File:Practical radiography - a handbook for physicians, surgeons, and other users of X-rays (1901) (14777636393).jpg

Identifier: practicalradiogr00isen (find matches)
Title: Practical radiography : a handbook for physicians, surgeons, and other users of X-rays
Year: 1901 (1900s)
Authors: Isenthal, A. W Ward, H. Snowden (Henry Snowden), 1865-1911
Subjects: Radiography X-rays X-rays Radiography X-Rays
Publisher: London : Published for The Photogram, Ltd. by Dawbarn and Ward, Ltd.
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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cylinder is fitted with sectors of insulatingmaterial, then, on rotating the bent tube, we obtain aseries of interruptions, the frequency of which is pro-portional to the number of contacts and the revolutions ofthe spindle. Eeplacing the contact pieces by others ofvarious shapes and widths we have it in our power to varyboth the number and relative duration of the contactperiods. After establishing contact, the mercury falls tothe bottom of the containing vessel in order to be againsucked up, and so on. Induction Coils and Interrupters 69 A vastly more convenient modification of a jet break isrepresented by a construction of Dr. Max Levy (Figs. 29 and30). Its novel features are a stationary mercury jet andthe method adopted for adjusting the duration of contact.The stationary jet is obtained by a simple displacementmotion, such as a couple of geared pinions rotating in aclosely-fitting case. By this means a jet is produced atvery low speeds to begin with, and as it is stationary the
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Fig. 29. splashing of the mercury is greatly reduced. Apart fromthe fact that it is better balanced, much higher speed andconsequently greater frequencies may be attained. Thenozzle from which the mercury jet issues can be raised orlowered from the outside, which property, in conjunctionwith the triangular shape of the contact pieces, enablesus to obtain very great variations in the duration of thecontact. The metallic contact pieces are fixed to thecircumference of a revolving drum and are easily inter-changeable. Their bases are on top and their apices pointdownwards. 7° Practical Radiography On reference to fig. 30, it will be seen that on rotating theblades past the nozzle (thus cutting the jet) contact is madefor a shorter or longer period during each revolution accord-ing to the level of the jet. If the latter is at its lowest posi-tion, the jet can only impinge for a very brief period on thecontacts, and as we raise the nozzle, larger and larger seg-ments of the triangular con

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