US2248670A - Flashlight lamp - Google Patents

Description

y 1941- HANS-JOACHIM HELWIG arm. 2,248,670

FLASHLIGHT LAMP Filed Ju1y'20, 1937 IIIMVENORS Hans-Joachim Helwig Max Mcetschke A TORNEY Patented July 8, 1941 anam- FLASHLIGHT LAM]? Hans-Joachim Helwig, Berlin-Schoneberg, and

Max Maetschke, Berlin-Charlottenburg, Germany, assignors to General-Electric Company, a corporation of New York Application July 20, 1937, Serial No. 154,676 In Germany July 28, 1936 2 Claims.

Our invention relates to evacuated devices comprising a sealed envelope or vessel containing a gaseous atmosphere at a pressure considerably below atmospheric, and more particularly to flash light lamps, mainly for photographic purposes, containing one or more light-developing combustible metal strips or foils, for instance of aluminium or magnesium, in a sealed vessel similar to the bulb of an incandescent lamp, which vessel contains oxygen at a pressure far below atmospheric; instead of the metal strip or foil metallic powder or a clue of metal wire may be used as well. This flash material is ignited by electric means.

Flash light lamps of this type have the drawback that, as soon as air has entered the bulb due to a crack, the lamp has a tendency to burst when being ignited. Therefore it already has been proposed to arrange inside the vessel a capillary tube filled with a small amount of air and closed by a drop of mercury, so that, provided the pressure of the oxygen is correct, the air enclosed in the capillary tube expands and, by moving the drop of mercury, causes a connection between two interrupted ends of the igniting wire; on the other side, if air has entered the vessel from outside, the drop of mercury moves to the opposite direction, leaving the two interrupted ends of the igniting wire unconnected, so that the lamp cannot be ignited.

This arrangement, acting as an indicating and a safe-guarding means at the same time, has the disadvantage of being manufactured only in a rather complicated way and of not acting with.

the certainty wanted, due to the tendency of the mercury to adhere to the Walls of the capillary tube or, even, to move in a way not wanted on account of the lamp being shaken by transport or by handling it.

The object of our invention is to provide a simple apparatus for evacuated devices such as flash light lamps, indicating the correct pressure of the gas-filling and not aiiected by shocks or similar influences.

According to the invention this indicating arrangement consists of a hollow body, preferably shaped like a ball, whose walls are formed by an elastic material, the body containing air at a pressure somewhat higher than the pressure inside the lamp-vessel, but lower than atmospheric pressure. Also, an elastic body of this kind is blown up as long as the gas-pressure of the bulb is correct and unchanged, but is compressed if air has entered the bulb due to a crack.

In the drawing accompanying this specification: The Figure 1 shows, in elevation, a typical flash light lamp, the Figures 2 and 3 show the bottom parts of two similar lamps but of a slightly different kind. The principal parts of the three lamps are constructed in the normal way.

The bulb l, as Figure 1 shows, is provided with a stem 2, lead-in wires 3-4, and an exhausting pipe 5. An igniting wire 6, carrying an igniter 6' of the known type, is fixed to the free ends of the leading-in wires inside the bulb l. Furthermore, the bulb l contains a flash material such as aluminium foil I, and a filling of oxygen at a pres sure below atmospheric, for instance 200 mm. of mercury. The upper part 8 of the exhausting pipe 5 extends far above the pinch 9 of the stem 2. Thus, the lower end of the part 8 is closed by the pinch, while the upper end is open. A ballshaped body In of an elastic material, such as rubber, pressed together as it is, is placed upon the upper end of the tube, yielding an airtight closing against the bulb. As soon as the bulb I has been evacuated and filled with the proper amount of oxygen, the compressed elastic body it] swells due to the air contained in the pipe 8. Thus a safe indication that the pressure inside the bulb is below one atmosphere and no air has entered the bulb is obtained. If, on the contrary, air has got into the bulb, the elastic body If), again, is pressed together, thus indicating by its shape being altered that the lamp must not be used.

It is not by all means, necessary that the elastic body 10 be placed on the top of a pipe. It may just as well, as is shown in Figure 2, be arranged as a closed ball filled with attenuated air, inside the neck l2 of the bulb l.

According to Figure 3 the elastic body, too, may have the shape of a bellows 13 consisting of any elastic material, preferably of a very thin elastic metal sheet. Preferably, the bellows I3 is fixed to the stem 2 of the lamp by means of a clip l4.

What we claim as new and desire to secure by Letters Patent oi the United States is:

1. A flash light lamp comprising a closed transparent vessel containing a combustible material, oxygen at a pressure below atmospheric, an igniter and a hollow rubber ball whose fillingpressure is somewhat higher than the correct pressure of the lamp, but lower than atmospheric pressure, the rubber ball being placed upon and having its interior communicating with the open end of a pipe whose other end is sealed airtight to a part of the interior of the vessel, so that the rubber ball blows up if the filling pressure of the pressure of the lamp, but lower than atmospheric pressure, the rubber ball being placed upon and having its interior communicating with the open end of a pipe whose other end is sealed airtight to the pinch of the vessel whereby said ball is normally expanded but is compressed upon leakage of air into the vessel.

HANS-JOACHIM HELVVIG. MAX MAETSCHKE.

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