Improvements in Photographic Cameras.
Year: 1887

page_text: COMPLETE SPECIFICATION.
Improvements in Photographic Cameras.
I, WALTER CLARK, of the City, County and State of New York, United States of
America, Artist, do hereby declare the nature of my invention for "IMPROVEMENTS
IN PHOTOGRAPHIC CAMERAS" and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement:-
The object of my invention is to improve and render more certain the action of the
devices which produce the instantaneous effect in photographic cameras; and also to
improve the devices for focusing.
My invention consists of a camera box preferably of the kind having the lens and
its tubes within the box provided with a hinged lid which when lifted carries with it
a ground glass focusing plate which is maintained in a horizontal position by a certain
arrangement of links, and is always at the same distance from the mirror upon which
the incident rays are received, that the said mirror is from the surface of the sensitive
plate. The ground glass plate is also provided with a hood so arranged as to fold
within the box when the lid is lowered.
My invention further consists in placing within the camera box, a drum revolving
upon a vertical axis under the action of an adjustable coiled spring, controlled by a
friction wheel, open for a portion of its cylindrical surface and provided in the closed
portion with a window for the admission of the light rays when the window passes
the aperture of the lens.
My invention further consists of certain details of construction of the various parts,
to render their action more certain and efficient, and to insure the entire exclusion of
light from the dark chamber. These minor features will be more fully hereinafter
set forth.
In the drawings, fig. 1 is a vertical section of the camera on the line
The lid is shown raised, a portion of the outer end of the lid being omitted.
is a horizontal section of the camera on the line x of fig. 1.
of fig. 2.
Figure 2

page_text: Fig. 3 is a cross section of the camera on the line yy of fig. 2 showing a vertical
projection, the entire lid raised and the hood in working position. Fig. 4 is a plan
view of the frictional device for controlling the motion of the revolving drum.
A is the camera box provided with the opening a, the partition A', plate holder
guides A. slates A³, and check pieces A, B is the lens tube operated by the pinion b,
and thumb piece 2, C is the plate holder, e, sensitive plate, c³, front and back opaque
slides,, springs to keep the holder in place. D is the internal lid hinged to the
front of the box at d, and having then opening & for light to pass from the mirror E,
to the ground glass focusing plate F; this lid D, when down is held in place by
certain projections on the plate holder resting upon it. By removing the plate
holder the lid I can be turned upon its hinged end and raised for the removal of the
drum H which is pivoted to the lid D and to a support G.
I, clock spring to rotate drum, K friction wheel to control the rotation of the drum,
h, window in the drum; m, m² links to support the lid 1, m³ link and m bar or
support attached to the camera box to support the outer end of the ground glass
plate F; these links are so contrived as to keep the plate always in a horizontal
position when the lid is raised. N is an India rubber hood mounted upon the
folding wire frame a.. O is a buffer to stop the rotation of the drum H, at the proper
point; Pa catch to hold or release the drum, operated from the outside of the camera
by the long rod R passing through the support .
The arrows indicate the direction of the motion of the various parts.
Taking up the drum H in detail it consists of a circular top having an opening in
the proper place to permit the light to be reflected upward to the ground glass plate,
a bottom plate much cut away, its shape being indicated by outer curved dotted lines
in Fig. 2, and a cylindrical plate extending around about of the circumference of
the drum, and provided with an aperture which I call a window, large enough to
permit of the passage of all the rays of light collected and transmitted by the lens; a
second opening is made use of in focusing. This drum is mounted so as to revolve
about a vertical axis, its bearings being below upon the plate G, and above in the
inner lid D. A clock spring I is attached to its inner end to the spindle A2, which
forms the lower journal of the drum, and at its outer end to a small spring crank and
pin, which by being caught in the various holes of G, places the clock spring I
under more or less tension. This spring causes the rotation of the drum H, when the
spring catch P is withdrawn by pressing upon the outer end of the rod R. To
counterbalance the weight of the mirror a small weight S is added to the top of
the drum.
The pivot at the top of the drum passes up through the lid D, and has fixed upon
it a smooth rimmed wheel K, against which a spring k, (fig. 4) presses with more
less pressure according to the position of the cam K, which is pivoted at /³ to the
lid D and presses against the latch sliding in k³.
The mirror, enclosed in a box open at the top, is secured in the drum at an angle
of 45° opposite the opening for focusing, by means of the upper and lower supports cc;
when the window his opposite the lens, it, the mirror, has turned away entirely out
of the way of the beams of light. The flanges h fitting into the grooves in slide D
effectually prevent any leakage of light into the camera at the top.
The operation is as follows: The camera having been placed in position and
directed at the object to be photographed the lenses are thrown out, the cap removed
and the lid raised until it is supported by the links mm², the ground glass F is
automatically brought into position and the hood distended. The drum is brought
into such position that the reflecting surface of the mirror is opposite the lens.
Upon looking at the ground glass plate the image of the object will be seen there
exactly as it would be thrown upon the sensitive plate were the drum in proper
position. When the lens have been adjusted so that the object is clearly defined
upon the ground glass the catch P is withdrawn by means of the lever or rod R and
the drum revolving in the direction of the arrow brings the window h opposite the
lens and continues to revolve until it is brought to a stop by the buffer O affixed to
the side of the camera. During the instant that the window h is passing by the lens

page_text: the beam of light transmitted from the object is free to pass to the sensitive plate and
act upon it and is then immediately cut off by the further revolution of the drum
bringing the enclosed cylindrical surface between the lens and sensitive plate.
Should more force be required to rotate the drum this can be obtained by winding
up the clock spring I by means of the spring arm and pin 2. This spring is
required at any required tension by the holes or notches into which the pin slips
and is retained by the spring arm i. To prevent the drum rotating too rapidly the
spring K can be brought to bear more firmly against the wheel K by the cam k
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. A photographic camera provided with an inner lid D, to which is pivoted a
revolving drum containing the focusing mirror; said inner lid being retained in
place by a projection on the plate holder, substantially as described and for the
purposes specified.
2nd. A photographic camera provided with a revolving drum mounted on a vertical
axis and placed immediately behind the lens; said drum carrying the focusing
mirror and provided with a window to admit the passage of light at the proper time
through the lens to the sensitive plate, as herein described and shown.
3rd. In a photographic camera the hinged lid L and ground glass plate F pivoted
thereto and raised and supported by the links m, m², m³, m²; the parts being so
arranged and adjusted that when raised the plate F is always the same distance from
the focusing mirror, as herein described and shown.
Dated this First day of March A.D. 1001.
WALTER CLARK.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.