Figure 5.—Hopkins’ Balance Arresting Device, the subject of U. S. patent 165830. This and the device illustrated in figure [4] originally were submitted together to the Patent Office on June 9, 1875, and later were divided into two patents.
Developing the Invention
Edward A. Locke had long been seeking a simple watch adapted to easy manufacture and a selling price of three to four dollars. While on a trip to Washington his attention was drawn to the Hopkins watch by William D. Colt of Washington.[8] A result of this meeting appears to have been the issuance to Jason 54 R. Hopkins of two patents,[9] in both of which half rights were assigned to William D. Colt. Patent 165831, relates to a barrel arbor for watches. The arbor will be seen (fig. [4]) to consist of two parts, one telescoped within the other and the composite arbor B-C supported at each end by the frame of the watch. The patent text limits itself to a bare description of the arbor. In the light of what we have seen of the shortcomings of the original model, however, the patent drawings tell that much more had been accomplished on the general design of a more workable rotary watch.
A square on arbor C at the back of the watch permits winding the main spring, which attaches to the largest diameter of C, a ratchet or winding click being supplied just under support F. The inner or front part B of the composite arbor projects from the front of the movement and revolves at the speed of the barrel arbor, which speed is not specified. Also, looking at the perspective view, we see that while the chronometer escapement has been retained, the balance has been placed eccentrically to make room for the center arbor. The balance now describes an orbit around the center of revolution. No driving train is shown, it being irrelevant to the patent, but there seems to be ample room for two intermediate wheels and their pinions between the escape wheel and the train cock boss, seen at the upper right in the perspective view of figure [4]. Adding one more wheel and pinion to the train would have the effect of reducing the number of revolutions required of the spring barrel. We have seen from examination of the patent model of the Hopkins rotary that this was necessary not only to reduce the number of turns of the main spring and barrel but also to reduce the force transmitted to the escapement. There seems little reason from the foregoing observations and considerations to doubt that these modifications had been realized by the time of this patent. Again no dial gearing is shown. If the need for special gearing existed at this time it seems strange that it was not covered by patent as was done in the later patent[10] assigned to William B. Fowle. The only way to avoid special gearing would be to revolve the barrel and train each hour so that the minute hand could travel with them as it travels with the center wheel in conventional watches. Once this condition was set up, the usual dial gearing would apply.
Companion patent 165830 (see fig. [5]) covers a mechanism to prevent overbanking of the balance wheel, primarily of a chronometer escapement. This, of course, was aimed at making it possible to use the escapement in connection with a mainspring of greatly varying power. We have seen that this condition of uneven power existed in the first Hopkins watch. While the condition was greatly improved in the second model (seen in fig. [4]), it was surely present to some extent, as it is associated with every spring. Overbanking protection may well have continued to be necessary, particularly if the gear ratio between escapement and barrel was low enough to permit hourly rotation of the barrel. The features covered by this patent were originally submitted as part of what later became patent 165831. Examination of the original manuscript patent file[11] shows that the patent application was separated into two on the suggestion of the patent examiner, who pointed out that two distinct and separate mechanisms were involved, either of which could be used without the other.
