Improvements in Shutters for Photographic Cameras.
Year: 1889

page_text: Date of Application, 1st July, 1889
Complete Specification Left, 6th Mar., 1890-Accepted, 12th Apr., 1890
PROVISIONAL SPECIFICATION.
Improvements in Shutters for Photographic Cameras.
I, JOHN KERSHAW of 47 Spring Gardens, Buxton Derbyshire Photographer do
hereby declare the nature of this invention to be as follows:-
The improvements which are the subject of this invention relate to the means
employed for closing the spring blind in the shutter of a photographic camera, and
the object of this invention is to construct a shutter that may be used either as an
instantaneous shutter or as a time shutter when an interval of time for exposure is
required in lieu of instantaneous exposure.
.
In this invention for the purposes as herein above set forth, I construct a shutter
in which is a spring blind with an aperture for exposure of light to sensitive plate.
By means of a gravatation lever in combination with a ratchet wheel on end of
liberating roller of spring blind as described in the specification of my invention for
which letters patent for Great Britain were granted to me bearing date the 21st day
of April A.D. 1885 and numbered 5014, the spring blind in shutter may be closed
instantaneously.
For the purpose of obtaining an interval of time for exposure when instantaneous
exposure is not required, I employ a secondary lever of an angular shape in combina-
tion with the aforesaid gravitation lever. I suspend this secondary lever to a stud
formed on a spring plate which I attach to side of shutter in proximity to gravita-
tion lever. I form an angular slot or cam groove in this secondary lever through
which I pass a stud which is attached to gravitation lever. On end of liberating
roller of spring blind I form or attach a worm which when said liberating roller
is revolved by the operator in order to wind the blind on said roller preparatory
to exposure, actuates a worm wheel affixed to side of shutter. I form this worm
wheel with a hole in the face thereof into which a stud attached to aforesaid spring
plate is caused to enter by action of spring plate when ratchet wheel is revolved
and the before mentioned hole comes opposite stud in spring plate. I attach a
pawl to aforesaid spring plate which engages with and prevents rotation of ratchet
wheel affixed to end of blind roller immediately said stud enters hole in face of worm
wheel, but not at any other time.
When it is required to close the spring blind instantaneously, the herein above
described secondary lever remains inactive and the spring blind in shutter is
instantaneously closed by one compression of air bulb which is attached to pneumatic
tube acting on gravitation lever: but when it is preferred to obtain an interval of
time for exposure, said secondary lever in which is a cam groove is set at an angle
which necessitates a second compression of air bulb in order to close blind or shutter,
the first compression causing the blind to open and remain open until the second
compression of air bulb, which releases pawl from ratchet wheel by return
of secondary lever to its original position, and thus permits the spring blind
to close.
To obviate concussion in checking blind when said blind is required to be kept
open to obtain a longer exposure I place in liberating roller a coil spring with
a resistance which is insufficient to neutralize the action of spring contained
in bottom or receiving roller for blind but is sufficient to prevent concussion.
When it is required to give more exposure to the foreground than to the sky I
cause the aperture in blind to open from bottom of shutter by placing the coil spring
in receiving roller in upper part of shutter by which means the blind is caused to
pass from liberating roller contained in upper part of shutter, over tension roller at
bottom of shutter and returning upwards wound on receiving roller.
Dated this 28th day of June 1880

page_text: COMPLETE SPECIFICATION.
Improvements in Shutters for Photographic Cameras.
I, JOHN KERSHAW of Spring Gardens, Buxton, in the County of Derbyshire,
Photographer 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 :-
The improvements which are the subject of this invention, relate to the means
employed for closing the spring blind in the shutter of a photographic camera, and
the object of this invention is to construct a shutter that may be used either as an
instantaneous shutter, or as a time shutter when an interval of time for exposure is
required, in lieu of instantaneous exposure.
In order more clearly to describe this my invention, I have annexed hereunto a
sheet of drawings: in the several views therein shown similar letters refer to similar
parts.
Fig. 1 is an end view of a shutter which is constructed according to this
invention. Figs. 2, 3, and 4 are end views of the same shutter, but with the
mechanism occupying different positions as hereinafter described, and according
to the requirements of the operator. Fig. 5 is a front view of the same, and
Figs. 6 and 7 are side and end views respectively of wheel n and spring plate j
with spring drawn to an enlarged scale. Fig. 8 is end view of shutter showing
positions of liberating and receiving rollers when aperture in blind is caused to open
from the bottom.
In this invention for the purposes as hereinabove set forth, I construct a
shutter a, in which is a spring blind b, with an aperture c for exposure of light
to sensitive plate: by means of a gravitation lever d, in combination with a ratchet
wheol e, on end of liberating roller of spring blind 6 as described in the
specification of my invention for which Letters Patent for Great Britain were
granted to me bearing date the 21st day of April A.D. 1885 and numbered 5014,
the spring blind bin shutter a may be closed instantaneously.
For the purpose of obtaining an interval of time for exposure, in lieu of instantaneous
exposure, I employ a secondary lever g, of an angular shape, in combination with
aforesaid gravitation lever d. I suspend this secondary lever from a stud formed
on a spring plate j, which I attach to side of shutter a, in proximity to gravitation
lever d. I form an angular slot or cam groove k in this secondary lever, through
which 1 pass a stud 1, which is attached to gravitation lever d. On the end of
liberating roller of spring blind b, I form or attach a worm m. When said liberating
roller is revolved by the operator in order to wind the blind on to roller f
preparatory to exposure, the worm m actuates a worm wheel n affixed to side of
shutter a.
I form this worm wheel with a hole n¹ in the face thereof, into which
a stud which is attached to aforesaid spring plate j is caused to enter by the
action of spring plate j when wheel n is revolved, and the before mentioned hole n¹
comes opposite stud j in spring plate j.
:
The hole n', and the stud are each bevelled on one side, in order that said stud
may leave the hole n² during the operation of winding the blind on to roller f
without requiring to be lifted out of said hole. I attach a pawl to spring plate j,
which when the liberating roller is released in order to close the blind b, engages
with the stud v formed on liberating roller f immediately the stud j¹ enters hole n'
in face of worm wheel n, thus arresting the rotation of said roller, and retarding the
closing of the blind the position of hole n¹ in face of wheel n is prearranged and
determined by the size of opening in blind. When it is required to close the spring
blind instantaneously, the herein above described secondary lever g, remains inactive,
and the spring blind in shutter is instantaneously closed by one compression of air
bulb, which is attached to pneumatic tube, not shown on drawings, but connected
with piston p which acts on gravitation lever d: but when it is preferred to obtain
an interval of time for exposure, said secondary lever g in which is cam groove k, is

page_text: set at an angle, which necessitates a second compression of air bulb in order to close
the blind b; the first compression of air bulb causes the blind b to open and remain
open, until the second compression of air bulb, which releases pawl from stud v by
return of secondary lever g to its original position, and thus permits the spring blind b
to close.
In Fig. 1 on drawings, the stud j¹ which is attached to spring plate is shown
within the hole n¹ on face of worm wheel n, and the pawl is acting on stud v,
while the stud / occupies a position on the right hand side of cam groove k. In
order to withdraw the stud j¹ from hole n' and disconnect the pawl from the stud v,
thereby making them inoperative, I reverse the switch r, which in this view is
shown in a raised position, to the opposite or downward position, as shown in Fig. 2.
on drawings.
In this view the heel of switch r acting against the spring plate ; which is
pivotted at jª³ releases aforesaid stud j¹ and pawl j² while the stud is caused to
occupy a position on the left hand side of cam groove k.
Fig. 2 thus represents the shutter with the mechanism arranged for instantaneous
exposure, by means of one compression of air bulb.
In Fig. 3, the mechanism is represented as having been set for prolonged exposure;
in this view the stud is shown resting on face of wheel plate n, and the secondary
lever g is set at. an angle by placing the stud in the position shown in cam groove k.
Fig. 4 represents the piston p as having actuated the lever by means of one com-
pression of air bulb, and caused the blind b to open, and to remain open in consequence
of the studentering the hole n' in face of wheel n and placing the pawlin
contact with the stud v, thereby preventing further revolution of the roller f
until released by a second compression of air bulb, while the lovers g and d would
return to the positions shown in Fig. 1.
By the action of a second compression of air bulb, the stud would cause the
spring plated to withdraw the stud j¹ from hole in plate n, and release the pawl.
from stud V₂
and thus allow the blind to close.
To obviate concussion while checking blind, when said blind is required to be
kept open in order to obtain a longer exposure, I place in liberating roller of a coil
spring with a resistance which is insufficient to neutralize the action contained in
bottom or receiving rollers for blind, but is sufficient to prevent concussion.
When it is required to give more exposure to the foreground than to the sky, I
cause the aperture in blind b to open from bottom of shutter, by placing the coil
spring in receiving roller s in upper part of shutter, and by these means the blind b
is caused to pass from liberating roller f which is also contained in upper part of
shutter, over tension roller t placed in bottom of shutter, and returning upwards is
wound on receiving roller s.
Having now particularly described and ascertained the nature of this 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, the combination of a gravitation
lever d with a secondary lever g, in which is a cam groove k, in order that said shutter
may be used either as an instantaneous shutter by the sole action of gravitation
lever d, or as a time shutter, when an interval of time for exposure is required, in
lieu of instantaneous exposure, by the combined action of gravitation lever d, and
secondary lever g, in the manner substantially as herein before described and
illustrated.
2nd. In the shutter of a photographic camera, in order to obtain prolonged
exposure for the foreground, the means employed for cansing the blind to open from
the bottom, substantially as herein before described.
THOMAS
PRESCOTT,
Arcade Chambers, St. Mary's Gate, Manchester, Agent for Applicant.