International projectionist (Jan-Dec 1955)

The Improved Strong 6135' Projection Ar clamp First publication anywhere of important changes in the design, construction and increase in operating efficiency effected in the Strong "135" projection arclamp now available to the trade. By ARTHUR J. HATCH Vice-President in Charge of Engineering THE STRONG ELECTRIC CORPORATION THE improvements effected in the design and construction of the latest Strong "135" arclamp are the result of steady engineering progress spurred on by the ever more severe demands by the projection field in order to cope successfully with the new techniques. This is not to infer that every change in technique requires the abandonment of those basic principles of design, construction and operation of arclamps which over the years have proven their worth — a statement as applicable to the Strong lamp as it is to other equipments. For example, retained in the improved Strong "135" are those salient features which have distinguished its predecessors, such as automatic positive carbon crater-positioning, singleadjustment carbon feed control, burner base focusing whereby the arc-gap is not disturbed when focusing the lamp on the aperture, and simple, sharp-line construction which enables the projectionists to keep the lamphouse clean. Automatic Crater Positioning Before presenting the run-down on the outstanding features of the improved Strong "135," the writer states that our review of the wide acceptance accorded the 161/2-inch diameter reflector lamp which we have been manufacturing for the last five years is due in no small measure to the automatic carbon crater-positioning unit contained therein. This device will continue to be a vital feature of the improved 18-inch and lC^-inch reflector lamps which will be delivered henceforth. Outstanding features of the improved Strong "135" are as follows: 1. 18-Inch, F:1.7 Reflector. This size mirror takes full advantage of the greater acceptance angle of the new F:1.8, 1.7 and 1.5 objective lenses. This Strong reflector, when used in conjunction with one of these highspeed lenses, will produce approximately 15 to 18% more lumens on the screen at the same arc current used with the 16^2-inch reflector. Important: this light gain will not be realized unless it is used in a projector which is properly cleared for the F:1.7 light beam. Heat Dissipation Vital 2. Improved Heat Filter. The dichroic heat filter is mounted in a holder which slides into a cast-aluminum housing which directs a stream of cooling air over the filter glass from a blower having a capacity of 100 cu. ft./min., operated from the D. C. arc supply voltage. Thus is insured a steady flow of air at all times that the lamp is operating. This filter removes 35% of the total energy at the aperture, while resulting in a visible light loss of only 8%. This filter will be standard equipment on all 18-inch reflector lamps because we feel that its use is mandatory (at least with black-and-white film) in view of the high efficiency of the improved Strong "135" optical system and notwithstanding the fact that the projector may have a water-cooled gate and, possibly, a pulsing jet of air to stabilize the position of the film in the aperture. 3. Improved Reflector Cooling and "Purging" of the front Surface. The 18-inch reflector lamp incorporates means for cooling the rear surface of the mirror by admitting air through an opening in the rear lamphouse door, this air being drawn in by action by the lamphouse stack exhaust fan which is part of the theatre exhaust duct system. This air is so distributed and directed as to pass over the rear of the reflector, thereby reducing its temperature to a point where heat differentials as a breakage factor are negligible. Recommended exhaust stack volume of air is at least 150 cu. ft./min. from each lamp. To further "purge" and keep the front surface of the reflector free from the products of combustion, two small nozzles supplied with air under pressure from the base of the lamp direct a stream of air upward and over the surface of the reflector. This air is supplied by blowers on the two carbon-feed motors, and this additional method of "purging" is used in conjunction with the same jet of air that is directed over the arc to chop off the tail-flame and which was used on all 16V2-inch reflector lamps made to date. Carbon Contacts; Flexibility 4. New-Style Positive Contacts. These feature a new type of current lead to the upper contact and will insure a life-span equal to that which should be expected from solid pure silver contacts. Another feature is that the upper contact is readily removable from its tension rods for inspection and cleaning. These contacts are cooled by air supplied from the burner base reservoir. 5. Flexibility. The 18-inch reflector lamp offers extreme flexibility The Strong Super 135 arclamp which boasts many improvements over its predecessor model, including an 18-inch, F:1.7 reflector, new long-life carbon contact, advanced cooling means and other note. worthy advances. 16 INTERNATIONAL PROJECTIONIST 9 APRIL 1955