AND DEVICE

Field of the Invention

This invention relates to a method and device for measuring and, if desired, recording the speed with which a filamentary structure, such as a thread or yarn or an optical fiber or the like, unwinds from a package, such as a winding supported on a cylindrical or a conical bobbin.

Background of the Invention

For some industrial purposes, whenever windings of filamentary structures are created, as in the textile industry, in the electrical motor industry, in many applications concerning optical fibers, etc., and for designing and testing unwinding methods and/or apparatus, it may be necessary to measure the speed at which a filamentary structure unwinds from a package, such as e.g. a winding supported on a cylindrical or conical bobbin. By "filamentary structure" is meant in this description and claims any continuous structure that is sufficiently flexible and has a sufficiently small cross-section to be windable on a support, such as a bobbin. Examples of such structures are monofilament and multifilament threads, yarns, optical fibers, wires, cables and the like. The support on which the filamentary structure is wound will be called herein "bobbin", regardless of whether it is conical or cylindrical, provided with flanges or not. The bobbin, together with the filamentary structure supported thereon, regardless of their shape, will be called herein "package".

It is highly desirable to be able to determine and register the speed of unwinding or payout of filamentary structures, preferably in a quasi-

continuous manner. By determining and recording a quantity that is a function of a variable "in a quasi-continuous manner" is meant herein determining and recording its value at very short intervals of the variable, e.g. of time, whereby to obtain a sufficient number of experimental points to be able to draw a curve through them with reasonable accuracy. In some cases, however, a determination that is definitely discrete and not quasi-continuous may be adequate, and this invention is applicable to obtain such discrete determinations as well. The unwinding or payout speed of a filamentary structure from a package undergoes, apart from systematic variations that are the foreseeable consequence of the package structure and of the forces that determine the unwinding, uncontrolled variations that are sometimes unpredictable and/or random or a function of environmental conditions, which generate undesirable variations in the tension of the filamentary structure and in the frictional engagement of the portion of the structure that is being detached from the package with the underlying layers of the package itself. It is desirable to control and to eliminate such variations insofar as is possible, and a preliminary step in doing so is to determine them accurately. On the other hand, they should be determined without interfering with the dynamics of the unwinding of the filamentary structure and without creating parasitic tensions and friction. Furthermore, sharp unwinding speed variations are indicative of irregularities in the unwinding process, which may have far-reaching negative consequences in any process of which the unwinding is a part, for example if the filamentary structure is an optical fiber which transmits information from a flying object or is a cable laid under water, or the like. It is to the detection of such sharp speed variations that this invention is particularly directed.

It is a purpose of this invention to provide a method and a device for measuring the unwinding or payout speed of a filamentary structure from a package, which afford determination and registration of the speed at very short intervals, viz. afford a "quasi-continuous" measurement and registration without interfering with the dynamics of the unwinding.

It is another purpose of this invention to provide such a method and device that are accurate, inexpensive and space-saving.

It is a further purpose of this invention to provide such a method and device which permit measurement and registration of the unwinding speed at desired time intervals, viz. with a desired degree of quasi- continuity, or, in other words, in a manner that can vary from the discrete to the practically continuous, as desired.

It is a still further purpose of the invention to provide such a method and device which can be carried into practice by the use of components that are readily available on the market.

Additional purposes and advantages of the invention will appear as the description proceeds.

Summary of the Invention

The method for measuring the unwinding or payout speed of a filamentary structure from a package, expressed as package turns unwound or paid out per unit of time - which will be called hereinafter, for the sake of brevity, "coil unwinding speed" - comprises measuring said speed by determining and recording the moment at which the filamentary

structure reaches and passes two fixed angular positions about the periphery of the package. The portion of each turn, that is comprised between said two fixed angular positions, will be called hereinafter "turn fraction" and the length of filamentary structure comprised in said portion will be called hereinafter "turn fraction length". If said two angular positions coincide, viz. the successive passages of the yarn through a single predetermined angular position are recorded, the fraction of a turn is actually an entire turn and the length of filamentary structure comprised therein will be called hereinafter "turn length". Since however this is not necessarily so - e.g., if there are two angular positions offset by 180° from one another, the turn fraction will be one half of a turn - the method of the invention may be defined, in general, as being characterized in that the time intervals, during which a predetermined fraction of a turn of the winding unwinds therefrom, are measured by determining and recording the moment at which the filamentary structure reaches and passes two fixed angular positions about the periphery of the package, which positions correspond to the beginning and the end of said turn fraction. The successive passages of the filamentary structure through the aforesaid angular positions are registered as pulses, the distance measured in terms of time between two successive pulses constituting the time interval through which the predetermined fraction of a turn of the filamentary structure is unwound.

According to an aspect of the invention, the passages of the filamentary structure through the aforesaid angular positions are detected by monitoring the interference of the yarn with radiation, preferably a narrow radiation beam, that is generated at said angular positions, said interference may e.g. consist of the reflection of the radiation by the

filamentary structure, whereby it will be deflected from its normal path to a -direction in which it will be sensed and detected, or of the interception of the radiation, whereby it will be deflected from its normal path, in which it is sensed and detected, to a direction in which it will not be so sensed and detected.

Since in the winding art it is known to determine, for any particular geometry of package, the length of filamentary structure comprised in a turn and in any given fraction thereof, the length of filamentary structure unwound per unit of time may be easily calculated from the coil unwinding speed determined according to the invention. However, in general, a good approximation is obtained by assuming the coil diameter as constant.

The hereinbefore mentioned "fraction of a turn" might even be a number of turns, e.g. a single angular position might be provided, and though all the passages of the yarn through said position would be sensed, not all of them, e.g. only one out of two or more, might be recorded. While this embodiment of the invention is generally not a preferred one, it might be adopted, if desired.

According to another aspect of this invention, a device for measuring the coil unwinding speed is provided. Said device comprises radiation emitter means located at least one angular position with respect to the package, radiation sensor means spaced from said radiation emitter means and located at a corresponding angular position, and means for continuously recording the response of said radiation sensor means to radiation emitted by the radiation emitter means and received by said radiation sensor

means, whereby changes in said received radiation, due to the interference with it of the filamentary structure passing in the zone in which said radiation emitter and sensor means are located, are detected and recorded. The passing filamentary structure may e.g. reflect towards the sensor means radiation which otherwise would not be received by it or intercept radiation that otherwise would be received by said sensor means. In either case the change in the radiation received by the sensor means is recorded and reveals the passage of the filamentary structure through the angular position at which the radiation is produced. In view of the speed with which the filamentary structure normally unwinds in the applications for which this invention is intended, the time interval through which the radiation sensor means respond to the interference of the filamentary structure with the radiation is very short and can be regarded as a substantially instantaneous pulse. In this sense, such expressions as "the filamentary structure passing in front of the radiation emitter and sensor means" should be understood. Actually the time interval through which radiation is interfered with by the filamentary structure is the time during which said structure traverses the space comprised in the angle between the angular position of the emitter and sensor means, but since said time is very short, said interference may be considered as practically instantaneous, viz. as a pulse.

The radiation preferably consists of narrow beams. The emitter means are conveniently, though not necessarily, LEDs or lasers and the radiation sensor means are conveniently, though not necessarily, the components known as "reflective sensors" or "photodetectors", and all are readily available on the market.

In an embodiment of the invention, the radiation emitter and the radiation sensor may be mounted on the support of the package itself. If the package is, e.g. a flanged bobbin, they are conveniently mounted at or close to its rim, in such a position that they will not interfere with the winding and unwinding of the filamentary structure and yet the sensor will maintain a line of sight with the unwinding filamentary structure. Only one pair of emitter and sensor may be used, and then they may be placed at any angular position. In that case the passage of the filamentary structure will be sensed and registered at each turn, and the time interval between pulses of the reflective sensor will correspond to the unwinding of one turn, viz. will be the inverse of the coil unwinding speed. Alternatively, a number of pairs of emitters and sensors may be located about the periphery of the package. If they are located at regular angular intervals, the time interval between pulses of the reflective sensors will correspond to the passage of a predetermined fraction of a turn. If, for structural reasons, it is preferred to located them irregularly, viz. at different angular intervals, about the periphery of the package, the means for recording the response of said radiation sensor means will be suitably programmed to take into account said different intervals, and the consequent differences in the various turn fraction lengths.

Description of the Drawings

In the drawings:

- Fig. 1 is a perspective view illustrating an unwinding package provided with a single, schematically indicated, pair of radiation emitter and sensor;

- Fig. 2 is a plane view from the top of the package of Fig. 1;

- Fig. 3 is a schematic illustration of the operation of the radiation emitters and sensors;

- Fig. 4 is a plane view from the top of an unwinding package provided with four, schematically indicated, pairs of radiation emitter and sensor;

- Fig. 5 is an example of the registration of pulses of a reflective sensor; and

- Fig. 6 schematically illustrates an another embodiment of the invention.

Description of Preferred Embodiments

In Figs. 1 and 2 an embodiment of the invention is schematically illustrated, in which the support of the filamentary structure package is a conical bobbin, generally indicated at 10, from which a filamentary structure 11, which may be, e.g., an optical fiber or textile yarn or thread, such as a single filament or multifilament thread, is unwound by unwinding means which is not shown, as it can be of any convenient, conventional kind. The fiber or yarn 11 assumes a generally spiral-like configuration after becoming detached from the package surface at the point indicated by 12. Numeral 13 indicates what will be called hereinafter a "filamentary structure passage detector", or briefly a "passage detector", which comprises a radiation emitter 14, such as a LED or a laser, and a radiation sensor 15, such as a photodetector.

Fig. 3 schematically indicates the operation of the filamentary structure passage detector, in the embodiment of Figs. 1 and 2, in which the interference of said structure with the radiation consists in reflecting it to a sensor that would normally not receive it. In the absence of a filamentary structure, the radiation of the emitter will not impinge on the sensor and sensitize it. When the filamentary structure 11, shown in greatly ^' enlarged scale, passes in front of the passage detector, viz. in front of the radiation emitter and sensor, or more precisely, in the angular interval indicated by α in Fig. 3, wherein the angle cc is greatly exaggerated for purposes of illustration, the radiation from the emitter 14 impinges on filamentary structure 11 and is reflected thereby to the sensor 15, thereby activating it. The sensor activation produces a pulse and the instants at which the pulses occur are registered in any convenient way, e.g., in the memory of a computer.

Fig. 4 illustrates ,an embodiment of the invention in which there are four filamentary structure passage detectors arranged at the periphery of the filamentary structure package at angles of 90° the one from the other. The pulses obtained from the various sensors in this way will be 4 for each turn of the filamentary structure and thus the time interval between two successive ones will indicate the unwinding of one-fourth of a turn of said structure.

Fig. 5 shows an example of a diagram recording the pulses produced by a sensor or sensors in an embodiment of the invention. The abscissa is the time in seconds. The ordinate measures, in any convenient scale, e.g. in units of electric tension, the intensity of the pulses. This intensity is not relevant in itself: it is sufficient that the pulses be clearly indicated by a

sharp variation thereof, as seen in the drawing. If the number of pulses per second is "p", and there are " " filamentary structure passage detectors, the coil unwinding speed will be p/m turns per second. The diagram of Fig. 5 may be printed if desired, but this is not necessary: it suffices that the coil unwinding speed as a function of time is stored e.g. in a computer memory (and if desired, is correlated to the turn length or turn fraction length expressed as functions of the number of turns unwound and therefore as a function of time).

Fig. 6 schematically illustrates another embodiment of the invention, in which the passage of the yarn through a predetermined angular position is signaled by its intercepting, instead of reflecting, a beam of radiation. The package support is a flanged bobbin (shown in schematic plan view) generally indicated at 21. A source of radiation 20 is mounted on flange 25 of the bobbin, which flange is fragmentarily shown, and emits a beam of radiation 22 towards a detector 23, which is placed at a distance from the bobbin. Filamentary structure 24 passes in front of said detector and intercepts the beam. In every other respect, this embodiment of the invention does not differ from the previously described ones. Of course, a plurality of emitter-detector pairs could be provided at different angular positions, instead of a single one. It will be understood that, when the yarn intercepts the beam, between each emitter and the corresponding detector there must be an unobstructed line of sight, and their locations with respect to the package must be such as to provide it. Provided that this condition is satisfied, the emitter or emitters could be placed either inside or outside the package, and the detector or detectors on the opposite side, either outside or inside the bobbin; or the emitter or emitters could

be placed on the bobbin, if its structure permits it, as in the case of Fig. 6, and the detector or detectors outside the package.

It is to be noted that this invention permits to measure very high unwinding or payout speeds, particularly since the turn fractions, the unwinding of which is counted, can be submultiples of a turn, viz. emitters and detectors can be placed at a plurality of angular positions. Further, it is applicable to all kinds of filamentary structures, including metal filaments, dielectric ones, coated or colored filaments of any kind, and so on. Therefore it provides a substantial improvement over prior art methods and devices.

While specific embodiments of the invention have been described for the purpose of illustration, it will be understood that the invention may be carried into practice by skilled persons with many modifications, variations and adaptations, without departing from its spirit or exceeding the scope of the claims.