Device for supplying weft thread in airjet weaving machines

Abstract: Device for supplying weft thread in airjet weaving machines, consisting of at least one nozzle (4, 5, 6), connected to a compressed air source (7), a buffer tank (18), a cutoff valve (9) placed in a funnel (8) between the compressed air source (7) and the nozzle (4, 5, 6), as well as a controlled throttling device (10), characterized in that the throttling device (10) is mounted after the buffer tank (18) and in the immediate surroundings of the cutoff valve (9) and consists of an inlet funnel (22), an outlet funnel (23) connected to the latter, a rotary throttling element (24) fitting in the inlet funnel (22) and a motor (25) to rotate the throttling element (24).

Description: This invention concerns a device for supplying weft thread in airjet weaving machines. It is known that in airjet weaving machines the weft threads are inserted in the shed by means of a number of nozzles, such as a main nozzle, an auxiliary main nozzle and relay nozzles. It is also known that in such airjet weaving machines the supply of the blow air is adjusted as a function of measurements carried out on the weft threads, in order to let the insertion of each weft thread happen in optimum circumstances. To this end the nozzles mentioned above are connected to a compressed air source via one or more cutoff valves, whereby said cutoff valves are opened and/or shut off sooner or later in the weaving cycle as a function of the values measured and parameters entered. In order to influence the insertion behaviour of the weft thread very precisely, foremost to modify the moment of arrival of the weft thread, it is also known to throttle the supplied blow air by means of a controlled throttling element. An example of such a device is described in the Belgian patent No. 904.260 (& EP-A-0 239 137), whereby the insertion of the weft threads is done by means of a main nozzle moving along with the sley and an auxiliary main nozzle mounted fixed in front of the latter, whereby the blow air in the auxiliary main nozzle is throttled. To this end, the auxiliary main nozzle has a cone and a counter-cone which both fit into each other and between which the blow air can be conducted, and whereby one of the cones can be moved towards, respectively removed from, the other, such that the passage of the blow air can be modified. Practical experience has shown that the use of an auxiliary main nozzle according to BE 904.260 for the present state of the art, with the ever-increasing machine speeds and the ever-extending range of yarn, leaves too little variation to modify the moment of arrival of the weft threads in relation to the weaving cycle. Current possible variations appear to take 8 to 14 milliseconds in a practical embodiment. As throttling of the blow air according to the Belgian patent No. 904.260 is done with a throttling element which is inseparable from the auxiliary main nozzle, the blow air is throttled exclusively in the fixed auxiliary main nozzle, as a result of which a higher flow is led to the movable main nozzle during the throttling, resulting in greater traction here, which has a partly counter-productive effect. The fact that the throttling is done on only one of the two main nozzles has the effect that, after the cutoff valve is shut off, all compressed air still present in the pipe between the cutoff valve and the main nozzles must escape through a smaller total opening, as a result of which the blow aftereffects after the moment that the cutoff valve is shut off are extended. It is also known that between the insertion periods of the weft threads a permanent airstream is provided in the main nozzles at low pressure, in order to hold the thread end present in said main nozzles. When the blow air is throttled in one of the main nozzles, this results also in the already low amounts of compressed air to hold the weft thread in the nozzles being throttled even more. Also, devices are known whereby the pressure of the blow air is controlled in the air receiver or buffer tank of the weaving machine. However, this technique has the disadvantage that each set pressure modification only shows after several insertions. It is therefore impossible to make adjustments during the insertion of a weft thread in order to modify the behaviour of this weft thread. The present invention concerns a device for supplying weft thread in airjet weaving machine, whereby the disadvantages mentioned above are excluded. Indeed, the present invention concerns a device whereby the throttling of the blow air allows a larger scope of adjustment of the moment of arrival of weft threads in the weaving cycle, namely double or more of the value reached previously, and whereby the throttling is made independent of the nozzles. The present invention also concerns a device for supplying weft threads whose throttling device is very compact. Another aim of the invention is to obtain very short reaction times between the activation of the nozzles on the one hand, and the blow action at the exit of said nozzles on the other hand, by both a specially adapted arrangement of the throttle device and by the use of a well-defined throttle device. According to a special embodiment the invention concerns a device for supplying weft thread, which makes use of a throttle device driven by means of a step motor, whereby the throttle device is constructed such that it allows a linear course of the time of arrival of the weft thread as a function of the rotation of the step motor. In order to reach the set goals, the invention concerns a device for supplying weft thread in airjet weaving machines, consisting of at least one nozzle connected to a compressed air source, and a buffer tank placed in the pipe between the compressed air source and the nozzle, a cutoff valve, and a controlled throttling device, characterized in that the throttling device is mounted after the buffer tank and in the immediate surroundings of the cutoff valve, and consists of an inlet funnel, an outlet funnel connected to the latter, a rotary throttling element fitting in the inlet funnel, and a motor to rotate the throttling element. As the throttling device is located after the buffer tank and in the immediate surroundings of the cutoff valve, even shorter reaction times are obtained, as further described below, whereby this effect according to the invention is reinforced by combining it with a throttling device using a rotary throttling element which allows any desired modification of the width of passage to be realized almost instantaneously. The best results are obtained when the throttling device is mounted after the buffer tank and immediately before, i.e. upstream of, the cutoff valve. Preferably, the throttling element is cylindrical and has at its top surface a profiled edge which operates in conjunction with the entry of the outlet funnel. The throttling element may be either a solid or a hollow cylinder. The hollow cylinder has the advantage that the short reaction time is reduced even more, because the motor needs only to rotate a very light mass. As a result it becomes possible to influence the time of arrival of the weft thread within the pick. In a special embodiment the profiled edge has such a shape that a linear course is obtained of the time of arrival of the weft thread as a function of the rotation of the motor for a well-defined supplying pressure of the blow air. Naturally, this effect may also be obtained by giving the entry of the outlet funnel a special shape. When two nozzles are used at the entry of the shed, a main nozzle and an auxiliary main nozzle respectively, according to the invention the throttling device is placed preferably in the common supply pipe and mounted in the immediate surroundings and preferably before the cutoff valve, such that lengthy blow aftereffects are avoided. In order to explain the characteristics of the invention, by way of example only and without being limitative in any way, the following preferred embodiments are described with reference to the accompanying drawings, where: fig. 1 shows a schematic representation of a device according to the invention; fig. 2 shows the course of the blow air pressure in the device in fig. 1 for various positions of the throttling device; fig.3 shows a variant of the device in fig. 1; fig. 4 shows the course of the blow air pressure in the device in fig. 3 for various positions of the throttling device; fig. 5 shows a practical embodiment of the part indicated by F5 in fig. 1; fig. 6 shows the part indicated by arrow F6 in fig. 5, to a greater scale; figs. 7 and 8 show views according to arrows F7 and F8 in fig. 6, to a smaller scale than the view in fig. 6; fig. 9 shows the shape of the edge of the element from fig. 6 in its unwound state. As indicated in fig. 1, the device according to the invention for supplying the weft thread 1 consists essentially of a supply package 2; a yarn storage feeder, such as an accumulator 3; a number of nozzles, in this case a main nozzle 4, an auxiliary main nozzle 5 and several relay nozzles 6; a compressed air source 7; and a cutoff valve 9 as well as a throttling device 10 in the pipe 8 between the compressed air source 7 and one or more of the nozzles mentioned above. In the embodiment shown only the main nozzle 4 and the auxiliary main nozzle 5 are connected to the cutoff valve 9 and the throttling device 10, while the relay nozzles 6 are controlled by separate valves, which are not shown. Fig. 1 also shows the sley 11, consisting of the sley shaft 12 and the reed 13 mounted on the latter. The main nozzle 4 operates in conjunction with the sley 11, while the auxiliary main nozzle 5 is mounted fixed. The cutoff valve 9 and the throttling device 10 are controlled by means of a control unit 14 as a function of several parameters, including for example the measured signal of a detector 15 which measures at the end of the shed the arrival of the weft threads for each weaving cycle, or a measured signal of any other detector operating in conjunction with the picking. Other examples are a winding detector at the accumulator 3, a bobbin transfer detector in case continuous weft thread supply is used, etc. Between the compressed air source 7 on the one hand and the cutoff valve 9 and the throttling device 10 on the other hand, there is also mounted a pressure control 17 and an air receiver 18, also named buffer tank, with a pressure gauge 19, whereby the pressure control 17 is mounted upstream of the buffer tank 18. The nozzles 4 and 5 are permanently provided with low-pressure blow air via a supply pipe 20 in order to keep the end of the weft thread 1 in the nozzles 4 and 5 between the insertions. This supply pipe 20 provides blow air of 20 to 500 millibar and is connected to the compressed air source 7, for example, by means of a pressure control 21 and/or throttling valve. According to the invention the cutoff valve 9 and the throttling device 10 are mounted in each others immediate surroundings, such that the blow aftereffects mentioned above are almost completely excluded. In the most preferred embodiment the throttling device 10 as shown in fig. 1 is mounted immediately before, i.e. upstream of, the cutoff valve 9. As shown in fig. 2 the throttling in the arrangement according to fig. 1 has no negative effect on the pressure reduction after the cutoff valve 9 has been closed. Hereby curve K shows the course of the pressure of the blow air when the throttling device 10 is fully opened, in other words when in that case there is no throttling. The curves L and M show the course for two different positions of the throttling device 10, respectively for a small and a greater throttling. The times t1 and t2 indicate the moments at which the cutoff valve 9 is closed and opened respectively. The reduction times are almost equal in all three cases. The pressure increase is as fast with throttling as without throttling. As indicated in curve M, the pressure increase for a stronger throttling may show a peak as a result of the volume present in the pipe between the throttling device 10 and the cutoff valve 9, where a pressure equal to the pressure before the throttling device 10 can occur after the cutoff valve 9 has been closed. In practice however, this pressure increase is not possible during the normal weaving process as a result of the speed of the weaving machine. Fig. 3 shows a variant whereby the throttling device 10 is mounted in the immediate surroundings of the cutoff valve 9 in accordance with the invention, but whereby they have been mutually exchanged, contrary to the embodiment in fig. 1. Fig. 4 shows the course of the pressure of the blow air in the curves N and O, respectively when there is throttling and when there is no throttling. To make a distinction, the curve Q is also shown, in case the throttling device 10 is located at a great distance from the cutoff valve 9, for example when the throttling device is built into the nozzles 4 and/or 5, as is known from the BE 904.260. In order to keep the reaction times to a minimum, use is made, according the invention, of a special construction for the throttling device 10, in combination with the fact mentioned above, i.e. that the throttling device 10 and the cutoff valve 9 are located in each others immediate surroundings. As indicated in fig. 5, to this end the throttling device 10 consists of an inlet funnel 22; an outlet funnel 23 connected to the latter; a rotary, cylindrical throttling element 24 fitting into the inlet funnel 22; and a motor 25 to rotate the throttling element 24. Preferably, the inlet funnel 22 and the throttling element 24 are cylindrical and the outlet funnel 23 is connected sideways to the inlet funnel 22 in a slanting manner. Hereby the top surface of the throttling element 24 has a profiled edge 26 which operates in conjunction with the entry 27 of the outlet funnel 23, such that the rotation of the throttling element 24 closes the entry 27 either more or less. In the most preferred embodiment the motor 25 consists of a step motor and the cylindrical throttling element 24 is attached directly to the motor shaft 28. Preferably, the edge 26 has such a shape that, in the device according to fig. 1, a linear course of the time of arrival at the detector 15 of the weft thread is obtained as a function of the rotation of the step motor 25, that is, for a certain setting of the pressure control 17. Very good results are obtained when using a throttling element 24 whose top surface has a shape as shown in fig. 6. Hereby the top surface has an edge 26 consisting of a closing part 29, a first slanting part 30 connected to it, a second slanting part 31 with preferably a greater slope than the first part 30 and finally a passage part 32. When the closing part 29 is directed to the entry 27, the latter is in its maximum closed position. When the passage part 32 is directed to the entry 27, a full passage is obtained. In all intermediate positions the blow air is throttled to a greater or lesser extent. The closing part 29 and the passage part 32 preferably extend over arcs L1 and L2, which are just large enough to make the closing part 29 and the passage part 32 operate in conjunction with the full passage of the entry 27. The first slanting part 30 extends over almost half the circumference, while the second slanting part 31 covers the remaining part of the circumference of the throttling element 24. As indicated in figs. 7 and 8 the slanting parts 30 and 31 are preferably part of a surface slanting at an angle, 33 and 34 respectively. The course of the edge 26 thus obtained is shown in fig. 9 in its unwound state. It is clear that the influence of the throttling element 24 on the time of arrival of the weft thread 1 when the motor 25 is rotated can be modified by changing either of the four following parameters when constructing the throttling device 10, namely the diameter D1 of the outlet funnel 23 in a slanting position, the angle A between the inlet funnel 22 and the outlet funnel 23, the diameter D2 of the throttling element 24 and the above-mentioned shape of the edge 26. Hereby it must be noted that in case the cylindrical outlet funnel 23 connects to the inlet funnel 22 in a slanting manner, this results in the entry 27 of the inlet funnel 22 becoming elongated according to the axial direction, with the advantage that the effect of the throttling is less subject to any possible tolerance deviations on the slanting parts 30 and 31 than if the outlet funnel 23 would be perpendicular to the inlet funnel 22. It is clear that such an elongated opening can also be obtained by forming a groove at the entry 27, with the outlet funnel 23 not necessarily in a slanting position in relation to the inlet funnel 22. In order to accurately manoeuvre the linearity mentioned above through the shape of the edge 26, the diameter D2 of the throttling element 24 is preferably considerably larger than the diameter D1 of the outlet funnel 23. In order to obtain a maximum closing or opening respectively of the entry 27 of the outlet funnel 23, the closing part 29 and the passage part 32 must both have an arc, L1 and L2 respectively, equal to the arc L3 covered by the entry 27. This makes clear that the ratio D1/D2 must be large enough so that the arcs L1 and L2 do not cover too large a part, in terms of percentage, of the circumference of the throttling element 24 and so that large enough a length L4 remains to be used for the setting. The throttling element 24 in fig. 6 also offers the advantage that switching from minimum throttling to maximum throttling, and vice versa, can be done very fast because the closing part 29 and the passage part 32 are in each others immediate surroundings. As indicated in fig. 5, the step motor 25 can be fitted with a detection device 35 to define at least a start and/or end position, formed for example from an element 36 which is mounted on the motor shaft 28 and which operates in conjunction with the proximity detector 37. In case of a device as indicated in fig. 1, whereby the weft thread 1 is supplied by means of both a main nozzle 4 and an auxiliary main nozzle 5, according to the invention both the cutoff valve 9 and the throttling device 10 are placed in the common pipe 8, which eliminates the counter-productive effect of the two nozzles 4 and 5, which was mentioned in the introduction. It must be noted that the part of the pipe 8 between the air receiver 18 and the throttling device 10 is kept as short as possible. In order to realize the above-mentioned characteristics in practice, the cutoff valve 9 and the throttling device 10 are preferably made in one piece, which, for example as shown in fig. 5, can be mounted against the wall of the air receiver 18. The cutoff valve 9 has the traditional construction and has a valve part 38 which can be moved by means of an electromagnet 39. The outlet funnel 23 mentioned above joins, preferably directly, the valve house of the cutoff valve 9. Also according to the invention, the pipe 20 mentioned above which supplies low-pressure blow air, is connected downstream of the throttling device 10 to the nozzles 4 and 5, so that this weak airstream is not further throttled. Although the invention is meant in the first place to control the main nozzle 4 and/or the auxiliary main nozzle 5, it is clear that it can also be used with reference to the supply of blow air to the relay nozzles 6.

Claims: Device for supplying weft thread in airjet weaving machines, consisting of at least one nozzle (4, 5, 6), connected to a compressed air source (7), a buffer tank (18), a cutoff valve (9) placed in a funnel (8) between the compressed air source (7) and the nozzle (4, 5, 6), as well as a controlled throttling device (10), characterized in that the throttling device (10) is mounted after the buffer tank (18) and in the immediate surroundings of the cutoff valve (9) and consists of an inlet funnel (22), an outlet funnel (23) connected to the latter, a rotary throttling element (24) fitting in the inlet funnel (22) and a motor (25) to rotate the throttling element (24). Device according to claim 1, characterized in that the throttling device (10) is placed before, i.e. upstream of, the cutoff valve (9). Device according to claim 1 or 2, characterized in that the shape of the inlet funnel (22), the outlet funnel (23) and the throttling element (24) is such that a predetermined characteristic for the influence of the time of arrival of the weft thread as a function of the rotation of the throttling element is obtained. Device according to claim 3, characterized in that the shape of the inlet funnel (22), the outlet funnel (23) and the throttling element (24) is such that a linear course between the time of arrival of the weft thread (1) at the end of the shed in function of the rotation of the throttling element (24) is obtained. Device according to any of the above claims, characterized in that the throttling element (24) is cylindrical and has a profiled edge (26) which operates in conjunction with the entry (27) of the outlet funnel (23). Device according to claim 5, characterized in that the throttling element (24) is hollow. Device according to claim 5 or 6, characterized in that the entry (27) of the outlet funnel (23) is elongated, with the longest size extending according to the axial direction of the inlet funnel (22). Device according to claim 7, characterized in that the outlet funnel (23) is cylindrical and joins the inlet funnel (22) in a slanting manner. Device according to any of claims 5 to 8, characterized in that the throttling element (24) has a top surface, whereby the edge (26) along the circumference is formed successively of a closing part (29), a first slanting part (30), a second slanting part (31) which has a steeper slope than the first slanting part (30) mentioned above and a passage part (32) which allows a completely free passage of the inlet funnel (22) to the outlet funnel (23). Device according to claim 9, characterized in that the first slanting part (30) and the second slanting part (31) each make up part of a different flat surface (33, 34). Device according to any of claims 5 to 8, in particular whereby the device forms the supply of at least one nozzle mounted at the entry of the shed (16), be it a main nozzle (4) or an auxiliary main nozzle (5), characterized in that the throttling element (24) has an edge (26) with such a shape that a linear course between the time of arrival of the weft thread (1) at the end of the shed as a function of the rotation of the motor (25) is obtained. Device according to any of the above claims, characterized in that the motor (25) is a step motor . Device according to any of the above claims, characterized in that the motor (25) is equipped with a detection device (35) which defines at least a reference position. Device according to any of the above claims, in particular whereby use is made of a moving and a fixed main nozzle (4, 5) characterized in that the cutoff valve (9) is mounted in the common supply pipe (8). Device according to any of the above claims, characterized in that the cutoff valve (9) and the throttling device (10) are built together to a whole. Device according to any of the above claims, of the type whereby use is made of a supply pipe (20) for low-pressure air meant to hold the thread ends in the nozzles (4, 5) concerned, characterized in that this pipe (20) is connected downstream of the cutoff valve (9) and the throttling device (10) to the supply pipe leading to the nozzle, respectively nozzles (4, 5) concerned.

Inventors: BAMELIS JEAN-MARIE, MARKEY HUGO, PEETERS JOZEF, VAN BOGAERT PHILIPPE, BAMELIS, JEAN-MARIE, MARKEY, HUGO, PEETERS, JOZEF, VAN BOGAERT, PHILIPPE
Applicants: PICANOL NV, PICANOL N.V.
Application year: 1991
Main classification: D03D47
IPC codes: F16K5, D03D47