INSTANTANEOUS PHOTOGRAPHIC DROP-SHUTTER
Year: 1886

page_text: :
I, THOMAS FORREST of 14 Market Street. Pontypridd in the County of
Glamorgan, Photographer do hereby declare the nature of my invention for
INSTANTANEOUS PHOTOGRAPHIC DROP-SHUTTER to be as follows:-
I construct a vertical frame about three times greater in height than in width,
having two separate pairs of vertical grooves which are divided by a central
partition, having an aperture near its bottom edge of suitable diameter to the lens
it is intended to employ in taking the photograph.
?
The upper edge of the central partition reaches to near the top of the grooved
frame and is finished with a smooth rounded edge, or I affix a small roller above
the central partition, instead of the smooth rounded edge.
Two plates, of Metal, Wood, Ebonite, Cardboard, or similar material, are made to
slide loosely in the grooves of the frame, one plate on each side of the central
partition, the two plates being connected together by cords or other flexible
material passing over the top of the central partition. The cords being of such a
length that when one of the plates is at the top of its grooves, the other plate will
be at the bottom of its grooves, where it will cover the aperture in the central
partition.
I make the top plate somewhat heavier than the bottom plate, so that if the top
plate is allowed to fall in its grooves, it will exert sufficient force, by gravity to
pull up the bottom plate by means of the cords which pass over the top of the
central partition. The rising of the bottom plate uncovers the aperture in the
central partition opening first from the bottom edge and as soon as the aperture is
wholly uncovered by the ascending plate it is reclosed by the descending plate,
such closing commencing from the top edge of aperture.
When necessary I accelerate the speed of the descending plate by weights or
springs or weights and springs combined. To the bottom edge of the lightest
plate I affix cords or other flexible material which pass through holes in the
bottom of the frame which cords I use to pull down the lightest plate to the
bottom of the frame thus causing the heaviest plate to rise to the top of the frame
where it is held by a catch from which it can be released when it is desired to
open and reclose the aperture in the central partition for the purpose of exposing
the photographic plate.
801
1
4000

page_text: I THOMAS. FORREST, of 14 Market Street, Pontypridd, in the County of
Glamorgan, Photographer do hereby declare the nature of my invention for AN
INSTANTANEOUS PHOTOGRAPHIC DROP SHUTTER 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 provide a means of admitting and cutting off
the rays of light through photographic lenses, in such a manner as to admit a due
proportion of light to the various parts of the photographic plate as is most
desirable; and with freedom from vibration of the photographic camera during the
exposure of the photographic plate.
I carry out my invention in the following manner (vis).
I construct a virtical frame (A) about three times greater in height than in
width, having two seperate pairs of virtical grooves which are devided by a central
partition (B) which has an aperture near its lower edge, of suitable diameter to the
lens it is intended to employ in taking the photograph. The upper edge of the
central partition reaches to near the top of the grooved frame and is finished with
a smooth rounded edge, or I affix a small roller above the partition instead of the
smooth rounded edge.
Two plates, (C. D) of metal, wood, ebonite, cardboard or other similar materials
are made to slide loosely in the grooves of the frame, (A) one plate on each side of
the central partition, the two plates being connected by cords (E) or other flexible
material passing over the top of the central partition, or the roller affixed above
the same, the cords being of such a length that when one of the plates is at the top
of its grooves, the other plate will be at the bottom of its grooves, where it will
cover the aperture in the central partition. I make the top plate (C.) somewhat
heavier than the bottom plate, (D) so that if the top plate is allowed to fall in its
grooves from the top of the frame it will exert sufficient force, by gravity, to pull
up the bottom plate by means of the connecting cords (E) which pass over the top
of the central partition (B) The rising of the bottom plate (D) uncovers the
aperture in the central partition opening first from the bottom edge, and as soon
as the aperture is wholly uncovered by the ascending plate, it is reclosed by the
descending plate, (C) such closing commencing from the top edge of aperture.
I make the plates either rectangular, or with pointed or rounded ends, the latter
two forms being used when it is desired to give an extra amount of exposure to
the lower corners and ends of the photographic plate.
: When necessary I accelerate the speed of the descending plate by weights, or
springs, (F) or weight and springs combined.
To the bottom edge of the lightest plate (D) I'affix cords (G) or other flexible
material which pass through holes in the bottom of the frame, which cords are
used to pull down the lighter plate to the bottom of the frame, thus causing the
heavier plate to rise to the top of the frame, where it is held by a catch, (H) from
which it can be released when it is desired to open and reclose the aperture in the
central partition for the purpose of exposing the photographic plate. The apparatus

page_text: may be affixed to the front of the photographic lens in place of the ordinary cap,
or between the lenses of a combination in, or near the place where the usual
Waterhouse Diaphragms are fitted.
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:-
1. A virtical frame having two pairs of grooves which are devided by a central
partition, having an aperture near its lower edge, substantially as herein before
described.
2. A pair of plates sliding in two pairs of virtical grooves devided by a central
partition, such plates being connected by cords or other flexible material passing
over the central partition, or roller affixed above same, substantially as herein before
described.