US1930083A - Starting apparatus for electric discharge devices - Google Patents

Description

; 10, 1933. LPH 1,930,083

STARTING APPARATUS FOR ELECTRIC DISCHARGE DEVICES Filed Oct. 3, 1928 I NW Patented Oct. 10, 1933 r UNITED STATES" PATENT; OFFICE STARTING APPARATUS FOR ELECTRIC DISCHARGE DEVICES Application October 3, 1928. Serial No. 310,057

10 Claims. (01. 176-124) The present invention relates to discharge devices, and particularly to gas or vapor discharge devices which operate with a hot cathode.

The particular object of the invention is to improve the starting and operation of such devices, but various other objects and advantages will be obvious from the following particular description of an apparatus embodying the invention or from an inspection of the accompanying drawing. The invention consists in certain new and useful features of construction and combinations of parts hereinafter set forth and claimed.

Gas or vapor discharge devices are commonly provided with means for impressing a high voltage of short duration upon their electrodes in order to induce a discharge when starting, and also in some cases have means for heating the cathode in order to facilitate starting. In such' cases the application of the high potential to the electrodes before the cathode has had time to heat up is injurious, as, if a discharge is started before the cathode has reached the proper temperature for free emission of electrons, the 25 -discharge is confined to one spot on the cathode, and tends to disintegrate the electron emitting material. The present invention is for an apparatus to delay the initial application of the high potential until a suitable interval for cathode heating has elapsed, said apparatus offering the advantage that it is simple and rapidly resets itself for a new cycle of operation, even while the discharge device itself is operating.

In the accompanying drawing there is shown 35 for purposesof illustration one form of apparatus embodying the invention, in which Fig. 1 is a schematic diagram of a discharge device and its connection to the associated apparatus,

Fig. 2 is a front elevation of a thermal delay mechanism which may be employed, and

Fig. 3 is a sectional view taken on the line 33 of Fig. 2.

In the drawings a transformer 1 is either directly or inductively connected to a source of alternating current. The discharge device 2 has two anodes 3 and 4 at one end which are respectively connected through ballast resistances 5 and 6 and leads 7 and 8 to opposite ends of said transformer 1. A cylindrical cathode 9, which is preferably of metal coated with barium oxide, but may be made of any material which freely emits electrons when in a heated condition or which is coated therewith, is located at the op- 5 posite end of said discharge device, and is coned to lead 10 at a point exterior to the discharge device, thence by said lead 10 and said cathode 9 to the other end of said resistance 13. A mercury switch 17, of a type commonly referred to as a shifter, has one terminal connected to said lead 10, and the other terminal is connected through resistance 27, lead 18, resistance 19 and lead 20 to lead 7. A bimetallic strip 21 is connected to one end of said resistance 19 and is adapted to curl into contact with a contact point 22 connected to the opposite end of said resistance 19 under the influence of the h'eat generated by resistance 19 when current is passed through it.

Figs. 2 and 3 show a preferred arrangement of thethermostatic element. A yoke 23 of porcelain or other insulating material at one end carries an end of the bimetallic strip 21, supporting it over an opening in said yoke which allows free access of air for cooling after operation. The resistance 19, which is on the order of 2000 ohms, is wound upon the strip 21, and has one end connected thereto. Lead 20 thus makes contact with both through the terminal 24. The other end of the resistance 19 is connected to the terminal 25 by means of a flexible lead 28. Said terminal also carries the contact point 22, extending into the central opening in the yoke 23 in which the bimetallic strip 21 freely moves, and adapted to make contact with a contact point 26 on the bimetallic strip 21 when said strip has been heated to a desired amount.

As is usual in circuits for discharge devices of this type the shifter 17 (which is only schematically shown) is normally in a circuit closing position, but has an armature in electromagnetic relation to the core of choke coil 11, so that when the current through said choke coil 11 is of the value which normally flows through said coil in operation of the device the armature is 05 attracted to said core and rotates said shifter to a circuit opening position. In the usual circuit prior to this invention the current flow through said choke coil 11, shifter 17 and resistance 27 (the resistance 19 not being heretofore used) was 11 sufficient to operate said shifter to an open position, thus producing a voltage surge on the electrodes of the discharge device, immediately upon application of electrical potential to the energizing transformer. But according to the present invention the resistance 19 is inserted, its resistance being so large that the shifter is not actuated to an open position until the thermostatic element 21 has short circuited said resistance 19 under the influence of the heat given off from said resistance, the time interval for which operation is so adjusted as to allow suflicient heating of the cathode, being on the order of 45 seconds. As soon as the resistance 19 has been short eircuited a larger current flows through the choke coil 11, thus attracting the armature of the shifter 17 and rotating it to the open circuit position, and allowing the choke 11 to produce a voltage surge on the terminals of the discharge device 2, the shifter 17 again closing the circuit as the magnetic field around choke 11 collapses (unless a discharge is set up within the discharge device) allowing recurrent voltage surges, once the cathode is hot, until the discharge is initiated, in the manner well known to the art. As soon as shifter 17 opens the circuit the bimetallic element 21 starts to cool, in order to be ready for starting the lamp again, but it has sufiicient thermal capacity to remain closed for several seconds. allowing a number of current surges, if necessary to start the discharge, before again inserting the resistance.

It is to be understood that the discharge device 2 may be filled with any desired gas such as neon, or source of vapor such as mercury, although for certain purposes a mixture of gases such as helium and neon may be used.

It is also to be understood that the structure shown and described is for purposes of illustration only, and that the invention can be embodied in other forms without departing from the spirit thereof. It is obvious that other forms of delay devices could be substituted for my thermal device, and that the invention is applicable to direct current as well as alternating current discharge devices.

I claim:

,1. In combination with a gaseous discharge device having a thermionic cathode adapted to give off electrons when heated, means for heating said cathode to a temperature at which the free electron emission therefrom will support the normal discharge current, means for supplying a voltage surge to said discharge device. and means for delaying said voltage surge until said cathode has reached said discharge supporting electron emitting condition.

2. In combination with a gaseous discharge device having a thermionic cathode adapted to give off electrons when heated, means for heating said cathode to a temperature at which the free electron emission therefrom will support the normal discharge current, means for initiating a discharge within said device, and means comprising a thermally controlled switch for delaying the operation of said means for initiating a discharge until said cathode has reached an operating discharge supporting electron emitting condition.

3. In combination with a gaseous discharge device having a thermionic cathode adapted to give off electrons when heated, means for heating said cathode to a temperature at which the free electron emission therefrom will support the normal discharge current, means for applying a voltage surge to said device and means comprising a thermally controlled switch for delaying said voltage surge until said cathode has reached said tdischarge supporting electron emitting condiion.

4. In combination with a gaseous discharge device having a thermionic cathode adapted to give off electrons when heated, means for heating said cathode to a temperature at which the free electron emission therefrom will support the normal discharge current, means for applying a voltage surge to said device comprising an inductance and a switch in parallel with a discharge path, and means for delaying the discharge of said inductance until said cathode has reached said discharge supporting electron emitting condition.

5. In combination with a gaseous discharge device having a cathode adapted to give olT electrons when heated, means for heating said cathode, means for initiating a discharge within said device, means for delaying the operation of said means for initiating the discharge until said cathode has reached an operating temperature, and means to automatically reset said delaying means upon initiation of the discharge through said device.

6. In combination with a gaseous discharge device having a cathode adapted to give off electrons when heated, means for heating said cathode, a means for supplying a voltage surge to said discharge device, a means for delaying said voltage surge until said cathode has reached an operating temperature, and means to automatically reset said delaying means upon initiation of the discharge through said device.

7. The method of starting a gaseous discharge device having a thermionic cathode adapted to give off electrons when heated, comprising heating said cathode to a temperature at which the free electron emission therefrom will support the normal discharge current, and applying 8. voltage surge to said device after said cathode has reached said discharge supporting electron emitting condition.

8. In combination with a discharge device having a thermionic cathode adapted to give off electrons when heated, means for heating said cathode to a temperature at which the free electron emission therefrom will support the normal discharge current, means for initiating a discharge within said device, and means for delaying the operation of said means for initiating a discharge until said cathode has reached said discharge supporting electron emitting condition.

9. The method of starting a discharge device having a thermionic cathode adapted to give off electrons when heated, comprising heating said cathode and initiating the discharge through said device after said cathode has reached said discharge supporting electron emitting condition.

10. In combination, an electric gaseous discharge device having a thermionic cathode, means to heat said cathode to a temperature at which the free electron emission ,therefrom will support the normal discharge current, means for initiating a discharge within said device, and means to prevent hot spotting of said cathode comprising means for delaying the operation of said means for initiating a discharge until said cathode has reached said temperature.

LEROY J. BUT'I'OLPH.

CERTIFICATE or CORRECTION.

Patent No. 1,930,033. October 10', 1933.

LERQX J. .BUTIOLRH,

It is hereby certi'fied' that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 67, claim 2, for "an operating" read said; and line 133, claim 9, after "cathode" insert the words to a temperature at which the free electron emission therefrom will support the normal discharge-current; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 28th day of November, A.- D. 1933.

F. M. Hopkins I (Seal) Acting Commissioner of Patents,

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