Year: 1888

page_text: Date of Application, 19th May, 1888
Complete Specification Left, 19th Feb., 1889
Complete Specification Accepted, 13th Apr., 1889
1, SAMUEL DUNSEITH MCKELLEN Photographic Apparatus Manufacturer Spring
Gardens, Manchester, do hereby declare the nature of this invention to be as
follows:-
My invention is intended to facilitate the use of an oblique mirror in connection
with photographic cameras, and is especially intended to be used in so-called 'detective'
cameras.
For this purpose I place a ground-glass focussing screen on the top of the camera
instead of as usual upon the back. The position of this ground-glass is usually at
right-angles to the sensitive plate in the camera for exposures. Midway between
the positions of the ground-glass and the sensitive plate I place a mirror in such a
way that the plane of its reflecting surface exactly bisects the angle formed by the
ground glass and the sensitive plate. This method of focussing by means of an oblique
mirror was adapted many years ago by a Mr. Sutton.
The mirror when in position for focussing is made to fit close down upon a frame
which prevents any light passing to the sensitive plate, either from the lens or the
ground-glass, but as an additional security against any light passing through the
focussing screen, I make the focussing glass of a non-actinic colour.. Various colours
may be used but I find light yellow all that is required.
The lens is attached to a front which moves backwards and forwards by the action
of a rack & pinion in the usual way.
The whole arrangement is enclosed in a box, by preference of an oblong form,
having four sides and two ends. The front end is pierced with an aperture of the
proper size to allow the light to pass to the lens. The top of the box is cut out so
that the ground-glass is visible through the opening, and a cover is hinged to one
side of this opening, which folds down and covers the ground-glass when not in use.
The front is made with two thicknesses of wood, with a space between to allow a
slide to move up and down, freely. This slide is connected with the before-named
cover, so that, when the cover is opened up to allow focussing to be done, the slide
moves away so as to allow the light to pass to the lens, and, when the cover is closed
LD

page_text: down, the slide covers the aperture in the front. But, as in some cases it may be
desirable for the cover to be closed when the lens open, I have arranged a connection
between it and the slide in such a way that the attachment between one and the other,
may be re-adjusted so as to allow the cover to be closed whilst the lens aperture
remains open. The front of the box is hinged, preferably at the top, so as to enable
it to be opened in order that the lens stops may be changed. To insure that no light
shall pass into the camera, except what passes through the lens, 1 fix an opaque
flexible diaphragm inside the box, and between the lens travelling front and the box
front. This diaphragm is attached by suitable means to the inside of the box sides,
and the centre of the flexible diaphragm is attached to the travelling front, near
to the lens flange, so that the travelling front may move backwards or forwards
for focussing.
The exposure may be either slow or rapid. For a slow exposure the slide working
in the box front may be used, and any length of exposure may be given by that
means, the mirror first having been lifted on its hinges out of the way of the sensitive
plate.
To raise the mirror I use a spiral spring working inside a roller at the top of the
box, and a winding roller at the bottom, with a curtain between the two rollers, in the
form used by Mr. B. J. Edwards in his well-known shutter. The middle of this
curtain attach to the front rail of the mirror frame. The curtain is first wound on
to the bottom roller by the hand. By so doing, the mirror is drawn into its oblique
position for focussing, and is prevented from returning by a click acting upon a
ratchet attached to the bottom roller. The releasing is done by removing the click
from the ratchet, either by hand, or by pneumatic action, when the upper roller
is caused to revolve by the spiral spring within it. This rolls the curtain
upwards, and carries the mirror with it, as far as it will go towards the top of
the box.
An aperture is cut in the curtain in such a position, that, when the mirror is
in its position. for focussing, the aperture will be opposite the back of the lens, so that
the rays of light may pass from the lens to the mirror, and thus to the focussing
screen. Another aperture is cut in the curtain, immediately beneath the mirror, so
that as the mirror rises to the top, the aperture is carried past the lens, and, in passing,
the rays from the lens pass through it direct to the sensitive plate. When the mirror
has risen to its highest, the aperture is past the lens, and the opaque portion of
the curtain presents itself and so blocks the rays. The speed of the exposure is
regulated by the tension put upon the spiral spring, so that exposures of various
rapidities may be given.
Other methods may be employed to give the exposure, as for instance, instead of
the opaque curtain, tapes attached to the roller may be used, and an instantaneous
shutter, of any of the usual forms, may be used with the lens, and released by the
action of the rising mirror,, one of the special objects of this invention being the
utilization of the movement of the mirror out of its oblique position to effect the
opening and closing of the lens.
and
The mirror may also be arranged to rise to the horizontal position without being in
Any way connected with the shutter, and the shutier may be made to
close by pneumatic action, or by the action of the hand, without being acted upon by
open
the mirror frame.
Dated this Eirhinanth
35
1000

page_text: I, SAMUEL DUNSEITH M°KELLEN of No. 3 Chapman Street, Hulme, Manchester,
formerly of Marriotts Court, Spring Gardens, Manchester, Watch, Clock, & Photo-
graphic apparatus manufacturer 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 is intended to facilitate the use of an oblique mirror in connection
with Photographic Cameras and is especially intended to be used in so-called detective
cameras.
For this purpose and as shown on annexed drawings I place a ground glass focussing
screen on the top of the camera instead of as usual at the back. The position of
this ground glass is at right angles to the sensitive plate c when in the camera for
exposure. Midway between the positions of the ground glass and the sensitive plate
I place a mirror d in such a way, that the plane of its reflecting surface exactly
bisects the angle formed by the ground glass and the sensitive plate. The mirror,
when in position for focussing prevents any light from getting to the sensitive plate
from the lens or ground glass focussing screen, and as an additional security I make
the latter of non-actinic coloured glass. The lens is fixed to a front e which stands
on a moveable board for frame and is moved backward or forward by rack g and
pinion in the usual way. The whole arrangement is enclosed in a box a by
preference of an oblong form, having four sides and two ends. The front end is
pierced with an aperture j of a proper size to allow the light to pass to the lens. The
A cover k is
top of the box is cut out so as to allow the ground glass to be seen.
hinged on one side of this opening which covers the ground glass when not in use.
On the front, either outside or inside, but by preference inside and covering the
aperture j is fitted a moveable cover which is caused to slide from over the aperture
when the camera is being used. This cover is attached to the ground glass cover k in
such a way that when the top cover k is raised to display the focussing screen the
front cover will slide from the hole in front and when the top cover is closed the front
cover will be closed also. But, as it is desirable sometimes to have the top cover
closed whilst photographing, it is arranged that the connection between the front and
top covers may be detached so that the two covers shall act independently of each
other for the time being. The Front a' is hinged to give access to the lens which
works inside. To make sure that no light shall pass to the inside from the front
except what passes through the lens I fix a flexible diaphragm m which by its
edges is attached to the sides of the box, and its centre is attached to the lens
board e close to the lens so that the lens board is free to travel back or forward.
This diaphragın inay be either in front of or behind the lens board. The back of
the mirror d is hinged at the angle formed by the ground glass b and sensitive plate c,
and its front edge d' is raised and lowered by two rollers n n' (which for convenienco
of reference I designate the winding and lifting roller) connected together by tapes o
or bands or a curtain o' in the form invented by Mr. J. B. Edwards and now commonly

page_text: called the curtain shutter. 1 attach the mirror frame to the middle of the tapes
bands, or curtain. The lifting roller n' contains the spiral spring. In working the
apparatus with a curtain between the rollers, it is first wound on the bottom roller
by the hand in the usual way of working curtain shutters. This brings the mirror d
into its position for focussing, which is done by viewing the image from the lens
reflected from the mirror to the ground glass b at the top of the box, and using the
rack and pinion to obtain correct definition. The curtain is retained on the
bottom roller n by a click acting on a ratchet p attached to the roller shaft. The
releasing is effected by removing the click from the ratchet either by hand or by pneumatic
action. The upper roller n' is now free to revolvo by the uncoiling action of its spring.
This rolls the curtain upwards and carries the mirror with it.
curtain o¹ in such a place that when the mirror is in the position for focussing the
An aperture is cut in the
aperture will be opposite the lens, allowing the rays to pass to the mirror. Another
aperture is cut in the curtain below the mirror so that as the mirror rises to the top
the aperture is carried past the lens, allowing the rays to pass to the sensitive plate.
The curtain may be made to pass at various rates of speed by means of the
spiral spring whose tension may be increased or diminished in the way usually adopted
in ordinary curtain shutters. When the whole of the curtain above the mirror has
rolled on the lifting roller, the bottom aperture has passed the lens, and the opaque
part has come behind it and so blocks the light.
Instead of the curtain being used to lift the mirror, it may be lifted by the before-
mentioned tapes o or bands working between the rollers and a curtain o independent
of the tapes but worked by the rollers may be used to close the lens, and this form I
prefer as the simplest and most effective. Or tapes or bands may be used as before
named and a shutter may be used of any convenient form which may be opened or
closed by the action of the mirror in falling or rising, or by the action of suitable
arrangements, attached to the mirror or to the tapes or bands, or by the action
of the revolving rollers, whose motion may be communicated to a shutter by suitable
means.
The exposures may be either prolonged or rapid. For prolonged exposures I use a
catch which is to be introduced before releasing the bottom roller. The mirror falls
against this stop and remains in the position to allow the rays from the lens to pass to
the plate, until the catch is removed, when the mirror is fully lifted to its place of rest
against the ground glass. The stop may be arranged in many ways, but the most
convenient is that described. Another method may be adopted, viz.-by having
it made to act on the rollers themselves, but I prefer what I have indicated as the
simplest.
also occasionally adopt the plan of stopping the mirror as described, and whilst it
is in the exposing position making use of an ordinary shutter to give exposure. This
can be arranged in any convenient manner according to the desire of the user or
maker. In the drawings to which I have herein before made reference, Fig. 1. is a
. side view, Fig. 2. longitudinal section, Fig. 3. transverse section on line A A Fig. 2.
and Fig. 4 an end view of a photographic reflecting Camera constructed according to
this invention.
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,
[1.7 '
1st. In a photographic reflecting camera, the use of non-actinic coloured glass for a
focussing screen.
2nd. In a photographic reflecting camera, the method of lowering and raising the
reflecting mirror by attaching it to tapes, bands or cords, or to a curtain, such
bands, cords, tapes or curtains, working between rollers substantially as described.
3rd. In a photographic reflecting camera, using the movement of the mirror to
actuate a shutter of any convenient form substantially as described.
vinth. In a photographic reflecting camera the use of the revolving rollers to commu-
nicate motion to a shutter by suitable connections.

page_text: 5th. In a photographic reflecting camera the use of the tapes, bands, cords, or
curtain to actuate a shutter of any convenient form.
6th. In a photographic reflecting camera the use of a curtain working between
rollers to admit and exclude light from the lens substantially as described.
7th. In a photographic reflecting camera the use of a flexible diaphragm to exclude
all light except what passes through the lens substantially as described.
8th. In a photographic reflecting camera the use of a hinged front to give access to
the lens.
9th. In a photographic reflecting camera connecting or disconnecting the top
cover with the front cover so that they may open & close together or separately as
required.
1
10th. The arrangement for stopping the movement of the mirror at the proper
position for giving a prolonged exposure, substantially as described.
S. D. M°KELLEN.