Improved Means for Regulating the Duration of Exposure in con- nection with Pneumatically Operated Photographic Cameras.
Year: 1898

page_text: Date of Application, 17th Dec., 1898-Accepted, 4th Mar., 1899
Improved Means for Regulating the Duration of Exposure in con-
nection with Pneumatically Operated Photographic Cameras.
We, FRIEDRICH WILHELM HERMANN RÖHRICH and HEINRICH LUDWIG AUGUST
SCHARRELMANN, both Mechanicians and Opticians, of 35, Schüsselkorb, Bremen,
Germany, do hereby declare the nature of our said invention and in what manner
the same is to be performed to be particularly described and ascertained in and
by the following statement;-
The present invention consists of improved means for regulating the duration
of exposure in connection with photographic cameras, which are momentarily
opened by pneumatic devices and the object of the invention is to make the
duration of the actual exposure independent of the time during which the air
ball is compressed by the operator.
And in order to render the present specification more easily intelligible reference
is had to the accompanying drawing in which similar letters of reference denote
similar parts throughout the several views:―
Fig. I is a vertical section through the device, Fig. 2 a plan of the adjustable
air escape chamber, Fig. 3 a vertical section through the same, Fig. 4 a plan
of the cover thereof, Fig. 5 a detail elevation of the throttle device when closed
and Fig. 6 a similar view of the throttle valve when open.
Within the housing A is mounted a box B having a pneumatic chamber therein
which is designated by C and when inflated expands upwardly. A piston F having
rod E, extending through the cover of the box B rests on the upper surface of
the chamber C and the latter is normally held down by means of a spring D
inserted between the upper surface of the piston F and the under surface of the
box cover.
A tube G communicates with the interior of the air chamber C at
the bottom thereof said tube being carried upwardly inside the housing A, then
extending approximately horizontally under the top cover of the said housing,
out at the side of the same and being connected by means of a flexible tube or
otherwise with the air ball H. The latter is compressed by hand in the well known
manner. The expansible pneumatic chamber Q, which operates the cap or cover
of the camera in the well known manner, is connected by flexible tubing 02 to
a valve housing 0¹ inside the housing A, the upper part of said housing O¹ being
in communication with a branch of the pipe G, the lip or check valve O being
inserted between the pipes O2 and G, said valve being adapted to close against
back pressure. The housing O' is further provided with a branch elbow T to
the end of which a piece of flexible tubing T¹ is affixed, the open end of which
is in communication with the open air. To the top of the box B a bracket W
is fixed, which carries a pivotally mounted bell crank-like lever V having a
horizontally directed upper arm (Figs. 1, 5 and 6) which under certain conditions
herein after set forth is adapted to compress the flexible tube T and throttle the
air passage through the same. This lever is held in the throttling position by
means of a spring s. When the apparatus is not in operation the tube T¹ is kept

page_text: open by means of the spring D, which is more powerful than the spring s and
depresses the pneumatic chamber C when no air is in the same, thus causing the
set screw e to press down the lower arm of the lever against the pressure of
springs and hold the throttle tube T open. The pipe G is provided with a valve
housing L and a lip or check valve L mounted therein and inserted in the said
pipe G, the part of the said housing L¹ below the valve being in open communi-
cation with the air escape chamber 1' by means of the pipe 7. The air escape
chamber P has a cover (Fig. 2) provided with an orificer which is prolonged to
a concentrically arranged gradually narrowing slot pl. The chamber P is other-
wise closed. Ground on to the cover of the chamber P so as to fit tightly thereon
is a rotary cover R (Fig. 4) having an orifice p to cover with the orifice r when
the said cover R is turned into the corresponding position on the chamber. The
cover or disc R is mounted to revolve on the chamber P by means of the central
screw r¹, to which is attached a pointer S adapted to move on a scale St. Obviously
when the cover R is turned on the chamber P, owing to the tapering form of the
concentric slot p¹ the air outlet or escape from the interior of the said chamber
will be varied in size according to the position of the said orifice p as regards the
slot p. Thus if the scale S is properly divided into degrees representing parts
of a second, the rate at which the air escapes from the chamber P and consequently,
as herein after set forth the duration of the exposure may be controlled and
accurately determined before the device is operated.
The operation of the device takes place in the following manner-
When the air ball H is compressed or squeezed, air passes along the pipe G to
both the valves O and L and passes simultaneously into the chamber C and
along 02 to the cover operating pneumatic chamber Q opening the cover and
effecting the exposure. At the same time the expansible chamber C is inflated
and pushes the piston F and with it the rod E upwards, taking the set screw e,
mounted on the said piston rod upwards with it and allowing the spring s to
operate the lever V to throttle the outlet T" (Fig. 1). The air in the chamber C
can escape backwards through G and under the lip valve L along the branch /
to the chamber P and out through the orifice p¹p, at a speed predetermined by
the position of the cover R on the slot p as previously described. According to
the rate at which the air is thus allowed to escape from P, the expansible
chamber C will collapse under the action of the spring D and bring the screw e
down on to the horizontal arm of the pivoted lever V freeing the tube T and
allowing the air to escape from Q whereupon the camera of the apparatus will be
closed. Thus by properly adjusting the position of the pointer S on the scale St
the duration of the exposure may be accurately predetermined.
It will be clear that ordinary metal check valves may be substituted for the lip
valves illustrated and that cylinders and pistons could be equally well substituted
for the expansible air chambers. The air escape could also be regulated by a
cock instead of the cover or disc R, without departing from the spirit of the
present invention.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is:
-
Device for determining the duration of the exposure in pneumatically operated
photographic cameras, which consists of an expansible air chamber inserted
between the air ball and the closure of the camera, the air pipe leading from the
air ball being branched off at G and 02 and each branch provided with a check
valve, the aid branch G leading to the expansible air chamber (C) and 03 to the
device for actuating the closure of the camera as specified, the said branch 03
being provided with an outlet T T between the camera closure and the check
valve O, said outlet at T being throttles by a spring pressed lever V when the
air chamber C is expanded or enlarged and being held throttled until the air of
the expansible chamber C has escaped through an adjustable air escape chamber P,

page_text: with means to adjust its outlet, whereupon, on the collapse of the air chamber C
the throttle device for the outlet T T is released so that the closure of the camera
may close, a scale being provided by means of which the outlet for the air escape
from C may be controlled substantially as described.
MARKS & CLERK,
18, Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham, Agents.