US2136924A - Lighting neon tubes - Google Patents

Description

Nov. 15, 1938. R. w. REITHERMAN LIGHTING NEON TUBES Filed slept. 24, 1934 Patented Nov. 15, 1938 UNITED STATES Lrcn'rme NEON 'runes Ralph W. Reitherman, Chicago, Ill., assigner to Joseph Weidenhoff, Inc., Chicago, Ill., a corporation of Illinois Application September 24, 1934, Serial No. 745,273

1Claim.

An object of this invention is to provide an improved means for lighting a neon tube, and more particularly in an assembly such as that fully shown and described in the patent to 5 Haskins No. 1,966,066 for Distributor tester.

Another object of this invention is to provide a means for lighting neon tubes wherein the initial current which controls the lighting of the. tube is of the order of a milliampere, or

less, this current controlling a greater current which is of sufficient strength to effect the light- Still another object of this invention is to provide a constantly applied direct current voltage for lighting the tube which of itself is insuicient either to light the tube or to maintain it lighted, and superimposing on that current a high frequency alternating current whose voltage combined with that of the direct current is sufiicient to light the tube and to maintain it lighted while the alternating current voltage is applied.

These and other objects, as will hereinafter appear, are accomplished by this invention which is fully described in the following specification and shown in the accompanying drawing, in

- which- Figure 1 is a diagram of connections of apparatus for lighting a neon tube; and Fig. 2 is a diagram of a modiiied form of thev apparatus.

The embodiment illustrated in Fig. 1 comprises essentially a neon tube A, a transformer B, the primary of which receives current from an alternating current power supply line, rectifying and filtering apparatus C adapted to supply a substantially constant direct current to the neon tube A of a voltage, however, in'suflicient to maintain the tube lighted, a breaker D, and a radio frequency oscillator circuit E which is controlled by the breaker D. Closing the breaker D takes the negative grid bias oil the oscillator tube, thereby causing it to oscillate at radio frequency which when added to the direct current'voltage which is constantly applied is sufcient to light the tube.

The transformer B consists of a primary P, 'a center tapped secondary S, the ends of which connect with plates Ill, II of the double wave rectifier tube I2, which has a filament I3 lighted by means of a. secondary S' of the transformer. A lead I4 taps the center of the secondary S and passes to the condensers I5 of the filter circuit. these condensers lying one on each side of a filter choke coil I6, this coil connecting through a lead I1 with the center of the secondary coil S', all this being well known in this art.

A high resistance voltage divider vI8 connects to the ends of the leads I4 and I1, the upper l end I8 of this resistance connecting through a lead I9, a limiting resistor 20, and a radio frequency choke coil 2l with the tuned frequency plate circuit of an audion oscillator tube 22. This audion tube has a lament 23 supplied with l0 current from any suitable source, such as the secondary coil S2 of the transformerB. This tube has a plate 24 which connects through a lead 25 with a radio frequency coil 26, the opposite end of which connects with the radio fre- 16 quency choke 2|. A variable condenser 21 is placed across the terminals of the coil 26, an extension 2li"L of the coil 26 being connected through a lead 28 with one end of the neon tube through a collector ring 28. and a brush 20 28h, the tube and brushbeing mounted on an arms 28 which is rotatable on a. shaft 29 which is driven directly or indirectly from the distributor shaft, while the opposite end of the neon tube is suitably grounded on the shaft 25 29. The neon tube is enclosed except for a narrow radial slit as illustrated in Haskins Patent No. 1,966,066 and has a graduated scale 22 mounted on an insulating housing 28.

The audlon oscillator tube 22 has a grid 3l $0 which connects through a grid leak condenser 3| with one end of a radio frequency coil 32, the opposite end being connected through s. lead 33 with a, radio frequency by-p'ass condenser I4, the opposite end of this condenser being con- 35 nected through a lead 35 with one o f the nia.'- ments 23 and with a second radio frequency bypass condenser 36, the opposite side of this con- 'denser being connected to the lower end of the coil 26. .A second variable condenser 31 is placed 40 across'the terminals of the coil 32. This provides an oscillator of a well known type having both a tuned plate circuit and a tuned grid circuit. The means for controlling the oscillation l of the circuit E will now be described. 45

A distributor breaker or the like D has a cam 38 mounted on a shaft 29 which preferably is the same shaft as that on which the arm 22 is mounted which carries the rotating neon tube A. The cam 38 operates a breaker 39 which as 5o it oscillates under the action of the cam is adapted to alternately make and break connections with the stationary breaker point 4I which con-M nects through a lead 42 with a ground 4I). The breaker connects through a lead 43 with the 55 i against oscillation and unblock the same.

lead 33, and also with -the lower end I8h of the voltage divider I8. The breaker point 4| also connects through the lead 42 with an intermediate tap I8 of the voltage divider, and through a lead M with the lead 35 which connects with the lament 23. The lower end of the voltage divider is negative and the upper end is positive. 'I'hus the .negative bias applied to the grid of the oscillator tube is suilicient to block that tubev and prevent it from oscillating. The instant the breaker points 38, 4I are closed the grid of the oscillator tube is grounded, thereby removing the biasing voltage and causing the tube to oscillate.

The potential applied to the neon tube from the voltage divider is not sufficient to ionize the tube, nor is'this potential suillcient to maintain ionization by itself, but this voltage plus the high frequency generated by the oscillator is suilicient to cause this tube to be brilliantly lighted and to remain lighted so long as the breaker point 39, 4| are closed.

As the cam 38 is rotated the breaker arm 39 will alternately rise and fall thereby opening and closing the circuit through the breaker point Il so as to alternately block the oscillator tube Since the neon tube A is rotating in synchronism with the distributor cam 38, the result is that a series of continuous bright flashes occur which very deiinitely mark the movement of the arm 26c during which the breaker points are closed. The neon tube operates under a graduated scale 284. Consequently, the operator is able to read on this scale with great accuracy the points of opening and closing the breaker points and to tellwhetherthere is any tendency of the breaker arm to bounce when the cam is rotating at high speed. y

In Fig. 2 the rotary arm of Fig. 1 has been omitted and the neon tube A is shown connected to the lead 28 on one side and the ground on the other. The Wiring diagram of this figure is substantially the same as that of Fig. 1, except for certain changes in the radio frequency amplifying circuit. The coil 32 and tuning condenser 31 are omitted, the grid :llln being connected through a by-pass condenser 50 with one side of the coil 26 and its tuning condenser 421". The grid also connects. to ground through a radio frequency choke coil l| and a grid leak 52, The tuning coil 26C is connected to ground through a variable condenser 53, so that the ground can also be tuned into resonance with the plate circuit.

Although not shown, the neon tube A is mounted on a rotating arm, as in Fig. 1, and is preferably rotatable on the distributor shaft 29a, or, if desired, it can be driven at a speed which is a multiple of the speed of the distributor shaft. The cam 38 is operable as before to move the breaker arm 39a to make and break contact with the xed contact dla. As Contact is made the grid of the oscillator tube is unblocked and the circuit oscillates as before, with the result that a greatly increased voltage is generated in the lead 28*i at the terminal of the neon tube which operates in the same manner as before.

It will be understood that the term neon tube" used in the specification and claims is intended to includeall gaseous discharge tubes, a'nd the like. Also, the oscillator circuits shown are illustrative only.

The direct current supply to the neon tubes is shown in heavy lines in both figures.

I claim:

In combination, a neon tube, a voltage divider, a distributor breaker, means for applying to the ends of the voltage divider a direct current potential below the ionization potential of the neon tube, an oscillator circuit including an audion tube, the positive end of the voltage divider being connected to one end ofthe neon tube, the opposite end of the neon tube being grounded, an intermediate point of the voltage divider being connected to the lament of the audion tube, to ground and to the stationary contact of the distributor breaker, and the opposite end of the voltage divider having a negative potential and connected to the grid of the audion tube, and to the movable arm of the breaker whereby closing the breaker points cancels the negative bias of the grid and permits the circuit to oscillate so that the radio frequency voltage thus generated, added to the direct current voltage applied to the tube will light the same and maintain it lighted so long as the breaker points are closed.

RALPH W. REITHERMA.

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