IN THE CANADIAN PATENT OFFICE
DECISION OF THE COMMISSIONER OF PATENTS
Patent application 3502,931 having been rejected under Rule 47(2) of the
Patent Regulations, the Applicant asked that the Final Action of the
Examiner be reviewed. The rejection has consequently been considered by
the Patent Appeal Board and by the Commissioner of Patents. The findings
of the Board and the ruling of the Commissioner are as follows:
Agent for Application
Ridout & Maybee
Suite 2300, Richmond-Adelaide Centre
101 Richmond St. W.
Toronto, Ontario
M5H 2J7
Commissioner's Decision
Obviousness: Electric Fuse
Multiple helical cadmium fuse elements embedded in sand grains
of specified purity now specified in the amended claims clear
the cited art.
Final Action: Reversed
This decision deals with the applicant's request for review by the
Commissioner of Patents of the Final Action on application 352,931 (class
306-157) filed on May 28, 1980. It is assigned to Kearney-National Inc.
and is entitled Electric Fuse and Method of Interrupting an Electric
Current. The inventor is Vojislav Narancic. The Examiner in charge issued
a Final Action on August 6, 1982 refusing to allow the application. In
view of information provided in supplemental letters subsequent to the
response to the Final Action, the Patent Appeal Board believes a review of
the evidence on file permits a sufficient assessment of the merits of the
application without conducting a Hearing. The Board recognizes that
Applicant's right to a Bearing has not been waived.
The subject matter of the application relates to electric fuses for
interrupting all values of electric current in a high voltage circuit.
Figures 2 and 3 are illustrated below.
<IMGS>
Helical fusible ribbon elements 11-15 are embedded in silica sand 10 within
tubular housing 1. These elements are attached to sleeves 8 and 9
contacting end caps 5 and 6. Each fusible element is provided with notches
16.
In the Final Action the Examiner refused the application in view of the
following patents.
United States Patents
3,835,431 September 10, 1974 Rosen et al
1,208,448 December 12, 1916 Arthur
3,529,270 September 15, 1970 Kozacka
Rosen et al relates to a high voltage fuse designed for low overcurrent and
short circuit duties. Figures 1 and 2 are shown here
<IMG>
An electrically-insulating former 11 has spaced longitudinal ribs 14 and a
plurality of silver strip fuse elements 15 that are wound in helical form
between end caps 12 and 13. Element 15 is provided with "short circuit"
necks 16 and 17 to ensure a rapid rate of arc extinction under short
circuit conditions.
Arthur describes an electric fuse using s fusible member of metallic
cadmium, as shown in Figure 1 below.
<IMG>
Insulating shell 2 has end caps 3 joined by a cadmium conductor 1. The
interior of shell 2 is filled with a filler 5 of silicic acid particles.
Kozacka shows an electric fuse filled with quartz and surrounding a cadmium
wire fusing element and having ends that are conductively connected by soft
solder joints to the terminal caps.
In the Final Action the Examiner stated (in part):
The applicant argues that, since neither Arthur nor Kozacka
disclose a high voltage, general purpose, multi-element fuse, a
person skilled in the art "would not be led to the structure as
claimed by their disclosures". This argument is not
persuasive. The object of the substitution of cadmium elements
in a multi-element fuse, such as shown by Rosen et al, is to
improve its reliability under sustained low intensity overloads
and both Arthur and Kozacka clearly teach that cadmium is the
most suitable material for this purpose. Furthermore, neither
Arthur nor Kozacka state that their fuses are of special-purpose
type, and Kozacka specifically states that his fuse is used in
an electric system having a circuit voltage is excess of 600
volts.
The applicant also argues that "the commutation action" is
recited in the claims in considerable detail and the purity of
cadmium is specified. The first of these two arguments is not
valid. Since no "details" of the commutation action are defined
in the claims apart from a mere functional statement that the
arcs are "extinguished in random sequence in fusible elements
via commutation action" (claim 1, last five lines and claim 7,
lines 27-29). It is also pointed out that a sequential random
melting and arcing "via commutation action" will occur in any
fuse comprising a plurality of elements connected in parallel,
as is clearly described in the Rosen et al disclosure (column 4,
lines 59-68 and corm 5, lines 1-18).
Regarding the argument concerning the specification of purity of
cadmium, it is obvious that the inherent properties of an
element depend on the degree of its purity and, therefore, it is
desirable to use material of the highest possible purity.
In view of the foregoing, it is held that the application
contains nothing of an inventive nature. Therefore this
application is refused.
In response to the Final Action the Applicant deleted all but two claims.
This was followed by two supplements so request for review. These
supplemental requests submitted additional amendments to the remaining two
claims as well as supplying affidavits from the inventor and the Director
of Advance Product Planning for the Applicant. Those responses stated (in
part):
Arthur and Kozacka each disclose fuses having s single fusible
element. Neither of these discloses a fuse having a plurality
of helical fusible elements as required by applicant's proposed
claims 1 and 2. This is a significant distinction. Reference
is made to the enclosed Affidavit of the inventor Mr. Narancic.
As noted in paragraph 2 of Mr. Narancic's Affidavit, multiple
elements, as required by applicant's proposed claims 1 and 2,
are used in high voltage, kilovoltage fuses, but are not used in
low voltage fuses....
....As noted in paragraph 3 of Mr. Narancic's Affidavit, one
reason why it would not have been obvious to employ cadmium in a
high voltage fuse is that it could sot have been predicted that
the residue remaining after the cadmium element melts would be
capable of holding up under the high voltages imposed across the
fuse.
Reference is also made to the enclosed Affidavit of Arthur C.
Westrom. It will be noted from paragraph 2 of Mr. Westrom's
Affidavit that the use of cadmium in the fuses produces distinct
advantages, notably simplified construction and drastically
reduced cost. As noted in paragraph 3 of Mr. Westrom's
Affidavit, the fuses which are the subject of the invention have
met with considerable commercial success.
It is believed applicant has demonstrated that the prior art
does not disclose or suggest applicant's fuse as claimed and
that applicant has provided reasons why his structure as claimed
would not have been obvious to one skilled in the art in view of
the applied references. Applicant's evidence of commercial
success supports the point. In view of the advantages and the
commercial success, this can hardly have been an obvious
development, since surely someone before the present applicant
would then have made the development, in view of the advantages
and the commercial possibilities....
....It may be noted, for example, that the prior publications of
use of cadmium in the Arthur and Kozacka patents use cadmium in
the context of a low voltage fuse. Arthur and Kozacka are not
analogous art, as suggested, and neither of these has been
reduced to commercial practice as far as applicant is aware.
The present invention is, like the Rosen et al and the Kozacka
patent 3,743,994, concerned with a high voltage fuse. A high
voltage fuse has requirements which distinguish it from low
voltage fuses and has structural features which distinguish it
from low voltage fuses. Thus, for example, because after the
fuse has operated it must withstand a high voltage, high voltage
fuses are considerably longer than low voltage fuses, so that
the high voltage fuse has the ability to withstand a high
voltage applied across it. In a high voltage fuse, one has to
employ a fuse element of a certain length which will ultimately
melt along its entire length and maximize the ability of the
fuse to withstand the high recovery voltage. This is in
contrast to low voltage fuses, where the simple opening of a gap
is sufficient to sustain the recovery voltage. In a high
voltage fuse, a plurality of individual fuse elements are used
and the fuse elements are ordinarily coiled helically, so as to
accommodate the relatively long fuse elements within compact
length.
The issue before the Board is whether or not the application presents
patentable subject natter in view of the cited references. Claim 1 as
amended by applicant's letter received on July 15, 1987 reads:
An electric general purpose current limiting fuse for use in
circuits of at least 1000 volts, said fuse comprising a tubular
housing of insulating material constructed to withstand the
circuit recovery voltage following a circuit interruption by the
fuse, a terminal cap mounted on each end of said tubular housing
and constituting closure elements thereof, quartz sand of
substantially spherical grains of which approximately 98% are
retained on sieve mesh size 100, approximately 75% on mesh size
50, approximately 30% on mesh size 40, and approximately 2% on
mesh size 30, said sand being formed in excess of 99% purity and
disposed within and substantially filling said housing, a
plurality of substantially homogeneous helical fusible elements
formed of cadmium of 95% to 99.999% purity embedded in and
supported on all sides by said quartz sand and having their ends
connected with said terminal elements respectively to form a
plurality of parallel conducting paths therebetween, said
fusible elements melting and interrupting currents many times
the rated current of the fuse with a high degree of current
limitation and each of said fusible elements being heated
throughout substantially the entire length thereof to a
temperature approximating the melting temperature thereof and
substantially below the boiling temperature thereof by currents
of low magnitude and slightly in excess of normal rated current,
whereby said fusible elements melt in random sequence and arcs
thereafter being established and extinguished in random sequence
in said fusible elements via commutation action for currents of
low magnitude and slightly in excess of normal rated current.
It is the Examiner's position that substitution by cadmium elements to
improve fuse reliability under sustained low intensity overloads is shown
by Arthur and Kozacka. Further, he maintains that the applicant's use of
notches in the fuse element is clearly shown in Rosen et al.
On the other hand, the Applicant argues that the Rosen et al fuse elements
are supported on a former or core which reduces in insulating properties at
the high temperatures produced during arcing. By supporting the fusible
elements on all eider by quartz sand, the Applicant's arrangement provides
numerous advantages much is relieving tension during heating and cooling
cycles and absorption of arc energy. While acknowledging that Rosen et al
indicates that silica sand may be used for arc quenching material, the
Applicant emphasizes that his filler material of 99% purity enhances the
efficiency of the fuse for he notes quartz sand tan itself pelt or fuse sad
this degree of purity is not suggested by the cited art.
Other disadvantages of Rosen et al pointed out by the Applicant are that
cores or formers made of organic materials produce carbon on the surface
during arcing conditions which can cause failure during the post-arc period
and the former or core is more costly than quartz sand. In addition, Rosen
et al uses a silver fuse element provided with an "M" spot to reduce the
selling point which complicates fuse construction and increases the price
of manufacturing that fuse.
Arthur discloses a single linear cadmium fuse element in fuses for circuits
carrying 4 amperes having 500 volts or less. Use of silica containing
substantial quantities of water is mentioned in Arthur. The application
before us is for circuits of 1000 volts or more and the plurality of
cadmium elements utilized therein have areas of reduced cross-section to
provide uniform fusing characteristics in circuits carrying more than 30
amperes of current.
Kozacka shows a single wire element of cadmium in a cartridge fuse for
electrical systems having a circuit voltage of 600 or more volts. It
describes the methods of connecting the cadmium element to the end caps of
the fuse. Quartz sand is used as a filling in the fuse but the degree of
purity of the sand or the cadmium element is not specified.
We have carefully reviewed the IEEE TRANSACTIONS on POWER APPARATUS and
SYSTEMS Vol. PAS-101, No. 7, July 1982, pages 1870 to 1877 submitted in
response to the Final Action. As evidenced by the discussions at the end
of this paper, it is clear that the use of cadmium in fuses carrying high
current at 15 KV or more was not obvious to people skilled in the art of
electrical power transmission.
Further we note that in a letter to the inventor dated July 6, 1982, the
Industrial Research sad Development Division of Dun & Bradstreet selected
the applicant's invention as one of the hundred cost significant
technological advances of the year. Data showing sales figures indicates
that the applicant's fuse enjoys considerable commercial success.
Amended claim 1 specifies a circuit of at least 1000 volts, quartz sand
grains of at least 99% purity, of which 98% are retained on a sieve mesh
size 100, 75% on mesh size 50, 30% on mesh size 40, 2% on mesh size 30, and
helical fusible elements formed of cadmium of 95% to 99.999% purity. It
may be argued that Rosen et al, Arthur and Kozacka to some extent show the
components used in the applicant's invention. We note from the Narancic
affidavit that prior to his invention multiple elements were not used in
low voltage fuses. Further, he adds when the cadmium elements melt and the
residue disperses onto the filler it is capable of withstanding high
voltage subsequently imposed across the fuse, something not possible in the
cited references. We believe that the Applicant's fuse containing multiple
helical cadmium elements of specified purity embedded in sand grains of the
specified purity represents a patentable advance in the art.
Consequently, we recommend withdrawal of the Final Action and acceptance of
the claims submitted with the Applicant's letter of July 15, 1987.
M.G. Brown S.D. Kot
Acting Chairman Member
Patent Appeal Board
I concur with the findings and recommendations of the Patent Appeal Board.
Accordingly, I remand the application for prosecution consistent with the
recommendation.
J.H.A Gari‚py
Commissioner of Patents
Dated this 16 day of November 1987
Hull, Qub‚c.
Ridout & Maybee
Suite 2300, Richmond-Adelaide Centre
101 Richmond St. W.
Toronto, Ontario
M5H 2J7