A method of tufting a carpet

Abstract

A method of tufting a carpet comprising inputting pattern data into a controller. The controller determines a nominal yarn feed rate to produce the yarns of the required height. It determines from the pattern data whether the transition in height from one loop to the next for each needle exceeds a predetermined threshold. If so it calculates an actual yarn feed rate based on a nominal yarn feed rate adapted by a transition parameter. The transition parameter is an operator input parameter representing the desired abruptness of the transition required between the loops of yarn where the predetermined threshold is exceeded. The carpet is tufted according to the actual yarn feed rate.

Description

[0001] A Method of Tufting a Carpet

[0002] The present invention relates to a method of tufting a carpet.

[0003] In particular, the invention relates to a method of tufting a loop pile carpet. When tufting a loop pile carpet, the pattern data frequently specifies a relatively large change in the loop pile height that each needle is required to produce. When transitioning from low to high pile heights without compensation, the tension and / or elasticity of the yarn can cause underfeeding of the yarn at this transition. Similarly, transitioning from high to low pile heights can cause overfeeding.

[0004] According to the present invention, there is provided a method of tufting a carpet according to claim 1.

[0005] The controller is able to automatically identify transitions which are likely to be problematic in that they require a needle to produce two adjacent loops at significantly different pile heights and can correct these and even provide enhanced pattern effects.

[0006] The controller may be a tufting machine controller, or it may be a separate controller for the pattern data remote from the tufting machine. In this case the operator can work on the carpet design remotely and apply the transition parameter to the input pattern data before this is fed to the tufting machine controller

[0007] The loops can potentially be corrected on a stitch-by-stitch basis where the threshold is exceeded. However, it also offers the possibility to correct all such problems, or identify a particular subset of issues for correction.

[0008] The method also offers a further tool beyond correcting for the under / over fed yarn in that the operator is able to input a transition parameter linked to the desired appearance of the carpet. For example, the operator can set the parameter to provide a number of desired transitions such as VERY ABRUPT / ABRUPT / NORMAL / SMOOTH / VERY SMOOTH. Alternatively, this can be input as a sliding scale between these various fixed points. Therefore, the method has an enhanced pattern capability. It is a simple matter for an operator to specify a set of conditions, tuft a carpet sample according to those conditions and adapt the parameters, if necessary, based on the finished product. The chosen set of

[0009] 17293350.EAM.EAM compensation settings can be saved to each particular carpet quality e-file (including, for example, nominal pile height / bedplate setting / yarn feed rate, stitch rate, pile weight, and yarn type / characteristics) so that the total desired carpet quality & compensation parameter settings can be returned without the need for retuning. The stored set of parameters can be used as they are, or can be further tuned for a new carpet.

[0010] The transition parameter may be applied in a number of ways. For example, it may be applied to adjust the pile height of the loop immediately after the transition. This allows for the over feeding of the yarn for a loop immediately following a low / high transition or the under feeding of a loop immediately following a high / low transition.

[0011] Additionally, the transition parameter may be applied to adjust the pile height of more than one loop of yarn adjacent to the transition. This provides additional patterning effects in that it allows the operator to do more than just compensate for the adverse yarn tension / elasticity effects, but to be able to set a desired contour for the profile of the yarn transition.

[0012] The transition parameter may be applied to all transitions where the transition height exceeds the predetermined threshold. Alternatively, it may be applied in a more selective manner. It could, for example only be applied to high / low transitions and not low / high transitions or vice versa.

[0013] In some patterns where there are relatively few loops between each transition, it may not be necessary or desirable to apply the transition parameter. In this case, the number of loops formed within predetermined height parameters immediately prior to a transition is determined and the transition parameter is only applied if this number is above a predetermined number. In other words, a transition parameter is only applied where relatively large areas are at a certain height before the transition.

[0014] The transition parameter may, for example, be entered as part of the pattern design process. However, preferably, input or adjustment of the transition parameter is via an operator interface. This allows the operator to set the transition parameter giving the benefits of design flexibility as set out above.

[0015] 17293350.EAM.EAM The operator interface may be in the form of a linearly variable control such as a rotatable knob or sliding switch which allows simple control of the variation of the transition parameter. Preferably, the operator interface is a screen which allows the operator greater flexibility in the setting of the transitions.

[0016] The transition parameter may be applied to all transitions exceeding the predetermined threshold in a predetermined area of the carpet. This allows different transitions to be set for different pattern features. Alternatively, the transition parameter is applied to all transitions exceeding the predetermined threshold of the carpet. This provides a simpler way of setting the transitions for the carpet as a whole.

[0017] The method may further comprise inputting a yarn elasticity parameter into the controller and incorporating the yarn elasticity parameter into the calculation of the actual yarn feed rate. This may be useful if the tufting machine is intended to be used with yarns of different elasticities. In the event that a yarn with high elasticity is used, over / under feeding of the yarn at a particular transition may be greater than it will be for yarn with low elasticity. This can be incorporated into the actual yarn feed rate in order to provide the desired outcome.

[0018] An example of a method in accordance with the present invention will now be described with reference to the accompanying drawings, in which:

[0019] Figs. 1 A to C are partial schematic cross-sections of the tufting machine showing the stages in the loop forming process;

[0020] Figs. 2A-5A are diagrammatic figures showing a number of different yarn feed profiles; Figs 2B-5B are diagrammatic figures corresponding to FIGS. 2A-5A respectively of the associated loop profile in the finished carpet;

[0021] Fig 6 is a map of the analysed pattern data showing the high and low stitches;

[0022] Fig 7 is a map similar to Fig 6 after the yarns where the transition from the previous stitch exceeds the predetermined threshold;

[0023] Fig 8 is a map similar to Fig 7 in which the transition parameter has been applied only to selected stitches identified in Fig 7; and

[0024] Fig. 9 is a screenshot showing the input of the pile parameters.

[0025] The tufting machine in Figs. 1 A-C is a known machine. As this is conventional, only the main components will be described here.

[0026] 17293350.EAM.EAM The backing medium 1 is fed through the tufting machine in a longitudinal direction depicted by arrow 2 and is supported in the tufting position by a needle plate 3. A line of needles 5 extends in a transverse direction perpendicular to the plane of Figs. 1 A to c). Each needle is threaded with yarn Y fed by a servo motor S. Each needle 5 is supported on a needle bar 6.

[0027] Beneath the backing medium 1 is a looper 8 associated with each needle 5. From the position shown in Fig 1 A, the loopers 8 will rock forwards as the needle 5 penetrates the backing medium 1 as shown in Fig 1 B to pick up a loop L of yarn formed by the needle 5. As the needle retracts as shown in Fig 1 C the loop L is formed by the looper 8.

[0028] The invention is applicable to various types of tufting machine including those which rely on not picking up the loop of the yarn from the needle which penetrates the backing medium 1 , so that loops of unwanted yarn are pulled back out through the backing medium.

[0029] Alternatively, each needle has an associated latch such that, if the needle is required to be reciprocated in a particular stroke, the needle can be selectively latched to the needle bar so that it will penetrate the backing medium. This may be combined with a LCL (level cut loop) attachment, or any other loop creating attachment.

[0030] The present invention relates to the manner in which the tufting machine processes transitions between low pile heights as described below.

[0031] Whilst many carpets are tufted at a single pile height, many others have various pile heights in order to provide decorative effects such as uniform geometry patterns (stripes, grids etc.) or more freeform patterns with areas of high pile heights mixed with areas of low pile heights.

[0032] Fig. 2A provides an example of transition from a high pile height represented by vector arrows 20A to a low pile height represented by arrows 21 A. The line of stitches depicted here are formed by a single needle 5. A plurality of needles 5 are arranged across the tufting machine and each will each have their own individual pile profile depending upon the pattern requirements. These may be the same as that shown in Fig. 2A if a uniform pattern is being produced and will be different in each case for a freeform pattern.

[0033] 17293350.EAM.EAM If the pattern is formed by uniformly feeding the yarn in direct proportion to the desired pile height, the effect of this will be as shown in Fig. 2B. Transitioning from the last high pile height 22A to the first low pile height 23A, the tension in the yarn is higher than it would be for adjacent low loops of yarn 21 A. As a result of this the first “low” loop 23B (Fig 2B) is pulled out of the backing medium 1 less than the subsequent loops resulting in a loop of intermediate height as shown in Fig. 2B. This effect can still be felt in one or more subsequent yarns as depicted by loop 24B. A steady state is reached for low pile height at 21 B.

[0034] Figs. 2A-5A represent pile height data input into the controller. The controller then analyses the data to determine whether this is above a predetermined threshold. In this case, with reference to Fig. 2A, the difference in pile height from stitch 22A and 23A is H1 which is above the predetermined threshold. Where the pattern data calls for a gradual change in pile height (for example in a region of the carpet with a contoured effect), this will be below the defined threshold and will not be by the flagged by controller for compensation. Where there is a more abrupt pile height then the threshold value is flagged.

[0035] This analysis results in a pattern map as shown in Fig. 6 in which the high pile 20A is depicted in white squares and the low stitch 21 A is depicted in dark squares. In Fig. 6, each vertical column of stitches C1 , C2, C3 etc. corresponds to a line of stitches produced by an individual needle (e.g. as depicted in Figs. 2A to 5A).

[0036] Arrow B in Fig. 6 represents the direction in which the tufted carpet will be formed, namely the direction in which, in practice, the backing medium 1 will be fed through the tufting machine. The pattern is divided into rows R1 , R2, R3, etc. All of the stitches in a single row will be formed by the needle bar before it moves to the next row.

[0037] The controller recognises a transition from a high stitch 20A to a low stitch 21 A in the direction of needle travel. This is represented in Fig. 6 by a transition (in the direction B) from a white square to a dark square. Similarly, a transition from a low stitch 21 A to a high stitch 20A (in the direction B) is represented by a transition from a dark square to a white square.

[0038] For simplicity, this has been described only in relation to two pile heights. However, it can also be applied to pattern data which specifies more than two different pile heights.

[0039] 17293350.EAM.EAM The threshold itself may be set by the tufting machine operator or the carpet designer to cover only those transitions where the effect is required. It is also possible to have more than one threshold value, namely a first threshold where there is a large differential in the pile height and a second threshold where there is a smaller differential. These can create different data sets and the two sets can be treated differently.

[0040] Having identified the transitions which exceed the predetermined threshold, the controller can apply a yarn compensation technique. This may be applied automatically, or the controller may generate an alert to an operator that some abrupt transitions have been identified giving the operator the option to apply a yarn compensation technique. Whether this is applied automatically, or following a manual trigger, the compensation techniques will now be described.

[0041] The yarn compensation technique for a high to low transition is shown in Figs. 3A and 3B. This is particularly apparent in contrast to the uncompensated version shown in Figs. 2A and 2B. In particular, the first low pile 23A is now fed at a significantly reduced rate indicated by a reduction in the height of the vector arrow 23A in Fig. 3A as compared to Fig. 2A.

[0042] This reduction in yarn feed results in the loop 23B in Fig. 3B being lower than it otherwise would be as in Fig. 2B. This provides a sharper transition at the high / low interface as is apparent from a comparison of Figs 2B and 3B.

[0043] The decrease in the yarn feed rate may be implemented in a number of ways. Typically the yarn is fed under the control of a servo motor. The lower yarn feed rate may be achieved by reducing the speed of the servo motor to a lower speed than would normally be used to produce a loop at this particular height. Alternatively, the lower speed of the servo motor may be the same as the lower speed normally used, but the servo motor may switch to the lower speed earlier or more quickly than normal.

[0044] As a further alternative, the yarn feed profile for a particular loop may be split into a number of segments which cause the servo motor to operate at different speeds so as to control the amount of yarn fed at different parts of the profile. In this case, for the loop 23B, the

[0045] 17293350.EAM.EAM profile may be adapted so that a greater proportion of the stitch may be fed at the lower rate.

[0046] As is apparent from Fig. 3A, stitch 23A is fed at a lower rate. The next stitch 24A is also underfed by an amount which is part way between the feeding of the stitch 23A and the normal stitches 21 A. This provides continuing yarn compensation into the second stitch 24B.

[0047] With reference to Fig. 7, the yarn compensation stitches 23A for the transition from the high to the low yarns are designated as diagonally shaded squares (replacing what were previously dark squares in Fig 6). The compensation for the stitch 24A is not shown in this figure for clarity.

[0048] The transition from the low to the high stitches will now be described with reference to Figs. 4A, 4B, 5A and 5B.

[0049] As with the previous Figs the following labelling is used. High piles 20A, high loops 20B, low piles 21 A and low loops 21 B.

[0050] In Fig. 4A, the differential between the low 21 A and high 20A stitches is designated H2. This is set to be the same as or different from differential H1 shown in Fig. 2A for the high to low transition.

[0051] In this case, at the transition from the low 21 A to the high 20A piles, the first loop 40B is intended to be high, but the yarn tension effects cause it to be underfed as represented in Fig. 4B. To compensate for this, the first high pile 40A is overfed as shown in Fig. 5A so that the first high loop 40B is the same height as the high loop 20B. As previously, the second pile 41 A after the transition may also be slightly overfed in order to provide a sharper transition.

[0052] The overfed stitches 40A are designated in Fig 7 as horizontally shaded squares (replacing what were previously white squares in Fig 6).

[0053] As will be appreciated from Fig. 7 the carpet pattern typically has a background of low (dark) stitches 21 A and regions of high (white) stitches 20A. The present method provides

[0054] 17293350.EAM.EAM an operator with a simple way of tailoring these transitions to provide the desired aesthetics for the carpet.

[0055] The examples in Figs 2A to 5A represent only some of the possibilities. They show an unmodified condition and a condition in which the under / over feed is “corrected” to ensure a uniform pile height at the transition.

[0056] Another possibility is that, rather than making a more abrupt transition, the controller could be set to overfeed the yarn at a low transition or underfeed the yarn at a low to high transition which results in a more gentle transition than is provided with the uncompensated yarn. Alternatively, the under compensation at a high to low transition or the over compensation at a low to high transition could go beyond what is needed to achieve the uniform loop height in Figs. 3B and 5B. This would produce an abnormally low / high loop (or loops) immediately after the high to low transition which sharpens the transition even further.

[0057] As described in relation to Figs. 3A and 5A, the yarn compensation is spread over the two stitches immediately following the transition. As described above, this could be done for a single stitch or could be spread over more than two stitches after the interface to provide a smoother transition.

[0058] Another alternative is shown in Fig. 8. In Fig 6 there are some single rows of high stitches 20A and low stitches 21 A. As can be seen in Fig. 8, the compensation has been applied only to the first transition (low 21 A to high 20A) encountered. For example, at the bottom of Fig. 6, there is a single row of high stitches 20A. At the first transition from low to high overfed stitches 40A are formed (Fig 7). However, after this single row the transition back from high to low, does not have compensated lower stitches 23A as depicted in Fig 8 where the stitches 23A in this row are replaced by normal low stitches 21 A (although these could be provided if necessary as they are in Fig 7).

[0059] When the pattern is quickly changing between high and low tufts the yarn compensation can be switched off entirely. This can be achieved by setting a minimum number of stitches which are formed at one height and using yarn compensation only once this number is exceeded. For example, it can be set such that compensation will only be applied to a

[0060] 17293350.EAM.EAM transition where the differential is greater than height H and the number of consecutive low or high stitches prior to the transition is greater than, say, 3.

[0061] Fig. 9 shows the operator interface integrated into the controller. It shows a screen 50 which provides the operator with a number of input parameters. A check box 51 allows an operator to turn the yarn compensation on and off. The adjustable parameters are described below.

[0062] 52 Colour number range.

[0063] Each pixel color has an associated number. This allows a set of colours to be selected for the yarn compensation parameters described below.

[0064] The “+“ sign to the left of box 52 allows a further group of boxes to be opened to define a second set of colour numbers. These can then be defined to have characteristics as defined below but which are different from those of the first set. For example, in a first screen settings for colour number 1 , 5, 7, 12-255 may be defined and, in a second screen, opened by the + button, the settings for colour numbers 2-4, 6, 8-11 may be defined.

[0065] More than two sets may be defined each with different characteristics.

[0066] 53 Threshold height difference.

[0067] This allows the operator to set the differential H1 , H2 in height between adjacent stitches of the same needle at which the yarn compensation is triggered. In the event that additional height differentials are used (e.g. if a different value is set for low / high and high / low transitions) additional inputs can be provided.

[0068] 54 Minimum number of stitches in transition.

[0069] This allows the operator to select the number of stitches over which the yarn compensation is spread. As described above, Figures 3A and 5A transition over two stitches, but this can be revised up or down by the parameter at 54.

[0070] 55 Correction value high to low.

[0071] This allows the operator to set the value of the percentage underfeed in the high to low transition. In this case, the value 20 indicates that the yarn for the first underfed stitch 23A is 20% less than that required for a normal low yarn 21 A.

[0072] 17293350.EAM.EAM - I Q -

[0073] 56 Correction value low to high.

[0074] This is essentially the same as the previous entry 55, but for the low to high transition. In this case, it represents a percentage increase required for the transitional stitch 40A compared to an uncompensated high stitch 20A.

[0075] In the event that box 54 is set at a level greater than 1 , more than one entry may be available at 55 and 56 to set correction for additional stitches in the transition.

[0076] 57 Minimum pile height.

[0077] The operator / designer cannot choose an underfeed that would correspond to a desired loop pile height lower than this parameter setting.

[0078] 58 Maximum pile height.

[0079] The operator / designer cannot choose an overfeed that would correspond to a desired loop pile height higher than this parameter setting.

[0080] Other boxes may be provided as necessary for additional parameters. For example, a further box may be provided for the input of the minimum number of stitches of a similar pile height required before the compensation is applied.

[0081] The operator will be aware of the elasticity of the yarn that they are using to create the carpet. This is something that they can compensate for in boxes 55 and 56 by entering a value which will compensate for the yarn elasticity. Alternatively, an additional input may be provided for a parameter relating to the elasticity. This can be automatically processed and a value suggested in boxes 55 and 56 taking into account the yarn elasticity. The operator is then able to amend this parameter to over or under compensate as they wish.

[0082] In practice, an operator can set the parameters on screen 50 as described above and then set off the tufting machine to produce a test sample of carpet. They can then examine the sample and easily change the parameters. An advantage provided by the invention is that it automatically identifies the areas where compensation may be needed and provides an easy way that the operator can adjust this for the whole carpet or for designated regions of the carpet. The setting of the color number ranges as described in step 52 above gives the

[0083] 17293350.EAM.EAM possibility to apply the compensation over designated regions (corresponding to these color numbers).

[0084] This process can be repeated a number of times until the operator is happy with the finished product.

[0085] The technique also lends itself to an Al based solution in which cameras are provided to monitor the finished product and can be used to provide training data which can be fed back into the machine controller. Thus, rather than the operator / designer going through the above iterative process, the controller can learn that, for given pattern data and based on the transition parameters, further adaptations to the yarn feed rate may be necessary in order to set a desirable outcome.

[0086] For Al based solutions a sensing unit (e.g. camera or laser), a storage unit, a processing unit, and a control unit are provided.

[0087] The sensing unit may consist of image capturing devices; this may be a very sophisticated laser and / or camera set up, typically described as laser triangulation technology, or a multicamera set ups catching on different viewing angles, or structured light camera scanner systems, to enrich the data.

[0088] Also, different working conditions should be taken into account, such as different light or dust environments.

[0089] A database with captured, processed and evaluated data regarding existing samples or tufted fabrics, including also some calibration height differences, can then be built up.

[0090] A processing unit capable of handling the huge amounts of data including camera data is also required. The camera data have to be stored, adding the detected height differences, abruptness of transitions and other quality parameters, and they can be linked to the design or desired fabric data.

[0091] A long carpet could be tufted with multiple height differences, with a range of differences and abruptnesses set.

[0092] The cameras could for example be integrated on the tufting machine. Alternatively there

[0093] 17293350.EAM.EAM could also be an offline set up, where a more sophisticated set up can be afforded to evaluate the fabrics from multiple tufting machines.

[0094] The set-ups could be used to measure height differences and transitions, combined with the know parameters of the fabric under inspection, and the settings used for the “dynamic loop” correction. The parameters and settings can be saved together with the design / fabric on the machine and / or offline at the design station.

[0095] With an offline setup, the tufted fabric may be scanned and suggested changes may be transferred to the operator for tufting the next products.

[0096] Alternatively, with an online setup on the tufting machine itself, in addition to making suggestions to the operator, the required settings to obtain the required transition result may be set automatically.

[0097] While the screen 50 provides a sophisticated control of the under compensation parameters, this can be reduced to a single linear input for example a rotary knob or slider which allows an operator to select the style of transition they require at a high level. For example, they may have the options of VERY

[0098] ABRUPT / ABRUPT / NORMAL / SMOOTH / VERY SMOOTH. Alternatively, this can be input as a sliding scale between these various fixed points. The machine controller can then determine various parameters required to achieve these effects and calculate the percentage yarn over / underfeed, potentially also applying yarn elasticity compensation.

[0099] 17293350.EAM.EAM

Claims

1. CLAIMS:1 . A method of tufting a carpet, the method comprising the steps of: inputting pattern data into a controller wherein the controller: determines a nominal yarn feed rate to produce the yarns of the required height, determines from the pattern data whether the transition in height from one loop to the next for each needle exceeds a predetermined threshold, and, if the predetermined threshold is exceeded, calculates an actual yarn feed rate based on a nominal yarn feed rate adapted by a transition parameter, the transition parameter being an operator input parameter representing the desired abruptness of the transition required between the loops of yarn where the predetermined threshold is exceeded; and tufting the carpet according to the actual yarn feed rate.

2. A method according to claim 1 , wherein the transition parameter is applied to adjust the pile height of the loop immediately after the transition.

3. A method according to claim 1 or claim 2 wherein the transition parameter is applied to adjust the pile height of more than one loop adjacent to the transition.

4. A method according to any preceding claim, wherein the number of loops formed within predetermined height parameters immediately prior to a transition is determined and the transition parameter is only applied if this number is above a predetermined number.

5. A method according to any preceding claim, wherein the input of the transition parameter into the controller is via an operator interface.

6. A method according to claim 5, wherein the operator interface is via a screen.

7. A method according to any preceding claim, wherein the same transition parameter is applied to all transitions exceeding the predetermined threshold in a predetermined area of the carpet.17293350.EAM.EAM8. A method according to any preceding claim, wherein the same transition parameter is applied to all transitions exceeding the predetermined threshold in the carpet.

9. A method according to any preceding claim, further comprising inputting a yarn elasticity parameter into the controller and incorporating the yarn elasticity parameter into the calculation of the actual yarn feed rate.

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