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to correctly graduate the locomotive-braking power at service applications, and to so operate that the power of the locomotive brake will be proportionately the same as that of the properly working car brakes during the different grades of application. In fact, it does all that a triple valve has done, and performs other additional functions that are individual to the E-T type of brake equipment.
It is necessary, therefore, to be familiar with the operation of a plain triple valve before it is possible to satisfactorily understand the distributing valve; and as the latter is as essentially the vital part of the E-T equipment as the triple valve is of the plain automatic brake, the working of a triple valve of the simplest design of construction will be exemplified, and will be followed by an ideal, or diagrammatic, illustration and explanation of the principal features of the distributing valve for comparison, and which will make it clear that the original theory of the automatic brake has not been departed from, but only strengthened.
Fig. 4 A represents a triple valve with the parts in the release position, together with the auxiliary reservoir, and brake cylinder and piston; the triple valve embodies the controlling mechanism, the auxiliary reservoir is to contain the pressure ready to be used in the application of the brake, and the brake cylinder is the place where the power of the compressed air is
Operation of the Triple Valve made to transmit its force to the brake shoes through the foundation brake, or rigging, by acting against the movable piston contained within the cylinder. Figs. 4 B, 4 C, and 4 D show the same triple valve with the operating parts in the service-application, service-lap, and emergency-application positions, respectively, but without the auxiliary reservoir and brake cylinderthe points of connection therewith being indicated -as their duties will be sufficiently understood after the explanation of the first diagram, Fig. 4 A.
Alluding to Fig. 4 A, the triple-valve piston, 26, contains a packing ring (not shown), to make a practically air-tight joint between the spaces on each side of it, and, seated between the shoulders of the stem of the piston is a slide valve, 31, that follows the piston, but with a certain amount of slack, or lost motion, which the piston must take up in either direction before the slide valve moves; the top of this slide valve forms the seat for another one of smaller design but similar in some respects, called the graduating valve, No. 28, which is combined with the piston and moves regularly with it; while piston 26 is air-tight on its edges, in the release position it is necessary that there shall be a slender opening between chambers p and x, and to serve this purpose a small groove, u, is cut in the wall of the triplevalve cylinder, but made so short that the triple piston must be fully in the release position, as here shown,
in order that air will feed through it. The connections of the triple valve are as follows: The brakepipe connection, as indicated on the plate, is to a branch of the main pipe that extends throughout the train from the engineer's brakc-valve, and which is constantly charged with pressure from the main reservoir, that the feed valve maintains at 70 pounds while the engineer's valve is in running position. The brake pipe was formerly known as the “train line,” and the duty of its contained pressure is two-fold: to maintain the air charge of the auxiliary reservoir on each car, and to be the medium by which the engineer can operate the triple valves on all of the cars simultaneously--reducing the pressure to apply the brakes, and increasing it to release them; the connection of the triple valve with the auxiliary reservoir is plainly seen in the opening through the front head of the reservoir to which the triple valve is attached; the tube L, extending through the auxiliary reservoir, furnishes the connection between the triple valve and the brake cylinder; the exhaust port to the atmosphere is indicated on the plate, and with the triple valve in release position, as shown, the pressure space of the brake cylinder is open to the atmosphere through the tube L, port h that opens into the seat of the triple-slide-valve, cavity k in the face of the slide valve, and the exhaust port. When pressure is released from the brake cylinder, the large spring
around piston rod, 12, holds the brake piston, 10, against the pressure head of the cylinder; the extension of the left, or non-pressure, head of the brake cylinder is to permit the nesting of the release spring for protection in case the piston should ever be permitted to travel the full, possible distance of the cylinder; but the slack in the brake rigging should be taken up enough that at a full-on application the piston will not travel much over one-half of its full stroke.
Air pressure from the brake pipe enters the triple valve as shown, filling chambers Þ. Þ, and passing through the feed groove, u, charges chamber x and the auxiliary reservoir, but slowly, under head of brake-pipe pressure at the rate of about one pound of reservoir charge per second; when the auxiliary reservoir has become charged to 70 pounds, or equal to the brake-pipe pressure, no movement of the triple-valve parts will automatically occur, as the piston is in a perfect equilibrium of brake-pipe pressure on one side and auxiliary-reservoir pressure on the other.
Fig. 4 B-SERVICE-APPLICATION POSITION: A reduction of brake-pipe pressure having been made-say of 10 pounds—the pressure in chamber p is now 60 pounds, and as the feed-groove, u, is too small to permit the auxiliary air to equally reduce by back flow through it, the 70-pounds pressure in chamber x forces the triple piston, 26, to the right until its knob