The Poppet Valve System-General Description62
The Poppet Valve64
The Operating Unit66
The Roller Crank67
Operation of the Poppet Valve68
The Poppet Valve Drain68
The Poppet Valve Controls70



As shown in the foregoing chapter on the firing system, the torpedo is ejected from the barrel by means of a charge of compressed air. As much of that air as possible must be removed from the barrel immediately after firing, before it has "a chance to escape through the muzzle door and out into the water. Otherwise, it would cause bubbles to rise and   one-fifth second after firing), and allowing the air charge to vent within the hull, then closing the vent before an unduly large amount of water has been admitted.

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

Figure 114 The poppet valve
Figure 114 The poppet valve, detached from tube, showing (A) Flange for connecting to barrel; (B) Access opening, with cover plate attached; (C) Access opening, with cover plate attached; (D) Flange for connecting to drain pipe; (E) Gag nut, for "gagging" valve; (F) Connection for rod link to poppet valve indicator.
create an excessive disturbance on the surface of the sea and disclose the location of the submarine.

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

  with an impulse tank pressure of 300 pounds per square inch, the poppet valve must be closed three to five seconds after the tube fires in order to secure satisfactory operation. From this it can readily be seen that the operation of the poppet valve system is very closely related to the operation of the firing mechanism, in fact, the operation of the two is practically simultaneous.

There are two types of poppet valve systems, one known as the basic, the other as the variant. The basic system is sometimes referred to as the Portsmouth system, and the variant is sometimes called the Mare Island system.

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

  the torpedo in the tube. In vessels already in commission, however, this location was at such a place in the ship's structure that it was impracticable to install roller trip units there. Hence these units were installed as far toward the muzzle as practicable (about seven feet from the breech), and a throttling valve was fitted in the actuating air line to introduce a time delay. In connection with this variant of the basic system, if ejection of the torpedo tended to be sluggish due to improper operation of the firing
Figure 115 Poppet valve in position on tube.
Figure 115 Poppet valve in position on tube. (A) Poppet valve housing; (B) Lead to drain; (C) Airline to poppet valve; (D) Poppet valve operating unit; (E) Connection from air supply line; (F) Casing through which pull rod from operating unit connects with roller crank.
the roller trip unit. This latter unit, however, is kept from moving so as to let the operating unit open the poppet valve by the presence of a torpedo in the tube. SS 198 and up, and in some earlier vessels in which poppet valves were also installed before their launching, the roller trip units, are located about 11 1/2 feet from the breech, so that the poppet valve will be opened at the proper point of the travel of   valve, this tendency would be aggravated by the opening of the poppet valve after a constant time delay instead of at a constant point in the travel of the torpedo in the tube.

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.


The poppet valve, assembled but removed from the barrel, is shown in Figure 114, while in Figure 115 it is shown in place on the barrel with the operating unit assembled. Figure 116 shows the parts of the valve disassembled, while Figure 117 shows the poppet valve housing with the access plates, or the access opening covers, and gaskets   disassembled, also the parts of the valve which are put in place through the access opening. In Figures 118 and 119, looking into the interior of the housing through the connection to the drain, the valve is shown both open and closed. An interior view of the poppet valve, with the outer casing broken away, is shown in Figure 120.
Figure 116 Parts of poppet valve disassembled Figure 116 Parts of poppet valve disassembled
Figure 116 Parts of poppet valve disassembled
A Valve stem, with cotter pins
B Rubber cushion
C Piston
D Piston nut
E Cylinder head
F Air inlet
G Gasket
H Plug
I Poppet valve spring
J Gag collar, with pin and chain
K Valve stem stud
L Gag collar, with taper pin
M Shoulder stud for link to poppet valve indicator

Figure 117 The poppet valve. Figure 117 The poppet valve.
Figure 117 The poppet valve, showing access opening cover plates removed and also attached, also the parts of the valve assembled through the large access opening.
A Nuts for attaching large cover
B Large access opening cover plate
C Nuts for attaching small cover
D Gasket for large cover
E Small access opening cover plate
F Gasket for small cover
G Large access opening, cover plate attached
H Small access opening
I Connection for air from operating unit
J flange for connection to drain pipe
K Flange for connection to barrel
L Gasket for connection to drain
M Gasket for connection to barrel
N Valve stem
O Screws for attaching retaining ring to valve disc
P Retaining ring
Q Rubber gasket
R Vent valve disc

Figure 118
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
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.


The poppet valve proper is actuated by the operating unit, which is shown removed from the tube in Figure 121. Figure 122, the reverse side, shows the interior of the operating unit, also the action of the pull rod which connects with the roller crank and   releases the valve as the torpedo moves forward in the tube. Figure 123 shows the position of the pull rod after the torpedo has left the tube and the valve is opened. The parts of the unit disassembled are shown in Figure 124.
Figure 121 Poppet valve
Figure 121 Poppet valve operating unit as it appears mounted on the tube
  Figure 122
Figure 122 Showing interior mechanism of poppet valve operating unit, from reverse side, position of pull rod being for torpedo in tube, vent valve closed. (A) Lead from vent closing valve; (B) Valve spring; (C) Air line to poppet valve; (D) Piston; (E) Piston fork; (F) Lead from air supply line; (G) Pull rod fork; (H) Pull rod.
Figure 124 Parts of poppet halve operating unit disassembled.
Figure 124 Parts of poppet halve operating unit disassembled. (A) Cap; (B) Washer; (C) Collar; (D) Piston; (E) Packing; (F) Piston ring; (G) Piston; (H) Collar and pin; (I) Housing; (J) Housing cap, with pin; (K) Pull rod guard and set screw; (L) Valve; (M) Valve spring; (N) Washer; (O) Cap; (P) Plug; (Q) Gland nut, washer, and packing ring; (R) Piston fork; (S) Pull rod fork; (T) Pull rod head; (U) Pull rod pin; (V) Cap; (W) Washer; (X) Shaft; (Y) Bolts and locating pins; (Z) Gasket.

Figure 126 shows the roller trip unit, "A" being the rod which connects the roller crank and the poppet valve operating unit. Figure 127 shows the roller trip unit disassembled. This figure shows two rollers, one for torpedoes and one for mines. In later   ships, minor changes have been made so that one roller can be used for both. The relative positions of the two units are shown in Figure 125, the connecting rod, or pull rod, passing through the casing seen on the side of the tube.
Figure 123 Roller Crank. Figure 125
Figure 123 Reverse side of operating unit, showing position for vent valve open.   Figure 125 Showing position of and connection between poppet valve operating unit and the roller trip unit. (A) Operating unit; (B) Casing through which the pull rod passes; (C) Roller trip housing
Figure 126
Figure 126 Interior view of the roller trip, unit. (A) Pull rod; (B) Roller crank; (C) Roller.
Figure 127
Figure 127 Parts of the roller trip unit, disassembled. (A) Pull rod; (B) Pull rod head; (C) Pull rod pin; (D) Cotter pin; (E) Roller crank; (F) Roller used with mines; (G) Roller used for firing torpedoes; (H) Roller pin and cotter pin; (I) Roller crank bracket; (J) Roller crank bracket pin; (K) Taper pin; (L) Bracket tap bolts; (M) Gasket; (N) Roller crank housing; (O) Location pins for attaching housing; (P) Tap bolts.

Tracing the operation of the poppet valve in so far as that operation relates to these three units, we find the following: Air is admitted to the piston cylinder and to the valve chamber of the operating unit by placing the setting lever of the vent closing valve (which is described on page 71) in the "On" position, and tends to force the piston toward the breech. The piston is restrained, however, by the piston fork, which is linked to the roller crank in the roller trip unit. As the fired torpedo moves toward the muzzle, the trip roller rides down the slope   of the torpedo's afterbody, releasing the restraint on the piston of the operating cylinder, and allowing it to move toward the breech end of the tube.

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.

All of the air charge can not be vented without some water also passing. The arrangements for disposing of the water which enters through the poppet valve vary somewhat in different submarines.

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 spring, its own weight and, when the main vent valve was open, by whatever air or water pressure existed in the tube. It opened by admitting air pressure from the ship's 200 pound air service line to the inlet side of the valve-operating piston by placing the hand setting lever of the vent-closing valve in its "on" position. It closed by the return of the hand setting lever to its "off" position, which closed off the 200 pound air supply and vented the space behind the piston.

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.


Figure 128 Lead from puppet valve to drain, with emergency stop
valve and linkage to hand wheel.
Figure 128 Lead from puppet valve to drain, with emergency stop valve and linkage to hand wheel. A Flange for connection to drain; B Lead to drain; C Emergency stop valve; D Poppet valve housing; E Emergency stop valve operating handle
The operating parts of the emergency stop valve, disassembled, are shown in Figures 129 and 130, Figure 129 showing the valve housing, the casting being the form shown in Figure 115 on page 63, and Figure 130 showing the valve bonnet and the other operating parts.

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

Figure 130 parts of emergency stop valve disassembled.
Figure 130 parts of emergency stop valve disassembled. (A) Pin for (B) Valve stem collar; (C) Valve bonnet; (D) Valve disc nut; (E) Pin for (F) Valve stem; (G) Cotter pin for (H) Valve disc; (I) Pin for valve stem; (J) Valve stem head; (K) Grease fitting; (L) Nuts for fastening (M) Gland; (N) Packing.

bilge or open tank which already contains water, some of the water will be blown up into the torpedo room when the impulse air is vented from the tube, giving the impression that water is entering through the poppet valve before such is actually the case. An interval of at least five seconds is to be expected between firing and the entrance of any large quantity   of water through the poppet valve, when firing at periscope depth. At greater depths the increased sea pressure causes the tube to flood in less time.

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 controls of the poppet valve system are located in the torpedo room, above the breech end of the tubes, as shown in Figure 131. These controls consist of a vent-closing valve, a quick-opening vent valve in the blow and vent manifold, and an emergency   vent-closing valve. These are shown, assembled, in Figures 132 and 133.

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.

Figure 131 The vent manifold valves, showing poppet valve controls.
Figure 131 The vent manifold valves, showing poppet valve controls. (A) Quick-opening vent valve; (B) Vent-closing valve; (C) Emergency vent-closing valve (quick-as-a-wink valve).

Figure 132
Figure 132 Blow and vent manifold, with quick-opening vent in open position.
  Figure 133
Figure 133 Quick-opening vent in shut position.
A Quick-opening vent in open position.
B Link connecting quick-opening vent and vent-closing valve.
C Latch release button.
D Vent-closing valve, cover plate removed to show interior.
E Setting lever.
F Emergency vent closing valve (quick as-a-wink valve).
G Quick-opening vent, in shut position.

Figure 135 shows the lever in the "off" position, the cover plate of the housing being removed to show the interior. Figure 136 shows the lever in the "off" position, with the cover plate in place on the housing. The parts of the vent-closing valve, dissembled, including the setting lever and the valve parts, are shown in Figure 137. Figure 138 shows the vent-closing valve with thumb on the latch release button.

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

  poppet valve must be closed, in one of the following ways:

(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 134
Figure 134 Vent-closing valve, with setting lever in on position, cover plate moved to show interior.
  Figure 135
Figure 135 Vent-closing valve, with setting lever in off position.
  Figure 136
Figure 136 Vent-closing valve, setting lever in off position, cover plate attached.

Figure 137

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.

  Considering that adequate safety is afforded by other means, the Bureau of Ships has authorized the omission of the emergency vent closing valves in new construction.

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


by setting lever. One of these valves is a shut-off and supply valve for the ships' service air to the Poppet Valve system. The other valve serves to vent the air line to the Poppet Valve when the setting lever moved to the "off" position thus relieving the pressure in the air cylinder of the vent valve and allowing the vent valve to close instantly.

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.


Figure 139 and 140
(A) Emergency vent-closing valve (quick-as-a-wink valve) in place on vent-closing valve; (B) Normal position; (C) Open position.

Figure 141, 142, 143
Quick-as-wink valve, detached, in normal position at left, in open position in center, parts disassembled at right.
A Valve body; B Stem; C Valve; D Sleeve; E Pipe adapter; F Handle; G Fork; H, I Nut, with cotter pin

Figure 144
Figure 144 Poppet valve indicator (A) in shut position; (B) and (C) Linkage to (D) Stud on poppet valve.

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
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.

Figure 146
Figure 146 Linkage from poppet valve to indicator. (A) Connection with shoulder stud on poppet valve; (B) Poppet valve indicator; (C) Linkage connected with shoulder stud on poppet valve.

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