Improvements in Shutters for Photographic Cameras.
Year: 1889

page_text: Date of Application, 20th Apr., 1889-Accepted, 22nd June, 1889
COMPLETE SPECIFICATION.
Improvements in Shutters for Photographic Cameras.
We CHARLES A. HOFFMAN; Manufacturing Optician, of 20 and 22 Fourth Street
South, and RALPH D. CLEVELAND, Photographer, of 221 Second Avenue South,
hoth of Minneapolis, State of Minnesota, United States of America 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 :-
J.
Our Invention relates to an improvement in a device for operating the shutters used
for excluding the light from a photographic camera, and the object we have in view is
to provide a shutter which can be used both for an instantaneous and protracted
exposure without any change in the operating, mechanism.
Our Invention consists generally in the construction and arrangement hereinafter
described and particularly pointed out in the claims.
In the drawings which form a part of this specification, Fig. 1 is a front elevation
of our improved shutter shewing the operating bulb connected thereto.
Fig. 2 is a side elevation of the same.
Fig. 3 is a front elevation and partial section on an enlarged scale shewing the
operating cylinder and shutter blades in position for a protracted exposure.
Fig. 4 is a front elevation shewing the parts in position after having made an
instantaneous exposure.
Fig. 5 is a front elevation with the outer plate removed to more clearly shew the
operation of the shutter blades.
Fig. 6 is a transverse section taken on line x x of fig. 4.
Figs. 7 and 8 are detail sections shewing the operation of the cylinder.
In the drawings 2 represents the face plate of the shutter upon which the operating
cylinder 3 is located. 4 represents the back plate of substantially similar size to the
plate 2, and this plate is preferably attached to the screw cap 5 by which the device is
secured to the camera. A ring 6 is preferably placed between the two plates 2 and 4
which conforms to the outer circumference of the said plates and allows a space between
them within the ring for the shutter blades 7 and 9. These blades are free to swing
within the said space.
The blade 7 is supported by a pivot pin 12 and the blade 9 by a pin 13. Each blade
is provided with an aperture 10 and when the blades are vertically in line as shewn in
full lines in Fig. 5 the apertures 10 register with each other and with a corresponding
opening in the plates 2 and 4. A pin 15 is preferably passed through the blades at a
point between the pivots 12 and 13, and by moving this pin in a straight line to the
right or left, will cause the blades to swing on their pivots in opposite directions and
close the aperture 10.
The cylinder 3 is preferably open at one end and is provided with the inlet pipe 17
at the other. A hollow follower 19 fits closely within the cylinder in which it slides.
The outer end of the follower is provided with a head 21 and the inner end is open to
the interior of the cylinder.
A piston 22 is arranged within the follower 19 and is free to slide therein, as this
piston is forced outward it strikes the solid head of the follower 19 and forces it
outward to the limit of its stroke.
A flexible tube 23 may be introduced over the inlet pipe 17 and provided with a
compression bulb 25 for the purpose of forcing air into the cylinder.
A dog 27 is preferably pivoted to the cylinder and provided with a lip 29 arranged
to fall in front of the follower head and retain it in its retracted position.
A bevelled catch 30 is preferably formed upon the head 21 in line with the dog 27
and is so arranged that the lip 29 will fall back of this catch where the follower is
in the extreme outward throw and be retained in this position.

page_text: A finger 32 having an inclined upper surface is secured to the piston 22 and slides
through an opening in the head 21. The inclined surface of this finger bears against
the lip 29 and raises it out of contact with the head.
The pin 15 which operates the shutter blades is preferably connected to the
head 21.
A stop 34 is preferably pivoted upon the plate 2 and may be brought in contact
with the head to limit its forward motion as shewn in Figs. 3 & 7 where
the apertures in the slides and plate correspond, this is used where a protracted
exposure is required.
A valve 33 inay be placed in the inlet pipe for the purpose of holding the pressure
of air in the cylinder and preventing the return of the piston.
A spring 31 may be located upon the plate 2. The upper end of this spring is
preferably attached to the follower by a suitable connecting link 35. The opposite end
is preferably attached to the plate by a pin 36 around which it is free to swing.
A tension brace 37 is pivoted upon the plate 2 with its outer end arranged to bear
against the spring 31. The point at which the brace 37 is pivoted is eccentric with
the curve of the spring so that as the said brace is moved about its pivot it will bear
against the spring and increase its tension.
Suitable pin holes 39 may be placed radially about the pivot of the brace 37 and a
suitable pin or projection on the brace may be arranged to fit either of the holes and hold
the brace in contact with the spring in any required position.
When the brace is in position shewn in fig. 3 it is out of contact with the spring
and the said spring is free to swing about the pin 36 and exert no tension upon the
follower. When it is desired to use the device for an instantaneous exposure the
brace 37 is brought in contact with the spring and secured in one of the holes 39, and
the tension of the spring is exerted to throw the follower forward and instantaneously
open and close the aperture 10. Any other convenient device may be used to secure
an adjustable tension upon this spring.
The operation of the device is as follows:-
When the device is in its normal position the follower 19 is retracted, the head 21 is
also drawn back to its extreme limit. The lip 29 on the dog 27 will then engage the
front of the head 21 and the pin 15 on the said head in contact with the shutter blades
will cause them to take the position denoted by dotted lines in figures 1 and 5 and the
aperture 10 will be closed. When it is desired to make an ordinary exposure the
stop 34 is placed in a horizontal position as shewn in figures 1, 3 and 7, thus bringing
it in line with the travel of the follower. The bulb 25 is now compressed and the air
forced into the cylinder 3. The compressed air in the cylinder acts against the
piston 22 forcing it forward. The finger 32 attached to the said piston slides out
through the slot in the head of the follower. The inclined upper surface of this finger
strikes the lip 29 and raises it out of contact with the head 21. The piston 22 advances
in the follower until the end of the said piston strikes the head 21, which being now
free from the retaining dog 27, will be forced out by the advancing piston until it
strikes the stop 34 as shewn in fig. 3, when this position is reached the pin 15 operating
the two shutter blades will be in line with the pivots 12 and 13 and the said blades
will stand in their middle position with the aperture 10 open as denoted in full lines in
fig. 5 and in dotted lines in fig. 3. This position of the parts may be maintained for
any length of time by keeping the bulb compressed and the air pressure in the
cylinder.
When the pressure is released from the bulb the distension of the said bulb will
sufficiently exhaust the air from the cylinder and draw the piston and follower back
to their original positions the retaining dog 27 will again engage the head, the shutter
blades will be closed and locked.
It may be convenient in some instances to hold the shutter open without retaining
the pressure upon the bulb, in order to do this the cock or valve 33 is provided which
controls the opening for admitting the air pressure from the bulb to the cylinder.
When the air is compressed in the cylinder sufficiently to operate the piston and
follower as before described, this valve may be turned to cut off the flow.
The

page_text: air pressure will then be retained in the cylinder, and the shutter remain open for
any length of time after the bulb has been released and will so remain until the
valve 33 is opened.
For an instantaneous exposure we prefer to throw the shutter blades from one
extreme to the other or from the position shown in dotted lines in figs. 1 and 3
to the position shewn in fig. 4. The apertures in the blades will register for an instant
in the passage by each other. To accomplish this result the full stroke of the follower 19
is required and the stop 34 is raised so as not to be in contact with the head.
The piston and follower are operated as before described except that the follower is
thrown outward to the limit of its stroke and when in this position the lip 29 falls
behind the catch 30 and the shutters are locked in this position thus avoiding the
possibility of a double exposure. When greater speed and certainty is necessary in
the action the brace 37 is brought into contact with the spring; this causes the tension of
the spring to act upon the follower. In this instance the air pressure merely raises
the catch and releases the follower which is immediately drawn out by the pressure
ot 'bre spring.
Having thus particularly described and ascertained the nature of our said Inven-
tior, and in what manner the same may be performed we declare that what we
claim is :-
1. In a photographic camera shutter, the combination of the two shutters arranged
one over the other and provided with openings adapted to register with each other,
pivots arranged at unequal distances from said openings and supporting said shutters
and a pin engaging both of said shutters at a point between said pivots whereby as the
pin is moved in either direction the said shutters are moved upon their pivots in
opposite directions substantially as described.
2. In a photographic camera shutter, the combination with the pivoted shutters of
the cylinder 3, the follower 19 arranged within said cylinder and provided with a
pin 15 engaging both of said shutters at a point between their pivots a spring 34
connected with said follower and the adjustable brace 37 adapted to be engaged with
said spring for the purpose specified.
3. The combination in a photographic camera shutter, with a pneumatic cylinder
controlling the operating mechanism of said shutter, a bulb connected with said
cylinder and a cut off valve between said bulb & said cylinder whereby communication
between said bulb and said cylinder may be cut off and the air confined in said
cylinder for the purpose set forth.
4. The combination in a photographic camera shutter with the movable shutters
of the cylinder 3, the follower 19 arranged therein and connected with said shutters,
the dog 27 arranged to engage said follower and the piston 22 arranged within said
follower and provided with the finger 32 adapted to release the dog 27 as the piston
is moved within the follower, substantially as described.
5. The combination in a photographic cameras shutter with the pivoted shutters of
the cylinder 3, the air bulb connected therewith, the follower arranged within said
cylinder and connected with said shutters and the pivoted stop 34 adapted to be
arranged in line with said follower substantially as described.
6. The combination, in a photographic camera shutter, with the movable shutters,
of the cylinder 3, the air bulb connected therewith, a follower in said cylinder
connected with said shutters and a lock holding said follower when it is drawn back
or forced out in said cylinder.
7. The combination in a photographic camera shutter, with the pivoted shutters of
the cylinder 3, the air bulb connected therewith, the follower 19 arranged within said
cylinder and connected with both of said shutters and the pivoted dog 27, adapted to
engage said follower and lock it either when it is forced outward in said cylinder or
retracted therein, substantially as described.
8. The combination in a photographic camera shutter with the movable shutters
of the cylinder 3, the follower 19 arranged therein and connected with said shutters,
the spring 34 connected with said follower, a locking device engaging said follower

page_text: and holding it in its retracted position against the tension of the spring, the piston 22
arranged within said follower and adapted to move therein and provided with a
releasing device engaging the lock which holds said follower, substantially as described.
Dated this 20th day of April 1889.
HUGHES, ELI & HUGHES,
76, Chancery Lane, London, Agents for the Applicants.