COMMISSIONER'S DECISION
Obviousness: Industrial Cooling Tower
The applicant claimed a highly stressed waisted tubular envelope as the main
component of the tower. The applicant has made a patentable advance in the
art over the cited reference. The reference cited required a pre-stressed
cable structure which supported an envelope type housing.
Final Action: Reversed
*******************
This decision deals with a request for review by the Commissioner
of Patents of the Examiner's Final Action dated September 10, 1976,
on application 180,985 (Class 62-115). The application was filed on
September 14, 1973, in the name of Fritz Leonhardt, and is entitled
"Industrial Cooling Tower".
The application relates to an industrial cooling tower, comprising a
waisted tubular envelope, the envelope is tensioned and suspended by
its upper end from a support which carries the vertical component of
the tensioning. The envelope consists of a membrane the material of
which is capable of supporting tension in all directions in its plane.
Figure 1, shown below, illustrates that arrangement.
(See formula 1)
In the Final Action the examiner refused the application in view of
Belgian patent 752877 - December 16, 1970 - Kugler. This patent
corresponds to United States patent 3,637,193. The patent discloses a
cooling tower for cooling gases and liquids in which the supporting
framework comprises a cable construction in which the bearing means
are connected to a common shaft or support. An envelope covers
the framework. The envelope is made from material such as reinforced
synthetic material. Figure 1, shown below, is illustrative of that
invention:
(See formula 1)
In the Final Action the examiner state his position (in part) as follows:
The reference shows a mantle or housing 6 made of reinforced
synthetic material or the like and held at an upper end
by a ring 2 on post 5 and attached at a lower end to founda-
tions by tensioning cable means (shown in figures 1 and 2, but
not labelled). It is noted that cables 7 serve to support
rigid structure 2, 8, 10, 4, 9 and 5.
No invention can be ascertained in this application over
Kugler in light of expected skill. Nothing in applicant's
response of July 8, 1976 convinces the examiner that this
rejection is not well founded. It is clear from Kugler
that his envelope 6 is tensioned by the cable-anchors attached
to its lower rim. Further cables 7 (in addition to those
holding down the lower envelope circumference) locate and
anchor rings 2 and 8 in concentric relation to vertical
support post 5. The waist of the envelope 6 appears at ring 2.
The applicant in his response to the Final Action had this to say (in part):
...
Applicants invention constitutes a unique innovation in the
construction of cooling towers, whereby the conventional
concrete shell is replaced by a waisted or hyperbolic
membrane which is relatively flexible and is pre-
stressed in a vertical direction sufficiently to create
tensile forces in all directions in the plane of the
membrane shell, which tensile forces are greater
than the compression forces created externally by the
wind. The tower is of the natural-draft or air cooled type.
...
Because of the waisted shape of the tubular membrane,
the stretching of the membrane in a vertical and axial
direction provides the vertical component of the pre-
tensioning, whereby the tensioned membrane becomes a
self-supporting membrane shell which is rendered wind-
resistant by the pre-tensioning creating tensile forces
in all directions in the plane of the shell. The pre-
tensioning is made sufficient to create such tensile
forces which are greater than the compression forces
created by the wind externally to the shell. The use
of the central mast 4 is not essential to the invention
since there may be substituted several internal masts
or any supporting structure located exteriorly to the
membrane and overhanging the latter, provided that the
supporting structure is capable of supporting the
vertical component of all forces created by the pre-
tensioning and sufficient to withstand external wind forces.
...
The construction of the cooling tower of the present
invention from a pre-stressed membrane shell, rather
than from concrete, enables the tower to be erected at
much larger heights than conventional cooling towers and
still be capable of withstanding wind compression forces
encountered at these heights, so that the tower may be
made of a sufficient size to be used for dry cooling by
air in areas where a water supply is not available to
provide water cooling. Thus, applicants' structure is
capable of being erected in heights of 900 feet and over.
At the same time, the shell wall is of relatively small
thickness and of relatively light weight so that it can
be easily erected.
...
To be more explicit it should be noted that the tower
of the applied United States patent No. 3,637,193
to Kugler comprises a cable construction (column 1, line 61).
Another feature of the tower of the applied patent is the
fact that the airtight housing of the cooling tower consists
of a material which is suitable to be held by a cable
construction (column 1, lines 68 to 70). Therefore, from
the outset of the description of the cooling tower of the
applied patent to Kugler it is apparent that the housing
or the mantle 6 thereof has not the same property and is
not put into the same working conditions as the envelope
of the present invention. It is evident that the housing
of the applied patent is held by a cable construction
contrary to the present invention wherein the envelope
itself between the two ring elements 2 is not supported
by any cable construction.
...
We have carefully considered the prosecution of this application and the
points and arguments made by the applicant. The issue to be considered
is whether or not the applicant has made a patentable advance in the art.
We note that the applicant agrees that the United States patent 3,637,193
(Kugler) corresponds with the Belgian cited patent. The following discussion
will therefore refer to that patent (United States) for the sake of facility.
We find that Kugler is concerned with the construction of a cooling tower.
Spoked rings 2 and 8 are fastened to a supporting central shaft or column 5
resting on a foundation 20. The rings serve for holding or guiding a cable
construction. The cable construction is pretensioned - "two cable parts
diametrically crossing each other are simultaneously pretensioned...."
The mantle or housing 6 is made of reinforced synthetic material or
impregnated canvas, wood or asbestos cement. The mantle is held at the
upper end by a stiffening ring 8 on support 5 and is connected to and
supported by the pretensioned cable construction. Guide cables are also
used to support the structure at a central portion of the mantle (see Figure 1.
of the patent supra). Claim 1 of that patent reads:
A ventilator-cooling tower of the round type for cooling
gases and liquids, which includes: central shaft means
forming a supporting member of said cooling tower, ventilator
means comprising ventilator blades, bearing means
journalling said ventilator means and supported by said
shaft means, spacer ring means extending around said
ventilator means and connected to said shaft means, said
spacer ring means having outer annular means, substantially
airtight envelope means extending around said spacer ring
means and being connected thereto, and cable means connected
to and supporting said envelope means.
We agree with the examiner that the general basic concept of having a centrally
supported cooling tower is taught by the cited patent. Therefore in order
for the present applicant to obtain a patent he must show that he has a new
and practical combination in a cooling tower construction which required
a degree of inventive ingenuity for fruition.
The tower structure disclosed in the present application comprises a
waisted or hyperbolic tubular membrane 1 (see Figure 1 of the application
supra), which is open at the top and bottom ends and is made of a continuous
membrane of relatively flexible material. This material may be made from
laminated fabric, plastic, thin sheet aluminum, steel or the like and
which upon tensioning, "is capable of supporting tension in all directions in
its plane." A stiffening ring 2 is attached to the upper end of the tubular
envelope or membrane 1, by means of which the envelope is suspended in
a vertical position from a central mast 4 through connecting cables 3.
At its lower end, the envelope 1 is provided with another stiffening ring
2' which is connected by an open latticework 5 to a ground support 6.
In erecting the tower, the envelope is anchored to the foundation 6 by
means of the latticework 5 and is stretched in a vertical direction to provide
the stressing thereof. Thus we see that the envelope is stretched between
the foundation and the upper end of the central mast in a highly tensioned
condition. The purpose of this is so that it will withstand external wind
forces.
We agree with the applicant that Kugler discloses a skin-clad cable con-
struction in which the main purpose of the mantle or housing is to serve
as an airtight wall. In that patent we find: "....The airtight housing
of the cooling tower consists of a material which is suitable to be held by
a cable construction..." (see Kugler column 1 lines 68 ff.). Kugler
also states at column 2, lines 12 ff.: "The mantle or housing 6 is made
of a material which is strong enough to be held by a pretensioned cable
construction and may be of a reinforced synthetic material..." (emphasis
added). Claim 1 of that patent also reads (in part): "... substantially
airtight envelope means extending around said spacer ring means and being
connected thereto, and cable means connected to and supporting said envelope
means" (emphasis added). It is clear from the above that the housing or
mantle in Kruger is connected to and supported by a pretensioned cable
construction and is not used for the same function or working condition
as the envelope in the present application. The present envelope is
unsupported between the two ring elements 2, by any cable construction
whatsoever, other than at the top and bottom.
We find therefore, that the mantle (envelope) of Kugler basically serves
only one purpose, namely, for building up the airtight outer wall.
The mantle is basically not highly tensioned, and does not serve as the
main structural component of the tower. In other words in Kugler the
cable construction undertakes the supporting and bearing function,
whereas the housing or mantle serves the sealing function; this in contrast
to the present arrangement where the membrane of the envelope is highly
tensioned and in a sense is a self-supporting housing between the two
ring elements 2. This feature, of course, is totally absent from the
reference. On the face of it this may not appear to be an important
feature. We must remember however, that these towers can be erected to
reach substantial heights.
In attempting to understand the position of the examiner however, we do
find in the drawings of the patent that the mantle or housing is secured
to the foundation by some means, not labelled, other than by the
pretensioned cable means 7. There is no discussion whatsoever of this
in the disclosure and it may be that it is just another means to secure
the mantle to the foundation to prevent such things as "wind flapping."
We are however, more inclined to think it is really the "flare" of the
draftsman concerned, because in Figure 2 it does not seem to make much
sense. In any event there is absolutely no teaching, when taking the
reference as a whole, that the mantle (envelope) is highly tensioned, or
what this applicant refers to as "pre-tensioned." The elimination of
the prestressed cable framework and the use of a high tension waisted
envelope is basically the essence of the present invention.
Some of the advantages, according to the applicant, are that "the shell
(envelope) wall is of relatively small thickness and of relatively light
weight so that it can be easily erected." In the present arrangement there
are generally no deformation caused by the wind forces in the tensioned
membrane shell. It is simpler and more economical to construct, because
it is formed of a light-weight membrane which is easily installed by
anchoring it at the bottom and suspending it at the top of a supporting
structure.
In summary, Kugler discloses a structure having a supporting framework (to
a center support) of pre-stressed cable construction which supports a
mantle (envelope) to form a cooling tower and which is supported intermediate
its ends. In other words the pre-stressed cable construction essentially
undertakes the supporting and hearing function, whereas the mantle essentially
serves the sealing or housing function. By contrast the present application
discloses a cooling tower comprising a support resting on a ground surface
and a waisted tubular envelope consisting of a continuous highly tensioned
membrane having an unbroken surface. The envelope is secured by support
rings 2 to the top of a supporting mast and to the foundation. No support
cables are used intermediate. the two ends.
We have no hesitation in concluding that the applicant has disclosed a
new combination. Furthermore, we are satisfied that there was a degree
of inventive ingenuity involved in producing a new or improved result in
a more expeditious manner. There is no teaching in Kugler of a "free
standing" structure of the type disclosed in this application. This not-
withstanding that we agree with the examiner that Kugler does show the center-
supported type of structure. We recommend that the decision in the Final
Action to refuse the application be withdrawn.
We now turn to the claims which were amended in response to the Final
Action. Amended claim 1 reads as follows:
An industrial cooling tower comprising a support structure
resting on a ground surface and a waisted tubular envelope
consisting of a continuous membrane having an unbroken
surface of saddle shape and made of a material which is
capable of supporting tension in all directions in its plane,
said membrane being pre-tensioned and carried with its
tubular axis upright from said support structure, an
open latticework anchoring the lower border of said membrane
to the ground surface and providing an inlet for entry
of cooling air into the interior of said membrane, said
membrane having an open upper end serving as an air
outlet opening and a ring connected to the upper border of
said membrane and to said support structure with said
envelope stretched in an axial direction between its upper and
lower borders, and with said support structure providing
the vertical component of said pre-tensioning, said support
structure being of sufficient strength to support said
membrane in a sufficiently stretched condition to cause said
pretensioning to create tensile forces in said membrane in
all directions in the plane of said waisted envelope, with
said tensile forces being greater than the compression forces
created by the wind externally to said shell, whereby said
tensioned membrane becomes a self-supporting membrane shell.
Before considering the allowability of this claim we are concerned with
two points. The first concerns the term "pre-tensioned," which is also
used in the disclosure. It is our understanding that the tubular envelope
is not "pre-tensioned" before use in the tower, but has high tension applied
during the tower construction. We believe the term should be amended,
possibly to "tensioned" or "post-tensioned," to more correctly depict
the facts. The second, point concerns the "self-supporting membrane shell"
(the last line in the claim). The membrane is simply not self supporting.
An amendment to correct this should also be made.
In considering the allowability of claim 1 we clearly find in the claim
the essence of the invention, as discussed above, over the Kugler patent.
The claim does not go beyond the invention made and restricts the monopoly
in an appropriate manner. This claim should be allowable when amended
according to the suggestions made above. Claims 2 to 10, which depend
directly or indirectly on claim 1, are also found to be allowable.
We are satisfied that the applicant has made a patentable advance in the
art and recommend that the decision in the Final Action to refuse the
application be withdrawn. It is also recommended that the claims be
amended to improve the form for clarity purposes.
J.F. Hughes
Assistant Chairman
Patent Appeal Board, Canada
I have studied the prosecution of this application and have carefully
reviewed the recommendation of the Patent Appeal Board. In the circumstances
I have decided to withdraw the Final Action and will accept the claims
when amended as suggested by the Board. The application is returned to
the examiner for resumption of prosecution.
J.H:A. Gariepy
Commissioner of Patents
Dated at Hull, Quebec
this 15th, day of September, 1977
Agent for Applicant
Robic, Robic & Associates,
2100 Drummond Street
Montreal, Quebec
H3G 1X5