GB2127158A - Batch weighing apparatus - Google Patents

Abstract

Continuous weigher 10 supplies material to be batched by way of outlet 24 to body 30 of a constantly driven weigh screw arrangement 32 supported by cantilever arms 34 whereon are sensors in the form of strain gauges 42 which ensure that the weigher 10 supplies a constant weight per unit time. A flow-interrupting valve 64 which receives the material from the body 30 is actuated at intervals of time in response to signals from a batch processing (e.g. packaging) machine 94, which also controls speed of continuous weigher 10 to maintain supply of material to match demand of packaging machine 94. <IMAGE>

Description

SPECIFICATION Batch weighing apparatus This invention concerns batch weighing apparatus for batch weighing and feeding particulate material or small articles, hereinafter referred to generally as "material" for the sake of convenience.

As hitherto propounded batch-weighing machines usually work on a cycle which involves the following: (a) Firstly a pre-feeder is started at fast speed, to fill the material into a weigh box which has a hinged flap or the like as its base and which is supported on a form of weigh balance which may embody a load-cell, a torsion balance, a flexure balance or the like; (b) upon the amount of material reaching about 90% of the desired batch weight, the pre-feeder is switched to a slow speed so that the material continues to be supplied into the weigh box at a trickle; (c) upon the amount of material in the weigh box equalling the desired batch, the pre-feeder is switched off; (d) the hinged flap is released to discharge the contents of the weigh box as a batch which, for instance, passes or is carried to a subsequent treatment machine (e.g. for packaging the same); (e) the flap is closed and the weigh balance is allowed to settle. This concludes the cycle which is then repeated from (a) above.

There are certain disadvantages arising from the known machines. Of these, probably the most important is the fact that the cyclic operation thereof restricts output. Where relatively small batches are being weighed and fed, operation at speeds as high as 20 batches per minute can be achieved; with large batches, for instance of the order of 2.5kg each, operating speeds may necessarily be as low as 10 or 8 per minute.

Another important disadvantage lies in the fact that weight inaccuracies can arise in the batches, with the known machines, due to the presence of "in flight" material between the pre-feeder and the weigh box at the instant when the pre-feeder is switched off. The pre-feeder may be a vibratory tray, a belt conveyor, screw feeder or the like, and the rate at which it feeds is not necessarily constant. In the case of vibratory tray feeders and belt type feeders the rate of supply, and consequently the weight of in-flight material is dependent, amongst other things, upon the depth of material on the tray or belt, which depth can, of course vary.With all pre-feeder arrangements operating with a cycle which involves stopping and starting the pre-feeder, any change in the density of the material will also alter the weight of the in-flight material, with consequential variation in the batch weights.

An object of the present invention is to provide a method of batch weighing, as well as apparatus for carrying the method into effect, in which the abovediscussed disadvantages are obviated, it being possible to achieve much higher operating speeds than has hitherto been possible, whilst maintaining the accuracy of batch weights.

A further object is to provide a form of batch weighing apparatus which lends itself particularly conveniently to being controlled in synchronism with subsequent processing apparatus, such as a batch packaging machine, so that variations in demand at the subsequent processing apparatus result in corresponding variations in the rate at which the material is fed by the pre-feeder.

Pursuant hereto, the present invention provides, as a first feature, a method of batch weighing and feeding material (as hereinbefore referred to) which comprises creating a continuous flow of the said material at a constant weight per unit time by means of a continuous weigher; passing the output from the continuous weigher to dividing means for dividing said output into discrete batches; and operating the dividing means to divide the output into material batches of constant weight.

In performing the method as aforesaid, the dividing means is preferably provided by a flow interrupting valve to which the output is supplied by gravity, this valve being operated at a substantially constant speed in dependence upon the demand of a subsequent processing machine.

The method may, also, be carried into effect in such a way that the speed of the continuous weigher is controlled in correspondence with the operational speed of the subsequent processing machine, thereby further to contribute to the accuracy of the batches of the material supplied to the subsequent processing machine.

For carrying the method of the invention into effect, the invention further provides batch weighing and feeding apparatus for feeding material (as herein before referred to) in batches of constant predetermined weight, which comprises a continuous weigher adapted for the material to be passed therethrough at a constant weight per unit time, and dividing means disposed to receive the output from the continuous weigher and adapted to be operated at a substantially constant speed to divide the said output into batches of constant weight.

Preferably the continuous weigher comprises a weigh screw, driven at constant speed, supported by a weigh beam and fed by a pre-feeder, the speed of operation of the pre-feeder being controlled, to supply material to the weigh screw at a constant rate, in response to the weight sensed by the weigh beam.

The dividing means conveniently comprises a flow-interrupting valve to which the output from the continuous weigher is supplied by gravity and which is adapted to operate in synchronism with batch demand of a subsequent processing machine.

The flow-interrupting valve may comprise a chamber accommodating one or more blades movable between positions respectively arresting the material and permitting it progress through the valve.

In one specific form, the valve may comprise a simple apertured sliding blade which can be shifted between an arresting position in which the aperture is outside the chamber, and a feeding position in which the aperture is within the chamber and permits the material to progress.

In another specific form, the valve comprises a rotor having a substantially horizontal axle from which project radial vanes which serve to define successive pockets in the chamber, means for actuating the valve then serving to index the rotor so as to move the pockets successively between filling and emptying positions.

The invention will be described further, by way of example, with reference to the accompanying drawings which illustrate preferred embodiments of the apparatus of the invention, and the manner in which the method of the invention is carried into effect, and in which: Figure 1 is a diagrammatic side elevation illustrating a practical embodiment of the apparatus of the invention; Figure 2 is a diagrammatic elevation of the flow-interrupting valve of the apparatus of Figure 1; Figure 3 is a diagrammatic sectional view corresponding to Figure 2; Figure 4 is a diagrammatic end view of the valve of Figures 2 and 3, the view being taken from the left hand side of Figure 2; Figure 5 is a diagrammatic sectional view corresponding to Figure 4;; Figure 6 is a diagrammatic end view illustrating an alternative form of flow-interrupting valve which may be incorporated into the apparatus of Figure 1, in the place of the valve which is illustrated in Figures 2 to 5; and Figure 7 is a diagrammatic plan view corresponding to Figure 6.

Referring firstly to Figures 1 to 5 of the drawings, the preferred embodiment of the batch weighing apparatus of the invention comprises a continuous weigher, indicated generally by the reference numeral 100. This comprises a pre-feeder screw arrangement including a tubular body 12 enclosing a feed screw (not visible in the drawings) driven by a feed motor 14, and supplied with material (i.e. particulate material or small articles) by means of a hopper 16.

A vibrator motor 18 is provided on the hopper 16 to ensure that the material is always properly available to the feed screw and does not become bridged in the hopper 16 which is supported by a frame 20 mounted upon a suitable base 22.

An outlet 24 from the pre-feeder screw body 12 connects by a flexible connector 26 with an inlet 28 at one end of tubular body 30 of a weigh screw arrangement, indicated generally by the numeral 32, which is supported by cantilever arms 34 extending substantially horizontally relative to a control/weigh cell cabinet 36. The arms 34 are fixedly located at their ends within the cabinet 36 upon an upright support 38 affixed to the base 22. Electromechanical transducers in the form of strain gauges 42 are bonded to the fixed ends of the cantilever arms 34.

These gauges 42 detect the strains within the arms 34 which are experienced by supporting the weigh screw arrangement 32 and any material therein. The strain gauges thus form a weight sensor for the material within the weight screw arrangement 32. A weigh screw (not visible), accommodated within the body 30 and having a spindle 48, is adapted to be driven continuously and at a substantially constant speed by a weigh screw motor 50 supported by the arm 34, by way of a belt 52.

An outlet 54 from the body 30, at the end of the latter remote from the inlet 28, connects by a respective flexible connector 56 to a fixed outlet spout 58 on the bottom of which is a fiange 60 by which the spout 58 is connected to inlet 52 of a flow-interrupting valve which is indicated generally by the numeral 64. This valve 64 incorporates, between the inlet 62 and an outlet 66 which is connected to an inlet 68 of a subsequent treatment (e.g. filling) machine, a generally cylindrical body 70 in which is accommodated a rotor 72 (see Figures 3 and 5) having a substantially horizontal axle 74 journalled in opposite side walls 76 of the body 70.

Radial blades 78 (which are four in number in the illustrated case, but may be more or less numerous as may be desired and practical) carried by the axle 74 serve to divide up the chamber defined by the body 70 into four pockets A, B, C and D as can be seen in Figure 3. As can be appreciated from Figure 5, one end of the axle 74, outside the body 70, carries one plate 80 of a clutch of which the other plate 82 is carried by a crank 84 connected with the rod 86 of a pneumatic ram 88 connected to an electropneumatic control valve 90. This control valve 90 is coupled, as indicated at 92, with a batch treatment machine 94 whose inlet 96 is connected to outlet 66 of the flow interrupting valve 64.

The batch treatment machine 94 in the illustrated case is a filling machine, but of course it may be any machine which serves to receive successive batches of material, for instance it could be a continuous packaging machine, or a forming and packaging machine. It comprises a speed sensor 98. This sensor 98 is connected, as indicated at 100, to a control 102 of the apparatus, which control 102, is connected to the weigh cell 42 and to the feed motor 14. The control 102 is shown in Figure 1 separated from the cabinet 36, but it will readily be understood that such control 102 will, in practice, be incorporated into the cabinet 36.

The manner of operation of the apparatus will readily be understood from the foregoing description. For initial starting up, firstly the batch treatment machine 94 is started up. As a result, successive signals 92 are supplied to the control valve 90 of the flow-interrupting valve 64. At each such signal the clutch is engaged, the rotor 72 is indexed around by one step as a result of extension of the rod of the ram 88 whereupon the clutch is disengaged and the rod of the ram is returned to its illustrated position ready for the next stepping movement of the rotor. Then, the weigh screw motor 50 and the feed motor 14 are switched on, with the control 102 set for the feed screw in the body 12 to supply material from the hopper 16 into the body 30 at a predetermined constant weight per unit of time as determined by the sensor 42 sensing the overall weight of the weigh screw arrangement 32.

With the filling machine 94 operating at a constant speed and supplying signals to the valve 64 at constant intervals, each of the pockets A, B, C and D is successively supplied with a constant flow of output material from the continuous weigher 10 for a predetermined period of time, so that once the apparatus is running normally constant amounts of the material are filled into each of the pockets and subsequently transferred to the filling machine.

As will be understood, the signals from the weigh cell 42 serve to ensure that the speed of the feed motor is controlled to give a constant throughput of the material through the weigh screw body 30.

Moreover, the connection 100 between the machine 94 and the control 102 enables the supply of the material to the body 30 to be matched to the demand of the machine 94.

Figures 6 and 7 illustrate an alternative possibility for the flow interrupting valve, which in this instance comprises a duct 200 which fits in the place of the valve 64 in the above-described embodiment of the apparatus, and comprises upper and lower parts 202,204 respectively, provided on their facing ends with seals 206 which provide sliding seals with a slide plate 208 guided by its edges in guides 210.

This slide plate 208 is connected to the rod 86 of the ram 88 and has an aperture 212 which registers with the duct 200 to permit material to flow to the machine 94 when the rod 86 has been extended.

When the rod 86 is retracted, the plate 208 defines the bottom of the pocket in which the material from the weigh screw accumulates.

Other forms of flow-interrupting valve are, of course possible.

The principal advantage of the apparatus of the invention lies in the fact that it is of a continuousrunning nature and therefore can be operated very much more rapidly than the prior known comparable discontinuously-operating apparatus. Tests seem to indicate that speeds as high as five times faster than available from the known machines can readily be achieved.

A second advantage is that weight inaccuracies due to inconsistent "in-flight" material are totally eradicated because, in the arrangement of the invention, the "in-flight" material is continuously weighed and is thus of a consistent value.

The invention is not restricted to the precise details of the illustrated examples and variations may be made thereto. Thus, for instance, it is not essential to the invention that the flow-interrupting valve should be controlled from some subsequent treatment machine, or that there should be feedback from such a machine to the control of the continuous weigher. It would be possible, for instance to arrange for the flow-interrupting valve to supply the material in constant weight batches at intervals onto a conveyor or other transportation device which does not require precise synchronisation of the arrival of the batches, simply by arranging for the valve to be operated at constant predetermined intervals of time in any suitable way.

CLAIMS (Filed on 18.5.83) 1. A method of batch weighing and feeding material (as herein before referred to) which com prises creating a continuous flow of the said material at a constant weight per unit time by means of a continuous weigher; passing the output from the continuous weigher to dividing means for dividing said output into discharge batches; and operating the dividing means to divide the output into material batches of constant weight.

2. A method as claimed in claim 1 wherein the dividing means is provided by a flow interrupting valve to which the output is supplied by gravity, this valve being operated at a substantially constant speed in dependence upon the demand of a subsequent processing machine.

3. A method as claimed in claim 2 wherein the speed of the continuous weigher is controlled in correspondence with the operational speed of the subsequent processing machine.

4. A method of batch weighing and feeding material substantially as herein before described with reference to the accompanying drawings.

5. Batch weighing and feeding apparatus for feeding material (as herein before referred to) in batches of constant predetermined weight, comprising a continuous weigher adapted for the material to be passed therethrough at a constant weight per unit time, and dividing means disposed to receive the output from the continuous weigher and adapted to be operated at a substantially constant speed to divide the said output into batches of constant weight.

6. Apparatus as claimed in claim 5 in which an output rate signal from a subsequent processing machine controls the speed of the continuous weigher to maintain supply of material to match the demand of the subsequent processing machine.

7. Apparatus as claimed in claim 5 or 6 wherein the continuous weigher comprises a weigh screw, driven at constant speed, supported by a weigh beam, and fed by a pre-feeder, the speed of operation of the pre-feeder being controlled, to supply material to the weigh screw at a constant rate, in response to the weight sensed by the weigh beam.

8. Apparatus as claimed in claim 5,6 or 7 wherein the dividing means comprises a flowinterrupting valve to which the output from the continuous weigher is supplied by gravity and which is adapted to operate in synchronism with batch demand of a subsequent processing machine.

9. Apparatus as claimed in claim 8 wherein the flow-interrupting valve comprises a chamber accommodating one or more blades movable between positions respectively arresting the material and permitting it progress through the valve.

10. Apparatus as claimed in claim 8 or 9 in which the valve comprises an apertured sliding blade which can be shifted between an arresting position in which the aperture is outside the chamber, and a feeding position in which the aperture is within the chamber and permits the material to progress.

11. Apparatus as claimed in claim 8 or 9 in which the valve comprises a rotor having a substantially horizontal axle from which project radial vanes which serve to define successive pockets in the chamber, means for actuating the valve serving to index the rotor so as to move the pockets successively between filling and emptying positions.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

**WARNING** start of CLMS field may overlap end of DESC **. subsequently transferred to the filling machine. As will be understood, the signals from the weigh cell 42 serve to ensure that the speed of the feed motor is controlled to give a constant throughput of the material through the weigh screw body 30. Moreover, the connection 100 between the machine 94 and the control 102 enables the supply of the material to the body 30 to be matched to the demand of the machine 94. Figures 6 and 7 illustrate an alternative possibility for the flow interrupting valve, which in this instance comprises a duct 200 which fits in the place of the valve 64 in the above-described embodiment of the apparatus, and comprises upper and lower parts 202,204 respectively, provided on their facing ends with seals 206 which provide sliding seals with a slide plate 208 guided by its edges in guides 210. This slide plate 208 is connected to the rod 86 of the ram 88 and has an aperture 212 which registers with the duct 200 to permit material to flow to the machine 94 when the rod 86 has been extended. When the rod 86 is retracted, the plate 208 defines the bottom of the pocket in which the material from the weigh screw accumulates. Other forms of flow-interrupting valve are, of course possible. The principal advantage of the apparatus of the invention lies in the fact that it is of a continuousrunning nature and therefore can be operated very much more rapidly than the prior known comparable discontinuously-operating apparatus. Tests seem to indicate that speeds as high as five times faster than available from the known machines can readily be achieved. A second advantage is that weight inaccuracies due to inconsistent "in-flight" material are totally eradicated because, in the arrangement of the invention, the "in-flight" material is continuously weighed and is thus of a consistent value. The invention is not restricted to the precise details of the illustrated examples and variations may be made thereto. Thus, for instance, it is not essential to the invention that the flow-interrupting valve should be controlled from some subsequent treatment machine, or that there should be feedback from such a machine to the control of the continuous weigher. It would be possible, for instance to arrange for the flow-interrupting valve to supply the material in constant weight batches at intervals onto a conveyor or other transportation device which does not require precise synchronisation of the arrival of the batches, simply by arranging for the valve to be operated at constant predetermined intervals of time in any suitable way. CLAIMS (Filed on 18.5.83)

1. A method of batch weighing and feeding material (as herein before referred to) which com prises creating a continuous flow of the said material at a constant weight per unit time by means of a continuous weigher; passing the output from the continuous weigher to dividing means for dividing said output into discharge batches; and operating the dividing means to divide the output into material batches of constant weight.

2. A method as claimed in claim 1 wherein the dividing means is provided by a flow interrupting valve to which the output is supplied by gravity, this valve being operated at a substantially constant speed in dependence upon the demand of a subsequent processing machine.

3. A method as claimed in claim 2 wherein the speed of the continuous weigher is controlled in correspondence with the operational speed of the subsequent processing machine.

4. A method of batch weighing and feeding material substantially as herein before described with reference to the accompanying drawings.

5. Batch weighing and feeding apparatus for feeding material (as herein before referred to) in batches of constant predetermined weight, comprising a continuous weigher adapted for the material to be passed therethrough at a constant weight per unit time, and dividing means disposed to receive the output from the continuous weigher and adapted to be operated at a substantially constant speed to divide the said output into batches of constant weight.

6. Apparatus as claimed in claim 5 in which an output rate signal from a subsequent processing machine controls the speed of the continuous weigher to maintain supply of material to match the demand of the subsequent processing machine.

7. Apparatus as claimed in claim 5 or 6 wherein the continuous weigher comprises a weigh screw, driven at constant speed, supported by a weigh beam, and fed by a pre-feeder, the speed of operation of the pre-feeder being controlled, to supply material to the weigh screw at a constant rate, in response to the weight sensed by the weigh beam.

8. Apparatus as claimed in claim 5,6 or 7 wherein the dividing means comprises a flowinterrupting valve to which the output from the continuous weigher is supplied by gravity and which is adapted to operate in synchronism with batch demand of a subsequent processing machine.

9. Apparatus as claimed in claim 8 wherein the flow-interrupting valve comprises a chamber accommodating one or more blades movable between positions respectively arresting the material and permitting it progress through the valve.

10. Apparatus as claimed in claim 8 or 9 in which the valve comprises an apertured sliding blade which can be shifted between an arresting position in which the aperture is outside the chamber, and a feeding position in which the aperture is within the chamber and permits the material to progress.

11. Apparatus as claimed in claim 8 or 9 in which the valve comprises a rotor having a substantially horizontal axle from which project radial vanes which serve to define successive pockets in the chamber, means for actuating the valve serving to index the rotor so as to move the pockets successively between filling and emptying positions.

12. Batch weighing and feeding apparatus sub

stantially as hereinbefore described with reference to and as illustrated in Figures 1 to 5 or in Figures 6 and 7 of the accompanying drawings.