LABEL FOR MARKING AND REMOTE SENSING OF OBJECTS

Abstract: Label for marking and remote sensing of objects, comprising a cassette-type socket (2) made from a non-magnetical and electrically non-conductive material with a strong resistance against external influence, said cassette being provided with a cavity (3) formed therein. At least one thin foil strip (1) of an amorphous magnetoelastic material is movably arranged in said cavity (3), the strip (1) extending in a rectilinear way and having a cross-sectional shape deviating from a planar cross-sectional shape, the strip (1) thereby maintaining its straightness despite the influence from forces normally acting upon the label in the detection zone.

Description: Label for marking and remote sensing of objects The present invention relates to a label for marking and remote sensing of objects, said label comprising at least one elongated strip or tape made from a magnetoelastical material with a high magnetomechanical coupling, the strip being movably arranged within a cavity of the label. Labels of the kind mentioned above are known from e.g. WO 88/01427, EP-B-0 096 182, and WO 93/14478; According to these publications the labels are provided with an internal cavity, in which at least one strip of an amorphous magnetoelastical material is arranged. The strip material has a high magnetomechanical coupling, i.e. a mechanical load on the strip also causes a change in the magnetic properties of the strip. The strip constitutes a kind of a mechanical resonance element with a resonance frequency in a certain frequency band. If more than one strip is provided, the frequency bands are normally displaced in relation to each other. According to a coding method the angles between the amorphous elements of the label are used to define the code position. Consequently, each element may be arranged to represent any desired code value within a predetermined number range. Label detection is carried out by exposing the strips to a magnetic interference signal, which forces the strips into a state of mechanical self-oscillation. By means of a magnetic detection coil the strip resonance may be detected. The strip resonance frequency is strongly influenced by a surrounding magnetic field, and hence a control field is used so as to vary the magnetic field in an interrogation zone, thereby making it possible to simultaneously detect identical strips, that are exposed to a magnetic field of different strength or direction. According to the Swedish patent application No. 9401436-2 from present applicant, which has not yet been published, it is suggested to use geometrically identical strips, i.e. strips with the same length, width, and thickness which are exposed to an influence for changing the strip mass, while preserving the magnetic properties of the strip. For example, the strips are provided at their respective ends with elements - weights - changing the strip mass. It is a common fact for all the applications mentioned above that the strips must be arranged in a label cavity, so that the strips may vibrate freely withour. contacting the walls of the cavity. Furthermore, they must be well protected against mechanical influence in the cavity. Since the strips being used are made from a thin amorphous magnetoelastical foil, the thickness of which is in the order of 25 μm, it is realized that the strips may be exposed to a bending force caused by influence from the gravity alone. If, in addition, the strips are provided with weights at their respective ends, the bending may become relatively large. Because of the risk of such a bending, the element cavity, in which the strip or the strips are to be arranged, has been dimensioned with a sufficient depth in order to prevent the strips from contacting the cavity walls, should such a bending occur. Obviously, this has influenced the label thickness undesirably. As previously mentioned, to detect the label, the strips are forced into a state of self-oscillation in the strip length direction, the strip resonance being detected by means of a magnetic-detection coil. In order to obtain a satisfactory detection result the straightness of the strips is important. If the strips are curved, there is a risk for loosing energy. A transition of the supplied energy to a bending mode of oscillation occurs, and the detection result is severely impaired. It is an object of the present invention by an appropriate design of the amorphous magneto-elastical strips contained in the label to provide the strips with a bending stiffness sufficient enough to prevent a harmful bending of the strips due to influences from forces in the detection zone, at the same time avoiding a harmful frictional influence caused by a strip contacting the cavity walls, e.g. static electricity. It is another object of the invention to facilitate a reduced label thickness in comparison with previously known labels of this kind, by appropriately designing said strips. The objects set out above are achieved by designing the label according to the features of the appended patent claims. The invention will be described below with reference to the embodiments shown on the accompanying drawings . FIG. 1 is an enlarged perspective view of a transducer element used in the label according to the invention. FIG. 2 is a cross-sectional view according to arrows A-A in FIG. 1. FIG. 3 is an enlarged perspective view of an embodiment of a transducer element used in the label . FIG. 4 is a cross-sectional view according to arrows B-B in FIG. 3. FIG. 5 is a sectional view of a label according to the invention, where only one transducer element is arranged in the label cavity. FIG. 6 is a sectional view of an embodiment of the label according to the invention, where several transducer elements are arranged in the label cavity. FIG. 7 is yet another embodiment of the label according to the invention. FIG. 8 is a horizontal sectional view of the labels according to FIGS. 5-8. FIG. 9 is an alternative embodiment of the label shown in FIG. 5, where the transducer element is supported at its ends rather than at its center. FIGS. 1-4 show examples of transducer elements for use in the label according to the invention. An element 1 of FIG. 1 consists of a thin strip of an amorphous magneto¬ elastical material. The strip has a length of about 5 cm, a width of about 1 or 2 mm, and a thickness of about 25 μm. Particularly from FIG. 2 it appears that the strip has a curved cross-section with an arched shape, which provides the strip with an increased bending stiffness as well as an increased torsional stiffness. By the increased bending stiffness the strip maintains its straightness within the label, despite the loads normally exerted on the label in the detection zone. In the embodiment shown in FIG. 3 and 4 the strip has an angular cross-section rather than an arched one. This cross-sectional shape also provides the strip with an increased bending stiffness, which enables the strip to maintain its straightness, even if the thickness of the strip material is small. In FIG. 5 an embodiment of a label according to the invention is shown, comprising a transducer element 1 arranged in a label cavity. The label comprises a cassette- type socket 2 made from a stiff material, which has a high resistance against external influence and which is non¬ magnetic and electrically non-conductive or only electrically conductive to a minor extent. Preferably the cassette 2 is formed by a stiff plastic material. The cassette 2 is provided with an internal cavity 3 for storing of least one transducer element 1 of the kind shown in FIGS. 1-4. In the embodiment according to FIG. 5 the label only comprises one transducer element 1 constituted by an elongated strip of an amorphous magnetic elastical material, which for instance is formed as shown in FIGS. 1 och 3. In this case the strip 1 is provided with small weights at its ends, the purpose of which is to change the element mass. The strip 1 is supported at its center by a pin 6 protruding from the bottom of the cassette 2, and the strip is fixed to the pin 6 by for instance gluing or form dependent engagement, or in any other suitable way. Thus, the strip 1 protrudes from the pin 6 in both directions while maintaining its straightness as well as the ability to freely oscillate in the longitudinal direction. By its bending stiffness the strip 1 is prevented from bending due to influence from forces normally existing in the detection zone to such an extent, that the strip contacts the bottom of the cassette 2 or a lid 4 closing the cassette 2. After the strip has been installed in the cassette 2 and the lid 4 has been attached, the label is ready to be used. In FIG. 6 a label according to the invention is illustrated as being provided with four transducer elements 1. According to this embodiment each transducer element 1, i.e. each strip 1, is arranged in a separate cassette 2, each of the respective cassettes substantially corresponding to the cassette 2 described in conjunction with FIG. 5. These cassettes or sub-cassettes 2 are arranged on top of each other in a pile, and the uppermost sub-cassette is sealed or closed by a lid 4. A horizontal sectional view of the label is shown in FIG. 8, from which it appears that the strips 1 are angularly displaced with respect to each other in predetermined angles between the strips 1. The embodiment according to FIG. 6 thus provides particular advantages with respect to the angular setting of the strips 1. Each strip 1 is mounted in advance in its respective sub-cassette 2, the sub-cassettes then being piled upon each other. The angular setting may then be carried out by turning the sub-cassettes 2 in predetermined angles with respect to each other, then attaching the lid 4, and fixing the sub-cassettes and the lid with respect to each other. For clarity reasons the label according to FIG. 6 is out of clarity reasons shown in an excessive scale and therefore seems to be have a substantial height, but the label has in fact quite moderate height dimensions. With a strip length of about 4 cm the label diameter becomes approximately 5 cm, and the total height should in practice turn out to be about 3-4 mm. In FIG. 7 there is shown a label according to the invention, the height dimensions of which being even smaller. This is accomplished by attaching the strips 1 directly on top of each other with a spacing means in the bearing points. However, for such an embodiment it is necessary to carry out the angular setting of the strips 1 already when the strips are mounted in the cavity 3 of the cassette 2. After the directions of the strips 1 have been set, the lid 4 is attached and the label is closed. In the embodiments described above of the label according to the invention the strips 1 are centrally supported in the label cavity 3. However, this need not be the case in all applications of the invention. An alternative embodiment is shown in FIG. 9, according to which the strips 1 are suspended with thin wires or springs 7 in the respective ends. The suspension of the strips 1 with thin wires or springs obviously must be carried out in such a way that the longitudinal oscillations of the strips 1 are not prevented. Thanks to the bending stiffness of the strips the strips 1 are extending along a straight line between the suspension points. The invention has been described above with reference to some examples, but the invention is not limited to those embodiments and may be varied within the scope of the appended patent claims.

Claims: CLAIMS 1. Label for marking and remote sensing of objects, comprising a cassette-type socket (2) made from a non- magnetical and electrically non-conductive material with a strong resistance against external influences and provided with a cavity formed in the interior of the cassette, at least one elongated strip of a magnetoelastical material with a high magnetomechanical coupling being movably arranged within said cavity, c h a r a c t e r i z e d in that at least one thin foil strip (1) of an amorphous magnetoelastical material is movably arranged in said cavity (3) , said strip (1) having a rectilinear extension and a cross-sectional shape deviating from a planar cross- sectional shape, the strip (1) thereby maintaining its straightness despite the influence from forces normally exerted upon the label in the detection zone. 2. Label according to claim 1, c h a r a c t e r i z e d in that each strip is supported at the center of the strip in said cassette cavity. 3. Label according to claim 2, c h a r a c t e r i z e d in that the label is composed of a number of sub-cassettes (2) arranged upon each other in a " pile, one strip (1) being mounted in each respective sub- cassette (2) . 4. Label according to claim 2, c h a r a c t e r i z e d in that a number of strips (1) are arranged in the same cavity in said cassette with angular displacements and with a spacing means in the bearing points between adjacent strips. 5. Label according to claim 1, c h a r a c t e r i z e d in that each strip (1) is suspended at its respective ends by means of at least one thin wire or spring. 6. Label according to any preceding claim, c h a r a c t e r i z e d in that each strip (1) has a cross-sectional shape with such a bending resistance, that the strip maintains its rectilinear length extension thanks to its bending stiffness resulting from said bending resistance, despite the influence from forces acting upon the strip in the detection zone.

Inventors: CLARK ARTHUR E, TYREN CARL, CLARK, ARTHUR, E., TYREN, CARL
Applicants: CLARK ARTHUR E, RSO CORP, TYREN CARL, CLARK, ARTHUR, E., RSO CORPORATION N.V., TYREN, CARL
Application year: 1995
Main classification: H04B1
IPC codes: G01S13, G01V3, G01V15, G06K7, G08B13