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RELEASE

RUNNING

Rotary Valve. Running Position

is only brought into play in the position of emergency application. The long, tunnel-like cavity through the rotary valve from port h in the face to the large, central

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SERVICE

EMERGENCY

Copyright, 1909, by The Norman W. Henley Publishing Co.

FIG. 26.-H-6 Brake-Valve. Top view of transparent rotary valve, and plan view of rotary-valve seat. Running position.

exhaust-cavity, now connects the latter with the port in the seat, "to dis.-valve exhaust"- that is, to the dis

tributing-valve release pipe; and it is through this connection that the application-cylinder pressure is exhausted when the brake-pipe recharge forces the lower, or triple-valve, portion of the distributing valve into release position, and thereby effects the release of the locomotive brake. The port in the rotary-valve seat connecting with the pipe to "excess-pressure governor head" is still receiving main-reservoir pressure through port s in the rotary valve and its lengthened cavity in the valve face, and the low-pressure feature of the governor is still controlling the action of the pump. All other ports are blanked between the face and seat of the rotary valve.

The movement of the brake-valve handle from running position to Holding Position (Fig. 27), while shifting all ports in the rotary valve a short distance, does not separate any of the connections that were held in the former position-except one: the "dis.-valve exhaust" port in the rotary-valve seat is cut off from the atmospheric port in the center of the brake-valve by the shift. of the formerly connecting port, h, which is now blind on the rotary-valve face. Holding position, thus becomes another running position, so far as the common functions of the brake-valve are concerned (although a lesser area of the feed-valve port is now opened in connection with the left-hand brake-pipe port in the seat), but it permits those functions while retaining

Rotary Valve. Holding Position

the application of the locomotive brake, by the closing of the distributing-valve release port; to secure this holding effect, the brake-valve handle must be brought

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Copyright, 1909, by The Norman W. Henley Publishing Co.

FIG. 27.-H-6 Brake-Valve. Top view of transparent rotary valve, and plan view of rotary-valve seat. Holding position.

from release position directly to Holding Position, passing the running position quickly so that none of

the application-cylinder pressure will be discharged. The small port, s, through the rotary valve is now in exact register with the port in the seat connecting with the "excess-pressure governor head"; and we have found that in the three positions of the brake-valve in which pressure is supplied to the brake pipe, mainreservoir pressure flows to the excess-pressure top of the pump governor, with the effect of regulating that pressure at its minimum figure.

The position of the rotary-valve handle in Fig. 28 shows that the brake valve is in the Lap Position. No pressure is supplied to the brake pipe, as the large, main-reservoir supply port through the rotary valve is blind on the seat, and the large cavity, ƒ, in the face of the rotary valve no longer connects the feed-valve and brake-pipe ports in the seat. Cavity k in the face of the rotary valve, while still lying over the port to chamber D, no longer connects the latter with the righthand brake-pipe port in the rotary-valve seat. The small port, s, through the rotary valve has finally parted with the port in the seat that is designated “to excess-pressure governor head," thus closing off the supply of main-reservoir pressure to and, in effect, cutting out that portion of the governor, and permitting the pump to increase the main-reservoir pressure to the amount permitted by the high-pressure top of the governor. The location of port j, now, over

Rotary Valve. Lap Position

the end of the channel that is an extension of the feedvalve port in the seat, is without results further than that it fills the feed-valve port, and pipe connecting,

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FIG. 28.-H-6 Brake-Valve.

Top view of transparent rotary valve and plan view of rotary-valve seat. Lap position.

with main-reservoir pressure, and this introduces a possibility that was not contemplated: In the No. 6

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