Differential controller valve and sequencer

A filtration system which may include multiple filters capable of being individually washed of clogging filtrate material by a "blow-down" or flushing operation, is regulated by a blow-down controller device. Each filter has a blow-down discharge valve which is normally maintained closed by a required level of fluid pressure in a pilot line connected to the valve. This pressure is supplied by the controller device, which draws pressure from an inlet line feeding all the filters. When the controller relieves pressure in one of the pilot lines, the filter associated with that pilot line is subjected to blow-down for a predetermined time period. To determine when blow-down of one or more filters is required, the controller senses pressure differential between the common inlet line and a common filter outlet line. When the pressure differential reaches a certain level, it indicates that the filters are sufficiently clogged by filtrate to require blow-down. The controller initiates blow-down in one or more of the filters sequentially, returning to the sensing mode after each blow-down cycle, until the pressure differential drops below the level indicative of the need for cleaning.

BACKGROUND OF THE INVENTION 
The invention relates to liquid filtration systems, and more particularly 
to the provision and control of automatic periodic cleaning of filter 
elements. 
Filter systems, particularly those associated with silt-laden water, often 
clog with filtrate rather frequently, requiring periodic cleaning. In the 
past, such cleaning has been provided through backwash or through a 
flushing process sometimes known as blow-down, involving a rapid rush of 
unfiltered liquid over but not through the filter mesh element to a 
blow-down discharge opening, carrying most of the clogging material along 
and cleaning the filter. This operation, which bypasses the normal filter 
outlet to dump the filtrate laden liquid as waste, continues for a short 
period of time, then the blow-down discharge valve is closed and normal 
filtration resumes. This blow-down type of filter assembly, and systems 
incorporating a group of such filter assemblies, are the type of 
filtration systems to which the present invention relates. 
Operation of such blow-down cleaning filter systems has previously been 
cumbersome or inefficient, or the systems have been expensive to set up 
and maintain. The operation and sequencing of the cleaning cycles has 
often been performed by hand or electronic systems which were expensive 
and rather sophisticated, in addition to requiring a source of electricity 
in sometimes remote locations. 
SUMMARY OF THE INVENTION 
The present invention provides a completely hydraulic and mechanical 
control system for use with blow-down discharge type filter systems, 
requiring no hand operations or electronic controls. Each filter assembly 
associated with the system of the invention includes a blow-down discharge 
valve which is operated by pressure in a pilot line connected to the 
valve. In such a valve, a predetermined level of pilot fluid pressure is 
required to close the valve and maintain it closed. Venting of the pilot 
line, so that the pressure falls below the predetermined level, opens the 
valve. In the system of the invention, the pilot line of the filter 
assembly valve, or the pilot lines from each valve of a plurality of 
filters having a common inlet and common outlet line, are connected to a 
blow-down controller which, by a connection to the inlet line of the 
filter or filters, normally supplies the required level of pressure in 
each of the pilot lines to keep each of the blow-down valves closed. 
The blow-down controller device is also connected to the filter outlet, or 
the common filter outlet of a multiple filter assembly, by a small line 
which monitors pressure at the outlet. By comparing the inlet pressure 
with the outlet pressure, the controller senses when the filter or filters 
require cleaning (blow-down) by determining when the pressure differential 
between the inlet and the outlet has reached a predetermined level. When 
this predetermined pressure differential is sensed, the controller 
relieves pressure in one of the blow-down valve pilot lines for a period 
of time to effect blow-down of that filter. 
On a single-filter installation the controller also closes the outlet valve 
via a pilot pressure assembly similar to that of the blow-down valve, by 
supplying inlet fluid pressure through an outlet valve pilot line during 
blow-down. This is usually necessary in a simple filter installation 
because inlet line pressure is normally not high enough for effective 
blow-down without outlet shutoff, whereas in a multiple filter system the 
pressure is considerably higher and the outlet of the filter being cleaned 
may be left open. 
Such multiple systems, however, require an ordered sequencing of blow-down 
of the various filters, since the common outlet pressure, rather than the 
outlet pressure at each filter, is monitored, and only one filter at a 
time should be blown down to avoid excessive pressure drop at the 
operating filters. Therefore, the controller includes means for subjecting 
one preselected filter to blow-down upon the sensing of the required 
pressure differential. When the blow-down cycle of the one filter is 
completed, the controller automatically selects the next filter in the 
sequence for blow-down when the controller again senses the required 
pressure differential. If the filters are significantly clogged and the 
cleaning of one filter is not sufficient, the controller may continue to 
sense the required pressure differential after blow-down of the first 
filter, so that blow-down is then performed on the next filter in the 
sequence. The controller in this way continues through the sequence of 
filters until, following completion of a blow-down cycle on a filter, the 
predetermined pressure differential is no longer sensed. The controller is 
then set on the next filter in the sequence for blow-down when the 
required pressure differential again occurs due to clogging of the 
filters. 
Following blow-down of a filter, the controller device re-supplies inlet 
line pressure to the pilot line of the blow-down valve. In the case of a 
single filter system, the controller also vents the outlet valve pilot 
upon completion of the blow-down cycle, so that the outlet valve is again 
opened for normal filtration. 
To perform its regulatory functions and the required switching of control 
pressures, the controller device includes a reciprocable piston with fluid 
chambers at either end, one end receiving inlet fluid pressure and the 
other receiving the fluid pressure of the common outlet. The piston 
position is shifted against the bias of a spring when the required level 
of pressure differential between the inlet and the outlet is reached. This 
actuates a rotary spool assembly which vents the selected pilot line, cuts 
off the inlet pressure source from the high pressure side of the piston, 
and connects the two fluid chambers together, with a restrictive orifice 
between them, so that pressure in the two chambers is equalized and the 
piston is returned over a time period to its original position. The return 
of the piston disconnects the two chambers, re-connects the high-pressure 
chamber to the inlet source so that sensing of the pressure differential 
again occurs, resupplies the vented blow-down pilot line with inlet 
pressure, and shifts a rotary sequencer to the pilot line of the next 
filter in sequence so that when blow-down is again required, this next 
sequential filter will be cleaned. 
The controller device and system of the invention thus provide an efficient 
mechanical and hydraulic means for cleaning one or a plurality of filters 
when the need for such cleaning is detected by an automatic sensing means. 
The need for manual steps or sophisticated electronic equipment is 
eliminated. It is therefore among the objects of the invention to provide 
a blow-down controller for a filtration system, and a system including 
such a controller, which provide for effective filter cleaning and avoid 
inlet pressure drop in the case of a multiple filter system, without 
resort to electric or electronic valving controls. 
Other objects, advantages and features of the invention will become 
apparent from the following detailed description, presented in conjunction 
with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Multiple Filter System 
In the drawings, FIG. 1 schematically represents a multiple filter system 
according to the invention, of which one filter generally indicated by the 
reference number 10 is shown connected to a blow-down controller assembly 
generally represented by the reference number 11. In the system to be 
described, each of the filter assemblies such as the filter assembly 10 is 
connected to the controller 11 by a blow-down pilot pressure line 12 
originating at a pilot operated blow-down valve 13 of the filter assembly. 
The controller 11 is also connected to a common inlet line 14 from a 
pressurized fluid source (not shown) via a control line 16 which feeds 
inlet pressure to the controller, and to a common outlet line 17 via a 
control line 18 which feeds system outlet pressure to the controller. Each 
of the filter assemblies including the assembly 10 is fed from the common 
inlet line 14 downstream of the point of connection with the control line 
16. Similarly, at the downstream end of the filtration system, each filter 
assembly including the assembly 10 feeds into the common outlet line 17 
upstream of the point of connection with the pilot line 18. 
As indicated schematically in FIG. 1, each filter assembly 10 includes a 
main filter 19 having a filter element the surface of which is indicated 
at 21, a flow channel indicated at 22 leading through an outlet valve 23 
to the common line 17, and a conduit 24 leading from the upstream side of 
the filter element surface 21 to the blow-down discharge valve 13. During 
normal filter operation inlet liquid flows through the line 14 and through 
the main filter 19 to the common outlet line 17, leaving much of the 
filtrate material on the face of the filter element 21. When this filter 
element becomes excessively clogged, it is desirable to clean as much of 
the filtrate material as possible off the filter element. This is 
accomplished by opening the blow-down discharge valve 13 for a short 
period, providing a path of much lower resistance for the inlet liquid and 
thus causing a rush of flushing liquid over the face 21 of the filter 
element and out of the filter assembly through the blow-down discharge 
valve 13. During this operation the outlet valve 23 may be left open and 
cleaning will nonetheless be effective since the blow-down offers such a 
lowered flow resistance. Because blow-down of a filter assembly always 
causes something of a pressure drop in the common inlet line 14 leading 
also to operating filters, it is preferable that only one filter assembly 
at a time in the system be subjected to blow-down. 
The blow-down controller assembly 11 automatically provides for blow-down 
of one or more of the plurality of filter assemblies in a specified 
sequence, when it is determined that the system as a whole has been 
sufficiently clogged to require blow-down cleaning of at least one filter. 
The controller senses the need for cleaning by comparing the pressure in 
the common outlet 17 (fed to the controller via the control line 18) with 
the pressure in the common inlet line 14 (fed to the controller via the 
control line 16). Outlet pressure is of course always lower than inlet 
pressure, but when the differential between the two pressures reaches a 
predetermined level, it indicates that the filter elements are excessively 
clogged and that one or more should be cleaned until the pressure 
differential is again brought below the predetermined level. Control of 
blow-down at each filter assembly 10 is accomplished through a blow-down 
pilot line 12 in conjunction with the blow-down discharge valves 13. The 
opened or closed condition of the pilot operated valve 13 is responsive to 
fluid pressure in the pilot line 12. The valve is biased toward the open 
position as schematically indicated, so that when pilot pressure drops 
below a certain pressure the valve opens; it closes and remains in the 
closed position schematically indicated in FIG. 1 when pilot pressure 
exceeds and remains above the specified pressure level. Thus, the 
blow-down valve 13 is normally held closed by the maintenance of 
sufficient fluid pressure in the pilot line 12, but when blow-down is 
necessary, pilot pressure is relieved to below the required level and the 
blow-down valve 13 is opened. The controller 11 accomplished these 
functions and also progressively sequences the filter assemblies for 
blow-down when cleaning is required. The sequencer, schematically 
indicated by the reference number 26, is always positioned to vent the 
pressure in one of the blow-down pilot lines 12 when required. FIG. 1 
illustrates a system wherein the controller is adapted to control four 
filter assemblies, the pilot connections of which to the controller 11 are 
denominated V.sub.1, V.sub.2, V.sub.3 and V.sub.4, with the V.sub.1 
connection shown selected for the next blow-down cycle. When the filter 10 
associated with the connection V.sub.1 has been cleaned, and the pilot 
line 12 has been repressurized, the sequencer 26 advances to the pilot 
connection V.sub.2 and again begins sensing for the required pressure 
differential indicating the need for cleaning. If the blow-down of a 
single filter was not sufficient to adequately clean the system, the 
indicative pressure differential is again sensed and the pilot line 
associated with the pilot connection V.sub.2 is vented for cleaning of the 
filter system associated with that pilot line. The cycle repeats until 
enough of the four filter assemblies have been cleaned to enable the 
pressure differential to drop into the normal range. During a blow-down 
cycle, all pilot lines other than the one being vented are pressurized by 
the controller to keep the respective blow-down lines closed; between 
blow-down cycles, all pilot lines are pressurized by the controller. 
Schematically indicated valving means 27 and 28 cooperate with the 
sequencer 26 to control the venting and pressurization of pilot lines and 
to control the duration and re-setting of the blow-down cycle. As 
indicated, inlet fluid-pressure from the control line 16 is provided to 
three of the pilot connections via one conduit arrangement, and to the 
fourth through the valve 27, which is normally in the position shown. An 
inlet pressure supply line from the inlet control line 16 is denoted I. 
Pressure from the inlet source is sufficient to hold each of the blow-down 
valves in the system closed. 
All of the fluid valving devices 26, 27 and 28 are controlled by the 
movement of a double-ended piston, both ends of which are indicated by the 
line 29 in the schematic representation at the bottom of FIG. 1. Inlet 
pressure is normally supplied to the high pressure side of the piston 29 
through the valving device 28, a line L, a first fluid chamber 31, a 
second fluid chamber 32 separated from the first by a flexible isolation 
diaphragm 33, and a third fluid chamber 34 adjacent to the piston and 
connected to the second chamber 32 through a restrictive orifice 36. Inlet 
pressure is thus communicated to the high pressure face of the piston 29. 
The piston is biased to the left in FIG. 1 by a compression spring 37 
positioned in a low pressure fluid chamber 38 on the low pressure side of 
the piston 29. Fluid pressure from the common outlet line 17 is supplied 
to the chamber 38 via the outlet control line 18 and the line 0. Inlet 
pressure is always higher than outlet pressure, but the piston 29 is 
normally restrained from movement to the right in FIG. 1 by the spring 37. 
However, when pressure drops sufficiently in the outlet chamber 38 due to 
filter clogging, providing a sufficient level of pressure differential 
between the chambers 34 and 38, the piston 29 moves to the right against 
the bias of the spring 37 and shifts the valving indicated at 27 and 28 so 
that (a) the selected pilot line at the sequencer 26 is connected to a 
drain or exhaust line D, cutting off inlet pressure from the pilot line, 
and (b) the line L is connected to the line 0 to equalize pressure between 
the chambers 31 and 32 and the chamber 38, so that fluid can begin to flow 
from the chamber 34 through the orifice 36 to the chamber 32, and from the 
chamber 31 through the lines L and 0 to the chamber 38. The return of the 
piston 29 occurs over a fixed time period irrespective of line pressure in 
the inlet 14, since inlet pressure is not connected into the piston 
assembly during this part of the cycle. Outlet pressure is connected by 
the line 18, but it acts the same in both directions and thus has no 
effect. 
When the piston 29 has substantially completed its return, it shifts the 
valving devices 27 and 28 back to their normal positions shown in FIG. 1, 
and advances the sequencer 26 into a position so that the next sequential 
pilot line is selected for venting on the next blow-down cycle. Thus, 
re-pressurization of the pilot line 12 for the blow-down valve 13 occurs 
and sensing of the inlet-outlet pressure differential again commences by 
separation of the lines L and 0 and reconnection of the line L to inlet 
pressure. 
The isolation diaphragm 33 separates the fluid chambers 31 and 32 so that 
the restrictive orifice is not subjected to inlet liquid which has not 
been thoroughly filtered. In fact, the isolated fluid in the chambers 32 
and 34 may comprise a separate liquid, such as water mixed with 
anti-freeze for the required viscosity and to prevent freezing on the 
downstream side of the orifice 36. Filters 39 and 41 may also be provided 
on either side of the orifice for increased protection, and a control line 
filter 42 may be provided in the control line 16 to separate larger 
filtrate particles from the inlet liquid. Since the volume of flow through 
the control line filter 42 is very low, it seldom needs cleaning. 
The mechanical apparatus of the controller 11 which accomplishes the above 
functions is illustrated in FIGS. 2 through 8. FIG. 2 shows the controller 
device 11 in perspective, partially broken away to indicate the piston 29, 
the fluid chambers 31, 32, 34 and 38, the isolation diaphragm 33 and the 
restrictive orifice 36. A housing 43 forms the various chambers, receives 
the piston 29 for sliding movement therein, and holds the compression 
spring 37 in position at the outlet end of the piston. The housing also 
supports a sequencer assembly 44 and provides connections for the line L, 
the drain line D, the line I and the line 0 (I and 0 connection sockets 
not visible in FIG. 2). Rolling diaphragm seals 46 and 47 may be provided 
to seal the ends of the piston against leakage of chamber fluids. A 
filling port 48 is provided for addition of the isolated fluid into the 
chambers 32 and 34. 
A spring-operated toggle or over-center device 50 translates the gradual 
movement of the piston 29 into an instantaneous snap action for operating 
the rotary components of the sequencer assembly 44. The toggle assembly 50 
includes a tension spring 51 connected at one end to a pin 52 on the 
piston and at the other end to a pin 53 on a lever arm 54 rotationally 
supported at its opposite end 56. Travel of the piston 29 to the right in 
FIG. 2 to a predetermined extent shifts the angle of the tension spring 51 
to the extent that it suddenly rotates the lever arm 54 about the end 56, 
to the maximum right position of the arm 54. The angle through which the 
lever arm travels is preferably about 34.degree.. This quick shifting of 
the lever arm 54 rotates a shaft 57, the end of which is seen in FIG. 2 
affixed to the end 56 of the lever arm. As indicated in FIGS. 2 and 3, the 
outer end of the lever arm 54 is exposed so that it can be manually 
shifted, if desired, to cause blow-down without shifting of the piston 29. 
FIG. 3 shows the blow-down controller device 11 in partially sectioned 
elevation with the sequencer assembly 44 oriented upwardly. The outer end 
of the lever arm 54 appears, with the pin 53 connected to the end of the 
spring 51. A portion of the piston 29 also appears. The sequencer assembly 
44 is seen in section to illustrate the rotary shaft 57 connected to a 
primary valving spool 58. Each time the lever arm 54 rotates through its 
arc of about 34.degree., the shaft 57 and primary valve spool 58 rotate 
similarly. Pawls 59 extending from the upper face of the primary spool 58 
are in engagement with ratchet teeth 61 of a secondary sequencer spool 62 
positioned just above the primary spool. On the stroke of the piston 29 at 
the beginning of the blow-down cycle (to the right in FIGS. 1, 2 and 3), 
the pawls 59 slip on the ratchet teeth 61 and the secondary spool 62 
remains stationary. On the return stroke of the piston 59 at the end of 
the blow down cycle, the return of the toggle lever arm 54 and the 
rotation of the primary spool 58 carries the secondary sequencer spool 62 
through an arc of 30.degree., via the pawl and ratchet connection. The 
additional few degrees of rotation traveled by the primary spool 58 ensure 
effective pawl engagement with the ratchet teeth 61. As will be seen 
below, the rotation of the secondary spool 62 through an increment of 
30.degree. provides the sequential shifting of blow-down pilot lines for 
venting, as illustrated by the schematic valve sequencer 26 of FIG. 1. 
FIG. 4 is an enlarged view of the sequencer assembly 44. As indicated, the 
primary spool 58 and the secondary spool 62 may each comprise two or more 
parts. Two housing components 63 and 64 connected to the main housing 43 
of the controller are sealed together by an O-ring 66, and the shaft 57 is 
sealed against the housing component 63 by an O-ring 67, to form a sealed 
fluid chamber 68 which receives inlet pressure as will be seen below. The 
chamber 68 is always open to all but one of the pilot connections V.sub.1, 
V.sub.2, V.sub.3, and V.sub.4 which are positioned in the end cover 
housing component 64 as shown in FIG. 4. The pilot connections V.sub.1 
through V.sub.4 may be threaded to receive pilot lines (not shown), or 
other connecting means may be provided. Each pilot connection includes an 
interior port, of which ports 71 and 73 of the pilot connections V.sub.1 
and V.sub.3, respectively, are seen in FIG. 4. One port at a time is 
connected to the interior 75 of the secondary spool by one of three ports 
76 in the upper surface of the spool 62, sealed against the surface of the 
housing component 64 by an O-ring 77. The interior 75 of the secondary 
spool 62 in turn connects, through a central hollow shaft or tube 78, 
extending from the primary spool 58 and sealed by an O-ring 79, with the 
interior 81 of the primary spool. A compression spring 80 urges the two 
spools apart for proper port engagement at top and bottom of the chamber 
68. The primary spool interior 81 either is open to the fluid chamber 68 
to provide inlet fluid pressure to the single selected pilot connection 
(V.sub.1 in FIG. 4), or makes connection with the venting drain, depending 
upon whether the controller is in a blow-down cycle, as will be seen 
below. Thus, the primary spool serves as the valving device 27 
schematically indicated in FIG. 1. 
Since the fluid chamber 68 is always connected to inlet pressure, an 
open-ended conduit 82 passing through the primary spool 58 is also 
continuously connected to inlet pressure at its upper end. As shown in 
FIG. 4, this conduit 82 is normally connected via an O-ring seal 83 to a 
passageway L leading to the line L, which in turn leads to the high 
pressure or inlet end of the piston 29 as discussed above. Thus, inlet 
pressure is normally supplied to the piston-controlling fluid chamber 31 
as seen in FIGS. 1 and 2. 
FIG. 5 shows the primary spool 58 in plan view, indicating the effect of 
its counterclockwise rotation through the 34.degree. arc during blow-down 
but showing the spool in its normal position. FIG. 6 shows the upper 
surface of the housing component 63 just below the primary spool 58. As 
indicated in FIG. 5, the central hollow shaft 78 extending upwardly from 
the primary spool is connected via the interior 81 of the primary spool, 
shown diagrammatically as a passageway in the primary spool, to a port 87 
in the bottom of the primary spool. This port 87 is normally open to the 
fluid chamber 68, and thus to inlet fluid pressure in accordance with the 
above discussion. However, upon rotation of the primary spool through its 
34.degree. arc, the primary spool port 87 becomes engaged with an O-ring 
sealed port and passageway D' in the surface of the housing component 63 
below (see also FIG. 6). This cuts off the interiors of the primary and 
secondary spools, and the one selected pilot connection, from inlet 
pressure and switches them to the venting drain D, to which the port and 
passageway D' are connected. In this way, the valving function of the 
schematically indicated valving device 27 of FIG. 1 is performed by the 
rotation of the primary spool 58. 
The rotation of the primary valve spool 58 also performs the function of 
the schematically indicated valving device 28 of FIG. 1, through shifting 
of a pair of ports 89 and 90 in the bottom of the primary spool, connected 
together by an internal passageway 91. As can be envisioned from FIGS. 5 
and 6, as the primary spool 58 rotates through its approximately 
34.degree. arc, the bottom port 89 moves into sealed engagement with the 
passageway port L', where the spool conduit 82 was formerly engaged, and 
the bottom port 90 moves into engagement with an O-ring sealed passageway 
port O' which connects with the line O leading to the low pressure piston 
chamber 38 and to the control line 18 from the common filter outlet. The 
port 0' is normally sealed off against the smooth bottom surface of the 
primary spool 58, so that inlet pressure maintained within the space of 
the fluid chamber 58 (see FIG. 4) cannot flow into the outlet lines 0 and 
18. Similarly, the O-ring sealed port D' is sealed against the bottom of 
the primary spool when the controller is not on blow-down cycle. 
As shown in FIG. 6, an inlet passageway I' through which inlet pressure 
communicates with the interior of the chamber 68 does not include an 
O-ring seal, unlike the passageway ports L', O' and D'. Inlet pressure is 
always required for all but one of the pilot lines of the filter system so 
that the passageway I' (leading from the inlet line I) should always be 
open. 
It is thus seen that the primary valving spool 58, in conjunction with the 
ports L', O' and D' below and with the fluid chamber 68 performs the 
functions of the two valving devices 27 and 28 of FIG. 1 through its 
toggle connection with the reciprocable piston 29. 
FIG. 7 shows the sequencer assembly of FIG. 4 from above, indicating the 
top of the cover housing component 64 and the secondary sequencer spool 62 
below in dashed lines. The pilot line connections V.sub.1 and V.sub.3 seen 
in FIG. 4, in addition to pilot connections V.sub.2 and V.sub.4, are 
indicated along with corresponding pilot ports 71, 72, 73 and 74. The 
secondary sequencer spool 62 below includes three O-ring sealed ports in 
its upper surface, each of which is in communication with the interior 75 
of the secondary spool: the port 76, shown in engagement with the pilot 
port 71 in FIGS. 7 and 4, and ports 93 and 94 each evenly spaced at 
120.degree. from the port 76 and from one another. As can be envisioned 
from FIG. 7, an incremental rotation of 30.degree. of the secondary spool, 
which occurs through engagement of the primary spool at the end of each 
blow-down cycle will always move the connected one of the ports 76, 93 and 
94 out of engagement with a pilot port and another into engagement with 
another pilot port. The order of this sequence will be V.sub.1, V.sub.2, 
V.sub.3, V.sub.4, V.sub.1, etc. The three pilot ports not engaged with the 
secondary spool are in direct communication with the fluid chamber 68 and 
inlet pressure, as indicated in FIG. 4. 
As a pilot port comes into engagement with a secondary spool port, it also 
communicates with the interior 75 of the secondary spool and the interior 
81 of the primary spool, as discussed below. Through primary spool 
porting, this normally feeds pilot line pressure to the subject pilot 
port, so that all pilot ports have inlet pressure, but during blow-down 
vents the subject pilot port by connecting it to the drain line D. 
Any number of pilot lines and filters from 1 to 4 can be regulated by the 
four-pilot sequencer assembly 44. If fewer than four pilot lines are 
involved, the unneeded pilot connections are simply sealed off. The result 
is that when one of the secondary spool ports 76, 93 and 94 comes into 
engagement with a sealed port, no pilot line is drained and the primary 
valving spool performs the function of the schematically indicated valve 
28 in FIG. 1 but not of the schematically indicated valve 27. Therefore, 
the piston 29 is returned over its timing cycle to its sensing mode, where 
it determines that blow-down is still required and it quickly moves to the 
blow-down position again. This occurs until one or more filters have 
actually been cleaned. 
FIG. 8 shows a modified form of cover housing component 64' and secondary 
sequencer spool 62' for use with five and six-filter multiple systems. Six 
pilot connections equally spaced at 60.degree. around the top of the 
housing component 64' are numbered P.sub.1 through P.sub.6, in the order 
in which they would be selected for the first six blow-down cycles as the 
secondary spool advances counterclockwise through one revolution. The 
secondary spool 62' below (dashed lines) includes two O-ring sealed ports 
96 and 97 in its upper surface, spaced 150.degree. apart. Thus, as 
indicated in FIG. 8, only one of the ports 96 and 97 at a time is engaged 
with a pilot port, the other being half way between a pair of pilot ports. 
As the secondary sequencer advances in 30.degree. increments, the 
indicated sequence results. Only the secondary sequencer spool and the 
sequencer assembly cover housing component need be interchanged to modify 
a controller device from four-filter capacity to six-filter capacity. As 
discussed above in connection with the four-filter embodiment, the 
six-filter controller may be used for fewer than six filters by sealing 
off unused pilot ports. 
Single Filter System 
FIG. 9 shows a single filter system including an automatic blow-down 
controller. As in the example filter of FIG. 1, the single filter assembly 
100 of the system of FIG. 9 includes an inlet line 101, a main filter 102 
with a filter element surface 103, and a blow-down discharge valve 104 
connected by a flow channel 106 to the main filter upstream of the filter 
element surface 103. The blow-down valve 104 is pilot operated in the same 
way as the valve 13 described above, with a pilot line 107 normally 
supplying inlet fluid pressure to maintain the blow-down valve closed. 
However, the filter assembly 100 also includes a pilot operated outlet 
valve 108 for shutting off flow through an outlet line 109 during 
blow-down. As indicated above, this shut-off is usually necessary in a 
single filter system, as opposed to a multiple filter system, because line 
pressure is generally lower and the pressure drop caused by an open outlet 
should be eliminated for effective cleaning. The outlet valve 108 is 
operated by pilot pressure through an outlet pilot line 111 in the same 
manner as the blow-down valve 104, except that the line 111 is normally 
vented so that it is normally open. During the blow-down cycle, pressure 
is provided in the pilot line 111 to shift the outlet valve 108 to the 
closed position for the duration of the cycle. 
In the single filter system, a blow-down controller generally indicated by 
the reference number 112 is connected to the filter 100 in much the same 
way as described above in connection with the multiple filter system. An 
inlet pressure control line 113 from the inlet line 101 normally supplies 
pressure through a valving assembly 28 to the high pressure side of a 
piston 29 by a line L, fluid chambers 31, 32 and 34, an orifice 36, etc. 
Outlet pressure is normally supplied to the downstream side of the piston 
29 by an outlet control line 114 and a line O. During the blow-down cycle, 
the valving device 28 shifts to connect the L and O lines and provide for 
the return of the piston. Also during the blow-down cycle, a valving 
device 27 disconnects the pilot line 107 from inlet pressure and connects 
it to a drain line D to shift the blow-down valve 104. However, the 
controller 112 does not include a pilot sequencer similar to the device 
schematically indicated at 26 in FIG. 1, but rather includes a third 
valving device 116 which normally connects the outlet pilot line 111 with 
the drain line D, but shifts at initiation of the blow-down cycle to 
supply inlet pressure in the pilot line 111, thereby closing the pilot 
operated outlet valve 108 during the blow-down cycle. The valving device 
116 is operated mechanically and hydraulically by travel of the piston 29, 
similarly to the valving devices 27 and 28. 
The discussion below will concentrate on the differences between a single 
filter controller 112 and multiple filter controller 11. The piston 
portion of the controller is identical to that described above, but there 
are some modifications in the sequencer assembly. As will be seen, a 
multiple filter controller may be converted into a single filter 
controller by interchange of only a few components. 
FIGS. 10 and 11 illustrate the structure and operation of a sequencer 
assembly 117 of the single filter controller 112, and the differences 
between the assembly 117 and the multiple filter sequencer assembly 44 
illustrated in FIGS. 4 - 8. The elevational section view of FIG. 10 is 
shown with certain parts not in their true rotational alignment for 
clarity of illustration. FIG. 6 should also be referred to along with 
FIGS. 10 and 11, since it diagrammatically illustrates the housing surface 
below the primary valving spool and the separate ports included therein 
for both the multiple filter and single filter controller embodiments. 
As shown in FIG. 10, the single filter controller sequencer assembly 117 
includes a substituted cover housing component 118 and modified forms of 
primary and secondary spools 119 and 121, respectively. In this sequencer 
assembly the primary and secondary spools rotate together through the 
approximately 34 degree arc through which the above described primary 
spool rotated. The spools 119 and 121 are connected together by a central 
blow-down control tube 122 and an outlet control tube 123, both of which 
are preferably press-fit into the primary spool 119. Compression springs 
124 and 126 are positioned around the tubes 122 and 123, respectively, to 
bias the secondary spool upwardly as shown against a surface of the 
component 118 and to bias the primary spool downwardly against the surface 
of the housing component 63, which is the same as that shown in FIG. 4 and 
diagrammatically indicated in FIG. 6. Two small tabs 125 may be provided 
on the upper surface of the upper spool 121 to contact the surface of the 
housing component 118 and balance the spool there against. 
The primary spool 119 itself is very similar to the primary spool 58 
described above, as seen in FIGS. 10 and 11. It includes a through conduit 
127 which normally connects with the O-ring bounded port and passageway L' 
leading to the line L (see FIGS. 1, 2 and 9) and with the interior fluid 
chamber 128 of the sequencer assembly 117, which is always supplied with 
inlet fluid pressure by the passageway and port I' leading from the line 
I. During blow-down, the through conduit 127 is displaced from the port L' 
so that the port L' no longer receives inlet pressure. Also, as 
illustrated in FIG. 11 in dashed lines, the primary valving spool 129 
includes bottom ports 133 and 134 and a connecting passageway 135 which do 
nothing except during blow-down when they connect the passageways L' and 
O' as indicated, thereby connecting the lines L and O as discussed above. 
The primary spool 119 thus serves as the valving device 28 illustrated in 
FIG. 9, similarly to the primary spool of the above described embodiment. 
The primary spool 119 also includes a central fluid chamber 129 connected 
to a central tube 122 and to a passageway and bottom port 130 (indicated 
in dashed lines in FIG. 10 although actually in front of the section 
plane) which is normally open to the housing chamber 128 and inlet 
pressure but which connects with the drain port and passageway D' during 
blow-down. This fluid path of the primary spool leads through the central 
tube 122 and an O-ring sealed connection 131 to the single blow-down pilot 
line connection 132. Thus, this part of the primary valving spool serves 
as the valving device 27 schematically illustrated in FIG. 9, venting the 
pilot connection 132 and the connected pilot line 107 (FIG. 9) during 
blow-down and reconnecting it to inlet fluid pressure between blow-down 
cycles. In FIG. 11 the flow path provided by the interior primary spool 
chamber 129 is indicated as a passageway between the central tube 122 and 
the passageway 130, as above in reference to the multiple filter 
embodiment. 
The primary spool 119 differs from the spool of the previously described 
embodiment in that it includes the tube 123 and a connected port 123' in 
the bottom of the spool. As indicated in FIGS. 10 and 11, this port 123' 
normally makes connection with the port and passageway D' leading to the 
drain line D. Thus, an outlet valve pilot connection 137 normally 
connected to the tube 123 via secondary spool O-ring connections 138 and 
139, is normally vented to the drain line, and the outlet valve 108 of 
FIG. 9 is normally open. 
However, during blow-down when the primary and secondary spools are rotated 
through their approximately 34.degree. arc, as envisioned with reference 
to FIG. 11 and also FIG. 10, the O-ring connection 138 at the top of the 
upper spool is broken and the port 123' at the bottom of the primary spool 
is disconnected from the drain passageway D', with the passageway D' then 
sealed off against the bottom of the primary spool. Therefore the outlet 
pilot connection 137 becomes open to inlet fluid pressure existing in the 
housing chamber 128 and the outlet valve 108 is closed as discussed above. 
In this way the primary and secondary spools 119 and 121 of the sequencer 
assembly 117 perform the function of the diagrammatically indicated 
valving device 116 of FIG. 9, discussed above. 
The sequencer assembly 117 does not include sequencer spool or sequencing 
device in the sense of the secondary sequencer spool 62 used in the 
multiple filter embodiment of the controller. The two spools of the single 
filter controller could be provided as a single component, but are 
preferably structured as described and illustrated in the interest of 
interchangeability. Thus, it can be seen by a comparison of FIGS. 4 and 10 
that only the cover housing component 64 and the primary and secondary 
spools 58 and 62 of FIG. 4 need be interchanged with the housing component 
118, the primary and secondary spools 119 and 121 and the various tubes 
and springs to provide the single filter controller sequencer assembly of 
FIG. 10. 
The above described preferred embodiments provide automatic blow-down 
controllers, and the systems in which they are incorporated, for 
filtration systems including a bank of parallel and commonly connected 
filters and for systems including single filters connected alone. The 
controllers and the control systems in which they are incorporated are 
relatively simple and inexpensive in manufacture but efficient and 
relatively maintenance free in operation, being entirely hydraulic and 
mechanical. Various other embodiments and alterations to these preferred 
embodiments will be apparent to those skilled in the art and may be made 
without departing from the spirit and scope of the following claims.