US 3863571 A
A fluidic battery activator utilizing the high temperature generated by a resonant tube placed within a supersonic fluidic stream. A projectile has a resonant tube located within it so that ram air will impinge upon the tube from a nozzle in the nose of the projectile causing oscillations which create a high temperature at the closed end of the resonant tube. The heat generated by the tube initiates operation of a battery activation system.
Description (OCR text may contain errors)
1.1mm @tates Patent Campagnu0l0 et a1. Feb. 4, 1975 FLUlDIC BATTERY ACTlVATOR 3,362,332 1/1968 Campagnuolo 102/81 Inventors: Carl J p g Chevy Chase; 3,416,451 12/1968 Hamerla 102/702 Allen B. Holmes, Rockville, both of MCL Przmary Examzner-Verl1n R. Pendegrass Attorney, Agent, or Firm-Nathan Edelberg; Robert P.  Asslgnee: The United States of America as Gibson; Saul Elbaum represented by the Secretary of the Army, Washington, DC.  ABSTRACT  Filed: July 17, 1968 I A fluidic battery activator ut111zmg the high tempera- PP NOJ 7 ture generated by a resonant tube placed within a supersonic fluidic stream. A projectile has a resonant [52 11.s.c1. 102/81, 102/702 R tube leeeted within it SO that ram air will impinge 51 1111. C1. F42c 15/23 P the tube from a nozzle the nose of the Prejee  Field 01 Search 102/702, 81 tile Causing eseilletiehs Whieh Create a high tempera- Y ture at the closed end of the resonant tube. The heat  References Cited generated by the tube initiates operation of a battery UNITED STATES PATENTS actwam System 3,277,825 10/1966 Maillard 102/49] 5 Claims, 3 Drawing Figures I 4 Q4 //l/l I2 PATENTED H975 3,863 571 SHEET 2 OF 2 r m 3 S (\i II 11 Q Q g a I i. --r- E5 n 0 2 O (J Lu 5Q V LLI Z P O D O O o O O O O O O O O O O N to m r m N (do) 1. HHFILVHHdINHJ.
INVENTORS CARL J. CAMPAGNUOLO ALLEN B. HOLMES BY ,W/Vl,
WM am flflc mia ATTORNEYS FLUIDIC BATTERY ACTIVATOR RIGHTS OF GOVERNMENT The invention described herein may be manufactured, used, and licensed by or for the United States Government for governmental purposes without the payment to us of any royalty thereon.
CROSS REFERENCES TO RELATED APPLICATIONS None.
BACKGROUND OF THE INVENTION In missile and projectile fuzes it is important that an electrical source be provided which will operate reliably for short periods of time. This is normally accomplished by activating a battery a short time after the missile or projectile has become airborne. Previous systems have consisted mainly of mechanical or electromechanical devices which have been relatively complicated and often unreliable in their operation.
In activating the battery, a system is required which is of simple design and does not necessitate the use of an internal energy source. This can be easily done by utilizing the ram air stream which is produced by the airborne projectile.
It is therefore an object of this invention to provide a fluidic means for activating a battery.
Another object of this invention is to provide a fluidic battery activator to imitate activation of a battery shortly after the device is placed within a fluidic ram air stream.
Still another object of the invention is to provide a fluidic battery activator which is of simple design and inexpensive.
Still another object of the invention is to provide a fluidic battery activator that is reliable in operation.
SUMMARY OF THE INVENTION A resonant tube closed at one end is axially aligned with the exhaust ofa nozzle placed in the nose ofa projectile. A supersonic flow through the nozzle causes the two to resonate and heats up its closed end which is thermally connected to a primer. After a predetermined temperature is reached the primer ignites, and the gases produced force a firing pin into the battery primer, initiating operation of the battery.
BRIEF DESCRIPTION OF THE DRAWINGS The specific nature of the invention as well as other objects, aspects, uses, and advantages thereof will clearly appear from the following description and from the accompanying drawing, in which:
FIG. 1 illustrates a fluidic battery activator in accordance with my invention.
FIG. 2 illustrates another embodiment of a resonant tube which can be used in the device of FIG. 1.
FIG. 3 is a graph used to explain the operation of the tube in FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT The activator shown in FIG. 1 is placed adjacent a battery mounted in a projectile which is to be launched either as a missile or a weapon type projectile. The projectile 20 has a nozzle 12 mounted in its nose to direct the ram air into the open end of a resonant tube 16 so as to produce internal resonant oscillations. The ram air can escape the inside of the projectile through air bleeds 14 and 15. Next to the closed end 18 of the resonant tube 16 there is a primer element 17 which can be any standard primer element such as the M420 primer. The primer 17 is thermally connected to the end 18 so that its operation will be initiated by heat produced at the closed end 18 of the resonant tube 16. The firing pin 23 will be actuated by primer 17 and will in turn initiate operation of the battery primer charge 25. Initiation of primer 25 will activate the battery 10 through the use of any of the well known systems.
In 1954, Dr. Sprenger in MITTEILUNGEN AUS DEN INSTITUT FUR AERODYNAMIK Vol. 2 1, pages 18 through 34, (A E R E LIBRARY TRANSLA- TION 687) disclosed that a resonant cavity, closed at one end, will become heated at the closed end when it is stimulated into oscillation by means of a free fluid flow. The resonant cavity becomes heated at its base or closed end because of the lack of flow at the base resulting from successive compression cycles associated with the frequency of the device.
Shadow-graph studies of resonant tubes indicate that shock waves exist within the tube which are generated by a normal shock in a state of instability oscillating between the mouth of the tube and the nozzle exit. When the normal shock is close to the nozzle exit, a compression wave travels down the tube which becomes steeper due to friction within the walls of the tube. The shock impinges at the closed end and is reflected. Upon exiting from the tube, it causes a lower pressure at the entrance. At this time, the normal shock moves across the region of instability and causes an expansion wave to be drawn into the tube. After reflection, the expansion wave arrives at the mouth of the tube and causes the normal shock to move back toward the nozzle. Thus, a new compression wave is generated and the cycle repeats.
The heating of the fluid is attributed to the friction within the tube and to a non-isentropic compression of the fluid across the shock wave. While a theoretical determination of the temperature in the tube is greatly complicated by the complex wave distribution, it suffices to say that extremely small tubes in the order of 0.2 inches in diameter can be used to produce extremely high temperatures in the range of 600 to l,O00 F., and these temperatures are sufficient to ig nite the primer used in the device of FIG. I. It should also be noted that the temperatures mentioned are generated in fractions of seconds from the time the fluid jet impinges upon the resonant tube.
During the operation of the device in FIG. 1 ram air will enter nozzle 12 in the nose cone of the projectile 20 and flow supersonically past the resonance tube 16 and out through the bleed holes 14 and IS. The supersonic flow sets the tube 16 into resonance, thus heating the tube at its closed end 18 due to the compression waves discussed above. The tube is insulated and the temperature within rises rapidly. Within approximately one-half a second, the primer l7 placed within the tube 16 ignites and hot gases force the firing pin 23 down into the battery primer 25 initiating it and activating the battery 10. If the primer 25 within the battery 10 were heat insulated, the battery 10 could be placed directly behind the tube 16 so as to eliminate the use of a primer l7 and firing pin 23.
The resonant tube 30 shown in FIG. 2 has been found to produce even better results than the resonant tube 16 used in the embodiment of FIG. 1. The tube consists ofa casing 32 with an open end 31 and a closed end 37. The tube is modified by placing a restrictor 34 within the resonant cavity. The function of the restrictor 34 is to trap some of the hot gas which would have been carried away from the closed end by the expansion wave. The position of the restrictor 34 within the tube 30 is very important and proper placement of the restrictor 34 will maximize the temperatures which can be obtained at the closed end 37.
The graph in FIG. 3 is a plot of the temperature at the closed end 37 of the resonant tube versus time for different values of L/l ratios where L is the length of the whole resonant cavity and l is the distance between the restrictor 34 and the closed end 37 of the tube 30. From the From the graph it can be seen that maximum temperature is produced at the closed end 37 when the L/l ratio equals 8. Without the restrictor 34 it is seen that where L/l is equal to infinity, at approximately 4 seconds, the temperature at the restrictor end would be about 450. Using the restrictor at maxim um placement with a ratio equal to 8 it can be seen from the graph that the temperature would be in excess of 600 F. after the same period of time. Experimentally, it is apparent that by using restrictor 34 the maximum temperature to be obtained at the closed end 37 of the resonant tube 30 is approximately 40 percent greater than would be obtained without the use of a restrictor. The use of this tube in the embodiment of FIG. 1 would assure sufficient temperatures to initiate operation of the primer charges.
The thermal properties of a resonant tube are ideal for many other applications. The simplicity, low cost, ruggedness, and small size of the resonant tube, make it a valuable asset to missile and projectile fuzing design.
While the fluidic battery activator device of my invention has been described in the context of this application in ordnance projectiles and missiles, it will be apparent to those skilled in the art that a wide variety of other uses are possible.
It will be further apparent that the embodiments shown are only exemplary and that various modifications can be made in construction and arrangement within the scope of the invention as defined in the appended claims.
We claim as our invention:
1. Apparatus for activating a battery in response to a fluid flow, comprising:
a. a resonant tube having an open end and a closed end;
b. a nozzle for directing said fluid flow onto said open end of said resonant tube to produce fluid compression waves therein; and
c. means responsive to heat produced at said closed end of said resonant tube by said fluid compression waves for initiating the activation of said battery.
2. The invention according to claim 1 wherein said resonant tube includes a restrictor located on the inner wall of said resonant tube for retaining within said resonant tube a portion of the heat produced at said closed end, said restrictor having an inner diameter that is smaller than the inner diameter of said resonant tube.
3. The invention according to claim 2 wherein said restrictor is placed in said resonant tube so that the ratio of the total length of the tube to the distance the restrictor is placed from the closed end of the tube is equal to 8.
4. The invention according to claim 3 wherein said battery activating means includes a first explosive primer whose operation is initiated by the heat generated at the closed end of the resonant tube.
5. The invention according to claim 4 wherein said battery activating means further includes a firing pin set in motion by the operation of said first explosive primer, said firing pin causing a second explosive primer to explode which is adapted to cause the battery to activate.