GB590146A - Improved raking mechanism for the screens of sewage and like apparatus, and means for automatically cleaning the raking device - Google Patents

Abstract

590,146. Straining liquids. FARRER, Ltd., W. E., and DAVIS, C. April 16, 1945, No. 9395. [Class 16] Rake mechanism for cleaning screens in apparatus for treating sewage, trade wastes &c. comprises a reciprocating carriage carrying a pivotally-mounted or angularly-movable raking device which is caused by a cam or projection to be moved towards the bars of the screen at or near the end of its downward movement, being returned in its operative position by a catch or retaining device until it is released or caused to swing back from its screen-raking position at or near 'the end of its upward movement, or after it has left the screen. In the construction shown, a raking device 3 for removing screenings from the bars 1 of a screen is mounted on a carriage 2 which is reciprocated between guides 4 by means comprising a cable 17, a winding drum 18, and a reversible electric motor 19. The carriage comprises side members 5 connected by crosstubes 6, 7. The raking device 3 is pivotally mounted on the tube 7 and comprises two sideplates, each in the form of a bell-crank lever, the lower arms 11 of which are joined by a bar 12 provided with prongs 13. Fixed to the tube 7 is a rake-cleaning plate 15. As the carriage 2 moves downwardly the raking device 3 is in the inoperative position until a roller 20 comes into contact with a stop 21 on the guide 4, whereupon the raking device is moved so that the prongs 13 engage the screen 1, the device 3 being held in the operative position by means of a catch 23. The stop 21 prevents further downward movement of the carriage 2 so that the cable 17 slackens allowing a balance weight 30 hung from a roller 29 to fall and operate a reversing switch 32. The carriage then moves upwardly until a tappet 33 thereon engages a reversing switch 34. Towards the end of this upward movement a cam 25 engages the catch 23, releasing the raking device which is moved by a balance weight 14 to the inoperative position. In a modification the screen is vertical and cam means on the carriage guides are provided for moving the raking device positively into the operative and inoperative positions.