GB998422A - Improvements in freeness testing apparatus and method - Google Patents

Abstract

998, 422. Paper stock freeness: measuring and/or controlling. BOLTON-EMERSON S.A. Oct. 11, 1962, No. 38597/62. Heading D2A. Apparatus, for testing the freeness of paper stock in a closed paper stock line 23, comprises a standpipe 34 forming a vertical chamber with an open lower end connected to the line 23, a screen 81 mounted across the bare portion of the chamber for separating the fibres from the liquid of the paper stock, and air exhaust and air pressure means connected to the upper portion of the chamber for respectively withdrawing air therefrom to permit liquid to flow upwardly in the chamber, and introducing air therein to clear the chamber of the liquid and the screen of the mat of fibres formed thereon. The pressure and exhaust means are controlled by a cycle timer, or perhaps manually, while the freeness is determined by the maximum level attained by the liquid in the chamber. The standpipe 34, of transparent plastic material, has indicia 63 marked on it. In one embodiment (Fig. 1 not shown) a liquid level recorder makes a permanent record of each freeness test. In another embodiment (Fig. 6) the recorder is replaced by a controller 66 which is connected to Jordan, Claftins or disc refiners by air lines 27, 28 to regulate the refiners when any variation from the prescribed freeness value occurs. The standpipe 34 is either attached to a valve 46 by bolts 87 or pivoted and clamped thereto so that the screen 81, which may comprise a single perforated metal sheet or a fine mesh grid on top of a coarse one, is easily removable. In the standpipe there may in addition be electric probes 70, 71 of different heights connected to an electric circuit 72 to illuminate further visual freeness indicating means 74.