| 摘要 |
An automatically retractable utility knife includes a housing and a blade carrier having a molded return spring, which may be integral with the blade carrier. The return spring is serpentine shaped and constructed of a resilient thermoplastic. The housing includes front and rear guide slots, with the blade carrier having a thumb piece extending through the front guide slot and a thumb piece extending through the rear guide slot for enabling the cutting device to be used by right or left-handed persons. The blade carrier may include a snap-off extension for limiting forward travel of the blade carrier with the snap-off extension in place. A method of manufacturing a utility knife includes the steps of providing a housing having an interior adapted to receive either an indexed blade carrier or an automatically retractable blade carrier, and assembling the housing with either an indexed blade carrier or an automatically retractable blade carrier therein. A locking mechanism for a utility knife includes a resilient locking arm on a first half of the housing, the locking arm having i) an upstanding portion oriented generally perpendicular to an axis of the housing, ii) an actuating arm extending laterally from a free end of the upstanding portion, so that downward force on the actuating arm causes a bending of the upstanding portion, and iii) a locking lip on the free end of the upstanding portion extending laterally in a direction opposite to the direction of bending of the upstanding portion. The second half of the housing includes a locking aperture, and a locking shoulder adjacent to the locking aperture. The locking arm and locking aperture are positioned to become aligned when the halves of the housing are aligned for assembly. The locking mechanism is released by pulling the halves apart in opposite directions generally perpendicular to the housing axis once the actuating arm has been depressed.
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