WO2012063206A2

WO2012063206A2 - Fault prevention system and method for tufting machines

Info

Publication number: WO2012063206A2
Application number: PCT/IB2011/054992
Authority: WO
Inventors: Shmuel Cohen
Original assignee: Elbit Vision Systems (Evs) Ltd.
Priority date: 2010-11-11
Filing date: 2011-11-09
Publication date: 2012-05-18
Also published as: WO2012063206A3

Abstract

A fault prevention system for preventing the development of defects during tufting includes an imager configured to image a plurality of yarn strands and a processor operable to analyze image data from the imager to detect yarn irregularities. Methods are described for performing various actions in response to the detection of yarn irregularities such as providing alerts and output signals or activating an override switch to shut down.

Description

FAULT PREVENTION SYSTEM AND METHOD FOR TUFTING MACHINES

FIELD AND BACKGROUND OF THE INVENTION

Embodiments of the present invention relate to carpet manufacture. In particular the invention relates to fault prevention systems for tufting machines.

Tufted carpet comprises an upper layer of tufted piles sewn into a primary backing material with a secondary backing adhered thereto by a bonding agent. Pile yarns in the upper layer may be looped or cut as required. Loop pile carpets, in which the tufted piles are left uncut, are generally more durable than cut pile carpets and are often used in high traffic or industrial environments. Cut pile carpets may be less resilient to wear and stress, but can provide a more luxuriant feel to the carpet and are often used in domestic environments. Combined cut and loop construction may be used to provide pattern effects within a single carpet. Various carpet defects are associated with incorrectly formed or missing tufts. The efficiency of carpet manufacture is dependent upon the detection, correction and prevention of such defects.

During the tufting process, yarn is threaded through a tufting needle which pierces the primary backing and pushes the yarn therethrough. A hook, known as a looper, engages the protruding yarn while the needle is withdrawn thereby forming a looped tuft. The backing material may then be shifted before the needle pushes the next tuft through. As required, the looped tufts thus formed may be cut to produce cut pile. In industrial tufting machines a great many needles, often over a thousand needles per twelve foot width, typically work in parallel to produce hundreds of stitches per minute. A broadloom tufting machine may therefore produce hundreds of square yards of carpet every day.

A yarn feed mechanism feeds a strand of yarn to each of the tufting needles from a creel behind the tufting machine. One common fault during carpet manufacture occurs when at least one of the strands of yarn being fed to the tufting needles is snagged or broken. When a strand breaks, the associated tufting needle continues to pierce the backing however no yarn is pushed through and thus no tufts are produced. Such faults may develop into end-out defects in the carpets along the line of the missing tufts. When such defects are detected, the tufting machine is generally stopped and the defect mended manually by means of a hand-held mender known as a mending gun. End-out faults are difficult to detect until the defects become visible. Therefore an inspector is generally stationed at each tufting machine in order to inspect the carpet fabric as it is produced to see if any tufts are missing. If a defect is sighted, the machine is stopped as soon as possible and repaired manually. This process is time consuming and labor intensive.

Because such faults are both common and costly, they represent a significant efficiency loss during the tufting process. The need remains therefore for a fault prevention system and method for tufting machines. Embodiments described herein address this need.

SUMMARY

A fault prevention system is disclosed herein configured to prevent development of defects during a tufting process. The system comprises at least one imager configured to image a plurality of yarn strands; and a processor operable to receive image data from the at least one imager and further operable to analyze the image data to detect yarn irregularities. Optionally, the system further comprises an automatic override switch.

Where required, the system may further comprise at least one output interface. For example, the output interface may be selected from at least one or a group consisting of: a warning light, a buzzer, an alarm, a visual display unit and the like as well as combinations thereof. Optionally, the processor may be further configured to send signals to an output interface to indicate detection of an irregularity.

The processor may be further configured to send a signal to an automatic override to shut down the tufting machine upon detection of a critical yarning irregularity.

Variously, the yarn irregularities may comprise indications that at least one yarn is at risk of breaking. Alternatively or additionally, the yarn irregularities may comprise indications that at least one yarn is snagged. Irregularities may be selected from at least one of a group consisting of, inter alia, thinning of the yarn, a reduced number of side fibers, a missing yarn, change in speed of the yarn and the like as well as combinations thereof.

Optionally, the imager comprises at least one camera. Alternatively or additionally, the imager may comprise an array of imaging devices directed towards a plurality of yarns being fed to a common tufting machine. In other systems, the imager comprises at least one imaging device mounted to a rail and configured to scan a plurality of yarn strands being fed to at least one tufting machine. Where appropriate, a plurality of the imagers may be configured to image yarn fed into a plurality of tufting machines. Accordingly, a method is taught for preventing flaws in tufted carpets, the method comprising: providing at least one imager configured to image a plurality of yarn strands; providing a processor operable to receive image data from the at least one imager; the imager collecting at least one image of the yarn strands; the imager sending image data to the processor; and the processor analyzing the image data to detect yarn irregularities.

Optionally, the method further includes the steps: providing at least one output interface; and the processor sending an alert signal to the output interface if an irregularity is detected.

Alternatively, or additionally, the method may further comprise: providing an automatic override switch and the processor sending an automatic shutdown signal to the override switch if an irregularity is detected.

In a particular example, the step of the imager collecting at least one image of the yarn strands comprises the imager collecting: at least a first image of a yarn strand at time t; and at least a second image of the yarn strand at a time t + 5t. Accordingly, the step of the processor analyzing the image data may comprise: determining the distance travelled by the yarn during time interval 5t; and calculating a speed value for the yarn.

Where the speed is thus determined, the method may further comprise the processor sending an alert signal to the output interface if the speed value is outside a target range of values. Alternatively or additionally, the method may further comprise the processor sending an automatic shutdown signal to the output interface if the speed value is outside a target range of values.

BRIEF DESCRIPTION OF THE FIGURES

For a better understanding of the disclosed system and method and to show how they may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings.

With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of selected embodiments only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of those embodiments. In this regard, no attempt is made to show structural details in more detail than is necessary for a fundamental understanding of the embodiments; the description taken with the drawings making apparent to those skilled in the art how the several forms of the disclosed system and method may be embodied in practice. In the accompanying drawings:

Fig. 1 is a schematic diagram representing a tufting machine of the PRIOR ART;

Fig. 2 is a schematic representation of a section of newly tufted carpet displaying an end-out defect of the PRIOR ART;

Fig. 3a is a block diagram representing the main components of a fault prevention system;

Fig. 3b is a block diagram representing a plurality of tufting machines being served by a common fault prevention system;

Figs. 4a and 4b represent how various embodiments of a fault prevention system may be integrated with the tufting machine of Fig. 1; and

Fig. 5 is a flowchart representing a fault prevention method for a tufting machine.

DETAILED DESCRIPTION

Reference is now made to Fig. 1 which shows a tufting machine 100 of the PRIOR

ART. The tufting machine 100 comprises a tufting bed 120, a series of tufting needles 130, a needle oscillator 140, a series of loopers 150, a yarn feed mechanism 160, a backing fabric feed roll 170 and a guide roll 180. A plurality of strands of yarn 220 are threaded through the tufting needles 130 and primary backing fabric 240 is fed from the backing feed roll 170 to the guide roll 180 over the tufting bed 120. The needle oscillator 140 is configured to oscillate each tufting needle 130 vertically such that, during operation of the tufting machine 100, each strand of yarn 220 is pushed through the backing fabric 240 where it is engaged by a looper 150. The backing fabric 240 may then be advanced over the bed 120 incrementally such that when a tufting needle 130 is withdrawn a loop pile 260 is formed on the underside of the backing fabric 240. Where cut pile is required, cutting loopers (not shown) may be provided to cut the loop piles 260.

An inspector 190, stationed by the tufting machine 100, inspects each section of carpet 200 being tufted and attempts to identify defects as soon as possible. When such a defect is detected, the inspector 190 will shut down the tufting machine and manually repair the carpet 200.

Referring now to Fig. 2, a schematic representation is presented of a section of carpet 200 being tufted by a row of tufting needles 130. Fig. 2 illustrates how an end-out defect may develop during the tufting process. Each tufting needle 130 has an associated strand of yarn 220 threaded therethrough. It will be noted that one strand of yarn is missing leaving a gap 222 in the yarn feed mechanism 160 (Fig. 1). As a result, when the empty tufting needle 132 associated with the missing yarn is pushed through the backing material 240 no pile is formed on the underside. Detection of the end-out defect 270 is particularly difficult because the tufting machine 100 continues to operate normally after the yarn detaches from the needle 132. If the missing yarn is not detected, the end-out defect 270 may be propagated along the carpet 200 as the tufting machine 100 (Fig. 1) continues to operate. Typically the defect 270 continues to grow until it becomes large enough for the inspector 190 to notice, at which point the machine is shut down and repairs are carried out.

It will be appreciated that the abovedescribed method of detection and correction of end-out defects is highly labor intensive, typically requiring an inspector to be stationed at each tufting machine. Moreover, the down time associated with shutting down the tufting machine and manually repairing the carpet is a further source of inefficiency in the tufting process. The systems and methods disclosed hereinbelow may allow end-out faults or the like to be prevented before they develop thereby improving the output of the tufting machine and the efficiency of carpet manufacture.

Referring now to the block diagram of Fig. 3a, the main components are shown of a fault prevention system 500 for a tufting machine 100. The system 500 is operable to reduce the prevalence of faults such as end-out faults and the like developing during the tufting process. The main components of the system 500 include an imager 520, a processor 540, an output interface 560 and an override switch 580. The imager 520 is configured to capture images of at least a section of the yarn feed mechanism 160 and to communicate to the processor 540 data pertaining to the captured images. Various imagers 520 may be used in the fault prevention system 500 as suit requirements, for example single or multiple imaging devices, such as cameras, optical detectors or the like, may be arranged so as to image all strands of yarns being fed to the tufting machine 100. Alternatively, scanning imaging devices may be used to sequentially image separate sections of the yarn feed mechanism 160.

The processor 540 is configured to receive data sent from the imager 520 and to analyze the image data in order to detect irregularities in the strands of yarn being fed into the tufting machine. Such irregularities may serve as indications that at least one strand of yarn is broken or is at risk of breaking. The processor 540 may be configured and operable to respond to such irregularities by sending signals to an output interface 560, an override switch 580 or the like.

The output interface 560 is operable to provide an alert that a yarn irregularity has been detected. Accordingly, alert devices 562, such as warning lights, alarms, buzzers or the like, may provide visual and audio alerts. Alternatively, the output interface 560 may provide more detailed information regarding the nature of the irregularity. Accordingly, multiple lights or sounds may indicate varying levels of alert perhaps using color coding or the like. Where appropriate, a visual display unit 564 may display the image of an irregularity or other related data for analysis. Other output interfaces 560 for providing fault risk warnings will occur to the practitioner.

The override switch 580 may be a manual switch operable by a machine operator when alerted by the output interface 560. Additionally or alternatively, automated override switches may be provided to automatically shut down the tufting machine 100 if the processor 540 detects a critical yarn irregularity. Various electronic switches are known which may be used as automatic overrides, such as MOSFETs, relays, magnetic release switches and the like.

It will be appreciated that because the fault prevention system 500 is configured to detect yarn irregularities even before a yarn snaps, it may be able to stop the tufting machine 100 before a potential fault develops. For example, a potential end-out fault may be prevented by the detection of a yarn irregularity, such as a strand of yarn thinning, stalling, displaying a reduced number of side fibers or the like, which may indicate that the strand has become snagged. When such irregularities are detected, the override switch 580 may be configured to automatically shut down the tufting machine before the strand breaks and therefore before the end-out fault occurs. Where appropriate, the fault prevention system 500 may be configured to detect yarn irregularities by monitoring the feed speed of the yarn. Accordingly, the feed speed of each yarn may be determined, for example, by recording a series of images for each yarn. The images may be analyzed to determine the distance travelled δΐ by the yarn during the time delay St between the images. The speed may be calculated from the ratio between the distance travelled SI and the time delay St.

Monitoring the feed speed of the yarn allows sudden changes in speed to be detected providing indication of yarn irregularities. Various speed monitors may be used such as the system described in the applicants copending international patent application number PCT/IB2011/054165, the contents of which are incorporated herein by reference. Other speed monitors will occur to those experienced in the art.

Referring now to the block diagram of Fig. 3b a fault prevention system 500' is shown configured to serve multiple tufting machines 100 'a-d. It will be appreciated that a single processor 540' may be configured to analyze image data from a plurality of imagers 520'a-d each associated with a separate tufting machine 100 'a-d. Thus a single fault prevention system 500' may be used to monitor a plurality of tufting machines 100'a-d. It is particularly noted that a visual display unit 564' may be provided to display output related to all monitored tufting machines to a single operator 590. Other output devices may be used additionally or alternatively as suit requirements.

For purposes of illustration only, reference is now made to Figs. 4a and 4b showing how two possible fault prevention systems 502, 504 may each be integrated with the tufting machine 100 shown in Fig. 1.

With particular reference to Fig. 4a, the fault prevention system 502 includes an array of three imaging devices 522a, 522b, 522c and an alarm 561. The three imaging devices 522a, 522b, 522c are mounted to the housing of the needle oscillator 140 and directed towards the yarn strands in the yarn feeding mechanism 160. Each imaging device 522a, 522b, 522c is operable to image a separate section of the yarn feeding mechanism 160 including a set of yarn strands 224a, 224b, 224c. It is noted that the frames of adjacent imaging devices may overlap to prevent borderline yarn strands being overlooked. Images are sent to a processor (not shown) for analysis and if an irregularity is detected, a signal may be sent to sound the alarm 561.

Upon detection of a yarn irregularity, the machine 100 may be shut down either manually or by an automatic override switch (not shown). Once the machine is shut down, a machine operator may repair the faulty yarn, before damage is caused to the carpet 200 itself. The early preventative detection greatly reduces downtime associated with traditional defect detection. Moreover it is noted that because the fault prevention system reduces the chances of a defect developing it may not be necessary to station an inspector at each tufting machine.

With reference now to Fig. 4b, an alternative arrangement of the fault prevention system 504 is presented including a single imaging device 524, a track 526 and a pair of warning lights 563a, 563b. The single imaging device 524 is mounted to the track 526 and directed towards the yarn strands 220. The mounted imaging device 524 is configured to travel along the track 526 taking sequences of images covering the extent of the yarn feed mechanism. The image sequences may be sent to a processor (not shown) for irregularity detection. When an irregularity is detected, a signal is sent to one or both of the warning lights 563a, 563b, thereby providing graduated warning. For example, the first warning light 563a may indicate that an inspection is considered necessary whereas the second warning light 563b may indicate that immediate shut down is recommended. Which of the graduated warnings is given may be determined for example, by statistical analysis of historical data relating to various irregularities and the number of false positives associated therewith.

The abovedescribed systems are presented for illustrative purposes only, other possible arrangements of the fault prevention system will occur to the skilled practitioner.

Reference is now made to the flowchart of Fig. 5. The flowchart shows the main steps of a method for preventing faults developing during the tufting process using a fault prevention system such as described herein. The method includes: collecting at least one image of the yarn strands fed into the tufting machine 602; sending image data to a processor 604 and the processor analyzing the image data 606. The processor is operable to detect yarn irregularities from the image data, if no yarn irregularities are detected, more image data is collected 608. If a yarn irregularity is detected then further analysis may be carried out to judge the severity of the irregularity 610. If the irregularity is not considered critical then an alert is provided 612 and more image data is collected 602. If the irregularity is considered critical then the machine is shut down 614 so that suitable checks and repairs may be undertaken. Where required, details about the detected fault may be displayed to assist with fault correction 616.

In a particular example of the method, the step of the imager collecting at least one image of the yarn strands 602 may involve the imager collecting a series of images, including a first image of a yarn strand collected at time t and a second image of the yarn strand collected at a time t + 5t. Accordingly, the step of the processor analyzing the image data 606 may comprise: determining the distance travelled by the yarn during time interval 5t; and calculating a speed value for the yarn.

Thus irregularities may be detected by recording variations in the feed speed. A target range of speed values may be defined possibly using predetermined values or using historical data gathered during use of the system. Accordingly, an alert signal may be sent to the output interface if the speed value is outside a first target range of values and the system shut down if the speed value is outside a second target range. It will be appreciated that monitoring the yarn speed allows the system to provide graduated output as required.

It is particularly noted that variations in feed speed may indicate the generation of further tufting faults in addition to the end-out faults discussed hereinabove. For example, high line and low line faults may be caused, for example, when too much yarn or too little yarn is tufted. This may occur when yarn has been punched through the backing and the tip of the loop is cut, for example, to create the appearance of a straight pile yarn. Often as these cutting mechanisms become worn over time the looping arms or cutting blades allow for variation in the position of the cut. This creates a vertical defect due to the height of the pile being too high or too low to match the surrounding ends.

It has long been very difficult to detect high line and low line defects which may run for hundreds of yards before being corrected. By monitoring the speed of the yarn being fed into the tufting machine the systems disclosed herein may provide a method for preventing the formation of high and low line defects.

The scope of the present invention is defined by the appended claims and includes both combinations and sub combinations of the various features described hereinabove as well as variations and modifications thereof, which would occur to persons skilled in the art upon reading the foregoing description.

In the claims, the word "comprise", and variations thereof such as "comprises",

"comprising" and the like indicate that the components listed are included, but not generally to the exclusion of other components.

Claims

1. A fault prevention system configured to prevent development of defects during a tufting process, said system comprising:

at least one imager configured to image a plurality of yarn strands; and

a processor operable to receive image data from said at least one imager and further operable to analyze said image data to detect yarn irregularities.

2. The system of claim 1 further comprising an automatic override switch.

3. The system of claim 1 further comprising at least one output interface.

4. The system of claim 3 wherein said output interface is selected from at least one or a group consisting of: a warning light, a buzzer, an alarm, a visual display unit and combinations thereof.

5. The system of claim 1 wherein said processor is further configured to send signals to an output interface to indicate detection of an irregularity.

6. The system of claim 1 wherein said processor is further configured to send a signal to an automatic override to shut down a tufting machine upon detection of a critical yarning irregularity.

7. The system of claim 1 wherein said yarn irregularities comprise indications that at least one yarn is at risk of breaking.

8. The system of claim 1 wherein said yarn irregularities comprise indications that at least one yarn is snagged.

9. The system of claim 1 wherein said irregularities are selected from at least one of a group consisting of: thinning of yarn, a reduced number of side fibers, a missing yarn, change in speed of yarn and combinations thereof.

10. The system of claim 1 wherein said imager comprises at least one camera.

11. The system of claim 1 wherein said imager comprises an array of imaging devices directed towards a plurality of yarns being fed to a common tufting machine.

12. The system of claim 1 wherein said imager comprises at least one imaging device mounted to a rail and configured to scan a plurality of yarn strands being fed to at least one tufting machine.

13. The system of claim 1 wherein a plurality of said imagers is configured to image yarn fed into a plurality of tufting machines.

14. A method for preventing flaws in tufted carpets comprising:

providing at least one imager configured to image a plurality of yarn strands;

providing a processor operable to receive image data from said at least one imager;

collecting at least one image of said yarn strands;

sending image data to said processor; and

analyzing said image data to detect yarn irregularities.

15. The method of claim 14 further comprising:

providing at least one output interface; and

said processor sending an alert signal to said output interface if an irregularity is detected.

16. The method of claim 14 further comprising:

providing an automatic override switch;

sending an automatic shutdown signal to said override switch if an irregularity is detected.

17. The method of claim 14 wherein the step of collecting at least one image of said yarn

strands comprises said imager collecting:

at least a first image of a yarn strand at time t; and

at least a second image of said yarn strand at a time t + St.

18. The method of claim 17 wherein the step of analyzing said image data comprises:

determining the distance travelled by said yarn strand during time interval δΐ and calculating a speed value for said yarn strand.

19. The method of claim 18 further comprising:

sending an alert signal to an output interface if said speed value is outside a target range of values.

20. The method of claim 18 further comprising:

sending an automatic shutdown signal to an output interface if said speed value is outside a target range of values.