Leo for Group 'A' Roads
Bowl Refractor Lantern
Crompton Lamps :-
| 250/400W | Mercury Electric Discharge | (MA/V) |
This light but robust lantern embodies the following features:-
- Enclosed dustproof construction.
- Smooth outer surface to bowl.
- Snap action toggle fasteners.
- Symmetrical, non-axial or axial distribution.
- Top or side entry.
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| Top | 250/400 MA/V | G.E.S. | S391DS | S391DN | S391DX |
| Side | 250/400 MA/V | G.E.S. | S396DS | S396DN | S396DX |
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Unless otherwise specified 1¼ B.S.P. entries will be supplied. |
| Dimensions, Bracket Entries And Weight |
| Height | 18 5/8" |
| Diameter | 13" |
| Side Entry B.S.P. (unthreaded) | 1¼" |
| Minimum length unthreated tube required | 3¾" |
| Top Entry B.S.P. | 1¼" |
| Minimum length thread required | 1" |
| Weight | 19 ½lbs. |
| Refractor Catalogue Numbers |
| Symmetrical | 4140 |
| Non-Axial | 2/4140 |
| Axial | 22/4140 |
1. Construction
The canopy of this lantern, available in two versions, one for side and the other for top entry, is a robust but lightweight aluminium alloy
casting. A central tapped boss with a locking nut is provided for the top entry version. In the case of the side entry lantern the bracket
entry is cast integrally with the canopy and includes a bracket stop and moisture baffle. A drainage channel is also provided to lead any
condensation from the bracket arm out of the lantern. Two Allen screws are used to secure the lantern to the bracket arm.
The outer prismatic bowl is carried in a light but strong cast aluminium alloy frame hinged on one side to the lantern canopy. Two snap
action toggle fasteners are provided on the other side of the canopy to secure the frame when closed whilst, for the exclusion of dust,
gaskets are interposed between the bowl and its frame and between the bowl frame and the lantern canopy.
Screwed to the inside of the canopy is a cast lampholder bridge piece. This is specially shaped so that, in the case of the top-entry
lantern, no condensate can fall on to the lampholder or the lamp itself. The lampholder is supplied ready wired with heat resisting cable to a
porcelain terminal block conveniently mounted near the bracket entry. A clearly marked earthing terminal is also fitted.
Light control is achieved primarily by the prismatic bowl. A top reflector is however fitted to ensure maximum light output.
2. Material And Finish
| Canopy, Bowl ring and Lampholder Bracket | Silicon aluminium alloy LM6M. Aluminium stoved enamel finish. |
| Reflector | Vitreous enamelled steel |
| Toggle clips | Steel, cadmium plated |
| Hinge pins | Stainless steel |
| Bowl retaining clips | Mild steel cadmium plated |
| Gaskets | Felt |
| Lampholder | Porcelain |
| Bowl Refractor | Heat resisting prismatic glass |
3. Focusing
Alternative sets of clearly marked bosses are provided for the mounting of the lampholder bridge so that the two sizes of
lamp are accommodated in the correct focal position.
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 For Non-Axial Refractor Bowl No. 2/4140
| Beam Angle Horizontal | 160° |
| Beam Angle Vertical | 75° |
| Light output ratio | 74% |
| Light flux in lower hemisphere | 84% |
| Directional Intensity Ratio | 2.8 |
FIG. 1
Polar distribution for 2/4140 bowl refractor with 400W 16800-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 2/4140 bowl refractor with 400W 16,800-lumen lamp.
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