With reference to
After the aforementioned components are assembled according to the above sequence inside the body (25), the operator is able to proceed macro adjustment of the engraving knife relative to the body (25). However, when proceeding with micro adjustment of the extension of the engraving knife relative to the body (25), there is provided with a safety mechanism to limit the rotation of the adjusting sleeve (22) relative to the body (25). The safety mechanism of the present invention includes multiple positioning recesses (224) defined in a bottom face of the head (221) of the adjusting sleeve (22), a stop (223) received in one of the positioning recesses (224), a slot (251) defined through a top face of the body (25), an urging spring (243) received in the slot (251), a guiding tube (242) received inside the slot (251) and having the urging spring (243) mounted therearound and a urging ball (241) partially received in the slot (251) and urged by the urging spring (243).
After the safety mechanism of the present invention is assembled, it is noted from the depiction of the accompanying drawings that when the urging ball (241) is right below the stop (223), the extent of extension of the engraving knife is set to be zero (0 extension). Rotation of the adjusting sleeve (22) in either directions allows the urging ball (241) to be selectively received in a corresponding one of the positioning recesses (224). No matter how much the adjusting sleeve (22) is rotated, eventually the urging ball (241) engages with the stop (223), which limits further rotation of the adjusting sleeve (22). Accordingly the adjusting sleeve (22) is always kept in contact with the body (25).
Further, everytime the urging ball (241) falls into the corresponding positioning recess (224), a clicking sound is generated to inform the operator how much the adjusting sleeve (22) is rotated, which also performs a positioning effect to the adjusting sleeve (22) to the body (25).
In addition, the mutual cooperation between the pitch of each threading of the adjusting sleeve (22) and the distance between two adjacent positioning recesses (224) provides precise extension of the engraving knife out of the body (25). For example, if the pitch is set to be 1.15 mm, movement of the urging ball (241) from one positioning recess (224) to the adjacent positioning recess (224) provides 0.2 mm extension of the engraving knife. Therefore, if there are five positioning recesses (224), rotation of the adjusting sleeve (22) from the first positioning recess (224) to the fifth positioning recess (224), there will be 1 mm extension of the engraving knife.
In order to facilitate understanding of how much the engraving knife is extended out of the body (25), first marks (A) of different patterns and a second mark (B) are formed on an outer periphery of the adjusting sleeve (22) and the body (25) to indicate the degree of adjustment.
Meanwhile, the adjusting sleeve (22) is provided with a recessed area (225) defined in a top face thereof to receive therein the securing cap (20) having an enlarged head (201) formed on top of the securing cap (20) so that the securing cap (20) is kept on a position where the operator can always have access to operate the securing cap (20).
It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.