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1948-49 Theatre Catalog, 7th Edition, Page 408 (395)

1948-49 Theatre Catalog, 7th Edition
1948-49 Theatre Catalog
1948-49 Theatre Catalog, 7th Edition, Page 408
Page 408

1948-49 Theatre Catalog, 7th Edition, Page 408

FIG. 4-Diagmm oi condenser mount.

as may be required for trimming.

A spring-operated collet clamps the rear end of the positive carbon to the rotating mechanism and the simple moving of a lever is all that is required to release instantly the collet to loosen the carbon for changing.

A nickel casting with a circular hole a little larger than the carbon constitutes the positive carbon guide. It is located just back of the positive contacts and the carbon is forced to the bottom of this hole by the angularly machined pads on the carbon contacts which keeps the carbon constantly in a fixed central position.

Floating positive carbon contacts of pure nickel are employed. The adjustable contact pressure spring is located well back from the heat of the arc, and a cam, operated by a special trimming wrench, is provided to spread the contact pressure arms to. facilitate easy insertion of new carbons.

By rotating this contact release cam to its limit the spring pressure is completely overcome and both contacts may be lifted upward out of their operating position for cleaning or replacement. g

Ahead of the positive contacts are located three nonmagnetic heat bafiies each spaced 17% of an inch apart from the other, to facilitate the radiation of air between them for cooling. These baffles are held in position by gravity, in machined grooves, hence are easily removable for inspection or cleaning. The first or front banie is made of a special metal alloy that is almost impervious to the disintegrating effect of the heat and hot gases of the arc.

The entire positive rotating carriage, as well as the baffles and contact spring arm at the front end of the burner, are thoroughly insulated so that current can only reach the carbon via the contacts,


thereby preventing the current from bypassing to the carbon through any moving or other parts of the burner.

The positive bus bar that conducts the current from the main terminal, located at the rear end of the burner base, to the positive contact shunt clamp base, located at the forward end, is provided with a movable collar attached to which is one of the ampere-meter leads. This bus bar therefore acts as the meter shunt and by the adjustment of the collar along the bus bar the meter reading can be adjusted at any time it might become necessary.

A permanent magnet of cast No. 5 ttAlnico" is employed to draw the positive tail dame of the are away from the rear condenser lens and also neutralize other stray magnetic fields that might detrimentally anect the burning arc. The magnet support bracket is designed for reversible mounting either to the front or rear face of the right front tube support casting of the burner. This permits a 1%6-inch change to be -made in the distance between the magnet and

FIG. S-Arc-image projector on right door.

the arc. The most rearward position is recommended for arc currents of from 120 to 150 amperes and the forward position for higher currents to 170 amperes (Fig. 6). '

Negative Carbon Carriage

In the design of the negative carbon carriage a substantial departure from conventional practice has been adopted because, instead of locating all its mechanism beneath the are where it is subjected to the intense heat thereof, it has been placed well to the rear and to the left side of the arc. This has enabled us to employ much more substantial construction as well as much closer bearing tolerances, since the temperature at this location is low enough to use ordinary lubricating oil without carbonizing.

The negative carbon is carried at an angle of 55 degrees from the positive carbon axis. This permits operation of the positive crater relatively close to the rear condenser without fear of interference between the negative carbon holder and the condenser-lens mount.

A rack and pinion on the negative carbon feed carriage permit rapid mane ual striking of the arc and the lowering of the carbon arm when a new carbon is to be inserted.

The negative carbon arm is accurately machined and readily removable and is attached to a metal dowel plate in advance of the insulation point, hence its removal for cleaning or replacement is accomplished without having to break down its insulation or performing any realignment operation.

To counterbalance the weight of the negative carbon arm and its carriage and likewise correspondingly decrease the load on the feed gearing and motor, a fiat clock spring is connected to the negative pinion shaft at its inner end

FIG. S-Burner mechanism.
1948-49 Theatre Catalog, 7th Edition, Page 408