Guide rod for standard penetration test equipment

摘要

PROBLEM TO BE SOLVED: To solve the problem such that, in a type of a device where a drive hammer is dropped utilizing a catcher, a coupling is attached to a guide rod by screwing, but tends to become loose, the looseness, although insignificant at first, causing test accuracy to decrease, and, if more serious, bringing about a bad effect such as the breakage of the guide rod.SOLUTION: A release coupling and a knocking coupling 29 are respectively inserted and fastened with screws at both ends in an axial direction of a rod body 23, with a screw-fastened portion being configured with a tapered screw. A clearance 41 is provided between the knocking coupling 29 and the rod body 23. For the tapered screw, the joint hardly becomes loose because a tapered reference plane is also in contact. When worn, the rod body 23 turns in a direction for tightening the knocking coupling 29, so that the vertical interval of the clearance 41 is narrowed down. Therefore, by visually checking the clearance 41, it is possible to determine the exact time to replace the rod body 23.SELECTED DRAWING: Figure 5