Improvements in means and appliances for testing the sight / [Nathaniel Davidson].

  • Davidson, Nathaniel.
Date:
1896
Catalogue details

Licence: Public Domain Mark

Credit: Improvements in means and appliances for testing the sight / [Nathaniel Davidson]. Source: Wellcome Collection.

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    N° 9510 1890 Date of Application, 5th May, 1896—Accepted, 27th June, 1396 COMPLETE SPECIFICATION. % Improvements in Means and Appliances for Testing the Sight. Nathaniel Davidson 27 Wallace Road Canonbury London N. Optician do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement:— 5 My invention relates to a novel device for testing the sight by means of two circular discs each containing lenses of different power and each revolving on a central axis supported by suitable upright standards which standards slide upon a horizontal bar so that they can be moved towards or away from each other at will, so as to bring the lenses in any desired position to the eyes of the person whose 10 sight is being tested. A lens or disc carrier projects from each standard in such a manner as to bring a lens placed therein exactly opposite or in line with the lenses in circular disc so that when circular disc is revolved a different combination of lenses is given. An arm projects from centre of horizontal bar fitted with a swivel joint and a 15 card or disc holder which is capable of being moved to the right or left according to whichever eye is being tested. The whole is mounted on a suitable base or stand. In the annexed drawings, like letters refer to like parts throughout the different views and 20 Figure 1 is front elevation. Figure 2 is side elevatiou. Figure 3 is plan. a a1 are circular discs or frames containing a series of lenses b around their outer edges and revolving on centres c, c1 which are supported by forks or uprights d dv 25 at the bottom of which are sockets e el. These sockets slide upon a square horizontal bar /supported by a suitable base g. From the centres c cl project two horizontal arms h h1 each carrying a lens or disc holder i il at the same distance from the centre c c1 as the lenses b in circular discs a a1 so that lenses placed in lens carrier i ix come opposite or in Hue with lenses b in circular discs a a1 thus 30 giving different combinations of lenses when discs a a1 are revolved or different lenses placed in lens carriers i A k kl are ornamental cover plates. I is an arm projecting from centre of horizontal bar having a socket m at its end in which works another arm n carrying a card or disc holder o which also works in a socket p. 35 Thus it will be readily understood that by means of the socket m and socket/? the card or disc holder o can be moved from side to side and brought to face lens holder i or il according to whichever eye is being tested, r r1 are stops screwed on to horizontal bar/ to prevent sockets e el from sliding off. s a1 are felt washers. t t1 are pointers attached to sockets e el which indicate upon a scale marked upon 40 horizontal bar /the distance between the centres of the lenses which are opposite to, or behind the lens carriers i i1. Having now particularly described and ascertained the nature of my said inven¬ tion and in what manner the same is to be performed I declare that what I claim is 45 (1.) In a sight testing machine two circular discs or frames carrying a series of lenses, the circular discs being placed side by side supported by uprights or [Price 8cf.]