Abstract:
The invention resides in a method and apparatus for conditioning an inner surface of a tube. A pressurized mixture of air and grit and is supplied to a nozzle having an opening with a given diameter through which diameter the pressurized grit and air pass. An elongated nozzle adapter is connected to said nozzle. The nozzle adapter has a passage having a diameter substantially equal to the diameter of said nozzle and said nozzle adapter is connected to said nozzle such that the opening in said nozzle and said passage are aligned with one another. The nozzle adapter is inserted into a tube and is axially moved and rotated in order to condition the inner surface thereof with a pressurized mixture of air and grit.

Description:
TECHNICAL FIELD 
     The present invention relates to an improvement in waveguide formation and relates more particularly to an improved method of conditioning a surface on a part made of a composite material, in preparation for subsequent bonding or metal coating applications. 
     High power multicarrier microwave space antenna waveguides are important to the communication capability of satellites. Conventional waveguides are hollow tubes made preferably from a graphite composite and are subsequently coated with a metal to effect electrical conductivity. Usually the metal coating used is copper or silver. The effect of creating a waveguide in a satellite with a composite structure coated with metal is to reduce the mass of the satellite payload by replacing waveguides normally made entirely of metal. In launching a satellite into space, weight of satellite components at lift off into orbit can cost thousands of dollars per pound to launch. Therefore, lightweight yet highly effective component parts of each satellite are mandatory and are an integral part of satellite construction. 
     As illustrated in FIG. 1, a prior art grit blast nozzle  1  is shown. Such a nozzle is commercially available and can be used to condition the inner surface of hollow tubes. However, this nozzle is adapted for use in a direct pressure grit blast system, which unfortunately is not always available or applicable in all manufacturing settings. One problem with this arrangement is that often times in the construction and fabrication of waveguides, it is often necessary to use different types of grit or sandblasting systems. One such other type of system is a grit or sandblasting system which requires a venturi effect to mix the air and grit together. That is, in many instances, only venturi type blasters are available wherein the mixture of grit and air requires a venturi effect to effect mixing. However the use of such a prior art nozzle design shown in FIG. 1 is prohibited in venturi type systems. That is, as seen in FIG. 1, a part of the nozzle  1  at location B is tapered in diameter to effect a constricted flow effect. A venturi effect pressure system has been found not to be functionally acceptable with nozzles as shown in FIG. 1 because of the constricted passage at the section B illustrated in FIG.  1 . This constriction of the air flow illustrated by the arrowheaded lines, hinders the ability of the nozzle to draw grit from the supply and mix it with air and thus to ultimately accomplish the desired grit blasting effect. 
     Accordingly, it is an object of the present invention to provide a grit blast nozzle adapter for surface conditioning of an internal tube which is capable of being used either in a direct pressure or a venturi effect pressure grit blast system. 
     It is a further object of the invention to provide a grit blast nozzle adapter of the aforementioned type whereby the inner surface of a hollow tube is capable of being conditioned in a 360° conditioning arc. 
     Still a further object of the invention is to provide a grit blast nozzle adapter of the aforementioned type wherein registration of said nozzle adapter to the central axis of the tube is affected with repeatability and ease of placement. 
     Further objects and advantages of the invention will become apparent from the following disclosure and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a showing of a prior art direct pressure grit blast nozzle. 
     FIG. 2 is a side elevation view of the grit blast nozzle adapter of the present invention. 
     FIG. 3 is an end view of a waveguide tube showing the grit blast nozzle adapter located in one half of its cross-section. 
    
    
     SUMMARY OF THE INVENTION 
     The invention resides in a method of conditioning an inner surface of a tube comprising the steps of: providing a pressurized mixture of air and grit and supplying same through a conventional nozzle having an opening with a given diameter through which diameter the pressurized grit and air pass; providing an elongated nozzle adapter having a deflector at the free end thereof and connecting the nozzle adapter to the nozzle; providing the nozzle adapter with a passage having a diameter substantially equal to or slightly larger than the diameter of the opening in the nozzle and connecting the nozzle adapter to the nozzle such that the opening in the nozzle and the passage are aligned with one another; said grit and air passing from the conventional nozzle through the nozzle adapter of the present invention and inserting the nozzle adapter into a tube and axially moving and rotating same in order to condition the inner surface thereof with a pressurized mixture of air and grit; and maintaining sufficient force to properly condition the inner surface. 
     The invention further resides in a device for treating an inner surface of a tube comprising: a supply of pressurized mixture of air and grit and a conventional nozzle having an opening with a given diameter through which diameter the pressurized grit and air pass; an elongated nozzle adapter having a deflector at the free end thereof connected to the nozzle; the nozzle adapter having a passage having a diameter substantially equal to the diameter of the opening in the nozzle and means for connecting the nozzle adapter to the conventional nozzle such that the opening in the conventional nozzle and the passage in the nozzle adapter are aligned with one another; and wherein the nozzle adapter is inserted into a tube and axially moved and rotated in order to condition the inner surface thereof with a pressurized mixture of air and grit. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG.  2  and the invention, it should be seen that the invention resides in a tool which employs a nozzle adapter indicated as  10  which is connectable to a conventional nozzle  12  of a grit blast system. The grit blast nozzle  12  is attached to a means  11  by which pressurized air and grit are provided so as to be expelled together through an opening  14  in the nozzle  12  in the indicated direction DD. The direction DD extends perpendicularly to the opening  14  in the nozzle  12  such that the grit is not redirected in a direction other than parallel to the direction DD through the opening  14 . A standard supply line  13  is provided and is threaded to the nozzle  12  at one end  15  thereof in a manner similar to the one shown in FIG. 1 at connection  18  to fluidically connect the means  11  with the nozzle  12 . 
     The means  11  by which the grit and pressurized air are mixed can be one that is conventionally known as a direct pressure system or a venturi pressure system for which the present invention adapter is capable of being used equally alternatively functionally. 
     The nozzle adapter  10  is comprised of a cylindrical hollow tube  30  having an internal conduit  22  therein, a deflector  26  located at and connected to the far end  33  of the tube  30 , and two mounting blocks  34 , 34  which have journalling openings  36 , 36  for receiving therein the circular outer surface of the tube  30 . The one end  15  of the tube  30  has a means  20  for connecting it over the nozzle  12 . This means may take many different forms, but in the preferred embodiment it takes the form of an increased inner diameter ID taken relative to the remainder of the inner diameter D of the tube  30 . The increased dimension of the inner diameter ID is provided such that the end  15  of the nozzle can be press fit over the nozzle end so as to fit snugly thereover. Alternatively, the end  15  may connect to the nozzle  12  using any other equivalent form, such as a screw thread, or over the center latches, but in any event, the connection is such that it does not interfere with the free flow of grit and air through the opening  14  in the nozzle and it is readily detachable therefrom. The tubular member  30  and the nozzle  12  are connected in this way such that each extends coextensively with the central axis CA of the nozzle adapter  10 . The nozzle adapter  10  central axis CA is also parallel to the expulsion direction DD of the grit blast. 
     The tubular conduit  22  has an inner diameter D which is slightly larger in size than the diameter of the opening  14  in the nozzle  12 . At the end  33  opposite from the nozzle end  12  of the tubular conduit  22  is the deflector  26  which is made of a hard material and which connects to the side of the tubular member  30  and is directed inwardly toward the central axis CA. The deflector has a length L such that the projected length, L; is shorter than the diameter D of tubular conduit  22  so as not to cause significant depressurization in the air flow passing through the tubular conduit  22  and impinging on the deflector. Thus a clearance S is provided between the deflector tip  27  and the inner surface of the conduit  22  to effect a flow passage as illustrated by the line DD. The tubular member  30  has a length LL of between 4-12 inches in the preferred embodiments, but could be longer or shorter as required. 
     Disposed about the tubular member  30  is a pair of locating blocks  34 , 34  each of which has a journaling opening  36 , 36  coaligned with one another and sized to receive the outer diameter of the tubular member  30 . The journaling blocks and the outside surface of the tubular member  30  may be provided with a corresponding annular retaining ring/groove arrangement which enables the two blocks to be rotated relative to one another yet be axially maintained positionally relative to one another on the member  30 . The blocks  34 , 34  can be made from many different types of materials, but in the preferred embodiments each is made from plastic. The locating blocks,  34 , 34  are optional; the nozzle can be used with or without them. 
     Referring now to FIG. 3, it should be seen that the waveguide or any tubular member illustrated as  40  has a generally rectangular cross section with side walls SW and long walls LW together creating a rectangular shape. The locating blocks  34 , 34  are square or rectangular in shape in the preferred embodiments and are sized such that the length of each wall W of the locating block is one half the length of the long wall LW and slightly smaller than SW of the waveguide if square, and slightly smaller than the walls SW and LW if rectangular. In this way, by sliding the square locating block laterally along the long wall LW (along line SL), the inner surface of the tubular waveguide  40  can be conditioned. That is, in order to treat about one half of the inner surfaces of the waveguide, the locating block is moved in abutment with one side wall SW of the waveguide  40  associated with that wall and then is rotated to condition the associated inner surface. The locating blocks could be circular or any shape to fit the shape of the tubular member to be conditioned. 
     More specifically, by rotating the tubular member  30  through an arc in the direction R with the deflector  26  pointed initially at TP and then after rotation pointing at BP, the right half of the inner surfaces  50  of the waveguide tube  40  are conditioned by the grit blast. In order to condition the other one-half of the inner surfaces of the waveguide tube  40 , the locating block is slid laterally along the length of the wall LW to a point where it abuts the opposite sidewall SW′ of the waveguide tube  40 , and the operation is repeated. By rotating the tubular member  30  through an arc in the direction R′ with the deflector  26  pointed initially at TP′ and then after rotation pointing at BP′, the left half of the inner surfaces  50  of the waveguide tube  40  are conditioned by the grit blast. In this way all the inner surfaces  50  of the waveguide tube  40  are conditioned. When using a rectangular locating block, once one half of the waveguide tube is conditioned as described above, the nozzle adapter and locating blocks are removed from the waveguide tube and reinserted into the waveguide tube with the nozzle adapter in the opposite (unconditioned) half of the waveguide tube and this half is treated in the same manner as described above. In this way, the interior surfaces of the waveguide tube  40  are conditioned by directing the grit blast essentially perpendicular to the surfaces  50  that are being conditioned. This allows the subsequent metal coating to be made in a repeatable uniform manner and also provides for uniform and repeatable adhesion of the metal coating to the inner surface. The nozzle adapter can be simultaneously rotated and moved axially along the length of the waveguide tube  40  in order to cover all the inner surface of the waveguide. 
     By the foregoing, an improved method and apparatus of treating a surface of the waveguide has been disposed in the preferred embodiment. However, numerous modifications and substitutions may be made without departing from the spirit of the invention. In particular, it should be seen that while two locating blocks have been disclosed in the preferred embodiment, it is also possible that a single such block may be used to affect registration of the adapter within the waveguide tube. Also, the tubular member  30  can be varied such that the inner diameter ID of the tubular member  30  can in fact be made equal to the opening diameter  14  if a means for connecting the tubular conduit  22  to the nozzle  12  is used such as to allow it to be butted up to the end surface of the nozzle. Also, the shape of the conditioned tube,  40 , can be any shape with adaptations to the locating blocks. Accordingly, the application has been described by way of illustration rather than limitation. While the present invention has been particularly described with respect to a preferred sequence of process steps in its preferred method and certain elements in its preferred embodiment, it will be understood that the invention is not limited to these particular methods and apparatus described in the preferred embodiments, the process steps, the sequence, or the final structures depicted in the drawings. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the scope of the invention defined by the appended claims. In particular, the scope of the invention is intended to include, for example, those devices and methods for conditioning any suitable tube, piping or structure. In addition, other methods and devices may be employed in the method and apparatus of the instant invention as claimed with similar results.