Improvements in Photographic Camera Shutters.
Year: 1890

page_text: Date of Application, 22nd Dec., 1890
Complete Specification Left, 20th July, 1891-Accepted, 22nd Aug., 1891
PROVISIONAL SPECIFICATION.
Improvements in Photographic Camera Shutters.
JOSEPH THACHER CLARKE, Architect, of Boston, Massachusetts, a Citizen of
the United States, at present residing at 3, College Road, Harrow, Middlesex, do
hereby declare the nature of this invention to be as follows:-
My invention has for its purpose to provide a photographic shutter of simple
construction, by which light is not admitted to the lens during the act of winding
or setting the shutter, and which is adapted for combination with a device for
increasing or diminishing the size of the exposure aperture and for visibly
indicating upon the exterior whether the shutter is, or is not, wound and ready for
exposure.
The main end in view is effected by making the movable plate or shutter of a
circular shape, with a single exposure aperture, by causing it to revolve in one
direction only, and by arresting it before the completion of an entire revolution by
means of a secondary spring detent which must be released before the shutter disc
can resume its normal position for the next exposure.
the camera.
A. convenient arrangement and construction of the mechanism by which this
improvement may be carried into effect is as follows:-The movable shutter plate
consists of a disc of thin sheet metal or other suitable material, revolving in one
direction only and centered or mounted upon a pivot borne by the front board of
In this shutter disc is pierced a single aperture through which light
is admitted during exposure, this aperture being situated in a concentric zone of
the disc and corresponding with the orifice of the lens tube, before, behind or
within which it passes during the revolution of the disc, according as the shutter is
placed before the lens mount, within the camera or between the combinations of the
lenses.
The motor mechanism of this shutter disc is an impelling spring, preferably
made in the form of a spiral coiled round the beforementioned pivot. This spring
is tightened by winding it one revolution for each exposure by means of a resetting
device, such as a spring retracted ratchet drum revolving upon the pivot and
operated by a cord which is thereby withdrawn and returned to its normal position
after each traction or setting. In order to assure the tightening of the spring by
one revolution, and by no more nor less, there need be but one single ratchet tooth
in the circle of the resetting device. Means of permanently increasing or decreasing
the tension of the impelling spring may be provided by the well-known device of a
ratchet and pawl located at the outer end of the pivot.
After the impelling spring has been wound the shutter disc is revolved and an
exposure effected by releasing a spring lever detent or exposing click which has
held the shutter in position by bearing upon a single notch or pin in or near the
periphery of the disc. The single aperture of the shutter disc is thereupon passed
at once before the lens, and the exposure is completed.
Opposite the exposing click is a secondary or retaining click which is kept in
constant contact with the periphery of the shutter disc by a light spring, and
which engages in the beforementioned single notch or pin in or near the periphery
of the disc. Thus the shutter disc on being released by raising the exposing click
is permitted to make but one half a revolution or thereabouts, being arrested at
this point by the secondary or retaining click. This retaining click must be
released in order to permit the shutter disc to complete its revolution and stand
ready for the next exposure. An advantageous method of performing this is to
connect the lifting arm of the retaining click with the beforementioned cord for
setting the impelling spring, which may conveniently be done by passing the said

page_text: cord through a loop formed in the lifting arm of the retaining click. The act of
winding the impelling spring thus releases the secondary or retaining click, and the
shutter disc is thereby freed to perform the second half of its revolution and to
resume its normal position ready for the next exposure. It will be readily under-
stood that this cöoperation renders it impossible to revolve the shutter disc more
than one half a revolution by releasing the exposing click, and likewise impossible
to make a second exposure-before having drawn the winding cord of the impelling
spring.
In order to vary the size of the aperture in the shutter disc a secondary or
auxiliary solid shutter, fan or stop, likewise of thin metal or other suitable material,
may be attached to the face of the shutter disc in such wise as to cover more or
less of the aperture therein. This auxiliary stop may conveniently be made of a
concentric or of a semicircular shape and of a radius somewhat smaller than that
of the shutter disc, (in order to avoid interference with the engaging notch or pin
in or near the periphery of the disc), yet sufficiently great to extend beyond the
limits of the concentric exposure aperture of the shutter disc. This auxiliary stop
may be attached to the shutter disc by one or more screws with milled heads or by
other means suitable to permit of its being moved so as to close a greater or less
extent of the exposure aperture of the shutter-disc-and-yet_to_ retain it with
sufficient firmness to prevent its relative position being unintentionally altered.
The ratio of the apertures uncovered in the shutter disc by moving the auxiliary
stop to and fro upon it may be engraved or otherwise marked upon the shutter disc
with visible lines and figures to which the stop can be accurately set.
22
When an auxiliary stop of the nature described is combined with the shutter
disc the exposure aperture in the disc may be extended concentrically to a length
of 180° or thereabouts, so that when the auxiliary stop is entirely slipped aside
from the said aperture the exposure effected by permitting the shutter disc to
make one half a revolution will be a socalled “
"time exposure, the shutter "disc"
when engaged by the secondary-or-retaining-click in this case still presenting a
sufficient portion-of-its-aperture-to-entirely-open the lens. The time exposure thus
effected is not concluded until the winding cord of the impelling spring is drawn so
as to permit the release of the retaining click, or until light is otherwise excluded
from the lens, as for instance by the employment of a separate cap. If, however,
no auxiliary stop be connected with the shutter disc the aperture in this disc must
not extend so far in a concentric zone as to admit light to the lens when the shutter
disc is engaged by the retaining click after one half a revolution. In order to
effect a time exposure under these conditions it is convenient to add to the
mechanism above described a third or time exposure click engaging with the notch
or pin in or near the periphery of the shutter disc and so situated as to hold the
disc, when retained thereby after its revolution through a small are, with the
exposure aperture before the lens. This third or time exposure click would, when
the exposures are intended to be rapid, be withdrawn from all contact with the
shutter disc by means of a screw or other similar device.
When an auxiliary stop is combined with the shutter disc the outer surface of
the stop may be brighter and more highly polished or of a lighter color than the
disc, the bright surface of the auxiliary stop being visible from the outside of the
camera while the shutter disc is held by the secondary or retaining click after one
half a revolution, the darker surface of the shutter disc itself being visible when
the shutter is fully set after its entire revolution. It will by this means be readily
ascertainable whether the impelling spring has, or has not, been wound for the
next exposure.
If no auxiliary stop be combined with the shutter disc the latter
may itself be polished or colored. in such a manner as to differentiate the portions
visible at the two. positions.
The cycle of operations may be reviewed as follows.
For rapid exposures
-:
-The shutter being set ready for operation the primary
or exposing click is released by pressure exercised upon its lifting arm, this
pressure being either directly applied by the finger or communicated by any of the

page_text: well-known devices for this purpose. Exposure having been thereby effected, the
shutter disc is automatically arrested at half revolution by the secondary or
retaining click. The act of winding the impelling spring so as to tighten it by one
turn thereupon releases the retaining click and the shutter disc completes its
revolution, being held again in position for the next exposure by the primary or
exposing click.
For time exposures:-The auxiliary stop is withdrawn entirely from the
aperture of the shutter disc, whereupon the exposure is commenced by pressing
the exposing click and terminated by drawing the cord of the winding device
which frees the retaining click and allows the shutter to return to its normal
position, closing the aperture. Or the third click introduced in case the shutter be
constructed without auxiliary stop is brought into operation so as to bear upon the
disc and the primary or exposing click is pressed, whereupon the lens will remain
open to light until the said third click be released so as to free in its turn the
shutter disc for further revolution into engagement with the secondary or retaining
click. A winding of the resetting device by traction of the cord completes the
cycle of operations in all cases.
Dated this 22nd day of December 1890
JOSEPH THACHER CLARKE:
COMPLETE SPECIFICATION.
Improvements in Photographic Camera Shutters.
1, JOSEPH THACHER CLARKE, of Boston, United States of America, but at
present residing at 3, College Road, Harrow, in the County of 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 :-
My invention has for its purpose to provile a photographic shutter of simple
construction, by which light is not admitted to the lens during the act of winding
or setting the shutter, and which is adapted for combination with a device for
increasing or diminishing the size of the exposure aperture and for visibly indicating
upon the exterior whether the shutter is or is not wound and ready for exposure.
The main end in view is effected by making the movable plate or shutter of a
circular shape, with a single exposure aperture, by causing it to revolve in one
direction only and by arresting it before the completion of an entire revolution by
means of a secondary spring detent which must be released before the shutter disc
can resume its normal position, ready for the next exposure.
And in order that my invention may be fully and clearly understood, I will
describe, with reference to the accompanying drawings, systems, modes or manners
in which it may be practically carried into effect.
P
Figure 1 is an elevation, viewed from the front of the camera, and Figure 2 is a
section, on the line 1-2 Figure 1 of a shutter constructed according to my
invention. The movable shutter plate d is formed of a disc of thin sheet metal or
other suitable material, revolving in one direction only, and centred or mounted
upon a pivot borne by the front board of the camera a. In this shutter plate d
is pierced a single aperture a through which light is admitted during exposure,
this aperture being situated in a concentric zone of the disc d, and corresponding
with the orifice of the lens tube or mount t, before, behind or within which in
passes during the revolution of the disc d, according as the shutter is placed before
the lens mount, within the camera, or, as shown in Figures 1 and 2, between the
combination of the lenses.
The motor mechanism of the shutter disc is an impelling spring, made in the
form of a spiral coiled around the beforementioned pivot p, having its outer end
attached to the shutter disc d, and its inner end attached to the winding wheel w
(the inner face of which is shown in Figure 3), which is mounted upon the pivot p

page_text: and is capable of being revolved independently of the shutter disc d. This
impelling spring is tightened by winding it one revolution for each exposure by
means of a resetting device consisting of a spring retracted drum (the outer face
of which is shown in Figure 4) revolving upon the pivot and operated by a
cord c which is thereby withdrawn and returned to its normal position after cach
traction or setting. The retracting springy of the resetting drum p is attached
by its outer end to the resetting drum, and by its inner end to the pivot p. The
resetting drum communicates its motion, during the act of winding, to the winding
wheel by a light spring catch which engages with the teeth of the winding
wheel when moved in the direction indicated by the arrow, Fig. 4, but which rides
over them in returning to its normal position while retracting the cord c. In order
to assure the tightening of the impelling spring by one revolution, no more nor
less, there need be but one single ratchet tooth p' upon the pivot p, in which is
caught the winding wheel click i². As the cord é is not wound around the drum r
more than one convolution and a half it is not possible to overwind the impelling
spring by giving two full revolutions to the winding wheel w by the act of pulling
the cord c.
e,
After the impelling spring has been wound the shutter disc d is revolved and
an exposure effected by releasing a lever detent or exposing click
which has
held the shutter in position by bearing upon a single notch or catch-n-in-the
periphery of the disc d. The single aperture a of the shutter disc d is thereupon
passed at once across the lens orifice o and the exposure is completed.
Opposite the exposing click e is a secondary or retaining click or detent s which
is kept in constant engagement with the periphery of the shutter disc d by the
pressure of a light spring and which engages in the beforementioned single
notch n in the periphery of the disc d. Thus the shutter disc d on being released
by raising the exposing click e is permitted to make but one half a revolution or
thereabouts, being arrested at this point by the secondary or retaining click-s.
This retaining clicks must be released in order to permit the shutter disc d to
complete its revolution and "stand ready for the next exposure. This is done in
the arrangement shown in Figure 1 by connecting the lifting-arm-of the-retaining
clicks with the beforementioned cord by passing the cord through a loop 2
formed in the lifting arm of the retaining click s. The act of winding the
impelling spring thus releases the secondary or retaining clicks, and the shutter
disc d is thereby freed to perform the second balf of its revolution and to resume
its normal position ready for the next exposure. It will be readily understood
that this cooperation renders it impossible to revolve the shutter disc more than
one half a revolution by releasing the exposing click e, and likewise impossible to
make a second exposure efore having drawn the winding cord c. In order to
vary the size of the aperture in the shutter disc d a secondary or auxiliary solid
stop or fan f, likewise of thin metal or other suitable material, may be attached
to the face of the shutter disc in such wise as to cover more
or less of the
aperture a pierced therein. This auxiliary stop f is made of a semicircular or
.segmental shape and of a radius somewhat smaller than that of the shutter disc d
(in order to avoid interference with the engaging notch n in the periphery of the
disc) yet sufficiently great to extend beyond the limits of the concentric exposure
aperture a of the shutter disc. This auxiliary or obscuring stop or fan f may be
attached to the shutter disc d by a set screw 'm with milled head which runs in a
thread cut upon a projecting boss 7 of the shutter disc d to permit of the stop or
fan being moved so as to close a greater or less extent of the exposure aperture a
in the shutter disc d and yet to retain it with sufficient firmness to prevent its
relative position being unintentionally altered. The ratio of the apertures
uncovered in the shutter disc by moving the obscuring fan to and fro upon it may
be engraved or otherwise marked upon the shutter disc with visible lines and
figures to which the stop can be accurately set.
When an auxiliary stop of the nature described is combined with the shutter
dise the exposure aperture a in the disc d may be extended concentrically to a

page_text: length of 180° or thereabouts, so that when the obscuring fan is entirely slipped
aside from the said aperture the exposure effected by permitting the shutter disc
to make one half a revolution through releasing the exposing click e will be a
so-called "time" exposure, the shutter disc when engaged by the secondary or
retaining click in this case still presenting a sufficient portion of its aperture to
entirely open the lens orifice o. The time exposure thus effected is not concluded
until the winding corde of the impelling spring is drawn so as to permit the
release of the retaining click s, or until light is otherwise excluded from the lens,
as for instance by the employment of a separate cap.
It is obvious, however, that if no auxiliary or obscuring stop be connected with
the shutter disc d the aperture a in this disc must not extend so far in a concentric
zone as to admit light to the lens orifice o when the shutter disc d is engaged and
held by the retaining click before having completed an entire revolution. In
order to effect a time exposure under these conditions there may be added to the
mechanism above described a third or time exposure click capable of engaging with
the notch in the periphery of the shutter disc and so situated as to arrest the disc,
after its revolution through a small are, with the exposure aperture before the lens
orifice. Such third or time exposure click could, when the exposures were intended
to be other than time exposures, be withdrawn from all contact with the shutter
disc by means of a catch or screw.
When an auxiliary stop is combined with the shutter disc the outer surface of
said stop may be brighter and more highly polished or of a lighter color than the
disc, the bright surface of the auxiliary stop being visible from the outside of the
camera through the lens orifice while the shutter disc is held by the secondary or
retaining click after one half a revolution, but the darker surface of the shutter
dise itself being visible through the lens orifice when the shutter is fully set after
its entire revolution. It will by this means be visually ascertainable whether the
impelling spring has, or has not, been wound for the next exposure. If no auxiliary
stop be combined with the shutter disc the latter may itself be polished or colored
in such a manner as to differentiate the portions visible through the lens orifice at
the two positions.
The cycle of operations in the arrangement displayed in Figures 1 and 2 may be
reviewd as follows. For rapid exposures:-The shutter being set ready for opera-
tion the exposing click e is released by pressure exercised upon its lifting arm, this
pressure being either directly applied by the finger upon the button or com-
municated by any of the well known pneumatic devices for this purpose. Exposure
having been thereby effected the shutter disc d is automatically arrested before the
completion of an entire revolution by the secondary or retaining click s.
The act
2
of winding the impelling spring by pulling the cord c thereupon releases the
retaining clicks and the shutter disc d completes its revolution being again held in
position for the next exposure by the primary or exposing click e.
For time exposures
-The auxiliary or obscuring stop is withdrawn entirely
from the aperture a of the shutter dise whereupon the exposure is commenced by
releasing the exposing click e and terminated by drawing the winding cord e which
frees the retaining clicks and allows the shutter disc d to return to its normal
position, thus closing the lens orifice o. Or the third or time click, introduced in
case the shutter be constructed without auxiliary stop, is brought into operation so
as to bear upon the shutter disc and the exposing click is released whereupon the
lens orifice will remain open to light until the aforesaid third or time click be lifted
so as to free in its turn the shutter disc for further revolution into engagement
with the secondary or retaining click. Traction of the winding corde in all cases
completes the cycle of operations.
With a shutter thus formed independent diaphragın stops, whether on the
Waterhouse plate or the Iris system, may be adopted.
The arrangement above described has been more particularly devised for use in
connection with detective cameras having a front board movable in relation to the
sides and bottom.of the casing, whereby the introduction of a cord is necessary for

page_text: the winding of any form of shutter. For those cameras in which the winding wheel may
itself be operated through a slit in the bottom board a simplification of the resetting
device has been found possible. In such modifications the spring retracted resetting
drum: may be omitted and the winding wheel operated upon from the bottom of the
camera, either directly or through, the intermediation of a, setting wheel. In the
arrangement, shown; by. Figure 5 in front elevation and by Figure 6 in, section en
the line 3 (Figure 5) the winding wheel itself is moved from: the outside of
the camera for the purpose of setting the impelling spring The operation is in
this case as follows. On the release of the exposing click e through pressure of the
button the shutter disc d performs one half a revolution, being arrested by the
secondary click, or detents, shown in side view by Figure 8. The winding wheel is
thereby freed so that it may be turned in the direction indicated by the arrow,
Figure 5. By its revolution- the inclined projection attached to the face of the
winding wheel w. lifts the secondary click or detent s from out of the notch n of the
.shutter disc d. The shutter disc: is thereby freed to complete its revolution, being
again; arrested, ready for the next exposure, by the double tongued explosing click e
shown in side view by Figure 7. The winding wheel, w, the retrograde motion of
which is prevented by the light spring catch is thereupon further revolved. until
a. projecting stop attached to it engages with the second or inner tongue of the
exposing click e which thus prevents overwinding. This double tongued exposing
click e is released from engagement with the stop of the winding wheel w by the
act of making the next exposure, inasmuch as the outer tongue, which after one
half a revolution of the shutter disc d rests upon the periphery of the said disc,
prevents the inner tongue from further engagement with the stop g. of the winding
wheel. A rewinding of the mechanism is thus in like manner possible only after
- an exposure has been effected and while the shutter disc d is held by the secondary
click or detent s.
:
Inasmuch as the winding wheel w has, in this arrangement, to be made of greater
diameter than the shutter disc d; in order to permit its being revolved from-the-
outside. of the camera through the bottom of which the shutter-disc-does-not-
protrude, it is obvious that the winding wheel will pass through the lens tube t and
in front of the lens orifice o. As the winding wheel when. held. by its stop g
engaging with the exposing click e will, however, invariably present one: and the
same portion of its surface to the lens orifice o this portion may be cut out, the
aperture forming the largest or normal diaphragm opening, giving the full aperture.
to the lens the winding wheel w being thus actually employed as a so-called
Waterhouse stop or plate. In like manner, circular apertures ', ², etc. having a
ratio to the one before mentioned which is in conformity with the well-known. U.S.
standard of exposure apertures, may be perforated as diaphragm openings in
the adjacent portions of said winding wheel w. And in order to ensure these
apertures corresponding accurately with the lens orifice o auxiliary set stops or
lugs and may be attached near the periphery of the winding wheel w in such
positions that when brought forward and engaged by the exposing click e they shall
hold the winding wheel with the corresponding diaphragm apertures or 2 con-
centric with the lens orifice o. These set stops g' and g² are pivoted near the
periphery of the winding wheel in such wise that they may be either pushed back
within its circumference so as to be no longer in operation, or brought forward as
shown by dotted lines in Figure 5, so as to project beyond its periphery for the
purpose of engaging as before described with the exposing click e. And, in order
that the diaphragm stop which is brought into effect by the respective set stop may
be clearly designated, the corresponding focal ratio fa, etc., or the standard U.S.
number may be engraved or otherwise visibly marked upon each set stop g', g², etc.
In all that appertains to the form and arrangement of the shutter disc and of the
obscuring fan which may be connected therewith the arrangement shown in
Figures 5 and 6 is precisely the same as that shown in Figures 1 and 2 and, herein-
before fully described.
'64
I would observe in conclusion that the details of the several parts of my inven-

page_text: tion can be varied without departing from the general principle of said invention.
For instance, if it be preferred to supply the lens with independent diaphragm
stops the winding wheel may be revolved through the intermediation of a setting
wheel engaging with it by cogs and projecting through the hottom of the camera.
The diameter of such setting wheel may be made a multiple, say six, of the diameter
of the winding wheel, and the number of its teeth will consequently be the same
multiple of the number of teeth of the winding wheel. Thus one sixth a revolution of
the setting wheel will cause the winding wheel to perform just that one entire revolu-
tion necessary to set the impelling spring. And in order to limit the revolution of the
setting wheel to the determined are of sixty degrees, there may be attached at
equal distances ou the periphery of said setting wheel six stops or lugs projecting
beyond the cogged teeth and so arranged as to pass in front or behind the winding
wheel and thus avoid interference with it. These stops or lugs would be serially
engaged by a double arm of the exposing click, and when this arm was released by
the act of exposure so as to permit the movement of the setting wheel from the out-
side of the camera would serve to lift and release the secondary click thus
carrying into effect the same principle of construction which has been hereinbefore
set forth. In this case, also, a winding of the mechanism would only be possible
after an exposure had been effected and while the shutter disc is held by the
secondary click or detent.
The principle of the invention may, in similar manner, be adhered to though
there be more than one exposure aperture pierced in the shutter disc, provided that
there be one engaging notch or catch in or near the periphery of said disc for each
such aperture therein.
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. A photographic camera shutter comprising a disc revolving in one direction
only and having one notch or catch for each exposure aperture pierced therein, this
notch or catch being engaged alternately by an exposing click and by a secondary
click or detent which must be released before the next exposure can be effected,
substantially as herein before described.
2. In a circular photographic shutter a segmental or fan-shaped obscuring stop
or plate, revolving with the exposing disc and so affixed to it as to permit of
relative adjustment for the purpose of increasing or decreasing the size of the
exposure aperture, substantially as hereinbefore described.
3. In a circular photographic shutter a two-armed or double-tongued exposing
click or detent, capable of engaging simultaneously with both the shutter disc and
the setting or winding wheel of the impelling spring, substantially as hereinbefore
described.
4. In a circular photographic shutter a secondary or auxiliary retaining click or
detent placed upon the side of the shutter opposite the exposing click so as to
engage with and arrest the shutter disc before the completion of an entire revolu-
tion, and so as to be released automatically by the process of rewinding the
impelling spring, substantially as hereinbefore described.
5. In a circular photographic shutter a setting or winding wheel pierced with
apertures of definite ratio and serving as a plate diaphragm or Waterhouse stop,
substantially as hereinbefore described.
6. The several arrangements and combinations of parts constituting the
apparatus for the purpose explained as hereinbefore described and illustrated in
the several figures of the accompanying drawings.
Dated this 20th day of July 1891
JOSEPH THACHER CLARKE.