CHANGING THE SLIDES OR PICTURES IN THE MAGIC LANTERN AND FOR EXHIBITING DISSOLVING VIEWS WITH A SINGLE LANTERN
Year: 1884

page_text: I BENJAMIN JOSEPH EDWARDS of No. 6 The Grove Hackney in the County of
Middlesex Photographer do hereby declare the nature of my Invention for
CHANGING THE SLIDES OR PICTURES IN THE MAGIC LANTERN AND FOR
EXHIBITING DISSOLVING VIEWS WITH A SINGLE LANTERN 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 exhibiting
a series of slides or pictures in the optical instrument commonly known as the
magic lantern and has for its object the changing of the slides or pictures
mechanically by one simple movement of a lever or handle without any movement
being perceptible upon the screen. This effect is produced by means of my
Invention with one single lantern in a manner which is more pleasing and less
fatiguing to the eyes than the usual method of dissolving views with two
lanterns.
+
In order to accomplish this object I first shut off the light and consequently the
picture from the screen by gradually closing or covering the front lens or objective
of the lantern, and during the momentary interval of darkness thus produced I
rapidly change the slide or view and substitute another one previously placed in
position and then by gradually uncovering the lens I allow the new picture to fall
upon the screeu. By means of my apparatus these various operations of closing
the lens, changing the slide or view, and re-opening the lens are performed
mechanically by one single continuous movement of a simple arm or lever. The
improved apparatus consists of a slideholder carrying two slides which by moving
the handle or lever are alternately placed in position in front of the condenser,
in connection with a screen or dissolver which alternately closes and opens the
lens.
•
In carrying out this my Invention in the simplest possible manner I fix a
short rod or spindle turning on its axis parallel to the optical axis of the lantern
and which spindle is rotated by a handle or lever. At the outer end of this rod
I attach an opaque screen projecting in front of the lens so as to cover or close it, a
certain portion of the screen being cut away so that during a part of the revolution
the lens is uncovered and the light, and consequently the picture is allowed to fall

page_text: upon the screen, and by means of suitable excentric gearing I connect the rod.
carrying this opaque screen to a swinging or sliding frame carrying two slides or
pictures arranged in such a position in the frame or carrier that when the lens is
not covered by the opaque screen or dissolver one or other of the pictures shall be
at rest in its proper position in front of the condenser, and I arrange the gearing
or excentric motion so that the sliding or swinging frame shall be set in motion
and the picture changed during the momentary interval of darkness caused by
the passage of the opaque part of the screen or dissolver in front of the lens. In
order that the darkening of the picture shall be gradual I make the aperture in
the dissolving screen with serrated edges; but I prefer instead of this revolving
screen to close and reopen the lens by means of two thin sliding plates or
diaphragms working in grooves attached in front of the lens, and I make the
sliding plates with both ends concave and I suspend these plates by means of a
cord passing over and once round a drum or pulley fixed to the rod in place
of the opaque screen before described. One of these plates being attached
to each end of the cord they balance each other one rising and the other
falling as the drum revolves. I make the plates of sufficient width to cover the
opening of the lens and of sufficient length to keep the light entirely shut off
during the time the position of the slide carrier is being changed and 1 arrange
that when the upper concave edge of the rising plate comes in contact with the
drum the lower concave end of that plate is just free of the upper edge of the
lens while the upper concave end of the falling plate is just clear of the lower edge
of the lens. For holding the slides or pictures in position I use a double carrier
of the usual construction but arranged by means of guides or runners to travel
easily in metal grooves attached to a second frame which is firmly fixed in the
lantern immediately in front of the condenser. The slide holder or carrier carrying
the slides or views is moved from side to side by means of a lever slotted at its
lower end and working on a pin fixed to the central division of the double slide
holder, the upper end of this lever is firmly fixed to a rod or spindle turning on
its axis and placed parallel to the spindle carrying the drum before described. In
order to connect the rod and lever which work the slideholder with the handle
and rod which works the drum and dissolving plates I adapt and make use of a
modification of the mechanism commonly used for regulating the winding of
ordinary Swiss watches in the following manner :- -To the drum spindle I fix a
circular disc of metal having a single tooth or pin working in a corresponding
recess or depression in another disc or segment of a wheel fixed to the spindle
which carries the slotted lever working the slideholder. This second wheel or
segment of a wheel has a recess cut in it in which the tooth of the disc on the
drum-spindle works and on each side of this recess a concave indentation of the
same radius as the disc on the drum-spindle. By this means the lever working
the slideholder is not only not moved by the rotation of the drum-spindle (except
during the time that the tooth is engaged in the recess,) but is securely locked by
the close contact of the periphery of the one disc with the circular indentations of
the other. The apparatus is so arranged that during the first portion of the
movement of the handle or lever the rotation of the drum causes the lens to be
gradually closed and kept closed by the passage of the dissolving plates one over
the other during the time the slide carrier is being shifted, when the latter portion
of the rotation of the drum-spindle uncovers the lens, the handle or lever being
arranged to describe about a semicircle during the completion of these movements.
Should any adjustment of the distance travelled by the slide carrier be required it
is readily increased by raising the position of the pin on the central division of the
slide-carrier or lessened by lowering it. During the time that the lens is uncovered
and a picture consequently being shown upon the screen the other half of the
slideholder is projected clear of the lantern so that the slide which is not being
shown can be removed and another substituted in its place the slideholder being
by the action of my improved apparatus securely locked so that the operation of
changing the slide does not disturb the slide being exhibited. By this means and

page_text: by alcately moving the name on the fens is alternately
covered and uncovered and the slide or picture is changed invisibly during the
moment of eclipse.
The accompanying Drawings clearly show the arrangement of the various parts
of my apparatus.
Fig. 1. is a side elevation.
Fig. 2 shows a front view, the dotted lines represent the opaque serein and
swinging slide holder first described.
A is the handle or lever.
B is the drum or pulley.
CC is the cord.
DD are the dissolving plates or diaphragms.
E is the disc or single-toothed. wheel.
F is the corresponding segment which works the slide changing lever.
G is the spindle carrying the slotted lever.
H is the spindle carrying the drum or pulley.
J is the moveable slide holder.
K is the frame or carrier fixed to the lantern.
L is the slotted lever moving the slideholder.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is
1st The closing and opening of the lens or objective of the lantern and
mechanically or automatically changing the slides or pictures by one continuous
movement of a lever or handle substantially as hereinbefore described.
2nd The special arrangement above described for opening and closing the lens
by means of plates or diaphragms worked by a cord and pulley or drum.
3rd The adaptation or application of the mechanical contrivance employed in
watches for the purpose of changing the slides in combination with the mechanism
for covering and uncovering the front lens of the lantern substantially as
herein before described.
Din Couth Jo of Tule. 1001.
B. J. EDWARDS.