| 摘要 |
A pen carriage assembly for automatic drafting machines is described having a scribe holder reciprocably driven by a pneumatic drive assembly. The scribe holder is driven in two modes, a pressure mode and a gravity mode. In the pressure mode, the pneumatic drive assembly includes a first pressure chamber, the expansion of which forces the movable portion of the assembly downward to move the scribe into writing engagement with the drafting paper. In the gravity mode, the pneumatic drive assembly includes a second pressure chamber, the expansion of which enables the movable portion of the assembly to be released from its support means to drop downwardly due to gravity and also to move the scribe into writing engagement with the drafting paper.
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