MEASURING AND DETECTION DEVICE FOR DETERMINING THE POSITION OF A BREAK IN A WARP THREAD ON WEAVING MACHINES

Abstract: Measuring and detection device for determining the position of a break in a warp thread on weaving machines, characterized in that it consists essentially of: two thread guides (14, 15) mounted at a distance from each other and which can be presented against the warp (2) on a weaving machine; a mechanism (16) for gripping the broken warp thread (11) and bringing it between the thread guides (14, 15); detectors and/or measuring devices (17, 18, 19, 29, 30) mounted on the thread guides (14, 15) and/or the above-mentioned mechanism (16) and which can be influenced by a warp thread (11) which has been gripped; and a processing unit (20) for processing the data obtained by means of the detectors.

Description: This invention concerns a measuring and detection device for determining the position of a break in a warp thread on weaving machines, such as known from EP-A-0 234 630 published on the 02.09.87. In particular, it concerns a device by means of which it is possible to check whether a broken warp thread has come free or has become entangled, and/or on which side of the device the break is situated, and/or at what distance from the device the break is situated. The measuring and detection device according to the invention can also be used to remove a section of a broken warp thread from the warp. The present invention concerns a measuring and detection device for determining the position of a break in a warp thread on weaving machines, characterized in that it consists essentially of: two thread guides placed at a distance from each other and which can be presented against the warp on a weaving machine; a mechanism for gripping the broken warp thread and drawing it between the thread guides; detectors and measuring devices mounted on either the thread guides and the above-mentioned mechanism or on the above-mentioned mechanism, and which can be influenced by a warp thread which has been gripped; and a processing unit for processing the data obtained from the detectors. The above-mentioned detectors can, as will be seen from the following description, be of various types, according to the particular purpose for which it is wished to use the measuring and detection device. In order to explain the characteristics of the invention, by way of example only and without being limitative in any way, some preferred embodiments are described, with reference to the accompanying drawings, where: fig. 1 is a schematic diagram of the measuring and detection device in a weaving machine; fig. 2 is a schematic diagram of the device according to the invention; fig. 3 shows the curve of a value such as can be deduced from the data obtained by means of the device shown in fig. 2; figs. 4 and 5 show two variants of the measuring and detection device according to the invention. Fig. 1 is a schematic diagram of a weaving machine, with the most important components being the warp beam 1, the warp threads 2, the backrest roller 3, the warp stop motion 4 fitted with drop wires 5, the frames 6, the heddles 7, the reed 8, the woven cloth 9 and the cloth beam 10. Also shown in the figure are a broken warp thread 11 and the break 12 in it. The measuring and detection device 13 according to the invention should preferably be positioned between the warp stop motion 4 and the frames 6; or it can operate in this zone on the warp 2. The positioning of the device 13 between the warp stop motion 4 and the frames 6 has the particular advantage that a broken warp thread 11 is simple to locate since all warp threads lie parallel to each other. Furthermore, most breaks 12 occur in this area. As shown in fig. 2, such a device 13 consists essentially of: two thread guides 14 and 15 which are mounted at a distance from each other and which can be presented against the warp 2; a mechanism 16 for gripping a broken warp thread 11 and drawing it between the thread guides 14 and 15; a number of detectors and measuring devices, 17 to 19 respectively; and a processing unit 20 for processing the data obtained from the detectors and measuring devices 17 to 19. In the embodiment shown in fig. 2, the thread guides 14 and 15 consist of elements, such as wires or similar, which can flex elastically in the direction of the warp 2, one end of which, 21 and 22 respectively, is fixed, and the other end of which, 23 and 24 respectively, is free to operate on the broken warp thread 11. The mechanism 16 for gripping the broken warp thread 11 and presenting it between the thread guides 14 and 15 consists in fig. 2 of a hook 25 which can move vertically. The thread guides 14 and 15 are fitted with detectors 17 and 18 consisting of strain gauges in order to detect the flexure of the elements. The above-mentioned mechanism 16 is in turn fitted with a measuring device 19 in order to measure the displacement H of the hook 25 relative to the warp 2. Finally, it should be observed that for the purpose of efficient measurement, the hook 25 should preferably be so constructed that the thread 11 is subject to fairly high friction as it passes through this hook. The operation of the device according to fig. 2 is as follows: first, the broken warp thread 11 is picked up by the hook 25 after said warp thread 11 has been separated from the other warp threads 2, for example following a method as described in European patent application 87201196 made by the present applicant, and drawn upwards in the direction H between the thread guides 14 and 15. If the break 12 is situated on the right hand side of the device 13, as shown in fig. 2, then clearly during the displacement of the hook 25 the broken warp thread 11 will not move past end 23 but past the hook 25 and the end 24 of the thread guide 15. As a result of frictional losses in the hook 25, the tensions T1 and T2 in thread ends 26 and 27, between the hook 25 and thread guide 14 and between the hook and thread guide 15 respectively, will be different from each other during the motion of the hook 25, with T1 being greater than T2. This results in different forces being exerted on the ends 23 and 24 of the thread guides 14 and 15, so that they flex by different amounts. By means of strain gauges 17 and 18 a signal can thus be measured which is proportional to the tensions T1 and T2. This signal can then be used by the processing unit 20. For example, the ratio of the two values measured is equal to the ratio T1/T2. As shown schematically in fig. 3, the value of this ratio is greater than "1" as long as the thread is present in the hook 25, and falls back to "1" as soon as the thread leaves the hook. When this occurs, the displacement H can be measured by the measuring device 19, so that the distance L at which the break has occurred is also known. Also, the ratio of the tensions T1 and T2 shows on which side of the device 13 the break 12 is situated. Should the break 12 ever be situated to the left of the device 13, unlike as shown in fig. 2, then clearly T1/T2 will be less than "1". Another possibility, in particular as regards fig. 2, is for the hook 25 to be raised until there is no more flexure of thread guide 15, which means that the full length of the broken warp thread 11 is located inside the device, at which moment H = L/2. Preferably, the device 13 should be fitted with a mechanism (not shown in the figures) to ensure that the tensile force which can be exerted by the hook 25 is limited to a certain maximum, in order to prevent a second break occurring. In such a case the weaver can intervene manually, to determine the point of the break manually. Fig. 4 shows another variant of the invention, which uses thread guides 14 and 15 fitted with detectors 28 and 29 which respond to the motion of the warp thread 11 as it passes the guides. Such guides can consist of e.g. motion-sensitive elements fitted with a sensor. In a similar manner to the previous variant, the sensor signals can be used either to determine the side of device 13 on which the break 12 is situated or to determine the above-mentioned length L. Fig. 5 shows yet another variant in which the mechanism 16 for gripping the broken warp thread is fitted with a detector 30, which in this case also responds to the motion of the broken warp thread 11 past said mechanism 16. This detector 30 may consist of e.g. a rotating element fitted with a sensor which supplies signals which are a function of the rotation and/or sense of rotation of the rotating element, from which the above-mentioned data may also be deduced. Clearly, said detectors and/or measuring devices 17 to 19 and 28 to 30 can be combined with each other in various ways within such a device 13. Clearly also, the mechanism 16 may also consist of a suction nozzle or suchlike.

Claims: 1. Measuring and detection device for determining the position of a break in a warp thread on weaving machines, characterized in that it consists essentially of: two thread guides (14, 15) mounted at a distance from each other and which can be presented against the warp (2) on a weaving machine; a mechanism (16) for gripping the broken warp thread (11) and bringing it between the thread guides (14, 15); detectors and measuring devices (17, 18, 19, 28, 29, 30) mounted on the thread guides (14, 15) and the above-mentioned mechanism (16) either or on the above-mentioned mechanism (16) and which can be influenced by a warp thread (11) which has been gripped; and a processing unit (20) for processing the data obtained by means of the detectors. 2. Measuring and detection device as in claim 1, characterized in that the thread guides (14, 15) are flexible and that their free ends (23, 24) can operate on the warp thread (11) which has been drawn up between the thread guides (14, 15), and that use is made of detectors (17, 18) which measure the flexure of the thread guides (14, 15). 3. Measuring and detection device as in claim 2, characterized in that the above-mentioned detectors (17, 18) consist of strain gauges. 4. Measuring and detection device as in claim 1, characterized in that the thread guides (14, 15) between which the warp thread (11) is drawn consist of detectors (28, 29) which respond to the motion of the warp thread (11) and which consist essentially of motion-sensitive elements coupled to a sensor which supplies a signal which is a function of said motion. 5. Measuring and detection device as in claims 1 to 4, characterized in that the mechanism (16) for gripping the broken warp thread (11) and bringing it between the thread guides (14, 15) consists of a hook (25). 6. Measuring and detection device as in claim 5, characterized in that it is fitted with a measuring element (19) by means of which the displacement (H) of the hook (25) can be measured. 7. Measuring and detection device as in claim 5, characterized in that the mechanism (16) for drawing the warp thread (11) between the thread guides (14, 15) is fitted with a detector (30) which responds to the displacement of the warp thread (11) moving past it, and consists essentially of a small rotating element fitted with a sensor which supplies a signal which is a function of the rotations experienced. 8. Measuring and detection device as in claim 5, characterized in that the mechanism (16) for bringing the warp thread (11) between the thread guides (14, 15) is fitted with a detector (30) which is sensitive to the motion of the warp thread (11) moving past it (11), and which consists essentially of a rotating element fitted with a sensor which generates a signal which is a function of the sense of rotation. 9. Measuring and detection device as in claim 1, characterized in that it is mounted between the warp stop motion (4) and the frames (6) of the weaving machine.

Inventors: GRYSON, DIRK, SHAW, HENRY
Applicants: PICANOL N.V.
Application year: 1988
Main classification: D03D51
IPC codes: D03D51, D03J1