Abstract:
A machine is described for producing a knitted fabric with at least partial use of fibrous material ( 10 ), in particular a circular knitting machine ( 1 ). At least selected knitting stations ( 6 ) are assigned drawing frames ( 8 ) for producing threads ( 11 ) which are formed from the fibrous materials ( 10 ). According to the invention, the drawing frames ( 8 ) lie in the reaching area of an operator ( 5 ) working on the machine ( 1 ) and can be opened downwards (arrow v) or to the side.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a machine for producing a knitted fabric from fibre material, in particular a circular knitting machine. 
     Machines of this type are distinguished by the predominant or exclusive use of threads that consist of largely untwisted staple fibres arranged parallel to one another instead of classic yarns. Such threads are produced in drafting devices connected directly in front of the stitch-forming points of the machine from slivers or bands fed to them, and to ensure a disturbance-free transport from the drafting devices to the stitch-forming points, are converted by means of spinning elements into temporary yarns, the twists of which are only removed again shortly before running into the stitch-forming points (false twist effect). Therefore, the threads actually processed into knitted fabric substantially consist of untwisted parallel threads, which is why the finished knitted fabric is distinguished by an extreme softness. While additional auxiliary threads consisting of classic yarns can be worked in, if required, this is not fundamentally necessary. 
     A known machine of the aforementioned type configured as a circular knitting machine (PCT WO 2004/079068 A2) has one drafting device for each stitch-forming point. Since the drafting devices cannot be configured as small as desired, a substantial space and handling problem results. Therefore, it has been provided, for example, to arrange the drafting devices at comparatively substantial distances from the circular knitting machine and to surround this with a raised work platform, from which the drafting devices are accessible. While it is possible as a result of this to arrange a large number of drafting devices on the periphery of the circular knitting machine, this poses the disadvantage that when a fault occurs in one of the drafting devices, the operator working on the circular knitting machine must leave his/her usual work area in front of the machine, get on the work platform, eliminate the fault from there and than return to his/her usual work area. This is not only inconvenient, but also requires special cost-incurring protective measures in the form of railings or the like that delimit the work platform in order to prevent the operator from accidentally falling from the work platform. Moreover, additional measures that further increase the production costs must be taken, which consist, for example, of a multiplicity of spinning elements and transport tubes following these for each stitch-forming point in order to securely transport the threads leaving the drafting devices as far as the knitting needles or other stitch-forming elements. If in order to avoid these disadvantages the drafting devices were arranged directly on the machine, in particular on the periphery of a circular knitting machine, then the space between the drafting devices would become ever smaller as the number of knitting points or systems increases, so that with the usual arrangement the drafting devices would no longer be accessible and economic maintenance operations and/or repairs of the drafting devices would thus be practically impossible. 
     In addition, it is also already known to combine the drafting devices in a bar shape to form three groups, which are arranged at angular distances of approximately 120° on the periphery of the circular knitting machine. However, this solution poses the additional advantage that the routes of the drafting devices to the stitch-forming points fluctuate greatly. This results in different friction conditions for the threads, in particular if transport tubes are also used in this case, which can result in different thread tensions and cause the threads exposed to an increased friction to break more easily. Apart from this, all solutions, in which two or more spinning elements operated mechanically or by compressed air are necessary for each stitch-forming point, have the disadvantage of increased energy consumption. 
     SUMMARY OF THE INVENTION 
     Working from this, the technical problem of the invention is to configure the machine of the aforementioned type such that even with high system numbers, the drafting devices can be arranged closely adjacent to the machine and still be easily operated, maintained and repaired, where necessary. 
     The invention provides the advantage that compared to the hitherto exclusive method, the drafting devices can be operated from below and/or from the side. For this purpose, press arms known per se, on which the so-called top rollers are mounted, can be arranged, for example, so that they can be pivoted downwards or to the side instead of upwards. Another preferred possibility is to mount at least selected function parts, in particular drafting device elements such as rollers or aprons, on a structural element that can be pulled out of the associated drafting device downwards or to the side in the manner of an insertion part. This enables the drafting devices to be moved closely adjacent to the stitch-forming or knitting points, wherein they are preferably arranged above the stitch-forming points, while still remaining within the reach of the operator working on the machine. The operator can therefore perform all the necessary work on the drafting devices by folding or pulling out the function parts downwards or to the side without having to leave his/her usual work area. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail below by way of exemplary embodiments in association with the attached drawings. 
         FIG. 1  shows a schematic vertical section through a first exemplary embodiment of a circular knitting machine according to the invention; 
         FIG. 2  is a plan view onto the circular knitting machine according to  FIG. 1  with the omission of an auxiliary thread; 
         FIG. 3  shows a schematic vertical section through a second exemplary embodiment of a circular knitting machine according to the invention; 
         FIG. 4  is a plan view onto the circular knitting machine according to  FIG. 3  with the omission of an auxiliary thread and with the addition of spinning devices; 
         FIGS. 4   a  and  4   b  schematically show a drafting device of the circular knitting machine according to  FIG. 4  with a usual press arm, respectively in a closed and open position, on an enlarged scale; 
         FIG. 5  shows a longitudinal section through a drafting device for the circular knitting machine of  FIG. 1  according to a first exemplary embodiment; 
         FIG. 6  shows a section taken approximately along a line VI-VI in  FIG. 5 . 
         FIG. 7  shows a longitudinal section through a drafting device for the circular knitting machine of  FIG. 3  according to a second exemplary embodiment; 
         FIG. 8  is a schematic side view through a third exemplary embodiment of a circular knitting machine according to the invention; 
         FIG. 9  is an enlarged side view only of one drafting device of the circular knitting machine according to  FIG. 8 ; 
         FIG. 9   a  is a slightly smaller representation compared to  FIG. 9  of the drafting device after an insertion part has been removed downwards; 
         FIG. 10  is a bottom view of three drafting devices arranged adjacent to one another on the periphery of the circular knitting machine according to  FIG. 8 , which is not shown; 
         FIGS. 11 and 12  are two perspective views of the drafting device according to  FIG. 9 , viewed from below; 
         FIGS. 13 to 16  are purely schematic representations of exemplary embodiments for further drafting devices according to the invention with insertion parts; 
         FIG. 17  is a plan view onto a drive means for the drafting devices; and 
         FIG. 18  is a perspective representation of a preferred embodiment of an insertion part in the form of a module. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention is explained in more detail below on the basis of a stitch-forming machine, which in the exemplary embodiments is a circular knitting machine that has a plurality of stitch-forming points in the form of knitting points or systems and stitch-forming elements in the form of usual latch needles. However, it is evident that the invention can also be conducted in the same manner or an appropriately adapted manner on other stitch-forming machines. 
       FIGS. 1 and 2  schematically show a circular knitting machine  1  with a rotatable needle cylinder  2 , in which knitting needles  3  are displaceably disposed. A work area  4 , which an operator  5  occupies during usual work on the circular knitting machine  1 , is indicated schematically in front of the circular knitting machine  1  or in a region surrounding this. The height of the circular knitting machine  1  is usually dimensioned such that a plurality of stitch-forming or knitting points  6 , which are formed in cam parts (not shown) and of which only one is shown in  FIG. 1 , lie within the reach of the operator  5 . The term “reach” is understood to mean the region that is preferably arranged at a particularly ergonomically favourable distance and/or a distance prescribed, for example, by work instructions, standards or similar above the ground  7  or the like, on which both the circular knitting machine  1  and the operator  5  stand. 
     The circular knitting machine  1  of interest within the framework of the present invention is configured as a so-called spinning-knitting machine. Each stitch-forming or knitting system  6  has an associated drafting device  8 , to which a sliver  10  removed from a can  9  is fed. This sliver  10  is attenuated to a thread  11  in the drafting device  8  in a manner known per se and is preferably fed by means of a thread guide  12  to the knitting needles  3  for stitch formation. In addition, an auxiliary thread that can also be fed to the thread guide  12  is indicated at reference  14 . 
     As  FIG. 2  shows, in the exemplary embodiment six drafting devices  8  are respectively combined to form a drafting device group  8   a , which feed the threads  11  for six adjacent knitting points, characterised here by the thread guide  12 . For this purpose, six drafting devices  8  with coaxially located rollers are respectively arranged adjacent to one another, for example, so that the bar-shaped arrangement evident from  FIG. 2  with four drafting device groups  8   a  results, for example, which are arranged on the periphery of the needle cylinder  2  and feed threads  11  for a total of 24 knitting points. 
     Stitch-forming machines of the described type are known to the person skilled in the art e.g. from the aforementioned publication PCT WO 2004/079068 A2, which is herewith incorporated into the subject of the present disclosure by reference to avoid repetition. 
     According to the invention, the drafting devices  8  are arranged so that, like the stitch-forming points  6 , they lie within the reach of the operator  5  working on the circular knitting machine  1 . For this purpose, the drafting devices  8  are fastened to a support ring  15 , for example, which is supported on a base or cam plate  17  of the circular knitting machine  1  by means of columns  16 . In a particularly advantageous manner, moreover, the arrangement is such that the nip lines formed by three or more pairs of function parts (e.g. drafting rollers  18  or the like) do not lie in horizontal planes, but lie in inclined planes in accordance with  FIG. 1 , wherein feed roller pairs facing the respective cans  9  lie higher above the ground  7  than withdrawal roller pairs facing the circular knitting machine  1 . 
     The exemplary embodiment according to  FIGS. 1 and 2  is distinguished by the axes of the drafting devices  18  all being arranged horizontally in the state of use. In order to ensure that the drafting devices  8  are not only reachable for the operator  5  from the work area  4 , but can also be easily maintained and/or repaired without having to be fully dismantled, the drafting devices  8  can be at least partially opened by their essential function parts being disposed, according to the invention, to be able to pivot at least partially downwards into the drafting devices  8 . This is indicated in  FIG. 1  by a structural element in the form of a press arm  19  supporting the so-called top rollers, which, in contrast to the conventional technique, lies at the bottom instead of at the top and can be pivoted in the direction of an arrow v around a horizontal pivot axis  20  indicated by way of example. As a result of this, the top rollers of a selected drafting device  8  can be exposed, if necessary, so that aprons present on these can replaced, fibre clumps present in the drafting device  8  can be removed and other work can be conducted without the operator  5  having to leave his/her work area  4 . 
     The exemplary embodiment according to  FIGS. 3 and 4  differs from the exemplary embodiment according to  FIGS. 1 and 2  primarily in that the drafting devices  8  here are mounted on the circular knitting machine  1  in a position rotated 90° relative to  FIG. 1  and in the position of use are arranged vertically instead of horizontally. Therefore, the same parts are provided with the same reference numerals in  FIGS. 3 and 4  as in  FIGS. 1 and 2 . Pairs of associated drafting devices  8  come to lie adjacent to one another in accordance with  FIG. 4 .  FIG. 4  additionally shows that here the press arms  19 , which support the so-called top rollers ( 18   a ), can be pivoted around pivot axes  20 , which are likewise arranged rotated 90° compared to  FIG. 1  and stand vertically. Therefore, the press arms  19  cannot be pivoted downwards, but to the side in the direction of arrows w ( FIG. 4 ). This can be seen more precisely in  FIGS. 4   a  and  4   b , which show a usual press arm  19  and its elements  19   a ,  19   b  provided for operation and locking in the closed state ( FIG. 4   a ) and in the open state ( FIG. 4   b ). 
     So that the press arms  19  have a sufficiently large pivoting area and do not immediately strike against an adjacent drafting device when a drafting device  8  is opened, according to the exemplary embodiment of  FIGS. 3 and 4  it can be provided, as is only indicated in  FIG. 4 , that the threads  11  leaving the drafting devices  8  are fed to the associated knitting points by means of spinning devices  21 . As is known from the aforementioned publication, these spinning devices  21  include, for example, at least one respective twist element  22  and a spinning tube or transport tube  23  connected to this. The purpose of the spinning devices  21  is to firstly convert threads  11  discharging from the drafting devices  8  into temporary yarns with genuine twists, which are released again between the ends of the spinning tubes  23  and the thread guides  12  associated with the knitting points  6  ( FIG. 3 ) because of the so-called false twist effect. Because of the selectable length of the transport tube  23  arranged radially to the circular knitting machine  1 , the distance of the drafting devices  8  from the centre axis of the needle cylinder  2  can be selected to be comparatively large and substantially as desired. As a result, the resulting distance in the peripheral direction between two adjacent drafting devices  8  can also be fixed at a preselected value allowing the press arms  19  to pivot. Corresponding spinning devices  21  can be provided in the exemplary embodiment according to  FIGS. 1 and 2 . 
     In addition, the exemplary embodiment according to  FIGS. 3 and 4  has the advantage over that according to  FIGS. 1 and 2  that because they stand vertically, the drafting rollers  18  can be driven in a simple manner by drive belts disposed in a circle, which are arranged above the drafting devices and extend in the peripheral direction of the needle cylinder  2 . For this, the shafts of each so-called bottom roller of the three roller pairs shown are provided on their upper side with a respective toothed pulley, for example. A corresponding drive could be provided for the bottom rollers of the exemplary embodiment according to  FIGS. 1 and 2 . However, the drive torques transferred by means of the toothed belt here would have to be converted by means of bevel gears or the like into torques for the bottom rollers standing horizontally here. 
     Finally, it is particularly advantageous according to the exemplary embodiment of  FIGS. 3 and 4 , as  FIG. 3  shows in particular, that two or also more drafting devices can be arranged here with their rollers  18  coaxially one above the other. As a result of this, it is possible to halve the space required for the drafting devices  8  in the peripheral direction or reduce this still further, since in this case two or more threads can be guided to the adjacent knitting points from each drafting device segment, as is indicated in  FIG. 3  by two threads  11 . As a result of this, the package density of the drafting means can be doubled or tripled. 
     The invention has been described thus far on the basis of drafting devices  8 , which are distinguished by the feature that the rotational axes of all the drafting device elements, which can also include function parts in the form of aprons  24  ( FIG. 4 ), are arranged parallel to one another. In particular, during operation the rotational axes of the exemplary embodiment according to  FIGS. 1 and 2  are arranged horizontally and the rotational axes of the exemplary embodiment according to  FIGS. 3 and 4  are arranged vertically. However, apart from this the invention should also be applicable to drafting devices having rotational axes that are arranged at preselected angles between 0° and 90° relative to one another. This applies in particular to so-called folding drafting devices, which fold the fibre materials during their transport through the drafting device elements around an axis parallel to the transport direction and thus reduce the width of the fibre materials by half or more. Such drafting devices are explained in more detail below on the basis of  FIGS. 5 and 6 , wherein  FIG. 5  is a schematic side view in partial section of a single drafting device  25  and shows its drafting device elements or function parts and also further details, whereas  FIG. 6  is a sectional view through the drafting device  25  taken approximately along line VI-VI of  FIG. 5 . It is evident therefrom that the drafting device  25  can be combined together with two adjacent drafting devices  25   a  and  25   b  according to  FIG. 6  and also possibly drafting devices (not shown) similar to  FIGS. 1 and 2  to form a group or a bar. 
     According to  FIGS. 5 and 6 , a fibre material  27  is directed through the drafting device  25  in a transport direction  26  indicated by arrows. For this, the drafting device  25  has four pairs I, II, III and IV of drafting device elements lying one behind the other in the transport direction  26 . The first pair I in transport direction  26  and the following second pair II include two rollers  28   a ,  28   b  and  29   a  and  29   b  respectively as drafting device elements, only one respective roller  28   a ,  29   a  of which is visible in  FIG. 5 . The following third pair III includes drafting rollers  31   a  and  31   b  respectively as drafting device elements  30   a  and  30   b , only one of which is visible in  FIG. 6 , deflection elements  32   a  and  32   b  associated with these, which can consist of deflection rollers or bars, and aprons  34   a  and  34   b , which are directed over the deflection elements  32   a ,  32   b  and the associated rollers  31   a ,  31   b  and in the manner known for double-apron drafting devices comprise a lower apron  34  and an upper apron  34   b , between which the fibre material  27  is guided after leaving the drafting rollers  31   a ,  31   b . Finally, the fourth pair IV, the last in transport direction, in turn includes two drafting device elements in the form of a respective roller  35   a  and  35   b . The rotational axes of the rollers  31  and  35  as well as the axes of the deflection elements  32  are arranged perpendicularly to the rotational axes of the rollers  28  and  29 . Apart from this, all four pairs I to IV define the usual nip lines  36 ,  37 ,  38  and  39 , indicated by dot-dash lines in  FIG. 5 , between the said rollers  28 ,  29 ,  31  and  35 . At the inlet to the drafting device  25  a feed funnel or trocar  40  is provided, through which the fibre material  27  is fed and slightly compacted. 
     According to  FIG. 5 , pairs I and II of the drafting device elements  28 ,  29  form a pre-drafting zone  41 , wherein the circumferential speeds of the drafting device elements  28 ,  29  are selected, for example, so that a drafting of between 5- and 15-fold of the fibre material  27  is achieved, which comes close to the drafting of a usual flyer frame. In contrast, the fibre material  27  between the nip lines  28  and  39  or in a zone  42  is subjected to a main drafting operation, which leads to a draft of the fibre material  27  of about 50-times or more, for example, and to a preselected final fineness. 
     Finally, the described drafting device  25  has at least two pairs of drafting device elements, which cause folding of the fibre material  27 . These are pairs II and III in  FIG. 5 , the nip lines  37  and  38  of which form a folding zone  43  between them. In contrast to the drafting zones  41  and  42 , only a tensioning draft occurs between the nip lines  37  and  38  that preferably amounts to 10%, for example, and is just sufficient to hold the fibre material  27  under tension and effect a defined folding. 
     For folding the fibre material  27  in the folding zone  43 , centre axes (not further shown) of the rollers  29   a ,  29   b  and the nip line  37  are arranged perpendicularly to the transport direction  26  and vertically, for example, during operation, while the centre axes of the rollers  31   a ,  31   b  intended to drive the aprons  34   a ,  34   b  and the nip line  38  also extend transversely to the transport direction  26 , but extend horizontally during operation. In other words, the centre axes of the rollers  31  of pair III are arranged tilted or pivoted 90° relative to the centre axes of the rollers  29  of pair II. In contrast, the centre axes of the drafting device elements  28  are arranged parallel to those of the drafting device elements  29  and the centre axes of the drafting device elements  35  are arranged parallel to those of the rollers  31 . 
     A consequence of the arrangement of the rotational axes of the rollers  29  and  31  pivoted 90° is that, while keeping to preselected conditions, the band-shaped fibre material  27  between the nip lines  37  and  38  is folded in a defined manner around at least one folding line, which extends parallel to the transport direction  26  and therefore causes a reduction in the width of the fibre material  27 . Similar would naturally also apply if the drafting device elements  30   a ,  30   b  only had the rollers  31   a ,  31   b , i.e. the aprons  34   a ,  34   b  unfold fully, or if both pairs II and III are provided with drafting device elements formed from rollers and aprons. There is no change to the type of folding as a result of this. 
     The type of folding that results is substantially dependent both on the selection of a distance D ( FIG. 5 ) between the nip lines  37  and  38  of the drafting device elements  29 ,  30  preferably pivoted 90° or of the length D of the folding zone  43 , as well as the selection of a width B ( FIG. 5 ) of the fibre material  27  leaving the rollers  29   a ,  29   b . With a decreasing distance D and an increasing width B, the folding changes from V-shaped via N-shaped and W-shaped to W-shaped with extensions, i.e. the shape of the fold is a function of the distance D and the width B. In a particularly advantageous manner, the distance D and the width B are set so that a W-shaped fold results and the original width B of the fibre material is reduced from 20 mm, for example, to an end width of approximately 5 mm. This width corresponds approximately to the diameter of a usual roving yarn with the result that fibre material reduced to this width can be spun and/or fed to the stitch-forming machines according to  FIGS. 1 to 4  in the usual manner without any further intermediate step. Such a folding is achieved if the distance D is about double the size of the width B. The desired conditions in the individual case can be easily determined by tests. 
     Further details relating to the described folding are explained in a parallel application DE 10 2006 006 504.2 (application date 13.02.06) of the same applicant, and this is incorporated herewith into the subject of the present disclosure by reference to avoid repetition. 
     For the purposes of the present invention it is above all significant with respect to  FIGS. 5 and 6  that the axes of the feed rollers  28   a ,  28   b  stand perpendicular to the axes of the withdrawal rollers  35   a ,  35   b . Therefore, it is unimportant, in principle, whether the distance D and the width B of the fibre material  27  in  FIGS. 5 and 6  are selected so that the described folding results, or whether the arrangement of the axes perpendicularly to one another serves other purposes, as will be explained in more detail below. 
       FIG. 6  shows that the drafting devices  25   a  and  25   b  are configured substantially the same as the drafting device  25  and the overall arrangement analogous to  FIGS. 1 and 2  is suitable in particular for bar-shaped grouping. For example, the three drafting devices  25 ,  25   a  and  25   b  lie adjacent to one another in  FIG. 6 . However, it is clear that groups of only two or even with more than three adjacent drafting devices could also be provided. Moreover,  FIG. 6  shows that the drafting devices  25 ,  25   a  and  25   b  preferably differ from one another through the relative positions of their rollers  28 ,  29 . Viewed in the transport direction  27 —the drafting devices  25   a  and  25   b  respectively have top rollers  28   b ,  29   b  located on the left, represented by double circles, and bottom rollers  28   a ,  29   a  located on the right, whereas in the central drafting device  25  the situation is reversed with the bottom rollers  28   a ,  29   a  lying on the left and the top rollers  28   b ,  29   b  on the right. Because of this and because the rollers  28 ,  29  stand vertically, for example, during operation, while the rollers  31 ,  35  are arranged horizontally, the terms “bottom roller” and “top roller” are misleading, since they no longer indicate the “bottom” or “top” position, as is exclusively usual in spinning technology. Therefore, for the purposes of the present application the bottom rollers  28   a ,  29   a ,  31   a  and  35   a  are generally referred to as the driving rollers and the top rollers  28   b ,  29   b ,  31   b  and  35   b  as the driven rollers. This additionally indicates that the rollers  28   b ,  29   b ,  31   b  and  35   b  do not generally have their own drive, but are pressed in a known manner by structural elements in the form of usual press arms  44  ( FIG. 6 ) or  19  ( FIGS. 1 and 4 ) and an elastic or pneumatic force, for example, against associated driving rollers  28   a ,  29   a ,  31   a  and  35   a  and are set in rotation by these as a result of frictional force. However, the driving rollers  28   a ,  29   a ,  31   a  and  35   a  have a respective forced drive. This is indicated in  FIG. 5 , for example. The driving rollers  28   a ,  29   a  are rotatably disposed here with shafts  45   a ,  45   b  in a bearing block or housing  46 , and the shafts  45   a ,  45   b  are provided, for example, with toothed pulleys, gear wheels or the like, which are in engagement with toothed belts, further gear wheels or the like and can be set in rotation by means of these by drive motors (not shown). The rollers  31   a  and  35   a  can be driven in a similar manner. As  FIG. 6  shows, it is also possible, analogously to the exemplary embodiment according to  FIGS. 3 and 4 , to configure the driven rollers  31   b  of two adjacent drafting devices (e.g.  25 ,  25   b ) in pairs on a common shaft  47  and/or arrange the driving rollers on a common shaft, which extends axially over all drafting devices  25 ,  25   a ,  25   b  present of the respective group, as is indicated schematically in  FIG. 6  for the withdrawal roller  35   a . Finally,  FIGS. 5 and 6  show that a respective spinning device  21  according to  FIG. 4  can connect to the withdrawal rollers  35   a ,  35   b  of pair IV. 
     To also allow the operator  5  ( FIG. 1 ) to have easy access to essential function parts, where necessary, when using the folding drafting devices  25 ,  25   a  and  25   b  according to  FIGS. 5 and 6 , these drafting devices  25 ,  25   a  and  25   b  are configured as further details in  FIGS. 5 and 6  show. 
     According to  FIG. 6  the distance between the individual drafting devices  25 ,  25   a  and  25   b  transversely to the transport direction  26  is selected so that the press arms  44  supporting the driven rollers  28   b ,  29   b  can be pivoted to the side or selectively opened and closed around a respective vertical pivot pin  48  disposed in the housing  46 , like rollers  28 ,  29 , in the direction of a double arrow x. Therefore, if the drafting devices  25 ,  25   a  and  25   b  are arranged in a similar manner to  FIGS. 3 and 4 , so that the axes of the feed rollers  28   a ,  28   b  stand vertically, then, as in  FIG. 4 , all the press arms  44  can not only be arranged within the reach of the operator  5 , but can also be operated by him/her without leaving the work area  4 . 
     In addition,  FIG. 5  shows that the driven roller  35   b  is rotatably disposed on a further structural element in the form of an arm  50 , which with a pivot pin  51  is disposed to be able to pivot on a part of the housing  46  lying right at the front in the transport direction  26 . The pivot axis is arranged parallel to the rotational axis of the roller  35   b . Therefore, the roller  35   b  in  FIG. 5  can be pivoted downwards in accordance with the double arrow v out of the drafting device  25  into a position indicated in dot-dash lines, in which the function part  35   b  and the exit gap between the aprons  34   a ,  34   b  are accessible. Moreover, the assemblies supporting the aprons  34   a ,  34   b  are also mounted on a pivoting arm  52 . The arm  52  is disposed to pivot on a rear portion of the housing  46  opposed to the arm  50  by means of a further pivot pin  53 , the pivot axis of which is extended parallel to the pivot axis of the pivot pin  51 . Therefore, the arm  52  and with it the apron assemblies according to  FIG. 5  can be pivoted back and forth in the direction of a double arrow z and for replacement of the aprons  34   a ,  34   b  or the like can be pivoted out of the drafting device  25  into a position shown in dot-dash lines. Moreover, the arrangement is such that the arm  50  can be pivoted counterclockwise and the arm  52  can be pivoted clockwise into the open position, so that firstly the roller  35   b  and then without hindrance also the apron assembly can be pivoted into the open position. 
     After any maintenance or repair work has been conducted, the arms  50 ,  52  are pivoted back into the operating position and fixed with locking means (not shown) in the housing  46 , as also applies to the press arms  44  ( FIG. 6 ) that are provided with usual locking means and could be configured, for example, in accordance with  FIGS. 4   a  and  4   b.    
     Moreover, in a manner not shown further, the arms  50 ,  52  are configured by means of springs, pneumatically or otherwise as press arms, which press the driven rollers or the like mounted on them against the associated driving rollers or the like. 
     As is indicated on the far right in  FIG. 5 , the drafting device  25  is preferably arranged at an angle of between 90° and 180° relative to the knitting needles  30 , so that approximately the angled position shown in  FIG. 1  for the drafting device  8  results. In this position, the pair I of feed rollers  28   a ,  28   b  is arranged slightly higher above the head of the operator  5  than the pair IV of withdrawal rollers  35   a ,  35   b . Thus, the operator can selectively pivot the press arms  44  to the side and/or the arms  50 ,  52  downwards to open the drafting device  25  with simple movements of the hand and without leaving the work area  4 . Corresponding conditions also result for the other drafting devices  25   a  and  25   b , as  FIG. 6  shows. 
     It is particularly advantageous to couple the two rollers  31   a  and  31   b , over which the aprons  34   a ,  34   b  run, by spur gears (not shown) situated in engagement, for example, at a location  54  ( FIG. 5 ). As a result of this, it is also possible to forcibly drive the upper rollers  31   b , which are normally only entrained by frictional force in  FIG. 5 , by positive locking. For this the driving roller  31   a  of the (lower) apron  34   a  in  FIG. 5  is expediently driven by means of a toothed belt indicated by arrows r, which is laid around a toothed pulley  55 , the rotational axis of which coincides with the pivot axis of the pivot pin  53 . The toothed pulley  55  is preferably fastened to a shaft, which is perpendicular to the feed rollers  28   a ,  28   b  and passes through the entire drafting device group and from which the drives for the rollers  31   a  of the other drafting devices  25   a ,  25   b  etc. are also derived. 
     It is additionally advantageous to provide the rollers  31   a ,  31   b  on the periphery with radial pins  56  ( FIG. 6 ), which engage in holes  57  formed on the edges of the aprons  34   a ,  34   b  and arranged one behind the other in the transport direction  26 . This enables both aprons  34   a ,  34   b  to be forcibly driven completely free from slippage, which promotes a uniform attenuation of the fibre material  27 . 
     In addition,  FIG. 5  schematically shows how despite the foldable arrangement of the different function parts, a suction/blower system can be provided to keep the drafting device  25  substantially free from fluff or the like. For this purpose, on both sides of the withdrawal rollers  35   a ,  35   b  at least one respective blower nozzle  58  is provided, into which blast air is introduced in the direction of the entered arrows. As a result, the rollers  35   a ,  35   b  remain substantially free from fluff. The exiting blast air flow is directed over filler pieces  59 , which are arranged on the rear side of the rollers  35   a ,  35   b  close to the exit gap between the aprons  34   a ,  34   b  and serve to optimise the blast air flow, onto the returning run of the aprons  34   a ,  34   b . From there the air flow is fed via air ducts  60  and  61 , which are configured on the lower and upper side of the housing  46  enveloping the drafting device  25  and in which a slight underpressure expediently prevails, to a central extraction means. To allow a pivoting movement of the arm  52  in spite of the lower air duct  60 , the air duct  60 , as separation points  60   a  in a front and rear region indicate, has a central section  60   b , which is fastened to the arm  52  in such a way that it can be pivoted together with this and the apron assemblies out of the housing  46  in the direction of arrow z ( FIG. 5 ). Moreover, the filler pieces  59  are expediently mounted on arm  50  or  52  so that they do not disturb the pivoting movements thereof. 
     In addition,  FIG. 6  shows that two further filler pieces  62  are respectively arranged in the pre-drafting zone  41  between the rollers  28   a ,  29   a  and  28   b ,  29   b  and between them form guide channels  63  for the fibre material  27 . The automatic threading of the fibre material  27  in the substantially closed drafting device  25  is substantially simplified as a result of this. The same applies to the other drafting devices  25   a  and  25   b.    
     Finally, a distance dimension  64  in  FIG. 6  shows that the guidance of the folded fibre material  27  through the roller pair IV expediently does not occur exactly centrally compared to the fibre path in the roller pairs I and II. As the rollers  35   b  ( FIG. 5 ), which are generally covered with a rubber layer, are subject to a certain amount of wear because of the high rotational speeds of e.g. 2000 rpm to 4000 rpm, the rollers  35   b  can be reversed where necessary. The running time of the rollers  35   b  can also be doubled as a result of this without any expensive changeover. 
     If necessary, the drafting device according to  FIGS. 5 and 6  can also be arranged in a position that is pivoted 90° around the longitudinal axis such that the arms  50 ,  52  can be pivoted to the side and the press arms can be pivoted downwards. 
       FIG. 7  shows a further exemplary embodiment for a drafting device  65  according to the invention, which in a similar manner to  FIGS. 3 and 4  is particularly suitable for a segment design, in which the number of the drafting devices combined to form one structural unit is comparatively small in comparison to the bar solution according to  FIGS. 1 and 2 , and amounts to two, for example. The drafting device  65  substantially corresponds to the drafting device  25  according to  FIGS. 5 and 6 , but differs from this through a characteristic angled or sloping position of a main drafting zone  66  in the region of a bend K. The function parts in a pre-drafting zone  67  and a folding zone  68  in  FIG. 7  are configured and arranged in a substantially identical manner to  FIGS. 5 and 6 , and are therefore provided with the same reference numerals. Like therein, the fibre materials  27  are thus guided through the pre-drafting and folding zones  67 ,  68  parallel to the floor  7  ( FIGS. 1 and 3 ) and perpendicularly to the knitting needles  3  before they are fed into apron assemblies  69   a ,  69   b . Two respective aprons  70   a  and  70   b  of these assemblies  69   a  and  69   b  are laid around two rollers  71   a ,  71   b  and two deflection elements  72   a ,  72   b  and between them form guide paths  73 , which begin at the exit of the rollers  29   a ,  29   b  about at the height of the path predetermined by the transport direction  26  and are then extended on an angle downwards in the direction of the deflection elements  72   a ,  72   b  located at a lower level. The angle of inclination amounts to approximately 45° to the floor  7 , for example. The main drafting zone  66  with the parts  35   a ,  35   b ,  50 ,  51 ,  58  and  59  adjoins the rollers  71   a ,  71   b  taking into consideration this angle of inclination in substantially the same manner as in  FIG. 5 . Because of the bend K formed by the described angled position in  FIG. 7 , the occurring fibre flows are introduced into the knitting needles  3  on an angle. A difference with respect to  FIG. 5  resulting from  FIG. 7  is therefore that while the threads discharging from the drafting devices  65  can be introduced into the knitting needles  3  on an angle as in  FIG. 5 , the pivoting press arms  44  ( FIG. 6 ) and the arms  52  are at the same time located lower than in  FIG. 5  and are therefore even more easily accessible for the operator  5  without restricting his/her head clearance. 
     A further exemplary embodiment of a drafting device  74  according to the invention that is particularly expedient for practical application is evident from  FIGS. 8 to 12 . According to  FIG. 8  the support ring  15  of the circular knitting machine  1  configured in accordance with  FIG. 1  is provided on its outer periphery with vertical mounting plates  75 , which serve to fasten a plurality of drafting devices  74 . For this purpose, each drafting device  74  has a flange plate  77  on a front side of a drafting device housing  76  (cf. in particular  FIG. 11 ), which is fastened to one of the mounting plates  75  with fastening screws  78  and locating pins  79 . 
     The drafting device  74  is configured analogously to  FIG. 7  and according to  FIGS. 9 to 12  is provided with four pairs I to IV of drafting device elements. The first pair I includes two feed rollers  80   a  and  80   b , which with rollers  81   a ,  81   b  of the second pair II form a pre-drafting zone, whereas the fourth pair IV includes two withdrawal rollers  82   a ,  82   b . During operation ( FIG. 8 ) the rollers  80   a ,  80   b  and  81   a ,  81   b  stand vertically, whereas rollers  82   a ,  82   b  stand horizontally. Arranged between the rollers  81   a ,  81   b  and  82   a ,  82   b  are two apron assemblies  83   a  and  83   b , which analogously to  FIG. 7  have rollers  84   a  and  84   b , deflection elements (not further shown) associated with these and also aprons  85   a  and  85   b  guided on these. Analogously to  FIG. 7 , the rollers  84   a ,  84   b  form a folding zone with rollers  81   a ,  81   b  and are therefore arranged horizontally during operation like the withdrawal rollers  82   a ,  82   b  and the deflection elements that are not shown. The aprons  85   a ,  85   b  form a guide path  86  ( FIG. 9 ) between them, which like the guide path  73  in  FIG. 7  is arranged on an angle to a rotational axis  87  ( FIG. 8 ) of the needle cylinder  2  and to the knitting needles  3 . A feed funnel or trocar  88 , through which the fibre material (not shown) is fed into the clamping gap between the feed rollers  80   a ,  80   b , is located at the inlet of the drafting device  74 . Moreover, in accordance with the above explanations the conditions are selected so that the fibre material is folded, for example, in a V-, N- or W-shape in the folding zone between the rollers  81   a ,  81   b  and  84   a ,  84   b  before it is fed by means of the aprons  85   a ,  85   b  to the exit gap between the withdrawal rollers  82   a ,  82   b  and is subjected to the main drafting operation by these. The fibre material discharging from the exit gap is then preferably converted by means of a spinning device  21  (cf.  FIGS. 4 ,  7  and  8 ) or another spinning element into a temporary yarn and transported to the knitting needles  3 . 
     A special feature of the drafting device  74  is that it can be at least partially opened by at least the apron assemblies  83  being mounted completely on a structural element in the form of an insertion part  89 , which is configured in the shape of a module and is made more clearly visible by hatching in  FIGS. 9 ,  9   a ,  11  and  12 . This insertion part  89  sits in a downwardly open recess  90  ( FIG. 9   a ) of the housing  76  and—viewed in the transport direction of the fibre material—has respective guide surfaces  90   a  ( FIG. 9   a ) as front and rear boundaries that cooperate with corresponding guide surfaces  90   b  ( FIGS. 8 ,  9  and  9   a ) defining the recess  90 . As  FIGS. 8 and 9 ,  9   a  show, the guide surfaces  90   b  stand vertically during operation. Therefore, the insertion part  89 , including the two apron assemblies  83   a ,  83   b , can be pulled downwards out of the drafting device  74  in the direction of a double arrow s ( FIG. 9 ), as is shown in  FIG. 9   a , or can be inserted again. Therefore, if, analogously to  FIG. 3 , the drafting device  74  is arranged above the stitch-forming points  6 , but within the reach of the operator  5 , then it is possible for him/her without leaving the work area  4  to pull out the insertion part  89  downwards in order to maintain and/or repair the function parts contained in the apron assemblies  83 . Alternatively, instead of the position of the guide surfaces  90   b  parallel to the rotational axis  87  ( FIG. 8 ), an angled position to the rotational axis  87  can also be provided, in which case the insertion part  89  could be pulled out downwards on an angle. 
     Otherwise, it is clear that the housing  76  and the insertion part  89  can be provided with interacting locking elements, which have been omitted for better clarity, and possibly also with further positioning elements to position and fix the insertion part  89  correctly in the drafting device  74  in the working position evident from  FIG. 9 . Moreover, the lower driven withdrawal roller  82   b  in  FIG. 9  is preferably also mounted on the insertion part  89  (cf.  FIG. 9   a ), so that its position relative to the driven aprons  85   b  can be easily adjusted when the insertion part  89  is pulled out. Apart from this, it is clear that the insertion part  89  can be provided with spring elements or the like (not shown) in order to press the driven apron assemblies  83   b  against the driving apron assemblies  83   a.    
     As shown in particular in  FIGS. 10 to 12 , two drafting device sections are preferably arranged next to one another in tandem configuration in each drafting device  74  in a similar manner to  FIG. 3 . Therefore, the drafting device  74  has two feed funnels  88 , two pairs of feed rollers  80   a  and  80   b , two aprons  85   a ,  85   b  etc., so that two fibre materials can be attenuated simultaneously in parallel operation and fed to adjacent knitting points of the circular knitting machine  1 . In this case, the driven rollers  80   b  of the pairs I are expediently arranged respectively on the outside of the housing  76  and there are rotatably disposed on pivoting press arms  91  (e.g.  FIGS. 10 and 11 ). The press arms  91  can be pivoted in a manner known per se to the side and outwards in the direction of arrows t ( FIG. 10 ) around pivot pins  92  ( FIGS. 10 ,  11 ) that are vertical during operation, as also applies accordingly for the press arms  44  shown in  FIG. 6 . Therefore, in the case of the exemplary embodiment according to  FIGS. 8 to 12 , the function parts can be made accessible by pulling out the insertion part  89  downwards and/or pivoting the press arms  91  to the side. If it is desirable to make at least the driven withdrawal rollers  82   b  accessible independently of the other function parts, they can be mounted on a separate downward pivoting arm, analogously to  FIG. 7 . Moreover, the press arms  91  can be configured in accordance with  FIGS. 4   a  and  4   b.    
     Finally,  FIG. 10  also shows that the drafting devices  74  can be arranged very closely adjacent to one another. Because of the described segment design, they lie radially to the centre axis  87  ( FIG. 8 ) of the needle cylinder  2  and therefore at the location where the threads exit have their smallest spacing a, whereas they have larger spacings b at the location where the fibre materials are fed. In association with the tandem design and despite the fact that the press arms  91  must be capable of pivoting to the side, this allows a comparatively substantial package density of the drafting devices  74  on the periphery of the needle cylinder  2  with the consequence that, even if the knitting machine  1  is provided with 72 or even 96 knitting points, the spinning devices  21  ( FIG. 3 ) only require comparatively short transport tubes  23  and only need a single twist element  22 , which is associated with a substantial energy saving. 
     In the exemplary embodiment of  FIGS. 8 to 12  the drive for the driving rollers  80   a ,  81   a  of the first and second pair I and II is achieved by means of vertically standing drive shafts, onto which toothed pulleys  94 ,  95  are drawn. This enables both toothed pulleys  94 ,  95  to be driven by means of a respective toothed belt, which surrounds the rotational axis  87  of the needle cylinder  2  essentially in a circular shape. Therefore, only one respective drive motor is required for all the rollers  80  and  81  present on the periphery of the circular knitting machine  1 . The desired transmission ratio and the necessary direction of rotation can be set by means of spur gears  96 ,  97  ( FIG. 9 ). In contrast, the drive for the driving rollers  84   a  of the apron assemblies  83   a  is transmitted onto the horizontally lying shafts of these rollers  84   a  by means of bevel gears  98  indicated schematically in  FIG. 9  of the drive shaft of the toothed pulley  95 . In particular, the arrangement is expediently such that these bevel gears  98  at the same time represent couplings, which cooperate with corresponding bevel gears on the shafts of the rollers  84   a . Therefore, when the insertion part  89  is pulled out of the drafting device  74  ( FIG. 9   a ) the separation thereof is automatically effected by the drive. However, if the insertion part  89  is run into the drafting device  74  again, then the cooperating bevel gears are automatically coupled to one another with respect to drive. 
     The driving rollers  82   a  of the withdrawal rollers IV, if they are also to be driven by means of vertically standing shafts, would likewise have to be coupled to these shafts via bevel gears. This could lead to problems in view of the high rotational speeds of these rollers  82   a ,  82   b , or require costly transmissions. Therefore, it is provided according to the invention to provide the driving withdrawal rollers  82   a  of the folding drafting devices  25 ,  65  and  74  with drives associated individually with them. This is indicated schematically in  FIGS. 9 and 9   a , according to which a motor  99  is housed in the housing  76  and coupled with respect to drive via a toothed belt  100  to a toothed pulley, which sits on the shaft of the driving withdrawal roller  82   a . Naturally, both (or more) withdrawal roller pairs IV can be driven with the same motor  99  if the drafting devices  74  are arranged for processing two (or more) fibre materials in parallel, as in  FIGS. 8 to 12 . 
       FIG. 13  shows as exemplary embodiment a 3-roller drafting device  102  according to  FIG. 3  with two drafting device sections working in parallel, which each have a pair I, II and III of drafting device elements, wherein in  FIG. 13  only one of the drafting device elements present in pairs is respectively visible. Each drafting device section contains two feed rollers  103 , two withdrawal rollers  104  and two respective apron assemblies  105  between these, each having a roller  106 . As in  FIG. 3 , all the drafting device elements are arranged parallel to one another and have rotational axes that stand vertically during operation, as is indicated respectively by dot-dash lines. In addition, adjoining the withdrawal rollers  104  is a nozzle assembly  107  consisting substantially of a closed housing, in which air nozzles (not shown further) intended for blowing on the withdrawal rollers  104  as well as extraction ducts for loose fibres and air supply means for the pneumatic twist elements  22  of the spinning devices  21  can be housed. As is indicated by broken lines, the apron assemblies  105  and the nozzle assembly  107  are respectively configured as insertion parts  108 ,  109 , which can be pulled downwards out of the drafting device  102  in the direction of the arrows u. The configuration of the insertion parts  108 ,  109  can be selected analogously to  FIGS. 9 and 9   a . As a schematically indicated coupling  110  for the insertion part  108  shows, the apron assemblies  105  can be decoupled when the insertion part  108  is pulled out by drive elements located above this, the shaft members of which are arranged parallel to those of the rollers  106 . In a corresponding manner, the feed rollers  103  and the withdrawal rollers  104  can also be arranged in a respective insertion part  103   a ,  104   a , which is connected with a further coupling  110  to the drive or is decoupled from this. 
     Alternatively, the driven rollers of pair I, also analogously to  FIGS. 8 to 12 , can be disposed on a common press arm (not shown) that can be pivoted to the side and that could also be replaced by two individual press arms. 
     The exemplary embodiment according to  FIG. 14  differs from that according to  FIG. 13  in that it is configured as a 4-roller folding drafting device  111  without bend K ( FIG. 7 ). Here, feed rollers  112  of the first pair I that are horizontal during operation and rollers  113  of the second pair II, which are also horizontal during operation and form the pre-drafting zone with said feed rollers, are arranged in a module forming an insertion part  114 . This can be configured and arranged analogously to  FIGS. 9 and 9   a  and be pulled out downwards in the direction of an arrow l. As a result of this, it is possible to make the space in front of the following apron assemblies  115  of the drafting device  111  completely free. 
     The axes of the feed rollers  112  and the rollers  113  of the pair II are arranged horizontally here, whereas the axes of the apron assemblies  115  and of withdrawal rollers  116  are arranged vertically. Therefore, as indicated in  FIG. 9  for rollers  84   a , the driving rollers of pairs I and II, are driven e.g. by means of bevel gears  117 ,  118 , which mesh with further bevel gears sitting on the shafts  112 ,  113  and at the same time serve as couplings when the insertion part  114  is pulled out or inserted. As a consequence of this, the rollers  112 ,  113  are automatically coupled to a drive (not shown further) explained further below or decoupled from this during the movements of the insertion part  114 . 
     The driven drafting device elements of the apron assemblies  115  and the withdrawal rollers  116  can be disposed analogously to  FIG. 4  on? press arms or the like that can be pivoted away to the sides of the drafting device  111 . However, a particularly preferred embodiment results when the apron assemblies  115  and the withdrawal rollers  116  are fastened, analogously to  FIG. 13 , to insertion parts  115   b  or  116   a , which can be pulled away downwards in the direction of the arrows l. 
       FIG. 15  shows a 4-roller drafting device  119 , which is currently considered to be the best exemplary embodiment of the invention and differs from that according to  FIG. 14  in that the axes of feed rollers  120 , apron rollers  121  and withdrawal rollers  122  are all arranged vertically during operation, whereas further rollers  123  arranged between the feed and apron rollers  120 ,  121  have horizontally located axes. In order to prevent the fibre materials from being folded between the rollers  120 ,  123  of the first and second pair I and II, even though these are arranged perpendicular to one another, the distances between the nip lines of these rollers in relation to the width of the feed sliver are selected so that the above-explained conditions that are necessary for folding are not met, in that, for example, the spacings of the nip lines are selected to be substantially larger than the widths of the slivers. Moreover, guide elements  124  or the like arranged on an angle or curved in a helical shape over an angle of 90° can be provided between the rollers  120  and  123  that prevent folding, while promoting a mere deflection of the sliver around 90°. 
     An advantage of the drafting device  119  according to  FIG. 15  is that during operation the axes of the rollers  123  can be arranged horizontally, while all the other rollers can be arranged vertically, as is preferred for reasons of a simplified drive, as will be explained in more detail below. The horizontal rollers  123  and possibly the guide elements  124  are expediently housed in an insertion part  125 , which can be pulled downwards out of the drafting device  119  in the direction of an arrow m, as also applies for the other function parts. Therefore, all rollers of the pairs I, II, III and IV are mounted here on the insertion parts or the like evident from  FIGS. 13 and 14 . Finally, only a single bevel gear  126  associated with the insertion part  125  and the rollers  123  is necessary, which at the same time serves as a coupling, whereas all the other insertion parts are coupled to the drive by means of the couplings  110 . 
       FIG. 16  finally shows an exemplary embodiment for a drafting device  127 , which is provided with vertically arranged rollers  128  and  129  in the region of pairs I and II. Analogously to  FIG. 15 , in the region of drafting device elements III and IV the drafting device  127  additionally has two respective pairs of apron assemblies  130  and withdrawal rollers  131 , the axes of which are also arranged vertically during operation. However, an additional pair V of drafting device elements comprising horizontally arranged rollers  132  is provided between the drafting device pairs II and III. In this case, the conditions are selected, on the one hand, in such a way that the rollers  129  and  132  form a folding zone in the sense of folding zone  43  according to  FIG. 5 , for example, by adjusting the starting width of the sliver in the nip line of the rollers  129  to 16 mm and the spacing of the nip lines between the rollers  129  and  132  to about 30 mm, so that a W-shaped fold results and the sliver leaving the rollers  132  only has a width of approximately 4 mm. On the other hand, the distance between the nip lines of rollers  132  and rollers  133  of the apron assemblies  130  is likewise adjusted to be sufficiently large, e.g. to 30 mm, compared to the still only approximately 4 mm wide sliver so that no new folding results here. It would also be conceivable to arrange guide plates corresponding to the guide elements  124  according to  FIG. 15  between rollers  132  and  133 . Otherwise, the drafting device  127  can be formed simply by additionally installing the rollers  132  between the rollers of the second and third pair of a conventional 4-roller drafting device. 
     The exemplary embodiment according to  FIG. 16 , like the exemplary embodiment according to  FIG. 15 , additionally has the advantage that only one drive bevel gear  134  is required to drive the rollers  132 , since the shaft members of all the other rollers  128 ,  129 ,  131  and  133  can be arranged vertically during operation and can be connected by means of the couplings  110 . Therefore, it is generally sufficient to only dispose the rollers  132  in an additional insertion part  135 , which can be pulled downwards out of the drafting device  127  in the direction of an arrow n, whereas the remaining roller pairs can be disposed, analogously to  FIGS. 13 to 15 , on the insertion parts described therein. Apart from this, it is clear that the exemplary embodiments according to  FIGS. 14 to 16  could also be provided with a nozzle assembly  107 . 
     The drive of the described drafting devices can be performed in a usual manner for drafting devices. When they are applied to circular knitting machines (cf.  FIGS. 3 and 8 ), however, it is expedient to arrange as many drafting device elements as possible so that their axes stand vertically and also, as shown in particular in  FIG. 8 , the shafts of these rollers project upwards beyond the drafting device housings and are provided there with toothed pulleys or the like (e.g.  94 ,  95  in  FIG. 9 ). It is then possible to drive all the toothed pulleys belonging to the same drafting device pairs (I, II etc.) by means of a respective toothed belt  137 ,  138  or  139  or the like that coaxially surrounds the centre axis  87  of the needle cylinder  2 . That is shown schematically in  FIG. 17 , in which three groups of toothed pulleys  140 ,  141  and  142  arranged in a circle are provided, wherein e.g. in accordance with  FIGS. 14 ,  15  and  16  the toothed pulleys  140  are respectively fastened to the shafts of the driving feed rollers (e.g.  112 ,  120 ,  128 ), the toothed pulleys  141  on the shafts of the driving apron assemblies (e.g.  115   a ,  121 ,  133 ) and the toothed pulleys  142  on the shafts of the driving withdrawal rollers (e.g.  116 ,  122 ,  131 ). Irrespective of the number of knitting points present, each toothed belt  137 ,  138  and  139  only needs one respective associated, schematically indicated drive motor  143 ,  144  and  145  and, if necessary, one respective associated press roller. 
     The horizontal drafting device elements can be driven substantially with the same drive motors. For this, in  FIG. 14 , for example, additional spur gears  146  are fastened to the shafts of the rollers  115   a  that mesh with further spur gears  147 , which are fastened to the shafts of the bevel gears  118 . A corresponding arrangement is shown in  FIG. 15 . In contrast,  FIG. 16  shows that two further spur gears  147  and  148  can mesh with the spur gear  146 , wherein the spur gear  147  serves to drive the horizontal rollers  132  by means of a bevel gear  134  corresponding to bevel gear  126  ( FIG. 15 ) and the spur gear  148  serves to directly drive the vertical rollers  129 . In the exemplary embodiment according to  FIG. 13  only two toothed belts and drive motors are necessary, since the rollers  103  and  106  can be coupled here, for example, by spur gears  150 ,  151  to a drive shaft of the rollers  106 . 
     Apart from this,  FIGS. 13 to 16  show that in all cases structural elements either configured in the form of insertion parts  108 ,  109 ,  114 ,  115   b ,  116   a ,  125  and  135  or press arms can be provided in order to make all the essential function parts accessible from the work area  4 , analogously to  FIGS. 1 ,  3  and  8 . However, it is expedient to use the insertion parts in particular in the location where, in accordance with  FIG. 10 , in the vicinity of the drafting devices particularly small distances a of e.g. few millimeters are desired between the drafting devices, since in such a case parts that can be pivoted or displaced to the side would hinder a close arrangement of the drafting devices. 
     A configuration of an insertion part  153  that is particularly preferred for the purposes of the invention is shown in  FIG. 18 . It includes a housing  154 , which is H-shaped in front view and is provided with screw holes, threaded bores  155  or the like on the upper sides of long legs  154   a . Two shafts extended parallel to the legs  154   a  are rotatably disposed in a short cross piece  154   b  of the H-shaped housing  154 . A respective roller  157   a ,  157   b  or  158   a ,  158   b  intended to drive an apron  156   a ,  156   b , for example, is fastened on these shafts on both sides of the cross piece  154   b , and the aprons  156   a ,  156   b  (the second apron pair is not visible in  FIG. 18 ) are guided as usual by these rollers and two deflection elements  159  spaced from these, as can be clearly seen in  FIG. 18  for the apron pair  156   a ,  156   b.    
       FIG. 18  further shows that the roller  157   a  or its shaft, for example, is configured longer than the adjacent roller  157   b  or its shaft and, for example, projects above the upper side of the legs  154   a ,  154   b , for example, with four or six-edged coupling pin  160 . This coupling pin  160  additionally passes through a cover plate  161  ( FIG. 13 ), for example, at the upper end of the drafting device housing. Moreover, a likewise four- or six-edged coupling sleeve  163 , which is intended to receive the coupling pin  160  in a manner fixed against rotation and is open towards this, is fastened on the lower end of a drive shaft  162  associated with this apron assembly, which is driven in the manner described on the basis of  FIG. 17 , for example. Therefore, if an insertion part  153  configured in accordance with  FIG. 18 , for example, is pulled downwards out of the drafting device housing in the direction of arrow u, then the parts  160  and  161 , which represent the couplings  110  indicated schematically in  FIGS. 13 to 15 , are automatically separated from one another. Otherwise, the arrangement is such that when the insertion part  153  runs into the drafting device housing the coupling pin  160  automatically enters the coupling sleeve  163  and thus connects the apron assembly to the associated drive. After the housing  154  is laid against the cover plate  161 , it is fastened with fastening screws screwed into the bore  155 . 
     The other described insertion parts with vertically arranged function parts can be configured accordingly, wherein the aprons are omitted, depending on the respective case. In a similar manner, such insertion parts that are provided with horizontal function parts (e.g.  123  in  FIG. 15 ) can also be provided. In this case, the bevel gears  98  described on the basis of  FIGS. 9 ,  9   a  or the spur gears  118  or  126  shown in  FIGS. 14 and 15  replace the coupling pin  160  and the coupling sleeve  163 . 
     Finally,  FIG. 18  shows that in accordance with the tandem design described above, the insertion part  153  has a respective double-apron assembly above and below the cross piece  154   b . In this case, the shafts or drive rollers of these assemblies are respectively only disposed on one side, i.e. on the side of the cross piece  154   b , and are thus cantilevered, so that after the insertion part  153  has been removed from the drafting device the aprons guided by these can be detached upwards or downwards and replaced. Therefore, when the tandem design is applied, it is expedient to configure the insertion parts so that they can be removed from the drafting devices completely, whereas in the case of insertion parts that only have one apron pair (e.g. the lower one in  FIG. 18 ), it would be sufficient if the insertion could be pulled so far downwards that the aprons to be replaced are easily accessible. Apart from this, the insertion parts  153  can be provided with resilient elements or the like, which press the driven aprons  156   b  against the driving aprons  156  during operation. 
     The invention is not restricted to the described exemplary embodiments, which can be modified in a simple manner. This applies in particular to the expressions “vertical” and “horizontal”, since positions of the different function parts are also possible with axes differing therefrom during operation. For example, the axes of the drafting devices  18  in  FIG. 1  could also be arranged at angles of between 0° and 90° to the centre axis of the needle cylinder  2 . The same applies to the relative arrangement of the nip lines of the rollers causing the folding (e.g.  29  and  31 ), which can also enclose angles other than 90°, e.g. 45° to 90°, relative to one another. Moreover, it is clear that the described pivot arms and insertion parts only represent examples, which can be deviated from in a variety of ways, and that the insertion parts in particular can be provided with means that are not further represented to press the driven rollers and aprons resiliently or pneumatically against the driving rollers and aprons during operation. In particular for function parts further removed from the centre axis of the circular knitting machine, insertion parts that can be pulled out laterally could also be provided. Moreover, it is clear that the function parts that must be maintained and possibly frequently replaced are preferably mounted on or in the pivoting arms, insertion parts etc. so that they can be easily replaced when these are in the open state. For this, it is above all recommended, as may be seen in  FIGS. 3 ,  6  and  18 , to fundamentally mount the rollers and deflection elements (e.g.  31 ,  32  in  FIG. 6 ) only at one end (cantilevered) and to arrange their free ends at the bottom or the side, so that at least the aprons can be removed towards the free ends of the driving rollers after the press arms, insertion parts etc., which are configured in virtually any desired manner, are pivoted or pulled out (cf. also  FIG. 18 ). In association with this, it is also advantageous in particular in the case of the tandem design ( FIG. 18 ) to configure the insertion parts such that they can be removed completely from the drafting devices, so that both double-apron assemblies present can be easily replaced. In addition, it is expedient, in particular in the pre-drafting zones, for example, to arrange filler pieces, which respectively face one another and form the guide channels for the fibre materials, between consecutive nip lines, as is indicated schematically, for example, in  FIGS. 6 ,  13  and  14 . Moreover, the number of pairs of drafting device elements used for each drafting device can differ depending on the individual case, i.e. 3-, 4-, 5-roller drafting devices etc. can be provided. In addition, the mounting of the drafting devices on a stitch-forming machine is only shown by way of example in  FIGS. 1 ,  3  and  8 . In fact, it would also be possible to mount the drafting devices in a different way, in particular on a separate frame that can be run close to the machine or surrounds this, e.g. to subsequently fit an already existing machine with the described drafting devices. Moreover, it can be advantageous to configure the aprons, e.g. those of the apron assemblies  30   a ,  30   b  in  FIG. 5 , to be longer than usual in transport direction  26  and to provide them with an associated clamping device, which is axially displaceable in the transport direction  26  and which in the main drafting zone creates an additional clamping zone in the gap formed by the aprons, as indicated schematically with an arrow in  FIG. 5 . As a result of this, the usual clamp dimension can be adapted to the length of the fibres used and the uniformity of the discharging fibre materials can be improved. Finally, it is understood that the different features can be applied in combinations other than those described and represented.