Year: 1891

page_text: Date of Application, 7th Feb., 1891-Accepted, 5th Sept., 1891"

page_text: To further adjust the instrument so that it shall stand at zero when a plane surface
or a straight edge is in contact with the points C, C, D, the studs C, C can be
screwed in or out until they stand in the proper relation to .the pin D. Where
neither side of the lens is plane, it is necessary to ascertain the curve of both faces
and to combine the readings in order to know the focal length of the lens
But in many cases, as for instance with periscopic spectacle lenses, a standard
curvature is adopted for one side of the lens, and to enable the focal length of
such lenses to be ascertained by direct reading, I provide the additional pointers K, L.
The usual fixed curvature of a periscopic lens is one and one half diopters, and I
have, therefore, shown the pointers K and I placed one and one half diopters on
each side, distant from the pointer J. The pointer K will give the power of
periscopic concave lens directly, while the pointer L will give the power of a
periscopic convex lens in like manner.
It is necessary in order to measure concave surfaces to employ contact points
such as have heretofore been described, but for measuring plane or convex surfaces,
especially cylindrical surfaces, accurate results may be obtained with much greater
case by substituting for contact points parallel edges as shown in Figures 4 and 5.
In said figures the edges C¹ C and D are substituted for the points C, C, D of
Figures 1 to 3. It is obvious that if a cylinder be placed so that its axis is
perpendicular to the edges C¹, C¹ its curvature will not be indicated, but the
reading of the scale will show that it is simply a straight line; but by turning
the cylinder until its axis becomes paralle with the edges C, C the sides of the
cylinder will make contact with the edges C, C throughout their length and the
cylinder will be in a proper position for ascertaining its outer curvature. It is also
clear that in measuring a spherical surface to ascertain its correct curvature by
the use of contact points requires that the lcns should be very carefully placed
thereon, as a change in its position will cause a change of the reading, but when
parallel edges are substituted for the points little or no care is required in placing
the lens in order to get a correct reading.
It is to be understood that although the center piece D is shown as movable and
the outer pieces C, C fixed, and such an arrangement is preferable on account of
its simplicity, yet the device would operate essentially as before if the outer pieces
should be made movable and the indicating devices attached thereto, it being only
essential that the relative positions of the centre and outer pieces be changeable
and that such changes be shown by the indicating devices.
It is further to be understood that more than three contact pieces might be
employed, but three only are essential.
By using a spring for projecting the movable contact piece as shown in Figures
and 2, I am enabled to use the instrument in any position; the range of its
usefulness being thereby much increased as it can be used upon surfaces of objects,
which, by reason of their size or from other causes, cannot easily be moved.
Having now particularly described and ascertained the nature of my inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is-
1°) The combination, in a lens measuring instrument, of contact devices
consisting of three contact pieces whose pointed ends lie in the same plane, the
position of the middle contact piece being variable relatively to the outer pieces,
and indicating devices consisting of a lever arm abutting against or attached to
said movable contact piece and gearing connecting said arm to a pointer moving
over a dial, said dial being graduated to show the focal length of the lens:
substantially as hereinbefore described and as illustrated by the accompanying
drawings.
2°) The combination in a lens-measuring instrument of contact devices consisting
of three contact pieces whose pointed ends lie in the same plane, the position of the
middle contact piece being variable relatively to the outer contact pieces; an
indicating devices operated by said movable contact piece, said indicating devices

page_text: consisting of a lever arm abutting against or attached to said movable contact
piece and having a fulcrum movable relatively thereto, and gearing connecting said
lever arm to a pointer moving over a dial graduated to show the focal length of
the lens; substantially as described and as illustrated in the accompanying
drawings.
3°) The combination of the fixed contact pieces C, C, the movable contact
piece D. all three of said contact pieces lying in the same plane, the sector H
against a projection of which the said movable piece abuts, said sector having a
fulcrum movable relatively to the contact piece D, the spring M, the pinion I
carrying the pointer J and the dial A graduated to show the focal length of the
lens placed against said contact pieces; substantially as described and as
illustrated in the accompanying drawings.
4°) The combination, in a lens-measuring instrument of three contact pieces, one
of said pieces being movable relatively to the other two, a pointer for indicating
the movements of the movable piece, a pinion on the pointer shaft, and sector in
contact with the movable piece connecting the pointer and the movable piece; and
an adjustable bearing, in which said sector is pivoted whereby the relative
movement of the movable piece and the pointer may be varied, substantially as
described and as illustrated in the accompanying drawings.
5°) The above characterized lens measuring instruments, substantially as .
described and as illustrated in the accompanying drawings.
1001
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.