US1938636A - Alternating current heated thermionic device - Google Patents

Description

Dec. 12, 1933. E, OOSTERHUIS 1,938,636

ALTERNATING CURRENT HEATED THERMIONIC DEVICE Filed Feb. 10, 1930 MMWT MWTWT INVENTOR EKKO 005TERHU\5 BY 7%Wm ATTORNEY Patented Dec. 12, 1933 UNITED STATES I ALTERNATING CURRENT HEATED THERIVIIONIC DEVICE Ekko Oosterhuis, Eindhoven, Netherlands, assignor to Radio Corporation of America, a corporation of Delaware Application February 10, 1930, Serial No. 427,170, and in Germany March 26, 1929 2 Claims.

The present invention relates to thermionic devices, and more particularly to improvements in, or relating to, circuit arrangements for amplifying valves heated with alternating current.

It is well known that in heating cathodes of thermionic devices to incandescence with alternating current, it is customary to connect the negative end of the anode circuit to the electrical mid-point of the incandescent cathode. This connection may be established in various ways. One of the best known methods consists in providing the mid-point of the incandescent cathode with a particular leading-in Wire which is taken through the wall of the tubes.

However, instead of connecting, the real midpoint to the anode circuit, as an alternative the virtual mid-point of the cathode may be connected thereto. There are various methods of connecting the virtual mid-point of the cathode. Thus, for example according to a well known method, the anode circuit may be connected to the mid-point of the secondary of the transformer from which the incandescent cathode is supplied. Alternatively, the terminals of the secondary may have connected across them a resistance, or more broadly an impedancathe mid-point of which may be connected to the anode circuit.

The present invention has for its main object a new method of obtaining the electrical midpoint of the cathode, and consistsin providing the secondary winding, which is wound in the usual manner, with an additional coil, the winding direction of the latter being opposed to that of the secondary winding, and being so large that the free end of the said auxiliary coil possesses, for example, the same potential as the mid-point of the filament.

The novel features which I believe to be characteristic of my invention are set forth in particularity in the appended claims, the invention itself, however, as to both its organization and method of operation will best be understood by reference to the following description taken in connection with the drawing in which I have indicated diagrammatically several circuit organizations whereby my invention may be carried into efiect.

In the drawing,

Fig. 1 shows an arrangement embodying the invention,

Fig. 2 shows the arrangement applied to a thermionic device having an indirectly heated cathode.

Referring to the drawing in which like reference characters in the different figures represent the same elements, in Fig. 1 is shown a triode having its cathode 1 heated by a source of alterhating current, the secondary 2 of the transformer T, having a coil 3 connected with it, the

coil 3 being in the anode circuit of the tube. This auxiliary coil is wound in a direction opposite to that of coil 2. Furthermore, the coil 3 is so proportioned that the free end 1 of the coil possesses the same potential as the electrical mid-point of the cathode 1.

The second coil 3 may be made of thin wire as no substantial current strength occurs therein. There is thus obtained the advantage that it is not necessary that the secondary winding 2 which is of thick wire shouldbe tapped at its .mid-point. The additional coil 3 may be proportioned (at will) so that the potential of the free end 4 is equal at all times to that of a suitable point of the incandescent cathode 1.

The invention is shown applied in Fig. 2 to tubes having an indirectly heated cathode 1. In this case the cathode is connected to the free end 4 of the additional coil 3. By the use of a thin wire for the additional coil the proportions of the transformer are not increased.

While I have indicated and described several systems for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular organizations shown and described, but that many modifications in the circuit arrangements, as well as in the apparatus employed may be made without .departing from the scope of my invention as set forth in the appended claims.

What I claim is:

1. In combination, an electron discharge tube including a heater element, a cathode, an anode and a grid, a source of pulsating heating current, a transformer between the element and the source, an auxiliary coil having one end connected with the transformer secondary and being wound in a direction opposite'to the latter, said cathode being connected to the other end of said coil.

2. In combination, an electron discharge tube including a heater element, a cathode, an anode and a grid, 2. source of pulsating heating current, a transformer between the element and the source, an auxiliary coil having one end connected with the transformer secondary and being wound in a direction opposite to the latter, said cathode, anode and grid being connected to the other end of said coil.

EKKO OOSTERHUIS.

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