Fluid filtering device

An annular filter disc for use in a fluid filtering device and being of crenellated shape having outwardly directed bay portions alternating with inwardly directed projecting portions, the latter having edges substantially located on a circular envelope substantially concentric with the disc.

The present invention relates to a fluid filtering device comprising a 
housing with inlet and outlet ports through which, fluid to be filtered 
flows into and out of the housing. A cylindrical filter is located within 
the housing with an inner surface thereof in flow communication with the 
inlet port and with an outer surface thereof in flow communication with 
the outlet port so that all flow of the fluid, through the housing, passes 
through the filter. 
The present invention is particularly concerned with such a fluid filtering 
device wherein the cylindrical filter is constituted by a stack of annular 
filter discs which are suitably mounted and held together so as to form a 
tubular cylindrical element, one or both of the adjacent contacting faces 
of each pair of juxtaposed discs being formed with grooves, indentations 
or the like such that fluid passes through the stacked filter discs via 
the grooves or the like, in which grooves or the like any contaminants are 
trapped. Such annular filter discs will hereinafter be referred to as "an 
annular filter disc of the kind specified" whilst a cylindrical filter 
constituted by a stack of annular filter discs of the kind specified will 
hereinafter be referred to as "cylindrical filter of the kind specified". 
With such fluid filtering devices means are generally provided for 
periodically cleaning the cylindrical filter, such means involving the 
creation of a reverse fluid flow through the filter so as to flush away 
entrained contaminants. Preferably the cleaning means is arranged to 
traverse periodically the entire inner surface of the cylindrical filter 
with the reverse flow, at any particular instant, being confined to a 
small area thereof and in this way the cleaning efficiency is increased 
whilst interference with the overall filtering function is reduced to a 
minimum. Fluid filtering devices with such cleaning means have long been 
known. Such a known device is shown, for example, in U.S. Pat. 
specification Ser. No. 828,556. 
With such fluid filter devices the efficiency of the device in effecting 
filtration is dependent, inter alia, on the inner surface area of the 
filter exposed to the fluid throughflow. With a conventional cylindrical 
filter of the kind specified, this area is essentially the area of the 
inner cylindrical surface of the filter. Furthermore, and with fluid 
filter devices having reverse flow cleaning means, the efficiency of the 
cleaning is largely dependent on the degree to which the reverse flow can 
in fact be confined to the small area of the filter at any one time. 
It is an object of the present invention to provide an annular filter disc 
of the kind specified for use in forming a cylindrical filter of the kind 
specified, in which the inner surface area of the filter thus formed is 
substantially increased and in which cleansing efficiency is substantially 
improved. 
According to the present invention there is provided an annular filter disc 
of the kind specified of crenellated shape having outwardly directed bay 
portions alternating with inwardly directed projecting portions, the 
latter having edges substantially located on a circular envelope 
substantially concentric with the disc. 
With a cylindrical filter of the kind specified and constituted by a stack 
of such annular filter discs in accordance with the present invention, the 
inner surface area of the cylindrical filter thus formed is very 
substantially increased as compared with that of filters formed of 
conventional filter discs. In addition however the crenellated shape of 
the discs, creating as they do bay portions, facilitates the concentration 
of the reverse flow cleansing action with a consequently increased 
efficiency of cleansing accompanied by a minimal interference with the 
normal filtration action.

The fluid filtering device shown in FIG. 1 comprises a housing 1 having an 
inlet port 2 and an outlet port 3. As can be seen, the inlet port 2 
communicates with a lower portion 4 of the housing 1 whilst the outlet 
port 3 communicates with an upper portion 5 of the housing 1 which 
portions 4 and 5 are separated by an annular disc 6. Located in the lower 
portion 4 of the housing 1 is a coarse filter 7 whilst located in the 
upper portion 5 of the housing 1 is a fine cylindrical filter 8 formed of 
a stack of annular filter discs in accordance with the invention. The 
relative disposition of the device components is such that fluid entering 
the housing 1 through the inlet port 2 passes through the coarse filter 7 
and via a central aperture in the separating disc 6 into the interior of 
the upper portion 5 defined by the inner side of the cylindrical filter 8 
and from there passes through the cylindrical filter 8 so as to emerge 
from the device via the outlet port 3. Extending through the housing is a 
central discharge conduit 9 which is coaxial with the cylindrical filter 8 
and which is rotatably displaceable by means of a suitable drive mechanism 
10 and which is adapted to communicate with the atmosphere via a valve 
mechanism 11. The portion of the discharge conduit 9 located in the upper 
portion 5 of the housing 1 is provided with a plurality of successive 
inlet limbs 12, each tangentially disposed with respect to the discharge 
conduit 9 and each having a flanged mouth 13 juxtaposed with respect to 
the inner surface of the tubular filter 8. 
The filter 8 is cleaned by arranging for the discharge conduit 9 to be 
vented to the atmosphere via the valve mechanism 11 and to be 
intermittently rotated so that a flushing fluid flow takes place through 
the filter 8 and the inlet limbs 12 and out of the discharge conduit 9. 
As seen in FIG. 2 of the drawings, the cylindrical filter 8 itself is 
constituted of a plurality of stacked annular filter discs 15 of which 
only the uppermost is shown in the drawings. Each disc 15 is of 
crenellated shape and comprises successive inwardly directed projecting 
portions 16 each such portion defining between them an inwardly directed 
bay 17. 
As can be seen from FIGS. 3 and 4 of the drawings, the disc 15 is formed of 
a central layer 18 having formed integrally on either side thereof 
substantially sinusoidal layers 19 on which are formed criss-crossing 
grooves 20. Thus, as can be seen, each inwardly projecting portion 16 is 
formed, on either side thereof with a substantially V-shaped grooved layer 
and with a central web portion. Each portion 16 is coupled to the 
succeeding portion 16 by a bridge portion 21 which is also provided on 
either side thereof with a grooved layer 22. Formed integrally with web 
portions at radially spaced apart locations are apertured coupling lugs 23 
through which pass mounting rods (not shown) serving to mount the stacked 
discs 15 in position. 
As can be seen, each projecting portion 16 is formed with an innermost edge 
24, the edges 24 of all the portions 16 lying on a substantially circular 
envelope concentric with the disc 15 itself. 
In use, and with the stacked discs 15 forming a cylindrical filter 8 and 
with the filter cleaning device constructed and operating in a known 
fashion, the crenellated filter surface is clearly of a relatively 
substantial surface area and this increased area renders the filter as a 
whole more efficient in its filtering action. Additionally however, in 
view of the fact that the stacked discs 15 present bays 17 to the flanged 
mouths 13 of the inlet limbs 12 then, and as can be seen from FIG. 2 of 
the drawings, each bay 17 is successively subjected to the entire reverse 
cleansing flow and thus all the contaminants which may have become trapped 
or entrained in that bay are effectively dislodged and removed. 
It will therefore be readily appreciated that the crenellated shape of the 
discs is instrumental in allowing for the construction of a highly 
efficient filter with increased efficiency of cleaning.