Individual needle control tufting machine

Abstract

A tufting machine and method for operating a tufting machine operating a needle selection mechanism based on pattern data by selecting a needle with yarn required for the pattern such that the selected needle is driven by a needle bar through the backing medium, to form a tuft while a needle that is not required for the pattern is not selected by the needle selection mechanism. Yarn is fed via a yarn feed mechanism comprising a plurality of actively driven yarn drives each driving a respective yarn to a respective needle, the yarn drives being at a location between a yarn creel and the needle. The method being characterised by operating the yarn feed mechanism to deliver at least 70% of the yarn required for a tuft as the needle moves from top dead center to bottom dead center.

Claims

1. A method for operating a tufting machine, the method comprising: feeding a backing medium through a tufting region using backing rollers; reciprocating a needle bar at the tufting region to drive needles into and out of the backing medium, the needle bar comprising at least one row of needles; receiving loops of yarn on gauge parts on the opposite side of the backing medium; controlling the operation of the tufting machine using a controller which receives pattern data for a carpet to be tufted; operating a needle selection mechanism controlled by the controller based on the pattern data by selecting a needle or group of needles with yarn required for the pattern such that the selected needle or group of needles is driven by the needle bar through the backing medium to form a tuft or tufts while a needle or group of needles that is not required for the pattern is not selected by the needle selection mechanism and is not driven through the backing medium as the needle reciprocates; and feeding yarn via a yarn feed mechanism comprising a plurality of actively driven yarn drives each driving a respective yarn to a respective needle, the yarn drives being at a location between a yarn creel and the needle; wherein the yarn feed mechanism delivers at least 70% of the yarn required for a tuft as the needle moves from top dead center to bottom dead center.

2. The method according to claim 1, further comprising operating the yarn feed mechanism to deliver at least 80% of the yarn required for a tuft as the needle moves from top dead center to bottom dead center.

3. The method according to claim 1, wherein the yarn is fed from the yarn drive to the needle without passing through a latch.

4. The method according to claim 1 wherein the yarn is fed from the yarn drive to the needle without passing through a pair of puller rolls.

5. The method according to claim 1, wherein the yarn is fed from the yarn drive to the needle without passing through any tension regulating or tension influencing components.

6. A tufting machine, the machine comprising; backing rollers to feed a backing medium through a tufting region; a needle bar on one side of the backing medium in the tufting region, the needle bar comprising at least one row of needles and being reciprocable at the tufting region to drive needles into and out of backing medium; gauge parts on the opposite side of the backing medium to receive loops of yarn formed by the needles; a controller which receives pattern data for a carpet to be tufted; a needle selection mechanism controlled by the controller based on the pattern data such that a needle or group of needles with yarn required for the pattern is selected by the needle selection mechanism to be driven by the needle bar through the backing medium to form a tuft or tufts while a needle or group of needles that is not required for the pattern is not selected by the needle selection mechanism and is not driven through the backing medium as the needle bar reciprocates; and a yarn feed mechanism comprising a plurality of actively driven yarn drives each yarn feed drive being configured to drive a respective yarn to a respective needle, the yarn drives being at a location, in use, between a yarn creel and the needle, wherein the yarn feed mechanism is configured to deliver at least 70% of the yarn required for the tuft as the needle moves from top dead center to bottom dead center.

7. The tufting machine according to claim 6, wherein the yarn is arranged to be fed from the yarn drive to the needle without passing through a latch.

8. The tufting machine according to claim 6, wherein the yarn is arranged to be fed from the yarn drive to the needle without passing through a pair of puller rolls.

9. The tufting machine according to claim 6, wherein the yarn is arranged to be fed from the yarn drive to the needle without passing through any tension regulating or tension influencing components.

10. The tufting machine according to any of claim 6, wherein the yarn feed mechanism is configured to deliver at least 80% of the yarn required for the tuft as the needle moves from top dead center to bottom dead center.

11. The tufting machine according to any of claim 6, further comprising a yarn compensation device to take up slack upstream each yarn feed drive.

12. The tufting machine according to claim 11, wherein the yarn compensation device comprises a weight for each yarn which pulls each yarn down to absorb slack.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) An example of a tufting machine will now be described with reference to the accompanying drawings, in which:

(2) FIGS. 1A-F to 10 are schematic drawings showing the operation of an individual needle control tufting machine in the prior art;

(3) FIGS. 2A to D are similar representations showing the same operation with a low pile height;

(4) FIGS. 3A to D are similar representations showing the same operation with a high pile height;

(5) FIG. 4 is a schematic cross section of a tufting machine according to the present invention;

(6) FIG. 5 is an enlarged view of a central portion of FIG. 4;

(7) FIG. 6 is a graphical representation of the rate of yarn feed in millimeters through two strokes of a tufting needle in accordance with a conventional yarn feed profile;

(8) FIG. 7 is a view similar to FIG. 6 according to the present invention for a selected needle;

(9) FIG. 8 is a view similar to FIG. 7 showing the yarn feed profile to a non-selected needle;

(10) FIG. 9 is a view similar to FIG. 8 showing the yarn feed profile to a non-selecting needle under different circumstances;

(11) FIGS. 10 and 11 are views similar to FIG. 7 to 9 showing variations in the yarn feed profile for the formation of a first stitch or where a needle has not been selected for some time.

DETAILED DESCRIPTION OF THE INVENTION

(12) A tufting machine according to the present invention is shown in FIG. 4. For the purposes the description, this consists of two main components namely the main tufting machine 1 forming the bulk of the tufting machine and the yarn feed mechanism 2 to feed the yarn to the main tufting machine 1.

(13) The tufting machine 1 is an individual needle control (ICN) machine as such as a ColorTec machine modified as set out below.

(14) In particular, it comprises rear 5 and front 6 backing feed mechanisms to feed a backing material 7 through the tufting machine. Beneath the backing material are a series of gauge parts including a series of hooks 8 and knives 9 which are arranged across the tufting machine in a direction perpendicular to the plane of FIGS. 4 and 5. A corresponding number of needles 10 are reciprocated by a needle bar 11 to which they are selectively latched by a latching mechanism 12 as described, for example, in GB2385604. As described to date, the tufting machine is a conventional ICN machine.

(15) In such a machine, the needle bar 11 is reciprocated to form tufts and is moved laterally to selectively align needles with different coloured yarns at a particular position. A controller receives pattern data and, when a needle with the colour demanded by the pattern is in the appropriate position, the latching mechanism 12 will operate to couple that needle 10 to the needle bar 11 such that, as the needle bar reciprocates, the yarn is driven through the backing material 7. The loop of yarn formed by that needle is picked up by the adjacent hook 8 to form a loop of yarn which is then cut by the knife 9 in order to form a cut pile carpet. This is how a conventional ICN machine operates. The machine may also be provided with a looper in place of the hook 8 and with no knife in order to produce a loop pile carpet, although ICN machines are not generally used in this way.

(16) The modifications relate to the manner in which the yarn is fed. In particular, the yarn latch traditionally associated with each needle in an ICN machine has now been eliminated.

(17) Instead, the yarn is fed by an actively driven yarn feed mechanism 2. This comprises a series of servo motors 20 each of which feeds an individual yarn 21 to a respective needle. As shown in FIG. 4, a pair of puller rolls 22 is provided via which the yarns pass in order to equalise the tension in the yarns coming from various different heights as is apparent from FIG. 4. The puller rolls are depicted in broken lines in FIG. 4 to signify that they are considered optional and are, in fact, not used in the preferred embodiment. Instead, the job of controlling the yarn tension is now done by the yarn feed mechanism 2.

(18) In some situations described below, it is necessary to operate the servo motors 20 in reverse. This can create slack yarn between the creel 30 and the yarn feed mechanism 2. If the slack reaches unacceptable levels, a compensation system 31 can be provided between the creel 30 and yarn feed mechanisms 2. This is in the form of a weight for each of the yarns which will effectively hang from the yarn and hence take up any slack if the respective servo motor 20 is driven in reverse.

(19) This will now be described with reference to FIGS. 6 to 11. All of FIGS. 6 to 11 depict two needle strokes starting from top dead center. All of them show the yarn which is fed in order to form a tuft as a dotted line. They also show the yarn which is fed as a backing stitch compensation in the smaller dashed lines. Backing stitch compensation happens in the case of a sliding needle bar where a needle is slid laterally across the machine from one position to another. Under these circumstances, the yarn feed mechanism has to feed additional yarn to the needle in order to compensate for the fact that it has moved, otherwise a needle will pull on the yarn as it is moved thereby increasing the yarn tension. The sum of the yarn feed to form the tuft and the yarn required for the backing stitch compensation represents the total yarn feed fed by each servo motor of the yarn feed controller and is represented by the large dashed line in FIGS. 6 to 11.

(20) FIG. 6 shows the yarn feed profile for a conventional yarn feed mechanism. As can been in FIG. 6, the yarn required to feed the pile height 61 is constant throughout the stroke while a small amount of yarn 62 is fed in the last half of the up-stroke and the first half of the down-stroke as backing stitch compensation. The total yarn feed is shown as 63.

(21) By complete contrast, in FIG. 7 shows no yarn feed for the tuft is fed for most of the down stroke as depicted by reference numeral 71. However, at top dead center the yarn feed ramps up rapidly as depicted by 72 in order to feed as much yarn as possible by bottom dead center. At bottom dead center, the yarn feed tails off rapidly as depicted by 73 and before the first half of the down-stroke has been completed, the yarn feed for the tuft is stopped entirely. Superimposed on this is the same profile 74 from the the back stitch compensation, providing a total yarn feed 75 which is still dominated by the feeding of the yarn for the tuft in the first half of the stroke. This is done because, all of the yarn required to form a tuft is consumed on the down stroke of the needle and, as the needle undergoes its upstroke, the yarn has to slide through the needle to leave the yarn in place for the tuft.

(22) FIG. 8 shows the situation where a needle is not selected and hence the yarn feed for the tuft 81 remains at zero while the yarn feed for the back stitch compensation 82 is as before and equates to the total yarn feed.

(23) FIG. 9 represents a slightly different situation where a needle is not selected such that the yarn required for the tuft 91 remains at zero. If, for a non-selective needle, the distance between a new stitching point and the last stitch is smaller than the distance between the previous stitching point and the last stitch, an excess of yarn will be present and needs to be recovered. In this situation, the backing stitch compensation feed becomes negative 9 indicating that the individual servo motor of the yarn feed system 2 is operating in reverse mode to recover yarn.

(24) Operating in reverse mode can cause slack upstream of the servo motor. As a result of this, a compensation system may be provided upstream of the yarn feed system 2. The compensation system preferably comprises passive elements, for example in the form of small weights which will take up any slack in the yarn.

(25) FIGS. 10 and 11 depict the yarn feed to a selected needle either where the needle is reciprocated for the first time or where the needle has not been reciprocated for a number of strokes but still receives the backing stitch compensation.

(26) FIG. 10 effectively corresponds to FIG. 8 in terms of the back stitch compensation 82 with the yarn feed for the tuft 72 from FIG. 7, while FIG. 11 is a combination of the negative yarn feed 92 according FIG. 9 with the yarn feed for the tuft 72 of FIG. 7. FIG. 10 represents the situation where the distance between a new stitching point and the last stitch is greater than the distance between the previous stitching point and the last stitch such that additional yarn 101 is fed while FIG. 11 represents a situation where the distance between a new stitching point (where the needle is not selected) and the last stitch is smaller than the distance between the previous stitching point and the last stitch such that some yarn 111 is held back.

(27) The above yarn feed profiles provides a superposition of the yarn feed needed to compensate for the backing stitch and the yarn feed needed to form the pile height with the desired height. This is done by concentrating the yarn feed in the first half of the cycle as described above. This provides a benefit that the yarn remains more stretched during the entire stitch cycle and slack can be avoided. The yarn feed profile could also advantageously be used in conventional tufting in order to provide better control of the yarn feed.