US2637185A - Flashlamp - Google Patents

Description

May 5, 195 3 J; A. M. VAN LIEMPT 2,637,185

FLASHLAMP Filed July 30, 1948 /N Vlf' N TOR Ja romes Alibi/21a Mar/a Min Hemp?- av X ATTORNEY Patented May 5, 1953 FLASHLAMP Johannes Antonius Maria Van Liempt, Eindhoven,Netherlands, assignor'to Corporacion cle Ventas de Salitre y Yodo de Chile, Valparaiso, Chile, a company of Chile Application July so, 1948, Serial No. 41,707

This invention relates to flash lamps, particularly for photographic purposes, consisting of a bulb containing materials which on ignition by electrical means emit strong actinic radiation; common materials are a metal, or metal alloy, usually aluminium or an alloy of aluminium and magnesium, with a filling of oxygen or an oxygen "3 Claims. (Cl. 67-31) compound, or a mixture of gases which will support combustion, at substantially less than atmospheric pressure.

There is known to be a risk of the bulb of such a flash lamp being shattered upon the lamp being ignited, and many safeguards have been proposed to diminish the danger; the reduced pressure of. the filling is the first of them. But it may happen that a leak develops in the lamp with the result that it fills with air to atmospheric pressure and is quite likely to be shattered when this air is heated by the combustion of the metal.

Attempts have been made to reduce the danger from such shattering by using a double-walled bulb, or by enveloping the bulb in varnish-coated gauze, or by making the bulb itself of laminated or other plastic. Other attempts have been made to prevent explosion by making the occurrence of leakage apparent to the user, for example by the provision of a manometer, or by causing the bulb to change colour on air entering it, for instance by the inclusion of nitric oxide in the filling or by putting in the bulb a complex cobalt compound which changes colour upon reaction with water vapour. Yet other attempts have been made to prevent ignition when it might prove dangerous, for instance by using a manometer to interrupt the electrical ignition circuit.

A principal object of the present invention is a flash lamp with a partly evacuated bulb the charge of which is rendered substantially noninflammable if leakage occurs.

A further object of the invention is a flash lamp containing-besides a combustible metal, a gas which will support combustion and a means of ignition=an additional reagent which upon leakage occurring combines with the metal and the gas or one of them and thereby renders subsequent vigorous combustion impossible.

A more specific object of the invention is a flash lamp containing a dry combustible metal, a dry gas at less than atmospheric pressure which will support combustion of the metal, a means of ignition, and an additional reagent which on moisture entering the lamp will combine with the metal or the gas and thereby prevent their subsequent vigorous combustion. Such a lamp depends for its protection on the fact that some ordinarily vigorous chemical reactions do not take place in the total absence of moisture. Air entering by leakage brings with it enough water to set the reaction in train, a very small amount sufficing since the water appears to act catalytically. While such a reaction may be designed to consume in mild fashion the oxygen in the bulb as well as any that enters by leakage, for instance by the oxidation of phosphorus or of finely divided iron, it is preferable to provide for the combustible metal itself to be attacked.

Accordingly, a further specific object of the invention is a flash lamp containing a dry combustible metal which is not acted on by dry iodine, a dry gas at less than atmospheric pressure which will support combustion of the metal, and a charge of iodine suflicient in the presence of moisture to corrode the Whole surface of the metal and thereby prevent subsequent vigorous combustion of the metal. It is not necessary wholly to consume the metal; it is enough if it becomes coated with a reaction product which will sufficiently hinderaccess of oxygen to the metal when a user attempts to ignite the bulb.

To this end a small amount of iodine is included in the bulb, or a small amount of an iodine compound from which iodine is set free in the presence of moisture. The bulb is made dry, and the metal whose surface is exposed in the bulb is one upon which iodine will not act in the absence of moisture. Magnesium is liable to be attacked by dry iodine under these conditions, and therefore magnesium, or alloys of aluminium with magnesium or other alkali or alkaline earth metals, should not be used unless they can be wholly encased in metal which is not attacked by dry iodine. Suitable metals unattacked by dry iodine are aluminium and alloys of aluminium with non-alkaline metals. Such alloys are already well known and in common use in flash lamps and their precise composition forms no part of this invention. Bromine is a less effective substitute for iodine, and has the disadvantage of being liquid.

As an example of the preferred method of carrying out the invention, a flash lamp bulb having aluminium foil or wire as the illuminant, may be filled with dry oxygen to a pressure of 400 mm. Hg, and a little re-sublimed iodine may be included in the bulb, for instance by placing a small rod of compressed iodine powder in the exhaustion tube of the lamp. On admission of moisture the aluminium is attacked and soon becomes coated with yellowish brown aluminium iodide, or with drops of a solution of that iodide. In course of time, if there is enough iodine, the whole of the aluminium will be converted into iodide. But that In the exhaustion tube 4 of the bulb there is placed a small rod 5 of compressed iodine powder.

The bulb is then evacuated through the-tubet in well known manner, and the withdrawnis, replaced by a filling of dry oxygen at a pressure of 400 mm. Hg. The filament leads are then connected to the terminals of the usual cap'G and the cap is cemented to the bulb.

The bulbs of flash lamps to which the invention is to be applied in this manner should not be coated on their inner surface with plastic; for safety purposes such a coating isnot necessary; if the coating is a vehicle for colouring matter there is a possibility of reaction. with iodine changing the colour, and therefore coatings for coloured lamps should be on the out.- side ofthe bulb.

I" claim:

1. A flash lamp comprising a transparent bulb containing aluminium foil, dry oxygen at less In close proximity to the filaa 4 than atmospheric pressure, suflicient iodine to corrode the Whole surface of the aluminium on access of moisture to the bulb, and an electric circuit for igniting the aluminium by the passage of current.

2. A flash lamp comprising a transparent bulb containing a metal, body=oi extendedform composedlat least chiefly of aluminium, dry, oxygen at less than atmospheric pressure, sufficient iodine to corrode the whole surface of the metal body on access of moisture to the bulb, and an electric circuit for igniting the metal body by the passage of a current;

3. Afiashlampcomprising a transparent bulb containing axmetalbody of extended form the surface of which consists chiefly of aluminium, dry oxygenat less than atmospheric pressure, sufiicient iodine to corrode the whole surface of the: metal body on access of moisture to the bulb, and an electric circuit for igniting the metal body, by the passage of current.

JOHANNESAN'IONIUS MARIA VAN-LIEMPT.

References Cited in the, fileof thispatenti UNITED STATES. PATENTS Number Name Date- Re. 18,678 Ostermeier Dec; 6,1932 989,572 Van-Liemptetal. Jan; 29, 1935'

Claims (1)

1. A FLASH LAMP COMPRISING A TRANSPARENT BULB CONTAINING ALUMINIUM FOIL, DRY OXYGEN AT LESS THAN ATMOSPHERIC PRESSURE, SUFFICIENT IODINE TO CORRODE THE WHOLE SURFACE OF THE ALUMINIUM ON

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