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Keith Blackman Limited full range | Gas Lanterns

Inverted High Pressure Gas Lamp
High pressure gas lamp. Revolutionary design for high pressure gas systems. Some of the heat from the hot products of the combustion of the gas was given to the gas-air mixture by means of a special heat interchanger. (This was a radical departure from the accepted theory that the burner of a high pressure gas lamp had to be kept as cool as possible.) Keith showed that the aim must be to heat the mixture to within a few degrees of its ignition temperature. Intensities of 50-60 candle power in the horizontal plane for each cubic foot of gas burner were achieved. First exhibited at the Franco-British Exhibition in 1908 and at the Scottish National Exhibition in Edinburgh in the same year. Designed for use in most of the principle streets of the City of Westminster in 1911, installed and maintained by the Gas Light and Coke Company. The lamps were used with the Keith Rotary Gas Compressor. This design of lamp is used for large units having two or three mantles each giving 1,500 candle power nominal. Each mantle has its separate burner system, so that it is possible to arrange for cutting out part of the light after midnight. Suitable controlling means are fitted to the tubular supports or, in some cases, to the bottom casting embodying the socket and arms.
??? 3,000-4,500 candle power
2-3 burners Post Top 1937 Paper
1937 Paper


Suspension Lamp / Keith Lamp
High pressure gas lamp. Some were fitted with special directional reflectors. Standard pattern suspension lamp of pleasing design, supplied with a special heat-resisting globe which alows the use of smaller casings. There are four models with illumination output of 500, 750, 1000 and 1500 candle power. Each of the lamps, when used for street lighting, can be supplied with raising, lowering and trversing gear for bracket and central suspension.
805 500 candle power
1 burner Top Entry 1932 catalogue
1944 Journal
805 750 candle power
1 burner Top Entry 1932 catalogue
1944 Journal
805 1000 candle power
1 burner Top Entry 1932 catalogue
1944 Journal
805 1500 candle power
1 burner Top Entry 1932 catalogue
1944 Journal


Suspension Lamp
High pressure gas lamp. Described as a smaller version of the City lamp. Could be fitted with 1932 pattern heaters
??? 2000 candle power
2 burners Top Entry 1932 catalogue


Suspension Lamp
High pressure gas lamp. Described as using the Standard Pattern. Used in the City of London and West End.
920 3000 candle power
2 burners Top Entry 1932 catalogue


City Lamp
High pressure gas lamp.
??? ??? candle power
2 burners Top Entry 1932 catalogue


nominal squat pattern lamp / squat type keith lamp
High pressure gas lamp. A range of Squat pattern lanterns were made. Some were fitted with special directional reflectors. A high pressure gas lamp, fitted with an automatic lighter, and largely employed for street lighting on raising, lowering and traversing gear. Short overall length, and fitted either with the standard 22" reflector, or smaller 16" reflector. Could also be used for shop front lighting.
807 1000 candle power
1 burner Top Entry 1932 catalogue
1938 programme
1945 Advert
1945 Programme
1946 Advert
1947 book
1951 book


supervia
A high pressure gas lamp made under licence from the patentees South Metropolitan Gas Company. It is also known as the Metro-Supervia lamp. Specially designed for street lighting. Large numbers of these are used in London and the provinces and the lamp is claimed to be the last word in street lighting by gas. Suited for bracket arm or central suspension. Can be fitted with axial or non-axial reflector. Believed to have been introduced in 1935. It has an important modification to the shape of the incandescent mantle, with a special slit burner. The mantle, in shape, is like a flat bag. The flat sides are kept from blowing out by cross stitches inside the mantle. The flat surfaces of the mantle are arranged to face up and down the street so that most of the light is given in the direction where it is needed. With it there is an increase in the flux of light above that obtaiend with the ordinary cylindrial mantle for a given gas consumption - this is probably due to an increased pre-heating of the combustible mixture: the mantle is fixed closer to the underside of the heater, and the mixture in passing through a narrow slit is more highly heated throughout than is possible in the final stage of heating in a cylindrical nozzle. Incldues a Holophane refractor giving maximum directional beam 10° below the horizontal. Made in two sizes with enamelled steel reflectors 22" diameter. Length with cup and ball joint and automatic lighter is 27½". The light can be reduced, say at midnight, by lowering the gas pressure.

Has a 'Type 1 Distribution' (Non Cut-Off) according to the draft 1945 specification.

Supervia ??? candle power
??? burners Top Entry 1935 Paper
1936 Journal
1937 Advert
1937 Programme
1937 Paper
1939 Journal
1944 Journal
1945 Programme
1945 Paper
1946 Advert
1947 book
1951 book


standard keith lamp
High pressure gas lamp designed for column fixing. The gas, at 3lbs pressure from the high-pressure main, enters the lamps by way of a stirrup fitting (A) which carries a tube (B) which is removable to allow easy withdrawal of the nipple holder (C) for cleaning, when necessary. The correctly formed venturi tube (D) enables the jet of gas to entrain all the air required for the complete combustion of the gas. The pressure of the gas and air mixture at the end of the venturi is sufficient to overcome the resistance of the parts of the gasburner system, including the mantle. A screw (E) adjustable from the outside of the lamp casing, is provided to enable adjustment of the quality of the mixture to be made, the air-to-gas ratio being dependent upon the resistance to the flow. This is necessary in order to attain the best possible lighting effect. It is to be noted that the injector is capable fo producing a mixture with an excess of air when the lamp is fully heated and the adjusting screw is open to the full extent. THis allows the necessary adjustment to be made when the lamp has reached normal working conditions by screwing (E) inwards. The heater (F) with its burner nozzle (G), is a most important component in the lamp. It is designed to allow the gas-air mixture to be heated by the hot gases leaving the incandescence mantle. This heater, or heat interchanger, paradoxically as it may seem, serves to keep the burner nozzle cool - or at least, keeps it from becoming heated to an undesirable temperature. This is effected by the rapid conduction of heat from the nozzle to the body of the heater through which the combustible mixture flows on its way to the burner heat. To aid the conduction of the heat from the end of the nozzle, the latter is of heavy section and is made of metal having good heat-conducting properties. The absorption of too much heat by the metal nozzle is prevented by surrounding it with a close fitting clay ring (H). To this ring the mantle (J) is attached and the clay ring is screwed on to the nozzle flame-tight. The nozzle is always the hottest portion of the burner, but with the arrangement described its temperature is kept below the ignition temperature of the combustible mixture, and provided this temperature is not exceeded, the hotter the nozzle the greater will be the light from the mantle. So that it may burn quietly, it is important to remove turbulence in the air-gas mixture before it issues from the nozzle. Eddying also increases the tendency for the flame to "strike back" into the heater. The heater (F) is formed of two dished cast-iron plates between which is clamped a metal diaphragm which is provided with a number of small holes neare its periphery. When the mixture issues from the older end of the venturi tube there is considerable turbulence, but in its passage over the diaphragm and through the small holes this is damped down. Any remaining turbulence is removed by means of a metal gauze (K) in the nozzle itself. This gauze also serves to prevent flash back of the flame on extinction, which might damage the mantle. It has already been noted that for the development of the maximum light the ideal mixture is one in which the correct amount of air is mixed with the gas for its complete combustion, and with such a mixture the speed of propagation of the flame through it is also at its maximum. Therefore, the special precuations indicated must be taken to prevent the flame striking back. The mantle, which is tied to the clay ring, is not incinerated until it has been screwed onto the metal nozzle. When first "burnt off" the fabric is in its most fragile condition, and it is, therefore, desirable to light the burner with a deficiency of air in the mixture, which gives gentle ignition. To avoid upsetting the quality of the combustible mixture by operating the adjusting screw, when re-mantling is necessary, a metal disc (L), attached to the end of a bi-metal strip, is provided in the upper half of the heater. When the lamp is cold this disc offers resistance to the flow of air; but when the heater is warmed the strip carrying the disc bends back and allows the proper quantity of air to flow with the gas. The time taken for this operation is only a few minutes. The lamp casing consists of an inner cylindrical body (M) fitted with a transverse box (N), and made usually of stainless steel. This material has been found to be the best for withstanding the high temperature and the corrision due to condensation in the first minutes of lighting. The transverse box is connected with the air inlet chamber (O) of the lamp and closed off otherwise from the chimney, so that the injector which it surrounds can only draw fresh air warmed up by the products of combustion which pass up the spaces between the box and the cylindrical body.
??? 1000 candle power
1 burner Top Entry 1937 Paper
1945 Advert
1945 Programme
1946 Advert


keith column lamp
High pressure gas lamp. Column version of the Standard Keith Lamp (above).
??? ??? candle power
1 burner Post Top 1937 Paper
1945 Advert
1946 Advert


Nominal Suspension Lamp / Keith Suspension Lamp
For use on high-pressure gas. Used for both street lighting and shop lighting. The lamp is complete with automatic lighter for distance lighting, and has a chromium-plated copper casing and dome, black enamel cowl and reflector, and forms a handsome unit. It is of multiple burner type, giving an output of 1000 candle power. The model can also be supplied with a single burner.
808 ??? candle power
1 burner Top Entry 1938 programme
1944 Journal


808 1000 candle power
3 burners Top Entry 1938 programme
1944 Journal




Magnalux / High Intensity Lamp / High Candlepower Low Pressure Lamp
Described as a "distinct innovation" in 1937. Based on ideas first put forward by Lucas. This operates on low-pressure gas mains and embodies novel principles to ensure much higher candle-power results than obtainable from ordinary low-pressure lamps. Introduced as the Magnalux in 1938, it offered 50% gerater efficiency than low-pressure lamps, with results approaching the performance of high-pressure gas. Fig. 11 is a diagram showing the principle of the new lamp: (A) is a mantle, or one of a row of mantles; (B) is a bunch of small tubes surrounded by a refractory mantle ring which fits closely to the heater body (C). The tubes (B) are fed with a mixture of gas and air having as high a proportion of oxygen as can be obtained by means of the low-pressure gas injector which feeds the chamber (D). The two chambers (EE) are connected to the space around and between the small tubes of the bunch (B). The crux of the problem is to cause the secondary air to enter this space against the resistance of the mantle and without the pull of the chimney. Surrounding the chimney body of the lamp is an outer chamber (F) similar to that used with an ordinary low-pressure lamp, which is supplied with air through baffled openings above the reflector. This chamber is not connected directly with the globe (G), so that no secondary air is allowed to enter the gloe, contrary to the practice in normal low-pressure lamps. THe chamber communicates at the top with the chimney by means of the openings (HH), so that the static pressure in the cmaber is approximately the same as that in the chimney. Two uprising tubes (JJ) are connected to the chamber (F) by the bends (KK). These tubes, which have internal spiral strips to facilitate heat transmission, rise through the chimney and are carried through the cowl and upwards for an appreciable distance. Return bends on the top are connected to two descending tubes (LL), the lower parts of which enter, by bends and horizontal tubes, the chambers (EE). These tubular systems form syphons which oeprate by the fact that the air in the rising members is heated by the chimney gases and in the descending members is cooled by exposure to the outside air. In this way a slight pressure above atmosphere is set up at the foot of the descending tube. By this means a supply of secondary air reaches the burning mixture, which issues from the tubes (B), in quantity slightly in excess of that required for complete combustion, and at a sufficient pressure to overcome the mantle resistance. The important point to note is that no matter how the suction of the main chimney is increased or reduced by the wind, it can have no influence on the pressure difference set up by the syphons. Fig 12 is the section at right angles and shows a row of mantles intended to be disposed broadside to the length of the street: Injector (M) provides the primary mixture. The gas supply is brought down the centre of the lamp in the usual way and passes through a special form of auto-lighter (N) to the gas nipple. Adjustment of the quality of the mixture is made by the needle valve (O). On the other side a box (P) contains a Horstmann electric lighter of the Comet type and its battery.

Fig 13 shows a modified prototype. The chimney is divided, which enables the mantles to be rasied nearer to the suspension point, so that this distance is no greater than in standard low-pressure lamps. The syphon tubes are arranged to straddle the bracket or other means of suspension. Both prototypes were shown at the 1937 Folkestone Conference with the lamp of Fig. 11 installed in Marine Terrace and Lower sandgate Road and the lamp of Fig. 13 was installed in Padnor Park Road.


Initially avaialble in three- and four-light options. A lumen output of 15,000 is obtained from the four-light size on gas supplied at a pressure of 5" w.g. THis increase in efficiency is of the order of 50% over that hitherto obtainable with low pressure outdoor lamps.

First installed along Woburn Place in Holborn in 1938.


"Small" High Intensity Lamp ??? candle power
1, 3, 4 burners Top Entry 1937 Programme
1937 Paper
1937 Journal
1938 Journal
1938 Advert
1938 Programme
1939 Advert
1939 Journal
1939 Programme
"Small" High Intensity Lamp ??? candle power
3 burners Top Entry 1937 Programme
1937 Journal
1938 Advert
1938 Programme
1939 Advert
1939 Journal
1939 Programme
"Large" High Intensity Lamp ??? candle power
4 burners Top Entry 1937 Programme
1937 Journal
1938 Advert
1938 Programme
1939 Advert
1939 Journal
1939 Programme


Decorative Lamp
High pressure gas lamp principally for shop facia lighting.
??? 1000 candle power
1 burner Top Entry 1945 Programme