Self-cleaning filter for cleaning liquids from suspended matter

A self-cleaning filter for cleaning liquids from suspended matter comprises a container with filtering partitions which divide said container into parallel sections for the contaminated liquid and into a cleaned-liquid section located between the first two sections. Each contaminated-liquid section is provided with a device for backwashing the filtering partition, said device being installed with a provision for moving over the filtering partition, being pressed flexibly against it and comprising a hollow body which is open at the side of the filtering partition and communicates with the atmosphere. Arranged around the entire perimeter of the body at its open side is a circular recess with through holes in its bottom. In this recess is installed a mating plate capable of reciprocating therein so that there is a clearance between its face and the bottom of the recess, said clearance forming a chamber which communicates with the contaminated-liquid section through said holes. The mating plate is made of an elastic material. Such a solution ensures a high quality of cleaning of the filtering partitions with a resultant increase in the capacity and reliability of the filter.

The present invention relates to cleaning devices and more particularly it 
relates to self-cleaning filters for cleaning liquids from suspended 
matter. 
The present invention can be used most successfully for cleaning river, 
utility and return water, industrial waste water fruit and vegetable 
juices and in various industries, e.g. chemical, metallurgical, paper, 
food, etc. 
Known in the previous art are self-cleaning filters for cleaning liquids 
from suspended matter (see, for example, Author's Certificate No. 210,092, 
Cl. BO1d MK, USSR) comprising: a container accommodating at least two 
filtering partitions which divide said container to form parallel sections 
for contaminated liquid and at least one section for cleaned liquid 
located between said first two sections; pipe connections for delivering 
contaminated liquid into the sections and discharging the cleaned liquid, 
and devices for backwashing the filtering partitions. Each backwashing 
device is installed in one of the contaminated-liquid sections with a 
provision for moving over the filtering partition, is flexibly pressed 
against the latter, and comprises a hollow body which is open at the side 
facing the filtering partition, communicates with the atmosphere and 
adjoins a circular mating plate at the open side along the perimeter. 
The contaminated liquid is fed into these filters under pressure. Each 
backwashing device is mounted in a frame which is secured rigidly on a 
hollow drive shaft. The hollow body of said device is installed freely in 
the frame and connected therewith by springs which press it against the 
filtering partition. Each body is provided with six springs, three at each 
side. The mating plate is made of metal, eg. bronze, and is rigidly 
secured to the body. 
Due to nonuniform tension of the springs, such a layout of the device 
causes cocking of the body with the mating plate on the filtering 
partition. As a result, the mating plate is subjected to heavy wear since 
it contacts the filtering partition only by one edge instead of by the 
entire surface. Besides, cocking of the mating plate creates a clearance 
between its lower surface and the filtering partition. The contaminated 
liquid leaks through this clearance past the filtering partition directly 
into the body of the backwashing device and is thrown out of the filter 
through the hollow shaft thus reducing the filter capacity. 
As the filtering partition becomes gradually clogged, the pressure 
difference between the contaminated and clean liquid sections increases 
causing the filtering partition to deflect. If the mating plate is made of 
metal, this fails to ensure its tight contact with the filtering partition 
while the latter is being washed. The clearance between the mating plate 
and the filtering partition reduces the pressure difference between the 
cleaned-liquid section and the hollow shaft communicating with the 
atmosphere and this impairs the quality of cleaning the filtering 
partition from the trapped suspended matter and, in turn, reduces the 
capacity and reliability of the entire filter. 
The main object of the invention resides in providing a self-cleaning 
filter for cleaning liquids from suspended matter comprising a backwashing 
device whose design would rule out cocking of the mating plate on the 
filtering partition and ensure tight contact of said plate with the 
filtering partition thus improving the standard of cleaning of said 
filtering partition, raising the capacity and reliability of the filter. 
This and other objects are accomplished by providing a self-cleaning filter 
for cleaning liquids from suspended matter comprising a container which 
accommodates at least two filtering partitions, said partitions dividing 
the container into parallel sections for contaminated liquid and at least 
one section for the cleaned liquid located between the first two sections, 
pipe connections for delivering contaminated liquid into the sections and 
discharging the cleaned liquid, and device for backwashing the filtering 
partitions, each device being installed in one of the contaminated-liquid 
sections with a provision for moving over the filtering partition, being 
flexibly pressed against it and comprising a hollow body which is open at 
the side directed to the filtering partition, communicates with the 
atmosphere and adjoins a circular mating plate at the open side along the 
perimeter. According to the invention, the body of the backwashing device 
is provided along its entire perimeter at the side facing the filtering 
partition with a circular recess whose bottom has through holes and the 
mating plate is installed in said recess with a provision for 
reciprocating therein so that there is a clearance between the face of 
said plate and the bottom of the recess, said clearance forming a chamber 
which communicates with the contaminated-liquid section through said 
holes. 
Such a solution provides additional uniform pressing of the mating plate 
against the filtering partition due to the utilization of the pressure 
built up by the contaminated liquid in the section which rules out cocking 
of the mating plate on the filtering partition and thus reduces its wear 
and raises the filter capacity. 
It is practicable that the mating plate should be made of an elastic 
material. 
Such a solution makes it possible to compensate for the clearance between 
the mating plate and the filtering partition caused by its deflection in 
case of an increased pressure difference in the sections which makes for a 
more efficient cleaning of the filtering partition from suspended matter. 
This steps up the capacity and reliability of the filter.

The self-cleaning filter for cleaning liquids from suspended matter 
comprises a cylindrical container 1 installed vertically on a foundation 
(not shown in the drawing). The container accommodates filtering 
partitions 2 identical in shape to the cross section of the container 1; 
said partitions divide the container into parallel sections 3 for the 
contaminated liquid and a section 4 for the cleaned liquid, located 
between the first two sections. The container 1 is provided with pipe 
connections 5 for delivering contaminated liquid into the sections 3 and a 
pipe connection 6 for discharging the cleaned liquid from the section 4. 
The pressure difference between the sections 3 and 4 is minimum, ranging 
from 0.1 to 0.2 kgf/cm.sup.2. 
Installed in each contaminated-liquid section 3 is a device 7 for 
backwashing the filtering partition 2. Said device is assembled in a frame 
8 rigidly secured to a hollow shaft 9 which is provided with an individual 
drive 10 at one of its ends. The shaft 9 is installed along the vertical 
axis of the container 1. The other end of the hollow shaft 9 is provided 
with a valve 9a communicating the inside space of the shaft with the 
atmosphere. The backwashing device 7 has a hollow body 11 (FIGS. 2 and 3) 
which is open at the side facing the filtering partition 2 as shown in 
FIG. 3. This body 11 has the shape of a semicylinder (as shown in FIG. 4) 
with closed ends and its length is equal essentially to half the diameter 
of the filtering partition 2. The body 11 is freely installed in the frame 
8 and connected with the latter by springs 12 which are fastened at one 
end to the frame 8 while at the other end they are secured to a bracket 13 
fastened rigidly to the body 11. These springs 12 press the backwashing 
device 7 flexibly against the filtering partition 2. At the bottom of the 
body 11, along its entire perimeter, there is a wider portion 14 provided 
with a circular recess 15. This recess 15 accommodates a mating plate 16 
installed with a provision for reciprocating therein. According to the 
invention, said mating plate is made of an elastic material, e.g. 
polypropylene, polyethylene or caprolon. A clearance between the face K of 
the mating plate and the bottom of the recess 15 forms a chamber 17. The 
bottom of the recess 15 beyond the space of the body 11 (as shown in FIG. 
3) has through holes 18 (FIGS. 2 and 3) which put the chamber 17 in 
communication with the contaminated-liquid section 3. The body 11 is 
communicated in a conventional manner by a flexible hose 19 (FIG. 1) with 
a hollow shaft 9 which communicates with the atmosphere through the valve 
9a. 
The self-cleaning filter functions as follows. 
The contaminated liquid is delivered under pressure through the pipe 
connections 5 into the contaminated-liquid sections 3 of the container 1. 
Passing through the filtering partitions 2, the liquid is cleaned of the 
suspended matter and enters the cleaned-liquid section 4 wherefrom it 
flows to the consumer through the pipe connection 6. As the filtering 
partitions 2 become gradually clogged, their hydraulic resistance grows 
which increases the pressure difference between the sections 3 and 4. As 
the pressure difference reaches the maximum permissible level, the valve 
9a is opened and the drive 10 of the hollow shaft 9 is turned on. This 
causes a pressure difference in the section 4 and in the bodies 11 of the 
backwashing devices 7 which communicate with the atmosphere through the 
hollow shaft 9 and are pressed by springs 12 against the filtering 
partitions 2. As a result, part of the cleaned liquid moves in a 
counterflow through the filtering partitions 2 in the zones occupied at 
the moment by the devices 7 and washes off the trapped suspended matter 
into the body 11 of the backwashing device 7 wherefrom said suspended 
matter is removed through the hollow shaft 9. 
The contaminated liquid flows through the holes 18 in the bottom of the 
recess 15 into the chamber 17 and builds up a pressure therein which is 
equal to the pressure in the sections 3. As a result, the mating plate 16 
is pressed still more tightly against the surface of the filtering 
partition, thus ensuring tight contact between them. The backwashing 
device 7 rotates together with the shaft 9 around the vertical axis of the 
container 1, moving over the entire surface of the filtering partition and 
cleaning it from the suspended matter trapped from the liquid. 
As the initial pressure difference between the sections 3 and 4 is 
restored, the process of washing the filtering partition 2 is completed. 
The valve 9a is closed and the drive 10 of the shaft is turned off. 
As the filtering partition 2 becomes again clogged, its washing is repeated 
and can be carried out on an automatic principle.