Improvements in or connected with Optical Projecting Apparatus.
Year: 1897

page_text: Date of Application, 25th Jan., 1897-Accepted, 10th Apr., 1897
COMPLETE SPECIFICATION.
Improvements in or connected with Optical Projecting Apparatus.
I, FRANZ PAUL LIESEGANG; Merchant, of Cavalleriestrasse 13, Düsseldorf, in-
the German Empire, 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 :-
This invention relates more particularly to a device for changing the plates or
transparent pictures in optical projecting apparatus, and has for its object, to-
provide convenient means for changing the said pictures from a distance, so that
this operation may be performed by the person who is explaining the pictures.
My invention serves not only to release the pictures, but also to actuate one or
several flaps or other devices adapted to intercept the light rays, while the picture.
is being changed.
In the accompanying drawings,
Fig. 1 is a side elevation of a projecting apparatus embodying my invention;
Fig. 2 is a vertical section along line A-B of Fig. 1; Fig. 3 is the same after
the hinged flaps have closed the opening O;
Fig. 4 is a horizontal section along line C-D of Fig. 1.
The transparencies or picture slides are placed upright in a vertical guide.
frame r, so that they drop automatically, when the stop or retaining device is.
released. In the example shown by the drawings the release of the stop and the
closing of the flaps is effected by pneumatic pressure through a flexible pipe
provided with an air bag b, but the same result could be produced by other
known means.
The pressure on the air bag 6 sets in motion the slide block S, which in its turn.
closes the flap k by means of the connecting rod C. The flap k is connected with
the flap k¹ by means of a rod C¹, and acts on the same, so that the flaps turn in.
opposite directions and close the opening O simultaneously from both sides.
The slide block S has a flange or projection which during its motion comes in
contact with an arm d' of a short lever supporting the transparency or picture-
slide, together with its frame. Consequently the arm d, which had been held in its
place by an antagonistic spring f, is withdrawn, and the picture slide which had
been exposed to the light is allowed to drop, and its place occupied by another slide.
which had been inserted above the same.
The exposed slide is caught by a lug or cross piece g, situated at the bottom of
the guide frame, and is taken out sideways.
In the example shown by the drawings, the supporting arm d remains drawn.
back, as long as the pressure on the air bag b continues; but the arrangement may
be modified so that a pressure on the bag b will cause the lever d to recede for a
moment only, after which it will snap back without being influenced by the return
motion of the slide. The guide frame r may be adapted to hold several slides or
images at the same time, in which case the latter are preferably supported on an.
inclined race, so that their weight will not exert any undue influence on the-
plate which has to be exchanged, and the said picture slide may slide off without.
injury.
Instead of flaps k, k', other suitable shutters may be employed.

page_text: 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:
1. In an optical projecting apparatus, the combination of the device for changing
or releasing the exposed picture slide or transparency, with a pair of flaps or other
shutters adapted to close automatically, while the slides are being changed,
substantially as described.
2. In an optical projecting apparatus, the combination of a pneumatic slide-
changing device with an automatic shutter adapted to operate substantially as
described.
Dated this 23rd day of January 1897.
FAIRFAX & WETTER,
37 & 39, Essex Street, Strand, London, Agents.