US1981860A - Vacuum tube life meter - Google Patents

Description

1934 L. A. GEBHARD ET AL VACUUM TUBE LIFE METER Filed Feb. 17, 1932 fl/ I ATTORNEY Patented Nov. 27, 1934 1,981,860 I VACUUM TUBE LIFE METER Louis A. Gebhard and George E. Jacobson,

Washington, D. 0.

Application February 17, 1932, Serial No. 593,598 4 Claims. (01. 161 -15) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) Our invention relates broadly to apparatus for use in electron tube circuits and more particularly to a circuit arrangement and construction for determining the life and hours of service of electron tubes;

One of the objects of our invention is .to provide means for checking the operation of electron tubes for determining the total number of hours of service an electron tube has given and to determine the number of hours over which the circuit containing the electron tube has been operated.

Another object of our invention is to provide a compact construction of meter which measures the time period over which an electron tube has been in use in order to warn the attendant with respect to the probable life of the tube and to provide a check upon the manufacturer with respect to the guaranteed life of the tube.

Still another object of our invention is to provide a construction of time actuated device of measuring electron tube circuits for accurately checking the performance of the electron tube while offering no interference to the normal operation of the circuits in which the electron tube under inspection is being operated.

A still further object of our invention is to provide a construction of electron tube life meter which is particularly adapted for electron tube circuits employing tubes having their cathodes energized from transformers having a grounded center tap-secondary winding, wherein the life of the tube may be determined without interfering with the normal operation of the transformer system.

Other andfurther objects of our invention reside in the construction of an electron tube life meter as set forth more fully in the specification hereinafter following by reference to the accompanying drawing, wherein:

Figure 1 diagrammatically illustrates the circuit arrangement for the electron tube life meter of our invention; Fig. 2 is a front view of the electron tube life meter; Fig. 3 is a top view 'of the electron tube life meter; Fig. 4 is a bottom view of the electron tube life meter; Fig. 5 is an enlarged view of the transmission shaft showing the manner of insulating the shaft for the protection of the power supply circuits leading to the cathode of the electron tube under measurement; and Fig. 6 is a cross-sectional view of the insulation means surrounding the drive shaft which leads to the counter in the electron tube life meter of our invention.

Where vacuum tubes are purchased on a guaranteed life basis it is desirable, and in fact necessary, to know the total number of hours of service the tube has given. Where tubes are not purchased on this basis it is desirable to know just how much life the tube has had so as to check up 80 on its performance. It is also desirable to know just how many hours a particular radio transmitter has been operated. This information may be obtained by use of the device of our invention which we have termed an electron tube life meter.

The meter shown in Fig. 1 consists of an electrically operated clock 1 which is connected to a counting mechanism 2 by means of a flexible shaft 3. The counting mechanism 2 is supoprted by insulated yoke. 4.from insulated panel 5. Insu- 7 lated panel 5 also supports the clock 1 by means of screws 6 and 7 which pass through ring member 1a which abuts against lugs lb projecting from the casing 1 of the electric clock. The electric clock is shown having a setting device 21 projecting from casing 1. Terminal 22 is grounded direct to the casing of the clock while the terminal 23 is insulatingly mounted on casing 1. Screws 8 and 9 fasten the mechanism to any desired surface, such as the panel 10 of the transmitting apparatus. The counting mechanism 2 is so arranged that one .turn of its shaft 11 will cause one number to be counted by its dial 12. The mechanism is so arranged that the dial 12 is visible through the aperture '16 in the front panel 86 of the radio transmitter or can be seen by opening a door in the front of the panel. The flexible shaft 3 consists of a spring which is shown in detail in Fig. 5. This flexible shaft 3 is con nected through a sleeve 17 to the shaft 18 which 90 carries the minute hand 13 of the clock mechanism 1. The sleeve 1'7 is screw threaded on its exterior to receive the end turns of the coil spring 3 as shown. The other end of shaft 3 is fastened to shaft 11 of counting mechanism 2 through an insulated'coupling. The'coupling includes an insulating sleeve 14 split longitudinally at one side thereof and placed between the shaft 11 and the spring head 15 as shown. The spring head 15 contains a set screw 15a. to lock the head on shaft 11 with insulated bushing 14 disposed therebetween. The spring head 15 has a stud portion 15b projecting therefrom and threaded to receive the end turns of the coil spring 3. The hour hand 19 carried by tubular shaft 20 is permitted to run free of any connection with the shaft 3.

In operation the electrical circuit of the clock mechanism 1 is connected to the cathode circuit of the radio transmitter as shown in Fig. 1. As

long as the filaments of the tubes are operated the clock mechanism will also operate. This is due to the arrangement of the electromagnetic actuating mechanism of the clock shown at 24 and vgrounded at 22 to the casing 1 and connected through binding post 23 with the external filament circuit of tube 25. We have selected the electric clock mechanism illustrated diagrammatically in Fig. l by reason of the ability of this type of electric clock to operate from direct current as well as alternating current. In lieu of the alternating current supply illustrated for the electron tube apparatus there are many installations where only direct current is available, in which event the vacuum tube life meter of our invention functions with the same precision as is obtainable with alternating current power supply. The electromagnet 24 and associated armature illustrated constitutes the actuating mechanism of the rewinding element of the clock mechanism which periodically stores energy into the clock spring to be expended in driving the clock mechanism and associated escapement as shown, for example, in the patent to Cooper 1,564,124, which issued December 1, 1925. The rewinding mechanism illustrated functions independently of the character of the power supply. However in the embodiment of the invention illustrated in Fig. 1, the power transformer 26 supplies the cathode heating potential from an alternating current source connected to theprimary winding 26a through circuit 26b. The secondary winding of transformer 26 is represented at 27 having a center tap 27a which is grounded to the panel 10 and connected to ground indicated at 28. The

case of the counting mechanism 2 is often grounded by reason of a connection established through the panel 10. It is therefore necessary that the casing of the counting mechanism 2 be suspended in the insulated yoke 4 and entirely insulated from the mechanism of the driving means. This insulation is assured by reason of the insulating sleeve 14 which wholly surrounds the counter shaft 11 and electrically isolates the flexible shaft 3 from the counter mechanism. The fact that the clock mechanism 1 is wholly supported away from panel 10 prevents short-circuiting with respect to the panel 10 and insures continuous operation of theclock mechanism so long as power is supplied through transformer 26 to the cathode 25a of the electron tube 25. It will be seen that the drive mechanism 24 is connected across the cathode 25a and is actuated so long as cathode 25a is energized. By virtue of the isolation of the counter mechanism from the clock mechanism, no interference to the operation of the circuits is offered as the meter continues to measure the total time period over which vacuum tube 25 operates. p

When the filaments are de-energized the clock is de-energlzed and therefore will stop and no longer register on the dial 12 of counting mechanism 2. When a new tube is put in the radio transmitter a note is made of the reading of dial 12. After this tube has burned out or has become inoperative for other reasons another note is madeof the reading of dial 12. These two readings are subtracted and the total life of the tube is obtained. Subtracting any two successive clock mechanism 1 is generally one terminal of its electrical circuit, it is desirable to insulate the case from ground. This is the reason for insulating part 5 and bushing 14. A counter mechanism 2 may then be mounted very close to the front panel of the radio transmitter which is generally grounded. A suitable aperture 16 cut into the front of the panel will then permit observation of the dial 12.

The readings taken on dial 12 may be recorded from time to time for checking the operation or performance of particular electron tubes for determining the service received. The vacuum tube life meter is applicable to electron tubes in amplification circuits of various descriptions such as telephone repeater circuits, radio transmitters, radio receivers, and all electron tube circuits, employing electron tubes of the more expensive types against which a careful check of performance must be maintained.

While we have described our invention in one of its preferred embodiments we desire that it be understood that modifications may be made and that no limitations upon our invention are intended except as are imposed by the scope of the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes, without the payment of any royalty thereon.

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

1. An electron tube life meter comprising a frame structure, an electric clock mounted on said frame structure, a flexible shaft extending from one of the driven shafts of said electric clock, an insulated yoke supported on said frame structure, a mechanical counter suspended in said insulated yoke and electrically insulated from said electric clock, and an insulated coupling between said flexible shaft and the driving shaft of said mechanical counter for driving said mechanical counter, said insulated coupling electrically insulating said mechanical counter from said electric clock.

2. An electron tube life meter comprising a frame structure, an electric clock carried by said frame structure, an insulated yoke supported by said frame structure, a. mechanical counter insulatingly suspended by said yoke with the axis of the driving shaft of the mechanical counter extending in a. plane normal to the axis of the shaft of said electric clock, and a flexible connection extending between the driven shaft of said electric clock and the driving shaft of said mechanical counter for effecting the operation of said mechanical counter, and means for electrically insulating said mechanical counter from said electric clock.

3. An electron tube life meter comprising a frame structure, an electric clock carried by said frame structure, an insulated yoke supported by said frame structure, a mechanical counter inof said mechanical counter, said coiled wire like member being turned to an angle of substantially QO" for operating said mechanical counter, said mechanical .counterhaving means supported by said frame structureand offset with' respect to the face of said electric clock, a mechanical counter supported by said insulated yoke 3 and electrically insulated from said electric clock, adriving member connected with said mechanical counter, and aflexible connection between the driven member of said electric clock and the driving member of said mechanical counter.

' LOUIS A. GEBHARD.

GEORGE E. JACOBSON.

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