| 摘要 |
An automatic retractable chalk snap string device having an improved brake structure for selectively braking the spring-biased hub on which the chalk string is retractably wound. The brake control includes a brake lever having a manipulating surface adapted to be engaged by a user's finger, such as the user's thumb, in a rocking motion, permitting the user to apply force in both removing the brake pad from the winding hub and to apply the brake pads to the winding hub in concert with a biasing spring similarly acting to urge the brake pads agains the hub. The hub is provided with projecting brake surfaces to be engaged by the brake pads to provide further improved, positive selective braking action. The arrangement of the brake lever is coordinated with the configuration of the housing of the device to permit facilitated one-hand control of the functioning of the device.
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