An Improved Indicator and Lock for the Shutters of Photographic Dark Backs or Slides.
Year: 1886

page_text: Date of Application, 9th Mar., 1886.
Complete Left, 9th Dec., 1886.
Complete Accepted, 8th Feb., 1887.
An Improved Indicator and Lock for the Shutters of Photographic
Dark Backs or Slides.
I, FREDERICK HAZELDINE of Lant Street in the Borough of Southwark Contractor
do hereby declare the nature of this invention to be as follows:-
My Invention relates to a combined indicator and lock for photographic dark slides
or backs whereby the operator can ascertain at a glance whether the shutter has, or
has not, been drawn out and whereby the shutter is absolutely prevented from being
accidentally drawn out a second time so as to give a double exposure to the same plate
or film.
The Invention consists essentially of a detent or latch capable of being set in such
position as to permit of the shutter being drawn out once for the purpose of exposing
the plate or film in the camera, and adapted to be automatically set in such other
position on the pushing in of the shutter after exposing that it will act as a stop to
prevent the shutter being drawn out a second time.
One arrangement is as follows;-The detent is pivoted to the frame of the dark
slide or back at one side of the shutter and is adapted to engage with a notch in the
edge of the latter. The detent is acted on by a spring and it may be set in such
position as to offer no obstruction to the drawing out of the shutter a first time, but on
the pushing in of the shutter after such first withdrawal it will be caused to assume a
different position and to engage in the notch of the shutter so as to prevent the with-
drawal of the shutter a second time. The detent may be pivoted between the two
limbs of a Ushaped spring which alternately act on the detent at opposite sides, the
other limb for the time being acting as a stop, but the spring may be otherwise
arranged so as to accomplish the same end. For instance, a single spring may be so
arranged as to act on the detent in opposite directions from its two extreme positions.
Prins 8d1

page_text: According to another arrangement the spring detent or latch is placed at the end o
the dark slide or back so as to engage with the inner end of the shutter. In this case
the detent is hooked and engages with a stud, or its equivalent, on the shutter.
The
detent may be set for the withdrawal of the shutter by being held back out of
engagement with the said stud by a shoulder on the shutter. On the withdrawal of
the latter the detent or latch falls into such position as to engage with the stud,
on the shutter being pushed in, so as to prevent the withdrawal of the shutter a
second time.
F. HAZELDINE.
By A. M. & Wm. Clark,
53, Chancery Lane, London,
Patent Agents.

page_text: Dark Backs or Slides.
I FREDERICK HAZELDINE of Lant Street, in the Borough of Southwark, Contractor,
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 relates to a combined indicator and lock for photographic dark slides
or backs whereby the operator can ascertain at a glance whether the shutter has, or
has not, been drawn out, and whereby the shutter is absolutely prevented from being
inadvertently drawn out a second time, so that it is impossible to give a double
exposure to the same plate or film.
The invention consists essentially of a detent or latch capable of being set in such
position as to permit of the shutter being drawn out once for the purpose of exposing
the plate or film in the camera, and adapted to be automatically set in such other
position on the pushing in of the shutter after exposing, that it will act as a stop to
prevent the shutter being unintentionally drawn out a second time.
Reference is to be had to the accompanying drawings forming part of this specifi-
cation, wherein Figure 1 represents a face view and Figure a cross section on
line 1-1 figure 1 of as much of a photographic dark slide or back as is necessary to
explain the invention, one form of my indicator and lock being applied thereto, and
shewn in the locked position. Figure 3 shews the lock and indicator as set in position
for permitting the withdrawal of the shutter for the purpose of exposure. Figure 4
shews the same in the position it assumes when the shutter is drawn out and Figure 5
shews it in the position it is caused to assume in the act of pushing in the shutter after
exposure and just before the shutter becomes relocked. Figure 6 shews another form
of the lock and indicator in the locked position. Figure 7 shews the same as set for
withdrawing the shutter and Figure 8 shews the parts as about to become re-engaged.
The same letters of reference indicate corresponding parts in all the figures.
The arrangement represented in Figures 1 to 5 is constructed and operates as
follows; The detent or latch a is pivoted at a¹ to the frame A of the dark slide or
back at one side of the shutter B and is adapted to engage with a notch bin the
rebated edge of the body of the shutter. The detent is acted on by a spring or
springs c and it may be set in such position as shewn in Figure 3, as to offer no
obstruction to the drawing out of the shutter a first time, but on withdrawing the
shutter, it assumes such a position as shewn in Figure 4, that on the pushing in of the
shutter after such first withdrawal, it will be caused by the shutter to assume the
position shewn in Figure 5, and on the shutter being quite pushed in it will be caused
by the spring c to engage in the notch of the shutter as shewn in Figure 1, in which
position it indicates that the plate covered by the shutter has already been exposed, and
renders it impossible to unintentionally withdraw the shutter a second time, should
the dark back notwithstanding such indication be inadvertently placed again in position

page_text: for exposing the same plate. If however the shutter has been drawn out and pushed
in again without exposing, the lock may be reset by dismounting the catch & replacing
it without going into the dark room.
The detent a is represented as being pivoted between the two limbs of a U shaped
spring c which alternately act on the detent at opposite sides, the other limb for the
time being, bearing against the circular end of the detent, which acts as an abutment
for the spring, but the spring may be otherwise arranged so as to accomplish the same
end. For instance, a single spring may be so arranged as to act on the detent in
opposite directions from its two extreme positions.
According to the other arrangement represented in Figures 6 to 8, the spring
detent or latch a is placed at the end of the dark slide or back A, so as to engage with
the inner end of the shutter B. In this case, the detent a is of hooked form as shewn,
and engages with a hooked stud bor its equivalent, fixed on the shutter as shewn in
Figure 6. The detent a is set for the withdrawal of the shutter, as shewn in Figure 7,
and on the withdrawal of the shutter, the detent or latch assumes the position shewn
in Figure S so as to engage with the stud as shown in Figure 6 on the shutter being
pushed in, thus preventing the withdrawal of the shutter a second time, as in the first
described arrangement.
In both arrangements herein before described, the detent is contained within a
recess in the frame of the dark slide, provided for its reception, so that it does not
project beyond the face of the slide, the recess not being, however, so deep as to expose
the flange of the shutter.
It is obvious that with either arrangement, the operation of setting the detent in the
position for withdrawal of the shutter, as shewn in Figures 3 and 7 must be performed
in the dark room or under similar conditions.
It will also be obvious that in both arrangements the relative positions of the
engaging parts might be reversed, that is to say, the detent or latch might be mounted
on the shutter, and engage with the frame of the dark back, but I prefer the arrange-
ment illustrated.
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 :-
1. The combination with a photographic dark slide or back, of an automatic locking
device, constructed and operating substantially as herein described and shewn in the
drawings, so that when suitably set, it will permit the withdrawal of the shutter of the
dark back once, and will by the act of pushing in the shutter after such withdrawal,
automatically lock the shutter in the closed position substantially as specified.
2. The combination with a photographic dark back or slide of the automatic locking
device and indicator substantially as herein described and illustrated in Figures 1 to 5
of the drawings and consisting of a spring actuated detent or latch, and of a notch or
shoulder for engagement therewith, the detent being arranged for operation at the side
of the shutter as specified.
3. The combination with a photographic dark back or slide of a spring actuated
hooked detent, and of a fixed catch for engagement therewith, substantially as
described and illustrated in Figures 6 to 8 of the drawings, the detent being arranged
for operation at the end of the shutter as specified.
F. HAZELDINE.
By A. M. & Wm. Clark,
53, Chancery Lane, London,
Patent Agents.