Page:The New International Encyclopædia 1st ed. v. 18.djvu/631

STEAM SHOVEL. 537 STEAM TURBIIJE. upward along a curved path; at the same time the crane man b.y means of the thrusting mechan- ism forces the dipper into the earth so that a layer is scooped off the face of the bank and falU into the dipper. The depth of the cut is so regu- piston ; in the case of the steam turbine the work is developed by the kinetic energ)' of particles of steam which are given a high velocity by reason of the steam expanding from one pressure to a lower pressure. In the :rolipile (q.v.) or 'Hero's steam engine,' invented by Hero of Alexandria (q.v.), we have the germ of the steam turl)ine. The next steam turbine was in- SECTION SHOWING MECHANISM OF STEAM SHOVEL. lated by the crane man that the dipper is jiist filled when at its topmost position. The dipper is then hauled back and the crane is swung so as to carry the dipper uver the car set along- side the sliovel, and the latch is pulled, setting free the swinging bottom of the dipper, which falls open and permits the contents of the dipper to fall into the ear. In actual operation these several movements are com- bined to a greater or less ex- tent, and are accomplished by various devices which will be found described in Hermann, ^team Shovels and Steam Shovel Work (New York, 1S94). The various parts of the shovel, body, mast, crane, and dipper handles, are con- structed either of wood or steel, the latter material being most generally used for the heavier types of shovels. The dipper is always made of steel or iron plates, and its size or capacitj' varies from one to five cubic yards, but capaci- ties of l."l>^, 2, and 2)^ yards are the ones most com- mon. For digging blasted rock the front edge or lip of the dipper has steel teeth. The excavating capacity of steam shovels varies from 2400 cubic yards of sand to 600 cubic yards of loose rock per ten hours, with a 2% cubic yard dipper. For extensive records of actual op- eration in various kinds of material, consult Hill, The Chicaqo Main Drainage Channel (New York, 1896). STEAM TURBINE. A form of prime motor in which the kinetic energy of expanding steam acts upon a wheel provided with vanes so as to cause rotation. The ordinary method of using steam to obtain power is to admit it into a closed cylinder, where it acts upon a movable piston. (See Ste.4m and Steam Engine.) In this case work is performed liy the static ex- pansive force of the steam pressing against the vented by Branca in 1020 and consisted simply of a jet of steam impinging upon the vanes of a paddle wheel and blowing it around. Branca's device was the first im])ulse steam turbine. Prac- tically no attention was given to the steam tur- bine from this time until the last quarter of the nineteenth century, when several inventors began experimenting, among whom C. A. Par- BECTION OF PARBONS'S STEAM TUHBISE. sons of England and Dr. de Laval of Sweden deserve particularly to be noted. Mr. Parsons built his first turbine in 1884, and Dr. de Laval recorded his first patent in 1889. The first Par- sons turbine developed 10 horse power at 18,000 I i fixed Blades Moving Blades —J)JMMMJ>M- Fixed Blades ^.V^WJ>— ACTION OF STEAM ON BLADES OF PARSONS'S TUHBINE. revolutions per minute, and proved entirely prac- tical. The Parsons turbine consists of several successive turbine wheels, or rows of blades, on