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of the aperature rectangle. All the components in motion should be well balanced to eliminate vibration and noises. The shuttle body should be of one rigid and light substance with good wearing properties. The claw tips should be designed with the correct shape to enter the film perforations without shock. The vertical stroke or pulldown action must be vertical with accelerated and decelerated motion. The claws must leave the perforations with horizontal motion and without jarring the film in any way.
Lubrication
The claw movement should be capable of long use without frequent lubrication. This latter condition is variable according to the type and design of the claw movement. Some claw intermittents are designed in a way that the shuttle and cam components are far away from the claw tips and film plane, so good lubrication can be secured without any risk of film damage. However, others are so close to the film plane, as previously mentioned, that lubrication becomes practically impossible.
In the claw intermittent mechanism, the film gate plays an important part due to the stopping action during the projection cycle. The tension placed on the film by pads should be sufficient to hold the film flat during the projection time but must be weak enough to let the claws pull the film without jerks and excessive tension. The abrasion of film base over the film gate tracks is overcome by using very hard stainless steel pads and heavy chromium alloy plating. Some modern projectors employ sapphire inserts in the lateral guides of film gates. Jumping and weaving of the image when magnified occurs occasionally even in high priced machines. The claw intermittent and film gate design, when carefully designed and constructed, should not allow movement in excess of 3/16 inch vertically or laterally at 120 times magnification.
Framing Methods
One of the features to bear in mind when claw intermittent mechanisms are designed, is the matter of framing the picture image on the screen. In some cases, framing is accomplished by moving the whole mechanism in a vertical path parallel to the film plane. This method is known as theatrical framing and is a must in television projection
INTERNATIONAL PROJECTIONIST • March 1956
P" right
from the great
Bausch & Lomb
SUPER CINEPHOR
Projection Lenses
New film techniques, in the great new pictures now being released, put new depth and clarity on the print. Make sure your prime lens can transmit all this new brilliance, color and vivid detail onto your screen. More than ever, these great movie advances are bringing customers out of the home and into the theatres again. Assure profitable repeat patronage with B&L Super Cinephor Lenses . . . for today's most thrillingly vivid screen images of all 35mm releases.
SEE THE BIG DIFFERENCE . . . FREE DEMONSTRATION!
Write, wire or phone for Catalog E-123 and for free demonstration. Bausch & Lomb Optical Co., 61603 St. Paul St., Rochester 2, N. Y. Phone: LOcust 3000. (In Canada, General Theatre Supply Co., Ltd., Toronto.)
Academy of Motion Picture Arts and Sciences Honorary Award for Optical Service to the Industry
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