Abstract: A single-stage servovalve has a movable member operatively arranged to selectively divide a continuously-discharged fluid jet between two receiver passages. The hydraulic output of the valve is the differential between the conditions in the receivers. In the event of a hard-over failure of the control system of which the servovalve is a part, a jet deflector surface becomes operative to create a substantially balanced hydraulic condition in the receiver passages, thus terminating control.

Abstract: Apparatus for controlling the infeed speed of a web of material relative to the outfeed speed so that damage to the web will be minimized. The control apparatus senses the length of a loose loop formed by the web and includes a moving belt provided with perforations along its length and which is, in part, positioned between a vacuum chamber and the downwardly depending portion of the web loop. The downwardly descending portion of the web loop is held in contact with the adjacent surface of the perforated belt by a low level vacuum in the vacuum chamber and the position of the loop, with respect to the number of the holes in the belt covered by the downwardly descending portion of the loop, regulates the degree of vacuum in the vacuum chamber. As the loop lengthens, the vacuum increases in a vacuum chamber behind the belt, conversely, when the loop shortens, the vacuum in the chamber decreases. A signal corresponding to the vacuum in the vacuum chamber is communicated to a pressure transducer-amplifier.

Abstract: In a web feed apparatus wherein a section of the web is maintained at a higher tension while accurately metering the feed of the web at a relatively lower tension, and wherein means are provided to isolate the low tension metering function from the higher tension section by anterior snubbing rolls, the web tension is controlled by modifying the gain produced by the snubbing rolls and feeding back any increase in tension from the lower web tension level to the higher web tension level. Such a gain is modified by controlling the total angle of wrap of the web about the snubbing rolls, or by varying the coefficient of friction between the web and the snubbing rolls.