GB2303224A - A knitted garment production process - Google Patents

Abstract

A process for producing a garment using alpaca or linen yarn involves use of mechanical parameter tables 4, each grid being associated with a variable mechanical parameter. As the machine performs the knitting operations according to a design file, design function commands act as triggers to access a fresh active row of one or more grids for mechanical parameter adjustment. Each grid includes a set of rows for each panel of an individual garment and therefore a single set of grids may be used for production of all of a garment, the panels being knitted in succession leaving the grids in memory. In this way, a continuous length of alpaca or linen yarn is used for an individual garment to provide for maximum uniformity. Ranges are provided for needles in a takedown data table, the range allowing use of an individual grid for a range of sizes for a particular design. The panels are linked together by point-for-point linking and are steamed on a single surface with a steam pressure of 5 bar.

Description

"A knitted garment production process" The invention relates to the production of knitted garments.

European Patent Specification No. 640707A1 and British Patent Specification No. GB 2148545A (Shima) describe methods for the programming of flat bed knitting machines in order to achieve a large degree of versatility and complexity in the knitting operations. In general, major advances have been made in the complexity of the knitting operations which can be carried out automatically. The arrangement of transfer cams can allow stitch transfer to be performed in either direction, regardless of the knitting direction. Other improvements, for example, are reductions in carriage weight and size, improvements in carriage drive arrangements, and provision of additional rollers for fabric take-down. These improvements have led to the ability to perform knitting operations of additional complexity and at a high speed.However, there are some situations where problems in terms of both quality and efficiency arise in operation of such machines.

Such a situation is where the knitting yarn is particularly difficult to handle, such as a linen yarn or an alpaca yarn. Such yarns are generally not used for knitting because of not only their cost, but also the problems which arise in handling of the yarn during the knitting process. Alpaca tends to have quite a number of fibres extending outwardly from the core of the yarn and these can become intertwined on the spool, thereby causing a non-uniform draw-off force requirement. Similar problems can arise for linen and in particular it has been found that linen can cause damage to parts of the machine such as the needles because of it's high strength if any of the settings are not correct for the particular course being knitted.

Further, where the machines are used in an environment where there is a very low batch size of possibly less than 100 garments in total per style and there are very frequent batch changes, change-over between batches can proportionally take a considerable amount of time. This is particularly the case with difficult yarns. Generally, a large amount of time is spent in performing trial and error experiments to adjust mechanical settings before the batch run begins.

The invention is directed towards provided a production process to overcome these problems.

According to the invention, there is provided a process for producing knitted garments using alpaca or linen yarn, the process comprising the step of:in a knitting machine of the flat bed type over which a carriage runs and comprising a take-down mechanism and a controller, setting minimum tension in overhead and lateral yarn guides for the yarn; the controller setting received fixed carriage stroke, carriage position and yarn measurement mechanical parameter values for the knitting machine; the controller automatically retrieving from a remote controller a mechanical control file associated with the style of garment to be produced, the control file comprising a grid of fabric take-down values, a grid of stitch cam settings, and a grid of carriage speed values, each grid being in a hard-coded fixed structure and wherein the grid for fabric take-down values includes a range of possible needles to be used and a range of main roller tensions to be used, said ranges encompassing all possible needles and tensions for all garment sizes for a particular style, and wherein each grid includes pre-set rows of values for each panel of an individual garment; the knitting machine knitting a waste row and subsequent rows of a panel and continuing knitting operations according to a garment design file stored in the controller; the controller monitoring design function commands of the design file and identifying those commands which act as triggers for automatic mechanical parameter adjustment according to pre-set indicators, and when such a command is identified accessing one or more of the tables in the control file and automatically identifying a fresh active row of the or each table, reading the values of the row and performing mechanical parameter adjustments accordingly; repeating the mechanical parameter adjustment operations for each relevant design function command trigger, and when the panel is complete, maintaining the control file in random access memory of the controller and knitting a next panel for the same garment using the design file and successive active rows of the tables, and repeating the knitting and adjustment operations for each panel of the same garment; performing the knitting and adjustment operations for panels of a garment having the same style and being a different size using the same control file loaded in random access memory; carrying out point-for-point linking of the panels of garments; and steaming the garments on a single-surface steam presser for final relaxation and pressing, and performing a final inspection.

In one embodiment, each table has a fixed size for all garments to be knitted, dummy values being inserted in cells of the table which are redundant for a particular garment.

Preferably, the tension value ranges are provided for main rollers, single values being provided for a comb and a sub-roller.

In one embodiment, the knitting operations include knitting of a pair of back loops in a transfer course where cross-over transfers are required, the back loops being located at either side of a cross-over location.

Preferably, the process further comprises the sub-steps of knitting a nylon draw thread for connection of the waste row to a set-up course at the beginning of a panel, and subsequently knitting a lycra elasticated course on the back bed after two set-up courses of the panel.

In another embodiment, the steam pressure applied for steaming is approximately 5 bar.

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which: Figs. 1(a) and l(b) are together a flowchart illustrating a production process of the invention; Fig. 2 is a perspective view of a knitting machine used to implement the process; Figs. 3(a) and 3(b) are views of an overhead yarn guide of the machine and the manner in which it is set for the process; Fig. 4 is a diagrammatic front view of a lateral take-up guide showing the manner in which it is set for the process; and Fig. 5 is a set of diagrammatic views of a take-down arrangement for the machine; and Fig. 6 is a perspective view showing the manner in which a garment is pressed.

q Referring to the drawings, there is shown a production process indicated generally by the reference numeral 1, which is carried out using equipment shown in Figs. 2 to 6 inclusive. As shown in Fig. 2, a knitting machine 40 is used in the process and this comprises a V-bed arrangement 41 over which a carriage 42 moves to perform the knitting operations. The machine 40 may be of the type marketed under the trade name SHIMA SEIKI SES-234FF. The machine 40 has a set of overhead yarn guides 43 and a set of lateral take-up guides 44 which direct yarn from spools 45 to the carriage 42. The machine 40 has a local controller 46 with a keypad and display interface and this is connected to a remote controller 47 comprising a microcomputer.

As the knitting operations are performed, a fabric panel is produced and this is drawn down by a take-down mechanism 48, not shown in Fig. 2. The fabric panel being knitted is indicated by the numeral 49.

The process 1 comprises steps 2 to 31 shown in Figs. l(a) and l(b) and the first step 2 involves creation of a design file. This step is performed on the remote controller 47 and is implemented according to the manufacturers supplied program. For example, a knitted design system such as that described in European Patent Specification No. EP 0640707A1 may be used. In this arrangement, design data for intarsia, jacquard, and structural stitches are separately stored and independently processed. However, any appropriate design file could be used for the process of the invention. As indicated by the decision step 3, a separate design file is created for each garment size.

An important aspect of creation of the design file is that for cross-over transfer course stitches such as for a cable design stitch, the design file includes instructions for generation of a pair of back-loops (2(a)) in the transfer course (2(b)). These loops are on each side of a centre line between cross-over transfer stitches as shown next to the decision step 2 of Fig. l(a). The design instructions include instructions to create these additional back-loops to provide a large degree of additional slack in the transfer course, and instructions for the loops to be pressed off before transfer.These design instructions have been found to be particularly important for knitting of a cable stitch using alpaca or linen yarns as they provide a significant degree of slackness at a location where it is particularly effective, in addition to that provided by the conventional design instructions.

In step 4 a mechanical control file is created for all sizes for a particular style of garment. Each control file comprises three grids having a fixed size with a fixed number of cells. There is a grid associated with each of the following parameters: (a) fabric take-down, (b) stitch cam settings, and (c) carriage speed.

The following is an example of a grid for the fabric takedown parameter: [1] Needle Number Start [2] Needle Number End [3] Main Roller Tension Start [4] Main Roller Tension End [5] Comb [%] [6] Comb (+sub roller) [%] [7] Sub Roller [1] [2] [3] [4] [5] [6] [7] Fabric Tk Dn 1 1 240 30 30 100 0 0 Fabric Tk Dn 2 71 152 35 50 100 0 0 Fabric Tk Dn 3 71 152 33 53 80 0 0 Fabric Tk Dn 4 71 152 45 53 100 0 0 Fabric Tk Dn 5 1 240 30 32 100 0 0 Fabric Tk Dn 6 1 240 31 31 100 0 0 (end of body panel) Fabric Tk Dn 7 116 160 20 25 80 0 0 Fabric Tk Dn 8 1 240 30 60 100 0 0 Fabric Tk Dn 9 1 240 30 60 100 80 100 Fabric Tk Dn 10 71 152 40 45 100 80 0 Fabric Tk Dn 11 71 152 34 45 100 80 0 (end of sleeve) Fabric Tk Dn 12 1 240 30 60 100 80 100 Fabric Tk Dn 13 1 240 30 60 100 80 100 Fabric Tk Dn 31 1 240 30 60 100 80 100 (dummy values) As illustrated diagrammatically in Fig. 5, the take-down mechanism 48 comprises a comb 71 having catches 74 for engagement with the lower stitches in the waste row of the garment 49 as it is being drawn down. There is a pair of main rollers 72 and a pair of sub-rollers 73. These are used in combination with each other or singly to draw the fabric panel down as it is being knitted. The parts shown in Fig. 5 are simply for illustration purposes to help understand the nature of the process. They are conventional on machines such as a Shima Seiki flat bed knitting machine.

Each grid applies to all of the panels for all sizes of a garment style. In the above example, therefore, rows 1 to 6 relate to the body panels and rows 7 to 11 relate to the sleeves. Rows 12 to 31 are redundant. Each row of the table represents a new set of values to direct in-line adjustment of the machine during the knitting of a panel.

The sub-parameters within the fabric take-down parameter include needle start and end numbers, main rollers start and end tensions, comb tension as a percentage of the main roller tension, comb and sub-roller combined tension as a percentage of main roller tension, and tension of the subroller alone. The ranges given in the table for needles and main roller tension encompass maximum ranges for all garment sizes. The machine 40 will always start with the lowest level and automatically increment the value, without necessarily reaching the maximum, as this applies only to the largest size within the style.

The following is an example of part of a grid for the stitch cam setting parameter. This grid includes front and back stitch cam setting values for both the first and second strokes of the carriage. The higher the value of the number, the slacker the stitch as a higher value causes a greater needle displacement.

No. 1 No. 2 Front Back Front Back 1 30 30 30 30 2 60 60 60 60 3 30 30 30 30 4 27 27 27 27 5 55 55 55 55 6 45 45 45 45 7 62 62 62 62 8 66 66 66 66 9 70 70 70 70 10 60 60 60 60 11 44 44 44 44 12 35 35 35 35 13 30 30 30 30 14 40 40 40 40 15 45 40 45 40 16 56 56 56 56 17 65 65 65 65 18 30 30 30 30 19 60 60 60 60 20 60 60 60 60 21 40 40 40 40 22 60 60 60 60 23 70 70 70 70 24 50 50 50 50 25 34 34 34 34 26 64 64 64 64 27 60 60 60 60 28 60 60 60 60 29 60 60 60 60 30 60 60 60 60 31 60 60 60 60 Rows 27-31 are redundant, rows 1-26 providing values for the different garment panels, the machine being programmed to start at the correct row at the beginning of each panel.

The third grid is much simpler and represents carriage speed and an example is given as follows.

(m/s) BASE ........... 1.00 No.=l .......... 0.70 No.=2 .......... 0.70 No.=3 .......... 0.40 No.=4 .......... 0.25 No.=5 .......... 0.70 No.=6 .......... 0.70 No.=7 .......... 1.00 As will be seen from this grid, the speed setting is relatively simple.

In step 5 of the process 1, the yarn is fed through the guides of the machine 40 from the spools 45. In order to minimise yarn tension, the spools are placed generally at one or other lateral side of the machine 40 - close to the lateral take-up guides 44. Figs. 3(a) and 3(b) show an overhead yarn guide 43 in detail. The guide 43 comprises a tensioner 50 comprising a threaded rod 51 supporting a nut 52 which presses against a coil spring 53 to adjust the pressure which is exerted upon the left of a pair of guide plates 54 between which yarn 61 is trained. The overhead guide 43 also comprises a yarn guide 60 of wire construction. As shown in Fig. 4, the lateral take-up guide comprises an opening 62 through which the yarn 61 is drawn to a roller 63 and then through the eye 64 of an Lshaped tensioner arm 65 which is biassed in the clockwise direction by a torsion spring arrangement 66.The yarn is fed from the eye 64 through an opening 67 in the side of the machine and thence to the carriage.

In step 5 of the process, the nut 52 is moved to its leftmost position to minimise the tension on the yarn 61 in the overhead guide 43, and the L-shaped tensioner 65 is set at a relatively small angle to the vertical, generally in the region of 15 to 250, to minimise tension on the yarn 61 as it is fed through to the carriage.

In step 10 of the method, the stroke, carriage position, yarn measurement and economiser settings are inputted into the knitting machine 40 using the local interface 46.

These are fixed for production of an individual garment.

In step 11, the machine 40 automatically retrieves a control file for a garment style from the controller 47 and proceeds to perform knitting operations using the yarn which has been drawn through the various guides as described above. In step 11 in particular, it knits a waste row in which their is knitted a first course at the end of which a draw thread of 40CF nylon is taken up, but not knitted. There is then a set of waste yarn courses, following which the nylon draw thread is knitted on the back bed with one stroke. A pair of set-up courses are then knitted, followed by knitting of a lycra course using the back bed on both strokes. It has been found that 40CF nylon is particularly suitable for draw thread as it is extremely strong and helps supply the necessary tension which is required for knitting with alpaca and linen yarns.Further, the elasticated course using lycra is particularly effective as it is not generally visible and helps to provide the necessary gathering tension which is needed at the extremity of a panel.

In step 12, the processor of the machine 40 proceeds to read the design file instructions and to knit the courses to produce the fabric panel 49. As indicated by the step 20, the machine reads a design function command, sometimes referred to in the industry as an "option line". Examples of option lines are "stitch change", "knit cancel", "stitch presser setting", and "leading stitch cam adjustment". These are functions in the design file which the machine reads and performs. However, in addition, the local controller 46 determines if the option line is a trigger for a mechanical parameter adjustment. If so, in step 22 the controller reads the next active row of the associated grid of the mechanical control file.

Initially, as it starts to perform the knitting operations, the controller automatically uses the settings of the first row of each of the three grids. Thereafter, the option lines are used as triggers to change over to the settings of the second and subsequent rows.

Therefore, in the example given above, the first change in settings will be so that the needle numbers used will be in the range 71 to 152, the main roller tension should gradually change from 35 to 50 until the next option line trigger is reached. The comb should operate at a tension of 100% of the main roller tension, and the sub-roller should not be in operation. At the next option line for which there is mechanical parameter adjustment, the controller will identify row 3 as being the active row and will make the appropriate adjustments. An important aspect of the fabric take-down data grid is that the largest range of needle numbers for columns 1 and 2 is wide enough to cover the full range of sizes for a garment style and therefore the same grid is used for all sizes.

The controller will start with the start number and will then use up needles as required, not necessarily to the higher value given in column 2 but using this value as a maximum. As indicated by the interrupted line between steps 23 and 22, a single option line may cause change of additional parameters such as the stitch cam settings or the carriage speed. In this case, the controller automatically determines the fresh active row and reads the data from this row and makes the necessary adjustments. In all cases where mechanical parameters are to be adjusted, the controller does not need to perform searching operations -it simply determines the next active row and makes the necessary settings. This provides for high-speed parameter changing because there are very few software processing operations.

It has been found that by providing for a large number of in-line mechanical parameter adjustments during knitting of a panel, the mechanical parameters are always at the optimum value for the design stage. This helps to ensure that problems do not arise, for example, in damage to needles caused by linen yarn. It has also been found that in combination with the low-tension settings for drawing of the yarn from the spools, the problems of nonuniformity of spooling of the yarns such as alpaca are minimised. These mechanical parameter adjustments are performed automatically using functions which are already present within the design file in any event and therefore there is very little additional processing required. The controller must simply identify each setting and must then retrieve the active row from the hard-coded grid.Such operations may be performed very quickly in a microprocessor. What has been achieved is full integration of the design and mechanical parameter control for optimum performance.

As indicated by the feedback lines in the flowchart of Figs. l(a) and l(b), the controller repeatedly changes the mechanical parameters as set by each subsequent row of the three grids. When a panel has been completed as indicated by the decision step 13, the control file is maintained in memory if another panel has to be knitted for that particular garment as indicated by the decision step 14.

Accordingly, the machine proceeds to knit each panel in succession for an individual garment, for example, front, back and two sleeve panels. The same mechanical control file applies to all of the panels. For example, row 7 of the fabric take-down grid provides the first set of takedown parameter settings for the sleeves. This helps to provide uniformity between the parameter settings and there is no delay for programming between different panels of the one garment.

When all of the panels for a garment have been produced, the machine 40 proceeds to knit the panels for another garment. If the next garment is of the same size and style, or a different size and the same style, the control file is again used.

As indicated by the decision step 14, in step 24, panels are linked together using point-for-point circular linking machines. After linking, the garment is inspected in step 25 and then any necessary tacking operations are performed. Finally, in step 30, the garment is pressed for relaxation of the fabric. For this operation, a pressing station 80 shown in Fig. 6 is used. This comprises a table 81 to which steam is delivered via a duct 82. The garment is simply pressed on top of the table 81 and is manipulated by a hand iron 83 until the necessary relaxation and garment manipulation takes place.

It has been found that a steam pressure of 5 bar is particularly effective for pressing garments of alpaca or linen yarn in this manner.

It will be appreciated that the invention provides for production of garments using difficult yarn with a requirement for very little re-work because of the manner in which the initial settings are made and by which parameters are adjusted. The mechanical control files provide for very easy batch changes between different styles in a knitting environment where there are very frequent design changes with very small batch runs. This is particularly so as a single control file applies to all panels of an individual garment and these are all knitted successively until a full set of panels for a particular garment have been knitted. This also helps to address the problems of non-uniformity in supplied yarn, as yarn for an individual garment is from the same length on an individual spool. Further, a single control file applies to all sizes for one style.

The invention is not limited to the embodiments hereinbefore described, but may be varied in construction and detail.

Claims (8)

1. A process for producing knitted garments using alpaca or linen yarn, the process comprising the steps of: in a knitting machine of the flat bed type over which a carriage runs and comprising a take-down mechanism and a controller, setting minimum tension in overhead and lateral yarn guides for the yarn; the controller setting received fixed carriage stroke, carriage position and yarn measurement mechanical parameter values for the knitting machine;; the controller automatically retrieving from a remote controller a mechanical control file associated with the style of garment to be produced, the control file comprising a grid of fabric take-down values, a grid of stitch cam settings, and a grid of carriage speed values, each grid being in a hard-coded fixed structure and wherein the grid for fabric take-down values includes a range of possible needles to be used and a range of main roller tensions to be used, said ranges encompassing all possible needles and tensions for all garment sizes for a particular style, and wherein each grid includes pre-set rows of values for each panel of an individual garment; the knitting machine knitting a waste row and subsequent rows of a panel and continuing knitting operations according to a garment design file stored in the controller;; the controller monitoring design function commands of the design file and identifying those commands which act as triggers for automatic mechanical parameter adjustment according to pre-set indicators, and when such a command is identified accessing one or more of the tables in the control file and automatically identifying a fresh active row of the or each table, reading the values of the row and performing mechanical parameter adjustments accordingly; repeating the mechanical parameter adjustment operations for each relevant design function command trigger, and when the panel is complete, maintaining the control file in random access memory of the controller and knitting a next panel for the same garment using the design file and successive active rows of the tables, and repeating the knitting and adjustment operations for each panel of the same garment;; performing the knitting and adjustment operations for panels of a garment having the same style and being a different size using the same control file loaded in random access memory; carrying out point-for-point linking of the panels of garments; and steaming the garments on a single-surface steam presser for final relaxation and pressing, and performing a final inspection.

2. A process as claimed in claim 1, wherein each table has a fixed size for all garments to be knitted, dummy values being inserted in cells of the table which are redundant for a particular garment.

3. A process as claimed in claims 1 or 2, wherein the tension value ranges are provided for main rollers, single values being provided for a comb and a sub roller.

4. A process as claimed in any preceding claim, wherein the knitting operations include knitting of a pair of back loops in a transfer course where cross-over transfers are required, the back loops being located at either side of a cross-over location.

5. A process as claimed in any preceding claim, further comprising the sub-steps of knitting a nylon draw thread for connection of the waste row to a set-up course at the beginning of a panel, and subsequently knitting a lycra elasticated course on the back bed after two set-up courses of the panel.

6. A process as claimed in any preceding claim, wherein the steam pressure applied for steaming is approximately 5 bar.

7. A process substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

8. A garment whenever produced by a process as claimed in any preceding claim.