GB2033931A - Weft knitting - Google Patents

Abstract

Two yarns are fed together to be knitted separately at the same feeder of a weft knitting machine of the double jersey kind (or other machine that has intercalating sets of needles). The yarns can be knitted on needle groups selected from either set (e.g. odd dial and even cylinder needles, or odd dial and even dial needles) by guiding the yarns to their needles from positions downstream of the point where the needles begin to rise to the knit position. The yarns can be fed from in front of the needles or behind the needles, and the groups of needles may be separated by delayed timing in the cam. Productivity is improved because all needles can knit at every feeder on many fabric constructions; and if desired, two separate single jersey fabrics can be made on a double jersey machine. <IMAGE>

Description

SPECIFICATION Weft knitting This invention relates to weft knitting, in machines of the kind having intercalating sets of selectable needles. Perhaps the most important machine of this kind is the double jersey machine having dial and cylinder needles, and the invention will be described with particuiar reference thereto, though it is to be understood that it is equally applicable to flat V-bed and other machines, though with suitable modifications to take account of their different configurations.

In the simplest of such machines, conventionally, a single yarn is fed at a single feeder. In high production machines, however, of the double jersey type, there is a plurality of feeders disposed around the cylinder, and associated with each feeder is a dial cam and a cylinder cam to control the needles so that selected needles rise to the knit position to engage the yarn fed through the feeder.

Conventionally, each feeder feeds a single yarn to the selected dial needles or the selected cylinder needles or some of each. So at each feeder, often at least half the needles are not forming stitches, and in some knitting constructions, only half or even only one third of either the dial or the cylinder needles are taking part in stitch formation.

It has been proposed in GB Patent Specification 1 341 636 (U.S. Specification 3672 186) to feed two yarns at one or more feeders of a rib gated double jersey machine with synchronous timing, each yarn going to some or all of the dial needles or to some or all of the cylinder needles, for the purpose of knitting a two ply segment of a fabric wherein the plies are independent of each other. This enables two feeders to do the work previously done by three feeders and, increases productivity by 50%. The method is said to apply also to flat V-bed machines.

The technique involves feeding the yarn to the dial needles around the back of the cylinder needles from a position upstream of the point where they are extended into the "knit" position by the knitting cam.

The yarn goes into the hook of the dial needle only after it has withdrawn from intercalation with the cylinder needles. Likewise, the other yarn is fed to the cylinder needles from an adjacent upstream point around the back of the dial needles.

The yarns cannot be fed from the normal feeder, which is used therefore solely to perform its latch guard function. Instead, a new feeder, with two guide apertures, is mounted upstream of the point where the needles begin their extension to the "knit" position.

The arrangement presents certain difficulties in operation, which are noted in the aforementioned patent specifications. The unusual feeder arrangement calls for very precise setting up of the machinery (which renders it unsuitable for a commercial environment), and that the method does not appear to have found any commercial application suggests that the difficulties noted are in fact experienced in practice to an extent that nullifies the theoretical advantages.

The present invention provides improved arrangements for feeding two (or even more) threads at a single feeder and for knitting fabrics using such arrangements.

The invention comprises a method for weft knitting in machines of the kind having intercalating sets of selected needles, characterised in that two yarns are fed separately at a single feeder position to two groups of needles, each group being selected from either or both sets of needles, so that one yarn knits on one group and the other yarn knits on the other group, the yarns being last guided from positions downstream of the point at which selected needles of either set begin to rise to the knit position before being engaged by the hooks of their needles at a position at which needles of the two sets are not intercalated.

One disadvantage of the method described in the GB and US patent specifications aforementioned is a tendencyforthe yarns to be cut by the scissor action of the closing latches. This disadvantage is substantially avoided by the present invention, which presents the yarn at such an angle to the needle hooks that it is not caught by the latch.

The invention can be utilised not merely in the production of fabrics having two ply segments, as described in the aforementioned patent specifications, but also in the production of two completely separate single jersey fabrics on a double jersey machine. Thus if there should be a demand for single jersey fabric rather than double jersey, the knitter can use his double jersey machines economically, whereas hitherto it has been very wasteful to produce single jersey fabric on the much more complicated and expensive double jersey machines.

However, the invention can also be utilised in the production of a whole range of knitted structures, not merely those involving two ply segments, that previously could be produced only comparatively slowly because of the need to knit only on every other or every third needle of one or both sets of needles at each feeder. These fabrics, using the invention, can be produced at a rate higher than can double jersey fabrics using conventional methods.

To feed either thread to its needles from directly behind extended needles of one or other set, a special feeder attachment is secured to the ordinary feeder, which may be used to feed the other or another thread to a different group of needles from in front of the extended needles of one or other set, but in any event performs its latch guard function.

Both threads, however, may be fed from in front of the extended needles of one or the other set, which requires only another guide eye or aperture in the standard feeder.

However, to feed both threads from the "conventional" position requires delayed timing, so that one thread is knitted on one group of selected needles upstream of the point at which the needles of the other group rise to the knit position. The conventional method of effecting delaying timing, namely by a rotational displacement of the dial with regard to the cylinder on a double jersey machine, would be inappropriate for all constructions except a very few in which the threads were knitted entirely on dial or entirely on cylinder needles. Instead, according to the invention, delayed timing is provided for in the design of the knitting cams themselves.

It is found to be possible, both in regard to the dial cams and the cylinder cams, to select two groups of needles at each cam position by making each cam constitute effectively two cams giving consecutive "envelopes" of selected needles at each feederposi- tion. If desired, for example, odd dial needles could be extended to the knit position within a first half of the angular extent of the cam, then the even dial needles extended in the second half of the cam space. Two threads can be fed, one to each group of extended dial needles, from separate guide eyes in the normal feeder.

At the same time, if desired, the same could be done with the cylinder needles, and two further threads fed to them, at the same feeder position, but from directly behind the extended dial needles. Thus it is possible - though it may not often be desired to feed four yarns at a single feeder to knit on four selected groups of needles. Often, of course, it will be desired to feed a single thread to selected needles from both dial and cylinder sets at the same feeder, and it may not then be possible to feed so many threads.

Methods and embodiments of apparatus for weft knitting according to the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a comparative schematic diagram showing the needle selection at various feeders for two prior art methods of knitting Punto di Roma, and the method according to the invention; Figure 2 is a diagram like Figure 1 for another knitting construction, and Figure 3 is a diagram like Figures 1 and 2, for yet another knitting construction;; Figure 4 is a perspective view of a conventional feeder with a novel attachment, useful in carrying out certain modes of the invention, Figure 5 is an end-on view of the feeder illustrated in Figure 4, showing its relationship to the needles and the thread paths therebetween, Figure 6 is a face-on view in the direction of arrow Vl-Vi of Figure 5, Figure 7 is a perspective view of a differently modified feeder arranged to feed two yarns, and Figure 8 is a perspective view of another arrangement feeding three yarns at a single feeder.

The conventional production of Punto di Roma fabric is illustrated in Figure 1A. A dial and cylinder knitting machine is arranged so that a yarn fed at a first feeder (Feeder I) knits on odd dial and even cylinder needles, a yarn fed at the next adjacent feeder (Feeder II) knits on even dial and odd cylinder needles. Yarn at feeder 3 knits on all the cylinder needles, but no dial needles, while yarn at Feeder IV knits on all the dial, but none of the cylinder needles.

In the method proposed in British Patent Specifica tion No. 1 341 636 aforesaid, two yarns are fed at feeders Ill and IV, the arrangements at feeders land II being conventional. This is shown in Figure 1B.

Although the feeder attachment described in the said Specification enables two yarns to be fed together so long as one yarn goes to dial needles only and the other goes to cylinder needles only, it is not capable of feeding two yarns together if either of them goes to needles selected from both dial and cylinder sets.

Using the method according to the present invention, however, the Punto di Roma construction can be made using only two feeders to feed all four yarns. The arrangement is illustrated in Figure 1C, one of the yarns being drawn in dashed line at Feeder I for clarity's sake.

Thus on a 36 feeder machine, whereas only 36 yarns could be fed using the conventional technique, 48 yarns can be fed according to Patent Specification 1 341 636 aforesaid - an increase in productivity of 33 to3%. However, using the present method, 72 yarns can be fed, representing an increase in productivity over the conventional method of 100%, and an increase of 50% over the method described in Patent Specification 1 341 636.

It should be pointed out, moreover, that the increase in productivity using the method described in Specification 1 341 636 is only theoretical; there is no record of anyone achieving this in production (as opposed to carefully controlled laboratory trials) using this method because of the disadvantages noted in that specification. However, the present invention can be used in practice without any of the said disadvantages and without loss of production through an undue failure rate.

Figure 2 shows, in similar fashion, the conventional method, the method according to Specification 1 341 636 and the method according to the present invention, of producing another knitting construction. Here, in the conventional method (Figure 2A) and in the method according to the Specification, Feeder I knits on alternate dial needles and some of the cylinder needles. In the conventional method, Feeder II knits on the cylinder needles missed at Feeder I, and Feeder III knits on the dial needles missed at Feeder I. In the method according to the Specification, Feeder II does the job of Feeders II and III of the conventional method - see Figure 2B.

Figure 2C shows how all three yarns are knitted on a single feeder according to the present invention.

One of the yarns is shown in dashed lines, as before, for clarity's sake.

Here, the method according to the present invention effects an increase in productivity of 200% over the conventional method, and 100% over the level theoretically possible according to Specification 1 341 636.

Figure 3 shows another construction also illustrated in Specification 1 341 636. As before, Figure 3A is the conventional arrangement, Figure 3B is the 1 341 636 arrangement, and Figure 3C is the arrangement according to the present invention. The drawing speaks for itself, in light of the previous examples. Here, whereas 1 341 636 proposes a 33 1//o productivity increase over the conventional method, the present invention achieves a 100% increase. This example illustrates the fact that with some knitting constructions it may still not be possible, even using the techniques of the present invention, to knit on all of the needles at every feeder; nevertheless it is possible to make substantial gains in productivity.

The means for achieving these increases in productivity are more particularly illustrated in Figures 4 to8.

Figures 4, 5 and 6 illustrate a conventional feeder 11 having an attachment 12 secured thereto by a screw 13 and provided with an adjusting slot 14. The attachment 12 has a first guide eye 15 and a second guide eye 16, which can be positioned more or less adjacent the normal guide eye 17 of the feeder 11.

Figures 5 and 6 show the feeder 11 in position relative to the dial needles 21 and cylinder needles 22 of a double jersey knitting machine. A first thread 23 can be fed through the guide eye 15 and bent round the back of the extended dial needles 21 to the second guide eye 22 of the attachment. From there it passes directly to the cylinder needles 22 at the point where they withdraw from intercalation with the dial needles. The second thread 24 is fed through the regular guide eye 17 to the dial needles 21 in the ordinary way.

Because the thread 23 is fed around the backs of the extended dial needles, it does not enter the hooks thereof, and since it is first presented to the cylinder needle hooks only afterthey have withdrawn from intercalation with the dial needles, the two sets of stitches do not interfere with one another. This is also the case with the arrangement described in Specification No. 1 341 636. However, in that case, the thread fed around the back of the extended needles was last guided from a point upstream of the position at which the needles begin to rise to their extended position, and consequently, the angle at which the thread eventually enters the hooks of the needles is such as to render it liable to be caught and snagged by the scissor action of the closing latch.This leads to filament breakage, giving the resulting fabric a more hairy appearance and an increased risk of th read failure or needle breakage, leading to faulty fabric and excessive machine downtime that nullifies the theoretical advantage of feeding two yarns at the same feeder.

In the present arrangement, however, the fact of guiding the thread to the cylinder needles directly from behind the extended dial needles ensures that it is presented at such an angle as to be clear of the scissor action of the closing latch. Of course, that is not to saythatthere might be some particular needle which, if fitted to the knitting machine, might have its latch in such a position as to make it possible, once again, to cut and snag the thread. However, with currently standard needles tried so far, it does not happen, and it is clear that a suitable needle can always be found (or, if required, designed expressly) whereas with the method described in Specification 1 341 636 this is notthe position.

Instead of, or in addition to the attachment 12, the feeder 11 may have an attachment generally similar to it but positioned so that a guide eye is directly behind the extended cylinder needles. This operates in exactly the same way to feed a thread to the dial needles afterthey have withdrawn from intercalation with the extended cylinder needles.

Although the attachment 12 has been shown as a simple bracket with inlet ceramic guide eyes 15, 16, it is to be understood that any suitable arrangement can be used to guide the thread to the feed position behind the extended needles. It may be convenient to have an adjustable guide tube, for example.

It is not necessary to feed threads from behind the extended needles if delayed timing is used. Accord ing to US Specification 3672 186, the method therein described eliminates the requirement for any delayed timing arrangement. However, according to the present invention, delayed timing is used very effectively, provided that it is brought about in the cams, rather than as, conventionally, the result of an angular displacement of the dial relative to the cylinder.

Figure 7 shows a feeder 71 feeding two threads, 72,73 to dial and cylinder needles 74,75 respectively. The feeder 71 is a conventional feeder modified only by the provision of a second guide bore 76 for the second thread 73. However, the cams (not shown) that extend the dial and cylinder needles to the knit position are so arranged that the cylinder needles are extended only over the first half of the normal cam space, while the dial needles are extended only overthe second half of the said cam space. Such modification of the usual "envelope" of the needle motion does not adversely affect the operation of the needles or the formation of stitches, rather it merely brings about the desired angular separation of the loci of the extended needles of the dial and cylinder sets so that the two threads can be fed one to each group of extended needles, without interference.

Figure 8 shows how a three feeder repeat can be condensed into a single feeder- as it might be for the construction illustrated in Figure 2, for example.

In the first half of the cam space alternate (say, long) dial needles and some cylinder needles are extended, and a first yarn 61 is fed to these needles through the regular feeder guide eye 62. The remain ing dial needles and the remaining cylinder needles are extended in the second half of the cam space, and second and third yarns 63, 64 are fed to these needles by additional guide eyes, one, 65, feeding the dial needles from directly behind the extended cylinder needles, the other feeding the cylinder needles from directly behind the extended dial needles.

This is a two hundred percent improvement in productivity of such fabric over conventional methods.

Of course, the same cam arrangement could be used with an additional guide eye attachment to make a fourfeeder repeat pattern, in which all four yarns are fed in at the same feeder, two yarns going, one each, to the dial needles and cylinder needles respectively that are extended in the first half of the cam space, and the other two yarns going, as before, separately to the remaining needles extended in the second half of the camspace.

The methods described can, with suitable modifi cation now well within the expertise.of the knitter, be used to produce many differe-ntfabrics, and is not restricted to conventional double jersey fab-ric pro duction. By feeding two yarnsseparately at each feeder,-one to knit on all the dial needles,=the other knit on all the cylinder needles, using either the in-cam -delayed-action method: :or féetling at least -one of the yarns-from directly behind the extended needles of the set on which the other is knitted, two single jersey fabrics will be produced, one (on the dial needles) inside, but completely separatefrom, the other, produced on the cylinder needles. This represents a very high rate of production of single jersey fabric, making it practicable and economic to use double jersey machines for this purpose.

Claims (7)

1. A method for weft knitting in machines of the kind having intercalating sets of selectable needles, in which two yarns are fed separately at a single feeder position to the needles of two groups, each group being selected from either set of needles, so that one yarn knits on one gronp and the other knits on the other group, characterised in that the yarns are last guided to their needle groups from positions downstream of the point at which the needles of either set begin to rise to the knit position.

2. A method-according to claim 1, characterised in that at least one yarn is fed from in front of extended needles of the set to which the other yarn is fed.

3. A method according to claim 1, characterised in that at least one yarn is fed from directly behind extended needles of the set to which the other yarn is fed.

4. A method according to claim 1, characterised in that one yarn is fed to needles of one set and the other yarn is fed to needles of the other set at a single feeder position.

5. A method according to claim 1, characterised in that the timing of selected needles of one set is delayed-with respect to selected needles of the other set.

6. A method-according to claim 1, characterised in thatthetwo groups of needles are selected from one set, the timing of one group being delayed with respect to the other group.

7. A method according to claitn 1, characterised in that two yards are fed-separatelyto groups of needles at a feeder, of which one group is selected with delayed timing with respecttó-the other group, the delay being produced by the cams associated with the feeder.