Apparatus for Controlling the Exposure of Photographically Sensitive Plates when using Flash Lamps.
Year: 1889

page_text: Date of Application, 16th Feb., 1889
Complete Specification Left, 16th Nov., 1889-Accepted, 11th Jan., 1890
PROVISIONAL SPECIFICATION.
Apparatus for Controlling the Exposure of Photographically
Sensitive Plates when using Flash Lamps.
1, FREDERIC WILLIAM HART of 8 and 9 Kingsland Green London Manufacturer
of Scientific Instruments do hereby declare the nature of this invention to be as
follows
The object of this invention is for controling the exposure of the sensitive photo-
graphic plate or plates in lighting single or grouped objects to be photographed by
flashing light or lights; It has been found that some persons and lower animals
involuntarily move either the body or more frequently close the eyelids very shortly
after the flash commences; To render this movement of little or no moment I employ
a stop-cock with two separate ways or two separate stop-cocks actuated simultaneously
by one lever or turnkey each way is connected with a separate air chamber in which
is air or gas under pressure, one conducting tube for air goes to the flash lamp and the
other to the pneumatic release of an exposing shutter, their relative times of discharge
is so adjusted that the shutter exposure takes place at the early part of the flash or
combination of flashes and according to the volume of light provided so the
actual exposure of the plates may be reduced to a very small fraction. It has been
found impracticable for many to accomplish the double movement for flash & shutter
by simple hand pressure on balls at the right instant of time; It has also been
suggested to connect the exposing shutter-release with the same air ball or chamber
that discharges the magnesium, but as the air does not escape at the shutter release
but exert pressure and on the other hand the tube to the flash lamp is practically open
it is seen that such an arrangement could exert no practical pressure at the shutter
release.
Dated this 16th day of February 1889.
COMPLETE SPECIFICATION.
Apparatus for Controlling the Exposure of Photographically
Sensitive Plates when using Flash Lamps.
I FREDERIC WILLIAM HART of 8 & 9 Kingsland Green London Manufacturer of
Scientific Instruments 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 object of this invention is for controlling the exposures of sensitive photo-
graphic plates in lighting single or grouped objects to be photographed by a flashing
light or lights.
It has been found that some persons and lower animals involuntarily move either
the body or more frequently close the eyelids very shortly after the flash commences.
To render this movement of little or no moment I employ a stopcock with two
separate ways or two separate stopcocks actuated simultaneously by one lever or
turnkey, each way is connected with a. separate air chamber in which is air or gas
under pressure, one conducting tube for air, goes to the flash lamp and the other to
the pneumatic release of an exposing shutter, their relative times of discharge is so
adjusted that the shutter exposure takes place at the early part of the flash or
combination of flashes and according to the volume of light provided so the actual
exposure of the plates may be reduced to a very small fraction of a second. It has
been found impracticable for many to accomplish the double movement for flasb and
shutter by simple hand pressure on balls at the right instant of time; It has also been

page_text: suggested to connect the exposing shutter release, with the same air ball or chamber
that discharged the magnesium but as the air does not usually escape at the shutter
release but exert pressure, and on the other hand the tube to the flash lamp is
practically open it is seen that such an arrangement could exert no practical pressure
at the shutter release.
In carrying my invention out in a practical form I construct apparatus in the
following manner as shewn in and by the accompaning description and drawings,
whereof Fig. 1 is a sectional drawing shewing two stopcocks C & D with their axis
in line, air chambers A and B., valves E and F., and adjusting disk P and index I.
Fig. 2 shews another method of opening stopcocks simultaneously by means of a
toothed wheel working in pinions on the plugs of the stopcocks.
Fig. 3 shews the plan of the disk P index I and set screws. When a stopcock
with two ways is employed the respective ways are drilled for the particular make of
exposing shutter but I prefer to make the stopcocks separate as shewn in Fig. 1
wherein adjustment can be made for various forms of pneumatic release shutters I
give the preference to those having metal cylinder and piston arrangement,-the
varying physical condition of rubber bellows and bags necessitating more frequent
adjustment of the index hand I as the said bellows may be soft or hard from time to
time as experience has shewn and when hardened by age they do not respond to the
pressure so readily.
The apparatus is used in the following manner at F. Fig. 1 is a double valve fitting
with india rubber ball G attached or for large capacity and pressures above 12 lb.
or 15 lbs. to the inch I employ metallic air force pumps to charge the reservoir B
according to the resistance offered by the amount of flashing material to be discharged
and the number, length and capacity of the conducting tubes proceeding to the lamps
to be discharged simultaneously by my distributor as discribed in Patent No. 356
1888. At E there is a similar double valve piece and ball or pump to charge the
compartment A separated from B by the airtight partition a on each of these com-
partments there are stopcocks C and D the stopcock C has a much smaller way
through it than that of D a good ratio will be about 1 to 10 in their respective
diameters, C is to be connected with the exposure shutter and D with the lamp or
Lamps. For adjustment I take any pneumatic shutter where the piston, bellows, or
bag lifts or sets free a detent having free action independent of the said piston,
bellows, or bag, after detent is set free.
The stopcock C and D are turned off and the chamber A and B charged with air.-
The set screw is loosened and d is then turned untill escape of air can just be
detected; The disk P is now turned untill air begins to escape from A the set screw i
is then tightened on the prolongation d of the stop-cock D, a universal joint may be
used as a part of that prolongation, to avoid any irregularity of the axial line of the
plugs. The position or index pointer I on the disk P is now noted and marked on
the disk, the plug D is passed over and an opposite point marked where the air will
just escape; between these two points the disk is divided into any convenient number
of spaces and thus the operator is enabled to control the exposure whether he desires
it at the very commencement of the flash or any intermediate part to the end
thereof. With closed bellows or bag form of India rubber release 1 insert a sinall
pet cock to relieve the pressure after each release of the shutter by the said closed
bellows or bag.
To discharge the lamps and shutter the leaver d is turned on quickly.
Having now particularly discribed and ascertained the nature of this invention
and in what manner the same is to be performed I claim.-
1st. The combination of a two-way stopcock, pneumatic release shutter and flash
lamp or lamps substantially and for the purpose as herein set forth.
2nd. The combination of two air or gas chambers & stop cocks in line the discharge
ports of the plugs being adjustable one to the other by means of a graduated disk and
index, substantially and for the purpose as herein set forth.
3rd. The combination of a two-way stopcock with separate air chambers, valves

page_text: and air compressing balls or pumps substantially and for the purpose as herein
set forth.
4th. The combination of two separate air chambers each with stopcock and their
plugs in line, their axes connected through a prolongation and set screw, or the stop-
cocks placed parallel and worked by an intermediate tooth wheel substantially and for
the purpose herein set forth.
Datad this 16th day of November 1889
FREDERIC WILLIAM HART,
8 & 9, Kingsland Green, London.