AN IMPROVED APPARATUS FOR APPLYING A GELATINOUS, RESINOUS, OR SIMILAR COATING OR COVERING TO PHOTOGRAPHIC PLATES AND OTHER ARTICLES
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by William Robert Lake at the Office
of the Commissioners of Patents on the 21st July 1880. A communication
from abroad by George Eastinan, of Rochester, New York, United States of
America.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "AN IMPROVED APPARATUS FOR APPLYING A
GELATINOUS, RESINOUS, OR SIMILAR COATING OR COVERING TO PHOTOGRAPHIC
PLATES AND OTHER ARTICLES." [A communication from abroad by George
Eastman, of Rochester, New York, United States of America.]
This Invention relates to an improved apparatus by which an even layer of
gelatine, albumen, gum dextrine, varnish, or any similar substance may be applied
expeditiously to surfaces of glass, metal, wood, papier-maché, or other material,
and is chiefly designed to be employed in the preparation of photographic dry
plates by the gelatino-bromide emulsion process, or of gelatine plates employed in
collotype printing, but may be used for coating other surfaces which require the
application of a uniform layer of either of the above mentioned or similar
substances.
In carrying the said Invention into practice I provide an upper reservoir or
chamber to contain the emulsion or other coating material, and this reservoir is
made preferably with its sides inclined so as to converge toward the lower part,
and the narrow or lower end enters a pipe or small chamber which is in communi-
cation with a valve in a slotted tube, hereinafter described. The said reservoir
and chamber are surrounded by a hot water jacket, which also extends below the
slotted tube, and is in connection with a trough designed to receive the overflow
or drip. I provide an exit pipe in the jacket. In the end of the slotted tube
below the emulsion reservoir the valve above named is situated. It is provided
with a stem extending outside the tube, and on the outer extremity of this stem
there is a stud by which the said stem may be operated when the valve is to be
opened. A spiral spring causes the valve to remain closed whenever there is no
pressure upon the said stud. I also provide a set-screw, by means of which the
extent to which the valve will open may be regulated. There are also screws for
levelling the apparatus. The aforesaid slotted tube is arranged in a horizontal
position, and has on its upper side a slit or opening which is as long as the widest
or longest plate designed to be coated, and in order to adapt the tube for smaller

page_text: f.
plates or articles I provide a wedge which can be adjusted along the slit or slot so
as to curtail the length of the same as may be desired. It is found that the
following are convenient dimensions for the tube, namely, 8 inches in length, and
half an inch in diameter, the width of the slot being 3/2nds of an inch.
I provide the emulsion reservoir with some suitable filtering material, which may
be a linen bag, and in using the apparatus the emulsion poured into the reservoir
is filtered as it passes into the pipe or small chamber at the lower part thereof.
Upon the aforesaid valve being opened the emulsion passes into the slotted tube,
the valve being kept open long enough for the said tube to become full. A splinter
of wood dipped in alcohol and passed along the slit removes any bubbles which
may gather therein and causes the emulsion to flow evenly from the slit. This
splinter only requires to be used at the commencement of working. The tube being
full of emulsion the operator takes a plate by means of a pneumatic holder which
he holds in one hand and places the edge of the plate nearest to himself over the
slot in the tube. He then presses the stud on the valve-stem with his other hand,
and at the same time draws the plate steadily forward, and as the plate leaves the
slotted tube he releases the stud and the valve immediately closes under the action
of the spiral spring. The plate is then reversed and placed upon a suitable
support. The emulsion as it flows from the slot or slit in the horizontal tube
adheres to the plate in an even. film, the thickness of which depends upon the
velocity given to the plate, the inclination thereof, and the consistency of the
emulsion. The excess of emulsion falls into the trough below the tube, and is
drawn from this trough and returned to the reservoir as required.
I may somewhat modify the construction as follows, that is to say, the slotted
tube is supported upon a stand separate from the reservoir, and this stand is placed
in a pan designed to catch the drip or overflow. The reservoir in this case is placed
in communication with the slotted tube by means of an india-rubber pipe, which
is attached at one end to a glass tube at the lower part of the emulsion reservoir,
and at the other end to the slotted tube, and I provide a spring clip to compress
the tube and control the flow of emulsion in place of the valve above mentioned.
By employing my improved apparatus the emulsion may be used to within half
an ounce or an ounce, and is therefore very advantageous for amateurs; also for
professional photographers who make their own plates in small quantities. No
bubbles can get on the plates, as the excess of emulsion put back into the reservoir
is always re-filtered before it reaches the plates. The said apparatus may more-
over be easily cleaned, is not liable to get out of order, and is inexpensive, there
being no delicate mechanism in its construction. No "wave" is left at either end
of the plate, and there will not be any parallel streaks lengthwise thereon.
I have described the operation of the said apparatus as used for coating
photographic plates, but it is obvious that it may also be used for coating other
articles.