Journal of the Society of Motion Picture and Television Engineers (1950-1954)

Record Details:

Title:
Journal of the Society of Motion Picture and Television Engineers
Date:
1950-1954
Publisher:
Easton, Pa. : The Society
Volume:
Journal of the Society of Motion Picture and Television Engineers
Leaf #:
000252
Language:
English
Collection:
Technical Journals
Format:
Periodicals
Contributor:
Prelinger Library
Sponsor:
MSN
Coordinator:
Media History Digital Library
Date Added:
July 19, 2022
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fastener which locks the mechanism to the lamp. Below and to the left is the theatrical-type framer control knob which shifts the moving film with respect to the aperture, and directly below it is the speed-shift control which changes the film speed from 24 frames/sec to 16 frames/sec. The motor switch is at the bottom of the control panel. Since it is impractical to interlock the projector motor and lamp power circuits as is done in incandescent lamp projectors, it was considered essential that the RCA Porto-Arc Projector incorporate an automatic film-speed operated fire shutter to protect the film in the event of accidental film stoppage. By careful mechanical design, it proved possible to combine this function with that of a hand-operated "dowser" for keeping the light off the screen until the start of picture action. A centrifugal clutch was added to the regular picture shutter hub, and this clutch, via suitable linkage details, lifts an auxiliary shutter or "dowser" blade whenever the mechanism film speed exceeds 14 frames/ sec, and provided the manual control lever for it is unlatched. This lever is visible in Fig. 5 just to the left of the framer control and may be identified by its horizontal knob. A simple notch in the lower edge of the lever provides the latched-shut feature. Slightly lifting the knob and pulling outward on it opens the dowser/fire shutter, but it Fig. 5. The 16mm. Projector Mechanism. Fig. 6. The projector's arc lamp. Hoehn, Cardile and Woods: 16mm Projector for 3-D 245