US 2405125 A
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Description (OCR text may contain errors)
1945 o. E. BARNARD 2,405,125
AUTOMATIC FIRE EXTINGUiSHER Filed Sept. 11, 1945 ['5 Mai mvmrmn QRALEQBARNARD AWOHN EYS Patented Aug. 6, 1946 AUTGMATIC FIRE EXTINGUISHER Oral E. Barnard, Montreal, Quebec, Canada, assignor to Dominion Merchants Company Limited, St. Laurent, Quebec, Canada Application September 11, 1943, Serial No. 501,922
This invention relates to automatic fire extinguishers and has particular reference to that type of fire extinguisher which is equipped with an explosive head containing a powder charge which is exploded to blow out a portion of the head and thereby provide a discharge opening through which the fire extinguishing substance is discharged from its container.
One objection to conventional fire extinguishers of the explosive head. type is that the exploded head must be scrapped and rep-laced by an entirely new head when the discharged container is turned in for re-charging. This is due to the fact that the wall of the powder chamber which is ruptured by explosion of the powder charge is cast integral with the body portion of the head in such manner that the rupture of said wall makes it impractical to repair the head for reuse and the only feasible alternative is the substitution of an entirely new head.
Another objection to conventional fire extinguishers of the explosive head type is that the explosive head is of intricate design and must be produced by a die casting operation which makes it diflicult to avoid porosity of the casting at the thin critical section of the powder chamber wall which is ruptured by explosion of the powder charge. In the conventional die cast explosive the powder chamber wall which is ruptured by the explosion constitutes a dividing wall between thepowder chamber and the interior of the container in which the fire extinguishing substance is contained. If the metal in this thin critical wall section. is porous, leakage of the fire extin uishing substance into contact with the Y powder charge is apt to ensue, thus wetting the charge and preventing its efficient explosion.
A further objection to the conventional explosive head is that the container must be charged through a side opening in the head. This side opening provides another possible point of leakage nd the machining thereof constitutes a very complicated and expensive operation.
The purpose of the present invention is to provide an explosive head for fire extinguishers which is free of the foregoing objections and which has certain characteristic advantages not heretofore obtained in such devices. This purpose is accomplished by making the head in two parts comprising (1) a body portion of simplified design which may be economically produced by the sand casting method and (2) a blow-out plug assembly which may be machined out of solid bar stock. The body of the head is provided with a cavity having a bottom opening which serves both as a filling and discharge opening for the container to which the head is applied. The plug assembly includes a stem comprising a solid upper portion and a cored out lower portion which are integrally joined together by a relatively thin frangible annular all section. This stem is arranged in the cavity of the head with the cored out lower portion of the stem screwed into and closing said opening. A sleeve is screwed onto the solid upper portion of the stem so that the lower face of the sleeve forms the upper wall of a pow der chamber whose outer side wall is formed by the circular wall of said cavity and whose remaining walls are formed by portions of said stem. The lower portion of the stem is cored out to provide a downwardly facing bore or cavity which is closed at the top by the solid upper portion of the stem and the frangible annular wall section which joins the two parts of the stem together. With this arrangement the explosion of the powder charge placed in the powder chamber results in the rupture of the thin wall section connecting the two parts of the stem and in the blowing out of the solid or upper part of the stem in such manner that the lower or cored out part of the stem, including flange 29, is left in place within said opening in the form of an open ended tube through which he contents of the container are discharged. This leaves the body of the head in an undamaged condition and when the fire exti. gu'sher is turned in for re-charging the portion of the head left in the combined filling and discharge opening may be readily removed to permit application of a new plug assembly to said body after the container has been re-charged through said opening.
Proceeding now to a more detailed description of this invention reference will be had to the accompanying drawing, in which Fig. 1 is a vertical sectional view of the body portion and plug assembly of an explosive head made in accordance with the invention.
Fig. 2 is a side elevational view of the stem portion of the plug assembly as it appears per se.
The body portion and the blow-out plug assembly of my improved explosive head are respectively indicated at 5 and 6. The body 5 is preferably a one-piece hollow sand casting provided with an internal transverse partition forming the bottom wall of an upper cavity 8 and the top wall of a lower cavity 9, said cavities communieating with each other through a combined filling and discharge opening ill provided in said partition. The body 5 is also provided with a later ally extending internally threaded socket H in which the holder E2 of a powder igniting fuse element l2a is screwed, said socket being in communication with the lower portion of cavity 8 through opening The lower wall portion It of cavity 53 is internally threaded as indicated at in for engagement with the usual threaded neck extension of a conventional container to which the head is applied, the container being charged and discharged through the opening Ill.
The plug assembly 6 comprises a stem iii and an associated sleeve I1. The stem is fabricated so that, in effect, it comprises a solid externally threaded upper part I8 and a tubular externally threaded lower part I9, the latter being screwed into opening I and being provided, at its juncture with the upper part I8, with an outwardly directed flange which overlies an annular bottom wall portion 2I of cavity 8 surrounding opening I 0. The flange 20 and the annular wall 2I are provided with relatively staggered annular sealing ribs 22a which, when the stem is screwed home, embed themselves in a sealing washer 23 arranged beneath flange 20. The bore IIa of tubular stem portion I 9 is open at its lower end and is closed at its upper end by the lower extremity of the upper solid stem portion I8, the two parts of the stem being integrally joined at the upper end of said bore by a thin frangible wall section 24 whose upper surface forms with the upper surface of flange 20 the bottom wall of a powder chamber 26, the top wall of which is formed by the lower surface of sleeve I! which is screwed onto the upper stem portion I8. The outer and inner side walls of powder chamber 25 are formed, respectively, by the circumferential wall of cavity 8 and by that portion of stem section I8 which lies between sleeve I! and the upper surface of flange 20, it being noted that the lower face of the sleeve is spaced an appreciable distance above said flange,
The inner circumferential Wall surface of cavity 8 is covered by a liner 28 composed of fibrous or other suitable non-metallic material, the lower end of said liner terminating in an inwardly directed flange I7. This liner prevents direct contact between. the inner circumferential wall of cavity 8 and the solder or other sealing substance 26a which is placed in the outer portion of the cavity,
A charge of powder is trapped in powder chamber 26 as indicated and when this charge is ignited by the fuse element IZa it explodes and the force of the explosion ruptures the thin wall 24 connecting the upper and lower stem parts I8 and I 9 and causes the upper part I8, together with the sleeve I7, to be blown clear of cavity 8, the stem part I9 and flange 20 being left in place in the opening ID in the form of an open-ended tube through which the contents of the container are discharged. Since the frangible wall 24 is readily ruptured by the force of the explosion no damage is caused to the body portion 5. Consequently, When the exploded container is turned in for recharging the screw threaded stem portion I9 may be readily removed from opening I0 to permit recharging of the container through said opening. A new plug assembly is then applied and the container is then ready for re-use.
It is important that flange 20 be left in place as a protective covering for the sealing washer surface 2| when the plug portion I8 is blown out since said surface is easily damaged and may be ruined if left exposed when the container is turned in for re-charging.
Having thus described the preferred embodiment of my invention it will be understood that various modifications may be resorted to within the scope and spirit of the invention as defined by the appended claims.
1. An explosive head for fire extinguishers comprising a body portion and a separately formed 29 engaging the lower face of sleeve blow-out plug assembly fitted together with a portion of the plug assembl removably inserted in and plugging an opening in the head through which the container with which the head is associated is charged and discharged, the portion of the plug assembly inserted in said opening comprising a lower tubular stem section whose bore is open at the container end thereof and is closed at the opposite end by another section of the plug assembly to which the tubular section is integrally joined by a relatively thin and weak connecting wall, said body and plug assembly presenting chamber forming walls conjointly providing a powder chamber in which the explosion of a powder charge is effective to rupture said relatively thin and weak connecting wall and to cause the second mentioned section of the plug assembly to be blown away from the tubular section, the latter being left in place in said opening in the form of a removable tubular section which is open at both ends to permit discharge of the container contents therethrough.
2. An explosive head for fire extinguishers comprising a hollow body provided with an internal transverse partition forming the bottom wall of an upper cavity and the top wall of a lower cavity, said cavities being in communication with each other through a combined filling and discharge opening in said partition, a stem arranged in said upper cavity and comprising a tubular lower section having its upper end integrally joined to a solid upper section by a relatively thin and weak connecting wall, said tubular section of the stem being removably inserted in said opening and the bore of said tubular section being open at one end to said lower cavity and being closed at the opposite end by the solid upper section of the stem and by said relatively thin and weak connecting wall, said stem and the circumferential wall of said upper cavity presenting chamber forming walls conjointly providing a powder chamber in which the explosion of a powder charge is effected to rupture said relatively thin and weak connecting wall and to blow the solid upper section of the stem out of said upper cavity, the lower tubular section of the stem being left in place in said opening in the form of a tube which is open at both ends to serve as a discharge outlet for the contents of the container to which the head is applied.
3. An explosive head as set forth in claim 2, in which the said upper section of the stem comprises a sleeve threaded on an integral stem portion, the said upper stem section being received in the said upper cavity and in which the outer side and top walls of said powder chamber are formed, respectively, by the circumferential wall of said upper cavity and by the lower face of said sleeve, the remaining walls of said powder chamber being formed by portions of said stem located immediately adjacent said relatively thin and weak connecting wall.
4. An explosive head as set forth in claim 2, in which the inner circumferential wall of said upper cavity is covered by a non-metallic liner which is interposed between said wall and said stem and which also covers portions of said wall lying above said stem, said liner serving to prevent fusion between said wall and sealing material placed in the upper end of said cavity above said stem,
ORAL E. BARNARD.