File:Appletons' cyclopaedia of applied mechanics- a dictionary of mechanical engineering and the mechanical arts (1880) (14779974605).jpg

Identifier: appletonscyclopa02dapp (find matches)
Title: Appletons' cyclopaedia of applied mechanics: a dictionary of mechanical engineering and the mechanical arts
Year: 1880 (1880s)
Authors: D. Appleton and Company Benjamin, Park, 1849-1922
Subjects: Mechanical engineering -- Dictionaries
Publisher: New York, D. Appleton
Contributing Library: Mugar Memorial Library, Boston University
Digitizing Sponsor: Boston University

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
apidity with which a hammer may operate when working on this principle, there is nothing gained,and much lost; and as this kind of action is imperative in any hammer that has a maintained orpositive connection between its reciprocating parts and the valve, it is perhaps fair to infer thatone reason why most automatic hammers act with elastic blows is either because of a want ofknowledge as to a proper valve arrangement, or the mechanical difficulties in arranging valve-gear toproduce dead blows. In working with dead blows, no steam is admitted under the piston until thehammer has finished its down stroke, and expended its momentum upon the work. So different is HAMMERS, STEAM, DIRECT-ACTING. 89 the effect produced by these two plans of operating, that on most kinds of work a hammer of 50 lbs.working with dead blows will perform the same duty that one of 100 lbs. will when acting by elasticor cushioned blows. This difference between dead and elastic strokes is so important, that it has
Text Appearing After Image:
served to keep hand-moved valves in use in many cases where much could be gained by employingautomatic-acting hammers. Some makers of steam-hammers have so perfected the automatic class, that they may be instantly 90 HAMMERS, STEAM, DIRECT-ACTING. changed so as to work with either dead blows or elastic blows at pleasure, thereby combining all theadvantages of both principles. This brings the steam-hammer where it is hard to imagine a want offurther improvement. The valve-gearing of automatic steam-hammers, to fill the two conditions ofallowing a dead or an elastic blow, furnishes one of the most interesting examples of mechanicalcombination. It was stated that to give a dead or stamp stroke, the valve must move and admitsteam beneath the piston after the hammer has made a blow and stopped on the work, and that sucha movement of the valve could not be imparted by any maintained connection between the hammer-head and valve. This problem is met by connecting the drop or hammer-head with

Note About Images