Note: Descriptions are shown in the official language in which they were submitted.
1 ~7667'~
ELEC~RIC HE~TER PLATE
~ he present invention relates to an electric heate:r
plate.
A general understanding can be obtained of ~he
S construction of electric heater pla~es by reading U,S.
patent 4,137,447 which issued on January 30, 1979. These
ele~ric heater plates are par~icularly useful as a back-
lite in a motor vehicle. Under fogging or icing condi-
tions, curr~nt is run through the electrical heater plate
10 to defog or deice the same thereby providing a clear window
in ~he rear of a vehicle. In fact, New Yor~ State pre-
sently requires that all vehicles sold in that State to be
equipped with such a device.
No search was conducted on the subj ect matter of
15 this specification in the U.S. Patent Office or any other
search facility.We are unaware of any prior art more
relevant to the subject matter of this specification than
that which will be set forth hereinbelow.
Also known at the time of the invention described
20 in this specification is an electric- heater plat~ 10, such
as ~hown in Figures 1 and 2 of the drawings. Such an elec-
~rical heater plate 10 is used in vehicles manufactured by
the Ford Motor Company which are equipped with electrically
hea~ed backlitesO In particular, the electrical heater
25 plate is formed from a base which is a glass sheet 12. The
glass sheet has an opaque, nonconductive coating 14 which,
in the embodiment shown in Figure 1, extends around the
entire perimeter of the glass sheet 12. The purpose of
this opaque, nonconductive coating is to provide a sigh~
30 shield for lending more uniform characteristics to the
appear~nce of the tempered glass sheet when viewed fr~m
1 178~77
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the opposite side of the vehicle. The opaque, non-
conductive coating is used to block out the color developed
by a layer of silver ceramic material which is used to form
the terminal areas for the electrically heated grid lines
on the electric heater plate 10. The opaque coating also
shields and protects the adhesive system used to mount the
backlite from direct sunlight. The color of the opaque,
nonconductive coating can be judiciously selected to give a
better color coordination with the exterior color of the
automotive vehicle in which the heater plate is to be
installed.
In a single operation, a plurality of thin lines
16-16 and larger terminal areas 18-18 are printed on the
glass sheet 12 using a silver ceramic material. The thin
lines 16-16 are printed on the surface of the
glass sheet 12 and the terminal areas 18-18 are printed on
the opaque, nonconductive coating 14. In effect then, the
opaque, nonconductive coating 14 is used as a sight shield
to block a view of the enlarged terminal areas 18-18 when
one views the electric heater plate 10 from the surface
which does not have printed material thereon. A conductor
strip ~0 is soldered at locations identified by the
numerals 22-22 to the enlarged terminal areas 18-18.
While the drawings in this case show only the left
hand side of the article being manuactured, it is obvious
that the right hand side of the same article is being
manufactured in the same manner. In this manner, a pair of
electrical leads are provided to the glass sheet so that an
interconnection may be made by these leads to an electrical
circuit, now shown, which provides the power to the thin
lines 16-16, which in turn provides heat to the glass sheet
in order to deice or defog the same.
Certain difficulties have been encountered in
manufacturing electric heater plates in accordance with the
above description. As described above, the conductive
silver ceramic for the terminal areas has been applied
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directly over the opaque, nonconductive ceramic coatings.
There is a defini~e mismatch of the expansion coefficients
between these two materials when the bac}clite is heated,
forme~ and quenched. This results in a weak solder bond o
5 the conductor strip to the silver c~ramic coating. Al~o, a
certain porosity can be developed in the curing and firing
of the opaque, non onductive ceramic coating and the
overlying silver ceramic coating because of an outgassing
of an organic portion of the opaque, nonconductive ceramic
coa~ing. The increased porosity of the silver ceramic
coating also results in a weakeni~g of the bond between the
silver ceramic coating and the opaque, nonconductiv~
coatlng as well as the solder joint between the conductor
strip and the terminal areas formed by the silver ceramic
material.
This invention relate~ to an electric heater plate
and, more particularly, to an electric heater plate which
finds principal use as an electrically heated backlite in a
mo~or vehicle. The bac~lite is heated in order to defrost
or defog the same~
In accordance with this invention, an electrically
heated backlite is constructed in the following manner.
A glass sheet is used as the substrate for the electrically
heated backlite. This glass sheet has an inner surface
which will face the interior of a vehicle when in an installed
position. The glass sheet also has an outer surface which
will face the exterior of the vehicle when in an installed
position.
An opaque, electrically nonconductive coating is
bonded to at least two portions of the inner surface of
the glass sheet. The two portions of the electrically non-
conductive coating are spaced apart from one another on
the inner surface of the glass sheet. Each of the portions
has atleast one open area formed therein in which the inner
surface of the glass sheet is exposed.
B ~ '7
~ n electrical resistance heater line having spaced
terminal ends is bonded over a majority of its bonding surface
area to the inner surface of the glass sheet. The heater
line extends in a length dimension from one of the portions
of the electrically nonconductive coating to the other of
the portions of the electrically nonconductive coating.
first of the terminal ends of the heater line (1) overlies
and is bonded to at least one of the portions of the electrically
nonconductive coating, and (2) overlies and is bonded to
all of the inner surface of the glass sheet exposed in the
open area formed in the one of the portions of the electrically
nonconductive coating. The second of the terminal ends
of the heater line (1) overlies and is bonded to at least
a part of the other of the portions of the electrically
nonconductive coating, and (2) overlies and is bonded to
all of the inner surface of the glass sheet exposed in the
open area formed in the other of the portions of the elec-
trically r~onconductive coating. The bond formed between
the terminal ends and the inner surface of the glass sheet
is stronger than the bond between that portion of the terminal
end which is bonded to the portion-of the electrically noncon-
ductive coating.
At least a pair of electrical conductors are providedO
Bonds are formed to bond individual ones of the conductors
to one of the terminal ends of the heater line at a location
where the terminal end overlies the inner surface of the
glass sheet exposed by the open area of the portion of elec-
trically nonconductive coating.
The open area of the electrically nonconductive
coating which exposes the inner surface of the glass sheet
may be completely open or may be formed in one of many
different patterns, for example, a plurality of elongated
slots, a plurality of small square openings or a plurality
of small circular openings.
The novel features that are considered characteris-
tic of the invention are set forth with particularity in
the appended claims. The invention itself, however, both
as to its organization and its method of operation, together
with advantages thereof, will best be understood from the
1~6~7'7
followlng description of specific embodiments when read
in connection with the accompanying drawings, wherein like
refer~nce characters indicate like parts throughout the
several figures, and in which:
Figures 1 and 2 are drawings which depict the prior
art known in this area which has been described in detail
above~;
Figure 3 is an elevation view of an electric
heater plate con~tructed in accordanc~ wi~h the ~eachings
10 of ~his invention; and
Figure 4 is an enlarged cross-section view ~aken
along llne IV-IV of Figure 3.
.. . . ... .
In Figures 3 and 4 there is shown an electrical
heater plate formed in accordance with the teachings of
15 this invention. ~hese figures show only the left side of
an electric heater plate which in this preferred embo-diment
will be an 21ectrically heated backlite for a motor
vehicle. The right side of the electricall~ heated
backlite is formed in a similar manner as the left side so
that an electrical potential may be applied across the
backlite in order to defog or defrost the same.
In accordance with ths teachings of this inven-
tion, an electrically heated backlite, generally desi~nated
25 by the numeral 30, is formed on a glass sheet 32. Th~
~lass sheet is made and cut to size by methods well kno~-
~in the art, so no further description thereof will be
undertaken herein. An opaque, nonconductive coating 34 is
provided, in the case of the e7ectrically heated backlite
30 30 of the preferred construction, around substantially the
~ 17667 ~
entire perimeter of the backlite. This opaque, noncon-
ductive coating is formed by silk screen printing a black
ceramic paste,such as paste#24-1802 manufactured by Ace
Drakenfeld Co~, on the glass sheet 32. This opaque,
nonconductive coating 34 is then dried so that it will not
smear. As is best seen in Figure 4, open areas 36-36 are
provided for purposes which will hereafter be described.
After the opaque, nonconductive coating 34 has
been dried on the glass sheet 32, a second silk screen
printing operation takes place to place a conductive silver
ceramic paste on the electrically heated backlite 30. This
silver ceramic paste forms thin grid lines 38-38 and a
plurality of terminal areas 40-40. The uppermost terminal
areas 40-40 shown in Figure 3 each are used to interconnect
a plurality of the thin grid lines 38-38. The materials
for use in this operation are discussed in detail in my
aforementioned patent, so no further discussion thereof
will be undertaken herein. The terminal areas 40-40 also
overlie in part the opaque, nonconductive coating 34 and
also in part an a~sociated one of the open areas 36-36 of
the opaque, nonconductive coating. This is illustrated
best in Figure 4.
~ fter the silver ceramic paste has been applied to
form the thin grid lines 38-38 and the terminal areas
40-40, the entire unit is then placed on a suitable fixture
and sent through a glass tempering lehr in which the glass
is heated to a temperature of about 650C. During this
heating process, the opaque, nonconductive coating and the
thin grid lines 38-38 and terminal areas 40-40 are cured~
In the case of the opaque, nonconductive coating 34, it
becomes thoroughly bonded to the surface of the glass sheet
32. In the case of the thin grid lines 38-38, they are
bonded over their length to the surface of the glass sheet
32. In the case of the terminal areas 40-40, they are in a
1 ~7~7'~
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small part adhered to the opaque, nonconductive coating 34,
but mainly are bonded to the sur~ace of the glass sheet 32
in the locations where the open areas 36-36 are locatedO
After the glass sheet 32 has been heated throughout its
entire extent, the entire glass sheet is rapidly quenched
in order to temper the same.
After the tempering operation, a conductor strip
42 is solder bonded by means of solder 44, shown only in
Figure 4, to the terminal areas 40-40 of the electrically
heated backlite 30. The solder bonding is carried out only
in those areas of the terminal areas 40-40 which overlie
the open areas 36-36 of the opaque, nonconductive coating.
The solder bonding is accomplished in these areas because a
stronger solder junction can be achieved between the
terminal area supported directly on the glass sheet 32 than
on areas of the terminal area which would be supported on
the opaque, nonconductive coating 34. The reason that the
junction is better is the absence of a third material with
a different coefficient of expansion between the conductive
layer and the base glass.
To make the electrically heated backlite 30
functional, electrical connection is made from the lower
terminal area 40 on both sides of the backlite, only the
left one being shown in the drawings, to the electrical
generation system of the motor vehicle. This generation
system provides the potential which when actuated causes a
flow of current through the thin grid lines and the re-
sultant resistance heating of the electrically heated
backlite 30 to cause a defogging or deicing thereof. The
manner of connecting and using such electrically heated
backlites is well known in the art, as is evidenced by the
many millions of vehicles currently on the road which have
such systems installed therein.
67~
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While particular embodiments of the invention have
been illustrated and described, it will be obvious to those
skilled in the art that various changes and modifications
may be made without departing from the invention and it is
intended to cover in the appended all such modifications
and equivalents as fall within the true spirit and scope of
this invention.
