Abstract:
A projectile receiver for receiving and stopping a high velocity projectile used in testing duct pipe which serves as a housing for fiber optic cables, as well as a method of using the projectile receiver, are disclosed. The receiver has a perforated housing that contains a rubber end stop therein adjacent a removable cap. The opposite end of the housing is stepped down to a diameter equal to that of a duct pipe being tested. The projectile receiver may be quickly and easily attached to and detached from a duct pipe to be tested using a clamping device, so that a single projectile receiver can be used to test a plurality of duct pipes in succession.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a projectile receiving system for use in testing the integrity of a duct pipe serving as a housing for fiber optic cables. More particularly, the invention relates to a projectile receiver selectively attached to the terminal end of a duct pipe for safely receiving (and subsequently removing therefrom) a projectile that has been forced through the duct pipe under high pressure. The invention also relates to a method of using the device. 
     2. Description of the Prior Art 
     In the optical fiber industry, small diameter, high-density polyethylene plastic pipes are used as conduits or ducts for housing optical fibers. These duct pipes usually run for many miles, and either lay in bundles in a trench or are aggregated within a larger pipe. Optical fibers are subsequently positioned within these previously placed duct pipes. 
     It, therefore, becomes critical that the length of pipe be continuous and unobstructed such that there is no interference with the optical fibers as they are inserted within the duct pipes. The pipes are, therefore, tested prior to installing the optical fibers therein. Pipes are currently tested for continuity and lack of obstructions by passing a projectile, or “bird”, having approximately the same diameter as the optical fiber through the pipe. 
     Specifically, the bird is placed in a first end of the pipe under high pressure of approximately 375 cfm. Under this high pressure and the force it exerts, the projectile, or bird, moves at high velocity through the pipe. Assuming the projectile reaches the terminal end of the pipe unencumbered, clear evidence is provided that the pipe is continuous and straight. 
     Such tests are performed every mile or so where a manhole, or a hand hole, is provided for accessing the pipe line. In practice, the projectile is inserted in one manhole (or hand hole) and exits at the next manhole (or hand hole) a mile or so away. This process is then repeated throughout the length of the pipe. Given the high speed of the projectile as it passes through the pipe, it is important to provide a safe system for stopping the projectile as it exits the duct pipe so that it does not cause damage to property or person. 
     The prior art addresses this problem by using things such as bales of hay situated near the manhole (or hand hole) opening. Upon exiting the duct pipe, the projectile impacts the hay bales, which impact is supposed to stop the flight of the projectile. The reality, however, is that the projectile often ricochets off the hay bales and causes damage during its wayward flight, both to property and to the body of the person overseeing the testing process. 
     As such, a need exists for a reliable, convenient and effective system for receiving, stopping and retrieving a high velocity projectile used in testing duct pipes. The projectile must be stopped in a safe manner and must be available for retrieval from the receiving device. The receiving device should be easily attached to and removed from the pipe being tested so it can be moved quickly from one pipe being tested to the next. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide a projectile receiver for receiving a projectile from a terminal end of a section of duct pipe being tested. The receiver includes a first section having a first tube with a first inner diameter, wherein the first tube has first and second ends. The receiver further includes a cap releasably secured to the first end of the first tube. The cap has a resilient, compressible end stop secured thereto and received within the first tube when the cap is secured to the first tube. The receiver also includes a second section composed of an apertured second tube having an inner diameter, wherein the second section has first and second ends, and the first end of the apertured second tube is coupled to the second end of the first tube. The receiver further includes a third section having a third tube with first and second ends, wherein the first end of the third tube is coupled to the second end of the apertured second tube and the second end of the third tube is shaped and dimensioned for selective coupling to a duct pipe. 
     It is also an object of the present invention to provide a method for testing fiber optic pipes with the receiver disclosed above. 
     Other objects and advantages of the present invention will become apparent from the following detailed description when viewed in conjunction with the accompanying drawings, which set forth certain embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of the projectile receiver of the invention. 
     FIG. 2 is a cross-sectional view of the projectile receiver of FIG.  1 . 
     FIG. 3 is a cross-sectional view of the projectile receiver of the invention attached to a section of duct pipe and ready for use. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The detailed embodiment of the present invention is disclosed herein. It should be understood, however, that the disclosed embodiment is merely exemplary of the invention, which may be embodied in various forms. Therefore, the details disclosed herein are not to be interpreted as limited, but merely as the basis for the claims and as a basis for teaching one skilled in the art how to make and/or use the invention. 
     With reference to FIG. 1, a projectile receiver  10  is disclosed. The receiver  10  includes a first section having a solid-walled metal first tube  11  with a cap  12  on a first end thereof According to a preferred embodiment, the metal first tube  11  is made of steel, although those skilled in the art will appreciate the variety of materials from which the first tube may be manufactured without departing from the spirit of the present invention. 
     The second end of the solid-walled first tube  11  is attached to a first end of an apertured second tube  13 . The apertured second tube  13  has a plurality of apertures  14  throughout its circumference. The apertured second tube  13  constitutes a second section of the receiver  10 . According to a preferred embodiment, the apertured second tube  13  is manufactured from plastic, specifically, high-density polyethylene. While specific materials are disclosed for the first and second sections of the projectile receiver of the invention, other materials may be utilized without departing from the spirit of the present invention. 
     The solid-walled first tube  11  and the apertured second rube  13 , which have substantially the same inner diameters as one another, are preferably joined by glue. However, it will be understood by those of ordinary skill in the art that the tubes could be joined by any other suitable means and still remain within the scope of the invention. As such, it is contemplated that a mechanical joiner comprising detents and slots may be a suitable alternate joining structure for use in accordance with the spirit of the present invention. 
     The opposite end of the apertured second tube  13  is welded, or otherwise coupled, to a solid-walled third tube  16  which is subsequently connected to a step-down flange  15 . The solid-walled third tube  16  and step down flange  15  form a third section of the present receiver  10 . The step-down flange  15  brings down the inner diameter of the receiver  10  to equal the inner diameter of a duct pipe to be tested. 
     It should be understood that the step down flange  15 , or reducer, is it&#39;s own separate piece of material. It is sized inside and outside to match second tube  13  and third tube  16  exactly. In accordance with a preferred embodiment of the present invention, butt fusion is used to couple the various components. A hot metal iron is used to heat each side of the reducer  15  and the matching sides of the tubes  16  and  13 . These butt fusions are done individually and are pushed together while the fusion of the high density polyethylene takes place. As with the other coupled members discussed above, a preferred coupling techniques is disclosed herein in accordance with a preferred embodiment of the present invention and various coupling techniques may be employed without departing from the spirit of the present invention. 
     With reference to FIG. 2, it can be seen that the cap  12  is removably mounted on the end of the solid-walled first tube  11  via screw threads, with internal threads  18  on the solid-walled first tube  11  and external threads  17  on the cap  12 . Alternatively, the threading arrangement could be reversed with the cap  12  having internal threads and the solid-walled first tube  11  having external threads. Additionally, any other means of attachment that would securely fix the cap  12  on the first tube  11  while allowing the cap  12  to be quickly and easily removed and reattached would also be an acceptable alternative to the arrangement shown. 
     Located within the solid-walled first tube  11  and adhesively attached to the cap  12  is a relatively soft, resilient, compressible end stop  19  for absorbing the impact of the projectile  26  as it is stopped by the receiver  10 . While rubber is one suitable material for the end stop  19 , those of ordinary skill in the art will understand that many other soft, resilient and compressible materials could be used as well. 
     FIG. 3 shows the projectile receiver  10  of the invention set up and ready for use. As can be seen in FIG. 3, a plurality of duct pipes  21 , which will each serve to house a fiber optic cable, are buried, and their ends are accessible via the opening of a manhole or hand hole  20 . The solid-walled third tube  16  of the projectile receiver  10  is connected to one of the duct pipes  21 . In the arrangement shown, a connecting tube  22 , having an inner diameter equal to that of both the duct pipe  21  and the solid-walled third tube  16 , is placed so that one end of connecting tube  22  abuts the end of the solid-walled third tube  16 , and the other end of the connecting tube  22  abuts the terminal end of the section of duct pipe  21  to be tested. At each of these abutments, a clamping member  23 ,  24  is placed over the ends of the two abutting tubes to join them exactly and securely. It will be clear to one of ordinary skill in the art that alternative arrangements for connecting the projectile receiver  10  to the duct pipe  21  may be utilized without departing from the spirit of the invention. Such alternative arrangements include, but are not limited to, direct abutment of the solid-walled third tube  16  to the duct pipe  21 , as well as clamping of the third tube  16  and pipe  21 . 
     In practice, when testing a section of duct pipe  21  both ends of the duct pipe section to be tested are accessed via manholes or hand holes  20 . The solid-walled third tube  16  of the projectile receiver  10  of the invention is secured to the terminal end of the duct pipe  21 , either directly or indirectly. The cap  12  of the receiver  10  is secured onto the end of the solid-walled first tube  11 . A projectile  26 , which is generally an aluminum slug having a diameter approximately equal to the diameter of the fiber optic cable to be inserted in the duct pipe  21 , is placed in the first end of duct pipe  21  under high pressure, typically approximately 375 cfm. 
     Assuming the duct pipe  21  is continuous and unobstructed, the projectile  26  proceeds at high speed from the first end, through the terminal end and into the projectile receiver  10 . As the projectile  26  approaches and enters the projectile receiver  10 , air is forced through the apertures  14  in apertured tube  13 . The passage of air in this way serves to slow the progress of the projectile  26 . The projectile  26  impacts end stop  19 , which absorbs the impact of the projectile  26  and brings it to a stop. The cap  12  is then removed from the first solid-walled tube  11  and the projectile  26  is removed. The projectile receiver  10  is separated from the duct pipe  21  and the entire process is repeated on additional sections of duct pipe  21  until the entire length of the duct pipe line is tested. 
     The ability of the present projectile receiver  10  to be quickly and easily attached to and separated from the duct pipe  21  allows the testing of the duct pipe  21  to be both safe and efficient. By using the present projectile receiver  10 , the potential for the projectile  26  to cause damage to person or property upon exiting the tested duct pipe  21  is substantially eliminated. 
     While the preferred embodiments have been shown and described, it will be understood that there is no intent to limit the invention by such disclosure, but rather, is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention as defined in the appended claims.