Year: 1886

page_text: I THOMAS PARSONS WATSON of 313 High Holborn in the County of Middlesex
Optician; 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 has for its object to provide a stop to prevent the shutter of a
dark slide or back being completely drawn out of its grooves without such stop
forming any projection either on the inner or outer face of the shutter; and the
Invention consists in providing the shutter at one or both sides with a lateral
shoulder or projection extending beyond the rebated edges of the shutter and
working in the same grooves as the said rebated edges; which shoulders come
against suitable stops or abutments at the outer end of the dark slide or back and
so prevent the shutter being drawn completely out.
Reference is to be had to the accompanying drawing forming part of this
Specification; in which figure 1 represents an inside face view of part of one half
of a double dark slide partly broken away to show the shoulders; figure 2 is a
cross section on line 1-1 figure 1 and figure 3 is a face view showing the outline
of the shutter separately on a smaller scale. The same letters of reference indicate
the same parts in all the figures.
a is the shutter, b are its ordinary rebated edges, c are the guide grooves for the
same, and d the shoulders constituting the stop of my Invention. The shoulders d
are formed or fixed on the shutter at either side near the inner end and are of the
same thickness as, and work in the same grooves c, as the rebated edges or flanges b,
the shoulders projecting slightly beyond the flanges to an extent equal to say the
width of the flanges (more or less) and the grooves c being correspondingly deepened
throughout to receive them. The shoulders may either be formed by making the
shutter of one width throughout and then cutting away so as to leave the shoulders
projecting as shown at the upper half of figure 1, or they may be pieces of metal f
let flush into the inner face of the shutter and screwed on froin the outside after
the shutter is finished and inserted in its grooves in the frame as in the lower half
of figure 1, both sides being of course made alike. The shoulders d abut against
any suitable stops or abutments near the outer end of the slide, the same being
[ Price lid I

page_text: formed either by hardwood dovetailed keys e driven into mortises in the frame so
as to stand across the grooves c in the path of the shoulders d, or by merely filling
up the ends of the grooves with a piece of hard wood or metal suitably fixed; but
the abutments may be formed in any other suitable way and I do not limit myself
in this respect.
Having now particularly described and ascertained the nature of the said
Invention, and in what manner the same is to be performed I declare that what
I claim is ;-
A stop for the shutter of a photographic dark slide or back, consisting of a
laterally projecting shoulder at one, or both sides of the shutter received in the
guiding grooves of the frame and abutting against any suitable stop at or near the
outer end of the frame; substantially as shown and described.