GB2119104A

GB2119104A - Weighing fluent material

Info

Publication number: GB2119104A
Application number: GB08308836A
Authority: GB
Inventors: David Brunnschweiler
Original assignee: Cosmopolitan Textile Co Ltd
Current assignee: Cosmopolitan Textile Co Ltd
Priority date: 1982-04-21
Filing date: 1983-03-30
Publication date: 1983-11-09
Also published as: GB8308836D0; GB2119104B

Abstract

In feeding measured quantity of fibre, or other flowable bulk solid material into a fabricating or manufacturing process, which material can have variable moisture content, adjustment is made during the weighing for the moisture content of the material. Capacitance methods may be used to determine the moisture content and volume of material in a weigh pan 13. Alternatively, the moisture content may be estimated from the relative humidity of the ambient atmosphere. A microprocessor 26 adjusts the weight or timing of cycles to give a desired rate of feed. <IMAGE>

Description

SPECI FICATION Weighing bulk solid material THIS INVENTION concerns weighing bulk solid materials such as fibre, flour or grain as part, for example, of a metering process in which the fibre or other material is fed to a fabricating or other manufacturing process (such as a dispensing or bagging operation), and in which the material being fed is subject to a varying moisture content.

It is desirable, in the interest of producing a product of correct weight or density when measured with a standard moisture content, to compensate for the moisture content of the material sent to the manufacturing process.

It would be possible, of course, to measure the moisture content of stocks of fibre or other material before use by laboratory testing with commercially available testing equipment, and adjusting the parameters of the metering process and the fabricating or other manufacturing process so as to finish up with the correct product. However, different bales or bags of material may have widely differing moisture content according to their manufacturing history and, perhaps more importantly, their recent transportation and storage history. And, quite apart from the general inconvenience and high cost, in terms of skilled labour, of this method, it is also liable to inaccuracy as a result of the moisture content of a bale of fibre or a bag of flour changing after being opened up but before it is actually consumed in the manufacturing orfabricating process.

The present invention provides a method for automatically compensating for moisture content which does not involve these problems.

The invention comprises a method for feeding measured quantities of fibre or other flowable bulk solid material into a fabricating or other manufacturing process which fibre or other material can have variable moisture content, comprising the step of metering the supply of the fibre or other material to the process by weighing successively fed charges thereof, and adjusting the rate at which the fibre or other material is fed compensatively with regard to the moisture content thereof.

The moisture content may be measured by a capacitance measuring device, which is preferably an a.c. device, in case any electrostatic charge should be present on the material being measured.

The moisture content, in another arrangement, can be estimated from a measurement of the relative humidity of the ambient atmosphere.

In addition to taking a moisture content measure ment, the volume of the solid being metered can be measured - this may be done by measuring the depth of the charge in a weigh pan.

A control arrangement predetermining the weight and/or frequency of successive charges of material may be supplied with such capacitance and or relative humidity volume information from which, together with the weight of the charge, it calculates the moisture content of the charge and adjusts the predetermined weight of the next succeeding charge or charges compensatively.

The invention also comprises apparatus for feeding measured quantities of fibre or other flowable bulk solid material into a fabricating or other manufacturing process which fibre or other material can have variable moisture content, comprising metering means for metering the supply of the fibre or other material to the process by weighing successively fed charges thereof, and compensating means for compensatively adjusting the rate at which fibre or other material is fed with regard to the moisture content thereof.

One embodiment of apparatus and a method for feeding measured quantities of fibre or other flowable bulk solid material according to the invention will now be described with reference to the accompanying drawings, of which: Figure 1 is a diagrammatic illustration of one embodiment, and Figures is a diagrammatic illustration of another embodiment.

Figure 1 illustrates an arrangement in which fibre 11 is dropped from a valve 12 into weigh pan 13 provided with claim shell floor members 14 openable and closable by means of a motor 15 under the control of an operations sequencer 16.

The weigh pan 1S is mounted on load cells 17 connected to a comparator 18 into which a predetermined weight is input from a weight setting control 19. When the measured weight is equal to the predetermined weight, the operations sequencer 16 closes the valve 12. At a later time, when all measurements have been completed after any fibre in transit after the closure of the valve 12 has finally settled in the weigh pan 13, the operations sequencer 16will open the floor members 14to release the fibre 11 to an outlet conveyor 20 which will take it on to a fabricating, for example a stitch bonding process, or a spinning process to be made into a yarn.

The basic metering operation can be performed as described in our UK Patent Application No. 7936211 Publication No. 2 060 947A- published on 7th May, 1981, or may be performed by the improved method described in our UK Patent Application No. 8211473 entitled"CYCLICALLYWEIGHING BULK SOLID MATERIAL" of even date herewith.

In addition, the weigh pan 13 contains condenser plates 21 suitably insulated and connected to a capacitance measuring circuit 22. The condenser plates 21 are mounted on the floor members 14, so that they will be covered completely even by small amounts of fibre in the weigh pan. The weigh pan 13 also contains a fibre volume measuring arrangement, shown here diagrammatically as a vertical array of capacitance sensors 23, which will be progressively affected as the fibre level rises in the weigh pan 13 thus giving an indication of the fibre heightfrom which volume can be calculated, knowing the dimensions of the weigh pan 13, by a volume calculator 24.

Weight and volume data are supplied to a density calculator 25, and the density, volume, weight and capacitance data are fed to a microprocessor 26 that computes the weight of fibre present in the weigh pan 13 adjusted for moisture content. It is possible theoretically to deduce a suitable algorithm for this, but probably easier to calibrate the microprocessor by performing a series of measurements on fibre charges of different weights and moisture content, differently compacted.

In any event, the microprocessor can be programmed to keep a running tally of the adjusted weight of fibres that pass through the metering arrangement and to feed into the comparafor a new reference weight at the beginning of each operating cycle or at the beginning of a series of operating cycles of the weigh pan 13 so that the adjusted weight equates to the desired weight per cycle or per unit time either by adjusting the desired weight for the next succeeding cycle or cycles or by keeping the weight constant but adjusting the time between cycles.

Instead of a weigh pan, a weigh plate can be used, as illustrated in Figure 2. In this case, fibre 11 can be fed by a conveyor 31 on to the plate 32, either in batches or continuously. A fixed plate 33 confines the fibre into a gap of known height. The fixed plate 33 and the weigh plate 32 can constitute the condenser plates forming the capacitance measuring device. Alternatively, a roller could be used instead of the upper, confining plate, and an additional condenser plate or plates used forthe capacitance measuring device.

Instead of making a direct measurement of the moisture content of the fibre or other material by for example measuring the capacitance of an arrangement in which the fibre or other material is present, the moisture content can in some circumstances be calculated from a knowledge of the properties of the material and the relative humidity of the ambient atmosphere.

Instead of the condenser plates 21 of Figure 1 or the fixed plate 33 and weigh plate 32 of Figure 2, a simple RH meter can be located nearto the weighing arrangement.

The measurement of atmospheric relative humidity can be fed directly into a controlling microprocessor, which can also have an input and special programming to calculate the moisture content from the RH and the fibre type - fibre type can be in put from a keyboard or from a multiposition switch. Of course, if only one fibre is being dealt with there will be no need for such a parametric input.

The circumstances under which such an indirect method of arriving at the moisture content will be appropriate will be where the fibre or other material spends a sufficiently long time in the vicinity of the weighing arrangement to achieve equilibrium or substantial equilibrium with the atmosphere - and, of course, where atmospheric conditions do not fluctuate too rapidly.

Claims

1. A method for feeding measured quantities of fibre or other flowable bulk solid material into a fabricating or other manufacturing process which fibre or other material can have variable moisture content, comprising the step of metering the supply of the fibre or other material to the process by weighing successively fed charges thereof, and adjusting the rate at which the fibre or other material is fed compensatively with regard to the moisture content thereof.

2. A method according to claim 1, in which the moistu re content of each charge or of a representative sample of charges is measured.

3. A method according to claim 2, in which the moisture content is measured by a capacitance measuring device.

4. A method according to claim 3, in which the capacitance measuring device is an a.c. device.

5. A method according to claim 1, in which the moisture content is estir-nated.

6. A method according to claim 5, in which the moisture content is estimated from a measurement of the relative humidity of the ambient atmosphere.

7. A method according to any one of claims 1 to 6, in which the volume of each charge or of a representative sample of charges is measured.

8. A method according to claim 7, in which the volume is measured by measuring the depth of the charge in a weighpan.

9. A method according to any one of claims 1 to 8, in which a measurement or estimation of moisture content is carried and while the charge is in a weighpan.

10. A method according to claim 9, in which a control arrangement predetermining the weight and/ or frequency of successive charges of material is supplied with capacitance or relative humidity and volume information from which it calculates the moisture content of the charge and adjusts the predetermined weightfor the next succeeding charge or charges compensating.

11. Amethodforfeeding measured quantities of fibre or otherflowable bulk solid material substantially as hereinbefore described with reference to the accompanying drawings.

12. Apparatusforfeeding measured quantities of fibre or other flowable bulk solid material into a fabricating or other manufacturing process which fibre or other material can have variable moisture content, comprising metering means metering the spply of the fibre or other material to the process, weighing meansforweighing successively fed charges thereof, and compensating means for compensatively adjusting the weight of fibre or other material compensatively with regard to the moisture content thereof.

13. Apparatus according to claim 12, comprising moisture content measuring means.

14. Apparatus according to claim 13, said moisture content measuring means comprising a capacitance measuring device.

15. Apparatus according to claim 14, said capacitance measuring device comprising an a.c. device.

16. Apparatus according to claim 12, comprising moisture content estimating means comprising an ambient atmosphere relative humidity measuring arrangement.

17. Apparatus according to any one of claims 12 to 16, comprising volume measuring means measuring the depth of charge in a weighpan.

18. Apparatus substantially as hereinbefore described with reference to the accoampanying drawings.