Patent GB-349466-A (GB)
Abstract: 349,466. Filters. THORNE, C. B., Hawkesbury, Ontario, Canada. Feb. 25, 1930, No. 6233. [Class 46.] Apparatus for separating particles from the water of pulp mills, paper mills, cellulose plants &c. by passage through screens on which deposited particles form a filtering layer comprises a number of screen chambers, arranged parallel to one another in a tank or channel and each consisting of two screen surfaces spaced apart by a framework, with means for raising the screen chambers out of the tank or channel so that the particles deposited thereon can from time to time be removed by mechanical means or spraying devices. In the apparatus shown in Figs. 1 and 2, the water under treatment is supplied to a compartment 20 and passes under a baffle 19 to the spaces outside screen chambers 26. The water filters into the screen chambers and is discharged through apertures 16, 17, outflow chambers 35, and flow boxes 37 to a sewer 38. The screen chambers 26 slide in guides 30, and between rollers on the frame 18 and are lifted for cleansing by means of pinions on shafts 65 which engage racks fixed to the chambers. When the clogging of any chamber causes reduced flow through the corresponding box 37, a float 43 therein operates a mercury switch 45 and closes a circuit comprising leads 47, 48 and a solenoid coil 49. Movement of the solenoid core releases a lever which operates the clutch of gear driving the corresponding shaft 65 and the screen chamber is raised. The driving gear is automatically reversed to lower the screen. As each screen chamber is raised the corresponding outlet 16, 17 is closed by a belt 94 which is attached to the screen, passes round a roller 95 and is connected to a cable 96 which after passing round rollers 97, 98, is connected to the opposite top corner of the chamber. Means for cleaning the screens is shown in Fig. 5. As a screen is raised the filtering layers on either side are removed by felt bands 81a, which pass round rollers 77, 81, and the material is conveyed to rollers 78 and thence by means of scrapers 82 to troughs 83. Fig. 7 shows an arrangement in which rollers 84 with elongated rubber teeth 85 take the place of the felt bands. In a further alternative arrangement each roller 84 is provided with a single helical blade. In the form of apparatus shown in Figs. 11 and 14 each screen chamber is divided into compartments by vertical partitions 126 which do not extend quite to the bottom. The chambers slide vertically on pipes 121, 123, the pipe 121 serving for the supply of the liquid under treatment to the interior of the chamber and the pipe 123 for the discharge of solid matter separated as the liquid passes outwards through the walls of the chamber. Each pipe 121 is fed from a head box 117 in communication with a common supply receptacle 116. As each element is raised the walls are cleansed by sprays from pipes 176 and the material of the filtering layers falls through the vertical compartments into the space 129 and is discharged thence into the pipe 123 when the element reaches its highest position. The elements are raised by means of beams 143 which rest on triangular hangers connected to endless chains, which pass round sprockets supported by the frame 131 and are in continuous movement. When an element becomes clogged the consequent rise of liquid level in the corresponding box 117 raises a float 171 therein and thereby, when the beams next fall, adjusts catches on the beams so that they engage hooks on the element. The element is consequently lifted by the beams. Valves for the corresponding spray pipes 176 are opened by tension rods 180 at the same time. As the element descends the first liquid passed through the element causes the deposition of a new filtering layer. This liquid is collected by troughs situated outside the elements at a level just below the upper ends of the elements when the latter are in their lowest position, and is returned to the supply for retreatment.