Abstract:
The invention is an aerosol search and rescue (SAR) grenade. A smoke signal is produced that is comparable to the smoke signal produced by a pyrotechnic grenade. An aspirating provides a propellant gas/air mixture to a reservoir of smoke material. A container configuration and gravity operated valve provide for a smoke plume only in the upward direction. The smoke grenade is useful in life rafts. It is also useful in inland areas posing a risk of fire.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 61/165,571, filed Apr. 1, 2009, which is incorporated herein by reference. 
    
    
     STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to ammunition and explosives. More particularly, the invention relates to a smoke marker. Most particularly the invention relates to an aerosol dispersing grenade. 
     2. Discussion of the Related Art 
     The invention relates to a military search and rescue (SAR) grenade. Smoke marker grenades are stowed in life rafts for use in rescue at sea. Smoke marker grenades are also used on land to draw attention and to mark a geographical position. 
     Most smoke grenades comprise a hand held body which contains a smoke forming charge, a discharge composition and a primer/bursting charge to activate the discharge composition and generate the smoke. The smoke grenade is set off by igniting the primer, which in turn ignites the smoke charge and the discharge composition. The grenade body functions as a pressure vessel to contain the ignition and initial combustion long enough for the smoke to be generated and then to facilitate discharge of the burning contents as smoke. A disadvantage of the ignition type smoke grenade is the discharge of ignition and combustion products that can cause fires in the surrounding area. This is undesirable on land, in a life raft at sea and in most military and civilian environments. 
     Non-incendiary aerosol smoke dispersing grenades have been developed which overcome the danger of starting fires when producing smoke. These grenades rely on an aerosol can of pressurized propellant gas. The propellant gas is released through a valve and carries a quantity of solid particles or liquid into the atmosphere to create a smoke plume. The size of the smoke plume produced is limited by the amount of propellant gas in the aerosol can. 
     Inventor has discovered that the problems and deficiencies associated with known incendiary and non-incendiary smoke grenades and can be solved or greatly reduced by the use of an aerosol smoke grenade. 
     SUMMARY OF THE INVENTION 
     An aerosol smoke grenade comprises a hand held canister. The canister has a curved side wall. A cross-section of the curved side wall displays a major axis and a minor axis. The major axis is longer than the minor axis. Inside the body are at least one gas cartridge and an actuator for initiating flow of gas from the cartridge to an aspirating nozzle. An aspirating nozzle has at least one air aspiration port and a discharge end. The nozzle discharges to a powder reservoir. The powder reservoir has a discharge conduit which transports gas and powder to two powder discharge ports traversing the side wall. The discharge ports are located on the side wall proximate opposite ends of the minor axis. 
     The hand held grenade is actuated and thrown. The shape of the curved side wall causes the grenade to come to rest in a position such that one smoke discharge port is pointing up and one is pointing down. The discharge port pointing down is stopped. This results in a smoke plume directed upward. The air aspiration nozzle forms a smoke plume of greater size than could be produced by the gas cartridge alone. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is an overhead view of an aerosol smoke grenade. 
         FIG. 1   a  is an end view of the aerosol smoke grenade of  FIG. 1 . 
         FIG. 2  is an overhead cross-sectional view of the aerosol smoke grenade of  FIG. 1 . 
         FIG. 3  is a sectional side view of the aerosol smoke grenade of  FIG. 1  along section  3 - 3 . 
         FIG. 4  is a sectional side view of the aerosol smoke grenade of  FIG. 1  along section  4 - 4 . 
         FIG. 5  is a sectional side view of the aerosol smoke grenade of  FIG. 1  along section  5 - 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is described with reference to the drawing. The drawing discloses a preferred embodiment of the invention and is not intended to limit the generally broad scope of the invention as set forth in the claims. 
     Reference is made to  FIG. 1  and  FIG. 1   a  showing a non-incendiary aerosol smoke grenade. The grenade has dimensions that allow it to be held in the hand and thrown. In this embodiment, the grenade has a length L 1  of 8 inches, a width W 1  of 3.5 inches and a height H 1  of 2 inches. The appearance of the grenade is that of the outer canister or body  10 . The canister has a continuously curved side wall made of plastic. In the end view shown in  FIG. 1   a , the curved side wall is generally oval or elliptical in shape. The curved side wall has a major axis A 1  and a minor axis A 2 . The proportions of the body are critical in that the length of the major axis A 1  is always greater than the length of the minor axis A 2 . Numerically, the major axis is greater in length than the minor axis by a ratio of 4:1 to 1.5:1, typically 2.5:1 to 1.5:1. This, together with the continuously curved side wall assure that the thrown grenade will land and come to rest with one powder discharge port  12  pointing upward and one powder discharge port  14  pointing downward. 
     The powder discharge port  12  is indented from the surface of the side wall by the depth of spray cone  13 , shown in  FIG. 3 . Twist knob  18  provides for manual initiation of the smoke grenade. Bolt  19  attaches twist knob  18  to the grenade. Air aspirating ports  15  are also shown. 
     Reference is made to  FIG. 2 . Bolt  19  attaches twist knob  18  through bayonet block  20  to mounting block  40 . Mounting block  40  has two bayonet sleeves  42 . Each sleeve provides for travel of a bayonet piston  46 . In each sleeve is positioned a bayonet assembly including a bayonet piston  46  attached to a grooved metal bayonet  50 . 
     Twist knob  18  is directly attached to bayonet block  20  and the two are manually rotated 10° to 30° on bolt  19  which is an axis of rotation. Bayonet block  20  includes ramps  25  in contact with bayonet pistons  46 . The left ramp  25  is shown with bayonet piston  46  in front of it. The right ramp  25  is shown in front of the bayonet piston  46 . As bayonet block  20  is rotated, bayonet piston  46  is forced up bayonet sleeve  46  for bayonet  50  to puncture the neck  68  of gas cartridge  70 . Two gas cartridges  70  are shown. There could be one or more than two. The limit is the desire for simplicity of construction and that the grenade be hand held. In this embodiment the gas cartridges have a diameter W 2  of 1.38 inch and a cylindrical body length L 2  of 7.48 inches. The cylinder  70  has an internal volume of 114 cubic centimeters (cc) and contains 86 grams of carbon dioxide gas (CO 2 ). These gas cylinders and bayonets are available commercially from Leland® Gas Technologies, 1611 Canady Road, Wilmington, N.C. 28411. Equivalent cylinders are available in a number of sizes containing carbon dioxide, Freon® or nitrogen. 
     Carbon dioxide gas flows through the neck  72  of cylinder  70  into expansion chamber  52  in mounting block  40  to confront rupture disc  54 . Expansion chamber  52  and rupture disc  54  provide a few seconds delay, e.g. 2 to 3 seconds, in the initial flow of gas before smoke flows out of powder discharge port  12 . 
     Rupture disc  54  breaks under gas pressure, allowing carbon dioxide gas to flow through aspirating nozzle  58 . As seen in  FIG. 5 , tubes  16  provide fluid communication with air aspiration ports  15  traversing outer container  10  and port  56  in aspirating nozzle  58 . The flow of carbon dioxide through aspirating nozzle  58  causes air to be aspirated into the aspirating nozzle  58  by the venturi effect so that the combined gas flow volume is 2 to 6 times the volume of gas flowing out of the cylinder. The gas flows into the entry junction  60  of agitator tube  65 . 
     Agitator tube  65  is positioned in smoke powder reservoir  68 , also shown in  FIG. 4 . The carbon dioxide/air mixture flows through multiple ports  66  into powder reservoir  68  and erodes and entrains powder on the way to discharge conduit  75 . 
     Smoke powder reservoir  68  contains packed powder for smoke or an obscurant. Smoke and obscurant compositions include a variety of metals, carbon and the like materials in the form of finely divided, solid particles. Such materials are used in the form of solid, finely divided powders, particles, flakes and the like collectively referred to herein as powder. Exemplary materials include titanium dioxide (TiDi), white silica powder, aluminum flakes, copper flakes, brass flakes and carbon flakes. Suitable finely divided solid particles or the like smoke forming materials may be prepared by conventional well known techniques. In addition, the powder may include inert powders to improve flow characteristics. The particle size and particle size distribution of the smoke forming materials can vary depending on the material used as well as the method of their preparation, as is known in the art. 
     In the alternative, smoke powder reservoir  68  contains a packed particulate non-lethal lachrymator powder. The particulate lachrymator is a powdered pepper derived substance, for example, oleoresin capsicum or capsaicin. CS (ortho-chlorobenzalmalononitrile) is tear gas powder. The active ingredient is in amount of at least 1% up to about 30%, with the remainder made up of an inert particulate matter or a marking particulate matter such as dye powder. More than one non-lethal irritant substance may be combined to provide a total of about 1% to about 30% or more lachrymator substance in the capsule. 
     Reference is made to  FIG. 2  and  FIG. 3  showing discharge conduit  75 . The end portion of discharge conduit  75  is a race  80  between smoke discharge port  12  and smoke discharge port  14 . Stopper  85  seen here as a ball travels under the influence of gravity in race  80  between smoke discharge port  12  and smoke discharge port  14 . The two smoke discharge ports are proximate opposite ends of the minor axis A 2 . In use, one port is vertically below the other with the lower port blocked by stopper  85  under the influence of gravity. 
     Smoke discharges from the upper port that is not blocked by stopper  12 . The smoke is carried typically by 3 times the gas that would be carried by gas from the cylinder alone. As a result, the smoke plume is larger and potentially higher than it would be with only gas from the cylinder. In addition, no gas is propelled in the downward direction and thereby rendered ineffective. 
     The foregoing discussion discloses and describes embodiments of the invention by way of example. One skilled in the art will readily recognize from this discussion, that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.