GB2259760A - Measuring weight per unit length of fibrous material - Google Patents

Abstract

A web of material 11 from a carding engine is guided between windows 16, 17 in an optical path including light sources 8 and detectors 9, 10. The sources 8 may be modulated to remove the effects of ambient light. The apparatus is calibrated using a known sample of material, and compensated for the effects of dirt and drift by measuring without material present. The average and standard deviation of a series of measurements are calculated to determine the evenness of the material. The system may be operated by keeping constant the light in the attenuated beam. The measurements enable production of wound packages of preset weight. <IMAGE>

Description

MEASUREMENT OF AVERAGE WEIGHT PER UNIT LENGTH, AND ITS VARIABILITY IN FIBROUS MATERIAL.

THIS INVENTION RELATES TO APPARATUS FOR MEASURING THE AVERAGE WEIGHT PER UNIT LENGTH OF FIBROUS MATERIAL AND ITS VARIABILITY.

APPARATUS IS KNOWN FOR PROCESSING FIBROUS MATERIAL SO AS TO PRODUCE A CONTINUOUS RIBBON OF MATERIAL IN WHICH THE CONSTITUENT FILAMENTS ARE ORIENTATED ALONG THE LENGTH OF THE RIBBON. THE WEIGHT PER UNIT LENGTH OF MATERIAL PRODUCED IS COMMONLY REFERRED TO AS THE YARN COUNT.

A MEASURE OF THE VARIABILITY IS COMMONLY REFEREE TO AS U%, WHICH IS EQUAL TO THE PERCENTAGE MEAN DEVIATION FROM THE AVERAGE WEIGHT PER UNIT LENGTH.

AS AN EXAMPLE. THIS PROCESS WOULD BE CARRIED OUT ON A CARDING ENGINE WHICH COMBS THE RNDOMLY ARRANGED FIBRES OF THE INPUT MATERIAL SO AS TO ALIGN THEM. THE CARDING ENGINE ALSO MIXES THE VARIOUS FIBRES FED INTO THE MACHINE SO AS TO PRODUCE A WEB CONSISTING OF AN EYEN BLEND OF CONSTITUENT FIBRES. FINALLY, THE WEB OF MATERIAL IS DIVIDED INTO STRIPS OF FIBROUS MATERIAL BY DIVIDING BELTS, LOOSELY ROLLED TO PROVIDE COHESION, AND WOUND INTO COIL FORM. KNOWN IN THE TRADE AS SLUBBING.

IN AN ALTERNATIVE ARRANGEMENT THE STRIPS OF MATERIAL COULD BE RECOMBINED TO FORM A SINGLE STRAND OF MATERIAL AND FURTHER PROCESSED WITH OR WITHOUT INTERMEDIARY STORAGE.

THE CORRECT OPERATION OF THE DIVIDING BELTS IS CRITICAL TO THE PROCESS.

IF THE QUALITY OF THE WEB OF MATERIAL ENTERING THE DIVIDING BELTS IS POOR IN RESFECT OF THICKNESS VARIATION OR FIBRE ALIGNMENT, OR IF THE DIVIDING BELTS ARE WORN OR INCORRECTLY SET UP, THE MATERIAL CONTENT OF THE RESULTANT STRIPS WILL BE VARIABLE, CAUSING SHORT- AND LONr-TERM VARIATIONS IN YARN COUNT.

FAULTY OPERATION t44Y ALSO OCCUR DURING THE ROLLING OF THE STRIP OF MATERIAL FORMED BY THE DIVIDING BELTS.YARN COUNT VARIATIONS ALSO EXIST ACROSS THE WIDTH OF THE MACHINE DUE TO MISALIGNMENT OF THE STRIPPER BLADES WHICH DETACH THE WEB OF MATERIAL FROM THE CARDING CYLINDERS.

IN THE PROCESS FOLLOWING THE CARDING ENGINE THE SLUBBING IS DRAWN AND SPUN SO AS TO LOCK THE FIBRES OF MATERIAL TOGETHER TO FORM A THREAD WHICH CAN BE USED FOR WEAVING. SINCE ANY BOBBIN OF THREAD ChN BE WHEN WITH ANY OTHER SELECTED AT RANDOM FROM THE TOTAL PRODUCTION RUN. IT IS IMPOR-rANT THAT THE AVtEPAGE YARN COUNT OF THE SLUBBING BE MAINTAINED CONSTANT THROUGHOUT THE ENTIRE PRODUCTION RUN. OTHERWISE THE WOVEN THREAD WILL BE PATTERNED BY VARIATIONS IN THE SURFACE FINISH.

SHORT-TERM VARIATIONS WILL PRODUCE A ROUGH SURFACE DUE TO IRREGULARITIE5 IN THE THREAD THICKNESS. SEVERE LOCALIZED YARN COUNT V.9RINTIONS ARE REFERRED TO IN THE TRADE AS THICK AND THIN PLACES.THIN PLACES CAUSE WEAKNESSES IN THE SPUN YARN LEADING TO BREAKAGES AND OPERATIONAL DOWNTIME. THICK PLACES ARE UNSIGHTLY IN THE WOVEN CLOTH.

IT IS DESIRABLE TO MEASURE AND CONTROL THE YARN COUNT AND U% TO ENSURE THAT THE MACHINE IS OPERATING WITHIN THE PRESCRIBED LIMITS REQUIRED BY THE SPINNING AND WEAVING PROCESSES. IN ORDER TO EFFECTIVELY MONITOR THE QUALITY OF THE FINAL PRODUCT, MEASUREMENTS SHOULD BE TAKEN WHEN THE SLUBBING HAS BEEN FINALLY FORMED AFTER THE RUBBINGS BELTS. THE MONITORING SHOULD BE CONTINUAL AND EVERY STRAND OF SLUBBING SHOULD BE MEASURED. IN PRACTICE, A REPRESENTTIVE NUMBER OF STRANDS WOULD BE MONITORED TO REPRESENT THE OVERALL PERFORMANCE OF THE MACHINE.

ACCORDING TO THE PRESENT INVENTION MEANS ARE PROVIDED FOR CONTINUALLY MEASURING THE fARN COUNT OF THE MATERIAL BEING PRODUCED IMMEDIATELY AFTER IT IS FORMED INTO COHESIVE STRIP FORM. MEANS ARE PROVIDED FOR MEASURING THE UNEVEN-NESS OR U% OF THE MATERIAL AND MEANS ARE PROVIDED FOR MEASURING THICK AND THIN PLACES. MEANS ARE ALSO PROVIDED FOR CALIBRATION OF THE MEASUREMENT SYSTEM TO PROVIDE CORRECTED READINGS FOR A RANGE OF MATERIAL COMPOSITION.MEANS ARE ALSO PROVIDED FOR MEASURING BUILD-UP OF WASTE MATERIAL IN THE MEASURING HEND AND APPLYING A CORRECTION FACTOR TO THE MEASURED YARN COUNT VALUE.

MEANS ARE PROVIDED FOR DATA STORAGE AND RECORDING OF PRODUCT EQUALITY.

THE DhTA STORED CAN BE RECALLED UPON REQUEST OR AUTOMATICALLY PRINTED WHEN A SIGNIFICANT EVENT OCCURS.

A SPECIFIC EMBODIMENT OF THE INVENTION WILL NOW BE DESCRIBED BY WAY OF EXAMPLE WITH REFERENCE TO THE ACCOMPANYING DRAWINGS IN WHICH: FIGURE 1 ILLUSTRATES A CARDING ENGINE COILING ARRANGEMENT FIGURE 2 ILLUSTRATES ssN ARRANGEMENT OF THE MEASURING HEAD FiGURE 3 ILLUSTRATES AN ARRANGEMENT OF THE CONTROL CIRCUITRY AS50CIATED WITH THE SENSOR.

FIGURE 4 ILLUSTRATES AN ALTERNATIVE ARRANGEMENT OF THE CONTROL CIRCUITRY ASSOCIATED WITH THE SENSOR.

FIGURE 5 ILLUSTAATES THE MEANS OF PROCESSING DATA OBTAINED FROM THE SENSOR.

FIGURE 1 ILLUSTRATES A TYPICAL ARRANGEMENT OF A CARDING ENGINE IN WHICH THE WEB OF MATERIAL 2 IS DETACHED FROM THE CARRYING DRUM 1 AND PASSED THROUGH DIVIDING BELTS 3 SO AS TO FORM SEPARATE TAPES OF COMPOSITE MATERIAL WHICH ARE THEN PASSED THROUGH OS5ILLATING AND ROTATING SLEEVES 4 SO AS TO IMPART SUFFICIENT COHESION TO THE INDIVIDUAL TAPES OF COMPOSITE MATERIAL SO AS TO ENABLE THEM TO BE COILED INTO Q PACKAGE OF MATERIAL 5 BY MEANS OF THE DRIVE ROLLERS 6. THE CARDING ENGINE IS ARRANGED TO FORM A LARGE NUMBER OF COILS OF MATERIAL CONCURRENTLY. SENSORS 7 ARE ARRANGED BETWEEN THE ROTATING SLEEVES AND THE DRIVE ROLLER 6, SO AS TO TAKE A NUMBER OF READINGS OF YARN COUNT REPRESENTATIVE OF THE MACHINE OUTPUT.

FIGURE 2 DEPICTS THE QRRANGEMENT OF Th'E SENSOR RELATIVE TO THE MATERIAL PASSING THROUGH THE OPTICAL PATH. LIGHT SOURCES 8 EMIT LIGHT BEAMS TOWARDS DETECTORS 9 TH20JSH SUBTANTIALY TRANSPARENT WINDOWS 16 1ND 17, WHICH CNN ALSO BE ARRRANGED TO ACT AS A FILTER TO AMBIENT LIGHT.A PROPORTION OF THE LIGHT EMMITTED BY 8 IS RECEIVED BY DETECTORS 10 ARRANGED ADJACENT TO EMITTERS 8.IN ORDER REDUCE EFFECTS DUE TO AMBIENT LIGHT IT MAY BE ADVANTAGEOUS TO USE A MODULATED LIGHT SOURCE WITH FILTER CIRCUITS ACTING IN CONJUNCTION WITH DETECTORS 9 AND 10.

THE MATERIAL 11 PRODUCED BY THE CARDING ENGINE IS GUIDED BETWEEN 10 AND .THE ASSEMBLY CONSISTING OF 8 AND 10 WOULD BE ENCLOSED IN A BOX 14 AND DETECTORS 9 WOULD ALSO BE ENCLOSED IN A BOX 15 TO AVOID CONTAMINATION. IF THERE IS NO MATERIAL PRESENT IN THE OPTICAL PATH, THE RATIO BETWEEN THE TRANSMITTED AND RECEIVED LIGHT IS DETERMINED SOLELY BY THE ABSORPTION OF THE WINDOWS 16 AND 17.

IF MATERIAL 11 IS INTRODUCED INTO THE OPTICAL PATH THERE IS A REDUCTION IN THE RECEIVED LIGHT DUE TO PRESENCE OF THE MATERIAL WHICH WILL BOTH ABSORB AND DIFFUSE A PROPORTION OF THE INCIDENT LIGHT. THIS LIGHT LOSS WILL BE PRCPORTIONAL TO THE WEIGHT OF MATERIAL PRESENT AND ITS OPTICAL CHARACTERISTICS. THE OPTICAL CHARACTERISTICS MAY BE REFERRED TO AS THE OPTICAL LOSS COEFFICIENT, AND WILL BE FIXED FOR A PARTICULAR MA1tHIAL OR BLEND OF MATERIALS. THUS THE WEIGHT OF MATERIAL PRESENT IN THE OPTICAL PATH CAN BE DIRECTLY RELATED TO THE ATTENUAT1ON OF THE LIGHT BEAM.

IF F1 IS THE TBNSMITTED LIGHT VALUE SHOWN AT 12 AND F2 IS THE RECEIVED LIGHT VALUE SHOWN AT 13, THEN F2=F1(1-K) WHERE K IS THE LOSS OF LIGHT DUE TO THE WINDOWS AND MATERIAL ACTING TOGETHER. REARRANGING THIS EQUATION, K=1-(F2/F1).

THE SPATIAL RELATIONSHIP BETWEEN THE EMMITTERS S AND DETECTORS 10. IS FIXED AND THUS THE LIGHT MEASURED BY 10 IS DIRECTLY PROPORTIONAL TO THE LIGHT OUTPUT 12.

THE RECEIVED LIGHT IS MEASURED BY DETECTORS 9 AND THUS THE RATIO BETWEEN THE EMMITTED LIGHT 12 AND THE RECEIVED LIGHT 13 1S PROPORTIONAL TO THE RATIO OF THE TWO DETECTORS OUTPUTS RESPECTIVELY.THE EGUNTLCN MAY NOW BE EXPRESSED AS K = 1- q(F2/F1), WHERE q IS A FACTOR TO ALLOW FOR HE FACT 1HAT ONLY A PROPORTION OF THE LIGHT FROM EMITTERS 8 IS SENSED BY DETECTORS 10. THIS CAN NOW BE RE-WRITTEN AS THE RELATIONSHIP K = 1-r(D2/D1) WHERE D2 AND D1 ARE THE OUTPUTS OF DETECTORS 10 AND 9 RESPECTIVELY, SENSING LIGHT VALUES F2 AND Fl RESPECTIVELY.

THE TRANSMITTED LIGHT WILL BE ATTENUATED BOTH BY THE WINDOWS AND THE MATERIAL INTRODUCED INTO THE OPTIC PATH. IF J1 IS THE ATTENNUATION DUE TO THE WINDOWS.AND J2 IS THE ATTENUATION WE TO THE MATERIAL, THE RESULTANT ATTENUAlION FACTOR J3 IS EQUAL TO JlxJ2. THE VALUE OF J1 CAN BE ESTABLISHED BY MEASUREMENT WITH NO MATERIAL PRESENT AND USED TO CALCULATE THE ATTENUATION DUE TO MATERIAL SINCE J2, THE ATTENUATION DUE TO THE MATERIAL, IS EQUAL TO J3/J1. THIS PROCEDURE PROVIDES A CONVENIENT METHOD OF AUTOMATICALLY NORMALISING THE ATTENUATION FACTORS BECAUSE THE NORMALISING COEFFICIENTS ARE COMMON TO NUMERATOR AND DENOMINATOR.

A SIGNIFICANT ADVANTAGE OF THE SYSTEM SO DESCRIBED IS THAT IF THE ATTENUATION FACTOR WITHOUT MATERIAL IS CHANGED BY DEBRIS ACCUMULATED WITH USE,THIS CAN BE TAKEN ACCOUNT OF BY TEMPORARILY MOVING THE MATERIAL OUT OF THE SENSOR AND READING THE NEW VALUE OF J1. THE NEW VALUE OF J1 CAN THEN BE USED FOR SUBSEQUENT CALCULATIONS. THIS RECALIBRATION PROCEDURE ALSO AUTOMATICALLY COMPENSATES FOR CHANGE IN CHARACTERISTICS OF THE DETECTORS WITH TIME AND TEMPERATURE, BECAUSE, HERE AGAIN, THE VARIATIONS ARE COMMON TO BOTH NUMERATOR AND DENOMIN.4TQR.

THE VALUE OF K THUS OBTAINED IS PROPORTIONAL TO THE LOSS OF LIGHT DUE TO THE PRESENCE OF MATERIAL IN THE OPTICAL PATH WHICH IS PROPORTIONAL TO THE WEIGHT OF MATERIAL PRESENT AND TO THE OPTICAL LOSS COEFFICIENT. WHICH WILL BE CONSTANT FOR A GIVEN MATERIAL OR BLEND OF MATERIALS.TH. OPTICAL LOSS COEFFICtENT CAN BE ESThBLISHED BY WEIGHING A KNOWN LENGTH OF MATERIAL AND CALIBRATING THE APPARATUS TO PROVIDE A MEASUREMENT OF WEIGHT PER UNIT LENGTH, KNOWN IN THE SPADE AS THE YARN COUNT. THIS MAY BE EXPRESSED UNITS SUCH AS TEX, DECITEX ETC. IT IS SOMETIMES EXPRESSED AS THE INVERSE IN UNITS SUCH AS YORKSHIRE SKEINS. A MEASURE OF LENGTH PER UNIT WEIGHT.

FIGURE 3 GEPICTS A TYPICAL ARRANGEMENT OF THE CONTROL CIRCUITRY ASSOCIATED WITH THE SENSOR. A CONSTANT REFERENCE VALUE 29 IS COMPARED WITH THE OUTPUT OF DETECTOR 9 SENSING THE ATTENUATED LEVEL OF THE LIGHT BERM 13. 21 REPRESENTS THE ATTENUATION FACTOR DUE TO THE WINDOWS AND MATERIAL IN THE OPTICAL PATH OF THE SENSOR.

THE DIFFERENCE IS PROCESSED BY CONTROL TERMS SHOWN AT 19 AND THE OUTPUT FROM 19 ACTS AS A REFERENCE WHICH IS COMPARED IN TURN WITH THE OUTPUT 23 FROM DETECTOR 10 SENSING A PROPORTION OF THE EMITTED LIGHT FROM EMITTERS 8. THE DIFFERENCE IS PROCESSED BY CONTROL TERMS 20 TO INFLUENCE THE OUTPUT FROM EMITTERS 8. IF THE CONTROL TERMS 19 AND 20 ARE INTEGRAL, BOTH CONTROL LOOPS OPERATE WITH ZERO ERROR WHICH IS ADVANTAGEOUS WHEN UTLISING LIGHT EMITTERS WHICH ARE GENERALLY NON-LINEAR DEVICES.

THE ATTENUATION DUE TO THE WINDOWS 16 ,17 TOGETHER WITH THE MATERIAL IN THE OPTICAL PATH MAY BE MEASURED BY DIVIDING THE VALUE OF DETECTOR 9 OUTPUT. 22.

BY 23. THE OUTPUT FROM DETECTOR 10. THIS FUNCTION IS IMPLEMENTED BY DIVIDER DEVICE 24, THE OUTPUT OF WHICH CORRESPONDS TO 53 IN THE DESCRIPTION OF FIGURE 2.

26 IS A MEMORY STORE WHICH RETAINS THE VALUE OF 24 OUTPUT WHEN THE MATERIAL IS REMOVED FROM THE OPTICAL PATH OF THE SENSOR. THIS VALUE CORRESPONDS TO THE ATTENUATON DUE TO THE WINDOWS, CHANGES IN THE DEVICE CHARACTERISTICS AND CCUMtJLATED DEBRIS PRESENT IN THE OPTICAL PATH, DESCRIBED AS J1 IN THE DESCRIPTION ACCOMPANYING FIGURE 2.28 IS A GATING CIRCUIT WHICH OPERATES IN CONJUNCTION WITH A MECHANICAL DEVICE FOR MOVING THE THREAD OUT OF THE OPTIMAL PATH FOR THE PURPOSE OF CALIBRATION.

DIVIDER 25 MEASURES THE RATIO J3/J1 WHICH IS KNOWN TO BE J2, THE ATTENUATION DUE ONLY TO MATERIAL IN THE OPTICAL PATH OF THE SENSOR. THE OUTPUT OF 25 IS SUBTRACTED FROM UNITY TO PROVIDE A VALUE PROPORTIONAL TO THE MATERIAL PRESENT IN THE OPTICAL PATH. 26 IS A GAIN-SETTING DEVICE USED FOR CALIBRATING THE SENSOR FOR MATERIAL CHARACTERISTICS.

FIGURE 4 DEPICTS AN ALERNATIVE ARRANGEMENT OF THE CONTROL CIRCUITRY IN WHICH THE OUTPUTS FROM DETECTORS 10 ARE COMPARED WITH A CONSTANT VALUE REFERENCE SIGNAL 29, THE DIFFERENCE SIGNAL BEING PROCESSED BY CONTROL TERMS AT 20.

OTHERWISE THE OPERATION OF THE CIRCUIT IS SIMILAR TO THNT DESCRIBED IN RELATION TO FIGURE 3.

FIGURE 5 ILLUSTRATES THE ARRANGEMENT USED TO PROCESS DATA OBTAINED FROM THE SENSOR CIRCUITRY. 27 IS THE VALUE OF YARN COUNT MEASURED BY THE SENSOR AND ASSOCIATED CIRCUITRY. 31 STORES A NUMBER OF SUCH VALUES AND CALCULATES AN AVERAGE VAL.UE. THE OUTPUT OF 31 IS PASSED TO 32 WHICH IN TURN CALCULATES AN AVERAGE VALUE OVER A LARGER LENGTH OF MATERIAL. DEVICE 33 CALCULATES AN AVERAGE OVER YET ANOTHER LENGTH. THE VALUE AT 27 IS SAMPLED AT DISCRETE INTERVQS OF LENGTH OF MATERIAL AS MEASURED BY ANGULAR DISPLACEMENT OF A SELECTED DRIVE SHAFT OF THE MACHINE, SO THAT THE OUTPUT OF 31 REPRESENTS AN AVERAGE VALUE OVER A LENGTH OF, TYPICALLY, 5 METRES. THE OUTPUT AT 32 WOULD TYPICALLY BE THE AVERAGE OVER 10 METRES, AND THAT AT 33 OVER 20 METRES.

INDIVIDUAL READINGS OF 27 ARE COMPARED WITH THE AVERAGED OUTPUT AT 31 AND CON'JERTED TO POSITIVE READINGS BY 34 ACTING AS A MODULUS OPERATOR. 35 STORES THE OUTPUTS FROM 34 AND COMPUTES THE AVERAGE VALUE OVER THE SAME LENGTH AS IS USED BY 31. 36 AND 37 OPERATE IN A SIMILAR MANNER TO 35 USING THE SAME AVEPEAGING LENGTHS AS 32 AND 33 RESPECTIVELY.

38 DIVIDES THE OUTPUT OF 35 BY THE OUTPUT OF 31 AND MULTIFLIES THE RESULT BY 100 TO GIVE THE PERCENTAGE MEAN DEVIATION OF THE SAMPLED VALUES AT THE INPUT TO 31. 39 AND 40 PERFORM SIMILAR FUNCTIONS FOR THE OTHER SAMPLE LENGTHS.

TAKING THE 5 METRE VALUES AS EXAMPLES, THE OUTPUT OF 31 IS THE YARN COUNT VALUE AND THE OUTPUT OF 38 IS THE U% VALUE FOR THE SAMPLED INPUT AT 27 OVER A LENGTH OF 5 METRES.

THE OPERATIONS DESCRIBED WOULD TYPICALLY BE CARRIED OUT BY A MICROPROCESSOR AND THE RESULTS WOULD BE DISPLAYED NUMERICALLY. AVERAGE VALUES CAN ALSO BE CALCULATED FOR A NUMBER OF SENSORS SELECTED TO REPRESENT SECTIONS OF THE MACHINE. AS AN EXAMPLE, THE AVERAGE VALUE OF THE LEFT-HAND SENSORS COULD BE CALCULATED FOR COMPARISON WITH THE AVERAGE VALUE OF THE RIGHT-HAND SENSORS, OR THE AVERAGE FOR THE ENTIRE MACHINE COULD BE USED TO MONITOR OVERALL MACHINE PERFORMANCE.

THE OUTPUTS FROM 31,32 AND 33 REPRESENT THE APPARENT YARN W COUNT OF THE MATERIAL. THE ABSORPTION FACTOR OF THE MATERIAL WILL VARY IN ACCORDANCE WITH THE COMPOSITION OF THE MATERIAL AND IT IS THEREFORE NECCESARY TO PROVIDE MEANS OF CALIBRATING THE OUTPUTS AT 31,32 AND 33 FOR THE ABSORPTION FACTOR OF THE MATERIAL BEING PROCESSED.THIS IS ACCOMPLISHED BY OFFWINDING A SAMPLE LENGTH OF MATERIAL AND MEMORISING THE AVERAGE READING AT 31 OCCURRING AT THE END OF THE SMAPLE LENGTH.THE RATIO BETWEEN THE APPARENT AND REAL YARN COUNT READINGS CAN NOW BE CALCULATED BY ENTERING THE TRUE VALUE INTO THE MICROPROCESSOR SYSTEM VIA THE OPERATOR KEYPAD.THE RATIO SO OBTAINED IS USED TO MODIFY THE OUTPUTS AT 31,32 AND 33 IN ORDER TO GIVE A CORRECTED VALUE OF YARN COUNT.

Claims (9)

1. APPARATUS FOR DETERMINING THE WEIGHT PER UNIT LENGTH OF MATERIAL IN AN OPTICAL FATH BY MEASURING THE ATTENUATION OF A LIGHT BEAM.THE APPARATUS MAY BE CALIBRATED TO TAKE INTO ACCOUNT THE OPTICAL CHARACTERISTICS OF DIFFERENT MATERIALS BY SAMPLE MEASUREMENTS.MEANS OF CORRECTION ARE PROVIDED WHICH AUTOMATICALLY COMPENSATE FOR CONTAMINATION OF THE OPTICAL PATH AND THE EFFECTS OF TIME AND TEMPERATURE ON THE SENSING ELEMENTS.

2. APPARATUS AS AT 1 IN WHICH MEANS ARE PROVIDED FOR TEMPORARALLY MOVING THE MATERIAL PATH OUT OF THE LIGHT BEAM IN ORDER TO MEASURE THE EFFECTS OF TIME, TEtAPERmRE AND CONTAMINATION.

3. APPARATUS AS AT 2 IN WHICH THE LIGHT BEAM IS MODULATED IN ORDER TO ELIMINATE THE EFFECTS OF AMBIENT LIGHT.

4. APPARATUS AS AT 3 IN WHICH FOR CALIBRATION PURPOSES THE AVERAGE WEIGHT PER UNIT LENGTH OVER A SELECTABLE LENGTH MAY BE STORED AND COMPARED WITH A TRUE VALUE MEASURED BY OTHER MEANS,THE RELATIONSHIP BETWEEN THE TWO VALUERS BEING USED AS A CORRECTION FACTOR.

5. APPARATUS AS AT 4 IN WHICH INSTANTANEOUS MEASUREMENTS OF ATTENUATION ARE USED TO CALCULATE MEAN DEVIATION OF THE READINGS FROM A SELECTED AVERAGE.

6. APPARATUS AS AT 5 IN WHICH THE READINGS FROM A NUMBER OF SENSORS MAY BE COMBINED TO CALCULATE AN AVERAGE VALUE FOR A RANGE OF PRESET LENGTHS.

7. APPARATUS AS AT 6 IN WHICH THE AVERAGE VALUE CAN BE USED TO WIND FINISHED PACKAGES OF MATERIAL TO A PRESET WEIGHT.

8. APPARATUS AS AT 1 IN WHICH THE LIGHT IS MODULATED IN ORDER TO ELIMINATE THE EFFECTS OF AMBIENT LIGHT.

9. APPARATUS AS AT 1 IN WHICH THE LIGHT RECIEVED FROM THE ATTENUATED BEAM IS MAINTAINED CONSTANT.