Abstract:
A tool and related method uses an insert for lap splicing two end to end connected tubes to one another. The insert is formed from plurality of members which together are receivable into the internal size and shape of the internal tubular member. The insert can be pulled out of the tubular members once the lap joint is formed. The invention also resides in a tool which locates a flange onto the outside surface at the end of the tubular member to effect registration of it in a flush and perpendicular manner.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an improvement in waveguide fabrication, and relates more particularly to an improved method of connecting end to end placed tubular members as well as improvements in connecting a waveguide tubular member perpendicularly to an end flange. 
     High power multi-carrier microwave space antenna waveguides are important to the communication capability of a satellite which is oribiting the earth. Conventional waveguides are hollow tubes made preferably from a graphite composite and are subsequently metal plated to effect electrical conductivity. Usually the plating used is copper or silver. 
     The process of launching satellites into space involves a very weight conscious process. It has been calculated that the cost for launching a pound of payload material into space is on the order of many thousands of dollars. Therefore, it is incumbent upon satellite manufacturers to use materials which are light weight, yet function with equal effectiveness as conventional metals such as aluminum. Thus, the use of graphite composite or other composite materials in the fabrication of waveguides has evolved as a standard practice. However, the fabrication of joints using composite materials which require exacting standards is problematic given that processes, such as, milling or machining, are not usually part of composite joint construction. 
     Accordingly, it is an object of the present invention to provide a method and tool for aligning tubular members used as waveguides in a satellite and connecting same with exacting tolerance. 
     It is a further object of the invention to provide a method for connecting the end of a tubular waveguide to a waveguide mounting flange at a perpendicular angle with repeatable accuracy. 
     A further object of the invention is to provide a continuous free path of conduction within the metal plated waveguide that does not allow RF energy within the waveguide to leak out. 
     Still a further object of the invention is to provide a method and apparatus which overcomes edge effects at waveguide ends due to bowing of the walls by keeping the cross section of the tubular members at the required dimensions during bonding. 
     Still a further object of the invention is to provide a tool which is readily removable and requires minimum work once bonding is complete for removal. 
     Yet still a further object of the invention is to keep excess adhesive on the inside of the waveguide contained close to the inner wall in the embodiment of the butt joint connection. 
     Still a further object of the invention is to provide tooling which is extracted from the waveguides using readily available means such as string. 
     Still yet a further object of the invention is to overcome the other problems known with edge effects at waveguide ends by keeping the cross section of the tubular members at required dimensions during bonding. 
     SUMMARY OF THE INVENTION 
     The invention resides in a method of connecting two tubular members in an end to end manner each having an internal confine extending in a longitudinal direction, wherein the method comprises the steps of: providing a tool correspondingly sized and shaped to fit within the hollow tubular confine of each of the tubular members; positioning the tool between the opposed ends of each tubular member such that a portion of the tool extends into one tubular member and portion of the tool extends into the other tubular member thereby bridging the two tubular members; applying adhesive and an exterior strap or straps between the opposed ends of each of the one and another tubular members and the tool, and constructing the tool from a material which does not adhere, or covering the tool with a material which does not adhere, to the adhesive used in forming the joint. 
     Ideally, the step of positioning the tool between the opposed ends of the tubular members further includes the step of first positioning the tool within one end of the one tubular member such that a portion of the tool extends outwardly therefrom and telescoping the other of the tubular members over the portion of the tool extending outwardly from the one tubular member and abutting the juxtaposed edges of the ends of the tubular members with one another. 
     Desirably, the tool is provided as a plurality of interconnected parts to make up a rectangular solid by providing each of the plurality of interconnected parts with longitudinally extending mating members which ate correspondingly sized and shaped to fit within corresponding members formed on the part to which one part is connected. 
     The step of providing the tool as a plurality of interconnected parts includes the step of connecting each of the plurality of parts making up the tool with a string or other connecting device and connecting at least two of the plurality of parts with the string in opposite directions within each of the tubular members and waiting for the adhesive to cure and thereafter pulling each of the strings apart from the outside end of the members to disassemble the tool from the connection joint. 
     The invention also relates to an apparatus having a central axis for aligning and butt connecting two tubular members to one another and comprises a plurality of parts each of the parts having one side edge and another side edge; the one side edge of one of the parts and the other side edge of the other of the parts having corresponding shaped portions which interfit and correspond to the height or width of the tubular member and are laterally slidable relative to one another such that when the one side edge and the other side edge of the parts are placed together the tool has a closed shape; and wherein the correspondingly shaped portions of the parts of the apparatus extend parallel to the central axis of the tool such that the parts slide relative to one another axially. 
     The invention further resides in a method of mounting and bonding a flange to a tubular member comprising the steps of: providing a tool having a base plate having an accurately formed top surface and a central point thereon; providing an insert correspondingly sized and shaped to be closely received within the inner confine of the tubular member; securing the flange to the base plate at a predetermined location relative to the central point thereon; providing the flange such that it has an inner surface which comes into contact with the tubular member outer surface; locating the insert within the tubular member and securing the insert to the base plate relative to the central point and applying adhesive between the flange inner surface and the tubular member outer surface in order to bond the surfaces together. 
     The invention also resides in an apparatus for locating a flange on a tubular member comprising: a base plate having a center; a plurality of primary holes formed geometrically about the center; the base plate having a plurality of secondary holes formed radially outwardly of the center beyond the primary holes; the secondary holes corresponding to the position of holes in a flange to be connected to a tubular member; an insert having a shape corresponding in size and shape to that of the interior surface of the tubular member; and the insert being located by some means (e.g. a hole) such that the central axis of the insert corresponds to the central point on the base plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical sectional view of the butt joint tool of the first embodiment taken through line  1 — 1  of FIG.  4 . 
     FIG. 2 is a side elevation view of the tool shown in FIG.  1 . 
     FIG. 3 shows an end view of the tool shown in FIG. 2 fabrication. 
     FIG. 4 is a vertical sectional view through the waveguide showing the tool during assembly. 
     FIG. 5 is an assembly view of the joint of the second embodiment. 
     FIGS. 6 a ,  6   b  and  6   c  are respectively a bottom view, a vertical section view and a top view of the waveguide insert. 
     FIG. 7 is a top plan view of the base plate of the connection of the second embodiment of the invention. 
     FIG. 8 is cross sectional view through the base plate taken through line Z-Z′ of FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As seen in FIGS. 1-4 the butt joint alignment and bonding tool illustrated generally as  10  is shown. As seen in FIG. 3, the tool  10  has four interfitted parts labeled respectively  1 ,  2 ,  3  and  4 . These parts when fitted together create a generally solid rectangular shape which is sized and shaped to fit within the correspondingly sized and shaped interior confine of two tubular members  12 ,  12 ′ which are to be butt joined together. The tool  10  has approximately the same outer dimensions as the inner dimensions of the tubular confines of the tubular members, but is about 0.001 to 0.002 inch smaller on each height H and width W dimension as defined in FIG. 3 to allow for easy installation and removal of tool  10 . The parts  1 - 4  are made of Delrin, Teflon or other adhesive non-bonding material that will not scratch or mar the internal surfaces of the tubular member illustrated as  12 , and  12 ′, or is coated or covered with such a non-bonding material. 
     Each of said plurality of interconnected parts  1 - 4  has longitudinally extending complimentary mating side edge portions which are correspondingly sized and shaped to fit within a corresponding portion formed on the part to which the other part is mated. In this way, the tool maintains a generally rectangular shape, but is capable of disassembly by sliding one or more of the parts  1 - 4  axially relative to the others. 
     The tool  10  is used to assemble the joint as illustrated in FIG. 4 such that corresponding waveguide pieces  12 ,  12 ′ fit together. Once the waveguide has been assembled, the tool  10  is removed. To form the assembly of the waveguide, the tool  10  is first placed half way in and half way out of one of the waveguide tubular members  12 ,  12 ′. The second waveguide tubular member is placed over the outwardly extending portion of the tool. Sections of the waveguides  12 ,  12 ′ are butt joined together. Splice straps  14 , 14  are bonded over the joint using clamps to apply pressure. After the adhesive is cured the tool  10  is removed by pulling the tool apart from either end zusing release devices preferably attached to each part  1 - 4  of the tool, for example, strings or other similar devices  1   a ,  2   a ,  3   a  and  4   a , respectively, that are connected to each part  1 - 4  through holes  15 . 
     More specifically, the tool  10  is positioned within and between the waveguide tubular parts  12 , 12 ′ and adhesive is applied at the gap between the two sections. Since the tool  10  occupies the void between the butt joint sections  12 ,  12 ′, adhesive completely fills the gap without voids and without dripping or creating excesses that will change the internal dimensions of the waveguide. Since the tool is made of or covered with a non-bonding material, the adhesive will not attach to it. The two sections  12 , 12 ′ are kept in proper alignment by virtue of the tool  10  being held within the joint acting as would a splice. The distance between the two sections  12 , 12 ′ can be controlled and remains minimal and consistent. The tool  10  in this capacity further straightens any bowing of the walls of the tube at the edges to maintain the desired dimensions during bonding. Any excess adhesive squeezed between the tube and the tool forms a film of approximately 0.001 inch or less, which will not compromise internal dimensions of the waveguide once coated, usually with a metallic material. Thus, interruption of electrical conductivity at the joint is eliminated. It was found in prior productions without such a tool that one or more coatings of silver filled adhesive on the outside of the joint was required to eliminate RF leakage followed by the coating of another adhesive to contain the silver adhesive. This practice is now obviated by the method of the present invention, which completely seals the joint preventing any RF leakage. 
     Referring now to FIGS. 5-7, it should be seen that a waveguide tube illustrated as  20  in FIG. 5 is adhesively bonded to a mounting flange  22  in a perpendicular manner. For this purpose, a tool  30  is provided and includes a base plate  32  having drilled holes  34  and  36  formed therein and a rectangular well  38  formed concentrically around the two holes  34  and  36 . The base plate  32  has an accurately formed top surface  40  which provides a support against which the end edge  41  of the waveguide tube is supported. 
     As shown in FIG. 7, the base plate  32  also has a plurality of mounting holes  42 , 42  surrounding the central openings  34  and  36 . These mounting holes are provided for securing the flange  22  to the base plate in the manner illustrated in FIG.  5 . 
     The tool  30  further has an insert part  50  which is inserted at the end of the waveguide tube proximate the base next to the end edge  41 . The insert part  50  has two through holes  49 , 49  through which are received bolts  52 , 52  which thread into a compression plate  55  located on the top surface of the insert part  50 . 
     The co-action between the bolts  52 , 52  located in the insert part  50  and in the through holes  49 ,  49  is caused by the bolts acting against the base plate  32  through the holes  34 ,  36  to draw the waveguide tube and insert  50  in toward the base plate  32  and maintain same in a perpendicular relationship thereto. The insert part  50  has substantially the same outer diameter, less 0.001 to 0.002 or smaller, as the internal dimensions of the waveguide tube  20 . The insert is made of Delrin or Teflon, or other non-bonding material or coated or covered with a non-bonding material that will not scratch or mar internal surfaces of the waveguide and will not become affected by adhesive which may ooze from the joint during fabrication. 
     The base plate  32  is a flat member made of a metal or other hard material. The mounting flange  22  to be bonded to the waveguide tube  20  is first connected to the base plate  32  of the tool  30  using mounting screws  23 , 23 . The waveguide tube  20  is placed over the insert part  50  and then the insert part  50  of the tool  30  is then installed on the base plate  32  via bolts  52 ,  52  through holes  49 ,  49  of the insert and holes  34 ,  36  of the base plate and screwed into compression plate  55 . Adhesive is at some point applied to the outer surface of the waveguide tube  20  proximate the end  41  and to the inner surface of the flange  22 . In this way, the flange  22  and the waveguide tube  20  will be aligned with the central axis CA such that the flange  22  rests flat and perpendicular to the waveguide tube  20  and the edge  41  of the waveguide tube lies flush with the end face  43  of the flange on the top surface  40  of the base plate  32 . The flange is bonded in one operation and kept perpendicular without any post bonding machining. The tool  30  furthermore straightens any bowing of the walls of the waveguide tube at the edge to maintain the dimensions during bonding. Any excess adhesive that squeezes between the waveguide tube  20  and the insert part  50  will form a film of about 0.001 inch or less which will not compromise the internal dimensions. To these ends, it should also be seen that the base plate  32  further has a rectangular well  38  cut into the tool support surface  40  to receive excess adhesive flowing from the joint. Also, as illustrated in FIGS. 7 and 8, the well  38  has through holes  60  in each corner provided for receiving excess adhesive which will flow downwards between the flange and the waveguide wall, and eliminating said excess adhesive through the holes  60 . 
     The insert part  50  is thus caused to be drawn towards the base plate  32  through the intermediary of the take-up bolts  52 , 52  when tightened. In so doing, the end  41  of the waveguide tube  20  is caused to be drawn against the tooled surface  40  of the base plate  32  by the compressive action of the bolts  52 , 52  drawing it into engagement with the accurately flat surface  40  while the adhesive cures. Thus the end  41  of the waveguide tube  20  is bonded flush with the perpendicular surface of flange  22 . Thereafter, the mounting screws  23 , 23  are unthreaded from the plate  32  and the bolts  52 ,  52  are removed from the tool  30  and the base plate  32  and insert  50  are separated and removed from the now adhesively bonded flange  22  and waveguide tube  20 . 
     Accordingly, the invention has been described by way, of illustration rather than limitation. 
     It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.