TENSION-EQUALIZER UNIT. 



25 



detail. 1 In this blower, a solid cylinder with two movable vanes 

 attached is placed eccentrically inside a hollow cylindrical chamber. 

 The rotary movements of the shaft and the compression and expansion 

 of springs acting upon the vanes force the air through the blower. 

 Later it was found that the blower manufactured by the J. Gilmer 

 Crowell Company of Brooklyn, New York, was more satisfactory. 

 This is mounted inside of a metal box, and may therefore be entirely 

 immersed in oil with the exception of the portion of the shaft extending 

 through the box to the driving pulley. Leaks around the shaft or in any 

 portion of the blower may thus be readily detected. It is necessary 

 of course to have the blower absolutely tight, as there is a difference of 

 pressure between the inside and the atmosphere of at least 50 cm. of 

 water. 2 The large wheel on the shaft of the blower is belted directly 



FIG. 5. Tension-equalizer with three-way valve and mouthpiece. 



g, rubber mouthpiece; m, three-way valve; a, union; c, tension-equalizer; h, rubber 



bathing cap ; b, tube leading to rotary blower. 



to a | h. p. electric motor. The driving-wheel is 26 cm. in diameter, 

 and by adjusting the size of the pulley on the motor, varying limits of 

 speed may be obtained. The speed is also regulated by a resistance 

 in series. Recently a bank of lamps in parallel and of varying candle- 

 power has been placed in series with the motor; by varying the number 

 of lamps used and their candle-power it is possible to get rates of speed 

 ranging from 295 to 480 revolutions per minute. The rate of ventila- 

 tion is usually adjusted to about 35 liters per minute. On the exit 

 pipe leading from the blower a metal pipe and petcock are attached for 

 trapping and drawing off any oil which may be mechanically carried 

 forward. Having once determined the rate of flow and knowing the 

 revolutions per minute of the blower shaft, the rate per minute can 

 be taken as an index of the actual ventilation. Under ordinary con- 

 ditions these blowers deliver about 120 c. c. of free air per revolution. 



J Atwater and Benedict, Carnegie Inst. Wash. Pub. No. 42, 1905, p. 18. 



2 With none of the blowers which have been used in this laboratory and which have been prop- 

 erly taken care of has there been any leak. The blowers are remarkably satisfactory and efficient. 



