Claims
- 1. Apparatus for closing the end of a tube when the pressure in an area surrounding the open end of said tube is lower than the pressure within said tube comprising:
- a. an annular valve seat within the open end of said tube having a central opening therein with an inwardly projecting shoulder,
- b. a shaft mounted coaxially within said tube for reciprocal movement between first and second positions,
- c. valve plate means mounted on said shaft and adapted to mate with said valve seat and close the end of said tube when said shaft is in said second position,
- d. a double-ended piston mounted on said shaft, said double-ended piston comprising first and second flanges radially extending from said shaft and adapted for reciprocal movement within first and second cylinders, respectively, the diameter of said first cylinder being larger than the diameter of said second cylinder, said first flange and said first cylinder defining a control chamber having a maximum volume when said shaft is in said first position and a minimum volume when said shaft is in said second position, said first flange, said first cylinder, said second flange and said second cylinder defining a variable volume relief chamber having a mimimum volume when said shaft is in said first position and a maximum volume when said shaft is in said second position, and the face of said second flange being exposed to the pressure of the fluid within said tube,
- e. relief vent means for maintaining atmospheric pressure within said relief chamber, and
- f. control vent means providing fluid communication between said control chamber and said area surrounding the open end of said tube.
- 2. Apparatus as defined in claim 1 including damping means for controlling the rate of movement of said shaft from said first position to said second position.
- 3. Apparatus as defined in claim 2 wherein said damping means comprises:
- a. a damping piston carried on said shaft and adapted for reciprocal movement within a cylinder having an enclosed end and an open end and defining a damping chamber having a maximum volume when said shaft is in said first position and a minimum volume when said shaft is in said second position,
- b. means providing slideable sealing engagement between the walls of said damping chamber and said damping piston,
- c. a port providing fluid communication between the interior of said tube and said damping chamber, said port positioned to be obstructed by said damping piston after said shaft has moved approximately one-half the distance between said first position and said second position, and
- d. vent means for controllably venting fluid from said damping chamber as said shaft moves from said first position to said second position.
- 4. Apparatus as defined in claim 3 including means for equalizing the pressure within said damping chamber and the interior of said tube as soon as said shaft reaches said second position.
Parent Case Info
This is a division of application Ser. No. 436,567, filed Jan. 25, 1974, now U.S. Pat. No. 3,901,276.
This invention relates to pneumatic launching apparatus. More particularly it relates to pneumatically operated launching apparatus including a pair of separable telescoping tubes having means for closing the open ends of each of the telescoping tubes simultaneously or nearly simultaneously with separation of the tubes.
Telescopically arranged tubes having a slideable seal therebetween and employing a high pressure gas source have long been used as a simple effective launch system. Either the inner tube or the outer tube is attached to or constitutes the launched vehicle and the other tube is rigidly mounted to act as the launcher. A pressurized gas such as air, nitrogen or the like is injected into the inner tube. Expansion of the gas propels the missile until the tubes separate.
It will be apparent that upon separation of the tubes the pressurized gas within both tubes will be vented directly to atmosphere. Obviously, if the pressure in the separating tubes at the point of separation is greater than atmospheric, an acoustic shock will be generated as the pressurized fluid is released. The intensity of noise generated will depend, of course, upon the pressure and volume of gas and the cross-sectional area of the open ends of the tubes.
Pneumatic launch systems of the general configuration described are frequently used to rapidly accelerate bodies in research and development applications to simulate transient conditions so that physical characteristics of the missile during such transient conditions or the interaction of other bodies with the missle during such transient conditions may be observed. A typical application of such pneumatically launched test apparatus is used in the aircraft industry to simulate transient stress on aircraft landing gear caused by impact thereof on a runway or carrier deck. For this purpose the landing gear to be tested is usually mounted in a vertically moveable test rack and a simulated carrier deck moved substantially horizontally through the test rack at aircraft approach and landing speeds. The landing gear is lowered to contact the moving deck, thereby simulating landing of the arcraft on a stationary deck. If desired, of course, the landing gear under test may be moved over a stationary deck in a similar manner.
It will be apparent that to effectively simulate the effect of aircraft landing on a carrier deck, relative speeds up to 130 knots must be attained. Furthermore, since the moving deck must be sufficient to withstand the impact of a landing gear simulating an aircraft of gross weight of up to 60,000 pounds approaching at a speed of up to 130 knots, the simulated deck must be rather substantial and may weigh as much as two tons or more.
Acceleration of such a large mass to such high velocities in reasonably short distances obviously requires a relatively powerful launcher. Typically a launcher of this type may be comprised of one or more pairs of telescoping tubes, the inner tube having an outer diameter of as much as 7.5 inches or more and a length of as much as 22 feet or more. To accelerate two tons of simulated carrier deck to the desired velocity, operating pressures of as high as 2000 psi or greater may be used. It will be apparent that upon separation of the tubes a large pressure differential exists between the interiors of the separating tubes and the surrounding atmosphere and a large volume of gas may be released.
Unless the open ends of the tubes are closed simultaneously with or immediately after separation, the pressurized gas in each tube will be vented directly to atmosphere. Obviously, the sudden release of a large volume of pressurized gas through a large opening causes a sensational acoustic shock. In fact, the shock may be so severe as to be damaging to the human ear as well as endangering other test equipment and structures in the immediate vicinity. Furthermore, the vented gas is lost to the environment and, when the launcher is reassembled for use it must be repressurized. Repressurizing from atmospheric pressure to operating pressure is not only time consuming, but wastes considerable energy and, where gases other than air are used, wastes large volumes of the pressurizing gas.
In accordance with the present invention, apparatus is provided for closing the open ends of both telescoping tubes immediately upon separation thereof to prevent the loss of pressurizing gas and therefore avoid the generation of a severe acoustic shock. The closure devices comprise a mechanically actuated flap valve carried within an enlarged extension of the open end of the outer tube and a pneumatically operated valve carried within the open end of the inner tube. The flap valve for closing the end of the outer tube is actuated by camming plates positioned adjacent the open end of the inner tube to activate the flap valve immediately upon separation of the telescoping tubes. The pneumatically operated valve carried within the inner tube is activated by the pneumatic pressure within the inner tube when the outer tube passes over a control vent releasing gas from a control chamber in the pneumatic valve to atmosphere. Accordingly, the open ends of both tubes are automatically closed immediately upon separation of the telescoping tubes, thereby containing all pressurizing gas within the tubes except for a relatively small amount lost through leakage at the moment of separation.
US Referenced Citations (13)
Divisions (1)
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Number |
Date |
Country |
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436567 |
Jan 1974 |
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Patent Grant
4017055
