Year: 1887

page_text: Date of Application, 23rd Apr., 1887
Complete Left, 20th Jan., 1888
Complete Accepted, 9th Mar., 1888
GEORGE SALLNOW MARTIN Birkbeck Institution Breams Buildings Chancery Lane
Optician do hereby declare the nature of this invention to be as follows:-
The special feature of invention named is one long spring at the side of shutter,
acted upon by air piston at the lower end which releases a small brass or chonite
shutter pulled upwards by a spring-there being a small pin or notch which allows a
projection on the top of side spring to catch a small pin projecting from side of above
shutter enabling the operator to detain it at will.

page_text: GEO. SALLNOW MARTIN Optician Birkbeck Institution Breams Buildings
London E.C. 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:-
My invention consists in an appliance used with photographic shutters whereby the
exposure may be prolonged indefinitely at the will of the operator.
My invention is best fitted for use with shutters of that form in which the exposure
is controlled by a plate which slides up and down in grooves. A shutter of this
description is shown in the accompanying drawing. To hold the shutter closed I use
a catch or detent fitted at one side. This is marked A. B. in the figure and is of a
well known form.
It works upon a pivot as at B and releases the shutter plate on being pressed
outwards. The motion is given to the shutter plate by a spring or band. These
arrangements are well known and do not require further description. In my improved
shutter prolong the arm A. B. of the detent beyond the pivot as shown at B. C. and
at or near the extremity I construct a cross piece or bend C. D. extending inwards
in such a way that it may be near the shutter plate when it rises but not so as to
interfere with its motion. On the shutter plate I fix a pin or projection E in such a
manner that when the arm A B C is in its normal position the pin just clears the end
of the crosspiece C D as the shutter plate ascends and descends. When the end A of
the arm A B C is pushed outwards it is obvious that the cross piece CD will incline
inwards, and as the shutter plate rises the pin E will now strike the end of the cross-
piece (.D. and from the form of the arm and crosspiece there will be a tendency
for the pin as it ascends to push aside the arm and crosspiece and pass above them.
1 assist this action by constructing the arm B C of such form and material as will
give a certain amount of elasticity to it and I also find it convenient to bevel the lower
portion of the end D of the cross piece. The bevel may be arranged so that the pin
passes by the side or underneath the end of the crosspiece as may be most convenient
provided that the elasticity of the arm be such as to allow it to be thrust away so that
the pin may pass when rising. The shutter plate is checked by a stop at the upper
end of the shutter frame and therefore at once descends. If the pressure is main-
tained at the end A the arm B C will still incline inwards and the pin on descending
will strike the upper side of the end of the cross piece. There is in this caso not so
much tendency to bend the arm and there is no bevel on the upper surface. There-
fore the pin is retained and the shutter plate held up as long as the pressure at. A is
maintained. As soon as pressure is removed the arin returns to its normal position
the pin passes the crosspiece and the plate descends and the light is shut off. The
pressure may be applied by hand or by a pneumatic piston or any mechanical
contrivance. In order that this arrangement may not interfere with the use of the
shutter for instantaneous exposures a movable pin may be employed, which may be

page_text: fixed in the upper part of the shutter frame in such a way as to prevent the shutter
plate rising sufficiently high to be detained by the crosspicce. The shutter will then
rise and return in the way in which shutters of the description indicated usually act.
I do not confine myself to the exact form of shutter indicated in the drawing and
description as my appliance may be used with any shutter of a form similar to that
described whether it consists of a simple rising and falling plate or such a plate
combined with a flap. My appliance may be fixed in front, inside or behind the
shutter frame as may be found convenient. It may be made of brass, other metal
or any suitable material and in one or more component parts.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed 1 declare that what I claim is-
In photographic shutters the combination with a catch or detent which holds the
shutter closed but releases it on pressure of an appliance substantially as described
and indicated which detains the shutter plate on rising as long as pressure is
maintained on such catch or detent.