| JP05195388 | FABRIC AND KNITTING |
| JP10072747 | PREVENTION OF DROP STITCH OF FLAT KNITTING MACHINE |
| WO/2005/035847 | CIRCULAR JERSEY KNITTING MACHINE FOR PLUSH FABRIC PRODUCTION |
PILOTELLI, Roberto (Via Roma, 102, lseo, I-25049, IT)
PILOTELLI, Renato (Via Campo 36, lseo, I-25049, IT)
PILOTELLI, Roberto (Via Roma, 102, lseo, I-25049, IT)
| Claims 1. A circular knitting machine comprising a needle cylinder and a set of control cams for the needles that comprise ascending branches for the needles and descending branches for the needles and form at least two overlapped tracks (P1 , P2) of control cams for the needles, and wherein in said needle cylinder at least two different types of needles (A1 , A2) are arranged, different from each other for the different distance between butt and hook, and are actuated each by a respective cam track (P1 , P2), characterized in that the control cams (A) of a track (P1) present at least the lower part of the respective descending branch displaced in the direction of the motion of rotation of the cylinder with respect to the lower part of the respective descending branch of the corresponding cams (R) of the other track (P2), so that, on each feed, the downward movement of the needles of one type (A1) following a cam track (P1) is advanced by a preset angle of rotation of the cylinder with respect to the downward movement of the needles of the at least one other type (A2) following another cam track (P2). 2. A machine as claimed in claim 1 , characterized in that two types (A1 , A2) of needle and two respective tracks (P1 , P2) of cams for actuating them are used. 3. A machine as claimed at least in claim 2, characterized in that the two types (A1 , A2) of needle are distributed around the cylinder mutually alternating, i.e. in a one-to-one arrangement. 4. A machine as claimed at least in claim 2, characterized in that the two types (A1 , A2) of needle are distributed around the cylinder alternating in pairs, i.e. in a two-to-two arrangement. 5. A machine as claimed in one or more of the previous claims, characterized in that this preset angle of angular delay is chosen in an interval from 2 to 5 needle passes. 6. A machine as claimed in claim 5, characterized in that this preset angle of angular delay is chosen equal to nearly 3 passes of needle. 7. A machine as claimed in one or more of the previous claims, characterized by presenting in at least one feed a thread guide (G) with at least two holes (G1 , G2) for feeding the yarn, said thread guide being designed to feed at least one yarn (X) only to the needles (A2) following the track (P2) with the descending profile that is "delayed" relative to the other needles (A1), and another yarn (Y) to all the needles (A1 , A2) of the cylinder. 8. A machine as claimed din claim 6, characterized in that the two types of needle (A1 , A2) are distributed uniformly in areas of the cylinder variously arranged to form a corresponding knit pattern effect. 9. In a machine according to one or more of the previous claims, a process for reducing the stresses of the processed yarn and the wear of the needles (A1 , 2) and of any sinkers, characterized by delaying by a preset distance the loop formation by the needles (A2) with respect to the loop formation by the other needles (A1), the needles (A1 , A2) being uniformly distributed and mutually interposed along the periphery of the cylinder (C). 10. In a machine as claimed in claim 7, a knitting pattern process to form an elastic fabric with mock rib, characterized by comprising the phases of: - uniformly distributing along the cylinder periphery two types of needles (A1 , A2) alternating them; - feeding the machine on at least one feed with two separate yarns (X, Y), the feed being provided with a thread guide (G) having respective holes (G1 , G2) to form with said yarns respective descending segments (X1 , Y1) mutually displaced in the direction of rotation the the needle cylinder, so that both the yarns (X, Y) can be taken only by the needles (A2) following the track (P2) with profiles of the descending cams (R) delayed relative to the corresponding profiles of the other track (P1), while the needles (A1) following this other track (P1) of cams (A) with advanced descending profiles can take only the yarn (Y); - utilizing as yarn (X) an elastic thread. 11. In a machine as claimed in claim 8, a process to form a vertically patterned fabric, characterized by comprising the phases of: - distributing in preset areas of the cylinder two types of needles (A1 , A2) uniformly alternating them in each area; - feeding the machine on at least one feed with two separate yarns (X, Y), the feed being provided with a thread guide (G) having respective holes (G1 , G2) to form with said yarns respective descending segments (X1 , Y1) mutually displaced in the direction of rotation of the needle cylinder, so that both the yarns (X, Y) can be taken only by the needles (A2) following the track (P2) with profiles of the descending cams (R) delayed relative to the corresponding profiles of the other track (PI), while the needles (A1) following this other track (P1) of cams (A) with advanced descending profiles can take only the yarn (Y). |
DESCRIPTION
Technical field
The present invention refers to the field of circular knitting machines.
State of the Art
In the known knitting machine, the loop forming process occurs by means of needles arranged in respective small guiding channels uniformly distributed on the periphery of a rotating cylinder. The needles move in the channels with an alternating motion, drawn through a respective "butt" actuated by a series of stationary cams mounted on specific cam-holders surrounding the cylinder. These cams present one or more channels, inside which the needle butts move and which define the work path of the needles. In general, to make various knit patterns of fabric, various types of needles are used, distributed on the cylinder periphery and differing from each other in length, i.e. presenting the butt at different distances from the hook. For each needle type a respective cam channel (P1 , P2, figure 2) is provided, suitable to define different work paths for the various types according to the knit pattern requirements or other.
In figure 1 two types of needle are shown by way of example: a first needle type A1 provided with a butt T1 suitable to be controlled with the cams of the track P1 (figure 2); and a second needle type A2, provided with a butt T2 suitable to be controlled with the cams of the track P2, these cam tracks being mounted on the cam-holders S fixed to the bearing structure B of the machine. The number of needle types can be greater than two and, for this type of machines, can also be five.
With the currently used system, at least in correspondence of the descending branches of the needles - along which the needles take the thread and knit on the edge of the cylinder or on the loop forming edge, in machines using them - all the various cam tracks are equal, i.e. in these branches the path followed by the various types of needle is the same, independently of the followed track.
Figure 3 shows the looping in a known machine at any of the yarn feedings of the machine. In this figure, the arrow F indicates the direction of rotation of the needle cylinder, C indicates the upper edge of the cylinder, A indicates the needles and G a thread guide suitable to put a thread H towards the needles.
To understand the problem arising during the formation of stitch, it should be taken into account the moment in which the needle, in its descending phase, goes below the level of the cylinder edge forming a loop of new stitch and contemporaneously casting off the previously formed stitch. In figure 4, which is a detail of figure 3, this situation occurs for the needle indicated with an asterisk.
Figure 5 shows in enlarged scale the situation of figures 3 and 4. The needles in the descending phase have been indicated with numbers 1 to 4. Number 2 indicates the needle going below the cylinder edge to form a new loop of stitch and casting off the previously formed stitch. It should be noted that the previously formed stitch, during the casting off phase, tightens the yarn of the new stitch around the hook of the needle 2. The needle 3, in its phase of forming the stitch loop, is still going down, as shown in figure 5 by the arrow FA arranged above it. This needle therefore takes further thread H from the thread guide to complete the formation of the new loop, as shown by the arrow F1. However, the thread H is not free to run as it is tightened by the previous stitch M that is passing over the head of the adjacent needle (the needle number 2) that is in the casting off phase. A tension peak therefore occurs in the segment of thread H arranged between the needles number 2 and 3, and the needle number 2 is therefore pulled towards the left in the drawing (as indicated by the arrow FB over it), bends and moves towards a wall of the cylinder channel inside which it is arranged. In this condition the needle does not work in a position centered in the corresponding channel, and it can come into contact (as in W) with the wall of the channel (or with the sinker, in machines using it), being therefore subjected, with the use, to wear. In the case of machines with sinkers, in addition to the needle also the sinker is displaced due to the traction on the yarn. The needle and the sinker, coming into contact with each other, are prematurely damaged and problems occur linked with this type of wear as the sinker gets thinner and it can also cut the yarns or, anyway, it can form, on the produced stitch, a serious faultiness constituted by vertical lines. The same phenomenon can relate the end of the needle latch: especially if of the spoon-shaped type, the latch can become thinner laterally and cut the yarns or it can form said faultinesses constituted by vertical lines.
Objects and Summary of the invention
The object of the present invention is to substantially reduce the above described problems and to allow producing particular knitted structures in a simple manner.
According to the present invention, in a circular knitting machine needles of different types alternate, which differ from each other in the different distance between butt and hook, each type of needle being actuated by a different stitch cam track and - for each feed - the stitch cams of one track present at least the lower part of downward movement of the needles offset in the direction of the rotation movement of the cylinder with respect to the corresponding part of the corresponding cams of the other track, so as in each feed to delay by a given angle the downward movement of the needles of one type with respect to the downward movement of the needles of the other type.
This delay can be in the order of some needle passes, and is chosen according to the fineness of the machine and/or the characteristics of the fabric to be produced in a range of values generally comprised between 2 and 5 needle passes.
With this arrangement, in correspondence of the needles that are gone below the loop forming edgeand that are forming loop, it is possible to avoid the stop of the running yarn due to the adjacent needles and therefore it is possible to prevent the needles from bending laterally.
Furthermore, with the cam arrangement according to the present invention, as the needles controlled by different cam tracks follow different mutually offset paths, in the descending segment of path it is possible to feed to the needles two yarns in a same feed by arranging them adequately so that only one of these yarn is knitted on the needles following the "advanced" path and both the yarns on the needles following the "delayed" path. With this arrangement and by varying at will the distribution of the needle types around the cylinder it is therefore possible to obtain particular knit pattern effects in the fabric without the need of other "yarn selection means".
Brief description of the drawings
The invention will be easier to understand by means of the description below and the attached drawing, which shows a non-restrictive practical embodiment of the invention.
More in particular, in the drawing:
figure 1 shows a perspective view of two types of needle generally used in the circular knitting machines;
figure 2 shows a partial perspective of the control cams for the needles mounted on adequate cam-holders, the set being shown from the side facing the needle cylinder;
figure 3 shows a perspective view of the needle path in correspondence of a feed, in a circular knitting machine of the known type; figure 4 shows an enlarged perspective view of the detail IV of figure
3;
figure 5 shows a schematic plan view of the detail IV of figure 3;
figure 6 shows a front view of three cams in an improved machine according to the present invention;
figures 7, 8A and 8B show respective schematic plan views of the needle path in the area of loop formation of a feed with respective different arrangements of the needles in a machine according to the invention;
figure 9 shows a view analogous to that of figure 6 for other types of cams used in the machines according to the present invention;
figure 10 shows a front view of a cam-holder group of a feed of an improved circular knitting machine according to the present invention, provided with needle control cams for two tracks; and
figures 11 and 12 show a cam-holder group in a side view according to XI-XI of figure 10 and in an exploded view respectively.
Detailed description of the invention
The general structure of the knitting machine in which the present invention is embodied is substantially corresponding to that of the traditional machines, and is illustrated in figures 1 and 2 and has been already described in the introduction of the present invention. Figure 6 shows frontally the cams used in a machine according to the invention instead of the traditional cams. More in particular, the cams according to the invention are of different types: cams hereinafter called "cam of type A" (figure 6) define a first track P1 (figure 2) and cams hereinafter called "cams of type R" define the second track P2. In figure 6 a third type of cam is also shown, called "cam of type N", used in the known machines both for the track P1 and for the track P2. In figure 6 again, F indicates the direction of rotation of the needle cylinder, and there are vertical lines LA, LR, LN in correspondence of the lowest point of the descending profile of the cams A, R, N, respectively. As it is clearly apparent in figure 6, in the descending branch the profiles of the cams A, R, N differ from each other in that, with respect to the line LN of the known type "N" cam, the line LA of the "type A" cam is advanced (with reference to the direction F of rotation of the cylinder), and the line LR of the "type R" cam is delayed.
In a machine according to the invention, the needles A1 - provided with butt T1 to follow the track P1 - are therefore guided by "type A" cams and, in each feed, they meet the tip (called "stitch formation tip") of the respective "type A" cam in advance relative to what occurs if they would be guided by a "type N" cam. Vice versa, the needles A2 - provided with butt T2 to follow the track P2 - are guided by "type R" cams and, in this feed, they meet the tip of the respective "type R" cam delayed relative to what occurs if they would be guided by a "type N" cam.
Traditionally, in each feed the cams A, R are fixed to a common slide SL (figures 0 to 12) slidable in a vertical guide V of a cam-holder support S, and their vertical position, that, as it is well known, determines the stitch length, is adjusted by means of any known system, for example a regulation knob CR that can rotate around a horizontal axis X-X.
According to a first arrangement of needles generally called "one-to- one", in the cylinder channels in odd position needles A1 are inserted with the butt T1 and in the channels in even position needles A2 with the butt T2 are inserted. With this arrangement the needles of even position make a path different than that of the needles of odd position as they are guided by respective cam tracks P1 , P2 having different profiles. In this way a situation occurs that is able to prevent the yarn from being tightened on the needle forming a new stitch, thus eliminating the lateral bending of the needles that damages prematurely needles and sinkers, if any. Figure 7 represents the loop formation with this "one-to-one" arrangement of needles and with two tracks P1 , P2, of control cams for the needles respectively with "type A" and "type R" cams. It is clearly apparent that the needles A1 with the butt T1 form loop in the point indicated with M1 and the needles A2 with the butt T2 form loop in the point indicated with M2. The needle indicated with A1 * in figure 7, engaged in the track P1 and forming the loop in the point M1 , is preceded by the needle indicated with A2* engaged in the track P2 and, differently from the common case of figure 5 described above, it is not into contact with the yarn Z being knitted and therefore it does not cause the tightening of the yarn and the bending of the needle A2*. In other words, the feeding yarn Z is free from obstacles and can be freely pulled by the needle A1 * to form loop without being subjected to a peak of tension in the branch between the needles A1 * and A2* and therefore without bending these needles. The needle A2 forming loop in the point M2 is preceded by the needle A1 ** that is going upwards. This latter "releases" yarn to the needle that is in the point M2 thus facilitating it in the loop formation.
With this arrangement the cause is therefore eliminated of the lateral bending of the needles, facilitating the loop formation both in the point M1 and in the point M2. As in this way the needles can run without lateral bending, the damage is avoided of the needles and of the sinkers, if any.
In a particular embodiment of the present invention, it is possible to use the arrangement of the control cams for the needles described above to make particular knitted fabrics by feeding to the needles two yarns in at least one feed so that - in at least one feed - a yarn is taken only by the needles lowered in advance, whilst the other yarn is taken by all the needles.
Figure 8A shows a first example of this use of the invention, wherein on the cylinder periphery two types of needles A1 , A2 have been used, distributed mutually alternate according to a so-called "one-to-one" arrangement and at each feed a thread guide G is used with two holes G1 , G2 for the pass of respective yarns X and Y, these holes being adequately arranged so that the descending segment X1 of the yarn X is displaced with respect to the descending segment Y1 of the yarn Y according to the direction F of rotation of the needle cylinder and to an extent so that it cannot be taken by the A1-type needles, that move downwards in advance along the cam track P1 , but only by the needles A2 - that follow the cam track P2 - together with the other yarn Y.
Therefore, while the needles A2 of the track P2 take both the yarn X and the yarn Y on the respective descending segments X1 , Y1 , the needles A1 - being lowered by cams of the track P1 having the advanced downward movement - take only the yarn Y in the descending segment Y1 and refuse the yarn X, whose descending segment X1 is adequately displaced in the direction of the arrow F. In other words, to form loop, the needles of the track P1 in this arrangement cannot take the yarn X but only the yarn Y and all the needles take the yarn Y.
Using as yarn X an elastomeric yarn and as yarn Y a substantially non-elastic yarn, such as for example a cotton thread or a synthetic thread, a fabric is obtained characterized by an optimum elasticity both in longitudinal and transverse direction, with a 30-40% save in elastomer relative to a knitted fabric formed by means of traditional cams working on each feed with two yarns (elastomeric and non-elastic thread). In this way, in addition to obtain a save in raw material, a fabric is obtained characterized by a lower weight relative to the fabric produced with elastomer on all the feed and presenting an aspect similar to that of the rib knitting that can be produced only on more complex double needle bed machines.
Furthermore, by modifying the arrangement of the needles, it is possible to choose the needles that must work with two yarns and the needles that must work with only one yarn, and therefore the above mentioned knit pattern effect can be distributed variously at will according to the knit columns. With this device it is for example possible to put a different type of knit pattern in any area of the piece and it is possible to obtain knit structures operated with vertical lines of various width characterized by their particular aesthetical appearance. On the currently known machines this is possible only with machines provided with movable cams, or with electronic selection or mini-jack. Figure 8B shows a different arrangement of the needles in a machine according to the present invention wherein, along the cylinder periphery, now are alternatively inserted pairs of needles A1 with the butt T1 and pairs of needles A2 with the butt T2, in a usually called "two-to-two" configuration. The machine is fed at each feed with two respective yarns X, Y passing through respective holes G1 , G2 of a thread guide G. The holes G1 and G2 are arranged so that the descending segment X1 of the yarn X is displaced with respect to the descending segment Y1 of the yarn Y according to the direction F of the movement of rotation of the needle cylinder, so that it cannot be taken by the type A1 needles, that move downward in advance along the track P1 , but only by the type A2 needles following the track P2.
Analogously to the case described above, when the needles A2 of the track P2 take the yarn, the adjacent needles A1 of the track P1 are lower, as they are controlled by cams with the advanced downwards movement. For this reason the needles of the track P1 cannot take the yarn X for forming loop, while all the needles take the yarn Y. In this way a knitted fabric is obtained characterized by pairs of stitches made with two yarns X, Y alternating with pairs of stitches made only with the yarn Y. From the viewpoint of the aesthetical appearance, the knit produced in this way is characterized by a series of vertical lines.
In a machine according to the present invention the arrangement of tracks of needle control cams having descending profiles respectively advanced and delayed as described above provides that this feature, shown in figure 6 for cams suitable to make single jersey, is applied also to the so- called "tucking" cams, i.e. cams suitable to perform tuck stitches. In figure 9, for comparison E indicates a tucking cam of the "type A" (i.e. with advanced descending profile) and H indicates a tucking cam of the "type R" (i.e. with delayed descending profile). The lines LA, LR show the different profiles as in figure 6.
Obviously in a machine according to the invention it is also possible to use common cams of the type called "floating cams", as in correspondence of these cams the needles do not make jersey but leave floated stitches. A circular knitting machine according to the present invention can be therefore adapted to perform all the various known knit patterns that can be usually performed on similar machines and containing tuck and/or floated stitches.
It is understood that the drawing only shows an example provided by way of a practical demonstration of the present invention, which can vary in forms and arrangements without however departing from the scope of the concept underlying the invention. Any reference numbers in the appended claims are provided to facilitate reading of the claims with reference to the description and to the drawing, and do not limit the scope of protection represented by the claims.