WO1996016214A1

WO1996016214A1 - Knitting machine

Info

Publication number: WO1996016214A1
Application number: PCT/GB1995/002661
Authority: WO
Inventors: John Miles Brown; Stephen Patrick Dunne; Robert John Aron
Original assignee: Textile Laboratory Services Limited
Priority date: 1994-11-19
Filing date: 1995-11-14
Publication date: 1996-05-30
Also published as: GB9423406D0; AU3852595A

Abstract

A colour changing apparatus for a sinker plate knitting machine is disclosed which permits automatic insertion and removal of the different yarns required without breaking the yarns and permits the changing of a single course. The colour changer is able to change both the contrast yarn and the background yarn which therefore enables the production of multi-colour Fair Isle fabric at a much faster rate than hitherto possible. The machine comprises a bed, carriage (12) and sinker plate assembly (14) and is characterised in that carriage extensions (16) are provided on either side of the flat bed, at least one yarn feed station (20) is provided adjacent to each carriage extension, and the sinker plate assembly is provided with yarn dismount levers which pick up a yarn from, or cast it off to, the or each yarn feed station.

Description

KNΠTING MACHINE

This invention relates to a knitting machine of the sliding sinker plate type and in particular relates to a modified form of such a machine having an improved yarn selection facility.

Knitting machines for domestic or "cottage" industry, in particular for the knitting of Fair Isle sweaters, are usually flat bed machines of the sliding sinker plate type. A single bed knitting machine in the horizontal position is fed with two yarns from spring wire tensioning units and the knitting carriage carries the two yarns across the knitting bed where each knitting needle is positioned so as to capture either the background or the contrast yarn according to the machine pattern controls. Typically these pattern controls are either punch card or computer controlled, the latter usually enabling individual needle selection while the punch card system tends to control repeats of successive batches of needles.

The conventional machine can accommodate only two yarns in the yarn feed unit of the knitting carriage and usually at least one of these is enclosed by a oveable barrier on the yarn holder in the sinker plate assembly. Since most Fair Isle patterns call for many more than two colours the only way to achieve this on these machines is for the operator to break off the yarn no longer needed and replace it with an extra required colour. This is a slow manual operation and leaves loose ends at the selvedge of the knitted fabric which must subsequently be sewn in or dealt with in other ways.

There have been previous proposals to provide colour changers for these machines but in general they can deal with only a few yarns (usually four) , can only change yarns at one side of the machine, are not automatic in operation and change the contrast yarn only and not the background yarn. To be able to change the colour of a single course means that the replacement yarn must be available at either side of the machine.

The invention seeks to provide a colour changing apparatus for a knitting machine which permits automatic insertion and removal of the different yarns required without breaking the yarns and permits the changing of a single course. The invention further seeks to provide a colour changer which is able to change both the contrast yarn and the background yarn which therefore enables the production of multi-colour Fair Isle fabric at a much faster rate than hitherto possible.

According to the present invention there is provided a knitting machine which comprises a flat bed, carriage and sinker plate assembly characterised in that carriage extensions are provided on either side of the flat bed, at least one yarn feed station is provided adjacent to each carriage extension, and the sinker plate assembly is provided with yarn dismount levers which pick up a yarn from, or cast it off to, the or each yarn feed station.

The yarn holder in the yarn feed unit of the apparatus of the invention may be modified so that access to the background as well as the contrast yarn is possible without interrupting knitting. In a preferred form, the entry and exit slots of the yarn holder are modified to remove the background yarn barrier and a spring divider is positioned so as to hold the yarns in place while knitting but which can release them when they need to be changed.

Preferably four yarn feed stations are provided, two on either side of the flat bed, one on each side carrying contrast yarns and one on each side carrying background yarns. The or each yarn feed station may comprise a number of needles, for example eight, each of which is solenoid operated under the control of the knitting control system. The or each needle may move from a retracted position in which it holds a yarn in storage to a forward position where it casts the yarn off so that it may be picked up by the carriage and knitted into the fabric. This has been found to be an effective and very ecomonical way of feeding in additional yarns.

Preferably, a control rail is provided along the full width of carriage operation. Conveniently, the control rail is provided with cams to operate the yarn dismount levers through suitable cam followers, although other forms of actuation such as solenoids or pneumatic cylinders may be used. The control rail may also be provided with micro-switches or other sensing means so that the position of the carriage at any given time is 'known' by a computer controlled operating system.

Preferably the computerised control system automatically selects the yarns needed for a given pattern. Furthermore the system may also be used prior to a given run in order to determine which colour yarns are to be loaded at what positions on a yarn creel and into which particular needles in the or each yarn feed station.

While the invention is primarily directed to flat bed knitting machines, it my also be also used with other types of machine, e.g. V-bed. Moreover, the invention may be used with manually operated machines or with powered machines.

The invention will described, by way of example, with reference to the accompanying drawings, in which:

Figure la is diagrammatic illustration of a conventional domestic sliding sinker plate knitting machine;

Figure lb is a diagrammatic view of fabric produced by the machine of figure 1;

Figure 2 is a similar view to figure 1 of a machine modified in accordance with the invention; Figure 3 is a diagrammatic representation of the computer control sequence;

Figure 4 is a simplified plan view of a control rail in accordance with the invention;

Figure 5a is a partial plan view of the sinker plate assembly and yarn feed station in accordance with the invention;

Figure 5b is a detail of the yarn guide bar;

Figure 6 is a diagrammatic view of the yarn supply system;

Figure 7 is a similar view to figure 5a illustrating the shape of the sinker plate assembly;

Figure 8 is a diagrammatic representation of the lower yarn dismount system; and

Figure 9 is a plan view of a modified yarn holder.

Referring to the drawings, the prior art system illustrated in figure 1 is a conventional domestic flat bed knitting machine of the sliding sinker plate type 10 and comprises a carriage 12 and sinker plate assembly 14. The single bed knitting machine illustrated is fed with two yarns 54 (respectively a background yarn and a contrast yarn) from spring wire tensioning units, and the knitting carriage 12 carries the two yarns across the knitting bed where each knitting needle (not shown) is positioned so as to catch either a background or a contrast yarn according to the machine pattern controls. Typically these pattern controls are either punch card or computer controlled. The knitting action occurs by the interaction of the needles against the sinker plate, i.e. the two together form the knitted loop. The knit fabric is prevented from being pushed forward, when the knitting mechanism causes the knitting needle to move forward in the knitting action, by means of the sinker plate attached to the knitting carriage which serves to press the knit fabric adjacent to the knitting point against pegs on the front of the machine.

The conventional machine can accommodate only two yarns in the yarn feed unit on the knitting carriage and usually at least one of these is enclosed by a oveable barrier on the sinker plate assembly 14. Since most Fair Isle patterns call for many more than two colours the only way to achieve this on these machines is for the operator to break off the yarn no longer needed and replace it with the next required colour. This is a slow manual operation and leaves loose ends up the selvedge of the knitted fabric (see figure lb) which must subsequently be sewn in or dealt with in other ways.

Referring now to the assembly of the invention, an existing knitting machine 10 and knitting carriage 12 of the sliding sinker plate type referred to above is provided with extension arms 16 and a control rail 18. In addition the sinker plate assembly 14 is modified as will be described more fully hereinafter, and four yarn feed stations 20 are provided. Also, lower yarn dismount levers 22 (described more fully hereinafter with respect to figure 8) are provided. The system is controlled by a suitably programmed computer 24 through an input output unit 26.

Referring now to figure 7, the sinker plate assembly 14 is modified in that an upper plate 28 of the general shape illustrated in figure 7 is provided having a central cut-out portion 30 giving access to the knitting position. The portion 30 has a central vertical divider 32, and in addition a pair of upper yarn dismount levers 34 are provided. As illustrated in figure 7 the right hand upper yarn dismount lever is in the knitting position and the left hand upper yarn dismount lever is in the casting off position. Turning now to figure 5, which is a similar view to figure 7 but showing only half of the plate 28, it can be seen that a yarn feed station 20 comprises a series of yarns store needles 36 (in this case eight) each with an associated solenoid 38 and a compression spring 40. The spring urges the needles to the right as viewed in figure 5 ensuring that the hooks 42 of the needles bear against a mounting bar 44 when they are not in operation. Each yarn feed station 20 has an associated yarn guide bar 46 having an elongate slot 48 into which the hooks 42 of the needles 36 can be inserted when the associated solenoids 38 are operated.

Figure 5 illustrates the operation of the upper yarn dismount levers 34. As the sinker plate assembly 14 moves in the direction of arrow 'A' in figure 5a, a cam follower 50 contacts a profiled cam 52 fixed to the control rail 18. This has the effect of pushing the upper yarn dismount lever 34 from the position shown dotted in figure 5a to the position shown in solid in figure 5a, i.e. moving the yarn 54 from the knitting position to the dismount position. The yarn 54, as the sinker plate assembly 14 continues to move in direction of arrow 'A', passes to the right of the yarn guide bar 46 and is pulled along the guide bar until it contacts the selected yarn store needle 36 which is in the forward position (with its hook within the slot 48 in the guide bar) . The yarn store needle then retracts under the control of the computer until its hook contacts the mounting bar 44 with the yarn in its hook, thereby capturing the yarn, then the cam follower 50 retracts (following the profile of the cam 52) moving the upper yarn dismount lever 34 back towards the knitting position. Each of the needles 36 may similarly carry a yarn in their hooks 42.

As the carriage reverses on its next traverse (going in the opposite direction to arrow 'A' in figure 5a) the operation of the yarn dismount lever 34 is reversed. A selected yarn may be released from the yarn feed station 20 by operating a solenoid 38 causing the hook 42 of the relevant needle 36 to enter into the slot 48 in the yarn guide bar thus pushing the yarn out of the hook and allowing it be guided over the yarn guide bar 46 into the upper yarn dismount lever 34 and then into the gap 30 of the sinker plate 28 to the knitting position. The timing of yarn release together with yarn guidance rods (not shown) ensure that the yarn is fed to the correct side of the divider 32 in the cut-out 30.

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In a modified, and currently preferred, form of the invention, the divider 32 is replaced by a modified yarn holder 66 (Figure 9) located below the cut out 30 in the top plate 28. The yarn holder has the background yarn barrier removed and the entry/exit slot 68 modified to the shape illustrated in Figure 9(b) . A spring wire divider 32' is held by screws 70 in such a manner that it allows the yarn to the right (as viewed in Figure 9) of the divider (background) to move to the rear holding zone 72 while a yarn to the left of the divider (contrast) can move no further than the front holding zone 74. The force to move the yarn into the knitting position is provided by the yarn tensioning device (described below) , and the positioning of the yarn in the correct knitting position is achieved by the use of guidance rods (not shown) beneath the yarn feed station and by timing the yarn release so that it hits the plate of the sinker plate assembly on the appropriate side of the central opening. In certain circumstances, it may be desirable provide a light spring barrier at the entrance to each knitting yarn hold position to prevent the yarns being inadvertantly displaced in use, but this is not normally necessary.

As illustrated in figure 2, two yarn feed stations are provided at each side of the existing knitting machine 10 thus up to sixteen yarns on each side may be provided. A base and a contrast yarn can be selected from either of the yarn feed stations 20 on the relevant side of the machine.

s can be seen from figure 6 yarns 54 are supplied from a creel/tensioner unit 56 to each of the yarn feed stations 20. Tension on each yarn may be provided by means of a falling weight on a pulley system linked to conventional spring loaded friction discs to ensure the correct tension in each of the yarns 54 at all times. A typical tension is 40g. The creel/tensioning unit 56 supplies sufficient yarns for the needles in the yarn feed stores, in the present case 32. Depending upon the machine programming, all the yarns may be different colours or some may be of the same colour. Moreover, the creel unit has a sufficient reserve of each yarn to accommodate the extended carriage movement in accordance with the invention.

A series of micro-switches 58 are provided on the control rail 18 activated by the passage of the carriage 12 so that the computer 24 "knows" where the carriage is at any given time.

Turning now to figure 8, which is a side view rather than a plan view, it can be seen that when the carriage 12 clears the area of the original knitting machine 10 and moves along an extension into the vicinity of the yarn feed stations 20, it is desirable to move the trailing yarns 54 into a position where they can more easily leave the sinker plate assembly 14 through the gap 30, i.e. nearly vertical. This is achieved by a lower yarn dismount lever 60 pivotally mounted at 62 and carrying a yarn collecting bar or hook 64 at is lower extremity. In operation the lever 60 is pivoted about 62 sweeping the yarns 54 from the position shown in solid to the position shown dotted in figure 8. The movement of the lower yarn dismount lever 60 is timed to occur as the carriage approaches the relevant yarn feed station 20.

The operating sequence is computer controlled as illustrated in figure 3. Firstly the desired colour sequence for the pattern wanted is keyed in and the computer first of all calculates yarn placement instructions saying which coloured yarns go where in the creel 56 and the yarn feed stations 20. The program also shows where in the knitting sequence blank courses or 'polarity reversals' (exchanging background and contrast colours) occur. Thereafter the computer controls the operation sequence by sensing the carriage position by means of the micro-switches 58 on the control rail 18 and outputting the necessary signals via the input/output unit 26 to operate the individual solenoids 38 in the relevant yarn feed stations 20 thereby releasing or capturing the relevant yarns 54.

In operation of the machine, as the carriage moves in the direction of arrow 'A' in figure 5 the upper yarn dismount lever 34 is operated by the cam 52 acting through the cam follower 50 to place the yarn behind the yarn guide bar 46 after which the lever 34 returns to its original position. The yarn 54 travels along the yarn guide bar until it is caught in a needle 36 in its extended position as selected by the computer 24. The needle then retracts trapping the yarn in its hook 42 against the bar 44. On the carriage's return, a selected yarn is released by operation, through the computer programme, of the relevant solenoid 38 allowing a needle 36 to move to its extended position whereby the hook 42 enters into the slot 48 pushing off the held yarn 54 and allowing it to be carried along the yarn guide bar 46 into the gap 30 and then the knitting position. The yarn 54 so-selected may be the same yarn or a different yarn from that previously cast off. The yarn 54 in this position is held in the hook of the relevant upper yarn dismount lever 34 so that after it has passed the knitting zone it is ready to be moved out again when the computer deselects it. Operation of the other upper yarn dismount lever 34 is exactly the same at the other side of the machine.

By careful selection of the yarns, in accordance with the computer programme, it is possible to ensure that the yarn required for a given colour in the pattern is always available at whichever side of the machine the carriage happens to be. This is contrast to previous proposals for patterning devices for sliding sinker plate machines. Moreover both the contrast and the base yarn can be changed rather than just the contrast yarn, again in contrast with prior proposals. The patterning potential of the system of the invention is very great not only for Fair Isle designs but for many other patterns as desired.

Claims

1. A knitting machine which comprises a knitting bed, carriage and sinker plate assembly characterised in that carriage extensions are provided on either side of the bed, at least one yarn feed station is provided adjacent to each carriage extension, and the sinker plate assembly is provided with yarn dismount levers which pick up a yarn from, or cast it off to, the or each yarn feed station.

2. A machine as claimed in claim 1 in which the yarn holder in the yarn feed unit of the apparatus of the invention is modified so that access to the background as well as the contrast yarn is possible without interrupting knitting.

3. A machine as claimed in claim 2 in which the entry and exit slots of the yarn holder are modified to remove the background yarn barrier and a spring divider is positioned so as to hold the yarns in place while knitting but which can release them when they need to be changed.

4. A machine as claimed in any of claims 1 to 3 in which four yarn feed stations are provided, two on either side of the flat bed, one on each side carrying contrast yarns and one on each side carrying background yarns.

5. A machine as claimed in claim 4 in which each yarn feed station comprises a number of needles, for example eight, each of which is solenoid operated under the control of the knitting control system.

6. A machine as claimed in claim 5 in which the or each needle may move from a retracted position in which it holds a yarn in storage to a forward position where it casts the yarn off so that it may be picked up by the carriage and knitted into the fabric.

7. A machine as claimed in any of claims 1 to 6 in which a control rail is provided along the full width of carriage operation.

8. A machine as claimed in claim 7 in which the control rail is provided with cams to operate the yarn dismount levers through suitable cam followers.

9. A machine as claimed in claim 8 in which the control rail is provided with micro-switches or other sensing means so that the position of the carriage at any given time is 'known' by a computer controlled operating system.

10. A machine as claimed in any of claims 1 to 9 in which a control system automatically selects the yarns needed for a given pattern.

11. A machine as claimed in any of claims 1 to 10 in which a creel/tensioner unit is provided to supply yarns to each of the yarn feed stations, wherein tension on each yarn is provided by means of a falling weight on a pulley system linked to conventional spring loaded friction discs to ensure the correct tension in each of the yarns at all times.

12. A machine as claimed in claim 12 in which the creel unit has a sufficient reserve of each yarn to accommodate the extended carriage movement of the machine.