Europaisches Patentamt J European Patent Office © Publication number: 0 652 314 A1 Office europeen des brevets EUROPEAN PATENT APPLICATION © Application number: 94117387.4 Int. CI 6 D04B 9/06 @ Date of filing: 04.11.94 ® Priority: 04.11.93 JP 301323/93 Takatsuki Osaka (JP) @ Date of publication of application: Inventor: Igarashi, Yoshiaki 10.05.95 Bulletin 95/19 10-16, Shinwadai 1-chome Kobe, © Designated Contracting States: Hyogo (JP) DE ES GB IT Inventor: Hayashi, Kiyoshi 1-20-801, Motoyamanaka-cho 1-chome, © Applicant: PRECISION FUKUHARA WORKS, Higashinada-ku LTD Kobe, 1- 5, Honjo-cho 1-chome, Hyogo (JP) Higashinada-ku Inventor: Ueda, Naganori Kobe, 4-3, Kofusa-cho Hyogo 658 (JP) Kashihara, Nara (JP) @ Inventor: Sawazaki, Masatoshi 2- 4, Tenjin-cho 1-chome, Suma-ku © Representative: Naumann, Ulrich Kobe, Patentanwalte Hyogo (JP) Ullrich & Naumann, Inventor: Shibata, Takao Gaisbergstrasse 3 2-25, Tenno-cho, D-69115 Heidelberg (DE) © Method and apparatus for adjusting the stitch length on a circular knitting machine. © A method of and circular knitting machine (20) for producing a knit fabric having more uniform stitches including yarn feeders (76) feeding a plural- ity of yarns (Y) to stitch forming instrumentalities, the spacing of which affects stitch length and which is subject to change during operation of the knitting machine, a sensor (86) for sensing the tension in the plurality of yarns which changes with changes in the spacing of the stitch forming instrumentalities, and generating a signal indicative of the average tension 00 in the yarns, a comparator for comparing the sensor signal with a pre-set desired tension, a convertor for CM m converting the comparison result into a drive signal, CO and an adjuster adjusting the spacing of the stitch forming instrumentalities responsive to the drive sig- nal. Rank Xerox (UK) Business Services (3. 10/3.09/3.3.4) 1 EP 0 652 314 A1 2 Field of the Invention tween the upper end of the needle cylinder and the periphery of the dial. Compensating structural The present invention relates to circular knitting members are provided as supports for the dial and machines and more particularly to such circular needle cylinder which thermally expand and con- knitting machines in which the stitch length in the 5 tract at the same rate as the knitting components. knit fabric is adjusted responsive to changing con- Such correlation between the rates of thermal ex- ditions. pansion and contraction requires that the com- pensating structural members be machined with Background of the Invention very high precision to extremely close tolerances. io Such manufacturing procedures are quite costly In circular knit fabrics, it is highly desirable to and difficult. have the stitch loops as uniform as possible. Var- ious changeable conditions substantially affect the Summary of the Invention stitch loops being formed on a circular knitting machine. Examples of such changeable conditions 75 With the foregoing in mind, it is an object of are the tension in the yarns being fed to the the present invention to provide a method and knitting instrumentalities and the spacing between apparatus for adjusting stitch loops being formed the upper end of the needle cylinder and the sinker by a circular knitting machine having multiple yarn cap in a single knit circular knitting machine or the feeding stations automatically responsive to chang- dial in a double-knit circular knitting machine. 20 ing conditions that affect such stitch loops. Generally, the stitch loops being formed by a This object is accomplished in one embodi- circular knitting machine are adjusted by a movable ment of the present invention by providing a ten- support for the stitch cams which is moved by an sion detecting means for detecting the tension in eccentric screw or rotating cam. Once the position the knitting yarns being fed to the knitting ele- of the stitch cam support is adjusted, the screw or 25 ments. The tension detecting means generates a cam is stopped by a stop means. With such adjust- signal indicative of the tension detected and trans- ment devices, the movement of the screw or rota- mits that signal to a control means. The control tion of the cam is conducted artificially by a me- means compares the tension signal to a desired, chanic or fixer and is not conducted automatically pre-set value and generates a driving signal based responsive to changing conditions. 30 upon the result of that comparison. The driving Recently, it has been proposed to adjust the signal is directed to an elevating means which stitch cam support by means of a rotary actuator. raises or lowers the stitch cam holder to control the However, the rotary actuator is too large for a length of the stitches and thusly provide a higher knitting machine having multiple yarn feeding sta- quality knit fabric. In a double knitting machine, dial tions. 35 needle stitch cam support ring adjusting means Further, it has been previously proposed in may be provided to adjust the dial needles respon- United States Patent No. 5,018,370 to provide a sive to the drive signal to control the length of central stitch length controlling apparatus for a cir- those stitches. cular knitting in which an elevating means vertically Alternatively, in a second embodiment, a sens- adjusts the stitch cam support ring to vary the 40 ing means for sensing the size of the gap between length of the stitch loops being formed. However, the upper end of the needle cylinder and the sinker the elevating means is manually operated and is cap or the dial periphery can be provided. The not responsive to changing conditions. sensing means creates a signal and transmits the In all of these prior stitch adjustments, the same to a control means. The control means com- stitch cam is stopped at a certain position when the 45 pares the signal from the gap sensing means with stitch adjustment is made. Therefore, variations in a pre-set value and generates a drive signal which the tension in the yarns being fed induced by the raises or lowers the dial or cap accordingly. inertia of the components of the knitting section and their thermal expansion and contraction are not Brief Description of the Drawings considered. Consequently, knitting flaws tend to 50 occur, resulting in less fabric quality than is desired Some of the objects and advantages of the and extremely poor productivity. present invention having been stated, others will One prior proposal contained in Japanese Pat- appear as the description proceeds when consid- ent Laid Open No. 195386 of 1993 does take ered in conjunction with the accompanying sche- dimensional variation of the knitting machine com- 55 matic drawings, in which: ponents caused by thermal expansion or contrac- Figure 1 is an elevational view of a circular tion into account. This proposal attempts to com- knitting machine having multiple yarn feeding pensate automatically for variations in the gap be- stations; 2 3 EP 0 652 314 A1 4 Figure 2 is a fragmentary schematic view of the thereof. A mounting plate 32, in the form of a ring, core of the knitting section of the knitting ma- mounts the cam holder 31 for vertical adjustment chine shown in Figure 1; on a guide ring 33. Guide ring 33 is mounted on Figure 3 is a vertical sectional view taken sub- the machine bed 24 by a plurality of bolts 34, only stantially along line 3-3 in Figure 2; 5 one of which is shown. Guide ring 33 has a plural- Figure 4 is an enlarged fragmentary sectional ity of upstanding guide pins 35, only one of which view of the medial portion of Figure 3; is shown, mounted thereon near the inner periph- Figure 5 is an enlarged fragmentary sectional ery thereof (Figures 3 and 4). Mounting plate 32 view taken substantially along line 5-5 in Figure has a plurality of holes 36 therethrough which re- 3; io ceive the upper end portions of the pins 35 therein Figure 6 is an enlarged fragmentary sectional to hold mounting plate 32 against rotation while view illustrating the spatial relationship between permitting vertical movement thereof relative to the the needle cylinder and sinker cap in a single pins 35 and guide ring 33 (Figure 4). knit circular knitting machine; Elevating means 40 for adjusting the vertical Figure 7 is a view similar to Figure 6 of the is position of the mounting plate 32, the cam holder spatial relationship between the needle cylinder 31 and thus the cams 30 relative to the guide ring and the dial of a double knit circular knitting 33 and needle cylinder 21 is provided on mounting machine; plate 32 and guide ring 33. The elevating means Figure 8 is a sectional view of the lower portions 40 preferably comprises a plurality of simulta- of the needle cylinder, stitch cams and cam 20 neously driven screw jacks, approximately six (6) in support and elevating means of a circular knit- number, equally spaced around the mounting plate ting machine in accordance with the present 32 and guide ring 33 and each including an inter- invention; nally threaded nut 41 mounted on mounting plate Figure 9 is a fragmentary sectional view of the 32 by bolts 42 and a clamp member 43. An exter- knitting section of a double knit circular knitting 25 nally threaded screw member 44 is rotatably machine incorporating the present invention; mounted on the guide ring 33 by a sleeve bearing Figure 10 is a fragmentary elevational view of 45, a washer 46 and a bolt 47. The shank portion the drive unit of a positive yarn feeder taken 44a of the screw 44 penetrates through the bearing substantially along line 10-10 in Figure 1; 45 and has the washer 46 mounted on the lower Figure 11 is a schematic view of a control de- 30 end thereof by the bolt 47.