Interference No. 103,036
Another embodiment of the battery-
strength indicator device of the present
invention is shown in FIG. 10. The indicator
device 10D is a strip like device having
first and second superimposed layers 30 and
32 which are attached together in the same
manner as strips 30 and 32 in FIG. 3. At
least one of the strips is transparent.
Conductive layers 64 are sandwiched between
the first and second layers. The conductive
layer is reduced to a small cross-section 65
in the indicator zone 66. Within the
indicator zone, the conductive layer is
covered with a small amount of a pyrotechnic
chemical 68 sensitive to heat. Surrounding
the pyrotechnic chemical is a color
indicating, heat-sensitive material 70 which
will undergo a visible color change, either
permanent or temporary, when the material is
heated to at least a predetermined
temperature. This battery-strength indicator
device is a one-shot device; the pyrotechnic
chemical will only decompose or react once.
The pyrotechnic chemical undergoes rapid
decomposition when it is heated to a
predetermined temperature. The resistance of
the conductive layer in the reduced cross-
sectional area 5 is selected such that
current flow at a minimum predetermined
voltage through the conductive layer will
raise the area to a predetermined temperature
which will cause the pyrotechnic chemically
to decompose or otherwise react. The
pyrotechnic chemical in turn will raise the
temperature of the color-indicating, heat
sensitive material to the predetermined
temperature for color change. [Emphasis
added.]
Although the indicator device of
FIG. 10D is shown with a color-indicating,
heat-sensitive material, the device can also
be fabricated with the pyrotechnic chemical
alone, thereby causing a slight charring to
the strip which is noticeable. One of the
strips can also be made of a material that is
sensitive to temperature and will undergo a
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Last modified: November 3, 2007