| 摘要 |
PCT No. PCT/GB89/00117 Sec. 371 Date Aug. 3, 1990 Sec. 102(e) Date Aug. 3, 1990 PCT Filed Feb. 8, 1989 PCT Pub. No. WO89/07690 PCT Pub. Date Aug. 24, 1989.The machine includes a reciprocating piston/hammer (10) assembly, which is constrained against rotation in the cylinder (8). This allows the cutting bit to apply concentrated action along a line, and thus is useful for cutting grooves. The cutting bars (40) are arranged in sequence to enter progressively deeper into the groove. Many bits are arranged side by side, for cutting parallel grooves simultaneously.
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