Liquid purification or separation – Structural installation – Flume stream type
Patent
1999-10-12
2000-10-03
Lithgow, Thomas M.
Liquid purification or separation
Structural installation
Flume stream type
210162, 210413, E03F 514, E02B 508
Patent
active
061268216
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a raked bar screen for a storm overflow.
Typical sewage systems are designed to accommodate not only normal flows of waste water but also flows of storm water resulting from heavy rainfall, flooding and the like. In a typical system, a storm water overflow is positioned alongside a sewage pipe. In storm conditions, the level of water in the pipe rises and flows up through a horizontal bar screen and out over a weir for discharge into a receiving watercourse. In some installations, the bar screen is arranged vertically. The purpose of the bar screen is to filter out floating solid matter from the waste water and retain it in the sewage pipe, so that the receiving watercourse does not become polluted. To prevent blockage of the bar screen, comb-like devices have been designed to continuously sweep the longitudinal spaces between individual bars of the bar screen during storm conditions.
DE-A-4 215 002 discloses a raked bar screen for a storm overflow. The screen comprises a grid of parallel spaced-apart bars attached at their ends to a framework. A comb assembly is provided with teeth which engage in the spaces between the grid bars. The comb assembly is pivoted about a central point above the grid and is caused to swing to and fro by a drive unit. The comb teeth accordingly sweep longitudinally back and forth between the grid bars. While this system satisfactorily keeps the central part of the grid free from solid blockage, it tends to sweep solid matter to each longitudinal end of the grid. As this solid matter builds up at each end, the amplitude of swing of the comb assembly is reduced. Not only is the effectiveness of filtration of the screen reduced, but mechanical stresses build up in the linkage with the drive unit, and can lead to breakdown.
GB-A-2 310 382 discloses a sewage screen having at least one pocket extending downstream of at least some portions of the screen, in relation to an intended direction of flow, to accommodate inorganic debris. Portions of the screen may slant upwardly at the ends. However, the screen is arranged in an upwardly extending overflow shaft, so solid material tends to accumulate in the pockets rather than being swept along in the flow of the sewage conduit.
The present invention provides a solution to the foregoing problems.
According to the invention, there is provided a raked bar screen for a storm overflow, comprising a grid of parallel spaced-apart bars attached at their ends to a framework; a comb assembly having teeth adapted to engage in the spaces between the grid bars, the comb assembly being longitudinally reciprocable, whereby the comb teeth can sweep longitudinally back and forth between the grid bars from end to end; the grid bars being shaped to provide a straight central portion and longitudinal end portions which are angled in relation to the straight portion, whereby in use sweeping of the comb teeth between the grid bars at the angled end portions will drive out entrapped solid matter; the framework including a solid cap portion joined to the ends of the bars and extending transversely thereto, and having a flat underside; and the comb teeth each having leading and trailing edges, a flat top edge and a bottom edge, the comb teeth being positioned such that, at their extremity of travel, the leading edges protrude through the angled end portions of the bars, and the top edges contact and slide at least partly along the underside of the solid cap portion.
The grid is preferably arranged substantially horizontally. The end portions of the grid bars are preferably upturned at an acute angle a which is less than the acute angle B formed between the leading and trailing edges of the comb teeth with the central portion of the grid bars. At their extremity of travel, the leading edges of the comb teeth protrude through the angled end portions of the grid bars.
The solid cap portion which supports the ends of the grid bars preferably incorporates a knife edge arranged near each end of the grid bars so as to scrape adhered solid matter
Lithgow Thomas M.
T J Brent Limited
LandOfFree
Raked bar screen does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Raked bar screen, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Raked bar screen will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-191475