GENERAL DESCRIPTION
 

Closing the vent, which is a manual operation, requires accurate timing. Experience in actual operation has demonstrated that, at periscope depth, and

The poppet valve (see Figures 114 and 115) is designed to perform that function of removing the impulse air before it escapes into the sea. This is accomplished by automatically opening an inboard vent from the tube immediately after the torpedo has received a sufficient launching impulse (about

In the basic system, the instant at which the inboard vent opens is determined by the travel of the torpedo in the tube. The poppet valve operating unit, when set to operate, is put under air pressure and will open the poppet valve when triggered by

In either the basic or the variant system, the poppet valve, or inboard vent, must be closed by manual operation, as will be described in later pages of this chapter.

Figure 118 (above left) Interior of poppet valve, looking through lead to drain, valve open.

Figure 119 (above right) Interior of poppet valve, looking through lead to drain, valve closed.

Figure 120 Interior view of poppet valve, showing, (A) Shoulder stud for link to poppet valve indicator; (B) Gag collar; (C) Gag nut; (D) Valve stem spring; (E) Valve stem; (F) Piston; (G) Rubber cushion; (H) Vent valve disc.

As the piston moves, its stem contacts the stem end of a valve in the breechward end of the cylinder housing, driving the valve open and allowing the air pressure to pass through to the piston chamber or cylinder of the poppet or vent valve, opening that valve against the pressure of air from the tube. This causes the impulse air in the tube to vent through the poppet valve.

In earlier vessels, various forms of ducts and hoods were installed to conduct the water into the bilges with the least practicable spray or splashing. In later vessels, there is a drain line leading from each poppet valve to an open tank beneath the working platform in the torpedo room. In some other vessels, all poppet valves on each side of each torpedo room open into a common drain, in which swig checks (non-return valves having a swinging flap with a hinge on one edge, which closes against an inclined seat) are installed.

One form of lead to the drain is shown in Figure 115 on page 63. Another more recent form is shown in Figure 128. In the lower part of the lead to the drain is the poppet system discharge angle valve, or the emergency stop valve (C in Figure 128). As originally installed in earlier vessels, this was an automatic stop valve, "backing up" the main vent valve. The automatic stop valve closed by means of

A drain valve was connected by piping to the bottom of the valve-operating piston cylinder, and could be used in an emergency to close the automatic stop valve in case the 200 pound air supply was not shut off and vented with sufficient rapidity by the operation of the vent-closing valve hand setting lever.

In poppet valve systems of later design, the automatic stop valves are replaced by manually operated stop valves, as shown in Figure 128, and the installation of this form of stop valve has been largely completed in those vessels which had the earlier installations.

When preparing the tube for firing, the manually operated stop valve must be opened so the drain line is clear. If the poppet valve discharges into a

Figure 129 One form of emergency stop valve housing (fits type shown in Figure 115, page 63).

An interval of about three seconds has been observed between firing and the entrance of solid water through the poppet valve drain at a depth of 120 feet.

The poppet valve must be set for each shot. This is done by setting the lever of the vent-closing valve in the "on" position, as shown in Figure 134.

About 3 to 5 seconds after the tube has fired, the

(1) By placing the lever of the tube vent valve (A in Figure 132) in the open position.

(2) By placing the setting lever of the vent-closing valve (Figures 134, 135, or 136) in the off position, after pressing its release button (see Figure 138).

(3) By moving the handle of the emergency vent-closing valve (see Figures 139 and 140) to the open position.

Figure 137
(A) Cover plate for top of housing, with screws; (B) Washer; (C) Latch pivot stud and pin; (D) hand lever latch; (E) Cover plate for side of housing; (F) Latch spring; (G) Guide pin; (H) Washer; (I) Setting lever; (J) Pivot stud; (K) Plunger; (L) Lever pivot stud and pin; (M) Gland, with bolts and packing; (N) Housing for setting lever and valve; (O) Vent valve; (P) Supply valve; (Q) Vent valve spring; (R) Supply valve spring; (S) Washers; (T) Valve adapters.

The poppet valve should be gagged closed by means of the gag nut (E in Figure 114), except when it is intended to function in connection with the firing of a torpedo or dummy.

The operation described under paragraph (1) above moves the lever of the vent closing valve to the "off" position by means of the link (B in Figure 132). This causes the vent (Poppet) valve to close while the tube vent valve remains open to allow the escape of any air which might still be in the tube. The tube vent valve is closed directly by the operator when venting is observed to be completed. The closing of this valve has no effect upon the Poppet Valve system,

The vent closing valve body contains two small valves of poppet type, both of which are operated

Figure 138 Vent-closing valve with thumb on latch release button.

The hand lever latch (D in Figure 137), when engaged insures that the two valves in the vent closing valve will remain in position to allow operation of the Poppet System until released intentionally and the lever returned to the "off" position by the operator.

The latch release button is furnished solely for releasing the latch. Continued thumb pressure on this button will move the setting lever some distance, but to insure that both valves in the vent closing valve are fully in the "off" position the setting lever should be pushed to the limit of its motion.

(A) Emergency vent-closing valve (quick-as-a-wink valve) in place on vent-closing valve; (B) Normal position; (C) Open position.

A "gagging" device (E in Figure 114) is provided for the purpose of gagging the poppet valve when its use is not desired. Also, after firing a torpedo, and when the firing operation has ended, the main vent valve, located in the poppet valve body, should be locked closed by means of this

Figure 145 Poppet valve indicator (A) in open position; note changed position of stud (B) on poppet valve.

gagging device. An indicator is also installed to show whether the poppet valve is open or closed. This indicator is shown, in "shut" position, in Figure 144, and in "open" position in Figure 145. Figure 146 shows the linkage from the poppet valve to the indicator.