GB485553A - Improvements in or relating to apparatus for producing liquid pulsations through screens - Google Patents

Abstract

485,553. Strainers. OESCH, E. G. Aug. 20, 1936, Nos. 22930/36 and 11386/37. [Class 46] In apparatus of the kind used in the paper industry for the screening of pulp and comprising a set of screen plates mounted in series in a slightly inclined plate over which the pulp flows to separate the fine particles or fibres from the coarse, a chamber is provided beneath each screen plate and, to assist the separation and prevent clogging of the slots, the liquid in the chambers is caused to pulsate by means of fluid pressure acting either on flexible diaphragms forming the bottoms of the chambers, on auxiliary diaphragms connected to the said diaphragms, or, in the case of hydraulic pressure, directly on the liquid in the chambers. The fluid pressure is delivered in the desired sequence to the screen sections by a distributing device connected to the source of fluid pressure and rotating in a casing having ports leading to the individual sections of groups of sections. Fig. 1 shows a screen made up of a series of screen plates e<1> ... e<7> mounted over chambers b<1> ... b<7> in which pulsations are produced by fluid pressure, the pressure being distributed in sequence to the group b<1>, b<4>, b<7>, to the group b<2>, b<5>, and the group b<3>, b<6>. The distribution is effected by a member 5 which is connected to an external source of fluid pressure or may, as shown in Fig. 2, be mounted in a body comprising a pump 1, the member 5 being connected to the outlet 4 of the pump. The member 5 rotates in a casing 7 having ports a, a<2>, a<1>, leading to the groups of screen sections. In the chamber b<7> the pressure acts directly on the liquid in the chamber, the distributing pipe terminating in a diffuser h<7>. In the chambers b<4>, b<5> and b<6> it acts on diaphragms forming the bottoms of the chambers, and in the chambers b<1>, b<2> and b<3> it acts on auxiliary diaphragms c<1>, c<2>, c<3> mounted in chambers d<1>, d<2>, d<3> and connected by stems f<1>, f<2>, f<3>, to the diaphragms forming the bottoms of the chambers b<1>, b<2>, b<3>. Each of the diaphragms on which the fluid acts is maintained in equilibrium by opposing springs, for example g<1> and h<1>, which may be tuned so that the frequency of oscillation of the diaphragms corresponds to the frequency of the pulsations. After the pressure pulse, the fluid flows back into the casing 7 and through the passage 8 either to discharge or to the inlet of the pump 1. If desired separate pipes may be used for conveying the pressure fluid to the chambers and discharging it therefrom.