Improvement to a cotton knitting machine

Abstract: An improved Cotton knitting machine, in which the needle bar (1) is actuated by a lever system which comprises an arm (4) which is fixed to the needle bar and is articulately connected to a first lever (5) provided with recesses (7,8) for engagement to a pivot (9) which is fixed on a second lever (11) which is radial with respect to a horizontal supporting shaft (12) and is controlled by an actuation cam (15) by way of a roller (14) which is urged onto the profile of the cam (15) by elastic elements (17), wherein the pivot (9) can be arranged on the second lever (11) so as to produce an oscillation of the arm (4), by action of the first lever (5), according to a preset criterion.

Description: The present invention relates to an improvement to a Cotton knitting machine. It is known that in Cotton knitting machines each fabric forming head has a bar, provided with slots in which sinkers slide, said sinkers distributing the thread among the needles of a bar which is known as needle bar. Said needles (known as beak needles) are shaped like hooks provided with a tongue which forms the eye of the needles. With the movement of the bar, the needles, after engaging the thread and with the tongue closed by the so-called presser, pass through the fabric and form the stitches (loops) of a new row. In order to form the stitches, the needle bar performs a combined movement, i.e., a movement which has a vertical component and a horizontal component. For this purpose, the needle bar is supported by a first arm of a lever which is pivoted in a rocker-like fashion to a shaft, known as lowering shaft, on the second arm whereof (arranged substantially vertically) there is a roller which is actuated by a spring against the profile of a radial actuation cam which is keyed onto the main shaft, known as eccentric shaft. The cam has a profile which is partly concentric and partly eccentric. When the roller runs along the concentric part, the needle bar remains motionless in the raised position; when instead the roller moves along the eccentric part, the lever lowers the needle bar. In order to move the needle bar horizontally, there is an additional lever system consisting of an arm which is fixed with one end to the needle bar and is articulated to a first lever (hereinafter termed linkage for convenience in description) in which there are usually two recesses adapted to be selected manually in order to engage on a pivot fixed in a central region on a second substantially vertical lever pivoted with an upper end on a shaft, known as pressing shaft, which is parallel to the lowering shaft. Said second lever is provided with a roller which engages, due to the action of a spring, the profile of a cam which is keyed on the eccentric shaft. In a position for the engagement of the pivot in one of the recesses of the linkage, the needles of the needle bar are in the active position. If the linkage is moved so that the pivot engages the second recess, the needle bar remains shifted in the inactive position. The length of the stitch, and therefore the density of the knitting, depends on the position in a horizontal direction of the needles of the needle bar. When the needles are moved toward the sinkers, the stitch is longer and therefore the fabric is less dense, i.e., looser. In order to adjust the density of the fabric, one acts on the angular position of the second lever by means of a third lever, keyed on an auxiliary shaft, which acts on the lower end of the second lever with an adjustable abutment screw. Substantial drawbacks are noted in the current structure of Cotton knitting machines. First of all, the cam-follower roller, depending on the length of the stitch, is at a different distance from the cam, i.e., is spaced from the cam along part of its profile. Accordingly, when the cam makes contact with the roller, an impact occurs; the higher the speed of the shaft on which the cam is mounted, the more said impact is violent. Another drawback is that adjustment of the length of the stitch requires an auxiliary shaft with corresponding adjustable abutments and supports which increase the complexity of the structure. In particular, in order to pass from a loose stitch to a tighter stitch or vice versa it is necessary to correct some movements of the needle bar and possibly of other stitch forming elements by acting on the position of inserts which determine the profile of the affected cams or by replacing said cams. The structure of current Cotton knitting machines is increased in complexity and bulk not only by said auxiliary shaft but also by the presence of the two lowering and pressing shafts. An example of a Cotton knitting machine is available from document US-A-2 084 732. The aim of the present invention is therefore to provide an improvement which allows to greatly simplify the construction of a Cotton knitting machine as regards the means that allow to adjust the length of the stitch and to form said stitch. Within this aim, an object of the present invention is to provide an improvement which allows to eliminate one of the two shafts onto which the lever systems that transmit the horizontal and vertical movements of the actuation cams to the needle bar are articulated. This aim and this object are achieved with an improved Cotton knitting machine according to the present invention, that has the features of claims 1 and 6. Further features of the present invention will become better apparent from the following detailed description of a preferred embodiment thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein: Figure 1 is a schematic view of the lever system for the horizontal and vertical actuation of the needle bar; Figure 2 is a schematic view of the needle bar with the needles in various operating conditions; Figure 3 is a sectional view of the region of articulation between the first lever and the second lever; and Figure 4 is a sectional view, taken along the line IV-IV of Figure 3. With reference to Figures 1 and 2, the reference numeral 1 designates the needle bar, which supports needles 2 that protrude upward. The reference numeral 3 designates sinkers which, by being pushed by the couliering cams by virtue of the undulations, push the thread, distributed in front of them, between the needles 2 of the bar 1. The distribution of the thread occurs when the needles are raised to a level at which their beaks lie above the sinkers 3. An arm 4 is rigidly coupled to the bar 1 of the needles 2, protrudes downward and has a first lever or linkage 5 articulated to its lower end; said linkage extends substantially horizontally toward the operator side and ends with an actuation handgrip 6. Two recesses 7 and 8 are formed in the lower edge of the linkage 5 and can be individually engaged on a pivot 9 which can be positioned along a slot 10 formed in a second lever 11 which is keyed, with an upper end, on a shaft 12 having a horizontal axis and supported so that it can oscillate in the structure of the Cotton knitting machine and constituting the pressing shaft. The slot 10 is shaped like a circular arc which is substantially concentric with respect to an axis 13 for articulation between the arm 4 and the linkage 5 and lies predominantly radially with respect to the oscillation axis of the shaft 12. The second lever 11 extends downward and supports, in a central position, below the slot 10, a roller 14 which follows a cam 15 keyed onto a main shaft 16 or eccentric shaft of the Cotton knitting machine. The roller 14 is actuated against the profile of the cam 15 by a traction spring 17 which connects the lower end of the lever 11 to a footing 18 of the Cotton knitting machine. The cam 15 has a profile which is mostly circular and has protrusions in the remaining part. It is evident that as already mentioned, as long as the roller 14 runs along the circular portion of the cam 15 the second lever 11 remains perfectly inactive, so that no oscillating movement is transmitted to the needle bar 1. However, when the roller 14 moves along the portion of the cam 15 that is provided with protrusions, the needle bar 1 performs an oscillating movement about the rod 18' by way of which it is articulately connected to the lever system that actuates the vertical movement (described below). The extent of this oscillation depends on the position of the pivot 9 along the slot 10. If the pivot 9 is arranged in the upper point F of the slot, the arc traced by the pivot 9 with respect to the axis of the shaft 12 is smaller than the arc traced when the pivot is at the midpoint M or lower point L. In any case, by virtue of the shape of the slot 10 which is concentric to the axis 13, the distance "d" between the axis 13 and the pivot 9 remains constant, so that the position for the closure of the needles 2 on the part of the press 19 does not occur only when the pivot 9 is in the midpoint M of the slot 10 but also occurs in any point along the slot 10. In particular, during the vertical movement of the bar the needles 2 always close against the press 19 in any position of the pivot 9 that lies between the point F (thick knitting) and the point L (loose knitting). Figure 2 illustrates the needle bar 1 with the needles 2 in the upper and lower positions of their vertical movement, which correspond to the position of the pivot in the points L, M and F of the slot 10. As can be seen, when the needle bar 1 is in the upper position which corresponds to the thread distribution position, depending on the position of the pivot 9 along the slot 10, the needles 2 are closer to, or further spaced from, the bar of the sinkers 3 and therefore are such as to determine the chosen length of the stitch (loop). When the pivot 9 is in the position L, one has looser knitting, since the bar 1 performs a smaller oscillation, moving slightly away the needles 2 from the sinkers 3, which can therefore penetrate between them by a longer extent. Vice versa, the position of the needles moves away from the sinkers as the pivot 9 is moved toward the points M and F of the slot 10, so as to reduce the length of the loops. When the needle bar 1 descends, the needles 2 are first closed by the presser 19 and then deposit the stitch onto the secondary lowering sinkers 20. It should be noted that the two paths L-L and F-F, traced by the needles 2 during the stroke for forming the tighter and looser stitch, intersect one another at the point of engagement on the presser 19. Another feature of the improvement according to the invention is that at the end of the descent stroke of the needle bar the position assumed by the needles 2 is such that when the pivot 9 is in the position F, the needles 2 are closer to the bar of the sinkers 3 than when the pivot is in the position L. This, with the aid of the favorable shape of the secondary sinkers 20, produces the correct formation of the stitch owing to the fact that the lowering is proportional to the length of the loops formed by the penetration of the sinkers between the needles. The described improvement fully achieves the intended aim and object. In addition to the elimination of the auxiliary shaft and the adjustable abutments for the lever 11, particular importance is given to the fact that the roller 14 remains constantly in contact with the perimeter of the cam 15 so as to avoid impacts, noise and abnormal mechanical stresses. According to another aspect of the invention, it is possible to use the shaft 12 as a lowering shaft, i.e., for the articulation of the rocker lever 21, which articulately supports the rod 18' with one arm 22 and is controlled, by means of the other arm 23 and by means of a roller 24 and a spring 25, by a cam 26 which is keyed onto the eccentric shaft 16. Numerous modifications and variations are possible in the practical embodiment of the invention, and all are within the scope of the inventive concept. Figures 3 and 4 illustrate a solution which allows to automate the position of the pivot 9 along the slot 10. For this purpose, the lever 11, at the level of the region of articulation to the linkage 5, has a seat 27 which is defined between two portions 28 and 29 of the lever 11. Two slots 30, 31 are provided in the portions 28 and 29 and are concentric to the axis 13. The opposite ends of the pivot 9 are guided in the slots 30, 31, and said pivot has a central expansion 32 which is guided in the seat 27. The threaded stem 33 is engaged by screwing in the central expansion 32 and constitutes the output shaft of a motor 34 which is articulated to the lever 11 along an axis 35 which is parallel to the pivot 9. The opposite ends of the pivot 9 protrude out of the slots 30, 31 in order to be able to engage recesses 36, 37 which are formed in two respective arms 38, 39 into which the linkage 5 is divided in order to externally wrap around the portions 28, 29 of the lever 11. From the above description it is evident that by actuating the motor 34 the pivot 9 is moved along the slots in order to adjust its position with respect to the shaft 12 and therefore adjust the oscillation of the needle bar 1. In another embodiment, the pivot 9 is stationary on the lever 11 and the slot 10 is provided in the arm 4 concentrically to the pivot 9. In this case, the axis 13 is preset to be adjusted along the slot 10. The disclosures in Italian Patent Application No. BO99A000630 form the basis from which this application claims priority. 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: An improved Cotton knitting machine, wherein the needle bar (1) is actuated by a lever system which comprises an arm (4) which is fixed to the needle bar and is articulately connected to a first lever (5) provided with recesses (7, 8) for engagement to a pivot (9) which is fixed on a second lever (11) which is radial with respect to a horizontal supporting shaft (12) and is controlled by an actuation cam (15) by way of a roller (14) which is urged onto the profile of said cam by elastic means (17), characterized in that it further comprises a slot (10), said slot (10) being formed on said second lever (11) concentric to an articulation axis (13) of said first lever (5) in said arm (4) and said pivot (9) being positionable in said slot (10) so as to produce an oscillation of said arm (4), by action of said first lever (5), according to a preset criterion. The improved knitting machine according to claim 1, characterized in that said a slot (10) is shaped as a circular arc which is concentric to the articulation axis (13) of said first lever (5) in said arm (4), the extent of said oscillation of said arm (4) depending on the position of the pivot (9) along the slot (10). The improved knitting machine according to claim 2, characterized in that said pivot (9) is adjustable along said slot (10) by means of an actuator (33,34). The improved knitting machine according to claims 2 or 3, characterized in that said second lever (11) comprises two portions (28, 29) which define, between them, a seat (27) and in which two respective slots (30, 31) are provided, said slots being concentric to the axis of articulation of said arm (4) with respect to said first lever (5), the opposite ends of said pivot (9) being guided in said slots (30, 31), said pivot being centrally provided with an expansion (32) which is guided in said seat (27), said opposite ends of said pivot being suitable to engage respective recesses (36, 37) formed in two respective arms (38, 39) into which said first lever (5) is divided in order to externally wrap around said portions (28, 29) of said second lever (11), a threaded stem (33) being engaged by screwing in said central expansion (32), said stem being actuated by a motor (34) which is articulated on said second lever (11). The improved knitting machine according to one of the preceding claims, characterized in that said needle bar (1) is actuated with a vertical motion by means of a lever system which comprises a lever (21) which is pivoted like a rocker on said articulation shaft (12) of said second lever (11) and is provided with a first arm (22) which is pivoted to said needle bar (1) and with a second arm (23) which is controlled by an actuation cam (26). An improved Cotton knitting machine according to claim 1, modified in that the slot (10) is provided in the arm (4) concentrically to the pivot (9) that is stationary fixed on the second lever (11), the articulation axis (13) between said arm (4) and said first lever (5) being adjustable along a said slot (10). The improved Cotton knitting machine according to claim 4, characterized in that said actuator comprises the threaded stem (33) that is engaged by screwing in the central expansion (32) provided at said pivot (9) and the motor (34), said threaded stem (33) constituting the output shaft of said motor (34) actuation whereof producing movement of the pivot (9) along the slots (30,31) provided in said second lever (11). The improved Cotton knitting machine according to one or more of the preceding claims, characterized in that said slot (10) comprises a midpoint (M) an upper point (F) and a lower point (L), positioning of said pivot (9) at the lower point (L) of the slot (10) providing loose knitting and positioning of the pivot (9) at the upper point (F) of the slot (10) providing thick knitting.

Inventors: CASADIO ALFIO, CASADIO, ALFIO
Applicants: TECNOTESSILE SRL, TECNOTESSILE S.R.L.
Application year: 2000
Main classification: D04B11
IPC codes: D04B11, D04B15