| 摘要 |
<p>MAINTENANCE OF CONSTANT WEB CLEARANCE AT CONTACTLESS TURNING GUIDE In a contactless turning guide controlling a running web through a change of direction, pressure air from a source thereof is delivered into a plenum chamber, from which it issues through slots that direct it between the web and a curved guide surface, to form a pressurized air cushion on which the web floats out of contact with said surface. A damper that controls flow of pressure air into the plenum chamber is automatically so positioned by a servo as to maintain a constant distance between said surface and the web, notwithstanding variations in web tension. For control of the servo, a supply pressure sensor produces a first output corresponding to above-atmospheric pressure of air in the plenum chamber, a cushion pressure sensor having an inlet at said surface produces a second output corresponding to above-atmospheric pressure in the air cushion, and a ratio-forming device to which said outputs are fed produces a ratio signal corresponding to a ratio relationship between the first and second outputs In a comparison device, the ratio signal is compared with a manually adjustable set-point signal to produce a control output which is so applied to the servo as to maintain said relationship substantially constant.</p> |
