COATING PHOTOGRAPHIC PLATES OR PAPER WITH GELATINE EMULSION
Year: 1884

page_text: COMPLETE SPECIFICATION.
I BENJAMIN JOSEPH EDWARDS of 6 The Grove Hackney in the County of
Middlesox Photographer do hereby declare the nature of my Invention for
COATING PHOTOGRAPHIC PLATES OR PAPER WITH GELATINE EMULSION and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:---
My Invention relates to an improved method of, and apparatus for, rapidly
applying an oven layer or coating of gelatine emulsion to sheets of glass, metal,
paper or other surfaces for photographic purposes.
In carrying out my Invention I make use of a trough or vessel containing the
emulsion and also of a metal roller working in bearings and made to revolve in
the trough which contains the emulsion with which the plates are to bo coated.
The length of the roller & trough must be slightly greater than the width of
the largest plate to be coated, and I fix the said roller and trough above and
across a travelling band or table which carries a continuous train of plates to be
coated.
In order to carry out my improved method of applying an even coating of
emulsion to the surface of the plates I make a scraper, preferably of sheet metal
or ebonite of suitable length and thickness and I fix this scraper parallel to the
roller so as to turn on pins or centres at, or near, the lower edge and by means of
a lever weight or springs the upper edge of the scraper is made to press against
the roller which revolves in the trough and I make the scraper of a convenient
shape and width and fix it at any suitable angle so that the lower edge rests upon,
or nearly in contact with, the surface of the plates, or paper, to be coated.
When the roller is made to revolve in the emulsion the solution which adheres
to the surface of the roller is taken off by the upper edge of the scraper towards
which the roller revolves-The emulsion then flows down the scraper to the
surface of the plates which are carried by the travelling band below, by this
means the plates are coated with an even layer of emulsion, the thickness of the
coating being regulated by the relative speeds of the roller and the travelling band
which carries the plates. In order to coat plates of various sizes I inako the above
described scraper removable and when required I replace it by another similar
scraper of the length required to correspond with the width of the plates to bo
coated. In order to admit of coating plates of different degrees of thickness I
make the centres, or pins at the lower edge of the scraper to work in bearings
fixed to a movable frame or pair of side rods pivoted or hinged at one end, and
carrying at the other end a roller or guide which rests upon the surface of the
plates as they pass beneath the scraper by this means the frame or rods carrying
the scraper rises and falls in proportion to the thickness of the plates, which are
thus allowed to pass under the scraper without obstruction, sometimes I attach the

page_text: scraper to the side of the trough and support the trough itself with the scraper
attached by means of pivots or bearings upon the movable frame, or side rods
before described.-In order to facilitate the cooling or setting of the emulsion after
it has been spread upon the surface of the platos I cause the travelling band
carrying the plates to pass over a table or slab artificially cooled by being kept 5
partially immersed in ice water or other cooling substance contained in a metal
tray within which the slab rests, and I cover the table or slab with a metal tank
containing ice or other cooling substance the tank is supported so that the under
side is only a short distance above the slab thus forming of the space between the
slab and the under sido of the tank or cover a cooling chamber or tunnel, through ]
which the plates pass. The cover or tank also serves to protect the plates from
light and dust after they have been coated with emulsion, by the abovo described
means the emulsion is rapidly set and the plates are very quickly ready to be
removed from the travelling band and placed in racks to dry.
In practico I prefer to make the travelling band in two separate portions of 1
unequal length that is I make two endless bands to travel in the same direction,
one of tliese bands which I call the coating band is used only to carry the plates
under the trough and scraper the plates then paas on to the other band which I
call the setting band and which carries the plates over the cold slab and through
the cooling chamber beforo described each of the above mentioned bands works 2
over a pair of rollers or drums fitted at one end with a driving pulley by means
of which the band is made to travel in the required direction, the setting or cooling
band being made to travel at a slightly greater speed than the coating band in
order to cause the plates to separate from each other as thoy pass into the cooling
chamber.
make
For the purpose of cleaning the back or under surface of the plates and removing
any emulsion which may have been spilled on to the coating band
another endless band of rubber cloth passing over a pair of rollers of suitable
diameter and I fix one of these rollers so that the cleaning band just touches the
coating band and the under sido of the plates after they are coated and I arrange
the other roller which is driven by a pulley so that it revolves in and carries the
endless band through a trough of warm water, by this means the back or under
surface of the plates is cleaned and the travelling bands which carry the plates are
kept clean and free from emulsion.
For coating paper with gelatine emulsion for photographic purposes I use my
improved machinery and apparatus substantially as above described and in a similar
manner with the exception that I dispense with the cleaning band and one of the
rollers and I use the other roller and the trough for the purpose of wetting or
damping the paper previous to its being coated and I uso another roller or squeegee
for the purpose of removing the excess of moisture and causing the paper to adhere
to the coating band before being passed under the trough and scraper, the paper
when coated passes through the cooling chamber after which it is cut into convenient
lengths and hung up to dry-In this manner a continuous length of paper can be
uniformly coated with a layer of gelatine emulsion of any desired thickness. In
using my improved machinery for coating plates or paper I actuate the rollers and
bands by means of pulleys of suitable diameters to give the speed required, and
driven by a gas engine or other suitable motor.
The endless bands may be made of india-rubber cloth or other suitable flexible
material-but I prefer to make the band which passes through the cooling
chamber of woven wire or thin metal plate in order to cool or set the emulsion as
rapidly as possible, sometimes instead of ice as above described I use a current of
cold air or vapour for the purpose of setting the emulsion on the plates or paper
in the cooling chamber, in any case this chamber or tunnel must be of sufficient
length to allow of the film of emulsion being perfectly set or stiffened before tho
removal of the plates or paper from the band, the length required will depend
greatly upon the speed at which the machinery is driven-with a moderate speed
find fifteen feet a convenient length for the refrigerating chambor or tunnel.

page_text: By moone of my improved machinery and appliances as above described,
photographic plates or paper may be prepared or coated with gelatine or other
ensitive emulsion with greater rapidity, certainty, and uniformity than has
itherto been practicable by any other method.
The accompanying Drawings show the various parts of my improved machinery
s described in the above Specification. I do not however confine myself to the
recise details of construction as shown or described, as the same may be somewhat
nodified without departing from the principle of my Invention.
A is the trough containing the emulsion.
аррпицея
above described,
photographic plates or paper may be prepared or coated with gelatine or other
ensitive emulsion with greater rapidity, certainty, and uniformity than has
hitherto been practicable by any other method.
The accompanying Drawings show the various parts of my improved machinery
s described in the above Specification. I do not however confine myself to the
precise details of construction as shown or described, as the same may be somewhat
modified without departing from the principle of my Invention.
A is the trough containing the emulsion.
B is the roller.
C is the movable and adjustable scraper.
D is the pivoted frame which carries the scraper and sometimes the trough.
E is the grinding roller.
FF is the travelling band for coating.
GGG are rollers carrying the travelling bands.
HH are similar rollers to carry the endless band for cleaning the plates.
J is the cleaning band.
K is the trough containing water for cleaning or washing the band.
LL is the travelling band carrying the plates through the cooling chamber.
M is the cooling chamber or tunnel closed at the sides and open at each end.
N is the cold slab over which the travelling band passes.
O is the metal tray in which the slab rests.
P. P. are the plates, before & after being coated.
R is the metal tank or cover over the cooling chamber.
S is the spring which presses the scraper against the roller.
X is a reservoir of emulsion for replenishing the trough.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to bo performed I wish it to bo
anderstood that I do not claim any novelty in the use of a roller revolving in a
trough of emulsion as hitherto used for applying a coating of emulsion to photo-
graphic plates and for other purposes, nor do I claim the use of an endless band
for carrying the plates as described in Swans Specification A.D. 1879 N° 4607
but I claim as my Invention,-
Firstly. The movable and adjustable scraper or scrapers of any suitable shape
or size, in combination with the roller and trough for the purpose of applying
the coating of gelatine or other emulsion to the upper surface of the plates as
lescribed.
Secondly. The cooling chamber or artificially cooled table or slab in combination
with the endless band carrying the plates in order to facilitate the setting or
cooling of the gelatine emulsion after it has been applied to the surface of the
olates or paper by means of the roller and scraper or by any other method.
Thirdly. I claim the endless band as above described for cleaning the back or
inder surface of the plates after they have been coated. I also claim the arrange-
nent of the pivoted frame or rods which carry or support the scraper and
ometimes the trough together with the roller or guide in order to allow of the
se of plates of various degrees of thickness.
June 5th, 1884.