International projectionist (Jan-Dec 1947)

PEERLESS HY-CANDESCENT LAMP (Continued from page 6) bon axis. Thus the positive crater may be operated relatively close to the rear condenser without interference between the negative holder and the lens mount. The negative carbon arm attaches to a metal plate in advance of the insulation point, which need not be broken down when cleaned or otherwise used. A flat clock spring is connected to the negative pinion shaft at its inner end and the spring housing at its outer end. This spring effectively counterbalances the negative carbon arm and its carriage and also lessens the load of. the feed gearing and motor. The result is a featherweight feed of the negative holder. Hy -Candescent Condenser System The Hy-Candescent lamp utilizes an F:2 condenser system manufactured on an exclusive basis for J. E. McAuley Co. by Bausch & Lomb Optical Co. The rear lens is obtainable made of either fused quartz or Pyrex glass. This lens, 6^ inches in diameter, has a % inch edge on the rear surface to accommodate several resurfacings when the lens is badly pitted. The front lens, made of B. & L. Corex glass, is 7% inches in diameter. Operating distance between arc crater and the rear lens is 3 inches, while the working distance between the front lens and the film is 12 13/16 inches. These distances were calculated to enable an 80% side-to-center screen light distribution. The exigencies of operating a condenser-type high-intensity lamp in the 160 to 180 amperes range require that some means be provided for effectively reducing the heat at the aperture and thus helping to prevent severe .damage to the film. To this end the J. E. McAuley Co. some years ago developed an air-cooled, glass heat filter unit. Special Heat Filter Unit The filter's main frame is attached to the rear face of the projector shutter housing. Fitted into this frame is the holder for the filter glasses. This holder is so constructed as to provide ample room between all sides of it and the main frame. A centrifugal electric blower is utilized to blow an adequate amount of air into this frame. Eight glass filter strips, each V2 inch wide, are mounted in the holder vertically and in a staggered pattern to provide for thermal expansion and assure maximum cooling effect. The air from the blower passes over the entire glass surfaces and ends. The manufacturer recommends that the blower motor be hooked-up to the open end of the arc lamp switch so that when this circuit is energized the blower may be started and stopped simultaneously. The air from the blower runs through a exible plastic tubing and is exhausted through the top of the lamp housing. The glass used is Coming's Aklo No. 3966. These filter units and blowers are now in use in many de luxe theatres throughout America, including the Radio City Music Hall and the Roxy Theatre in New York City, the Chicago Theatre, Chicago, and in many drive-in operations which utilize high-amperage projection. Water-Cooled Positive Contacts As an aid to certain experimental work now being conducted with carbon arcs pulling up to 290 amperes, the J. E. McAuley Co. developed and made avail able for these research programs a Peerless Hy-Candescent lamp which, among other modifications, includes a watercooled positive contact assembly. The facing halves of the contacts are made of pure silver, while the rear halves are brass castings. Each pair of castings is so constructed that when assembled they afford a hollow compartment for the circulation of the water. The water runs through a copper tube to the top of the compartment, the outlet being by another tube at the bottom. A measure of the effectiveness of this unit may be had from the appended table which was included in a paper on this topic presented before the recent SMPE convention. These readings were taken on an arc pulling 290 amps and with only a %-inch positive carbon protrusion from the face of the contacts and without the usual heat baffle plates being used. The figures are shown in Table A. Total water flow (Approx. 1 Gal) Degrees F Room temperature during test .... 72 Outlet water temperature before test 69 Outlet water temperature after 10 min. operation 88 Outlet water temperature after 20 min. operation 93 Maximum temperature rise of water above room temperature 21 Maximum temperature rise of water after 20 min. operation 24 So successful were the tests made with this water-cooled unit on experimental lamps operating at 290 amperes that the J. E. McAuley Co. expects to make it available to those theatres now using the standard McAuley 120-180 ampere lamp and who are willing to supply the necessary water connections in their projection rooms. LOS ANGELES PROJECTIONISTS LOCAL UNION NO. 150 extends to all its friends in the I. A. T. S. E. the ^eudon 5 LjreetL inaS r 24 INTERNATIONAL PROJECTIONIST • December 1947