US1654295A - Device for starting intensifiers and oscillators - Google Patents

Description

Dec. 27, 1927.

S. LOEWE DEVICE FOR STARTING INTENSIFIERS AND OSCILLATORS Filed Aug. '25. 1921 /N V N70)? SQ at B) 5 @M A770/7/VEY5 Patented Dec. 27, i927.

UNlTED STATES 1,654,295 PATENT OFFICE.

SIEGMUND LOEWE, 0F BERLEN, GERMANY, ASSIGNOR T0 WESTINGHOUSE ELECTRIC 6: MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

nnvrcn son STARTING rn'rnnsiirrnns AND OSCILLATORS.

Application filed August 26, 1921, Serial No. 495,782, and in Germany August 6, '1917.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 4.1 STAT. L, 1313.)

This invention relates to electrical systems using vacuum devices. It has been found that, in such systems, particularly when the ballastresistance is used, the filament shows a more rapid deterioration than would ordinarily be expected. This deterioration is due, at least in part, to the temporary excessive temperature which ocours in the filament a moment after the circuit of the device is first closed.

It is'an object of this invention to provide a means for preventing such excessive temperature. More specifically stated,-the object of the invention is accomplished by makin sure that the ballast resistance has sutficienu time to become heated before the temperature of the filament reaches its full value.

Other objects of the invention will be ap parent from the disclosure in the following detailed description and the accompanying drawings, wherein Figure 1 is a diagrammatic illustration of a circuit involving this invention.

Fig. 2 is a diagrammatic illustration of a modified form of the invention and Fig. 3 is a partially diagrammatic View of a form of filament which may be used-either in the'circuits shown in Fig. 1 or'that shown inllig. 2.

The circuit includes a battery 1, or any other desirable source of current, a switch 4:, a vacuum device including a filament 3, and a resistance 2, all in series. The resistance 2 is of any of the usual types of ballast resistance, having a positive temperature coefiicient. The type most readily available consists of an iron wire enclosed within a glass housing.

When the switch L is first closed the filament 3 and the ballast resistance 2 are both cold, the resistance of each of them is there fore, smaller than after conditions have be come steady. Ordinarily the time required for the current to rise to its maximum value is less than that required for the ballast resistance to heat up. Consequently, the filament 3 will be subjected to an excessive current which lasts until the resistance 2 has become hot. The filament is heated by the current. Its heating is the more rapid because the current is excessive. If, by the time the filament has reached its intended standard temperature, the ballast resistance has not yet reached its-limiting value, the temperature of the filament will continue to rise and The i will so be excessive for ashort time. excessive temperature of the filament is remedied when the increasing resistance of the ballast 2 stops the excess of current.

It is therefore, necessary to in some way delay the rise of the current until the ballast resistance 2 becomes hot enough to prevent an excessive current through the filament. This may be accomplished by inserting an inductance in the circuit or any othermeans of delaying the rise of the current to its full value maybe employed.

In Fig. 2, this is accomplished by associating the resistance '6 with the switch a. Various taps 8, 9, 10 and 11, leading from separate points in the resistance 6, enable the operator to cut the resistance out of the circuit step by step by moving the handle 5, which with the. switch member 4;, constitutes a lever pivoting about the point 7. Obviously, it is not possible to move this lever instantaneously. The phenomenon which has been discussed above takes place more quickly than the change in resistance due to the movement of the switch in this arrangement. Therefore, the filament 8 is not subjected to the full current until after the ballast resistance 2 has had ample time to get hot.

The filament 3 may be in any vacuum device, for example, it may be the cathode in a detector, a generator or an amplifier. In systems using the last three, the operator would use the lever 5 repeatedly in switching on and off the several tubes in order to change the system from sending to receivmg arrangement or in. order to change the number of stages of amplification.

Another way of securing the same result is by ensuring that the thermal time lag of the ballast resistance is less than that of the filament, this may be done either by decreasing the thermal capacity of the ballast 2 or increasing that of the filament 3. One way of increasing the thermal. time lag of thefilament is to wind it upon a support. This is illustrated in Fig. 3 where the filament 3 is shown as coiled upon a support 12 of quartz fibre or-other refractory material. When the current turn d 01 in such a filament, the quartz fibre 12 must be heated in addition to the filament. The increased thermal capacity of the system composed of filament and support will cause the filament to approach its final temperature asy1nptotically. Obviously, any other cool bodies near the filament may be used to produce the same result. For example, the junctions where the lead-in wires are connected to the filament may be made massive to absorb heat. 'lhis will sufiiciently delay the heating of the filament to ensure that the ballast resistance 2 will be heated first.

lnstead of increasing the thermal time lag of the filament, theheat capacityof the ballast resistance may be diminished. This may be done by choosing the size or material of the wire for this purpose or by properly selecting the enclosing vessel and the gas or degree of vacuum within it.

lVhile I have shown and described only a limited number of embodiments of my invention it will be obvious that various changes n'iay be made herein without departing from the spirit thereof and it is desired, therefore, that only such limitations shall be imposed there-on as are indicated in the appended claims or required by the prior art.

I claim as my invention:

1. In an electron-discharge-tube device, a hermetic envelope, a. filament in said envelope, a source of energy, means for connecting said source in series with said filament to heat the same to incandescence and means associated with the filament to cause it to respond to the heating current as if the thermal capacity of the filament were increased whereby momentary unbalance in the resistance or the elements in said series circuit tending to abnormally increase :the

voltage applied to said filament immediately upon closing the filament energizing circuit is prevented.

2. In combination, a vacuum. device having a filament, a circuit for energizing said filament to heat the same, a ballast resistance connected in series with said energizing circuit and means for abstracting heat energy from the filament and thus insuring that, upon closing the circuit, the ballast resistance will arrive at its steady temperature before the filament reaches its maximum ten'iperature.

ln combination, a vacuum-tube device having a filament, a circuit for heating said filament, heat-absorbing means cooperating with said filament to term a combination of greater thermal capacity than said filament to thereby so delay the rise of temperature of said filament upon closing said circuit that the temperature of said filament never exceeds its ten'u ierature under steady operating conditions.

l. In an electron-discharge device, an evacuated container, a filament in said cntamer, a source of energy, a circuit includng said source, said filament and connecting elements, a device thermally associated with said filament and producing therewith a combination having such thermal characteristics that the relation thereof to the thermal characteristics of the connecting elements will prevent the voltage applied to the filament in'm'iediately upon closing the circuitabnormally rising by reason of the dill'erence between the temperature of i said filament then and after the temperatures throu hout the circuit have become stable.

lntestimony whereo'fl alfix my signature.

DR. SIEGMUN D LOENV E.

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