The motion picture projectionist (Nov 1931-Jan 1933)

February, 1932 Motion Picture Projectionist 31 in Court, by getting a preliminary injunction pending the outcome of a suit? A. 5 — It is the common practice of the courts not to grant a preliminary injunction except on an adjudicated patent and it often proves difficult to have an exception made of this rule. One exception to this, however, is the case of patents which have run for many years and their validity has been acquiesced in by the public as evidenced, for instance, by the taking out of many licenses. Theory and Fundamentals (Continued from page 24) films having less shrinkage, and should be decreased for films of greater shrinkage. If in operation the lagging edge of sprocket holes are found to be torn, further damage can oftentimes be prevented by reducing the film wrap. The tooth base thickness is usually reduced to a value which will operate properly taking into account the maximum film wrap and the maximum film shrinkage expected. An Opposite Condition In the preceding discussion we have been concerned primarily with those cases in which the sprocket hole pitch is equal to or less than the tooth pitch. Figure 3 shows the case in which the sprocket hole pitch is greater than the tooth pitch. Obviously this condition could not exist unless a sprocket of too small a diameter is used, because film never stretches with use but always shrinks. The sketch has purposely been drawn to include only two teeth in the wrap. Tooth No. 4 is shown engaged. The leading edge of the sprocket hole is shown buckled at tooth No. 3. The amount of buckling depends upon the difference in pitches (D), and the amount of film damage, and sound distortion will also depend upon the difference in pitches. If tooth No. 2 were to be included in the wrap, the film would strike the leading edge of the tooth, and the buckling would be twice as great as for tooth No. 3. Likewise, the film would strike still further up on the face of tooth No. 1, and the buckling would be three times that for tooth No. 3. If leading the edge of sprocket holes are found torn by a feed sprocket, it is fairly certain that the sprocket diameter is too small. In summarizing it may be pointed out that for any feed sprocket, first, the ideal sprocket is one which has a tooth pitch equal to the film pitch (a condition which seldom exists), second, sprockets having a tooth pitch greater than the sprocket hole pitch (within limits) do operate and can be made to operate properly by properly adjusting the shape of the teeth, and third, sprockets having a tooth pitch smaller than the sprocket hole pitch cannot be made to operate with Super Cinephor Improves the Show From Any Seat in the House/ THE new Super Cinephor gives the sharper definition and higher screen brilliance that make every screen showing more satisfactory . . . from any seat in the house. Available in focal lengths down to 2 inches, Super Cinephor produces a clear cut image right to the margin of either standard or large screens. It throws an image that's in true critical focus, and the field is as flat as your screen. Super Cinephor is the first true anastigmat . . . fully corrected for Spherical and Chromatic aberration, and with the new B & L Condensing System it transmits to the screen 50 to 100 percent more light . . . giving a clarity and brilliance that any patron can, and will appreciate. See your supply man right away and try a Super Cinephor. If you write, Catalog E-16 gives all details. Bausch & Lomb Optical Co. 680 St. Paul Street Rochester N. Y. BAUSCH6LOA\B • PHOTO-ELECTRIC CELLS • • • (CAESIUM ARGON TYPE) DUOVAC's most recent contribution to the science of better Sound Projection. A new Photo electric cell of the caesium argon type. Guaranteed longer life, unaffected by heat through continuous usage and offers a new degree of tone fidelity — the result of Duovac painstaking research. Guaranteed, non-michrophonic. There is a DUOVAC TUBE for every projection requirement. Complete tube eQUlpment now available for the following sound systems: WESTEEN ELECTBIC, E. C. A. PHOTOPHONE, De POEEST PHONOFILM, PACENT, and every other standard make. Write for descriptive folder illustrating the new 242, Power Amp. 264A, designed to replace the 239A, and the 2051). Also other tubes for all sound systems. For particulars write DUOVAC RADIO TUBE CORP., 360 Furman St., Brooklyn, N. Y. Guaranteed! BETTER S«MI\D_ Lesser Cost