US2030404A - Electric discharge device - Google Patents

Description

Feb, 131, 1936. w RYDE r AL 2,030,404

ELECTRIC DISCHARGE DEVICE Filed Nov. 17, 1951 INVENTORS XZWM ATTORNEY Patented Feb. 11, 1936 UNITED STATES PATENT OFFICE ELECTRIC DISCHARGE DEVICE York Application November 1'7, 1931, Serial No. 575,654

- In Great Britain December 3, 1930 6 Claims.

The present invention relates to electric discharge devices generally and more particularly the invention relates to such devices useful for advertising, decorative, or display purposes.

In the specification of our British Patent Number 349,261 granted 13th August 1931 we have described a method of modifying the appearance of the discharge in an electric discharge lamp by continually admitting to the lamp a stream of impurity which is cleaned up by the action of the discharge. The modification introduced by the method there described is a wandering of the positive column over the cross-section of the tube; this is here called a-ripple effect. We have now found that the application of the same method in rather different conditions produces another type of modification.

According to the present invention an electric discharge lamp containing a rare gas is provided with means for introducing a stream of impurity therein whereby a permanent striated discharge is obtained.

Thus if the permanent filling of the lamp consists of neon or a mixture of neon and helium, and if the current through the lamp and the rate of introduction of impurity are rightly adjusted the positive column does not wander, but breaks up into striae of approximately fixed position. A striated discharge of this kind can also be produced by the same method in helium and probably in the other rare gases; but it seems to be more difiicult to produce in these gases and the effect is not so striking. Of course we are aware that striated discharges have often been described, but they are less common in rare gases than in common gases. Our experiments indicate that they are produced in rare gases only when impurities are present. The object of our invention is the production of a permanent striated discharge in a rare gas by the continual introduction of impurity which is cleaned up by the discharge. By permanent we mean capable of being produced for a time comparable with the life of lamps of similar construction in which the discharge is not striated.

In the drawing accompanying and forming part of this specification an embodiment of the invention is shown in side elevation.

Referring to the drawing the new and novel electric discharge device comprises a container I, said container I having a diameter of between 20 and 40 mm. Said container 1 is provided with graphite electrodes 2 and 3 and is filled with neon or a neon-helium mixture to a pressure preferably between 2 and 3 mm. The striae can be produced at higher pressures, but the pressure that we have named is most suitable. The impurity is introduced by the method described in the above mentioned previous specification. Side tubes 4 and 5 are sealed to the main tube I near the electrodes 2 and 3 respectively on the portion of the tube that lies between the electrodes as shown in the drawing and not on the portion lying between an electrode and an adjacent end. A single side tube may be used if desired. The side tubes 4 and 5 contain naphthalene separated from the gas in the lamp by graphit" plugs 6 and 1 through which the naphthalene vapour diffuses. The rate at which vapour diffuses into the lamp should be considerably greater than in the example of the previous application which referred to argon, and accordingly the area of graphite exposed to the lamp must be greater. The appropriate rate is similar to that given in the example which referred to neon; a length between 0.5 and 1 cm. when the graphite plugs 6 and I are 6 mm. in diameter will give about the 4 right area.

The lamp should be supplied preferably with alternating current; the stria: effect, like the ripple effect is not so easily obtained with direct current. In order to develop the striations strongly and in their most attractive form, it is an advantage to increase the current through the lamp to about 100 to 150 milliamperes for a few seconds and then quickly to reduce it to about 15 milliamperes. After this the striations remain developed for a period of, say, half an hour when the above process may be repeated. A suitable means of varying the current through the lamp comprises a variable choke conventionally shown at l0 and which may be controlled by a time switch, a thermostatic switch or any other suitable switch means well known in the art, said variable choke l0 being connected in the leads II and 12 to the primary of the transformer 8, 9 connected to the lamp' l by leads l3 and Hi.

If the current through the lamp is of the order of 50 to milliamperes, the ripple effect will be obtained, but if the current is reduced to an order of 15 milliamperes, the luminous column breaks up into steady stria: and the effect according to the invention is obtained. At intermediate currents a mixture of the ripple effect and the striae is sometimes obtained.

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

1. An electric discharge lamp comprising an envelope containing a discharge supporting rare gas and provided with means for introducing a stream oi. organic vaporous impurity therein, said means comprising a porous body through which the impurity diffuses.

2. An electric discharge lamp comprising an envelope containing neon for supporting the discharge and provided with means for introducing a stream 01' organic vaporous impurity therein, said means comprising a porous body through which the impurity difluses.

3. An electric discharge lamp comprising an envelope containing a discharge supporting mixture of neon and helium and provided with means for introducing a stream of organic vaporous impurity therein, said means comprising a porous body through which the impurity diffuses.

4. An electric discharge lamp containing a rare gas and provided with means for introducing a stream of vaporous impurity therein, said means comprising a porous body through which the impurity difluses and means for automatically increasing the current through the lamp to a larger value for a short period and reducing it to a smaller value for a longer period.

5. An electric discharge lamp containing a rare gas and provided with a source of impurity thereon for introducing a stream of vaporous impurity therein to alter the characteristic appearance of the discharge in the rare gas and means for increasing the current through the lamp to a larger value for a short period and reducing it to a smaller value for a longer period to strongly develop striations in the discharge.

6. An electric discharge lamp comprising an envelope containing a discharge supporting rare gas and provided with a source of naphthalene vapor for introducing a stream of said vapor therein, said naphthalene vapor producing a permanent striated discharge in said rare gas.

JOHN WALTER RYDE.

HENRY GRAINGER JENENS. 20

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