Patent Publication Number: US-6662883-B2

Title: Charge tube assembly for a perforating gun

Description:
FIELD OF THE INVENTION 
     The present invention relates to a charge tube assembly for a perforating gun. 
     BACKGROUND OF THE INVENTION 
     Canadian Patent 2,243,178 (Buzinsky) discloses a charge tube retaining and orienting structure for a perforating gun. The Buzinsky reference describes use in the prior art of disk-form end plates which are held in place by screws. The Buzinsky reference then goes on to teach the use of externally threaded annular disks. These disks are positioned by threading into a threaded end of a carrier tube. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an alternative charge tube assembly. 
     According to the present invention there is provided a charge tube assembly for a perforating gun which includes a tubular body having opposed ends. Integrally formed engagement members are positioned at each of the opposed ends. Detachable end plates are secured to each of the opposed ends. Each of the end plates has openings engagable with the engagement members. 
     The charge tube assembly, as described above, provides a number of advantages. It does not require screws or other fasteners. There is, therefore, no concern about handling or losing small components in the field. It can be made from thinner material as it does not need to have sufficient thickness to support the machining of an engagement thread. The result is an easy to handle and cost effective alternative to existing charge tube assemblies. 
     As will be further described with illustrated embodiments, once the basic teachings of the invention are understood the configuration of engagement member and configuration of detachable end plate can vary. 
     A preferred form of engagement which will hereinafter be illustrated and described for the first or upper one of the opposed ends has a peripheral edge with at least two circumferentially spaced inwardly extending axial slots along the peripheral edge forming arcuate engagement members. The engagement members having deformable locking tabs to prevent the accidental displacement of the end plate. One reason that this form of engagement is preferred relates to alignment. When the axial slots are asymmetrically positioned along the peripheral edge, the engagement members must be positioned in a particular orientation in order to engage the end plates. This addresses the alignment issue, as the detachable end plates can only fit in one orientation. 
     A preferred form of engagement for the second or lower engagement members is hook shaped. By rotation of the end plate when the engagement members are positioned in the openings of the end plate, the engagement members are moved into an engaged positioned engaging the end plate. For those end plates that are rotated into locking engagement, a tool coupling is positioned on the end plate which is adapted to engage a tool. One form of tool coupling will be illustrated, but alternative forms of tool coupling could be used. 
     An alternative and equally workable form of engagement involves the use of engagement members which are deformable. The engagement members are positioned in the openings of the end plates and then deformed to engage the end plates. 
     The configuration of the openings in the end plates can vary. An embodiment will hereinafter be illustrated and described in which the openings in the end plates are slots. An embodiments will also hereinafter be illustrated and described in which the openings in the end plates are cavities positioned along an inner sidewall which defines a central bore. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to in any way limit the scope of the invention to the particular embodiment or embodiments shown, wherein: 
     FIG. 1 is a side elevation view, in section, of an upper end of a perforating gun having a charge tube assembly constructed in accordance with the teachings of the present invention. 
     FIG. 2 is a side elevation view, in section, of a lower end of a perforating gun having a charge tube assembly constructed in accordance with the teachings of the present invention. 
     FIG. 3 is bottom plan view of the charge tube assembly illustrated in FIG.  2 . 
     FIG. 4 is top plan view of the charge tube assembly illustrated in FIG.  1 . 
     FIG. 5 is perspective view of an upper end of a tubular body forming part of the charge tube assembly illustrated in FIG.  1 . 
     FIG. 6 is perspective view of a lower end of the tubular body forming part of the charge tube assembly illustrated in FIG.  2 . 
     FIG. 7 is top plan view of an upper or first end plate forming part of the charge tube assembly illustrated in FIG.  1 . 
     FIG. 8 is bottom plan view of a lower or second end plate forming part of the charge tube assembly illustrated in FIG.  2 . 
     FIG. 9 is bottom perspective view of the charge tube assembly illustrated in FIG. 2, positioned within a perforating gun. 
     FIG. 10 is top perspective view of the charge tube assembly illustrated in FIG. 1, positioned within a perforating gun. 
     FIG. 11 is a perspective view of an alternative configuration of upper or first end plate. 
     FIG. 12 is a perspective view of an alternative configuration of lower or second end plate. 
     FIG. 13 is a top plan view of an alternative configuration of upper or first end plate. 
     FIG. 14 is a perspective view of an alternative configuration of lower or second end plate. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment, a charge tube assembly for a perforating gun generally identified by reference numeral  10 , will now be described with reference to FIGS. 1 through 14. 
     Various embodiments of charge tube assembly  10  will be described. All embodiments that will be described have tubular bodies with opposed ends. Integrally formed engagement members are formed at each of the opposed end. Detachable end plates are secured to each of the opposed ends. Each of the end plates has openings engagable with the engagement members. The embodiments have been selected to demonstrate that the form of engagement members and the form of end plates can vary widely. 
     Structure and Relationship of Parts 
     Referring to FIGS. 1 and 2, charge tube assembly  10  includes a tubular body  12  having an upper or first end  14  as illustrated in FIG. 1 and a lower or second end  16 , as illustrated in FIG.  2 . Referring to FIG. 5, first end  14  of body  12  has a peripheral edge  18  with three circumferentially spaced inward extending axial slots  20 . Slots  20  divide peripheral edge  18  into three integrally formed arcuate first engagement members  22 . Referring to FIG. 4, first engagement members  22  have deformable locking tabs  24 , as will be hereinafter further described. Referring to FIG. 6, second end  16  of body  12  has a second peripheral edge  26  with circumferentially spaced integrally formed hook form second engagement members  28 . Referring to FIGS. 1 and 4, a disk form detachable first end plate  30  is adapted to mate with first end  14  of body  12 . Referring to FIG. 7, first end plate  30  has a first outer circumferential edge  32  with an outwardly extending alignment key  34 . A three arcuate slotted first openings  36  are provided. Referring to FIGS. 1 and 4, first openings  36  are adapted to receive first engagement members  22 , as will hereinafter be further described. Referring to FIG. 7, first end plate  30  has first radially inwardly projecting members  38  adapted to engage the axial slots  20 . Referring to FIGS. 5 and 7, it will be noted that each of axial slots  20  are made in different sizes, as are each of radially inwardly projecting members  38 . This is done intentionally so that first end plate  30  will only fit onto first end  14  of body  12  in a particular orientation. Referring to FIG. 2, a disk form detachable second end plate  40  is positioned at second end  16  of body  12 . Referring to FIG. 8, second end plate  40  has arcuate slotted second openings  42 . Referring to FIGS. 2 and 3, second openings  42  are engaged by second engagement members  28 . Referring to FIG. 8, second end plate  40  has tool coupling receptacles  44  which are adapted to engage a tool. Referring to FIG.  2  and as will hereinafter be further described, by rotation of second end plate  40  when second engagement members  28  are positioned in second openings  42  of second end plate  40 , second engagement members  28  are moved into a locking engagement with second end plate  40 . 
     Operation 
     The use and operation of charge tube assembly  10  will now be described with reference to FIGS. 1 through 14. Referring to FIGS. 1 and 2, a perforating gun  50  is illustrated that has a barrel  52 . Barrels  52  come in various sizes and may be sized from 2⅞ inches up to 5 inches. It is only by selecting the appropriate size of first end plate  30  and second end plate  40  that charge tube assembly  10  can be adapted for use with a particular perforating gun. The outer diameter of first end plate  30  and second end plate  40  must always be selected to fit the inner diameter of barrel  52 . In addition, second end plate  40  must have an inner diameter to suit a wireline adaptor or a TCP (tubing conveyed product) adaptor. One of the advantages of the present system is that an inventory of detachable end plates can be readily maintained and quickly attached to body  12  to suit the size requirements of the intended application. Having selected an appropriate size of first end plate  30  and second end plate  40 , charge tube assembly  10  can be rapidly assembled. Referring to FIG. 1 and 7, first openings  36  of first end plate  30  are slid over first engagement members  22  at first end  14  of body  12 . As previously described with reference to FIGS. 5 and 7, each of axial slots  20  are made in different sizes, as are each of radially inwardly projecting members  38 . First end plate  30  will, therefore, only fit onto first end  14  of body  12  in a particular orientation. Referring to FIG. 4, once first end plate  30  is in position, tabs  24  on first engagement members  22  are deformed to prevent first end plate  30  from being removed. Second end plate  40  can be just as readily locked into position. Referring to FIG. 2, second openings  42  of second end plate  40  are slid over second engagement members  28 . Referring to FIG. 3, second end plate  40  is then rotated to until second end plate  40  is engaged by the hook like portions of second engagement members  28 . 
     Referring to FIGS. 1,  2 ,  9 ,  10 , once assembled, charge tube assembly  10  must be inserted into barrel  52  of perforating gun  50 . Referring to FIG. 1, alignment key  34  is used to ensure the correct orientation of charge tube assembly  10  within barrel  52 . Referring to FIG. 2, charge tube assembly is supported from below by a snap ring  54 , that engages second end plate  40 . 
     Variations and Alternative Embodiments 
     FIGS. 11 shows an alterative form of first end plate, identified by reference numeral  130 . FIGS. 12 and 14 show different sizes of an alternative form of second end plate, identified by reference numeral  140 . Referring to FIG. 11 first end plate  130  has first openings  136  to receive first engagement members  22 . However, the configuration of first openings  136  differs from first openings  36  in first end plate  30 . First openings  136  in first end plate  130  are cavities  137  positioned along an inner sidewall  139  which defines a central bore  141 . Referring to FIG. 12, second end plate  140  has second openings  142 . However, the configuration of second openings  142  differs from second openings  42  in second end plate  40 . Second openings  142  in second end plate  140  are cavities  137  positioned along an inner sidewall  139  which defines a central bore  141 . Referring to FIG. 13, an alternative form of first end plate  230  is shown with openings  236  that have a different shape and which are not of uniform dimensions. 
     In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. 
     It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the claims.