Supreme Court of Canada
Slater Steel Industries Ltd. v. Lacal Industries Ltd., [1972] S.C.R. 29
Date: 1971-04-05
Slater Steel Industries Limited (Defendant) Appellant;
and
Lacal Industries Limited (Plaintiff) Respondent.
1970: November 12, 13; 1971: April 5.
Present: Ritchie, Hall, Spence, Pigeon and Laskin JJ.
ON APPEAL FROM THE EXCHEQUER COURT OF CANADA
Patents—Patent relating to suspension brackets for power lines—Impeachment—Counterclaim for infringement—Patent invalid for want of subject-matter—Patent Act, R.S.C. 1952, c. 203.
The plaintiff brought an action to impeach the validity of a patent for an invention relating to suspension brackets as part of a conductor suspension assembly. The defendant patentee counter-claimed for damages for infringement. The trial judge, from whose decision the defendant appealed to this Court, held the patent to be invalid for want of subject-matter.
Held: The appeal should be dismissed.
What the issue between the parties came to was whether there was inventiveness in hitting upon the optimum distance between the conductors and the lowest insulators on bundle conductor transmission lines within which equal distribution of voltage would be best controlled and with it insulator corona, or within what range of distances would this be the result. In view of the already known electrical implication of the effect of bundle conductors in their proximity to insulator strings, this Court agreed with the trial judge that the patent was invalid for want of subject-matter.
APPEAL from a judgment of Jackett P. of the Exchequer Court of Canada, declaring a patent invalid and void. Appeal dismissed.
J.F. Howard, Q.C., and P.R. Hayden, for the defendant, appellant.
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R.A. Smith, Q.C., and R. Saffrey, for the plaintiff, respondent.
The judgment of the Court was delivered by
LASKIN J.—This appeal arises out of a successful declaratory action by Lacal Industries Limited to impeach the validity of Canadian patent No. 652,027 for an invention relating to suspension brackets as part of a conductor suspension assembly. The defendant patentee, Slater Industries Limited, counter claimed for damages for infringement, and it is common ground that there has been infringement if the patent is valid. Jackett P. of the Exchequer Court held it to be invalid for want of subject-matter, but rejected other grounds of attack, among which were that (1) the alleged invention lacked novelty; (2) it was not that of the named inventor; and (3) he was not the first inventor. The learned trial judge also rejected Lacal’s submission of invalidity for failure to meet the requirement of specificity prescribed by s. 36 of the Patent Act, R.S.C. 1952, c. 203.
The patent in question was issued on November 27, 1962, pursuant to an application filed on March 22, 1960. Section 46 of the Act gives the patentee priority as of the date of the granting of the patent but, in relation to ss. 28(1)(a) and 63(1), the patentee asserted a date of invention as early as the period between May and November, 1958, and, in any event, as being February 4, 1959.
The specification of the patent, in one of its material parts for the purposes of this appeal, is as follows:
This invention relates to an improved construction of suspension bracket for use in supporting a plurality of high tension cables in a predetermined parallel relationship to each other. When the current to be transmitted along any given transmission line is sufficiently great to render it desirable to employ more than one conductor for each phase, it is
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customary to support these electrically common conductors from the towers or other fixed elevated structures by cradling such conductors in seats spaced apart from one another on a common suspension bracket, which bracket is then suspended from the lowermost insulator of a chain of insulators depending from the fixed structure.
The modern trend to transmit electrical energy at higher and higher voltages has given rise to two problems encountered in the design of suspension brackets for this service. Firstly, there is the problem of corona loss, which under stormy conditions has been known to reach a value as high as 30KW per mile of line on a 345 KV line. It is known that corona losses can be reduced by designing the high tension parts with a minimum of sharp edges and corners, but nevertheless conventional suspension brackets include many separate components joined together by bolts, pins, nuts, etc. which inevitably provide, the sharp edges conducive to corona discharge. The second problem of high tension transmission lines with which the present invention is concerned is that of disproportionate voltage gradients across the individual insulators of the chain of insulators by which the cables are suspended. This problem has long been appreciated, and such devices as grading rings and shields have been evolved to render the voltage gradients more uniform and hence relieve the stress across the insulators situated nearest the line, which line insulators would otherwise bear disproportionately high fractions of the total line to ground voltage.
It is an object of the invention to provide a form of suspension bracket which improves the uniformity of the voltage gradients across the various insulators without the need to resort to such complications as grading rings and shields.
This object is achieved according to the present invention by locating the seat for at least one of the cables so that such selected cable lies generally outwardly from and proximate to the lowermost insulator, or at least in the general vicinity of the lowermost two or three insulators.…
The foregoing description is supplemented in the patent grant by a statement of embodiments of the invention under twelve different but related claims. Two drawings are attached, each showing a four-conductor (or cable) suspension
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assembly, and they are explained in the specifications in the following concluding paragraphs thereof:
In Figures 1 and 2 it will be seen that the two upper cables are substantially level with and in the comparatively close vicinity of the lowermost insulator 35. This construction may be modified by the cables being placed somewhat higher, if preferred, so as to be level with the second, or even the third insulator.
It is also within the concept of this invention to place the cables lower or indeed below the level of the lowermost insulator and achieve substantially the same effect. In this case the cables would still be disposed outwardly from the lower insulator but not necessarily at the height of the horizontal level of the lowest insulator. The important requirement is that the cables be in the general vicinity of the lower few insulators so as to act to generate an electrostatic field that will tend to reduce the natural tendency for a disproportionately high share of the total voltage gradient to be distributed across the lower few insulators. In this respect the cables act electrically in the same manner as grading rings and shields, but the result is achieved without the need to provide separate devices for this purpose.
Although the arrangement is more symmetrical with two cables arranged at the high elevation, i.e. proximate the lowermost insulators, substantially the same effect can be obtained with a single cable. It is thus only necessary to have one cable at the high elevation, should the shape of the framework or the number of cables employed so dictate. It will be appreciated that a suspension bracket adapted to carry a number of cables other than four, for example two, and to arrange the cables in a grouping different from that illustrated in the drawing, will lie within the broad concept of the invention provided the grouping is such as to locate at least one of the cables proximate the lower insulators.
It will be apparent that by means of the invention there has been provided a novel and improved form of suspension bracket having the merit of extreme simplicity of construction, combined with an operational performance at least as advantageous as that of the much more complex constructions employed in the devices hitherto commonly in use.
Neither the design nor the fabrication of the suspension brackets mentioned in the grant of patent is claimed as integral to the invention. What is claimed as being invention (as the
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specifications themselves disclose, albeit the disclosure deserved more felicitous phrasing on this point) is an idea, realizable through the suspension brackets, for reducing if not completely eliminating insulator corona loss on extra high voltage power lines (or conductors); and, even more important, for improving the equal distribution of the voltage gradients across conductor suspension assemblies, and especially across the string of insulators, forming part of such an assembly, without the use additionally of grading rings or shields. In brief, Slater asserts an improvement patent, and I turn now to an elaboration of the history of the problem which Slater’s inventor, one Robert G. Baird, allegedly met by what is alleged to be inventive ingenuity.
The problem began with the increased demand for power, which in turn was met by increasing the voltage range of conductors from high voltages of 150 and up to 230 kilovolts (KV) to extra high voltages ranging from 345 KV to over 600KV. The high voltages could be carried by a single conductor transmission line, consisting of a series of steel towers supporting the electrical cables which carried the power from its point of generation to its points of use. Although the conductors on transmission lines were insulated from the ground and from the towers by air (which is a non-conductor of electricity), the fact that the conductors were fastened to their tower supports meant that solid insulators were necessary to prevent current flow that would otherwise result between the conductors and the towers and the conductors and the ground. Suspension brackets were used to hold the conductors in position relative to insulators.
Voltage sets up an electrical stress on or across the insulating air. It increases with the voltage, and may result in destroying the insulating capacity of the air so that it becomes itself a conductor and causes the formation of an electric arc or, as likely, a halo glow effect known as corona. This phenomenon may be found in connection with insulators as well as conductors and suspension brackets, and it results in radio
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interference as well as signifying power loss. Corona from brackets or from insulator coupling devices could be effectively controlled by rounding and smoothing the edges of this hardware, and it was not contended that any patentable idea or process was involved in this widely known method of control. Bracket and insulator corona were dealt with originally by grading rings or shields, and I shall deal with them in greater detail later in these reasons.
Extra high voltage resulted in increased corona, with greater voltage losses, and their control was a matter of considerable importance. Building on European experience which saw the use there of two or three conductors to carry extra high voltage on a transmission line, North American power companies began to plan for similar systems; and in respect of the issue in appeal a four-conductor bundle was the prototype. Extra high voltage transmission lines in North America began, however, with two-conductor bundles. There is evidence that such a line was put into service in British Columbia in 1952 at 230 KV but using only one of the two conductors, and it was not until 1956 that the line was fully energized at 345 KV. A similar line at the same extra high voltage was put into service in 1956 in the State of Washington. In both of these cases, grading rings were used.
There was a dispute between the parties both as to the necessary use and as to the purpose and effect of grading rings on bundle conductor transmission lines. Grading rings or shields (also referred to in the evidence as corona rings) are metallic devices which encircle the lowest insulator on the insulator string and are electrically connected to the conductor close by, with the result that the distribution of voltage, (which is otherwise disproportionate at the lower insulators closest to the conductor) is improved, and there is also a controlling effect (as already noted) on bracket and insulator corona.
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I have already referred to the use of grading rings on single-conductor transmission lines, but they were also used on bundle conductor transmission lines in Europe prior to 1958, in part because a different kind of insulator was in service there, and the rings were needed to control corona as well as to improve the distribution of voltage across the insulator string. Bundle conductor transmission lines in North America, and certainly in Ontario, used a different kind of insulator which did not need grading rings for all the purposes for which they were used in Europe; and the dispute between the parties related in large part to whether grading rings were used here only to control insulator corona. This issue went to the question of “obviousness” which in turn related to the length of time that the problem of insulator corona existed without effective solution.
Baird, named as the inventor by the appellant patentee, and who was at the material time its chief engineer concerned with the design of hardware for suspension brackets for transmission, distribution and communication lines, testified that the idea which was later translated into the patent came to him in 1954 when the patentee company was testing hardware which it hoped to supply for a 345 KV line for Quebec Hydro. He appreciated that grading rings were redistributing the voltage charge from the conductor across the chain of insulators; and it appeared to him that the same result could be realized if the conductor could be moved up alongside the lowermost insulators or even a little higher. Nothing came of the idea because there first had to be a solution of a mechanical problem, namely, getting the single conductor (which was then in use) to stay up alongside the lower insulators without the latter tipping over. The idea returned to him, so he stated, in 1958 when it became known that Ontario Hydro was proposing to erect extra high voltage transmission lines with multiple conductors. Ontario Hydro at first had a three bundle conductor in mind but eventually settled on a four bundle one, in part at least because there
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was no great cost differential. Baird considered that the mechanical problem could now be mastered.
Visits to and consultations with Ontario Hydro’s engineering and research departments ensued with a view to the development of a design for the proposed transmission lines, the chief interest of the appellant company being in the design of suspension brackets which it then hoped to sell to Ontario Hydro. In this it was ultimately successful. Particular stress was laid on two reports of May 13, 1958, and July 8, 1958, prepared by one Madeyski who then worked under Baird, the first relating to a visit that Madeyski made on May 8, 1958, to Ontario Hydro’s research division and the second reporting on information obtained from that division, including the fact that Ontario Hydro proposed to design and test “rigid spacers and rigid suspension clamps” for a three-conductor bundle, that the conductor spacing would be 15 inches and that “an effort will be made to place the conductors as close as possible to the insulators”. As a result of these reports, Baird asked Madeyski to prepare sketches of bracket suspension assemblies that would provide stable support of the uppermost conductor or conductors alongside or above the lowermost insulators. The definitive drawing produced by the patentee company, illustrating (in Baird’s words) “a typical four-bundle self-shielding suspension assembly”, was completed on February 4, 1959, a date mentioned earlier in these reasons. A wooden prototype of the bracket assembly was produced for testing by Ontario Hydro in the summer of 1960, but the ultimate product sold was in a different style although embodying the same idea. I may note here that even before the patent impugned herein was issued to the appellant, it was agreed between Ontario Hydro and the appellant that the former would be given a patent licence without any royalty obligation.
Baird, on his own evidence, did not read up on the available technical literature referable to the
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control of insulator corona on bundle conductor transmission lines. He had stated on discovery that at the time of the patent application he did not know whether a better distribution of voltage gradients across insulators could be achieved with bundle conductors than with a single conductor, but on giving evidence at the trial he changed his answer and said unequivocally that he did know that a better distribution could be achieved with bundle conductors. I would add at this point that Madeyski’s testimony was that it was Baird who suggested to him to put the uppermost conductors at the level of the lowermost insulator when preparing his sketches late in 1958. The trial judge accepted Madeyski’s evidence that the sketches were prepared after July 8, 1958, and before a meeting, hereinafter mentioned, on December 10, 1958. This was a finding which was certainly one for him to make.
The most prominent person on the Ontario Hydro side of the consultations that were held with the patentee’s representative was one McMurtrie, then the senior transmission design engineer. He described the tests that were performed with different hardware combinations suspended below the insulators in connection with a four-conductor bundle, and the impression that he gained that the four-conductor bundle had a better grading effect in respect of insulator corona, thus suggesting the possibility of eliminating grading rings. In these tests, or at least in some of them, the conductor bundle was located 6 to 12 inches below the lowest insulator. McMurtrie said that he discussed the tests with Baird, but principally from the standpoint of cost if grading rings were to be eliminated and in place thereof brackets and associated clamps were used which would have to be shaped and rounded for effective results. According to McMurtrie, he also discussed with Baird the locating of the conductors on a line parallel with the bottom skirt of the lowest insulator, which would enable Ontario Hydro to keep the insulator string as short as possible. Spacing between the
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suspension clamp around the conductor and the skirt on the insulator was important, but no specific conclusion was reached on this point at the time; McMurtrie did say too that in mid‑1959 or later that year Ontario Hydro decided on an 18-inch spacing between the subconductors, having earlier considered the advantage of 15 and 16-inch spacing and having experimented in a range of 8 to 18 inches. Although the patentee’s drawing of February 4, 1959, had no dimensions on it, it was full scale and McMurtrie measured this spacing as being 16 inches.
As Jackett P. pointed out, there was a conflict in the evidence of Baird and McMurtrie as to when and, indeed, whether the latter told Baird that a bracket should be designed to enable the conductors to be put on a line parallel with the bottom skirt of the lowest insulator. The occasion was said to be a meeting on December 10, 1958, at which an associate of Baird, one McDermid who was not called as a witness, was also present. McMurtrie had also had discussions with an American manufacturer seeking Ontario Hydro’s business. The trial judge said that McMurtrie might have spoken of such a design to that firm and after anxious consideration he concluded that he should accept Baird’s assertion that the latter had acted on the revived idea he first had in 1954 and ordered the sketches by Madeyski without any prompting from McMurtrie.
The evidence shows that in September, 1959, one Kalns, who worked under McMurtrie, was assigned to develop a bracket that would permit the conductors to be raised up to the level of the lowest insulator. It does not appear that anything came of this, apparently because the appellant company offered a licensing agreement, already mentioned. I do not think that this
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evidence can be regarded as putting in doubt the favourable rulings of the trial judge on the credibility of Baird and Madeyski.
Jackett P. made two findings on the evidence which, slightly rephrased, were that (1) transmission line design engineers knew by 1958 that the distance of a conductor from the insulator string was a factor in the amount of insulator corona; and (2) they also knew by that date that the use of a bundle conductor instead of a single conductor made it possible, by an appropriate design, to reduce considerably the unequal distribution of voltage across the string of insulators and thus reduce insulator corona. This was not an automatic consequence of using bundle conductors. The appropriate design had to take into account, of course, the higher cost that was involved in erecting towers capable of sustaining bundle conductors with accompanying insulator strings and hardware, in such a fashion as to maintain proper insulation and avoidance of injurious electrical stress.
These findings were, in my opinion, well supported by the record. Related to these findings is the critical question whether the proper positioning of conductors in relation to the string of insulators, in order to equalize voltage distribution, was also a matter of mechanical know‑how or whether it went beyond that to inventiveness.
A strong attack was made by the appellant on the trial judge’s adverse finding on this question. It contended that the problem of unequal distribution of voltage and insulator corona in connection therewith relative to bundle conductor transmission lines had resisted solution for about ten years before Baird hit upon it; and the trial judge was hence wrong in saying that the problem had not existed for a long time. Counsel conceded the simplicity of the remedy which did not, of course, rule out inventive ingenuity; but he sought to show, by reference to technical literature current in the period 1947 to 1958, and
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much earlier as well, that the thinking on the problem of improving distribution of voltage across the insulator strings and reducing insulator corona was in terms of grading rings.
The evidence shows, however, and this is acknowledged by the appellant, that, to quote one of its witnesses, Professor Barton, “traditional methods for reducing the non-uniformity of voltage distribution include mounting the conductor as high as possible under the lower insulator, and where this is insufficient, the addition of grading rings”. The emphasis, no doubt, remained on grading rings when bundle conductors first came into use (because they had been necessary on single conductor lines and also served purposes other than helping to reduce insulator corona), but design engineers could appreciate the modifying effect of bundle conductors themselves according to their position vis à vis the insulator strings. The vagaries of electrical stress depended, inter alia, on the design and construction of the towers, the diameter of the conductors, the type of insulator and the shape and smoothness of all accompanying hardware, but this did not mean that the effects from a functioning transmission line differed in other than degree.
What the issue between the parties came to was whether there was inventiveness in hitting upon the optimum distance between the conductors and lowest insulators within which equal distribution of voltage would be best controlled and with it insulator corona, or within what range of such distances would this be the result. The patentee conceded that the state of the art at the material time was to have the conductors from 5 to 12½ inches below the lowest insulator to achieve an acceptable grading effect. It claimed as the area of its patent the positioning of conductors in the range of 5 inches below the lowest insulator up to the level thereof. The embodiments of the patent do not specify any such range but speak simply of proximity to the lowermost
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insulators and of a horizontal positioning on substantially the same level with such insulators.
In concluding in his reasons that the patent lacked subject-matter, the trial judge referred to McMurtrie’s appreciation of the advantage of shortening the suspension assembly and keeping the conductors close to the insulators. The reliance placed on this by Jackett P. was challenged on the ground that McMurtrie was concerned with design and economy, and not with what the appellant called the electrical idea. Although this is a valid distinction, the objection loses force in this case because McMurtrie’s evidence does not stand alone but merely reinforces, from the mechanical point of view, the already known electrical implication of the effect of bundle conductors in their proximity to insulator strings. Since I agree with the trial judge on the question of subject-matter, it is unnecessary to deal with other issues which arise only if this ground of attack on the patent was rejected.
I would dismiss the appeal with costs.
Appeal dismissed with costs.
Solicitors for the defendant, appellant: Blake, Cassels & Graydon, Toronto.
Solicitors for the plaintiff, respondent: Wahn, Mayer, Smith, Creber, Lyons, Torrance & Stevenson, Toronto.
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