An Improvement in Photographic Cameras and Dark Slides for same.
Year: 1892

page_text: Date of Application, 1st Dec., 1892
Complete Specification Left, 1st Sept., 1893—Accepted, 7th Oct., 1893
PROVISIONAL SPECIFICATION.
An Improvement in Photographic Cameras and Dark Slides
for same.
I LARS SEVERIN ZACHARIASEN of 57 Charing Cross London S.W. Civil
Engineer do hereby declare the nature of this invention to be as follows:-
This invention relates to an improved form of double dark slide and the means of
working it in a camera. The dark slides are by preference made to hold two
sensitive films or plates, and each slide is to consist of two folding parts hinged
together or to a back common to both, the joints between the two parts and the
back being made light tight by means of beads and grooves, or in other convenient
manner.
Each of the two folding parts is to consist of a suitable framework and of a
back plate made of wood cardboard metal or other suitable material; grooves are
cut in the framework near the back plate, in which grooves the sensitive film or
plate is inserted and held in place against the back plate, the sensitive surface being
on the side away from the back, so that when the slide is closed the two sensitive
surfaces will be facing each other. When folded the slide is locked by means of
suitable fastenings acting automatically.
The camera to be used in connection with this form of dark slide I prefer to
make with a parallel body the lens being fixed on the front in any convenient
manner; the back of the camera may be made so as to hold any number of the
dark slides, and is to be fitted so as to hold one of them in position for exposure,
and with a door to cover in the slide or slides, which will thus be entirely enclosed
in a light tight chamber and therefore securely protected against stray light. When
pushed home in the camera the automatic fastenings of the slides will engage with
suitable projections and are thereby released, leaving the front part of the slide
free to be swung on its hinges by means of a lever or levers operated from the
outside of the camera; when the front part is thus swung out of the way the
sensitive film or plate contained in the back part faces the lens and may be exposed
to the action of the light through the lens. During the exposure the sensitive film
or plate contained in the front part of the slide is protected by a screen or curtain
made of some opaque material and of a suitable form, hinged to the front of the
camera behind the lens, and caused to move into position so as to screen the
sensitive film or plate from light. The screen or curtain may be moved by inde-
pendent mechanism, but is by preference actuated by the same as that which is used
for the double slide.
Dated this 30th day of November 1892.
COMPLETE SPECIFICATION
An Improvement in Photographic Cameras and Dark Slides
for same.
I, LARS SEVERIN ZACHARIASEN of 57 Charing Cross, London, S.W. Civil
Engineer, 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 :-
1
11 and the mesene of working

page_text: films or plates and each slide consists of two folding parts or flaps hinged together
(or to a block or part common to both) the joints between the two flaps (and the
block if used) being made light tight by means of tongues and grooves or in other
convenient manner.
Each of the two folding parts (which may consist of a suitable framework and
back plate or of other suitable construction) is made of wood cardboard metal or
other suitable material and grooves are cut or formed in each such folding part or
flap in which grooves the sensitive film or plate is inserted and held in place in any
suitable manner or the sensitive surface may be mounted on the inner side of each
flap in any suitable manner as desired so that when the slide is closed the two
sensitive surfaces will be facing each other.
When folded the slide is locked by means of suitable fastenings acting auto-
matically i.e. fastenings which will engage and snap or lock the two parts
or flaps together automatically whenever said two parts are pressed together.
The camera to be used in connection with this form of double dark slide I find it
advantageous to make with a parallel body the lens being fixed on the front in the
usual or any convenient manner; the back of the camera may if desired be made so
as to hold any number of the dark slides and is to be fitted so as to hold one of
them in position for exposure and a door or cover is provided to give access to the
interior of the camera and which also serves to cover in the slide or slides-the
slide in the aforesaid position for exposure of the film etc. therein will thus be
entirely enclosed in a light tight chamber and therefore securely protected against
stray light.
When the slide to be exposed is pushed home in the camera the aforesaid
automatic fastenings thereof will engage with suitable projections-or releasing
devices in the interior of the camera case-and are thereby released leaving the
front part of the slide free to be swung on its hinges by means of a lever or
levers operated from the outside of the camera; when the front flap or part
is thus swung out of the way the sensitive film or plate contained in the back part
or flap faces the lens ready to be exposed to the action of the light through
the lens.
While the sensitive surface on one side or flap of the hinged slide is thus placed
ready for exposure the sensitive film or plate contained in the other flap or front
part of the slide is protected by a screen or curtain made of any suitable light tight
material and of any suitable form hinged to the body of the camera behind
the lens and caused to move into position so as to screen and cover in the last
named sensitive film or plate from light. The screen or curtain may be moved by
independent mechanism but is advantageously actuated at the same time and by the
same mechanism (or in connection therewith) as that which is used for actuating
the double slide.
And in order that my present invention may be easily understood and readily
carried into practice I will proceed to describe same with reference to the drawings
hereunto annexed.
DESCRIPTION OF THE DRAWINGS.
Fig. is a sectional side view showing the interior of a camera fitted and
arranged to act according to my present invention-showing the double dark slide
and the screen (for one side i.e. the front flap of the said slide) down in its normal
position.
Fig. 2 is same view as Fig. 1 with the back flap of the double dark slide
uncovered ready for exposure and the other side or flap thereof thrown up
and screened from light during such exposure by the aforesaid hinged screen.
Fig. 3 is a sectional plan of the camera with the double dark slide removed.
Fig. 4 is an end view on line 1-1 Fig. 3 looking in the direction of the
arrow c.
Fig. 5 is a "local" cross-sectional view on line 2-2 Fig. 2 showing sectional
edge view of the screen and of the front flap of the double dark slide thrown up

page_text: and screened by the aforesaid screen while the other side of the double back is being
exposed.
Fig. 6 is a front view of the double dark slide according to my present
invention.
Fig. 7 is cross section of said slide on line 3-3 Fig. 6.
Fig. 8 is a bottom edge view of Fig. 6 i.e. looking in the direction of the
arrow z.
Fig. 9 is a "local" sectional view on line 4-4 Fig. 6 showing the snap or
locking device for holding the two sides or flaps of the said double dark slide
together at their bottom ends-said sides being hinged together at their top
ends.
Similar letters of reference indicate corresponding parts throughout.
a is the camera case.
b is lens.
c is external handle on lever d the latter being keyed or rigidly attached or
connected to the transverse bar e.
fis arm extending from bar e to nearly the opposite side of the interior of the
camera and having a hooked or turned up eud i thereon so that by turning the
lever d about the fourth part of a circle (for instance by moving d from position
shown in dotted lines in Fig. 1 to the position shown in dotted lines in Fig. 2)
thereby the end f' of the arm f will be swung from the vertical position shown in
Fig. 1 to the horizontal position shown in Fig. 2.
ggare studs or projections on the bottom of the camera.
h is an upwardly extending arm or stop also fixed on the bottom of the
camera.
i is the hinged screen mounted so as to be free to turn on the hinged pin or axisj
on or near the partition k inside the camera.
1 is extending arm or projection either integral with or rigidly attached to the
screen so that any pressure or force exerted on the free end of 1 so as to move
same upwards will thereby simultaneously move upwards the screen i. The lower
end of i is turned over or flanged at about right angles as shown at Figs. 1 and 2
and the sides also of i are turned up at 2 (see Fig. 5) so that the screen i is thus
formed dished or set back so as to temporarily enclose and keep sufficiently light
tight the raised side of the double dark slide while the other part thereof is being
exposed see Figs. 2 and 5.
m is one side or flap of the double dark slide and n the other flap or side thereof
both of which are hinged to the common block or bar o.
The opposing faces of the two sides m and n are grooved and tongued see
Figs. 1, 2, 5 and 7 or otherwise suitably formed or mounted so that when closed a
perfectly light tight joint is made between such contact faces.
The ends of m and n opposite to where same are hinged to o i.e. the bottom
or free ends of m and n are held firmly together by suitable catches or locking
appliance which are capable of being automatically released when the double
dark slide is pushed home into its position for exposing the film etc. in the
camera.
For this purpose I mount a spring catch p on the one side m and a corre-
sponding spring catch q on the other side n. This spring catch normally presses
outward from the bottom of the double dark slide i.e. in the opposite direction
to the arrow (Fig. 6) and has an incline head thereon so that (on closing together
the said two flaps m and n) the latter will ride up and be pressed inwards by the
bar s which is fixed on the bottom of m and a similar bars on the bottom edge
of n, and the said head or projection on p and q respectively will spring outwards
on the outside of each such bar s and thereby lock and hold the two parts m and n
firmly together.
A recess is cut out of each such locking bars see Fig. 8 so as to allow the
releasing studs or projections 9 to act as hereinafter described.
The bottom edge of m has a small part thereof cut away or recessed at t see

page_text: Figs. 6 and 8 and the bottom edge of n has a similar recess or cut out part u as and
for the purposes hereinafter explained.
These recesses or cut away parts t and u on m and n respectively are formed in
such position that if the double dark slide be inserted in the camera as in Fig. 1 the
recess will coincide with the turned up end f¹ of the actuating arm f while on the
other hand if the double dark slide be turned round the other way then the recess u
will exactly coincide with the position formerly occupied by t over the said turned
up end f¹.
v is a door or cover hinged at w to the camera case a by opening which access is
gained to the interior of the camera to insert and withdraw the double dark slides
as required.
yy are spare compartments or storage spaces in which to carry one two or more
of the double dark slides but these storage spaces y may be dispensed with if
desired.
The operation is as follows:-
The double dark slide (Figs. 1, 2, 3, 6, 7, 8 and 9) having been opened and a
sensitive surface (plate film etc.) having been mounted in any suitable manner on
the inside of m and a second sensitive surface having been suitably mounted on the
inside of n the two sides m and n are brought together and the catches p q lock
and firmly hold same so that the sensitive surfaces which are now facing each other
are then held perfectly light tight.
When an exposure is to be made to place the double dark slide in position in the
camera the door or cover v is opened and the double dark slide is inserted between
suitable guides or guideways inside of the camera case and is pushed right
down until the catches p and q come in contact with the fixed studs 9 on the
bottom of the camera case whereupon such projections g force upwards the
spring catches and and thereby release these fastenings or catches which
hold m to n.
At the same time the recess t (in the side m which is towards the back of
the camera) coincides with the upwardly projecting point f¹ of the arm while
the bottom edge of the side a lies within and between the said turned up end fi
and the arm see Fig. 1 and furthermore the upwardly extending arm or stop h
lies within the recess u in the flap n of the double dark slide and prevents any
movement of the other part m as such part m is now firmly held between this fixed
stop and the guide or guideway at the back of m.
The door is closed and the slide can now be opened ready to give exposure.
For this purpose the lever d is moved by the handle c or other suitable means
and thereby the arm fand with it the side n are swung forwards and upwards until
the bottom end of the arm f strikes the under side of the projection on the
screen whereupon the latter is rapidly moved rearwardly and upwardly and
caused to assume the position shown in Fig. 2 where it is locked and held in such
position by the arm the sensitive surface on the inside of n being completely
covered in by the screen and protected from light when same is admitted to the
interior of the camera on exposure being given to the sensitive surface on the
inside of m.
After the exposure of the sensitive surface on the inside of m the lever d is
moved back again to its original position thereby the arm fis moved down the
screen i dropped out of the way, the two sides m and n are brought into close
contact and on opening the door v and withdrawing the double dark slide the
catches P and 9 thereupon again lock and secure the two sides m and n together so
that the said slide can be safely withdrawn from the camera and reversed and
re-inserted whereupon the operation is repeated as before described the inside
plate etc. on m being covered in by the screen while the side n occupies the position
occupied formerly by m and thereby exposure given to the sensitive surface on the
iuside of n both sensitive surfaces on the inside of the double dark slide can thus be
very easily and rapidly got ready for exposure while the double dark slides con-
structed according to my present invention are much more compact than heretofore

page_text: used by reason of my doing away with the back or partition which is usually
inserted between the two sensitive surfaces whereas according to my invention there
is no partition whatever between the two sensitive surface which on the other hand
face one another when the double dark slide is closed.
This double dark slide and camera may be made to work on its side or in any
other position instead of vertically as shown.
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. A double dark slide for photographic cameras consisting of two flaps or sides
such as m and n hinged to one another or to a part supporting both, means to mount
a sensitive surface on the inside face of cach such flap so that when said flaps are
closed such sensitive surfaces face one another, a catch or catches to lock and hold
the two flaps together and adapted to be automatically released by contact with
studs or projections in the interior of the camera, in combination and acting in
conjunction with a lever arm such as ff' controlled from the exterior of the
camera and adapted to swing one side or flap of said slide upon its aforesaid hinge
and a screen or cover such as i adapted to be raised or operated by the movement
of the aforesaid arm f so as to thereby temporarily screen and cover the sensitive
surface on the said side or flap which has been thus swung on its hinge substantially
in the manner and for the purposes hereinbefore described and represented in the
drawings hereunto annexed.
2. The combination with a double dark slide of the character described of an
externally controlled lever arm such as ff and a screen or cover such as i hinged
or equivalently mounted in the interior of the camera case and having some part or
connection thereof such as interposed in the path of travel of said lever arm
substantially in the manner and for the purposes hereinbefore described and
illustrated in the drawings hereunto annexed.
3. In a photographic camera and double dark slide of the character described
adapted to be used in such camera I claim a movable screen or cover adapted to be
moved into position to screen or cover one side or flap of a double dark slide
while the exposure is being given to the sensitive surface on the other flap or side
in combination and acting in conjunction with such double dark slide having the
two sensitive surfaces facing each other when closed and adapted to be swung
open for exposure in the interior of the camera substantially as hereinbefore set
forth.
DL: 11
1009
TONGUE & BIRKBECK,
34, Southampton Buildings, Chancery Lane, London, W.C.,
Agents for the Applicant.