Needle selection device in a circular knitting machine with elastic jacks

Abstract: A device for selecting needles (2) in a circular knitting machine of the elastic jack type, comprising auxiliary jacks (14) positioned below and in the same tricks as the elastic jacks (13). The auxiliary jacks (14) are selected electromagnetically so that they act to radially lock the elastic jacks (13) while these are in their flexed position within the tricks so that they cannot return outwards and thus engage their raising cams and activate their needle.

Description: This invention relates to circular knitting machines and in particular to the selection of needles in such machines for the purpose of producing patterned knitwork, and provides a device and method for selecting those needles which are to pick up the yarn from the feeds to form knitwear articles. Circular knitting machines are known to consist essentially of one or two needle cylinders which, as shown in Figure 1, are provided with tricks 1 in their outer cylindrical surface. The tricks represent the guides for the needles 2 which during their travel form the stitch loops in cooperation with the sinkers. The number of tricks is equal to the number of needles 2 which slide reciprocatingly in them. Generally, in hosiery machines the number of tricks and needles is between 200 and 400 per cylinder. The needles operate with reciprocating movement between a maximum position and a minimum position into which they are moved by suitable cams acting on the needle and jack butts. The cylinder is rotated and with it there rotate the needles which during their reciprocating movement are fed with yarn in an angularly fixed position when in their highest point of travel. To produce hosiery articles generally only part of the available needles are used at the same time and in the same manner, except for the plain knitwork parts, for which all the needles are operated between their maximum and minimum level, all being fed with yarn at each knitting course, and all being moved in the same manner. When the machine is not producing plain knitwork, in order to produce other types of knitwork (such as mesh or patterned knitwork) some needles are required to produce stitch loops while others have to be raised to an intermediate level to take up yarn without clearing the previous stitch in order to form a tuck stitch, or have to be raised with a certain delay so that they do not pick up the yarn fed into a certain angular position and therefore do not form new loops with it. In other words a needle selection has to be made. This means that for each feed it has to be determined which and how many needles must undergo a certain travel and which and how many other needles must undergo a certain different travel or indeed undergo no travel. Again with reference to the arrangement shown by way of example in Figure 1, this selection is made by the jacks 3 which slide in the same tricks 2 as the needles lying above them, to push these latter upwards to a higher level in order to seize the yarn. Figure 1 shows an elastic jack 3, able to radially inflect its lower end. The needles 2 are driven reciprocatingly by cams 4 and fixed counter-cams which cause them to move to form the stitch loops. When the jacks 3 have moved the needle into its working position they withdraw from the needle butt and return downwards. If the needle, after completing its task of seizing the yarn and forming the stitch loop and therefore being at its minimum level, is not required to pick up a further yarn from another feed it remains at this level because its control jack remains in its lower rest position. The jack 3 has a special shape which corresponds to a precise function. Although not shown on the drawings, it is slightly curved, or bowed, in a direction perpendicular to the plane of Figure 1. This curvature keeps the jack lightly forced towards the inside of the trick and ensures its accurate positioning and lack of vibration by keeping it properly adhering to the trick walls, but requiring the application of a certain force to move it either axially or radially. The shank of the jack comprises in its middle part a projection 6, ie the upper guide butt, which comes into engagement with its own control cam 7 for urging the jack downwards when it has completed its task of pushing the needle 2. Proceeding downwards along the jack shank there is a lower butt 8 which comes into engagement with the cam ring 9 provided with a raising contour 10 which raises the jack together with its overlying needle, this therefore being selected to seize the yarn, and with an inner face 11 which causes the elastic jack to approach the interior of the trick. The lowering cam and the raising and approach contours are obviously offset angularly and operate at different times on each jack. The elastic jacks 3 tend spontaneously to move their lower butt 8 outwards to engage the raising contour 10 and be raised. The jacks 3 are maintained in position by one or more circular springs 12 which surround their upper part. They themselves are held in position by one or more circumferential grooves in the cylinder, so that the springs lie internal to the face of the needle cylinder. The springs 12 must be sufficiently strong to oppose the forces which flex the shank 13 of the jack so that the flexural forces acting on 8 induce said flexure, so that the upper part of the jacks does not leave the tricks. The purpose of the selection mechanism and procedure is to exclude from this totality of jacks the jacks which control those needles which in forming the particular stitch are not required to be raised. In the known art, the mechanism for selecting or inactivating the needles consists of a plurality of levers or slides which come into contact with a plurality of butts on the lower part of the jack, in an intermediate position between 6 and 8, and which urge the jack back into the trick 1 so preventing it making contact with the raising cam. The traditional selection procedure therefore consists of bringing a certain number of slides or levers into contact with a certain number of jacks 3 via the pattern butts located at the same height, by radially moving only some of the slides towards the outer surface of the cylinder. If a determined jack is to be left engaged when one or more of the slides have approached the needle cylinder, the butts corresponding to the height of those levers are removed from the jack. The number of levers or slides available for selection control is generally equal to the number of available pattern butts. The selection procedures of the known art generally consist of producing contact between the non-removed butts of the jacks and the inactivating members, whether levers of slides, by rotating said inactivating members into a position of approach to the cylinder. Obviously those inactivating members which are not required to inactivate the jacks whose butts are in a position corresponding with them are kept in the retracted position at the moment in which they would have made contact. The devices which operate in accordance with this procedure include those of GB 2,147,015 of Bentley Eng. Co. and Italian patents 1,183,228 and 1,186,475 of Officine Savio S.p.A. Needle selection by mechanical devices places very restrictive limits on the machine speed and the possible sequence combinations of needles in their raised position and needles in their lowered position. Known from FR-A-2231791 is a circular knitting machine with a plurality of individually selectionable needles guided in grooves housing flexible needle selection elements. The needle selection elements can be selectively flexed by electromagnets according to a path along which it is desired to guide the needle for forming a stitch or for withdrawing the needle from a working position. FR-A-2179414 teaches a circular knitting machine having a plurality of needles accommodated in the grooves of a needle cylinder, and a stationary frame extending around the cylinder and supporting magnetic selection means located upstream of a selection station. Flexible selectors elements are housed in the grooves of the needle cylinder below the needle and are moved radially by the magnetic selection means. Known form GB-A-1165955 is a circular knitting machine with electromagnetic selection of the knitting needles, wherein jacks provided for controlling the cylinder and/or dial needles are advanced initially by spring force, said jacks having cutout portions engaged by hooks provided on spring rods for locking the jacks in their lowest and/or innermost position, each spring rod being provided with an armature and wherein control magnets are provided at each selection point, the movement of selected jacks being initiated on the selective energisation of said magnets by the spring force through the retraction of the hooks from the cutout portions of the jacks, the armatures associated with the cylinder jacks being disposed at different heights and/or the armatures associated with the dial jacks being disposed at different radial distances from the cylinder axis, the number of superimposed control magnets provided at each selection point corresponding to the number of said different height levels and/or radial distances. The hooks provided on the spring rods are projections provided on the armatures. DE-B-1585206 describes yet another control system for a knitting machine in particular a positioning system for control magnet which is comprised of a control coil enclosing one of the magnet poles. Known from FR-A-2030533 is a circular knitting machine having oscillatable selectors housed in needle cylinder grooves below the needles and acted on by magnetic means controlled by a computer program. DE-A-2436764 describes a template for a knitting machine with a particular control device for the knitting needles, wherein the control device provides for an exact positioning of the needles prior to the knitting process. DE-A-2424190 describes a similar electronically controlled template device for a knitting machine. The most recently proposed solutions of the known art are based on electromagnetic selection of the jacks 3 via a single pattern butt, using fixed electromagnetic selection members. In Italian patent application No. 19918 A/88 of the present applicant one selection member is provided in a fixed position for each feed, whereas in other patent publications such as European patent application 219029 in the name of Lonati S.p.A., GA patent application 2,008,157 in the name of Shima Center Co. Ltd, GB patent 1,436,607 in the name of Precision Fukuhara Works Co. Ltd. and French patent 1,564,603 in the name of Mayer the selector devices consist of a pack of electromagnetically operated selectors positioned at a point preceding each feed. In GB patent application 2,043,712 in the name of Dainippon and others, the electromagnetic selector device is provided needle by needle, but the engineering involved is very complicated, especially for machines of high rotational speed. These needle selection devices are fixed and operate on the jacks which raise the needles into activation when said jacks, during their rotation together with the cylinder, appear in front of the fixed selection station which precedes each machine feed station. The time available for setting, initiating and completing the selection is very small, being of the order of a few thousandths of a second, and determined by the small angular sector within which the rotating jacks face the selection member, which for its part must be immediately ready to select those needles or more precisely those needle jacks which at that moment are presented to them. Most recently, the solution to the problem has turned towards mobile selection devices rotating together with the cylinder, so that the time available for selection is not limited to the moment in which the jacks appear before the stationary selection device. In this manner each jack is constantly presented to its selection member, so that the selection can take place within a wide angle of the cylinder rotation. In this manner the selection setting time is not so drastically small and the selection can be effected reliably and safely. In EP Publ. No. 0 379 234, this needle selection is effected by controlling the radial position of the jacks by means of other horizontal jacks which slide radially. These horizontal jacks are selected by electromagnetic devices, by being caused to assume a position withdrawn from the cylinder to thus allow the corresponding needle to operate, or a position close to the cylinder to thus inactivate the needle. In EP Public. No. 0 441 005 of the present applicant, the radial position of the jacks is controlled by axially deformable elastic forks which rotate together with the cylinder. The present invention is described hereinafter by way of nonlimiting example with reference to Figures 2, 3, 4 and 5. As stated heretofore, the jack 3 is of special conformation, ie in the form of an elastic jack. In this respect, its lower part 13 is made more slender than normal so that it is flexible in the plane of Figures 1 and 2 between a position, shown by full lines, in which it is flexed by the effect of the radial thrust of the face 11, which urges it into the trick 1 so that it does not engage the contour 10 and remains lowered, and a non-flexed or lesser-flexed position shown by dashed lines in which its butt 8 engages 10 so that the jack is consequently raised. In contrast to traditional jacks there is no need for radial cams to urge the butt 8 outwards. The selection device is shown in Figure 2, of which Figure 2A shows the device in the selection configuration which activates the needle 2 by raising the jack 3 by means of the contour 10, and Figure 2B shows the device in the configuration for inactivating the needle 2. Beneath each jack 3 in the same trick 1 there is an auxiliary jack 14. This consists of two parts 15 and 16. The trick portion holding the auxiliary jack 14 can be of different depth, width or profile. The relatively more rigid upper part 15 can undergo only axial movement, being restrained by the trick 2, the inner ring 17 and the contour of the lowering cam 18. The lower part 16 is however slender and flexible in the plane of the drawing, and is subjected to the action of an electromagnetic selection device 19 cooperating with a fixed can ring 20, shown in the subsequent figures, consisting of a raising contour 21 and an outward radial withdrawal contour 22, these being angularly offset from each other. In the embodiment illustrated by way of example in Figures 2A and 2B, the auxiliary jack 14 is shown divided into two separately formed parts 15 and 16 connected together by providing in the bottom of 15 a slot in which the upper end of the stem 16 is inserted. The retention of the stem 16 can be achieved by other means, however it is essential that any radial force applied to the lower part of 16 causes it to flex. This separate formation results in simpler construction. The jack 14 can perform the same function even if of one-piece construction, for example by blanking. Figure 2C shows by way of exanple a different embodiment of the auxiliary jack 14, in which the parts 15 and 16 are axially independent. The cams 18' axially move the part 15, while the flexible part 16 is retained upperly by the ring 17' so that its lower part flexes by the effect of withdrawal contours 22 on the ring 20, and is free to slide axially within the tricks 1. The electromagnetic selection device 19 consists, in its essential components, of a part energized by a permanent magnet 23 which permanently attracts into contact with it the stems 16 flexed by the action of the contour 22, and an interposed part either energized or not energized by an electromagnet 24, in the former case it releasing the stems so that they return to their non-flexed position and are able to rise on the contour 21, and in the latter case it retaining them flexed, and away from the next contour 21. An electromagnetic selection device of this type is significantly illustrated in the Czechoslovakian note of author No. 216358. With reference to Figure 3A, which shows the form and relative position of the ring 20 and device 19 for an anticlockwise rotating machine with four feeds A, B, C and D, the needle selection is effected as follows. The stem 16 travels along the ring 20 with anticlockwise movement and reaches the withdrawal cam 22 which flexes it and moves it to the face of the device 19. This happens for all stems 16. The flexed stems 16 travel along the initial part of the device 19 energized by the permanent magnet, remaining in an outwardly flexed position. The contour 22 terminates before that part of the device 19 energized by the action of the electromagnet 24. Figure 3B shows the structure of a typical embodiment of the device 19 in greater detail. It consists of a plate 19 of ferromagnetic material of quadrangular annular shape with an inner cavity containing the electromagnet 24. That edge of the plate which is presented to the stems 16 is divided into two regions, namely an outer region divided into two outer parts 19' connected to the permanent magnet 23, and an inner region 19" connected to the electromagnet 24 and more specifically to the pole piece of its core, located within the winding 25. The two regions are magnetically separated from each other for example by inserts of diamagnetic material such as brass. In a preferred embodiment of the invention, the plate 19 or at least the edge presented to the stems 16 is protected by an antiwear covering. The electromagnetic device 24 can either be energized to create a magnetic field opposing that of the permanent magnet 23 so that during their passage in front of 19" the resultant magnetic attraction on the flexed stems is strongly reduced, their elastic force then causing them to return to a non-flexed position distant from 19, or be energized to create a magnetic field in the same sense as that of the magnet 23, so as to maintain the action which retains the stems 16 in a flexed position in contact with 19. If the angular aperture of the region 19" is sufficiently wide, it is sufficient merely not to energize 24 to make the elastic force of the stems prevail. If however they have to be retained, 24 must be energized in the same sense as 23. If however this aperture is narrow, it is not sufficient merely not to energize 24 to release the stems retained in their flexed state. In this case to release the stems the electromagnet 24 must be energized in the opposite sense to 23. If a stem is retained in the flexed state it continues its travel in position 16A of Figures 2A and 3. In this respect the second region 19' retains it adhering to itself and does not allow it to rise on the raising contour 21 of the ring 20. It continues along the external path resting against the outer face of the cam 21. However, if a stem 16 is released it continues its travel in position 16B of Figures 2B and 3. It is in a withdrawn state and no longer undergoes substantial attraction by the second part of 19', so that it is able to rise on the raising contour 21. Figure 3C shows in greater detail the selection of the stems 16. This takes place by the effect of the region 19" positioned at the gap between the flexure contour 22 and the raising contour 21. All the stems 16 are flexed, and the selection then made at said gap. The stems 16B are released whereas the stems 16A are retained. According to a preferred embodiment of the raising cam 21, it is provided with a raised edge 21A which retains the stems 16B on the raising cam and prevents the subsequent rising of any stems 16A which have been imperfectly retained by the device 19. Consequently when the stem 16 rises into the position 16B of Figure 2B, the part 15 is raised and prevents the flexible part 13 of the jack 3, which has flexed into the trick 1 by the radial thrust of the face 11, from returning outwards at the end of the face 11, by engaging its tooth 26 with its upper end 27 before the action of the face 11 ceases. The jack 3 can therefore no longer return outwards and engage its butt 8 with the contour 10 to activate the overlying needle 2. In contrast, in the configuration of Figure 2A the stem 16 in the 16A configuration does not rise and does not cause 15 to rise, so that the two parts 26 and 27 do not mutually engage, with the result that when the thrust of the face 11 ceases the part 13 is freely released and the butt 8 engages the contour 10, causing the jack 3 to rise and activate the needle 2. On termination of its action by which it locks the jack 3 in the inactivation position, the auxiliary jack 14 is returned downwards by the cam 18, which engages a butt on its part 15. As stated heretofore, in circular knitting machines there is a requirement for high speed and a consequent problem of limited time available for needle selection. In the device according to the invention, during the time period in which each stem 16 passes in front of the part 19" of the electromagnetic selection device 19, the electromagnet 24 must be energized in the opposite sense to or same sense as the permanent magnets, or alternatively not be energized, and the stem must have the time, if required, to return to its unflexed position before again entering the angular sector of influence of the second part of the region 19'. The present invention has the advantage of allowing variations in the configuration of the stems so that they can be divided into several series of mutually alternating stems with a consequent in the times and angular spaces available for the selection. There is also a space problem in that the jacks subjected to selection are very close to each other, with a pitch of 1 mm or even less. Figure 4 shows a typical embodiment of the invention with this type of variation. It renders the invention particularly suitable and reliable for high-speed high-productivity machines. In this preferred embodiment the stems 16 are shaped differently in the plane of the figure, with at least one projecting part 28 or one recessed part 29 at different heights in adjacent stems, so as to present the appropriate stems in an ordered manner in proximity to their magnetic selection members 19, also disposed at different heights, while keeping the adjacent stems distant from these selection members, by which they must not be influenced. In the embodiment of Figure 4A, the stems are shown by way of example with only two different height values for simplicity. They comprise projections at two levels, the odd numbered stems having an outwardly projecting part 28₁ which makes contact with the corresponding magnetic selectors 19₁ at a height H₁, the projecting part 28₂ of the even numbered stems, positioned at the height H₂, then not being substantially influenced by these. For the same reason the corresponding magnetic selectors 19₂ of these latter, also positioned at the height H₂, do not influence the odd stems, and come into contact only with the even stems. In the embodiment shown by way of example in Figure 4B, the stem which is not to be influenced by a magnetic selector positioned at a certain height is shaped with an inwardly recessed part 29 at that height, which thus keeps it out of the range of action of that selector. In Figure 4B, the stem 16₁ with the recessed part 29₁ at the height H₁ is selected by the selector 19₁ at the height H₂ and is not influenced by the selector 19₂, from which it is separated by its recessed part. Conversely, the stem 16₂, with its recessed part at the height H₂, is selected by the selector 19₂ positioned at the height H₁. A different embodiment comprising variations in stem configuration is shown in Figure 5. This embodiment not only allows higher machine speed and production, but also prevents or considerably limits magnetic interference between adjacent stems. In this embodiment the stems 16 are shaped with different lengths and are located on circumferences of different radius relative to the parts 15. In the embodiment of Figure 5 and 6 the stems 16 of different configuration alternate mutually, for example those of even number 16 P are longer than and more internal than those of odd number 16 D , The longer and more internal even stems 16 P are selected by the selector 19 P located in the lower and more internal position, whereas the shorter and more external odd stems 16D are selected by the selector 19 D located in the higher and more external position. The two selectors 19 D and 19 P are positioned on a support frame 30. The stems 16 D and 16 P are guided by concentric grooved ring structures 31 D and 31 P each provided with staggered grooves 32 D and 32 P in a number equal to one half of the tricks 1 provided in the needle cylinder. Specifically, the grooves 32 D are positioned to correspond with the odd numbered tricks 1, whereas the grooves 32 P are positioned to correspond with the even numbered tricks 1. With the stem series 16 D there is associated a higher more outer cam ring 20 D provided with a withdrawal contour 22 D and a raising contour 21 D , these being respectively upstream and downstream of the each stem selector 19 D . With the stem series 16 P there is associated a lower more inner cam ring 20 P likewise provided with contours 22 P and 21 P upstream and downstream of the even stem selectors 19 P . The distance between the circumferences of the even and odd stems can be indicatively 3-6 mm, whereas the pitch between two corresponding adjacent stems is now about 2 mm instead of 1 mm. These distances, associated with the fact that the stems are contained by the ring structures 31 D and 31 P , which are preferably constructed of ferromagnetic material, in practice eliminates possible magnetic interference which might otherwise disturb the selection operation. In providing varying stems 16, the auxiliary jacks 14 can be of one-piece construction, as shown in Figures 2A and 2B, or divided into two pieces as shown in Figure 2C. This latter design is preferable because of its ease of construction and assembly. This two-level arrangement of the varying stems of the embodiments shown in Figures 4 and 5 enables the angular width of the space available for needle selection to be doubled. It is apparent that by providing three, four or more levels in the arrangement of the stems and selectors, this space is correspondingly tripled, quadrupled or multiplied.

Claims: A circular knitting machine of the elastic jack type, having a needle cylinder provided with tricks (1) in which the needles (2) and their elastic jacks (3) slide reciprocatingly, these latter able to assume at their lower end a flexed inactive position for maintaining their needles (2) out of operation, or an unflexed active position for urging their needles (2) into operation by means of the raising contour (10) of the cam (9), characterised by comprising auxiliary jacks (14) positioned below the jacks (3) in their tricks (1) and consisting of a rigid part (15) able to undergo only axial movement and a flexible part or stem (16) able to undergo both axial movement and flexure in a plane radial to the needle cylinder, said axial movement being determined by a raising contour (21) and said flexure being determined by a withdrawal contour (22) preceding the contour (21) in the direction or rotation of the machine, and further comprising an electromagnetic selection device (19) angularly interposed between said contours (22) and (21) to effect selection on all stems (16) flexed by the contour (22) by separating those stems to be released into position (16B) and be allowed to engage the contour (21) to thus lock the overlying jacks (3) in their inactive position, from those stems to be kept flexed in position (16A) and not be allowed to engage the contour (21), to thus leave the overlying jacks free to be correspondingly raised in order to activate their needles. A circular knitting machine of the elastic jack type as claimed in claim 1, characterised in that the electromagnetic selection device (19) is constituted by the lateral edge of a ferromagnetic plate divided into two regions (19') and (19"), of which the region (19') is divided into two peripheral parts and is connected to a permanent magnet to assume its magnetic polarity, and the central region (19") assumes the polarity of the pole piece of the core of the electromagnet (24), said regions being separated from each other by diamagnetic material. A circular knitting machine of the elastic jack type as claimed in claim 2, characterised in that the plate (19), or at least that edge thereof which makes contact with the stems (16), is protected by an antiwear covering. A circular knitting machine of the elastic jack type as claimed in one or more of the preceding claims, characterised in that the stems (16) are not identical and comprise projections and/or recessed parts at different heights, adjacent stems having mutually different configurations. A circular knitting machine of the elastic jack type as claimed in claim 4, characterised in that those electromagnetic selection devices (19) for selecting adjacent stems are located at different heights, in positions corresponding with the heights of the projections and/or recessed parts of those stems to be involved or not involved in the selection respectively. A circular knitting machine of the elastic jack type as claimed in one or more of claims 1 to 3, characterised in that the stems (16) are not identical and pertain alternately to two different-length series located on concentric ring structures of different radii, each stem series being moved by its own cam ring (20) provided with contours (21) and (22), and being subjected to selection by its own selection devices 19. A circular knitting machine of the elastic jack type as claimed in claim 6, characterised in that the stems are of two different configurations (16 D ) and (16 P ). A circular knitting machine of the elastic jack type as claimed in one or more of claims 6 to 7, characterised in that the various cam rings and electromagnetic selection devices (19) for selecting the stems of each series are located at different heights. A method for selecting needles in a circular knitting machine with a device as defined in claims 1-8 characterized in that it comprises the steps of; energizing said electromagnet (24); generating a magnetic field with said electromagnet (24) which is opposite with respect to the magnetic field of the permanent magnet 23, and; releasing the flexed stems presented to the electromagnetic selection device (19). A method for selecting needles in a circular knitting machine with a device as defined in claims 1-5 characterized in that it comprises the steps of; energizing said electromagnet (24); generating a magnetic field with said electromagnet (24) which is the same as the magnetic field of the permanent magnet 23, and; maintaining flexed and retaining the flexed stems (16) presented to the electromagnetic selection device (19). A method for selecting needles in a circular knitting machine with a device as defined in claims 1-8 characterized in that it comprises the steps of; engaging the bottom (26) of the elastic jack (3) with the top (27 of the auxiliary jack (14) while the elastic jack is still subjected to the action of the face (11) of the cam (9) which urges it into its inactive position within the trick (1), and; locking the jack corresponding to a needle to be kept inactivated in its inactive position.

Inventors: ARIA PIERO, ARIA, PIERO
Applicants: MATEC SRL, MATEC S.R.L.
Application year: 1991
Main classification: D04B15
IPC codes: D04B15, D04B9