Hydraulic safety circuit

A hydraulic circuit for prevention of inadvertent weapons launches in which a hydraulic firing valve provides hydraulic pressure to a backup select valve rather than the backup select valve receiving hydraulic pressure directly from a ship supply header. This hydraulic pressure shifts the backup select valve to allow hydraulic pressure to pass to a mode select control valve that actuates a controllable air-firing valve, until a hydraulic firing valve for the weapon is opened. The backup select valve actuation can only occur with the initiation of the hydraulic firing valve. Only after the hydraulic firing valve is open, does the backup select valve initiate hydraulic pressure to the mode select control valve thereby preventing hydraulic actuation of the backup select valve.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a hydraulic circuit and method of use for initiating and preventing inadvertent weapons launches.

(2) Description of the Prior Art

Weapon system failures on submarines have catastrophic consequences. For example: the inadvertent operation of an air valve may result in a serious event such as firing valves that provide the last isolation of high pressure air from entering critical launch system components, such as a launch air turbine. Once the high pressure air enters the launch air turbine, a full or partial launch can occur. With a weapon loaded in a torpedo tube, an accidental launch could be disastrous.

Several remedies to prevent inadvertent launch have been proposed with many of the remedies implemented. One such remedy, a software modification, has prevented numerous inadvertent launches from occurring; however, the software modification does not totally eliminate the risk of an inadvertent launch.

Modifications to the hydraulic control circuit have also been proposed to prevent inadvertent launches. However, these hydraulic modifications require the design and fabrication of new valves that would increase the weight and volume of the launch system. These modifications would also require a launch system redesign to accommodate the hydraulic valve and a new qualification test series to certify them with the result of complicated and costly changes.

A mechanical option in the hydraulic system would include the incorporation of a stronger coil spring used to bias the control valve to a closed position. This mechanical option is difficult and costly to implement.

As such, a need exists to substantially eliminate the possibility of an inadvertent launch in hydraulically actuated weapon systems.

SUMMARY OF THE INVENTION

The present invention is the modification of an existing hydraulic circuit to prevent inadvertent weapons launches. The hydraulic circuit has a backup select valve that is substantially devoid of actuating hydraulic pressure; a mode select control valve effective for actuating a controllable air-firing valve; in which the mode select control valve is communicatively connected to and responsive to actuating hydraulic pressure sent by the backup select valve. The hydraulic circuit also includes a hydraulic firing valve for the weapon, that once opens, provides actuating hydraulic pressure to the backup select valve effective to initiate hydraulic pressure to the mode select control valve. The hydraulic circuit is particularly useful in a controllable air-firing valve type system, such as a horizontal weapons system.

The present invention also details a method for preventing inadvertent weapons launch comprising the steps of providing a hydraulic circuit that prevents inadvertent weapons launches.

The present invention provides an active weapons launch platform (a ready-to-launch platform) where an actual weapon (s) launch can be initiated, with a reduced risk of inadvertent launch.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a hydraulic control circuit designed to prevent inadvertent operation of a weapons system, particularly a submarine weapons system. Although particularly applicable to a submarine-based launch system, the hydraulic circuit of the present invention may be generally applied to any hydraulically operated launch system. As the hydraulic circuit provides positive control until a proper launch time, this control ensures the safety of the crew and non-destruction of the weapons platform. A failsafe launch resulting from the use of the hydraulic control circuit, described herein, is possible without having to perform excessive and costly redesign work, or requiring new valves or extensive modifications to the existing valves.

FIG. 1depicts an existing electro-mechanical device used in the launch of a torpedo. The device is a hydraulically operated controllable air firing valve2that provides high pressure air to a launch system through a system that opens and closes an air piston4to the launch system.

FIG. 2represents the prior art configuration of the launch assembly hydraulic control circuit10without the modifications of the present invention incorporated therein. InFIG. 2, the valves that make up the hydraulic control circuit10are identified. This positioning of the launch system is done through the cascading use of a direct drive valve20and a servo valve30.

The direct drive valve20is an electro-hydraulic valve capable of electronics control. The direct drive valve20provides hydraulic pressure to position the servo valve30by controlling the direction of hydraulic fluid to the servo valve30. The servo valve30is a three-position valve that provides hydraulic pressure to a mode select control valve40. With the input from the direct drive valve20to drive the position of the servo valve, the servo valve controls the direction of hydraulic fluid to the air piston4.

The intermediate position of the servo valve30is used to minimize the electrical loads required to operate the direct drive valve20and to speed up the responsiveness of the system; otherwise, a servo valve would not be necessary and the direct drive valve could provide direct control of the air piston.

An additional valve represented in the hydraulic control circuit ofFIG. 2is backup select valve50. The backup select valve50provides hydraulic pilot pressure to the mode select control valve (MSCV,40) such that the mode select control valve is positioned for a NORMAL mode launch. The existing hydraulic circuit, shown inFIG. 2, shifts the MSCV40into NORMAL by first electrically energizing the backup select valve (BSV,50). Because a constant supply of hydraulic pressure is maintained at the BSV50, once the BSV is electrically energized, hydraulic pressure is allowed to immediately pass through to open the MSCV40. This is potentially dangerous as the BSV50is energized every time a torpedo tube slide valve (not shown) is opened. Especially dangerous, in that the slide valve may remain open for extended periods of time before a weapon launch is actually performed.

The BSV50is electrically actuated and also hydraulically actuated. The hydraulics of the BSV50has a positive supply pressure available at all times. The electrical actuation of the BSV50is only energized when a launch is pending (i.e., when the slide valve is open). When the slide valve opens, the electrically applied force on the BSV50is larger than the constant hydraulically applied force. In this way, the electrical solenoid force overcomes the hydraulic force to open the BSV50. The electrical solenoid force is later removed from the BSV50after the launch event is complete. The dominant hydraulic shift force automatically returns the BSV50to a closed position. This automatic return of the BSV50removes the hydraulic pressure from the MSCV40allowing the MSCV to close.

As seen inFIG. 2, the MSCV40is a three-position, dual piloted valve that controls hydraulic pressure. The MSCV40is positioned to either the NORMAL or BACKUP mode from the CLOSED mode, by pilot pressure applied to the MSCV by the BSV50and/or a hydraulic firing valve (not shown). If the MSCV40is aligned in the NORMAL position, the servo valve (SV,30) hydraulic pressure of the passes through the MSCV to drive the launch assembly. Once the torpedo tube slide valve is opened, an electrical command is supplied to the BSV50to shift the MSCV40into NORMAL position. With the MSCV40in the NORMAL position, the air piston4can be controlled by directional porting of hydraulic fluid through the SV30and direct drive valve (DDV,20).

With the MSCV40in the center CLOSED position, control of the air piston4is blocked, and until the MSCV shifts into NORMAL position, the air piston cannot open regardless of the SV30and DDV20positions. The third MSCV40position, the BACKUP position, is used in the event of an electrical failure. In the event of both pilots having pressure applied simultaneously, the larger NORMAL mode pilot will override the smaller BACKUP pilot and shift the MSCV40to a NORMAL launch mode. Conventionally, the hydraulic firing valve provides hydraulic pilot pressure directly to the MSCV40, and does not provide any hydraulic pressure to the BSV50.

During an initial part of the firing sequence for a normal weapon launch, the MSCV40shifts into NORMAL position. The hydraulic firing valve is later actuated. An inadvertent launch only occurs after the MSCV40has been shifted into NORMAL position. A proper launch does not begin until when the hydraulic firing valve is opened. After the hydraulic firing valve opens, a launch must occur, but not before.

Concurrent with the opening of the hydraulic firing valve, electrical control of the DDV20is simultaneously started. Prior to this step, the DDV20should be in a biased-closed position. However, due to mechanical drift, software timing/control errors, large electrical spikes, or other occurrences, the DDV20may improperly drift into a biased-open position. This may cause an inadvertent launch as soon as the MSCV40shifts into NORMAL. This remains a concern every time the torpedo tube slide valve is opened such as when the BSV50has switched the MSCV40to NORMAL but prior to the hydraulic firing valve being opened.

If an inadvertent launch does not occur with the opening of the slide valve, launch may still occur anytime thereafter while the slide valve remains open. Under these conditions, an inadvertent launch is possible when the DDV20is improperly positioned to port hydraulic fluid to open the air piston4before called for electrically. With the DDV20biased to open, the air piston4will immediately start opening once the MSCV40shifts into the normal launch position. The proper sequence of events requires the DDV20to port hydraulic fluid to close the air piston4before the MSCV40shifts into NORMAL and then hold that position until the hydraulic firing valve opens. Only at that point (after the hydraulic firing valve opens) should the DDV20begin with electrical control to open the air piston4.

There is a likelihood that the DDV20hydraulic alignment improperly biases to an open position without electronic input at the time the MSCV40shifts into NORMAL, whereas the DDV had been designed to remain in a biased CLOSED position. Once the DDV20drifts into a biased OPEN position, only the MSCV40prevents the air piston4from opening. In a regular firing sequence opening the MSCV40prior to the hydraulic firing valve could cause an inadvertent launch to occur.

The present invention, shown inFIG. 3, incorporates much of the existing hydraulic circuit, but remedies the problems, associated with the hydraulic circuit shown inFIG. 2. InFIG. 2, the BSV50is shown to be supplied a constant hydraulic pressure from the ship supply header.

The present invention, shown inFIG. 3, provides hydraulic pilot pressure line100directly from the hydraulic firing valve to the BSV50rather than directly from the ship supply header. This hydraulic pilot pressure shifts the BSV50to allow hydraulic pressure to pass to the MSCV40and to provide the pass through hydraulic pressure to the MSCV. As the hydraulic circuit of the present invention uses a BSV that is substantially devoid of actuating hydraulic pressure from the ship supply header; actuation can only occur with the initiation of the hydraulic firing valve.

Although the MSCV40in the present invention is hydraulically connected and responsive to actuating hydraulic pressure sent by the BSV50, the BSV is fed actuating hydraulic pressure from the hydraulic firing valve, and only after the HFV is open, does the BSV initiate hydraulic pressure to the MSCV.

In operation, the hydraulic circuit of the present invention is used for prevention of inadvertent weapons launches by causing the BSV50to open in response to opening of the hydraulic firing valve. Once the BSV50has been supplied with hydraulic pressure from the hydraulic firing valve, the BSV causes the MSCV40to shift to its NORMAL position. Preferably, actuating hydraulic pressure is maintained in the hydraulic firing valve after a weapon launch effectuates the closure of the BSV50. The present invention restricts the MSCV40to remain in the CLOSED position until a launch becomes absolute.

Elimination of an inadvertent launch is achieved by eliminating the constant supply of hydraulic pressure to the BSV50. Instead, hydraulic pressure is only provided to the BSV50after the hydraulic firing valve opens when a launch is absolute. No changes are necessary to the electrically energized side of the BSV50, and preferably the situation would remain unchanged. Additionally no change is necessary to the hydraulic side of the BSV. In this way, it is the MSCV40not the BSV50which serves as the final line of protection against inadvertent launches, because regardless of the DDV20position, the air piston4cannot be opened when the MSCV is in the CLOSED position.

In addition to the timing delay for control of the DDV20, the only required modification to the circuit is the elimination of hydraulic supply line60to the BSV50from the ship supply header and the addition of the hydraulic line100connecting the hydraulic firing valve to the BSV50. The tasks to eliminate the constant hydraulic supply to the BSV50and to install the new hydraulic line100are well known by those skilled in the art hydraulic systems. As such, the present invention is useful for reconfiguring current hydraulic systems, as well as for incorporation into newly manufactured hydraulic systems.

By using the hydraulic firing valve to supply hydraulic pressure to the BSV50, the MSCV40cannot shift into NORMAL even though the BSV has already been electrically energized. Consequently, the slide valve can be opened and remain open as long as necessary without the risk of an inadvertent launch. This is because no hydraulic pressure will be available to the BSV50until the hydraulic firing valve opens, which is when a launch must be performed. When the electrical force is later removed from the BSV50(after the launch event is complete), the HFV pressure still remains. This ensures that the BSV50closes. The BSV50then remains closed after the hydraulic firing valve pressure is removed and all valves are returned to their safe standby position until the next launch.

The number of valves required to prevent inadvertent launch is minimized, as the present invention does not require any additional valves over the number used in the previous design. More valves would only increase the complexity of the controllable air firing valve2operation, placing a greater demand on the hydraulic system by increasing system flow losses. Complex software modifications to the existing electronic control programs also remain unnecessary. Because additional valves are not required, costs and weight increases are minimized. The cost of designing, fabricating, and testing a new valve is also avoided. Other mechanical modifications, such as a stiffer coil spring in the DDV20to help bias the DDV closed are unneeded.

The hydraulic circuit of the present invention ensures an active weapons platform at the appropriate time, after the hydraulic firing valve has been initiated. Once the hydraulic firing valve has been initiated, the present invention eliminates the risk of an inadvertent launch. The hydraulic circuit is applicable to any appropriate controllable air-firing valve system, such as a horizontal weapons system.

The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive nor to limit the invention to the precise form disclosed; variations are possible in light of the above teaching. Such modifications and variations that may be apparent to one skilled I the art are indicated to be included within the scope of this invention as defined by the accompanying claims.