Improvements in Photographic Shutters.
Year: 1893

page_text: Date of Application, 24th Feb., 1893.
Complete Specification Left, 19th Aug., 1893-Accepted, 23rd Sept., 1893
PROVISIONAL SPECIFICATION.
Improvements in Photographic Shutters.
We, JOHN EDWARD THORNTON and EDGAR PICKARD, of Altrincham, in the
County of Cheshire, Manufacturers, do hereby declare the nature of this invention
to be as follows :-
The improvements forming the subject of this invention apply to photographic
shutters of the roller blind type that work close before the sensitive plate or film,
generally known as focal plane shutters.
A shutter of this kind is usually constructed with a narrow transverse slit in the
spring blind, through which the light is admitted to the sensitive plate during the
passage of the blind from the winding roller on to the spring roller.
The object of our improvements is to so form the blind that the width of the slit
can be adjusted when required, which we do as follows:-
The two sides of the blind, which form the edges of the slit, are turned over and
stitched (or otherwise fastened) a sufficient distance to form a hem or loop through
which a strut is passed. The strut is formed of a piece of thin channelled steel, like
a half tube, terminating at each end in a point. A short piece of tube is fitted in
or over each end of one of the said struts.
The two struts are connected together by light chains at each side of the blind,
which practically form the ends of the transverse slit. These chains are per-
manently fastened to the two ends of one of the struts, and one of the links of cach
chain engages with the point on the end of the other strut. The ends of the two
chains pass through the two short tubes into or along the grooved strut, and are
connected together by an elastic band.
To decrease the width of the slit it is only necessary to shorten the chains at each
side by hooking the points of the strut into other links, the rubber band inside the
strut taking up the loose ends of the chains into the hem.
To increase the width of the slit the chains are each lengthened by pulling out
more links through the tube, and hooking on to the points; in doing so the elastic
band is stretched.
We do not bind ourselves to the exact details of construction hereinbefore
described, as they may be varied without departing from the main principle of the
invention; for instance, the strut may be formed of a light tube, instead of a
grooved strip with tubes on the end, and a spiral wire spring may be used inside
instead of the elastic band. If found necessary both struts may be provided with
elastic bands instead of having the chain permanently fastened at one end.
Dated this 24th day of February 1893.
JOHN EDWARD THORNTON.
EDGAR PICKARD.
COMPLETE SPECIFICATION.
Improvements in Photographic Shutters.
We, JOHN EDWARD THORNTON, and EDGAR PICKARD, of Altrincham, in the
County of Chester, Manufacturers, 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 :-
This invention relates to photographic shutters of the roller blind type that work
close in front of the sensitive plate or film and are well known as "focal plane
shutters "

page_text: Shutters of this type have hitherto been constructed with a narrow transverse
slit in the spring blind through which the light is admitted to the sensitive plate
during the passage of the blind from the winding roller on to the spring roller the
width of the slit being in most instances constant and unalterable.
This invention is designed to construct or form the blind so that the width of the
slit can be adjusted when required either by increasing or reducing it.
It consists essentially in applying a flexible chain or other looped band to each of
the longitudinal edges of the blind between the two transverse edges which form
the slit the chains being lengthened or shortened by passing the links over a
projecting point or pin at each end of the slit carried on a stud placed along one
side of it.
It will be fully described with reference to the accompanying drawings which
show sufficient of a blind of this type to illustrate our invention.
Fig. 1. front view with slit open to full extent.
Fig. 2. front view with slit closed to the narrowest width.
Fig. 3. enlarged views showing position of chain on the projecting point or pin
with which the links engage.
Fig. 4. side elevation.
The
Fig. 5. perspective view in detail of parts removed from the blind.
The blind A is formed and attached to the rollers in the usual manner.
two sides of the blind which form the slit B we form with a loop or slot a by turning
over the edges and stitching or otherwise fastening them down. Through the slot
in each side of the blind is passed a strut or stay C of thin channelled steel like a
half tube. One of the struts C terminates at the ends in an eye c and the other in
a projection or point c¹. A ring or short piece of tube c¹¹ is fitted over the ends of
the strut which carries the points c¹.
The two struts C are connected together at their ends by light chains D one at
each side of the blind, the chain being attached to the eyes c of one strut and
passing down through the rings or tubes c¹ on the other the links engaging with
the points or projections c¹. The chains D thus placed form the ends of the
transverse slit B. The two ends of the chains which pass over the points o' and
through the rings or tubes el lie inside or along the groove in the strut C and are
connected together by an elastic band or spring E. Instead of the two ends being
connected to one elastic band they may each be connected to a separate elastic band
the other end of which is attached to the strut C.
To decrease the width of the slit B it is only necessary to shorten the chains D
at each side by hooking the points c¹¹ of the strut C into other links, the rubber
band E inside the strut C taking up and drawing the loose ends of the chains D
into the loop or slot a.
To increase the width of the slit B the chains D are each lengthened by pulling
out more links through the ring or tube c¹¹ and hooking them on to the points c¹ in
doing so the elastic band E is stretched.
We do not bind ourselves to the exact details of construction herein before
described as they may be varied without departing from the main principle of the
invention; for instance, the strut may be formed of a light tube, instead of a
grooved strip with tubes on the end and a spiral wire spring may be used inside
instead of the elastic band. And instead of the chains D a strip of leather or
woven or flexible band may be employed provided with holes loops or the like to
engage with the projections.cl on the end of the strut C. If found necessary both
struts may be provided with elastic bands instead of having the chain permanently
fastened at one end.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
In a focal plane shutter for photographic cameras the combination with the
blind of the atmuto w
LD

page_text: which connect the two parts together, the projections at the sides of the blind c
with which the links of the chains engage to adjust the width of the slit and the
spring band E which draws the ends of the chains into the slot a substantially as
described and shown.
Dated this 16th day of August 1893.
WM. P. THOMPSON & Co.,
6, Bank Street, Manchester, Patent Agents.