[LB012218], Letter from Richard Nott Dyer to Thomas Alva Edison, April 25th, 1882



I have examined at your request the three English patents of Dr John Hoopkinson Nos 2481 and 4653 of 1879 and [2989] of 1881 [---] correction with his statement dated 24th Feby 18[--], and have [--] report as follows.##No. 2487, dated 21 June 1879. A patent cannot be a [----] in the arrangement described in this patent in the united Statement [that] an interference with [----] patent no. 232,253 (dated Sep. 14 80). It is true that [----] application was filed July 3d 1880 over a year after the date of Dr Hopkinson's patent, but in an interference [----] would be [all--] to [illegible] of invention, while Dr. Hopkinson [---] to be limited to the date of his English patent. If Dr. Hopkinson's patent was known to th e Examiner at the time [Field's] case was examined (as it should have been and probably [was] Field should have been required under the [practice] then existing to establish (by his own statement under oath) a date of invention earlier than the date of Dr Hopkinson's patent. Whether or not this was done I have no [access] of knowing.##The chances of success in an interfrence with [Field] would be largely in favor of Field.##No. 465[3] dated 14th november 1879.##The specific arrangement shown in figures 1 and 2 of this patent might be covered by a separate application if there is no patent already issued claiming the same thing. If a single application has been filed including all the inventions covered by Dr Hopkinson's two patents 24[8]1 and 4653 of 79, it is not likely that an examination was made in the Patent Office as to the specific arrangement just referred to.##It seems to me a matter of small importance, since it is only one of a number of ways of doing the same thing, and especially since you consider a current receiver as a more practicable thing for the purpose.##In regard to the arrangement shown in figure 3 to 6 inclusive, viz: the mounting of the brushes upon a pivoted yoke so that they can be swung directly around upon the commutator cylinder The application of this device to a machine such as that of Gramme or Siemens, when it has been before applied to a machine of the character shown in [--ssey's] United States patent no. 166,527 (dated Aug. 10th 1875), does not seem to me to be broadly patentable. I also understand that it is quite common in electro-motors to mount each brush on a spindle adjustable in a slot so that it can be adjusted to any point within the limits of a half circle.##No. 2989 dated 7th July 1881.##I have looked into this patent carefully and, think that patents can be obtained upon the devices described in the United States. Two applications would have to be filed to cover all the devices - one on the construction shown in figures 1, 2, 3 and 4, and one on that shown in figures 5, 6 and 7. It should be borne in mind that there is an inherent weakness in patents taken by foreigners residing abroad in the United States. They [rest] on the date of the foreign patent when attacked. If an agreement is entered into with Dr Hopkinson it should be made conditional upon the grant of the patent.##[R.B.] In regard to this last patent, it seems to me that the device shown in figures 5 and 6 is impracticable although the principle involved is good. When the metal cross bar [Q] touches N and [P] it will connect I and M and cut out the motors entirely for an instant. This would prove disastrous.









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[LB012218], Letter from Richard Nott Dyer to Thomas Alva Edison, April 25th, 1882

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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University

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