Bristol Co. v. Brown Instrument Co.

291 F. 403, 1923 U.S. Dist. LEXIS 1412
CourtDistrict Court, E.D. Pennsylvania
DecidedAugust 1, 1923
DocketNo. 2423
StatusPublished

This text of 291 F. 403 (Bristol Co. v. Brown Instrument Co.) is published on Counsel Stack Legal Research, covering District Court, E.D. Pennsylvania primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

Bluebook
Bristol Co. v. Brown Instrument Co., 291 F. 403, 1923 U.S. Dist. LEXIS 1412 (E.D. Pa. 1923).

Opinion

DICKINSON, District Judge.

This case concerns three letters patent: (1) No. 783,503, issued February 28, 1-905, to William H. Bristol. (2) No. 869,668, issued October 29, 1907, to Charles B. Thwing. (3) No. 1,301,434, issued April 22, 1919, to Edwin J. Heitman.

[404]*404Patent No. 783,503.

The first-mentioned patent has lost all juridical importance, and has dropped out of the case, because the patent has expired and the plaintiff has withdrawn it from consideration.

Patent No. 869,668.

[ 1 ] This is known as the Dr. Thwing patent. The invention relates to that type of pyrometer which is operated by the use of a thermoelectric couple. The principle which is the basis of the invention is well known. Great merit is claimed for the' invention, in that the troublesome element in .the problem was used to eliminate the trouble, and invention is denied because what was done was so obviously the thing to do. There was need, however, to be done what Dr. Thwing did, and there was resort to various means of reaching the desired result, and even also to this; but Dr. Thwing was the first to apply this now obvious means. The desired measurement is that of the temperature of what is termed the “hot end” of the thermo-electric couple. What, without the needed correction, is obtained is the difference in temperature of the two ends. None of the several tried expedients to reach the desired result were satisfactory. One difficulty was presented because the temperature of the cold end varied. Dr. Thwing’s thought was to let it vary as it listed, but to measure it and have it indicated, so that a corresponding correction would be made in the reading of the “hot end” temperature. This was accomplished by having such a construction as that the needle marking the hot end temperature would be set so as to malee the reading vary in accordance with the temperature of the cold end when no current was passing, whatever the latter might be. It is the handicapping or time allowance principle applied in athletic sports.

There is another obstacle to accurate reading of the hot end temperature in what is known to this record as “copper error.” Allowance or compensation for this may readily be made. Its practical importance depends upon the instrument in respect to its being of relatively high or low resistance. This broad and roughly outlined description of the patent will suffice for the purpose of applying the legal principles involved, although as a description of the instrument which embodies the invention claimed or of the principles of its operation, it is neither complete nor accurate.

There is in the record of the trial no blunt averment of inutility, but something approaching it in the characterization of the patent as a “paper” one. As has often been observed, a denial of utility comes from a strange source, when it comés from one who is himself using the patented invention and is fighting for the right to continue its use. Litigation over an inutile patent is the most futile of pursuits, and the litigation is of itself most persuasive evidence of at least the commercial value of its subject-matter.

The defense is rather a qualified denial of invention, in that the principle underlying the patented instrument is one which has been long known and applied in numberless ways, so that invention is necessarily limited to the particular instrument devised, and that the in[405]*405strument of the defendant does not infringe either upon any possible cl'aim which the patentee might have made to an invention, and is clearly not within any of the claims which were allowed by the Patent Office. The epithet of “paper patent” has some justification in the fact that the inventor himself voluntarily discontinued the mánufacture of the patented instrument. The occasion for this discontinuance, as explained, does not, however, argue inutility, because Dr. Thwing became interested in a different type of instrument and for the time being had no place for this type.

Others, however, including the plaintiff, had a place for it, and it has some bearing upon the fact that the invention was one which stared every one in the face that the chief officer of the plaintiff, in his search for such an instrument, hit upon one which was the counterpart of that which Dr. Thwing had patented. The long search which he had prosecuted, and the several modes of accomplishing what the instrument in suit does, which Bristol and others had found, is very persuasive evidence that the idea was not as obvious as it now seems to be. The fact that Bristol finally hit upon the same idea which Dr. Thwing had applied does not detract from the merit of the claim of the latter to invention. It merely proves that Dr. Thwing was the first to apply it. The plaintiff, having learned of Dr. Thwing’s patent, admitted its priority in time and right, and paid for it what, although not a large, was at the same time a substantial, sum. The point which bears the main burden of the defense is that the feature of the Thwing patent which gives it its patentable value is that it is an instrument which “indicates” the temperature of the “cold end,” while the instrument used by the defendant is not only without this feature, but it is one which is of no importance, and indeed, if the instrument is used for such a purpose, the reading would mislead as the departure from the correct reading would be from IS to ISO per cent.

The basis of this defense, and at the same time what seems to us to be the unsoundness of it, will most clearly appear from a listing of the principles of operation involved in the construction of the two instruments. The objective, as already stated, is the true reading of the temperature of the “hot end.” The means of measurement employed is the current, which manifests its -presence when the two ends of a thermo-electric couple have different temperatures. The measurement, however, is not of the temperature of either end, but of their difference. If one is known and kept constant, and the difference is known, the temperature of the other can be learned. This method was employed by keeping the cold end at a known and constant temperature. There are conductors leading from the thermo-couple to the galvanometer. If the resistance of these conductors is made to vary in correspondence with the variations in the temperature of the cold end, the desired result may thus be attained. This method was devised and patented by Bristol.

If the marking hand or needle, which marks the measurement made by the current passing, is so placed at the start as to compensate for the temperature of the cold end, the needle will indicate on the scale, not the difference between the ends, which the extent of its movement [406]*406really measures, but the temperature of the hot end, which is the measurement desired to be known. This placement was made manually. As already stated, none of these methods was in all respects satisfactory. What in this respect Dr. Thwing did was to do by his device automatically what had been before done manually. As again before stated, the correct reading may be affected by the circumstance that the conductivity of copper varies with the temperature, and a correction or compensation for this so called copper error may be needed. If the copper error be negligible or ignored, the position of the marker in the Thwing method will' indicate the temperature of the marker when no current is passing. If allowance be also made for copper error, then the temperature indicated will not correspond with the cold end temperature, when no current is passing.

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Bluebook (online)
291 F. 403, 1923 U.S. Dist. LEXIS 1412, Counsel Stack Legal Research, https://law.counselstack.com/opinion/bristol-co-v-brown-instrument-co-paed-1923.