| 摘要 |
<p>Multiple threaded screw comprises a shaft (4) with end sections (41, 42), a first threaded unit (5) containing a first spiral thread (51) and a second threaded unit (6) having a structure with a double rotation with two second spiral threads (61). Preferred Features: The first spiral thread has a lower end. The end section (42) of the shaft has a tip, one of the second spiral threads has an upper end joined to the lower end of the first spiral thread and a lower end extends up to the tip of the end section (42).</p> |
