Fluid handling – Larner-johnson type valves; i.e. – telescoping internal valve...
Reexamination Certificate
1999-06-25
2001-03-20
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Larner-johnson type valves; i.e., telescoping internal valve...
C091S045000, C092S027000, C137S312000, C251S031000, C251S049000, C251S094000
Reexamination Certificate
active
06202671
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a valve construction, particularly for controlling flow of a cryogenic liquid propellant.
BACKGROUND
A valve construction of this type is used as a propellant control valve in rocket engines and must remain in the open position from the beginning of ignition up to shutdown of the engine. It is known from DE 3,609,765 A1, DE 4,221,230 C1 and DE 4,323,846 C1 to form an actuator controlled by a pressure medium for effecting the valve switching, the actuator being constructed as a single or double acting piston-cylinder unit which is spring-loaded in the direction of the valve closing position. In each of the two end positions of the piston-cylinder unit, a locking device, which moves transversely to the piston rod of the piston-cylinder unit, acts to lock the piston-cylinder unit in the respective valve position, even when there is a drop in the control pressure. The locking device is provided with two locking surfaces that are pre-stressed by a spring and act opposite one another. A pressure-controllable multiple piston arrangement, acts to release the respective locked locking surface by overcoming the pre-stress of the spring with a stroke activation of the piston cylinder unit from a form-fitting engagement with the piston rod, while the other locking surface remains engaged with the piston rod under the spring force until it engages in a corresponding recess of the piston rod at the end of stroke of the piston-cylinder unit. Such a valve construction with a pressure-controlled double-locking device acting in opposite directions has a relatively complicated mechanical structure and operation and is relatively sensitive to wear due to the frictional contact between the end-position locking device and the piston rod during the stroke motion, whereby it has limited switching reliability and the danger exists that the locking surfaces and the piston rod will jam in the opening stroke resulting in a blockage of the piston-cylinder unit in a partially opened, intermediate position of the valve.
SUMMARY OF THE INVENTION
An object of the invention is to provide a valve construction of the above type with a simplified construction and reduced weight and which has increased switching reliability.
The above and further objects are achieved by a valve for controlling flow of a cryogenic liquid propellant in a rocket engine which comprises a double acting piston-cylinder unit having a first position in which the valve is closed and a second position in which the valve is open, a locking device engageable with the double acting piston-cylinder unit to lock the unit in the first position when the valve is closed, the locking device including a control piston, a locking member coupled to said control piston to selectively lock and unlock said piston-cylinder unit, spring means acting on the control piston to urge the locking member to lock the piston-cylinder unit, and a control chamber capable of receiving a pressure medium to urge the piston, against the opposition of the spring means, to unlock the piston-cylinder unit when the piston-cylinder unit is in said second position and the valve is open. A two-way control valve has a first position in which the control chamber is connected to a source of the pressure medium and a second position in which a first operating chamber of the piston-cylinder unit is connected to the pressure medium to urge the valve to the closed position, the control chamber in the second position of the two-way control valve being vented, said first operating chamber in the first position of the two-way valve being vented, the piston-cylinder unit having a second operating chamber connected via a passageway to the control chamber to receive the pressure medium and urge the valve to said open position when the two-way control valve is in said first position.
In addition to the feature that the double-acting piston-cylinder unit is not pre-stressed by a spring in the valve closing direction, as in the prior art, the valve is held securely in the valve open position, even in the case of a drop in control pressure, by the pressure of the operating medium acting on the valve disk, i.e. the liquid propellant in the rocket engine. Thus, according to the invention, the expensive double-locking device of the prior art, which is subject to friction in both stroke directions, is eliminated and instead, the piston-cylinder unit is only mechanically locked by a locking member in the closed position of the valve. The complexity of the structure and of the end-position locking device of the prior art is reduced while wear of the valve drive will also be reduced. Additionally, the risk of jamming will also be considerably reduced, since the piston rod has absolutely no contact with the end-position locking device during the opening stroke. The valve according to the invention is thus excellently suitable for applications in which high precision and reliability are combined with strict weight limitations under extreme temperature conditions, such as in outer space. The connection to the operating chamber of the piston-cylinder unit which produces the valve opening stroke is closed in the closed position of the valve by the end-position locking device, whereas the connection to the valve closing chamber of the piston-cylinder unit is open. In this way, the cylinder chamber effecting the opening stroke of the valve will be pressure-activated only after the complete release of the end-position locking device so that the operation is substantially free from wear and jamming during the unlocking operation.
In a preferred embodiment, a delayed pressure activation of the piston-cylinder unit is produced in a simple manner by providing a passageway connecting the control chamber of the control piston and the valve opening chamber of the piston-cylinder unit and wherein the displacement of the control piston controls the opening of said passageway to the control chamber.
Preferably, said passageway contains a throttle or choke forming a constricted cross-section, in order to compensate for the pressure force applied to the valve disk by the operating medium, typically the liquid propellant, which adds to the stroke motion of the valve opening chamber by a relatively intensified pressure medium activation of the valve closing chamber without a choke and, in this way, a symmetrical switching property of the valve in the opening and closing directions is obtained.
In many cases, especially for the preferred use as a valve for low-temperature liquid fuels, the dynamic seals at the piston-cylinder unit do not offer sufficiently secure separation between the control pressure medium and the operating medium flowing through the valve. In a particularly appropriate embodiment of the invention, the piston-cylinder unit has two individual pistons rigidly connected together and wherein the pistons respectively define with an intermediate wall in the cylinder of the piston-cylinder unit arranged between the pistons, the operating chambers, and on opposite sides of the pistons, permanently vented relief chambers. In this way, a pressureless buffer zone is formed for each of the two operating chambers, which absorbs and discharges any fluid leakages both of the operating medium from the operating chambers and control pressure medium during operation of the valve thereby providing a highly secure, mutual isolation of the two pressure medium systems.
REFERENCES:
patent: 5365828 (1994-11-01), Sperber et al.
patent: 3736750 (1983-05-01), None
patent: 3609765 (1987-09-01), None
patent: 4221230 (1993-07-01), None
patent: 4323846 (1994-11-01), None
patent: 0601794 (1994-06-01), None
Daimler-Chrysler AG
Ladas & Parry
Michalsky Gerald A.
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