| 摘要 |
A drive system that normally moves a web of material at a generally constant linear speed includes a device for controlling the size of a loop formed by the web as it is moved through a preselected path. The sensing orifice of a flapper amplifier is positioned relative to the loop and in a preset spaced relation to a surface of the web. Any change in this spaced relation due to a change in the loop size causes the bellows of the amplifier, through an appropriate linkage, to exert a force on a drive control roller having a variable effective diameter. As the roller diameter changes, the linear speed of the web changes and the normal linear speed is attained when the preset spaced relation between the web and sensing orifice is restored.
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