GB2145120A - Straight bar knitting machine (cotton system) - Google Patents

Description

1 GB 2 145 120 A 1

SPECIFICATION

Flat weft knitting machine (cotton system) The invention relates to a flatweft knitting machine 70 (Cotton system) of the kind setforth in the classifying portion of claim 1.

Weft knitting machines of that kind have at least one needle barfitted with rigidly mounted bearded needles. Loopforming is effected by a portion of yarn being laid by means of a yarn guide overthe shanks of all needles involved in the knitting operation, that portion of yarn then being formed into loops by means of loop-forming sinkers in orderto drawthe necessary length of yarn out of the yarn guide, and then finally stitches are formed simultaneously with all needles.

While the needle bar performs a combined horizon tal and vertical movement in the stitch forming operation, the yarn guide is reciprocated on a linear track parallel to the needle bar. The loop-forming sinkers which are mounted movably in a sinker head are individually and successively extended by means of a sinker cam (slurcock) which is also reciprocated along the needle track, wherein pivotally mounted jacks may be provided as transmission elements between the sinkers and the sinker cam.

The travel of the yarn guide is restricted at both sides of the needle bar byfixed stops which are set according to the desired operating or pattern width. It is therefore necessary for the yarn guide on the one hand to be entrained by way of a friction brake which slips on a guide bar and on the other hand to be provided with shock absorbers in order to avoid excessively hard impacts and rebounding of the yarn guide when impinging againstthe stops. Instead of only one yarn guide, the machine frequently has a plurality of yarn guides which can be selectively entrained and selectively brought into operation by means of clutch devices.

The linear movement of the yarn guide and the 105 sinker cam is derived from the rotary movement of a main eccentric shaftwhich is driven by means of an electric motor and a steplessly controllable transmis sion or a Ward-Leonard circuit. In order in that respect also to permitthe movement of the sinker cam to be matched to the desired operating width which may possibly be very small in comparison with the width of the needle bar, the rotary movement of the eccentric shaft is converted into a reciprocating motion with adjustable stroke length for the sinker cam by means of a sinker eccentric device, a so-called rocking arm, bevel gears, worm-gear spindles, toothed racks orthe like.

There are a number of disadvantages with the above-described basic, really complicated mechanical 120 structure of a flat weft knitting machine (Cotton syste m.), which has scarcely changed since it was first conceived. First of all, the friction brake which is used for driving theyarn guide must permit such an amount of slippage that no blocking action occurs 125 when the stops are reached, while on the other hand it must grip so firmly that no slippage occursthroughout the desired phases of movement as otherwise the usual lead of the yarn guide in comparison with the sinker cam could be adversely affected. Adjusting the 130 friction brake in that way is not without its difficulties as the frictional conditions frequently fluctuate widely as between the cold condition of the machine and the condition in which the machine has warmed up. In addition, the shock absorbers give rise to problems as they additionally require space and increasethe cost of the machine. Furthermore, the stops detrimentally affect in particularthe patteming options and production speed. When knitting stripes for example the yarn guides required are often atthe wrong side of the needle barso that idle courses are required, which reducethe production rate. If intarsia patterns areto be produced, additional mechanical switching mechanisms are required, in the form of worm gear spindles, stepping mechanisms, cam discs orthe like, in orderto be ableto displacethe stopstowards both sides, which further increases the cost of the arrangement and has a further adverse effect on the conditions in respect of space,which are in any case already poor. Apartfrom that, movements of that kind, dueto the structural design involved, can only be performed in small steps so that idle strokes are required if greater movements are desired. Finally, when producing check and intarsia patterns, the machine must be frequently stopped when changing colours, for manually changing the association of the coloured yarns with the yarn guides or re-setting all stops. That is a time-consuming operation and involves high production losses.

In orderto eliminate the friction brakes, it is already known (German laid-open applications (DE-OS) Nos 29 51332 and 29 51386) for both the sinkercam and the yarn guidesto be moved in a slip-free manner by means of a differential drive. In that arrangement, the drive members carrying the yarn guides and the sinker cam come to a haitjust afterthe yarn guides impinge againstthe stops. However, even a drive mechanism of that kind does not make it possible to eliminate eitherthe stopsforthe yarn guide means and the resultant restrictions in regard to possible patterns and production rate, orthe complex mechanical components which are required for deriving the linear movement of theyarn guides and the sinker cam from the rotary movement of the main eccentricshaft.

The invention istherefore based on the problem of providing the flatweft knitting machine (Cotton system) of the general kind setforth in the opening part of this specification, with a new design of drive for the yarn guides and/orthe sinker cams, which renders redundantthe stops and a large number of previously required mechanical components forthe yarn guides and/orthe sinkercam, simplifiesthe production even of complicated patterns, and increases production speed.

The characterising features of claim 1 are provided to solve that problem.

Embodiments of the invention are setforth in the subsidiary claims.

The invention provides considerable advantages. Firstly, the direct drive of each yarn guide or each sinker cam has the resuitthat al 1 stops and friction brakes and all those components which hitherto were required for deriving the linear movements of the yarn guides andthe sinker cam from the rotary movement of the main eccentric shaft can be omitted. In addition, 2 all those components which hitherto were required, in the production of patterns or also in a fashioning operation, to setthe stops for the yarn guides in accordance with the pattern can be eliminated. In addition, the production speed is substantially in creased because the yarn guides can be rapidly and precisely setto a different operating region by means of the direct drives and forthat purpose also there is no need of movements which are derived from the rotary motion of the main eccentric shaft, for it is only necessary to setfresh reference values forthe servo motors, in accordance with the pattern to be pro duced. Finally, the operating region of the weft knitting machine is substantially free of mechanical lever, spindle and switching mechanisms becausethe 80 drive assemblies can be arranged in a drive region which is disposed adjacentthe operating region and therefore onlytheyarn guide and sinkercam bar members and the sliding bearings required for guiding same remain in the operating region. That 85 permits a substantial simplification in accessto the operating region when knitting-in and when carrying out repair operations.

The invention is described in greater detail hereinaf terwith reference to an embodiment, in conjunction 90 with the accompanying drawings in which:

Figure 1 is a diagrammatiGview of a drive according to the invention for a yarn guide, Figure 2 is a diagrammatic frontview of a weft knitting machine according to the invention (Cotton system) having an operating region and a drive region disposed therebeside, Figure 3 is a diagrammatic front view of the drive region of Figure 2, on an enlarged scale, and Figure 4 is a view in section taken along line IV-IV in Figure3.

Figure 1 shows a diagrammatic view of a preferred embodiment of the drive arrangement according to the invention, independently of theflatweft knitting machine. It includes a servo motor 1 and a belt arrangement which is generally denoted by reference numeral 2. The belt arrangement 2 is driven bythe output shaft 3 of the servo motor 1 by way of a transmission 4which is diagrammatically shown in the form of a belt transmission. The belt arrangement 2 has a drive shaft 5 which is connected to the output of the transmission 4, with a belt pulley 6, and an idly rotatable countershaft 7 which is parallel to the shaft3, carrying a belt pulley 8. A belt 9 having a substantially horizontal upper run and a lower run is passed around both belt pulleys 6 and 8 so thatthe belt9 is reciprocal in the direction indicated bythe double-headed arrow v, in dependence on the respective direction of rotation of the servo motor 1. The belt 9 is preferably an endless belt, the two ends of which are connected together in the region of the upper run by a belt fastening or lock 10 to which a carriage 11 is secured.

Alternatively, the belt may be an endless belt with the carriagell being directly secured to the upper run thereof.

Thecarriagell has a through bore which is parallel to the upper run of the belt 9 and through which projects a guide bar 12 which is also arranged parallel tothe upper run ofthe belt9 andthe ends of which are fixed in the machine frame. The carriage 11 also 130 GB 2 145 120 A 2 ca rries a n entrain ment member 13 to which there is secu red a ya m g u ide ba r mem ber 14 which is a rrang ed paral lei to the u pper ru n of the belt 9, for h oldi ng at least one operating el ement (not shown in Figure 1), for example a yarn guide.

The servo motor 1 is connected to a control circuit 18 by way of lines 15, 16 and 17. The control circuit 18 is supplied with actual value signals relating to the respective instantaneous actual position of the yarn guide bar member 14, byway of the line 15. The actual value signals are compared in a comparator 19 to the limit position signalswhich are predetermined by a reference value generator2O.The resulting difference is applied in the form of an analog voltageto a circuit 21 which converts the analogvoltage into a reference value signal which presetsa reference value in respect of the speed of the servo motor 1 andwhich isfed to a comparator 22. By way of the line 16, the comparator 22 also receives actual value signals in respect of the instantaneous speed of the servo motorl, and compares those two signals. The difference is fed to a control amplifier 23 which causesthe servo motor 1 to rotate in one direction orthe otheruntil the actual position of the yarn guide bar member 14 corresponds to the preset reference position. In that respect, the difference between the actual position and the reference position becomes smaller and smaller so thatthe speed of rotation of the servo motor 1 also progressively drops until it finally comes to a haltwhen the actual position is reached.

The servo motor 1 is preferably a permanent magnet-energised synchronous motorfrom Indramat GmbH of 8770 Lohr am Main. Aservo motor 1 of that kind is controllable in respectof speed of rotation, speed control being effected by electrical commutation and control of the current in the statorwinclings. It also has all means required for detecting the instantaneous actual position and for producing a desired reference position, in the form of a feedback unit which can be used for electrical commutation, speed feedback and incremental position detection (actual value generator) so thatthere is no need for additional components for detecting the actual position of the yarn guide bar member 14.

The reference value generator 20 alternately produces the reference values required for producing any item of knitwear, for the yarn guide limit positions at both ends of the article being knitted. Preferably, connected to the input side of the reference value generator 20 is a program control 24for producing different reference values according to the pattern. In that connection, those-reference values may be stored in any desired manner, for example on film, punch, drum or card storage means or in the memories of an electronic data processing installation orthe like. The stored data are then interrogated after each revolution of the main eccentric shaftof the weft knitting machine and offered in the desired sequence to the comparator 19 which can be in the form of a differential amplifier. It is also desirable forthe main eccentric shaft to be provided with a rotary generator orthe like in such a way thatthe latter produces a synch ronisation signal in each revolution and feeds the synch ronisation signal to the reference value generator 20 or the program control 24 so thatthe reference value signals 3 GB 2 145 120 A 3 are prepared in the operating cycle of the weft knitting machine and the yarn guide bar members 14 are thus displaced synchronously with respect to the rotary motion of the main eccentric shaft.

The mode of operation of the above-described drive arrangement for the yarn guide bar member 14 is as f0frows:

Instead of the reciprocating movement of theyarn guide bar member 14 being derived from the rotary motion from the main eccentric shaft, the yarn guide bar member 14 is reciprocated by means of the belt 9 driven by the servo motor 1. When that happens, the reciprocating rotary movements of the servo motor 1 are produced in responseto a switching signal by means of the control circuit 18which, underthe control of the referencevalue generator20 orthe program control 24, atthe sametime establishesthe respective limit positions of theyarn guide bar member 14at both ends of the path of travel thereof.

Conversion of the positional difference into a speed referencevalue signal provides thatthe yarn guide bar member 14 does not need to be broughtto an abrupt halt atthe respective limit positions, but approaches the limit positions at a gradually decreasing speed.

Therefore, the use of the servo motor 1 on the one hand permits a movement of the yarn guide bar member 14 which is independent of the drive of the main eccentric shaft, with the exception of the synchronisation effect, while on the other hand permitting the omission of a number of mechanical 95 components which were hitherto required for deriving its movementfrom the rotary motion of the main eccentric shaft, for shock absorbing, for braking orfor displacing the stops in accordance with the pattern.

For entering the program and the other instructions, 100 depending on the type of machine, it is desirable to provide a control panel with a keyboard, wherein visual display means can facilitate checking and trouble-shooting.

In accordance with the invention, the reciprocating 105 movement of the sinker cam is produced in the same manner as described above with referenceto the yarn guide bar member 14. That provides the further advantage thatthat movement also does not need to be derived from the rotary motion of the main eccentric shaft, the mechanically expensive compo nents which were hitherto required for setting the stroke movement of the sinker cam can be omitted, and the desired lead of the yarn guide bar membercan be ensured in a simple manner, in both directions of movement, by suitable switching of the servo motors.

Reference will now be made to Figures 2 to 4 and the diagrammatic views therein to describe a flatweft knitting machine (Cotton system) having a plurality of operating elements in theform of a plurality of yarn guides and a sinker cam, with each of which is associated a respective yarn guide or sinker cam bar memberwhich is moved by a respective drive as shown in Figure 1. In other respects, Figures 2 to 4 only showthe components of the flat weft knitting machine (Cotton system) which are required for comprehen sion of the invention.

Referring to Figure 2, the frame 25 of the flatweft knitting machine (Cotton system) is subdivided into a drive region 26 which is shown on the left and an 130 operating region 27 which is shown on the right beside the drive region 26. The operating region 27 includes a needle bar 28 carrying bearded needles (not shown) on which a knitted article 29 is being pro- duced, a sinker cam bar member30 which carries a sinker cam 31, a plurality of yarn guide bar members 32a to i of which Figure 2 shows onlythe bar members 32a and 32f and which each carry a respectiveyarn guide 33a to i which feeds yarns 34to the needles, and a main eccentric shaft 35 with eccentrics 36. The sinker cam bar member 30, the yarn guide bar members 32 and the main eccentric shaft 35 are mounted for horizontal displacement and rotary movement respectively in the machine frame 25 and each project with axial extension portions into the drive region 26. Mounted in the drive region 26 is a servo motor37 which is preferably like the servo motor 1 and which directly drivesthe main eccentric shaft 35. Disposed abovethe servo motor 37 is a belt arrangement38 which corresponds to the belt arrangement 2 shown in Figure 1 and which essentially comprises a driven belt pulley 39, an idly rotatable belt pulley 40 and an endless belt4l which passes therearound, the two ends of the belt being connected by a beltfastener which carries a carriage 42. Secured to the carriage 42 is an entrainment member 43 and secured thereto is the horizontally displaceably mounted sinker cam bar member 30 which is disposed parallel to the two long runs of the belt4l. As shown in Figure 3, the pulley 39 which isfixed on a drive shaft44 is rotated byway of a transmission 45, by a servomotor 46 which is mounted in theframe 25 and which is of a design corresponding to that shown in Figure 1, while the pulley 40 is fixed on an idly rotatable countershaft 47. In other respects, the arrangement corresponds to the arrangement described above with reference to Figure 1, in relation to the example of the yarn guide bar member 14.

As can also be seen from Figures 2 and 3, mounted within the drive region 26 and abovethe driveforthe sinker cam 31 is a total of nine belt arrangements 48a to 48i corresponding to the belt arrangements 2 shown in Figure 2. As shown in Figures 2 and 3,the belt arrangements are disposed in two stages ortiers one abovethe otherwhile as shown in Figure 4, they are also disposed in juxtaposition in each stage. In that connection, Figures 2to 4 each only show as many components of the belt arrangements 48 and the yarn guide bar members 32a to 32i driven thereby, as is possible, while ensuring sufficient clarity in the drawing.

As shown in Figures 2 and 3, each belt arrangement 48 comprises a servo motor49a to 491 which is only diagrammatically indicated and which correspondsto the servo motor 1. Byway of a transmission (not shown),the servo motor49a to 49i can rotate a drive shaft 50a to 50i and an idly rotatable countershaft 51 a to 51 i. In that connection, the drive shafts 50a and 50b are disposedwith their axes parallel and at a spacing from each other in a left-hand frame portion 52 and in the lower stage, while the countershafts 51 a and 51 b associated therewith, in the same stage, are mounted with their axes parallel and at a suitable spacing, in a right-hand frame portion 53. In addition, the countershafts 51 c and 51 d in the lowerstage are mounted in 4 the left-hand frame portion 52, whereas mounted in the right-hand frame portion 53 in a corresponding manner are the associated drive shafts 50c and 50d, the shafts being disposed with their axes parallel to each other and at respectively equal spacings. Drive and countershafts are arranged alternately one beside the other. Byvirtue of that interleaved mode of construction, sufficient space for mounting the servo motors 50a to 50d is provided in the region of each drive shaft 50 so that, in spite of the number of shafts and servo motorsAhe drive region 26 can be of relatively small width. The upper stage of the drive region 26 has a corresponding interleaved arrange ment of the shafts 50e to 50i and 51 a to 51 i.

Secured on each drive shaft 50 and on each 80 countershaft 51 is a belt pulley 52a to 52i and 53a to 53i respectively (see Figure 2). A respective belt 54a to 54i extends around each pair of the belt pulleys, in the manner shown in Figure 2; Figu res 2 and 3 each show only one belt 54a in the lower stage and one belt 54e in the upper stage. Each belt 54 carries a carriage 55a to 55i each having an entrainment member 56a to 56i and a respective yarn guide bar member 32a to 32i, wherein the carriages 55a to 55d in the lower stage or tier are secured to the upper runs of the belts 54a to 54d and the entrainment members 56a to 56d project upwardly while in the upper stage of tier the carriages 55eto 55i are secured to the lower runs of the belts 54e to 54i and the entrainment members 56e to 56i project downwardly, thus providing a compact and spacesaving arrangement.

Finally, Figure 4 shows thatthe carriages 55a to 55d and therewith the pulleys 52 and 53 respectively of the lower stage ortier are each disposed one besidethe other between a front frame portion 59 and a rear frame portion 60, that is to say, displaced relative to each other in the axial direction of the associated shafts. A similar arrangement applies in respect of the carriages 55eto 55i of the upperstage ortier. The entrainment members 56a to 56i secured thereto are each bent towards the middle of the machine frame 26 so thatthe yarn guide bar members 32a to 32i carried thereby are disposed in close juxtaposition and the yarn guides 33 carried by the bar members can be arranged in the usual manner as is required for laying intheyarns.

Figure 4 also shows that, in a preferred embodiment of the invention, unlike the arrangements shown in Figures 1 to 3, each carriage 55 is guided bytwo guide bars 62a to 62i and 63a to 63i respectively. In that arrangement, the guide bars 62 comprise round bars or rods which are disposed in corresponding bores in the carriages 55. In contrast, the guide bars 63 comprise flat barswhich respectively engage into a front or a rear recess in the carriages 55. In that arrangement, in orderto save space, the guide bars 63 are used by two respective carriages, as shown for example in Figu re 4 in respect of the guide bar 63b, which projects into a f ront and a rear recess in each of the two carriages 55b and 55e respectively. The additional guide bar 63 provides a compact guide arrangement for the carriages 55, while preventing tipping thereof.

Finally, Figure 4, as a view in cross-section of Figure 3, also shows the servomotor 49i which drives the GB 2 145 120 A 4 drive shaft 51 i (not shown) byway of a transmission 65, and also the countershaft5lf with the belt pulley 53f forthe carriage 55f, the servomotor 49d which drives the drive shaft 50d with the pulley 52d byway of a transmission 66, and the cou ntershaft 47 with the pulley 40 for driving the carriage 42 which carries the sinker cam bar member 30. In that connection, the shafts 51f and 50d, like the other shafts, are each rotata bly mounted in the front and rear frame portions 59,60 by means of ball bearing assemblies 67 orthe like.

The drive according to the invention substantially facilitates operation on the flatweft knitting machine (Cotton system). In that arrangement, associated with each servo motor49 is a control circuit 18 with a reference value generator 20 and possibly a program control 24, as shown in Figure 1.

When producing smooth, unpatterned articles, all yarn guides except one are cut out. The yarn guide which is in the operative condition, driven by the servo motor 49, reciprocates over the entire operating width or a selected partthereof. In that respect, no stops, friction brakes, transmissions coupled to the main eccentric shaft 35 orthe like are required as the servo motor 49 automatically comes to a halt atthe ends of its path of movement, underthe control of the control circuit 18. The sinkercam 30 is reciprocated in a corresponding manner and also independently of the main eccentric shaft 35. Forthe purposes of synchronising the rotary movements of the main eccentric shaft 35 with the linear movement of the sinker cam and the yarn guide, it may be provided that a rotary generator is disposed on the main eccentric shaft 35, in the form of a discwhich has markings which indicate the respective rotary position of the main eccentric shaft and which are scanned by a scanning means, the output signals of which are fed to the control circuit 18, the reference value generator 20 and/orthe program control 24 in order to cut outthe reference values orthe program and to activate the control circuit 18 at the appropriate times by a switching sig nal'controller release'. Rotary generators of that kind and the associated circuits are generally known in the flat and circular knitting machine art and therefore do not need to be described in greater detail herein.

If the operating width is constantthe reference value generators 20 only need to supplytwo reference value signals alternately, corresponding to the limit positions of the yarn guides and the sinker cam respectively. If, in contrast, a fashioned article is to be produced, the program controls 24 must supply varying reference value signals which correspond to the limit positions of the yarn guide and the sinker cam, which change in accordance with the pattern. No other adjustments on the machine are required for that purpose, that is to say, in particularthe adjustments which were required hitherto in respect of the stops forthe yarn guide and the sinker cam, and the generally very expensive mechanisms forthat purpose can be eliminated.

If a stripe pattern is to be produced, in conventional weft knitting machines, it is always necessary to provide an empty row or course during which the machine does not knit, when the yarn guide required kit$ Z14b -MU A b in the nextfollowing course of stitches is positioned at the wrong end of the needle bar. In contrast,when using the weft knitting machine according to the invention,the main eccentric shaft only needs to be 5 stopped for a comparatively shorttime in orderto transportthe sinker cam, which is atthe wrong position, to the correct end of the needle bar, because the movementthereof is independent of the cycle of movements of the main eccentric shaft, and operation of the machine can then be continued immediately. Therefore, each such change involveswasting a substantially smaller amount of timethan thetime corresponding to afull course of stitches.

The production of intarsia patterns is also simplified asthe program controls 24 of all yarn guides can respectively producevarying reference value signals forthe limit positions of theyarn guides,which change accordingtothe pattern being knitted. Therefore,the conventional right-hand and left-handworm gear spindles for adjusting the stopswhich were required hitherto are no longer necessary. Asthose spindles and the control components requiredfor controlling them take up a great deal of space,they were generallyonly associated with some selected yarn guides. In contrast,when using the drive according tothe invention, all yarn guides can be easily used for intarsia patterns, bysimple program control. Because that drive is independentof the rotary motion of the main eccentricshaft, it is also possible to provide comparatively large changes in the limit positions of the yarn guides in each operating cycle.

Finally, considerable advantages are also achieved when producing such cheek or intarsia patterns which comprise coloured panels which are disposed in rows 100 in a staggered or chessboard-like configuration, in which howeverthe colour can constantly change within the individual coloured panels. Hitherto, the operators of such machines generally madeto with a mode of operation which provided thatthe machine 105 was stopped after producing a complete row of checks and then the yarns guided bythe yarn guideswere interchanged, while retaining the stop positions, or the stops were suitably altered, while retaining the association of yarns.When using the invention, it is 110 only necessaryto program the program controls 24 in a suitable manner and, after a row of checks has been produced, to displace the yarn guidestowards one side orthe otherto such a distance that, during the operation of knitting the next row of checks, they are 115 associated with the knitting region which is then required. Forthat purpose also, the main eccentric shaft has to be stopped only briefly in each change overoperation.

The servo motors 1, 37,46 and 49 according to the 120 invention are operated for exam pie at speeds of up to 2000 rpm which are reduced to a preselected value by means of the transmissions 4,65 and 66. Those speeds can easily produce linear movements of the yarn guides orthe sinker cams of 100 to 120 m/min, 125 which are sufficientto operatethe weft knitting machine (Cotton system) at a speed of for example courses of stitches per minute over a full operating width.

The invention is not restricted tothe above- 130 described embodiments. Instead of the illustrated belt arrangements, it is also possible to use for example chain, gear and gear rack arrangements orthe likefor converting the rotary motion of the output shafts of the servo motors into a linear movement of the yarn guide and sinkercam bar members. Apartfrom that, the belts, in orderto avoid slip, preferably comprise toothed belts whilethe belt pulleys correspondingly comprise toothed belt pulleys. Thetransmission arrangements illustrated can be replaced by any other transmission units. Itwould also be possibleforthe belt arrangements orthe liketo be causedto act directly ontheyarn guides and sinkercams, andfor thernto be mounted reciprocally slidably on station- aryguide bars orthe like. In addition, instead of the above-mentioned servo motors, itis possibleto use otherservo motors provided thatthey permit precise positional control. Corresponding servo motors can also be used for displacing the narrowing bars of pattern narrowing means if such are provided. Forthe purposes of producing the position reference signals, all program controlswhich are known forthat purpose from the knitting machine art can be used, in particular alsothose having microprocessors and electronic data processing equipment. Forthe purposes of determining the actual position signals,the actual value generatorswhich are integrated into the servo motors can be replaced by other means, for example thosewith bar patterns which are disposed on the

Claims (12)

guide rocisforthe carriages and which are scanned by devices mounted on the carriages. In addition, the invention may be applied to flatweft knitting machines (Cotton system) having more than one needle bar. It is also possibleforthe arrangement of the drive and countershaftsto be differentfrom that shown in Figures 3 and 4, orfor a respective drive region forthe servo motorsto be arranged on both sides of the needle bar. Finally, a plurality of yarn guides or sinker cams may be secured to each yarn guide or sinker cam bar member respectively, such yarn guides or sinker cams being associated with a corresponding plurality of operating regions within the needle bar, in order in known mannerto produce a plurality of knitted articles atthe same time one beside the other on a needle bar. CLAIMS

1. A flat weft knitting machine (Cotton system) having at least one needle bar in which, for the purposes of stitch forming, at least one operating element in theform of a yarn guide and/or a sinker cam is mounted reciprocally between two preselected limit positions, and having a drive meansfor producing the reciprocating motion, characterised in thatthe drive means has a servo motor (1) and an electronic control circuit (18) connected thereto.

2. A machine according to claim 1 characterised in thatthere is provided a plurality of operating elements (31,33) and the drive meansfor reciprocating each individual operating element has a respective servo motor (46,49) and a respective electronic circuit co n n ected th e reto.

3. A machine according to claim 1 or claim 2 characterised inthatthe control circuit (18) comprises a reference value generator (20) for producing limit position signals, an actual value generator for produc- 6 GB 2 145 120 A 6 ing actual position signals, a comparator (19) for comparing the limit and actual position signals and a control amplifier (23) which is connected to the output side of the comparator (19) and which controls the servomotor (1) in such away thatthe servomotor stops whenever a preselected limit position is reached.

4. A machine according to claim 3 characterised in thatthe control circuit (18) has a program control (24) which is connected on the input side of the reference value generator (20), forvarying the limit position signals in accordance with a pattern.

5. A machine according to at least one of claims 2 to 4 characterised in that each operating element (31, 33) iscoupledto a belt (41,54) which is apart of a belt arrangement (38, 48) coupled to the servomotor (46, 49).

6. A machine according to claim 5 characterised in that the belt arrangements (38,48) and servomotors (46,49) of all operating elements (31,33) are disposed in a drive region (26) which is disposed laterally beside the needle bar (28) which includesthe operating region (27).

7. A machine according to claim 6 characterised in that each operating element (31,33) is secured to a bar member (30,32) which is displaceable parallel to the needle bar and which projects laterally into the drive region (26).

8. A machine according to claim 7 characterised in that each belt arrangement (38,48) has a carriage (42, 55) which is guided on at least one guide bar (62,63) and which is coupled to the associated belt (41,54) and to which the bar member (30,32) of the associated operating element (31, 33) is secured.

9. A machine according to at least one of claims 5 to 8 characterised in that each belt arrangement (38, 48) has a drive shaft (44,50) which is coupled to the associated servo motor (46,49), and an idly rotatable countershaft (47,51), which carry belt pulleys (39,40 and 52,53 respectively) forthe belts (41, 54).

10. A machine according to claim 9 characterised in thatthe drive and countershafts (44,50 and 47,51 respectively) are arranged in a plurality of stages parallel to each other and in alternate juxtaposition, whereasthe belt pulleys (39,40 and 52,53) respectively) and belts (41, 54) of each stage are arranged displaced relative to each other in the axial direction.

11. A machine according to at least one of claims 1 to 10 characterised in that it has a rotatably mounted main eccentric shaft (35), a servomotor (37) and a control circuit also being provided for driving same.

12. A machine according to at least one of claims 1 to 11 characterised in that it has a narrowing means with narrowing rods, with each of which are associ- ated a respective servomotor and control circuit.

Printed in the United Kingdom for Her majesty's Stationery Office, 8818935, 3185,18996. Published at the Patent Office, 25 Southampton Buildings, London WC2A lAY, from which copies may be obtained.