The American X-Ray Journal A JOURNAL OF Progressive Therapeutics Electrical Science X-Ray Photography Electro Therapy Radio Therapy Thermo Therapy Hydro Therapy Mechano Therapy Animal Therapy Psycho Therapy Official Organ of The American Electro Medical Society $3.00 per year, in advance. The American X-Ray Publishing Co. Masonic Temple, 55 State Street Vol. IV and Radiology December, 1904 Original Contributions. THE STATIC MACHINE AND THE RADIOGRAPH.* By John Townsend Pitkin, M. D., of Buffalo, N. Y. No. 12 Let us consider the static machine and the radiograph, as the end links of a chain, the intermediate segments thereof are the Crookes tube, the X-ray field, the photographic surface, the exposure, skillful development of the exposed negative, printing of the X-ray positive, development of the radiograph. It is necessary that each subdivision of the chain shall be thoroughly understood by the operator and that he shall employ implements, material and forces, specially adapted to the purpose and to each other. Failure to comply with all of the requirements, means a defective link, a failure or compromise in the results attainable, for our metaphorical chain conforms to the axiom, "A chain is never stronger than its weakest link." The static machine is a continuous current generator or dynamo, the revolving plates and their support are the armature, the stationary plates and their inductors of tinfoil and paper are the fields, the collecting combs are commutators, the prime conductors the outlet of the external circuit. Two revolving and two stationary plates with their accessories, constitute a static unit, the value of which is proportionate to the number of square inches of the revolving plates, that can be electrically excited without sustaining internal leakage. The static unit resembles a Leyden jar or condenser, the two coatings of tinfoil are upon opposite sides of the apparatus, the revolving plates that pass near them and are inductively magnetized, taking the place of the glass wall of the jar. The electrical capacity of this Leyden jar will depend upon the amount of foil, paper and glass that can be excited to saturation without overflowing. Again the static machine is a double electrophorus, the primary charged discs of opposite polarity, covered with glass and resin are the stationary plates. The secondary discs or segments of discs inductively charged therefrom, are the revolving plates. The latter structures being constantly removed by turning, carry a bond or induced charge of electricity with them, to the opposite side of the machine, but give up a free electrical charge at the place of induction, which charge passes externally over the prime conductors, and internally over the neutralizing rod, conductors that are placed in constant electrical touch with the revolving members. Speaking more specifically of the disposition of the bond *Read at the Fifth Annual Meeting of the American Roentgen Ray Society, at St. Louis, Mo., Sept. 8th to 13th, 1904. or induced charge carried by the revolving plates to the opposite sides of the generator, the prime conductors receive a major portion, the neutralizing system acting as a shunt, takes a minor portion, the inductors acting as a second shunt, receive a third portion, a distribution of the current which places the static machine in the classification of dynamos of the compound wound type. In the complex static machine for X-ray purposes, a number of units, from ten to thirty or more, can be operated in synchronism, an arrangement similar in effect to the wiring of a group of battery cells in multiple relation to each other, to increase the volume or quantity of the electrical outflow. The complex static machine resembles the human economy in the symmetry of its formation, distribution of functionating parts in pairs, in the possibility of utilizing all available space for useful purposes. It has a body, arms, legs, a circulatory system, a voice weak, snarly and snappish, from the feeble generator, but strong, frank and sonorous from the more efficient. To the unsophisticated it seems possessed of a whimsical, even a mulish disposition, but in the hands of the experienced, it is an ever faithful and obedient servant. Again, the static machine resembles a regiment of soldiers in the correctness and precision of alignments, in the definite position and relation its constituents bear to each other. During atmospheric disturbances, two clouds or a cloud and the earth become charged with opposite kinds of electricity, the intervening atmosphere is strained by a magnetic field of force, until the limit of its strength is reached, the dielectric breaks at the weakest point, a lightning flash and a crash, are the manifestations of the action of one of Jehovah's Leyden jars, the disruptive discharge of the static machine of the Omnipotent. Similarly when we operate several large static machines, in multiple relation to each other, we can can produce a thunder storm in miniature. The force generated by the static machine is electro-magnetism, the conductors are electrified, the glass plates and the atmosphere magnetized. The high tension current is a property or attribute of the excited dielectrical material employed in its construction. Should the physician desire to build a Holtz static machine for his own use, he will find it necessary to enlist under his banner a cabinet-maker to make the case or frame-work, a hard-rubber company to furnish collars and tubing, the tubing to cover the axle, prime conductors and neutralizing rod, a metal worker to make the steel shaft, brass boxes or bearings, great brass balls, the collecting and discharging rods. A few oak boards, two to four cases of window-glass, many hard-rubber pieces, a bar of steel, some brass tubing, a little brass fly screening and some scraps of brass, the last mentioned to be cast into balls and bearings, this heterogeneous collection of crude material in the hands of the artisans can be converted into the constituent parts of the static generator. In order that the generator shall yield the operator a maximum quantity of electricity at the prime conductors, it is necessary that the material, electrical and dielectrical, from these diverse sources, shall bear a definite relation to each other in their conformation and arrangement. With this object constantly in the foreground, let us proceed to build an apparatus. The framework of a static machine may be considered as an oblong box, from which enough of each surface has been cut away to convert the remain ing portions into window casings. Only enough woodwork is left to be consistent with strength and firmness. Two central upright, wooden mullions, one placed anteriorly the other posteriorly, divide the corresponding facades of the case into two equal portions. These mullions afford a firm, unyielding support for the axle collars and revolving plates, they also contribute strength and firmness to the framework, they do not encroach upon valuable space in the interior of the case, they are lined upon the inside surface with hard-rubber sheeting as an insulation measure. One or both of the mullions can be removed and leather straps or clothes lines used as a temporary support, in case the revolving portions of the machine require repair or replacing. The case of the machine is completed by windows, two in front, two in the rear, one on either end, and one upon the top. They are made of thick beveled plate glass set in frames. Any or all of the windows can be easily removed to afford free access to every portion of the internal mechanism. The prime conductors pass through apertures in the center of the anterior windows, thus affording for those structures perfect insulation. For purposes of description, let us consider first the revolving portion or armature, and subsequently the stationary portion, or fields of the static mechanism. My illustration shows the naked steel shaft, twenty-eight inches long, in situ, also the flanges of the plain brass boxes, and the upright wooden mullions. In the next illustration may be seen the shaft covered from flange to flange, with a hard-rubber sleeve, half an inch in thickness. A fine thread runs the entire length of the sleeve, to receive the hard-rubber collars, similarly threaded. The sleeve was firmly shrunk upon the shaft at the hard-rubber factory. In the next illustration may be seen the hard-rubber collars, narrow and wide, six inches in diameter, they alternate with each other in position. The narrow collars measure half an inch, the wide collars an inch in thickness. Soft rubber packing is shown interposed between them. Large hexagonal nuts with setscrews are placed at the extreme ends of the hard-rubber sleeve to prevent the collars from turning laterally upon the axle, which would throw the revolving, the stationary plates and the collecting combs, all out of alignment with each other. When wooden collars are employed, or the shaft is not incased, the collecting combs must be made short to prevent sparking into the wood and axle, and more of the area of the revolving plates remain electrically inactive. Although the transverse inside measurement of the case is but twenty-three inches, twenty revolving plates are operated upon the axle without crowding or sustaining electrical leakage. The revolving plates are twenty-nine inches in diameter, of which fourteen inches or an outer circle of seven inches is electrically excited, consequently the length of spark between the discharging rods is fourteen inches. To lengthen the external sparking capacity of our machine, it would be necessary to reduce the amount of each wheel that is electrically useful, and proportionately lessen the volume of the current, therefore we may enunciate as a law the following: All other things being equal, the length of spark from a static machine is inversely as to the strength of the current. When the wheels exceed twenty-nine inches in diameter, the warp of the glass interferes with proper alignment and a high velocity endangers their integrity. The interspaces for the collecting combs, between the revolving plates, are but one inch wide; this was found to be suf ficient room, provided each collecting comb was made to accurately fit into the interspace in which it was to functionate. The stationary plates, as is usual with the Holtz machine, are made of oblong pieces of glass, but instead of using single lights in the machine under consideration they are double, with the inductors of tinfoil and paper interposed between them. As the inductors are the fountain-head, or reservoirs of energy in which the electrical current has its source, it follows that the total capacity of these structures will govern the efficiency of the generator, hence the amount of tinfoil and paper that the double plates could carry without leakage was carefully determined. Large sheets of tinfoil and paper were attached to the glass and the machine tested in the darkened apartment, where internal sparking could be detected. Little by little the excess of the material was scraped away with repeated observations, until the external spark was of ample length and there was no internal sparking. In this manner we were able to determine the maximum area to be seven by ten inches, for the foil, and seven by fourteen inches for the paper. On account of its electrical properties, carbon paper was substituted for the plain white variety. The width of the fields once determined, other structures take their measurement therefrom. The width of the fields being seven inches the electrically active circles of the revolving plates would likewise be seven inches in width, the four sets of collecting combs must be seven inches long. Many other structures were made seven inches or some multiple thereof. The electrically inactive circles of the revolving wheels seven inches, the length of the external spark, 2x7, the width of the entire wheel a little more than 4x7, the length of the axle 4x7, the stationary plates including the interspace cut away between them 5x7 by 6x7, the window frames of the case front and back 6x7 by 7x7. The stationary plates and their end frames are supported by six hard-rubber axles, threaded to receive buttons made of the same material. These axles are placed at the ends and middle of the apparatus, superiorly and inferiorly. |