Patent Publication Number: US-8117966-B1

Title: Stun grenade

Description:
PRIORITY CLAIM 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/005,600 filed 6 Dec. 2007. 
    
    
     BACKGROUND 
     1. Technical Field 
     The field relates to non-lethal missiles for practice, controlling crowds and subduing individuals, and more particularly to non-pyrotechnic grenade simulators and stun grenades. 
     2. Description of the Art 
     Stun grenades are typically hand thrown missiles which include a small pyrotechnic charge to create a flash of light and noise. A common factor in injuries caused by stun, diversionary and practice grenades used by the military for training and police for subduing suspects and controlling crowds has been the pyro-technic charge. With any pyro-technic device there is always a potential for fire resulting from their use. 
     Non-pyrotechnic grenade type devices are known, including the “Thumper TG6” training grenade sold by Airsoft World Ltd. of the United Kingdom. This device utilizes compressed carbon dioxide to rupture a burst diaphragm to produce a load noise. 
     U.S. Pat. No. 6,767,108 for a Non-Lethal Flash Grenade provides a transparent housing enclosing an array of flash lamps and an ignition circuit for activating a first, centrally located lamp in the array with the remaining array lamps being sympathetically activated in response to flash of the centrally located lamp. 
     SUMMARY 
     Provided is a grenade like device, missile, or stun grenade, for generating a flash followed by a loud, explosive sounding noise. The missile includes a canister housing a compressed gas source. The compressed air source is connected by a conduit to an inflatable bag. A valve in the conduit controls the discharge of gas through the conduit from the compressed gas source to the inflatable bag to first inflate and then rupture the bag. A manually actuated external trigger is installed on the canister for use in activating the valve to discharge gas to the inflatable bag. A flash source is installed on the canister for generating external illumination. The canister has an open end. A cap fitted over the open end houses the inflatable bag situated at the lower end prior to inflation. A control circuit is installed within the canister for illuminating the flash source and for actuating a solenoid controlling the valve. The external handle mounted on the canister triggers operation of the printed circuit board upon release. A safety pin prevents unintended operation of the external handle until removed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Understanding of the following description may be enhanced by reference to the accompanying drawings, wherein: 
         FIG. 1  is perspective view of a stun grenade. 
         FIG. 2  is a side elevation illustrating the safety pin and trigger handle of the stun grenade. 
         FIG. 3  is a cross-sectional view of the stun grenade with the inflatable bag deployed. 
         FIG. 4  is a cross-sectional view of the stun grenade prior to deployment of the inflatable bag. 
         FIG. 5  is a control schematic of the firing circuit for the stun grenade. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings and in particular to  FIGS. 1 and 2 , a stun grenade  10  is illustrated. Stun grenade  10  includes a housing in the form of a hard shell plastic, cylindrical canister  12 , which is sized to be easily grasped in an adult&#39;s hand. Canister  12  is topped by a faceted cap  14 , which protects a flash bulb and which is made of a transparent or translucent material to transmit light. The facets of cap  14  may be sections of a Fresnel lens, which is useful in focusing emitted light into zones of high intensity light. Cap  14  transmits a light burst associated with use of the device. The bottom of the canister is closed by a readily removable soft plastic cap  16 . Cap  16  is blown free of the canister  12  during use of the stun grenade  10  and accordingly is made of soft plastic to minimize the chance of injury to people nearby should the cap strike them. 
     On the exterior surface of the canister  12  are light emitting diode (LED) indicator lights  18  and a timing select switch  20 . Stun grenade  10  operates on compressed gas, and indicator lights  18  may be used to indicate presence of a charged gas cylinder in the canister  12  and whether a pressurization line leading from the gas cylinder to an inflatable bag is charged. Alternatively the status lights  18  may simply indicate that the stun grenade  10  has power and is armed. The use of status lights  18  is optional. The LED indicator lights  18 , if present, operate only when stun grenade  10  is active to save power and may emit red and green light, respectively, to indicate ready to use status and gas cylinder availability. 
     The illustrated stun grenade  10  is intended to emulate a conventional U.S. Military issue hand grenade in handling. Accordingly, a safety pin  28  and a triggering handle  24  are provided installed on the exterior of canister  12 . Handle  24  is pivotally mounted on a fulcrum  26  extending outwardly from the canister  12 . Handle  24  is spring loaded to open outwardly below fulcrum  26  on release of the handle resulting in the internal gas cylinder being pierced to release compressed gas. During storage and prior to use the handle  24  is restrained from opening by a pin  22  fitted through the fulcrum at a point downwardly displaced from the pivot  25  of the fulcrum  26 . Pin  22  is removed from the fulcrum on turning and pulling safety ring  28 . Other configurations of size, shape and triggering sequence for a stun grenade are of course possible. 
     Referring now to  FIG. 3 , the internal components of the stun grenade  10  and its operation are described. Stun grenade  10  works on the principal that a loud, explosive like noise is generated upon an inflated inflatable bag  44  bursting. Inflatable bag  44  is fabricated from like or similar material as used in an automotive inflatable bag, and includes a rupture seam  47  which is designed to part abruptly at a predetermined extension. The sudden opening the inflatable bag  44  at a predetermined degree of stretching of the inflatable bag, or more precisely, tension on the rupture seam, produces an explosive sound. However, unlike automotive applications where a pyrotechnic gas generator is used to achieve rapid deployment, the present invention uses compressed gas to inflate the bag. While inflation rates matching those obtained using pyrotechnic devices are not needed, inflation should be rapid enough to prevent an unprepared witness from deducing the true character of the device. Compressed gas is supplied from a compressed gas cylinder  30  installed within canister  12 . Compressed nitrogen is used due to avoid major changes in available pressure which would result from using common compressed carbon dioxide cylinders when ambient temperature changes can subject the contents of the cylinder to wide pressure variation. It may be possible to use compressed air in many situations, or even carbon dioxide, if ambient conditions are not expected to affect the device. Gas is discharged from cylinder  30  to inflatable bag  44  in two stages along a conduit  46  which connects the cylinder to the inflatable bag. First, a piercing mechanism actuated by opening of handle  24  discharged gas from the cylinder into the conduit. Gas is released from the conduit  46  into the bag upon opening of a valve  42  in the conduit by operation of a solenoid  40 . 
     Upon opening of valve  42  gas is released into inflatable bag  44  which rapidly expands, displacing cap  16  from the bottom of canister  12 . In order to achieve sufficiently rapid deployment of the inflatable bag  44  it is desirable that gas be pressurized in cylinder  30  to the range of 800 to 1000 psi. The flow volume of conduit  46  should be at least 60 cubic feet per minute at the working pressure of the cylinder  30 . The high rate of inflation is desirable in order to give the target individual or crowd little or no time to appreciate the situation upon use of the grenade  10 . 
     The noise is generated not from inflation of the air bag  44 , but upon rupture of the inflatable bag  44  along seam  47  and the consequent explosive release of gas from the inflatable bag. In order to achieve the greatest possible noise an N-wave shockwave of high intensity should be developed. The volume and pressure of inflatable bag  44  at the moment of rupturing determine the peak pressure of the resulting shock wave. The target intensity is 170-175 db at one meter distance from the inflatable bag  44 . In order to achieve this level of sound intensity the inflatable bag  44  is preferably inflated to a volume in the range of 800 to 900 cubic inches at the moment of rupture. Rupture should occur at an internal pressure in inflatable bag  44  at a minimum pressure of about 150 psi, but in any event in a narrow range around the selected target pressure. Fabrication of rupture seam  47  using a thread of known diameter and known tensile strength allows rupture calibration to be made relatively exact. Other pressure targets and volumes may be selected for applications other than for use of the missile as a stun grenade  10 . For example, a missile set up for use as a practice grenade may rupture at a smaller volume and lower pressure. 
     The psychological effect of the stun grenade  10  may be enhanced by providing a flash before the report from the expanding inflatable bag  44  is heard. Accordingly a magnesium based flash bulb  32  is located at the top of cylinder  12 , under the transparent cap  14 . Flash bulb  32  is illuminated just before rupturing of the inflatable bag  44  as described below. 
     Operation of the flash bulb and the solenoid  40  are electronically controlled. A printed circuit board  36  is located within canister  12  to support the circuitry necessary to implement operation of the flash bulb  32 , deployment of the inflatable bag  44  and operation of the LED status lights  18 . Printed circuit board  36  is supplied with power from a button cell  34 . When stun grenade  10  is armed by removal of safety pin  22 , the printed circuit board  36  may report an active status by illuminating an LED status light  18 . Opening of handle  24  provides a signal to the printed circuit board to illuminate flash bulb  32  and to actuate solenoid  40 . These actions occur upon programmed delays of a few seconds, with the illumination of the flash bulb  32  occurring 10-12 milliseconds before rupturing of the inflatable bag  44 . Power to illuminate flash bulb  32  is provided by a wire  50 . The delay between release of the handle  24  and occurrence of the flash and report of the rupturing inflatable bag  44  may be selected using the slide switch  20  which may be connected to a potentiometer to provide a variable strength signal to the printed circuit board  36 . 
     Referring to  FIG. 4 , inflatable bag  44  is illustrated as folded within cap  16  of the stun grenade  10 . Cap  16  fits around the exterior of canister  12 , and is retained in place by friction between the interior of the cap and the exterior of the canister. Inflation of the inflatable bag  44  will push the cap  16  from the end of the canister  12 . 
       FIG. 5  illustrates control arrangements for the device in a schematic fashion. The controls provide for arming, setting timing and triggering the device. In addition, operational readiness can be signaled. Electrical power is supplied to a controller  37  from a battery/coin cell  34  via an on/off switch  61  operation of which arms the device. On/off switch  61  may be operated by removal of pin  22 , or by another, dedicated pole mounted on an outside surface of the canister  12 . Switches  21  and  121 , which are series connected with differentiated resistors, are scanned by controller  37  to determine if the device has been trigger handle  24  and if an intact compressed air cylinder is in place. Switch  21  is closed by operation of the trigger A rheostat  221  is provided which can be adjusted to vary the time delay between activation of the flash bulb  32  and operation of the solenoid  40 , which is used to open a valve to discharge air from a storage cylinder. LED status lights  18  are used to indicate that the device is usable or not. Aural signals may be substituted for LEDs. A charging capacitor (not shown) may be used to operate the flash bulb  32 . 
     The stun grenade has been shown in only a few of its possible configurations. It is not thus limited but is susceptible to various changes and modifications.