Multi-position valve for backflushing filters

A valve comprises a housing having an inlet port, an outlet port, and a backflush port for discharging the dirt from the filter during a backflushing operation. A first passageway interconnects the inlet port and outlet port, and a second passageway interconnects the outlet port and the backflush port. A displaceable valve member is movable to a filtering position to effect a filtering operation wherein the inlet port is connected to the outlet port via the first passageway, or to a backflushing position to effect a backflushing operation wherein the outlet port is connected to the backflush port via the second passageway.

BACKGROUND OF THE INVENTION 
The present invention relates to a multiposition valve for use in fluid 
lines containing filters in order to backflush the filter. Such valves are 
widely used in water irrigation systems having filters for removing solid 
particles from the water, which filters are periodically cleaned by a 
backflushing operation. 
The presently available backflush valves usually include a housing having 
an inlet port connectable to the inlet line supplying the pressurised 
fluid (e.g., water), an outlet port connectable to the outlet line 
containing the filter, and a backflush port for discharging the dirt from 
the filter during a backflushing operation. Such valves also include a 
first passageway interconnecting the inlet port and the outlet port, a 
second passageway interconnecting the outlet port and the backflush port, 
and a displaceable valve member movable either to a filtering position to 
effect a filtering operation wherein the inlet port is connected to the 
outlet port via the first passageway, or to a backflushing position to 
effect a backflushing operation wherein the outlet port is connected to 
the backflush port via the second passageway. 
A main disadvantage of the presently available backflush valves, however, 
is that they waste considerable quantities of clean water through the 
backflush port. Thus, they normally operate by first connecting the 
backflush port to the outlet port, and then disconnect the inlet port from 
the backflush port. 
An object of the present invention is to provide a backflush valve having 
advantages in the above respects. 
BRIEF SUMMARY OF THE INVENTION 
According to the present invention, there is provided a valve of the 
aforegoing type characterized in that the valve member includes surfaces 
movable with respect to the passageways effective when the valve member 
moves from its filtering position wherein the first passageway is open and 
the second passageway is closed, to the backflushing position wherein the 
first passageway is closed and the second passageway is open, to maintain 
the second passageway closed until the first passageway is closed, and 
then to open the second passageway; and when the valve member moves from 
its backflushing position wherein the first passageway is closed and the 
second passageway is open, to the filtering position wherein the first 
passageway is open and the second passageway is closed, to maintain the 
first passageway closed until the second passageway is closed, and then to 
open the first passageway. 
It will thus be seen that a valve constructed in accordance with the 
aforegoing features eliminates or substantially decreases the waste of 
clean water during a backflushing operation. Another advantage, as will be 
most particularly described below, is that when the valve is actuated from 
the backflushing mode to the filtering mode, the inlet port is opened 
positively and completely to its limit even under low inlet pressure. 
In the described preferred embodiment, the first passageway includes a 
first circular opening, and the second passageway includes a second 
circular opening having a throat whose mouth is coaxial with and faces the 
first circular opening. A sealing ring is carried at the end of the valve 
member facing the second circular opening. The second circular opening is 
of smaller diameter than the first circular opening but its throat is of 
the same diameter as the first circular opening. The valve member is of 
the same diameter as the first circular opening and the throat of the 
second circular opening, and has a length less than the distance between 
the first and second circular openings, but greater than the distance 
between the first circular opening and the mouth of the throat of the 
second circular opening. 
Thus, when the valve member moves from its filtering position wherein the 
first passageway is open and the second passageway is closed, to the 
backflushing position wherein the first passageway is closed and the 
second passageway is open, the valve member within the mouth of the throat 
maintains the second passageway closed until the first passageway is 
closed, and then opens the second passageway. On the other hand, when the 
valve member moves from its backflushing position wherein the first 
passageway is closed and the second passageway is open, to the filtering 
position wherein the first passageway is open and the second passageway is 
closed, the valve member maintains the first passageway closed until the 
second passageway is closed by the valve member reaching and entering the 
throat of the second passageway, and then opens the first passageway. 
In a second described embodiment, the length of the cylindrical valve 
member is greater than the distance between the openings of the first and 
second passageways. In this embodiment, the end of the cylindrical valve 
member facing the second passageway is formed on its outer surface with 
recesses establishing communication between the outlet port and the 
backflush port via the second passageway in the backflushing position of 
the valve member. 
The novel backflush valve may be controlled by the application of a fluid 
pressure from a hydraulic device to a control chamber, e.g., automatically 
in response to the pressure drop across the filter as sensed by a sensor, 
or manually. The valve may also be controlled manually by a rotary handle. 
In either embodiment, the displaceable valve member may also be moved to a 
third, shut-off position, shutting-off the inlet port from the outlet port 
and also the backflush port from the outlet port. 
Further features and advantages of the invention will be apparent from the 
description below.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The backflush valve illustrated in FIGS. 1 and 2 is particularly useful for 
water irrigation systems including a filter for removing dirt particles 
from the water before applied to the water sprinklers or other irrigation 
devices. FIG. 1 illustrates the valve in its filtering position to effect 
a filtering operation wherein the inletted water is supplied to the line 
containing the filter, whereas FIG. 2 illustrates the valve in its 
backflushing position to effect a backflushing operation wherein the 
pressurised line containing the filter is connected to a backflush port 
for backflushing water through the filter in order to clean it. For 
purposes of example, FIG. 1 illustrates the filter as being actuated by a 
hydraulic device HD in the form of a 3-way pilot valve, which may be 
controlled automatically in response to the pressure drop across the 
filter (not shown), or manually, as known in backflush valves of this 
type. 
The backflush valve illustrated in FIGS. 1 and 2 comprises a housing, 
generally designated 2, having an inlet port 4 connectable to the inlet 
line, an outlet port 6 connectable to the outlet line containing the 
filter, and a backflush port 8 through which the dirty water is discharged 
during the backflushing operation. Housing 2 further includes a circular 
opening serving as an inlet seat 10 circumscribed by an inlet throat 12, 
defining a first passageway interconnecting the inlet port 4 with the 
outlet port 6. Housing 2 further includes a circular opening serving as a 
backflush seat 14 defining a second passageway interconnecting the outlet 
port 6 with the backflush port 8. 
A valve member 16 is displaceable within housing 2 and is movable with 
respect to the inlet seat 10 and the backflush seat 14 in order to effect 
either a filtering operation (FIG. 1), or a backflushing operation (FIG. 
2), according to the position of the valve member. The valve member may 
also be moved to a third, shut-off position, schematically shown by the 
broken lines 16' in FIG. 2. 
Valve member 16 is carried at one end of a stem 18 passing through the 
valve member and secured to it by a washer 20. The opposite end of stem 18 
is secured to the center of a diaphragm 22 by means of a disc 24 and nut 
26 clamping the diaphragm between them. A spacer sleeve 28 encloses stem 
18 between disc 24 and valve member 16. 
The outer circumference of diaphragm 22 is clamped between an annular 
flange 30 formed in housing 2 and a cover plate 32 by means of bolts 34. 
The space between diaphragm 22 and cover plate 32 defines a control 
chamber 36 connected to the hydraulic device HD via a control port 38 for 
controlling the pressure within the chamber, and thereby the position of 
valve member 16. Hydraulic device HD is a 3-way pilot valve and includes a 
displaceable member HD-1, such as a piston or diaphragm, movable to 
connect control port 38 (1)to a source of hydraulic pressure HD-2, (2) to 
a vent HD-3, or (3) to an intermediate position, as shown by the broken 
lines HD-1'. As indicated earlier, hydraulic device HD may be actuated 
automatically, (e.g., in response to a predetermined drop of pressure 
across the filter in the line), or manually. 
Valve member 16 is of cylindrical configuration. Valve seat 10 and 
backflush seat 14 both of circular configuration, are coaxial with the 
valve member and of substantially the same diameter. As can be seen 
particularly in FIG. 2, the length of valve member 16 is less than the 
distance between the two seats 10 and 14, so that when the valve member is 
seated in the inlet seat 10, there is a substantial space 39 between the 
opposite face of the valve member and the backwash seat 14, thereby 
opening the passageway connecting the backwash port 8 with the outlet port 
6 to the filter. However, the length of valve member 16 is greater than 
the distance between seat 14 and the mouth of throat 12 of seat 10, so 
that the valve member does not clear throat 12 to open seat 10 until it 
has been received within seat 14. A sealing ring 40 clamped between valve 
member 16 and washer 20 is seatable in backflush seat 14 during the 
filtering mode of operation (FIG. 1), and in the inlet seat 10 during the 
backflushing mode of operation (FIG. 2). 
The valve of FIGS. 1 and 2 operates as follows: 
FIG. 1 illustrates the valve during the filtering mode of operation, 
wherein sealing ring 40 of valve member 16 is seated in the backflush seat 
14. Accordingly, during the filtering mode of operation, inlet port 4 is 
connected to the outlet port 6 so that the pressurized water applied 
through the inlet port is directed by the valve, via outlet port 6, to the 
outlet line containing the filter, (not shown) whereas the backflush port 
8 is shut-off by valve member 16 from the outlet port 6 as well as from 
the inlet port 4. In this condition of the valve, the displaceable member 
HD-1 of the 3-way pilot valve HD connects the control port 38 of control 
chamber 36 to the vent HD-3, so that the inlet pressure maintains valve 
member 16 in its fully open condition as illustrated in FIG. 1. 
A backwashing operation is initiated by moving the movable member HD-1 of 
hydraulic device HD to connect control port 38 to a source of pressurized 
fluid, such as the downstream side of the filter, via port HD-2. As 
indicated earlier, this may be done automatically by a sensor, sensing the 
pressure drop across the filter, or manually, by a manually movable 
member. When this occurs, control chamber 36 becomes pressurized 
sufficiently to overcome the inlet pressure applied to valve member 16, 
thereby causing the valve member to start to move downwardly towards the 
backflushing position illustrated in FIG. 2. 
During the initial movement of valve member 16, its sealing ring 40 unseats 
from backflush seat 14, but the outer surface of the cylindrical valve 
member 16 being of the same diameter as that of the backflush seat, 
maintains backflush seat 14 still closed with respect to both the inlet 
port 4 and the outlet port 6, and prevents flow of water from either port 
to the backflush port 8. Although the outer surface of valve member 16 
does not form a perfect seal with backflush port 14, the leakage if any 
would not be significant until the complete length of the valve member 16 
has passed through backflush seat 14. This occurs just as sealing ring 40 
reaches and is received within the mouth of throat 12 of the inlet seat 
10. At this instant, the opposite end of valve member 16 completes its 
passage through backflush seat 14 and continues to move away from that 
seat until sealing ring 40 seats against the inlet seat 10 as shown in 
FIG. 2. 
It will thus be seen that the passageway through backflush seat 14 
interconnecting the outlet port 6 with the backflush port 8 does not start 
to open until valve member 16 has closed the inlet port 4 by first 
engaging throat 12. Accordingly, no flow will be produced through the 
backflush port 8 until the inlet port 4 has been completely closed, so 
that the flow through the backflush port 8 will be only that from the 
filter line connected to the outlet port 6. Thus, no clean water from the 
inlet port 4 will be wasted through the backflush port during the 
change-over to the backflushing mode of operation wherein the filter 
connected to the outlet port is backflushed via the outlet port 6 and the 
backflush port 8. 
When the backflushing operation has been completed, the displaceable member 
HD-1 of the 3-way pilot valve HD is moved (automatically or manually) to 
connect the control port 38 to the venting port HD-3 (the position shown 
in FIG. 1), whereupon the pressure within control chamber 36 will be 
vented to the atmosphere. The inlet pressure at the inlet port 4 will then 
be applied to valve member 16 and will positively move the valve member 
away from the inlet seat 10 towards the backflush seat 14. 
During the initial movement of the valve member, its sealing ring 40 still 
engages throat 12 of inlet port 10 so as to maintain the inlet port closed 
until the opposite (upper) end of valve member 16 reaches the backflush 
seat 14 to close the backflush port 8. Only after the backflush port has 
thus been closed will valve member sealing ring 40 start to move away from 
throat 12 to open the inlet port 14. The valve member continues to move 
until its sealing ring 40 seats within backflush seat 14, as shown in FIG. 
1, thereby completing the transition to the filtering mode of operation. 
It will thus be seen that during this transition of the valve from the 
backflush to the filtering mode of operation, the inlet port 4 remains 
closed until the backflush port 8 is closed by the outer cylindrical 
surface of valve member 16 being received within the backflush port 14. 
Thus, also here there is no significant wastage of clean water from the 
inlet port 4 through the backflush port 8 during the transition from the 
backflushing mode of operation to the filtering mode of operation. In 
addition, since this transition is effected directly by the inlet 
pressure, and without overcoming a spring, the valve member 16 is moved 
positively to its fully open position with respect to the inlet port 4 and 
is maintained in its fully open position, even under low inlet pressures. 
Valve member 16 may also be moved to an intermediate position, shown by 
broken lines 16' in FIG. 2, to shut-off the flow both from the inlet port 
4 and the outlet port 6. This may be done by moving control member HD-1 of 
the 3-way pilot valve HD to the intermediate broken-line position HD-1' 
when the valve member 16 has moved to its intermediate position 16', 
wherein one end of the valve member closes backflush seat 14, and sealing 
ring 40 at the other end of the valve member engages the outer end of the 
inlet throat 12. 
FIG. 3 illustrates a modification in the construction of the valve of FIGS. 
1 and 2 for operation by a rotary control handle, generally designated 
100, rather than by a hydraulic device, such as shown at HD in FIG. 1. For 
this purpose, the valve illustrated in FIG. 3 does not include a control 
chamber, diaphragm or space sleeve, corresponding to elements 36 in FIGS. 
1 and 2, nor a diaphragm, corresponding to diaphragm 22, nor a spacer 
sleeve corresponding to sleeve 28. Instead, the manually-motatable 100 is 
fixed to the outer end of stem 118, and the stem is formed with external 
threads 119 received within an inernally threaded bore formed in cover 
plate 132. By rotation of handle 100 the valve member 116 may thus be 
moved: (1) to its filtering position, wherein its sealing ring 140 seats 
within the backflush seat 114 to effect the filtering mode of operation; 
(2) to its backflushing position, wherein sealing ring 140 seats within 
the inlet seat 110 to effect the backflushing mode of operation; or to its 
shut-off position wherein one end of valve member 116 is within backflush 
seat 114, and the sealing ring 140 at the opposite end of valve member 
engages throat 112 of the inlet seat 110. In all other respects, the valve 
illustrated in FIG. 3 is constructed, and operates in the same manner, as 
the hydraulically-controlled valve illustrated in FIGS. 1 and 2. 
FIG. 4 illustrates a variation in the construction of the 
hydraulically-controlled valve of FIGS. 1 and 2. In this variation, the 
valve member, therein designated 216, has a length which is greater than 
the distance between the inlet seat 210 and the backflush seat 214; in 
addition, substantialy one-half the valve member, namely the half at the 
end (upper end) facing the backflush seat 214, is formed with a plurality 
of longitudinally-extending recesses 256 circumferentially spaced around 
the valve member circumference. 
FIG. 4 illustrates the valve member 216 in its backflushing position, 
wherein communication is established via recesses between the outlet port 
206 (leading to the filter) and the backflush port 208, to produce a 
backflushing operation. 
In the modification illustrated in FIG. 4, the inlet port 204 is not 
circumscribed by a throat, corresponding to throat 12 in FIGS. 1 and 2. 
However, the inlet opening 210 and the backflush opening 214 are both 
provided with circular sealing rings 252, 254. In addition, valve member 
216 is of longer length than the distance between the inlet seal 252 and 
the backflush seal 254. Further, valve member 216 is formed with a 
plurality of axially-extending, circumferentially-spaced recesses or 
grooves 256. With these modifications, it will be seen that the valve 
illustrated in FIG. 4 operates in substantially the same manner as 
described above with respect to FIGS. 1 and 2. 
Thus, during the movement of valve member 216 upwardly from its 
backflushing position (the lower position illustrated in FIG. 4) to its 
filtering position, the inlet port 204 will remain closed until the 
backflushing port 208 has been closed by the movement of the non-recessed 
part of valve member 216 into the backflush opening 214 into engagement 
with its seal 254. Also, during the movement of the valve member 216 
downwardly from its filtering position to its backflushing position, the 
inlet port 204 will be closed by the engagement of the lower end of the 
valve member 216 with the inlet seal 252 before the backflush port 208 is 
opened via recesses 256 to the outlet port 206. Valve member 216 of FIG. 4 
may also be moved to an intermediate position, as shown by the broken 
lines 216', to shut-off the flow with respect to both the inlet port 204 
and the outlet port 206. 
The valve illustrated in FIG. 4 will therefore also avoid wastage of clean 
water via the backflush port 208 during the transition from or to the 
backflushing position. Also, the valve member will move to its fully-open 
position positively, even under low inlet pressure, since the full inlet 
pressure is applied to it. 
FIG. 5 illustrates a backflush valve constructed according to FIG. 4, but 
equipped with a manually rotatable handle, therein designated 300, 
corresponding to handle 100 in FIG. 3, for moving the valve member 
manually to its filtering position or to its backflushing position (the 
latter illustrated in FIG. 5). In the modification of FIG. 5, handle 300 
is fixed to one end of an externally-threaded stem 318 received within an 
internally-threaded opening formed in the cover plate 332, as described 
above with respect to FIG. 3 and will therefore operate as the FIG. 3 
embodiment. It will also be seen that, as in FIG. 3, handle 300 may be 
rotated to move valve member 316 to an intermediate, shut-off position 
316', wherein its lower face is substantially flush with the inlet seal 
252, whereby the non-recessed cylindrical surface of valve member 316 
closes both the inlet seat 310 and the backflush seat 314, and thereby 
shuts-off the flow both through the inlet port 304 and through the 
backflush port 308. 
While the invention has been described with respect to several preferred 
embodiments, it will be appreciated that many other variations, 
modifications and applications of the invention may be made.