Abstract:
A fire suppression device characterized by a plunger that is extendible from a housing for delivery of a fire suppressant foam. The plunger may be equipped at its outer end with a puncture tip that can penetrate through the wall of a container or cargo cover for delivery of the fire suppressant foam directly to the cargo, preferably after full or almost full extension of the plunger. The plunger may be driven outwardly under high force by a pressurized gas that may also be used as a propellant for mixing with a liquid foaming agent, preferably within a foaming chamber carried by the piston. Provision may also be made for connection to a source of pressurized fluid to effect retraction of the plunger.

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional application No. 60/661,849 filed Mar. 15, 2005, which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention herein described relates generally to fire suppression systems and more particularly to a pneumatic puncture system for such fire suppression systems. 
     BACKGROUND 
     Every day freight is shipped using various modes of shipping including trucks, trailers and aircraft. The freight is usually shipped inside storage areas and/or containers and some freight can be composed of flammable material. The freight often is stored in an area separate from personnel handling or watching over the truck, trailer, aircraft or storage facility. Consequently, the start of a fire in a container or storage area may go undetected for a prolonged period of time. Once a fire condition has been detected, the container or storage area in which the fire is located may not be immediately known because many different containers may be located in a storage area. Even when the fire is detected and the involved container located, access to the container may be difficult, as in the case where a number of containers are located in an aircraft cargo area in close-packed arrangement. 
     Freight carried by modern commercial freighter aircraft usually is transported in containers or on pallets. The containers or pallets are generally referred generically as Unit Load Devices or “ULDs”. The containers may be constructed of high-strength aircraft grade aluminum alloy, sometimes with sides constructed partially of Lexan polycarbonate. Under Federal Air Regulations, ULDs are considered aircraft appliances, are FAA certified for the specific type of aircraft, and are typically manufactured to specifications contained in National Aerospace Standard (NAS) 3610. An example of a very commonly used ULD for main deck freight stowage is an AMJ-type container configured to fit within the main deck stowage area. A number of these containers and/or pallets may be stored in a cargo area of the aircraft. 
     If a container contains flammable material and the temperature rises too high or the material is otherwise ignited, a fire could start in the container. Unless someone is in the cargo area at the time the freight combusts, which is unlikely, such a fire could remain undetected by the ground and/or flight crew. If undetected, the fire could spread to other containers or areas and compromise the aircraft. 
     U.S. Published Patent Application No. 2001/0054964 discloses a system for detecting and suppressing a fire condition in a storage unit. Sensors are provided to detect a fire condition and transmit detection of such an event to a control center, such as the cockpit of an aircraft. In addition, a fire suppression device is configured to discharge a fire suppressant material into the storage unit upon detection of the fire condition. In the case of a plurality of storage units, a plurality of sensors are employed along with a plurality of fire suppression devices for respective storage units. 
     The fire suppression devices disclosed in the above-mentioned published application include a source of pressurized fire suppressant material and a popup device disposed between one of the storage units and the source. The popup device is configured to apply the fire suppressant material to the storage unit upon detection of the fire condition. The storage unit may be a container with a base including a hole, and the popup device may include a valve aligned with the hole, such that the fire suppressant material is discharged into the container through the hole in the base. In an aircraft fire suppression system, the fire suppressant material may be centrally located and distributed via a manifold to the storage units. 
     Other fire suppression devices have used a liquid foaming agent and a pressurized gas for agitating and aerating the foaming agent to generate a foam. It has been proposed to provide an aircraft fire suppression system with respective supplies of a liquid foaming agent and pressurized gas that are connected to a plurality of fire suppression devices respectively associated with container and/or pallet locations in an upper deck freight storage area of an aircraft. The fire suppression devices each would be individually actuated upon detection of a fire condition in the associated container or pallet. A further proposal was to provide such a fire suppression device that could penetrate the container or pallet cover to deliver fire retardant foam directly to the contents of the container or pallet. 
     SUMMARY OF THE INVENTION 
     The present invention provides a fire suppression device characterized by a plunger that is extendible from a housing for delivery of a fire suppressant foam. The plunger may be equipped at its outer end with a puncture tip that can penetrate through the wall of a container or cargo cover for delivery of the fire suppressant foam directly to the cargo, preferably after full or almost full extension of the plunger. The plunger may be driven outwardly under high force by a pressurized gas that may also be used as a propellant for mixing with a liquid foaming agent, preferably within a foaming chamber carried by the piston. Provision may also be made for connection to a source of pressurized fluid to effect retraction of the plunger. 
     Accordingly, the invention provides a fire suppression device for dispensing a fire retardant foam into an aircraft cargo compartment, comprising a housing including a piston chamber, a gas inlet for connection to a source of pressurized gas, a gas flow passage for connecting the gas inlet to an extend side of the piston chamber, and a foaming agent inlet for connection to a source of a foaming agent; a plunger including a piston movable in the piston chamber between a retracted position and an extended position when pressurized gas is supplied to the extend side of the piston chamber via the gas inlet and gas flow passage; and a foaming chamber a discharge opening through which fire retardant foam is dispensed from the foaming chamber, the foaming chamber being connected at its inlet end by an inlet passage that communicates with the foaming agent inlet when the plunger is in its extended position. 
     The plunger may include the foaming chamber, which may be in the form of a foaming cartridge. The plunger may include a plunger gas passage for connecting the extend side of the piston chamber to the foaming chamber, and a valve member for opening and closing the plunger gas passage respectively to permit or restrict the flow of pressurized gas from the extend side of the piston chamber to the foaming chamber via the plunger gas passage. A plunger position-responsive actuator may be provided for moving the valve member to an open position when the plunger reaches its extended position, thereby allowing the pressurized gas to flow into the foaming chamber for mixing with the foaming agent. 
     The housing may also includes a second gas inlet for connection to a source of pressurized gas, and a second gas flow passage connecting the second gas inlet to a retract side of the piston chamber in the housing. The inlet may open to a side of the plunger such that it becomes exposed to the retract side of the piston chamber during retraction of the plunger, and the plunger may include a poppet valve for closing the inlet passage to the foaming chamber when pressurized gas is supplied to the second gas inlet, thereby to prevent the pressurized gas from escaping through the foaming chamber. 
     According to another aspect of the invention, a fire suppression device for an aircraft cargo compartment fire suppression system, comprises a housing including a piston chamber, a gas inlet for connection to a source of pressurized gas, a gas flow passage for connecting the gas inlet to an extend side of the piston chamber, and a foaming agent inlet for connection to a source of a foaming agent; and a plunger including a piston movable in the piston chamber between a retracted position and an extended position when pressurized gas is supplied to the extend side of the piston chamber via the gas inlet and gas flow passage, the plunger being configured to receive therein a cartridge including a foaming chamber, and the plunger including foaming agent flow passage communicating with the foaming agent inlet when the plunger is in its extended position. The plunger may be releasably held in the retracted position by a retention device until gas pressure in the extend side of the piston chamber exceeds a prescribed amount. The retention device may include a coil spring having one side thereof protruding laterally from a side wall of one of the plunger and housing and releasably captured by a side wall of the other of the plunger and housing. 
     According to a further aspect of the invention, a method of operating a fire suppression device for dispensing a fire retardant foam into an aircraft cargo compartment, comprising the steps of using a pressurized gas to extend a plunger from a housing under sufficient force to allow a puncture tip at the end of the plunger to penetrate a container wall or cargo cover; and automatically dispensing from a discharge end of a foaming chamber a fire retardant foam upon the plunger reaching an extended position. The method may further comprise the step of allowing the pressurized air to enter the foaming chamber upon the plunger reaching the end of an extend stroke, for mixing with a foaming agent supplied to the foaming chamber, and the step using a second pressurized gas to retract the plunger after it has been extended, to reposition the plunger at a retracted position in the housing. 
     The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the annexed drawings: 
         FIG. 1  is a schematic representation of an exemplary fire indication and suppression system which includes a fire suppression device according to the invention; 
         FIG. 2  is an end view of an exemplary fire suppression device according to the invention; 
         FIG. 3  is a cross-sectional view of the fire suppression device, taken along the line A-A of  FIG. 2 , showing the device in an un-deployed, retracted position; 
         FIG. 4  is a cross-sectional view of the fire suppression device, taken along the line B-B of  FIG. 2 , showing the device in an un-deployed, retracted position; 
         FIG. 5  is an enlargement of the upper portion of  FIG. 3 ; 
         FIG. 6  is an enlargement of the upper portion of  FIG. 4 ; 
         FIG. 7  is an enlargement of a portion of  FIG. 6 ; 
         FIG. 8  is a cross-sectional view of the fire suppression device similar to  FIG. 3 , but showing the device in a deployed, extended position; 
         FIG. 9  is an enlarged partial cross-sectional view of the fire suppression device taken along the line B-B of  FIG. 2 , with the device in a deployed, extended position; 
         FIG. 10  is an enlarged partial cross-sectional view of the fire suppression device taken along the line C-C of  FIG. 2 , with the device in a deployed, extended position. 
     
    
    
     DETAILED DESCRIPTION 
     The principles of the present invention can be applied in various types of fire suppression systems, as will be appreciated by those skilled in the art. The present invention, however, is particularly applicable to aircraft fire suppression systems used to protect cargo stowage areas such as those which can contain a plurality of ULDs such as cargo containers and covered pallets. Accordingly, an exemplary embodiment of the invention will be described in relation to such type of aircraft fire suppression system, although it should be understood that the invention can be applied to other types of fire suppression systems as well. 
     Referring initially to  FIG. 1 , an aircraft fire suppression system is indicated generally at  20 . The system  20  comprises a foaming agent supply  21 , a pressurized gas supply  22 , a heat sensor  23  and a fire suppression device  24 , all shown in diagrammatic relation to a ULD  25  (such as a container or pallet) in a cargo storage space of an aircraft. The heat sensor  23  is used to monitor the ULD  25  for a condition indicative of a fire, such as a temperature significantly higher than the ambient temperature in the cargo storage space. The heat sensor may be, for example, an infrared sensor that looks at the infrared signature of the ULD. 
     The fire suppression device  24 , which is described in greater detail below, is connected via suitable piping  27  to the supply  21  of a foaming agent which typically will be a liquid. The device  24  also is connected via suitable piping  28  to the source  22  of a pressurized gas, such as nitrogen gas or other nonflammable gas compatible with the foaming agent. The gas typically will be a nonflammable gas that is mixed with the foaming agent as a propellant and/or reactant for the generation of a fire retardant foam that is dispensed by the fire suppression device. 
     If the heat sensor  23  detects a fire condition, the fire suppression device  24  is caused to deploy a plunger that may be equipped with a puncture tip that can penetrate an exterior wall of the ULD  25  so that the dispensing end of the plunger will be located inside the ULD for delivery of the fire retardant foam directly to the contents of the ULD. After the plunger is deployed, the pressurized gas is mixed with the foaming agent for producing and dispensing the fire retardant foam. The heat sensor  23  may also supply a signal to the cockpit to alert the flight crew of a fire situation in the cargo storage area. 
     Since most aircraft can carry a plurality of ULDs, a heat sensor and fire suppression device may be provided at each ULD location. Separate foaming agent tanks and pressurized gas tanks may be provided for each station, or multiple fire suppression devices may be connected to a common foaming agent tank (or tanks) and pressurized gas tank (or tanks). 
     Turning now to  FIGS. 2-4 , the illustrated exemplary fire suppression device  24  can be seen to comprise a housing  30  including a piston chamber  31 , a plunger  32  including a piston  33  movable in the piston chamber between a retracted position ( FIGS. 3 and 4 ) and an extended position ( FIGS. 8-10 ), and a foaming chamber  34  having a discharge opening  35  through which fire retardant foam is dispensed from the foaming chamber. The foaming chamber may be formed in a cartridge  37  inserted into a lower tubular portion  38 , or stem, of the plunger and suitably secured within the plunger stem by suitable means. The discharge opening  35  of the foaming chamber opens to the interior of an annular puncture tip  40  that has an angled knife edge and which may be secured to the outer end of the plunger. In the retracted position of the plunger shown in  FIGS. 3 and 4 , the puncture tip may be surrounded by a tubular protective guard  41  attached to or forming a part of the housing  30 . 
     The housing  30  may be assembled from several parts including a tubular body  45 , an end cap  46 , a lower body extension  47  and the above mentioned protective guard  41  which may be unitary with the lower body extension as shown. As illustrated, the tubular body  45  may have a cylindrical wall portion forming the piston chamber  31  which is closed at one end by the end cap  46 . The other end of the piston chamber is closed by a lower end portion of the tubular body  45  that has a central passage  48  through which the stem portion  38  of the plunger is supported for sliding telescopic movement. The plunger may also be supported by a bushing  49  retained in the lower body extension. 
     The end cap  46  includes a gas inlet  50  for connection to the source  22  ( FIG. 1 ) of pressurized gas, and a gas flow passage  51  for connecting the gas inlet to an extend side of the piston chamber. The flow of pressurized gas through the end cap may be controlled by a valve  53 , such as a solenoid valve secured to the end cap at a threaded port. The control valve  53  may be opened in response to a signal from the heat sensor  23  ( FIG. 1 ) signaling a fire condition and initiating deployment of the fire suppression device  24 . 
     The lower end portion of the body  45  has a foaming agent inlet port  56  for connection of the fire suppression device to the foaming agent supply  21  ( FIG. 1 ). The inlet port  56  is connected via a radial passage  57  to an opening, specifically an annular chamber  58  formed in the inner diameter surface of the lower housing end portion. As shown, suitable annular seals  59  and  60  are provided to seal the plunger stem  38  to the lower body end portion at opposite axial sides of the annular chamber  58  to seal against fluid leakage along the stem of the plunger. When the plunger is retracted as shown in  FIGS. 3 and 4 , the plunger stem will block and thus close the chamber  58 . Consequently, the foaming agent inlet port  56  can always be connected to the foaming agent supply  21  even though the latter typically will be under pressure for delivery of the foaming agent to the fire suppression device. 
     The plunger  32  includes one or more axial passages  60  ( FIG. 10 ) for connecting the extend side of the piston chamber  31  to the foaming chamber  34 , and a valve member  61  for opening and closing the plunger gas passages  60  to permit or restrict the flow of pressurized gas from the extend side of the piston chamber to the foaming chamber via the plunger gas passages. In the illustrated embodiment and as best seen in  FIGS. 5 and 6 , the valve member  61  is a disc-like member that is resiliently biased by a spring  63  against an annular seal  64  that forms an annular valve seat. The spring  63  is axially interposed between the valve member  61  and the bottom of a well  65  formed in a piston end plate  66 . The piston end plate is secured to a piston body  67  and has an annular groove at its outer diameter in which an annular piston seal ring  68  is trapped to effect a sliding seal between the piston and piston chamber wall. 
     As seen in  FIGS. 5 and 6 , the well  65  has on its outer diameter surface a ledge  70  for interacting with a retention device  71  that releasably holds the plunger in its retracted position. In the illustrated embodiment, the retention device  71  includes a coil spring circumferentially retained in a groove in the housing end cap  46 . The coil spring protrudes radially inwardly from the groove to catch the ledge  70  for releasably latching the piston to the end cap. The plunger will be retained in the retracted position until pressure applied to extend the piston produces enough force to cause the coils of the spring to collapse on themselves thereby releasing the ledge to allow the plunger to extend. The spring coils will resiliently return to their uncompressed condition after passage of the ledge thereby. 
     The annular well  65  has a central opening  74  for passage of pressurized gas from the inlet  50  to the backside of the valve member  61  such that pressurized gas will also serve to hold the valve member seated against the annular valve seat  64 . The annular seal/valve seat surrounds an annular well  76  that is connected to an annular manifold chamber  77  by the axial passages  60  (see  FIG. 10 ) in the plunger  32 . The annular chamber  77  serves as a manifold for a supplying pressurized gas to the foaming cartridge  37  and more specifically to a ring of inlet openings  79  in the top wall  80  of the cartridge. When the valve member  61  is closed against the valve seat  64  as shown in  FIGS. 5 and 6 , pressurized gas is blocked from flowing from the inlet  50  to the foaming cartridge  37 . 
     The top wall  80  of the foaming cartridge  37  has a central tubular nipple  83  that fits in a correspondingly sized counterbore at the top end of the cartridge chamber in the plunger, which nipple is provided with an annular seal  84  for sealing to the plunger. The nipple has a central passage  85  for connecting the interior of the foaming cartridge to an central axial passage  87  in the plunger. The central passage  87  opens at a poppet valve seat  88  to a larger diameter chamber  89  in which a poppet valve member  90  is disposed for axial movement. The poppet valve member  90 , which has a valve head  91 , is normally biased by a spring  92  to seat the valve head against the seat. The poppet valve chamber  89  has a lower portion communicating with a radial passage  95  that opens to the exterior of the plunger stem at the retract side of the piston. The poppet valve chamber also has an intermediate portion that is connected by a radial passage  98  to the exterior of the plunger at a location axially between the radial passage  95  and the piston  66 . 
     The poppet valve member  90  has a valve stem provided with a radially enlarged piston portion  100  sealed to the poppet chamber between the radial passages  95  and  98 . The poppet valve member also a annular shoulder  101  engaged by one end of the spring  92 . The other end of the spring engages the bottom of a central cup portion  103  of the valve members  61 . The central cup portion has a cylindrical interior wall surface that slides on a correspondingly sized post of the piston body  67  to maintain the valve member perpendicular to the valve seat during axial movement of the valve member. As shown, the interface between the cup portion and post is sealed to prevent fluid communication between the poppet valve chamber  89  and the pressurized gas flow passage in the plunger piston  33 . 
     When the control valve  53  is opened to allow pressurized gas to enter the extend side of the piston chamber  31 , gas pressure will cause the plunger  32  to extend from the housing. As above indicated, the valve member  61  will be held closed to prevent pressurized gas from passing through the plunger to the foaming chamber  34 . Fluid on the retract side of the piston will be exhausted through a port  107  connected via a passage  108  to a counterbore  109  at the end of the piston chamber  31  opposite the inlet for the pressurized gas. 
     The force acting on the plunger  32  causes the plunger to release from the spring retention device  71 . In addition, the force preferably is such that the puncture tip  40  will be urged with sufficient force to penetrate through an adjacent wall of a ULD. As will be appreciated the wall of the ULD will need to be spaced from the end of the plunger by a distance less than the length of the stroke of the plunger to enable the plunger to engage and penetrate the ULD. 
     While the plunger  32  is being deployed, the valve member  61  will remain closed until the piston  33  reaches the end of the piston chamber  31 . At this point a valve opening member  112  will force the valve member open against the spring force and fluid pressure acting to close the valve member against its valve seat  69 . As seen in  FIG. 6 , the valve opening member  112  can be an axially extending pusher pin that normally projects from the retract side of the piston. The pusher pin is positioned to engage the bottom of the piston chamber when the piston reaches the end of its extend stroke as seen in  FIG. 9 . Until such engagement the pusher pin will be held in the position shown in  FIG. 6 . The pressurized gas will be precluded from passing through the hole in the piston through which the pusher pin extends by reason of a seal  114  surrounding a reduced diameter stem portion of the pusher pin. The piston has an enlarged head portion that cannot fit through the hole for the stem, whereby the pin is axially trapped for limited axial movement between the valve member and the piston. 
     As the piston  33  reaches the end of the piston chamber, the pusher pin will be caused to move in the direction opposite the movement direction of the piston and this in turn will cause the pusher pin to push the valve member  61  off its valve seat  64 . This will allow the pressurized gas to pass into the foaming chamber  34 . At the same time, the side passage  95  in the plunger stem will become aligned with the annular chamber  58  in the housing  30  to which the foaming agent is being supplied, typically under pressure. With the plunger in the position shown in  FIGS. 8-10 , the foaming agent can now pass into the foaming chamber for mixing with the pressurized gas and dispensing of fire retardant foam from the discharge opening  35  of the foaming chamber and into the interior of the ULD. The pressure of the foaming agent will act on the poppet piston  100  and cause the poppet valve  90  to open to allow the foaming agent to pass into the foaming chamber. 
     After a fire event (or a test procedure), the control valve  53  is operated to close the main inlet  50 . The plunger  32  can be retracted into the housing  30  by connecting the second pressurized gas inlet  107  to a source of pressurized gas, such as carbon dioxide gas from a supply thereof. This will cause pressurized gas to act on the retract side of the piston to move the plunger back into the housing. The pressurized gas will also flow through the side poppet passage  98  to act on the poppet piston  100  to close the poppet valve and thereby prevent the pressurized air from escaping through the foaming chamber  34  and its discharge opening. The pressure of the gas should be sufficient enough to force the retention post on the piston through the retention spring whereby once again the plunger will be releasably retained in its retracted position. The control valve  53 , when de-energized, may serve to vent the extend side of the piston chamber  31  as the plunger is being retracted. 
     Although the invention has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.