Method and apparatus for detecting the condition of unsuccessful formation of one or more stitches in a textile machine

Abstract

 Method and apparatus for detecting the condition of unsuccessful formation of one or more stitches by one or more needles (8) in a textile machine which exhibits a front (3) whose trailing edge (30) faces the region for supplying the thread (1) for the formation of the stitches, wherein provision is made for selecting a plurality of needles (8) each of which is intended to form a corresponding stitch by its moving forward and beyond the trailing edge (30) of said front (3) for picking up the thread (1) and subsequently moving back to form the stitch, and wherein provision is also made for sensing the pressure exerted by said thread (1) in a predetermined point of the machine, during the formation of the stitch by the corresponding needle (8), and operating the stopping of the machine when said pressure is zero or leass than a preset value.

Description

[0001] The present invention refers to a safe method and apparatus for textile machines, especially for detecting the condition of unsuccessful formation of a stitch.

[0002] It is well known that in a textile product, those defects commonly known as "ladders" stem from the unsuccessful formation of one or more stitches due to various and unforseeable events such as, for example, the breaking of one or more threads, the presence of structural defects, the presence of improper joining knots, which prevent the threads from moving freely within the thread-guide means usually associated with the very weaving means, the interruption of threads supply to the needles by the respective supply means, the breaking of one or more stitch-forming needles, or the malfunction of the needles-driving means.

[0003] In addition to this, it is not always possible or convenient to ensure the constant presence of an operator in charge of the production control in real time, so that the formation of defects in the products may occur for a prolonged time before they can be detected and the concerned machines stopped to allow for suitable intervention.

[0004] The main object of the present invention is to overcome the said drawback.
This result has been achieved, according to the invention, by providing a method and apparatus having the features indicated in the claims 1 and 3. Further characteristics being set forth in the dependent claims.

[0005] The advantages deriving from the present invention lie essentially in that it is possible to detect, in real time and with the greatest operating accuracy, the state of operation of each active point of the needles front, and to automatically and timely cut off the production in case of failure, by one or more needles intended for the formation of the stitches, to pick up the thread; that an apparatus according to the invention is relatively easy to make, cost-effective and reliable even after a prolonged service life, and also able to be constructed in more separate modules so as to facilitate its manufacturing, storage, transport, assembly and any maintenance as required.
These and other advantages and characteristics of the invention will be best understood by anyone skilled in the art from a reading of the following description in conjunction with the attached drawings given as a practical exemplification of the invention, but not to be considered in a limitative sense, wherein: Fig. 1 shows schematically a scrap view of an apparatus according to the invention and mounted on the needles front of a rectilinear knitting machine; Fig. 2A is a detail of the apparatus of Fig. 1 showing the advancement of a needle of the front; Fig. 2B is the detail of Fig. 2A showing the needle in its retracted position and the thread being picked up; Fig. 2C is the detail of Fig. 2A showing the retracted needle and the unsuccessful formation of the stitch due to the breaking of the thread; Fig. 3A shows the apparatus of Fig. 1 according to a possible embodiment; Fig. 3B shows a detail of the apparatus of Fig. 3A; Fig. 4 shows the apparatus of Fig. 1 according to a further embodiment; Fig. 5A is a detail of the apparatus of Fig. 4 showing the advancement of a needle of the front; Fig. 5B is the detail of Fig. 5A showing the needle in its retracted position and the thread being picked up; Fig. 5C is the detail of Fig. 5A showing the retracted needle and the unsuccessful formation of the stitch due to the breaking of the thread; Fig. 6 shows the apparatus of Fig. 1 according to a further alternative embodiment; Fig. 7A is a detail of the apparatus of Fig. 6 showing the advancement of a needle of the front; Fig. 7B is the detail of Fig. 7A showing the needle in its retracted position and the thread being picked up; Fig. 7C is the detail of Fig. 5A showing the retracted needle and the unsuccessful formation of the stitch due to the breaking of the thread; Fig. 7D shows a detail in enlarged scale of the apparatus of Fig. 6; Fig. 8 shows a cutaway perpsective view of an apparatus according to the invention and mounted on a circular knitting machine; Fig. 9 shows the detail of Fig. 2A according to an alternative embodiment; Fig. 10 shows the detail of Fig. 5A according to an alternative embodiment; Fig. 11 shows the detail of Fig. 7A according to an alternative embodiment; Fig. 12 shows a simplified block diagram of the means for controlling a textile machine provided with an appartatus according to the invention.

[0006] Reduced to its basic structure, and reference being made to the figures of the attached drawings, a method for detecting the condition of unsuccessful formation of a stitch by one or more needles (8) of a textile machine with a plurality of needles (1) received in corresponding slots (5) of a front (3) whose trailing edge (30) faces the region for supplying the thread (1) for the formation of the stitches, according to the invention, comprises the following operative steps:

• selecting a plurality of needles (8) each of which is intended to form a corresponding stitch by its moving forward and beyond the output edge (30) of said front (3) for picking up the thread (1) and subsequently moving back to form the stitch;
• sensing the pressure exerted by said thread (1) in a predetermined point of the machine, during the step for the withdrawal of the relevant needle (8), that is, of formation of the stitch by; and
• operating the stopping of the machine when said pressure is zero or leass than a preset value.

[0007] The selection and movement of the needles (8) intended to form the stitches, and the supply of the needles (1) as well, are operations performed by the use of electronic means and, therefore, will not be described herein in detail. By way of non limitative example, the selection of the needles (1) may be carried out by means of jacks operating from the back of the needles, according to a technique known per se, and the movement of the needles in a programmed sequence related to the very characteristics of the product to be obtained, may be carried out by cam means - not shown - acting on heels (80) of the same needles (8) .

[0008] Advantageously, according to the invention, provision is made for sensing the pressure exerted by the thread (1) of each of said needles (8) intended to form the stitches, in correspondence of the trailing edge (30) of the front (3), that is, in the vicinity of the stitch formation point.

[0009] As far as the apparatus for implementing the above method is concerned, it comprises in correspondence of each needle (8) of the front (3), a detector (7) able to sense the pressure exerted by the thread (1) of the relevant needle (8) disposed for the formation of a stitch: said detector (7) being electrically coupled with means (M) for controlling the needles (8) and cause make them to stop when the pressure exerted by the thread (1) at a preset point of the machine, and with the relevant needle (8) being disposed for the formation a stitch, is less than a preset value.

[0010] Advantageously, according to the invention, each of said detectors (7) is positioned on the trailing edge (30) of the said front (3) on the opposite side of the needle (8) with respect to the thread (1), so that the thread (1), being disposed for the formation of the respective stitch, will result interposed between the needle (8) and the detector (7).

[0011] In case of straight and circular fronts of horizontal needles (1), each detector (7) is located beneath the axis of longitudinal motion of the relevant needle (8).
In case of circular fronts of vertical needles (8), each detector (7) is in a centripetal position with respect to the corresponding needle (8).

[0012] In case of a proper picking up of the thread (1) by any of the needles (8) being selected for the formation of the stitches, the retraction of the needle (8) disposed for the formation of the corresponding stitch is cause for the thread (1) to exert a pressure of known and preset value onto the respective detector (7). On the contrary, in case of unsuccessful formation of the stitch, possibly occurring either for failure to pick up the thread (1) by the respective needle (8) or following the breaking of the thread (1) or of the needle (8) itself, no pressure will result on the respective detector. This will imply the generation of an electric signal to be transmitted via an electric lead (90) to the means (M) for controlling the machine in order to cause the latter to stop at once and to activate acoustic and/or light means - if any - capable of signalling the malfunction thus occurred.

[0013] Advantageously, according to the invention and with reference to the figures of the attached drawings, each of said detectors (7) consists of an electric or electromagnetic spring button: said spring (70) being of spiral type with orthogonal or oblique axis with respect to the direction of motion of the needles (8) or of lamina type oriented according to a direction substantially parallel to that in which the needles (8) move, so that said button will result in lowered position during the formation of a stitch by the corresponding needle (8) and in lifted position in case of failure to form the stitch, thereby causing the closing, respectively the opening of the relevant contacts suitably associated to the means (M) for the control of the needles (8) in order to cause the latter to stop in case of a lifting of the button.

[0014] Advantageously, reference being made to Figs. 6-7C of the attached drawings, said button (7) is engaged to elastic means (70) acting in a direction at an angle to the axis of motion of the corresponding needle (8) and being normally in lifted up position, with its upper end at a level lower than that of said needle (8) in order to not interfere with its movement, and in lowered position, during the formation of a stitch, as determined by the load exerted thereon by the corresponding portion of the thread (1). In such case, the stopping of the needles (1) by the means (M) is operated when the button (7) remains in lifted condition also after the retraction of the corresponding needle (8) disposed for the formation of the respective stitch. Such a condition actually corresponds to the unsuccessful formation of the stitch. Advantageously associated to said button (7) are two corresponding side legs (2) which allow for a better guide of the thread (1).

[0015] It should be understood that the spring (70) is suitably gauged in relation to the pressure normally exerted by the thread (1) during the formation of a stitch.
Each of said detectors (7) is able to be positioned in a corresponding seat of the front (3) of needles (8) or within a box-like case (6) capable of holding a predetermined number thereof.
In the first case, the application of the present apparatus to existing machines can be simply made by disassembling the front (3) of the needles (8) and forming on its trailing edge (30) the seats for the detectors (7) and the passages for the leads connecting the respective contacts to the means (M) for the control of the needles (8), while the application of the same apparatus to recently manufactured machines, the trailing edge (30) of the front (3) may be directly provided with said seats.
In the second case, it is sufficient, advantageously, to removably fix the case to the trailing edge (30) of the front (3). In such case, the operations for assembly, set-up and maintenance of the apparatus will result easier as - whenever a malfunction of a sensor (7) takes place - it will be sufficient to remove the relevant case (6) and replace it with another.
It is also advantageously provided to interpose a printed circuit plate (9) between the trailing edge (30) of the front (3) and said buttons (7), which plate (9) has, for each button (7) a pair of contacts (900) connectable via the cable (90) to means (M) for the control of the needles (8) and coupled to corresponding contacts (71) of the button (7). In the case of buttons (7) of the type with vertical and oblique spindle, said plate (9) is provided with corresponding holes (91) to allow the movement thereof.

[0016] Advantageously, the said plate (9) may have such a length as to allow it to be housed in a container (6) of the type above mentioned, so as to make it an integral part thereof (see Figs. 9-11): the contacts (900) of said plate (9) being coupled via the cable (90) to the means (M) for the control of the needles (8) through corresponding leads (92) whose common terminal connector (93) is integral and external to the container (6).
Provided in correspondence of the trailing edge (30) of the front (3) are vertical legs (4) projecting sideway of the slots for the guide of the needles (8) in order to better guide the thread (1) in correspondence of each needle (8).

Claims

1. Method for detecting the condition of unsuccessful formation of one or more stitches by one or more needles (8) in a textile machine which exhibits a front (3) whose trailing edge (30) faces the region for supplying the thread (1) for the formation of the stitches, comprising the step for selecting a plurality of needles (8) each of which is intended to form a corresponding stitch by its moving forward and beyond the trailing edge (30) of said front (3) to pick up the thread (1) and subsequently move back to form the stitch, characterized in that it comprises sensing the pressure exerted by said thread (1) in a predetermined point of the machine, during the formation of the stitch by the corresponding needle (8), and operating the stopping of the machine when said pressure is zero or leass than a preset value.

2. Method according to claim 1, characterized in that it comprises sensing the pressure exerted by each of said thread (1) intended to form the stitches, in correspondence of the trailing edge (30) of the front (3), that is, in proximity of the point of stitch formation.

3. Apparatus for detecting the condition of unsuccessful formation of one or more stitches by one or more needles (8) in a textile machine which exhibits a front (3) whose trailing edge (30) faces the region for supplying the thread (1) for the formation of the stitches, characterized in that it comprises, in correspondence of each needle (8) of the front (3), a detector (7) able to sense the pressure exerted by the thread (1) of the relevant needle (8) disposed for the formation of a stitch: said detector (7) being electrically coupled with means (M) for controlling the needles (8) and cause them to stop when the pressure exerted by the thread (1) at a preset point of the machine, and with the relevant needle (8) being disposed for the formation a stitch, is less than a preset value.

4. Apparatus according to claim 3, characterized in that each of said detectors (7) is positioned on the trailing edge (30) of the said front (3) on the opposite side of the needle (8) with respect to the thread (1), so that the thread (1), being disposed for the formation of the respective stitch, will result interposed between the needle (8) and the detector (7) .

5. Apparatus according to claim 3, characterized in that each of said detectors (7) consists of an electric or electromagnetic spring button: said spring (70) being of spiral type with orthogonal or oblique axis with respect to the direction of motion of the needles (8) or of lamina type oriented according to a direction substantially parallel to that in which the needles (8) move, so that said button will result in lowered position during the formation of a stitch by the corresponding needle (8) and in lifted position in case of failure to form the stitch, thereby causing the closing, respectively the opening of the relevant contacts suitably associated to the means (M) for the control of the machine to cause the latter to stop in case of a lifting of the button.

6. Apparatus according to claims 1 and 5, characterized in that each of said buttons (7) is engaged to elastic means (70) acting in a direction at an angle to the axis of motion of the corresponding needle (8) and being normally in lifted up position, with its upper end at a level lower than that of said needle (8) in order to not interfere with its movement, and in lowered position, during the formation of a stitch, as determined by the load exerted thereon by the corresponding portion of the thread (1). In such case, the stopping of the needles (1) by the means (M) is operated when the button (7) remains in lifted condition also after the retraction of the corresponding needle (8) disposed for the formation of the respective stitch.

7. Apparatus according to claims 1, 5 and 6, characterized in that said spring (70) is gauged in relation to the pressure normally exerted by the thread (1) during the formation of a stitch.

8. Apparatus according to claim 3, characterized in that each of said detectors (7) is able to be positioned in a corresponding seat of the front (3) of needles (8) .

9. Apparatus according to claim 3. characterized in that each of said detectors (7) is able to be positioned within a box-like case (6) capable of holding a predetermined number thereof.

10. Apparatus according to claim 3, characterized in that a printed circuit plate (9) is interposed between the trailing edge (30) of the front (3) and said detectors, which plate (9) has, for each button (7) a pair of contacts (900) connectable via the cable (90) to means (M) for the control of the needles (8).

Drawing