PNEUMATIC TOOLS 



4716 



PNEUMONIA 



widths in such a way that the greatest thick- 

 ness is in the center. A strip of fabric known 

 as the breaker strip is sometimes placed under 

 the tread. From the builders, the core and its 

 wrappings are sent to the press room, where 

 they are put into molds and subjected to pres- 

 sure and heat. After being thus vulcanized, 

 the tire is removed from the mold and is sent 

 to the finishing room. 



Automobile tires are warranted to run from 

 3,500 to 5,000 miles, according to quality. The 

 maximum air pressure they are rated to with- 

 stand is twenty times the diameter of the tube. 

 That is, a new tire four inches in diameter 

 should sustain a maximum pressure of eighty 

 pounds to the square inch, and one three inches 

 in diameter should sustain a pressure of sixty 

 pounds. The cost of automobile tires depends 

 upon size and quality and varies from about 

 $15 to $45. Akron, Ohio, is the greatest center 

 in the world for the manufacture of pneumatid 

 tires. It is estimated that the American auto- 

 mobile industry requires about 15,000,000 rub- 

 ber tires a year. See AUTOMOBILE; MOTORCY- 

 CLE ; BICYCLE. C.H .H . 



PNEUMATIC TOOLS, implements used in 

 industry which are operated by compressed air. 

 The word is derived from the Greek pneumati- 

 kos, meaning relating to air or wind. Pneu- 

 matic tools are of two classes those which op- 

 erate by striking and those which rotate. In 

 the striking class are included hammers, rivet- 

 ing, caulking, chipping and rock-drilling tools. 

 Drills and boring tools belong to the rotating 

 class. 



Probably the most efficient of all pneumatic 

 tools is the hammer, with a piston in the handle 

 working with a backward and forward motion. 

 The power is supplied by compressed air through 

 a flexible hose which allows the tool to be 

 worked at any required angle. With such a 

 hammer it is possible to deliver up to 20,000 

 blows per minute; city dwellers are familiar 

 with its noisy operation in the processes of 

 riveting the steel work in modern office build- 

 ings. The compressed air usually has a pres- 

 sure of from eighty to 125 pounds per square 

 inch, and is controlled by a valve in the handle 

 of the tool. 



PNEUMATIC TUBES, or PNEUMATIC 

 DISPATCH, a system or method of sending 

 mail, dispatches and parcels through tubes, 

 either underground or above, by means of air 

 pressure. In 1667 this method was first sug- 

 gested by Denis Papin, who read a paper be- 

 fore the Royal Society of London explaining a 



device for sending a carrier containing mail 

 through tubes by means of suction. Improve- 

 ments on his suggestion, which were not com- 

 mercially adopted until 1835, have led to the 

 development of various forms of pneumatic 

 transportation devices in every civilized coun- 

 try. 



The necessary apparatus consists of a series 

 of tubes, an air compressor and air-tight cylin- 

 drical carrying cases. The first pneumatic dis- 

 patch tubes installed only allowed the carriers 

 to be sent in one direction, and to but one des- 

 tination. This was improved upon by the use 

 of alternate suction and pressure which allowed 

 the carriers to travel both ways. This form 

 was further modified by circular systems in 

 which a current of air kept continually moving 

 and the carriers could be withdrawn from the 

 tubes at regular intervals or stations. 



The pneumatic dispatch system has siiu-i- 

 1870 proved successful in connection with the 

 general post office, London, especially in the 

 telegraph department, and there is now in use 

 in this connection in that city a series of un- 

 derground tubes over forty miles in length. The 

 postal authorities and the telegraph companies 

 in the United States have installed pneumatic 

 dispatch systems in all large cities. Depart- 

 ment stores and large retail stores in the States 

 and in Canada employ the principle in tubes 

 for conveying money from the counters to the 

 cashier's desk. The development of pneumatic 

 dispatch has not been so rapid in America as 

 in Europe, but it is greatly increasing, the sys- 

 tem having been proved economical and effi- 

 cient. 



In pneumatic tubes of two and a quarter 

 inches in diameter, worked with an air pressure 

 of ten pounds per square inch, containing car- 

 riers which hold seventy-five ordinary messen- 

 ger forms, a speed is obtained in transit of a 

 mile in two and one-half minutes. Large tubes 

 for pneumatic dispatch, eight inches in diame- 

 ter, are built for conveyance of carriers seven 

 inches in diameter and twenty-four inches long. 

 These tubes require an air pressure equal to 

 thirty horse power, and the carriers are pro- 

 pelled through the tubes at the rate of thirty 

 miles an hour. 



Consult Batcheller's The Pneumatic Dispatch 

 Tube System. 



PNEUMONIA, numo'nia, a dangerous and 

 common disease in which the most serious 

 trouble is inflammation of the lungs. Accord- 

 ing to the United States Census Bureau, about 

 one-third of all the deaths occurring in a year 



