Ashcraft v. National Theatre Supply Co.

25 F. Supp. 426, 1938 U.S. Dist. LEXIS 1660
CourtDistrict Court, D. Maryland
DecidedNovember 18, 1938
DocketNo. 2445
StatusPublished
Cited by2 cases

This text of 25 F. Supp. 426 (Ashcraft v. National Theatre Supply Co.) is published on Counsel Stack Legal Research, covering District Court, D. Maryland primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

Bluebook
Ashcraft v. National Theatre Supply Co., 25 F. Supp. 426, 1938 U.S. Dist. LEXIS 1660 (D. Md. 1938).

Opinion

WILLIAM C. COLEMAN, District Judge:

This is a patent infringement case involving patent to C. S. Ashcraft, No. 1,983,-430, filed April 16th, 1934 and issued December 4th, 1934, relating to an electric arc and a method of producing it, used principally in motion picture projectors and search lights. One of the defendants, National Theatre Supply Company, is a seller, and the other defendant, the Grand Company — owner and operator of a motion picture theatre — is a purchaser of an arc lamp alleged to infringe the patent.

The plaintiff’s rights in the patent and the jurisdictional prerequisites are established. The defences to the suit are the usual ones: (1) Non-infringement, and (2) invalidity of the patent on grounds, hereinafter specifically referred to.

Broadly speaking, lamps for the projection of moving pictures may be divided into two classes: First, those with low intensity arcs, and second, those with high intensity arcs. Again, these two types may be broadly differentiated by saying that the low intensity arc is produced by pure carbon electrodes which do not contain cores of arc-sustaining material; that it has a great economy and low maintenance cost, but that it gives a yellowish white light, whereas the high intensity arc is produced by carbon electrodes having cores of arc-sustaining material, and it gives a snow white light generally considered more desirable for the projection of motion pictures, although its initial and maintenance costs are much greater than those of the low intensity arc, because of greater carbon and power consumption.

The electric arc or flame is produced by sending an electric current of suitable voltage through a pair of carbons, one a positive, the other a negative electrode, which are placed with their ends adjacent to each other, thus producing a flame between these ends. Since the earliest days of the art, the light emitted from the positive crater of a carbon arc was known to possess the highest intrinsic brilliancy or candle power per unit area of any incandescent light source.

Up to the time of the issuance of the Ashcraft patent, while both alternating and direct current had been used in connection with various types of arcs falling within the broad classification just mentioned, the one commercially most attractive was a high intensity alternating current arc which gave better screen illumination than low intensity arcs, making available to the smaller theatre a white light, very similar to that obtained from the direct current high intensity arcs. Ashcraft, however, pointed out certain disadvantages that still existed in the high intensity arc, describing them as follows in his patent: “In the first place, the maintenance costs are very high. Due to high amperage and voltage the carbons burn very rapidly, and, furthermore, there is a rela[428]*428tivély high cost in the replacement of parts which quickly deteriorate due to the high intensity operating conditions of such arc. Furthermore, the operating costs are relatively high by reason of a high power consumption. Although this so-called high intensity arc produces good illumination, the light is of a bluish white color which is better adapted for motion-picture projection work than the yellowish colored light produced by the so-called low intensity arc, it is not, however, the most satisfactory light.” He claimed that he had overcome these disadvantages in that he had discovered “a method of producing and operating a so-called high intensity electric arc in which excellent illumination or light intensity is attained, in which there is great economy by reason of low carbon consumption, in which the maintenance costs are low because the replacement of parts is less frequent, in which the operating costs are low due to a relatively low power consumption, and in which the light produced thereby is of a pure white color.”

The patent contains numerous other separate statements of the various objects of the' Ashcraft invention which need not be quoted, because largely paraphrasing each other. Suffice it to quote the following which perhaps best of all describes, in a brief way, the characteristics of the electric arc, produced by the method prescribed in the patent: “Another object of my invention is to provide a- method of producing an electric arc in which a negative flame is directed against a positive flame to produce a body of luminescent gas having a substantially flattened surface and having its periphery extending rearwardly and surrounding the end of the positive electrode.” The term “luminescent gas” is defined in the patent as meaning any gas giving a brilliant flame and includes a gas in which incandescent particles may be present.

The carbons called for are preferably copper coated, the positive carbon having a core composed of a material which during operation produces a brilliant, gaseous flamé; and the negative carbon having a core of arc-sustaining material. The positive carbon is preferably 7 mm. and the negative carbon 6 mm. in diameter, the two being placed in axial alignment, that is, parallel with each other, the distance between their ends being maintained at approximately one-quarter of an inch. The specifications recite that best results are to he obtained with a current of 46 amperes and a gap voltage of 36 volts, although the range of current is stated as low as 40 and as high as 65 amperes.

While all of the twelve claims of the patent are here in suit, plaintiff relies primarily upon Nos. 1, 5 and 6. They are all method claims and we here quote claim 6 as being typical: “The method of producing an electric arc which comprises positioning a positive electrode, capable of emitting a positive flame of luminescent gas, ádjacent a negative electrode and substantially coaxial therewith, causing a current to flow between said electrodes sufficient to form said luminescent flame and a negative flame, directing said negative flame against said positive flame in such a manner as to form a crater in said positive electrode and substantially flatten a portion of said luminescent flame so as to form a substantially flattened luminescent surface in front of the crater, whereby the area of the crater is substantially completely covered by said flattened portion of said luminescent flame and said luminescent gas contacts substantially the entire area of said crater.”

Shorn of technical language and considered in the light of the single drawing attached to the patent, it appears that the alleged invention of Ashcraft lies in the fact, as he claims, that he was the first to conceive of a combination of the various factors in electric arc production, whereby the flame from the negative carbon would be so impinged upon the flame from the positive carbon as to build up on the face of the latter a shield of luminescent gas, the negative flame pressure being gradually built up to a point where the positive flame is flattened into a disc, surrounding the end' of the positive carbon. That is to say, this flattening of the positive flame or luminescent gas, flowing out of the crater at the end of the positive carbon, is claimed to be beneficial, in that this disc of luminescent gas forms a distinct polarized shield which prevents the flame from the negative carbon from flowing past the crater face of the positive carbon and enveloping the end .of this carbon.

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Bluebook (online)
25 F. Supp. 426, 1938 U.S. Dist. LEXIS 1660, Counsel Stack Legal Research, https://law.counselstack.com/opinion/ashcraft-v-national-theatre-supply-co-mdd-1938.