Die for a semi-product of a combination nipple that connects a flexible hose to a rigid pipe

Abstract

In a die for forging a metal tube to form a semi-product of a unitary combination nipple, a die body has annular first, second and third inner surfaces, and a die cavity. The die cavity includes a large-diameter outer cavity portion with a uniform diameter defined by the first inner surface and adapted to permit insertion of the tube into the die cavity therethrough, a small-diameter inner cavity portion with a uniform diameter smaller than that of the outer cavity portion and defined by the second inner surface, and a polygonal cavity portion disposed between the outer and inner cavity portions and defined by the third inner surface. The second inner surface is located inside the first inner surface, and the third inner surface is located inside the first inner surface but outside the second inner surface.

I claim:  
     
         1 . A die for forging a metal circular tube to form a semi-product of a unitary tubular combination nipple, the nipple being employed to connect a flexible hose to a rigid pipe, and having an externally threaded pipe-connecting portion, a hose-connecting portion with a plurality of annular grooves formed in an outer surface thereof, and a polygonal portion that is disposed between the pipe-connecting portion and the hose-connecting portion and that can be rotated by a spanner, the semi-product having a large-diameter circular tubular portion to be formed as the pipe-connecting portion, a small-diameter circular tubular portion to be formed as the hose-connecting portion, and a polygonal portion that is disposed between the large-diameter and small-diameter circular tubular portions, the large-diameter circular tubular portion having an outer diameter larger than that of the small-diameter circular tubular portion and equal to that of the circular tube, said die comprising: 
 a die body having an annular first inner surface, an annular second inner surface, an annular third inner surface, and a die cavity which includes 
 a large-diameter outer cavity portion with a uniform diameter that is defined by said first inner surface and that is adapted to permit insertion of the circular tube into said die cavity therethrough;  
 a small-diameter inner cavity portion with a uniform diameter that is smaller than that of said outer cavity portion and that is defined by said second inner surface, said second inner surface being located inside said first inner surface; and  
 a polygonal cavity portion disposed between said outer and inner cavity portions and defined by said third inner surface, said third inner surface being located inside said first inner surface and outside said second inner surface.