| 摘要 |
An improved knob lock commonly used, which comprises a bell inside. The main part of which is a rotator which is turned by rotating either of the knobs and has two extending-out springs to which are attached a steel ball respectively at their ends. Hindrance rods, which are used to prevent the springs from passing freely, make the springs bend until they are forced past the hindrance rods to knock hard on the bell giving out a ringing sound at the same time. |
