29,358. Hencke, H. Dec. 31. Pneumatic filters; rotary filters; discharging solid matter; cleansing.-A rotary vacuum filter, stated to be specially applicable for treating liquids containing substances such as beet-root slices, spent grain, or malt, is arranged so that the vacuum is released under those portions of the filtering-drum where the liquids are supplied, the solids removed, and the medium cleansed. The liquid is supplied by the pipe 44, and the greater part filters into the drum as it revolves on trunnions 8, 9 in the trough 14, which is provided with a perforated false bottom 19. The separated solids adhere to the drum in a layer regulated by a flap 20. The filtering- surface consists of a layer 23 of cotton, wool, metal, silk gauze, or like fabric, supported on a perforated cylinder 22 separated from the inner drum 2 by longitudinal ribs 25, which divide the intermediate space into compartments 26. These compartments communicate by passages 27 with slots 28, 29 in a suction head 30, Fig. 4, connected to an air pump. The head is mounted on bolts 33, screwed into the bearing 10, and pressed by springs 34 against the trunnion. The slots are placed so that the vacuum is released from the compartment 26, which is approaching an auxiliary vacuum drum 38 revolved from the main drum by gearing 45, 46 or by frictional contact. The solids are compressed by the drum, and then released to pass on to the conveyer track 63. The filter-cloth is then cleansed by the brush 42 and by water from a rotary spray pipe 43. Suction starts again when the compartment passes the pipe 44. There is a partition 34<a> between the slots 28, 29, so that, at starting, the compartments 26 in the trough can be submitted to vacuum before those which are leaving the trough on the farther side. It is stated that an arrangement might be made for forcing the air into the compartments released from the suction effect. Apparatus having more than one auxiliary drum 52 is shown in Fig. 10. The material is supplied regularly by blade mechanism 54 from the funnel 53. Suction is applied just after the first drum 52, which distributes the material evenly, and is released just before the last one, which loosens the solids for discharge on to the track 63. The cover 49 may be filled with water for cleaning the filter-cloth. It may, however, be replaced by rods connecting the end-pieces 3 of the frame. Fig. 11 shows arrangements for removing matters collecting in the trough 14. A channel 69 is provided with a conveyer worm, and is either arranged obliquely or has its discharge end inclined, so that solids rising to the side are drained and discharged by the shoot 71. A slide or door 73 may be arranged at the bottom. Nozzles 74 are shown as an alternative means of supplying the liquid to be treated. It is stated that the auxiliary drums may be placed at the bottom of the apparatus. Also that, instead of the filter-cloth and perforated surface 22, the compartments 26 may be provided with walls of a suitable filtering-substance. Porcelain, earthenware, wood, and glass are mentioned in this connection.