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Topic: What is a gate cooling system??

Andy Davis
Film Handler

Posts: 49
From: Gainesville, FL
Registered: Dec 1999

posted 12-13-1999 11:26 PM

A friend recently told me about a "gate cooling system" and I was wondering what this does and why it would be beneficial. My best guess is that it has something to do with preventing the metal from expanding and warping, thus reducing distortion. But wouldn't projector manufacturers compensate for this? Please enlighten me.

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Ken Layton
Phenomenal Film Handler

Posts: 1452
From: Olympia, Wash. USA
Registered: Sep 1999

posted 12-13-1999 11:46 PM

You probably mean "water cooled gate" option.
The back of the gate casting has a small loop of copper tubing attached. Water flowing thru the tubing cools the casting thus reducing the temperature of the film to prevent blistering and scorching. Also keeps the machine cooler and improves focus. This option is usually used with 4000 watt lamps (particularly popular in driveins and 70mm equipped theaters).

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 12-14-1999 08:12 AM

As Ken mentioned, "water cooled" gates are a good option for projectors using lamps greater than 4000-watts. The gates remain cool to the touch, increasing operator comfort during threading. The cooler gate rails are less likely to abrade the emulsion and "bake on" hardened deposits of gelatin emulsion from the film. However, water-cooled gates will NOT prevent film damage from excessive radiant energy ("hot spot" damage including blistering, scorching and dye-migration), since this damage is usually caused by excess radiant energy being absorbed by the film, and not by the film contacting the hot metal parts of the gate. Damage from excess radiant energy is best prevented by using efficient heat filters ("cold mirrors" or dichroic heat filters) and proper alignment and focus of the lamphouse optics to avoid "hot spots".

------------------
John Pytlak, Senior Technical Specialist
Worldwide Technical Services, Professional Motion Imaging
Research Labs, Building 69, Room 7419
Eastman Kodak Company
Rochester, NY 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 12-14-1999 09:42 AM

There are several methods of cooling a gate of a projector. The simplist is a stream of air which many shutters provide (the small l shaped blades attached to the shutter)
A blower as used by Simplex and Cinemecanica
and finally a water cell physically attached to the gate to cool that casting with a recirculated water (or coolant)
I always water cool above 2500 watts and usually there is very little perf abrassion even on green prints that high moisture level can cause sticking to the rails when hot

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John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 12-14-1999 10:55 AM

Would you consiter the Century "Cinefocus" a gate cooling option _and_ improved focus, or just a improved focus alone?

BTW, we sent two JJ's back to Century awhile ago to rebulid, and I got annoyed at them because they didn't drill out the hole for the Cinefocus while they were there. I wanted to add it later, and could'nt do it easily.

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 12-14-1999 01:30 PM

The Century Cine-Focus system was primarily for improving focus stability by reducing heat-related film "flutter" in the gate. A blower provided positive air pressure on the lens side of the gate. The air flow was probably not enough to actually cool the film. Cine-Focus was often used in conjunction with a very efficient dichroic "Century UVIR" filter, which filtered out much of the harmful ultraviolet and infrared radiation from the lamphouse.

Air cooling and stabilization of the film is not a new idea. Kodak published a paper in the December 1949 SMPTE Journal: "Air Cooling of Motion Picture Film for Higher Screen Illumination" by Frederick J. Kolb. Willy Borberg published a paper "Modulated Air Blast for Reducing Film Buckle" in the August 1952 SMPTE Journal.

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Stefan Scholz
Expert Film Handler

Posts: 223
From: Schoenberg, Germany
Registered: Sep 1999

posted 12-14-1999 03:14 PM

The Bauer projectors always used a compressed air cooling system, which cooled the film and gate. Special compressors were installed in seperate rooms, and send an air stream of 800 hpa through the gate construction and ended in special nozzles to cool the film on both sides. The system prooved to be extremely efficientz, as most heat and absorbed radient energy was taken off the film.
Unfortunately the small compressors and the nozzles were quite noisy, and when the compressor was installed within the projector's foot, like at Bauer U2, it was impossible to sit next to it. This is mainly why the system disappeared. Water cooling has never been efficient in keeping absorbed energy off the film.
I remember, as beeing high school student, we placed nitrate film in the gate, ran our HI arclamps at 65 Amps, and disengaged the safety shutters. The film stayed in focus for nearly 40 minutes, and never caught fire.
Without the blower running, it caught fire immediately, the moment we opened the shutter. This proved quite well on effectiveness.

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Ben Wales
Jedi Master Film Handler

Posts: 602
From: Southampton. England
Registered: Jul 99

posted 12-14-1999 04:23 PM

It would be most essential on Xenon's on high current, where I work presently we just installed two new Cinemeccancia Victoria 8's with both water (chilled) gates and air cooled, in addition a heat filter, these have
been fitted with a 7kw Xenon consoles and run only 70mm film at present.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 12-15-1999 12:06 PM

The original ToddAo install at the Rivoli with the Gertner Ventarcs used refrigerated air jets to cool the film includeing nitrate 35mm

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Charles Lubner
Film Handler

Posts: 78
From: Milwaukee, WI USA
Registered: Sep 1999

posted 12-15-1999 01:04 PM

Which Rivoli Theatre? I know of several. I assume you're talking about the one in New York that is no longer a theatre?

I'm curious because I work at the Rivoli Theatre in Cedarburg, Wisconsin (suburb of Milwaukee). Wisconsin also has the Rivoli of LaCrosse, complete with original neon marquee!

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 12-16-1999 09:52 AM

When mentioning Todd-Ao and the Rivoili THeatre (with suitably hussed voices) is referring to there first theatre in New York There are pictures of the booth in one of Cameron's books on projection

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