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1954-55 Theatre Catalog, 12th Edition, Page 204 (168)

1954-55 Theatre Catalog, 12th Edition
1954-55 Theatre Catalog
1954-55 Theatre Catalog, 12th Edition, Page 204
Page 204

1954-55 Theatre Catalog, 12th Edition, Page 204



(Model SP. 1) or a manual changer (SM. 1).

In the automatic slide changer the slides are inserted around a disk and, depending on its dimension, six, 12, or 18 slides can be used.

An adjustable time device exposes each slide for five, seven, 10, or 20 seconds. It operates in the following sequence:

-an image is projected on the screen

-the timing device comes into action

ea shutter blacks out the image%losing from both sides like a theatre curtain.

--the disk rotates to bring the next slide into the optical system (1/2 second)

ethe shutters open briskly

(1/3 second)

(1/6 second)

ethe new image is projected on the screen..

Total time 1 second

The rotation of the disk is not visible

on the screen as it is done entirely during the black-out period.


An electric motor drives two blowers which cool the slides and the 3000 watts bulb. The capacity of the blowers is 220 cubic feet per minute. One of the blowers has its outlet placed just under the slide which is in the light beam. As soon as the slide enters the light beam it starts to be cooled by the air stream. After cooling the slide, the air stream cools the disk holding the slides. Therm fore, the other slides mounted in the disk also get cooled. Both sides of the slides

FIGURE 3. is an example of projection on a wall with the slide projector on a: root. Optical axis makes angle 80 degrees with horizontal.


get the impact of the cold air. Part of the air blown by the slide blower cools the optical system enclosed in a housing which remains absolutely cold even after several hours operation.

The second blower has its outlet exactly under the 3000 watts bulb. The air strikes the glass bottom of the bulb and moves vertically toward the top of the bulb and comes out of the lamphouse through a mesh screen without being slowed down by any obstruction.

The sides and the back of the lamphouse have double walls to increase the cooling and reduce the temperature of the outside of the lamphouse. Its front is cooled indirectly by the slides blower.

This very strong cooling system is necessary because in certain applications the slide projector will operate without interruption for hoursseven 24 hours a day. For such application of projection of theatre backgrounds the slides have to resist the projection heat for a long period of time without breaking.


The slide projector is built to "withstand corrosion and the action of atmospheric agents. The castings are

FIGURE 2. presents a diagram showing how the width at the image compares with the distance between the wide angle projector and the screen.

made of aluminum. The steel parts, which are not made of stainless steel, are Parkerized, plated, or specially painted; to assure long life even when used in unfavorable weather conditions.

To protect the slide projector from the direct impact of rain, snow, and wind it is recommended that it be placed in a wooden or metal "box" slightly larger than the projector itself.

The motors, gears, and other mechanie cal parts have been engineered with the idea that the automatic slide changer would operate for thousands of hours (or several years) with a minimum of wear and maintenance. When the bulb is to be replaced every 100 or 150 hours, the maintenance man will spend a couple of additional minutes to clean the lenses and put a few drops of oil to guarantee smooth operation of the automatic slide changer. The mechanism should operate for thousands of hours without failure. The slide projector will often be placed on a roof and switched on automatically when night comes, and switched noi?" at about 1:00 A.M. Nobody will take care of the lamp for several days. During that time the slide changer mechanism is expected to operate perfectly: Model SP. 1 is built and shop tested with that in mind.


This unit is mostly for advertising as it is entirely automatic. It can be placed on a roof to project an image on a nearby white wall. The best locations are the spots where crowds pass or assemble at night, for instance, theatre and shopping areas, railroad stations, amusement parks, and also concession areas of drive-in theatres.

Excellent spots are also those that can be seen from cars having to slow down for traffic lights or tolls, or near the axis of a long, straight road on which a sign can be seen for a full minute by the occupants of a car using this road.

Indoors, the slide projector is placed in areas that are slightly darker than the rest of the room; in theatre lobbies; in large stores to advertise the days specials; or make intriguing window displays; in arenas to announce future events, or advertise the concession products.

The projection of large images is very impressive because of the rapidity of the

1954-55 Theatre Catalog, 12th Edition, Page 204