Abstract: A vacuum filtration apparatus is provided with one or more vacuum chambers fixedly secured at predetermined positions. The interior of the vacuum chamber alternates between a partial vacuum and atmospheric pressure. An endless filter belt has a horizontal section disposed above the vacuum chamber. A slurry is fed from one or more slurry feeders onto the horizontal section of the endless filter belt so as to create a cake of solid particles. Water is fed from one or more water feeders onto the cake to wash the solid particles on the endless filter belt. The endless filter belt intermittently advances by a predetermined length. When the endless filter belt is stopped, the vacuum chamber is under a vacuum so as to draw the liquid constituent from the slurry, thereby obtaining a purified cake of the solid particles. The vacuum filtration apparatus is provided with a coupling bar at which the slurry feeder and the water feeder is attached.

Abstract: Suction apparatus for holding workpieces such as semiconductor substrates or wafers having different diameters comprises a table having an upper surface with a plurality of concentric circular air grooves having different diameters and a plurality of sleeves in radial arcuately spaced bores, respectively, for selectively switching a vacuum source to all or less than all of the grooves. In a preferred embodiment, each sleeve is rotatable about its axis and has a plurality of axially spaced holes which communicate with the vacuum source through the central axial passage in the sleeve. Correspondingly axially spaced holes in the table connect the respective grooves with the bore and are registerable with the sleeve holes through selective rotation of the sleeve to connect the vacuum source and the grooves.