WO2005038115A2

WO2005038115A2 - A cam device for selection and control of needles of a knitting machine and machine comprising said device

Info

Publication number: WO2005038115A2
Application number: PCT/IT2004/000569
Authority: WO
Inventors: Pierangelo Zola
Original assignee: Pilotelli Macchine Tessili S.R.L.
Priority date: 2003-10-21
Filing date: 2004-10-20
Publication date: 2005-04-28
Also published as: TW200517542A; WO2005038115A3; EP1680540A2; ITFI20030267A1

Abstract

The device comprises a stitch cam (25) and cam elements (29, 31, 33; 41, 47, 49) adjustable in different positions to carry the selected needles to idle, tuck and clearing positions respectively. The cam elements comprise at least two raising cams (31, 33; 47, 49) adjustable with a movement essentially orthogonal to the direction in which said needles slide, and at least one counter-cam (29; 41), adjustable according to an adjusting movement essentially parallel to the direction in which said needles slide.

Description

A cam device for selection and control of needles of a knitting machine and machine comprising said device DESCRIPTION Technical Field The present invention relates to a cam device for selecting and controlling the needles in a circular knitting machine, wherein the needles are equipped with a main butt and with at least a selection butt and slide according to a longitudinal direction. More specifically, the invention relates to a so called "lock" device of the type comprising a stitch cam and cam elements adjustable in different positions to carry the selected needles to idle, tuck and clearing positions respectively. The invention also relates to a circular machine that comprises one or more of said devices to control the cylinder needles and/or dial needles. State of the Art In knitting machines, especially those with a large diameter utilized to produce tubular knitted fabrics, which are subsequently wound in rolls, it is necessary to have systems that allow rapid and accurate adjustment of the cams to select and control the needles, both in the needle dial and in the needle cylinder, without the need to disassemble or reassemble machine parts. The groups of cams, also called "locks", are configured to act on the selection butts of the needles to cause raising of the needles, selectively and according to the mesh to be obtained on the final fabric. Raising is intended both as a movement in an essentially vertical direction, for the cylinder needles and radial movement to extract the needles, for the dial needles. In this context the term raising shall be utilized in this special and broader meaning. According to how the cams of the locks are adjusted, that is, according to the "configuration" for each lock, these can act on the selection butts to keep the needles idle, or to take them to the tuck position, or yet again to take them to the clearing position. Idle position is intended as a position in which the needles are not raised and thereby remain in their respective sliding channels. In the tuck position the needle is raised to an extend sufficient to take up the yarn fed by the yarn-guide, without clearing the previous stitch formed and possibly engaged by said needle. From this partially raised position, the needle is then taken towards the inside of the channel, engaging the yarn and-forming-a-stitch-orloop-!n-the- clearing position, the needle is raised to a greater extent with respect to the tuck position. Any loop present in the hook of the needle is cleared, as the needle is raised to an extent that carries the loop beyond its latch. The locks have cams that control raising of the needles to the tuck or clearing position. These cams are normally called raising cams. In particular, they comprise a tuck cam, which raises the needles to the tuck level and a clearing cam that raises the needle further to the clearing level. When the two raising cams are idle, that is, not acting on the selection butts of the needles that travel in front of the cams, the needles remain in the idle position and are held there by specific retaining cam profiles. The raising cams act on the selection butts of the needles. If the machine has needles with selection butts at different heights, that is, in different positions along the longitudinal extension of the shank of the needle, raising cams with different heights are also provided to act on one or on the other of the selection butts of the needles. Moreover, the locks have a stitch cam which, by acting on the main butt or stitch butt of each needle, returns the needles inside their channels. Further, fixed counter-cams are used to control movement of the needles acting on the main or stitch butts to prevent the needles from being raised beyond the position defined by the raising cams. Knitting machines usually have several feeds, that is, several feed points of the yarns with which the fabrics are formed by means of the needles of the rotating needle beds. A lock is provided at least at the level of each feed, the cams of which control in the desired way selection and the raising movement of the needles, so that said needles are in the idle, tuck or clearing position, respectively, when they pass in front of the feed with which the lock is associated. Adjacent locks or tracks to hold the needles in their position during travel from one feed to the next may be provided between consecutive feeds. To modify the design of the fabric according to need, locks have been designed wherein the raising cams are adjustable in different positions according to whether the needles that travel at the level of the lock are in the idle position or raised in the tuck or clearing position. Adjustment takes place without disassembling the cams and/or needles or other parts of the machine. DE-C-4240037-desGribes-a-!θGk-of-this-type_^Here_τ-a-pair-Gf-raising-cams respectively tuck and clearing cams, are provided for each selection butt. The two cams are both adjustable with a movement essentially parallel to the direction in which the needles slide in their channels, that is, parallel to the axis of the cylinder in the case of locks for the needle cylinder and radially with respect to the needle cylinder in the case of locks for the dial. In addition to cam profiles acting on the selection butts to cause raising of the needles, the two raising cams also have counter-cam profiles, that is profiles designed to act on the upper or outer side of the selection butts to hold each needle downwards, that is, inwards, either in the idle position or in the tuck or clearing position. This prior art device is not without defects. Among others, in the case in which the stitch butt or main butt of a needle breaks (as is occasionally the case on these machines), it is impossible to prevent the needle from being raised beyond the clearing position, as the counter-cam profiles of the raising cams do not act on the selection butts in the section of the needle path corresponding to the position of the stitch cam. A different lock device of the aforesaid type is described in EP-A-694640. This prior art device is destined to control needles each equipped with a double selection butt, as well as the main or stitch butt and thereby requires the use of special needles. Objects and summary of the Invention The object of the present invention is to produce a new type of lock for circular knitting machines, which allows the configuration to be changed without disassembling the lock and/or the needles. The object of a preferred embodiment of the invention is the production of a lock that allows greater control over the needles, avoiding damage to the machine even if the stitch butt or main butt should break. The object of a further preferred embodiment of the invention is a lock that allows more complete control of the path of the needles in the idle position. Essentially, according to the invention the lock has cam elements adjustable in different positions to carry the selected needles respectively to the idle, tuck and clearing positions, wherein said cam elements comprise at least two raising cams adjustable with a movement essentially orthogonal to the direction in which said needles slide in their channels, that is, with a sinking movement; and -at -least one counter-cam, adjustable according to a movement of adjustment essentially parallel to the direction in which said needles slide. The raising cams are carried alternatively, to the sunken position, that is, withdrawn with respect to the path of the selection butt of the needles or in an operating position, that is, in which they interfere with the selection butts. In the first case the raising cam does not act on the selection butt of the needles that travel in front of the cam, in the second case it interferes therewith and causes raising of the needle. According to whether one or both of the raising cams are in the extracted, that is, operating, position, they carry the butt to the tuck position or to the clearing position. The raising cams are also called tuck and clearing cams, as the first raises the needles to the tuck position and the second raises them further to the clearing position. The counter-cam adjustable parallel to the raising movement of the needles acts on the side of each selection butt opposite the one on which the raising cams act. It holds back the needle, limiting the raising movement. It may be above the clearing cam, or in front of the clearing cam, or even in front of the tuck cam, according to whether the clearing cam or both the raising cams are in the sunken position, that is, withdrawn with respect to the selection butt of the needles. In a per se known way, the lock advantageously also has an upper fixed counter-cam acting on the main or stitch butts of the needles and associated with the stitch cam, which constitutes the continuation of the upper counter-cam. A lower fixed counter-cam, acting on the main butts of the needles, is also provided, on the opposite side with respect to the one on which the first fixed counter-cam and the stitch cam act. More specifically, according to an advantageous embodiment of the device or lock according to the invention, the cam elements comprise: -a first raising cam (clearing cam) movable in a direction essentially orthogonal to the direction in which the needles slide, between an active position, wherein it cooperates with the selection butts of the needles to raise the needles, and a withdrawn position, wherein it is drawn back with respect to said needles; -a second raising cam (or tuck cam) movable in a direction essentially orthogonal to the direction in which the needles slide, between an active position, wherein it cooperates with the selection butts of the needles to raise the needles, and a withdrawn position, wherein it is drawn back with respect to said needles; -a first counter-cam movable in a direction essentially parallel to the direction in which the needles slide, equipped with a cam profile that holds down the needles, limiting or preventing the raising movement. The first adjustable counter-cam may advantageously take: -a clearing position of the needles, when the first and second adjustable cam are in the active position to act on the selection butts of the needles to carry the needles to the clearing position; -a tuck position, wherein it is in front of the first raising cam, positioned in a withdrawn position with respect to the selection butts of the needles, and wherein it cooperates with the second adjustable cam disposed in an active position, to carry the needles to the tuck position; -and an idle position, wherein it is in front of the second adjustable cam, with the first and the second adjustable cams both positioned in a withdrawn position with respect to the selection butts of the needles, to hold the needles in an idle position. To guarantee improved and more complete control of the path of the needles that are idle, the first adjustable counter-cam can advantageously have a depressed portion and be partially housed under a portion of the lower fixed counter-cam. The lower fixed counter-cam has a cam profile acting on the selection butts of the needles to lower them in the event of breakage of the corresponding main butts. It must be understood that the terms upper and lower, with reference to the cams and counter-cams, in the context of the present description and appended claims, are used to define the position with respect to the raising movement of the needles. When said raising movement is a radial movement, as these are the needles of the dial, upper and lower are intended as two elements that are respectively in the outermost and innermost radial positions. In a per se known way, the arrangement of raising cams and fixed and adjustable counter-cams described above may be multiplied by the number of positions in which the selection butts of the various needles of the machine can be found. Typically, said selection butts will be provided at two distinct heights along the axial extension of the needles. In other terms, there will be needles with a selection butt at a first distance with respect to the stitch butt and, intercalated between these, for example in a 1 :1 ratio, needles that have selection butts at a different height with respect to the stitch butt. Two distinct groups of adjustable selection and control cams act on the butts at the two different heights and the cams can adopt a different position in the two groups, that is the lock may have different configurations for the two types of butt. Lock configurations for more than two types of needle would also be possible. Further advantageous characteristics and embodiments of the lock according to the invention are indicated in the appended claims and shall be described in greater detail hereunder with reference to the drawings that show an advantageous embodiment of the invention with reference to a lock for a dial. Moreover, it must be understood that a lock produced in an analogous way may be associated with the cylinder of the knitting machine. Normally the machine will have locks according to the invention both on the dial and on the needle cylinder.

Brief description of the drawings The invention shall now be better understood following the description and accompanying drawing, which shows a non-limiting practical embodiment of the invention. More specifically, in the drawings, in which identical numbers indicate identical parts: Figure 1 shows a partial section, along a vertical plane containing the axis of the needle cylinder, of a circular machine, showing a sector of cylinder cams and a sector of dial cams; Figure 2 shows a front view, from the side of the needles, according to the arrow ll-ll in Figure 1 , of a sector of dial cams, in a first possible position of adjustment of the cams, positioned to carry the needles to the clearing position; Figure 3 shows a section according to Ill-Ill in Figure 2; Figure 4 shows a side view of the two types of needles employed in the machine using sectors such as the one in Figures 2 and 3; Figure 5 shows a view of the block housing the cams and the adjustment elements, on the opposite side with respect to the position of the needles; Figure 6 shows a local section of the cam adjustment elements, in the layout adopted when the cams are in the position in Figure 2; Figures 7 and 8 shows local sections according to VII-VI! and VIII-VIII in Figure 6; Figure 9 shows a local section according to IX-IX in Figure 7; Figure 10 shows a view analogous to Figure 2, in a different adjustment position of the cams, which are in tuck layout; Figure 10A shows a local section according to XA-XA in Figure 10; Figure 11 shows a local section of the cam adjustment elements, analogous to the section in Figure 6, in the layout adopted when the cams are in the position in Figure 10; Figure 12 shows a view, analogous to the view in Figures 2 and 10, with the cams adjusted in the idle position; Figure 12A shows a local section according to XIIA-XIIA in Figure 12; Figure 13 shows a local section analogous to the section in Figures 6 and 11 , with the adjustment elements adjusted to obtain the position of the cams in Figure 12. Detailed description of the preferred embodiment of the invention Figure 1 shows a local section of the area with the needles of the cylinder and dial of a circular knitting machine. The section is produced at the level of two sectors of cams produced with the devices according to the invention. As indicated hereinbefore, the invention may be implemented both in the sectors of cams or locks pertaining to the needle cylinder or in the sectors of cams or locks relative to the dial. In Figure 1 the numeral 1 indicates as a whole a lock device for the needle cylinder, while the numeral 3 indicates a corresponding device for the dial. The remaining figures show in detail the elements and functions of the device relative to the dial, it being understood that the device relative to the cylinder may be produced in an essentially identical way. Again with reference to Figure 1 , A-A indicates the axis of the cylinder, indicated with 5. The numeral 7 indicates one of the grooves inside which one of the needles 9 of the cylinder slides. The numeral 9A indicates the hook or head of the needle 9. The cylinder 5 is provided in a per se known way with a plurality of channels 7 with corresponding needles 9 which form the circular needle bed of the knitting machine. Analogously, the dial, indicated with 11 , has radial grooves 13 inside which corresponding needles 15 slide, one of which is shown in Figure 1 and the hook or head of which is indicated with 15A. The cylinder 5 and the dial 11 rotate about the axis A-A, while the devices 1 and 3 are fixed to fixed structures 17 and 19 of the machine. In practice, the machine may have a number of devices 1 placed side by side in a circular arrangement which extends for the entire extension of the cylinder 1 , or may have one or more devices 1 at the level of each feed of yarn, while annular elements to hold down the needles may be interposed between one lock 1 and the, next, according to per se known arrangements. The devices 3 associated with the dial may have an analogous arrangement. The cam elements of a single device 3 associated with the dial, used to select and control the needles 15, will be illustrated hereunder with reference to Figures 2 to 3. Figure 4 shows two types of needle for which the device 3 has been configured. The two needles, indicated here with 15X and 15Y, each have a shank or stem 21 , terminating at the top with the respective hook 15A with which a latch 15B is associated. Each needle has a main butt or stitch butt, indicated with 15D. The main or stitch butts of all the needles 15X, 15Y are at the same height, that is at the same distance with respect to the hook 15A. The cams that control the movement to form the stitch act thereon, in a per se known way. Besides the main or stitch butt 15D, each needle 15X, 15Y has a selection butt, indicated with 15E for the needle 15X and with 15F for the needle 15Y. The selection butts 15E, 15F of the two types of needle are disposed at different distances with respect to the main butt 15D. The two types of needle 15X, 15Y may be disposed, in the needle bed, with a 1 :1 ratio, that is, with a needle 15Y interposed between two needles 15X. The device 3 has a block 21 which houses various cam elements and the corresponding elements to adjust the position of the cams. In. the upper area in Figure 2, which corresponds to the radially outermost area of the dial (see Figure 1), the device 3 has an upper fixed counter-cam 23, fixed to the block 21. It has a lower cam profile 23A that acts on the upper (that is, radially outermost) side of the main butt 15D of the needles 15X, 15Y. The cam profile 23A of the upper fixed counter-cam 23 is disposed to form a continuous track with the cam profile 25A of a stitch cam 25. The stitch cam 25 is adjustable in a position according to the double arrow f25 by means of an adjustment element described hereunder. The position of the stitch cam 25 is adjusted to adjust the length of the stitches formed by the needles controlled by the lock or device 3. This type of adjustment is known to those skilled in the art and does not require further description. The stitch cam 25 also has a further lower cam profile 25B that forms with a section of the profile 25A a channel inside which the main butts 15D of the needles travel. Fixed below the upper or outer fixed counter-cam 23 on the block 21 is a second fixed counter-cam 27, hereinafter called lower fixed counter-cam, which is in the radially innermost position with respect to the upper counter-cam 23. The lower fixed counter-cam 27 has an upper cam profile 27A that acts on the lower, that is, radially innermost, side of the main butt 15D of the needles 15X, 15Y in the way and for the purposes to be described hereunder. The counter- cam 27 is produced in two parts. A first part is constituted in one piece with the counter-cam 23, as can be seen in particular in Figure 3, while a second portion 27B is produced by a separate element and fixed to the block 21 by a screw 28 (Figure 2). The portion 27B forms a lower cam profile 27C that acts - in specific conditions to be illustrated hereunder - on the upper side of the selection butt 15F of the needles 15Y. Disposed under the lower fixed cam 27 (that is, in the radially innermost position) is a first movable counter-cam 29 provided with an adjustment movement according to the arrow f29 in a direction parallel to the direction in which the needles 15X, 15Y slide in the relative seats of the dial 11. In the position in Figure 2, the counter-cam 29 is positioned against the fixed counter- cam 27 and is housed in a corresponding lower (that is, radially inner) molding of said fixed counter-cam 27. The first adjustable counter-cam 29 has a cam profile 29A facing downwards, that is radially inwards, which acts on the upper side of the selection butts 15F of the needles 15Y. Moreover, said adjustable counter-cam 29 has a depressed area 29B that is inserted under the portion 27B of the fixed counter-cam 27, which for this purpose is produced to leave space thereunder to house said depressed portion of the counter-cam 29A. Disposed underneath (that is, in the radially innermost position) the fixed counter-cam 27, 27B and the first adjustable counter-cam 29 is a first raising cam 31 provided with a cam profile 31A, adjustable according to a direction orthogonal to the plane of Figure 2 and indicated by the arrow f31 in Figure 3. The cam profile 31A acts on the lower (that is, radially innermost) side of the selection butts 15F of the needles 15Y. The first adjustable raising cam 31 is shaped to cooperate with a second raising cam 33, also adjustable in a direction f33 (Figure 3) orthogonal to the plane of Figure 2 and, therefore, to the direction in which the needles 15X, 15Y slide. The adjustment movement allows each cam 31 , 33 to be disposed in an active position, wherein it interferes with the butts 15F, or in a deactivated position wherein it does not interfere with said butts, for the purposes described hereunder. The cam profile 33A of the cam 33 constitutes, with the cam profile 31 A of the cam 31 , a single continuous profile when the two cams 31 , 33 are both in the extracted position, as shall be described hereunder. Disposed underneath (that is, in the radially innermost position) the raising cam 33 is a second adjustable counter-cam 41 , with essentially the same form as the adjustable counter-cam 29. Just as the first counter-cam 29, said adjustable counter-cam 41 is also equipped with an adjustment movement according to the double arrow f41 , in a direction parallel to the radial direction in which the needles 15X, 15Y slide. It has a cam profile 41 A that acts on upper, that is, radially outermost, side of the selection butts 15E of the needles 15X. Just as the counter-cam 29, the counter-cam 41 also has a depressed area 41 B that allows said counter-cam to be inserted under a fixed counter-cam 43, fastened to the block 21 by a screw 45. The fixed counter-cam 43 has a cam profile 43A acting on the upper edge of the selection butt 15E of the needles 15X in specific conditions that shall be described hereunder. Associated with the second adjustable counter-cam 41 are a third and a fourth raising cam, indicated respectively with 47 and 49, with a form essentially identical to the form of the raising cams 31 and 33. The raising cams 47 and 49 have an adjustment movement according to the arrows f47 and f49 (Figure 3) in a direction orthogonal to the plane in Figure 2 and to the direction in which the arrows 15X, 15Y slide. The adjustment movement allows the cams to be disposed in an active position, wherein they interfere with the butts 15E, or in a deactivated position wherein they do not interfere with said butts, for the purposes described hereunder. Cam profiles 47A and 49A of the cam 47 and 49 are analogous to the profiles 31A and 33A, acting on the lower (that is, radially innermost) sides of the selection butts 15E of the needles 15X. Finally, disposed under the raising cams 47 and 49 is a fixed cam 51 , integral with the block 21 , which has a cam profile 51 A. ln the position illustrated in Figures 2 and 3, the two adjustable counter- cams 29 and 41 are in maximum raising position, that is in the radially outermost position, beyond the raising cams 31, 33 and 47, 49 respectively. The counter- cam 29 is positioned against the lower fixed counter-cam 27, while the counter- cam 41 is positioned against the raising cam 33. The raising cams 31 , 33 and 47, 49 are all in the operating position, that is, extracted with respect to the block 21. As can be seen in Figure 3, in this position the raising cams are flush with the counter-cams 29 and 41. In Figure 2, the direction of movement of the needles 15X, 15Y with respect to the lock or device 3 is indicated with F. This Figure also schematically indicates the upper, that is, radially outermost, ends of the needles, represented by the hooks 15A thereof, and the main butts 15D and the selection butts 15E and 15F respectively. In Figure 2, it can be observed that the selection butts 15F of the needles 15Y encounter, in their movement according to F, the cam profile 33A and subsequently the cam profile 31 A of the raising cams 33 and 31, thanks to the fact that these cams are in an extracted or operating position. As a consequence thereof, the needles 15F are raised, by the effect of the thrust exerted by the profiles 33A, 31 A on the lower side of the selection butts 15F. All the needles 15Y reach the height indicated as clearing position, which constitutes the height of maximum raising, that is, of maximum extraction of said needles in a radial direction. As is known, this position is called clearing position as the loops formed by the needles are cleared under the latch thereof. The needle raising movement is limited at the top by the cam profile 23A of the upper fixed counter-cam 23. After having reached the maximum raising position, the needles start to return by the effect of the descending portion of the cam profile 23A and subsequently by the effect of the profile 25A of the stitch cam 25. This thrusts the needles towards the inside of their grooves in the needle bed of the dial. In this movement, the selection butts 15F follow the descending portion of the cam profile 31A and 33A of the raising cams 31 and 33. The adjustable counter-cam 29 does not act on the butts of the needles 15Y. If the stitch butt or the main butt 15D of one or more of the needles 15Y, on which the stitch cam 25 acts, were to break, the profile 27C of the portion 27B of the fixed counter-cam 27 acting on the upper side of the corresponding selection butt 15F would prevent the needle from remaining in the raised position beyond the stitch forming area and controls its return. Moreover, if the main butt were to break, the needle would also be held by the profile 29A of the adjustable counter-cam 29. The needles 15X are selected and controlled in an essentially equivalent way by the respective selection butts 15E and the main butts 15D. The raising butts 49 and 47, by means of the profiles 49A and 47A, raise the needles 15X to the clearing position, while the upper fixed counter-cam 23 with the profile 23A prevents the needles from projecting beyond the limit defined by the clearing position. Each needle 15X is then made to return by the descending profile of the upper fixed counter-cam 23 and by the profile 25A of the stitch cam 25. The profile 43A of the fixed counter-cam 43 acts on the upper side of the selection butt 15E if the main butt 15D is broken, causing the needle to return to its groove. Upstream and downstream of the device 3 illustrated in Figure 2, analogous devices or guide channels of the butts of the needles may be disposed to hold said needles in the positions reached by the locks directly upstream with respect to the movement of the needles. In Figures 2 and 3 the device 3 is in the configuration required to select all the needles 15X and 15Y in the clearing position. On the contrary, in Figures 10 and 10A the device 3 is shown in a configuration wherein the cams and counter- cams are adjusted to carry all the needles 15X and 15Y to the tuck position. In this configuration, the two raising cams 31 and 47 are in a withdrawn position, so that they do not interfere with the trajectory of the selection butts 15E and 15F of the needles 15X and 15Y. The withdrawn position is reached by moving the cams back towards the block 21 with a movement essentially orthogonal to the direction in which the needles slide in their grooves of the needle bed. This movement is known as "sinking", as the cams are "sunk" under the operating plane, represented by the plane on which the needle butts slide. The adjustable counter-cams 29 and 41 have been carried to a first active position, with a movement essentially parallel to the movement with which the needles slide in their grooves. The counter-cam 29 has been carried in front of the cam 31 which in a withdrawn position, while the counter-cam 41 has been carried in front of the cam 47. The movement according to F of the needles with respect to the lock causes the following effect of the cams and counter-cams on the butts. The butts 15F of the needles 15Y encounter the raising profile 33A of the raising cam 33 and this causes raising (that is, extraction in a radial direction) of the needles. Nonetheless, the raising movement is limited with respect to the movement obtained with the cams in the configuration in Figure 2, as the raising cam 31 is idle. The butts 15F thereby remain at the height of the cam profile 29A of the adjustable counter-cam 29, which acts on the upper, that is, radially outermost, side of the butts 15F. The height reached by the needles is indicated as tuck position. It corresponds to the position wherein the hooks of the needles are at a height that engages the yarn fed by the feed associated with the lock 3, without clearing the stitch previously formed, which remains superposed on the latch of the respective needle. The main butt 15D of each needle comes into contact with the profile 23A of the upper counter-cam in a position downstream (with respect to the direction of forward movement of the needles with respect to the lock) of the point of maximum raising defined by said profile. Subsequently, it encounters the stitch cam 25 which with its profile 25A causes return of the needles. The needles 15X are subject to the same action and the same movements by the effect of the raising cam 49 with its profile 49A and of the lower adjustable counter-cam 41 with its profile 41 A. The main butts 15D come into contact with the profile 23A of the upper fixed counter-cam and subsequently with the profile 25A of the stitch cam 25 which causes return of the needles. Also in this configuration, if the main butt 15D of a needle were to break, this needle would be returned inside the groove in which it slides by the profile 27C in the case of a needle 15Y or by the profile 43A in the case of a needle 15X. Figures 12 and 12A show the device 3 in the configuratfon adjusted to carry or keep all the needles 15X, 15Y to or in the idje position, that is, with the hooks at a height that does not engage the yarn fed from the feed corresponding to the lock which is set in this configuration. In this case all the raising cams 31 , 33 and 47, 49 are in the position withdrawn towards the inside of the block 21, that is, they have been carried with a sinking movement out of the plane of travel of the needle butts. The adjustable counter-cams 29 and 41 have been lowered further, with a movement parallel to the movement with which the needles slide in the respective grooves, to superpose the raising cams 33 and 49 respectively. As can be seen in Figure 12, the selection butts 15F of the needles 15Y are in this case held downward, that is, in a position radially drawn back with respect to the lower profile 29A of the counter-cam 29. The main butts 15D do not touch the profile 23A but come into contact only with the end part of the profile 25A and with the profile 25B of the stitch cam. The hooks 15A of the needles thereby remain in the idle position. The needles 15X behave analogously, with the selection butts 15E engaged at the top (that is, on the radially outermost side) by the profile 41 A of the counter-cam 41, which holds them inside the needle bed. The main butts 15D thereof follow the same path as the main butts 15D of the needles 15Y described hereinbefore. The device 3 described has a double arrangement of selection cams and counter-cams to operate on two different types of needles 15X and 15Y which are distinguished by the fact that the selection butts 15E and 15F are in different positions with respect to the head of the needles. It must be understood that this arrangement may be simplified, using only one group of cams or also multiplied, to obtain three or more groups of cams to operate with three or more different types of needles. It must also be understood that while in the figures described the cams of the two groups are in the same adjustment position (that is, both in the clearing, tuck or idle position respectively), in practice in each device 3 provided around the needle bed the cams acting on the butts 15E of the needles 15X will in general have a different configuration with respect to the cams acting on the butts 15F of the needles 15Y. For example, the needles 15X may be carried to the clearing position and the needles 15Y to the tuck position, or any other combination of the three configurations described hereinbefore may be provided. The elements used to adjust the position of the various cams and counter- cams shall now be described, with particular reference to Figures 3 to 9. The system to adjust the position of the stitch cam 25 is not shown as it is essentially identical to known systems. As can be seen in Figure 5, the block 21 (shown here in a view from the opposite side with respect to the side of the cams and the needles and isolated, that is, without the mechanical parts mounted therein), has four cylindrical seats 61 , 63, 65, 67, each of which has a base wall with an arcuate slotted hole 61 A, 63A, 65A and 67A and a blind circular hole 61 B, 63B, 65B, 67B. The slotted holes 61 A and 63A pass through the block 21 , while the holes 65A and 67A are blind. Inserted in each of the seats 61 and 63 is a respective adjustment element 71 , essentially cylindrical in form and provided with a circular projection 71 A which engages in a through-hole of a closing plate 73 applied to the block 21. In the drawing and in the description hereunder reference shall be made to the adjustment element 71 inserted in the seat 61 , the arrangement being essentially identical for the seat 63. The adjustment element 71 has a recessed hexagonal seat 71 B (Figures 7 and 9) for a hexagonal adjustment key. On the opposite face with respect to the recessed seat 71 B and to the circular projection 71 A, the adjustment element 71 has a series of three hemispherical notches 71 C, 71 D and 71 E, which cooperate alternatively with a ball 75 positioned at the level of the blind hole 61 B and stressed against the inner face of the adjustment element 71 by a helical spring 77 housed in the blind hole 61 B. This arrangement is used to define, by triggering of the ball 75 in one or other of the notches 71 C, 71 D, 71 E alternatively, three adjustment positions, corresponding to the three positions described hereinbefore that can be adopted by the counter-cam 29 (or counter- cam 41). On the same inner face of the adjustment element 71 on which the notches 71 C, 71 D and 71 E are produced is a pin 79, which passes through the arcuate through-hole 61A and engages, with its distal end, in a groove 81 (Figure 7) of a slide 83 integral with the counter-cam 29. The slide 83 slides in a . guide groove 85 produced in the block 21. Rotation of the adjustment element 71 causes, with the pin 79, the slide 83 to slide along the groove 85 so that the counter-cam 29 adopts the three positions described hereinbefore. An analogous arrangement is provided at the level of the seat 63 to adjust the position of the counter-cam 41. Disposed in each of the seats 65 and 67 is an adjustment element 91 essentially identical for the two seats, which is used to adjust the raising cams 31 , 33 and 47, 49 respectively. In the drawing and in the description hereunder reference shall be made to only one of these adjustment elements, the other being essentially identical. The element 91 has a circular projection 91A which engages in a hole of the closing plate 73 and a hexagonal recessed seat 91 B for an adjustment key. Moreover, it has a cam profile 91 C which acts on corresponding profiles of control rods of the cams 31 and 33 as shall be described hereunder. On the opposite face to the one facing the plate 73 the adjustment element 91 has a series of three hemispherical notches or recesses 91 D (only one of which is visible in Figure 8), into each of which a ball 93 can be inserted, disposed at the level of the blind hole 65B. The ball 93 is stressed elastically by a helical spring 95 housed in the blind hole 65B. The arrangement is such as to define three angular positions of the adjustment element 91, corresponding to the three positions of the raising cams described hereinbefore. Provided on the same face of the adjustment element 91, on which the notches 91 D are produced, is a guide pin 97 that is inserted into the arcuate slotted hole 65A. The raising cam 31 is integral with a rod 101 (Figure 3) which has a notch 101 A cooperating with the cam profile 91 C produced on the adjustment element 91. Rotation of the adjustment element 91 from the position in Figure 3 causes the cam 31 to retract. With a further rotation in the same direction this adjustment element acts with said cam profile 91 C on a notch 103A produced in a rod 103 integral with the cam 33 (Fig. 8). This causes the cam 33 to retract. The rod 101 also forms a projection 101 A. This projection is positioned so that it contrasts with the cam 33. In this way the cam 33 cannot be moved back, that is, sunk, unless the cam 31 has been sunk first. On the contrary, the cam 31 cannot be extracted (from the sunken position) unless the cam 33 has been extracted, that is, carried to the operative position, first. This prevents the risk that the cam 33 is in the withdrawn position and the cam 31 in the operating position, a configuration incompatible with correct operation of the device. The sinking movement of the cam 33 is guided by a guide rod 105, integral with the block 21, which also delimits the extraction travel to the active position. This guide rod 105 is inserted into a through-hole of a slider 107 with which the cam 33 is integral. Contact between the cam profile 91 C and the notches 101 A, 103A is guaranteed by compression springs 109, 111 disposed between annular projections of the rods 101, 103 and the closing plate 73 (Figures 8 and 3). Rotation of a single adjustment element 91 thereby allows, according to the angular position that it adopts, the two corresponding raising cams (31, 33 or 47, 49) to be disposed in one or other of the three positions described hereinbefore. The arrangement and functions described hereinbefore may be implemented in an essentially identical way for the locks of the cylinder, wherein the conformation of the block 21 is simply varied to have parallel side walls, instead of the converging side walls of the dial. It is understood that the drawing purely shows a practical embodiment of the invention, which may vary in forms and arrangements, without however departing from the scope of the concept on which the invention is based. Any reference numerals in the appended claims are provided solely to facilitate reading in the light of the description hereinbefore and of the accompanying drawings and do not in any way limit the scope of protection.

Claims

CLAIMS 1. A cam device for selection and control of needles (15X; 15Y) in a circular knitting machine, said needles being provided with a principal butt (15D) and at least one selection butt (15E; 15F) and which slide according to a longitudinal direction in corresponding grooves of a needle bed, comprising a stitch cam (25) and cam elements (29, 31 , 33; 41 , 47, 49) adjustable in different positions to carry the selected needles to idle, tuck and clearing positions respectively, wherein said cam elements comprise at least two raising cams (31 , 33; 47, 49) adjustable with a movement essentially orthogonal to the direction in which said needles slide, and at least a counter-cam (29; 41) adjustable according to an adjustment movement essentially parallel to the direction in which said needles slide.

2. Device as claimed in claim 1 , comprising an upper fixed counter- cam (23) acting on the principal butts (15D) of said needles (15X, 15Y) and associated with said stitch cam (25), said stitch cam constituting the continuation of said upper counter-cam, and a lower fixed counter-cam (27) acting on said principal butts (15D) of said needles.

3. Device as claimed in claim 1 or 2, wherein said cam elements comprise: -a first raising cam (31) movable in a direction essentially orthogonal to the direction in which the needles slide, between an active position, wherein it cooperates with the selection butts (15E, 15F) of the needles to raise the needles, and a withdrawn position, wherein it is drawn back with respect to said needles; -a second raising cam (33) movable in a direction essentially orthogonal to the direction in which the needles slide, between an active position, wherein it cooperates with the selection butts (15E; 15F) of the needles to raise the needles, and a withdrawn position, wherein it is drawn back with respect to said needles; -a first adjustable counter-cam (27) movable in a direction essentially parallel to the direction in which the needles slide, equipped with a cam profile (29A) that holds down the needles, limiting or preventing the raising movement.

4. Device as claimed in claim 1 , 2 or 3, wherein said first adjustable counter-cam (29) can adopt: -a clearing position of the needles, when the first and second raising cams (31, 33) are in said active position to act on the selection butts of the needles to carry the needles to the clearing position; -a tuck position, wherein it is in front of the first raising cam (31), positioned in said withdrawn position with respect to the selection butts of the needles, and wherein it cooperates with the second raising cam disposed in an active position, to carry the needles to the tuck position; -and an idle position, wherein it is in front of the second raising cam (33), with the first and the second raising cam both positioned in a withdrawn position with respect to the selection butts of the needles, to hold the needles in an idle position.

5. Device as claimed in at least claim 2, wherein said first adjustable counter-cam (29) has a depressed portion (29B) and is partly housed under a portion (27B) of said lower fixed counter-cam, said portion having a cam profile (27C) acting on the selection butts (15F) of the needles to lower them in the case of breakage of the corresponding main butts (15D).

6. Device as claimed in claim 5, wherein said lower fixed counter-cam (27) is produced in two pieces, the first adjustable counter-cam (29) being inserted under one of said two pieces of the lower fixed counter-cam.

7. Device as claimed in one or more of the previous claims, wherein said cam elements also comprise: -a third raising cam (47) movable in a direction essentially orthogonal to the direction in which the needles slide, between an active position, wherein it cooperates with the selection butts of the needles to raise the needles, and a withdrawn position, wherein it is drawn back with respect to said needles; -a fourth raising cam (49) movable in a direction essentially orthogonal to the direction in which the needles slide, between an active position, wherein it cooperates with the selection butts of the needles to raise the needles, and a withdrawn position, wherein it is drawn back with respect to said needles; -a second adjustable counter-cam (41) movable in a direction essentially parallel to the direction in which the needles slide, equipped with a cam profile (41 A) that holds down the needles, limiting or preventing the raising movement.

8. Device as claimed in claim 7, wherein said second adjustable counter-cam (41) can adopt: -a clearing position of the needles, when the third and fourth raising cams (47, 49) are in said active position to act on the selection butts of the needles (15E, 15F) to carry the needles to the clearing position; -a tuck position, wherein it is in front of the third raising cam (47), positioned in said withdrawn position with respect to the selection butts of the needles, and wherein it cooperates with the fourth raising cam (49) disposed in an active position, to carry the needles to the tuck position; -and an idle position, wherein it is in front of the fourth raising cam (49), with the third and the fourth raising cam both positioned in a withdrawn position with respect to the selection butts of the needles, to hold the needles in an idle position.

9. Device as claimed in claim 7 or 8, wherein said second adjustable counter-cam (41) has a depressed portion (41 B) and is partially housed under a fixed cam (43) having a cam profile (43A) acting on the selection butts of the needles to lower them in the case of breakage of the corresponding main butts.

10. Device as claimed in claim 8, wherein in said clearing position the second adjustable counter-cam (41) is positioned against the second raising cam (33).

11. Device as claimed in one or more of the previous claims, wherein said first and said second raising cam (1, 33) are each equipped with a rod (101 ,

103) sliding in a corresponding seat of a supporting block (21) and equipped with a control profile (101 A, 103A) cooperating with a corresponding control profile (91 C) of an adjustment element (91) for adjusting the position of said raising cams, said element being accessible from the side of said block opposite the side facing the needles and on which said cams are carried.

12. Device as claimed in claim 11 , wherein said adjustment element comprises a single control profile (91 C) cooperating with the control profiles produced on the two rods (101 , 103) of the first and of the second raising cams, as a function of the position adopted by said control profile.

13. Device as claimed in claim 12, wherein said adjustment element rotates about an axis essentially parallel to the axis of said rods.

14. Device as claimed in claim 11 , 12 or 13, wherein said rods are elastically stressed towards the active position of the corresponding raising cams.

15. Device as claimed in one or more of claims 7 to 10, wherein said third and said fourth raising cams (47, 49) are each equipped with a rod (101 , 103) sliding in a corresponding seat of a supporting block and equipped with a control profile cooperating with a corresponding control profile of an adjustment element of the position of said raising cams, said element being accessible from the side of said block opposite the side facing the needles and on which said cams are carried.

16. Device as claimed in claim 15, wherein said adjustment element comprises a single control profile cooperating with the control profiles produced on the two rods of the third and of the fourth raising cam, as a function of the position adopted by said control profile.

17. Device as claimed in claim 16, wherein said adjustment element rotates about an axis essentially parallel to the axis of said rods.

18. Device as claimed in claim 15, 16 or 17, wherein said rods are elastically stressed towards the active position of the corresponding raising cams.

19. Device as claimed in one or more of the previous claims, wherein said first counter-cam is integral with a slider (83) sliding in a guide (85), which has a groove (81) inside which a pin (79) engages, integral with a roller (71) to adjust the position of said first counter-cam (29).

20. Device as claimed in one or more of claims 7 to 10, wherein said second counter-cam is integral with a slider sliding in a guide, which has a groove inside which a pin engages, integral with a roller to adjust the position of said second counter-cam.

21. Device as claimed in one or more of the previous claims, configured to be associated with a dial of a circular knitting machine.

22. Device as claimed in one or more of claims 1 to 20, configured to be associated with a cylinder of a circular knitting machine.

23. A circular knitting machine comprising one or more devices for selection and control of the needles as claimed in one or more of claims 1 to 22.