The Improvements in Photographic Dark Slides.
Year: 1897

page_text: Date of Application, 22nd Mar., 1897
Complete Specification Left, 20th Dec., 1897-Accepted, 12th Feb., 1898
I, HERBERT WILLIAM VICTOR WILSON, of "Fernleigh," Church Street, Egremont,
Cheshire, Engineer, do hereby declare the nature of this invention to be as
follows:
The object of my invention is to combine with any pattern of photographic
dark slide a suitable device that will prevent any possibility of the sensitised plates
contained in the slide being exposed more than once.
To effect this purpose I
attach to the slide suitable automatic catches, that are operated by the opening
and closing of the shutters, and are so constructed that they will not permit of the
said shutters being opened and closed more than once without resetting.
resetting of the catches liberates the shutters, and I prefer to construct the arrange-
ment in such a manner that this can only be effected when the slide is open. It
must be understood that these catches can be fixed to slides having any number
of shutters.
Dated this 20th day of March 1897
The
Improvements in Photographic Dark Slides.
I, HERBERT WILLIAM VICTOR WILSON, of "Fernleigh," Church Street, Egremont,
in the County of Cheshire, 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:-
The object of my invention is to combine with any pattern of photographic dark
slide a suitable device that will prevent any possibility of the sensitised plates
contained in the slide being exposed more than once.
To effect this purpose I attach to the slide suitable automatic catches that are
operated by the opening and closing of the shutters, and they are so constructed
that they will not permit of the said shutters being opened and closed more than
once without resetting.
The resetting of the catches liberates the shutters, and I prefer to construct the
arrangement in such a manner that this can only be effected when the slide is open.
In the drawings, A represents the top portion of a photographic dark slide, B the
sbutter, C a metal frame which is let into the body of the slide A in such a position
that its top face shall be level with the top face of the slide and its front and
back faces shall be flush respectively with the inside and outside faces

page_text: of the slide. The latter being the surface against which the shutter B
works, this frame has a top piece C¹ attached at right angles to itself so as to form
a cover for the mechanism and is also provided with a vertical slot that allows a
free passage for the engaging pin K.
D is a flat piece of metal that is free to move sideways its line and limit of travel
being guided and governed by two guide pins E E that are fastened to the
frame C, E E¹ are slots in the sliding piece D that work on the pins E E, F is a
part of the sliding piece D that projects at right angles to the main body and
which is used for setting purposes, G is a spring that being fastened at one end to
a guide pin and at the other to the trigger F tends to draw the sliding piece D in
the direction of the arrow.
In the sliding piece D, I provide two slots, one of which H is so formed as to
permit of free egress to the engaging pin K, and the other J is provided with a pro-
jecting piece J¹.
The engaging pin K is secured to the shutter.
The mechanism is enclosed by a front cover plate similar to the frame C but
this has been omitted from the drawings for the sake of simplicity. In this cover
plate there is a slot through which the trigger F projects.
The mode of operation is as follows. The shutter is withdrawn until the engag-
ing pin K is out of engagement with the sliding piece D, then by means of the
trigger F the sliding piece. D is drawn against the action of the spring G into such
a position that the engaging pin K is in line with the slot H, the shutter is then
pushed home and the slide is set, as shown in Figure 1.
When the shutter is withdrawn for the purpose of making an exposure the sliding
piece D is released from the engaging pin K and drawn over by the spring G into
the position shown in Figure 2.
In closing the shutter after exposure the engaging pin K coming in contact
with the projecting piece J¹ forces back the sliding piece D which on the further
passage of the pin K is drawn over by the spring & until it assumes the locked
position shown in Figure 3.
It must be understood that these catches can be fixed to slides having any number
of shutters.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what I
claim is:-
The combination with a photographic dark slide of an automatic catch or
catches made as herein before described and shown with reference to the accompany-
ing drawings.
Dated this 18th day of December 1897