GB2240990A - Axminster carpet loom - Google Patents

Abstract

In order to detect yarn take up by grippers (12) in a more reliable manner than hitherto, a housing (20) provides separate channels through which the tips of respective grippers (12) pass as they move between yarn take up and insertion positions. Respective photoreceptors (34) are associated with each channel and a light source (24) illuminates the channels as the tips of the gripper (12) pass therethrough. If the gripper tips are carrying yarn (36) they draw it after them through the respective channels and this blocks light transmission between the source (24) and the relevant receptor (34). Thus the presence or absence of yard (36) at each position can be detected and by use of microprocessing control means the loom can be stopped whenever the overall frequency of missing yarn exceeds a pre-set threshold, or specific omission by individual grippers (12) is excessive. <IMAGE>

Description

AXMINSTER CARPET LOOM This invention concerns an Axminster carpet loom, and more specifically the provision, in such a loom, of a sensor mechanism whereby the take up of yarns by grippers for insertion as tufts into a warp shed, as a base fabric is woven, can be monitored.

In an Axminster carpet loom, in each cycle (for production of each row of carpet tufts) carriers, in each of which ends of a plurality of yarns (e.g. of different colours) are located at spaced intervals, are displaced to respective selected positions so that the selected yarns to be woven are presented at predetermined aligned positions along the loom for taking up by respective grippers. In this respect, there is a gripper associated with each carrier, and the displacement of the individual carriers to present the correct yarn at the take up position is controlled either by a Jacquard mechanism, or by a computer programme. This may be accomplished by way of any one of a number of known mechanisms.For example, a displaceable toothed entrainment device may engage a projection provided on the carrier or on a device connected to the carrier, or a displaceable bar may engage a selector peg which has been caused to project from the carrier or from a device connected to the carrier, so as to bring about the required displacement of the carrier, and the aforesaid interengagement, or else the projection of the relevant selector peg, may be effected, for example, by a solenoid-actuated plunger under control of the Jacquard mechanism or the computer programme (whichever is used).

The respective grippers reciprocate between yarn take up positions and yarn insertion positions. At its take up position each gripper grips the yarn end presented at that position by the carrier. On commencing its return stroke the gripper draws off the yarn, and the yarn is then severed at a predetermined length by a knife which traverses the loom adjacent to the aligned positions where the carriers present the selected yarn ends. The gripper carries its severed length of yarn to the insertion position in the warp shed, and releases the yarn once it has been secured there by the subsequent weft pick of the backing fabric.In this respect, each gripper conventionally comprises a pair of jaws which close to grip the yarn end in the take up position, remain firmly closed during the draw off (return) stoke, and open to release the yarn in the insertion position, before returning to the take up position.

Any slight inaccuracy, for example in the displacement of a carrier or of a gripper, or in the timing of the sequence of operations, or even in the tensioning of the yarn, might result in failure of a gripper to take up the selected yarn from its associated carrier, leading to a gap in the eventual carpet pile, where that yarn tuft is missing. A certain small proportion of randomly dispersed missing tufts can be tolerated as the gaps will not be readily apparent in the pile of the finished carpet. On the other hand, a high overall proportion of missing tufts, or a distinct row of missing tufts, as caused by persistent take up failure by a particular gripper, cannot be tolerated as these will adversely affect the appearance of the finished product.It is therefore important that the take up of yarn ends by the grippers is monitored and that the machine is stopped and repairs effected if a high proportion or specific repetition of take up failure is detected.

Traditionally loom operatives have monitored yarn end take up by the grippers by visual inspection. Since it is desirable to avoid the need for such close and continuous observation, so that one operative can oversee several looms, numerous proposals for sensor mechanisms for automatically monitoring yarn end take up have been proposed, but none have so far proved entirely satisfactory.

Sensor mechanisms involving use of a light source and photo receiver in the vicinity of the knife blade to ascertain the presence or absence of a yarn therebetween have proved impractical owing to the overlap in the path of adjacent knives and/or to the cloud of yarn fragments released as the knife severs the yarns. Other mechanisms based on the provision of separate feelers registering the presence of absence of a taut yarn adjacent the carriers just prior to severance have worked, but introduce added mechanical complexity and risk of malfunction.

It is an object of the present invention to provide improved sensor means whereby the take up of yarns by grippers for insertion into the base fabric can be monitored in a simpler and more reliable manner than hitherto.

With this object in view, the present invention proposes an Axminster carpet loom comprising a plurality of carriers which are displaceable under the influence of pattern control means to bring selected yarns to aligned take up positions, a respective gripper associated with each carrier, each gripper being reciprocable between a yarn take up position for taking up a yarn end presented by the associated carrier and a yarn insertion position for inserting a severed yarn end into a warp shed for binding into backing fabric as it is woven, and at least one knife operative to sever the yarn ends prior to their insertion into the warp shed, and further including yarn take up detector means comprising housing means configured to provide separate channels, flanked by respective side walls, for passage therethrough of the tips of respective grippers as they move between their take up and insertion positions, and having respective photosensitive receptors associated with each channel, and a light source operative to illuminate the channels as the tips of the grippers pass therethrough so that in operation of the loom, yarn ends will be drawn through the respective channels, between the light sourse and the respective photoreceptors, by the respective grippers, and the presence or absence of such yarn ends will be detected by the photoreceptors.

In accordance with the invention, the housing means of the detector arrangement can be mounted at any suitable location along the path of the grippers between their take up and insertion positions. In this respect, the housing means is advantageously mounted at a location remote from the knife so as to minimise the risk of malfunction of the detector by the photoreceptors being clogged by fragments of yarn. However, if there is, at any location, a risk of such clogging, this can be overcome by the expedient of providing an air blower to remove any dust or other detritus by periodic blasts of air.

Since each individual gripper tip is caused to pass through a separate channel, and since there is a respective photoreceptor associated with each channel it is possible to detect with considerable accuracy whether or not each gripper is carrying a length of tufting yarn. In this respect, the photoreceptors are advantageously electrically connected, in known manner, to a common microprocesssor control unit, and the arrangement may conveniently be such that each photoreceptor transmits a signal to the control unit whenever it receives light from the source (indicative of the absence of yarn therebetween) during a pre-set time interval immediately following passage of the associated gripper through the channel.

The housing means advantageously comprises a single elongate element or a number of such elements, each configured to provide a plurality of side by side channels defined by the spacings between a plurality of ridges, partitions or fins, such that each ridge, partition or fin constitutes a common side wall to adjacent channels.

The aforesaid ridges, partitions or fins may usefully taper in their longitudinal direction.

The housing elements, where provided, are advantageously pivotally or slidably mounted so that they can be readily moved out of position when access to the grippers or carriers is required for repair. The respective photoreceptors are preferably mounted in the housing means in or below the base of each channel. In this position susceptibility to extraneous interference is minimised, thus minimising the risk of emission of false signals.

The light source may conveniently be common for all grippers, or a considerable number. In this respect it may comprise one or more strip lights extending across the loom.

In an advantageous embodiment the light source may be mounted on the gripper reciprocation means, for example on a gripper shaft which rotates to and fro to swing the grippers between their take up and insertion positions. The light beam may then be directed at the tips of the grippers so as to move in synchrony therewith, and be directed into the channels of the detector housing means only while the gripper tips are passing therethrough.

Alternatively, of course, the light source may be mounted so as to remain stationary and be permanently directed towards the channels of the detector housing means, yet only switched on intermittently during the short intervals of time while the grippers pass through the channels from their take up to their insertion positions.

The light source may conveniently be an infrared source, and the photo receptors may conveniently be infrared detectors. Nevertheless, the invention is intended to encompass use of any known type of source and receivers of electromagnetic radiation, and the terms "light source" and "photoreceptor" as used herein should be construed accordingly.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic side elevation illustrating sufficient components of an Axminster carpet loom to enable the invention to be understood; Fig. 2 is a diagrammatic side elevation, to a greatly enlarged scale compared to Fig. 1, illustrating part of a modified version of Axminster loom incorporating a preferred embodiment of the tufting yarn take up detector mechanism in accordance with the present invention; Fig. 3 is an enlarged scale, partial, perspective view of a housing element of the yarn take up detector shown in Fig. 2; and Fig. 4 is a corresponding diagrammatic, partial front view of such a housing element, in the direction of arrow IV in Fig. 3.

Fig. 1 illustrates the mechanism for take up and insertion of tufting yarn in a conventional Axminster carpet loom.

A main gripper shaft 10 extends transversely across the loom and has mounted thereon a plurality of grippers 12, turning of the shaft 10 serving to swing the grippers 12 between tufting yarn take up positions which are indicated in full lines in Fig. 1 and yarn inserting positions which are indicated in dotted lines. Each gripper 12 introduces a respective tufting yarn length into warp shed 14 close to the fell at reed 16, to be anchored into the fabric being woven.

Associated with each gripper 12 is a respective elongate yarn carrier in the form of a bar 18 which is disposed on edge, so that the number of such carrier bars 18 and grippers 12 may be very large, there being, for example, up to eight of such bars 18 and grippers 12 to each inch (2.5cms) of the effective length of the shaft 10. These bars 18 may be disposed vertically, horizontally, or (as shown) at an angle therebetween and they are longitudinally slidable in a manner which is well known in the art and need not be described for the purposes of the present invention.

Near to its bottom end, each yarn carrier bar 18 has a plurality of openings 34 therethrough, these being equally spaced apart and each accommodating a respective tufting yarn 36 so that the extremity of each such yarn 36 projects from the underside of the bar 18 if it is horizontally or obliquely arranged, or from the front if it is vertically arranged, by an amount sufficient to enable it to be gripped and drawn off by the respective gripper 12. In the illustrated case, there are eight openings-34 and eight tufting yarns 36 which come from a suitable creel (not shown) and which may all be of different colours.

In each cycle of operation of the loom, the carrier bars 18 are raised (or displaced sideways if horizontally disposed) and returned, and a selector mechanism (of any one of many know types which need not be described for purposes of this invention) causes each bar 18 to come to rest either at a selected displaced position or at its start position so that a selected one of the tufting yarns 36 is presented to the associated gripper 12 at the yarn take up position. As the shaft 10 rotates, the grippers 12 act in unison to grip and then draw off the selected yarn ends for a short distance, whereafter the drawn off portions of yarn are severed by a knife 104, which tranverses the loom, and carried down to the insertion position at the shed 14.

Referring now to Fig. 2, a connection piece 22 whereby the gripper 12 is attached to the gripper shaft 10 is shown in more detail, but the mechanism in general is identical. The gripper 12 is shown, here, in broken lines in the yarn take up position, and the gripper beak only is shown at the position of severance of the yarn 36 by the knife 104, then the whole gripper 12 is shown in full lines as it passes a yarn take up detector housing 20.

By virtue of the rotation of the shaft 10, the grippers 12 move along an arcuate path between take up and insertion positions.

This exemplary embodiment of yarn take up detector means comprises the aforesaid housing 20, which is mounted to the loom frame so as to lie at any suitable position closely adjacent the arcuate path described by the tips of the grippers 12, and an infrared light source in the form of a strip lamp 24, which is mounted onto the connection piece 22 by way of a bracket 26.

As shown in greater detail in Figs. 3 and 4, the housing 20 is in the form of an elongate channel section strip, for example of aluminium, having a central or base web 28 provided externally with a plurality of parallel fins 30, extending transversely to the longitudinal extent of the strip. The fins 30 are equally spaced and the gaps therebetween constitute narrow channels, through which the tips of the respective grippers 12 pass as theymove between their take up and insertion positions. Thus the overall structure of the housing 20 is rather like a comb or reed through which the gripper tips pass.

In the case of a standard loom having seven or eight grippers 12 per inch (2.54cm), the detector housing 20 will have a corresponding number of channels between its fins 30, so that each fin may be approximately lmm thick and the gap therebetween approximately 2mm.

A series of apertures 32 is provided in the central or base web 28 of the housing 20 and a plurality of infrared detectors 34 are arranged along the inside of the housing 20. In this respect there is a single aperture 32, maybe of only 1.5mm diameter, in the base of each channel, and a respective detector 34 in alignment with each aperture 32, i.e. corresponding to each individual channel. Opposite to the central web 28, the housing 20 may be closed by a cap, through which respective connectors (not shown) lead from the IR detectors 34 to a common electronic monitoring unit.

The housing 20 is preferably mounted on the frame by a pivot shaft 36 so that it can be swung back, as indicated by the arrows, when necessary to allow access to the yarn take up positions.

The IR lamp 24 is mounted on the connector piece 22 approximately 15 to 20cm from the tips of the grippers 12 so that its beam is directed at said tips.

In use, the IR lamp 24 swings to and fro with the connection piece 22 and so only directs its beam at the detectors 34 as the tips of the grippers 12 pass through the respective channels of the housing 20. However, if a gripper 12 has correctly taken up its length of tufting yarn 36, it will be drawing the yarn through the channel after it (as shown clearly in the full line position in Fig. 2) and this will block reception of the IR beam by the associated individual detector 34. Thus the detectors 34 will only transmit electrical pulses, indicative of IR reception when yarns are missing. The central monitoring unit will total the pulses at each cycle and stop the loom if the number of missed yarns exceeds a pre-determined threshold.The central monitoring unit should also be capable of detecting repeated sequences of misses by any individual gripper 12, in view of the individual detectors 34 therefor, and can also stop the loom if such a sequence exceeds a preset small number.

The IR lamp 34 can simply be switched off in the second half of the cycle when the gripper shaft 10 swings the grippers 12 back after insertion of tufts and the gripper tips pass back in the direction through the channels of the housing 20. Alternatively, the detectors 34 may only be operative in the first half of the cycle, possibly switched on by a limit switch as the connector piece 22 swings away from the take up position and off as the insertion position is reached.

Many variations in the detailed structure of the detector housing and in its mounting are possible so long as individual channels and individual photoreceptors are provided for the respective gripper tips.

Claims (14)

1. An Axminster carpet loom comprising a plurality of carriers which are displaceable under the influence of pattern control means to bring selected yarns to aligned take up positions, a respective gripper associated with each carrier, each gripper being reciprocable between a yarn take up position for taking up a yarn end presented by the associated carrier and a yarn insertion position for inserting a severed yarn end into a warp shed for binding into backing fabric as it is woven, and at least one knife operative to sever the yarn ends prior to their insertion into the warp shed, and further including yarn take up detector means comprising housing means configured to provide separate channels, flanked by respective side walls, for passage therethrough of the tips of respective grippers as they move between their take up and insertion positions, and having respective photosensitive receptors associated with each channel, and a light source operative to illuminate the channels as the tips of the grippers pass therethrough so that in operation of the loom, yarn ends will be drawn through the respective channels, between the light source and the respective photoreceptors, by the respective grippers, and the presence or absence of such yarn ends will be detected by the photoreceptors.

2. A loom as claimed in claim 1 where the housing means of the detector arrangement is at a location remote from the knife.

3. A loom as claimed in claim 1 or 2 wherein the detector arrangement is provided with an air blower operative to provide periodic blasts of air to remove any dust or other detritus from the channels of the housing.

4. A loom as claimed in claim 1, 2 or 3 wherein the photoreceptors are electrically connected to a common microprocessor control unit, and each photoreceptor transmits a signal to the control unit whenever it receives light from the source (indicative of the absence of yarn therebetween) during a pre-set time interval immediately following passage of the associated gripper through the channel.

5. A loom as claimed in any preceding claim wherein the housing means comprises a single elongate element or a number of such elements, each configured to provide a plurality of side by side channels defined by the spacings between a plurality of ridges, partitions or fins, such that each ridge, partition or fin constitutes a common side wall to adjacent channels.

6. A loom as claimed in claim 5 wherein the aforesaid ridges, partitions or fins taper in their longitudinal direction.

7. A loom as claimed in claim 5 or 6 wherein the housing elements are pivotally or slidably mounted so that they can be readily moved out of position when access to the grippers or carriers is required.

8. A loom as claimed in any preceding claim wherein respective photoreceptors are mounted in the housing means in or below the base of each channel.

9. A loom as claimed in any preceding claim wherein a common light source is provided for all grippers, or for a considerable number of grippers in the form of one or more strip lights extending across the loom.

10. A loom as claimed in any preceding claim wherein the light source is mounted on the gripper reciprocation means.

11. A loom as claimed in claim 10 wherein the light source is mounted on a gripper shaft which rotates to and fro to swing the grippers between their take up and insertion positions, the light beam being directed at the tips of the grippers so as to move in synchrony therewith, and be directed into the channels of the detector housing means only while the gripper tips are passing therethrough.

12. A loom as claimed in any of claims 1 to 9 wherein the light source is mounted so as to remain stationary and be permanently directed towards the channels of the detector housing means, yet is only switched on intermittently during the short intervals of time while the grippers pass through the channels from their take up to their insertion positions.

13. A loom as claimed in any preceding claim wherein the light source is an infrared source, and the photo receptors are infrared detectors.

14. A yarn take-up sensor mechanism for an Axminster carpet loom substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.