Improvements in or relating to Apparatus for the Exposure, Separation, and Storing of a Pack or Series of Photographic Films.
Year: 1893

page_text: Date of Application, 6th Feb., 1893-Accepted, 25th Mar., 1893
COMPLETE SPECIFICATION.
Improvements in or relating to Apparatus for the Exposure,
Separation, and Storing of a Pack or Series of Photographic
Films.
I, JOSEPH THACHER CLARKE, of Boston, Massachusetts, United States of
America, but at present residing at 3 College Road, Harrow, in the County of
Middlesex, Architect, 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:-
The chief purpose of my invention is to provide an apparatus, of the type
customarily described as a "changing box," by means of which a pack of sensitized
films or like flexible sheets may be exposed in connection with an ordinary photo-
graphic camera and may thereafter be transferred seriatim to a light-tight
receptacle, where they are stored in another pack or series. Certain features of
my invention, notably the differentiating indicator wheel, the interlocking pressure
board, and the means for attaching the selecting devices to their supports, are,
however, directly applicable to photographic film changing apparatus of other
types, such, for instance, as a self-contained hand camera. This adaptability will
be readily understood from a description of my improved changing box for photo-
graphic films, and will, moreover, be especially referred to hereinafter.
My invention is more particularly intended for the manipulation of films notched
upon two of their sides and arranged in alternate sequence, as described in Letters
Patent No. 23315 of 1892. A pack or series of such notched films: may be exposed,
separated and stored in my improved changing box without the intervention of
carriers or sheaths, and without previous separation of the films by the photo-
graphic operator. Means by which similarly notched films may be selected and
separated seriatim from a pack or series have been described by me in Letters
Patent No. 11891 of 1890, where they are referred to by the numerals D 12, and
the separating device which I employ in my present invention is, in principle,
identical therewith.
My improved changing box consists of two receptacles. The first of these
(which will hereinafter be referred to as the dark slide) contains the pack of
unexposed films, and is provided with a rebate or with catches for attachment to
ordinary photographic cameras, in the same manner as are the double backs which
are in everyday usage for the exposure of glass dry plates.
The second receptacle (hereinafter called the receiver) is adjoinable to the dark
slide, face to face, by a light-tight fitting, and serves to store the exposed films
which are transferred thereto.
The faces of both dark slide and receiver are closed by light-tight shutters which
may be withdrawn for the respective purposes of making the photographic
exposure, of transferring the films from one receptacle to the other, and of removing
the exposed films. The dark slide has an opening at its back to permit of the
insertion of the pack of unexposed films, together with a spring follower or back-
board serving to press the films forward against the selecting and separating
devices which hold the foremost sheet in register.
For the purpose of making an exposure upon the foremost film in the dark
slide the procedure is as follows: This receptacle is attached to a photographic
camera in the same manner as an ordinary double back; the shutter of the dark
slide is withdrawn ; light is admitted to the camera lens in the customary way, and
the shutter is replaced. The dark slide is then detached from the camera and
adjoined, face to face, to the receiver, being held in an approximately horizontal
position, face downwards. The shutters of both dark slide and receiver are with-
drawn together, and the film separating mechanism is operated by means provided

page_text: for this purpose upon the outside of the case. This releases the exposed film and
allows it to fall into the receiver. The shutters are thereupon replaced, and the
receptacles separated. These operations may be repeated as many times as there
are unexposed films in the dark slide. When it is desired to remove the exposed
films for the purpose of development in the photographic dark room, this may be
readily done by withdrawing the receiver shutter.
Having thus outlined the arrangement and performance of the apparatus, I
will, in order that my invention may be fully and clearly understood, describe
the details of the improved changing box with reference to the appended drawings,
where identical parts are designated throughout by the same numerals.
Figure 1 is a side view of the dark-slide and of the receiver, the two casing
_frames of the dark slide being separated for the purpose of showing their con-
formation and mode of attachment.
Figure 2 is a view of the back of the dark slide.
Figure 3 is a face view of the main casing (C Fig. 1) of the dark slide, the fore
casing (D Fig. 1) being omitted for the purpose of displaying the details of the
film separating mechanism. In this view no films are shown within the holder, the
spring pressure board resting directly upon the sorting teeth.
Figure 4 is a transverse section on the broken line Z-Z Figs. 2 & 3, of the dark
.slide and receiver adjoined. In this section a pack of unexposed films, together
with their spring pressure board, are shown in the dark slide, and a number of
exposed films are shown in the receiver.
:
Figure 5 is a longitudinal section, on the broken line Y-Y Figs. 2 & 3, of the
dark slide and receiver adjoined. In this section no films or pressure board are
represented.
Figure 6 shows the indicator mechanism, separately, as it would be seen were the
back of the dark slide removed.
The box or casing of the dark slide, A Fig. 1, is constructed, preferably of wood,
in two separable parts: the main casing C and the fore casing D, the latter fitting
closely over the former, as is shown in the sections Figs. 4 & 5. The film changing
mechanism, preferably of thin sheet metal, is, as will be presently described,
connected with the main casing C, while the face of the fore casing D is, for the
purpose of making a photographic exposure, applied to the back frame of the
camera, in the position otherwise occupied by the ground glass focussing screen.
Hence it will be evident that the distance between the back frame of the camera
and the plane of the foremost sensitive surface within the dark slide,--or, as it is
technically termed, the focal register,-may be adjusted by sliding the fore casing D
forwards and backwards upon the main casing C in a direction at right angles to
the plane of the sensitive surface. An adjustment in this sense is requisite in order
to render the dark slide adaptable to photographic cameras of various makes, which
differ somewhat in respect to the distance between the back frame and the surface
of the ground glass focussing screen. The distance which the casings may require
to be shifted in relative position is comparatively small, seldom exceeding one-
eighth of an inch, and the overlap afforded by the width of the fore casing D is
amply sufficient to permit of this. When the register has been accurately
adjusted, the fore casing D is permanently attached to the main casing by the
screws 1, 1, or by other suitable means. This improved method of adjusting the
register obviates the necessity of cutting away from or adding to the thickness of
the fore casing of the dark slide..
The main casing C of the dark slide A is provided with a lining 2, which forms
the support for the film changing mechanism and is rigidly attached to the walls of
the casing by screws 3, 3, or other suitable means. This lining (taking the place
of the holder in self-contained hand cameras) is made to somewhat loosely fit the
films which are to be introduced into the changing box, a space of one or two
hundredths of an inch being allowed on all sides for clearance.
The means more directly employed for retaining the foremost film in position and
for selecting and separating it from the remainder of the pack, consist of the

page_text: sorting teeth or stops 4, 4, which are formed by turning over at right angles suitable
projections of the movable plates or sliders 5, 5. The number and position of the
separate sorting teeth is determined by the number and position of the apertures or
notches in the edges of those films which are to be manipulated by the film changing
apparatus. The length of the sorting teeth is somewhat less than the depth of the
said notches, while their width may be advantageously made about one third that
of the notches. In the operation of film changing these selecting devices move to
and fro along the sides of the holder or lining, thus causing the sorting teeth to
correspond, in their positions at the end of each travel, to the apertures or notches.
in the edges of the films of odd or of even series. When the sorting teeth no longer
bear upon the projections between the notches in the foremost film this film is
released from support and retention thereby, and falls from the containing
receptacle. This mode of discharging the separate sheets of a pack or series of'
sensitized films is now widely known in photographic practice, being customarily
referred to as the "Frena" system.
The sliders 5, 5, are attached to the lining 2 by a fitting of novel design, which
may be carried into effect in the following manner. The overlapping catches or
hooks 6, 6, which prevent the sliders from moving out of position, and which are
so spaced as not to interfere with the lateral play of the sorting teeth 4, 4, are
formed by strips of metal projecting from the outer edge of the lining 2 and bent
twice around at right angles so as to assume a form which can be compared to
nothing so well as to that of a Greek gamma with a serif. The sorting teeth or
stops 4, 4, slide to and fro between these hooks 6, 6, with their lower, or inner,.
surfaces in contact with the outer edge of the lining, the distance between the said
outer edge and the inner surfaces of the hooks 6, 6, being equal to the thickness of
the sorting teeth 4, 4. For the purpose of inserting the sorting teeth into the
hooked projections 6, 6, gaps or slots 7, 7 are cut into those parts of the edge of
the lining 2 which are between the hooks 6, 6, but are not traversed by the sorting
teeth 4, 4, in that movement which they perform to and fro for the purpose of film
changing. These slots 7, 7, have a depth greater by a small clearance than the
thickness of the sorting teeth 4, 4, plus the length of the reversed ends, or serifs as
they have been termed, of the hooked projections 6, 6. In fitting the sliders 5, 5
to the lining 2 the sorting teeth are inserted into the bottom of the gaps 7, 7; the
sliders are pressed closely against the outer surface of the lining; are then pushed
upwards until the fore edge of the sliders, between the sorting teeth, is engaged in
the hooks 6, 6; and are finally moved along in a longitudinal direction, so that the
lower or inner surfaces of the sorting teeth rest upon the outer edge of the lining:
the sliders being thus confined between this edge and the hook of the projection 6, 6.
This method of attachment, while working securely and smoothly on broad surfaces,
has the advantages of being readily effected, without the employment of screws,
rivets, or other adjuncts, and of being as readily detached for the purpose of
adjustment or repairs.
It will be obvious that this improved means of fitting the sliders to their supports
is directly applicable to the holders of other forms of apparatus which may serve
the purposes of film changing by means of sorting teeth. As regards this feature
of my invention it is immaterial whether the support for the sliders is the lining of
a changing box or the sides or frame of the film holder of a self-contained hand
camera. Entire freedom from any tendency of the sliders to tilt and to travel
unevenly may, in adaptations where the outside support of a casing is not available,
be secured by lengthening the re-entering ends or serifs of the hooked projections 6, 6,
so that these ends form a guide for the greater part of the back or outer surfaces of
the sliders 5, 5.
In my improved changing box the sliders 5, 5, are connected at one end by a
cross bar 8, rigidly affixed thereto. By the traction of this cross bar in a direction
parallel to the longer axis of the receptacle the sliders 5, 5, together with their
sorting teeth 1, 4, are caused to move along the sides of the lining 2, simultaneously
and in the same direction. In order to operate the cross bar 8 by means of a

page_text: handle or knob projecting upon the outside of the casing and sliding to and fro in a
direction transverse to the said longer axis, an intervening push plate 9 is intro-
duced in connection therewith, contiguous to the cross bar 8 and working in a plane
parallel to it. This pusli plate 9 is pierced by two diagonal slots, 10, 10, in which
play two pins 11, 11, projecting from the cross bar 8. The angle of said slots 10, 10,
and the position of said pins 11, 11, upon the cross bar 8 are so determined that
when the sorting teeth 4, 4, are at one end or the other of their travel, in a position
to discharge the films of odd or of even series, the push plate 9 is at one end or the
other of its travel in a transverse direction and the pins 11, 11, are at the corre-
sponding ends of the diagonal slots 10, 10.
A lobe of the push-plate 9 projects through a slot 12 in the end wall of the
casing, and is provided, upon the outside of the dark slide, with a handle or
knob 13. By sliding this knob to and fro in a transverse direction, the film
changing mechanism may be operated from the outside of the case in the manner
above described.
In order to prevent light from having access to the films within the dark slide
through the slot 12, this slot is covered by a sliding plate 14 of sufficient length to
entirely obscure the aperture in both positions of the handle or knob 13, to which
it is affixed and together with which it moves.
To the back of the casing of the dark slide, immediately beneath the push
plate 9, is attached the indicator wheel 15, turning loosely upon the axis 16. This
indicator wheel, being designed to differentiate invariably between the discharged
films of odd and even number, is of a peculiar arrangement and method of operation.
The wheel 15 is provided with one-half as many teeth as it has numerals engraved
upon it, and is operated by a species of escapement formed by the two pallets 17, 17,
which project downwards at right angles from the sides of the push plate 9 and
move together with it. In Fig. 6 these pallets are represented at their extreme
position to the right; in either of the normal positions of repose they will serve to
lock the indicator, as shown, this locking taking plate alternately on diametrically
opposite edges of the five-toothed wheel. Hence it will be apparent that, as the
push plate is shifted to and fro in the act of film changing, the pallets 17, 17, must,
at each operation, move the indicator wheel 15 around a distance of one-half a
tooth, or, in other words, from one numeral to another, thereby effecting a
differentiation by odd and even numbers which cannot be disarranged and which
serves to designate the films of alternate sequence forming the improved pack or
sequence described in the before mentioned Letters Patent No. 23315 of 1892.
Owing to this invariability of operation it may be at once ascertained, from the
reading of the indicator, whether the first film to be introduced into an empty dark
slide should have its notched corners or its unnotched corners placed towards that
end of the slide which bears the indicator.
It is obvious that an indicator of this improved design may be directly and
advantageously employed in film changing apparatus of other types intended to
manipulate films notched and packed in accordance with this system. For instance,
in a self-contained hand camera for the separation of a pack or series of such
notched films an indicator wheel of substantially identical design, advancing one-
half a tooth at each step and operated by pallets or similar escapements connected
with any suitable movable part of the film changing mechanism, will serve to give
the same indication as regards the alternate positions of the sorting teeth and the
sequence of the films of odd or even series.
In my improved dark slide the numerals of the indicator wheel 15 are visible
from the back of the casing, through the inspection hole 18. These numerals may
be rendered more easily legible by the insertion of a small plano-convex lens in
the inspection hole.
The films contained within the dark slide A are pressed forwards, so that they
rest against the sorting teeth 4, 4, by means of a pressure board 19, provided with
aspiral spring 20. This pressure board also serves to lock the film changing
mechanism as soon as the last film has been discharged from the holder. For this

page_text: purpose the edges of the pressure board 19 are provided with two series of sinkings
or pans 21, 21, and 22, 22, corresponding to the alternate positions occupied by the
sorting teeth 4, 4, when at the ends of their travel. These sinkings 21, 21,
and 22, 22, are of sufficient depth to engage the sorting teeth 4, 4, and to prevent
them from being shifted to and fro by the film changing mechanism. The
photographer will thus be warned that the last film within his dark slide has been
discharged, inasmuch as it will be impossible for him to thereafter shift the position
of the handle or knob 13 upon the outside of the case. This warning is of
advantage, as it will deter the photographer from attempting to make a series of
exposures after his supply of films has been exhausted.
It is obvious that a pressure board provided with pans or sinkings such as 21, 21,
and 22, 22, may be employed with like advantage in film changing apparatus of¸
other types, as, for instance, in the holders of self-contained hand cameras.
The pack of unexposed films and the spring pressure board are introduced into'
my improved dark slide through an aperture in the back of the case which is
closed by a light-tight door or flap 23, provided with a hinge 24, and secured by
any suitable form of catch, such as the hook 25, and the eyelet 26.
For the purpose of making a photographic exposure upon the foremost film'
contained therein, the dark slide may be attached to any ordinary camera by the
rebate 27 or by such other means as are customarily employed for this purpose.
The exposure aperture of the dark slide is closed by a dark slide shutter 28,
formed of thin sheet vulcanite or other suitable material. In making a
photographic exposure, after the dark slide has been attached to a camera as before
described, this shutter may be entirely withdrawn from its receptacle, a spring
light-occluding strip 29 closing the end of the slot when the shutter is removed.
Such light-occluding strips are in common usage, and well-known to those skilled
in the art.
The handle piece 30 of the dark slide shutter 28 is provided upon both sides.
with two catch grooves 31, 31, corresponding to the positions occupied, when the
push plate 9 is at one end or the other of its transverse travel, by a bolt 32 which
projects from the push plate knob 13. These catch grooves 31, 31, serve, when
the dark slide shutter is closed, to engage and retain the bolt 32 in one or the
other of its normal positions, and thus to prevent the handle knob 13 from being
shifted, through accident or meddlesomeness, before the dark slide shutter has
been withdrawn. As the dark slide shutter may be entirely detached from its
receptacle for the act of making an exposure, and as it is convenient to be able to
replace it in either position, the two sides of the handle are made alike and
reversible.
The receiver B, shown in side view in Fig. 1, and in two sections in Figs. 4 & 5,
is adjoiuable to the dark slide A, face to face, for the purpose of transferring
the exposed films. A light-tight fitting between these two receptacles, when thus
adjoined, is provided by the rim or flange 33, which extends around all four sides
of the face of the receiver, and fits closely into the exposure aperture of the fore
casing D of the dark slide A.
When united for the process of film changing the two receptacles are securely
pressed together by the hand of the operater, being naturally grasped near those'
ends into which the shutters slide. In order to prevent the farther end of the
receiver B from separating from the dark slide A. during this process, and thus
admitting light to the sensitive films, an automatic locking device is provided.
This may conveniently assume the form of the catch plate 34, affixed by screws or
other suitable means to the face of the dark slide A, and the hook plate 35, affixed
in like manner to the face of the receiver B. When the two receptacles are:
adjoined the projecting lip of the hook plate 35 slides or hooks under the edge of:
the catch plate 34, and thus holds the receiver B securely locked to the dark
slide A. Should want of space render it desirable, the light-tight flange 33 may
be omitted from the farther edge of the receiver aperture, inasmuch as the, catch
plate 35 will itself prevent the admission of light at this end.

page_text: The aperture of the receiver B is closed by a receiver shutter 36. This shutter,
while capable of being withdrawn sufficiently to permit of the transference of
films to the interior of the receiver, is constructed with an upturned or thickened
end or block 37, or with other suitable means for preventing it from being entirely
withdrawn and removed from its receptacle.
The handle piece 38 of the receiver shutter 36 is furthermore provided upon its
face with one or more projections or locking pins 39 which correspond in relative
position to, and, when the dark slide A and the receiver B are adjoined for the act
of film changing, engage with, the slots or sinkings 40 in the handle piece 30 of the-
dark slide shutter 28. By this means the dark_slide-shutter 28 and the receiver
shutter 36 are coupled-together so as to be withdrawn or replaced by one and the
same movement. The importance of these two shutters being simultaneous in
their action during the process of film changing will have become sufficiently
evident from the foregoing description. Should either be withdrawn alone, and a
film be thereupon discharged, this film would infallibly be exposed to light and
spoiled during the subsequent operations.
Another useful feature of my invention is secured by the combination of the
shutter coupling device, described in the foregoing paragraph, with the block 37
which prevents the receiving shutter 36 from being entirely withdrawn. Upon this
is dependent the peculiar operation of the dark slide shutter 28, which may be
entirely withdrawn and separated from its receptacle when the dark slide A is not
adjoined to the receiver B for the process of film changing, but which cannot be
entirely withdrawn and separated from its receptacle when the dark slide is thus
adjoined to the receiver. The dark slide shutter 28 is not in itself provided with
means for preventing it from leaving the groove in which it slides, as the entire
withdrawal of this shutter will generally he found to be convenient and advan-
tageous in making an exposure: the dark slide being for this purpose attached to
the back of a photographic camera, and often covered with a focussing cloth.
During the act of film changing, on the other hand, the dark slide shutter 28 is
automatically coupled, as before explained, to the receiver shutter, and as this
latter cannot be entirely withdrawn and removed from the grooves in which it
slides, by reason of the block 37, neither can the former when coupled thereto.
By this arrangement the work of the photographer in changing an exposed film is
facilitated; he is not obliged to reinsert the two shutters into their grooves, which
would require a certain amount of time and attention, neither is he liable to inter-
change the two shutters 28 and 36, as might occasionally occur if both were
detachable from their receptacles.
Thus a cycle of safeguards assures the correct action of my improved changing
box for packs or series of sensitized films. As has been hereinbefore set forth, the
dark slide and the receiver cannot be adjoined face to face without interlocking
automatically; the two shutters, being coupled together, cannot be withdrawn.
separately when their receptacles are adjoined; the dark slide shutter can be
detached for an exposure, but is not liable to become so during the act of film
changing; the film changing mechanism cannot be put in motion until the dark,
slide shutter has been withdrawn, nor can this shutter be replaced until the handle
of the film changing mechanism has been moved to the end of its travel, so as to
occupy one of its two normal positions; it is impossible to operate the film changing
mechanism after the last film has been discharged from the holder; and, finally,
the indicator cannot be disarranged so as to fail to differentiate between the films
of odd and even series.
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:
1. In a photographic changing box the combination with a dark slide A, adapted
to expose and to discharge seriatim a pack or series of sensitized films without the
intervention of sheaths or carriers, of a receiver B interlocking with the dark

page_text: slide when adjoined thereto for the act of film changing, substantially as and for
the purposes herein before set forth.
2. In a photographic changing box for the exposure, separation and storing of a
pack or series of sensitized films the combination with a dark slide A and a
receiver B of a dark slide shutter 28 and a receiver shutter 36, the said shutters
coupling together by the conjunction of the two receptacles for the act of film
changing, substantially as and for the purposes hereinbefore set forth.
3. In a photographic changing box for the exposure, separation and storing of a
pack or series of sensitized films the combination with a dark slide A and a
receiver B of a dark slide shutter 28 which can be entirely withdrawn and separated
from its receptacle when the dark slide is not adjoined to the receiver for the act of
filin changing, but which cannot be entirely withdrawn and separated from its
receptacle when the dark slide is adjoined to the receiver for the act of film
changing, substantially as and for the purposes hereinbefore set forth.
4. In a photographic dark slide for the exposure and separation of a pack or
series of sensitized films the combination of the two separable casings C & D so
adjustable in their relative positions as to vary the distance between the plane of
the face of the fore casing D and the parallel plane of the foremost sensitive
surface supported by and within the main casing C, substantially as hereinbefore
illustrated and described.
5. In a photographic dark slide for the exposure and separation of a pack or
series of sensitized films a dark slide shutter so interlocking with the film changing
mechanism that this mechanism cannot be operated until the said dark slide
shutter has been withdrawn, substantially as herein before illustrated and described.
6. In a photographic dark slide for the exposure and separation of a pack or
series of sensitized films, the combination with the sliders 5, 5, the cross bar 8
rigidly affixed thereto, and the push plate 9, of means such as the slots 10, 10, and
the pins 11, 11, for conveying a longitudinal movement to the cross bar and sliders
by a transverse movement of the push plate from the outside of the case,
substantially as hereinbefore illustrated and described.
7. In a photographic apparatus for the exposure and separation of a pack or
series of sensitized films the combination with the sliders 5, 5, having sorting
teeth 4, 4, of the hooks, 6, 6, and the slots 7, 7, serving for the attachment of the
sliders to their supports, substantially as hereinbefore illustrated and described.
8. In a photographic apparatus for the exposure and separation of a pack or
series of sensitized films, an indicator wheel, such as 15, operated by the film
changing mechanism so as to advance one-half a tooth at each movement, thereby
invariably differentiating between the alternate positions of the film selecting
devices by odd and even numbers, substantially as hereinbefore illustrated and
described.
9. In a photographic apparatus for the exposure and separation of a pack or
series of sensitized films a spring pressure board such as 19 provided with means
such as the sinkings 21, 21, and 22, 22, for interlocking with the sorting teeth 4, 4,
and thereby arresting the action of the film changing mechanism as soon as the last
sheet has been discharged from the film holder, substantially as hereinbefore
illustrated and described.
10. The photographic changing box for the exposure, separation and storing of
a pack or series of notched films, substantially as hereinbefore described and
illustrated in the several figures of the accompanying drawings.
Dated this 6th day of February 1902
JOSEPH THACHER CLARKE.