US1797990A - Heater construction for cathodes - Google Patents

Description

March 24, 1931. A. N. I UclAN 1,797,990

HEATER CONSTRUCTION FOR CATHODES Filed Feb. 6' 1925 ARSENE N.LUCIAN BY 4 e 5 A O EY Patented Mar. 24, 1931 UNITED` STATES ABSENE N. LUCIAN, OF PHILADELPHIA, PENNSYLVANIA HEATER CONSTRUCTION FOR CATHODES Application led February 'lhis invention relates to'resistance heaters lor cathodes.

The object ot' the invention is to improve the construction of a heater of this type. To this end, one objectis to maintain the resistance element in the form of a helix open in its interior to permit the free circulation ot' gas therein and therethrough so that convection currents may be employed for heat 1o interchange. A further object of the invention is to surround the heater by a shell made of a highly magnetic material such as soft iron. in order to completely shield the cathode and the internal elements otl the, tube cooperating with the Cathode from any magnetic lields which the heating current in the heater may set up. Another object of the invention is to produce a similar magnetic shielding eiiect by placing inside the heater either a solid or laminated iron core. A still further object is to so associate the magnetic shell surrounding the heater and the iron core inside it as to produce, by eddy current and hysteresis effect, additional heat to be tra-nsmitted to the cathode.

rlhe above Will better be understood by reference to the illustrative embodiments of my invention described in the following specilication in connection with the accompanyingr drawings which form a part hereof. It is to these illustrative embodiments that the claims are directed but solely for purposes ot' illustration and not limitation.

ln the drawings,

Fig. 1 is a vertical cross-section with parts broken away of a preferred embodiment of my invention;

F 2 is a similar View of a modification;

Fig. 3 is a similar View of a further modi- 40 tication; and

Fig. 4 is a section through the plane of line IV-IV of Fig. 2, parts being shown in plan.

This invention is applicable to any design of hollow cathode although itis shown applied to the cathode C, more particularly described in my co-pending applications.

Preferably. but not essentially, I interline the inner walls of the cathode C with an electro-magnetic shield 1 of soft iron shaped to G, 1926. Serial N0. 86,389.

tit snugly against the inner cathode wall 2. Also l place a highly magnetic core, preferably solid, inside the heating coil, When this is Wound inductively.

The heater A is removable and preferably comprises a plug 3 of insulating material having channels 4 and 5 to accommodate the heater leads 6 and which may be nickel, in any suitable manner as by meansof cement seals 8 and 9, it being understood that the leads extend out to any appropriate socket or connecting device. l

Outstanding from the end l0 of the plug 3 is the heater element in the form shown in Fig. l. This comprises a curl or small diameter helix 1l of suitable resistancel Wire, such as nichrome With this curl or small diameter helix itself disposed in the form of a larger helix 12 co-axial with the axis of the plug 3. An annular groove 13 in the end of the plug serves to seat the contiguous convolution of this helix 12 Which may be cemented in place by a filling of'suitable cement 14 such as alundum or the like. It ispreferred that the convolut-ions of the helix 12 -be slightly spaced axially and the space be filled with cementitious material 15 similar to that indicated by 14 so that the entire structure takes on the form of a cylinder and is readily selfsustaining outstanding from the end of the plug ln its construction the rim of the electroanagnetic shield 1 may be engaged by the end of the plug 3 to accommodate as a spacer in assembling the heater. Within the helix 7 of the heater I prefer to position a soft iron core 6 preferably flared at its base and either forming a part of lead 6 or With lead 6 traversing its axis as shown. This core and the shell may be made so that they conneet at both ends to complete a magnetic circuit about the helix or such magnetic circuit may be only. substantially complete as shown. If the magnetic circuit is complete it is best that shell 1 be out of contact With cathode C. vIn this construction all heat generated in the core and shell by eddy currents and vhysteresis is conserved and imparted to the cathode.

In the modification of Figs. 2 and 4 designed for lowervpotential Work and conse- 1 standing position of the open helix 120. A

plurality of wire supports such as 31, 32, 33 and 34 may also be provided having hooked ends 35, having staying engagement with an appropriate convolution of the helix 120 and with their feet cemented in pockets 36 in the end of the plug 30. It is, of course, to be understood that the electro-magnetic shield 1 may or may not be employed in this modiication, as desired.

In Fig. 3, a further modification is shown in which the heater helix 12 is formed of twin wires electrically connected on their far end 130 and stayed to a strut 131 seated at its foot in a pocket 132 formed in the plug 3. In this construction, the leads 4 and 5 extend each to the beginning of the convolution contiguous to the plug 3 so that the circuit is such that the heating current traverses each Vot the twin resistance conductors in opposite directions producing a noninductive eii'ect on account of the fact that the electro-magnetic eld set up byl each resistance wire interlinks with the other o1' twin resistance wire.

It is to be understood in connection with the showing in Fig. 3 that this modification is intended to be somewhat diagrammatic and to include a non-inductive heater o'f the type shown in Fig. 1, in which the curl or helix of small diameter is itself formed of twin resistance wire and is built up in the form of a cylinder just' as is th-e cylinder of Figs. 1 and 3. However, it should be understood that the leads for such modification do not extend to the far end of the heater coil as does the tip 16 of the lead 4, but extends to the convolution contiguous to the end of the plug 3 just as shown 'in Fig. 3.

The inventive thought may have a variety ot' expressions as is contemplated in what 'I claim and desire to secure by United States Letters Patent' as follows:

1. In a cathode construction for an audion, a hollow cathode tube, a shell of magnetic material for .a lining for said tube near one end, a plug of insulating material adapted to fit in said tube, a heater element supported on said plug so as to lie within said cathode and shell when the plug is in place and a core of magnetic material for the heater element encircled thereby and supported on said plug.

2. A structure comprising a cathode, an

` electrical heating coil for the cathode in proximity thereto, a magnetic shield for the heating coil between it and the cathode and a magnetic core for the heating coil forming a substantially closed magnetic c1rcu1t' wlth

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