality of memories (54-1, 54-2, ... 54-8) corresponding to said hoppers  means for delivering said weight signals sequentially to the memories in synchronism with the rotation of the chute  - arithmetic means (62) for adding the inputs of these arithmetic means and for producing an output signal when the sum has a value located in a predetermined domain  - a plurality of switches (60-a, 60-2 ... 60-8) normally open for coupling the outputs of said memories respectively to the inputs of arithmetic means  - switch control means (58), coupled to the control inputs of said switches for selectively closing said switches according to predetermined combinations and, a temporary memory (64) for successively storing the outputs of said switch control means and for apply the contents of this memory at this time to the reset inputs of the respective memories in the form of reset signals and, at the same time, to the grids of the respective hoppers in the form of gate signals, in response to the output of the arithmetic means so as to free said memories corresponding to the closed switches and, at the same time, to open the gates of the hoppers corresponding to these memories.  2. An automatic weighing machine according to claim 1, characterized in that said switch control means comprise a binary counter having the binary digit outputs respectively coupled to the control inputs of said normally open switches and a pulse generator. clock coupled to the input of said counter.  3. Automatic weighing machine according to one of the preceding claims, characterized in that said memories are designed and produced so as to produce pilot outputs indicating the existence of their contents in response to the recording of their contents, respectively , in that it comprises an AND circuit 56 whose inputs are respectively coupled to the pilot outputs of said memories and in that said switch control means are designed and produced so as to initiate operation in response to the output of said AND circuit .  4. Automatic machine according to claim 3, characterized in that it includes a NAND circuit (80) whose inputs are respectively coupled to the outputs of said AND circuit and said arithmetic means and alarm means (82) actuated by the output of said NAND circuit.  5. An automatic weighing machine according to any one of the preceding claims, characterized in that said intermittent rotation means comprise means making it possible to detect the lack of content of said storage hoppers (42-1, 42-2 ... 42-8) to generate vacancy signals and means for rotating said chute (26) in response to the vacancy signal until the outlet port (40) of the chute is located opposite the vacant hopper.