A multiple-disc type fluid filter is described wherein the housing includes an outer tubular section, and an inner section having two tubular members with an end plate at one end of one tubular member and securable to an open end of the outer housing section. The two tubular members of the inner housing section include ribs for supporting the filter discs. The end plate and the tubular member to which it is secured are open and constitute one of the filter ports, e.g. the inlet port, and the opposite end of the same tubular member is closed and terminates short of the outer housing section. The second tubular member, which is longitudinally spaced from the closed end of the first tubular member, constitutes the other filter port, e.g. outlet port. The stack of filter discs are all of substantially the same uniform thickness, but there are included a plurality of further discs of non-uniform thickness such as to correct the accumulation of non-uniformities in the latter discs.

BACKGROUND OF THE INVENTION 
The present invention relates to filters, and particularly to the 
multiple-disc type filter such as are now widely used in filtering 
particles from irrigation water and in many industrial and other 
applications. 
The multiple-disc type filter includes a housing in which the filter body 
within the housing is in the form of a stack of like, centrally-apertured, 
filter discs of substantially uniform thickness along their widths and 
having grooved side faces defining filtering channels between the adjacent 
discs in the stack. In some applications of such filters, the outer face 
of the stack of filter discs constitutes the upstream side of the filter, 
in which case the fluid being filtered passes from the outer face to the 
inner face of the stack; and in other applications of such filters, the 
inner face of the stack constitutes the upstream side of the filter, in 
which case the fluid being filtered passes from the inner to the outer 
face through the filter stack. 
Multiple-disc type filters have a number of advantages over other known 
types of filters, for example, the cylindrical-screen type filter. Thus, 
the multiple-disc filter has a larger capacity for removing and retaining 
dirt particles since the dirt particles may be retained also between the 
side faces of the discs, in addition to being retained on the upstream 
surface as in the cylindrical-screen type filter. Another advantage in the 
multiple-disc filter is that it is not as easily ruptured as the screen 
type and therefore there is less danger that because of a malfunction, 
unfiltered water may pass through and clog sprinklers or other devices 
downstream of the filter. The latter advantage is particularly important 
in self-cleaning filters wherein the upstream face of the filter is 
cleaned by a cleaning nozzle which, in the case of a screen-type filter, 
may rupture the screen by particles becoming wedged between the cleaning 
nozzle and the filter screen. 
However, one of the disadvantages of the multiple-disc type filter is that, 
although the filter discs are of substantially uniform thickness, there is 
nevertheless some variation, because of manufacturing tolerances, between 
the discs, and these variations accumulate in the stack. Thus, a variation 
of a mere 0.05 mm. in the thickness of one disc, although within a 
reasonable manufacturing tolerance for an individual disc, becomes 
problematical when this variation is multiplied by the number of discs, 
e.g., 150 discs, in the stack. Such thickness variations when multiplied 
by the number of discs in the stack may result in very significant 
non-uniformities in spacings between the discs, and therefore non-uniform 
filter channels. Moreover, since the fluid being filtered seeks the path 
of least resistance when flowing through the filter body, these 
non-uniformities in the disc spacings may cause "streaming" therethrough, 
thereby actually bypassing the filtering channels. 
SUMMARY OF THE INVENTION 
One object of the present invention is to provide a multiple-disc type 
filter having advantages in the above respects. 
Another object of the present invention is to provide a filter requiring 
but a few simple parts which can be manufactured and assembled at low 
cost, and which can also be conveniently disassembled for cleaning 
purposes. Another object of the invention is to provide a filter which, by 
the addition or substitution of a few simple parts, can be converted to 
one having a manual on-off control, automatic shut-off should the filter 
become overly-clogged, or automatic regulation in response to the outlet 
pressure. 
According to one aspect of the present invention, there is provided a fluid 
filter including a housing having inlet and outlet ports and a cylindrical 
filter body extending longitudinally within the housing, characterized in 
that the housing includes an outer housing section of generally tubular 
configuration open at both its ends; an inner housing section including 
first and second longitudinally-extending tubular members and an end plate 
at one end of the first tubular member and securable to a first open end 
of the outer housing section; and means on the outer face of the first and 
second tubular members for supporting the cylindrical filter body; both 
the end plate and the one end of the first tubular member being open and 
constituting one of the filter ports; the opposite end of the first 
tubular member being closed and terminating short of the outer housing 
section; said second tubular member being open at both ends, with one end 
longitudinally spaced from the closed end of the first tubular member, and 
the opposite open end received within the second open end of the outer 
housing section and constituting the other of the filter ports; a first 
passageway through the wall of the first tubular member between its closed 
end and the end plate, establishing communication between the one filter 
port and the outer face of the filter body; and a second passageway 
between the closed end of the first tubular member and the adjacent open 
end of the second tubular member for establishing communication between 
the outer face of the filter body and the second tubular member 
constituting the other of the filter ports. 
According to another aspect of the present invention, there is provided a 
filter comprising a housing and a filter body therein including a stack of 
a plurality of like, centrally-apertured, filter discs of substantially 
uniform thickness along their widths and having grooved side faces 
defining filtering channels therebetween, characterized in that the stack 
of like filter discs include one or more further discs also 
centrally-apertured but of non-uniform thickness such as to correct the 
accumulation of non-uniformities in the thickness of the stack of like 
filter discs.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The filter illustrated in FIGS. 1-3 of the drawings comprises a housing 
constituted of an outer cylindrical section 2 open at both ends; and an 
inner section including an end wall 4, a first tubular member 6, and a 
second tubular member 8 longitudinally spaced from member 6. End wall 4 is 
secured to one end of the outer tubular section 2 by means of an outer 
ring 10 engageable with annular flanges 12 and 14 formed on end wall 4 and 
housing section 2, respectively, these two members being sealed by an 
annular sealing ring 16 between them. 
End wall 4 of the inner housing section is formed with a central opening 20 
constituting the inlet port of the filter, which opening is in alignment 
with tubular member 6 integrally formed with end wall 4. Tubular member 6 
is of substantially uniform diameter, equal to that of the inlet port 20, 
for most of its length as shown at 6a, but tapers at its rear end 6b and 
is closed by a curved end wall 22. 
Tubular member 8 of the inner housing section is open at both ends and 
constitutes the outlet port 24 of the filter. Member 8 is integrally 
joined to tubular member 6 by a plurality of axially-extending, 
circumferentially-spaced ribs 26 providing passageways 27 between the ribs 
and leading into the interior of tubular member 8. The latter member is 
received within a central opening formed in the outer housing section 2 
and is sealed therein by means of an annular sealing ring 28 engaging an 
inwardly extending rim 29 circumscribing the opening in the outer housing 
section 2. 
Tubular member 6 of the inner housing section is formed on its outer face 
with an annular ring 30 at a location slightly inwardly of end wall 4. 
Annular ring 30 serves as one end stop for the stack 32 of filter discs 
33, applied over the outer edges of the axially-extending ribs 26. The 
filter discs 33 may be of conventional construction, having central 
apertures for receiving the ribs 26, and grooved side faces defining 
filter channels between adjacent discs. These discs are firmly secured in 
stack form by an end ring 34 threadedly received on the outer face of 
tubular member 8. 
The illustrated filter includes a tube 35 having one end connected to the 
downstream side of the filter body 32, and the opposite end connected to 
an outlet tap 36 to provide thereat a pressure corresponding to that at 
the downstream side of a filter body 32, which is substantially the same 
as at the outlet port 24 of the filter. This pressure tap 36 may be used 
to provide an indication of the pressure drop across the filter body, and 
thereby of the amount of dirt which has accumulated on or within the 
filter body, to indicate whether or not the filter should be cleaned. 
The tubular member 6 is formed with a plurality of openings 37 at its end 
just inwardly of the end wall 4. Openings 37 constitute a first passageway 
for the fluid to flow from the filter inlet port 20 to the outer faces of 
the filter stack 32, which outer faces constitute the upstream surface of 
the filter stack accumulating the dirt particles separated by the filter. 
The fluid then passes through the spaces between the filter discs 33 of 
the stack 32, and from there through the spaces between the 
radially-extending ribs 26 joining tubular member 6 to tubular member 8, 
the latter spaces constituting an outlet passageway 27 for the fluid 
leading to the filter outlet port 24. 
It will be appreciated, of course, that port 24 could serve as the inlet 
port whereupon the inner faces of the filter disc stack 32 would 
constitute the upstream surface on which the separated dirt particles 
accumulate, the filtered water then passing through openings 37 and then 
to port 20 which would then constitute the outlet port for the filter. 
As mentioned earlier, the filter discs 33 are all of like construction and 
are of substantially uniform thickness, but nevertheless, because of 
manufacturing tolerances, there variations in their thicknesses which are 
accumulated by the large number of discs within the stack 32. Thus, such 
stacks frequently include as many as 150 discs so that small 
non-uniformities in thicknesses among the discs are so multiplied by the 
number of discs in the stack that the accumulated variations in disc 
thickness become very substantial. The non-uniform spacings between the 
discs thus degrade the filtering action by forming non-uniform filtering 
channels, as described earlier. 
To minimize this disadvantage of multiple-disc filters, the filter 
illustrated in the drawings includes a plurality of further discs, therein 
designated 40, 42, and 44, which are provided to correct the accumulation 
of non-uniformities in the thicknesses of the filter discs 33 of the stack 
32. These corrective discs 40, 42, and 44 are not of uniform thickness 
from their inner to their outer edges, but rather are of varying 
thicknesses, the thickness preferably changing uniformly from the inner 
edge to the outer edge of the respective disc. Thus, corrective disc 40 
illustrated in FIG. 1 has a thickness which is larger at its inner edge, 
the thickness uniformly decreasing to its outer edge; whereas corrective 
disc 44 has a thickness which is smallest at its inner edge and increases 
uniformly to its outer edge. 
Preferably, the assembler or user would be provided with a large number of 
these corrective discs (e.g. 40, 44), of varying thicknesses, some being 
thicker at their inner edges and uniformly decreasing to their outer edges 
as illustrated by disc 40, and others being thinnest at their inner edges 
and increasing in thickness uniformly to their outer edges as illustrated 
by disc 44. The user or assembler would insert the appropriate discs at 
the appropriate locations in the stack in order to correct for any 
accumulation of non-uniformities in the individual filter discs 33 of the 
stack. 
It will be noted that disc 42, which is more particularly illustrated in 
FIG. 3, is of a slightly different construction than the other correction 
discs 40 a designated 42a in FIG. 3, which portion varies in thickness 
from its inner to its outer edge as discs 40a and 44. Thus disc 42 
includes not only the main disc portion and 44 described above, but also 
include a plurality of ribs or arms 42b extending from its outer face in a 
radial direction such as to engage the inner face of the outer housing 
section 2. Thus, when one or more of such correction discs 42 are included 
within the filter stack 32, their radial arms 42b engaging the inner faces 
of the outer housing section 2 provide additional mechanical support for 
the housing, thereby enabling the housing to be constructed of less 
expensive material. 
It will be appreciated that the radial arms 42b could be provided on only 
one of the correction discs 42, as shown in FIG. 1, in which case the 
respective correction disc would preferably be located centrally of the 
filter stack in order to support the midportion of the outer housing 
section 2; on the other hand, the filter stack could include a plurality 
of such correction discs having the radially-extending arms 42b so as to 
provide support at a plurality of locations along the length of the outer 
housing section 2. 
The filter illustrated in FIG. 4 is of the same general construction as 
that of FIGS. 1-3. It also comprises a housing constituted of two main 
sections, namely an outer cylindrical section 102 open at both ends; and 
an inner tubular member 106, and a second tubular member 108 
longitudinally spaced from member 106. End wall 104 is secured to one end 
of the outer tubular section 102 by means of an outer ring 110 engageable 
with annular flanges 112 and 114 formed on end wall 104 and housing 
section 102, respectively, these two members being sealed by an annular 
sealing ring 116 between them. 
End wall 104 of the inner housing section is formed with a central opening 
120 constituting the inlet port of the filter, which opening is in 
alignment with tubular member 106 integrally formed with end wall 104. 
Tubular member 106 is of substantially uniform diameter, equal to that of 
the inlet port 120, for most of its length as shown at 106a but tapers at 
its rear end 106b and is closed by a curved end wall 122. 
Tubular member 108 of the inner housing section is open at both ends and 
constitutes the outlet port 124 of the filter. Member 108 is integrally 
joined to tubular member 106 by a plurality of axially-extending, 
circumferentially-spaced ribs 126 providing passageways 127 between the 
ribs and leading into the interior of tubular member 108. The latter 
member is received within a central opening formed in the outer housing 
section 102 and is sealed therein by means of an annular sealing ring 128 
engaging an inwardly extending rim 129 circumscribing the opening in the 
outer housing section 102. 
Tubular member 106 of the inner housing section is formed on its outer face 
with an annular ring 130 at a location slightly inwardly of end wall 104. 
Annular ring 130 serves as one end stop for the stack 132 of filter discs 
133, applied over the outer edges of the axially-extending ribs 126. The 
filter discs 133 may be of conventional construction, having central 
apertures for receiving the ribs 126, and grooved side faces defining 
filter channels between adjacent discs. These discs are firmly secured in 
stack form by an end ring 134 threadedly received on the outer face of 
tubular member 108. 
The illustrated filter includes a tube 135 having one end connected to the 
downstream side of the filter body 132, and the opposite end connected to 
an outlet tap 136 to provide thereat a pressure corresponding to that at 
the downstream side of a filter body 132, which is substantially the same 
as at the outlet port 124 of the filter. This pressure tap 136 may be used 
to provide an indication of the pressure drop across the filter body, and 
thereby of the amount of dirt which has accumulated on or within the 
filter body, to indicate whether or not the filter should be cleaned. 
The tubular member 106 is formed with a plurality of openings 137 at its 
end just inwardly of the end wall 4. Openings 137 constitute a first 
passageway for the fluid to flow from the filter inlet port 120 to the 
outer faces of the filter stack 132, which outer faces constitute the 
upstream surface of the filter stack accumulating the dirt particles 
separated by the filter. The fluid then passes through the spaces between 
the filter discs 133 of the stack 132, and from there through the spaces 
between the radially-extending ribs 126 joining tubular member 106 to 
tubular member 108, the latter spaces constituting an outlet passageway 
127 for the fluid leading to the filter outlet port 124. 
It will be appreciated, of course, that port 124 could serve as the inlet 
port whereupon the inner face of the filter disc stack 132 would 
constitute the upstream surface on which the separated dirt particles 
accumulate, the filtered water then passing through openings 137 and then 
to port 120 which would then constitute the outlet port for the filter. 
It will thus be seen that the filter of FIG. 1 is constructed of a few 
simple parts which can be produced and assembled in volume and at low 
cost, and which can be conveniently opened for cleaning purposes. 
FIGS. 5-7 illustrate how the filter of FIG. 4, with the addition of a 
minimum of parts, can be converted to perform various additional 
functions, This is accomplished by exploiting the interior of the closed 
tubular member (106 in FIG. 4) to accommodate a valve member which is 
displaced with respect to the inlet openings (137 in FIG. 4) to control 
the flow of the fluid through these openings. 
The filter illustrated in FIG. 5 is adapted for turning on or off the fluid 
flow through the filter under the control of a manual controller, 
genera11y designated 240. Controller 240 inoludes a lever 242 manually 
movable to a first position, as illustrated in FIG. 5, wherein it has one 
passageway 242a connected to the outlet tap 236 for tube 235 connected to 
the interior of the closed tubular member 206, and a second passageway 
242b connected to tap 244 at the filter inlet port 220; thus, in the 
illustrated position of lever 242, the inlet pressure is applied to a 
chamber 246 within tubular member 206. Lever 242 is movable to a second 
position wherein its passageway 242a is connected to port 248 leading to 
the atmosphere, and its passageway 242b is connected to tap 236 leading to 
chamber 246, so that when the lever is in this second position, the 
interior of chamber 246 is vented to the atmosphere. 
Chamber 246 is defined by the closed end 222 of the tapered portion 206b of 
tubular member 206, and a displaceable member or piston 250 movable within 
cylindrical portion 206a of tubular member 206, so that chamber 246 serves 
as a control chamber which is expansible and contractable according to the 
displacement of member 250, Displaceable member 250 carries, at the side 
thereof facing chamber 246, a stem 252 which is aligned with another short 
stem 254 fixed to the closed end wall 222 of tubular member 206. The two 
stems receive a light coil spring 256 tending to bias displaceable member 
250 in the rightward direction, i.e. to expand chamber 246. The opposite 
side of displaceable member 250 carries a second stem 258 which passes 
through an apertured wall 260 secured, as by threading, to the interior of 
tubular member 206. Stem 258 carries a valve member 262 movable towards 
and away from an annular valve seat 264 at the upstream side of the inlet 
openings 237 formed through the wall of the tubular member 206. Valve 
member 262 is received within a cylindrical socket in wall 260 and is of 
smaller cross-sectional area than piston 250. 
It will be seen that the space between piston 250 and wall 260 defines a 
second chamber 266 which is also expansible and contractable according to 
the displacement of piston 250. This second chamber 266 is vented to the 
atmosphere via a vent, generally designated 268, including an opening 268a 
through the wall of tubular member 206, and a second opening 268b through 
end wall 204. 
The operation of the filter illustrated in FIG. 5 will be apparent from the 
above description: 
Thus, when lever 242 of controller 240 is in the position illustrated in 
Fig. 5, the inlet pressure is applied via passageways 242b and 242a of the 
controller, and tap 236 to control chamber 246 within the closed tubular 
member 206. Since chamber 266 at the opposite side of piston 250 is vented 
to the atmosphere, this inlet pressured applied to piston 250 moves the 
piston rightwardly causing its valve member 262 to move across the inlet 
openings 237 and to seat against the annular valve seat 264, thereby 
interrupting the flow of the fluid from the inlet port 220 to the filter 
body 232. 
However, when lever 242 of controller 240 is moved to the second position 
(not illustrated in FIG. 5), wherein its passageway 242a becomes aligned 
with the port communicating with control chamber 246 via tap 236, chamber 
246 is vented to the atmosphere. Although control chamber 266 at the 
opposite side of piston 250 is also vented to the atmosphere, 
nevertheless, the inlet pressure applied to valve member 262 is sufficient 
to overcome the light spring 256 and to move the valve member to the 
illustrated open position with respect to the inlet openings 237, so that 
the fluid passing through the inlet port 220 can thus pass through the 
inlet openings 237 to the outer face of the filter body 232, then through 
the filter body 232, through the space 227 between the radial ribs 226, 
and out through the outlet port 224. 
FIG. 6 illustrates the manner of adapting the filter for automatic shut-off 
when the pressure drop across the filter body therein designated 332, 
reaches a predetermined magnitude indicating that the filter is overly 
clogged with dirt particles. 
Thus, the filter illustrated in FIG. 6 also includes the displaceable 
piston 350 dividing the interior of the closed tubular member 306 into a 
first expansible chamber 346, and a second expansible chamber 366 on 
opposite sides of the piston. Piston 350 is also connected by a stem 358 
to the valve member 362 which is movable towards and away from the valve 
seat 364 in order to control the flow of the fluid through the inlet 
openings 337. 
In the arrangement illustrated in FIG. 6, however, control chamber 346 is 
continuously connected to the inlet pressure by an axial bore 370 formed 
through stem 358. In addition, chamber 366 on the opposite side of piston 
350 is continuously connected to the downstream side of a filter body 332 
by a bore 372 through the tubular member 306 just inwardly of the 
apertured wall 360 secured within the tubular member. The filter 
illustrated in FIG. 3 further includes a coil spring 374 interposed 
between the fixed wall 360 and piston 350 biasing the piston leftwardly, 
i.e. to contract control chamber 346, and thereby to move valve member 362 
away from its seat 368 to fully open the inlet openings 337. 
It will be seen that the filter illustrated in FIG. 6 operates as follows: 
While the filter body 332 is reasonably clean, there will be a small drop 
in pressure through the filter body, and therefore the inlet pressure 
within control chamber 346 will be substantially the same or only slightly 
greater than the outlet pressure within control chamber 366. Accordingly, 
spring 374 will move piston 350 to the illustrated position wherein valve 
member 362 fully opens the inlet passageways 337. 
Now, as dirt accumulates on the outer face of the filter body 332, the 
pressure drop across the filter will increase, so that, while the inlet 
pressure within chamber 346 remains substantially the same, the outlet 
pressure within chamber 366 will drop. When it has dropped to a sufficient 
point indicating that the filter is overly clogged, the inlet pressure 
applied to piston 350 will move valve member 362 against the valve seat 
368 to thereby terminate the flow of the fluid through the filter will 
thus be terminated, which condition will continue until the filter body is 
cleaned to thereby permit piston 350 to move to the position illustrated 
in FIG. 6. 
FIG. 7 illustrates the manner of converting the filter to one for 
automatically regulating the fluid flow in response to the outlet 
pressure. For this purpose, the closed tubular member 406 is again 
provided with a displaceable piston 450, a fixed wall 460, and a valve 
member 462 coupled to the displaceable piston 350 by a stem 458, with a 
spring 474 biasing displaceable piston 450 in the direction attending to 
contract conttol chamber 446 and to expand control chamber 466 on the 
opposite side of the piston 450, which is the condition illustrated in 
FIG. 7. It will be seen that in this condition, valve member 462 is in its 
fully open position with respect to the inlet passageway 437. 
In the arrangement illustrated in FIG. 7, however, control chamber 446 is 
connected to the downstream side of the filter body by means of an opening 
480 formed through the end wall 422 of the closed tubular member 406, so 
that this chamber 446 is now subject to the outlet pressure of the filter. 
In addition, chamber 466 at the opposite side of piston 450 is connected 
to the atmosphere, as in the FIG. 5 embodiment, by an atmospheric vent 
generally designated 468, including an opening 468a formed through tubular 
member 206, and an opening 468b formed through end wall 404. 
The filter illustrated in FIG. 7 thus operates as follows: 
So long as the outlet pressure, which is present within control chamber 
446, does not exceed a predetermined value, piston 450 and valve member 
462 carried by it will be in the positions illustrated in FIG. 7, wherein 
the valve member 462 fully opens the inlet passageways 437. 
However, should the outlet pressure rise above a predetermined value, this 
will increase the pressure within chamber 466 which is applied against 
piston 450, such that the piston moves against the force of spring 474 and 
the force applied by valve member 462, to move the latter valve member 
rightwardly and thereby to partially close the inlet passageways 437 until 
the outlet pressure drops. Thus, the arrangement illustrated in FIG. 7 
automatically controls the inlet passageways 437 to regulate the filter 
outlet pressure. 
While the invention has been described with respect to several preferred 
embodiments, it will be appreciated that these are shown for purposes of 
example only, and that many other variations, modifications, and 
applications of the invention may be made.