United States Patent [119]
`Anderson, III et a1.
`
`‘[11] Patent Number:
`[45] Date of Patent:
`
`4,510,489
`Apr. 9, 1985
`
`[54] SURVEILLANCE SYSTEM HAVING
`MAGNETOMECHANICAL MARKER
`[75] Inventors: Philip M. Anderson, III, Chatham;
`Gerald R. Bretts, Livingston,
`of
`N.J.; James E. Kearney, New Hyde
`park, N_Y_
`_
`_
`'
`_
`[73] Assignee: Allied Corporation, MOITIS
`Townshlp, Morns County, NJ.
`
`[21] Appl. No.: 373,061
`_
`[22] Flledi
`
`Apr' 291 1982
`
`[511 1nt_ CL; _ _ _ _ _
`_ I , _ I _ _ . _ _ _ _ __ G03B 13/26
`[52] us. c1. ......................... .. 340/572; 340/551
`[58] Field Of Search ............. .. 340/572, 552, 561, 567,
`340/568, 551; 343/6.8 R, 6.5 R, 6.5 SS, 6.8 LC;
`324/201, 260
`
`[56]
`
`.
`References cued
`U.S. PATENT DOCUMENTS
`3,990,065 11/1976 Purinton et a]. .................. .. 340/572
`4,l58,434 6/1979 Peterson ............................ ,. 340/572
`4,215,342 7/1980 Horowitz .......................... .. 340/572
`
`4,298,862 11/1981 Gregor et a1. .................... .. 340/572
`4,321,586 3/1982 Cooper et a1. .................... .. 340/572
`FOREIGN PATENT DOCUMENTS
`France I
`‘
`Primary Examiner-Donn1e L. Crosland
`Attorney, Agent, or F1'rm—-Ernest D. Buff; Gerhard H.
`Fuchs; Paul Yee
`
`ABSTRACT
`[57]
`_
`‘
`i
`.
`-
`_
`A magnetlc article surve111ance system marker is
`adapted, when armed, to resonate at a frequency pro
`
`vided by an incident magnetic ?eld applied within an
`interrogation Zone The marker in an elongated ductile
`Strip of magnetostriotive ferromagnetic material dis
`posed adjacent to a ferromagnetic element which, upon
`being magnetized, magnetically biases the strip and
`arms it to resonate at said frequency. A substantial
`change in effective magnetic permeability of the marker
`at the resonant frequency provides the marker with
`slgnal Identity
`
`32 Claims, 7 Drawing Figures
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`1/13
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`US. Patent Apr. 9, 1985
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`Sheetl of5
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`4,510,489
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`FIG.
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`I I
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`TRANSMITTER
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`I
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`I
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`RECEIVER
`ALARM
`L_________________l
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`R E W E C E R
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`US. Patent Apr.9, 1985
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`Sheet20f5
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`4,510,489
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`FIG 3
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`22
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`US. Patent Apr. 9, 1985
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`Sheet3of5
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`FIG. 5
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`U.S. Patent Apr. 9, 1985
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`5:1O4tCC..nS
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`4,510,489
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`U.S. Patent Apr. 9, 1985
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`SheetSofS
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`NON
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`1
`
`SURVEILLANCE SYSTEM HAVING
`MAGNETOMECHANICAL MARKER
`
`4,510,489
`
`5
`
`20
`
`2
`Such markers may be readily deactivated by the appli
`cation of a dc magnetic field pulse triggered by the
`cashier. Hence, handling costs associated with the phys
`ical removal requirements of resonant-circuit and anten
`na-diode markers are avoided.
`One of the problems with harmonic generating, ferro
`magnetic markers is the difficulty of detecting the
`marker signal at remote distances. The amplitude of the
`harmonics developed in the receiving antenna is much
`smaller than the amplitude of the interrogation signal,
`with the result that the range of detection of such mark
`ers has heretofore been limited to aisle widths less than
`about three feet. Another problem with harmonic gen
`erating, ferromagnetic markers is the dif?culty of distin
`guishing the marker signal‘from pseudo signals gener
`ated by belt buckles, pens, hair clips and- other ferro
`magnetic objects carried by shoppers. The merchant’s
`fear of embarrassment and adverse legal consequences
`associated with false alarms triggered by such pseudo
`signals will be readily appreciated. Yet another problem
`with such ferromagnetic markers is their tendency to be
`deactivated or reactivated by conditions other than
`those imposed by components of the system. Thus,
`ferromagnetic markers can be deactivated purposely
`upon juxtaposition of a permanent magnet or reacti
`vated inadvertently by magnetization loss in the second
`ferromagnetic element thereof. For these reasons, arti
`cle surveillance systems have resulted in higher operat
`ing costs and lower detection sensitivity and operating
`reliability than are considered to be desirable.
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention relates to article surveillance systems
`and markers for use therein. More particularly, the
`invention provides a ferromagnetic metal marker that
`enhances the sensitivity and reliability of the article
`surveillance system.
`2. Description of the Prior Art
`The problem of protection of articles of merchandise
`and the like, against theft fromretail stores has been the
`subject of numerous technical solutions. Among these, a
`tag or marker is secured to an article to be protected.
`The marker responds to an interrogation signal from
`‘transmitting apparatus situated either at the exit door of
`the premises to be protected, or at the aisleway adjacent
`to the cashier or check out station. A receiving coil on
`the opposite side of the exit or aisleway from the trans
`mitting apparatus, receives a signal produced by the
`marker in response to the interrogation signal. The
`presence of the response signal indicates that the marker
`has not been removed or deactivated by the cashier, and
`that the article bearing it may not have been paid for or
`properly checked out.
`Several different types of markers have been dis
`closed in the literature, and are in use. In one type, the
`functional portion of the marker consists of either an
`antenna and diode or an antenna and capacitors forming
`a resonant circuit. When placed in an electromagnetic
`?eld transmitted by the interrogation apparatus, the
`antenna-diode marker generates harmonics of the inter
`rogation frequency in the receiving antenna; the reso
`nant circuit marker causes an increase in absorption of
`the transmitted signal so as to reduce the signal in the
`receiving coil. The detection of the harmonic or signal
`level change indicates the presence of the marker. With
`this type of system, the marker must be removed from
`the merchandise by the cashier. Failure to do so indi
`cates that the merchandise has not been properly ac
`counted for by the cashier.
`A second type of marker consists of a ?rst elongated
`element of high magnetic permeability ferromagnetic
`material disposed adjacent to at least a second element
`of ferromagnetic material having higher coercivity than
`the ?rst element. When subjected to an interrogation
`frequency of electromagnetic radiation, the marker
`causes harmonics of the interrogation frequency to be
`developed in the receiving coil. The detection of such
`harmonics indicates the presence of the marker. Deacti
`vation of the marker is accomplished by changing the
`state of magnetization of the second element. Thus,
`when the marker is exposed to a dc magnetic ?eld, the
`state of magnetization in the second element changes
`and, depending upon the design of the marker being
`used, either the amplitude of the harmonics chosen for
`detection is signi?cantly reduced, or the amplitude of
`the even numbered harmonics is signi?cantly changed.
`Either of these changes can be readily detected in the
`receiving coil.
`Ferromagnetic harmonic generating markers are
`smaller, contain fewer components and materials, and
`are easier to fabricate than resonant-circuit or antenna
`diode markers. As a consequence, the ferromagnetic
`marker can be treated as a disposable item affixed to the
`article to be protected and disposed of by the customer.
`
`SUMMARY OF THE INVENTION
`The present invention provides a marker capable of
`producing identifying signal characteristics in the pres
`ence of a magnetic ?eld applied thereto by components
`of an article surveillance system. The marker has high
`signal amplitude and a controllable signal signature and
`is not readily deactivated or reactivated by conditions
`other than those imposed by components of the system.
`In addition, the invention provides an article surveil
`lance system responsive to the presence within an inter
`rogation zone of an article to which the marker is se
`cured. The system provides for high selectivity and is
`characterized by a high signal-to-noise ratio. Brie?y
`stated, the system has means for de?ning an interroga
`tion zone. Means are‘provided for generating a mag
`netic ?eld of varying frequency within the interrogation
`zone. A marker is secured to an article appointed for
`passage through the interrogation zone. The marker
`comprises an elongated, ductile strip of magnetostric
`tive ferromagnetic material adapted to be magnetically
`biased and thereby armed to resonate mechanically at a
`frequency within the frequency band of the incident
`magnetic ?eld. A hard ferromagnetic element, disposed
`adjacent to the strip of magnetostrictive material, is
`adapted, upon being magnetized, to arm the strip'to
`resonate at that frequency. The strip of magnetostric
`tive material has a magnetornechanical coupling factor,
`k, greater than 0, where
`
`k=\l (1- 2/122) .
`
`f, and fa being the resonant anti-resonant frequencies,
`respectively. Upon exposure to said dc magnetic ?eld
`the marker is characterized by a substantial change in its
`effective magnetic permeability as the applied ac ?eld
`
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`4,510,489
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`3
`tion zone 12. The marker comprises an elongated duc
`sweeps through at least one of the resonant and anti
`tile strip 18 of magnetostrictive, ferromagnetic material
`resonant frequencies that provide the marker with sig
`nal identity. A detecting means detects the change in
`adapted, when armed, to resonate mechanically at a
`coupling between the interrogating and receiving coils
`frequency within the range of the incident magnetic
`at the resonant and/or anti-resonant frequency, and
`?eld. A hard ferromagnetic element 44 disposed adja
`distinguishes it from changes in coupling at other than
`cent to the strip 18 of ferromagnetic material is adapted,
`those frequencies.
`upon being magnetized, to magnetically bias the strip 18
`and thereby arm it to resonate at that frequency. The
`strip 18 has a magnetomechanical coupling factor, k,
`greater than 0, where
`
`Ul
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The invention will be more fully understood and
`further advantages will become apparent when refer
`ence is made to the following detailed description of the
`preferred embodiment of the invention and the accom
`panying drawings in which:
`FIG. 1 is a block diagram of an article surveillance
`system incorporating the present invention;
`FIG. 2 is a diagrammatic illustration of a typical store
`installation of the system of FIG. 1;
`FIG. 3 is a graph showing the voltage induced by
`mechanical energy exchange of an article surveillance
`marker over a preselected frequency range;
`FIG. 4 is an isometric view showing components of a
`marker adapted for use in the system of FIG. 1;
`FIG. 5 is an isometric view showing a ?exible casing
`adapted to protect the marker of FIG. 4 against damp
`mg;
`FIG. 6 is a schematic electrical diagram of an interro
`gation and detection scheme comprising part of the
`article surveillance system of FIG. 1; and
`FIG. 7 is a schematic electrical diagram of an interro
`gation and detection scheme comprising a part of an
`alternative embodiment of the article surveillance sys
`tem of FIG. 1.
`
`25
`
`30
`
`35
`
`45
`
`f, and fa being the resonant and anti-resonant frequen
`cies, respectively.
`Upon exposure to the magnetic ?eld within interro
`gation zone 12, marker 16 is characterized by a substan
`tial change in its effective magnetic permeability at the
`resonant and/or anti-resonant frequency (shown in
`FIG. 3 as f, and fa) that provides marker 16 with signal
`identity. A detecting means 20 is arranged to detect
`changes in coupling produced in the vicinity of the
`interrogation zone 12 by the presence of marker 16
`therewithin.
`Typically, the system 10 includes a pair of coil units
`22, 24 disposed on opposing sides of a path leading to
`the exit 26 of a store. Detection circuitry, including an
`alarm 28, is housed within a cabinet 30 located near the
`exit 26. Articles of merchandise 19 such as wearing
`apparel, appliances, books and the like are displayed
`within the store. Each of the articles 19 has secured
`thereto a marker 16 constructed in accordance with the
`present invention. As shown in FIG. 4, the marker 16
`includes an elongated, ductile magnetostrictive ferro
`magnetic strip 18 that is normally in an activated mode.
`When marker 16 is in the activated mode, placement of
`an article 19 between coil units 22 and 24 of interroga
`tion zone 12 will cause an alarm to be emitted from
`cabinet 30. In this manner, the system 10 prevents unau
`thorized removal of articles of merchandise 19 from the
`store.
`Disposed on a checkout counter near cash register 36
`is a deactivator system 38. The latter can be electrically
`connected to cash register 36 by wire 40. Articles 19
`that have been properly paid for are placed within an
`aperture 42 of deactivation system 38, whereupon a
`magnetic ?eld is applied to marker 16. The deactivation
`system 38 has detection circuitry adapted to activate a
`desensitizing circuit in response to coupling signals
`generated by marker 16. The desensitizing circuit ap
`plies to marker 16 a magnetic ?eld that places the
`marker 16 in a deactivated mode, by either increasing or
`decreasing the magnetic bias ?eld strength of the hard
`ferromagnetic material, by an- amount suf?cient to
`move the f, and fa outside of the frequency range of the
`applied ?eld or to decrease the coupling factor k suf?
`ciently to make it undetectable. The article 19 carrying
`the deactivated marker 16 may then be carried through
`interrogation zone 12 without triggering the alarm 28 in
`cabinet 30.
`The theft detection system circuitry with which the
`marker 16 is associated can be any system capable of (1)
`generating within an interrogation zone an incident
`magnetic field of variable frequency, (2) detecting
`changes in coupling at frequencies produced in the
`vicinity of the interrogation zone by the presence of the
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`The magnetomechanical marker of article surveil
`lance system 10 can be fabricated in a number of diverse
`sizes and con?gurations. As a consequence, the inven
`tion will be found to function with many varieties of
`surveillance systems. For illustrative purposes the in
`vention is described in connection with an antipilferage
`system wherein articles of merchandise bearing the
`markers are surveyed by the system to prevent theft of
`the merchandise from a retail store. It will be readily
`appreciated that the invention can be employed for
`similar and yet diversi?ed uses, such as the identi?ca
`tion of articles or personnel, wherein the marker and the
`system exchange magnetomechanical energy so that the
`marker functions as (1) personnel badge for control of
`access to limited areas, (2) a vehicle toll or access plate
`for actuation of automatic sentrys associated with
`bridge crossings, parking facilities, industrial sites or
`recreational sites, (3) an identi?er for check point con
`trol of classi?ed documents, warehouse packages, li
`brary books and the like, (4) product veri?cation. Ac
`cordingly, the invention is intended to encompass modi
`?cations of the preferred embodiment wherein the reso
`nant frequency of the marker provides animate or inani
`mate objects bearing it with signal identity.
`Referring to FIGS. 1, 2 and 4 of the drawings, there
`is shown an article surveillance system 10 responsive to
`the presence of an article within an interrogation zone.
`The system 10 has means for de?ning an interrogation
`zone 12. A ?eld generating means 14 is provided for
`generating a magnetic ?eld of variable frequency within
`interrogation zone 12. A marker 16 is secured to an
`article 19 appointed for passage through the interroga
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`the magnetic coupling between the driving solenoid and
`a second pickup solenoid. The voltage induced by the
`purely magnetic energy exchange is linear with fre
`quency and the change in voltage with frequency is
`small over a limited frequency range. The voltage in
`duced by the mechanical energy exchange is also linear
`with frequency except near mechanical resonance. For
`a thin ribbon the mechanical resonance frequency is
`given by:
`
`where L, E and D are the length, Youngs modulus and
`mass density of the ribbon. Therefore, when the fre
`quency of the ac magnetic ?eld is swept around f,, a
`characteristic signature is generated. The resonance
`peak is closely followed by an antiresonance peak
`shown in FIG. 3. This anti-resonant peak occurs when
`the mechanical energy stored is near zero.
`The transfer of magnetic and mechanical energy de
`scribed above is called magnetomechanical coupling
`(MMC), and can be seen in all magnetostrictive materi
`als. The ef?ciency of this energy transfer is proportional
`to the square of the magnetomechanical coupling factor
`(k), and is de?ned as the ratio of mechanical to magnetic
`energy. Phenomenologically, k is de?ned as
`
`10
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`20
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`4,510,489
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`marker and (3) distinguishing the particular resonant
`and/or anti-resonant changes in coupling of the marker
`from other variations in signals detected.
`Such systems typically include means for transmitting
`a varying electrical current from an oscillator and am
`pli?er through conductive coils that form a frame an
`tenna capable of developing a varying magnetic ?eld.
`An example of such antenna arrangement is disclosed in
`French Pat. No. 763,681, published May 4, 1934, which
`description is incorporated herein by reference thereto.
`In accordance with a preferred embodiment of the
`invention, marker 16 is composed of a magnetostrictive
`amorphous metal alloy. The marker is in the form of an
`elongated, ductile strip having a ?rst component com
`posed of a composition consisting essentially of the
`formula MaNbOCXdYeZf, where M is at least one of iron
`and cobalt, N is nickel, O is at least one of chromium
`and molybdenum, X is at least one of boron and phos
`phorous, Y is silicon, Z is carbon, “a”-“f’ are in atom
`percent, “a” ranges from about 35-85, “b” ranges from
`about 0-45, “c” ranges from about 0-7, “d” ranges from
`about 5-22, “e” ranges from about 0-15 and “f” ranges
`from about 0-2, and the sum of d+e+f ranges from
`about 15-25.
`It has been found that a strip 18 of material having the
`formula speci?ed above is particularly adapted to reso
`nate mechanically at a preselected frequency of an inci
`dent magnetic ?eld. While we do not wish to be bound
`by any theory, it is believed that, in markers of the
`aforesaid composition, direct magnetic coupling be
`tween an ac magnetic ?eld and the marker 16 occurs by
`means of the following mechanism.
`When a ferromagnetic material such as an amorphous
`metal ribbon is in a magnetic ?eld (H), the ribbon’s
`magnetic domains are caused to grow and/or rotate.
`This domain movement allows magnetic energy to be
`stored, in addition to a small amount of energy which is
`lost as heat. When the ?eld is removed, the domains
`return to their original orientation releasing the stored
`magnetic energy, again minus a small amount of energy
`lost as heat. Amorphous metals have high ef?ciency in
`this mode of energy storage. Since amorphous metals
`have no grain boundaries and have high resistivities,
`their energy losses are extraordinarily low.
`When the ferromagnetic ribbon is magnetostrictive,
`an additional mode of energy storage is also possible. In
`the presence of a magnetic ?eld, a magnetostrictive
`amorphous metal ribbon will have energy stored mag
`netically as described above but will also have energy
`stored mechanically via magnetostriction. This me
`chanical energy per unit volume stored can be quanti
`?ed as Ue=(%) TS where T and S are the stress and
`strain on the ribbon. This additional mode of energy
`storage may be viewed as an increase in the effective
`magnetic permeability of the ribbon.
`When an ac magnetic ?eld and a dc ?eld are intro
`duced on the magnetostrictive ribbon (such as can be
`generated by and ac and dc electric currents in a sole
`noid), energy is alternately stored and released with the
`frequency of the ac ?eld. The magnetostrictive energy
`storage and release are maximal at the material’s me
`chanical resonance frequency and minimal at its anti
`resonance. This energy storage and release induces a
`voltage in a pickup coil via flux density changes in the
`ribbon. The flux density change may also be viewed as
`an increase in effective magnetic permeability at the
`resonant frequency and a decrease at anti-resonance,
`thus, in effect, increasing or decreasing, respectively,
`
`60
`
`25
`
`30
`
`35
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`45
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`55
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`where f, and fa are the resonant and anti-resonant fre
`quencies described above. The larger the k factor, the
`greater the voltage difference between resonant peak
`and anti-resonant valley. Also, the larger the k, the
`larger the difference in frequency between resonance
`and anti-resonance. Therefore, a large k facilitates the
`observation of the MMC phenomena.
`Coupling factors are influenced in a given amorphous
`metal by the level of bias ?eld present, the level of
`internal stress (or structural anisotropy) present and by
`the level and direction of any magnetic anisotropy.
`Annealing an amorphous metal relieves internal
`stresses, thus enhancing k. The structural anisotropy is
`small due to the ribbon’s amorphous nature, also en
`hancing k. Annealing in a properly oriented magnetic
`?eld can signi?cantly enhance coupling factors. Do
`main movement can be maximized when the ribbon has
`a magnetic anisotropy which is perpendicular to the
`interrogating ?eld. Because of demagnetizing ?eld ef
`fects, it is practical to interrogate the ribbon only along
`its length (this being the longest dimension). Therefore,
`the induced magnetic anisotropy should be transverse
`to the long dimension of the ribbon.
`Maximum values of k are obtained by annealing the
`ribbon in a saturating magnetic ?eld which is perpendic
`ular to ribbon length (cross-?eld annealed). For a % inch
`ribbon, a ?eld of a few hundred oersted is required. The
`optimum time and temperature of the anneal depends on
`the alloy employed. As an example, an iron-boron-sili
`con alloy yields an optimum coupling (k>O.90) when
`cross-?eld annealed at 400° C. for 30 minutes. This
`anneal yields an optimum bias ?eld of 1 0e. For alloys
`having the compositions speci?ed hereinabove, the
`annealing temperature ranges from about 300° to 450°
`C. and the annealing time ranges from about 7 to 120
`min.
`The anneal also affects the bias ?eld required to opti
`mize k. For a given amorphous metal with a given
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`4,510,489
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`The amorphous ferromagnetic metal marker of the
`anneal, the coupling depends strongly on the bias ?eld.
`invention is prepared by cooling a melt of the desired
`At zero and saturating ?elds, the coupling is zero (no
`resonant and anti~resonant phenomena). For a given
`composition at a rate of at least about 105° C./sec, em
`ploying metal alloy quenching techniques well-known
`alloy, an optimum bias ?eld exists which yields a maxi
`mum k. For alloys having the compositions speci?ed
`to the amorphous metal alloy art; see, e.g., U.S. Pat. No.
`3,856,513 to Chen et al. The purity of all compositions
`herein, the bias ?eld required to optimize k ranges from
`is that found in normal commercial practice.
`about 0.1 to 20 Oe.
`A variety of techniques are available for fabricating
`Even though most magnetostrictive materials will
`continuous ribbon, wire, sheet, etc. Typically, a particu
`exhibit some MMC, amorphous metal yield extremely
`lar composition is selected, powders or granules of the
`high coupling factors, and are, therefore highly pre
`ferred. As-cast amorphous metals yield higher k than
`requisite elements in the desired portions are melted and
`homogenized, and the molten alloy is rapidly quenched
`most other magnetostrictive materials. No material has
`higher k than amorphous metals when cross-?eld an
`on a chill surface, such as a rapidly rotating metal cylin
`nealedQAmorphous metals have high k because they
`der.
`Under these quenching conditions, a metastable, ho
`have:
`(a) low magnetic losses (no grain boundries, high
`mogeneous, ductile material is obtained. The metastable
`resistivity), (b) low structural and stress anisotropy, (0)
`material may be amorphous, in which case there is no
`long-range order. X-ray diffraction patterns of amor
`reasonable magnetostriction and (d) can be given a
`bene?cial magnetic anisotropy.
`phous metal alloys show only a diffuse halo, similar to
`Amorphous metal alloys make good targets because
`that observed for inorganic oxide glasses. Such amor
`(a) they have high k—even as-cast, (b) they are mechan
`phous alloys must be at least 50% amorphous to be
`sufficiently ductile to permit subsequent handling, such
`ically strong, tough and ductile, (0) they require low
`bias ?elds and (d) they have extremely high magnetos
`as stamping complex marker shapes from ribbons of the
`trictivity (they develop a large force upon resonating
`alloys without degradation of the marker’s signal iden
`tity. Preferably, the amorphous metal marker must be at
`and are, therefore, more dif?cult to damp out). It will be
`least 80% amorphous to attain superior ductility.
`appreciated, therefore, that the amorphous metals of
`which the marker of this invention is composed need
`The metastable phase may also be a solid solution of
`the constituent elements. In the case of the marker of
`not be annealed, but may be incorporated into the
`the invention, such metastable, solid solution phases are
`marker “as cast”.
`not ordinarily produced under conventional processing
`Examples of amorphous ferromagnetic marker com
`techniques employed in the art of fabricating crystalline
`positions in atomic percent within the scope of the in
`alloys. X-ray diffraction patterns of the solid solution
`vention are set forth below in Table l.
`'
`alloys show the sharp diffraction peaks characteristic of
`TABLE 1
`crystalline alloys, with some broadening of the peaks
`AS-CAST k
`OPTIMAL ANNEALED k
`due to desired ?ne-grained size of crystallites. Such
`metastable materials are also ductile when produced
`under the conditions described above.
`'
`The magnetostrictive strip 18 of which marker 16 is
`comprised is advantageously produced in foil (or rib
`bon) form, and may be used in theft detection applica
`tions as cast, whether the material is amorphous or a
`Examples of amorphous metals that have been found
`solid solution. Alternatively, foils of amorphous metal
`unsuitable for use as article surveillance system markers
`alloys may be heat treated to obtain a crystalline phase,
`are set forth in Table 2.
`preferably ?ne-grained, in order to promote longer die
`TABLE 2
`life when stamping of complex marker shapes is con
`templated.
`W
`The amorphous ferromagnetic material of strip 18 is
`EXAMPLE 1
`EXAMPLE 2
`exceedingly ductile. By ductile is meant that the strip 18
`can be bent around a radius as small as ten times the foil
`thickness without fracture. Such bending of the strip 18
`produces little or no degradation in magnetic properties
`generated by the marker upon application of the inter
`rogating magnetic ?eld thereto. As a result, the marker
`retains its signal identity despite being flexed or bent
`during (1) manufacture (e. g., cutting, stamping or other
`wise forming the strip 18 into the desired length and
`con?guration) and, optionally, applying hard magnetic
`biasing magnets thereto to produce an on/off marker,
`(2) application of the marker 16 to the protected articles
`19, (3) handling of the articles 19 by employees and
`customers and (4) attempts at signal destruction de
`signed to circumvent the system 10.
`In assembly of'marker l6, strip 18 is disposed adjacent
`to a ferromagnetic element 44, such as a biasing magnet
`capable of applying a dc ?eld to strip 18. The biasing
`magnet has a con?guration and disposition adapted to
`provide strip 18 with a single pair of magnetic poles,
`each of the poles being at opposite extremes of the long
`
`Ni at. % 71.67
`wt. % 84.40
`Cr at. % 5.75
`wt. % 6
`B at. % 12.68
`wt. % 2.75
`Si at. % 7.10
`wt. % . 4
`Fe at. % 2.23
`wt. % 2.5
`C at. % .25
`wt. % .06
`P at. % .032
`wt. % .02
`S at. % .031
`wt. % .02
`A1 at. % .093
`wt. % .05
`Ti at. % .052
`wt. % .05
`Zr at. % .027
`wt. % .05
`Co at. % .085
`wt. % .1
`
`ALLOY
`
`Fe73Si9B13
`Fe79Si5B16
`FCBIBILSSllSCZ
`Fe67Co13B|4Si1
`Fe40Ni33M04B|g
`
`0.35
`0.31
`0.22
`0.45
`0.23
`
`>090
`>090
`>0.90
`0.72
`0.50
`
`15
`
`25
`
`30
`
`35
`
`40
`
`50
`
`55
`
`60
`
`65
`
`Ni at. % 65.63
`wt. % 76.97
`Cr at. % 11.55
`wt. % 12.0
`B at. % 11.58
`wt. % 2.5
`Si at. % 7.13
`wt. % 4
`Fe at. % 3.14
`wt. % 3.5
`C at. % .12
`wt. % .03
`P at. % —
`wt. % ——
`S at. % —
`wt. % ——
`A1 at. % -
`wt. % —
`Ti at. % ——
`wt. % —
`Zr at. % -—
`wt. % —
`Co at. % .85
`wt. % 1.0
`
`10/13
`
`DOJ EX. 1011
`
`

`
`4,510,489
`9
`dimension of strip 18. The composite assembly is then
`placed within the hollow recess 60 of a rigid container
`62 composed of polymeric material such as polyethyl
`ene or the like, to protect the assembly against mechani
`cal damping. The biasing magnet 44 is typically a flat
`strip of high coercivity material such as SAE 1095 steel,
`Vicalloy, Remalloy or Arnokrome. Such biasing mag
`net 44 is held in the assembly in a parallel, adjacent
`plane, such that the high coercivity material does not
`cause mechanical interference with the vibration of the
`strip 18. Generally, biasing magnet 44 acts as one surfce
`of the package. Alternatively, two pieces of high mag
`netic coercivity material may be placed at either end of
`strip 18, with their magnetic poles so arranged as to
`‘induce a single pole-pair therein. This con?guration of
`the assembly is thinner but longer than that utilizing a
`single piece of high coercivity material in an adjacent
`parallel plane to the permeable strip. Alternatively the
`bias ?eld can be supplied by an external ?eld coil pair
`disposed remotely from the marker in the exit or aisle
`20
`way. In ‘this embodiment, the biasing magnet made of
`high coercivity material would not be required. Such a
`marker is not readily deactivated in the manner of mark
`ers equipped with biasing magnet 44. Further biasing
`magnet 44 can comprise a plurality of pieces of high
`magnetic coercivity material, as in the order of up to 10
`or more pieces, disposed longitudinally of strip 18. Ac
`cordingly, marker con?gurations in which the bias ?eld
`is provided by a hard ferromagnetic material located
`proximate strip 18 are preferred.
`‘
`As shown in FIG. 5, a soft, semi-?exible package may
`be used to protect strip 18 against damping. Thus, strip
`18 may be sandwiched between the faces of two pieces
`or either a ?ocked or velvet fabric 75. By adjusting the
`planar dimensions of each piece of the fabric to be some
`what greater than the corresponding dimensions of the
`strip 18, the edges of the fabric can be pressed together
`with adhesive tape 80, glued, heat sealed, sewn or other
`wise joined to form a compliant, sealed closure. The
`desired piece of high coercivity material required for
`magnetically biasing the strip 18 is then placed on the
`back surface of one of the fabric pieces, and adhered to
`it in order to prevent movement relative to the strip 18.
`The fabric sandwiched strip 18 is then placed inside an
`air-tight casing of polymeric ?lm just large enough to
`contain it. The package is sealed with a quantity of air
`contained therein to form a pillow-like shape. This
`package is ?exible and smaller in overall volume than is
`the corresponding rigid package. It is, however, more
`easily subjected to external pressure, which will damp
`the vibrations of the strip 18. This package is readily
`produced at high speed on standard packaging machin
`ery such as that used to package confectionary or dis
`posable medical supplies.
`Unlike markers which generate harmonics of the
`interrogation frequency in the pickup coil, resonant
`frequency markers generate a distinctive increase in the
`voltage induced in the pickup coil when the primary or
`drive frequency equals the resonant frequency. In the
`case of harmonic generating markers, the feature which
`distinguishes the presence of the high magnetic permea
`bility material