GB921546A - Improvements in and relating to screens and screen rake mechanism for use in the treatment of sewage or other flows - Google Patents

Abstract

921,546. Sifting-apparatus. HARTLEYS (STOKE-ON-TRENT) Ltd. Sept. 22, 1961 [Sept. 22, 1960], No. 32514/60. Class 117. A sewage screen has upright channel members 30 at each side and a travelling rake mechanism mounted on carriages 25 having inner wheels 27 which move up and down in the channels, each carriage carrying a pivoted lever mechanism on which the screen rate 32 is supported and which has operating rollers 37 which move in and out of the channels at suitable points in the travel and thereby impart a rocking movement to the levers by which the rake is moved in and out of engagement with the screen. The carriages 25 are secured to the ends of a cross-bar to which the lower ends of chains 22 are attached, these chains passing over sprockets 21 driven from a reversible motor 17 and over idling sprockets 51, their free ends having weights 52 attached, to balance the rake mechanism. The motor 17 is controlled by a limit switch 41 which is actuated by a tappet 40 carried by one of the chains. When the rake 33 is in its lowest position the operation of the limit switch reverses the motor 17 in a direction which raises the carriages 25. The rake 33 is carried on the ends of arms 32 of three-armed levers which are pivoted, one on each carriage, at 31. A second arm 34 carries a weight 35 which biases the rake towards the screen. On the end of the third arm 36 is a roller 37 which strikes a pivoted catch plate 46 near the top of the travel of the rake. The plate 46 is pivoted so that it allows upward movement of the roller 37 but, on the return, downward, movement, it deflects the roller 37, which passes through a suitably placed gap 45 in the channel, and pivots the three-armed lever in a direction to move the rack away from the screen. The return downward movement is caused by operation of the limit switch 41 and consequent reversal of the motor 17. Near the bottom of the travel the presence of a further gap 48 in the channel allows the weight 35 to restore the three-armed lever to its first position. The three-armed lever on the carriage at the other end of the cross-bar is similarly controlled, whereby the rake is moved to and fro as desired. When the rake is at its top position refuse may be swept into a receiver 54 by a rotary brush 55.