Yarn length control system for a flat knitting machine

Abstract: In a flat knitting machine where in a plurality of knitting locks work on a single needle bed to knit, the consumption of each yarn is measured 9 and compared 33 with the standard yarn length, and the stitch cam adjustment values of the respective knitting locks are corrected 32. The stitch cam adjustment data is stored for the respective combinations of stitch cams and yarns. Correction is not limited to the stitch cam which knitted the yarn of which consumption was measured. Correction by the same value is also given to the stitch cam adjustment values of other stitch cams relative to the yarn. As a result, for any combination of a stitch cam and a yarn which appears suddenly in the latter half of knitting, the stitch cam adjustment values have been corrected on the basis of the measurement of consumed yarn lengths of other stitch cams, generating no knitting gaps.

Description: The present invention relates to improvements of yarn length control systems for flat knitting machines. The present applicant proposed yarn length control systems for flat knitting machines as disclosed in Provisional Japanese Patent Publication No. SHO-62-62977, Japanese Patent Publication No. HEI-1-49816 and Provisional Japanese Patent Publication No. HEI-6-25953. In Provisional Japanese Patent Publication No. SHO-62-62977, the standard yarn length LA for stitches of a specified number of courses is compared with the actual yarn length LB, and the stitch cam of the knitting machine is adjusted to bring the consumed yarn length close to the standard yarn length. In Patent Publication No. HEI-1-49816, the tension in the yarn is adjusted on the basis of a similar comparison. The variation in the consumed yarn length from the standard yarn length is fed back to the tension in the yarn rather than the stitch cam. In Provisional Patent Publication HEI-6-25953, a sample garment is knitted before the actual garment is knitted so as to compare the yarn length of the actual garment with that of the sample garment. In comparing yarn lengths, moving averages of yarn lengths over several knitting courses are used, and stitch cams are adjusted so that the yarn length of the actual garment equals that of the sample garment. Such a yarn length control brings the loop lengths of various parts of the garment close to the specified values. As a result, a garment of the desired size will be knitted, and fluctuations in loop size within one garment will be prevented. Causes of variation in the loop length from the specified length are mainly related to yarns. For example, even when the stitch cam conditions are identical, if the material of the yarn, the dyestuff, the tension in the yarn, the diameter of the cone of the yarn, etc. vary, the loop length will vary. The second group of causes of variation in loop length is related to the flat knitting machine itself. For example, the knitting speed, the tension applied to the knitted fabric for lowering, etc. will vary the loop length. In addition, changes in temperature, humidity, etc. will vary the loop length. As the causes of variation in the loop length are mainly related to the yarns, even for a given stitch cam, if the kind of the yarn differs, the appropriate stitch cam adjustment value will differ. Hence the unit of adjustment of the stitch cam was decided to be the pair of yarn and stitch cam or the combination of yarn and stitch cam. Thus, stitch cam adjustment data is stored for every pair of yarn and stitch cam, and the stitch cam adjustment data is corrected for every pair on the basis of the comparison between the consumed yarn length and the standard one. The present inventor, however, found the following problems as to the control of yarn length. For example, if one specific combination of yarn and stitch is used for the first time in the latter half of the knitting of a garment, the stitch cam conditions for the specific combination will be the initial values, while for the other combinations of yarn and stitch cam, the stitch cam conditions will have been controlled to bring the respective loop lengths to the desired values. As a result, the loop length will change sharply at a part in which the new combination of yarn and stitch cam is introduced, producing a knitting gap along the boundary of the preceding portion. Such knitting gaps are generated at a considerable frequency and are conspicuous and as a result, the value of the garment as merchandise will be lost. Such a problem may occur, for example, when a knitting lock differing from one which has been used previously is allocated to a yarn at the V-neck portion of a sweater. The conventional yarn length control methods cannot overcome the problem of knitting gap occurring, and in such a case, the garment design must be modified so that the allocation of knitting locks are not changed in the latter half of the knitting process. There is a problem similar to the above-mentioned problem. This is the use of a new yarn in the latter half of knitting of a garment. In this case, as the yarn is used for the first time in the latter half of the knitting of the garment, the stitch cam conditions are just those at the time of the start of knitting. Hence no correction has been made for changes in the conditions from the start of knitting till the start of the use of this yarn. As a result, knitting gaps will be generated at a considerable frequency. For the conventional yarn length control, knitting of a garment of such a design is virtually impossible. It is therefore necessary to modify the design so that the specific yarn is used in the first half of knitting of the garment as well to avoid the use of a new yarn in the latter half of the knitting process. All of these problems are attributed to the fact that, for a certain combination or combinations of yarn and knitting lock, no adjustment is made and so knitting with these starts with the conditions appropriate at the commencement of knitting of the garment, while for other combinations of yarn and knitting lock, stitch cam adjustment data is constantly fed back. As the loop length of other yarns is controlled, variations in the loop length of the specific combination or combinations become conspicuous, appearing as knitting gaps. The present invention is for use with a flat knitting machine, wherein a plurality of yarns are fed from yarn feeding means to at least one needle bed, said needle bed is provided with a plurality of knitting locks, each knitting lock has an onward stitch cam and a rearward stitch cam, each knitting lock operates the needle bed to form series of stitches from the fed yarns, and the respective stitch cam positions are corrected by the stitch cam adjustment data to alter the stitch size. The yarn length control system of the present invention comprises: a measuring means for measuring the consumption of each yarn; a comparing means for comparing the measured consumption with the standard yarn length; and an adjusting means which generates correcting data for the stitch cam adjustment data according to the results of comparison by the comparing means and corrects, by the above-mentioned correcting data, the position of at least one stitch cam of the knitting lock that operated the needle bed for the yarn of which consumption was measured, relative to the yarn, and is characterized in that said adjusting means corrects, by said correcting data, at least one stitch cam datum of one other knitting lock, relative to said yarn. Thus, the present invention prevents or at least reduces the generation of knitting gaps by adjusting, in advance during knitting of preceding courses, the stitch cams. Preferably, it adjusts every pair of knitting lock and yarn which appears for the first time after a considerable number of courses since the start of knitting. Preferably, the stitch cam adjustment data for the specific pair of yarn and knitting lock is corrected without knitting with the specific pair, and this correction of the stitch cam adjustment data is made during knitting of preceding courses. The measuring means mentioned above may be a means for measuring length, such as a rotary encoder provided on a side-tensioner of the flat knitting machine; any means that can measure the yarn length will do. The standard yarn length may be, for example, one that is calculated from the specified yarn length per loop; the standard yarn length is compared with the actual yarn length consumed, and the result is fed back to the stitch cam adjustment data to form stitches of the specified loop length. The correction of the stitch cam adjustment data is preferably made for each pair of a yarn and a knitting lock, or more preferably for each pair of a yarn and a stitch cam as a unit. The stitch cam adjustment is preferably not limited to the yarn of which yarn length was measured and the knitting lock which is involved in knitting of the yarn. In a particularly preferred embodiment, the stitch cam adjustment data will be corrected, by the same value, for other knitting locks which relate to the yarn. There is no need to uniformly correct the stitch cam adjustment data for all knitting locks. For example, if a certain knitting lock is not used for a certain yarn, there is no need to correct the stitch cam adjustment data for that knitting lock. Moreover, when a specific yarn is used alternately by two knitting locks, there is no need to applying the correcting data, which was determined for one knitting lock, to the other knitting lock. Preferably, when at least one stitch cam of a knitting lock which operated the above-mentioned needle bed and at least one stitch cam of said other knitting lock have the same direction for the onward/rearward movement and the stitch cam adjustment data is corrected for one stitch cam, the stitch cam adjustment data of the other stitch cam having the same direction is also corrected. Here, preferably, a memory means is provided for storing stitch cam adjustment data for each pair of a stitch cam and a yarn as a unit. When the flat knitting machine has a single carriage, the above-mentioned respective knitting locks are contained in said carriage. However, when the flat knitting machine has a plurality of carriages, the respective knitting locks may be separately contained in different carriages. The present invention is also characterized in that in a yarn length control system for a flat knitting machine, wherein a plurality of yarns are fed from yarn feeding means to at least one needle bed, said needle bed is provided with a plurality of knitting locks, each knitting lock has an onward stitch cam and a rearward stitch cam, each knitting lock operates the needle bed to form series of stitches from the fed yarns, and the respective stitch cam positions are corrected by the stitch cam adjustment data to alter the stitch size, said yarn length control system comprises: a measuring means for measuring the consumption of each yarn; a comparing means for comparing the measured consumption with the standard yarn length; and an adjusting means which generates correcting data for the stitch cam adjustment data according to the results of comparison by the comparing means and corrects, by the above-mentioned correcting data, the position of at least one stitch cam of the knitting lock that operated the needle bed for the yarn of which consumption was measured, relative to the yarn, wherein said adjusting means corrects, by said correcting data, said stitch cam data of the knitting lock which operated the needle bed for the yarn of which consumption was measured, relative to other yarns. In the present invention, correction data for the stitch cam adjustment data determined for a combination of a yarn and a knitting lock is also preferably applied to the adjustment of other knitting locks relative to the specific yarn. For example, suppose a combination of a first yarn and a first knitting lock is used to knit a fairly large number of courses, then a different combination of the first yarn and a second knitting lock is used. In the conventional control cases, the stitch cam adjustment data for the combination of the first yarn and the second knitting lock remains the same as the one at the start of knitting; changes in the conditions after the start of knitting are neglected. As a result, when the knitting is started by the new combination, the loop length will deviate from the specified value, generating a knitting gap. In the present invention, however, when knitting is carried out by the combination of the first yarn and the first knitting lock, the stitch cam adjustment data may also be changed for the combination of the first yarn and the second knitting lock. Hence a sudden use of the combination of the first yarn and the second knitting lock will not generate a knitting gap. This in turn will increase the degree of freedom of designing a garment, enabling knitting of designs which were impossible in the past, Each knitting lock has two stitch cams; one onward stitch cam and one rearward stitch cam. Preferably, separate stitch cam adjustment data are corrected for the onward stitch cam and the rearward stitch cam, respectively. Thus, when the stitch cam adjustment data is corrected relative to the first yarn and the onward stitch cam of the first knitting lock, the stitch cam adjustment data are also corrected relative to the same first yarns and the onward stitch cams of other knitting locks. For this purpose, it is desirable to measure separately the consumed yarn length in the onward direction and the consumed yarn length in the rearward direction. In the onward direction and in the rearward direction, the directions of the tension applied by the yarn feeding means are opposite to each other, relative to the direction of motion of the knitting lock. For example when the loop length shifts away from the specified value due to tension variation, it may be necessary to correct the stitch cam adjustment data so that the loop length is increased for the onward direction while it may be necessary to correct the, stitch cam adjustment data so that the loop length is decreased for the rearward direction. To handle these cases, it is therefore preferable to correct the stitch cam adjustment data separately for the onward direction and for the rearward direction. There may be a design wherein a certain yarn is used suddenly in the latter half of the knitting of a garment. In the conventional cases, the stitch cam adjustment data for this yarn would be just the same as those set at the time of the start of knitting, and as a result knitting gaps would be generated. However, if the correcting data for the stitch cam adjustment data for a certain knitting lock and a certain yarn are applied for one other yarn which is involved with the knitting lock, no knitting gap will be generated. Thus relative to the yarn to be used only in the latter half of the knitting, the stitch cam adjustment data has been corrected for changes in knitting conditions. In this way, the loop length is prevented from changing suddenly. As a result, such a design becomes feasible. Certain embodiments of the invention will now be described, by way of example only and with reference to the accompanying drawings in which:- Fig. 1 is a front view of a flat knitting machine used in the embodiment. Fig. 2 is a diagram showing the layout of stitch cams in the carriage of the machine. Fig. 3 is a block diagram of the yarn length control system of the embodiment. Fig. 4 is a diagram showing a stitch cam adjustment table stored in a memory block. Fig. 5 is a diagram showing assignment of the yarns to the knitting locks for knitting a garment. Fig. 6 is a flow chart showing the control of yarn length in the embodiment. Fig. 1 is a front view of a flat knitting machine 1. The flat knitting machine 1 is provided with, for example, a pair of needle beds, one in the front and one in the rear, with their fronts being opposed to each other. The needle beds 2 support a large number of knitting needles in such a way that the needles can be freely moved forward and backward. On the needle beds 2, a carriage 3 for controlling forward and backward movements of the knitting needles is slidably arranged. The respective yarns 6 are fed from a plurality of cones 5 on the frame 4 of the flat knitting machine 1 to the knitting needles of the needle beds 2 via the top tensioners 10, the side tensioners 7 provided on both sides of the knitting machine, and the yarn feeders 8 which reciprocate in synchronization with the travel of the carriage 3, The side tensioners 7 are provided with yarn length detectors 9 such as rotary encoders for the respective yarns; thus the consumed yarn length of each yarn is detected for, for example, every knitting course. Fig. 2 shows a carriage 3 used in the embodiment. The carriage 3 has a front carriage 20 corresponding to the front bed and a rear carriage 21 corresponding to the rear bed. The front and rear carriages 20, 21 have three knitting locks (20A, 20B, 20C), (21A, 21B, 21C), respectively. For simplicity, the knitting locks on the left side are called knitting locks L, the knitting locks in the middle are called knitting locks C and the knitting locks on the right side are called knitting locks R. Each knitting lock is provided with a stitch cam 22A which operates in the onward movement (from the left to the right in the diagram) and a stitch cam 22B which operates in the rearward movement (from the right to the left). Each stitch cam 22A or 22B is provided with a stitch cam adjustment motor 24 which adjusts the stitch cam value. The stitch cam adjustment motor 24 adjusts the stitch cam value or the height of the stitch cam 22A or 22B when the direction of travel of the carriage 3 is reversed. Fig. 3 shows the yarn length control system of the embodiment. Control block 30 uses, for example, a microcomputer to control the entirety of the yarn length control system. It is provided with a correction data generator 32 which generates correction data of stitch cam values and a yarn length comparator 33 which compares the consumed, yarn length with the standard yarn length. Memory 40 stores various data and programs. A knitting data memory 41 stores knitting data comprising knitting patterns, various control data, loop length, etc. inputted from a secondary memory 45 such as a floppy disc. Stitch cam adjustment table 42 stores stitch cam adjustment data for the respective stitch cams 22A, 22B. The stitch cam adjustment table 42 stores the stitch cam adjustment data for each stitch cam in the form of a pair of the stitch cam and a yarn, and stores such data for, for example, single, double and triple knitting, respectively. Single, double and triple indicates the number of knitting courses knitted at a time. For example, the area Q of Fig. 5 is of single knitting, and the area P is of double knitting. Hence the total number of stitch cam adjustment values to be stored for one stitch cam is the number of yarns to be used x 3 (single, double, triple). These stitch cam adjustment values are stored separately for every stitch cam. For example, the stitch cam adjustment values for the stitch cam 22A of the knitting lock 20A are stored separately from those for the stitch cam 22A of the knitting lock 21A. In the embodiment, the data of stitch cam adjustment values of the front carriage 20 and the data of stitch cam adjustment values of the rear carriage 21 are common to each other, The configuration of the stitch cam adjustment table itself is discretionary. Fig. 4 shows an example of the stitch cam adjustment table 42. It indicates areas where data is present, neglecting the distinction between single, and double. When the stitch cam adjustment value is 0, it is a default value and indicates data is not present in Fig. 4. In Fig. 4, the second and third yarn feeders are used, and the knitting lock C is not used. Hence the stitch cam adjustment values are stored for the combinations of the knitting locks L, R and the second and third yarn feeders. The knitting data specify the loop lengths of the respective courses. The specified loop lengths are converted into stitch cam values and stored in the stitch cam data memory 43. These stitch cam values are free of any adjustment. When the stitch cam adjustment values are added to them, the actual stitch cam values is obtained. Memory 44 stores a loop length routine program. This routine is executed before the actual knitting of a garment. The specified standard yarn length and the actually consumed yarn length are compared, for example for each course, by the yarn length comparator 33. The correction data generator 32 corrects the stitch cam adjustment values so that the consumed yarn length equals the standard yarn length with a precision of, for example, ±1%. The stitch cam adjustment values at the time of completion of the loop length routine are the initial values of the stitch cam adjustment table. The loop length routine requests the user to specify the desired combinations of yarns (actually yarn feeders 8) and knitting locks to be used together with the knitting types, single, double and triple. The routine is executed for the specified combinations. The knitting data may be read by the control block 30 prior to the execution of the loop length routine to determine the combinations of yarn feeders 8 and knitting locks to be used. Then the loop length routine can be done for the combinations thus determined. A yarn length detector 9 outputs the yarn length of a yarn 6 fed by a yarn feeder 8 as a number of pulses. The yarn length encoder 52 converts the number of pulses into a consumed yarn length and inputs the consumed yarn length into the yarn length comparator 33. The yarn length comparator 33 compares the consumed yarn length with the standard yarn length based on the loop length contained in the knitting data. The correction data generator 32 corrects the stitch cam adjustment values according to the results of comparison. For simplicity, we assume that the knitting data specify a constant loop length, and ignore the stitch cam data memory 43. On the basis of the correction of the stitch cam adjustment values, the motor drive 53 controls the stitch cam adjustment motors 24 to adjust the heights of the respective stitch cams 22A, 22B. In the course of knitting, the yarn length comparator 33 compares the standard yarn length and the consumed yarn length for, for example, every course. Then according to the difference between them, the correction data generator 32 corrects the stitch cam adjustment value by a unit of, for example, +1. The correction of the stitch cam adjustment table 42 is made for a plurality of stitch cams relative to one yarn feeder 8 as a unit. A yarn feeder 8 has one to one correspondence to a yarn. Assume, for example, that as a result of the yarn length measurement it is necessary to correct the stitch cam adjustment values by +1 for the combination of the onward stitch cam 22A of the knitting lock L of the front carriage 20 and the second yarn feeder. In Fig. 4, this correcting value +1 is also applied to the combination of the stitch cam 22A of the knitting lock L, of the rear carriage 21 and the second yarn feeder. The same correcting value is also applied to the onward stitch cams 22A of the knitting locks R, irrespective of the front carrier 20 and the rear carrier 31. The reason of applying the result at the knitting lock L to the knitting lock R only is that the knitting lock R alone uses the second yarn feeder among other knitting locks. Every stitch cam of the front carriage 20 and the stitch cam in the corresponding position of the rear carriage 21 share a common stitch cam adjustment value for the same yarn. The stitch cam adjustment values of the six onward stitch cams 22A may be uniformly adjusted by +1 relative to the second yarn feeder, irrespective of the front carriage 20 and the rear carriage 21 of Fig. 2. The scope of correction may be limited to the three onward stitch cams 22A of the front carriage 20; thus the front carriage 20 and the rear carriage 21 may be treated separately. Moreover, all the 12 stitch cams 22A, 22B may be uniformly corrected by +1 at a time relative to the yarn feeder 8, irrespective of the onward and rearward types. When the yarn feeder 8 is used on the onward side, the yarn feeder 8 may be used in many cases on the rearward side for some preceding or following courses. In such a case, the measurement of the consumed yarn length for a rearward course gives correcting values of the stitch cam adjustment values. Hence there is no need to apply the correcting values for stitch cam adjustment values determined for the onward side to the stitch cams 22B on the rearward side. Moreover, when the tension in the yarn is increased, if we assume that the yarn is fed from the left of Fig. 1, the loop length will be decreased on the onward side, and the loop length will be increased on the rearward side. Hence in such a case, the stitch cam adjustment values on the onward side must be corrected in a direction opposite to those on the rearward side. It is, therefore, desirable to update the stitch cam adjustment values of the onward stitch cams 22A independently of those of the rearward stitch cams 22B. It should be noted that the initial values of the stitch cam adjustment values determined by the loop length routine vary from stitch cam to stitch cam. Hence the stitch cam adjustment values are varied, reflecting the differences of their initial values. The control of the stitch cam adjustment values does not necessarily require the use of the stitch cam adjustment table 42 of Fig. 4. For example, the stitch cam adjustment table 42 may store the initial values of the stitch cam adjustment values obtained by the loop length routine. Then the correcting values for the stitch cam adjustment values are stored for the onward stitch cams and the rearward stitch cams, respectively, relative to each yarn feeder as a unit. When these data are added to the data of the stitch cam adjustment table, we will obtain the same stitch cam adjustment values as those of Fig. 4. A case of knitting, for example, a V-necked sweater by using the above-mentioned embodiment will be described. Fig. 5 shows the relationship between the yarn (yarn feeder number) and the knitting lock when the front body of the V-necked sweater is knitted. A mark P indicates an area from the end of the bottom rib to the V-neck formation portion (not inclusive). In this area, the left and right knitting locks R, L are used to produce double knitting. The leading knitting lock (R when travelling to the right, and L when travelling to the left) uses the second yarn. The trailing knitting lock (L when travelling to the right, and R when travelling to the left) uses the third yarn. The knitting locks to be used for the respective yarns are switched over at every turn of the knitting direction. For example, the knitting lock R uses the second yarn feeder during onward travelling (travelling to the right), and the knitting lock L uses the second yarn feeder during rearward travelling (travelling to the left). As double knitting is used, two courses of stitches are formed in the body for every traverse of the carriage. The V-neck formation area Q is of single knitting. The knitting lock L and the second yarn are used for the right half portion, and the knitting lock R and the third yarn are used for the left half portion. In the area Q, the same knitting lock is assigned to one yarn for both the rightward and leftward movements, and one course of stitches on the left and one course of stitches on the right of the neck are formed by every traverse of the carriage. In Fig. 5, the front body of the sweater is seen from your side. Thus the right half portion of the sweater is shown on the left of the diagram. Fig. 6 shows the processes of knitting the above-mentioned garment. In Step 1, the process starts. For example, the user specifies the combinations of yarn feeders and knitting locks to be used. In Step 2, prior to knitting the actual garment (V-necked sweater), the loop length routine is executed. In this routine, yarns to be used for the garment are used to determine stitch cam adjustment values for producing loops of the specified loop lengths. In the example of Fig. 5, stitch cam adjustment is made for the knitting lock R (for rightward movement) and the knitting lock L (for leftward movement) relative to the second yarn and for the knitting lock L (for rightward movement) and the knitting lock R (for leftward movement) relative to the third yarn for double knitting. The initial values of stitch cam adjustment values are determined to obtain the desired loop lengths, and these initial values are stored in the columns of double knitting of the stitch cam adjustment table 42. In a similar manner, stitch cam adjustment is made, in single knitting, for the knitting lock L (both the rightward and leftward movements) relative to the second yarn, and for the knitting lock R (both the rightward and leftward movements) relative to the third yarn. The stitch cam adjustment values thus determined by single knitting are stored in the columns of single knitting of the stitch cam adjustment table 42. The stitch cam adjustment values are determined by distinguishing the onward stitch cams and the rearward stitch cams, namely, 22A and 22B, and the consumed yarn lengths are measured for the onward side and the rearward side, respectively. The stitch cam adjustment values relative to other yarns and the stitch cam adjustment values for the knitting lock C remain to be zero, default value. To economize the consumption of the yarns in the loop length routine, the loop length routine may be executed for a part of combinations of the yarns and the stitch cams to be used. For the remaining combinations, appropriate values may be estimated from the stitch cam adjustment values determined by the loop length routine. In Step 3, the stitch cam adjustment values of the respective combinations of yarns and stitch cams are used to knit an actual garment. In Fig. 6, i indicates the course number, and i = 0 is the initial value. For example, when one course is knitted, the course number i will be incremented by 1 (Step 4). The consumed yarn length of the course and the standard yarn length are compared with each other (Step 5). If the difference is not within a specified range, the correction data generator 32 updates the stitch cam adjustment values (Step 6). For example, the yarn length of the second yarn consumed by the knitting lock R (stitch cam 22A) is measured in the rightward knitting course and compared with the standard yarn length. If the difference is not within the specified range, the stitch cam adjustment value is corrected by +1 or -1. This correction is given to the stitch cam adjustment value of the stitch cam 22A of the knitting lock R in the double knitting column of the stitch cam adjustment table 42, and to the stitch cam adjustment value of the stitch cam 22A of the knitting lock L in the single knitting column of the table 42. If there are any other combinations of the second yarn and the stitch cam 22A or 22B, the same correction is given to their stitch cam adjustment values. In a similar manner, the stitch cam adjustment values on the leftward side relative to the second yarn are corrected. For example, on the basis of the consumed yarn length (double) of the stitch cam 22B of the knitting lock L in the area P the stitch cam adjustment value of the stitch cam 22B (double and single) of the knitting lock L is corrected. Similar correction of stitch cam adjustment values is given relative to the third yarn. On the basis of the consumed yarn length (double) of the stitch cam 22A of the knitting lock L in the area P, the stitch cam adjustment value of the stitch cam 22A of the knitting lock L for double knitting and the stitch cam adjustment value of the stitch cam 22A of the knitting lock R for single knitting are corrected. Moreover, on the basis of the consumed yarn length of the stitch cam 22B (double) of the knitting lock A in the area P, the stitch cam adjustment value of the stitch cam 22B (double and single) of the knitting lock A is corrected. As a result of these operations, during the knitting of the area P of Fig. 5, the stitch cam adjustment values are corrected for knitting of the area Q. In the V-neck area Q, the second yarn is processed by the knitting lock L in both the rightward and leftward movements. Of these movements, the leftward movement is identical to that in the area P, except for the difference between single and double knitting. Hence for this portion, the correction may be given by the same values to the stitch cam adjustment values by ignoring the difference between single knitting and double knitting. A problem here is that the knitting lock L is used for the rightward movement in the area Q whereas the knitting lock R is used for the rightward movement in the area P. In the embodiment, correction to the stitch cam adjustment value is given relative to the use of the knitting lock L for the rightward movement in the area Q according to the result of the use of the knitting lock R for the rightward movement in the area P. As a result, the effects of various factors of fluctuation for the period from the start of the knitting till the arrival at the area Q have already been processed. Hence when the knitting lock L uses the second yarn to knit in the rightward direction in the area Q, no knitting gap will be generated because of the loop length differing from other portions. The conventional methods generate a knitting gap along the boundary between the area P and the area Q since for the rightward knitting of the second yarn for example, the stitch cam adjustment value at the time of execution of loop length routine is effective in the area Q, and changes in the knitting conditions in the area P, etc. are not considered at all. This also applies to the third yarn. The results of knitting by the knitting lock L in the area P are fed back to the knitting lock R for the area Q; the loop length of the stitches of the rightward knitting of the third yarn will not change abruptly at the start of the area Q. It should be noted that the design of Fig. 5 is one that cannot be knitted by the conventional yarn length control. The use of any conventional methods will generate knitting gaps at a considerable frequency. The inventor has confirmed that, by means of the embodiment described herein, the generation of knitting gaps along the boundary of the area P and the area Q of the design of Fig. 5 can be prevented. Moreover, the inventor has also confirmed that when assignment of knitting locks for the second and third yarns is frequently alternated in the area P, for example, in a design for which the knitting locks R, L are alternately used for rightward knitting of the second yarn, the embodiment can make satisfactory knitting without any troubles such as oscillation of the stitch cam adjustment values. The correction of stitch cam adjustment values is made similarly in the area Q. The correcting value for the stitch cam 22A obtained by the knitting lock L relative to the second yarn is substituted to the column of the stitch cam 22A of the knitting lock R. Similarly, a correcting value for the stitch cam 22B obtained by the knitting lock L is substituted to the column of the stitch cam 22B of the knitting lock R, etc. Moreover, When a correction is made to stitch cam adjustment data of any one of the types single, double and triple, a correction is also given to the stitch cam adjustment values of the same stitch cams of other types relative to the same yarn. In the embodiment, the front and rear carriages 20, 21 have the common stitch cam adjustment values. Step 7 checks whether all the courses of knitting the garment are completed. If there is a subsequent knitting course or courses, it returns to Step 4 to continue knitting. When it is confirmed by Step 7 that all courses are completed, it moves to Step 8 to complete knitting of the garment. In the following, a second embodiment will be described. For this embodiment, it is desirable to use a flat knitting machine which is provided with a buffer such as a well-known yarn retainer between a cone and a yarn feeder so that knitting can be made by keeping the tensions in the respective yarns constant during knitting. The garment to be knitted in the present embodiment is identical to that of Fig. 5 except a fourth yarn is used for the right body and a fifth yarn is used for the left body in the knitting area Q, The knitting procedures are identical to those of Fig. 6 except Step 6 has been changed. In Step 1, the process starts. In Step 2, prior to knitting an actual garment, the loop length routine 44 is executed to determine stitch cam adjustment data for the respective stitch cams of the respective knitting locks relative to the respective yarns. Next, in Step 3, the stitch cam adjustment values relative to the respective yarns obtained above are used to start knitting an actual garment (i = 0 at this time, and i indicates the knitting course). In Step 4, the (i+1)th course is knitted, and the consumed yarn length of the yarn for a specified range is measured for each knitting lock by the yarn length detector. In Step 5, the yarn length comparator 33 compares the consumed yarn length with the standard yarn length, and if the difference is outside the specified range, the correction data generator 32 updates the stitch cam adjustment value in Step 6. In the rightward knitting courses, the yarn length of the second yarn consumed by the knitting lock R (stitch cam 22A) is compared with the standard yarn length, and if the difference is outside the specified range, the stitch cam adjustment value is corrected by +1 or -1. The newly obtained adjustment value is added to the adjustment value of the stitch cam 22A of the knitting lock R stored in the stitch cam adjustment table 42 so as to update the adjustment value. At the same time, the newly obtained stitch cam adjustment value is added to the adjustment value of the stitch cam of the same direction relative to the fifth yarn (the stitch cam 22A of the knitting lock R) so as to update the adjustment value. Similarly, the stitch cam adjustment value of the stitch cam 22A of the knitting lock L relative to the third yarn is updated, and at the same time, the stitch cam adjustment value of the stitch cam 22A of the knitting lock L relative to the fourth yarn is corrected by the same value. In the leftward knitting courses, the updating of the stitch cam adjustment values is similar to that in the rightward knitting courses. The correcting value for the stitch cam adjustment value obtained by the stitch cam 22B of the knitting lock L relative to the second yarn is applied to the same stitch cam 22B of the same knitting lock L relative to the fourth yarn. Similarly, the correcting value for the stitch cam adjustment value obtained by the stitch cam 22B of the knitting lock R relative to the third yarn is applied to the same stitch cam 22B of the same knitting lock R relative to the fifth yarn. If the stitch cam adjustment values are updated in the above-mentioned manner, when the V-neck formation area Q is knitted, the stitch cam adjustment values of the knitting lock L relative to the fourth yarn and the stitch cam adjustment values of the knitting lock R relative to the fifth yarn have been updated in the knitting area P. Hence at the time of switchover from the area P to the area Q the stitch cam adjustment values stored at the time of execution of the loop length routine do not work as is the case of the conventional methods, and knitting is continued under the current knitting parameters. As a result, generation of any knitting gaps can be prevented. Subsequent Step 7 and Step 8 are processed similarly to the first embodiment. Preferred embodiments of the present invention have been described. It should be noted, however, that the present invention is not limited in any way to the embodiments. For instance measurement of the yarn length may be done for every plural courses rather than for every single course. The method of measuring the yarn length itself is discretionary. What is preferred with regard to the measurement of the yarn length is separate measurement of the onward side and the rearward side and separate correction of the stitch cam adjustment values of the onward side and the rearward side. In the embodiments, the case of a single carriage 3 is shown, but a plurality of carriages may be provided on the needle beds. In this case, three carriages may be used in correspondence with the knitting locks L, C and R, or two carriages in correspondence with the knitting locks L and R.

Claims: A yarn length control system for a flat knitting machine (1), wherein a plurality of yarns (6) are fed from yarn feeding means (8) to at least one needle bed (2), said needle bed (2) is provided with a plurality of knitting locks (20A,20B,20C,21A,21B,21C), each knitting lock has a pair of an onward stitch cam (22A) and a rearward stitch cam (22B), each knitting lock operates the needle bed (2) to form series of stitches from the fed yarns, and the respective stitch cam positions are corrected by the stitch cam adjustment data to alter the stitch size, said yarn length control system comprising: a measuring means (9) for measuring the consumption of each yarn (6); a comparing means (33) for comparing the measured consumption with the standard yarn length; and an adjusting means (32) which generates correcting data for the stitch cam adjustment data according to the results of comparison by the comparing means (33) and corrects, by the above-mentioned correcting data, the position of at least one stitch cam of the knitting lock that operated the needle bed (2) for the yarn of which consumption was measured, relative to the yarn, characterized in that said adjusting means (32) corrects, by said correcting data, at least one stitch cam datum of one other knitting lock, relative to said yarn. A yarn length control system as claimed in Claim 1, wherein at least one stitch cam (22A,22B) of a knitting lock which operated the above-mentioned needle bed and at least one stitch cam (22A,22B) of said other knitting lock have the same direction for the onward/rearward movement. A yarn length control system as claimed in Claim 2, wherein the yarn length control system has a memory means (42) for storing stitch cam adjustment data for each pair of a stitch cam and a yarn as a unit. A yarn length control system as claimed in any of claims 1, 2 or 3, wherein the flat knitting machine has a single carriage (3) and said respective knitting locks are contained in said carriage. A yarn length control system as claimed in any of claims 1, 2 or 3, wherein the respective knitting locks are contained in separate carriages. A yarn length control system for a flat knitting machine (1), wherein a plurality of yarns (6) are fed from yarn feeding means (8) to at least one needle bed (2), said needle bed (2) is provided with a plurality of knitting locks (20A,20B,20C,21A,21B,21C), each knitting lock has a pair of an onward stitch cam (22A) and a rearward stitch cam (22B), each knitting lock operates the needle bed (2) to form series of stitches from the fed yarns, and the respective stitch cam positions are corrected by the stitch cam adjustment data to alter the stitch size, said yarn length control system comprising: a measuring means (9) for measuring the consumption of each yarn (6) ; a comparing means (33) for comparing the measured consumption with the standard yarn length; and an adjusting means (32) which generates correcting data for the stitch cam adjustment data according to the results of comparison by the comparing means (33) and corrects, by the above-mentioned correcting data, the position of at least one stitch cam of the knitting lock that operated the needle bed (2) for the yarn of which consumption was measured, relative to the yarn, characterized in that said adjusting means (32) corrects, by said correcting data, said stitch cam data of the knitting lock which operated the needle bed for the yarn of which consumption was measured, relative to other yarns. A flat knitting machine (1), wherein a plurality of yarns (6) are fed to a needle bed having a plurality of knitting locks (20A,20B,20C,21A,21B,21C), the knitting locks having stitch cams (22A,22B) arranged to operate the needle bed to form stitches from the yarns (6), the respective stitch cam positions being correctable by stitch cam adjustment data to alter the stitch size, the machine further comprising: a measuring means (9) for measuring the consumption of one of the yarns (6); a comparing means (33) for comparing the measured consumption with a predetermined standard; and an adjusting means (32) arranged to generate correcting data for the stitch cam adjustment data dependent on the results from the comparing means (33) and thereby to correct the position of at least one stitch cam of the knitting lock that operated the needle bed (2) for the yarn of which consumption was measured, relative to the yarn, characterised in that said adjusting means (32) is also arranged to correct at least one stitch cam datum of one other knitting lock, relative to said yarn or said stitch cam data of the knitting lock which operated the needle bed for the yarn of which consumption was measured, relative to other yarns. A flat knitting machine (1) as claimed in claim 7 operating in accordance with the system of any of claims 1 to 6. A method of operating a knitting machine (1) comprising the steps of: a) measuring the consumption of a yarn (6) caused by a stitch cam (22A,22B) of a first knitting lock; b) comparing the measured yarn consumption with a pre-determined standard and thereby adjusting the position of the stitch cam in order to make the actual yarn consumption closer to the pre-determined standard, charaterised in that either the position of a stitch cam of a second knitting lock is also adjusted relative to the same yarn or the position of the stitch cam of the first lock is also adjusted relative to other yarn(s). A method as claimed in claim 9 using the flat knitting machine of claim 7 or 8.

Inventors: KOMURA YOSHIYUKI, NISHITANI HIROKAZU, KOMURA, YOSHIYUKI, NISHITANI, HIROKAZU
Applicants: SHIMA SEIKI MFG, SHIMA SEIKI MANUFACTURING, LTD.
Application year: 1996
Main classification: D04B7
IPC codes: D04B15