Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
1999-09-17
2001-04-17
Wu, Daniel J. (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S551000, C340S457100, C340S286080
Reexamination Certificate
active
06218944
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a label for marking and remote detection of objects, comprising a capsular housing of a material, which is non-magnetic, electrically non-conductive and resistant against external influences, the housing comprising a lower portion and a cover, between which a cavity is formed, and at least one elongated sensor element, which is arranged in the cavity and consists of amorphous magneto-elastical material with high magneto-mechanical coupling.
DESCRIPTION OF THE PRIOR ART
Labels of the kind described above are disclosed in for instance the European patent publications EP-A2-0 093 281 and EP-A2-0 096 182, in the American patent publication U.S. Pat. No. 4,647,917, in the international patent publication WO88/01427 and in the published Swedish patent application 9402943-6. According to these publications the labels are provided with an internal space, in which one sensor element or a plurality of sensor elements is/are arranged.
Each sensor element has the shape of a ribbon, a strip or a wire and consists of an amorphous metal alloy with specific compositions, which give the sensor element magneto-elastical properties with high magneto-mechanical coupling. Through its magneto-mechanical coupling a sensor element may be forced into mechanical resonance by supplying magnetic energy thereto, for instance as an interrogation or interference signal. The sensor element will oscillate in its longitudinal direction, and this longitudinal resonance may be detected by means of a suitable magnetic detection means, such as a coil.
Furthermore, each label is often provided with several sensor elements as described above. By designing the sensor elements of a label in a way, such that the resonant frequency of each sensor element lies within a unique frequency band, the resonant frequencies of all sensor elements present in a label may be simultaneously detected. By arranging the sensor elements of each label in given relationships with respect to each other, a code for identifying the label, and hence also for identifying the object to which the label is attached, may be obtained. According to an encoding procedure the angles between the sensor elements of the label are used for defining a code value, and consequently any given code value may be obtained within a predetermined number range by varying the angles.
In WO88/01427 a method is disclosed for simultaneous detection of several identical labels or sensors in a detection zone. For this purpose a magnetic bias or control field is used, which is heterogeneous inside the detection zone as regards the direction and/or strength thereof. The resonant frequencies of the sensor elements are strongly influenced by the surrounding magnetic field, and thanks to the varying magnetic bias field such sensor elements may be simultaneously detected, which are identical but which are located at different positions within the detection zone and are thus exposed to magnetic fields of different strength or direction.
It is very important for labels of the kind described above that the longitudinal resonance oscillations of the sensor element may occur with a minimum amount of disturbance from the environment. Common sources of disturbance are for instance the inevitable gravity force, limited freedom of movement due to the suspension or mounting of the sensor element in the label, frictional losses due to contact between the sensor element and the surrounding walls of the internal space of the label, etc. To be as useful as possible in sensor applications the sensor element should in principal exhibit a fully uniform oscillation, which completely lacks directional dependence. In an ideal situation this can be regarded as a sensor element freely floating in vacuum, but this is impossible to realize in a real situation, obviously enough.
Previously known methods for housing the sensor elements in their labels suffer, among other things, from the following considerable disturbances and defects:
A sensor element which is lying flat or standing from a longitudinal side will be restricted, in terms of its resonance oscillation, by frictional forces due to the weight of the element as well as the frictional properties as regards the contact surface to the label.
If the sensor element is arranged standing from a short side, the oscillating movements of the element will be transmitted into surrounding parts of the label, thereby causing a fifty per cent decrease of the resonant frequency of the element or causing intermittent oscillation modes.
A sensor element, which for some reason is too bended or twisted, will cause a considerable reduction of the longitudinal oscillation amplitude.
For physical reasons it would be highly recommendable to mount the sensor element at the center point thereof. However, for manufacturing reasons it has proven difficult to locate this center point exactly, and even very small deviations from a correct center point will lead to beats in the resonance oscillations. Considerable manufacturing costs are required in order to obtain a sufficiently precise center point mounting. Furthermore, the ends of the ribbon may be bended due to the gravity field of the earth.
As an alternative, if the sensor element is supported at its ends, which would be reasonable from a physical point of view, a non-negligible risk of bending due to the gravity and the element weight exists in this situation too.
If the sensor element is mounted or supported at other points than the ones described above, undesired disturbances will be present in the resonance oscillations of the element.
In the Swedish patent application No. 9402943-6 previously filed by the present applicant a label design is disclosed, where the risk has been reduced for harmful influence on the sensor elements contained in the label from for instance the surrounding gravity field. The sensor elements have been given a non-planar sectional shape, said shape enabling the elements to maintain their straightness in a better way. However, at least one mounting point is still required for each sensor element, thereby causing problems as described above. Furthermore, a non-planar sectional shape is disadvantageous in that the external height of the label becomes larger, since the sensor elements require more space in the vertical direction inside the label, and in that the sensor elements are difficult—and consequently expensive—to produce.
EP-A2-0 093 281 and EP-A2-0 096 182 suggest to place the sensor elements between two pieces of fabric, said pieces of fabric in turn being contained in a wrapping of polymeric film. Such a label has the advantage of a small size, but on the other hand the label has a poor protection against external influences due to its softness.
EP-A1-0 704 828 suggests the possibility of placing a magneto-elastical or magneto-strictive sensor element in a corresponding cavity, which is formed as an integrated portion of the apparatus housing of for instance a clock radio. Alternatively, the sensor element may be placed in a cavity in a packing made of carton or the like for the goods. Accordingly, the sensor element will be relatively well protected against external forces, but the internal forces—due to the friction—in the cavity may severely reduce the sensor function of the element. In addition this solution does not seem cost efficient.
SUMMARY OF THE INVENTION
It is an object of the present invention to remedy the problems described above and provide a label, in which the sensor element or sensor elements is/are arranged or stored in the label with minimum damping and risk of interference and in which the sensor element will be given a good protection against external mechanic influences thanks to the design of the label. Furthermore, the label shall be very simple and inexpensive to massproduce and must not interfere with the magnetic flux therethrough.
In particular the present invention aims at providing a label, where twisting or bending of the sensor element is prevented, where the need for a fix mounting or storing of
Kiesewetter Lothar
Tyren Carl
Zillessen Harald
James Ray & Associates
Nguyen Tai T.
Wu Daniel J.
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