Improvements in Detective Cameras.
Year: 1891

page_text: COMPLETE SPECIFICATION.
Improvements in Detective Cameras.
I, NEWNHAM BROWNE, of 73 Cheapside, in the City of London, Fellow of the
Institute of Patent Agents do hereby declare the nature of this invention which
has been communicated to me by Friedrich August Fichtner, of 6 Elisenstrasse,
Dresden in the Empire of Germany, Joiner, and in what manner the same is to
be performed to be particularly described and ascertained in and by the following
statement:-
The detective camera illustrated in the annexed drawing is constructed with a
plate changing arrangement enabling plates of relatively large size to be employed
with economy of space without rendering it necessary to make the camera of
greater internal width than the dimensions of the plates employed.
This improved camera is further provided with a double controlling device
showing what plates (according to the sequence of the numbers) have been changed
and what plates are ready for exposure.
A further improvement in the camera consists in enabling the iris diaphragm
inside the camera to be adjusted from the exterior as required.
The camera is further provided with a lens stop of simple construction relatively
to the diaphragm.
In order to change the plates that is to say for lifting out the foremost plate
which has already been exposed and transporting it to the back the following
arrangement is employed as represented in Fig. 1.
Underneath the bottom of the camera a there is provided a flexible slide & the
front extremity of which is turned upwards towards the interior of the camera
being flush with the internal surface of the bottom. In place of this flexible slide
a rigid vertical slide & may be employed as indicated by the dotted lines.
A couple of fingers b' on the end of the slide 6 engage with the lower edge of the
foremost plate e in the magazine a¹. In the top of the camera above the plates
there are two slots d and d extending from one side to the other. These two slots
are protected by a changing bag e.
The changing of the front plate c after exposure is effected as follows:
The flexible slide b (or a rigid slide) is pushed towards the magazine a' by means
of the knob or handle on the outer end. The slide being thus pushed up inside
the camera is guided in suitable grooves fat each side. The plate standing on the
fingers is thus pushed out through the slot d into the bag e. The plate can
then be taken hold of and transferred through the slot 'to the back of the
magazine.
The controlling or indicating device consists of two ratchet wheels 9 and i
Figure 1 provided with as many teeth as there are plates contained in the
magazine a' being 12 in the example illustrated. The spindles of these two wheels
are passed through the sides of the camera and are provided on their outer ends
with a pointer working over a dial. In place of employing pointers travelling over
the dials the dial may be secured on the end of the spindle and arranged to rotate
before an aperture so as to display one figure at a time in the usual way.
The ratchet wheel " g" is worked by a lever "h" and pawl h¹ and the wheel i
by a sliding pin "k" and pawl k¹. The end of the lever "h" projects into one of
the grooves "f" being correspondingly inclined to the movement of the slide.
The end of the pin "A rests upon the flexible slide "6" and is bevelled in the
direction of the forward movement of the latter. When a rigid slide "6" is
employed the arrangement of this second indicator is correspondingly modified.
When none of the plates in the magazine have been exposed the indicator
stands at 12 and the indinate: 1
g hh'

page_text: *
On moving the slide 6 forwards for the purpose of changing the first plate it
comes in contact with the end of the lever which projects within the guide
groove "f" and acting on the incline on the lever causes the latter to oscillate.
The pawl then acts on the wheel "g" and rotates it to the extent of one tooth
thereby displacing the indicator to the amount of one figure or division causing it
to stand at 1 in the present instance. This shows that. the first plate has been
changed.
In moving forwards the slide is withdrawn from under the pin "k" which is
then pushed down by a spring to such an extent as to cause a spring pawl k¹ to
slip over one tooth of the ratchet wheel i. On the return of the slide the end
acting on the incline on the end of the pink pushes up the latter into its original
position and moves the indicator to the extent of one figure or division or from 1
to 2 for instance thus indicating that the second plate is ready for exposure.
The lever ''when released by the slide is returned to its original position by a
suitable spring not shewn in the drawing.
By means of this controlling or indicating mechanism the operator is enabled
on one hand to avoid changing an unexposed plate and on the other hand to avoid
exposing the same plate twice over.
The ordinary iris diaphragm working inside the lens mounting is composed as
represented in Fig. 2 of a number usually 8 plates 'l' pivoted upon axes.
All these axes are situated in a circle concentric to the axes of the lens. The
plates are provided with pins working in slots (Fig. 3) in a disc m placed
upon the plates. According to the direction in which the plate ' m' is rotated
the ends of the plates 'l'are caused to approach or recede from the centre and
produce a corresponding contraction or enlargement of the opening.
The disc m being in the interior of the lens mounting is worked by means of
any convenient actuating mechanism such for example as a pin connected with
an external ring n on the outside of the lens mounting so that by rotating the
ring the opening of the iris diaphragm is enlarged or contracted.
By means of the arrangements hereinafter described iris diaphragms are enabled
to be employed in detective cameras in which the diaphragin being situated in
the interior of the camera requires to be worked from the exterior.
A portion of the periphery of the ring n (Fig. 1) corresponding to the angle
through which it has to be rotated is provided with teeth. A toothed segment o
works in gear with these teeth. The width of the teeth on the toothed segment
is such as to allow for the displacement of the lens in focussing without causing the
teeth on the ring n to go out of gear. The toothed segment o works on a
spindle o, one end of which projects outside the camera and is provided with a
knob or handle p by means of which it can be rotated so as to work the iris
diaphragm and regulate the amount of light admitted. A graduated scale in
connection with a pointer on the spindle o' indicates the amount of opening.
The shutter mechanism illustrated in rear elevations in Figs. 4, 5 and 6 as
employed in this camera differs advantageously from all other arrangements
employed with the same object inasmuch as only one shutter q is employed which
acts as a cap and also as a shutter capable of being employed either for time
exposures.or for instantaneous work.
is
This shutter is not influenced by the winding up of the shutter apparatus but
remains in the. closed position into which it is moved and retained by a helical
spring r. A. spindle s arranged outside the centre of oscillation of the shutter ५
provided externally with a knob and in the interior of the camera with the following
parts arranged in different planes, underneath and opposite to the shutter q it is
provided on one hand with an arm t and on the other hand with a tappet or catch u
next to these comes a drum v to which a cord v¹ is attached which passes over a
guide pulley and is connected with a helical spring which tends to retain the
drum and parts connected therewith in their normal position or position of rest,
and to draw them back to the same. Next to the drum v is an arm w. An arm.g
on the shutter q projects to such a height that the arm w can move freely under it.

page_text: The arm w. is provided with a pin w³ moving at right angles to it under the action
of a spring w (Fig. 4). The upper end of the pin w³ is inclined or bevelled so
that when the arm w. is moved backwards, in the drawing or winding on, it is
depressed by the arm gl and slips over the latter but when the arm w is moved
in the opposite direction it is pushed out by the spring w¹ and bears against the
arm q¹.
The two armed lever a acted on by a helical spring a³ acts as a stop for the motor
mechanism t. u. v. w. Sliding plates y and z. acted on by springs y¹ and
serve to
take off the stop from the motor mechanism the former being employed for time
and the latter for instantaneous exposures.
A screw 1 provided with a knob outside the camera serves to regulate the
tension of the spring and the rapidity of the return movement of the motor
mechanism.
The knobs 2 and 3 likewise situated outside the camera are connected the former
with the slide y and the latter with the slide z.
The action of this shutter is as follows.
By moving the motor mechanism t. u. v w. upon the spindle s. by means of the
aforesaid knob on the outside of the camera in the direction of the arrow in Fig. 4
until the stop lever a. engages with a recess provided for the purpose in the arm t
so as to retain the latter as represented in Fig. 5 the motor mechanism is wound up
and the spring v³ in tension.
In order to obtain a time exposure the slide y is pushed by pressing the knob 2.
This slide then by means of a pin y² imparts a backward motion to the lever x in
consequence of which the arm t and motor mechanism are released and under the
action of the spring v³ and cord ' receive a return movement in the course of which
the pin acting upon the arm of the shutter g, imparts to the latter a movement
which uncovers the aperture of the lens.
So long as the knob 2 is pressed inwards the front end of the slide y projects in
the path of the tappet u so that the latter and the motor mechanism with which it
is connected are stopped after moving for a short distance.
In the course of this movement the shutter g has been moved to its extreme
position represented in Fig. 6 and is retained in this open position so long as the
pressure continues to be applied to the knob 2 and the motor mechanism is locked.
Directly the pressure is removed the spring y' pushes back the slide y and the motor
mechanism is released. As the latter now continues its return motion the pin 10²
first ceases to act upon the arm of the shutter the latter is thereupon quickly
pulled back to the closed position by the action of the spring r Fig. 4.
On pressing on the knob 3 the slidez is pushed inwards and acts by means of its
arm upon the lever a so as to release the motor mechanism being actuated by the
spring this mechanism performs its return movement without interruption and in
the first place the pin to³ moves the shutter to the open position Fig. 6 but directly
the shutter q has reached its extreme position the action of the pin w³ thereon
ceases so that the shutter is immediately brought back to the closed position by
the action of the spring r. These movements taking place in quick succession the
aperture of the lens is only momentarily uncovered."
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed as communicated to me by
foreign correspondent I declare that what I claim is
A detective camera distinguished by :—
(a.) For the purposes of changing the plates c the combination of a flexible or a
rigid slide 6 and a bag e upon the top of the camera the former being capable of
being pushed up inside the camera so as transfer the front plate to the bag which
enables the said plate to be transferred to the back of the magazine in the known
manner.
(b.) A duplex controlling or indicator mechanism consisting of the two ratchet
wheels
g and i with the lever (h) and pin (k) with spring pawls h¹ and k³ the former

page_text: being worked by the forward motion and the latter by the return motion of the
slide for the purpose of indicating on the one hand the number of plates that have
been changed and on the hand the number of plates available for exposure.
(c.) The arrangement for working the internal iris diaphragm from the exterior
of the camera consisting of a toothed segment o gearing with teeth provided on the
sliding ring n the segment teeth being made of a width corresponding to the greatest
axial displacement of the lens and being connected by the spindle of with a knob or
lever p on the exterior of the camera.
(d.) A shutter mechanism for the camera referred to in which a single shutter
worked by a motor mechanism comprising the arm t tappet or catch u drum v
lever w with a moveable pin w² and spring performs the function of a cap and
also by the aid of the motor wound up and stopped or controlled by the lever
can be caused to operate either as a timing shutter or as an instantaneous shutter
according as the release of the motor or lever a is produced by the action of the
knob 2 and slide y or by means of the knob 3 and slidez the return movement of
the motor in the former case being interrupted when the shutter 7 (Fig. 6) is in
its extreme open position by the action of the slide y engaging with the tappet or
catch u and in the other case being allowed to proceed without interruption.
Dated this 18th day of July 1891.
NEWNHAM BROWNE.