MXPA97010009A - Piezoelectric device of detection of broken filaments and method to use the mi - Google Patents

Abstract

A piezoelectric filament break detection device is used to detect the breakage of a continuous material passing through an access path. The device contains a support member and a sensor member and is positioned adjacent, but spaced apart from the access path so that continuous material passing through the access path does not contact the device. The sensor member has a fixed end and a free end and has on the first face surface thereof (1) a deflectable tongue placed on the free end, (2) a piezoelectric film operably coupled with the deflectable tongue, and (3) an internal switch-circuit element coupled with the piezoelectric film. As the continuous material passes through the access path, the broken ends or ends formed during the breakage of the material come into contact with the deflectable tab. The tongue undergoes a deviation to end or broken end with which it is put in contact. Each deviation causes the piezoelectric film to generate a signal, each signal being processed by the internal circuit switch element and by actuating the switch element internal circuit to a closed position

Description

"PIEZOELECTRIC DEVICE OF DETECTION OF BROKEN FILAMENTS AND METHOD TO USE THE SAME" BACKGROUND OF THE INVENTION This invention relates to a device for detecting broken filaments. More particularly, this invention relates to a device that uses a piezoelectric film to detect and signal the presence of broken filaments, and an internal switch-circuit element to respond to the signals generated by the piezoelectric film. Broken filaments often occur during operations involved in the processing of filaments into strands or strands into strands. The filament breakage may be due to excessive mechanical stresses produced during winding or twisting operations or a defective filament structure caused by a problem in the manufacturing process. Regardless of the cause of the filament breakage, broken filaments that tend to extend out of the strand or yarn at essentially right angles from the shaft of the strand, usually degrade the quality of the articles formed thereof. For example, these articles tend to have gaps or discontinuities that considerably decrease the strength of the articles. In this way, the presence of broken filaments has frequently led to considerable loss of time and product, particularly when large quantities of defective products have formed from the strands containing these filaments. Therefore, it is desirable to provide a means for the early detection of broken filaments in order to avoid product and time loss and increase production. Shock detectors for detecting broken filaments are known in the art. Reference is made, for example, to U.S. Patent Nos. 3,635,413; 5,043,708; 3,800,162; 3,999,695; 4,677,387 and 4,610,707; all references cited above being incorporated herein by reference thereto in their entirety. By means of a resistance change, switch closure, output or output current voltage and the like, the shock detectors provide an indication that a change or event has occurred eg, filament breakage. The use of piezoelectric films in shock detectors to detect broken filaments is also known in the art. Reference is made, for example, to U.S. Patent Nos. 5,136,202; 5,209,119; 4,393,647; 4,110,654; 4,258,565; 5,089,741; 4,605,875 and 4, 361, 111; all references cited above being incorporated herein by reference thereto in their entirety. The use of piezoelectric films provides shock detectors with several benefits. For example, because piezoelectric films spontaneously generate a voltage impulse during the shock, the shock detectors containing these films do not require voltage input or elaborate interface circuitry. In addition, the low sensitivity to dirt and mechanical strength of piezoelectric films make these films particularly suitable for use on or in machines that process yarns. In addition, because piezoelectric films are also relatively inexpensive and simple in structure, the shock detectors using these films also tend to be relatively less expensive and less complicated than shock detectors that do not employ piezoelectric films. Therefore, shock detection devices containing piezoelectric films are continuously desirable to be used to detect broken filaments.

Furthermore, it is desirable to provide a piezoelectric device for detecting broken filaments and a method for using same, wherein the detection device contains an internal switch-circuit element that can be activated by a signal generated by the piezoelectric film in order to allow to take into account the broken filaments through a specified period of time, which is important for the reasons that will be presented below. It is further desirable to provide a piezoelectric device for detecting broken filaments and a method for using same, wherein the detection device need not be in contact with the filament or strand being monitored prior to the breakage of the filament or strand. The continuous contact with the strand or filament imposes a continuous voltage on the piezoelectric film and in this way causes the film to generate a multitude of signals indicating only the continuous contact between the detection device and the passage of the filament or unbroken strand. This continuous contact between the filament or strand and the device, subjects the film to undesirable levels of wear and tear, and complicates the circuit necessary to distinguish between those signals that indicate filament / wire breakage than those signals that reflect continuous contact .

Because filament breakage can be caused by torsion, re-winding and / or other mechanical handling of a strand, the number of broken filaments in the strand can serve as a guide to know if the steering equipment is working properly. and / or if the quality of the fiber manufacturing process is sufficient. For example, the information obtained by means of a broken filament detector can be processed or recorded to determine whether a normal number of defects occurs in a specific thread line, thereby locating defective coils or defective prior processing equipment. Since the defective yarn line is identified, it becomes possible to automatically repair the yarn line with a resulting increase in efficiency and reduction in labor costs. In addition, it is desirable to determine the effect of broken filaments on the total quality of a strand and the effect on strand breakage of changes in the manufacturing process or in the management of the strand. These effects can be determined by determining the number of broken filaments per unit length of the strand to a high degree of accuracy and reliability. Since the number of broken filaments per unit length can be an indication of the cavity of the filaments themselves, the exact detection of these filaments can be an important factor in the control of the process. However, with the number of strand breaks per unit length of the strand, which vary widely not only in a single coil, but also among the number of coils from the same forming package, the breakage of the strands in a strand has always been found that it is of an extremely random nature. The random nature of filament breakage makes it difficult to know for sure if it was a specific measurement, taken from a relatively short length of strand, accurately reflecting the average amount of breakage that occurs in the total strand. In this way in order to accurately monitor the quality of a filament manufacturing process and / or the mechanical handling of the filament strands, it would be desirable to provide a broken filament detection device and a method for using same, wherein the The detection device may be used in conjunction with a recording apparatus or counter to provide an accurate measure of the degree of breakage of filaments that occur in a specific strand during a specific manufacturing or processing operation. Accordingly, a main object of this invention is to provide a shock detection device and a method for using same, wherein the detection device is capable of detecting filament breakage and providing an output signal indicative of this event. A further object of this invention is to provide a broken filament shock detection device and a method for using same, wherein the detection device uses a piezoelectric film to detect and signal the presence of broken filaments. A still further object of this invention is to provide a broken filament shock detection device and a method for using same, wherein the detection device contains an internal switch-circuit element. Another object of this invention is to provide a broken filament shock detection system and a method for using same, wherein the shock detection system is capable of obtaining an accurate account of the number of broken filaments that occur in a strand to through a specified period of time. Still another object of this invention is to provide a broken filament shock detection device and a method for using same, wherein the shock detecting device does not need to have physical continuous contact with a continuous material that is being monitored. These and other objects that are achieved in accordance with the present invention can be readily discerned from the following description.

COMPENDIUM OF THE INVENTION The present invention provides a piezoelectric device for detecting broken filaments and a method for using same, for detecting the breakage of a continuous material that moves through an access path, wherein the device contains: (A) a member of support positioned adjacent to and separated from the access path such that the continuous material passing through the access path does not contact the detection device; and (B) a sensor member having a fixed end and a free opposite end, the fixed end being integral with the support member, wherein the sensing member further contains on a first facial surface thereof: (1) a deflectable tab placed on the free end of the sensor member, the deflectable tab is positioned to receive the broken ends formed from the continuous material during the breaking thereof in the access path, wherein the deflectable tab is adapted in such a way that each shock of a broken point in it causes the tongue to experience a deviation; (2) a piezoelectric film operably coupled with the deflectable tab so as to generate a signal for each deviation of the tab, the deflectable tab and the piezoelectric film each having a sufficient length to effectively detect the impact of a broken line; and (3) an internal switch-circuit element coupled with the piezoelectric film in order to process each signal generated by the film. In the preferred embodiments of the device of this invention, a screw is fixed with bolts on the first face surface of the sensor member at the fixed end thereof, the screw extends above a portion of the deflectable tongue and can be rotated to apply tension to the tongue in order to reduce false alarms caused eg by the air tubule. In the device of this invention, the piezoelectric film and the deflectable tab are placed mutually in such a way that the deviation of the deflectable tab transmits a deformation stress on the piezoelectric film which in turn causes the film to generate a signal which is then transmits to the switch-circuit element. Preferably, the switch-circuit element will be placed in an open position if there is no signal or if an insufficient signal is generated by the piezoelectric film and placed in the closed position upon receipt of a sufficient signal or signal from the piezoelectric film. The closure of the switch-circuit element can be designed to activate a digital counter or brush registration apparatus placed in electrical communication therewith to enable account to be given of the broken filaments that occur in a given strand over a specified period.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a broken filament detection device, within the scope of the present invention. Figure 2 is a simplified schematic top view of a broken filament detection system incorporating the detection device of this invention, and a digital counter electrically coupled to the device.

DETAILED DESCRIPTION OF THE INVENTION Although for convenience purposes the filaments or yarn are of specific continuous materials described herein in connection with the present invention, it should be understood that the present invention is applicable to any type of continuous material that is to be supervised for breakage. However, in the preferred embodiments of the invention, the broken filament detection device and the method of this invention are used in relation to materials having a relatively high denier, e.g., carpet yarn. As used herein, the term "broken end" or "broken filament end" refers to the projection end of a single filament or to a fragment that has completely separated from a broken filament. As stated in the above, the device of this invention contains a support member and a sensing member. The support member is preferably adjacent to an access path through which a continuous material passes, preferably in a longitudinal direction. The sensing member has a displaceable tongue, a piezoelectric film operably coupled with the deflectable tongue and a switch-circuit element electrically coupled to the piezoelectric film on a first face surface thereof. The path of the continuous material preferably is provided by a guide means placed in a package winding system. Preferred winders include those used for winding devices for plastic filaments and in other yarn processing devices. The support member is a rigid structure that serves as a base or clamp for a fixed end (s) of the sensing member. Although it can be formed of any rigid material, the support member typically is formed of a conductive material, e.g., a metal or an insulating material, e.g., plastic. If it is composed of an electrically conductive material, the support member must be isolated from the piezoelectric film in order to avoid shorting the film. The preference sensing member is in the form of a cantilever beam wherein one end of the beam is integral with or otherwise secured to the support member while the other end of the beam is free. The preference sensor member is composed of a metal, preferably zero, such as eg, spring steel SAE 1095, tempered with blue heat. The sensor member has a first facial surface where a deflectable tab, a piezoelectric film and an internal switch-circuit element are formed. The deflectable tab is placed on the first portion of the facial surface of the free end of the sensor member. The deflectable tab is positioned to experience a deflection each time it is incised by a broken cape formed when the continuous material breaks while passing through the adjacent access path. Preferably, the deflectable tab is relatively thin with a preferred thickness of less than 1.0 millimeter. A piezoelectric film is operably coupled with the deflectable tab in order to generate output signals when the tab is incised by one end of the broken filament. Preferably, the piezoelectric film is in the form of a strip that is linked to the first face surface of the sector member which, as stated above, is preferably in the form of a cantilevered beam. Preferably, the positive side of the film is placed between the negative side of the film (which is connected to ground) and the first facial surface of the sensor member (which is also connected to ground). The piezoelectric film can be attached to the sensor member by means of an adhesive, e.g., a conventional gauge adhesive. The adhesive may also function to electrically isolate the positive side of the film from the first facial surface of the sensor member. A conductor can be attached to the non-adhesive side of the film, eg, by an appropriate conductive epoxy material. The sensitivity of the piezoelectric film will generally depend on the length of the film. The length of each of the deflectable tab and the piezoelectric film must be one that is sufficient to effectively detect the impact of the broken end or end. Preferably, the piezoelectric film used in the present invention will have a length of about 1.1 centimeters to about 4.1 centimeters, more preferably from about 2.1 centimeters to about 4.1 centimeters, and especially preferably from about 3.0 centimeters to about 4.1 centimeters.

The deflectable tab used in the present invention preferably has a length of about 2.4 centimeters to about 6 centimeters, more preferably from about 3 centimeters to about 6 centimeters, and especially preferably from about 4.5 centimeters to about 6 centimeters. The thickness of the piezoelectric film will depend on several factors, including, for example, the specific piezoelectric properties desired, the specific application of the film and the method used to deposit the film. For applications proposed by means of the present invention, the piezoelectric film preferably has a thickness of about 0.762 millimeter. Appropriate piezoelectric films that may be used in the present invention include, e.g., those disclosed in U.S. Patent No. 5,136,202, which has been incorporated hereinbefore in its entirety. Therefore, a piezoelectric film can be composed for example of a polymeric piezoelectric material such as polyvinylidene fluoride (PVDF); a vinylidene fluoride (VDF) copolymer such as a VDF copolymer with at least one of trifluoroethylene (TrFE), tetrafluoroethylene, hexafluoroethylene, or vinylidene chloride; a polyvinyl chloride polymer; or a polymer of an acrylonitrile. A specific preferred material for the film is polyvinyl fluoride (PVF2) • As stated above, the piezoelectric film generates a signal during a deflection of the deflectable tab thereby indicating that filament breakage has occurred. This signal is then detected and processed by the switching-circuit element coupled with the piezoelectric film. Any suitable switch-circuit element can be used to process the signals produced by the piezoelectric film. As mentioned hereinabove, the switch-circuit element is preferably adapted in such a way that in the absence of a signal or a sufficient signal generated by the piezoelectric film, the switch-circuit element is placed in an open position , while during receipt of a sufficient electrical signal generated by the piezoelectric film, the switch-circuit element is driven to a closed position. As also stated hereinabove, the switch-circuit element may also be electrically coupled by means of an external circuit means with a brush registration apparatus in order to determine the magnitude of a filament break or with a digital counter to determine the number of broken filaments. The external circuit means is preferably placed on a circuit board that is fixed to a portion of the support member of the detection device. The present invention is further directed to a detection system for detecting the breakage of a continuous material. This system is comprised of a detection device of this invention coupled with a control function device such as a digital counter or a brush registration apparatus. Another aspect of the present invention is directed to an apparatus for forming and / or processing a continuous material, preferably filaments or strands, composed of a continuous material forming processing device coupled with the detection device or detection system of this invention, wherein the detection device is placed adjacent to an access path through which the continuous material passes, in addition where the detection device is separated from the access path in such a way that the continuous material passing to through the access path does not contact the detection device. This apparatus is preferably composed of a filament spinning device or other thread processing device. A further aspect of this invention is directed to a method for detecting breakage of a continuous material by means of the detection device of this invention. Broadly, this method involves: (i) providing the piezoelectric filament break detection device of this invention; (ii) placing the device adjacent to, but detached from, the access path such that the continuous material passing through the access path does not contact the device; and (iii) directing the continuous material through the access path in such a way that the broken ends or ends formed during the breakage of the material in the access path are brought into contact with the deflectable tongue in such a way that the tongue undergoes a deviation for each broken line that comes in contact with the tongue, causing the deviation that the piezoelectric film generates a signal in response to the deviation, the signal being processed by the internal circuit-switch element and actuating the switch element -Internal circuit in a closed position. Typically, the "access path" through which the thread passes in accordance with the present invention is the guide pulley where the thread rotates around the guide pulley. In general, the detection device of this invention will be placed perpendicularly with respect to the guide pulley since the broken filaments will detach from the guide pulley as the threads rotate about it. Typically, the detection device will be placed at a distance no greater than about 2.54 centimeters from the guide pulley. In some applications, eg, winding of the multiple lengths of the yarn in the warp beam, a large number of detection devices within the scope of this invention can be used, with each device preferably being coupled with a counter. digital, where each thread length is monitored by an individual detection device and a counter system. The multiplexing circuit may be provided to transfer the data in each of the corresponding latching circuits in sequence to the corresponding storage locations, for example, in a microprocessor or computer.

The present invention will now be described with reference to Figures 1 and 2 of the present. In Figure 1, the broken filament detection device 100 includes a sensor member that is in the form of a flat cantilever beam 102 having a free end portion 106. Positioned on the end portion 106 is a deflectable tab 108 that is flat and extends outwardly. The end portion 104 of the beam 102 is fixed to the support member 110 (shown in dashed lines). Placed on a first facial surface 112 of the beam 102 is a deflectable portion 114, a piezoelectric film 116 and a switch-circuit element 118. In the end portion 104 conductors 120 and 122 are placed. In a preferred embodiment of device 100, a pexiglass tab (not shown) is fixed with bolts to the device 100 in 124 and 126, and extends over an upper portion of the deflectable tab 108. The plexiglass tongue has a screw on the opposite end that can be rotated to apply tension to the tongue 108 in order to reduce false alarms due to air turbulence. In another embodiment of this invention, a control function device (not shown), such as a digital counter or brush recording apparatus, can be electrically coupled to the switch-circuit element 118 via leads 120 and 122. Figure 2 illustrates a detection system within the scope of this invention, wherein the system contains a detection device within the scope of this invention coupled with a control function device which is preferably either a digital counter or a brush registration device. In Figure 2, "R] _" and "R2" represent first and second current limiting resistors respectively; "V" represents a power or voltage supply means; and "Vg ^ i ^" represents the output voltage. In Figure 2, the system 200 is comprised of a detection device 202 and a function-control device 204 that are electrically connected to one another by means of an external circuit 206 having conductor wires 208 and 210. The electrical signals generated by a piezoelectric film (not illustrated) in the device 202 and processed by a switch element and a circuit (not shown) in the device 202, are transported through the circuit 206 to the device 204 through the lead wires 208 and 210. If the device 204 is a digital counter, the counter counts the signals generated by the piezoelectric film and the switch-circuit element. This count will continue until a stop or stop signal is received by device 204 from the circuit-switch element. The number of signals received by the counter will be characteristic and will identify the faulty strand line. This information can be used directly and can be converted to another form if desired.

EXPERIMENTAL Examples A and B of Comparison and Examples 1 and 2 of the Invention In Examples A and B of comparison and the Examples 1 and 2, four cantilevered sensor members coated with piezoelectric films of variable film lengths (as measured from the front edge of the silver ink) and deflectable tabs of different lengths and different thicknesses were tested to determine the capacity of the films. same to detect the broken filaments. In the examples presented below, the detection device was placed perpendicularly with respect to the guide pulley.

In Comparative Example A the piezoelectric film had a length of about 1.1 centimeters while the deflectable tab had a thickness of about 0.762 millimeter and a length of about 2.4 centimeters. In Comparison Example B, the piezoelectric film had a length of about 1.1 centimeter, while the deflectable tongue had a thickness of approximately .0762 millimeters, and a length of approximately 4.5 centimeters. In Example 1 of the invention, the piezoelectric film had a length of approximately 2.1 centimeters while the deflectable tab had a thickness of approximately 0.762 millimeters and a length of approximately 4.5 centimeters. In Example 2 of the invention, the piezoelectric film had a length of about 4.1 centimeters and a deflectable tab had a thickness of about 0.762 millimeters and a length of about 5.0 centimeters. Only the detection devices of Examples 1 and 2 of the invention detected filaments. The device in Example 2 had a detection rate of 50 percent and was no more sensitive than the device in Example 1. The device in Example 1 was damaged when the strand line broke. With a graphics recorder connected in parallel with the digital counter, the detection rate for all devices increased dramatically. The devices in Examples 1 and 2 were also more sensitive to air turbulence than the devices in Comparison Examples A and B. Although preferred embodiments of the present invention have been shown and described, it should be understood that the invention is not limited thereto, but may be encompassed in several other manners and be practiced within the scope of the following claims.

Claims (12)

R E I V I N D I C A C I O N S

1. A method for detecting the breakage of a continuous material passing through an access path, comprising the steps of: (i) providing a piezoelectric device for detecting broken filaments; (ii) placing the device adjacent to, but separated from, the access path such that the continuous material passing through the access path does not contact the device, wherein the device comprises: (A) a support member positioned adjacent to, and spaced from, the access path such that the continuous material passing through the access path does not contact the detection device; and (B) a sensor member having a fixed end and an opposite free end, the fixed end is integral with the support member, wherein the sensor member further contains on a first face surface thereof: (1) a deflectable tab placed on the free end of the sensor member, the deflectable tab is positioned to receive the broken ends formed from the continuous material during the break thereof in the access path, wherein the deflectable tab is adapted in such a way that each shock of a broken end in it causes the tab to experience a deviation; (2) a piezoelectric film operably coupled with the deflectable tab to generate a signal during each deviation of the tab, the deflectable tab and the piezoelectric film each having a sufficient length to effectively detect the impact of an end or end broken; and (3) an internal switch-circuit element coupled with the piezoelectric film in order to process each signal generated by the film; and (iii) direct the continuous material through the access road.

2. A method according to claim 1, wherein each signal generated by the film causes the internal switch-circuit element to move to a closed position.

3. A method according to claim 1, wherein in the absence of a signal from the film, the internal switching element is placed in an open position.

4. A method according to claim 1, wherein the sensor member is a cantilevered beam.

5. A method according to claim 1, wherein the deflectable tab has a length of about 2.4 to about 6.0 centimeters.

6. A method according to claim 1, wherein the piezoelectric film comprises a material that is selected from the group consisting of polyvinylidene fluoride; a vinylidene fluoride copolymer; a copolymer comprising vinylidene fluoride and at least one of trifluoroethylene, tetrafluoroethylene, hexfluoroethylene and vinylidene fluoride; a polyvinyl chloride polymer; and an acrylonitrile polymer.

7. A method according to claim 6, wherein the piezoelectric film comprises polyvinyl fluoride.

8. A method according to claim 1, wherein the piezoelectric film has a thickness of about 0.762 millimeters.

9. A method according to claim 1, wherein the piezoelectric film has a length of about 1.1 to about 4.1 centimeters. A method according to claim 1, wherein the device further comprises an external circuit means coupled to the switch-circuit element. 11. A method according to claim 10, wherein the device further comprises a control function device electrically coupled to the switch-circuit element by means of an external circuit. 12. A method according to claim 11, wherein the control function device is a digital counter or a brush registration apparatus.