WO2013017486A1

WO2013017486A1 - Single-cylinder knitting machine without sinkers and related process

Info

Publication number: WO2013017486A1
Application number: PCT/EP2012/064537
Authority: WO
Inventors: Renato Pilotelli; Roberto Pilotelli
Original assignee: Pilotelli Macchine Tessili S.R.L.
Priority date: 2011-08-02
Filing date: 2012-07-24
Publication date: 2013-02-07
Also published as: ITFI20110159A1

Abstract

The single-cylinder knitting machine without sinkers comprises latch needles (3) sliding in respective tracks (2) of the cylinder (1). The upper end of at least some walls of the tracks (2) of the cylinder is configured to form a stitch retaining element (7) integral with the cylinder (1). The retaining element can be in the form of a beak partly rising above the stitch forming surface (P) and facing the axis (X-X) of the cylinder. The needles (3) are moved radially outwardly during the lifting movement thereof, to safely bring the stitch (M) under the stitch retaining element (7).

Description

"SINGLE-CYLINDER KNITTING MACHINE WITHOUT SINKERS AND RELATED PROCESS"

Description

Technical field

The present invention relates to single-cylinder knitting machines without sinkers comprising latch needles sliding in respective tracks of the cylinder.

Unless differently indicated, term "sinkers" is understood herein as movable sinkers, i.e. knitting members provided with a cam-controlled movement during the knitting process. A machine without sinkers shall therefore be understood as a machine without movable sinkers.

State of the art

A circular knitting machine without sinkers is described for example in WO- A-2007/074486.

In the production of knitted fabric on circular machines without sinkers there is greater difficulty in forming the stitch with respect to corresponding machines with sinkers. In particular, in situations where operation takes place without knitted fabric hooked to the needles (for example when starting the production of a new item from the empty cylinder), or when there is a breakage of one or more yarns, with consequent formation of openings in the knitted fabric, the stitch being formed is loose, on all the needles of the machine in the first case or locally at said openings in the second case. In this situation, the needles, in their raising movement to engage the yarn, tend to draw therewith the last knitted stitch produced thereby which thus cannot be cleared and remains on the needles, preventing regular operation of the machine.

EP-A-0172145 describes a knitting machine for the production of pantyhose. Some embodiments of the machine disclosed in this prior art document are without sinkers. In these embodiments the upper ends of the walls forming the tracks of the cylinder in which the needles slide are configured to have a retaining element in the form of a beak extending partly above the stitch forming surface and facing the axis of the cylinder, said retaining elements being configured to intercept the stitches being formed. These stitch retaining elements are named fixed sinkers in the above mentioned publication.

The dimension of the retaining elements is closely linked to the fineness of the machine and to the density of the fabric produced and, in the above mentioned known machine this can result in a limitation of the range of widths of the stitches that can be produced.

Summary of the invention

To overcome this limitation, in some embodiments of the present disclosure the machine comprises stitch retaining elements in combination with needle moving members, for moving at least the upper end of the needles away from the axis of the needle cylinder, along at least part of the raising travel of the needles. In this way the needles, bending or moving radially outwardly toward the outside of the cylinder, pull the stitches retained by the needles, thus causing the stitches to engage under the adjacent stitch retaining elements regardless of the length of the stitches.

In a preferred embodiment of the invention, the distance of the tip of said stitch retaining elements from the axis of the cylinder is greater than the distance of the highest point of the internal profile of the hook of the needle from the axis of the cylinder, in such a manner that said stitch retaining elements do not obstruct the formation of the stitch on the stitch forming surface. Moreover, the distance of the tip of the stitch retaining elements from the axis of the cylinder is preferably less than the distance of the tangent to the cheek of the needle from the axis of the cylinder. In this way, when being lifted the cheek of each needle shifts the stitch engaged with the needle, moving the stitch away from the axis of the cylinder to cause it to engage under said adjacent stitch retaining elements, thus preventing the stitches from being drawn further upward by said needle during the lifting movement thereof.

According to some embodiments, the movement of the upper end of the needles away from the axis of the cylinder is obtained by elastic inflection of the needles to move the hook thereof radially outwardly, i.e. toward the outside of the cylinder, by providing the machine with specific needle inflecting members.

According to some embodiments of the invention, these needle inflecting members comprise at least one butt provided with a radial extraction pawl on each needle. Moreover, said needle inflecting members further comprise, for each feed of the machine, at least one radial extraction cam for extracting said butts, which is arranged to act on said radial extraction pawl.

In another embodiment, said inflection members comprise on each needle a bridge portion provided with a butt in a preferably approximately central position and, for each feed of the machine, at least one radial compression cam for radially pushing said central butt toward the axis of the cylinder.

In a further embodiment of the invention, the needle inflecting members comprise, for each feed of the machine, a magnet or an electromagnet configured to attract the stem of the needles.

The radial extraction cams or the radial compression cams, or the permanent magnets are preferably movable between an active position, to inflect or move the needles as described, and an inactive position, to prevent said inflection or movement of the needles. Moreover, a control arrangement can be provided, configured to shift said cams of one or more feeds to one of said two positions, to enable personnel operating the machine to perform said needle inflection toward the outside of the cylinder only when required, for example at the start of knitting a new piece, or to resume operation after yarn breakage or the like. After this critical phase has passed, the inflection members can be made inactive and the machine left to operate in a conventional manner. This enables a reduction in wear and in the noise generated by the machine.

Alternatively, to the same end, when electromagnets are provided, these latter can be activated or deactivated electrically by means of an electric control (switches or the like).

The invention also relates to a process for facilitating clearing of the needles from the last stitches formed when the needles are raised to engage the yarn, wherein during raising thereof each needle carries with its cheek the stitch engaged therewith under a stitch retaining element integral with the cylinder, inflecting or moving at least the upper end of the needles radially outwardly by means of specific needle moving or inflecting members , thus facilitating clearing of the stitch under the tip of the open latch of the needle, said needle moving or inflecting members being configured to be selectively de-activated or put into operation by means of suitable control devices.

Brief description of the drawings

The invention will be better understood by following the description and accompanying drawing, which shows practical non-limiting embodiments of the invention. More in particular, in the drawing:

Fig.l shows a partial axial sectional view of the cylinder of a knitting machine;

Fig.2 shows a top view according to II-II of Fig.l; Fig.3 shows a view of the detail III of Fig.1 enlarged, for a needle at stitch forming level;

Fig.4 shows a partial view according to IV-IV of Fig.3;

Fig.5 shows a view similar to that of Fig.3 of a needle during raising thereof, for engaging a new yarn;

Figs.6/A to 6/1 show in sequence and in reduced scale respective views, similar to that of Fig.1, of a needle during raising for engaging a new yarn;

Figs.7 and 8 show views analogous to those of Figs.5 and 1, respectively, in a machine according to an embodiment of the invention;

Fig.9 shows a partial perspective inclined, top view from the outside, of the machine of Fig.8, showing the supports of the needle control cams of two adjacent feeds;

Fig.10 shows a perspective view of one of the supports of the cams of Fig.9 as it appears after being separated from the machine and rotated through 180° with respect to that of Fig.9;

Figs.11 and 12 each show a view similar to that of Fig.8 for machines according to two different respective embodiments of the invention;

Fig.11 A shows a plan view according to XIA-XIA of Fig.11 ;

Fig.13 shows a view similar to that of Fig.12 of a preferred embodiment of the invention;

Fig.14 shows an enlarged view of the detail XIV of Fig.13 for a section implemented in a position angularly shifted about the cylinder of the machine with respect to the view of Fig.13 and at a control pinion;

Fig.15 shows a sectional view according to XV-XV of Fig.14;

Fig.16 shows a slightly enlarged plan view according to XVI-XVI of Fig.14;

Fig.17 shows the enlarged detail XVII of Fig.14.

Detailed description of embodiments of the invention

Here below reference will first be made to Figs. 1 to 61, where a machine with fixed stitch retaining elements is disclosed. This first embodiment is described for a better understanding of the subsequently described embodiments of the invention, which are shown in Figs 7 to 17.

With reference to Figs. l and 2, the cylinder of a knitting machine is indicated with 1. The cylinder 1 is rotatable about a vertical rotation axis X-X. On the external periphery of the cylinder 1 there are provided tracks 2 uniformly distributed around the circumferential extension of the cylinder 1. The tracks 2 extend parallel to the axis X-X of the cylinder 1. Respective needles 3 are slidingly arranged in the tracks

2, on needle 2 being arranged in each track 2. The needles are latch needles and are retained in the tracks 2 against the periphery of the cylinder 1, for instance by coil springs 5, which surround the cylinder 1. In the example illustrated two coil springs 5 are provided, but alternatively a different number of springs, for example only one spring, could be used. In other embodiments, containment cams can be used instead of or in combination with the spring or springs. Each track 2 is delimited by two substantially parallel lateral walls 2a, between which the respective needle 3 is arranged.

At the upper edge of the cylinder 1, the latter is provided with a plurality of preferably beak-shaped stitch retaining elements 7, hereinafter simply called beaks 7, extending above the stitch forming surface P. The beaks 7 are arranged with the respective tips facing the axis X-X. As will be described in greater detail below, the beaks 7 have the function of retaining the stitches as they are formed by the needles

3, to prevent the needles from drawing the stitches therewith when the needles are raised, i.e. partly extracted from the tracks 2, to engage a new yarn.

In the example illustrated in Figs.1 and 2, each beak 7 is formed at the upper end of a flat element 9, made of sufficiently wear-resistant material, for example steel. The flat element 9 is secured in a respective groove obtained in the upper end portion of the cylinder 1. Preferably, there are as many beaks 7 distributed along the upper edge of the cylinder as there are needles 3. Each flat element 9 lies in a respective intermediate plane between two respective adjacent needles, thus forming the upper portion of the lateral walls of the tracks 2 along which the the needles 3 slide. In other embodiments, the flat elements 9 can be formed as a single piece extending from the lateral walls 2a of the tracks 2, instead of being formed by separate elements 9. The use of separate elements is advantageous as it allows individual damaged beaks 7 to be replaced.

In the example illustrated in Figs.l and 3 the stitch- forming surface or plane P is formed by a horizontal rectilinear portion of the top end of each flat element 9, which can be higher than the top end lb of the body of the cylinder 1, as in the case of Fig.1. This allows the stitch- forming surface P to be formed of the flat elements 9, without problems of alignment with the edge lb of the cylinder 1.

According to some embodiments, the tip of each beak 7 (Fig.3) is located above said stitch- forming surface P and has a distance R from the axis X-X of the cylinder 1, said distance R being slightly greater than the distance Rl of the top of the needles 3 from the axis X-X of the cylinder 1, so that, during the retraction movement of the needle 3 inside the respective track 2 to form the stitch M, the tip of the beak 7 does not interfere with the yarn being knitted.

Moreover (as shown in Fig.5), according to some embodiments, the radial distance R of the tip of the beaks 7 from the axis X-X of the cylinder 1 is less than the distance R2 of the outermost point of the cheek 3C of the needle 3 from said axis. This arrangement enables each needle 3 to move each just formed stitch M outwardly by pulling it with the needle cheek 3C , thus introducing the stitch M under the two adjacent beaks 7, during the raising movement of the needle 3 to catch the yarn for forming the subsequent loop.

The operation of the beaks 7 described above is illustrated in the sequence of Figs.6/A to 6/1, which show various moments during the raising step of a needle 3 introducing the stitch M under the beaks 7. In Fig.6A the needle is in a withdrawn position, with the latch 3L closed and the stitch M engaged by the hook 3H of the needle. In Fig.6B the needle starts to rise and the latch 3L is gradually opened. Continuing to rise (Figs. 6C-6I), the needle is carried with the open latch 3L to a height such that the lower end of the latch 3L is positioned over the beak 7, while the stitch M has remained engaged under the beak 7, or more precisely under the two beaks adjacent to the track 2 wherein the needle 3 slides. The stitch M is then correctly cleared and the beaks 7 prevent it from being raised, drawn through friction by the needle 3 in its raising movement.

In the embodiment described and with reference to Figs.3 and 5, it is clear that, if the length of the formed stitch were to exceed the difference between the dimensions R2-R, the retaining action of the beaks 7 could not take place.

Also in order to overcome this limitation, according to preferred emodiments, during the raising movement of the needles 3, the latter are moved or inflected to shift the upper end thereof toward the outside of the cylinder drawing therewith the last-formed stitches, inserting said stitches under the respective adjacent beaks 7, thus making the height R less restricting. The outward shift of the needles 3 is schematically shown in Fig.7. The outward shift is schematically represented by arrow F2. The needles 3 can be translated radially outwardly and/or a portion thereof can be flexurally deformed, i.e. inflected. For example, as will be explained in greater detail here below, a portion of the stem of the needles can be inflected to move the upper part of the needles radially outwardly towards the beaks 7.

Figs.8, 9 and 10 show an embodiment wherein, to obtain inflection of the needles, each feed has a radial extraction cam 11 and each needle 3 is provided with an extraction butt with a radial extraction pawl 3 a configured to engage with the radial extraction cam 11.

In each feed of the machine, the radial extraction cam 11 can slide radially to the cylinder according to the axis Y-Y in a support 13, which is secured to the support 15 of the cams 17, which control the raising and lowering movement of the needles 3. In the support 13, the radial extraction cam 11 can be positioned along the axis Y-Y in an operating position (shown in Fig.8), in which the extraction butt 3a engages with the radial extraction cam 11 , or in an inactive position closer to the cylinder 1, in which the radial extraction cam does not interfere with the butt 3a. The radial extraction cam 1 1 is shaped to pull the butts with the pawls 3 a of the needles 3 radially outwardly, while the needles are raised to engage the yarn. This radial outward movement causes movement or inflection of the upper part of the stems of the needles 3 while said stems, in the lower part thereof, are retained adjacent or adherent to the cylinder 1 by the raising cams 17 and by the retaining springs 5.

Therefore, at each feed of the machine, the upper part of the needles 3 can be extracted in the direction of the arrow F2 and then returns elastically to rest against the cylinder 1 after the action of the radial extraction cam 11 has ceased.

The radial extraction cams 11 of the various feeds can be made to operate all together to inflect the needles 3, or released all together in the inactive position under the action of a respective spring 19, by means of a centralized control, not represented in the drawing. In some embodiments, individual controls can be provided for each radial extraction cam 1 1 or group of radial extraction cams 1 1, so as to activate or deactivate the radial extraction cams selectively.

Figs.11 and 11A illustrate another embodiment of the invention wherein a bridge portion 103b of the needle stem is provided in the part of the stem comprised between raising butts 103a and the hook 3H of each the needle 3. Each bridge portion 103b is in turn provided with an inflection butt 103c. In the embodiment of Fig.l l, the inflection butt 103c is in a median position with respect to the length of the bridge portion 103b, but this is not binding and the inflection butt 103c could also be in a non-median position of the bridge portion 103b. Similarly to the previously described embodiment, in each feed of the machine a support 113 is secured to the support 15 of the raising and lowering cams 17 of the needles 103. Inside the support 113 a flattening or radial compression cam 111 can slide according to an axis Y-Y. The radial compression cam 111 is configured to be positioned selectively in an operating or in an inactive position. In the inactive position the radial compression cam 111 is farther away from the cylinder axis X-X than in the operative position and is radially extracted with respect to the cylinder 1, such as not to interfere with the butts 103c. In the operative position, conversely, the radial compression cam is located such as to press the inflection butt 103c of the needles 103 toward the axis X-X of the cylinder 1, causing inflection of the needles 103.

The radially inwardly oriented pressure exerted by the radial compression cam 111 causes the stems of the needles 103 to inflect elastically in such a manner as to shift the upper part of each needle 103 radially outward toward the beaks 7 of the cylinder 1, to facilitate engagement and retention of the stitch M by the corresponding beaks 7.

Fig.12 shows a further embodiment of the invention, similar to that of Fig.8, but wherein the needles 3 do not have an extraction butt, but are of a conventional type. The outward inflection of the needles 3 according to the arrow F2 can be caused in each feed of the machine by a permanent magnet 211 placed in proximity of the stem of the needles 3. During rotation of the cylinder 1 the needles 3 pass in front of the permanent magnet 211. In this way, and as will be better illustrated below (with reference to Figs.16 and 17), the permanent magnet 211 acts directly on the stem of the needles 3 attracting them during raising of the needles and causing inflection thereof.

Preferably, each permanent magnet 211 is embedded in a respective cam 212 in such a manner that the front surface 21 la of the magnet 211 facing the cylinder 1 remains slightly behind the corresponding edges 212a, 212b of the cam 212, to prevent direct contact of the front surface 21 la of the magnet 211 with the needles 3, thus preventing wear of said front surface 211a. The edges 212a, 212b facing the cylinder 1 of the cam 212 and the front surface 211a of the permanent magnet 21 1 are shaped to define the radial extraction travel of the needles 3 during the raising stroke thereof, similarly to the embodiment described below with reference to Figs.16 and 17. In advantageous embodiments, the permanent magnet 211 and the respective cam 212 are slidingly mounted in a support 213 secured to the support 15 of the raising and lowering cams 17 of the needles 3. A control device (not shown) moves the support 213 selectively in an operating position or in an inactive position. The operating position is closer to the cylinder 1, so that the permanent magnet 211 attracts the stem of the needles 3, inflecting them, while these latter are raised to engage the yarn. In the inactive position the permanent magnet is at a distance from the needles sufficient to prevent the magnetic force of the permanent magnet 21 1 from attracting the needles 3, so that they are not inflected.

In other embodiments, the magnet 211 can also be an electromagnet rather than a permanent magnet. In this case the electromagnet can be energizable or de- energizable by means of an electric control, according to need. In this case, it is not necessary to provide a mechanical system for moving the magnet toward/away from the needles 3, as extraction is active only when the electromagnet is energized.

Figs.13 to 17 illustrate a further embodiment of the subject matter disclosed herein. According to this embodiment, in each feed of the machine and just as in the embodiment of Fig.12, the needles 3 can be moved away from the cylinder 1 by means of the action of permanent magnets, during raising of the needles to engage the yarn.

In particular, for each feed there is provided a permanent magnet 311 (see

Figs.16 and 17) secured, for example by gluing, in a respective support block 312 of magnetic material. The support block 312 is in turn secured, for example by means of screws, to a magnet-carrying slide 313. The front surfaces 313a of the magnet- carrying slide 313 facing the cylinder 1 and the exposed face of the magnet 311 are configured as a cam (see Fig.16) remaining slightly spaced apart in a plan view by a portion Z (Figs.16 and 17) which can, for example, be a few tenths of millimeter, for example two tenths of millimeter. In this way, the needles 3 attracted by the magnet 311 are in contact only with the magnet-carrying slide 313, preventing wear of the exposed face of the magnet 311, and follow the profile of the magnet-carrying slide 313 during their radial extraction travel.

For each feed, the magnet-carrying slide 313 with respective magnet 311 is movable radially, with respect to the cylinder. To this end the magnet-carrying slide is slidingly arranged in a respective radial recess 314 (Fig.14) of a supporting ring 315. The supporting ring 315 is coaxial with the cylinder 1 of the machine and is supported by brackets 316 (Fig.13) secured to the supports 317 of the yarn-carrying unit 318 of the machine. The supports 317 are, for example, six in number and distributed angularly around the cylinder. In some embodiments the magnet-carrying slide 313 is guided with minimum clearance in the recess 314 by edges 313b and by retaining plates 319 (Fig.15).

In proximity of the end opposite to the edge 313a, each magnet-carrying slide 313 has a slot 313c. Said slot 313c is inclined with respect to the longitudinal axis W-W of the magnet-carrying slide 313. A second ring 321 (Figs.13 and 14) coaxial with the cylinder 1 is rotatable freely by means of a series of balls 322 with respect to the support ring 315 and can be made to rotate by a limited angle with respect to this latter by means of a pinion 323 (Fig.14) which meshes with a toothed part of the second ring 321. The pinion 323 is rotatable in a hole of the ring 315 and the axis thereof terminates above the ring 315 with a square 323a in which a control handle (not shown in the drawing) can be inserted.

For each feed the rotatable ring 321 has a pin 320 that penetrates with minimum clearance in the slot 313c of the slide 313 of the respective feed.

In this way, by operating the pinion 323 manually, the magnets 31 1 of all the feeds can be moved closer the cylinder 1 in an active position to extract the needles 3 as described above, for example in the case of resuming operation after breakage of yarn, or at the start of knitting a new piece. Vice versa, the magnets 311 can be moved away from the cylinder 1 to make them inactive during normal operation of the machine, thereby preventing contact with the needles 3.

Irrespective of the structure of the needle moving members, which move the needles radially outwardly during raising thereof for picking up the yarn and form a new loop, the lastly formed stitch M is engaged and retained by the respective beaks 7 quite in the same manner as described with respect to Figs.2 to 61. The sequence is substantially as shown in Figs. 6A-6I, but the lifting movement of the needle is combined with a lateral radial movement according to arrow F2, as schematically represented in Fig.7.

Claims

1. A single-cylinder knitting machine without movable sinkers comprising a needle cylinder (1) and latch needles (3; 103) sliding in respective tracks (2) of the needle cylinder (1), wherein a stitch retaining element (7) is arranged at the upper end of at least some of said tracks (2). for retaining the stitches (M) being formed, during a raising travel of said needles, said stitch retaining element (7) being stationary with respect to the needle cylinder (1); characterized by comprising needle moving members (11, 3a; 103b, 103c, 11 1; 211; 311) for moving the upper end of the needles (3; 103) away from the axis of the cylinder (X-X) during at least part of a raising travel of the needles.

2. The machine according to claim 1, characterized in that said stitch retaining element (7) is in the shape of a beak partly rising above a stitch forming surface (P) and facing the axis (X-X) of the needle cylinder (1).

3. The machine according to claim 1 or 2, characterized in that the upper ends of all the tracks (2) have a respective stitch retaining element (7).

4. The machine according to claim 1 or 2 or 3, characterized in that each track (2) is delimited by respective lateral walls (2a) extending parallel to the axis (X-X) of the needle cylinder (1), each wall (2a) separating two adjacent needles (3; 103); and that each stitch retaining element (7) is integral with a wall (2a) of the respective track (2).

5. The machine according to claim 4, characterized in that each stitch retaining element (7) is made in once piece with the respective wall (2a) of the track (2)·

6. The machine according to claim 4, characterized in that each of said stitch retaining elements (7) is formed in a plate (9) secured to the top end (la) of the needle cylinder and forming part of the respective wall (2a) of the respective track (2)·

7. The machine according to claim 6, characterized in that at the top end thereof said plates (9) have an edge forming a stitch forming surface (P) higher than the upper edge (lb) of the needle cylinder (1).

8. The machine according to one or more of the preceding claims, characterized in that the distance (R) of the tip of said stitch retaining elements (7) from the axis (X-X) of the needle cylinder (1) is greater than the distance (Rl) of the highest tip of the internal arched profile of the hook (3H) of the needle (3; 103) from the axis (X-X) of the needle cylinder and less than the maximum distance (R2) of the cheek (3C) of the needle from the axis (X-X) of the needle cylinder (1) so that each needle, during raising thereof, with its cheek shifts the stitch engaged therewith, moving it away from the axis (X-X) of the needle cylinder (1) to take it to engage under and with said adjacent stitch retaining elements (7), preventing the stitch from being drawn further upward by the needle.

9. The machine according to one or more of the preceding claims, characterized in that said needle moving members are configured for moving the upper end of the needles (3; 103) away from the axis of the needle cylinder by causing an elastic inflection of the stem of the needles.

10. The machine according to one or more of the preceding claims, characterized in that said needle moving members comprise for each needle at least one butt with a radial extraction pawl (3a) and, for each feed of the machine, at least one radial extraction cam (1 1) to move said butts with the radial extraction pawl (3 a) away from the axis (X-X) of the needle cylinder (1) and thus move the upper end of the needles away from the axis (X-X) of the needle cylinder (1), inflecting said needles.

11. The machine according to one or more of claims 1 to 9, characterized in that said needle moving members comprise for each needle (103) a bridge portion (103b) provided with an inflection butt (103c) and, for each feed of the machine, at least one radial compression cam (111) configured to exert a radial pressure toward the axis (X-X) of the needle cylinder (1) on said inflection butt (103c) for inflecting said bridge portion (103b) of the needle (103) in such a manner as to move the upper end of the needle (103) away from the axis (X-X) of the needle cylinder (1).

12. The machine according to claim 11, characterized in that, in each needle, said butt (103c) is located in an approximately central position of said bridge portion (103b).

13. The machine according to 10, 11 or 12, characterized in that said radial extraction cams (11) or said radial compression cams (111) are movable between an active position, adapted to radially extract the upper part of the needles toward the outside of the needle cylinder, and in inactive position, and that control arrangements are provided, configured to shift said radial compression cams or said radial extraction cams of one or more feeds to one of said two positions.

14. The machine according to one or more of claims 1 to 9, characterized in that said needle moving members comprise, for each feed of the machine, at least one magnet (211; 311), adapted to attract the shaft of the needles so as to move the upper end thereof away from the axis (X-X) of the needle cylinder.

15. The machine according to claim 14, characterized in that, for each feed of the machine, the magnet (211; 311) is secured to a respective guide cam (212; 313) of the needles (3) and the edge or edges (212a, 212b; 313a) of said guide cam facing the needle cylinder (1) are shaped like the face (211a) of the magnet (211; 311) facing the needles but projecting in a plan view relative to the face of the magnet by a distance (Z) sufficient to prevent contact of the needles with said face (211a) of the magnet.

16. The machine according to claim 15, characterized in that said distance (Z) is in the order of a few tenths of millimeter.

17. The machine according to claim 16, characterized in that said distance (Z) is two tenths of millimeter.

18. The machine according to one or more of claims 14 to 17, characterized in that said magnet (211; 311) is a permanent magnet and in that means are provided for radially moving the magnet to move the magnet either to a position sufficiently near to the stem of the needles (3) to inflect the needles by means of attraction, or to an inactive position sufficiently spaced apart from the stem of the needles to prevent the needles from being attracted.

19. The machine according to claim 18, characterized in that said means for moving the magnets (311) toward/away from the needle cylinder (1) comprise for each magnet a slide (313) on which the magnet (311) is secured, said slide sliding radially in a guide (314) formed in a fixed ring (315) integral with the frame of the machine and coaxial with the needle cylinder (1) of the machine, a movable ring (321) coaxial with the needle cylinder (1) being rotatably connected to the fixed ring (315) and having for each feed of the machine a pin (320) which is inserted in a slot (313c) of the respective slide (313), said slot being inclined with respect to the axis (W-W) of the slide (313), so that rotation of the movable ring (321) relative to the fixed ring (315) by a predetermined angle causes simultaneous movement of all the magnets (311) away from or toward the needles.

20. The machine according to one or more of claims 14 to 17, characterized in that said magnet is an electromagnet and in that an electric control is provided to activate one or more of said electromagnets when required.

21. A process for clearing the stitches from needles (3; 103) in a single- cylinder knitting machine without movable sinkers, when said needles (3; 103) are raised to engage the yarn, comprising the step of retaining the last stitches (M), formed by the needles (1; 103), during raising of the needles (3; 103) by means of stitch retaining elements (7) stationary with respect to the needle cylinder (1); characterized by moving the needles radially outwardly toward the outside (F2) of the needle cylinder during raising thereof.

22. The process according to claim 21, wherein each needle (3; 103), during raising thereof, carries with its cheek the respective stitch formed thereby under said stitch retaining element (3) so that the stitch is retained under said stitch retaining element, thus facilitating clearing of the stitch under the open latch of the needle.

23. The process according to claim 23, characterized in that said needles are moved radially outwardly by means of elastic inflection.

24. The process according to claim 25, characterized in that said needles are moved radially outwardly by means of magnetic attraction.