| 摘要 |
1,265,715. Extension rods for percussion drill strings. SANDVIKENS JERNVERKS A.B. 1 April, 1969 [10 April, 1968], No. 17039/69. Heading B4C. [Also in Division F2] A tubular extension rod for a percussion drill string comprises threaded end portions for coupling the rod to other similar rods, one end portion having an external thread and the other end portion a complementary internal thread wherein the external surface of the internally threaded end portion is continuous with and equal in diameter to an unthreaded middle portion of the rod. The Figure illustrates two similar rods connected together. The end surface 15 of the rod 12 abuts against a surface 14 of the rod 11. The abutment surfaces may be conical. The threads are formed in parts of the rods upset radially inwardly. |
