Abstract:
A grenade device produces a delayed bang upon coupling to a pressurized canister containing gas. The device includes an annular housing, an awl, a sleeve, a diaphragm, a base and a cap. The housing has first and second axial ends and an internal bulkhead disposed therebetween with a choke flow-through orifice. The awl extends axially outward from the bulkhead. The sleeve connects to the housing at the first axial end. The diaphragm is disposed between the sleeve and the housing to form an annular chamber. The cap inserts into the housing at the second axial end and receives the canister facing the awl. The base connects to the housing at the second axial end. When the canister is compressed towards the device the awl punctures the canister to release the gas, which flows through the choke orifice to pressurize the chamber, and the diaphragm ruptures upon exceeding a pressure threshold.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described was made in the performance of official duties by one or more employees of the Department of the Navy, and thus, the invention herein may be manufactured, used or licensed by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 
    
    
     BACKGROUND 
     The invention relates generally to devices that produce a loud but delayed sudden noise, such as a bang. In particular, the invention relates to a device, such as a grenade, that rapidly expands a compressed gas to produce a high-amplitude acoustic signal after a controllable interval from its activation event. 
     SUMMARY 
     Conventional flash-bang grenades yield disadvantages addressed by various exemplary embodiments of the present invention, such as controlled delay and specific noise level. Moreover, such devices are not modular, such that the components cannot be reused and reassembled. 
     In particular, various embodiments provide a modular grenade device to produce a delayed bang upon coupling to a pressurized canister that contains gas. The device includes an annular housing, a puncture awl, a sleeve, a diaphragm, a base and a cap. The housing has first and second axial ends and an internal bulkhead disposed therebetween. The bulkhead has a choke flow-through orifice. The awl extends axially outward from the bulkhead at the second axial end. 
     In various embodiments, the sleeve removably connects to the housing at the first axial end. The diaphragm is disposed between the sleeve and the housing to form an annular chamber between the diaphragm and the bulkhead. The cap inserts into the housing at the second axial end. The cap receives the canister so as to face the awl. The base removably connects to the housing at the second axial end. In response to axial compression of the canister towards the device: the awl punctures the canister to release the gas, the gas flows through the choke orifice to pressurize the chamber, and the diaphragm ruptures upon exceeding a pressure threshold in the chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and various other features and aspects of various exemplary embodiments will be readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, in which like or similar numbers are used throughout, and in which: 
         FIGS. 1A and 1B  are exploded isometric views of components for a delayed bang projectile (DBP) device; 
         FIG. 2  is an isometric cross-section view of a DBP subassembly; and 
         FIGS. 3A and 3B  are isometric assembly and cross-section views of the DBP device. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized, and logical, mechanical, and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
     Various exemplary embodiments provide a delayed bang projectile (DBP) device as a grenade equipped with a controllable time interval between an activation event and the resulting action, i.e., rapid expansion. The DBP device has been developed as a non-lethal payload for an existing grenade launcher projectile. The DBP device has been designed to be safe during loading and handling, and activates due to either the setback forces imposed on the system after firing, or the force due to impact with the target. As is the case with most noise-making devices, the DBP device has been designed so as to have a time delay before making the noise, so that it can be positioned some distance from the operator after initial activation. 
       FIGS. 1A and 1B  show exploded isometric views  100  of delayed bang projectile (DBP) device disposed along a longitudinal axis. The components include an upper hexagonal sleeve  110 , a circular diaphragm disk  115 , an annular housing  120 , a flange pin  130 , a rubber gasket  140 , a canister cap  150 , an o-ring  155 , a lower hexagonal mount base  160 , and a pressurized carbon dioxide canister  170 , also called a cartridge or bottle. 
     The housing  120  has proximate and distal ends along the axis, with the sleeve  110  attaching by screw-threaded interfaces to the proximate end, and the base  160  attaching by screw-threaded interfaces to the distal end. Leland 8-gram carbon dioxide (CO 2 ) cartridges are commonly used in paint-guns to propel marker balls and in pellet pistols to fire BB-pellets, as well as to provide carbonation for soda water, although other manufacturers also supply such cartridges. Each “sparklet” cartridge has a length of 2.56 inches and a diameter of Ø0.71 inch, weighs about 0.86 oz (24.5 g) and can maintain a pressure of 850 psi for storing compressed CO 2 . These are preferably suitable to serve as the canister  170  to provide pressurized gas to activate the DPB device. Alternatively, custom-filled cartridges that store compressed helium (He) or nitrogen (N 2 ) can be employed for such purposes without departing from the scope of the claims. 
       FIG. 2  shows an isometric cross-sectional view  200  of the DBP sub-assembly  210 . The upper sleeve  110  within the housing  120 . The diaphragm disk  115  is disposed between sleeve  110  and an upper annular ledge  220  on the housing  120 . The gasket  140  is disposed between a cylindrical bulkhead  230  and the cap  150  within the housing  120 . The canister  170  attaches at its muzzle to the DBP subassembly  210  facing a lower ledge  240  of the cap  150  that surrounds the o-ring  155 . The pin  130  is secured at its proximal end through the bulkhead  230  includes a puncture point or awl at its distal end to release the pressurized CO 2  gas from the canister  170 . Preferably the pin  130  serves as an awl or punch for puncturing the canister  170  at its top near the neck. The pin  130  screws into the bulkhead  230  to facilitate replacement during testing. The canister  170  is cushioned from the cap  150  by the o-ring  155 . 
     A recess orifice  250  (divided into larger and smaller diameter segments) traverses through the bulkhead  230  adjacent the pin  130 . The recess orifice  250  provides a constraint for choked gaseous flow, being limited to sonic velocity. The diaphragm disk  115  includes cruciform indentations or grooves  260  to weaken its structure along these rupture fault lines. A chamber  270  resides between the diaphragm disk  115  and the bulkhead  230 . After the pin  130  punctures the canister  170 , the chamber  270  fills with CO 2  gas, the pressure rise rate within being attenuated by the recess orifice  250  until the diaphragm disk  115  ruptures along the grooves  260 . Along its circumferential edge, the diaphragm disk  115  includes a protrusion between the sleeve  110  and the housing  120 , indicated within the oval region  280 . This protrusion serves for assembly alignment and leakage mitigation. 
     For exemplary embodiments, most of the components, such as sleeve  110 , housing  120 , cap  150  and base  160  are made of stainless steel 304. The pin  130  comprises mirraloy or steel. Exceptions to this include diaphragm disk  115 , gasket  140  and o-ring  155 . Exemplary diaphragm disks  115  comprise either Mylar or aluminum depending on performance objectives. The gasket  140  and o-ring  155  are made of rubber. 
       FIGS. 3A and 3B  show isometric views  300  of the DBP subassembly  210  installed with the canister  170  as a DBP device  310 .  FIG. 3A  shows an assembly view of the assembly  310 .  FIG. 3B  shows a cross-section view of the DBP device  310 . The canister  170  inserts into the cap  150 , preferably via threaded interfaces, and can translate axially fore and aft, as the gasket  140  and the o-ring  155  can be elastically compressed along that direction enabling the cap  150  to press towards the bulkhead  230  and thereby the canister  170  into the pin  130 . The gasket  140  above the cap  150  is optional depending on the application, but preferably aids in shock mitigation at impact after firing the DBP device  310  from a gun. 
     An exemplary design of the DBP device  310  includes the following dimensions. The housing  120  preferably has an axial length of 1.05 inches and an outer diameter of Ø0.725 inch. The sleeve  110  and the base  160  have threaded interface diameters of Ø0.6875-24UNF-2A (to connect with the housing  120 ) with ⅝ inch hex rim, respective inner diameters of Ø0.450 inch and Ø0.375 inch and respective axial lengths of 0.315 inch and 0.385 inch respectively. The cap  150  has an outer diameter of Ø0.560 inch with a chamfer (of 0.055 inch chord depth), an inner threaded recess diameter of Ø0.375-24UNF-2B, a through-hole diameter of Ø0.150 inch, and a length of 0.440 inch. 
     Exemplary diaphragm disks  115  have thicknesses of alternatively 0.012 and 0.014 inch. In the examples tested, the diaphragm disk  115  includes cruciform indentations or grooves  260  milled into the material at approximately 0.004 inch. The resulting etched thickness of about 0.009 inch, coupled with the pressure from the canister  170  and the blow-down rate through the recess orifice  250 , directly affects the time delay interval and sound intensity of the DBP device  310 . For the configuration shown, the diaphragm  115  fails along the grooves  260  at less than the 850 psi deliverable by the canister  170 , depending on the desired sound intensity and time delay. Field and lab testing produced time delays up to 2 minutes upon initiation, and sound intensities of 147 dB. 
     Control of both the time delay and the sound intensity are functions of the storage pressure of the canister  170 , the diameter of the recess orifice  250 , material of the diaphragm disk  115 , and the diaphragm score depth along the grooves  260 . The recess orifice preferably has a diameter of Ø50-micron (about 0.002 inch) for the smaller portion, or a choke-flow area of 3×10 −6  square inch. An alternative diameter is Ø0.0156 inch. Assuming substantially constant storage pressure of the canister  170 , the recess orifice  250  controls the blow-down into the chamber  270  just below the diaphragm disk  115 . With this flowrate established, the optimal manner to control time delay and sound intensity involves tailoring a diaphragm disk  115  to rupture at a given pressure. 
     Various exemplary embodiments provide a loud blast or bang type noise to be produced at a given time after impact. The DBP subassembly  210  includes a rupture diaphragm or burst disk  115  and a pressurized container, such as a typical commercial off-the-shelf (COTS) CO 2  8-gram canister  170 . The delay time and amplitude of the sound created by the DBP device  310  can be tailored by selecting the appropriate diaphragm disk  115  and container pressure. Due to the compact size of the complete assembly, the DBP device  310  can be installed in any number of housings, ranging from hand-throw type devices to munitions fired from a weapon. 
     The DBP device  310  is assembled as shown in exploded view  100 . The instructions below describe a process by which to assemble and therefore use the DBP device  310 :
         1. Install the flange pin  130  into the annular housing  120  and tighten.   2. Install the rubber gasket  140  on the annular housing  120 .   3. Install the canister cap  150  on the gasket  140  in the housing  120 .   4. Install an o-ring  155  in the canister cap  150 .   5. Install the lower hexagonal base  160  on the annular housing  120  and tighten along the screw threads.   6. Install the diaphragm disk  115  on the annular housing  120 .   7. Install the upper hexagonal sleeve  110  on the diaphragm disk  115  and tighten along the internal screw threads.       

     Upon assembly of the DBP device  310 , the diaphragm disk  115  is captured between the annular housing  120  and upper hexagonal sleeve  110 . These pieces include a groove and matching protrusion, shown in region  280 , thereby preventing leakage around edges of the diaphragm disk  115  when under pressure and also prevent the diaphragm disk  115  from being pushed out prior to rupture. The pressurized canister  170  is threaded into the canister cap  150 , ensuring the o-ring  155  is properly disposed to prevent pressure leakage. 
     Upon impact at either end of the DBP device  310 , the assembled canister cap  150  and canister  170  translate to impinge against the flange pin  130 , thereby puncturing the canister  170 . Then, CO 2  gas escapes the canister  170  and forces through a very small hole in the recess orifice  250  in the bulkhead  230  of the annular housing  120  disposed below the diaphragm disk  115 . This hole controls the flowrate of the gas and can be sized depending upon its choke-flow diameter and pressure in the canister  170 . The chamber  270  pressurizes, and subsequently ruptures the diaphragm disk  115  along the grooves  260 . 
     The DBP device  310  can be tailored to a number of applications depending on the desired sound level and delay. Due to its compact size, the DBP device  310  can be packaged for a wide range of applications, alternatively scaled using substantially congruent components. Crowd control, training, and a range of war fighting applications can benefit from this technology, having been developed for a Department of Defense (DoD) program as a non-lethal capability. The DBP device  310  has demonstrated effectiveness during range testing and is being promoted to outside vendors. Due to its simplicity and range of application, the DBP device  310  can be easily tailored to a wide range of projectile platforms. 
     Components of the DBP device  310  are reusable after disassembly, with the exception of the diaphragm disk  115  (after rupture) and the canister  170 , being scalable to increased or decreased sizes. The DBP  310  device can be packaged in a wide range of applications, constitutes a simple, safe mechanical assembly, and can be sized to function in different configurations, such as a multi bang hand throw grenade. The DBP device  310  can be coupled with other technologies, such as mal-odorants placed in the pressurized container, or iron-sulphide powder, which flash brightly when in contact with air (flash-bang device). 
     While certain features of the embodiments of the invention have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments.