A HIGH POWER VACUUM TUBE 7 



The tube is shown in Fig. 1. The anode consists of a platinum 

 cylinder A, 7" long and .625" wide, which is scaled into the center of 

 the glass cylinder B. The end of the platinum cylinder remote from 

 the seal is closed. The anode is surrounded by the grid C and by 

 the filament D, which are supported by the glass arbors E. The 

 current for the filament is led into the tube through the platinum 

 thimbles F. 



The anode is kept cool by means of a supply of water passing into 

 the anode through the tube G and leaving by the tube H. 



A number of tubes having this general type of construction were 

 made up and it was found possible to dissipate as much as 15 k. w. 

 in the anode. 



As soon as the pressure of work more directly connected with the 

 necessities of the war would permit, Mr. W. G. Houskeeper and Dr. 

 M. J. Kelly undertook the further improvement of the water-cooled 

 tube, the former assuming the task of developing the mechanical 

 structure, and the latter that of determining the electrical design and 

 the process of tube exhaust. 



Mr. Houskeeper adopted into the construction of the tube a remark- 

 able type of vacuum seal which he had previously developed. These 

 seals are made between glass and metal and can be made in any desired 

 size. They are capable of withstanding repeated heating and cooling 

 over wide ranges of temperature, from that of liquid air to 350° C, 

 without cracking and without impairment of their vacuum holding 

 properties. 



It is no exaggeration to say that the invention of these seals has 

 made possible the construction of vacuum tubes, capable of handling 

 in single units, powers of any magnitude which may be called for in 

 wireless telegraph and telephone transmission. 



The underlying principle connected with the making of this seal 

 consists in obtaining an intimate connection between the glass and 

 metal, either by chemical combination or by mere wetting, and in so 

 proportioning the glass and metal portions of the seal that the stresses 

 produced when the seal is heated or cooled will not be great enough to 

 rupture either the glass or the junction between the glass and metal. 



The three principal types of seals developed by Mr. Houskeeper 

 are known as the ribbon seal, the disc seal and the tube seal. 



If a copper ribbon is directly sealed through glass it is found that 

 the glass and copper adhere along the flat faces of the seal but that 

 ruptures occur along the edges as shown in Fig. 2 (a). This is due to 

 the fact that as the seal cools after being made, the glass in contact 

 with metal is capable of resisting the shearing and tensile stresses 



