GB799416A - Improvements in and relating to automatic roller lifting devices for fabric calenders - Google Patents

Abstract

799,416. Fabric calenders. KLEINEWEFERS, P., [trading as KLEINEWEFERS SOHNE, J.]. March 21, 1956 [March 25, 1955], No. 8793/56. Class 42 (1). [Also in Groups XXXVII and XL (c)] In a fabric calender in which a fabric seam 4 is detected by a mechanical-electrical or opticalelectrical feeler and the resulting pulse is employed to release the pressure setting between two pressure rollers 2, 3, two feelers 5, 6 are arranged one in advance of the other but laterally offset and their pulses are tested in a switching device so that the latter responds only if the pulses are transmitted within an interval of time corresponding to the speed of the fabric. By this means the roller pressure is not released by response of one feeler to machine vibration or to a knot or dirty spot in the fabric. The pulses from the feelers are fed to a switching device for a roller-lifting relay, in which the interval of time between the pulses may be tested by the release of delayed relays or by mechanical indexing units, the switching device having been set, for the speed of the fabric. Alternatively, an electronic control may be used; the first feeler operates to fire a thyratron to charge a condenser which then discharges through a variable resistance set according to the speed of the fabric; the condenser potential controls a second thyratron, preventing it from firing on operation of the second feeler if the potential has fallen below a certain value; if the second thyratron fires, it actuates a rollerlifting relay and also fires a tliird thyratron which later switches off the relay and restores roller pressure.