DEVICE FOR REMOVING WEFT IN WEAVING MACHINES

Abstract: The purpose of the device is to improve reliable weft withdrawal in weaving machines from the shed upon detecting a weaving fault. The device is simple in its design and operates without impacts at constant speed. This is achieved by that the rotatable boom (7) is provided with a driving mechanism, consisting of an air damper (22), axial displacement of boom (7), air reactive driving unit (25) and a centrifugal governor (30) of speed.

Description: This invention relates to a device for removing weft thread in weaving machines of the hind referred to in the preamble portion of claim 1. Such a device is known from EP-A-200168, having a winding unit, of which the winding and the pivoted members are mounted in a tubular case. Both the winding and the pivot member are arranged mutually coaxially, the winding member being mounted for rotation and for performing an axial sliding motion on a bar, mounted in a sliding bearing. The rotary member is rotatably mounted in ball bearings and is coupled for drive via a gearing with the driving motor. About the circumference of the free end of the winding member, a conical winding surface is formed, which corresponds in its shape to the conical recess in the rotary member. The conical recess of the rotary member passes over to the ejecting channel of the rotary shaft, which opens into the waste box. In the central part of the winding member, a nozzle is formed which is directed towards the ejecting channel of the rotary member. The nozzle is connected to a connection mounted on the bush for distributing the pressure fluid via said bush. Both the winding and the rotary member are thus arranged contrary to each other, with a suitable gap therebetween inside the case. Transversally to the case, a guiding tube is mounted, which opens thereinto in a position corresponding to the space between the rotary member and the winding member. Both the winding and the rotary member are axially aligned with the longitudinal axis of the weft inserting nozzle. Against the orifice of the guiding tube is mounted, outside the weft path, the guiding nozzle in such manner, that the weft path is situated therebetween. When necessary to withdraw the faulty picked weft from the shed, weft is fed from the inserting nozzle and blown by the guiding nozzle into the guiding tube and further, by intermediary of the nozzle in the winding member, into the ejecting channel of the rotary member. Thereafter, weft feeding from the inserting nozzle is stopped and the auxiliary cutter, situated between said nozzle and the guiding tube, separates said weft part. Thereupon,the winding member is displaced towards the rotary member as far as their conical surfaces are in contact. The driving motor begins to rotate the rotary member via gearing and said rotary member starts to rotate the winding member, which is in contact therewith. By the rotary motion of the winding member, weft begins to be wound on to its conical surface, thus being withdrawn from the shed back to the main nozzle in single length. Upon winding up the faulty picked weft length on to the conical surface of the winding member, said fuzz ball is blown by the winding member nozzle via the ejecting channel into the waste box. The known device for removing the faulty picked weft as specified above is disadvantageous already by its positioning on the weaving machine in the area of the inlet part of the shed. For the purpose of securing weaving under unchanged conditions, the device must be positioned outside the weft path, thus complicating the drawing-in of the weft into the winding unit by the drawing-in nozzle. Moreover, in this system of arrangement, the weft is drawn back directly in single length without preceding release from the interlacing point of the fabric. Thus, particularly with delicate yarns, there exists the danger of surpassing the limiting stress in the weft, this being the reason of breakage of the weft to be withdrawn, without the possibility of finishing the withdrawal automatically. This danger is still enhanced by the guiding tube, in which an excessive rubbing of the weft about its edge takes place due to the change of direction of the weft to be withdrawn. The winding unit as such has the disadvantage of rigid mechanical bonding of the drive by gearing, without securing any compensation of an increased tensile stress in the weft, caused e.g. by its local trapping in the weft, this being again a possibility of breakage of the weft to be withdrawn. The drive of the rotary member then increases the exacting character of the arrangement of the winding unit design. The positioning of the ejecting nozzle in the axis of the winding member is disadvantageous in view of low usage of the pressure fluid energy, acting initially only upon the free weft end, this possibly causing, upon tightening the winds of the weft fuzz ball on the cone of the winding member, the incapability of the nozzle to transport the wound up weft into the waste box. The disadvantages mentioned above are mitigated by the device as disclosed by the features of claim 1. This object will be solved by the features of claim 1. Dependent claims are directed on preferred embodiments of the invention. For the purpose of even withdrawal of the weft, the device secures constant revolutions, and a twisting moment easily adjustable by air pressure control. A further advantage of the device is the positioning of the blow off nozzle, whereby a reliable removal of the weft fuzz is obtained. The present invention is represented in the accompanying drawing in cross section of an embodiment in form of example. The device for removing the weft is mounted on the end side of the weaving machine shed in the weft path, where it is fastened outside the range of operation of a not represented beat-up reed. The device consists of body 1, in which is slidably mounted hub 2, in the cylindrical hollow of which is rotatably mounted shaft 4 by intermediary of a pair of radial bearings 3. The said bearings 3 are braced inside the hub by means of a tubular clearance filler 5. In the lower part, a boom 7 with an outer conical surface 8 is fastened to shaft 4 by means of screw 6. Boom 7 is displaceable into engagement with the inner conical surface 9 of contact ring 10 mounted in body 1. A further conical surface 12 of opposite conicity links up the inner conical surface 9 of ring 10 and forms in said ring 10 a diffuser. The free part of the outer conical surface 8 of rotary boom 7 is in engagement with the inner conical surface 9 of ring 10 in the weft inlet hole 13. The inner conical surface 9 forms, together with a further conical surface 12, a through opening 14 for ring 10, which passes into the suction chamber 15 in the bottom of body 1 of the device. The suction chamber 15 is connected to a-not represented-suction mechanism by hose 16. At the point of the orifice of inlet hole 13 for the weft, body 1 of the device is provided with a sensor 17 for recording the presence of weft. From upside, a pneumatic nozzle 18 opens into the inlet hole 13 in inclined position, the orifice of said nozzle being directed into the through opening 14 of ring 10. Hub 2 is in its upper part extended as far as the inner circumference of the cylindrical shell 19, fastened to body 1 of the device. Shell 19 is covered from upside by cover 20. In the central part of cover 20, a hollow projections is drawn into the device, forming a stationary piston 21 of air damper 22 of rotatable boom 7. The cylinder 23 of damper 22 is loosely set up on piston 21 and fastened to shaft 4 of boom 7. In the lower part of cylinder 23, four hollow arms 24 of the reactive driving unit 25 project radially therefrom. Each arm 24 is provided at its end with a blindage 26, surpassing its outer circumference. In proximity of blindage 26, each arm 24 has a transversal outlet hole 27, which forms a nozzle of the pneumatically reactive driving unit 25. The outlet holes 27 are situated for coincident sense of rotation. More remote from the blindage, nearer to the axis of rotation of driving unit 25, each arm 24 is provided with an opposite direction limiting nozzle 28, opening into the hollow of arm 24. The limiting nozzles 28 are directed oppositely relative to the outlet hole 27 of driving unit 25. On each arm 24, is displaceably mounted a control weight 29 of the centrifugal govenor 30 of the speed of driving unit 25. Each control weight 29 is provided on both faces with bevels, said bevel from the blindage 26 side being internal and from the sides of cylinder 23 external. At rest position, rotatable boom 7 is inserted into the hollow of body 1, by action of coil spring 31 mounted in the circular groove 32 of body 1 of the device, one end of said spring being supported against the bottom of circular groove 32 and the other end against hub 2 at the point of its enlargement. In that rest position, the upper end of cylinder 23 is situated in a further circular groove 33 in cover 20. For the purpose of free exit of pressure air during operation of the reactive driving unit 25, opening 34 is made in cover 20. Damper 22 with driving unit 25 and centrifugal govenor 30 of speed thus constitute together the driving mechanism of the device. Upon withdrawal, the weft ― not represented ― is at first sucked in on its free end by the ejector consisting of pneumatic nozzle 18 and the diffuser of the through opening 14 of ring 10. The weft ― not represented ― is sucked in by inlet hole 13 via through opening 14 into suction chamber 15 of the device. Thereafter, by introduction of pressure air through the hollow of piston 21 into cylinder 23, the resistance of coil spring 31 is overcome and the rotatable boom 7 is continuously displaced into inlet hole 13. The outer conical surface 8 of rotatable boom 7 comes into contact with the inner conical surface 9 of ring 10, and the weft remains stationarily clamped between them. By transferring the rotatable boom 7 into engagement of its outer conical surface 8 with inner conical surface 9 of contact ring 10, said contact ring is removed from permanent magnet 11. Simultaneously, the rotatable boom 7 begins to rotate by action of the reactive driving unit 25, as the compressed air begins to flow out through the transversal outlet holes 27 of arms 24. The driving unit 25 rotates the rotatable boom 7 with constant speed as, upon its increase, the control weights 29 of centrifugal govenor 30 are displaced on the arms 24 in the direction of action of centrifugal force, thus closing the outlet holes 27 of driving unit 25. Simultaneously with the displacement of control weights 29, the oppositely directed limiting nozzles 28 are opened, by means of which the speed is reduced. Upon limiting speed, the inner bevels of control weights 29 act very effectively, by means of which the air pressure, which overcomes their limited centrifugal force, displaces the control weight 28 back, thus forming an equilibrium state. In that manner, the weft is wound on to the rotatable boom 7 absolutely uniformly at a guaranteed speed and without impacts. According to need, it is possible to adjust easily the torque of the rotatable boom 7 by controlling the pressure of air entering the driving unit 25. The change of torque is independent of the speed of the rotatable boom 7. During winding weft, the contact ring 10 removed from permanent magnet 11 rotates in its magnetic field coincidently with boom 7 without any undesired friction. The weft is clamped, upon withdrawal, between conical surface 8, 9 by constant force of the magnetic field of permanent magnet 11. Upon finishing winding, the inlet of pressure air into cylinder 23 is closed and the coil spring 31 returns the rotatable boom 7, together with the driving unit 25 into the rest position. By back displacement of boom 7, ring 10 bears against magnet 11, whereby the engagement of the outer conical surface 8 of rotatable boom 7 with the inner conical surface 9 of ring 10 is abolished. The fuzz of the not represented weft is removed by introduction of compressed air into pneumatic nozzle 18, in which the air flow is guided over the outer conical surface 8 of rotabable boom 7 into through opening 14 of ring 10. By ejection effect, this fuzz of weft is sucked into suction chamber 15 of the device and outside the device via hose 16 by means of a not presented sucking device. The magnet 11, which retains the ring 10 in body 1 of the device, the clamping contact of ring 10 with the extended boom 7 nad free rotation therewith, can be either permanent, or also an electromagnet. Magnet 11 can have the shape of a continuous ring, or of separate bodies distributed about the circumference of body 1 at the point of the through opening 14. The device specified above can be used in all types of weaving machines, and its position on the weaving machine need not be only in the weft path.

Claims: 1. Device for removing weft thread in weaving machines comprising a driving mechanism (25) and a rotatable boom (7) with an outer conical surface, displaceable into engagement with an inner conical surface (9) of a coaxially arranged ring (10), characterized in that the driving mechanism is provided with a pneumatically reactive driving unit (25). 2. Device according to claim 1, characterized in that the driving unit(25) is provided with a centrifugal speed governor (30). 3. Device according to claim 1 or 2, characterized in that the driving unit (25) is formed by at least one hollow arm (24) with at least one transversal outlet hole (27). 4. Device according to claim 3, characterized in that the centrifugal governor (30) has in the arm (24), which is provided with control weight (29), an oppositely directed limiting nozzle (28). 5. Device according to one of the preceding claims, characterized in that the outer conical surface (8) of the rotatable boom (7) faces the orifice of a stationary pneumatic nozzle (18) which is directed toward a through opening (14) of a contact ring (10). 6. Device according to claim 5, characterized in that at least one magnet (11) is interposed between the contact ring (10) and a body (1) of the device. 7. Device as claimed in claim 6, characterized in that the magnet (11) is mounted in the body (1) of the device. 8. Device as claimed in claim 1 characterized in that the driving mechanism comprises an air damper (22) of the axial displacement of the rotatable boom (7).

Inventors: BUCEK, PAVEL, KALINA, JAROSLAV, PAJGRT, JAN, PUS, MILAN, SMETAK, VINCENC, ZEMEK, MICHAL, Smeták, Vincenc
Applicants: ZBROJOVKA VSETIN, A.S.
Application year: 1989
Main classification: D03D51
IPC codes: D03D51