An Improvement in Lens Measurers.
Year: 1895

page_text: Date of Application, 3rd Oct., 1895
Complete Specification Left, 20th July, 1896-Accepted, 22nd Aug., 1896
An Improvement in Lens Measurers.
I, WILLIAM HENRY DOUGLAS of 59 High Street, Stourbridge in the County
of Worcester, Watchmaker, do hereby declare the nature of this invention to be
as follows:
My improvement consists in the application to lens measurers of three terminals
in the form of a tripod or isosceles triangle on which to place the lens at right
angles to a moveable central feeler attached to a registering dial or lens measurer,
whereby I obtain a much steadier rest and more accurate measurement than in
other lens measurers already in use.
Dated this 2nd day of October 1895.
HENRY F. TALBOT,
7 Cherry Street, Birmingham, Agent for the Applicant.
I, WILLIAM HENRY DOUGLAS of 59 High Street Stourbridge in the County
of Worcester, Watchmaker, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement, reference being had to the accompanying
drawings and to the letters and figures marked thereon :-
My improvement consists in the application to lens measurers of three terminals
in the form of a tripod or isosceles triangle on which to place the lens at right
angles to a movable central feeler attached to registering dial or lens measurer
whereby obtain a much steadier rest and more accurate measurement than in
other lens measurers already in use.
The accurate measurement of extremely slight curves depends upon the extreme
reliability of the stationary bearing points, but it is necessary to use blunt ends to
the stationary terminals in order to avoid scratching the surface of the lenses, on
the other hand a delicacy of measurement is required as if you were measuring
from an absolute point or points. This can only be accomplished by using three
blunt bearings arranged in such position that the lines connecting their centres
will form an isosceles triangle, and cannot be accomplished by the use of a greater
or less number of bearings used for that purpose.
Fig. 1 is an elevation shewing the dial of the instrument.
Fig. 2 is a view of the interior.
And Fig. 3 a plan of the portion upon which the bearing points are situated.
I do not claim any special mechanism to which to apply my improved arrange-
ment of terminals, I have therefore illustrated my invention as applied to a well
known form of instrument.
a, b, c, are the three terminals or bearing points, and da centre movable pin
working in the usual way.

page_text: The terminals b and c are situate relative to the terminal a so that a line drawn
from terminal a to terminal b would pass close to one side of the centre pin d and
a line drawn from a to c would pass equally close to the other side of the centre
pin d.
By placing the bearing points or terminals in the positions relative to each other
shewn and described perfect accuracy is arrived at. e Figs. 1 and 2 is a lens onto
the surface of which the terminals are placed and it will be seen by Fig. 2 that a
perfectly steady bearing can be obtained.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is :
In lens measurers the application of three fixed terminals or bearing points
substantially as herein described and illustrated by the accompanying drawings.
Dated this 18th day of July 1896.
HENRY F. TALBOT,
7 Cherry Street, Birmingham, Agent for the Applicant.