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Sirius for Group 'B' Roads

Bowl refractor lantern

Crompton Lamps :-

100/200W.Tungsten filament(G.L.S.)
80/125W.Mercury Electric Discharge(M.B./V.)
80W.Mercury Fluorescent(M.B.F./V.)

This simple but robust lantern embodies the following features:-

  • Automatic focusing of lamp and registration of refractor.
  • Dustproof lantern construction.
  • Single piece bowl refractor, with external surface mainly smooth, available in two distributions.

Lamp Wattage
and type
Complete Lantern Catalogue No.
100/200W GLSB.C.S141AOS141AV
100/200W GLSE.S.S141BOS141BV
80/125W MB/V
80 MBF/V
3-pin B.C.S141COS141CV
Unless otherwise specified standard ¾ B.S.P. tapping will be supplied.

Dimensions, Tapping & Height
Tapping B.S.P.¾";
Minimum length of thread required7/8"

Refractor Catalogue Numbers

1. Construction

There are only four main parts, viz. body casting, lamp holder bridge assembly, refractor bowl and bowl retaining ring. The reflector is cast with the body which is arranged for top entry and provided with two sets of tapped bosses for the fixing of the lampholder bridge assembly. This consists of a simple bridge piece, carrying the lampholder, with bayonet slots to engage fixing screws in the bosses. The bayonet slots allow the bridge to be changed from one set of bosses to the other or to be removed for wiring without complete withdrawl of the fixing screws.

Both types of refractor used with this lantern are of the single piece bowl type with prisms on the internal surface, the external surface being smooth. Correct angular location of the bowls is ensured by the engagement of a projection on the bowl with a cut-out in the bowl retaining ring.

The refractor, which is held in position by three substantial fixing clips is carried in a hinged retaining ring. Two gaskets effectively seal the interior against the ingress of dust.

Lugs on the bowl retaining ring engage with a self retaining wing nut on the lantern body providing a simple yet secure fastening.

2. Material And Finish

BodySilicon aluminium alloy LM6M, exterior finish aluminium, interior finish white and underside of reflector white
Bridge pieceMild steel cadmium plated
Refractor bowlCrystal glass
Bowl retaining ringSilicon aluminium alloy LM6M, finish aluminium

3. Distribution

Typical Polar Curves and an Iso-Candle diagram for the 2/4115 refractor bowl are given in Figs. 1 and 2.

FIG. 1
Polar distribution for 2/4115 refractor with 80W. MB/V 3000-lumen lamp
A: In vertical plane through the centre of the main beam
B: Plan distribution of 75° cone

FIG. 2
Iso-candle diagram for 2/4115 refractor with 80W. MB/V 3000-lumen lamp.

4. Focusing

The bosses to which the lampholder bridge should be fixed for each lamp size are clearly marked within the lantern.

5. 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.

6. Optical Data For 2/4115 Refractor

Beam Angle Horizontal160°
Beam Angle Vertical75°
Light output ratio74%
Light flux in lower hemisphere86%
Directional Intensity Ratio3.4