Improved device for measuring the mechanical tension of the yarn in weaving systems and the like

Abstract

 The device comprises a couple of thread guide eyelets that are spaced on a rectilinear support (X) and a sensor (S) placed between said eyelets, external to the rectilinear support, under the pressure of the yarn running from one eyelet to the other, thereby defining two path segments reciprocally inclined at a predetermined angle (α). The thread guide eyelets (O'1-O'2) are inclined in opposite directions with respect to the rectilinear support (X), so that the yarn (F) passes diagonally through the eye of each thread guide eyelet; and the inclination of the eyelets with respect to the support (X) is chosen so that contact arises between the yarn and two points (C1-C2) of each eyelet, whereby the inclination of the path segments (T1-T2) of the yarn in the spans between the eyelets and the sensor (S') is kept constant.

Description

[0001] This invention is concerned with an improved device for measuring the mechanical tension of the yarn in weaving systems and the like, and more particularly a measuring device capable of generating an analog signal proportional to the mechanical tension acting on the yarn being monitored. The analog signal is typically used as a feedback in the control circuit of a yarn braking device, in order to keep constant the mechanical tension in the yarn.

[0002] In order to measure the mechanical tension of the yarn, it is known to use devices comprising a sensor, generally consisting of a strain gauge or a piezoelectric sensor, and pressed by the yarn, which is tensioned between two thread guide eyelets that are suitably spaced on a rectilinear support, and between which the sensor is arranged.

[0003] As it appears on Fig. 1 of the attached drawings, which shows a known measuring device, a sensor S is placed outside the plane of rectilinear support X on which two thread guide eyelets O1-O2 are borne, so that yarn F leans on said sensor, deviating from a straight path and defining a broken line path whose vertex lies on sensor S, where the adjacent path segments join in such a way as to form an angle α.

[0004] In order to accurately measure the mechanical tension in the yarn, said angle α at the vertex of the yarn path must have a predetermined value resulting from the tangential contact of the yarn with points a and b of eyelets O1-O2. Moreover, that value must not change during the operation of the device, e. g. in consequence of an undesired displacement or an faulty arrangement, causing the contact between the yarn and the thread guide eyelets to move towards points A and B, and thereby changing angle α.

[0005] It is the main object of the present invention to improve the known device of Fig. 1 in such a way as to prevent any change of the angle α with which the yarn leans on the sensor, and to provide an accurate and reliable measure of the mechanical tension in the yarn, independently of any accidental or intentional cause which may produce undesired changes or faulty inclinations of angle α.

[0006] This object is achieved, according to the present invention, by means of an improved device having the features defined in the following claims.

[0007] Substantially, this invention is based on the innovative concept of inclining the two thread guide eyelets in opposite directions -with respect to the rectilinear support- so that the yarn passes diagonally through the eye of each thread guide eyelet, while maintaining contact with two diametrically opposite points of the eyelet which are symmetrical with respect to the centre of the eyelet. The inclination of the path segments preferably equals the inclination of the diagonal of the eye of the corresponding thread guide eyelet, which joins said yarn contact points.

[0008] The features, aims and advantages of the improved device according to the present invention will appear from the following detailed description, with reference to the attached drawings, wherein:

Fig. 1 is a schematic view of said known device,

Fig. 2 is a schematic view the like to Fig. 1 showing the improved device that is object of the present invention,

Fig. 3 is a detail to an enlarged scale of Fig. 2.

[0009] As shown in Fig. 1, a yarn F, passing through two thread guide eyelets O1-O2 of a known device D, leans on sensor S placed between said eyelets in such a way as to define a broken line path comprising two inclined path segments T1-T2, which are tangent to the respective eyelets in points a and b and join at sensor S, in such a way as to form an angle α.

[0010] From inspection of the drawing of Fig. 1, it will be evident that, if the contact zones of the path segments with the respective thread guide eyelets during operation of the device move towards points A and B of the eyelets, whether accidentally or not, said path segments will become aligned along corresponding dashed segments T'1-T'2, with a corresponding change of the angle α and, consequently, of the measure signal se generated by sensor S.

[0011] In order to avoid that drawback, the present invention provides the improved device D' shown in Fig. 2, comprising two thread guide eyelets O'1-O'2 that are inclined, in opposite directions, with respect to rectilinear support X, so that the yarn passes diagonally through the eye of each thread guide eyelet while mantaining contact with two diametrically opposite points C1-C2 of the eyelets, which are symmetrical with respect to the centre of the eyelet itself (Fig. 3). The inclination of the eyelets with respect to support X is preferably adjustable by means of respective hinged linkages CE1-CE2 which are lockable in position, and is chosen so that the yarn comes into contact with said points C1-C2 of the eyelets. That condition keeps constant the inclination of yarn path segments T1-T2, in the spans between each of the eyelets and sensor S'. Moreover, the inclination of said path segments T1-T2 preferably equals the inclination of the diagonal d of the eye of the corresponding thread guide eyelet (Fig. 3) which joins said contact points C1-C2.

[0012] By this arrangement, a predetermined, constant inclination α between path segments T1-T2 is obtained, according to the stated aim, in the spans between sensor S' and the two thread guide eyelets, independently of the incoming and outgoing directions of the yarn, respectively upstream and downstream the eyelets with reference to the sliding motion of the yarn.

Claims

1. A device for measuring the mechanical tension of a yarn in a weaving system, comprising a pair of thread guide eyelets spaced on a rectilinear support (X) and a sensor (S) interposed between said eyelets, externally to the rectilinear support, bearing the pressure of the yarn as it runs from one eyelet to the other and defining two path segments mutually inclined at a predetermined angle (α), characterized in that said thread guide eyelets (O'1-O'2) are inclined in opposite directions with respect to the rectilinear support (X) so that the yarn (F) passes diagonally through the eye of each thread guide eyelet; and in that the inclination of eyelets with respect to the support (X) is chosen so that the yarn comes into contact with two diametrically opposite points (C1-C2) of each eyelet, which are symmetrical with respect to the centre of the eyelet itself, whereby the inclination of path segments (T1-T2) of the yarn in the spans between each eyelet and sensor (S') is kept constant and, correspondingly, the angle (α) between said path segments is also kept unchanged, independently of the incoming and outgoing directions of the yarn upstream and downstream of said thread guide eyelets (01-02).

2. The device of claim 1, characterized in that the inclination of each path segment (T1-T2) equals the inclination of the diagonal (d) of the eye of the corresponding thread guide eyelet which joins said two contact points (C1-C2) of the yarn with the eyelet.

3. The device of claim 1 or 2, characterized in that said thread guide eyelets (01-02) are linked to said rectilinear support (X) by means of respective hinged linkages (CE1-CE2) that are lockable in position, thereby allowing the relative inclination of said eyelets with respect to said support (X) to be adjusted.

Drawing