Thermal measuring and testing – Temperature measurement – Composite temperature-related paramenter
Reexamination Certificate
2002-10-02
2004-08-17
Verbitsky, Gail (Department: 2859)
Thermal measuring and testing
Temperature measurement
Composite temperature-related paramenter
C374S102000, C374S004000, C374S057000
Reexamination Certificate
active
06776521
ABSTRACT:
The invention relates to a data carrier having an electrical circuit with the help of which indication means are implemented that are arranged to indicate a change of a parameter influencing the data carrier in relation to a threshold value of the parameter, which threshold value divides a first parameter range from a second parameter range.
The invention further relates to a circuit for a data carrier with the help of which indication means are implemented that are arranged to indicate a change of a parameter influencing the data carrier in relation to a threshold value of the parameter, which threshold value divides a first parameter range from a second parameter range.
The invention further relates to a method of determination for determining the occurrence of a change of a parameter influencing a data carrier, the occurrence of the change of the parameter being determined in relation to a threshold value of the parameter, which threshold value divides a first parameter range from a second parameter range.
A data carrier of the kind defined in the first paragraph, a circuit of the kind defined in the second paragraph, and a method of determination of the kind defined in the third paragraph are known from patent WO 99/53279.
The known data carrier is in the form of a passive data carrier, is suitable for detecting a change in the ambient temperature of the data carrier in relation to a temperature threshold, is intended for use in a vehicle tire, and has indication means that are implemented in the form of a mechanical maximum temperature measuring switch that forms a sensing means for sensing the ambient temperature. In essence, the maximum temperature measuring switch comprises two bars that slightly overlap one another in an overlapping region and that do not touch one another at a starting temperature. Each of the bars has a laminated structure comprising a layer of metal and a plurality of mutually differing layers of silicon. The laminated structure causes the two bars to bend in the same direction by virtue of the bimetallic effect if there is a change in temperature, with the first bar—due to the fact that it is differently sized from the second bar—undergoing less bending than the second bar. Hence, beginning from the starting temperature, the second bar bends relative to the first bar when there is a rise in temperature until it touches the first bar on one side of the latter. As the temperature continues to rise up to the threshold temperature value, the two bars slide against one another in the overlapping region. When the threshold temperature value is exceeded, the two bars lose physical contact with one another and—due to the removal of the force exerted on the first bar by the second bar—the first bar springs back substantially to its starting position. In this state the two bars differ appreciably from one another in the bending they show and, similarly to the situation that exists at the starting temperature, are not in physical contact with one another. Only if the ambient temperature falls back to the starting temperature is the bending of the second bar reduced sufficiently for it eventually to touch the first bar at a point of contact. In this situation, the maximum temperature measuring switch forms an electrically conductive, closed contact, which closed contact can be detected by means of an electrical circuit belonging to the data carrier. Hence it is only at this starting temperature that the maximum temperature measuring switch is controlled to its active state and is thus suitable for determining the fact that there has, at least once in the past, been a change in the ambient temperature of the data carrier in relation to the temperature threshold. This characteristic of the maximum temperature measuring switch is not critical especially if, following a temperature change of this kind occurring for the first time, the starting temperature obtains again at the time when the temperature change is determined to have occurred by means of a communication station provided and arranged to cooperate with the known data carrier.
In connection with a bimetallic sensor of the kind described above, reference may be made, for example, to U.S. Pat. No. 5,712,609. Reference should be made in this connection to FIGS. 1A to 1D, 2A to 2D, and 3 and the related passages in the description. This reference to the patent in question is deemed to incorporate the disclosure thereof in the present document by reference.
There is a problem with the known data carrier in that, if the ambient temperature is higher than the threshold temperature value and the passive data carrier is fed with power at this time, it cannot be clearly determined with the maximum temperature measuring switch—due to the fact that this can only be done intermittently as a function of ambient temperature—whether there was a temperature change of this kind in the past, given that the two bars are not in contact with one another when the starting temperature exists, both before any such temperature change occurred for the first time and after a temperature change of this kind. This fact may well not be critical where the application is to a vehicle tire, because a vehicle tire is virtually always able to cool down to its starting temperature after a run during which a temperature change of this kind may possibly have occurred. In other cases however, the fact described above may have disadvantageous consequences.
It is an object of the invention to overcome the problems outlined above in a data carrier of the kind defined in the first paragraph above and in a circuit of the kind defined in the second paragraph above and in a method of determination of the kind defined the third paragraph above, and to provide an improved data carrier and an improved circuit and an improved method of determination.
To achieve the object detailed above, in accordance with the invention, provision is made, in a data carrier of the kind defined in the first paragraph above, provision is made for the indication means to be arranged so as to give a permanent indication of the change of the parameter during the time following the occurrence of the change for the first time.
To achieve the object detailed above, in accordance with the invention, provision is made, in a circuit of the kind defined in the second paragraph above for the indication means to be arranged so as to give a permanent indication of the change of the parameter during the time following the occurrence of the change for the first time.
To achieve the object detailed above, in accordance with the invention, provision is made in a method of determination of the kind defined in the third paragraph above for the determination of the occurrence of the change of the parameter to be permanent during the time following the occurrence of the change for the first time.
The provisions according to the invention provide the advantage that, regardless of a parameter that exists momentarily and influences the data carrier, a permanent indication of high reliability can be obtained of a change of the parameter that has already occurred earlier, and as a result the occurrence of this change can be determined. This is of advantage principally if the parameter is formed by the ambient temperature and if the data carrier is used with a deep-frozen foodstuff to determine that there has been, in the past, an unwanted break in the deep-freezing. In connection with the determination of a break in the effect of deep-freezing on a foodstuff, or in other words when determining the occurrence of a change in temperature in relation to a defrosting point of the foodstuff that forms a threshold temperature value, it is possible to avoid deleterious effects on the health of human beings by means of the provisions according to the invention, because people can be prevented from eating a foodstuff of this kind that may possibly have already been defrosted once in the past and have then been deep-frozen again.
In a solution according to the invention, it has also proved advantageous if t
Simons Kevin
Verbitsky Gail
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