Classifications

• • D—TEXTILES; PAPER
  • D03—WEAVING
  • D03D—WOVEN FABRICS; METHODS OF WEAVING; LOOMS
  • D03D51/00—Driving, starting, or stopping arrangements; Automatic stop motions
  • D03D51/18—Automatic stop motions
  • D03D51/20—Warp stop motions
  • D03D51/28—Warp stop motions electrical
• • D—TEXTILES; PAPER
  • D02—YARNS; MECHANICAL FINISHING OF YARNS OR ROPES; WARPING OR BEAMING
  • D02H—WARPING, BEAMING OR LEASING
  • D02H13/00—Details of machines of the preceding groups
  • D02H13/02—Stop motions
  • D02H13/04—Stop motions responsive to breakage, slackness, or excessive tension of threads, with detectors for individual threads or small groups of threads
  • D02H13/08—Stop motions responsive to breakage, slackness, or excessive tension of threads, with detectors for individual threads or small groups of threads electrical
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04B—KNITTING
  • D04B35/00—Details of, or auxiliary devices incorporated in, knitting machines, not otherwise provided for
  • D04B35/10—Indicating, warning, or safety devices, e.g. stop motions
  • D04B35/14—Indicating, warning, or safety devices, e.g. stop motions responsive to thread breakage
  • D04B35/16—Indicating, warning, or safety devices, e.g. stop motions responsive to thread breakage with detectors associated with a series of threads

Definitions

• the present invention is applicable to the sector of weaving and knitting looms and specifically relates to a warp-guard device for detecting one or more broken yarns in a series of warp yarns.
• monitoring or warp-guard devices have been developed, said devices in the majority of cases being of the drop wire type, described and claimed, for example, in the European patents EP-A-0, 1 1 ,261 , EP-A-0,262,724, EP-A-0,284,591 , EP-A-0,508,51 4, EP-A-0, 1 87,745 and EP- A-0,276,206.
• each yarn is inserted into a fork-shaped metal drop wire which is combined with a bar formed by a metal core and by a casing, also made of metal, which are electrically isolated from each other and connected to the terminals of an electric circuit.
• a yarn breaks, the drop wire falls onto the bar, physically closing the electric circuit which l causes stoppage of the machine.
• Chinese Patent Application CN-A-20761 1 5 describes a device used for the processing of particularly delicate yarns, which may break as a result of the intrinsic weight of the drop wire.
• a rotating comb is used, said comb collecting the ends of the broken yarns, winding them around their axis of rotation and allowing tensioning of a cable which is parallel to the axis of rotation and which actuates a switch located at one of the ends.
• the drop wire devices cannot be used in the processing of yarns made of conductive materials such as, for example, carbon fibres, since these may create false contacts with the drop wires, or in potentially dangerous environments owing to the risk of producing electric arcs when there is contact between the drop wires and the bars.
• yarn-guard devices of the electro-optical type i.e. devoid of mechanical elements such as the drop wires and consisting essentially of a coherent light source or a lower-power laser beam between an emitter and one or more receivers, have been developed.
• United States patents US-A-4, 1 77,838 and US-A-4,248,272 discloses an electro-optical device which comprises a low-power laser aimed transversely with respect to the warp yarns underneath the plane in which they lie, while a receiver is located at the opposite end in a position aligned with the radius. In the event of breakage, a yarn falls from the plane in which it lies, or intersects with others, forming an obstruction between the two warp planes and interrupting the laser beam.
• Another known electro-optical device envisages a light source located underneath the weaving surface and a detector consisting of several elements located above the weaving surface.
• the configuration of the warp is acquired and the image obtained is compared with successive other configurations acquired with each beating-up operation of the machine, in synchronism with the movement of the weaving members. From this comparison a signal as to breakages of yarns during processing is obtained.
• the main object of the present invention is that of eliminating the abovementioned drawbacks, by providing a warp-guard device which has characteristics of high reliability, flexibility and safety.
• a particular object is that of providing a warp-guard device which is able to perform detection of the broken yarns with a high degree of precision and with yarns made of any material.
• Another particular object is that of devising a warp-guard device which is substantially insensitive to dust, moisture and external disturbances.
• a further object is that of providing a warp-guard device which is intrinsically safe in any environment and operating conditions.
• Another particular object is that of devising a warp-guard device which may be mounted in different positions and after preparation of the machine onto which it will be applied.
• a warp-guard device for weaving looms, warping machines and knitting machines, comprising sensor means for detecting one or more broken yarns forming part of a series of yarns lying in a warp plane, monitoring means associated with said sensor means for signalling the broken yarns and stopping the machine, characterized in that said sensor means are located inside a tubular body located in the vicinity of the plane of said series of yarns, said tubular body being connected to suction means and being provided with at least one longitudinal slit for sucking through it at least one of the ends of one or more broken yarns intended to interact with said sensor means.
• the device does not possess the traditional drop wires and therefore does not require insertion thereof and for this reason is also suitable for very delicate yarns.
• the device may be arranged in different positions between the beam and the frames, does not required synchronization mechanisms, is self- cleaning and is substantially insensitive to dust and moisture.
• the device may be used safely also with yarns made of conductive material and in potentially dangerous environments since there are no contacts which may cause sparks.
• Fig. 1 shows a schematic perspective view of a weaving machine in which a warp-guard device according to the invention is installed
• Fig. 2 shows a laterally sectioned view of the machine and the device according to Fig. 1 ;
• Fig. 3 shows a perspective view of a partially sectioned detail of the device according to the invention
• Fig. 4 shows a view of the detail of Fig. 3 sectioned along a transverse plane
• Fig. 5 shows a cross-sectional view, on a larger scale, of a detail according to Fig. 4;
• Fig. 6 shows a cross-sectional view of the detail of Fig. 4 along a plane indicated by VI-VI;
• Fig. 7 shows a plan view of the detail according to Fig. 5 in the direction of the arrow VII;
• Fig. 8 shows an exploded view of the detail according to Fig. 4.
• Fig. 9 shows a representation of the operating diagram of a detail of the device according to the preceding figures.
• Fig. 1 0 shows an operating diagram of the circuit logic of the device according to the invention
• Fig. 1 1 shows a block diagram of the software installed in the device according to the invention.
• a warp-guard device denoted in its entirety by the reference number 1 , may be installed on a weaving or knitting loom, on a warping machine or on similar machines in which at least one series of warp yarns F arranged in a plane O are present.
• Figs. 1 and 2 schematically shows a weaving loom which is indicated T and in which two separate warp-guard devices 1 are shown, mounted in two different positions between the beam S and the heald-carrying frames L.
• the device 1 comprises sensor means for detecting one or more broken yarns FR forming part of the yarn O and associated with control means for signalling the abovementioned broken yarns and stopping the machine T.
• the sensor means are of the opto-electronic type and any consist of a first series of emitting elements 2 able to emit light beams B and a second series of receiving elements 3 able to receive the light beams B and interact with a broken yarn. Under normal conditions, the light beams sent by the emitting elements 2 will be captured by the receiving elements 3, generating an electric signal with a constant value which will indicate the continuity of the yarns.
• the emitting opto-electronic elements 2 may consist of infrared LEDs, while the receiving opto-electronic elements 3 may consist of phototransistors sensitive to the same light frequency band as the emitting elements. Both these types of electronic components are widely available commercially and have an extremely low cost.
• the sensor or opto-electronic means 2,3 are housed inside a tubular body 4 located in the vicinity of the yarns F of the warp O and the tubular body 4 is connected, by means of a duct 5, at one or both its ends, to external suction means 6.
• the tubular body 4 is provided with one, or preferably two longitudinal slits 7, 8 for sucking inside it one or both the ends Fi , F 2 of a broken yarn F. Once sucked inside the tubular body 4, the ends Fi, F 2 of the broken yarn will interfere with the light beams B emitted by the emitting elements 2 and will interrupt the electric signal produced by the receiving elements 3, thus allowing the system to detect the breakage and stop the machine.
• the external suction means 6 may consist of a volumetric pump or blower which is low-cost and is widely available on the market and which has a delivery and head sufficient to ensure suction of several yarns inside the tubular body 4.
• these characteristics may be modified by varying the speed of the motor driving the pump or blower by means of an inverter.
• the latter are situated at a predetermined minimum distance D, greater than the height H of the cross-section of the pipe, so as to ensure in any case interruption of the light beams in the event of breakage.
• the tubular body 4 may consist of a profiled section or extruded pipe made of metallic or plastic material, having a constant cross- section and substantially rectangular with rounded edges, with slits 7, 8 arranged along one of its larger sides.
• each receiving element 3 is connected to a corresponding signalling opto-electronic element 9 which emits a light signal W in the event of broken yarns FR being detected.
• the emitting opto- electronic elements 2 and receiving opto-electronic elements 3 which are distributed uniformly over the whole length of said tubular body may be moved towards each other, with a small interval P as required, in keeping with the dimensions of the said elements.
• the emitting opto-electronic elements 2 and receiving opto-electronic elements 3 as well as the signalling elements 9 are mounted on modular printed boards 1 0 which comprise circuit components which are designed to scan the breakages.
• each modular printed circuit comprises about 25 emitting elements 2 and a corresponding number of receiving elements 3 and signalling elements 9.
• the various modular circuits 1 0 are mounted on the tubular element so as to cover its whole longitudinal extension.
• Fig. 10 shows a possible diagram of the circuit logic of each modular board
• All the modular circuits 10 are connected to the same timing signal generator 1 3 and reset signal generator 1 4.
• the microprocessors have, installed them, a program for detecting, filtering and managing the incoming signals as well as for actuating the output commands.
• FIG. 1 1 An example of a program, schematically shown in Fig. 1 1 , envisages an auto- test upon start-up, followed by repetitive and asynchronous cycles for monitoring the infrared LEDs of each modular board 1 0, with a predetermined scanning frequency which is determined on the basis of the following considerations.
• the minimum duration of the signal generated by detection of a broken yarn is equal to about 1 ms
• a sampling frequency of at least 2 kHz for each LED/phototransistor pair is required. Since the pairs installed on each circuit board are equal to about 25, a minimum scanning frequency equal to about 50 kHz is required. Therefore, for safety reasons, a scanning frequency of about 70 kHz was prechosen.
• the counter associated with the corresponding sensor 3 is incremented by one unit. If this counter reaches a predetermined number N of events, it produces stoppage of the machine and the corresponding breakage signal.
• the counters mounted on each board 1 0 are reset cyclically every interval of TRC seconds in order to prevent the accumulation of false events due to disturbances or impurities of the air inside the tubular body 4.
• the electronic circuit may also comprise an interface of the CAN-bus or serial type 1 5, for connection to a central control unit CPU or to a personal computer PC as well as to other external communication devices for the collection, transmission and analysis of the breakage detection data and their statistical frequency, in order to establish a correlation with the possible causes.
• the signalling elements 9 face an element for deviating the optical path, which is located outside the tubular body in order to allow a clear view, on the outside, of the breakage signal.
• this deviating element may consist of a prismatic bar 1 6 with a triangular or trapezoidal cross-section, resting on an open profiled member 1 7 opposite a longitudinal opening 1 8 facing the signalling elements 9.
• the light beams W emitted by the signalling elements 9 may be viewed from the outside on the inclined lateral surfaces of the prismatic bar 1 6.
• the warp-guard device according to the invention achieves the predefined objects and in particular attention is drawn to the high degree of reliability and safety in any surrounding environment, the flexibility of use and positioning on any weaving machine or warping machine, the possibility of use with any type of yarn, the absence of stress for the yarns being monitored, the possibility of connection to PCs or other intelligent devices.
• the device according to the invention has the advantages of an extremely simple and compact structure, a limited weight, a low cost compared to the technological advantages, a notable insensitivity to disturbances of both an electromagnetic and an environmental nature and an extremely low emission of electromagnetic disturbances.
• warp-guard device according to the invention may be subject to numerous modifications and variations all falling within the inventive idea expressed in the accompanying claims. All the details may be replaced by other equivalents without departing from the scope of the invention.
• the warp-guard device has been described with particular reference to the accompanying figures, the reference numbers used in the description and in the claims are used in order improve understanding of the invention and do not constitute any limitation as to the scope of protection claimed.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Looms (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 2000
  • 2000-01-24 IT ITVI20000019 patent/IT1315177B1/it active
• 2001
  • 2001-01-23 WO PCT/IB2001/000076 patent/WO2001053580A1/en not_active Application Discontinuation
  • 2001-01-23 EP EP01901319A patent/EP1252381A1/de not_active Withdrawn

Non-Patent Citations (1)

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