WO1992007129A1

WO1992007129A1 - Knitting machine and component thereof

Info

Publication number: WO1992007129A1
Application number: PCT/GB1991/001817
Authority: WO
Inventors: Keith Jeffcoat; Dennis John Williams; Gerald Francis Day
Original assignee: Courtaulds PLC
Current assignee: Akzo Nobel UK PLC
Priority date: 1990-10-22
Filing date: 1991-10-17
Publication date: 1992-04-30
Anticipated expiration: 1993-04-22
Also published as: GB9022952D0

Abstract

A weft knitting machine having a needle bed (1, 2) with a yarn feed carrier (36) reciprocal along the length of the bed, there being provided a yarn tensioning device (41, 42) on the yarn feed carrier to take-up slack in the yarn (43) as knitting is stopped and started.

Description

KNITTING MACHINE AND COMPONENT THEREOF

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to knitting machines and has particular reference to components associated with the control of yarn in a knitting machine.

2. Discussion of Prior Art

Knitting machine technology is a highly developed art- Weft knitting machines, particularly flat bed weft knitting machines, have been in production in excess of 100 years. A particularly important form of weft knitting machine is the flat V-bed knitting machine. A flat V-bed knitting machine is made up of 2 flat rows of needle guides. The needle guides or tricks are assembled in beds and are inclined at an angle of typically 110" one to the other. Such flat V-bed knitting machines are well known. A knitting head, often referred to as a cam box, is reciprocated over the flat V-beds to operate the needles in sequence to effect knitting. Yarn is fed to the knitting head to permit knitting to continue.

Originally the yarn was fed to the knitting head from a yarn package positioned above the flat V-beds. With more modern machines, however, it has become conventional practice to feed the yarn to the knitting head from the ends of the bed. In the case of most machines a plurality of yarns are used in the knitting operation, or at the very least the machine is capable of operating with a plurality of yarns to produce the knitted structure. In such a case a conventional practice is to provide each yarn with a separate yarn feed carrier which is mounted on a rail parallel to the flat V-beds but positioned above the beds. During the knitting sequence the knitting head picks up the yarn carriers to effect knitting with the particular yarn leading through that carrier and when that yarn is no longer required that yarn carrier is disconnected from the knitting head and a different yarn carrier with a different yarn is selected.

There may be 3,4,5,6 or even more yarn carriers associated with a flat V-bed knitting machine with each yarn carrier being located on a separate rail positioned above the flat beds of the knitting machine. Each yarn carrier is provided with a separate yarn and at the end of the bed from whence the yarn is supplied there is provided means to maintain a tension in the yarn. The means to maintain the tension normally comprises a spring-loaded thin wire arm looking rather like a small fishing rod having a ceramic guide at its free end and able to swing backwards and forwards to maintain the yarn under tension. Considerable ingenuity has been expended on the design and manufacture of the tensioning means used at the end of the flat beds of the knitting machine. This has been particularly necessary as the speed at which the machines operate has increased and the length of the flat beds has increased putting the tensioning arm potentially further away from the knitting head. In addition to making the tensioning means react more rapidly, efforts have been concentrated on reducing the weight of the moving parts of the tensioning means to decrease their inertia and hence increase their speed of response.

SUMMARY OF THE INVENTION

By the present invention there is provided a weft knitting machine having a needle bed and incorporating a movable yarn feed carrier reciprocal along the length of the bed to supply yarn to the needles being knitted, there being provided on or adjacent the yarn carrier and reciprocal with the yarn carrier means to maintain a tension in the yarn.

The present invention also provides a yarn feed carrier for a flat bed knitting machine, the yarn feed carrier being

SUBSTITUTE reciprocal along the length of the bed, the yarn feed carrier incorporating means to take-up slack in the yarn.

The present invention also provides a weft knitting machine including a knitting head which is reciprocal on a needle bed to activate needles mounted in the bed, the knitting head incorporating or having associated therewith a yarn feed carrier, the yarn feed carrier incorporating means to take-up slack in the yarn.

The knitting machine may comprise a flat V-bed knitting machine. The yarn feed carrier may be integral with a knitting head which is reciprocal on the needle bed to effect knitting. Alternatively, or additionally, the yarn feed carrier may be mounted on a rail lying parallel to the direction of movement of the knitting head and may be selectively moveable with the knitting head. There may be a plurality of yarn feed carriers, each mounted independently on the rail or a plurality of rails, and each selectively moveable with the knitting head.

The yarn may be fed to the yarn feed carrier from a location adjacent the end of the needle bed. The location may incorporate further means to maintain tension in the yarn. The further means may comprise a resilient movable member. The resilient moveable member may be a spring loaded wire. There may be a ceramic eyelet at the moveable end of the wire through which the yarn is fed.

The means to take-up the slack on the yarn feed carrier may comprise a resiliently moveable member displaced by the action of the yarn feeding through the member, and able to recover the yarn when the yarn feeding is terminated. The resiliently moveable member may be a spring located at one end on or adjacent the yarn feed carrier and having a yarn guide at the other end. The spring may be a coil spring or a leaf spring or may be a resilient rod of a resilient material such as a plastics material such as neoprene or a

SUBSTITUTE SHEET silicone rubber.

The resilient moveable member may be a pulley rotatable by the yarn in frictional engagement with the periphery of the pulley to wind up a spring and subsequently permit the yarn to feed over the surface of the pulley until the yarn tension subsides to a level such that the pulley is rotated to take up the slack in the yarn by unwinding of the spring.

The means to take-up the slack may comprise an arm carrying a magnet, the arm being pivoted at one end and carrying a yarn guide at the other, there being a magnet fixed on or adjacent the yarn feed carrier so positioned relative to the arm magnet that one at least of identical poles on both magnets face each other so as to repel each other and bias the arm away from the magnet on the yarn feed carrier, the action of the yarn feeding through the yarn guide moving the repelling poles of the magnets towards one another.

It will be appreciated that taking-up the slack in the yarn at the yarn feed carrier normally involves applying a tension to the yarn after this slack has been taken up. It is, however, possible that the yarn slack may be taken up without applying significant tension to the yarn and the present invention envisages such a device.

It will further be appreciated that the most convenient mechanism for operating the present invention may comprise the combination of yarn feed take-up mechanisms located on the yarn feed carrier itself together with further means to take-up yarn slack and/or provide tension at the ends of the flat beds.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example, embodiments of the present invention will now be- described with reference to the accompanying

SUBSTITUTE drawings, of which:-

Figure 1 is a schematic view of a flat V-bed knitting machine,

Figure 2 is a perspective view of a part of a flat V- bed knitting machine incorporating yarn carrier rails,

Figure 3 is an end view of a machine similar to that of Figure 2 but incorporating three rails,

Figure 4 is a front general view of a prior art yarn feed carrier,

Figure 5 is a view of the carrier of Figure 4 along the line of arrow V,

Figure 6 shows a modified yarn carrier in accordance with the present invention,

Figure 7 shows an enlarged view of the assembly of Figure 6 with the yarn carrier in tension,

Figure 8 shows an enlarged alternative structure for a yarn carrier in accordance with the present invention,

Figure 9 shows an alternative form of yarn carrier in accordance with the present invention, and

Figures 10 to 13 show enlarged views of the tensioning device of Figure 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figure 1, this shows in schematic form a general arrangement of a flat V-bed knitting machine. A pair of beds 1,2 are arranged in a frame angled at an angle

3 of approximately 110^*. Each bed 1,2 is made up of a

SUBSTITUTE SHEET series of needle guides or tricks in which reciprocate the needles which carry out the knitting. A knitting head or cam box generally indicated by 4 reciprocates along the beds 1,2 in the direction of arrows 5,6. As the knitting head 4 is reciprocated, cams lift up the needles in the tricks to effect the knitting in a manner well know per se. The yarn to be knitted is fed to the knitting head from a yarn package 7 via a guide 8 and a tensioning means indicated generally by 9. The yarn 10 is maintained in tension by a spring-loaded wire arm 11 having a ceramic guide 12 at its end, which forms the assembly 9. The guide 8 may in fact comprise a motor driven mechanism to feed yarn to the knitting machine at the appropriate rate. It will be appreciated that the function of the tensioning device 9 is to maintain the yarn 10 in tension at such times as the knitting head 4 stops moving in the direction of arrow 5 and reverses to move in the direction of arrow 6.

The machine illustrated in Figure 1 is capable of knitting with only one yarn, and in commercial practice such machines are a relatively minor part of the large knitting machine business. More typically such a knitting machine would be used to knit with a plurality of yarns. Illustrated in Figure 2 and 3 are flat V-bed structures incorporating rails for a plurality of yarn feed carriers. As can be seen in Figure 2 the beds 13,14 have located above them a series of rails 15,16. The number of rails provided dictates the number of yarns which can be knitted on the machine. It can be seen from Figure 2 that the machine is provided with two rails. In the machine illustrated schematically in Figure 3, three rails 17,18,19 are provided above the flat beds 20, 21. Running on each of the rails is a yarn feed carrier indicated generally by 22 in Figure 4.

It can be seen from Figure 4 that there is provided a rail engaging block 23 which is provided with inwardly directed lips 24,25 (Figure 5) which engages with one of the rails such as rail 16. The block 23 would typically be formed of a carbon fibre filled plastics material so as to have high strength but low mass. Secured to the block 23 by means of screws 26 is a yarn feeder arm generally indicated by 27. It can be seen from Figure 5 that the arm 27 does not depend vertically from the block 23 but is inclined so that its tip 28 is not below the centre line of the block 23. The tips of adjacent yarn feed carriers are designed to rub against one another as they pass each other. Referring to Figure 3, it can be seen that the rails 17,18,19 are in spaced parallel relationship and typically the arms 27 would be displaced from the centre line of the block 23 so that each tip lies close to the centre line 29 between the beds 20 and 21.

Fixed to the arm 27 is a star guide 30 which is in the form of a circular block having three radially extending walls 31,32,33. Each of the walls is apertured so that thread may pass through the walls for guiding purposes. It will be appreciated that thread can pass through the aperture in wall 31 to pass onwardly to a further yarn carrier guide if the knitting machine is provided with a plurality of knitting heads on a very elongate flat bed. Alternatively the yarn can be fed from either the right hand side or the left hand side as shown in Figure 4 and through apertures in walls 33 and 32 respectively and then down through an aperture 34 in the tip 28 to the needles on the needle beds. The design of the yarn feed carrier shown in Figures 4 and 5 is conventional.

It will be appreciated, however, that the yarn feed carriers illustrated in Figures 4 and 5 do no more than guide the yarn from a tensioning means (such as device 9) into the knitting zone of the knitting machine.

Referring to Figure 6 this shows a yarn feed carrier 36 in accordance with the present invention. Such a feed carrier is shown in conjunction with an external tensioning device similar to that illustrated at 9 in Figure 1.

Again the yarn feed carrier 36 incorporates a mounting block 36a shown mounted on a chain dotted rail 37 and having dependent from it an arm 38. The tip 39 of the arm 38 5 incorporates an aperture in exactly the same way as the arm 27 illustrated in Figures 4 and 5 carries tip 28 with its aperture 34. Provided on the arm 38 is a star guide 40 but secured to the star guide 40 is a tubular spring 41 having attached to its free end a ceramic yarn guide 42. Yarn 43

10 is led from a yarn package 44 via a cymbal tensioning device 45, a knot detector 46, and a pivoted hook 47 which can detect breaks in the yarn and operate a mechanism (not shown) to stop knitting. From the hook 47, the yarn is passed through an eye (unnumbered) and then over a trapper

15 47a, and through an aperture 47b at the end of a looper arm 47c which is spring loaded by an adjustable spring 47d. The yarn then passes through apertured wall 48 and on through the ceramic guide 42 and back into the apertured tip 39 for feeding to the needles in the conventional manner.

20 The effect of the provision of the spring 41 on the yarn feed carrier can be more clearly understood by reference to Figure 7. In Figure 7 the original rest position of the spring 41 is shown in solid lines. During knitting, however, the movement of the yarn carrier arm 38

25 imposes a tension on the yarn 43 and because of the geometry of the spring 41 and the position of the yarn guide 42 between the apertured wall 48 and the tip 39, the spring 41 is deflected to the position shown dotted at 49.

It will be appreciated that the geometry of the 30 assembly illustrated in Figure 7 is such that the length of yarn shown dotted at 50 between points 48 and 39 is less than the length of yarn shown as solid line 51 between points 48 and 39. Thus when the knitting head reaches the end of its traverse, such as the end of its traverse in the 35 direction of arrow 5 (Figure 1) and commences its movement in the opposite direction as shown by arrow 6 (Figure 1), the yarn which has been held in tension and displaced to the position shown dotted at 50 is able to return to 51 under the action of the spring 41. This means that there is an instantly active take-up of the slack in the yarn and there is much less tendency for incorrect loop formation on the needles being knitted. As needle beds get longer and as the reciprocating speed of the knitting heads increases, the provision of the yarn take-up mechanism at the end of the beds means there is increasing delay in the reaction of the yarn take-up mechanism to the stopping of the needle head or to the cessation of knitting on a particular yarn.

It will be appreciated that when knitting several different yarns the individual yarn feed carriers are picked up and dropped by the knitting heads at various times during the knitting sequence. Thus the knitting head would have a mechanism to engage the carrier block, such as block 36, to permit a particular yarn to be knitted, and after knitting had ceased on that yarn, the knitting block would be released by the knitting head and would stop. Ideally the yarn feed carriers should be dropped and parked as close to the end of the knitting as possible. However, if two or more yarns are knitted from a single point, the two or more yarn carriers must be longitudinally spaced, otherwise if the yarn carriers are all stopped at the same point, the tips of the yarn carriers would all lie next to each other and in contact with each other in the same transverse plane to the knitting bed. This means the tips will be spread sideways and can result in jamming of the brushes (not shown but which are used to close the needle latches) against the side-by-side yarn carriers. This can damage the machine. It is, therefore, the practice to drop off and park the yarn carriers at longitudinally spaced positions along the needle bed, even if the yarn all has to be fed to the same start/stop point.

To prevent excessive tightening of the threads or to prevent excessive loosening of the threads, the provision of a take-up mechanism directly on the yarn carrier enables almost instantaneous take-up of yarn to occur. Because yarn is an elastic material the external take-up mechanism such as mechanism 47b, 47c, 47d (Figure 6) cannot react instantaneously as there has to be a delay associated with the extension of the thread before the take up mechanism can react. Clearly to increase the speed of reaction, the strength of the take-up spring 47d (Figure 6) could be increased but this carries with it a risk of over tightening of the stitches immediately below the tip of the carrier when the carrier comes to a halt. If the tension in the spring 47d is reduced to avoid excessive tensioning of the stitches then there is a danger that the yarn take-up mechanism will react too slowly producing excessively large loops and even the possibility of loops of one thread becoming entangled with loops of another thread.

Experiments have shown that for yarn feed carriers in which the distance between the point 48 and the point 39 is 80 mm, a spring 41 of steel spring wire having a wire diameter of 0.42 mm can be wound in 21 pitches to form a steel spring having an external diameter of 5.5 mm and a length of 31.75 mm (rated such that it will extend under a load of 325 gms from 31.75 mm to a total length of 95.25 mm) produces a yarn feed carrier which works very effectively on a automatic flat V-bed knitting machine having a bed length of 2 metres.

Rather than using the spring structure illustrated in Figure 7, alternative structures can be used such as a leaf spring or a wire or a solid rod of elastomeric material such as silicone rubber or neoprene. It will further be appreciated that arrangements may be provided in which the guide wall 48 and the spring 41 are formed integrally and either attached to the arm 38 or are formed integrally with the arm 38.

SUBSTITUTE SHEET Rather than using spring elements, magnetic means may be provided to produce the tension at the yarn feed carrier. Illustrated in Figure 8 is such a mechanism. In this arrangement a yarn feed carrier arm 52 is provided with a pivoted arm 53 having a ceramic guide 54 at one end and a freely moveable pivot 55 at the other end. Yarn is fed through a further yarn guide 56 mounted on the arm 52 to a tip 57 of the carrier arm 52. Positioned on the pivoted arm 53 is a magnet 58 which cooperates with a further magnet 59 located directly on the carrier arm 52. By having the north poles and south poles positioned opposite one another as illustrated in Figure 8 the magnets 58 and 59 will repel each other so as to effectively produce a springing effect similar to that illustrated in Figure 7. The greatest repulsion is effected when the magnets 58, 59 get closest to one another and thus the speed of response of the system will be at its greatest when the yarn is trying to be as close to a straight line between points 56 and 57 as possible.

The devices illustrated in Figures 6,7 and 8 all provide means for taking up the slack on the yarn on the yarn carrier.

The apparatus illustrated in Figures 9 to 13 provides an alternative way to take-up slack in the yarn.

In the apparatus illustrated in Figures 9 to 13 there is provided a carrier block 60 adapted to move along a rail such as rail 15 or 16 and incorporating a slider cut-out portion 61 to engage the rail. Secured to the back of the block 60 by means of screws 62 is a dependent arm 63 having a hinge member 64 at its lower end. Secured to the hinged member 64 is the upper portion of a further arm member 65 carrying a camming passing mechanism in the form of a block 66. Located on the block 66 is a hollow guide tip 67 which is secured to the block 66 via an upstanding arm portion 68 and a screw 69.

SUBSTITUTE SHEET Yarn 70 passes to the tip 67 via a yarn take-up device 71. The device 71 can be seen more clearly in Figures 10 to 13. Referring to Figure 10, this shows a spring loaded wheel 72 having a bridge 73 on its front face. At the end of the bridge is an eyelet 74 through which the yarn 70 is passed. The bridge 73 is shown in contact with a stop member 75 in Figure 10. The position of the take-up device in Figure 10 corresponds to that in which the yarn carrier is knitting yarn and it can be seen that the yarn has a smooth path through the eyelet 74, down towards the tip 67 of the carrier.

When the yarn carrier is parked and slack has to be taken up, the wheel 72 is rotated anti-clockwise (as shown in Figures 10 and 11) by an internal spring to carry the bridge 73 and the eyelet 74 to the position shown in Figure 11. It can be seen that in this position the yarn 70 is wrapped partly around the surface of the wheel 72. For reasons of clarity, the yarn 70 is shown spaced from the surface of the wheel 72 in Figure 11, although it will be appreciated that the yarn would actually lie on the surface in use.

Figure 12 shows an underneath view of the wheel 72 and it can be seen that the eyelet 74 mounted on the bridge 73 leads the yarn passing through the eyelet directly onto the surface 75 of the wheel 72. Referring to Figure 13, which is a cross section of the wheel 72, it can be seen that inside the wheel is a spiral hair-spring 76 which rotates the wheel 75 so that in its rest position it will be as shown in Figure 11. Thus on parking, and forming slack in the yarn 70, the take-up wheel will adopt the position shown in Figure 11 and under the tension of knitting the take-up wheel is rotated clockwise to provide a smooth path for yarn as is shown in Figure 10. The amount of tension applied by the hair-spring may be varied by winding the hair-spring to a different tension. The provision of take-up of slack for the yarn directly at the yarn feed carrier enhances reproducibility of knitting, in that it reduces the likelihood of excessive loop tension producing too tight a stitch which can lead to a held stitch in knitting or on the other hand being so loose that excess yarn forms loops which show on the surface of the knitting. These malformed stitches have a serious deleterious effect on the appearance of a knitting structure particularly for a double jersey knitted fabric. This is particularly the case when shaping fabric structures as there is a^" variation in traverse and rapid turn round of the knitting head to permit shaping to occur. With such systems the external looper or take-up system is unable to react quickly enough because of the time constant effect associated with the need to take-up tension in the yarn. It will be appreciated that although the tensioning means has been shown as being directly on the yarn feed carrier a separate mechanism could be provided adjacent to the yarn feed carrier provided that it moved with the yarn feed carrier so as to provide rapid take-up of slack by the feed carrier rather than relying on the external loop tension system.

Although only one loop of yarn is shown as being taken up by the spring operated mechanisms or the magnet operated mechanisms of Figures 6 to 8, it will be appreciated that more than one loop could be provided on the yarn carrier to increase the total amount of slack which can be taken up by the system.

SUBS I

Claims

1. A yarn feed carrier for a flat bed knitting machine, the yarn feed carrier being reciprocal along the length of the bed, the yarn feed carrier incorporating means to take-up slack in the yarn.

2. A yarn feed carrier as claimed in claim 1, in which the means to take-up slack comprises a resiliently moveable member displaced by the action of the yarn feeding through the member, and able to recover the yarn when the yarn feeding is terminated.

3. A yarn feed carrier as claimed in claim 2, in which the resiliently moveable member is a spring located at one end adjacent to the yarn feed carrier and having a yarn guide at the other end.

4. A yarn feed carrier as claimed in claim 3, in which the spring is selected from the group consisting of a coil spring, a leaf spring or a resilient rod of a resilient plastics material.

5. A yarn feed carrier as claimed in claim 2, in which the resilient moveable member is a wheel rotatable by the yarn in frictional engagement with the periphery of the wheel to wind up a spring, and subsequently permit the yarn to feed over the surface of the wheel until the yarn tension subsides to a level such that the wheel is rotated to take up the slack in the yarn by unwinding of the spring.

6. A yarn feed carrier as claimed in claim 1, in which the means to take-up the slack comprises an arm carrying a magnet, the arm being pivoted at one end and carrying a yarn guide at the other, there being a magnet fixed on or adjacent the yarn feed carrier so positioned relative to the arm magnet that one at least of identical poles in both magnets face each other so as to repel each other and bias the arm away from the magnet on the yarn feed carrier, the action of the yarn feeding through the yarn guide moving the repelling poles of the magnets towards one another.

7. A weft knitting machine having a needle bed containing needles to be knitted upon and incorporating a moveable yarn feed carrier reciprocal along the length of the bed to supply yarn to the needles as they are knitted upon, the yarn feed carrier being as claimed in any one of claims 1 to 6.

8. A weft knitting machine as claimed in claim 7, the machine being provided with at least two opposed needle beds and a plurality of yarn feed carriers as claimed in claim 7.

9. A weft knitting machine as claimed in claim 8 and having four needle beds.

10. A weft knitting machine as claimed in any one of claims 7 to 9 and further including means, preferably spring loaded loopers, located at, or effective from, the ends of the needle beds to maintain tension in the yarn.