Patent Publication Number: US-5253507-A

Title: Method of forming a spacer used to space end to end piping

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a method of forming a spacer used to separate end to end piping which are to be welded together. 
     A problem prevalent in welding is maintaining the separation of a pipe and the internal shoulder of the fitting to which the pipe is to be welded. The spacer of this invention is of similar construction and function of that spacer in U.S. Pat. No. 4,346,918 granted Aug. 31, 1982. Many industries that utilize the spacer require it to pass a stress corrosion cracking resistance test. This ASTM. G36-87 test involves immersing the spacer in a 42% boiling magnesium chloride solution that accelerates destructive forces to simulate long term usage of the spacer. On all previous occasions when this test has been conducted on a spacer in which all the protrusions were formed at one time, hairline cracks were noticed at the base of the center protrusion after seven days of exposure to the solution, definite evidence of cracking at the base of the center protrusion was noticed after fourteen days of exposure and the spacer actually broke at the base of the center protrusion after twenty-one days of exposure. 
     To alleviate this stress inherent in the spacer due to cold forming, the present method forms the rear or center protrusion of the spacer first allowing stresses from this rear hump to escape or be relieved through the split in the ring. Then, the remaining protrusions of the spacer are formed. This minimizes the compressive stress within the spacer between protrusions. For example, when the test utilizing the magnesium chloride solution is performed on this spacer, no evidence of discoloration, cracking, or deterioration of the rings was revealed after twenty-eight days of exposure to the solution. 
     SUMMARY OF THE INVENTION 
     The forming of the spacer begins with a round wire which is wound around a mandrel to form a circle. A segment is cut from the wire to form a split with the spacer ends being separated from each other. The spacer is then inserted between a male and a female die parts to form the center protrusion. Therefore, the spacer is placed in the die to form the remaining protrusions. 
     Hence, it is an object of this invention to form a spacer which has separated protrusions and which will not fracture between protrusions during long term use. 
     It is another object of this invention to form a spacer which has separated protrusions and can withstand the stress corrosion cracking resistance test. 
     Other objects will become apparent upon a reading of the following description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the invention has been depicted for illustrative purposes only wherein: 
     FIG. 1 shows a perspective view of the male die and the female die used to form the spacer. 
     FIG. 2 is a top perspective view showing the spacer placed on the edge of the female die to form the rear protrusion. 
     FIG. 3 is a top perspective view showing the spacer placed into the center of the female die to form the remaining protrusions. 
     FIG. 4 is a perspective view showing the spacer in completed form. 
     FIG. 5 is a perspective view showing the spacer in its round ring form before it is placed in the dies. 
     FIG. 6 is a sectional view taken along line 6--6 of FIG. 6. 
     FIG. 7 is a sectional view taken along line 7--7 of FIG. 5. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment herein described is not intended to be exhaustive or to limit the invention to the precise form disclosed. It is chosen and described to explain the principles of the invention and its application and practical use to enable others skilled in the art to follow its teachings. 
     Referring to FIGS. 5 and 7, a wire ring 2 is formed from a round MIG stainless steel welding wire 10. The wire is first wound around a cylindrical mandrel (not shown) having a diameter substantially equal to the desired diameter of the completed spacer. The wire is then clipped or cut to remove a section or segment to form an enlarged split 4 between spaced ends 18 of the ring 2, as shown in FIG. 5. 
     The ring 2 is then initially placed in a stamping die 12 by a worker 17 as shown in FIG. 2. The die 12 has a cylindrical male part 6 and a cylindrical female part 8 as depicted in FIG. 1. The female part 8 has three equal angularly spaced elongated grooves 14, generally U-shaped in cross section, formed on its top surface 20. Each groove 14 extends radially from the center of the female part 8 to its outer edge. The male part 6 has three equal angularly spaced elongated lands 16 which are generally of an inverted U-shape in cross section formed on its bottom surface 22. Each land 16 extends radially from the center of the male part 6 to its outer edge. The lands 16 and grooves 14 interfit when the die parts are urged together as illustrated by the arrows in FIGS. 2 and 3. 
     Ring 2 is first positioned at its center portion between the female and male parts of the die 12 such that the arc or edge 24 opposite from the split 25 of the spacer is centered over a groove 14 of the female die as seen in FIG. 2. The die parts are then pressed together forming the center undulate protrusion 26 of the spacer and also flattening the center portion of the spacer. The male die part 6 is then moved away from the female die part 8. The ring is then rotated 180° and centered in the middle of the female die part with protrusion 26 fitted into a groove 14 as shown in FIG. 3. The parts of the die are then pressed together flattening the remainder of the ring and forming the remaining two undulate protrusions 30 and 32 shown in FIG. 4. 
     Previously, when protrusions 26, 30 and 32 were formed at one time in the die, by cold forming, the stresses in the flattened spacer portions between protrusions at the center protrusion 26 were locked in by protrusions 30 and 32 at the center protrusions and were subject to fracture. In the present invention by forming the center protrusions first, the stress within the spacer at the center protrusion is significantly relieved. 
     The above description is not to be considered as limiting the invention to those details above-given, which may be modified within the scope of the following claims.