Improvements in or relating to Photographic Shutters.
Year: 1893

page_text: COMPLETE SPECIFICATION.
Improvements in or relating to Photographic Shutters.
I, JOSEPH THACHER CLARKE, of Boston, Massachusetts, a citizen of the
United States, at present residing at 3 College Terrace, Harrow, Middlesex,
Architect, 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 :-
a
This invention relates to certain points of detail in the arrangement and
construction of photographic shutters, and has for its purpose, firstly to provide
set-off of novel and simple design, adapted to shutters of various types, by means
of which both time and rapid exposures may be effected with one and the same
set-off bolt, and secondly to provide, in shutters of the type described in Letters
Patent No. 20852 of 1890 and No. 9820 of 1892, improved means for securing the
adjustable obscuring stop to the shutter disc, for the purpose of regulating the
effective size of the aperture therein.
In order that my invention may be clearly understood, and readily carried into
practice by those skilled in the art, I will describe, by way of example, and with
reference to the appended drawings, a shutter embodying the two improvements
which form the subject of my claims.
Figure 1 shows a front view of this shutter, and Figure 2 shows a section thereof
on the broken line Y-Z, Figure 1.
The shutter plate is alternately retained and released by the set-off 2. This
set-off is provided with slots 3, 3, through which pass the stems of the screws or
rivets 4, 4, attaching it to a carrier plate 5. The set-off 2 is thus free to move to
and fro, for a certain distance, in the direction of the arrow A, as well as in the
direction of the arrow B. In order that the set-off 2 may be caused to return to
its normal position, whether moved to the right or to the left, two toggles or
dogs, 6 and 7, are provided, these toggles being sprung together by a spiral spring
of coiled wire 8, and thereby caused to abut against the sides of the gaps 9 and 10,
cut in the carrier plate 5. The distance between the sides of these gaps 9 and 10
is equal to the width of the set-off 2. Thus, as will readily be understood, the
toggle 7 will be moved in the direction of the arrow A, when the set-off' 2 is
operated by pushing inwards the set-off' bolt 11, and, being thus caused to stretch
the spiral spring 8, will tend to return the set-off to its normal position when the
pressure of the operator's finger is removed from the set-off bolt 11. When, on the
other hand, the set-off bolt 11 is pulled outwards, the toggle 6 will be similarly
moved' in the direction of the arrow B, with' similar tendency.
It is obvious that the set-off may be sprung in both directions, so as to effect the
same return, by means of a single blade spring, rigidly affixed at its base, and
bearing upon one point of the set-off. Such an arrangement has, in fact, been
carried into practice. Various other forins of springs may be employed as
nechanical equivalents.
Convenient means for bringing the set-off 2 into contact with the shutter plate 1,
while permitting these parts to work in different planes, is provided by the turned
down lobe 12, projecting at right angles from the shutter plate 1, and by the three
turned up catches 13, 14, & 15, projecting at right angles from the set-off 2. The
first of these catches, 13, which may be termed the exposure catch, serves to retain
the shutter plate 1 in its normal position, ready for an exposure. When the set-off
bolt 11 is pushed inwards, and the set-off 2 moved in the direction of the arrow A,
this exposure catch 13' is passed aside from, and out of contact with, the lobe' 12,
permitting the shutter plate 1 to revolve until the lobe 12 is brought up against the
retaining catch 14, which has, by the same movement of the set-off 2, been pushed

page_text: into its path. During this revolution the whole of the exposure aperture 16 of the
shutter plate 1 is passed across the lens orifice 17, and a rapid shutter exposure is
effected. On the pressure of the finger being removed from the set-off bolt 11,
the set-off 2 is returned to its normal position by the spring action above described,
and, the retaining catch 14 being thus removed from the path of the lobe 12, the
shutter plate is permitted to complete its entire revolution, coming again into
engagement with the exposure catch 13. The purpose of the retaining catch 14 is,
as will be evident to those familiar with the state of the art, to prevent the lobe 12
from being carried past the exposure catch 13, thus forestalling any liability of the
shutter disc to perform, under the impetus of its impelling spring, more than one
entire revolution.
is
When, on the other hand, the set-off' bolt 11 is pulled out, and the set-off 2 is
thus moved in the direction of the arrow B, the shutter plate 1 will be arrested
after having performed but a fraction of its revolution, by its lobe 12 being brought
up against the time exposure click 15 which has been moved into the path of
revolution of said lobe. While the shutter plate is held in this position, the
exposure aperture 16 remains in front of the lens orifice 17, and a time exposure
thereby commenced. This time exposure may be terminated by pressing in the
set-off bolt 11, so that the set-off 2 is moved in the direction of the arrow A, and
the time exposure catch 15 is carried away from the lobe 12. The shutter plate 1
will thereupon continue its revolution until it is brought to a standstill by the
retaining catch 14, the procedure thenceforth being as above described for rapid
exposures.
Thus, with a set-off constructed according to my invention, both rapid and time
exposures may be effected by means of one and the same set-off bolt: the operator
being instructed to press this bolt inwards for rapid exposures, and, for time
exposures, to first pull it out for the purpose of opening, and thereafter to press it
in for the purpose of closing the lens.
In the appended illustrations my improved set-off has been shown in connection
with a circular shutter which works in one direction only. But it will be obvious
that the same device is capable of direct application to shutters of other types, as,
for instance, to shutters with drop, or with oscillating plates. In all cases the
exposure catch will stand in engagement with the shutter plate when this is in its
normal position, ready for an exposure, and the secondary or time catch will be
brought into engagement with the shutter plate when the set-off is moved in one
direction, but not when it is moved in the contrary direction. It will, furthermore,
be obvious that a retaining catch, having the functions of the catch 14 in the
appended drawing, will not be necessary in shutters of the drop or oscillating types,
inasmuch as such shutter plates cannot, in any event, be carried beyond the
exposure catch by the impetus of the impelling spring.
In order to vary the size of the exposure aperture 16 in the shutter plate 1 from
a narrow radial slit to a concentric zone extending to a length of 180 degrees,-in
accordance with the invention set forth in Letters Patent No. 20852 of 1890 and
No. 9820 of 1892, before cited, the shutter plate 1 is provided with an auxiliary
or obscuring stop 18, which may be rotated upon the face of the shutter plate 1, as
is now well understood. Hitherto the means for so affixing the obscuring stop to
the shutter plate 1 that the relative position of these two parts should not be
unintentionally altered have been provided either by a set screw with milled head,
or by a separate spring clip. It has, however, been found to constitute an improve-
ment upon these devices to form the obscuring stop 18 of a thin springy metal
plate, for example, of steel or German silver,—to adjoin it at its centre by a boss,
screw plate, or some similar device, in close juxta position to the shutter plate,
and to furnish its rim with means for engaging, at the desired positions, with the
rim of the shutter plate, against which it will press by reason of its springy nature.
Simple and effective means for such engagement are provided by the holes 19, 19,
in the rim of the obscuring stop 18, which receive the pin 20 projecting from the
rim of the shutter plate 1.

page_text: In releasing the obscuring stop 18 from engagement with the shutter plate 1,
for the purpose of altering the effective speed of the shutter during rapid
exposures, the stop 18 will be gently pressed forward against its own inherent
spring, so that the pin 20 is disengaged from the hole 19, whereupon the
auxiliary or obscuring stop may be freely rotated into another position, and
another engagement. This rotation of the obscuring stop may be rendered easy
to the fingers of the operator by the rim of the stop being roughened or scratched,
as shown in Figure 1.
It will be observed that, for the purpose of effecting a time exposure by
pulling out the set-off bolt 11, as hereinbefore described, it would be necessary,
in a shutter having the proportions and relative positions of parts shown in the
appended illustrations, to revolve the obscuring stop 18 entirely away from the
exposure aperture 16, in order that light should gain unobstructed access to
the lens.
And, finally, it is evident that the shutter plate may be arranged behind,
between, or in front of the lens combinations, and that the impelling spring,
the spring catch to engage the same, the winder, and the stop to prevent over-
winding (all of which constitute no part of the present invention), may be of any
of the various forms well known to those skilled in the art.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. In a photographic shutter a set-off, such as 2, so sprung as to pull out,
as well as to push in, and so provided with releasing and retaining catches as
to open and hold open the shutter for time exposures when operated in one of
these directions, and as to effect a rapid exposure when operated in the other
direction, substantially as herein before illustrated and described.
2. In a photographic shutter the combination with the shutter plate of an
obscuring stop, such as 18, formed as a spring, and provided with means such
as the holes 19, and the pin 20, for engaging in set positions with the shutter
plate, substantially as and for the purposes hereinbefore set forth.
Dated this 20th day of September 1893.
JOSEPH THACHER CLARKE.