COMMISSIONER'S DECISION
OBVIOUSNESS; SECTION 45(4): Windshield Defogging Device
The differences between the applicant's device and the prior art do not
amount to invention. In the three rejected claims the sensor which activates
the heating element is inoperative below 100% humidity. The prior art sensors
are activated below 100% R.H.
Final Action: Affirmed.
This decision deals with a request for review by the Commissioner of
Patents of a refusal of claims C1 to C3 inclusive of patent application
130,413. The refusal was made under Section 42 of the Patent Act, and
was made by a letter dated November 25, 1975 issued as the result of
re-examination of the claims under Section 45(4) during conflict pro-
ceedings.
The application was filed on December 17, 1971 in the name of Takeomi
Nagasima for a "Defogging Glass Plate". Mr. N. Hewitt represented the
applicant at the Hearing conducted by the Patent Appeal Board on June 16,
1976.
This invention is for a glass plate containing electric heating elements
which drives off any moisture condensing on the glass. It may be, for
example, an automobile windshield, which is kept clear of moisture, frost,
ice etc. by the heating element. The electrical heating strip on the
glass surface is actuated by a moisture sensor containing a pair of spaced
electrodes. When moisture is detected by the sensor, an electric heating
circuit is actuated to remove the moisture by heat. Figures 1 and 3
given below show the basic component elements of the invention.
(see Figures I and III)
Claim C1, which is typical, reads as follows:
A defogging glass plate which comprises an electric heating
element in contact with the glass plate, said glass plate
having a moisture detecting sensitivity amplifying region
provided thereon, a sensor having a pair of electrodes which
are arranged in parallel with a gap of 0.2 mm therebetween and
which are fitted on the surface of the glass plate for
automatically detecting the presence of a water film in said
gap, a detecting circuit actuable by said sensors in detecting
a water film in said gap, and a control circuit actuable by
said detecting circuit to cause heating of the electric heating
element when a water film is present in the gap.
In the office letter claims C1 to C3 were refused for failing to patentably
distinguish over the following prior art
British Patent 884,967 Dec. 20, 1961 Miskin
U.S. Patents 3,071,746 Jan. 1, 1963 Kohl
2,735,907 Feb. 21, 1956 Inman
2,424,735 July 29, 1947 Boothroyd
3,255,324 June 7, 1966 Ovshinsky
The Miskin citation discloses a vehicle windscreen combined with
electrical heating means. Sensors in the form of spaced electrodes on
the glass surface respond to changes in electrical resistance produced
by mist formation and actuate the heating means. Claim 1 of Miskin reads
as follows:
A vehicle windscreen or other transparent body of electric-
ally non-conductive material or of a material of high
electrical resistance, having upon its surface electrodes
connected to means responsive to changes of electrical
resistance and associated with and arranged to control
the operation of means to prevent or reduce misting of the
said surface when this tends to take place as a result
of conductive deposits such as would be produced by con-
densation of water vapour thereon.
The Kohl patent claims a humidity sensing device which comprises spaced
sensing electrodes mounted on the surface of an adsorbing base, such as
quartz. Figure 1 in the Kohl patent depicts his invention.
(see formula I)
The Inman reference shows a moisture activated circuit sensor for measur-
ing the presence of falling rain. Boothroyd is concerned with a humidity
control apparatus for use in a refrigerated compartment. Ovshinsky relates
to an electrical moisture-responsive controlling device for closing an
electrical circuit. It is activated by moisture in the surrounding
environment.
The office letter stated (in part):
Claim C1 defines: Prior art describes:
A defogging glass plate See Miskin at page 1
etc., ...the glass plate, lines 20-28 and claim 2
wherein he describes and
claims an electrical heating
element to reduce or prevent
misting of a glass surface such
as a vehicle windscreen,
said glass plate having a While Miskin does not discuss
moisture detecting sensit- such a structure in his patent,
ivity amplifying region pro- yet it is held to be an obvious
vided thereon, and uninventive step in view of
Kohl who describes a humidity
sensor similar to that of
applicant having an electrode
bearing quartz surface, roughened
by grinding to reduce resistivity
of the sensor. See Figs. 5 and
6 (40, 42, 44) and Column 1
lines 29-38 and Column 3 lines
18-27,
a sensor having a pair of Miskin in his patent, describes
electrodes which are two strip electrodes attached to
arranged in parallel with a a glass window and arranged in a
gap of 0.2 mm therebetween parallel configuration as may be
etc., ...in said gap, seen at page 1 lines 33-42 and in
his lowermost drawing. The
definition whereby the gap is
0.2 mm. lacks patentable signifi-
cance in that such spacing may be
varied to produce any desired
operating point of the sensor
determined by voltage and degree
of moisture to be sensed. Miskin
discusses an electrode spacing of
six inches while the cited patents
of Inman and Boothroyd who both
show humidity sensors of the type
claimed in C1, describe a gap of
approximately 0.4 mm. See
Boothroyd at Column 4 lines 59-63
and Inman at Column 2 lines 28-31,
a detecting circuit Miskin describes a circuit in
actuable etc., .., when a his disclosure and as illustrated in his
water film is present in upper figure of the drawings, which
the gap. includes the detecting and control
circuit as claimed in C1.
Claim C2 defines: Prior art describes:
The defogging glass plate As discussed supra in conjunction
of claim 6 (C1) wherein with Kohl, see Figs. 5 and 6 (40, 42, 44)
said moisture detecting and Column 1, lines 29-38
sensitivity amplifying and Column 3, lines 18-27.
region is prepared by sand
blasting to the glass
plate.
Claim C3 defines: Prior art describes:
The defogging glass plate See Ovshinsky at Column 2
etc., ...by applying hydro- lines 3 to 21 and Column 5
philic material to the lines 6 to 30 who describes
glass plate. the use of a lithium
compound or composition
having hydrophilic prop-
erties which is applied
to the base on which are
supported spaced, parallel
electrodes to reduce
electrical resistance
between the electrodes.
In his responses of March 24, 1976 and June 1, 1976 to the Office letter,
the applicant stated (in part):
In particular, it is respectfully submitted that clearly
Miskin does not disclose or teach the necessity of having
a moisture detecting sensitivity amplifying region provided
on the glass plate and the Examiner in order to overcome
this omission of Miskin takes the position that this feature
is obvious and uninventive in view of the humidity sensor
of Kohl and the Examiner refers to Figures 5 and 6 of Kohl
and the description associated therewith. Clearly, as
admitted by the Examiner, Kohl is concerned with an electrode
bearing quartz surface which is a completely different surface
from a glass plate and the moisture detecting sensitivity
amplifying region of Kohl is completely different from that
of the present invention. Further, in the sensor of the
present invention it is a critical feature that the sensor
has a pair of electrodes which are arranged in parallel with
a gap from 0.1 to 10 mm therebetween and which are fitted to
the surface of the glass plate for automatically detecting the
presence of a water film in the gap. It is respectfully
submitted that neither Miskin nor Kohl disclose such a
feature and the Examiner takes the position insofar as the
size of the gap is concerned that the particular limitations
asserted by the applicant and for example in the conflict
claims 0.2 mm lacks patentable significance. Clearly, within
the overall range the spacing may be varied to produce any
desired operating point for the sensor determined by voltage
and degree of moisture to be sensed outside the aforesaid range
as is clearly set forth in the disclosure the sensitivity is such as
to severely limit the usefulness of the defogging plate. The primary
reference upon which the Examiner is relying is Miskin which has
an electrode spacing of six inches. It is respectfully submitted,
that to modify Miskin where the gap is six inches which is of
the order of 16 cm or a gap of 0.2 mm or the maximum 10 mm in
claim 1 would not be obvious to a person skilled in the art as
Miskin is concerned with a different type of sensor and the
teachings of Inman and Boothroyd is submitted have no relevance in
this direction. It is therefore submitted that the claims at
present on file clearly distinguish over the art cited by the
Examiner. It is further submitted that conflict claim C1 defines
an invention over the art. Insofar as conflict claims C2 and C3 are
concerned, it is respectfully submitted that these clearly dis-
tinguish over the art. As aforesaid insofar as conflict claim C2 is
concerned Kohl is concerned with a completely different material
and a completely different type of humidity sensor and with regard
to conflict claim C3 the Examiner has had to refer to Ovshinsky
which is still a further reference in an attempt to anticipate the claim.
It is respectfully submitted that the teachings of Ovshinsky which
are again concerned with a different type of sensor have no relevance
to the disclosures of Miskin which is the primary reference relied
on by the Examiner.
...
It is respectfully submitted that the disclosure of Kohl and the
invention set forth in Kohl is the fine grinding of a water adsorb-
ent substrate in a sensor for sensing the relative humidity of the
atmosphere and is for the purpose of reducing the circuit resistance
of such a substrate at relative humidities in the range 0 to 100% as
shown in Fig. 10 of Kohl. In contrast thereto conflict claims C1
is directed inter alia to the said blasting of a non-adsorbent
substrate i.e. plate glass for the purpose of causing water vapour
condensed thereon when the relative humidity is above 100% to form
a water film to cause current conductance between the electrodes
to actuate the detecting circuit. Thus it is submitted that Kohl
effects a different process (fine grinding) of a different substrate
(water adsorbent substrate) for a different purpose (to reduce circuit
resistance) in the different device (relative humidity sensor) and
as such the teachings of Kohl would have no relevance to the
invention as set forth in conflict claim C1 (er C2). Further, the
treatment of Kohl fine grinding in a plate glass substrate would
have minimal effect in enhancing the formation of the water film.
What we must determine is whether claims C1 to C3 are directed to a patent-
able advance in the art.
At the hearing Mr. Hewitt conceded that the Miskin reference was directed to
a similar device as his clients. The difference is in the sensor arrangement.
He stated that the applicant's invention detects the presence of a water film,
as compared to the detection of condensed vapor in the form of water droplets in
Miskin. We agree that the Miskin sensor is different from that used by the
applicant since in Miskin maximum sensitivity is obtained when his electrode
elements are spaced six inches apart. In the applicant's device the gap
ranges from 0.1 to 10 mm.
Considering the Kohl reference, we find there a humidity sensor having a
roughened adsorbing element in which "comb" type electrodes are mounted. The
applicant argues that Kohl "effects a different process (fine grinding) of a
different substrate (water adsorbent substrate) for a different purpose (to
reduce circuit resistance) in a different device (relative humidity sensor)."
Before commenting on Kohl we think it is important to define what is meant by
"humidity". According to the text "Heating and Air Conditioning," by
Burgess H. Jennings, March 1956, atmospheric air is defined as a "mechanical
mixture of gases." Further:
Another important constituent of air is water vapor (steam).
This vapor usually occurs in the form of superheated steam as an
invisible gas. However, when air is cooled to a certain tempera-
ture (the so-called dew point) the steam in the air starts to
condense and may be visible - as mist or fog, or as condensation
on cold surfaces (dew).
The water vapor (steam) mixed with dry air in the atmosphere is
known as humidity.
Relative humidity is defined as the ratio of the partial pressure
of water vapor in the air to the pressure which saturated water
vapor exerts at the temperature of the air.
Kohl's sensor for measuring relative humidity utilizes "nonporous material
having adsorbing characteristics." He stated (Col. 1) that "materials which
have been found to possess excellent adsorbing characteristics, with the
exception of their respective resistance ranges for 10 to 100% relative
humidity, are quartz (single crystal), fused quartz (poly crystalline) and
glass (high silica content i.e. 96% silica and over)." He continues "the
above-mentioned materials have a relatively smooth surface. However, it has
been found that by roughening that surface which is to be used for measuring
humidity the resistance range is appreciably lowered, that is lowered enough
to bring it within limits of practical utility."
It would appear that roughening the adsorbing surface will allow the vapor
molecules to adhere more readily and thereby develop sufficient resistance
sensitivity to enable. the electrodes to detect over a broad range of vapor
conditions. These conditions are indicate<< in Kohl to be from 10% to 100%
relative humidity. The applicant maintains that he is only concerned with
a sensor "to determine the formation of a water film on the glass plate."
From this analysis we conclude that as the relative humidity increases, the
number of molecules adhering to the surface increase until the dew point is
reached, at which time drops of moisture become visible. Consequently the
measurement of relative humidity envisaged by Kohl from 10 to 100%, and the
measurement of water film, as envisaged by the applicant, both utilize the
change in resistance due to water film thickness. We see no difference in
the formation of the "water film" pools of the applicant's arrangement from the
formation of the "water film" pools in Kohl.
Further the applicant states that he uses a moisture detecting sensitivity
amplifying region on his "plate glass" surface, This is prepared by a "sand
blast method" or by "imparting a hydrophylic property by coating." He argues
that this is different than Kohl, who uses fine grinding with #500 grit.
In Column 4, line 36, Kohl also specifies that roughness can be obtained by
acid etching. In our view roughening of the surface is to increase its
molecular attraction, and it is immaterial whether this is attained by sand
blasting or fine grinding, since both enhance the formation of a water film
by reducing the surface tension of the water.
On page 3 of the applicant's letter dated June 11, 1976, it is stated: "...
that by specifying high silica glass as a suitable material, normal plate glass
which forms the defogging glass plate of conflict C1 is not such a material
having adsorbing characteristics suitable for forming the substrate of the
device of Kohl and therefore the teachings with regard to such a relative
humidity sensor as set forth in Kohl have no relevance to the invention
set forth in conflict claim C1."
We find that Kohl, in column 1, line 26, does specify glass (96% silica
or over) comparable to the plate glass used by the applicant. Therefore we do not
see how the adsorbing material used by the applicant acts differently from the
adsorbing material indicated in Kohl.
On page 7 of the disclosure the applicant states that the "maximum electrical
resistance for the sensor for detecting moisture can be selected in the range
of 100,000 ohms to 10,000,000 ohms." Figure 10 of Kohl shows the range of
finely ground SiO2 to be from 100,000 ohms to 1,000,000,000 ohms. Since there
is a broad range of resistance values as the relative humidity changes, there
would be no problem in selecting any desired value to actuate a heating circuit
whether it is relative humidity below the dew point us in Kohl, or above 100
percent humidity as intended by the applicant.
It is true that Kohl is silent as to the gap between the electrodes, but since
the resistance values obtained are similar to that of the applicant it is a fair
assumption that the required electrode gap would be similar to that used by
the applicant.
Therefore, we conclude that the sensor arrangement used by Kohl is not a
different device from the moisture detecting sensitivity amplifying region
of the applicant. In Niagara Wire Weaving Co. vs Johnson Wire Works Ltd.
1939 Ex. C.R. at 273 Maclean J. stated that ["small variations from, or slight
modifications of, current standards of construction, in an old art, rarely
are indicative of invention; they are obvious improvements resulting from
experiences, and the changing requirements of users."] Claim C1 therefore, in
our view, fails to recite a patentable advance in the art.
Dependent claims C2 and C3 which specify sand blasting and the application
of hydrophylic material to the glass plate do not make a patentable combination
over what was recited in refused claim C1.
The Board recommends that the decision of the examiner to refuse claims
C1, C2 and C3 as lacking patentable subject matter be affirmed.
Gordon Asher
Chairman
Patent Appeal Board
I have reviewed the findings of the Patent Appeal Board and agree that
Claims C1 to C3 inclusive should be refused. The applicant has six
months within which to remove those claims or to appeal under Section 44
of the Patent Act.
J.A. Brown
Acting Commissioner of Patents
Dated at Hull, Quebec
this 14th.day of July, 1976
Agent for Applicant
Marks & Clerk
Box 957, Station B,
Ottawa, Ont.