Abstract:
A portable containment chamber for disposing of explosive threat devices comprises a cylindrical chamber body with a hinged interiorly convex outward-opening access door. The door closes against a tapered seat whereby explosion pressure enhances a gas-tight seal. In closed position the door is locked by interconnected expandable locking shoes which engage an annular locking channel in the mouth of the chamber with a simultaneous crank-and-piston linkage. The door is actuated by a pneumatic mechanism which first traverses laterally it into alignment with the chamber, then traverses it axially into sealing engagement with the chamber mouth, and then moves the expandable locking shoes into locked position. A first interlock prevents axial door movement when in standby position, and a second interlock inhibits detonation of a donor explosive charge within the chamber if the door locking shoes are not fully locked.

Description:
FIELD OF THE INVENTION 
     This invention relates to the containment of and safe disposal, including by controlled detonation, of explosive threat objects. Such objects may include improvised explosive devices (IEDs), suicide vests, pipe bombs, and suspicious packages of all kinds which may be discovered through various means including, but not limited to, x-ray imaging, trace explosives analysis, canine indications, or other explosives detection methodologies. 
     BACKGROUND OF THE INVENTION 
     An explosive threat device, once identified as either real or suspected, must be disposed of safely. At present this is commonly done by trained “bomb squad” explosives technicians who are required to dismantle the device and disable its operating components at great risk to themselves and their surroundings. 
     In addition, the level of equipment and technology available to bomb-makers, whether mentally disturbed persons or actual terrorists, is steadily advancing. In addition to the simple black-powder-and-fuse bombs of the past, bomb technicians must now deal with an increasing variety of explosives, whether commercial such as TNT, dynamite, and pentaerythritol tetranitrate (PETN), or homemade such as triacetone tri peroxide (TATP). These explosives are triggered by an equally expanding variety of initiation mechanisms ranging from simple time fuses to digital watches and cell phones wired to conventional blasting caps with ordinary nine volt batteries. Further, in every case the technician must confront the possibility that in a given threat device there may be more than one trigger mechanism, one of which might be designed to explode upon the mere opening or disassembling of the device. 
     For these reasons it has been recognized that the most direct and safe way to neutralize a suspected explosive threat device is to destroy it in a controlled explosion. In the past this has been done by transporting the threat to a remote area such as a gravel pit and detonating it there. This has the obvious disadvantages of requiring the threat object to be transported over public roads, and the resulting explosion generally creates a great deal of noise, smoke and flying debris. 
     A more sophisticated approach to the problem is to destroy the threat by exploding it within a sealed blast chamber using a small remotely detonated donor or booster explosive charge. If the threat device is small enough in terms of estimated weight of explosive, the chamber can be small enough to be carried to the site of the threat on a truck bed or wheeled carriage, which eliminates much of the danger of transporting the object from a public facility and over public roads to a remote location. This approach has been taught by Ohlson, US 2008/0314903 (published Dec. 25, 2008); King, U.S. Pat. No. 7,506,568 (Mar. 24, 2009); and King, U.S. Pat. No. 775,910 (Aug. 3, 2010). Larger, but non-portable, chambers are disclosed by Ohlsson, U.S. Pat. No. 4,478,350 (Oct. 23, 1984); Ohlsson, U.S. Pat. No. 4,632,041 (Dec. 30, 1986); Donovan, U.S. Pat. No. 6,354,181 (Mar. 12, 2002); and Ohlsson US 2990/0044693 (published Feb. 19, 2009). 
     A principal disadvantage of these prior art devices is that they are necessarily large and bulky because they rely for blast containment on a large internal chamber volume enclosed by a relatively thin spherical chamber body, often of aluminum. While providing greater physical volume can better contain and suppress a controlled detonation, it also requires a larger chamber opening. Such a large opening, while facilitating the loading of a threat device, necessarily results in a greatly increased door surface area. Thus the total separation force from a given internal explosion pressure are equally increased. When combined with relatively weak construction materials and unreliable door-sealing mechanisms, these prior art devices can become unreliable or even dangerous from a safety standpoint. Because of the stresses and deformation that necessarily accompany a detonation of any size (10 lb or TNT or more), certain of these aluminum-body spherical chambers are believed to be one-shot tools at best. 
     It is therefore a principal object of the invention to provide an improved portable blast-attenuating chamber which is strong, compact, repeatedly usable, and easily transported to the location of a suspected threat device where it can be quickly employed, preferably under remote control, to neutralize the threat either on the spot, or in a nearby safe location. 
     A further object is to provide a compact self-propelled blast-attenuating chamber capable of being moved quickly in and through the halls and doorways of public buildings, train stations and airports to the location of a suspected threat, and thereafter to a safe nearby area where the threat may be neutralized quickly and without undue danger to personnel or building structure. 
     Another object is to provide such a chamber with a closure door which is outward-opening for ease of inserting a threat object, and which can be positively locked to the chamber body with moveable locking shoes covering at least 270 degrees of door circumference. A related object is to provide such a door which extends convexly into the body of the chamber, such that it becomes self-tightening with increasing explosion pressures. 
     Yet another object is to provide a chamber and door in which all the elements of the locking mechanism are interconnected such that each element is mechanically constrained to lock simultaneously with the others, which together with an inhibition signal blocking means, prevents the initiation of detonation of a threat device unless the door is in a fully sealed and locked condition. 
     A more detailed object is to provide such a chamber and door in which the door is attached to the chamber body in a manner which permits opening and closing in a two-stage operation, with the door being swung into axial alignment with the chamber body in a first stage, and then traversed axially into engagement with the chamber opening in a second stage, whereupon the locking mechanism can be engaged. A related object is to provide self-contained pneumatic operating means for each stage of door operation such that the door must be correctly axially aligned with the chamber prior to insertion, and in which the locking mechanism cannot be actuated until full insertion is achieved. 
     SUMMARY OF THE INVENTION 
     The invention comprises a portable explosion containment chamber for safely disposing of suspected threat devices comprising a hollow chamber body and cylindrical chamber door preferably made of explosion-resistant impact-hardening manganese steel alloy, although other castable high-strength metals can also be used. The chamber door fits into an opening having an inwardly tapered, preferably stepwise, sealing surface. 
     The door itself has a convex surface facing the interior of the chamber, whereby internal pressures tend to expand the door into enhanced gas-tight sealing engagement. The mouth of the chamber, at the outside edge of the door, has an annular locking channel into which a plurality of expandable interconnected locking shoes are employed to lock the door in closed position. The locking shoes are commonly driven by a crank-and-piston linkage such that all the locking shoes must move in unison, thereby eliminating the chance that one shoe might be out of position after the door is closed and locked. 
     The invention employs remotely operated pneumatic door opening and closing mechanisms which operates in three stages. From a closed and locked position, the mechanism first retracts the locking shoes, freeing the door for axial movement. Next, the mechanism withdraws the unlocked door axially until it is free of the chamber mouth. At this point the door is free to be rotated over to one side, thereby providing clear access to the interior of the chamber. In closing and locking, the sequence of movements is reversed. 
     Preferably, pneumatic power means is utilized in each of the above steps, although hydraulic means or even hand operation may be employed to equal advantage. Pneumatic cylinders are employed to selectively move the locking shoes in and out of locking engagement with the internal annular locking channel in the mouth of the chamber, to translate the door axially in and out sealing engagement with the chamber body, and to move the disengaged door rotationally away from the chamber door opening to provide access for inserting a threat device, or removing the debris from an earlier controlled detonation. 
     For safety purposes, a first interlock means is provided to prevent axial opening and closing movement of the chamber door when in a standby position rotated away from the chamber mouth. A second interlock means prevents actuation of the locking shoes until the door is fully seated in the mouth of the chamber. A third interlock means inhibits detonation of a donor explosive charge within the chamber if all of the door locking shoes are not in fully locked position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective of the improved portable explosion containment chamber of the present invention, with the chamber door in standby position rotated away from the chamber central axis; 
         FIG. 2  is a partial perspective of the chamber door and hinge mechanism, illustrating the axial translation means for moving the door in and out of engagement with the chamber mouth; 
         FIG. 3  is an exploded partial perspective of the pneumatically-operated door locking shoe actuation system of the invention; 
         FIG. 4  is a sectional plan view of the chamber showing the door in open position; 
         FIG. 5  is a detail of the sectional plan view of  FIG. 4  showing the door in closed position; 
         FIG. 6  is a schematic elevation view of the pneumatically-operated door locking shoe actuation system of  FIG. 3  showing the locking shoes in a retracted (door openable) position from their corresponding locking channel in the chamber body; 
         FIG. 6A  is a sectional partial side elevation of the door locking system of  FIGS. 3 and 6  showing the locking shoes in retracted position; 
         FIG. 7  is a sectional partial side elevation similar to  FIG. 6  showing the mechanical interconnection of the individual locking shoe connecting rods with the central locking crank, and pneumatic power means for simultaneous engagement of the locking shoes. The locking shoes are shown in extended (locking) position engaged with a corresponding circumferential locking channel in the chamber body; 
         FIG. 7A  is a sectional partial side elevation of the door locking system of  FIGS. 3 and 7 , again showing the locking shoes in engaged position; and 
         FIG. 8  is a schematic diagram showing a first interlock means for preventing axial opening and closing movement of the chamber door when in standby position rotated away from the chamber mouth, a second interlock means for preventing the actuation of the locking shoes until the door is fully seated against the chamber opening, and a third interlock means for inhibiting detonation of a donor explosive charge within the chamber if the door locking shoes are not in fully locked position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning to the drawings,  FIG. 1  illustrates in perspective view the improved portable explosion containment chamber assembly  10  of the present invention. In the preferred embodiment, the chamber body  11  is a unitary hollow casting, preferably of impact-hardening manganese alloy steel alloy, with cast-in external stiffening ribs  12 . The advantage of manganese alloy steel is that its surface becomes harder and stronger with the impact of each detonation. In the illustrated embodiment the ribs  12  are circumferential, but they may also be arranged in a cross-hatched or waffle pattern for additional strength. 
     The chamber assembly  10  is mounted on a self-powered transporter  13  propelled, or by a self-powered transporter (not shown) which can be connected to the dolly with an articulated hitch, making it easily steerable. The transporter  13  may be propelled by any suitable means, such as electric batteries or a small gasoline engine and has manual controls operated from a position safely opposite the opening end of the chamber. The explosion products from the detonation may be vented through a baffled vent  39  either immediately, or after cooling and testing to determine that they do not present a fire or environmental hazard. 
     According to the invention, the chamber, dolly and transporter are sufficiently compact such that the entire assembly has a width, length and weight which will allow the device to be transported in freight elevators, through corridors, and through doorways throughout the device&#39;s intended operating environment. Optimally, the device has a width under 36 inches, a maximum length of six feet, and a weight of under 5000 lbs for full operational mobility within airports and other public buildings. Similarly, the wheels of the dolly  13  and transporter  15  are desirably fitted with narrow pneumatic rubber tires of 15 inches diameter or greater to allow relatively easy movement over door sills and the like. 
     As best shown in  FIGS. 1 and 2 , the chamber body  11  is closed by a door assembly  16  suspended by a side-mounted hinge  17 , which permits the relatively heavy door assembly to easily swing on a horizontal plane in and out of axial alignment with the chamber. The door itself, like the chamber body, is preferably of impact-hardening cast manganese steel. 
     As a feature of the invention, the door assembly  16  is suspended from the hinge  17  in a manner so as to allowing it to be inserted and withdrawn from the chamber mouth  18  in two sequential movements. In fully open position (FIGS.  1 , 4 ) the door assembly  16  is positioned away from the chamber access and to one side, allowing direct access to the chamber mouth  18  for insertion of a threat device (not shown), while in fully closed position ( FIG. 5 ) the door assembly is axially aligned with the centerline of the chamber  11  for ease of insertion and withdrawal. 
     The sequence of operation is as follows. Starting with the door in standby position, fully open and rotated away from the chamber central axis ( FIGS. 1 and 4 ), a threat device and detonation initiator  40  are placed within the chamber  11  by suitable means, such as a remotely operated robot carrier or bomb squad personnel wearing protective gear. In practice, a small electrically operated explosive charge (not shown) is attached to the threat device, having an initiator capable of triggered remotely by any suitable means, such as radio control or an electrical feed-through terminal  39  in the chamber wall. 
     To position the threat device and initiator the chamber body  11  may be provided, for example, with a string mesh hammock (not shown). If desired, plastic bags of water (not shown) may also be placed into the chamber with the threat device and initiator to help attenuate the explosive energy, in the way taught by Donovan Re. 36,912. In practice, the mass of explosive (in TNT equivalent) is preferably matched by an equal mass of water suspended within the chamber for optimum attenuation effect. The bottom of the chamber may also be lined with a layer of granular shock absorbing material such as pea gravel or the like (not shown), as taught by Donovan Re. 36,912 and Donovan U.S. Pat. No. 6,354,181. 
     With the threat device and initiator properly placed within the chamber body  11 , the door assembly  16  is closed in two discrete steps. In the first step, the door is swung about its hinge  17  in a horizontal plane into alignment with the central axis of the chamber  10  ( FIGS. 2 and 5 ). This may be accomplished by hand, or preferably by a first remotely actuated pneumatic closing means  19 . 
     When the door assembly  16  is correctly aligned with the chamber central axis, in the second step it is translated axially into the chamber mouth  18  by a second remotely actuated closing means  20 . The door assembly  16  is supported and guided for in-and-out axial movement by three guide pins or rods  21  (“Thomson rods”) carried in spaced parallel array by the hinge plate  22 , along with the second pneumatic door actuating means  20  ( FIGS. 4-5 ). 
     As is best shown in the exploded view of  FIG. 3  and sectional elevations of  FIGS. 5-7A , the door assembly  16  comprises three major components. The first component is the door  23 , again preferably a manganese steel casting, which projects convexly into the chamber body  11  ( FIGS. 4-5 ). The door  23  is machined to fit snugly into a corresponding step-tapered seat  24  within the chamber mouth  18 . 
     The second component group comprises three movable locking shoes  25  which are constrained at their edges by hold-down wedges and retainers  26  for radial in-and-out movement, whereby each shoe may slide outward to engage a corresponding annular locking channel  27  machined into the inner surface of the chamber mouth  18  ( FIGS. 4-5 ). The illustrated embodiment has three locking shoes  25 , each of which engages the locking channel  27  over an arc of at least 90 degrees, for a combined arc of circumferential engagement of at least 270 degrees. The invention is not confined to the use of three shoes, and four or more may also be utilized, with corresponding smaller individual arcs of engagement. 
     The third component group is a crank-and-piston linkage  28  ( FIGS. 3 ,  6  and  7 ) comprising a crank element  29  pivoted to a central boss  30 . The crank element connects to each of the axially slidable locking shoes  25  by over-center link elements  31 , much like the crank-and-piston arrangement of an automobile engine. 
     To lock the door assembly  16  into explosion-resistant contact with the tapered seat  24 , the crank element  29  is rotated by a third remotely actuated pneumatic means  32  ( FIGS. 2 ,  6 - 7 ) which simultaneously drives each of the locking shoes  25  into over-center locking engagement with the annular locking groove  27 . Once in locked position, and like an automobile engine crankshaft, connecting rod and piston at TDC (Top Dead Center), the locking shoes  25  are incapable of disengagement unless and until the crank  29  is rotated past TDC, thereby rotating the links  31  away from direct alignment with the crank central axis. 
     As another feature of the invention, the corresponding mating edges of the locking shoes  25  and locking groove  27  are beveled to cooperate in a wedging action when the shoes are simultaneously fully engaged, whereby the door  23  is locks and sealed firmly against its tapered seat  24 . 
     Because the door  23  projects convexly into the chamber  10 , and as an additional feature of the invention, the pressure wave from a detonation within the chamber body  11  tends to flatten and broaden the convex casting, further increasing the pressure holding the door  23  against the seat  24  and further enhancing the seal. The invention is not confined to the use of a convex door, however, and a properly designed flat door may also be employed. If desired, to accommodate minor dimensional misalignments, either the door  23  or seat  24  may also be provided with a circumferential heat-resistant silicone o-ring or a labyrinth seal (not shown). 
     As a further feature of the invention, and as best shown in  FIG. 8 , first and second interlock means are provided to prevent mechanical interference of the door assembly  16  with the chamber mouth  18  during opening and closing the chamber, and also to inhibit the electrical triggering of an initiating charge within the chamber unless all of the locking shoes are in a simultaneously fully locked position. 
     To assure that the door assembly  16  is properly aligned with the central axis of the chamber  10  for axial in-and-out movement, a first position sensor  33 , such as a microswitch, optical position sensor or the like ( FIG. 8 ) is provided to indicate the relative position of the hinge body  22  and door assembly  16  to the chamber body  11 . When the door assembly is properly aligned with the chamber central axis for axial in-and-out movement, position sensor  33  disinhibits (allows) the actuation of a first pneumatic control interlock  34 . The first interlock  34  has two functions. First, it inhibits the first door-closing pneumatic means  19  against unintended withdrawal of the door assembly  16  from its aligned in-and-out position, and second, it simultaneously disinhibits (releases) the second remotely-operated pneumatic closing means  20  to move the door axially in and out of sealed position. 
     At the point when the door  23  is fully engaged with its tapered seat  24 , a second position sensor  35  disinhibits (releases) a second interlock means  36  to permit actuation of the third remotely actuated pneumatic means  32 , which is then enabled to simultaneously drive the locking shoes  25  into locking position. A third position sensor  37  ( FIG. 8 ) detects when all of the shoes  25  are in locked position and sends a signal to disinhibit (permit closure of) the connection between an electrical detonation initiation means  38  and the initiation charge of the threat object which is now sealed within the chamber. The threat object may then be instantly and safely detonated and thus neutralized.