Document nmyRgZob8n0OMY54eJ58qQxwm

y. Electron-Tube and Mercury-Arc-Rectifier Constructions- MEANS Grophite anode CooHaq cof-- Arc bef/tti _ Votmm Mercury ttrerner* GrvpAite - bor Cta'tofiO* pod cathode---" GooNnq-mOter CoihodO'Coolinq /octet-. AfC'itottmQ device - 0\ Q Thl* 3 Yemeni hiph-vocuum tube Q#vj* directly beefed cathode, cyltn- dricol metat onede ord splrol wire Qrid 4Q 3-element electron tube has indirect V ty hooted metat ribbon cathode, dome-shaped anode and carbon-disk arid rtbboa spiral, Fig. 14 to 16. The heat er* are tungsten or tuagsten-molybdenum-elloy wire end the enclosing sleeve or spiral Is a nickel alloy coaled with an electron-emitting material. The beater is insulated from the sleeve and la used only to bring the sleeve and its coating to an electron-emitting temperoture. Useful electron emission does not take place (rom the heater wire. One of the advantages of the heater-cathode design is that it permits close spacing between 'cathode and anode. Directly heated cathodes heat more quickly than indirectly heated onea and are used where quick heating Is needed. Whencathodes are indirectly heated a much larger electron-emitting surface can be heated efficiently; consequently they are used for medium and large cur rents. Later we will discuss other meens o! liberating electrons (torn e cathode, as by a light beam in the photoelectric lube and an arc in the mereury-arc rectifier. Anode Material. Every electronic tube has on electron-producing element, just described, and on electron-collect ing element, known as the plate or anode. The earlier designs of anodes were in, the form of a Oat piste. Fig. 17. Frequently two plates were used in parallel, with the cathode between. Be cause of its form the electron-collecting element became known as the'plate, and is frequently called that today even though anodes ere generally cylindrical or oval in construction, Fig. 18 to 24. To be satisfactory, an anode material must be reasonably easy to form into shapes, must retain its shape at operat ing temperatures, radiote heat readily so it operates at a reasonably low tem perature, have a low gas content and be easily degassed when the vacuum is created in the tube. Tungsten was one ol the first, materials used lor anodes. It has many of the qualities desirable for anode material but is difficult to fabricate' Into the shapes required for anodes In modem electron tubes sad* so Is now little used for that purpose'', Heat-dissipating qualities of i denum are. not the best, but its < characteristics make it a desirable anode material and it is quite axtea-sfvely used. Roughing of its sar/ece bycarborundum blasting and the addition * of fins. Fig. 19 and 20, improves tbe^ thermal qualities of anodes mads (' this material. Graphite, another commonly used- material lor anodes, contains consider ably more absorbed gas than some of, the others. It is, however, readily^ degassed, has good heat-dissiptiiag^' qualities, can be readily formed into modern anode shapes, end does cot;! warp because of high lempetilure. Ffc-. 21 to 23 show forms of graphite anode.' Nickel readily form# into anode#1 shapes, but it has low heai-dusipatiog. qualities. Treating the outside surfsee,j of (heso anodes to a thin layer of (Continued on page 130) 100 (3M| POWER IN BOILER !blow-down 1 SERVICE SUN'Rectus* they eliminate the commonestsource Rftrouble and expense in ordinary blow-off service, Varway Seatless Blow-Off Valves mtka ret! economy to boiler plant operators. tttf'srwep tt0 teat to score, wear, clog anti M(t*L Lubrication is usually the only mainte* Bpin they require. Rtftrwey introduced the seatlcss principle Efiih th* balanced sliding plunger many QKfOLH ago .. . has constantly improved and Qtdspted it to meet modern service requirefififeents. Mechanical and metallurgical research S'to' Ysrwoy'j own Steam Laboratory amiciTM$ptfes changing conditions... keeps Varway gitlve design ahead. wijere is a Yarway Blow-Off VaW for gevery pressure. gjlMO FOR FACE BLOW-OFF VALVg BOOKLET. HIM! ' BpNOJCAfl THE PRESSURE OF TOUR BOILERS. Iyarnall-waring company 100Mermaid Avenue, Philadelphia 18, Pa. $&: m (Afevr)--Cross section of Tp Seatless Angle Valve, flanged. OPERATION: After valve hi closed, shoulder on balanced plunger contacts upper follow* forcing it down into body < pressing packing above and Del making an absolutely tight valvj (BrW)-Type "D" Balanced] Plunger, Packing Rings and( TSRJWfir BLOW-OFF VALVES