8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 98 



FLASH-BOILER DEVICES 



It would be convenient if it were practicable to have the glass 

 vacuum jacket open at both ends so that water could flow in at the 

 bottom and go out as steam at the top. But the unequal linear expan- 

 sion of the inner and outer tubes of the glass jacket is difficult to 

 allow for in a permanent sealage. Accordingly, I have preferred to 

 make the vacuum jacket, surrounding the boiler tube, like an elongated 

 thermos bottle with open end up. This requires the water tube enter- 

 ing at the top to pass through the steam to the lower end of the boiler. 

 I introduce two metallic tubes sealed upon the water tube within the 

 boiler, called, respectively, the spreader tube and the vacuum jacket 

 tube. The spreader tube encloses the water tube in the lower two- 

 thirds of the length of the boiler tube, and forces the water to circu- 

 late in a thin layer against the inner wall of the boiler tube, so as to 

 be most favorably situated to burst into steam. The vacuum jacket 

 tube is sealed upon the water tube in the upper one-third of the length 

 of the boiler tube, so as to reduce the tendency of the entering water 

 to cool the superheated steam in the upper part of the boiler tube. 



AUTOMATIC REGULATION OF FLOW OF BOILER WATER 



I accomplish automatic regulation of the water supply as follows : 

 A pump is provided whose stroke is continuously adjustable between 

 the limits zero and the greatest required. The essence of this regula- 

 tion consists in an eccentric pin forming part of a shaft driven by 

 the same small synchronous motor that rotates the mirror. One end 

 of the pin is coaxial with the shaft bearings, but the other end revolves 

 in a small orbit. The shaft carrying the pin is mounted in a carriage, 

 displaceable longitudinally, so that according to its longitudinal posi- 

 tion the pin gives more or less throw to the pitman that works the 

 pump. 



To govern the position of the carriage I impart motion by a screw, 

 driven by a tiny direct-current motor operated by dry cells. The 

 operation of this motor forward or backward is governed by a suitable 

 multiple contact switch. The switch is operated by a lever system 

 worked by the differential expansion between the boiler tube and an 

 invar tape attached to the lower end of the boiler tube. Hence the 

 temperature of the boiler, which is the index of the prevailing steam 

 pressure, governs the position of the carriage. There is mounted 

 upon this carriage the uniformly rotating eccentric pin, and this in 

 turn governs the stroke of the pump which forces water into the boiler. 



