WO2001053575A1 - Textile yarn containing magnetic fibers for use as magnetic marker - Google Patents

Abstract

A magnetic marker comprises a composite textile yarn which is a combination of textile fibers and soft magnetic fibers. The marker may function as a detector element incorporated in an article of commerce or in product label, tag or packaging. The amount of magnetically soft metal within the marker can be easily varied without significantly changing the dimensions, tensile strength or handling requirements of the marker. Thus the marker may be used to apply the desired minimum amount of magnetically soft detectable material to packages or products of different sizes, in a convenient and cost-effective manner. Deactivation of the marker may conveniently be achieved using one or more mechanically continuous wires or strips, which have been treated so as to comprise an arrangement of both magnetizable and non-magnetizable body segments.

Description

TEXTILE YARN CONTAINING MAGNETIC FIBERS FOR USE AS MAGNETIC MARKER

TECHNICAL FIELD This invention relates to a detectable magnetic marker for use as a surveillance marker. BACKGROUND ART

Theft of articles has long been, and continues to remain, a serious problem for the retail industry. Stock shrinkage may account for several percent of inventory and has a serious impact on the small profit margin of the typical retail outlet. In a similar way public lending institutions, such as libraries, also suffer severe losses through the unlawful removal of items.

Several security systems are currently available to reduce the risk of theft. Electronic article surveillance (EAS) systems generally comprise a marker, which is attached to the article to be protected, and a transmitter/receiver able to detect the marker as it passes through an interrogation zone. In most cases the marker is additionally provided with the ability to be deactivated, so that the marker does not have to be removed from the article upon legitimate purchase or authorized borrowing, but may simply be deactivated. Such deactivation capability is of particular importance when the marker is incorporated within the protected article, or within its packaging, because it may not be practical to find and remove the marker. Typically the marker is in the form of a tag which is applied to the article in the store or lending institution. Increasingly, in order to save on labor cost, retailers have pressed manufacturers to incorporate the tag either in the article at the time of manufacture or else into the packaging, so-called Source Marking. Source Marking places two major requirements on the markers that are to be included in the packaging: The marker must be able to be incorporated into the package without being easily detected or easily removed, and, as all packages are tagged as opposed to just a sample, as is currently the case, the marker must be low in cost, both for the item itself and its application. An important requirement is ease of integration of the step of incorporating the marker into the package in high-speed commercial manufacturing and packaging production lines. For example, tags that are in the form of labels or label- sized objects are often difficult to incorporate within the article, and applying them to the packaging typically slows up the production rate and hence increases the manufacturing cost. Also the packaging materials or process may seriously interfere with the operation of the marker, causing it to be ineffective. Some anti-pilferage markers, for example, those operating at radio frequencies, become undetectable if surrounded by an electrical conductor, such as a metal foil, while other types are ineffective if distorted or otherwise subjected to a mechanical force.

Markers in the form of discrete labels present handling problems for source marking, since even high speed label applicators generally cannot keep pace with typical production lines which manufacture packaging materials. Moreover, the majority of existing discrete labels have physical dimensions too large to incorporate into packages in an unobtrusive manner.

There is therefore a need for Source Marking tags that are low in cost, that are unaffected by normal packaging materials or procedures and that are available in a form that allows high speed application either to the product or to its package.

Electromagnetic marker materials in the form of metal strips or wires can be unobtrusive and are generally unaffected by packaging materials and procedures and are amenable to high speed application if dispensed in continuous form into packaging materials, and thereafter cut with the packages when the packages are cut out. In such a process, the marking of each package requires a length of marker material approximately the length of the package itself. However, detection performance of such marker materials can generally be achieved with much shorter lengths, and the additional marker length within the package, or lost in the processing, is an undesirable waste and a prohibitive expense. For example, markers as taught in U.S. Patent RE 32427, which consist of a strip of soft magnetic material with distinct pieces of a second harder magnetic material affixed to one side, are typically too expensive to apply in the lengths of many packages.

Fabrication of much thinner strips or wires of such marker materials, to provide the minimum mass of magnetic materials per package length, would be costly and impractical and would present numerous handling challenges due to the fragility of such materials. A continuous marker material, in which the loading of costly magnetic components per unit length could be tailored to give the correct amount per package length, without strongly affecting the marker strength, dimensions or handling requirements would clearly be beneficial.

Markers that are used in retail anti-theft systems can also be used to tag objects with a view to detecting their presence or absence. An example is the tagging of surgical sponges. (See U.S. Patents 5,456,718 and 5,664,582) to reduce the chance of their being accidentally left in a patient after a surgical procedure. Current markers are unsuitable for this application being too large and of an inappropriate form to be attached to the sponge. The present invention is designed to overcome these drawbacks; and to provide a marker which can be employed alone or in conjunction with a deactivating element, depending on the intended use. DISCLOSURE OF THE INVENTION The invention seeks to provide a detectable magnetic marker for surveillance purposes.

The invention also seeks to provide a product label, tag or packaging, or an article of commerce having incorporated therein a magnetic marker of the invention. Still further the invention seeks to provide a combination of the magnetic marker of the invention and a deactivating element for the marker.

Still further the invention seeks to provide a composite article comprising the magnetic marker of the invention and a deactivating element for the marker.

Still further the invention seeks to provide a product label, tag or packaging, or an article of commerce having incorporated therein a magnetic marker or combination as described hereinbefore.

In accordance with one aspect of the invention there is provided a magnetic marker comprising a composite textile yam, said yam comprising a combination of textile fibers and soft magnetic fibers.

In accordance with another aspect of the invention there is provided a deactivatable magnetic marker assembly comprising: at least one detectable magnetic marker adapted to provide a desired magnetic signal, in combination with at least one deactivating element, said deactivating element as magnetized, deactivating said magnetic member, said at least one detectable magnetic marker being a magnetic marker of the invention. In accordance with still another aspect of the invention there is provided a product label, tag, packaging or an article of commerce having incorporated therein a magnetic marker of the invention.

In accordance with yet another aspect of the invention there is provided a product label, tag, packaging or an article of commerce having incorporated therein a deactivatable magnetic marker assembly of the invention.

DESCRIPTION OF BEST MODES i) Magnetic Marker The textile fibers of the composite textile yarns may be selected from conventional textile fibers, for example, synthetic fibers such as polyester, polyamide, polypropylene, Nylon fibers or rayon; or natural fibers such as cotton or wool or semi-synthetic fibers.

The textile fibers may be filaments or staple fibers. Suitable staple fibers have a length of 1.5 to 20, preferably 5 to 12 cm and a cross- sectional diameter or width of 10 to 50, preferably 20 to 30, and typically 25 microns.

The textile fibers comprise the major component of the composite textile yam by volume. In general, on a weight basis, the soft magnetic fiber content of the composite yam is in the range of 0.5 to 95%, preferably 5 to 60% and most preferably 20 to 40%, by weight.

The composite yarn generally has a mass of 10 to 500, preferably 5 to 200 and most preferably 50 to 150 mg/meter. The detectable soft magnetic fibers are, in particular, metal or metal alloy fibers suitably having a value magnetostriction close to zero and a coercivity of less than 0.1 kA/m. The soft magnetic fibers may be filaments or staple fibers. Suitable staple fibers typically have a length of 1.5 to 15, preferably 3 to 10 cm and a diameter or cross-sectional width of 10 to 80, preferably 20 to 40, more preferably 25 to 35 and typically 30 microns. The soft magnetic fibers are typically contained within the textile yam in an amount of 1 to 100 mg/m, preferably 5 to 30 mg/m of the composite yam. The loading is determined in large part by the ratio of magnetic fiber to textile fiber in the manufacturing process of the composite yam. The magnetic fibers may be of an amorphous metal or a crystalline metal. The magnetic fibers may suitably be formed by rapid solidification of a molten metal or metal alloy, especially a molten ferromagnetic metal of alloy. Rapid solidification results in fibers in a state of stress, and a molecular orientation that is favourable with regard to magnetic properties in the fiber as solidified. The fiber form also results in a favourable length to diameter ratio that maximizes the magnetic response.

The composite yarn of the invention permits the use of fine metal fibers whereby the total amount of magnetic metal employed in the marker can be significantly reduced as compared with a strip or wire, but the marker has good manipulatability and handleability, provided by the textile fibers which form the dominant component of the composite yam.

Furthermore, the composite yam of the invention permits the loading of the magnetic metal to be readily selected to provide a desired amount of detectable fibers within a length corresponding to the product or package length.

Furthermore, yam production techniques are versatile and readily permit incorporation in the composite yam of flexible strengthening elements to further improve the strength and flexibility characteristics of the composite, thereby enhancing the manipulatability whereby the composite yarn is more readily handled in industrial manufacturing procedures without danger of breakage of the yam.

The strengthening elements have the additional advantage of greatly assisting the manufacture of the composite yam.

Thus the composite yam may additionally include one or more flexible strengthening elements, for example, one or more fine yams or filaments having a diameter significantly less than the diameter of the composite textile yam. The strengthening elements may be formed from any non-magnetic, multi- or mono-filament thread, fine yam or wire.

In the case of a single strengthening element this may conveniently extend centrally along the core axis of the composite yam, but it is not essential that it be exactly central.

In the case of a plurality of strengthening elements, these may suitably extend along a core of the composite yarn in a dispersed or partly dispersed arrangement, for example, a first central strengthening element extending generally axially, centrally of the yam and a plurality of second strengthening elements disposed about the first strengthening element in spaced apart relationship, and extending the length of the yarn. The strengthening elements thus offer benefits which may be summarized as follows: i) improved reliability in the manufacturing process; ii) increased tensile strength with the composite yam; iii) increased uniformity in the composite yam; iv) greater amenability of the composite yard to handling with high speed automated equipment; v) more reliable integration of the composite yam into products or packaging in an unobtrusive manner. The strengthening element or elements are suitably fine yarns or filaments having a diameter of 10 to 500, preferably 50 to 200; and may be, for example, of 100 μm diameter.

It is highly advantageous that the metal marker fibers be substantially aligned along the yam with a minimum of bent or kinked fibers and that protrusion of fibers and fiber ends from the yam body be minimized. In this way the marker function of the metal fibers is optimized.

In order to minimize protrusion of fibers or fiber ends from the yam body and maintain alignment of the metal fibers it is advantageous to employ at least one flexible containment element wrapped about the composite yam along the length of the ya . In particular the containment element may be a wrapping yam or filament wound spirally about the yam with a pitch of 1 to 10 mm, suitably 5 to 7 mm; the wrapping yam or filament preferably being in a taut, compacting engagement with the yam so as to firmly hold the composite ya together and minimize projections of magnetic fiber ends from the yam surface.

The containment element may be formed from any nonmagnetic, multi- or mono-filament thread, fine yam or wire. There may be one or more such containment elements, which containment elements offer benefits which may be summarized as follows: i) improved efficiency of manufacture of the composite yam by reducing the amount of metal fiber lost in the manufacture process; ii) reduce the amount of metal fiber lost during handling of the composite yam; iii) reduce protrusions of metal fibers from the yam body; iv) render the composite yam more wear resistant; v) render the composite yam more amenable to handling with high speed automated equipment such as employed in packaging production lines; vi) render the composite yam more reliably integrated into products or packaging in an unobtrusive manner. The soft magnetic fibers provide an identifying magnetic signal when placed in a magnetic field of appropriate characteristics, which magnetic signal can be detected by a sensing system. Sensing systems and magnetic field characteristics are well established and are understood by persons in the art and the present invention is not concerned directly with such sensing systems and magnetic field characteristics.

The form of the marker allows it to be incorporated in a continuous manner within an article at the time of manufacture or within the packaging. Another advantage of the marker is that the loading can be chosen to match the size of article to be tagged in such a way that no more magnetic fiber is included within the tagging than is needed for detection, thereby keeping the cost of tagging to a minimum. Soft magnetic fiber made of amorphous material by a suitable process such as melt-extraction as taught in U.S. Patent 5,003,291 may be detected in currently available commercial EAS systems (such as those manufactured by Meto GmbH, Hirschhom, Germany) in quantities as small as 1 to 2 mg.

A further advantage to the marker is that it may be easily attached to a surgical sponge or dressing either by coating it with an appropriate polymer to contain the composite yam and directly incorporating it within the weave of the sponge or by incorporating it within the X-ray opaque yarn currently attached to many such sponges.

The magnetic marker of the invention may be employed alone or in conjunction with a deactivating element which, when magnetized, is capable of deactivating the magnetic marker. When employed alone, the composite yarn forming the magnetic marker is incorporated in a product label, tag or packaging, or directly in an article of commerce.

Yet another advantage of the marker is that it may be made deactivatable by winding it with, or otherwise placing it in close proximity to, a deactivating element, for example, a continuous semi-hard magnetic wire, which has been treated so that alternate sections of it are nonmagnetic. Magnetic fiber made by a suitable process such as melt- extraction may be deactivated by such a wire made of commercially available drawn stainless steel.

The deactivating element may also function as the strengthening element.

ii) Deactivating Element The deactivating element may be selected from conventional deactivating elements which have been developed for the deactivation of magnetic markers. Such deactivating elements and the principle of operation are described in U.S. Patent 3,747,086. Deactivating elements are in particular formed of magnetically semi-hard material of low permeability and in use are disposed in close proximity or in contact with the magnetic marker. When the deactivating element is magnetized, it carries a remanent magnetic flux which saturates the nearby soft magnetic marker, in such a way as to make the soft magnetic marker undetectable in a surveillance device in a surveillance or interrogation zone. Conventional deactivating elements are generally categorized into three classes. First, and most simply, the deactivating element consists of one continuous piece of semi-hard magnetic material which is very nearly the same length as the detected element within the marker. In order to deactivate such a marker, a DC magnetic field is applied sufficient to saturate the semi-hard material of the deactivating element. The deactivation element thereafter acts like a single bar magnet where the magnetic flux generated is adequate to locally saturate or magnetically bias the detected element, making the detected element undetectable in the interrogation device.

Deactivating elements of this class are described in U.S. Patents 3,747,086; RE32,427 (4,298,862); RE32,428 (4,484,184); 5,401 ,584; 4,857,891 and 5,181 ,021. In a second class, the deactivating element is again a continuous piece of semi-hard magnetic material which is very nearly the same length as the detected element in the marker. In this class, however, deactivation is achieved by magnetizing the semi-hard material in such a way as to create a pattern of alternating magnetic dipoles within the material. Where like ends of these dipoles meet, magnetic flux is forced out from the material sufficiently to saturate the nearby detected element, making the detected element undetectable in the interrogation zone.

The principle problem with deactivation elements of this class is that a complex deactivating tool is required to create the necessary pattern of magnetization within the deactivating element, and the use of such a tool requires passing the marker in near contact to the tool, with a carefully controlled orientation and direction of travel. In addition, such deactivation elements tend to be costly because magnetic material of rather high magnetic coercivity and remanence is required to retain the magnetization pattern, and generate adequate deactivating flux.

Deactivating elements of this second class are described in U.S. Patents 4,568,921 ; 4,665,387 and 4,684,930. In the third class, the deactivation element contains multiple pieces of semi-hard material, each of significantly shorter length than the detected element, and distributed more-or-less uniformly along the length of the detected element. A marker using such a deactivating element is deactivated by applying a sufficiently large magnetic field to saturate the semi-hard pieces comprising the deactivating element, leaving them each magnetized.

The spaces between the separate pieces of semi-hard magnetic material play the important role of allowing the magnetic flux generated by the pieces to locally saturate the nearby detected element. These saturated regions effectively break up the magnetic continuity of the detected element and make it undetectable in the interrogation zone.

As compared to the other two classes, a cost saving is possible because less semi-hard material is required to achieve the same deactivation performance. An additional cost reduction is possible because a semi-hard material of a lower magnetic remanence may be used.

Examples of this third class of deactivating element include the use of short wire pieces, flakes, chips, pieces of ribbon and magnetic powders. The principle problem with manifestations of this class is that care must be taken to size and position the small separate pieces of semi- hard along the marker, and to ensure a relatively uniform distribution of such pieces. While material handling and placing solutions have been developed to address this problem, there remain limitations on the production rate and cost of such markers. Deactivating elements of this third class are described in U.S.

Patents 5,121 ,106; 5,191,315; 5,246,522; RE32,427 (4,298,862); RE32,428 (4,484,184) and 5,146,204. Especially preferred in the present invention is a class of deactivating element which comprises an elongate member having a body consisting of a plurality of first and second alternating body segments, each of the first segments being of a magnetizable material having a magnetic remanence of at least 0.2 Tesla, and each of the second segments being of material having a magnetic saturation of not more than 0.05 Tesla.

The elongate member of the deactivating element may suitably be a metal wire, strip or ribbon which has been treated or physically modified so as to comprise a plurality of magnetizable body segments and a plurality of non-magnetizable body segments, the magnetizable and non-magnetizable body segments being in alternating relationship. In this way each adjacent pair of magnetizable body segments is separated by a non-magnetizable body segment; and each adjacent pair of non-magnetizable body portions is separated by a magnetizable body portion along the length of the elongate member.

In this Specification magnetizable material means material having a magnetic remanence of at least 0.2 Tesla and non-magnetizable means having a magnetic saturation of not more than 0.05 Tesla. In particular, the magnetizable body segments are magnetically semi-hard having a coercivity in the range of 1 to 25 kA/m, preferably 2 to 10 kA/m. The non-magnetic segments act as magnetic gaps where the magnetic flux generated by the magnetizable segments, when magnetized, is available to saturate the soft magnetic material of the detectable soft magnetic marker. The deactivating element may be formed from a weakly magnetic alloy steel; in a particular embodiment the deactivating element is formed from a cold drawn 304 stainless steel wire (classification of the American Iron and Steel Association). In other embodiments the deactivating element is formed from other stainless steel alloys or an iron or cobalt rich alloy designed to be magnetically semi-hard, for example, Crovac, Vicalloy or Semivac.

The elongate member is conveniently formed as a mechanically continuous wire or strip and is thus convenient to fabricate, handle and incorporate into markers both at high speed and low cost. Because the deactivating element contains magnetic gaps, it is possible to achieve additional cost savings since effective deactivation can be obtained using less magnetic material and material of lower magnetic remanence. This is particularly important in efforts to make smaller, more flexible and more visually discrete markers. More particularly, the wire geometry lends itself to deactivation the composite textile yam magnetic marker of the invention An additional benefit is that a complex deactivating tool is not required. Deactivation is accomplished by simply applying a DC magnetic field of sufficient magnitude, as may be achieved with a simple deactivating tool possessing a coil or permanent magnet assembly. Provided the magnetic field from the deactivating tool is large enough, such markers may even be deactivated at a considerable distance from the tool and with a relatively forgiving range of orientation and direction of travel. The most preferred deactivator element of this class is in the form of a wire of circular or near circular cross section because: 1) The degree and distribution of strain required to provide the desired magnetic properties is more easily obtained in a cold drawn round wire, as compared to a flattened wire of the same material. 2) In the case of local heating to form the non-magnetic sections, the near round cross section leads to more uniform heating, and therefore a more uniform and consistent magnetic structure along the length of the wire. 3) The guiding and application of round wire is easier than for strip, since strip requires greater care in the prevention of twisting.

4) In comparing round to strip deactivators of the same cross sectional area placed beside the yam, the material of the strip will be, on average, further from the yam, making deactivation more difficult. On the other hand, placing flat strip on top or under the yarn results in an undesirably thicker marker.

5) Round wire is easier to make and therefore of significantly lower cost than strip.

iii) Method of Manufacture of Deactivating Element

The method of manufacture involves fabrication of a wire or strip containing alternate segments of magnetizable and non-magnetizable material. Key to realizing this is the fact that numerous materials have magnetic properties which depend strongly on their thermal and mechanical history. For example, weakly magnetic stainless steel alloys can be made magnetizable by cold working, as in the case of cold drawing of wire. In addition it is possible to strongly diminish the magnetic remanence and coercivity of such wire by heating the material to elevated temperatures. The semi-hard magnetic properties of such materials depend strongly on the state of internal strain (ref. Plonus, Applied Electromagnetics, McGraw Hill, 1978, Chapter 9) which can be relieved by annealing. It is possible to strongly diminish the magnetic remanence of other semi-hard magnetic alloys (e.g. Semivac 90) by the same method. By restricting the heating or mechanical working of a material to local regions, a deactivating element is created wherein the magnetic properties vary markedly from place to place. For example, a wire of semi-hard magnetic material can be locally heated in isolated segments along its length to create a wire which possesses alternating segments of magnetizable material and non-magnetizable material. The resulting wire has mechanical and magnetic stmcture ideal for forming a marker deactivating element. The physical modification may comprise cold working the elongate member to render the material of the member magnetizable throughout, and heating a plurality of spaced apart portions of the cold worked member to render the spaced apart portions non-magnetizable, with magnetizable portions therebetween. In this case the magnetizable portions between the spaced apart portions are maintained in a non-heated condition to maintain them magnetizable.

The heating may be effected by passing an electrical current, having a heating effect, through the spaced apart portions, or the local heating might similarly be achieved by laser radiation or electromagnetic discharge.

The physical modification, in more general terms, may be considered a localized mechanical strain in a plurality of spaced apart zones, thereby forming the magnetizable body segments. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a schematic representation of a magnetic marker of the invention;

Fig. 2 is a schematic representation of a magnetic marker of the invention in a different embodiment;

Fig. 3 is a schematic representation of a magnetic marker of the invention in yet another embodiment;

Fig. 4 is a schematic representation of a magnetic marker of the invention in still another embodiment; Fig. 5 is a schematic representation of a deactivatable magnetic marker assembly of the invention;

Figs. 6a and 6b are schematic representations, in end elevation of deactivatable magnetic marker assemblies of the invention in different embodiments;

Figs. 7a and 7b are schematic representations, in end elevation of deactivatable magnetic marker assemblies of the invention in still further embodiments;

Figs. 8a and 8b are schematic representations, in end elevation of deactivatable magnetic marker assemblies of the invention in yet further embodiments;

Fig. 9 is a schematic representation of yet another deactivatable magnetic marker assembly of the invention; and

Fig. 10 is a schematic representation of still another deactivatable magnetic marker assembly of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS WITH REFERENCE TO DRAWINGS

With further reference to Fig. 1 , a yam 10 has a yam body 12 composed of staple textile fibers 14 and staple soft magnetic metal fibers

16, the fibers 16 being more or less uniformly distributed along the length of yam 10, and being substantially aligned along the yam.

With further reference to Fig. 2, a yam 18 has the same general form as the yam 10 of Fig. 1 , but additionally includes a strengthening yam 20 extending along the core of yam body 12.

With further reference to Fig. 3, a yarn 22 is of the same general form as the yam 10 of Fig. 1, but additionally includes a wrapping yarn 24 wound in a spiral about and along the length of yam body 12, wrapping yam 24 being taut sufficient to apply a compacting or compressing pressure on yarn body 12. Wrapping yam 24 serves to better maintain the metal fibers 16 within yam body 12 and in aligned arrangement.

With further reference to Fig. 4, there is shown an especially preferred embodiment of the invention wherein a yarn 26 employs the features of Figs. 1 , 2 and 3.

With further reference to Fig. 5, there is shown a deactivatable magnetic marker assembly 100 comprising a yam 10 of Fig. 1 and a deactivating element 28. It will be understood that yarn 10 can be replaced by yam 18 of Fig. 2, yam 22 of Fig. 3 or yam 26 of Fig. 4. Deactivating element 28 comprises a metal wire 30 having magnetizable segments 32 and non-magnetizable segments 34 in alternating relationship along the length of wire 30. The yam 10 and deactivating element 28 are juxtaposed in close proximity and in generally parallel relationship. With further reference to Fig. 6a, there is shown an alternate arrangement of assembly 102 which is a variation of assembly 100; assembly 102 employs a single yam 10 of Fig. 1 (or yam 18, 22 or 26 of Figs. 2, 3 and 4, respectively) and a pair of deactivating elements 28, each of which comprises wire 30 as illustrated in Fig. 5, the wires 30 being juxtaposed to the yam 10.

With further reference to Fig. 6b, there is shown an assembly 104 which is a variation of assembly 102 of Fig. 6a, in that it comprises a pair of deactivating elements 36 each in the form of a strip 38 in place of the wires 30. With further reference to Fig. 7a, there is shown an assembly

106 which is a further variation of the assembly 100 of Fig. 5 in employing a pair of the yams 10 of Fig. 1 (or the yams 18, 22 and 26 of Figs. 2, 3 and 4) and a deactivating element 28 comprising a wire 30 as illustrated in Fig. 5.

Fig. 7b shows an assembly 108 which is a variation of assembly 106 of Fig. 7a in employing a deactivating element 36 in the form of a strip 38.

Figs. 8a and 8b show assemblies 1 10 and 1 12 respectively which represent further variations on the assembly 100 of Fig. 5 employing a yam 10 of Fig. 1 (or a yam 18, 22 or 26 of Figs. 2, 3 and 4) in conjunction with a detecting element 36 comprising a strip 38. With further reference to Fig. 9, there is shown an assembly

1 14 which represents a further variation of an assembly 100 of Fig. 5 in that yam 10 (or ya 18, 22 or 26) is spirally wound about wire 30 of detecting element 28.

With further reference to Fig. 10, there is shown in a further embodiment, an assembly 1 16 in which a deactivating element 28 comprising a wire 30, as illustrated in Fig. 4, forms the core of a yam 40 having a wrapping yam 24. Ya 40 is otherwise similar to ya 10 of Fig. 1 having a yam body 12 of staple textile fibers 14 and soft magnetic metal fibers 16. EXAMPLES Example 1

A composite textile yam was produced from polyester textile fibers and soft magnetic metal fibers using commercial textile processing steps, including combining of the polyester fibers with the metal fibers, carding and yam spinning. The yam contained 10 cm long, 4 denier crimped polyester fiber combined with metal fiber of average diameter 30 micron cut into average 7.5 cm lengths. The yarn had a total mass of 145 mg/meter of which the metal fibers comprised 14 percent by weight. A 10 cm length marker cut from the yam was reliably and consistently detected in commercial EAS system manufactured by Meto GmbH of Hirschhom, Germany. The marker remained detectable when bent or otherwise deformed, or when subjected to stress or pressure.

Example 2

The marker of Example 1 was incorporated in a deactivatable magnetic marker assembly illustrated schematically in Fig. 9.

The marker was made deactivatable by being wound with a semi-hard magnetic wire treated so that alternate sections of the wire were non-magnetic. The wire when magnetized generated sufficient magnetic flux to saturate the magnetization of the soft magnetic fiber and so make it undetectable in commercial EAS systems. The magnetic sections of the wire had a magnetic coercivity low enough to be magnetized in the deactivators of commercial EAS systems, but not so low as to be demagnetized by the alternating interrogation magnetic field of the detector of commercial EAS systems. The coercivity was in the range of 2 to 10 kA/m.

A textile yam of total mass 145 mg/meter, as described above, was wound with a 0.004 inch diameter 304 stainless steel wire, thermally annealed so that segments of 5 mm length of non-magnetic material alternated with segments of 5 mm length of magnetic material. The yam and wire were wound together with a pitch of 6 mm. The composite product exhibited the same detectability when not deactivated as the yam alone, and was undetectable in detectors of commercial EAS systems when deactivated by deactivator of a commercial EAS system. Example 3

A composite yam was produced from polyester textile fibers and soft magnetic amorphous metal alloy fibers using commercial textile processing steps including combining the polyester textile fibers with the metal fibers, carding and yam spinning. The yam contained 10 cm long, 4 denier crimped polyester fiber combined with metal fibers having an average diameter of 30 μm and an average length of 7.5 cm. The composite yam had a total mass of 83 mg/m, of which the metal fiber loading was 20 mg/m.

The composite yam was employed as the yam 10 in the assembly 102 illustrated schematically in Fig. 6a. The two deactivating elements 28 of the assembly 102 each comprising a wire 30 of 304 stainless steel having an average diameter of 125 μm. The two wires 30 differed in that one wire had magnetizable segments (32 in Fig. 5) having a length of 7 mm separated by non-magnetizable segments (34 in Fig. 5) having a length of 6 mm, whereas the other wire had magnetizable segments having a length of 4 mm separated by non-magnetizable segments having a length of 2 mm. The wires (30) were spaced so that their centers were 0.5 mm apart The assembly exhibits the same detectability when not deactivated as the yam alone, and is undetectable in detectors of commercial EAS systems when deactivated by a deactivator of a commercial EAS system.

It will be understood that references herein to the diameter of the textile and magnetic fibers is not an indication that the fibers must be of circular cross-section, but is an indication of the cross-sectional width of the fibers, which typically will be of a generally circular cross-section.

Claims

1. A magnetic marker comprising a composite textile yam, said yam comprising a combination of textile fibers and soft magnetic fibers.

2. A marker according to claim 1 , wherein said textile fibers are selected from staple fibers and filaments; and said soft magnetic fibers are selected from staple fibers and filaments.

3. A marker according to claim 1, wherein said textile fibers are staple fibers having a length of 1.5 to 20 cm and a diameter of 10 to 50 microns; and said soft magnetic fibers are staple fibers having a length of 1.5 to 15 cm and a diameter of 10 to 80 microns.

4. A marker according to claim 1 , 2 or 3, said soft magnetic fibers are present in an amount of 1 to 100 mg/m of said composite yam; said yarn having a mass of 10 to 500 mg/meter of which the soft magnetic fibers comprise 0.5 to 95%, by weight.

5. A magnetic marker according to claim 1, 2, 3 or 4, wherein said soft magnetic fibers are of an amorphous metal having a value of magnetostriction close to zero.

6. A magnetic marker according to claim 1 , 2, 3 or 4, wherein said soft magnetic fibers are of a crystalline metal.

7. A magnetic marker according to claim 1, 2, 3 or 4, wherein the soft magnetic fibers are made by rapid solidification.

8. A magnetic marker according to any one of claims 1 to 7, wherein said yam further includes at least one flexible strengthening element extending along a core of said yam.

9. A magnetic marker according to claim 8, wherein said at least one flexible strengthening element is a fine yam or a thread having a diameter significantly less than the diameter of said composite textile yam.

10. A magnetic marker according to claim 8, wherein said at least one flexible strengthening element is a filament.

11. A magnetic marker according to any one of claims 1 to 10, further including at least one elongate, flexible containment element wrapped about said composite textile yam along the length of the composite textile yam.

12. A magnetic marker according to claim 1 1 , wherein said at least one containment element is a wrapping yam or filament wound spirally about said composite textile ya .

13. A magnetic marker according to claim 12, wherein said at least one containment element is in a taut, compacting engagement with said composite textile yam.

14. A magnetic marker according to any one of claims 1 to 13, wherein said soft magnetic fibers have a coercivity of less than 0.1 kA/m.

15. A deactivatable magnetic marker assembly comprising at least one detectable magnetic marker adapted to provide a desired magnetic signal, in combination with at least one deactivating element, said deactivating element as magnetized, deactivating said magnetic member, said at least one detectable magnetic marker being as defined in any one of claims 1 to 14.

16. An assembly according to claim 15, wherein said deactivating element is of a semi-hard magnetic alloy.

17. An assembly according to claim 15, wherein said deactivating element comprises an elongate member having a body consisting of a plurality of first and second alternating body segments, each of said first segments being a magnetizable material having a magnetic remanence of at least 0.2 Tesla, and each of said second segments being of a material having a magnetic saturation of not more than 0.05 Tesla.

18. An assembly according to claim 17, wherein said second segments have a magnetic permeability of less than 100 and said first segments have a coercivity in the range of 2 to 10 kA/m.

19. An assembly according to claim 18, wherein said second segments have a permeability less than 5.

20. An assembly according to claim 17, 18 or 19, wherein said body is derived from weakly magnetic alloy steel and said elongate member is in the form of a wire or strip.

21. An assembly according to claim 17, 18, 19 or 20, comprising a single said detectable magnetic marker, and wherein said at least one deactivating element comprises a pair of deactivating elements juxtaposed to said single detectable magnetic marker.

22. A product label, tag, packaging or an article of commerce having incorporated therein a magnetic marker as defined in any one of claims 1 to 14.

23. A product label, tag, packaging or an article of commerce according to claim 22, wherein said magnetic marker is woven therein.

24. A product label, tag, packaging or an article of commerce having incorporated therein an assembly of claim 17, 18, 19, 20 or 21.