Improvements in or relating to Packs or Series of Sheets with Notched Edges, more particularly applicable to Packs of the Flexible Sensitized Films in Photographic Usage.
Year: 1892

page_text: Date of Application, 19th Dec., 1892-Accepted, 21st Jan., 1893
COMPLETE SPECIFICATION.
Improvements in or relating to Packs or Series of Sheets with
Notched Edges, more particularly applicable to Packs of the
Flexible Sensitized Films in Photographic Usage.
I, JOSEPH THACHER CLARKE, Architect, of Boston, Massachusetts, a citizen of
the United States, but at present residing at 3 College Road, Harrow, Middlesex,
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 relates to packs or series of such sheets or films as are notched
upon opposite edges so as to be capable of separation by means of selecting devices
working in connection with a suitable holder. Packs of films of this type,
together with selecting devices for manipulating them, were first described by me
in a Specification bearing Number 11891, of 1890, and are now widely known in
practice.
Hitherto the separate sheets of which such packs have been composed have
been of two distinct patterns, non-identical in outline, the notches of the one
pattern differing from those of the other as regards their situation relative to that
axis of the sheet or film which is at right angles to the serrated edges.
The beforementioned selecting devices are, in certain apparatus, employed upon
two sides only of the holder, and in consequence, two edges only of those sheets or
films which are to be operated upon therewith require to be notched. In packs
composed of sheets of this form it has been found desirable,-(in order to avoid
the confusion of that four-fold differentiation which would result from the existence
of a dissimilarity between the tops and the bottoms, as well as between the two
distinct patterns of the sheets or films),- to make each of the beforementioned
patterns absolutely symmetrical as regards that axis of the sheet which is at right
angles to the serrated edges.
A different method may, however, be followed in the arrangement of such packs
or series of notched sheets. This method is attended with practical advantages,
hereinafter specified, and forms the subject of the present application.
My invention provides a new and improved pack or series of sheets or films, in
which each individual sheet is of identical outline, the differentiation between the
sheets of odd and even number in the pack being dependent upon an alternate
reversal of the ends of the sheets. This principle I carry into effect by so designing
the outline of the separate sheets or films that the notches correspond alternately
with the projections when the alternate sheets are revolved 180° in the planes of
their faces, or, in other words, when the alternate shects are reversed as regards
top and bottom.
In order that my invention may be fully and clearly understood I will now
particularly describe, with reference to the appended drawings, the new and
improved pack or series of sheets or films.
Figure 1 represents the outline of a sheet or film adapted to be arranged in a
pack or series according to my invention. The axes of the notches are indicated
by the broken lines N, N¹, and N³, and N. The axes of the corresponding
projections are indicated by the broken lines P, P1, P2, and P'. Assuming
the electing devices or stops to be placed at equal distances along the sides of the
holder into which the pack or series of sheets or films to be introduced, the
distances between the axes N and N¹, N' and N2, and N' and N³, will be likewise
equal. The distances between the axes N and P, N¹ and P', N' and P', and N'
and P, will each be equal to one-half the distance between the axis N and N'.
The axis of the first notch N from the end of the sheet or film marked L is equal

page_text: to the distance of the axis of the last projection P³ from the end of the sheet
marked R, being in both cases as great as the distance from the axis N to P plus
the width of the selecting device or stop, and plus a small allowance for clearance.
It thus results that that main axis of the pack which is at right angles to the notched
edges, namely C-C, is equidistant from the axes P and N³.
Figure 2 represents the outline of the same sheet or film revolved 180° in the
plane of its face. By this reversal as regards right and left the axes N and P³, P
and N³, N¹ and P2, and P¹ and N', become congruent, or, in other words, identical
in position as regards the main axis C-C.
Figure 3 represents the side or edge of a pack or series of sheets or films thus
notched and arranged in alternate sequence as regards the positions of the ends,
according to my invention. A pack or series of sheets or films thus arranged is
adapted for manipulation by the means set forth in the Specification No. 11891 of
1890, before referred to, it being assumed that the selecting devices on both sides
of the holder move simultaneously in the same direction, as is now customary in
practice, and well known to those skilled in the art.
It will be evident, on analysis, that my new and improved pack or series of sheets
or films thus involves a fundamentally different principle from that obtaining in the
pack hitherto in use, which it is intended to supplant. Whereas in the old pack
the differentiation between absolutely symmetrical sheets was effected by the
adoption of two distinct patterns, in the new pack the differentiation is effected
between shects of identical pattern by means of axial dissymmetry in design,
coupled with reversal as regards relative position.
It is obvious that the number of the notches and of the corresponding projections
upon the separate sheets or films which form the improved pack or series may be
increased or diminished without departing from the spirit of my invention. This
number will depend upon the number of selecting devices or stops working upon
the sides of the holder into which the pack or series of sheets or films is to be
introduced. Thus the distance of these selecting devices, from axis to axis, having
been found by experiment to answer well when equal to about five-sixths of an
inch, the notches on each side of a sheet or film four and a quarter inches in length
may advantageously be made five in number, as shown upon the accompanying
drawings. In a sheet six and a half inches in length the notches may be eight in
number, and so on.
It is equally obvious that, if the selecting devices or stops upon the opposite
sides of the holder be caused to work simultaneously in reverse directions, instead
of in the same direction, the packs or series may be composed, in accordance with
my invention, of sheets or films in which the notches upon one side are opposite to
the projections upon the other.
My invention is more particularly applicable to packs or series of flexible
sensitized films, intended for exposure in photographic cameras. It is well under-
stood that such translucent films must be provided, during exposure, with a backing
impermeable to actinic light. This may be done either by providing the back of
the film itself with a non-actinic coating, which may subsequently be removed, or
by interleaving the separate sensitized films with sheets of opaque paper or card-
board. When such separate sheets are introduced into a pack of sensitized films
arranged according to my invention, it is evident that, if one movement of the
selecting devices is to discharge both film and backing, each backing sheet must be
notched in the same manner and placed in the same relative position as that
sensitized film behind which it is situated.
Packs or series of sheets or films arranged according to my invention possess two
chief advantages over those which have hitherto been in use.
In the first place, owing to the fact that the axes N and P³ Figure 1 are at equal
.distances from the main axis C, the support afforded to the film by selecting devices
such as those shown in the beforementioned Specification No. 11891 of 1890 will
be equally efficient as regards the ends of the sheets or films, whether these
selecting devices are situated in the axes N, N', N³, and N³, so as to support the

page_text: sheets or films designated by even numbers on Figure 3, or whether the selecting
devices are situated in the axes P, P1, P2, and P³, so as to support the sheets or
films of odd number. This is an improvement of distinct practical importance,
particularly as regards the larger sizes of flexible photographic films. The more
evenly such films are supported, and the nearer to the ends the pressure of the
spring back-board is taken up, the less will be the liability of the sensitized sheets
to present a wavy surface to the lens, or to become so curled as to interfere with
the action of the selecting devices.
In the second place, all the separate sheets of the pack or series may be cut with
one and the same die, the differentiation between those of odd and even number in
the pack being brought about by the simple process of reversal as regards right
and left, as hereinbefore explained. Thus dispensing with the use of a second
die a considerable economy is effected, not only in the outlay for appliances, but,
more especially, in the labor involved in the preparation of the packs.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
The improved pack or series of notched sheets or films of identical pattern,
arranged with ends reversed in alternate sequence, the notches upon the sheets
of odd number corresponding, when thus arranged, with the projections upon the
sheets of even number, substantially as and for the purposes hereinbefore set
forth.
Dated this 19th day of December 1892.