Venting lifting plug for munitions

Abstract

A venting lifting plug is provided for an unfuzed munition having a cavity with internal threads.

Claims

1. A gas pressure discharge valve for an unfuzed munition having a fuze cavity with internal threads, said discharge valve comprising a ring threaded externally and having a smooth interior surface, with the external threads adapted to engage internal threads on the threaded fuze cavity, and the smooth interior surface on the ring adapted to facilitate attachment of the ring to a lifting plug, said lifting plug comprising a lifting ring connected to a neck portion which in turn is connected to an engagement portion having an external surface, a lower portion of said external surface comprising a groove and an upper portion of said external surface comprising a protrusion extending from external surface, wherein a gap is created that allows solder to flow between the interior surface of the ring and the external surface of the engagement portion of the lifting plug, the solder comprising one or more eutectic materials having a melting point below a predetermined critical temperature and pressure of cook-off gases generated by the munition.

2. The gas discharge valve of claim 1, wherein the lifting plug separates from the ring when cook-off gas temperatures have risen high enough to melt the eutectic solder of the between the interior surface of the ring external surface of the engagement portion of the lifting plug and pressure build-up of cook-off gases is sufficiently high to cause separation of the lifting plug.

3. The gas discharge valve of claim 1, wherein the ring is formed of carbon steel, stainless steel, titanium, or other alloys thereof.

4. The gas discharge valve of claim 1, wherein the one or more eutectic materials wet the surfaces of both the lifting plug and ring and creates an environmental and pressure seal.

5. The gas discharge valve of claim 4, wherein the one or more eutectic material seals the gap and prevents release of cook-off gases until these gases reach a predetermined temperature, and the exterior surface of the engagement portion of the lifting plug, and the interior surface of the ring are boated with a wetting agent to facilitate wetting of the gap by the one or more eutectic material.

6. The gas discharge valve of claim 1, wherein the one or more eutectic material is selected from the group consisting of bismuth, lead and tin.

7. The gas discharge valve of claim 1, wherein there is a sufficient clearance between the interior surface of the ring and the external surface of the engagement portion of the lifting plug to facilitate flow of eutectic material into the gap, and the ring is formed from a material stronger than the material from which the neck of the lifting plug is formed, whereby to maintain a damage indicator of the lifting plug neck.

8. A venting lifting plug for an unfuzed munition having a fuze cavity with internal threads, said venting lifting plug comprising a ring threaded externally and having a smooth interior surface, with the external threads adapted to engage internal threads on the treaded fuze cavity, and the smooth interior surface on the ring adapted to facilitate attachment of the ring to the lifting plug, said lifting plug comprising a lifting ring connected to a neck portion which in turn is connected to an engagement portion having an external surface, a lower portion of said external surface comprising a groove and an upper portion of said external surface comprising a protrusion extending from said external surface, wherein a gap is created that allows solder to flow between the interior surface of the ring and the external surface of the engagement portion of the lifting plug, the solder comprising one or more eutectic materials having a melting point below a predetermined critical temperature and pressure of cook-off gases generated by the munition, and the ring is formed of carbon steel, and the one or more eutectic material wets surfaces of both the lifting plug and ring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a perspective view of a prior art lifting plug adapted to be in threaded engagement with a threaded fuze cavity on an unfuzed munition, illustrating in particular the threaded portion of the lifting plug.

(2) FIG. 1B is a side view of a prior art lifting plug, also illustrating the neck portion connecting the threaded portion of the lifting plug.

(3) FIG. 2A is a side view of a prior art lifting plug with a broken neck portion which is designed to break or deform when subjected to excessive loads, so as to provide a visual indication of possible damage to the munition.

(4) FIG. 2B is a side view of a prior art lifting plug with a bent neck portion which has been designed to deform when subjected to excessive loads, thus providing a visual indication of possible damage to the munition.

(5) FIG. 3 is a side view of a prior art lifting plug illustrating particularly a round cavity in the center of the plug which is filled with wax designed to melt and vent high temperature cook-off gases and energetics from the munition.

(6) FIG. 4 is a perspective exploded view of a lifting plug of the present invention which can be used in combination with a ring designed to be in tight engagement with the lifting plug and threaded engagement with the threaded cavity on the munition.

(7) FIG. 5 is a side view of a lifting plug of the present invention with a ring inserted thereon in tight engagement, and which also is in sealing engagement with the lifting plug by virtue of a sealing solder of eutectic metal.

(8) FIG. 6 is a side view of another embodiment of a lifting plug of the present invention with a ring inserted thereon in tight engagement, and which also is in sealing engagement with the lifting plug by virtue of a sealing solder of eutectic metal.

(9) FIG. 7 is a side view of another embodiment of a lifting plug of the present invention with a ring inserted thereon in tight engagement, and which also is in sealing engagement with the lifting plug by virtue of a sealing solder of eutectic metal.

(10) FIG. 8 is a side view of another embodiment of a lifting plug of the present invention with a ring inserted thereon in tight engagement, and which also is in sealing engagement with the lifting plug by virtue of a sealing solder of eutectic metal.

(11) FIG. 9 is a side view of another embodiment of a lifting plug of the present invention with a ring inserted thereon in tight engagement, and which also is in sealing engagement with the lifting plug by virtue of a sealing solder of eutectic metal.

(12) FIG. 10 is a magnified view of a portion of the lifting plug illustrated in FIG. 9.

DETAILED DESCRIPTION

(13) In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical changes may be made without departing from the scope of the present invention. The following description of example embodiments is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims.

(14) The Abstract is provided to comply with 37 C.F.R. 1.72(b) to allow the reader to quickly ascertain the nature and gist of the technical disclosure. The Abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

(15) As used herein, the term substantially refers to the complete or nearly complete extent or degree of an action, characteristic, property, state, structure, item, or result. For example, an object that is substantially flat would mean that the object is either completely flat or nearly completely flat. The exact allowable degree of deviation from absolute completeness may in some cases depend on the specific context. However, generally speaking the nearness of completion will be so as to have the same overall result as if absolute and total completion were obtained.

(16) In certain embodiments, the present invention provides a venting lifting plug for munitions such as artillery shells, bombs, rockets, torpedoes, and any other munition which is transported and/or stored without a fusing mechanism. The venting lifting plug contains a lifting plug with a ring that is eutectically bonded to the lifting plug. In order to maintain the thread engagement capabilities of the lifting plug, the external threads of the ring match the prior art lifting plugs thread design, and the thread of the fuze cavity.

(17) In order to attach the ring onto the lifting plug, the lifting plug needs to have its base made smaller to attach the ring, whilst keeping the final external diameter of the lifting plug the same as prior art lifting plugs. Stated another way, when assembled, the lifting plug and ring will have the same external profile as a conventional, or prior art lifting plug. Additionally, the joint of the lifting plug and ring will be sealed with one or more eutectic materials. The eutectic seal is to allow the lifting plug portion to remove itself off the ring and vent the cook-off gases from munitions when the energetics reaches a predetermined dangerous temperature. The lifting plug is used as a shipping means to not only lift the munitions but to also protect the munitions from the environment until the fuze is attached.

(18) In general, munitions have operating temperatures between about 60 F. to about 160 F. In case of a fire, the temperature of the munition raises beyond a safe operating temperature of, for example, about 160 F., and the energetics inside the munition phase change from solid to liquid causing an internal hoop pressure that causes the munition to explode in a high order reaction when a temperature higher than about 160 F. is reached. This reaction is undesired and if the internal hoop pressure could be relieved, the energetics would not undergo high order detonation but instead a combustion rather than an explosion would occur.

(19) This phase change phenomena also creates a hoop pressure inside the munition that the lifting plug of the present invention uses to release the lifting plug from the ring. The hoop pressure rises as the temperature increases above the operating temperature of the munition. The lifting plug has a eutectic seal at the joint between the lifting plug and the ring. The eutectic seal is maintained until a specific temperature is reached at which point, the eutectic material phase changes from solid to liquid. At this point, any mechanical features that bond the lifting plug to the ring are nullified, and the lifting plug is free to separate from the threaded ring via the hoop pressure forces of the energetics within the munitions and thus not allowing the munition to have a high order reaction. In having the energetic reaction reduced to a combustion, rather than a high order reaction allows for firefighting efforts in what would normally be a hazardous environment. A firefighting capability is most useful for ship board fires as well as in ammunition depot fires.

(20) FIG. 4 shows the threaded ring 47 of the present invention which facilitates venting of hot cook-off gases from the munition and separation of the lifting plug from a munition. Ring 47 is designed to release a modified lifting plug 55 from ring 47 when assembled in a fuze cavity of a munition. Release of lifting plug 55 is due to the hoop pressure developed within the munition as its temperature rises. In this case, the energetics goes through a phase change from solid to liquid as the temperature rises, thus generating a volume differential or internal cavity pressure.

(21) This internal cavity pressure increases at elevated temperatures and is taken advantage of because a eutectic material is used to solder the joint 57 between modified lifting plug 55 and ring 47. This soldered joint 57 remains solid until the eutectic melts at a predetermined temperature above the operating temperature of the munition. That is, the eutectic changes to a liquid and then becomes a lubricant for the modified lifting plug 55 to be able to easily release from the ring 47.

(22) Ring 47 has two surfaces: external threads 51 and internal surface 53. External threads 51 match the current threads on the fuze cavity. Internal surface 53 facilitate attachment of ring 47 to lifting plug 55, so that a gap is created to have the reflow of solder/eutectic between the lifting plug and the ring.

(23) The gap between the lifting plug 55 and the ring 51 is about 0.002 to about 0.005 inches per side around the circumference, but in other embodiments this gap can be 100% or more, smaller or greater. This results in the lifting plug being able to support greater than 450 pounds at ambient temperatures. Advantageously, by removing the threaded interface between the engagement portion 50 and the ring 47, the venting area is enlarged thereby providing greater venting capability.

(24) In a preferred embodiment, the joint 57 facilitates the flow of the one or more eutectic material. Preferably, the base metals of the new lifting plug 55 and ring 47 can be plated with a material to improve the wicking action of the eutectic.

(25) As the temperature rises in the interior cavity of the munition, the internal pressures are exerted on lifting plug 55. When the eutectic composition in joint 57 melts or phase changes, then the internal pressure causes the lifting plug 55 to separate.

(26) In one embodiment, the eutectic composition melts or phase changes at about 200 F. In an alternate embodiment, the eutectic composition melts or phase changes at about 250 F. In an alternate embodiment, the eutectic composition melts or phase changes at about 280 F. The temperature can be controlled with the type of eutectic being used. Each eutectic has its own melting temperature and can be specified as needed.

(27) In one embodiment, the eutectic composition is selected from the group consisting of B.sub.i58S.sub.N42, B.sub.i57S.sub.n42A.sub.g1, and S.sub.n51.2P.sub.b30.6C.sub.d18.2. The eutectic materials that have a melting temperature range include; B.sub.i55P.sub.b44S.sub.n1, B.sub.i4P.sub.b55.5S.sub.n40.5, S.sub.n42A.sub.g1, B.sub.i57S.sub.n42A.sub.g1

(28) The present description is further illustrated by the following examples, which should not be construed as limiting in any way. The contents of all cited references (including literature references, issued patents, and published patent applications as cited throughout this application) are hereby expressly incorporated by reference.

(29) Lifting plug comprises a lifting ring connected to an engagement portion 50 via a neck. The engagement portion comprises an exterior surface 48 for interfacing with internal surface 53 of ring 47. Ring 47 can be fabricated from a material stronger than the base metal of the lifting plug. This feature retains the current lifting plug's ability to indicate damage transparent to the new design. Additionally, ring 47 allows for the load bearing capability to be maintained as in the current design.

(30) As shown in FIG. 4, current lifting plug design 37 is maintained except the lifting plug 37 has a ring 47 added. Ring 47 external thread 51 has the thread needed for threaded engagement with fuze cavity (not shown) in a munition. In this embodiment, ring 47 internal surface 53 is a means of assembling same onto outer surface 48 of engagement portion 50 of new lifting plug 55. When assembled, ring 47 and new lifting plug 55 are soldered together with a eutectic solder that can be one or more eutectic materials (not shown), at a joint 57 as illustrated in FIG. 5. The one or more eutectic material flows as solder would, and provides a solid bond between new lifting plug 55 and ring 47. According to the present invention, the new lifting plug 55 can detach itself from the ring 47 upon reaching an elevated predetermined temperature.

(31) Although engagement portion 50 is shown as being circular in FIG. 4, in other embodiments engagement portion 50 can be any other suitable shape, such as a triangular shape, a square shape, a rectangular shape, a pentagon shape and so on. In these other embodiments, the interior surface 53 of ring 47 would have a corresponding shape, such as when engagement portion 50 is a square shape the interior surface 53 would have a corresponding square shape. In these other embodiments, the external threads 51 of ring 47 would still be of a shape needed for threaded engagement with the fuze cavity of the munition.

(32) As shown in FIG. 5, internal surface 53 of ring 47 is a flat or substantially flat surface and exterior surface 48 of engagement portion 50 is also flat or substantially flat. In other embodiments, the exterior surface 48 can include two surfaces and internal surface 53 also includes two surfaces, as shown in FIG. 6. Although FIG. 6 illustrates two surfaces, three or more surfaces can be included in both exterior surface 48 and internal surface 53.

(33) Another embodiment is illustrated in FIG. 7, in this embodiment internal surface 53 and exterior surface 48 are curved, with the center of their radius of curvature being toward the center of the engagement portion 50. Although a single radius of curvature is illustrated in FIG. 7 for internal surface 53 and exterior surface 48, in other embodiments, internal surface 53 and exterior surface 48 can include two or more radii of curvature.

(34) Manufacture and assembly of the lifting plug may be improved by varying the profile of the internal surface 53 and the exterior surface 48. The internal surface 53 and exterior surface 48 may interface to provide a positive stop for the engagement portion 50 within the ring 47. In addition, the internal surface 53 and exterior surface 48 may interface such that the engagement portion 50 is self-locating within the ring 47.

(35) Further, although internal surface 53 and exterior face 48 are described as flat surfaces and curves in the disclosed embodiments, any other shape or configuration to allow for lifting plug 55 to move in the direction of arrow 59 upon melting of eutectic joint 57 are suitable.

(36) Further still, internal surface 53 and exterior surface 48 are illustrated in the figures as being smooth, but in other embodiments, both internal surface 53 and exterior surface 48 can be variable along their height. For instance, one or both of internal surface 53 and exterior surface 48 can be irregular.

(37) In another embodiment of lifting plug 55, engagement portion 50 can include a groove 60 that extends along the upper portion of outer surface 48, as shown in FIG. 8. Groove 60 can be included with any shape of internal surface 53 and exterior surface 48, such as being combined with any embodiment disclosed above and those illustrated in FIGS. 4-7. In some embodiments groove 60 can be filled with the eutectic material in eutectic joint 57, in other embodiments groove 60 can be left substantially empty or empty, as shown in FIG. 8.

(38) In another embodiment of lifting plug 55, engagement portion 50 can include a groove 62 that extends along the upper portion of outer surface 48, as shown in FIG. 9. Groove 62 can be included with any shape of internal surface 53 and exterior surface 48, such as being combined with any embodiment disclosed above and those illustrated in FIGS. 4-8. Also included in this embodiment is protrusion 64 that extends from the upper portion of outer surface 48. Protrusion 64 can be included with any shape of internal surface 53 and exterior surface 48, such as being combined with embodiments disclosed above and those illustrated in FIGS. 4-7.

(39) In embodiments in which the groove 60 is filled with eutectic material in eutectic joint 57, groove 60 provides a convenient location for dispensing eutectic material onto the lifting plug in a manufacturing process.

(40) A magnified view of the protrusion 64 and groove 62 is shown in FIG. 10. As can be seen from FIG. 10, the upper surface of ring 47 rests on the lower surface of protrusion 64. The interaction of the lower surface of protrusion 64 and upper surface of ring 47 provides a positive stop for the engagement portion 50 within the ring 47.

(41) The described embodiments and examples of the present disclosure are intended to be illustrative rather than restrictive, and are not intended to represent every embodiment or example of the present disclosure. While the fundamental novel features of the disclosure as applied to various specific embodiments thereof have been shown, described and pointed out, it will also be understood that various omissions, substitutions and changes in the form and details of the devices illustrated and in their operation, may be made by those skilled in the art without departing from the spirit of the disclosure. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the disclosure. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the disclosure may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. Further, various modifications and variations can be made without departing from the spirit or scope of the disclosure as set forth in the following claims both literally and in equivalents recognized in law.