| 摘要 |
A flexible band carries jack actuation control means for determining when the machine jacks are moved so that their butts engage the lower cam race and cause lifting of the needles. The control means may be projections carried by the band, or holes in the band through which actuators can project, or light-transmitting regions in the band for controlling light-responsive jack actuators. The band may be endless, and trained about a drum. The jacks are moved vertically when actuated, and a magnet or spring is provided to hold the jacks down when not actuated.
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