Patent Publication Number: US-8117871-B2

Title: Method and knitting machine for producing a knitted product from substantially untwisted fibre material

Description:
The invention relates to a method and a knitting machine of the types specified in the preambles of claims  1  and  5 . 
     Known methods and knitting machines referred to as spinning-knitting machines of this type (e.g. PCT WO 2004/079068 A2) are distinguished by the fact that the knitting product is not produced from usual twisted yarns, but from a fibre material provided in the form of a sliver, which is formed from substantially untwisted staple fibres arranged parallel to one another. This sliver is fed to the knitting systems by means of drafting devices known from spinning technology. To transport the sliver from the drafting devices to the knitting systems, the sliver is firstly converted by means of spinning and transport devices, which each contain at least one twist element and a transport tube connected thereto, into a temporary yarn with a plurality of twists, which are maintained during the entire transport operation. As a result of this, it is possible to transport the sliver over longer distances despite its low strength compared to usual yarns. The twists in the temporary yarn are then reduced to zero (false twist effect) over the short distance from the outlet end of the spinning or transport device to the inlet of the sliver into the knitting elements, so that the fibre material actually processed in the knitted fabric does not consist of a twisted yarn, but of a substantially untwisted sliver. As a result, a knitted product of extreme softness is obtained as end product. 
     Alternatively, however, the spinning device can also be fitted for the formation of a permanently bonded yarn, in particular a so-called unconventional yarn, and be configured, for example, as an air spinning device (cf. e.g. patents EP 1 518 949 A2 and EP 1 826 299 A2). Such a yarn also has some twists or windings, but, like a bundle or covering yarn, for example, it is not a yarn in the classic sense. The spinning operation is preferably set so that, like in the above-described case of the temporary yarn, a sliver that is sufficiently firm for the desired transport purposes is formed, but a sufficiently soft knitted product is still obtained. 
     Moreover, knitting machines, in particular circular knitting machines, are known (PL 350 489 A), to which drafted and substantially untwisted fibre material is fed by guiding a fibre material preferably provided in the form of flyer frame sliver through the clamping gap between two feed rollers and subjecting it to a preselected drafting process between this roller pair and an associated work area of the knitting machine. 
     As in the case of conventional methods and knitting machines, there is the disadvantage that a break or run-out of the sliver results in holes in the knitted product or even causes the already formed tubular knit to drop off the knitting elements. This is caused by the knitting elements being raised further into a fibre take-up position despite there being no sliver feed, and the previously formed stitches being knocked over from the knitting elements as a result. The term “knocking over” is to be understood to mean that, irrespective of the type of knitting elements (e.g. latch needles, compound needles, hook-shaped elements etc.), as these are raised into a fibre take-up position the old stitches firstly slip onto a blade of the knitting elements and when the knitting elements are later lowered, slide over their hooks and the newly formed stitches slide off the knitting elements completely. 
     It is therefore known (DE 10 2005 031 079 A1) to monitor the feed of the sliver with a monitoring device that has thread sensors and is configured in the same way as usual thread monitors. If the monitoring device detects a fault, an error signal intended to switch off the knitting machine and the drafting device is then generated. 
     The sensors of the known monitoring device are arranged at a location lying in front of the drafting device in the transport direction of the sliver. This should prevent the drafting device from running empty and remove the necessity for a complicated insertion of a new sliver, which is associated with various disadvantages. Moreover, the objective is to stop the knitting machine before the end of the sliver reaches the respective knitting system. 
     However, the known procedure leads to two disadvantages. Firstly, a break in the sliver in a region located between the monitoring device and the knitting machine cannot be detected, and therefore the formation of holes or detachment of the tubular knit cannot be prevented if the fault in the sliver occurs before it runs into the drafting device. Secondly, it is not at all assured that the knitting machine will come to a standstill before the end of the sliver reaches the respective knitting system, since this is substantially dependent on the length of the drafting device, its distance from the knitting machine and the “stopping distance” of the knitting machine used in the individual case, in particular is dependent on the needle cylinder thereof, for example, if this is a circular knitting machine with a rotatable needle cylinder. Therefore, the sensors would have to at least be so far removed from the fibre inlet points into the knitting systems that the sections of the slivers located inbetween are also sufficient at the highest conceivable speed of the knitting machine to cover the existing sliver requirement up to the final machine stoppage. 
     In addition, it has already been proposed (DE 10 2006 056 895) to configure the knitting machine of the aforementioned type so that a single knitting system is switched over to non-knitting operation if no fibre material is present or if any other fault occurs, and conduct the switchover automatically by means of a thread monitor. No further details are evident from this proposal. Regardless of this, the formation of longer holes in the knitted product cannot be securely avoided in this way, since the length of such holes is dependent on the time actually required for the switchover to be completed. 
     Working from this, the technical problem of the present invention is to configure the aforementioned methods and knitting machines so that the holes that occur in the knitted product when a sliver breaks or similar can be kept comparatively short and virtually all the breaks that occur in the sliver can be detected. 
     This object is achieved by the characterising features of claims  1  and  5 . 
     The invention provides the advantage that monitoring occurs at a location that lies between a roller pair, which is the withdrawal roller pair of a drafting device or a feed roller pair according to PL 350 299 A2, for example, and the knitting system, and the knitting elements are raised out of an intermediate position again without thread take-up. Therefore, on the one hand, the sensors of the monitoring means can be arranged in very close proximity to the respective knitting system, if required, with the result that breaks or the like of the sliver that occur directly in front of the knitting systems can also be reliably detected. On the other hand, because of the special control of the knitting elements it is possible to keep the number of knitting elements, which will still unavoidably move into the fibre take-up position after an error signal occurs, and thus also the resulting holes in the knitted product, as low as possible even when the sections of the slivers located between the sensors and the fibre inlet points are comparatively short. 
     Further advantageous features of the invention are evident from the sub-claims. 
    
    
     
       The invention will be explained in more detail on the basis of exemplary embodiments in association with the attached drawings. 
         FIG. 1  schematically shows a circular knitting machine suitable for the purposes of the invention for the production of knitted products from fibre materials, which substantially comprise untwisted staple fibres; 
         FIG. 2  is a schematic plan view onto a circular knitting machine according to  FIG. 1  with a multiplicity of knitting systems; 
         FIGS. 3 and 4  are front views of possible cams for the knitting machine according to  FIG. 1 ; and 
         FIG. 5  shows a latch needle of the circular knitting machine according to  FIG. 1  located in a fibre take-up position according to the invention. 
     
    
    
       FIG. 1  is a highly schematic vertical view in partial section of a circular knitting machine  1  with a needle cylinder  2 , in which usual knitting elements in the form of latch needles  3  are displaceably disposed, which have hooks  3   a  and pivoting latches  3   b  and at a knitting point referred to hereafter as knitting system  4 , can be moved into a fibre take-up position suitable for taking up fibre material  6  by means of cams  5  (not further shown). The circular knitting machine  1 , which can be configured as a plain circular knitting machine, for example, stands on a schematically indicated floor of a workshop or knitting room. An operator can operate the knitting machine  1  from the workshop floor. In addition, a plurality of cans  7 , in which card slivers  8  consisting of fibres are deposited, for example, are placed on the workshop floor. 
     The card slivers  8  are fed to a drafting device  10  by means of transport elements  9  (not shown in more detail). Each of a plurality of knitting systems  4 , of which only one is shown in  FIG. 1 , has such an associated drafting device  10 , which in a manner known per se has, for example, three pairs of drafting rollers  11 . 
     The fibre material coming out of the drafting device  10 , which consists of substantially untwisted staple fibres arranged parallel to one another, is fed in the known manner to an associated knitting system  4  by means of a spinning or transport device given the general reference  12 . The transport device  12  contains at least one twist element  14  and a spinning or transport tube  15  connected to this, wherein in the exemplary embodiment according to  FIG. 1  three twist elements  14   a ,  14   b ,  14   c  and transport tubes  15   a ,  15   b ,  15   c  are connected one behind the other because of the comparatively substantial distance of the circular knitting machine  1  from the drafting device  10 . The first twist element  14   a  in the transport direction of the fibre material is arranged directly behind a withdrawal roller pair  11   c  of the drafting device  10 , whereas the last transport tube  15   c  in transport direction terminates very close to the hooks  3   a  of the latch needles  3  raised into a fibre take-up position on the respective knitting system  4 . 
     The spinning device  12  or each transport unit comprising a twist element  14  and transport tube  15  serves to initially convert the sliver discharged from the drafting device  10  into a temporary yarn  17  with genuine twists. For this purpose, the twist element  14  is formed, for example, from a substantially hollow cylindrical body, the inside cavity of which receives the leading section of the transport tube  15 , and has at least one air duct, preferably multiple air ducts, which are all arranged on an angle to the centre axis of the transport tube  15 . The air ducts pass through the wall of the body and the transport tube  15  and terminate at an inside wall of the transport tube  15 . During operation, compressed or blast air is fed to the outer ends of the air ducts by means (not shown), so that the twist element  14  pulls the fibre material fed by the withdrawal roller pair  11   a  into the transport tube  15  and at the same time also directs it on through the transport tube  15  in the direction of the respective knitting system  4 . In addition, because of the sloping arrangement of the air ducts air is swirled in the transport tube  15  in such a manner that the fibre material coming from the withdrawal rollers  11   c  is not only sucked up, but is also spun into a temporary yarn by giving it a plurality of twists, which at the same time compress the fibre material. The temporary yarn  17  retains the twists substantially until the end of the last transport tube  15   c , whereupon these twists are then released again, i.e. are reduced to zero (false twist effect), until the last received fibre material  6  enters the knitting needles  3 . Therefore, a compressed, but virtually untwisted, sliver  6  enters the knitting needles  3 . Between the different transport units  14 ,  15  a respective gap  18  with an associated extraction means  19  is preferably provided to extract excess air coming from the twist elements  14  and loose impurities located in the fibre material. 
     In a schematic plan view  FIG. 2  shows that a multiplicity of devices according to  FIG. 1  are distributed around the periphery of the circular knitting machine  1 , the spinning and transport device  12  only having two respective transport units  14 ,  15  here. Moreover, a special feature of the exemplary embodiment is that four respective drafting devices (e.g.  10   a ,  10   b ,  10   c  and  10   d ), which each guide a sliver, are arranged adjacent to one another in pairs, are fastened on opposite sides of a common mounting  20  and are combined to form a drafting device group  21 . Moreover, each drafting device group  21  has two drives (not shown), of which one drives all four feed and central rollers  11   a ,  11   b  and another drives all four withdrawal rollers  11   c  of the respective drafting roller group  21 . The circular knitting machine  1  shown in  FIG. 2  is therefore provided with 24 individual drafting devices, which each feed a respective sliver  6  to one of 24 knitting systems. 
     Circular knitting machines of the described type are known, for example, from document PCT WO 2004/079068 A2 and DE 10 2006 006 502 A1, which are herewith incorporated into the present disclosure by reference to avoid repetition. 
     According to the invention, the described circular knitting machine  1  is provided on each knitting system  4  with at least one sensor  22 , which is suitable for detecting the presence or absence, and particularly advantageously also the movement and stoppage, of the fibre material being fed to the knitting system  4 , and which is arranged at a location that is preferably located between the withdrawal roller pair  11   c  of the drafting device  10  and the knitting system  4 . This monitoring can be achieved on the basis of the sliver  6  discharging from the last transport tube  15   c  of the transport device  12 , on the basis of a temporary yarn  17  guided in the gaps  18  between two transport units  14 ,  15  or also on the basis of a temporary yarn  17  guided in a transport tube  15 . In the last-mentioned case, the respective transport tube  15  preferably has a window or an intermediate section made of a fully transparent material, through which the temporary yarn  17  can be detected by the sensor  22 . In the exemplary embodiment of  FIGS. 1 and 2 , three such sensors  22   a ,  22   b  and  22   c  are respectively provided for each system, which are each associated with a transport tube  15   a ,  15   b ,  15   c . It is particularly advantageous if at least one sensor  22  is arranged as closely as possible to the respective knitting system  4 , so that breaks occurring there or other faults in the fibre material can also be discovered. 
     Usual sensors that are used as thread monitors in normal knitting machines can be provided as sensors  22 , which in the absence or stoppage of the fibre material to be monitored emit an electrical error signal. This error signal is used according to the invention to no longer allow the needles  3  passing through the respective knitting system  4  to pass into the fibre take-up position, but to be raised out of an intermediate position again without taking up any fibre. This process is shown schematically in  FIGS. 4 and 5 . 
     It is presumed in  FIG. 3  that the needles  3  themselves or selectors or jack selectors  24  associated with them ( FIG. 1 ), like in usual knitting machines, are provided with raising butts  25  ( FIG. 3 ), which interact with the cams  5  arranged on the knitting systems  4 . As a result, all the needles  3  are firstly raised, for example, out of a through- or non-knitting position along a raising path  26  into a fibre take-up position and then withdrawn again along a withdrawal path  27  in order to advance them again into the through-position after passing through a cast-off or coulier path  28 . The movement of the needles  3  in relation to the cams  5  occurs in the direction of an arrow v in  FIG. 3 . The fibre take-up position is reached close to a highest point  29  of the raising path  26  and serves to arrange the needles  3  in a position where they are raised to such a distance that the stitches located in their hooks  3   a  and formed in a preceding knitting system  4  slide over the open latches  3   b  onto a needle blade  3   c  ( FIG. 1 ), while the fibre material  6 , e.g. at a location  30  that indicates a thread guide eyelet, can be advanced so that it is laid in the hooks  3   a  of the needles  3  at the latest during their withdrawal. However, the withdrawal of the needles  3  serves to pull the inserted fibre material  5  through the previously formed stitches suspended on the needle blades  3   c  and at the same time fully knock over the old stitches over the hook  3   a  as the latch  3   b  closes. 
     To prevent the needles  3  from being further raised into the fibre take-up position when a break or similar of the fibre material occurs and thus knock over the old stitches without taking up fibre material again, a branch  31  can be provided at the beginning of the raising path  26  according to  FIG. 3 , at which branch the butts  25  can be guided selectively onto the raising path  26  or into a through-path  32 , as is indicated for some butts  25   a . For example, an electromagnet  33  arranged in the region of the branch  31  can serve as selector means, as is generally known in the case of needle control systems. This electromagnet  33  could be controlled so that in response to an error signal of a sensor  22 , all the needles  3  on the respective knitting system  4  are directed into the through-path  32 . As a result of this, the old stitches are prevented from being knocked over. 
     However, the described control is not optimal, since in  FIG. 3  all the needles  3  arranged to the right of the selector magnet  33  have already gone past the branch  31  when the error signal occurs and therefore can no longer be prevented from being raised into the fibre take-up position. This results in a hole forming in the knitted product, the length of which corresponds at least to a length y indicated in  FIG. 3 , since at least all the needles  3  located in region y still knock over their stitches before reaching the fibre take-up position. The size of such a hole depends on the individual case, the needle pitch and other properties. 
     Therefore, it is proposed according to the invention to arrange a branch  34  and the associated selector magnets  33  in the raising path  26  and at a height h above the through-path  32 , as shown in  FIG. 4 . It is additionally proposed to connect the branch  34  to an intermediate path  35 , which leads past butts  25   b  arranged on it below the fibre take-up position and allows it to feed into the withdrawal path  27  at a location  36  in order to ensure that the associated needles  3  do not take up any fibres. Moreover, the height h is dimensioned such that because the raising action occurred by the time the branch  34  was reached, the latches  3   b  of the needles  3  are already open in accordance with  FIG. 5 , while the old stitch indicated by a thread  37  is arranged just above the free latch tip and therefore cannot pass under the latch  3   b  onto the needle butt  3   c  during transport of the needle  3  along the intermediate path  35 . 
     This measure assures that, when an error signal emitted by the sensor  22  occurs, it is only those needles  3  that have already passed the branch  34 , i.e. that are already arranged in a section y-x of the knitting system  4 , that can no longer be directed into the intermediate path  35  by the selector magnet  33 . Conversely, all those needles  3  that are located in a region x in  FIG. 4  can still be directed into the intermediate path  35  by the selector magnet  33 . The section y-x, within which the needles  3  can no longer be prevented from knocking over the old stitches, is therefore substantially narrower than dimension y, so that a hole in the knitted product caused by fibre material  6  not being present also has a correspondingly reduced length. The length of the hole is therefore reduced overall by the dimension x in comparison to  FIG. 3 . 
     Moreover, the arrangement according to  FIG. 4  has the advantage that the needles  3  are raised into an intermediate position C ( FIG. 4 ), which is defined by the position of the branch  34  and can be optimised in the sense of  FIG. 5 . The intermediate path  35  can be placed at any desired expedient height h, so long as it only lies between the through-path  32  ( FIG. 3 ) and the highest point according to  FIG. 5 , at which the old stitches have not yet been knocked over. Moreover, it is advantageous to optimise dimension x in accordance with knitting-related design features and to be as large as possible, while selecting the horizontal distance between the branch  34  and the location  30 , at which the fibre materials are taken up by the needles, and thus also the number of needles that do not take up any fibres in the event of a break in the fibre material, to be as small as possible. 
       FIG. 1  shows the connection of the sensors  22  to the rest of the control elements of the circular knitting machine  1 . This includes as central control element in particular a standard machine control unit  41 , which is connected via electric lines to a machine drive  42  and the selector magnets  33  in the same way as e.g. for circular knitting machines with electronic selector devices for the knitting needles that can be controlled by electromagnets. A microprocessor  43  is additionally provided according to the invention, which is connected on one side to the machine control unit  41  and on the other side to the sensors  22  and also a control device  44 , which serves to control the different drives of the drafting devices  10 . 
     Two preferred methods for controlling the circular knitting machine  1  are provided in particular for the purposes of the invention. Both methods work on the basis of a design of the drafting devices  10  shown in  FIG. 2 , according to which two respective adjacent drafting devices  10  arranged on the same side of the mountings  20  form a pair. The top rollers of the two drafting devices  10  of this pair are respectively rotatably disposed on a common press arm or swinging support. Each press arm is biased on one side by a spring or the like in a known manner in order to press the top rollers against the bottom rollers with a preselected force and on the other side is disposed to pivot on a drafting roller housing, so that this can be opened for repair and maintenance work. It is additionally provided according to  FIG. 2  that each drafting device group  21 , which consists of four drafting devices  10  mounted on the same mounting  20 , has two associated motors, of which one serves to drive the feed and central rollers  11   a ,  11   b  and the other to drive the withdrawal rollers  11   c.    
     On this basis, the first method for controlling the circular knitting machine  1  provides that an error signal, which is fed to the microprocessor  43  by any one sensor  22  and indicates the presence of a sliver  6  or temporary yarn  17 , is forwarded immediately to the machine control unit  41 . This transmits a control signal to the selector magnet  33  of the associated knitting system  4  so that all the needles  3  passing the selector magnets  33  are immediately directed into the intermediate path  35  ( FIG. 4 ) and are therefore no longer raised into the fibre take-up position  29 . The implementation of this measure can occur very quickly despite the unavoidable signal running and calculation times caused by the electronic system. Therefore, as described above, with the exception of few additional needles, only those needles  3  that had already passed the selector magnets  33  when the fault occurred are no longer detected. However, all following needles  3  pass into the intermediate path  35 , so that a hole forming in the knitted product is thus comparatively short. 
     When the error signal occurs, the machine control unit  41  continues to send a control signal to the machine drive  42  to thus stop the drive motor for the circular knitting machine  1  or the needle cylinder  2 . The needle cylinder  2  thus comes gradually to a standstill, during which it still makes a quarter or half rotation, for example. However, this stopping time is of no importance for knocking over stitches from the needles  3 , since this has already been prevented by the switchover of the selector magnet  33 . 
     Finally, a control signal is also transmitted via the microprocessor  43  to the control device  44 , whereupon this also stops the drive motors of all the drafting devices  9  synchronously with the stoppage of the circular knitting machine  1  or the needle cylinder  2 . 
     After stoppage of the circular knitting machine  1 , the damage at the respective drafting device  10  can be remedied and the circular knitting machine  1  can then be manually restarted by means of a corresponding switch on the machine control unit  41 . As a result, the sensor  22 , which has emitted the error signal, can be brought into its active monitoring state again by means of the microprocessor  43 , while the drives of the drafting devices  10  are switched on again. However, the selector magnet  33  of the knitting system  3  affected by the fault is only brought into the state, in which it directs all passing needles  3  into the raising path  26  at the branch  34  ( FIG. 4 ), when the respective sensor  22  indicates that the drafting device  10  monitored by it is feeding fibre material again and is moving the fibre material, i.e. transport is occurring in the direction of the needles  3 . 
     If according to the above description two respective adjacent drafting devices  10  are connected to the same press arm, then when an error signal occurs, the selector magnet  33  of the knitting system  4  belonging to the adjacent drafting device  10  of the same pair is also switched over automatically in the described manner. This is expedient because elimination of the indicated fault generally requires the common press arm to be opened, as a result of which the fibre flow in the actually intact adjacent system is also interrupted or at least disturbed. As a result of the joint switchover of the two adjacent systems to the intermediate path  35 , it is possible in a simple manner to create the same conditions in both adjacent drafting devices  10  of a pair before the circular knitting machine  1  starts again. 
     The procedure is similar if the top rollers of more than two drafting devices  10  are connected to a common press arm. 
     The second preferred method according to the invention provides causing the circular knitting machine  1  to continue running despite detection of a fault by one of the sensors  22 . This can be expedient to avoid substantial outage periods, if an immediate removal of the fault is not possible or desirable for some reason. 
     In this case, when a fault is indicated by one of the sensors  22 , not only the needles  3  on those two knitting systems  4  belonging to the pair affected by the fault are directed into the intermediate path, but also the needles  3  of those knitting systems  4  belonging to the two other drafting devices  10  of the respective drafting device group  21  in  FIG. 2 . In addition, the two drive motors of this drafting device group  21  are switched off by means of the control device  44  in order to prevent fibres from continuing to be fed to the respective systems  4  even though no further fibres are being taken up. As a result, the circular knitting machine  1  is now in a state, in which a complete drafting device group  21  is no longer operating. Nevertheless, the circular knitting machine  1  can be further operated without problem, since in the exemplary embodiment the outage of a drafting device group  21  only results in there being four less stitch rows than usual for each needle cylinder revolution, since a stitch row is formed on each knitting system  4 . So long as all the remaining knitting systems  4  work perfectly, this indeed leads to a reduction in production, but does not result in a decrease in quality of the produced knitting goods in most cases. A reduction in quality can also be prevented because the take-off device of the circular knitting machine  1  is adjusted to the reduced output by means of the machine control unit  41 . 
     If at any time later there is a need to eliminate the fault present on the stopped drafting device group  21 , then the circular knitting machine  1  can be stopped manually and the fault removed by opening and closing the respective drafting device  10  in a similar manner to that described above. The circular knitting machine  1  is then restarted manually, wherein the selector magnets  33  belonging to the drafting devices  10  of the respective drafting device group  21  remain in switched over position until all the respective sensors  22  detect fibre material again, preferably moving fibre material. The selector magnets  33  are then switched over to also raise the needles  3  on the knitting systems  4  controlled by them into the fibre take-up position again. However, it is also alternatively possible to remove the fault with the machine running and then switch over the selector magnets  33  again without stopping the machine as soon as the sensors  22  detect the transport of fibre material. It can be expedient with both described methods to briefly switch off all the sensors  22   a ,  22   b  and  22   c  present on the circular knitting machine  1  after a machine stoppage in order to prevent control errors when the circular knitting machine is restarted. Moreover, it is advantageous to also incorporate the twist elements  14  and suction devices  19  into the described control in order to adapt the blast and suction air flows associated with these to the respectively changed operating conditions by means of suitable regulator devices or the like. 
     The procedure is similar if a plurality of sensors  22  emit an error signal at the same time. 
     Both methods can be applied analogously if the fibre material fed to the knitting system  4  is supplied by a feed roller pair in accordance with patent PL 350 489 A, i.e. when a classic drafting device is not present. 
     For control of the needles  3  in the sense of  FIG. 4 , patterning devices used hitherto predominantly for needle selection in the 3-way technique are suitable (e.g. DE 40 07 253 C2 and DE 103 21 737 A1). There, it is generally known to selectively control needles with a first selector magnet into a through-path or into a raising path, as is shown in  FIG. 3 . The needles guided on the raising path can then be selectively directed by means of a second selector magnet into a catch position or be moved on in the raising path and into a thread take-up position, as shown in  FIG. 4 . However, according to the invention the selector magnets serving to select between the through-path and the raising path could be omitted, since the needles are normally all controlled into the thread take-up position during spinning-knitting. 
     It is clearly evident to the person skilled in the art that instead of electromagnetic selector means that allow a single selection of the needles  3 , selector arrangements in the form of electrically controllable cam switches, which can be switched over between a fibre take-up position and an intermediate position, can also be used (e.g. DE 1 123 425, DE 35 07 496 C2) to direct the needles into an intermediate path when a break in the fibre occurs. In addition, switchable cams or pivoting swing levers (e.g. DE 15 85 229 C2) can be used to control the needles  3  into the intermediate path  35 . Purely electrical patterning devices, e.g. operating with piezoelectric elements (e.g. DE 21 15 332 C3) or pneumatically operating patterning devices (e.g. DE 15 85 188) can also be used. It is not particularly significant for the purposes of the invention what means are used to direct the needles  3  into the intermediate path  35  when a fault occurs in the sliver. 
     Moreover, other knitting elements such as e.g. compound needles, for which the likewise electromagnetic selector devices are known (e.g. DE 16 35 844 C3), can also be used instead of the latch needles  3 . The application of hook-shaped knitting elements is also possible in this context. 
     Suitable sensors within the framework of the present invention are in particular all those sensors that are also suitable for monitoring normal knitting yarns and that operate optically, mechanically or purely electronically (e.g. DE 44 21 225 A1, EP 0 761 585 A1, DE 195 43 229 A1 or DE 44 08 312 C2). 
     All the abovementioned documents are herewith incorporated into the present disclosure by reference to avoid further repetition. 
     The invention is not restricted to the described exemplary embodiments, which can be modified in a variety of ways. In particular, it is clear that the intermediate path  35  evident from  FIG. 4  does not necessarily have to run exactly parallel to the through-path  32  at the height of the intermediate position C of the needles  3 . According to a particularly preferred exemplary embodiment, the intermediate path  35  instead has a quite steep downward slope adjoining the branch, as is indicated by broken lines  35   a  and  35   b  in  FIG. 4 . The intermediate path  35  does not then open into the withdrawal path  27  at location  36 , but into the through-path  32  at a location lying more in front of the thread guide eyelet  30 , and therefore the needles  3  are withdrawn earlier—viewed in the transport direction—than if they were to run into the withdrawal path  27  only at the location  36 . This results in the advantage when spinning on a knitting system or on all knitting systems of the knitting system that sections of fibre material already inserted into the needle circle can definitely not be engaged by the needles  3  transported along the intermediate path  35  or pass between these. In order to avoid steep cams, the slightly flatter course  35   b  is regarded as currently the best embodiment of the invention. Moreover, the control system of the circular knitting machine  1  evident from  FIG. 1  only represents one example that can be varied in a variety of ways. This also applies to the position and number of sensors  22   a ,  22   b  and  22   c  shown in  FIG. 1 , which could also lie at any other location on the path of the fibre material, e.g. in or in front of a drafting device. In principle, it is sufficient to provide a single sensor  22  for each knitting system  4 . Moreover, it is not necessary to arrange the drafting devices  10  according to  FIG. 2  in pairs of two and groups of four drafting devices. For the purposes of the invention, arrangements are also suitable, in which each individual drafting device  10  is arranged and driven separately. Moreover, in addition to sensors  22 , further sensors intended for monitoring the fibre flow can also be provided on the knitting machine, in particular such sensors that are arranged in front of the drafting devices in the transport direction of the fibres in a manner known per se. Finally, it is clear that the different features can also be applied in other combinations than those described and represented.