Web guide using fluid amplifier

Claim 1

Apparatus for maintaining a lightweight, traveling web in a given path comprising: a. means for guiding the web in the given path; b. means for displacing the guiding means; c. means for controlling the displacing means; and d. means for sensing the web position and actuating said controlling means, the improvement wherein the controlling means comprises a proportional fluid amplifier, including: i. a power stream; ii. first and second output chambers; iii. a first control input for directing said power stream to divide the flow thereof between said first and second output channels in varied proportions, said first control input being in communication with said sensing means for receiving a pressure signal therefrom and being located to divert a greater portion of said power stream flow respectively into said first or said second output channels in response to pressure indicating a deviation of said web in one or the other transverse direction from said given path; said proportional fluid amplifier means providing a substantially immediate response at said output channels to said deviation and maintaining that response continuously until said web returns to said given path; and said guiding means comprises: i. a pair of support members arranged on opposite sides of said path; and ii. a guide member slidably mounted on said support members for movement transversely of said path and having means defining two variable volume chambers at its opposite ends, one chamber communicating with said first output channel and the other communicating with said second output channel, which chambers vary reversely in volume in response to pressure signals from said channels to move said guide member transversely of said path.