METHOD AND APPARATUS FOR DETERMINING THE KNITABILITY OF YARNS
United States Patent 3757536
This invention mounts the stitch cam of a tubular knitting machine on a tongue and measures the strain of the tongue as a function of the load imposed on the stitch cam by the yarn coming into the machine to be knit. Tension of the yarn running to the machine is controlled and monitored.
Application Number:
05/019819
Publication Date:
09/11/1973
Filing Date:
03/16/1970
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Export Citation:
Assignee:
Dixie Yarns, Inc. (Chattanooga, TN)
Primary Class:
Other Classes:
66/146, 66/54, 73/160, 66/57
International Classes:
D04B15/38; D04B15/32; D04B1/00; D04B15/44
Field of Search:
73/144,9,160 66/146,1,54,8,154A,57 242/155M
Other References:
Knapton and Munden, A Study of The Mechanism of Loop Formation on Weft Knitting Machinery, Textile Research Journal, Dec. 1966, pp. 1081-1091. .
Knapton, Knitting Performance of Wool Yarns: Instrumentation Studies, Textile Research Journal, July 1967, pp. 539-551. .
Henshaw, Cam Forces in Weft Knitting, Textile Research Journal, June 1968, pp. 592-598..
Primary Examiner:
Reynolds, Wm Carter
Claims:
What is claimed is
1. A method of determining knitability of yarn that comprises: supplying yarn under conditions of controlled tension to needles slidably mounted on a needle bed of a knitting machine for movement along a cam track; serially engaging contiguous groups of said needles by a stitch cam in said track of said knitting machine at a yarn engaging level of said needles such that needles of each group simultaneously engage said stitch cam; driving said needles by said stitch cam from said yarn engaging level to a knockover level of said needles; and measuring the vertical component of the load imposed on said stitch cam in drawing down the needles from said yarn engaging level at least to said knockover level while maintaining the tension on said yarn supplied to said needles constant while the load on said cam is being measured.
2. The method according to claim 1, comprising the further steps of supplying said yarn to said needles through a yarn guide and monitoring the tension imposed on said yarn guide by the movement of the yarn therethrough while measuring the load imposed on said stitch cam during drawdown.
3. For use in a knitting machine having a needle bed with needles slidably mounted thereon for movement along a cam track of said knitting machine, yarn being supplied to said needles under conditions of controlled tension, apparatus for measuring the load imposed on said needles during drawdown, comprising:
4. The apparatus according to claim 3, wherein said measuring means comprises: a member fixed at one end against movement relative to said knitting machine, the other end of said member being unsupported to permit movement thereof relative to said mqchine, said stitch cam being mounted on said other end; and means to measure the strain on said member resulting from stress imposed by said needles on said cam.
1. A method of determining knitability of yarn that comprises: supplying yarn under conditions of controlled tension to needles slidably mounted on a needle bed of a knitting machine for movement along a cam track; serially engaging contiguous groups of said needles by a stitch cam in said track of said knitting machine at a yarn engaging level of said needles such that needles of each group simultaneously engage said stitch cam; driving said needles by said stitch cam from said yarn engaging level to a knockover level of said needles; and measuring the vertical component of the load imposed on said stitch cam in drawing down the needles from said yarn engaging level at least to said knockover level while maintaining the tension on said yarn supplied to said needles constant while the load on said cam is being measured.
2. The method according to claim 1, comprising the further steps of supplying said yarn to said needles through a yarn guide and monitoring the tension imposed on said yarn guide by the movement of the yarn therethrough while measuring the load imposed on said stitch cam during drawdown.
3. For use in a knitting machine having a needle bed with needles slidably mounted thereon for movement along a cam track of said knitting machine, yarn being supplied to said needles under conditions of controlled tension, apparatus for measuring the load imposed on said needles during drawdown, comprising:
4. The apparatus according to claim 3, wherein said measuring means comprises: a member fixed at one end against movement relative to said knitting machine, the other end of said member being unsupported to permit movement thereof relative to said mqchine, said stitch cam being mounted on said other end; and means to measure the strain on said member resulting from stress imposed by said needles on said cam.
Description:
This invention relates to methods and apparatus for testing yarns to determine their suitability for knitting.
It is recognized in the textile industry that knitting, although old in the art, is still plagued by multitudinous variables that affect in one form or another the performance of the yarn in knitting and, of course, the quality, appearance, and dimensions of the finished fabric. At the present time the reasons why these variables affect production and how they can be controlled is but little known. While efforts have been made to develop testing techniques which will hopefully give the knitter a way of measuring or predetermining the knitability of any particular yarn, no technique heretofore known is sufficiently sensitive to produce data from which knitability can be predicted. This is true even though it has been proposed, as a part of the prior art, to use the knitting machine itself as a testing apparatus to determine yarns which are suitable for knitting therein. The prior art includes proposals continuously to measure and to record the power consumption of a knitting machine so as to indicate as a function of fluctuation in power demand, variations in tension or other lack of uniformity on the part of a yarn subjected to test. It has also been proposed continuously to measure the output torque of the motor which drives a knitting machine, again to give an indication of variations of yarn knitability as a function of torque variation. The results achieved by these efforts to use the knitting machine as an instrument for determining knitability have been disappointing perhaps because the measurements encompass too many variable in addition to the yarn itself.
It is therefore an object of the present invention to overcome these disadvantages and to provide a very sensitive and accurate means of measuring knitability while, at the same time, by the use of the knitting machine itself avoiding the inaccuracies which result from taking the measurement at a point too remote in the machine driving mechanism from the needles which pull the new yarn into the machine to be knit.
It is also an object of this invention to measure knitability by sensing directly a function of the strain imposed upon the very portions of the knitting machine which draw the yarn into it and so to eliminate any inaccuracies resulting from the presence of a train of machine parts between a point of measurement and a point of introduction of the yarn into the machine.
Another object of this invention is to eliminate variations in the tension of the yarn being fed to a knitting machine so that variations in the measured load on the knitting machine are confined to those variations caused by variation of yarn properties.
Other objects and advantages of the present invention will be apparent upon consideration of the following detailed description of several embodiments thereof in conjunction with the annexed drawings wherein:
FIG. 1 is a view in vertical section of a device according to the present invention for detecting and recording the load imposed upon the stitch cam of a knitting machine in actuating the needles which draw the yarn into the machine to be knit;
FIG. 2 is a view in transverse section taken on the line 2--2 of FIG. 1;
FIG. 3 is a schematic view showing an arrangement according to the present invention for maintaining uniform the tension of the yarn running to the knitting machine and for monitoring same;
FIG. 4 is a schematic view of a modified arrangement in which the yarn is fed to the guide from which the yarn is drawn into the machine under controlled and monitored tension and in which the variations in drag imposed by said guide are measured and recorded; and
FIG. 5 is a graph representing a typical use of the present invention in evaluating the quality and uniformity of application of a yarn lubricant.
Referring now in greater detail to FIGS. 1 and 2, the numeral 10 designates the stitch cam of a tubular knitting machine of the type in which the needles are moved in a circular cam track or path in respect to a stationary cam which, in the course of the needle movement through the circular path, serially engages and changes the vertical position of the needles to pull the yarn into the machine from a yarn engaging level to a knockover level and beyond and to effect the loop engagements and releases of the knitting operation. The cam 10 is shown in FIG. 1 in relation to a single needle 11. Both the cam and the needle are of entirely conventional construction. However, the manner of mounting of the cam 10 forms an important part of the present invention. The cam 10 is attached to a metal tongue 12 which is cantilever supported from a frame having an upper plate 13, a lower plate 14, and compression blocks 15 and 16 held together by bolts 17 in such a way that the tongue 12 is very rigidly held in the machine, but, because of the cantilever support, is subject to some strain as a result of the stress imposed by the needles on the cam 10. It is this strain that is used as an index of the load that is being imposed upon the yarn running to the machine and, in order to measure the strain, there is located a strain gauge 18 mounted on the upper plate 13 of the frame which supports tongue 12. Strain gauge 18 does not itself form part of the present invention but is manufactured by Statham Instruments, Inc., of Los Angeles, Calif. This type of strain gauge has a probe 19 which senses the strain encountered by the tongue 12 and is internally a transducer which puts out an electric signal proportional to the magnitude of the displacement of the probe 19 which in turn is proportional to the magnitude of the strain of tongue 12. This signal is amplified in a bridge amplifier 20 schematically shown in FIG. 1 and the output of the amplifier 20 is recorded by conventional means indicated at reference numeral 21.
In experimental work a Statham bridge amplifier model SC 1100 has been used as the amplifier in the position 20. Parts 18 and 20 are described in unnumbered Product Bulletin of March 1967 for the transducer 18 and Product Bulletin No. SC 101 of June 1967 for the bridge amplifier 20.
It can be seen upon reference to FIGS. 1 and 2 that the load imposed on the yarn in drawing the same into the knitting machine is directly transferred in terms of stress to the tongue 12. The resulting strain of tongue 12 which is recorded at 21 is very accurate and completely free of error such as might result from a strain measurement taken remote from the point of application of the stress. Furthermore, by making the tongue 12 wide in relation to the probe 19 error which could result from lateral stress caused by the movement of the needles in a circular path is prevented.
In FIG. 3 there is shown an arrangement which is used in feeding the yarn to the needles 11. In FIG. 3 not only the needle 11 connected to the stitch cam and strain gauge similarly as shown in FIG. 1 but several adjacent needles 11a, 11b, and 11c of a group are shown. The yarn passes to the machine from a source 22 through a Lawson-Hemphill Universal Compensating Tension Device 23 described in U.S. Pat. No. 3,575,360, and from that device passes over sheaves 24 and 25 to the needle 11. Sheave 25 is mounted in a yoke 26 which is connected to another Statham transducing cell 27 similar to the cell 18. Thus the yarn running between the sheave 24 and the needle 11 is furnished at a reliable accurate tension which is continuously monitored by the transducer 27 which may be connected through an amplifier to a recording device such as is shown at 21 in FIG. 1.
A further modification of this invention is shown in FIG. 4 wherein there is provision for measuring the tension variations which are produced by the eyelet which in the yarn path immediately precedes the first needle. In the arrangement of FIG. 4 the yarn source bears numeral 28 and the yarn passes from this source over a sheave 29 which may be either an idler or a Lawson-Hemphill Universal Compensating Tension Device. The Lawson-Hemphill device imposes a controllable drag on the yarn through a spring drum clutch. From the sheave 29 the yarn passes over a sheave 30 and then through a stationary guide 31 to the first needle 11 of the knitting machine. Needles 11 engage a stitch cam and cooperating measuring device in the same manner as shown in FIG. 1. The sheave 30 is connected to a Statham transducing cell 32 similar in structure and function to the cell 27, and the eyelet 31 is also connected to a transducing cell 33 of the same type. By the arrangement of FIG. 4 one is able to determine the precise effect of drags imposed by the eyelet 31 and, of course, differences in yarn such for example as might result from lack of uniformity in the application of the yarn lubricant.
Some interesting results achieved by the use of this invention are depicted in FIG. 5. In the figure, the abscissa represents various types and applications of finish whereas the ordinate represents load on the stitch cam as measured by the equipment of the present invention. By the use of this apparatus it has been possible to measure the efficacy of certain types of yarn lubricants; and if one will compare the solid line of the graph with the broken line, it can be seen that yarns of different types refinished with one of the lubricants are very uniform in their behavior in the knitting machine whereas different lubricants produced very different loads on the stitch cam. The results were found to correlate when the same yarns were used in knitting.
It is recognized in the textile industry that knitting, although old in the art, is still plagued by multitudinous variables that affect in one form or another the performance of the yarn in knitting and, of course, the quality, appearance, and dimensions of the finished fabric. At the present time the reasons why these variables affect production and how they can be controlled is but little known. While efforts have been made to develop testing techniques which will hopefully give the knitter a way of measuring or predetermining the knitability of any particular yarn, no technique heretofore known is sufficiently sensitive to produce data from which knitability can be predicted. This is true even though it has been proposed, as a part of the prior art, to use the knitting machine itself as a testing apparatus to determine yarns which are suitable for knitting therein. The prior art includes proposals continuously to measure and to record the power consumption of a knitting machine so as to indicate as a function of fluctuation in power demand, variations in tension or other lack of uniformity on the part of a yarn subjected to test. It has also been proposed continuously to measure the output torque of the motor which drives a knitting machine, again to give an indication of variations of yarn knitability as a function of torque variation. The results achieved by these efforts to use the knitting machine as an instrument for determining knitability have been disappointing perhaps because the measurements encompass too many variable in addition to the yarn itself.
It is therefore an object of the present invention to overcome these disadvantages and to provide a very sensitive and accurate means of measuring knitability while, at the same time, by the use of the knitting machine itself avoiding the inaccuracies which result from taking the measurement at a point too remote in the machine driving mechanism from the needles which pull the new yarn into the machine to be knit.
It is also an object of this invention to measure knitability by sensing directly a function of the strain imposed upon the very portions of the knitting machine which draw the yarn into it and so to eliminate any inaccuracies resulting from the presence of a train of machine parts between a point of measurement and a point of introduction of the yarn into the machine.
Another object of this invention is to eliminate variations in the tension of the yarn being fed to a knitting machine so that variations in the measured load on the knitting machine are confined to those variations caused by variation of yarn properties.
Other objects and advantages of the present invention will be apparent upon consideration of the following detailed description of several embodiments thereof in conjunction with the annexed drawings wherein:
FIG. 1 is a view in vertical section of a device according to the present invention for detecting and recording the load imposed upon the stitch cam of a knitting machine in actuating the needles which draw the yarn into the machine to be knit;
FIG. 2 is a view in transverse section taken on the line 2--2 of FIG. 1;
FIG. 3 is a schematic view showing an arrangement according to the present invention for maintaining uniform the tension of the yarn running to the knitting machine and for monitoring same;
FIG. 4 is a schematic view of a modified arrangement in which the yarn is fed to the guide from which the yarn is drawn into the machine under controlled and monitored tension and in which the variations in drag imposed by said guide are measured and recorded; and
FIG. 5 is a graph representing a typical use of the present invention in evaluating the quality and uniformity of application of a yarn lubricant.
Referring now in greater detail to FIGS. 1 and 2, the numeral 10 designates the stitch cam of a tubular knitting machine of the type in which the needles are moved in a circular cam track or path in respect to a stationary cam which, in the course of the needle movement through the circular path, serially engages and changes the vertical position of the needles to pull the yarn into the machine from a yarn engaging level to a knockover level and beyond and to effect the loop engagements and releases of the knitting operation. The cam 10 is shown in FIG. 1 in relation to a single needle 11. Both the cam and the needle are of entirely conventional construction. However, the manner of mounting of the cam 10 forms an important part of the present invention. The cam 10 is attached to a metal tongue 12 which is cantilever supported from a frame having an upper plate 13, a lower plate 14, and compression blocks 15 and 16 held together by bolts 17 in such a way that the tongue 12 is very rigidly held in the machine, but, because of the cantilever support, is subject to some strain as a result of the stress imposed by the needles on the cam 10. It is this strain that is used as an index of the load that is being imposed upon the yarn running to the machine and, in order to measure the strain, there is located a strain gauge 18 mounted on the upper plate 13 of the frame which supports tongue 12. Strain gauge 18 does not itself form part of the present invention but is manufactured by Statham Instruments, Inc., of Los Angeles, Calif. This type of strain gauge has a probe 19 which senses the strain encountered by the tongue 12 and is internally a transducer which puts out an electric signal proportional to the magnitude of the displacement of the probe 19 which in turn is proportional to the magnitude of the strain of tongue 12. This signal is amplified in a bridge amplifier 20 schematically shown in FIG. 1 and the output of the amplifier 20 is recorded by conventional means indicated at reference numeral 21.
In experimental work a Statham bridge amplifier model SC 1100 has been used as the amplifier in the position 20. Parts 18 and 20 are described in unnumbered Product Bulletin of March 1967 for the transducer 18 and Product Bulletin No. SC 101 of June 1967 for the bridge amplifier 20.
It can be seen upon reference to FIGS. 1 and 2 that the load imposed on the yarn in drawing the same into the knitting machine is directly transferred in terms of stress to the tongue 12. The resulting strain of tongue 12 which is recorded at 21 is very accurate and completely free of error such as might result from a strain measurement taken remote from the point of application of the stress. Furthermore, by making the tongue 12 wide in relation to the probe 19 error which could result from lateral stress caused by the movement of the needles in a circular path is prevented.
In FIG. 3 there is shown an arrangement which is used in feeding the yarn to the needles 11. In FIG. 3 not only the needle 11 connected to the stitch cam and strain gauge similarly as shown in FIG. 1 but several adjacent needles 11a, 11b, and 11c of a group are shown. The yarn passes to the machine from a source 22 through a Lawson-Hemphill Universal Compensating Tension Device 23 described in U.S. Pat. No. 3,575,360, and from that device passes over sheaves 24 and 25 to the needle 11. Sheave 25 is mounted in a yoke 26 which is connected to another Statham transducing cell 27 similar to the cell 18. Thus the yarn running between the sheave 24 and the needle 11 is furnished at a reliable accurate tension which is continuously monitored by the transducer 27 which may be connected through an amplifier to a recording device such as is shown at 21 in FIG. 1.
A further modification of this invention is shown in FIG. 4 wherein there is provision for measuring the tension variations which are produced by the eyelet which in the yarn path immediately precedes the first needle. In the arrangement of FIG. 4 the yarn source bears numeral 28 and the yarn passes from this source over a sheave 29 which may be either an idler or a Lawson-Hemphill Universal Compensating Tension Device. The Lawson-Hemphill device imposes a controllable drag on the yarn through a spring drum clutch. From the sheave 29 the yarn passes over a sheave 30 and then through a stationary guide 31 to the first needle 11 of the knitting machine. Needles 11 engage a stitch cam and cooperating measuring device in the same manner as shown in FIG. 1. The sheave 30 is connected to a Statham transducing cell 32 similar in structure and function to the cell 27, and the eyelet 31 is also connected to a transducing cell 33 of the same type. By the arrangement of FIG. 4 one is able to determine the precise effect of drags imposed by the eyelet 31 and, of course, differences in yarn such for example as might result from lack of uniformity in the application of the yarn lubricant.
Some interesting results achieved by the use of this invention are depicted in FIG. 5. In the figure, the abscissa represents various types and applications of finish whereas the ordinate represents load on the stitch cam as measured by the equipment of the present invention. By the use of this apparatus it has been possible to measure the efficacy of certain types of yarn lubricants; and if one will compare the solid line of the graph with the broken line, it can be seen that yarns of different types refinished with one of the lubricants are very uniform in their behavior in the knitting machine whereas different lubricants produced very different loads on the stitch cam. The results were found to correlate when the same yarns were used in knitting.