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36 EXCHEQUER COURT OF CANADA [1940 1939 BETWEEN: A 2 p 4-2 8 1 ' NORTHERN ELECTRIC CO. LTD., May 1. AND WESTERN ELECTRIC CO. PLAINTIFFS; July 29. INC. AND BROWN'S THEATRES LIMITED DEFENDANT. PatentsInfringementSubject-matterCombination patentInventacn UtilatyPatentabilityIndustrial valueBenefit to the publzc. The action is one for infringement by defendant of five patents owned by plaintiffs. The Harrison patent claimed an invention for a horn constructed according to the exponential law and having a mouth diameter approximately one-quarter the wave length of the critical frequency of the horn; the Court found that there was no infringement of this patent because the defendant's construction does not fall within the ambit of the particular construction described and claimed by Harrison. The invention claimed in the Wente patent relates to improvements in acoustic devices such as are used in receiving and transmitting sound, and ordinarily referred to as loud speakers; the distinguishing characteristic is the use of a spherical plug in the sound chamber for the purpose of decreasing the cross-sectional area of a portion of the sound chamber. The Court found that the sound chamber employed by the defendant and that described by Wente are not alike, nor can defendant's sound chamber be said to be the equivalent of Wente's sound chamber, and there was no infringement. The object of the Miller patent is stated to be a film sound reproducing system operating on alternating current. This patent was held to lack subject-matter and therefore there was no infringement. The Wilson patent relates to improvements in electron discharge devices. The Court found that there was subject-matter in Wilson and there had been infringement by the defendant. The DeForest patent claims an invention for the control of electric currents by and in accordance with variations of light; this patent was found to be without utility and therefore void and without subject-matter. Held: That a claim for a particular means to effect certain purposes is not infringed where the same purposes are effected by different means; nor is a combination to effect certain results infringed by a combination of similar parts operating in a different manner, though the results effected are the same. 2. That it is not permissible to claim an article which as an article requires no inventive ingenuity merely because, if used in a particular way, it will be useful in achieving a particular purpose.
Ex. C.R.] EXCHEQUER COURT OF CANADA 37 3. That the combination disclosed in the Wilson patent is in principle 1939 to be differentiated from that disclosed in prior patents, and is novelORTHERN and possesses subject-matter. iiE+L,LEEcCTR Y IC 4. That an invention to be patentable must confer on the public a Co. LTD, benefit; utility, as predicated of inventions, means industrial value AND WESTERN and no p a tent can be granted for a worthless art or arrangement. ELECTRIC Co. INC. V. ACTION by plaintiffs herein to have it declared that BRo N's five patents owned by them are valid and were infringed LITERS by defendant company. Maclean J. The action was tried before the Honourable Mr. Justice Maclean, President of the Court, at Ottawa. O. M. Biggar, K.C. and R. S. Smart, K.C. for plaintiffs. H. N. Chauvin, K.C. and Frank B. Chauvin for defendant. The facts and questions of law raised at the trial are stated in the reasons for judgment. THE PRESIDENT, now (July 29, 1939) delivered the following judgment: This is an action for the infringement of five patents owned by the plaintiffs. The applicants for these patents were Harrison, Wente, Miller, Wilson and Deforest respectively, and by these names I shall designate the several patents here in question. The evidence, and arguments of counsel, were directed to these patents in the order named, and this order I shall observe in my discussion of them. It was admitted in writing by the defendant that it has installed and is operating at the Community Theatre located in Toronto, Ontario, a sound reproducing and amplifying equipment according to the arrangement shown in certain drawings of the Cincinnati Time Recorder Company attached to the admission. It was also admitted that the sound reproducing and amplifying equipment employs a high frequency loud speaker constructed as shown in certain drawings of the Jensen Radio Manufacturing Company accompanying the admission. The Harrison patent, No. 302,394, issued on July 22, 1930, and is a reissue of patent No. 258,045, dated Febru-ary 9, 1926, and that is the first to be considered. The
38 EXCHEQUER COURT OF CANADA [1940 1939 following paragraphs extracted from the specification will NORTHERN reveal the main characteristics of the invention and its ELECTRIC objects: CO. LTD , AND This invention relates to acoustic devices such as horns used in con- WEsTERN junction with loud speaking receivers and phonographs, an object being ELECTRIC INc. to produce a horn capable of faithfully and efficiently transmitting sound Co. v. vibrations over a broad range of frequencies. BROWN'S Another object is to produce a horn which is adapted to be con- T LI H M E IT A E T D R . ES strutted in compact form suitable for mounting in a cabinet. In accordance with the general features of the invention a horn is Maclean J. provided in which the progressive increase in cross-sectional area follows the exponential law. Specifically this feature contemplates a horn having a rate of taper such that the areas of successive wave fronts increase by a constant per cent per unit of length, and a mouth opening properly related to the other constants of the horn as is more particularly explained hereinafter. After a definition of certain technical terms, and reference to certain formule, the specification proceeds: Although any horn constructed in accordance with the above formule will have a uniform rate of change of impedance, for best results it is preferable to proceed as follows: First, the two end areas should be chosen The area of the small end is preferably chosen to correspond with the opening in the receiver or acoustic device with which the horn is to be used. The mouth area is usually determined from the conditions under which the horn is to be used and the larger it can be made, granted there is sufficient horn length, the lower are the frequencies it can effectively radiate. It has been found that the mouth of a horn is a poor radiator of vibrations having wave lengths greater than twice its diameter, vibrations having longer wave lengths being largely reflected. Next the rate of taper of the horn is determined as this in properly designed horns determines the length of the horn. A rate of taper should be chosen such that the horn freely transmits all frequencies which the mouth can radiate. The rate of taper should be such that the wave length of the critical frequency is several times the mouth diameter, a wave length of four times the mouth diameter has been found satisfactory. The critical frequency is that frequency below which the surge impedance of an infinite length of horn is a pure reactance. The claims entering into the controversy are 1 and 17, which are as follows: 1. A horn having an opening in which the progressive increase in cross-sectional area is substantially according to the exponential law, and a mouth diameter approximately one-quarter the wave length of the critical frequency. 17. A horn having a substantially constant rate of increase in cross-sectional area per unit of length throughout its length, and a mouth opening equivalent in area to that of a circle whose diameter is approximately one-quarter the wave length of the critical frequency of the horn These two claims mean substantially the same thing.
Ex. C R.] EXCHEQUER COURT OF CANADA 39 The invention claimed by Harrison is a horn constructed 1939 according to the exponential law and having a mouth N ORTHERN diameter approximately one-quarter the wave length of nixT Rio Co T T. n the critical frequency. What is claimed is not a horn made A. D according to the exponential law but a horn made accord- ËLr Txic ing to that law and which has a mouth opening whose Co. INC diameter is approximately one-quarter the wave length BRowN's of the critical frequency of the horn. The critical fre- LzxgEDS quency is that frequency below which the horn ceases to function satisfactorily; it will not radiate satisfactorily Maclean J. frequencies below the critical frequency. A horn may be regarded as a transmission line or link between the loud speaker diaphragm and the outside air. The exponential horn is a device for coupling the motion of the loud speaker diaphragm to the volume of air which it is desired to excite, and the shape of the horn follows a known mathe- matical equation. According to the exponential law the taper of the horn increases constantly, so that the cross-sectional area of the opening enlarges as the flare increases. The exponential law does not, as I understand it, fix the rate of taper; it requires only that the cross-sectional area increase con- stantly. The rate of increase may be selected, but it is the constant increase of whatever rate is selected that is taught by the exponential law. And the exponential law does not prescribe any rule as to where one should stop in the construction of a horn, that is, so far as length is concerned. A horn made according to the exponential law would not be patentable, and in fact I do not understand this to be claimed by Harrison. The mathematical for- mula for the law of rythmic or logarithmic shape was con- ceded by Harrison to have been long known. It was dis- closed and explained in the article of Webster, which was read at a meeting of the American Physical Society in 1914, and which was published in 1918. Webster gives the transmission characteristics of horns of different forms, in- cluding the cylindrical, the conical, and the exponential, and he works out these characteristics mathematically. He states the fundamental mathematical principles of these horns from which one skilled in mathematics and in the acoustic art may arrive at the complete solution of the problem of acoustical transmission by means of expon- ential horns. The formulk mentioned by Webster are the
40 EXCHEQUER COURT OF CANADA [1940 1939 same as those shown in Harrison. The latter sets forth NORTHERN in his specification the same fundamental equations but ELECTRIC expresses them in different symbols. All that Harrison CO. LTD , AND purports to add to Webster is to teach where the length WESTERN ELECTRIC of an exponential horn might end and at the same time Co. INC. give a satisfactory radiation of the frequencies desired to V. BROWN'S transmit. And the rule he lays down in this connection THEATRES LIMITED. is that the mouth diameter is to be approximately one-fourth the wave length of the critical frequency, though Maclean J limits above and below that dimension are stated. To state it with greater precision Harrison discloses where one may terminate the length of a horn and yet radiate and transmit the low frequencies as well as the higher frequencies. Harrison, who gave evidence at the trial, admitted that there was no difficulty in radiating the higher frequencies beyond the audible limits. The problem Harrison sought to solve was the construction of a horn that would radiate the lower frequencies and yet be of a usable or convenient size. He had in mind horns of six feet and over in length and he was concerned with the dispensing of horns of great length and bulk, and the construction of the shortest horn possible according to the exponential law, but one which would radiate the lower frequencies desired, as well as the higher frequencies. That was his problem, and his solution, as stated in claims 1 and 17, was to make a horn according to the exponential law, and which had a mouth diameter approximately one-quarter the wave length of the critical frequency, and it is claimed that if a horn were so constructed it would be of a convenient dimension and would radiate the low frequencies as well as the higher frequencies, that is to say, it would transmit sound vibrations over a. broad range of frequencies. Harrison states a formula, number 5, for ascertaining the critical frequency of any exponential horn, and, I think it has been established quite clearly by the evidence that this formula corresponds with one of the formulae set forth in Webster's paper for ascertaining the critical frequency of an exponential horn. Now, as I have more than once stated, the particular type of horn described and claimed by Harrison is an exponential horn the mouth diameter of which is one-quarter the wave length of the critical frequency. When the critical frequency is ascertained that must be accepted
Ex. C.R.] EXCHEQUER COURT OF CANADA 41 definitely as the stage at which the horn will just operate 1939 and below which it will not operate, and consequently the NOR I IR N theoretical point between operativeness and inoperative- EL o"i; o ANT» ness is not a useful one to rely upon for fidelity in the o transmission of low frequencies. In order to be on the ÉLEc H c safe side Harrison, as I understand it, after ascertaining Co. INC. the critical frequency suggests doubling the critical fre- BRo > N'S quency, to ensure a clear radiation, and this has the effect TF[ E,TR T i:vi.[TEn.s of reducing the wave length by one half. This is a new -- frequency for transmission, reached by doubling the actual Maclean J. critical frequency, and the mouth diameter of the horn is then to be one-quarter the wave length of that frequency instead of one-half, as mentioned at one stage in Harrison's specification wherein he says that the wave length should not be greater than twice the diameter of the horn. I am not certain that I have succeeded in stating this clearly, or perhaps quite accurately, but, if I have failed, it is not, I think, a matter of great consequence. The defendant was concerned not with a broad range of frequency as was Harrison, but with a narrow range of the higher frequencies, from 1,200 up to 6,000 cycles, and it claims that in the use of its horn there was no relation- ship between the mouth opening and the wave length of the critical frequency, as is claimed by Harrison. The frequencies that Harrison was concerned with were those as low as 100 or 200 cycles and up as far as the horn would transmit. The defendant's horn has a mouth diameter of 5.1 inches, and the wave length of the calculated critical frequency is 11 inches. If a horn has a mouth diameter substantially greater than one-quarter the wave length of the critical frequency the radiation will be more satisfactory for the high fre- quencies than one made according to Harrison, but it would not radiate the low frequencies as satisfactorily as would a horn made according to Harrison. The defendant's horn, having a larger mouth opening than that prescribed by Harrison, will not radiate the lower frequencies but it will function more satisfactorily for the higher frequencies, and for this it was particularly designed and is used. The contention made on behalf of the defendant is that there is no infringement because the mouth diameter of the defendant's horn is substantially greater than one- quarter the wave length of the critical frequency, or the
42 EXCHEQUER COURT OF CANADA [1940 1939 limits above and below that, as stated in Harrison. It was NORTHERN argued by Mr. H. N. Chauvin that if the mouth diameter ELECTRIC is greater than one-quarter the wave length of the critical Co. LTD , AND frequency, there would be no problem to solve, because WESTERN ELECTRIC the ratio between the mouth diameter and the wave length Co. INC. of critical frequency is such that there could be no doubt u. BROWN'S as to the capacity of the horn to radiate satisfactorily the THEATRES higher frequencies. Harrison, he states, was seeking a LIMITED. horn which would radiate low frequencies, which, I think, is Maclean J. correct, and there would be no problem about the higher frequencies. Harrison was not concerned with a device such as the defendant's where the frequencies do not go below 1,200 cycles; he was attempting to demonstrate that a horn might be designed to transmit the low frequencies and still be of a reasonable size, and if there is any invention in Harrison it lies in that. In the construction described and claimed by Harrison there is the factor of mathematical precision, which in turn demands an arbitrary requirement as to the physical dimensions of the mouth diameter of his horn, and to that, I think, he is tied. When he claims an exponential horn having " a mouth diameter approximately one-quarter the wave length of the critical frequency" those words are, I think, to be regarded as words of physical description of the apparatus claimed. The defendant's horn cannot, I think, be said to fall within any such description of Harrison's alleged invention. I need not decide whether or not there is subject-matter in Harrison, and I did not understand defendant's counsel to contend that there was not. I think, however, that there is no infringement because the defendant's construction does not fall within the ambit of the particular construction described and claimed by Harrison. Next, I core to the Wente patent which issued in Feb-ruary, 1929, on the application of Edward C. Wente filed in May, 1927. The invention is said to relate to improvements in acoustic devices such as are used in receiving and transmitting sound, and ordinarily referred to as loud speakers. A specific object of the invention was to improve the transmission characteristics of loud speaking receivers at the upper portion of the sound frequency range.
Ex. C R.] EXCHEQUER COURT OF CANADA 43 A great deal of evidence, and elaborate arguments by 1939 counsel, were directed to various phases of this patent and N 0R'FHERN its alleged infringement by the defendant, to which I have EL s 1 c r Rra given full consideration, but, I think, the real question ~A n' here at issue may be dis l p ~ osed of in fairlybrief terms. ELL ELC•;CTTRRIIC This patent was fully considered by me in the case of Co. INC Western Electric Co. Inc., et al. v. Baldwin International BRowN's Ld. (1), and I need not repeat what I there said. I held L$2Ts the patent to be valid and to have been infringed, for Maclean J. the reasons there appearing. The elements of Wente's combination patent are set forth in claim 4, the claim in suit here, as follows: " An acoustic device comprising a piston diaphragm having a flexible peripheral portion and a substantially dish-shaped central portion, means for driving said diaphragm at the periphery of its central portion, a horn, a sound chamber between said diaphragm and said horn, a plug in said sound chamber for decreasing the cross-sectional area of a portion of the sound passage therethrough." Loud speakers, so called, were known and in use prior to Wente. I think it is quite correct to say that the claim to invention in Wente resides in the inclusion in the combination of a sound chamber having a dome shaped plug inserted therein, which decreases the area of a portion of the sound passage. The diaphragm and plug are so shaped and arranged that converging sound passages are formed thereby, extending from the centre of the diaphragm and from its peripheral portion to a common sound chamber. The detailed description of the invention relates almost entirely to the sound chamber and the spherical plug, and the method of construction and assemblage. The vital importance attached to Wente's sound chamber, that is, a sound chamber having a plug secured therein, will be recognized from the following excerpt from Wente's specification, wherein he states: When employed in conjunction with a horn having no inherent losses, a loud speaker constructed in accordance with the above description has an efficiency of approximately 30 per cent, measured from the electrical energy input to the acoustic energy output, over a wide range of frequencies. Measurements made on a loud speaker of this type, from which the plug 23 has been removed from the sound chamber, and which employs a diaphragm about 2.75" in diameter, show that the frequency (1) (1933) Ex. C R. 13.
44 EXCHEQUER COURT OF CANADA [1940 1939 response falls off at frequencies above about 3,000 cycles per second at such a rate that practically no radiation takes place at a frequency of NORTHERN about 6,300 cycles. By inserting the plug into the sound chamber the ELECTRIC Co. LTD , frequency response characteristic of the loud speaker is improved to such AND an extent that the point of low radiation is moved up to a frequency WESTERN of about 14,000 cycles per second and the efficiency of the loud speaker ELECTRIC is practically uniform up to a frequency above 5,000 cycles CO. INC. V. BROWN'S It will therefore be observed that the distinguishing THEATRES LIMITED characteristic of Wente is the use of a spherical plug in the sound chamber for the purpose of decreasing the cross- Maclean J. sectional area of a portion of the sound chamber, and the favourable results produced thereby are described in that portion of the specification which I have just quoted. A sound chamber associated with a diaphragm, in acoustic devices, being old, it was the particular arrangement of parts, including a sound chamber with a plug secured therein, that gave novelty and utility to the combination of Wente, and the evidence in Western Electric Co. v. Baldwin, supra, appeared sufficient, in my opinion, to establish invention for the combination. The defendant's sound chamber is simply an open aperture, the walls of which are diverging. It is, I think, the conventional sound chamber used in a loud speaker and which I apprehend anyone might use in any such device. The defendant's sound chamber is entirely different in conception and form from that of Wente, and I see no room for debate about this, so significant and obvious is the distinction between the two sound chambers. One could hardly be heard to say that these sound chambers are alike, or that the defendant's sound chamber is the equivalent of Wente's sound chamber. It has been laid down time and again that a claim for a particular means to effect certain purposes is not infringed where the same purposes are effected by different means; nor is a combination to effect certain results infringed by a combination of similar parts operating in a different manner, though the results effected are the same; but the claim is infringed when a variation in detail which amounts only to a colourable imitation is used. Wente chose a certain combination of parts, and in particular a combination with a sound chamber in which was inserted a plug, and to that he must be held, and though the form of his sound chamber required a particular shaped dia-
Ex. C R.] EXCHEQUER COURT OF CANADA 45 phragm, that is of no consequence. I do not think it can 1939 be said that the defendant's combination is merely a colour- NORTHERN able imitation of Wente. ELECTRIC Co. LTD., I think the defendant's sound reproducing device is AND in fact a combination different from that described and É EcTa c claimed by Wente. The plaintiffs, by cutting from the Co. INC. walls of the defendant's sound chamber, a spherical plug BRov N's shaped section, and suggesting in some way its replace- Lx ;T n s ment in the sound chamber from whence it came, sought to establish a similarity between the two sound chambers Maclean 3. in question, but with this effort I was not impressed. My conclusion is that there is no infringement of Wente by the defendant. The Miller patent will next be considered. This patent issued in June, 1933, on the application of Miller made in September, 1931. This patent relates to sound repro- ducing systems, and more particularly to sound repro- ducing systems operated from an alternating current source. The specification first points out that various types of sound reproducing systems such as known types of phonographs and radio sets, have been operated from alternating current sources with reasonable success. However, it is said, difficulty has been experienced in operating an alternating current film sound reproducing equipment suitable for sound picture systems, due to the very high amplification between the photoelectric cell and the sound radiator and the high quality of reproduction necessary. The specification then states: Heretofore, known types of film sound reproducing systems have been mainly or entirely operated by direct current sources. Commercial types of direct current g enerators are not suited to service of this type due to the pronounced ripple produced in their output by the usual method of commutation which produces a steady hum in the reproduced sound. Special generators designed to overcome this difficulty are difficult to construct due to the small power and size required and have not proved an entire success. As a result, the direct current used in sound reproducing systems has been mainly supplied by storag e batteries. The storage batteries required, however, are bulky, require skilled operation and maintenance and a separate current supply and apparatus for charg ing. Owing to the disadvantages attendin g the use of storage batteries, attempts have been made to replace the storage batteries with a source of supply derived from commercial alternating current circuits due to the constancy and reliability of these circuits and the ease with which the volta g e may be transformed to any desired value. Rectified alter-natin g current has been successfully used on the amplifiers feeding
46 EXCHEQUER COURT OF CANADA [1940 1939 directly into the sound reproducers and has resulted in a system having economic and operating advantages over the use of storage batteries. NORTHERN The use of rectified alternating current as a power supply for the other ELEOTRic CO. LTD., circuits in the reproducing system, has not heretofore proven commercially AND successful. Due to the very high amplification of the output of the photo- WESTERN electric cell, it has been found that in known systems the ripple remaining ELECTRIC due to incomplete rectification produces a hum in the output of the Co. v I . N c. sound reproducer which is detrimental to the enjoyment of the sound. BROWN'S By using extreme precautions, it is possible to produce a supply of recti- TâEATRES fled alternating current which is practically as constant as the supply LIMITED, from the storage battery but the elaborate and complicated installation Maclean J. required has prevented these systems from becoming commercially successful. In known systems of film sound reproduction, a certain amount of noise is produced by the sound radiator even during supposedly silent periods. This noise is caused by various irregularities in the system such as fluctuations in the output from the amplifiers, lack of cleanliness and uniformity in the sound record, and many others. The total volume of noise due to these causes is kept low enough that no disagreeable effect is produced on the listener. The volume of noise is generally near to or below the threshold of audibility of the listener. J. C. Steinberg has shown in his article " The Relation Between the Loudness of a Sound and its Physical Stimulus," the Physical Review, Second Series, Vol. 26, October, 1925, that when the components of a complex sound near the threshold of audibility have values less than the values required for them to be audible when heard alone, they do not contribute to the loudness of the complex sound. In the present invention, the power supply is so arranged that the noise produced by variations in the supply is reduced to near the threshold of audibility and thus does not contribute to the loudness of the noise due to other causes. The total noise produced is thus not appreciably greater than the noise produced when the system is operated by storage batteries. At the same time, the system is so arranged that the irregularities m the power supply do not tend to cause a modulation of the sound frequency currents, It has been found that a system having the degree of imperfection in rectification limited as described above voids the complications which have prevented the systems producing practically constant current from an alternating current source from becoming