Circular knitting machine with a device for repeating the selection of the needles at least at one thread feed

Abstract: The present machine (1) has a device for repeating the selection of the needles at least at one thread feed, which includes a memory element (12) arranged proximate to the lower end of the selectors (5), which can oscillate in a plane radial to the needle cylinder (2) by virtue of the action of selection levers arranged upstream of a thread feed of the machine (1), according to the direction of the rotation imparted to the needle cylinder (2) about its own axis (2a). The selectors (5) can individually oscillate in a radial plane with respect to the needle cylinder (2) from an extraction position, whereat they protrude from the needle cylinder (2) with a main heel (5a) so as to engage actuation cams (7) arranged about the needle cylinder (2), to a sunk position, whereat they do not engage the cams. The memory element (12) is controllably movable from an inoperative position, whereat it does not interfere with the oscillation of the selectors (5), to an operative position whereat, between two feeds of the machine (1), it maintains the position of the selectors (5) imparted by the selection levers upstream of the first feed so that the performed selection is maintained at the second feed as well without requiring a new selection.

Description: The present invention relates to a circular knitting machine with a device for repeating the selection of the needles at least at one thread feed. As known, circular knitting machines are generally constituted by a needle cylinder which has, on its lateral surface, a plurality of grooves which extend along a direction which is substantially parallel to its axis. A needle and a selector arranged below said needle are accommodated in each of said grooves so as to be slidable in a direction which is parallel to the axis of the needle cylinder. Each selector can oscillate in a radial plane of the needle cylinder, by virtue of the action of selection means which are arranged laterally facing the needle cylinder, from an extraction position, in which a main heel of the selectors protrudes radially from the needle cylinder, to a sunk position, in which said main heel is contained within the radial dimensions of the needle cylinder. One or more actuation cams are arranged around the needle cylinder, proximate to the main heel of the selectors, and define paths which can be engaged by said main heel when the selector is in the extraction position. The paths defined by the actuation cams have rising portions, so as to move upward the selectors which are engaged with their main heel within said paths so that they act with their end on the overlying needle to move it into a position suitable for engaging the thread fed at a thread feed of the machine, or so as to cause the passage of the heel of the overlying needle, which protrudes radially from the needle cylinder and is engaged within paths defined by other actuation cams which are located at the level of the heel of the needles, from one path to the other so as to diversify the knitting of the needles according to requirements. The selection means are generally constituted by a plurality of levers which are mutually stacked in a direction which is parallel to the axis of the needle cylinder and are individually movable so as to interfere or not interfere with selection heels located at mutually different levels along the longitudinal extension of the selector. Extraction means are arranged upstream of the selection levers according to the direction of the rotation imparted to the needle cylinder about its axis relatively to the actuation cams; said extraction means act on the selectors in a sunk position so as to move them into the extraction position in order to undergo the action of the selection levers. According to the actuation of given selection levers and to the positioning of the selection heels along the selectors, the passage of preset selectors from the extraction position to the sunk position is caused, whereas other selectors arranged below the needles which must be moved to take the thread at the immediately subsequent feed are kept in the extraction position so as to engage the actuation cams which cause the lifting of the selectors and therefore of the overlying needles. Known from EP-A2-0303926 is a device for locking selectors on the bottom of the needle cylinder grooves in circular knitting machines. The device comprises a locking element which extends around the needle cylinder of the machine proximate to the lower end of the selectors, accommodated in the grooves of the needle cylinder. The locking element is controllably movable in a direction substantially parallel to the axis of the needle cylinder from an inoperative position, wherein the locking element is arranged substantially below the lower end of the selectors to allow the lower end of the selectors to perform an extraction movement from the related groove in a radial direction with respect to the needle cylinder, to an operative position, wherein at least one portion of the locking element is arranged above the lower end of the selectors for their retention in an inserted position in the related grooves, and vice versa. However, during some types of knitting, the need is felt to be able to repeat a same needle selection at a plurality of successive feeds of the machine without necessarily using the selection means every time, in order to contain costs. For this purpose, the Applicant has already provided a device, which is the subject of the Published European Patent Application No. EP-A3-0092133, which comprises a memory element arranged proximate to the lower end of the selectors and can maintain the position of the selectors, previously set with the selection means upstream of a first feed, between the first feed and a second feed, so that the same needles which knitted at the first feed knit at the second feed without the need to perform a new selection between the two feeds. More particularly, said memory element comprises a fixed cam constituted by a raised portion on the resting plane of the lower end of the selectors. Said raised portion defines two diversified paths for the lower end of the selectors, and more particularly: a first path, arranged between the raised portion and the selector actuation cams, within which the lower end of the selectors which are in extraction position after the selection performed upstream of the first feed engages, and a second path, arranged between the raised portion and the needle cylinder, within which the lower end of the selectors which are in sunk position after said selection engages. Since the raised portion is fixed to the resting plane of the lower end of the selectors, in order to obtain the repetition of the selection only when required, upstream of said raised portion there is a cam which is movable in a radial direction with respect to the needle cylinder and moves, after the first feed, the lower ends of all the selectors in the first path, i.e. returns the selectors from the sunk position to the extraction position, so that the previously performed selection is cancelled and the selectors can be selected by further selection means arranged between the first feed and the second feed. Through the years, research in this field has been aimed mainly at obtaining high rotation rates of the needle cylinder in order to increase the productivity of these machines. Due to this fact, the above described memory devices have some disadvantages in modern circular knitting machines. More particularly, the use of a movable cam followed by a fixed cam, in this kind of device, causes an excessive wear of the selectors at high speeds which compromises the correct operation of said selectors. Again due to the fact that the combination of a fixed cam and of a movable cam is used, in order to avoid excessive impacts between said cams and said selectors great precision is furthermore necessary both in the execution of these elements and in their registration during assembly. Even a very precise execution and registration in any case do not avoid impacts at high speeds between the selectors and the movable cam, since the selectors in a sunk position tend to move into the extraction position due to centrifugal force. The aim of the present invention is to obviate the above described disadvantages by providing a circular knitting machine with a device for repeating the selection of the needles at least at one thread feed, which has excellent reliability in operation, even with high rotation rates of the needle cylinder, without causing excessive wear of the selectors. Within the scope of this aim, an object of the invention is to provide a machine with a device for repeating the selection of the needles which is composed of a small number of elements which are simple to manufacture. Another object of the invention is to provide a machine with a device for repeating the selection of the needles which prevents accidental passage of the selectors from the sunk position to the extraction position even at high rotational speeds of the needle cylinder. This aim, these objects and others which will become apparent hereinafter are achieved by a circular knitting machine with a device for repeating the selection of the needles at least at one thread feed, which comprises: a needle cylinder with a plurality of grooves defined on its lateral surface, said grooves being substantially parallel to the axis of said needle cylinder, a needle and at least one selector below said needle being accommodated inside each of said grooves so as to be slidable along a direction substantially parallel to the axis of the needle cylinder, said selector being controllably oscillable, in a radial plane of the needle cylinder, from an extraction position, in which it protrudes radially from the needle cylinder with a main heel, to a sunk position, in which said main heel is contained in the radial dimensions of the needle cylinder; actuation cams arranged laterally facing the needle cylinder and defining paths engageable by said main heel, with said selector in an extraction position, for the movement of said selector along the related groove parallel to the axis of the needle cylinder upon the actuation of said needle cylinder with a rotary motion about its axis relatively to said actuation cams; at least two feeds mutually angularly spaced with respect to the axis of the needle cylinder; selection means arranged upstream of at least one of said feeds according to the direction of rotation of the needle cylinder relatively to said actuation cams and controllably interacting with said selectors for their passage from said extraction position to said sunk position or vice versa; characterized in that it comprises a memory element arranged proximate to the lower end of the selectors and having at least one portion with a curvilinear shape concentric to said needle cylinder, said memory element being arranged between said two feeds and is controllably movable from an inoperative position, whereat it does not interfere with the oscillation of said selectors, to an operative position, whereat it defines differentiated paths for the lower end of said selectors to maintain the position of said selectors set previously by said selection means. Further characteristics and advantages of the invention will become apparent from the description of a preferred but not exclusive embodiment of the machine according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figure 1 is a partially sectional lateral elevation view of a detail of the machine related to a portion of the needle cylinder and to the device for repeating the selection of the needles according to the invention, with the memory element in an inoperative position; figure 2 is an enlarged exploded view of a detail of figure 1; figure 3 is a partially sectional view, taken similarly to figure 1, with the memory element in an operative position; figure 4 is a view, taken similarly to figures 1 and 3, with the memory element raised further to lock the selectors in a radial direction; figure 5 is a schematic sectional view of the machine, taken along a plane which is perpendicular to the axis of the needle cylinder, proximate to the lower base of said needle cylinder; figure 6 is a schematic and partially sectional perspective view of a part of the machine, with the needle cylinder removed and with the memory element in an inoperative position; figure 7 is a perspective view of the machine, taken similarly to figure 6, with the memory element in an operative position; figure 8 is a perspective view, taken similarly to figures 6 and 7, with the memory element in the position illustrated in figure 4; and figure 9 is a view of the planar extension of a portion of the memory element according to the invention. With reference to the above-cited figures, the machine according to the invention, generally indicated by the reference numeral 1, comprises a needle cylinder 2 which can be actuated with a rotary motion about its axis 2a and in which a plurality of grooves 3 are defined along its lateral surface and extend parallel to the axis 2a. A needle 4, and a selector 5 below said needle, are accommodated inside each groove 3 and can slide in a direction which is parallel to the axis 2a. Each selector 5 has, proximate to its lower end, a main heel 5a which is directed toward the outside of the needle cylinder and, above said main heel, a plurality of secondary selection heels 5b. The selectors 5 can individually oscillate in a radial plane of the needle cylinder from a sunk position, in which the main heel 5a and the secondary selection heels 5b are contained in the radial dimensions of the needle cylinder, to an extraction position, in which the heel 5a and the secondary heels 5b protrude radially from the needle cylinder 2. Actuation cams 6 are arranged around the needle cylinder 2 and define paths which can be engaged by the main heel 5a of the selectors in the extraction position. In the illustrated embodiment, which relates to a circular machine with four feeds, the arrangement whereof is schematically indicated in figure 5 by the reference letters A, B, C and D, the actuation cams are constituted by an annular cam 7 which extends around the needle cylinder proximate to the lower end of the selectors 5. Said annular cam 7 has four raised portions 7a, 7b, 7c, 7d proximate to the machine thread feeds, i.e. four raised portions which are mutually angularly spaced with respect to the axis 2a of the needle cylinder. Upstream of each feed, the selectors 5 which are in extraction position, by rising along the corresponding raised portion of the annular cam 7 with their main heel 5a, push the overlying needles along a direction which is parallel to the axis 2a to engage the thread at the feed being considered. In order to determine which needles must engage the thread at a preset feed, selection means are provided upstream of said feed along the direction of rotation of the needle cylinder and comprise a plurality of selection levers 8 which are mutually stacked along a direction which is parallel to the axis 2a and are arranged with one of their ends 8a facing the needle cylinder. The selection levers 8 are arranged at mutually different elevation levels corresponding to the various levels of the secondary heels 5b of the selectors. Each selection lever can be actuated in a known manner so as to interfere or not interfere with a secondary heel 5b of the selectors to move the related selector from the extraction position to the sunk position. The actuation of given selection levers, combined with the arrangement of the secondary selection heels 5b along the selectors, allows to keep in an extraction position only the selectors which are arranged below the needles which must knit at the feed being considered. The selectors which are in the extraction position after they have passed the selection levers 8 due to the rotation of the needle cylinder rise along the related raised portion 7a, 7b, 7c, 7d of the annular cam 7, pushing the related needle to engage the thread, whereas the selectors which are pushed by the selection levers 8 from the extraction position to the sunk position pass with their main heel 5a sunk in the related groove 3 inside the annular cam 7 and therefore do not act on the related needles, which are not moved to engage the thread at that feed. An extraction element 9 is provided upstream of each set of selection levers and acts on the selectors in a sunk position to move them into extraction position so as to indergo selection on the part of the levers 8. More particularly, the annular cam 7 has a lower edge 10 in the shape of a planar annulus which is concentric with respect to the needle cylinder and defines a resting plane which is substantially perpendicular to the axis 2a for the lower end of the selectors 5. The extraction elements 9 are individually pivoted to said lower edge 10 about axes 11 which are parallel to the axis 2a and have a profile 9a which acts on the inner side of the lower end of the selectors 5 in sunk position to move them to the extraction position. By virtue of the oscillation of the extraction element 9 about the axis 11 it is possible to move the profile 9a toward the inside of the needle cylinder, preventing, if required, its interference with the selectors in a sunk position. According to the invention, there is a memory element 12 which is arranged proximate to the lower end of the selectors 5 and has at least one portion with a curvilinear extension which is concentric to the needle cylinder. The element 12 is arranged between two contiguous feeds of the machine and is controllably movable, parallel to the axis 2a, from an inoperative position, in which it does not interfere with the oscillation of the selectors, to an operative position in which it defines differentiated paths for the lower end of the selectors so as to maintain the position of the selectors set previously by the selection means arranged upstream of the first feed. The memory element 12 is constituted by an annular body which is arranged concentrically to the needle cylinder 2 and is accommodated in a seat 13 defined below the lower edge 10 of the annular cam 7. The seat 13 is open upwardly to allow the passage of the upper edge of the annular body 12. The upper edge of the annular body 12 has recesses 14 at the region affected by the extraction elements 9 and by the selection levers 2 upstream of the feeds at which a needle selection is to be performed in any case. Recesses 14 are provided, in the illustrated machine, immediately upstream of the first feed A and of the third feed C. The depth of said recesses 14 is such that when the annular body is in its operative position the base of the recess 14 is below or at the same level as the resting plane of the lower end of the selectors which is defined by the lower edge 10 of the annular cam 7. Each selector conveniently has, on its lower side which is directed toward the resting plane defined by the edge 10, an indent 15 which can be engaged astride the upper edge of the annular body 12, except for the region affected by the recesses 14, when said annular body 12 is in an operative position and the selector is in an extraction position. The annular body 12 has, in diametrical opposite positions, two pins 16 which are arranged radially on its outer surface. The pins 16 pass through a vertical slot 17 defined in the annular cam 7 and engage actuation means arranged externally to said cam 7. Said actuation means comprise an actuation ring 18 which surrounds the annular cam 7 and has, at the pins 16, a shaped slot 19 with horizontal portions 20, 21 and 22 which are mutually connected by rising portions 23 and 24. The actuation ring 18 is rotatable about the axis 2a, for example by means of pneumatic actuators of a known type which cause its partial rotation so as to move the pins 16 to engage the portions 20, 21 or 22. When the pins 16 are engaged with the portion 20, the annular body 12 is in inoperative position; when the pins 16 are engaged with the portion 21, the annular body 12 is in an operative position; when the pins 16 are engaged with the portion 22, the upper edge of the annular body 12 protrudes further from the resting plane defined by the edge 10. In this last position, the annular body 12 protrudes above the edge 10 by an extent which is greater than the depth of the recesses 14 so as to define a continuous circular barrier to the outside of the selectors which have been moved into sunk position beforehand. In this manner, for knittings in which a selection of the needles is not required since said needles are actuated autonomously by means of cams 25 which act directly on the heel 4a of the needles, it is possible to achieve high rotation rates of the needle cylinder about its axis 2a with no risk that the selectors may pass, due to the centrifugal force, from the sunk position to the extraction position. The operation of the machine according to the invention is as follows. If the same needles which were selected at the preceding feed, i.e. at the first feed A and at the third feed C, are to be moved to knit at the second feed B or at the fourth feed D, the memory element 12 is moved into its operative position. With the memory element 12 in this position it is possible to perform the required selection at the first feed A and at the third feed C, moving the selectors 5 into extraction position by means of the corresponding extraction element 9 so that they undergo the selection imposed by the levers 8. It should be noted that in this step the memory element 12 does not interfere with the selectors during the extraction operation performed by the elements 9, since said memory element 12 has the recesses 14 at the extraction element 9 and at the levers 8 which are arranged immediately upstream of the feeds A and C. The selectors which are moved to the sunk position pass with their lower end inside the memory element 12 at the end of the recesses 14 as well, whereas the selectors which are in an extraction position after the performed selection rise along the raised portions 7a, 7c and move the related needles to knit. During the descent from the raised portions 7a, 7c, the selectors engage the indent 15 with the upper edge of the memory element 12 and are therefore kept in extraction position. Due to this reason, the same selectors which had risen along the raised portions 7a and 7c remain engaged with the annular cam 7 and also rise along the subsequent raised portions 7b and 7d, moving the same needles which had knitted at the preceding feed A, C to knit at the subsequent feed B, D. The selectors which have their lower end inside the memory element 12 are kept in sunk position by the presence of the memory element 12 even if the cylinder is actuated with a high rotation rate. Therefore, between the feed A and the feed B, as well as between the feed C and the feed D, it is not necessary to perform the selection by means of the selection levers 8, and the related extraction element 9 is moved, by exploiting its ability to oscillate about the related axis 11, in a position of non-interference with the lower end of the selectors in a sunk position. If a repetition of the selection of the needles performed upstream of the feeds A and B is not required, the memory element 12 is moved into inoperative position, and the extraction elements 9 related to the feeds B and D are actuated so as to move all the selectors into extraction position so as to undergo a new selection on the part of the levers 8 arranged upstream of the respective feeds. When no needle selection is required, with all the selectors in a sunk position, the memory element 12 is raised beyond the operative position so as to lock the selectors 5 in the sunk position, allowing to achieve high rotation rates of the needle cylinder without problems. In practice it has been observed that the machine according to the invention fully achieves the intended aim, since it allows to maintain, at a subsequent feed, the same needle selection performed at a preceding feed without necessarily having to perform a new selection, reducing impacts and wear of the selectors even with high speeds of actuation of the needle cylinder with respect to conventional machines. The machine thus conceived is susceptible to numerous modifications and variations, all of which are within the scope of the inventive concept; all the details may furthermore be replaced with other technically equivalent elements. In practice, the materials employed, as well as the dimensions, may be any according to the requirements and the state of the art. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: Circular knitting machine with a device for repeating the selection of the needles at least at one thread feed, which comprises: a needle cylinder (2) with a plurality of grooves (3) defined on its lateral surface, said grooves (3) being substantially parallel to the axis (2a) of said needle cylinder (2), a needle (4) and at least one selector (5) below said needle (4) being accommodated inside each of said grooves (3) so as to be slidable along a direction which is substantially parallel to the axis (2a) of the needle cylinder (2), said selector (5) being controllably oscillable, in a radial plane of the needle cylinder (2), from an extraction position, in which it protrudes radially from the needle cylinder (2) with a main heel (5a), to a sunk position, in which said main heel (5a) is contained in the radial dimensions of the needle cylinder (2); actuation cams (6, 7) arranged laterally facing the needle cylinder (2) and defining paths engageable by said main heel (5a), with said selector (5) in an extraction position, for the movement of said selector (5) along the related groove (3) parallel to the axis (2a) of the needle cylinder (2) upon actuation of said needle cylinder (2) with a rotary motion about its axis (2a) relatively to said actuation cams (6, 7); at least two feeds (A, B, C, D) mutually angularly spaced with respect to the axis (2a) of the needle cylinder (2); selection means (8) arranged upstream of at least one of said feeds (A, B, C, D) according to the direction of rotation of the needle cylinder (2) relatively to said actuation cams (6, 7) and controllably interacting with said selectors (5) for their passage from said extraction position to said sunk position or vice versa; a memory element (12) arranged proximate to the lower end of the selectors (5) and having at least one portion with a curvilinear shape concentric to said needle cylinder (2), said memory element (12) being arranged between said two feeds and is controllably movable parallel to the needle cylinder axis (2a) from an inoperative position, whereat it does not interfere with the oscillation of said selectors (5), to an operative position, whereat it defines differentiated paths for the lower end of said selectors (5) to maintain the position of said selectors (5) set previously by said selection means (8), said actuation cams (6, 7) comprise an annular cam (7) extending around the needle cylinder and having raised portions (7a, 7b, ,7c, 7d) proximate to said feeds (A, B, C, D), said memory element (12) being arranged between the inner side of said annular cam (7) and the needle cylinder (2) and comprising an annular body (12) arranged concentrically to said needle cylinder (2) and accommodated in a seat (13) defined below a ring (10) for the resting of the lower end of the selectors (5), said selectors (5) having on their lower side arranged facing said resting ring (10), an indent (15) which can be engaged astride the upper edge of said memory element (12), in said memory position, with said selectors (5) in an extraction position. Machine according to claim 1, characterized in that said selection means (8) comprise a plurality of levers (8) arranged laterally facing said needle cylinder (2) and being stacked in a direction which is parallel to the axis (2a) of the needle cylinder (2), and an extraction element (9) arranged upstream of said selection levers (8) according to the direction of rotation of the needle cylinder (2) about its axis (2a), said extraction element (9) controllably acting on said selectors (5) for their passage from said sunk position to said extraction position. Machine according to claim 1, characterized in that said annular body (12) which constitutes said memory element (12) has, on its outer surface, at least one pin (16) which passes through a slot (17) which is substantially parallel to the axis (2a) of the needle cylinder (2) and defined in said annular cam (7), actuation means (18) being provided externally to said annular cam (7) and acting on said pin (16) for its movement along said slot (17) for the passage of said memory element (12) from said inoperative position to said operative position and to said locking position or vice versa. Machine according to claim 3, characterized in that said actuation means (18) comprise an actuation ring (18) which is rotatably associated about said annular cam (7) and in which a shaped slot (19) is defined, said slot (19) being engaged by said pin (16) and having rising portions (23, 24) which mutually connect three portions (20, 21, 22) which are arranged in planes which are substantially perpendicular to the axis (2a) of the needle cylinder (2) at mutually different elevation levels which correspond to the inoperative, memory and locking positions of said memory element (12) for the actuation of said memory element (12) by means of the partial rotation of said actuation ring (18) about the axis (2a) of the needle cylinder (2).

Inventors: LONATI FRANCESCO, LONATI, FRANCESCO
Applicants: LONATI SPA, LONATI S.P.A.
Application year: 1990
Main classification: D04B15
IPC codes: D04B15, D04B9