Improvements in or connected with Photographic Shutters.
Year: 1894

page_text: Date of Application, 19th Sept., 1894--Accepted, 8th Dec., 1894
COMPLETE SPECIFICATION.
Improvements in or connected with Photographic Shutters.
We CARL PAUL GOERZ, of 140 Hauptstrasse, Schöneberg, near Berlin,
Manufacturer and EUGEN ALBRECHT RICHARD NERRLICH, of 19, Zehdenicker-
strasse, Berlin, Engineer both in the German Empire, do hereby declare the
nature of this invention and in what mauner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
Our invention relates to a time and instantaneous shutter for photographic
apparatus, in which a number of circularly arranged sectors is so operated that the
rotation of the sectors through a greater or less angle gives rise to a central opening
of correspondingly larger or smaller diameter, which opening is closed again by
the motion of the sectors in the reverse direction. In order that the apparatus
may be placed between the lenses of even short objective combinations, the axes of
rotation of the sectors are not situated in different planes, one above another, but
are arranged in one and the same plane.
In the closed condition illustrated at a in Figure 5 the sectors, which have all
the same form, lie with their lateral edges in such relation to each other that they
form a complete and even disc. The edges lie close together when the shutter is
fully opened, as illustrated at Figure 5, whilst in all the intermediate positions
they are parallel to each other as illustrated at c Figure 5.
?"
The proof of this fact, and the proportions of the sectors necessary to the
formation of the shutter, result from the following considerations. Let the lines
DE, FG, (Figure 1) be the edges of two sectors, which lie in apposition in the
final positions AB and A' B. "Let R and be the radii, and m the distance of
the points of rotation, C, c, from one another. R and r, being verticals to one
straight line, are parallel to each other. If both radii be rotated through the
same angle, they remain parallel to each other, as also their verticals, the tangents
DE and FG, until the two come into apposition again, which happens after a
rotation 28.

page_text: The angle of rotation 2ẞ is thus greater than the angle a of the sector, when the
point of rotation lies outside the two sides, and smaller when it lies within them :
the two are equal when it lies upon one side of its sector. The maximum opening 30
of the sectors, i.e. the maximum diameter of the polygonal opening which results
from the rotation 2ẞ is

page_text: Formula V shews that the same opening may be attained although a may vary
(with a varying number of sectors) :
by one with eight plates, with the same opening
180
4 p sin -8), then in the latter
8
the points of rotation must lie = 7.5° from one side of a sector on the circle P
between the sides of the sectors, i.e., to the extent of th of the arc.
If the edges of the sectors abut obtusely on each other, as seen in Figure 1, then
in the closed condition the closure will not be perfectly light-tight, and as the
sectors move lateraly ray-like openings will occur. To avoid this, the edges of
the sectors are caused to engage over or under one another, and the apices of the
upper and the lower plate are provided with a small round plate, which covers the
central point where the apices of the sector plates meet. The amount of covering
thus provided varies with the angle of rotation (Formula II). The edges which
are parallel to the radial edges of the sectors follow the same law as the former,
according to the general equation I.
A shutter of this kind for time and instantaneous exposures, with varying
duration of exposure and extent of opening is shewn in plan from above in
Figure 3; Figure 4 is a side view of the releasing lever.
The circularly arranged sector plates are provided with pins, which engage in
corresponding slots in the disc a in such a way that when the disc a rotates, the
sector plates rotate on their axes b, forming a smaller or larger polygonal opening.
If the disc a be then rotated back through the same angle, the opening is again
closed. The disc a is operated by the frame c, which is actuated by a spring d,
which constantly tends to force the frame e downward. In its upper set position,
in which it can be secured, this frame engages by a pin e with a rotating carrier f
which is secured to the disc a. If now the frame c be released, it is pushed
downward by the spring d whereupon the pin e, by means of the carrier f, takes
the ring a along until the arm of the carrier strikes on projection g fastened
to the casing, the carrier f being then released. The projection g can be shifted
in the direction of rotation of the frame c upon the casing, so that according to its
position the release of the carrier is effected sooner or later. By shifting the
projection g,
the opening of the shutter may thus be made smaller or larger.
When the carrier is released, the ring a remains in its position until, as the frame c
continues to move, a projection h on its other side strikes against a pin i on the
ring a, and thereby pushes the ring in the opposite direction to that before
mentioned so that the shutter is closed again. When the frame c is pushed back
to set the shutter, the pin e passes the yielding carrier, without shifting the ring a,
so that the shutter remains closed whilst being set.
The fixing and release of the frame c are effected by the cranked lever 1, which
furnished with projections 1, 2, 3 and can be turned on its pivot by the piston m
worked by pneumatic pressure. The cranked lever can, in addition, be
approximated to or removed farther from the frame c by means of a pin o
eccentrically attached to a rotating knob n, according as it may be desired to make
time or instantaneous exposures.
When the shutter is set, the pin p of the frame c comes to lie against the
projection 1 of the cranked lever 1, and is thus held in position. The piston m
being now actuated by pneumatic pressure in the usual way, the lever / turns to a

page_text: small extent and releases the pin p, so that the spring d is free to push the frame c
downward. The projections 2 and 3 are shorter than the projection 1, so that the
pin p if the cranked lever, as shewn in Figure 4 is removed away from the plate o,
can slide freely under the projections 2 and 3, so that the frame is able to reach its
terminal position without hindrance.
If, on the other hand, by rotating the knob n through 180 degrees the cranked
lever is approximated to the frame c, the projections 2 and 3 lie within reach of
the pin p.
If now, as the lever rotates, the pin is allowed to escape by the
projection 1, it comes into contact with the projection 2. At this moment, the
disc a has already opened the sectors, and is at rest, for the carrier has been
released. If the pressure upon the piston-m diminishes, the cranked lever
springs back to its initial position. The pin p is thus released by the projection 2,
and abuts against the projection 3. As this movement proceeds, the disc a
remains out of engagement with the frame c, so that the sectors remain in the
open position. It is only when the pressure on the piston m is repeated that the
pin p is again released so that the frame c is able to take up its terminal position
without opposition, the sectors being then shut. If the lever returns to its
initial position so quickly that the pin p of the frame fails to meet the projection 2,
it abuts directly upon the projection 3.
Thus, whilst, for instantaneous exposures a single pressure upon the piston m
suffices to release the frame and make the exposure, after the shutter has been
set, for time exposures it is necessary to make pressure twice, once to open the
shutter and a second time to shut it.
In order to be able to vary the speed of the shutter and thereby the time of
exposure for instantaneous exposures, the movement of the frame during the time
that the shutter remains open, i.e., that the frame is out of engagement with the
ring a, can be regulated by means of a pneumatic piston q. With this piston q
engages a two armed lever s rotating on a pin which lever can, by means of the
pin r, be shifted vertically to the direction of the motion of the frame in the
casing, and is acted upon, according to its position, by the pin t in the frame.
If the pin be pushed quite over to the left, then when the frame is shifted the
pint does not come into contact with the lever s, so that the frame will be pushed
downward quickly and the sectors also will be quickly closed. If on the contrary
the pin be shifted to the right, so that the pin t comes to lie between the
projections 4 and 5, then when the frame is released the pin t will meet the
projection 5, when the shutter has reached its full opening, and will thereby turn
the levers so that the piston q is pressed upon, until the pin t slides off the
projection 5 as the frame continues its movement. By moving the piston q
upwards, the air in its cylinder is rarefied, and the speed of the frame c is
diminished as the resistance of the piston q has to be overcome by the frame. The
sectors cannot be closed therefore as quickly as in the first case, where the pin t did
not meet the projection 5. The speed of the sectors when they are closed depends
therefore upon the time during which the pin is in contact with the projection
of the levers. According to the position of the lever s the piston q is forced up
more or less, and the time of exposure varied. In setting the shutter the
pint strikes against the projection 4, so that the piston 7 is driven into its
cylinder.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what
we claim is :-
1. A time and instantaneous shutter for photographic apparatus, in which the
points of rotation for the circularly arranged sectors lie in one plane, and in which
the adjacent sides of the two adjoining sectors, which sides always remain parallel
to each other, overlap one another to such an extent that in no position of the
shutter are radial slits formed, substantially as set forth.
2. A shutter of the kind referred to in Claim 1, in which the to-and-fro rotation

page_text: of the disc which actuates the sectors, is effected by a frame which as it moves in
a single direction acts upon the two opposite sides of the disc in succession,
substantially as hereinbefore described.
3. A shutter of the kind referred to in Claim 1, with a releasing lever so
furnished with projections that for time exposures the striking pin of the frame
which actuates the sectors meets two projections successively, whilst the shutter
remains open, so that the closure of the shutter does not take place until the
release has been twice effected, substantially as hereinbefore described.
4. The improved photographic shutter hereinbefore described and illustrated in
the accompanying drawings.
01 1
.
1004
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.