Manufacture of pipe thread protectors

A method of manufacturing a cup shaped thread protector comprising a cup shaped or hollow cylindrical member of soft, elastic thermoplastic material having a rear end or closed end wall, a cylindrical side wall and an open forward end,

• a plurality of circumferentially oriented lugs spaced circumferentially from each other on and extending from the inner surface of said side wall and integral therewith, and
• each of said lugs being of a size and shape permitting the same to be forced over the threaded end of a pipe and to fit into and engage the threads thereof to prevent easy and accidental removal therefrom,
• said method comprising:
• providing injection molding apparatus comprising a first mold member having a cylindrical female mold cavity and a second mold member comprising a male mold member having recesses in the surface thereof forming a negative image of said lugs on said cup shaped or hollow cylindrical member,
• placing said second mold member inside said first mold member to define a cup shaped or hollow cylindrical mold cavity,
• injecting hot, fluid, thermoplastic resin into said cup shaped or hollow cylindrical mold cavity to fill the same,
• allowing said resin to cool and solidify in said cup shaped mold cavity to produce said cup shaped or hollow cylindrical member,
• twisting said second mold member a fraction of a turn, sufficient to compress the lugs on said cup shaped or hollow cylindrical member into the cylindrical wall thereof, after said resin has solidified but before the same has cooled substantially.
• withdrawing said second mold member from said cup shaped member and from said first mold member, and
• separating said cup shaped or hollow cylindrical member from said first mold member and allowing said lugs to recover from compression into said cylindrical wall into an inwardly extending position and to cool in such position.