The collector is made in the same form as the commutator. It is composed of the two metallic segments E E' and the two insulating segments F F', bound together by a band, C. The metallic segments E E' are of the same or practically the same width or extent as the insulating segments or spaces of the commutator. The collector is secured to a sleeve, B', by screws g g, and the sleeve is arranged to turn freely on the shaft A. The end of the sleeve B' is closed by a plate, f, upon which presses a pivot-pointed screw, h, adjustable in a spring, H, which acts to maintain the collector in close contact with the commutator and to compensate for the play of the shaft. The collector is so fixed that it cannot turn with the shaft. For example, the diagram shows a slotted plate, K, which is designed to be attached to a stationary support, and an arm extending from the collector and carrying a clamping screw, L, by which the collector may be adjusted and set to the desired position.
Mr. Tesla prefers the form shown in Figs. 246 and 247 to fit the insulating segments of both commutator and collector loosely and to provide some means—as, for example, light springs, e e, secured to the bands A' B', respectively, and bearing against the segments—to exert a light pressure upon them and keep them in close contact and to compensate for wear. The metal segments of the commutator may be moved forward by loosening the screw a'.
The line wires are fed from the metal segments of the collector, being secured thereto in any convenient manner, the plan of connections being shown as applied to a modified form of the commutator in Fig. 251. The commutator and the collector in thus presenting two flat and smooth bearing surfaces prevent most effectually by mechanical action the occurrence of sparks.
The insulating segments are made of some hard material capable of being polished and formed with sharp edges. Such materials as glass, marble, or soapstone may be advantageously used. The metal segments are preferably of copper or brass; but they may have a facing or edge of durable material—such as platinum or the like—where the sparks are liable to occur.
| Fig. 251. | Fig. 252. |
In Fig. 248 a somewhat modified form of the invention is shown, a form designed to facilitate the construction and replacing of the parts. In this modification the commutator and collector are made in substantially the same manner as previously described, except that the bands B C are omitted. The four segments of each part, however, are secured to their respective sleeves by screws g' g', and one edge of each segment is cut away, so that small plates a b may be slipped into the spaces thus formed. Of these plates a a are of metal, and are in contact with the metal segments D D', respectively. The other two, b b, are of glass or marble, and they are all better square, as shown in Figs. 249 and 250, so that they may be turned to present new edges should any edge become worn by use. Light springs d bear upon these plates and press those in the commutator toward those in the collector, and insulating strips c c are secured to the periphery of the discs to prevent the blocks from being thrown out by centrifugal action. These plates are, of course, useful at those edges of the segments only where sparks are liable to occur, and, as they are easily replaced, they are of great advantage. It is considered best to coat them with platinum or silver.
In Figs. 251 and 252 is shown a construction where, instead of solid segments, a fluid is employed. In this case the commutator and collector are made of two insulating discs, S T, and in lieu of the metal segments a space is cut out of each part, as at R R', corresponding in shape and size to a metal segment. The two parts are fitted smoothly and the collector T held by the screw h and spring H against the commutator S. As in the other cases, the commutator revolves while the collector remains stationary. The ends of the coils are connected to binding-posts s s, which are in electrical connection with metal plates t t within the recesses in the two parts S T. These chambers or recesses are filled with mercury, and in the collector part are tubes W W, with screws w w, carrying springs X and pistons X', which compensate for the expansion and contraction of the mercury under varying temperatures, but which are sufficiently strong not to yield to the pressure of the fluid due to centrifugal action, and which serve as binding-posts.
In all the above cases the commutators are adapted for a single coil, and the device is particularly suited to such purposes. The number of segments may be increased, however, or more than one commutator used with a single armature. Although the bearing-surfaces are shown as planes at right angles to the shaft or axis, it is evident that in this particular the construction may be very greatly modified.