Patent Publication Number: US-7895862-B2

Title: Knitting machine with latch needles and without sinkers

Description:
The present invention relates to a knitting machine with latch needles and without sinkers. 
     BACKGROUND OF THE INVENTION 
     As is known, knitting machines with latch needles are generally equipped with sinkers which cooperate with the needles in forming knitting. 
     More particularly, sinkers define a knitting forming plane on which the portion of knitting that lies between two contiguous needles rests while said needles, after engaging the thread at a feed or drop of the machine, retract into the needle holder in order to form a new loop of knitting and lower the previously formed loop of knitting and tension the loop of knitting on the shank of the needle while said needle is extracted with its tip and with part of its shank from the needle holder of the machine in order to engage the thread dispensed at a feed or drop of the machine and form a new loop of knitting. The engagement of the sinkers with the knitting which achieves tensioning of the loop of knitting on the shank of the needle, in this step, also prevents the loop of knitting from following the needle in its extraction movement and achieves assuredly the opening of the latch and the passage of the loop below said latch. The knitting loop tensioning action on the shank of the needle by the sinkers is generally assisted by traction of the already-formed knitted fabric, which is performed generally by means of pneumatic traction devices in small-diameter circular machines and by means of mechanical devices in the other machines. 
     Usually, the sinkers are located in appropriately provided slots which are formed, at the end of the needle holder from which the needles protrude to engage the thread at a feed or drop of the machine, directly in the needle holder or in a supporting element which is fixed to the needle holder. The sinkers are generally actuated by means of appropriately provided cams, which face the region of the needle holder in which the sinkers are accommodated and define paths which can be engaged by heels of the sinkers, which protrude from the needle holder, as a consequence of a movement of the needle holder with respect to such cams. 
     In many types of high-gauge knitting machine, in which the space between the needles is extremely reduced, there are no sinkers. 
     In these machines, the absence of the sinkers, forced by size requirements, causes problems and drawbacks. The absence of the sinkers, during accidental breakage of the yarn being knitted, in fact prevents automatic resumption of the formation of knitting and forces manual intervention to release the new loops of knitting on the shank of the needles which, as a consequence of the breakage of the thread, have lost the knitting. 
     Moreover, owing to the fact that in these machines the tensioning action of the loops of knitting on the shank of the needles while said needles are extracted with their tip from the needle holder to engage the thread at a feed or drop of the machine is performed exclusively by the fabric tensioning device, this tension can be insufficient, also due to the large number of needles which engage the knitting, to ensure the passage of the loops of knitting below the latch of the needles while said needles are extracted from the needle holder, causing knitting errors. 
     In order to limit these problems, in some cases these machines are actuated by moving to knit in each instance, at a feed or drop of the machine, only one needle of every two contiguous needles, so that the needle that is not used to form knitting performs a retention action on the loops of knitting formed by the contiguous needles which are made to knit. However, this solution has the drawback of not allowing to use fully the production potential of the machine. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to provide a knitting machine with latch needles and without sinkers which ensures the correct formation of knitting without thereby limiting the needles that knit, thus allowing to utilize fully its production potential. 
     Within the scope of this aim, an object of the invention is to provide a knitting machine which ensures high reliability in operation even if it has a very high gauge. 
     Another object of the invention is to provide a machine which allows automatic resumption of knitting even in case of accidental loss of the yarn on the part of the needles. 
     This aim and these and other objects which will become better apparent hereinafter are achieved by a knitting machine with latch needles and without sinkers, comprising a needle holder on one face of which there are multiple side-by-side slots which are open at one of their longitudinal ends on a side of the needle holder which defines the knitting forming plane, each slot accommodating a needle which can be actuated with a reciprocating motion along the corresponding slot with an extraction motion, by means of which the needle is extracted from the needle holder with its tip and with a portion of its shank through said longitudinal end of the corresponding slot in order to release, onto its shank, the previously formed loop of knitting and/or engage the yarn or yarns dispensed at a feed or drop of the machine, and with a retraction motion, by means of which the needle is made to retract with its tip into the corresponding slot in order to form a new loop of knitting by lowering the loop of knitting previously formed in order to produce knitting, characterized in that it comprises, in at least part of the regions of the needle holder comprised between two contiguous slots, elements for retaining the knitting, each of which has a portion which forms a stop shoulder for the knitting, each knitting retention element being movable on command from a first position, in which it does not interfere with the knitting being formed, to a second position, in which it is inserted with said portion between two contiguous needles in a region which faces said knitting forming plane, in order to retain the portion of knitting that lies between two contiguous needles, contrasting the entrainment of the knitting along the needles during the extraction motion of said needles, actuation means being provided for actuating said knitting retention element for its passage from said first position to said second position and vice versa in a manner which is coordinated with the actuation of the contiguous needles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further characteristics and advantages of the invention will become better apparent from the description of two preferred but not exclusive embodiments of the machine according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein: 
         FIGS. 1 to 4  are views of the machine according to the invention in a first embodiment, and more particularly: 
         FIG. 1  is a schematic sectional view of a machine according to the invention, taken along a plane which is parallel to the sides of the slots of the needle holder, with the knitting retention element in the first position; 
         FIG. 2  is a schematic sectional view of the machine according to the invention, similar to  FIG. 1 , with the knitting retention element in the second position; 
         FIG. 3  is a sectional view of  FIG. 2 , taken along the line III-III; 
         FIG. 4  is a schematic and partially exploded perspective view of a portion of the machine according to the invention; 
         FIGS. 5 to 16  are views of the machine according to the invention in a second embodiment, and more particularly: 
         FIG. 5  is a schematic perspective view of a portion of the machine according to the invention with some elements omitted for the sake of greater clarity and illustrating a needle, two knitting retention elements, and the corresponding actuation means, shown in an exploded view; 
         FIG. 6  is a schematic perspective view of a portion of the machine according to the invention, with some elements omitted for the sake of greater clarity and with two knitting retention elements in the first position; 
         FIG. 7  is a schematic sectional view of a portion of the machine according to the invention, taken along a plane which is parallel to the sides of a slot of the needle holder which accommodates a needle with the knitting retention elements in the first position; 
         FIG. 8  is a schematic enlarged-scale sectional view of  FIG. 7 , taken along the line VIII-VIII, with the means for actuating the knitting retention elements omitted; 
         FIG. 9  is a sectional view of a portion of the machine according to the invention, similar to  FIG. 7 , with the knitting retention elements in the second position; 
         FIG. 10  is a sectional view of two knitting retention elements, similar to  FIGS. 7 and 9 ; 
         FIG. 11  is a side elevation view of two knitting retention elements; 
         FIG. 12  is a perspective view of a constructive variation of the knitting retention elements; 
         FIG. 13  is a side elevation view of the constructive variation of the knitting retention elements of  FIG. 12 ; 
         FIG. 14  is a sectional view, similar to  FIG. 8 , of the machine with knitting retention elements of the type shown in  FIGS. 12 and 13  fitted thereon; 
         FIG. 15  is a schematic perspective view of a portion of the machine according to the invention, in a constructive variation of the needle holder, with some elements omitted for the sake of greater clarity and with some needles and two knitting retention elements of the type shown in  FIGS. 5 to 11  shown in exploded view; 
         FIG. 16  is a schematic perspective view of a portion of the machine according to the invention, in the constructive variation of the needle holder shown in  FIG. 15 , with some elements omitted for the sake of greater clarity and with two knitting retention elements in the first position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiments shown in the cited figures refer to circular single-bed knitting machines, but the solution according to the invention may also be adopted in double-bed knitting circular knitting machines and in rectilinear knitting machines. 
     With reference to the figures, the knitting machine with latch needles and without sinkers according to the invention, generally designated by the reference numerals  1 ,  101  in the two embodiments and shown only partially for the sake of simplicity, comprises a needle holder  2 ,  102 , on one face of which there are multiple side-by-side slots  3 ,  103 , which are open at one of their longitudinal ends onto a side of the needle holder  2 ,  102  which forms the knitting forming plane  4 ,  104 , i.e., the plane on which the portions of loop linking knitting rest during the formation of the loops of knitting, as will become better apparent hereinafter. 
     A needle  5  is arranged in each of the slots  3 ,  103  and can be actuated in a per se known manner along the corresponding slot  3 ,  103 , with a reciprocating motion which is composed of an extraction motion, by means of which the needle  5  is extracted with its tip  5   a  and with a portion of its shank  5   b  from the longitudinal end of the slot  3 ,  103  formed in the knitting forming plane  4 ,  104  to release, onto its shank  5   b , the previously formed loop of knitting and/or to engage the yarn or yarns dispensed at a feed or drop of the machine, and a retraction motion, by means of which the needle  5  retracts with its tip  5   a  into the slot  3 ,  103 , thus forming a new loop of knitting and lowering the previously formed loop of knitting in order to form knitting. 
     According to the invention, the machine comprises, in at least part of the regions of the needle holder  2 ,  102  comprised between two contiguous slots  3 ,  103  and preferably in each region of the needle holder  2 ,  102  comprised between two contiguous slots  3 ,  103 , a knitting retention element  6 ,  106 ,  156 , which has a portion  6   a ,  106   a ,  156   a  which forms a stop shoulder  7 ,  107 ,  157  for the knitting. Said knitting retention element  6 ,  106 ,  156  can move on command from a first position, in which it does not interfere with the knitting being formed, to a second position, in which it is inserted, with its portion  6   a ,  106   a ,  156   a , between two contiguous needles  5  in the region which faces the knitting forming plane  4 ,  104 , in order to retain, by means of the stop shoulder  7 ,  107 ,  157 , the portion of knitting that lies between two contiguous needles  5 , so as to contrast the entrainment of the knitting by the needles  5  during their extraction motion. The machine is provided with actuation means for actuating the knitting retention element  6 ,  106 ,  156  in order to perform its transfer from the first position to the second position and vice versa in a manner which is coordinated with the actuation of the needles  5 . 
     More particularly, the knitting retention element  6 ,  106 ,  156  has a laminar shape and is arranged on a plane which is parallel to the side walls of the slots  3 ,  103  between which it is arranged. The knitting retention element  6 ,  106 ,  156  can oscillate on its plane of arrangement with respect to the needle holder  2 ,  102  in order to pass from the first position to the second position cited above and vice versa. 
     The knitting retention element  6 ,  106 ,  156  faces the face of the needle holder  2 ,  102  in which the slots  3 ,  103  are formed and is arranged on a plane which is substantially perpendicular to said face. If the needle holder  2 ,  102  is constituted by a cylinder, i.e., if the machine is a circular knitting machine, the knitting retention element  6 ,  106 ,  156  is arranged on a radial plane of the cylinder, i.e., on a plane which passes through the axis of the cylinder. 
     The knitting retention element  6 ,  106 ,  156  has a longitudinal end which defines the portion  6   a ,  106   a ,  156   a  and protrudes beyond the knitting forming plane  4 ,  104 . Said longitudinal end of the knitting retention element  6 ,  106 ,  156  protrudes toward the needle holder  2 ,  102 , so as to form, with its side directed toward the knitting forming plane  4 ,  104 , the stop shoulder  7 ,  107 ,  157 . 
     In the first embodiment, shown in  FIGS. 1 to 4 , the end  6   b  of the knitting retention element  6  which lies opposite the portion  6   a  is pivoted to a slat or lamina  9  which is fixed to the needle holder  2  in the region thereof comprised between two contiguous slots  3 . More particularly, the slat  9  is partially inserted in the face of the needle holder  2  in which the slots  3  are formed between two contiguous slots  3 . 
     The pivoting between the slat  9  and the end  6   b  of the knitting retention element  6  is performed preferably by a hook-shaped portion  9   a , which is directed toward the needle holder  2 , of the slat  9  which mates with the end  6   b , which is shaped correspondingly like a hook directed away from the needle holder  2 , of the knitting retention element  6 . In this manner, the knitting retention element  6  is pivoted to the slat  9  about a pivoting axis  10  which is oriented substantially at right angles to the plane of arrangement of the knitting retention element  6 , which can oscillate about said pivoting axis  10  with respect to the slat  9  in order to pass from the first position to the second position and vice versa. 
     The knitting retention element  6  is accommodated, with a portion thereof starting from the end  6   b  which is pivoted to the slat  9 , in a containment compartment  11  which is formed in the needle holder  2 . 
     Moreover, the knitting retention element  6  has, on its side directed toward the needle holder  2 , in an intermediate region of its extension parallel to the longitudinal extension of the slots  3 , a guiding heel  12 , which in the transition of the knitting retention element  6  from the first position to the second position is inserted in a compartment  13  which is formed in the face of the needle holder  2  which faces the knitting retention element  6 . The guiding heel  12 , in the transition of the knitting retention element  6  from the first position to the second position and vice versa, slides between the shanks  5   b  of the two adjacent needles  5 . 
     The actuation means for actuating the knitting retention element  6  comprise an actuation cam  14 , which faces the side of the knitting retention element  6  which is directed away from the needle holder  2 , which can be actuated, in a per se known manner, with respect to the actuation cam  14 , along an actuation direction, indicated by the arrow  20  in  FIG. 3 , which is substantially perpendicular to the longitudinal extension of the slots  3 . The actuation cam  14  has an actuation profile  14   a  which gradually approaches the needle holder  2  concordantly with the motion of the needle holder  2  along the actuation direction  20  with respect to the actuation cam  14 . The actuation profile  14   a  of the actuation cam  14 , during the motion of the needle holder  2  with respect to the actuation cam  14 , engages the knitting retention element  6  in a region  22  which is spaced from the pivoting axis  10 , causing its rotation about the pivoting axis  10  with respect to the slat  9 , in the direction of rotation which moves its end  6   a  toward the needle holder  2 , i.e., causing its transition from the first position to the second position cited above. 
     The actuation cam  14  is arranged so as to act on the knitting retention element when the contiguous needles  5  begin their extraction motion or just before the contiguous needles  5  begin said extraction motion, as will become better apparent hereinafter. 
     The actuation means of the knitting retention element  6  also comprise elastic means  15 , which contrast elastically the passage of the knitting retention element  6  from the first position to the second position caused by the actuation cam  14  and produce, by elastic reaction, the transition of the knitting retention element  6  from the second position to the first position when the action of the actuation cam  14  ceases. 
     The elastic means  15  are constituted preferably by an elastically flexible wing  16 , which is formed monolithically with the knitting retention element  6 . The elastically flexible wing  16  extends from the side of the knitting retention element  6  that is directed toward the needle holder  2  and rests against the needle holder  2  in the region comprised between two contiguous slots  3 . 
     More particularly, the elastically flexible wing  16  is connected with one of its ends to the body of the knitting retention element  6  at the connecting region of the guiding heel  12 , on the opposite side with respect to the portion  6   a , and rests, with its opposite end, against the bottom of the containment compartment  11 , being arranged along a direction which is inclined with respect to the longitudinal extension of the slots  3  on the opposite side with respect to the knitting forming plane  4 . 
     It should be noted that the nose of the hook-shaped portion  9   a  of the slat  9  forms a support  19  for the end  6   b  of the knitting retention element  6  which mates therewith, and said support  19  delimits the arc of the rotation of the knitting retention element  6  about the pivoting axis  10  in its transition from the second position to the first position. The action of the elastically flexible wing  16  in combination with the support  19  formed by the hook-shaped portion  9   a  has the effect of retaining the knitting retention element  6  in the containment compartment  11  even in the absence of the actuation cam  14 . 
     Preferably, additional means are provided for retaining the knitting retention element  6  and for keeping it within the containment compartment  11  during interventions on the machine which require the removal of the actuation cam  14 . 
     Said additional retention means comprise an elastically extensible wire-like element  17 , which is associated with the needle holder  2  and engages the side of the knitting retention element  6  that is directed away from the needle holder  2  in a region which is spaced from the pivoting axis  10 . At the region of contact of the wire-like element  17 , on the knitting retention element  6  there is a recess  18  in which the wire-like element  17  is inserted. 
     In the second embodiment, shown in  FIGS. 5 to 16 , the knitting retention element  106 ,  156  has, on its side directed toward the needle holder  102 , an intermediate portion  121 ,  171 , which is preferably shaped like a circular sector and rests, on the face of the needle holder  102  on which the slots  103  are formed, in the region comprised between two contiguous slots  103 . This intermediate portion  121 ,  171  forms an oscillation axis  110 ,  160  of the knitting retention element  106 ,  156  with respect to the needle holder  102 . The oscillation axis  110 ,  160  is oriented substantially at right angles to the plane of arrangement of the knitting retention element  106 ,  156 , which can oscillate about said oscillation axis  110 ,  160  with respect to the needle holder  102  in order to pass from the first position to the second position or vice versa. 
     The actuation means for actuating the knitting retention element  106 ,  156  to produce its transition from the first position to the second position or vice versa comprise at least one actuation cam  114 , which faces the face of the needle holder  102  on which the slots  103  are provided. The needle holder  102  can be actuated, along an actuation direction which is substantially perpendicular to the longitudinal extension of the slots  103 , with respect to the actuation cam  114 , and said actuation cam  114  has a profile  114   a ,  114   b  which is contoured so as to act alternately on the knitting retention element  106 ,  156  in two regions  122   a ,  122   b ,  172   a ,  172   b  arranged on mutually opposite sides relative to the oscillation axis  110 ,  160  in order to produce the oscillation of the knitting retention element  106 ,  156  about the oscillation axis  110 ,  160  with respect to the needle holder  102  in one direction or in the opposite direction for the transition of the knitting retention element  106 ,  156  from the first position to the second position or vice versa. 
     In the second embodiment being described, there is a single actuation cam  114  with a double profile  114   a ,  114   b , but it is possible to provide two separate actuation cams, each having a corresponding profile  114   a ,  114   b  which acts respectively on the region  122   a ,  172   a  or on the region  122   b ,  172   b  of the knitting retention element  106 ,  156 . 
     The profiles  114   a ,  114   b  are contoured so as to progressively move toward and away from the needle holder  102  concordantly with the direction of actuation of the needle holder  102  with respect to the actuation cam  114  or the actuation cams. More particularly, the profile  114   a  has a portion which approaches progressively the needle holder  102  at a portion of the profile  114   b  which moves progressively away from the needle holder  102  and a portion which moves progressively away from the needle holder  102  at a portion of the profile  114   b  which approaches progressively the needle holder  2  so that the profile  114   a  causes the oscillation of the knitting retention element  106 ,  156  about the oscillation axis  110 ,  160  for its transition from the first position to the second position while the profile  114   b  allows this oscillation, and so that the profile  114   b  causes the oscillation of the knitting retention element  106 ,  156  about the oscillation axis  110 ,  160  for its transition from the second position to the first position while the profile  114   a  allows this oscillation. 
     Conveniently, means are provided for retaining the knitting retention element  106 ,  156  so as to keep it with its intermediate portion  121 ,  171  in contact with the needle holder  102  when the actuation cam  114  is removed during maintenance. These retention means comprise a wire-like element  117 , which is elastically extensible and is constituted for example by a spring wire, which is associated with the needle holder  102  and engages the side of the knitting retention element  106 ,  156  which is directed away from the needle holder  102 . Preferably, on said side of the knitting retention element  106 ,  156 , in an intermediate region at the portion  121 ,  171 , there is a recessed seat  118 ,  168  in which the wire-like element  117  rests. 
     The slots  103  are preferably delimited, at least proximate to the knitting forming plane  104 , by laminas  123  which are inserted in mutually parallel slits  124  formed in the body of the needle holder  102 . Said laminas  123  protrude from the body of the needle holder  102  and each needle  5  is arranged between two contiguous laminas  123 . 
     For the sake of simplicity and greater clarity,  FIG. 5  shows only two laminas  123  and  FIGS. 6 ,  15  and  16  show only four laminas  123 , without altering the fact that the slits  124  and the laminas  123  are distributed along the entire face of the needle holder  102  in order to form the slots  3 . 
     Each knitting retention element  106 ,  156  is inserted, with its intermediate portion  121 ,  171 , in a slit  124  which accommodates one of the laminas  123  and rests with its intermediate portion  121 ,  171  on the bottom of the corresponding slit  124 , as shown in  FIGS. 7 and 9 . 
     Each knitting retention element  106 ,  156  is shaped so as to be inserted, with its intermediate portion  121 ,  171 , in the slit  124  which accommodates a lamina  123 , which is designed to face, with one of its portions, the side, directed away from the needle holder  102 , of the lamina  123  which is arranged in said slit  124  and so as to surmount said lamina  123  with its end which constitutes the portion  106   a ,  156   a  which protrudes beyond the knitting forming plane  104 . 
     Each of the laminas  123  has, in a region which is spaced from the knitting forming plane  104 , a protrusion  123   a  which protrudes more from the face of the needle holder  102  on which the slots  3  are formed and the knitting retention element  106 ,  156  is inserted, with a portion  125 ,  175  thereof, between the protrusions  123   a  of two contiguous laminas  123 . 
     The laminas  123 , which delimit the slots  103  laterally, are preferably connected to each other in pairs proximate to their side which is directed away from the needle holder  102  and more specifically at the protrusion  123   a . Each needle  5  is arranged in each instance between two contiguous laminas  123  which are mutually connected and between two contiguous laminas  123  which are not connected to each other. 
     In the embodiments shown in  FIGS. 5 to 11  and in  FIGS. 15 and 16 , the knitting retention elements  106  also are connected to each other at least two by two proximate to their side which is directed away from the needle holder  2 . In the embodiment shown in  FIGS. 5 to 11 , the two knitting retention elements  106 , which are mutually connected, are arranged in slits  124  which accommodate two laminas  123  which are not mutually connected. 
     The connection between two laminas  123  and between two or more knitting retention elements  106  is preferably such as to mutually rigidly couple the laminas  123  or the knitting retention elements  106  which are mutually connected. This connection can be performed by providing monolithically, as shown, the two or more elements to be mutually connected or by welding or by means of rivets or pivots or other known types of connecting element. 
     In this manner, one obtains pairs of knitting retention elements  106  which have, as a whole, an increased thickness and therefore have a greater resistance to deformation during use. 
     Optionally, in order to further increase the resistance to deformation of the knitting retention elements  106 , it is possible to mutually connect even more than two contiguous retention elements  106 . 
     The portion  125  of the knitting retention elements  106  which is inserted between two contiguous laminas, in the embodiments shown in  FIGS. 5 to 11  and  FIGS. 15 and 16 , is constituted by a narrower region of each pair of knitting retention elements  106  which are connected to each other. More particularly, each pair of mutually connected ring knitting retention elements  106  has, on its outer sides, at the protrusion  123   a  of the corresponding laminas  123 , a recess  126  which reduces the thickness thereof at the portion  125 , which in this manner can be inserted between the two contiguous laminas  123  which are not mutually connected and are arranged in the same slits  124  in which the two mutually connected knitting retention elements  106  are arranged. The insertion of the portion  125  between two contiguous laminas  123  allows to keep the knitting retention elements  106  correctly positioned even during their oscillation about the oscillation axis  110  in the transition from the first position to the second position or vice versa. 
     It should be noted that the connection in pairs of the laminas  123  and the connection of the knitting retention elements  106  in pairs or more achieves higher resistance to deformation of these elements, which is particularly useful in the case of high-gauge machines, in which the thickness of a single lamina  123  and of a single knitting retention element  106  would indeed be so low as to expose these elements to easy deformations. 
     The constructive variation of the knitting retention element  156  shown in  FIGS. 12 to 14  is designed to be used preferably with laminas  123  which are not mutually connected in pairs. In this constructive variation, the knitting retention element  156  has, along its longitudinal extension, in the region designed to be at the level of the protrusion  123   a  of the laminas  123 , two double folds  173 ,  174  for placing the portion  175 , which lies between these pairs of double folds  173 ,  174 , on a plane which is parallel and spaced laterally with respect to the plane of arrangement of the remaining portion of the knitting retention element  156 . In this manner, the portion  175  is arranged laterally with respect to the protrusion  123   a  of the lamina  123  which is arranged in said slit  124  and the portion  175  can be inserted between the protrusion  123   a  of the lamina  123  which arranged in the same slit  124  and the protrusion  123   a  of the contiguous lamina  123 . 
     In this constructive variation also, the insertion of the portion  175  between the protrusions  123   a  of two contiguous laminas  123  allows to keep the knitting retention elements  156  correctly positioned even during their oscillation about the oscillation axis  160  in the transition from the first position to the second position or vice versa. 
       FIG. 14  illustrates the use of knitting retention elements  156  on a machine which is provided with laminas  123  which are mutually connected in pairs. For this reason, there is a knitting retention element  106  every two laminas  123  which is inserted with its portion  175  between two pairs of laminas  123 , each composed of two mutually connected laminas  123 . If the laminas  123  are not mutually connected in pairs, it is possible to provide a knitting retention element  156  for each lamina  123 . In this case, the knitting retention element  156  is inserted with its portion  175  between two contiguous laminas  123 . 
     In this constructive variation also, the knitting retention elements  156  may be mutually connected in pairs, in threes, or in larger sets. 
     For the sake of completeness in description, it should be noted that additional laminas  127  are inserted in the slits  124  formed in the body of the needle holder  102  in the regions not occupied by the laminas  123  and by the knitting retention elements  106 ,  156 , and said additional laminas, in said regions, delimit the slots  103  laterally. 
     It is important to point out that in the machine according to the invention, the knitting retention elements  6 ,  106 ,  156  are designed to be arranged at the space comprised between two contiguous slots  3 ,  103  of the needle holder  2 ,  102  so as to utilize this space to the benefit of the thickness of the knitting retention elements  6 ,  106 ,  156 . This refinement, optionally combined with the mutual connection of two or more contiguous knitting retention elements  6 ,  106 ,  156 , allows to provide knitting retention elements which are sufficiently strong even in high-gauge machines. 
     The slots  3 ,  103  inside each of which a needle  5  slides can be delimited laterally by laminas or slats  9 ,  123 ,  127  which are inserted in slits or compartments  124  which are formed in the body of the needle holder  2 ,  102  or by fins which are provided monolithically with the needle holder body  2 ,  102 . In both cases, the knitting retention elements  6 ,  106 ,  156  are each arranged at the space comprised between two contiguous slots  3 ,  103 , providing the absence or interruption of the laminas or slats  9 ,  123 ,  127  or of the fins at the region occupied by the knitting retention element  6 ,  106 ,  156 , which may be inserted, with its intermediate portion or wing  16 ,  121 ,  171 , in the same slits  124  of the needle holder  2 ,  102  which accommodate the laminas or slats  9 ,  123 ,  127  or in slits provided specifically in the body of the needle holder  2 ,  102 , or can also simply rest against the face of the needle holder  2 ,  102  in the region comprised between two contiguous slots  3 ,  103  which is not provided with slits  124  and with fins in said region. In this case, the knitting retention elements  6 ,  106 ,  156  are in any case guided by the needles  5  and by the optional insertion of the guiding heel  12  or of their portion  125 ,  175  respectively in the compartment  13  or between the protrusions  123   a  of the laminas  123 . 
     As shown in  FIGS. 15 and 16 , which refer to a variation of the needle holder  102 , the knitting retention elements  106  may also rest on the bottom of a recessed region  102   b  which is formed on the face of the needle holder  102  in which the slots  103  are provided. In  FIGS. 15 and 16 , the elements of the machine that correspond to elements that have already been described in  FIGS. 5 to 11  have been designated by the same reference numerals. It should be noted that knitting retention elements  106  identical to the ones shown in  FIGS. 5 to 11  have been shown in  FIGS. 15 and 16 , but knitting retention elements  156  identical to the ones shown in  FIGS. 12 to 14  might also be used. 
     In all of the embodiments, although preferably, in order to achieve optimum knitting retention, all the regions of the needle holder  2 ,  102  comprised between two contiguous slots  3 ,  103  are occupied by a knitting retention element  6 ,  106 ,  156 , i.e., a knitting retention element  6 ,  106 ,  156  is present between two contiguous needles  5 , even only some of these regions can be occupied by knitting retention elements  6 ,  106 ,  156 , i.e., with a knitting retention element  6 ,  106 ,  156  every two needles, as shown for example in  FIG. 14 , or every three needles or more, according to the requirements and the gauge of the machine. 
     Preferably, the machine according to the invention is constituted by a single-cylinder circular knitting machine, as shown, and the needle holder  2 ,  102  is constituted by a cylinder which has a vertical axis  2   a ,  102   a  or needle cylinder with the slots  3 ,  103  formed on its lateral surface and oriented parallel to its axis  2   a ,  102   a.    
     In this case, the needle holder  2 ,  102  can be actuated with a rotary motion about its own axis  2   a ,  102   a  with respect to the actuation cam  14 ,  114 . 
     Preferably, the machine according to the invention has a gauge comprised substantially between 32 and 60 needles per inch. 
     Operation of the machine according to the invention as regards the knitting retention elements  6 ,  106 ,  156 , is as follows. 
     During the production of knitting, the needles  5  are extracted cyclically with their tip  5   a  and with a portion of their shank  5   b  from the corresponding slot  3 ,  103  so as to release onto their shank  5   b , below the latch  5   c , the previously formed loops of knitting and/or engage the yarn or yarns dispensed at a feed or drop of the machine and are then made to retract into the corresponding slot  3 ,  103  so as to form new loops of knitting, while the portion of knitting that mutually connects the loops of knitting being formed rests on the knitting forming plane  4 ,  104 . During the retraction movement of the needles  5  into the slots  3 ,  103 , the knitting retention elements  6 ,  106  or  156  arranged in the regions of the needle holder  2 ,  102  arranged between the slots  3 ,  103  are kept in the first position by the contact of the wing  16  against the bottom of the compartment  11  or by the action of the profile  114   b  of the actuation cam  114  on the region  122   b  or  172   b  so as to not interfere with the knitting being formed, as shown in  FIGS. 1 ,  6 ,  7  and  16 . 
     After the needles  5  have retracted into the corresponding slot  3 ,  103  of the needle holder  2 ,  102 , just before the beginning of their extraction motion or at the beginning of the extraction motion of the needles  5 , the knitting retention elements  6 ,  106  or  156 , as a consequence of the action of the profile  14   a  of the actuation cam  14  on the region  22  or of the profile  114   a  of the actuation cam  114  on the region  122   a  or  172   a , are moved into the second position, so as to make the stop shoulder  7 ,  107  or  157  face the knitting forming plane  4 ,  104 . In this position, the knitting retention elements  6 ,  106  or  156  form a sort of comb, which retains the loops of knitting carried by the needles  5 , preventing them from following the needles  5  in their extraction motion. In this manner, the loops of knitting are retained proximate to the knitting forming plane  4 ,  104  while the needles  5  move with their latch  5   c , which is thus assuredly opened, beyond the loops of knitting retained by the knitting retention elements  6 ,  106  or  156 , as shown in  FIGS. 2 and 9 . 
     By virtue of this fact, even in the presence of reduced or insufficient traction of the knitting, correct formation of knitting is achieved, and if the yarn or yarns that feed the needles break it is possible to resume knitting without the need for manual intervention. 
     In practice it has been found that the machine according to the invention fully achieves the intended aim, since though being provided without sinkers, due to the presence of the knitting retention elements which can be adopted without problems even in the case of high gauges, it ensures correct formation of knitting without thereby imposing a limitation of the active needles, thus allowing to utilize fully its production potential. 
     In the exemplary embodiments described above, individual characteristics, cited in relation to specific examples, may actually be interchanged with other different characteristics that exist in other exemplary embodiments. 
     Moreover, it is noted that anything found to be already known during the patenting process is understood not to be claimed and to be the subject of a disclaimer. 
     The machine thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims; all the details may further be replaced with other technically equivalent elements. 
     The disclosures in Italian Patent Applications no. MI2006A001320 and MI2007A001096, from which this application claims priority, are incorporated herein by reference. 
     Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.