Abstract:
An initiator assembly having a base, first and second conductive elements, a first electrically insulating member and an energetic material. The first conductive element, which is configured to receive an electrical input, is coupled to the base and includes a tip. The first electrically insulating member is disposed over the tip. The second conductive element has a bridge that is disposed over the first electrically insulating member. The bridge is configured to vaporize in response to transmission of the electrical input from the tip of the first conductive element to the bridge. The energetic material is disposed over the bridge. Energy produced during vaporization of the bridge is transmitted to the energetic material to initiate at least one of a combustion event, a deflagration event and a detonation event in the energetic material. A method for operating an initiator assembly is also provided.

Description:
FIELD 
     The present disclosure relates to a bursting switch. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Exploding foil initiators, and more specifically the low energy exploding foil initiators (LEEFI&#39;s) pioneered by Reynolds Systems, Incorporated of Middletown, Calif., represent an evolutionary step in the design of igniters and detonators due to their improved reliability and safety. It is desirable in some instances to include switch capabilities with a LEEFI to provide further enhancements in safety. Heretofore, such switch capabilities have been provided either with a stand-alone switch device or a switch device that is integrated into the LEEFI in the manner shown in U.S. Pat. No. 6,851,370 and 873,122. 
     The use of a stand-alone switch device is not typically desirable as such devices tend to be relatively costly and more importantly, because such devices are typically difficult to package into the device that is to be ignited or detonated. The devices detailed in the &#39;370 and &#39;122 patents are somewhat less costly, but can significantly increase the space (area) that is needed to package the LEEFI into the device that is to be ignited or detonated. In some instances, it is simply not possible to increase the size of the “foot print” of the LEEFI to incorporate the switching capabilities that are described in the &#39;370 and &#39;122 patents. Accordingly, there remains a need in the art for an improved LEEFI having integrated switch capabilities. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     In one form, the present disclosure provides an initiator assembly with a base, a first contact coupled to the base, a first electrically insulating member, a bridge, a flyer layer and a barrel. The first contact defines a first switch element. The first electrically insulating member is disposed over the first switch element such that the first switch element is disposed along an axis between the base and the first electrically insulating member. The bridge is coupled to the first electrically insulating member such that the first electrically insulating member is disposed along the axis between the first switch element and the bridge. The flyer layer is coupled to the bridge. The barrel is coupled to the base and is disposed over the bridge and at least a portion of the flyer layer. The barrel is disposed along the axis. 
     In another form, the present disclosure provides a method that includes: providing an initiator assembly having a first switch element, a bridge, a flyer layer and a barrel, the first switch element and the bridge being spaced vertically apart along an axis, the flyer layer overlying the bridge, the barrel defining a barrel aperture and being disposed over at least a portion of the flyer layer; and applying electrical power to the first switch element to vaporize the bridge, wherein vaporization of the bridge causes a portion of the flyer layer within the barrel aperture to be expelled from the barrel. 
     In still another form, the present disclosure provides an initiator assembly that includes a base, a first conductive element coupled to the base, a first electrically insulating member, a second conductive element and an energetic material. The first conductive element includes a tip and is configured to receive an electrical input. The first electrically insulating member is disposed over the tip. The second conductive element has a bridge that is disposed over the first electrically insulating member. The bridge is configured to vaporize in response to transmission of the electrical input from the tip of the first conductive element to the bridge. The energetic material is disposed over the bridge. Energy produced during vaporization of the bridge is transmitted to the energetic material to initiate at least one of a combustion event, a deflagration event and a detonation event in the energetic material. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a schematic illustration of an initiator assembly constructed in accordance with the teachings of the present disclosure in operative association with an electronic safe-and-arm device; 
         FIG. 2  is an exploded perspective view of a portion of the initiator assembly of  FIG. 1 ; 
         FIG. 3  is a top plan view of a portion of the initiator assembly depicting a portion of a manufacturing process where a first switch contact is coupled to a base; 
         FIG. 4  is a top plan view of a portion of the initiator assembly depicting a portion of a manufacturing process where a first insulating member is disposed over a portion of the first switch contact; 
         FIG. 5  is a top plan view of a portion of the initiator assembly depicting a portion of a manufacturing process where a second switch is disposed over a portion of the first insulating member; 
         FIG. 6  is an enlarged portion of  FIG. 5 ; 
         FIG. 7  is a top plan view of a portion of the initiator assembly depicting a portion of a manufacturing process where a second electrically insulating member is disposed over a portion of the second switch; 
         FIG. 8  is a top plan view of a portion of the initiator assembly depicting a portion of a manufacturing process where a bridge is disposed over a portion of the second insulating member; 
         FIG. 9  is an enlarged portion of  FIG. 8 ; 
         FIG. 10  is a top plan view of a portion of the initiator assembly depicting a portion of a manufacturing process where a third electrically insulating member is disposed over a portion of the bridge; and 
         FIG. 11  is a view similar to that of  FIG. 2  but depicting an alternately constructed initiator assembly. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     With reference to  FIG. 1  of the drawings, an initiator assembly constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral  10 . The initiator assembly  10  is illustrated as being housed in a housing  12  and in operative association with a conventional safe-and-arm device  14  that is used to selectively couple the initiator assembly  10  to a source of electrical power  16 . 
     With reference to  FIG. 2 , the initiator assembly  10  can include an initiator device  20 , a flyer layer  22 , a barrel  24  and an input charge  26 . In the particular example provided, the initiator assembly  10  is similar to a low energy exploding foil initiator (LEEFI) in that when the initiator assembly  10  is operated, a portion of the initiator device  20  is vaporized and causes a portion of the flyer layer  22  (i.e., the flyer  22   a  that is illustrated in phantom line) to be sheared from a remaining portion of the flyer layer  22  and travel through a barrel aperture  28  in the barrel  24  where it impacts another structure, such as the input charge  26 , to initiate a wavefront that travels through the input charge  26  to cause an intended reaction, such as detonation. 
     The initiator device  20  can include a base  40 , a first contact  42 , a first electrically insulating member  44 , a trigger switch  46 , a second electrically insulating member  48 , a second bridge element  50  and a third electrically insulating member  52 . The base  40  can be formed from an electrically insulating material, such as ceramic, glass, polyimide, or silicon and can define a planar surface  60 . 
     With reference to  FIG. 3 , the first contact  42  can be formed from one or more suitable electrically conductive materials, such as nickel, copper, gold, silver and alloys thereof, and can be fixedly coupled to the planar surface  60  of the base  40  in an appropriate manner, such as by vapor deposition. The first contact  42  can define a first bridge element  64  that can be disposed along an axis  66  that can be perpendicular to the planar surface  60 . In the particular example provided, the first bridge element  64  has a tip with a semi-circular shape that is defined by a radius. 
     With reference to  FIG. 4 , the first electrically insulating member  44  can be disposed over a portion of the base  40  and the first contact  42  and can cover the first bridge element  64 . The first electrically insulating member  44  can be formed of any suitable insulating material and can have a thickness that is selected to provide a desired level of electric insulation. In the particular example provided, the first electrically insulating member  44  is formed of polyimide and has a thickness of about two microns. The first electrically insulating member  44  does not extend over the entirety of the first contact  42  and the base  40 . The uncovered portion of the first contact  42  is configured to be coupled to an electric lead (e.g., wire or contact) that is electrically coupled to the safe-and-arm device  14  ( FIG. 1 ). 
     In  FIGS. 5 and 6 , the trigger switch  46  defines a switch element  70  and a pair of second switch contacts  72  that are disposed on opposite sides of the switch element  70 . The switch element  70  can be disposed over the first bridge element  64  such that it is centered on a line that defines an end of the semi-circular shape of the tip of the first bridge element  64 . The trigger switch  46  can be formed in a desired manner, such as vapor deposition, from one or more suitable electrically conductive materials, such as nickel, copper, gold, silver and alloys thereof, and can be layered over the base  40  and the first electrically insulating member  44 . In the example provided, portions of the second switch contacts  72  are mounted directly to exposed portions of the planar surface  60  of the base  40 , while the remaining portion of the trigger switch  46  is mounted to the first electrically insulating member  44  such that the first electrically insulating member  44  is disposed along the axis  66  between the first bridge element  64  of the first contact  42  and the trigger switch  46 . 
     In  FIG. 7 , the second electrically insulating member  48  can be disposed over a portion of the trigger switch  46  and the first electrically insulating member  44 . The second electrically insulating member  48  can be formed of any suitable insulating material and can have a thickness that is selected to provide a desired level of electric insulation. In the particular example provided, the second electrically insulating member  48  is formed of polyimide and has a thickness of about five microns. The second electrically insulating member  48  does not extend over the entirety of the second switch contacts  72  and the base  40 . The uncovered portion of each of the second switch contacts  72  is configured to be coupled to an electric lead (e.g., wire or contact) that is electrically coupled to the safe-and-arm device  14  ( FIG. 1 ). 
     It will be appreciated that the trigger switch  46  and the insulating material between the trigger switch  46  and the second bridge element  50  (i.e., the second electrically insulating member  48  in the particular example provided) are optional and may be omitted from a design in which the additional triggering capabilities provided by the trigger switch  46  are not desired. If the trigger switch  46  and the second electrically insulating member  48  are omitted, the initiator assembly can be operated by applying electrical power having a voltage that is sufficient by itself to penetrate through the insulating material that is disposed between the first contact  42  and the second bridge element  50 . 
     In  FIGS. 8 and 9 , the second bridge element  50  can be formed in a desired manner, such as by vapor deposition, from one or more suitable electrically conductive materials, such as nickel, copper, gold, silver and alloys thereof, and can be fixedly coupled to the second electrically insulating member  48  such that the second electrically insulating member  48  is disposed along the axis  66  between the switch element  70  and the second bridge element  50 . The second bridge element  50  can have a semi-circular end  80  that can be defined by a radius that is centered on the axis  66 . The semi-circular end  80  of the second bridge element  50  can overlap the first bridge element  64  of the first contact  42 . More specifically, the semi-circular end  80  of the second bridge element  50  and the semi-circular segment of the tip of the first bridge element  64  can cooperate to define a circular area that is bounded by a circle. The second bridge element  50  can be electrically coupled to a bridge contact  84  that is mounted to the second electrically insulating member  48  and the base  40 . The bridge contact  84  can be formed in a desired manner, such as by vapor deposition, from one or more suitable electrically conductive materials, such as nickel, copper, gold, silver and alloys thereof. 
     In  FIG. 10 , the third electrically insulating member  52  can be disposed over the second bridge element  50  and a portion of the bridge contact  84 . The third electrically insulating member  52  can be formed of any suitable insulating material and can have a thickness that is selected to provide a desired level of electric insulation. In the particular example provided, the second electrically insulating member  48  is formed of polyimide and has a thickness of about three microns. The uncovered portion of the bridge contact  84  is configured to be coupled to an electric lead (e.g., wire or contact) that is electrically coupled to the safe-and-arm device  14  ( FIG. 1 ). 
     Returning to  FIG. 2 , the flyer layer  22  and the barrel  24 , which can both be formed of polyamide, can be mounted to the initiator device  20  such that the barrel aperture  28  is centered about the axis  66 . Optionally, the flyer layer  22  can be the third electrically insulating member  52 . 
     The input charge  26  could be formed of any desired energetic material, such as a primary or secondary explosive. Suitable secondary explosives include RSI-007, which is available from Reynolds Systems, Inc. of Middletown, Calif., and hexanitrostilbene (HNS). The input charge  26  can be positioned relative to the barrel  24  to receive impact energy from the flyer  22   a  when the initiator assembly  10  is operated. 
     With reference to  FIGS. 1, 2 and 8 , when the initiator assembly  10  is to be operated, electric energy can be provided by the safe-and-arm device  14  and can be applied to the first contact  42  and the bridge contact  84 , and optionally to the second switch contacts  72  with current and voltage that is necessary to vaporize the first and second bridge elements  64  and  50 , and optionally the switch element  70 . Vaporization of the switch element  70  can be configured to damage or degrade the first and second electrically insulating members  44  and  48  in an area that is vertically between the first bridge element  64  and the second bridge element  50 , which reduces the electric potential that would otherwise be needed to transmit electric energy from the first bridge element  64  of the first contact  42  through the first and second electrically insulating members  44  and  48  to the second bridge element  50  to vaporize the first and second bridge elements  64  and  50 . Vaporization of the first and second bridge elements  64  and  50  applies a force to the flyer layer  22  that causes a portion of the flyer layer  22  (i.e., the flyer  22   a ) to shear from the remainder of the flyer layer  22  and travel through the barrel aperture  28  where it impacts a structure, such as the input charge  26 . 
     In  FIG. 11 , another insulating member  90  can be disposed between the second bridge element  50  and the third electrically insulating member  52 . This additional insulating member  90  can define an aperture  92  that can be centered on the first and second bridge elements  64  and  50  and can be sized so as to not interfere with the breakdown (i.e., transmission of electrical energy) between the first and second bridge elements  64  and  50 . The additional insulating member can increase the dielectric strength everywhere except in a zone where the first and second bridge elements  64  and  50  overlap one another along the axis  66 . This has the effect of forcing the breakdown to occur in a desired location and reduces the area over which extreme visual inspection (to identify defects in the dielectric materials) is needed. Given the difficulty in positioning the various elements in an exact alignment, we contemplate that the circle that is defined by the tip of the first bridge element  64  and the end of the second bridge element  50  can be about 0.0080 to about 0.0090 inch in diameter, while the aperture  92  in the additional insulating member  90  can be about 0.0060 to about 0.0070 inch in diameter. 
     From the foregoing description, those of skill in the art will appreciate that switching capabilities can be integrated into a LEEFI in a manner that directs the discharge of electrical energy from a switch device into the LEEFI in a vertical direction so that the area or “foot print” of the LEEFI is not increased relative to the area or foot-print of a LEEFI that does not have switch capabilities. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.