Corona II for Group 'A' Roads

Bowl refractor lantern

Crompton Lamps :-

This popular lantern is now available in two types, a standard lantern with accommodation for the lamp alone, and a type 'SG' lantern with accommodation both for the lamp and the necessary CROMPTON lamp control gear. The lanterns differ only in the depth of the top canopy and the arrangements of the internal reflector and fixings.

Features:

• High optical performance
• Dustproof construction
• Snap action toggle fasteners
• 'Perspex' bowl with smooth internal and external surfaces
• Hermetically sealed 'Perspex' refractor plates.
• 'Perspex' bowl with smooth internal and external surfaces
• Available for side or top entry.

1. Construction

The strength of this lightweight lantern is derived from its single piece cast canopy. This constitutes a weatherproof hood and provides a rigid support for the optical system capable, in normal usage, of resisting all stersses due to vibration and windage. For pendant suspension a canopy with a central tapped boss and locking nut is supplied. The alternative side entry canopy is secured by two Allen screws and incorporates a bracket stop, moisture baffle and drainage channel to lead any condensation from the bracket arm out of the lantern. Fixed to either canopy is a cast bracket, carrying a B.C. holder, a lamp support and an 'over-lamp' reflector.

The enclosing bowl is carried in a light but strong cast frame hinged to the canopy on one side and secured by snap action toggle fasteners on the other. Gaskets are interposed between the bowl and its frame and between the bolw frame and canopy to prevent the ingress of dust.

The lampholder is wired with heat resisting cable to a porcelain terminal block mounted on the underside of the canopy adjacent to bracket entry. A clearly marked earthing terminal is also fitted.

Light control is achieved primarily by means of prismatic 'Perspex' plates hermetically sealed to the inside of a 'Perspex' bowl so that all prismatic surfaces are permanently protected from dust and all exposed surfaces of the bowl and plates, both inside and out, are completely smooth to facilitate maintenance. Maximum light output is ensured by the overlamp reflector.

2. Material And Finish

3. Focusing

The lampholder and lamp support ensure that either size of lamp is correctly placed relative to the refractor plates.

4. Maintenance

The aluminium alloy from which this lantern is cast is highly resistant to corrosion in both industrial and marine atmospheres. Additional protection can be provided by occasional painting in service.

5. Optical Data

FIG. 1
Polar distribution with 140W 10640-lumen lamp
A: In vertical plane normal to lantern B: Plan distribution of 75° cone

FIG. 2
Iso-candle diagram with 140W 10640-lumen lamp.