Patent Publication Number: US-6701970-B2

Title: Carpet weaving

Description:
BACKGROUND TO THE INVENTION 
     In making carpet, particularly patterned Axminster carpet, a yarn tuft forming unit is used to provide yarn of a particular colour to each weaving point of the carpet. In conventional Axminster weaving there are two principal ways which the yarn tuft formation is carried out. The first way is on a Jacquard Axminster loom, and the second is on a spool Axminster loom. 
     On a gripper Jacquard Axminster loom each weaving point includes a yarn carrier which is normally fed by eight yarns usually of different colour and the Jacquard mechanism moves the carrier to bring a selected yarn to the yarn selection position. A gripper moves towards the carrier, grips the yarn at the yarn selection position then relative movement apart of the gripper and the carrier pulls a predetermined length of yarn from the carrier. The yarn is then cut to form a tuft and moved by the gripper to the weaving point. The tuft carried by the gripper is of the appropriate colour for the tuft to be supplied to the next row of carpet to be woven. For a conventional 12 foot (4 m) loom there are over a 1000 weaving points across the loom and thus the creel supplying yarn to the loom has to have the potential of carrying over 8000 yarn packages. Typically, when the creel includes measured quantities of yarn in each yarn package, an allowance of an additional eighteen metres of yarn is provided in each yarn package. Accordingly, the greater the number of yarn packages the greater the wastage. In spite of such a large creel size a designer of such carpets is relatively limited since the number of colours available for each column of tufts extending in the warp direction of the finished carpet and corresponding to a single weaving point is limited to only eight throughout each pattern repeat. Jacquards are also known in which the yarn carrier can hold sixteen different yarns. These require an even larger creel. 
     Spool Axminster looms provide a designer with greater flexibility. In spool Axminster looms a separate spool is provided for each row of the pattern repeat and each spool has a separate yarn winding for each weaving point along each row. Therefore, at least theoretically, the designer has an infinite number of colour choices for each column and row of each pattern repeat. However, in practice, as the number of colour choices used for each column and row of the design increases, the number of yarn packages needed for the spool winding operation also increases. Further, the spool winder must be set up differently for the winding of each spool which is time consuming. When a large number of different colours are used in both the column and row or warp and weft direction of each pattern repeat the number of different coloured yarn packages supplying the spool winder can be even larger than those on a creel of a typical Jacquard Axminster loom. The pattern repeat on spool looms is limited by the number of spools available in the spool chain. Further, there is considerably greater yarn wastage from a spool Axminster loom than a gripper Axminster loom because, on completion of a run, waste is generated from each weaving point of each row of the pattern repeat. 
     DISCUSSION OF PRIOR ART 
     In both the Jacquard and spool Axminster looms a row of tufts for a complete row of the carpet is created simultaneously and transferred to the weaving point at which they are woven into a backing to produce the carpet. An entirely different approach to yarn selection for carpet production has recently been proposed in WO 95/31594. In this, it is proposed that tufts of yarn to form a row of the carpet are produced by first loading yarn tufts into a tuft carrier and then transferring the yarn tufts from the tuft carrier to the weaving points. To achieve this a large number of different tuft forming units, typically one per weaving point, are provided along the length of a path with typically each tuft forming unit being supplied with yarn of only a single colour. As the tuft carrier is moved along the path it receives tufts of appropriate colour in each of its tuft holding sites. The tuft carrier is subsequently moved so that all the tufts for each row can be gripped by grippers and transferred to the weaving point simultaneously. Thus, the tufts are not usually all formed simultaneously and hence the tuft formation is, at least to some extent, decoupled from the weaving operation. Therefore, tuft formation can take place at the same time as the weaving operation and thus tuft formation can take place substantially continuously throughout the operation of the loom. This is to be contrasted with conventional spool or gripper type looms where tuft formation takes place over only about half of each weaving cycle. 
     In examples given in WO 95/31594 it is suggested that partly as a result of forming the tufts throughout the entire weaving cycle it is possible to, for example, increase the speed of the tuft forming operation by four times. It is also explained that if this were possible and it was intended to operate the loom at the same speed as a conventional loom then it would be possible to reduce the size of its creel to a quarter since, in effect, each tuft forming unit would supply tufts for four weaving points. However, nowhere in this document does it exemplify an arrangement in which there are less yarn packages than the number of weaving points. 
     Whilst the above document specifically exemplifies only the supply of yarn of a single colour to each tuft forming unit it does disclose the theoretical possibility of providing yarn of a number of different colours to each tuft forming unit and somehow, in an unspecified way, selecting yarn of an appropriate colour for each weaving point. If this teaching is followed the creel size would not be reduced significantly. The document also discusses the theoretical possibility of holding the yarn carrier stationary whilst moving the tuft forming unit. However, neither of these theoretical possibilities are exemplified nor is it explained how they could be achieved nor what advantages would accrue. 
     SUMMARY OF THE INVENTION 
     According to this invention a carpet weaving loom includes at least one tuft forming unit for forming sequentially yarn tufts of a number of different colours, means to receive and hold at yarn tuft holding sites yarn tufts supplied sequentially by the tuft forming unit, and transfer means to transfer all of the tufts held by the yarn tuft holding sites simultaneously to their corresponding weaving points, the or each tuft forming unit supplying yarn tufts to at least twenty yarn tuft holding sites between successive operations of the transfer means. 
     The number of tuft forming units provided on the loom varies with the width of the loom and its required operating speed. For example, on a loom used to make carpet samples there will usually only be a single tuft forming unit and this tuft forming unit may supply tufts to, for example, three hundred, or more, tuft holding sites. On a typical twelve foot (4 m) loom there may be twelve tuft forming units each supplying tufts to less than one hundred and twenty holding sites and typically around eighty tuft holding sites. However, to be able to operate such a loom at the highest possible speed the number of tuft forming units may be increased to twenty four or even thirty with each supplying just over forty or about thirty five tuft holding sites. In the case of there being more than one tuft forming unit these are preferably subsequently equidistantly spaced across the loom. 
     Taking the typical case given above of a twelve toot (4 m) loom including twelve tuft forming units and assuming an equal choice of different yarns, eight, as used in a typical conventional gripper Axminster loom, the creel of such a loom only requires ninety six different yarn packages. This is nearly a hundred-fold decrease in the number of yarn packages from that required in the conventional loom. Taking the case of thirty tuft forming units this still leads to at least a thirty-fold decrease in the number of yarn packages. Reducing the size of the creel by such amounts leads to an equivalent reduction in the set-up time required to thread up the loom as well as potentially having significantly less waste as a result of a much smaller number of yarn packages on the creel. 
     Preferably the or each tuft forming unit is capable of forming tufts from at least eight different yarns and preferably at least ten. The number of different yarns fed to the or each tuft forming unit may be as high as twenty four or even thirty two. Increasing the number of different yarns fed to the or each tuft forming unit increases the number of yarn packages in the creel but gives a carpet designer a greater number of colour choices in each column of tufts extending in the warp direction over a conventional loom. In spite of any increase due to the greater colour choice there is always a significant reduction in the overall number of yarn packages in the creel. 
     Preferably the or each tuft forming unit comprises a yarn selector wheel with provision for holding a number of different yarns arranged around it, means to drive the selector wheel into a selected one of a number of angularly discrete positions to bring a selected yarn to a loading position, a puller for engaging the selected yarn at the loading position and for pulling a predetermined length of the selected yarn from the selector wheel, and a cutting mechanism to cut the selected yarn to form a tuft of predetermined length. 
     The yarns may be arranged around the periphery of the selector wheel generally parallel to its axis of rotation but preferably the yarns extend generally radially to the periphery of the selector wheel. Typically, such a yarn selector wheel has provision for containing more than 10 different yarns and typically 12, 16, 24 or 32 different yarns. Preferably the selector wheel is driven into and between its predetermined angular positions by a servomotor under the control of a computer. 
     Preferably the motion required to operate the cutter, provide opening and closing movements of the jaws of the puller, and to move the puller forwards and backwards to pull yarn from the selector wheel and in turn from the creel are all driven from a so-called “gearbox” forming part of the tuft forming unit. The gearbox may be driven by a servomotor under the control of a computer and in this way it can be ensured that the timing of the puller and cutter movements can be synchronised with the rotation of the selector wheel. 
     Alternatively a separate computer controlled servomotor may be provided to drive each motion of the cutter and puller and, in this case, the computer ensures the appropriate timing of the motions in synchronism with the rotation of the selector wheel. 
     Preferably the or each tuft forming unit also includes a yarn detector to ensure that yarn is present between the puller and the selector wheel after the puller has moved away from the selector wheel. Typically this yarn detector is formed by a simple light emitter and detector arrangement on opposite sides of the path of the yarn. In this way when the optical detector detects the presence of light emitted by the emitter this indicates that no yarn is present. Typically, such an indication is used to stop the operation of the loom until any problem has been rectified to ensure that each and every tuft required is formed correctly. 
     The carpet weaving loom may be formed in a way which is generally similar to that described in WO 95/31594 in which the or each tuft forming unit remains generally stationary and the means to receive and hold the yarn tufts at yarn tuft holding sites is formed by a tuft carrier which moves past the or each tuft forming unit. After being completely filled the tuft carrier is then transferred to a position to enable the tufts for a whole row to be taken from it simultaneously to be woven into a carpet. Alternatively, the or each tuft forming unit is arranged to traverse all or part of the width of the loom and provide tufts for the weaving points passed as the tuft forming unit or units move transversely across the loom. 
     As an example of the latter of these, the means to receive and hold yarn tufts may be formed by yarn tuft carriers which extend transversely across the loom. The, or each tuft forming unit moves along one of the yarn tuft carriers filling each of its tuft retention sites in turn with sequentially cut tufts, and, once all of the sites have been filled that yarn tuft carrier is moved towards the transfer means and an empty yarn tuft carrier is moved into a position adjacent the or each tuft forming unit. The yarn tuft carriers may be mounted equiangularly spaced around an axis and rotated as each yarn tuft carrier is filled. Alternatively, they may be mounted parallel to one another on an endless belt which moves the yarn tuft carriers from adjacent the or each tuft forming unit to the transfer means. In this case the transfer means correspond to the gripper arrangement of a conventional Axminster gripper loom and grip the cut tufts held in the yarn tuft carrier and move them to the weaving point at which they are woven into the carpet and released. 
     In another example the means to receive and hold yarn tufts may include a pocket which is associated with each weaving point and which receives the yarn tuft after it is formed by the or each tuft forming unit. Each tuft may be directed towards its associated pocket by an air flow created by applying a vacuum to the particular pocket next to receive a cut tuft. Preferably the vacuum is applied to the pockets in turn as the or each tuft forming unit moves along the row of pockets. One way of achieving this commutation between the supply of vacuum and the pockets is to provide an elongate vacuum chamber with an apertured sliding front plate; the plate being arranged to move with the tuft forming unit or units transversely across the loom so that the aperture or apertures in the plate are aligned with air exhaust ports of a particular pocket or particular pockets as the tufts for that pocket or those pockets are cut. The air flow entrains each cut tuft and guides it into its respective pocket. 
     Preferably the pockets are bounded at their bases by retractable pins and whilst the tufts are being formed the pins are in their forwards position defining a floor for each of the pockets. The pockets that hold each tuft are preferably formed at the upper end of a channel and when all of the pockets have been loaded with cut tufts, the pin floor is retracted and then punchers, one for each pocket, are rotated to engage each tuft and push it along its respective channel to engage it with a nose board of the loom. As the punchers withdraw, the tufts are then woven into the backing and once the punchers have withdrawn, tufts to form the next row are fed into the pockets. In this example the channels and punchers thus form the tuft transfer means. 
     A rapier drive for weft insertion, the shedding of the warp threads and a lay beam with beat up reeds for a beat up operation on the woven in tufts are provided in both of the above examples and, in general, they are entirely conventional in arrangement and operation. 
     By providing sufficient tuft forming units the loom can operate as fast as a conventional gripper Axminster loom and so weave at a rate of about forty rows of tufts per minute. With the time saved in threading up the loom and creel there is a great reduction in “downtime” which leads to a considerable increase in carpet production from each loom which also typically provides an increase in the choice of colours throughout the woven carpet with less waste of yarn. It is also possible to have fewer tuft forming units and have the loom operating at a slower weaving speed than a conventional loom and still achieve a similar carpet output as a result of the shorter “downtime” offsetting the slower weaving speed. 
     One of the most significant contributions to the speeding up of the tuft forming operation and hence to the practicality of the present invention is the arrangement of the so-called “gearbox” that provides the puller and cutter motions in the or each tuft forming unit. Preferably the gearbox comprises a housing carrying three parallel shafts on which are mounted three equal size pinions meshed together. One of the shafts is driven, typically by a servomotor, and all three pinions or shafts carry eccentric pins. One end of the puller is pivoted to the housing and its other end is bifurcated to provide a pair of jaws. One of the eccentric pins is connected to a rod mounted for sliding movement along the puller body and carrying an orthogonal jaw operating pin. The eccentric pin causes the puller to pivot backwards and forwards and the orthogonal jaw operating pin to move up and down. The up and down movement of the jaw operating pin between facing cam surfaces of the bifurcated jaws causes the jaws to open and close. Thus the puller moves forward, the jaws close, the puller moves backwards, the jaws open and the cycle is repeated for each rotation of the shaft. Another of the eccentric pins drives a knife blade via a link to cut the yarn to form a tuft. 
     Another important preferred feature of the tuft forming unit is to handle the tuft positively at all times so that it is always under control. One way of achieving this is to include a pair of cheeks spaced apart and mounted perpendicularly to the knife blade. As the knife blade is lowered to cut the yarn to form a tuft, the yarn to form the tuft is trapped between the cheeks so that, even when released from the puller and cut, it is still held positively between the cheeks. In this case the tuft forming unit preferably includes a pusher which passes between the cheeks to push the tuft out from between them. The pusher is driven via a link and a centrally pivoted first order lever from the remaining eccentric pin. The cheeks may be arranged to move up and down and also be driven from the remaining eccentric pin, or by being mounted on the knife blade. The eccentric pins are timed with respect to one another so that then yarn is held between the cheeks; the tuft is released from the jaws of the puller; the pusher initially engages the yarn whilst it is held between the cheeks; then the yarn is cut to form the tuft; and then the pusher finally pushes the cut tuft out from between the cheeks. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Particular examples of a loom in accordance with this invention will now be described with reference to the accompanying drawings, in which: 
     FIG. 1 is a sectional side elevation of a first example of loom during the tuft forming process and showing the puller in a first position; 
     FIG. 2 is a sectional side elevation of the first example of loom during the tuft transfer operation and showing the puller in a second position; 
     FIG. 3 is a partial front elevation of the first example of loom; 
     FIG. 4 is an underplan of the selector wheel to a larger scale; 
     FIG. 5 is a sectional side elevation of a first example of tuft forming unit drawn to a larger scale and from the opposite direction; 
     FIG. 6 is a front elevation of the first example of tuft forming unit drawn to a larger scale showing the cutter; 
     FIG. 7 is a front elevation similar to FIG. 6 but with part of the cutter cut away to show the puller in more detail. 
     FIG. 8 is a sectional side elevation of a second example of loom during the tuft forming process; 
     FIG. 9 is a simplified sectional side elevation of a second example of tuft forming unit, drawn to a larger scale and from the opposite direction, at the start of the tuft forming operation; 
     FIG. 10 is a simplified sectional side elevation of a second example of tuft forming unit, drawn to a larger scale and from the opposite direction, at the end of the tuft forming operation; and, 
     FIG. 11 is a simplified front elevation showing two of the second examples of tuft forming units. 
    
    
     DESCRIPTION OF PARTICULAR EMBODIMENTS 
     Both examples of Axminster loom are capable of weaving 12 foot (4 metre) wide Axminster carpet at a pitch of seven tufts per inch (25.4 mm). Tuft yarn is supplied from a creel (not shown) to twelve tuft forming units  1 , equidistantly spaced across the loom. The tuft forming units  1  are mounted on a common framework. The framework and tuft forming units are moveable transversely backwards and forwards across the loom by a recirculating ball nut assembly  5  driven from a servomotor  6  (shown in FIGS.  3  and  11 ). 
     In the first example the framework includes plate  2 , shaft  3  and hangers  4 , and can also be pivoted about the shaft  3  by a pneumatic ram (not shown) so that the yarn transfer units  1  move between the positions shown in FIGS. 1 and 2. The tuft forming units  1 , which will be described in more detail subsequently, form tufts  7  which fall into pockets  8  formed in the top of a fin pack assembly  9 . The fin pack assembly  9  consists of a number of parallel plates separated by shaped spacers to provide clearance between adjacent plates for passage of punchers  10  and beat up reeds  11 . The spacers also define an air channel  12  between each pocket  8  and a vacuum chamber  13 . The air channels terminate in a series of rounded apertures  14  located at the side of each of the pockets  8 . The fin pack  9  also includes an aperture  15  for the needle or rapier  16  and weft threads. 
     After the tuft forming units  1  have loaded tufts  7  into each of the pockets  8 , the tuft forming units  1  are pivoted into the position shown in FIG.  2  and then the punchers  10  rotate in the clockwise direction, as shown in FIG. 1, to transfer the cut tufts  7  from the pockets  8  to a position against a nose board  17  where they are woven into the backing of a carpet by weft threads inserted by the rapier  16 . The punchers  10  return to their initial position to allow the tuft forming units  1  to pivot backwards and start loading the pockets  8  with further tufts  7  to form the next row whilst the reeds  11  perform a beat up operation on the row of tufts that have just been woven in to produce the finished carpet  18 . Stuffer and chain warp yarns  19  pass through a conventional shedding arrangement  20  to shed the warp yarns  19  between each lash of the rapier  16 . 
     Each tuft forming unit  1  includes a rotatable selector wheel  20 , shown most clearly in FIG. 4, which is mounted on a shaft driven by a servomotor  21 . The selector wheel  20  includes twenty-four generally radially extending channels  22  each of which carries a tuft forming yarn  23  of a different colour. The tuft forming yarns  23  are fed from the creel to the tuft forming units using entirely conventional yarn tubes and guides and then pass through multi-aperture guides  24 ,  25  and  26  before passing through a series of apertures  27  formed in a portion of the selector wheel  20 . The yarns are held in place in the channels  22  by spring fingers (not shown). 
     Each tuft forming unit  1  also includes a cutter  28  and puller  29  which are shown most clearly in FIGS. 5,  6  and  7 . The cutter  28  comprises a fixed blade  30  with an aperture  31  and a moving blade  32 . The aperture  31  is adjacent the edge of the selector wheel  20  and the free ends of the yarns  23  extending radially outwards from the selector wheel  20  extend into the aperture  31 . The moveable blade  32  is pivoted around a pivot  33  and driven by a pivoted link  34 , pivotally connected to a crank  35  forming part of the moving blade  32  and a crank  36  mounted on shaft  37 . The puller  29  comprises a generally U-shaped portion  38  with elongate parallel limbs  39  and  40  and gripping jaws  41  and  42  secured to their free ends. This is shown most clearly in FIGS. 5 and 7. The gripping jaws  41  and  42  are normally held closed by the resilience of the U-shaped portion  38 . However, by moving a pin  43  downwards as shown in FIG. 7 between a pair of raised cam-surfaces  44  and  45 , the limbs  39  and  40  move apart and so open the jaws  41  and  42 . The puller  29  is also mounted for rotation about shaft  46 , shown in FIG. 5, between the position shown in FIG. 5 and a forwards position shown in FIG. 1 with the gripping jaws  41  and  42  extending into the aperture  31  in the fixed cutting knife blade  30  and adjacent the selector wheel  20 . 
     The rotation of the shaft  37 , the up and down movement of the pin  43  and the oscillation of the shaft  46  are all driven through a gear box  47  which will be described in more detail subsequently. The gear boxes  47  are all driven from a toothed pulley  48  mounted on a shaft, not shown. The pulleys  48  of all of the tuft forming units  1  are driven via toothed belts  50  from pulleys  51  mounted on a shaft  52  driven by a servomotor  53 , shown in FIG.  3 . The shaft  52  and servomotor  53  are mounted on the frame  2 ,  3  and  4  and so move transversely with the tuft forming units  1 . 
     A light emitting diode and photo detector (not shown) are coupled to ends of optical fibres which are located in apertures  54  located between the jaws  41  and  42  and the knife  28 . When the puller  29  has gripped the free end of one of the yarns  23  and pulled it out, and before the knife  28  operates, the yarn  23  is positioned in between the optical fibre coupled to the photo detector and that coupled to the photo emitter and so blocks light from the emitter reaching the detector. Provided light from the photo emitter is prevented from reaching the photo detector at this time it is assumed that a yarn has been successfully pulled out of the selector wheel  20  by the puller  29 . However, if at this time in the operating cycle of the tuft forming unit light from the photo emitter is detected by the photo receiver then it is assumed that the tuft has not been correctly formed and a stop signal is given to the loom to prevent its further operation until the situation has been rectified. 
     During each tuft forming cycle the servomotor  21  drives the selector wheel  20  into a predetermined angular position so that either a blank space  55  at a central position is adjacent the puller  29  or one of the yarns  23  is adjacent the puller  29 . During each tuft forming cycle the puller rotates in the anti-clockwise direction as shown in FIG. 5 around the axis of shaft  46  so that the jaws  41 ,  42  move forward and close together, then, the puller rotates clockwise about the axis of shaft  46  so that the jaws move backwards and then the jaws  41  and  42  open. Thus, during each tuft forming cycle either a central blank position  55  is adjacent the puller when no carpet is to be woven, or yarn of a selected colour is presented to the puller  29  upon indexing of the selector wheel  20  to the required angular position. Thereupon the puller  29  grabs the yarn end presented to it, pulls a predetermined length of yarn, typically half of an inch (12.5 mm), from the yarn supply on the creel and then the yarn is severed by the knife  28  to produce a yarn tuft  7 . The selector wheel  20  is then free to rotate to a different angular position to provide the next tuft to be formed. The puller  28  then releases the yarn before moving forward again to form the next yarn tuft  7 . 
     The operation of the servomotor  21 , the servomotor  6  and the servomotor  53  are all controlled by a computer driven controller to ensure that appropriate coloured yarns are provided to each weaving point to provide the required pattern in the resulting carpet  18 . The computerised controller has inputs corresponding to the transverse position of the tuft forming units  1  across the width of the loom and for any particular row of a pattern which is to be woven at any instant, to enable it to control the tuft forming units  1  effectively. 
     After the tuft  7  is formed, cut by the knife  28  and released by the jaws  41 ,  42  of the puller  29  it is pulled down into the required position in the pocket  8  by an air flow generated by the vacuum chamber  13 . The front of the vacuum chamber  13  is closed by a sliding shutter plate  57  containing twelve slots, the number corresponding to a number of tuft forming units  1 . The sliding shutter plate  57  is connected to the framework  2 ,  3  and  4  and so moves with the tuft forming units  1 . Each of the apertures in the sliding shutter plate  57  is generally aligned with its respective tuft forming unit  1  so that when the tuft forming unit  1  is in place above a particular pocket  8  the aperture in the shutter is aligned with the rear edge of the arcuate channel  12  to apply a vacuum to the rear of channel  12  and hence to the apertures  14  so that air is drawn into the pocket  8 , through the apertures  14 , through the arcuate channel  12  and into the vacuum chamber  13 . It is this airflow which entrains the tuft  7  after it is cut by the cutter  28  and released by the puller  29  to pull the tuft down into the pocket  8 . The bottom of each pocket  8  is defined by a retractable pin (not shown). As the tuft forming units  1  move along so the sliding shutter commutates the vacuum from the chamber  13  to the next pocket  8 , and so on across the width of the loom. 
     Once all of the pockets  8  have been loaded with tufts  7  the tuft forming units  1  are pivoted into their position shown in FIG.  2  and the pins forming the floor of each of the pockets are retracted. The punchers  10  then rotate in a clockwise direction and so move forwards and downwards. An angled face  58  on each of the punchers  10  engages its corresponding tuft  7  to push it downwards between adjacent fins of the fin package  10 . By providing a predetermined angle on the contact face  58  of the puncher  10  and, in particular a notch  59  at the end of the contact face  58 , whilst the puncher  10  is forcing the tuft  7  between adjacent fins of the fin package the tuft  7  moves along the angled face  58  of the puncher  10  until its end is stopped by the notch  59 . This precisely locates the tuft  7  in a predetermined position so that when it reaches the weaving point defined by the nose board  17  it is in the correct location. At the weaving point the punchers  10  push the cut tuft  7  against the nose board  17  and then the tuft is woven into position by the application of weft threads using the rapier  16  as the puncher  10  returns anti-clockwise to its starting position. To complete the formation of the carpet  17  a lay-beam with attached reeds  11  beats up the tuft and weft yarns to complete the formation of that row of carpet whilst the tufts  7  for the next row are being placed in the pockets  8 . 
     The second example of loom shown in FIG. 8 is generally similar to the first, especially in operation, but instead of the finpack and punchers for transferring the cut tufts to the weaving point, it includes a pair of tuft carriers  70  mounted for rotation about an axis  71  and a set of conventional grippers  72  that are entirely conventional in construction and use. As the tuft forming units  1  traverse the loom, tufts are placed in tuft retention sites  73  formed along the top edge of the tuft carrier  70 . When all of the tuft retention sites have been loaded, the tuft carrier  70  rotates clockwise (as seen in FIG. 8) about the axis  71  to move the loaded tuft carrier  70  into the lowermost position and to move an empty tuft carrier  70  into the uppermost position. The tuft forming units  1  then load tufts  7  into the uppermost tuft carrier  70  as they traverse backwards across the loom. The grippers  72  move upwards, clockwise as seen in FIG. 8, with their beaks open and then close to grip all of the tufts  7  held by the lowermost tuft carrier  70 . The grippers  72  then rotate in the opposite direction to move the tufts  7  to the weaving point where the tufts  7  are woven into the carpet and the grippers  72  open to release the tufts  7 . The beat up reeds  11  and rapier weft insertion mechanism have been omitted from FIG. 8 for clarity but are entirely conventional and similar to those used on conventional gripper Axminster carpet looms. 
     Another difference between the first and second examples is the mounting of the tuft forming units  1 . In the second example the tuft forming units  1  are mounted on a framework  80  including grooved rollers  81  which run on beveled rails  82 . This permits the tuft forming units  1  and the framework  80  to move transversely across the loom and once again it is driven by a recirculating ball-nut/screw mechanism  83  driven by servomotor  5 . 
     The second example of tuft forming unit  1  shown in simplified form for ease of explanation in FIGS. 8 to  11  provides positive handling of each yarn tuft  7  during its formation and upon insertion into each tuft holding site on yarn carrier  70  or into each pocket  8  so avoiding the need for the vacuum chamber  13  and airflow arrangements described previously. Each yarn tuft forming unit  1  includes a gear box shown in a simplified fashion in FIGS. 9 to  11 . It consists of three parallel shafts  90 ,  91 ,  92  on which are mounted three equal sized pinions  93 ,  94 ,  95  which are meshed together. One of the shafts  90 ,  91 ,  92  is driven directly by the servomotor  53  or via the toothed belt and pulley arrangement already described or by a further pinion  96  as shown in FIG.  11 . All three shafts  90 ,  91 ,  92  are drilled to carry eccentric pins. Pin  97  is mounted in shaft  90  and is connected to rod  98  and pin  99 . Rod  98  is journalled into body  100  of the puller  29  so that it can slide up and down as seen in FIGS. 9 and 10. The body  100  is pivoted at its upper end on pivot  101 . Consequently, as shaft  90  rotates, counterclockwise as seen in FIG. 9, the pin  97  and rod  98  move up and down with respect to the body  100  and the body  100  is caused to pivot backwards and forwards about its pivot  101 . In this example the puller includes a pair of pivoted limbs  102 ,  103  with jaws  104 ,  105  mounted at their lowermost ends. The upper ends of the limbs are urged together by a spring  106  to cause the limbs to pivot and open the jaws  104 ,  105 . The pin  99  moves up and down with respect to cam surfaces  107 ,  108  on the limbs  102 ,  103  to urge the jaws  104 ,  105  together when in its uppermost position and, in its lowermost position, allow the limbs  102 ,  103  to respond to the bias exerted by the spring  106 , to open the jaws  104 ,  105 . 
     The moveable blade  32  of the knife assembly is driven up and down by a link  109  connected between the moveable blade  32  and an eccentric pin  110  mounted in the shaft  91 . The rear face of the moveable knife blade carries a pair of guide cheeks  112  which locate between the limbs  102 ,  103  when they are in their forwards position. An eccentric pin  113  in the third shaft  92  drives one end of a first order lever  114  via a link  115 . A pusher  116  located at the other end of the first order lever  114  moves up and down between the guide cheeks  112 . 
     To produce each tuft, the yarn selector motor  21  rotates the selector wheel  20  to bring the selected yarn to a location adjacent the puller  29 . The body  100  of the puller is pivoted forwards with the pin  99  towards its lowermost position so that the jaws  104 ,  105  are open. As the shaft  90  continues to rotate the pin  99  lifts and is moved between the cam surfaces  107 ,  108  so closing the jaws  104 ,  105  and clamping the free end of the yarn between them. Further rotation of the shaft  90  causes the body  100  of the puller  29  to pivot backwards so pulling yarn from the selector wheel  20 . Rotation of shaft  91  causes the moveable blade  32  of the knife assembly  29  to move downwards. As the blade moves downwards the length of yarn being pulled by the puller  29  is trapped between the guide cheeks  112 . Once the puller  29  has moved backwards to its maximum extent the continued downwards movement of the knife blade  32  cuts the yarn to form a tuft  7  which is held between the guide cheeks  112  as the knife blade  32  continues to move downwards on an overtravel. Meanwhile rotation of shaft  92  causes the pusher  116  to move downwards between the guide cheeks  112 . Further rotation of shaft  90  causes the pin  99  to be lowered away from the cam surfaces  106 ,  107  so that the jaws  104 ,  105  open under the action of the spring  106 . Further rotation of the shaft  92  brings the pusher into contact with the top of the tuft  7  held between the guide cheeks  112  and continued rotation of the shaft  92  causes the tuft  7  to be pushed into a tuft retention site  73  on the tuft carrier  71  or into the pocket  8  in the first example. Continued rotation of the shaft  91  moves the moveable knife blade  32  upwards. Meanwhile the yarn selector motor  21  moves the selector wheel  20  to bring the next yarn to be selected into position. Continued rotation of shafts  90  and  92  move the puller  29  forwards into position to grip the next yarn and move the pusher  116  upwards ready for the next cycle of operation. 
     With this second arrangement of tuft forming unit, since the tuft is positively held at all times, whether by the jaws  104 ,  105 , the guide cheeks  112 , or the pusher  116  the tuft is always at a known and fixed position. This leads to improvements in tuft placement in the carpet and hence to less waste of tuft yarn as a result of less material being removed during a subsequent shearing step. Positive handling of the cut tuft, particularly by the pusher  116  also enables the jaws  104 ,  105  to have matching serrated teeth so that they grip the yarn more positively whilst drawing the yarn through the selector wheel  20  and from the creel. Preferably the serrated teeth are similar to those used on the grippers of a conventional Axminster loom.