An Improvement in Changing Backs for use in Colour Screen Photography.
Year: 1897

page_text: Date of Application, 27th July, 1897
Complete Specification Left, 27th Apr., 1898-Accepted, 23rd July,
1898
PROVISIONAL SPECIFICATION.
An Improvement in Changing Backs for use in Colour Screen
Photography.
I, JOHN JOLY, of 39, Waterloo Road, Dublin, Ireland, Civil Engineer, do
hereby declare the nature of this invention to be as follows:-
This invention relates to apparatus for use in the process of colour photography
described in the Specification of Letters Patent granted to me No. 14,161 of 1894
wherein it is necessary to expose the sensitive plate behind a screen ruled with
fine lines of certain alternating colours.
The object of the present invention is to facilitate the exposure of several such
plates behind the same screen without having recourse to manipulation in the
dark room.
For this purpose the ruled screen is mounted in a changing back
immediately behind the shutter and provision is made whereby the plate and
screen may be brought into close contact during exposure and may be separated
after exposure so that during the operation of moving the exposed plate into or
away from position at the exposure aperture the plate shall not be in sliding con-
tact with the screen. This approximation and separation of the plate and screen
may be effected either by moving the plate (which has by the ordinary operation
of the changing back been brought forward and placed behind the screen but not
in contact with it) forward or by moving the screen backward until plate and
screen are in close contact, the operation in either case being performed by the
aid of levers or springs manipulated from the outside of the changing back or
camera and the reverse movement being effected after exposure in order to
separate the plate and screen sufficiently to avoid scratching resulting from the
sliding motion of the plate over the screen.
Dated shin 07th dow of Tul. 1907
An Improvement in Changing Backs for use in Colour Screen
Photography.
I, John Joly, of 39, Waterloo Road, Dublin, Ireland, Civil Engineer, 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 follow-
ing statement:—
This invention relates to apparatus for use in the process of colour photography
described in the Specification of Letters Patent granted to me No. 14,161 of 1894

page_text: wherein it is necessary to expose the sensitive plate immediately behind, and in
close contact with, a screen ruled with fine lines of certain alternating colours.
The object of the present invention is to facilitate the exposure of several such
sensitive plates behind, and in close contact with, the same screen without having
recourse to manipulation in the dark room. For this purpose the ruled screen
is mounted in a changing back immediately behind the shutter thereof, and pro-
vision is made whereby the sensitive plate and screen may be brought into close
contact and so maintained during exposure of the plate, and may be separated after
exposure, so that during the operation of moving the sensitive plate into, or away
from, the exposure position, the plate shall not be subjected to sliding contact
with the screen.
This approximation and separation of the screen and sensitive
plate may be effected either by moving the plate (which has by the ordinary opera-
tion of the changing back been brought forward and placed behind the screen
but not in contact with it) forward, or by moving the screen backward, until
plate and screen are in close contact, the operation in either case being performed
by the aid of levers or springs manipulated from the outside of the changing back
or camera; the reverse movement being effected after exposure, in order to
separate the plate and screen sufficiently to avoid the scratching which would
result from sliding contact of the plate with the screen when the plate is moved
in its own plane.
The accompanying drawing represents in vertical section and on an enlarged
scale a changing back embodying one form of my invention. A is the body of
the changing back having transverse slots a, a¹ in the top towards the front and
back and enclosed at top by a leather changing bag B. Each plate is enclosed in
a sheet metal sheath Chaving a central projecting tongue c on top, the tongues
emerging through a slot connecting the slots a, a¹ in the top of the changing
back, in order that they may be gripped through the bag for the purpose of
changing the plates. The plates are pressed forward by springs and the front
plate of the series rests, by the flanges of its sheath against projecting ledges d
at the sides of the box by which the plate is restrained from moving forward
beyond the position shown. E is the taking screen supported in a metal mount e
and is so much smaller than the sensitive plate as to clear the flanges of the
sheath when pressed backwards as hereafter described, in order that the ruled
surface of the screen may come into close contact with the sensitive plate. The
screen E is supported within the changing back immediately behind the light
tight slide F and is normally pressed forwards by springs e¹ of any suitable form
bearing against the flange of its mount e so that the screen will be then separated
by a sufficient interval from the foremost plate which rests against the ledges d
to admit of said plate being slid through the slot a in the top of the box A, into
or out of position for exposure, as the case may be.
Upon transverse shafts g mounted on the front of the changing box are pairs
of eccentric cams gl adapted to bear against the mount e of the screen, so that
when turned by milled heads & the cams will force the screen backwards until it
is in contact with the foremost plate, the throw of the cams being sufficient to
ensure this by slightly forcing the plate back from the ledges d against the
pressure of the springs.
The changing back is shown as holding twelve plates, the exposed and un-
exposed plates being separated by a travelling partition H.
The changing back is adapted to slide in the grooves of the camera body in the
usual way and it is opened for removing the plates and recharging by removing
either the front carrying the light tight. slide F and the taking screen or prefer-
ably by removing the back of the box.
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:-
1st. The hereindescribed improvements in changing backs for use in colour
'

page_text: screen photography wherein each of a succession of plates is moved into or out of
exposure position by a sliding motion in its own plane, which improvements con-
sist in providing for the approximation and separation of the screen and sensitive
plate in the manner and by means substantially as specified, whereby to avoid
sliding contact of the screen and plate.
2nd. The combination with a photographic changing back wherein the sensitive
plates are successively placed in, or removed from, exposure position by motion
of each plate in its own plane, of a ruled screen for colour screen photography,
the screen being mounted within the changing back immediately behind the
shutter, and of means whereby to effect the approximation and separation of the
plate and screen by the motion of the one in a direction perpendicular to the plane
of the other as described.
0211
1 1000
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.