IMPROVEMENTS IN THE SHUTTERS OF PHOTOGRAPHIC CAMERAS
Year: 1885

page_text: I, JOHN KERSHAW of 10 Quadrant Buxton, in the County of Derby Photographer
do hereby declare the nature of my invention for IMPROVEMENTS IN THE SHUTTERS
OF PHOTOGRAPHIC CAMERAS to be as follows:-
In the shutter of a photographic camera, an arrangement for instantaneously
closing the spring blind, or for prolonged exposure, as required, for photographic
purposes.
For instantaneously closing the spring blind in this shutter, in place of the
means usually adopted, such as a spring lever working into a ratchet at the end of
the roller of a spring blind, and which is actuated by pneumatic pressure or other
similar means, I employ a lever, which being suspended at one end falls into
position by its own weight, and termed a gravitation lever: One end of this lever is
forked, and by the force of gravitation works into a ratchet wheel fixed on the
end of the roller of a spring blind in a shutter in which is an aperture for exposure
of light to sensitive plate: When the blind is required to be instantaneously
closed, the said gravitation lever is released by pneumatic action or other suitable
means in the same way as when a spring lever is used.
For a lengthened exposure or when it is necessary to give more exposure to the
foreground than to the sky, I use a separate attachment, placed at one end of the
shutter frame, consisting of a metallic shoe or box, in which is contained an elastic
cylinder in connection with an ordinary pneumatic or hydraulic tube and reservoir:
by means of a lever resting on the said elastic cylinder, being pivotted at one
end to the said box, and the opposite end attached by a cord which is wound on
the end of the roller of a spring blind before the blind is opened, the lever coin-
presses the said cylinder: by the expansion of the cylinder the blind is opened and
may if required be retained in position by the gravitation lever or the gravitation
lever may be prevented acting on the ratchet wheel attached to the blind roller,
by a stop or catch, so that the blind can be made to rise and fall at the will of the
operator, by pressing or releasing the reservoir at the end of the tube: This
action is obtained by attaching a cord from the compression lever to the winding
up roller: The cord which is attached to the compression lever is unwound from
the roller of the spring blind, but with the end remaining attached to it, by the
pressure in the cylinder causing the loose end of the compression lever to rise and

page_text: retain the cord in tension: When the spring blind is required to be closed, the
pressure is released and the cord which is attached to the compression lever on the
cylinder, rewinds on the roller of the spring blind: the resistance in the com-
pression of the cylinder allows the spring blind to close being regulated by the
tension on the spring connected with the roller blind.
COMPLETE SPECIFICATION.
Improvements in the Shutters of Photographic Cameras.
I, JOHN KERSHAW of 10 Quadrant, Buxton in the County of Derbyshire
Photographer do hereby declare the nature of my invention for IMPROVEMENTS IN
THE SHUTTERS OF PHOTOGRAPHIC CAMERAS and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement :-
In the shutter of a photographic camera an arrangement for instantaneously
closing the spring blind, in place of the means which are usually adopted, such as
a spring lever which works into a ratchet wheel at the end of the roller of a spring
blind, and which is actuated by pneumatic pressure or other similar means.
In this invention I employ a lever which being suspended at one end, falls into
position by its own weight, and termed a gravitation lever: One end of this lever
is forked and by the force of gravitation works into a ratchet wheel on the end
of roller of a spring blind contained in a shutter in which is an aperture for
exposure of light to sensitive plate: When the blind is required to be instan-
taneously closed, the gravitation lever is. released by pneumatic action, or other
suitable means in the same way as when a spring lever is used.
In order that my invention may be fully understood, I now refer to and describe
the accompanying sheet of drawings, similar letters indicating similar parts in the
several views.
Fig. 1 is an end view of a shutter in a photographic camera and Fig. 2 is a
front view of the same shutter, in which the spring blind b on rollers d and d¹ is
represented in dotted lines contained in the shutter or case a.
The gravitation lever y is suspended by a pin h and is formed with a fork or
projection which by the action of gravitation in the lever g falls into the teeth of
the ratchet wheel e as the spindle f of the spring blind b is turned round: the
spring blind being thus retained in position when opened by the operator: In
these views the blind is shown open with the gravitation lever g suspended from
the pin h, the fork i thereby resting in the teeth of ratchet wheel e.
When it is required to close the spring blind instantaneously, the fork i is raised
from the wheel è by the end g¹ of the lever g being pushed out of the centre, this

page_text: may be effected by pneumatic action or other suitable means, such as are usually
adopted when a spring lever is used: Fig. 3 represents end view and Fig. 4 front
view of a shutter with the spring blind b closed.
The end g¹ of gravitation lever g pressed back by the piston having released
the fork or projection i from the ratchet wheel e and thereby caused the instantaneous
closing of the blind b.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the. same is to be performed, I declare that what
I claim is
1st In the shutter of a photographic camera, for the purpose of instantaneously
closing the spring blind, the use of a lever, which is suspended at one end, and by
the force of gravitation, falls into position by its own weight the said lever being
suitably formed with a fork or projection for working into a ratchet wheel at the
end of the roller of a spring blind, contained in the shutter, for retaining the said
blind in position: the lever being released by pneumatic pressure if preferred, or
by any other suitable means when the spring blind is required to be instantaneously
closed, substantially in the manner as herein before described and illustrated.
Dated this 21st day of November 1885