An Improvement in Photographic Focussing Magnifiers.
Year: 1889

page_text: Date of Application, 9th Sept., 1889
Complete Specification Left, 5th June, 1890-Accepted, 5th July, 1890
PROVISIONAL SPECIFICATION.
An Improvement in Photographic Focussing Magnifiers.
I, FRANK BISHOP of the firm of Marion and Co. of 22 and 23 Soho Square,
London, W. Dealers in Photographic Materials do hereby declare the nature of this
invention to be as follows:-
My Invention has for its object to provide a means whereby a focussing magnifier
sometimes used in focussing a picture in the photographic camera may be temporarily
fixed against the focussing screen in position for viewing the image, so that the
hand of the operator instead of being occupied in holding the magnifier is at liberty
to make the necessary adjustments of the camera.
The Invention consists in the combination with the focussing magnifier of a
suction device in the form of an india rubber cupped disc which when pressed flat
against the focussing screen remains adherent thereto, by atmospheric pressure, in
the manner of a sucker, with sufficient tenacity to support the focussing glass in
position against the screen and permit of its being shifted about thereon.
Dated this 9th day of Sep ember 1889.
ember 1869.
F. BISHOP.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.
COMPLETE SPECIFICATION.
An Improvement in Photographic Focussing Magniflers.
I, FRANK BISHOP, of the firm of Marion and Co., of 22 and 23 Soho Square
London, W. Dealers in Photographic Materials, 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 :-
My Invention has for its object to enable a magnifier (used in accurately focussing
a picture in the photographic camera) to be temporarily fixed by simple pressure
against the focussing screen in any desired position for viewing the image to be
focussed so that the hand of the operator instead of being occupied in holding the
magnifier against the screen is at liberty to make the necessary adjustments of the
camera.
The Invention consists in the combination, with the focussing magnifier, of a
sucker consisting of a cupped disc of india-rubber which when pressed against the
focussing screen remains adherent thereto by atmospheric pressure, with sufficient
tenacity to support the magnifier in position against the screen and permit of its
being shifted about thereon without becoming detached.
Reference is to be had to the accompanying drawings, forming part of this
specification, wherein figure 1 is a side elevation of the magnifier held in position
against the screen, the suctional appliance and the screen being in section, and
figure 2 is a face view of the same. The same letters of reference indicate the same
parts in both figures.
A is the magnifier made in the ordinary way, comprising an objective and eye
piece lenses mounted in an inner tube fitted to slide friction-tight within a split
outer tube a for the purpose of adjustment for focussing the image in the magnifier.
To the side of the outer tube is affixed a smaller cylindrical casing B whose rear end
is open and flush with the rear end of the outer tube a of the magnifier and within
this casing is mounted a cupped disc C of india-rubber whose forwardly presented
concave side has a circumferential lip or flange that projects from the open end of
the casing B sufficiently to admit of being applied against the surface of the
ID 1

page_text: focussing screen with sufficient pressure to slightly flatten the disc so that when
the pressure is relieved the tendency of the disc to resume its cupped form will
cause it to adhere to the surface by suction. The cupped disc is preferably of the
form shewn in section in figure 1, that is to say thicker towards the middle than at
the edges and the flange or lip being of V-form in section, and it is provided with
a central shank c of india-rubber which is cemented or otherwise fixed in an aperture
at the apex of a conical holder b fixed within the casing B so that when the edge
of the disc is applied to the screen the pressure against the shank c will tend to
collapse the disc at the centre and expel the air from within the cavity of the disc
and so cause a partial vacuum to be formed when the disc tends to resume its cupped
form. In order the better to ensure this vacuum being formed and maintained,
it is desirable to slightly moisten the lip of the disc before applying it against the
screen.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is ;-
The combination, with a photographic focussing magnifier, of a suction device
substantially as specified adapted to hold the magnifier against the focussing screen
by atmospheric pressure, as described.
1000
1000
ACOT own a 10
Lun me
F. BISHOP.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.