APPENDIX.TXT

INTRODUCTION TO THE APPENDIX







THE reader who has followed the foregoing narrative



may feel that inasmuch as it is intended to



be an historical document, an appropriate addendum



thereto would be a digest of all the inventions of



Edison. The desirability of such a digest is not to



be denied, but as there are some twenty-five hundred



or more inventions to be considered (including those



covered by caveats), the task of its preparation would



be stupendous. Besides, the resultant data would



extend this book into several additional volumes,



thereby rendering it of value chiefly to the technical



student, but taking it beyond the bounds of biography.







We should, however, deem our presentation of Mr.



Edison's work to be imperfectly executed if we neglected



to include an intelligible exposition of the broader



theoretical principles of his more important inventions. In



the following Appendix we have therefore endeavored



to present a few brief statements regarding Mr. Edison's



principal inventions, classified as to subject-



matter and explained in language as free from



technicalities as is possible. No attempt has been made



to conform with strictly scientific terminology, but,



for the benefit of the general reader, well-understood



conventional expressions, such as "flow of current,"



etc., have been employed. It should be borne in



mind that each of the following items has been treated



as a whole or class, generally speaking, and not as a



digest of all the individual patents relating to it.



Any one who is sufficiently interested can obtain copies



of any of the patents referred to for five cents each



by addressing the Commissioner of Patents, Washington,



D. C.















APPENDIX







THE STOCK PRINTER







IN these modern days, when the Stock Ticker is in universal



use, one seldom, if ever, hears the name of Edison



coupled with the little instrument whose chatterings have



such tremendous import to the whole world. It is of much



interest, however, to remember the fact that it was by reason



of his notable work in connection with this device that



he first became known as an inventor. Indeed, it was



through the intrinsic merits of his improvements in stock



tickers that he made his real entree into commercial



life.







The idea of the ticker did not originate with Edison, as



we have already seen in Chapter VII of the preceding narrative,



but at the time of his employment with the Western



Union, in Boston, in 1868, the crudities of the earlier forms



made an impression on his practical mind, and he got out



an improved instrument of his own, which he introduced in



Boston through the aid of a professional promoter. Edison,



then only twenty-one, had less business experience than the



promoter, through whose manipulation he soon lost his financial



interest in this early ticker enterprise. The narrative



tells of his coming to New York in 1869, and immediately



plunging into the business of gold and stock reporting. It



was at this period that his real work on stock printers



commenced, first individually, and later as a co-worker with



F. L. Pope. This inventive period extended over a number



of years, during which time he took out forty-six patents on



stock-printing instruments and devices, two of such patents



being issued to Edison and Pope as joint inventors. These



various inventions were mostly in the line of development of



the art as it progressed during those early years, but out



of it all came the Edison universal printer, which entered



into very extensive use, and which is still used throughout



the United States and in some foreign countries to a



considerable extent at this very day.







Edison's inventive work on stock printers has left its



mark upon the art as it exists at the present time. In his



earlier work he directed his attention to the employment of



a single-circuit system, in which only one wire was required,



the two operations of setting the type-wheels and of printing



being controlled by separate electromagnets which were



actuated through polarized relays, as occasion required, one



polarity energizing the electromagnet controlling the type-



wheels, and the opposite polarity energizing the electromagnet



controlling the printing. Later on, however, he



changed over to a two-wire circuit, such as shown in Fig. 2



of this article in connection with the universal stock printer.



In the earliest days of the stock printer, Edison realized the



vital commercial importance of having all instruments recording



precisely alike at the same moment, and it was he



who first devised (in 1869) the "unison stop," by means of



which all connected instruments could at any moment be



brought to zero from the central transmitting station, and



thus be made to work in correspondence with the central



instrument and with one another. He also originated the



idea of using only one inking-pad and shifting it from side to



side to ink the type-wheels. It was also in Edison's stock



printer that the principle of shifting type-wheels was first



employed. Hence it will be seen that, as in many other



arts, he made a lasting impression in this one by the intrinsic



merits of the improvements resulting from his work



therein.







We shall not attempt to digest the forty-six patents above



named, nor to follow Edison through the progressive steps



which led to the completion of his universal printer, but



shall simply present a sketch of the instrument itself, and



follow with a very brief and general explanation of its theory.



The Edison universal printer, as it virtually appears in



practice, is illustrated in Fig. 1 below, from which it will be



seen that the most prominent parts are the two type-wheels,



the inking-pad, and the paper tape feeding from the reel,



all appropriately placed in a substantial framework.







The electromagnets and other actuating



mechanism cannot be seen plainly



in this figure, but are produced



diagrammatically in Fig. 2, and somewhat



enlarged for convenience of explanation.







It will be seen that there are two electromagnets, one of which, TM, is known



as the "type-magnet," and the other, PM, as the "press-magnet,"



the former having to do with the operation of the type-



wheels, and the latter with the pressing of the



paper tape against them.  As will be seen from the



diagram, the armature, A, of the type-magnet



has an extension arm, on the end of which is



an escapement engaging with a toothed wheel placed at the extremity of the shaft



carrying the type-wheels. This extension arm is pivoted



at B. Hence, as the armature is alternately attracted



when current passes around its electromagnet, and



drawn up by the spring on cessation of current, it moves



up and down, thus actuating the escapement and causing a



rotation of the toothed wheel in the direction of the arrow.



This, in turn, brings any desired letters or figures on the



type-wheels to a central point, where they may be impressed



upon the paper tape. One type-wheel carries letters, and



the other one figures. These two wheels are mounted rigidly



on a sleeve carried by the wheel-shaft. As it is desired



to print from only one type-wheel at a time, it becomes



necessary to shift them back and forth from time to time, in



order to bring the desired characters in line with the paper



tape. This is accomplished through the movements of a



three-arm rocking-lever attached to the wheel-sleeve at



the end of the shaft. This lever is actuated through the



agency of two small pins carried by an arm projecting from



the press-lever, PL. As the latter moves up and down the



pins play upon the under side of the lower arm of the rocking-



lever, thus canting it and pushing the type-wheels to the



right or left, as the case may be. The operation of shifting



the type-wheels will be given further on.







The press-lever is actuated by the press-magnet. From



the diagram it will be seen that the armature of the latter



has a long, pivoted extension arm, or platen, trough-like in



shape, in which the paper tape runs. It has already been



noted that the object of the press-lever is to press this tape



against that character of the type-wheel centrally located



above it at the moment. It will at once be perceived that



this action takes place when current flows through the



electromagnet and its armature is attracted downward, the



platen again dropping away from the type-wheel as the



armature is released upon cessation of current. The paper



"feed" is shown at the end of the press-lever, and consists



of a push "dog," or pawl, which operates to urge the paper



forward as the press-lever descends.







The worm-gear which appears in the diagram on the shaft,



near the toothed wheel, forms part of the unison stop above



referred to, but this device is not shown in full, in order to



avoid unnecessary complications of the drawing.







At the right-hand side of the diagram (Fig. 2) is shown a



portion of the transmitting apparatus at a central office.



Generally speaking, this consists of a motor-driven cylinder



having metallic pins placed at intervals, and arranged



spirally, around its periphery. These pins correspond in



number to the characters on the type-wheels. A...