Fluid filter and indicator

A versatile filter structure adaptable for use in differently ported configurations includes accommodation for variations of bypass and shutoff valving and for filter element replacement from either end or centrally of the structure. A head casting is secured to a tubular housing and either may be the mounting device for the filter. A funnel shaped diverter having an oblique edge is removably mounted in the head casting and provides separation between inlet and outlet portions of the filter structure by means of an eliptical O-ring seal at the edge which engages the interior of the head casting. The diverter provides a smooth transition for fluid flow to the interior of the filter, supports one end of the filter element in the tubular housing, optionally houses a shutoff valve operative automatically upon filter element removal, and further houses a bypass valve for safeguarding against filter element blockage. The remote end of the housing which also supports the filter element consists in the different configurations of a welded-closed or removable end assembly, with or without a port and shutoff valving. An indicator mounted on the head casting is in fluid communication with opposite sides of the O-ring seal to monitor inlet and outlet pressure differentials. Dual diaphragms actuate and isolate a sensing piston in the indicator and a dual spring arrangement biases the piston for normal operation and to provide an indication of lack of filter element in the housing.

BACKGROUND OF THE INVENTION 
This invention relates to fluid filters and more particularly to a 
hydraulic fluid filter having a differential pressure indicator. 
Hydraulics filters of this type are commonly used as suction line filters, 
return line filters and pressure filters as well as in other 
configurations and it is conventional to employ specific designs of the 
filter housing for each of such applications. 
In all these arrangements it is necessary from time to time to replace the 
filter element and it is often desired to accomplish such changeover 
without shutdown of the associated fluid system. Further, each filter 
design must be efficient in structure not only to achieve the results of 
adequate removal of particles of a particular size from the system but 
also to achieve sufficient dirt capacity in a convenient housing structure 
along with a favorable fluid flow versus pressure drop characteristic. 
Still further in fluid filters of this type it is desirable to have means 
for monitoring the condition of the filter element to determine when the 
latter has become contaminated and requires replacement. 
It would be desirable to have a common filter structure which is suitable 
for use in many of these different applications, wherein servicing of the 
filter element may be accommodated through either end of the filter 
housing or even from the central portion thereof and wherein the typical 
filter characteristics of quality of filtering are not sacrificed. Further 
it is desirable as well to provide means for indicating not only the 
condition of the filter element but also the presence or absence of same 
in the filter housing, with such indication provided either at the filter 
housing or at a remote location. 
SUMMARY OF THE INVENTION 
A versatile filter structure is provided in a two-piece housing consisting 
of a head casting and tubular filter container wherein the filter element 
can be reached for servicing through either end of the housing or 
alternately at the central portion thereof when the head casting and 
tubular housing are separated. 
A unique diverter structure provides means for separating the head casting 
into inlet and outlet partitions in fluid communication respectively with 
the inner and outer portions of a tubular filter element. The diverter is 
in a truncated funnel shaped configuration mounted at its larger periphery 
within a cylindrical cavity in the head casting and slidable therethrough 
together with the filter element for replacement purposes. The diverter 
structure provides an efficient means for transmitting fluid flow between 
a transverse port of the housing and the axially aligned filter element, 
and enhances the fluid flow versus pressure drop characteristic of the 
filter. The smaller, necked down end of the funnel-shaped diverter serves 
to direct fluid flow to the interior of the filter element and further 
supports one end of the filter element within the housing. An optionally 
removable end closure at the distal end of the housing provides coaxial 
support for the filter element and, further, optionally includes access 
ports to the interior of the housing and may mount associated valving 
devices. 
The eliptical mounting edge of the diverter separates the head casting into 
two chambers and this allows the convenience of mounting an indicator on 
the exterior of the head casting with fluid access to the chambers across 
the edge of the diverter element. A dual diaphragm arrangement supports a 
piston for slidable movement in the indicator housing to positions 
dictated by the fluid pressure differential to provide visual or remote 
indications of the filter characteristics. A compound spring arrangement 
is utilized to bias the piston and retains same at one end of the housing 
in the absence of any fluid differential to provide an indication of the 
absence of the filter element in the housing.

DETAILED DESCRIPTION OF THE DRAWINGS 
Referring to FIG. 1 a first embodiment of the filter 10 comprises a 
generally tubular head casting 11 and a tubular filter housing 12, the 
latter having an annular flange piece 14 at one end welded to the housing 
12. The flange 14 has arcuate slots therein (not shown) for receipt of 
mounting bolts 15 engaging threaded holes in a flange portion 16 of the 
head casting 11 to provide a quick-release fastening arrangement. An 
O-ring seal 18 between the flanges 14, 16 provides a fluid seal. 
In this embodiment of the invention the head casting 11 includes an inlet 
port 20 and outlet port 21, generally in alignment with one another and 
both disposed substantially transverse to the longitudinal axis of the 
tubular housing 12. The head casting 11 comprises a generally cylindrical 
inner surface 22 extending therethrough, being closed at one end by 
inwardly-dished cover member 24 secured in place at its periphery by bolts 
25 in a quick change slotted arrangement similar to that of the mounting 
flange of the filter housing 12 secured by bolts 15. The distal end of the 
filter housing 12 is fitted with a cup-shaped closure member 26, welded at 
its periphery to the end of the housing 12, the closure member 26 further 
including a central closed end tubular projection 27 which serves as a 
support member. 
A diverter structure 30 is included in all embodiments of the invention 
supporting at one end a tubular filter element 32 and integrally therewith 
a bypass valve 33, which structures will be explained in further detail 
with reference to the enlarged showings of the different embodiments of 
the invention in FIGS. 2 and 3. In these representations the same 
reference numerals are employed for corresponding parts for ease of 
understanding. 
Referring now to FIG. 2 and a second embodiment of the invention the 
diverter structure 30 is shown in more detail as comprising a 
funnel-shaped structure having a hollow conical wall portion 35 joined to 
a generally tubular necked-down section 36 at the central portion thereof. 
The conical wall 35 of the funnel 30 is terminated at its outer end in a 
raised edge 38 which is oblique with respect to the longitudinal axis of 
the filter. The edge 38 is generally an oblique section of a cylinder 
conforming to the inner surface 22 of the head casting 11 and disposed 
along a plane angled with respect to the longitudinal axis of the filter 
10. The edge 38 is substantially an annulus in the form of an elipse 
having the longer axis lying in the plane of the paper. A groove 40 is 
formed at the periphery of the edge 38 of the diverter 30, being bounded 
in part by the inward rim 42 which serves to secure an O-ring 34 in the 
groove 40. 
The rim 42, forming a part of the edge 38 of the diverter 30 is seated 
against an internal ledge 45, the latter partially circling the inner 
surface 22 of the head casting 11 at an oblique angle, generally extending 
from just outside the outlet port 21 toward a location inside the inlet 
port 20. The inner surface 22 consists of a larger diameter portion 
providing clearance for the diverter 30 and a reduced diameter seating 
portion 37, joined by the bevel 39. The head casting 11 is a die cast 
aluminum part and requires no further finishing for the internal surfaces 
thereof, including the seal seating portion 37 and the lead-in bevel 39. 
The cover member 24 which is in sealed engagement with the head casting 11 
by means of O-ring 48 may engage the outer portion of the edge 38 or be 
slightly spaced therefrom, as shown, to retain the diverter 30 in a seated 
position. A projection at 49 on edge 38 and a mating notch in inner 
surface 22, assure proper orientation between the diverter 30 and the head 
casting 11 so that the tubular portion 36 is concentric with the 
longitudinal axis of the housing 12. A pair of supports 50 provide a 
mounting device for transversely extending pin 51 which is used for 
gripping to assist in removing the diverter structure 30 from the head 
casting 11. The diverter 30, thus may be readily removed from or inserted 
in the head casting 11 by non-rotative axial movement, the bevel 39 
providing an initial compression of the seal 34 upon insertion. Engagement 
of projection 49 in its mating notch and the geometry of the seating parts 
of the diverter edge 38 and ledge 45 provide the proper orientation for 
the installation. 
The diverter 30, which is a molded plastic part, is preferably mounted in 
the head casting 11 with the operative axis of the bypass valve 33 
oriented at an angle of 45 from the axis of the outlet port 21. In this 
location, an optimum length of opening is provided for the poppet of the 
bypass valve 33 so that it will not obstruct the outlet port 21 or engage 
the interior wall 22 of the head casting. This arrangement provides 
sufficient spacing from the interior wall 22 so that the mounting boss for 
the bypass valve 33 does not disrupt significantly, the smooth flow of 
fluid about the exterior of the conical wall 35 of the diverter. Further, 
such orientation provides a relatively direct flow of fluid to the outlet 
port 21 when the bypass valve is opened. Still further, such orientation 
minimizes any jet stream effect upon the poppet due to inpingement of 
fluid from the inlet port 20. 
The filter element 32 consists of a cartridge type filter having a 
perforated tubular wall structure consisting of concentric inner and outer 
walls 54, 55 respectively, secured together at either end by means of end 
caps 56 and sealed at either end by annular rubber grommets 58. The filter 
element 32 thus is supported in the housing 12 on the tubular portion 36 
of the diverter 30 at one end and at the other end on the tubular 
projection 27 of the enclosure 60 in coaxial alignment with the tubular 
housing 12. 
In this embodiment of the invention end closure 60 comprises a cup-shaped 
member having a central tubular projection 27 with closed inner end 62. 
The closure member 60 in turn is releasably secured to the filter housing 
12, being welded to intermediate tubular adapter member 65, the latter 
having a radially extending flange 66 secured by the mounting bolts 68. 
The adapter member 65 slidably fits within a tubular extension member 69 
of the filter housing 12, the extension member 69 being of slightly 
greater diameter and welded in place to the filter housing. A groove 70 is 
formed in the adapter member 65 adjacent its inward end to retain O-ring 
seal 71 which provides fluid-tight engagement with the I.D. of the housing 
extension 69. The arrangement allows relative sliding movement between the 
housing extension 69 and the adapter member 65 while maintaining a 
fluid-tight seal. The flange 66 of the adapter member 65 includes slotted 
grooves therein forming a quick-connect coupling with the tubular 
extension 69 similar to that used at the housing flange 14 proximate to 
the head casting 11, as well as that for the cover member 24. Thus it may 
be seen that the end closure 60 may be rotated a slight amount to be freed 
from the loosened mounting bolts 68 and then withdrawn from the end of the 
tubular extension 69, maintaining fluid-tight engagement until the O-ring 
71 separates from the extension 69, a handle 72 being provided to 
facilitate this movement. 
A conical compression spring 74 is provided between projections 75 on the 
diverter 30, forming a spring retainer, and the inner end cap 56 of the 
filter element 32 thereby urging the filter element 32 into engagement 
with the closure member 60, being limited in movement by the shoulder 76 
on the latter. Thus as the closure member 60 is withdrawn from the tubular 
housing 12 it will be seen that the spring 74 urges the filter element 32 
outwardly such that the outer grommet 58 of the filter element 32 will 
maintain engagement with the shoulder 76 of the enclosure 60. The axial 
length of the tubular extension 69 is selected to be sufficiently long so 
that fluid-tight engagement between O-ring 71 and extension 69 is 
maintained until a position is reached wherein the inner grommet 58 clears 
the outer end of the tubular portion 36 of the diverter 30 to establish 
fluid communication between the interior of the housing 12 and the 
interior of the diverter 30. 
In a typical application for such filter embodiment depicted in FIG. 2 
housing 12 could be oriented in a vertical position within a fluid 
reservoir having a fluid level intermediate the end caps 56 of the filter 
element 32. In such arrangement the filter 10 is supported by bolts 68 in 
an aperture in the top wall 78 of the reservoir with fluid flow occuring 
between the inlet and outlet ports 20, 21. End closure 60 may be removed 
as described for replacement of filter element 32 and this will introduce 
air into the upper part of the reservoir, which if drawn into a pump 
connected to the fluid system could cause cavitation and possible damage. 
This is prevented by the automatic displacement of the filter element 32 
from the tubular support 36 of the diverter 30 under the urging of spring 
74, prior to breaking the fluid seal effected by O-ring 71. Thus it may be 
seen that fluid communication is achieved between the inlet and outlet 
ports 20, 21 by way of the central tubular portion 36 of the diverter 30 
without the introduction of air into the fluid system. In this described 
arrangement the interior of tubular portion 36 is entirely free of any 
structure. 
An alternative embodiment however, as fully depicted in FIG. 2, includes a 
check valve 80 disposed within the tubular portion 36 of the diverter 30. 
The valve 80 consists of a shutoff piston 81 carrying an O-ring seal 82 in 
a groove adjacent its inner end. The piston 81 is biased outwardly toward 
the distal end of the tubular housing 12 by means of spring 84 acting 
between spring retainer 85 and the retaining clip 86, the latter secured 
in a groove at the outer end of the piston 81. The check valve 80 is shown 
in the closed position in FIG. 2 however under normal operating conditions 
such check valve would be in an open position with fluid communication 
being provided via axial slots 87 through the wall of the piston 81, with 
the O-ring seal 82 being disposed inwardly within the hollow cone of the 
diverter element 30. An actuating device is provided for this purpose 
comprising rod 88 threaded at one end and secured to the piston by means 
of bolts 89 and engaging at the outer end the closed wall 62 of the 
tubular portion 27 of the closure member 60. 
The length of the actuator rod 88 is adjusted so that when the end closure 
member 60 is in a fully inward position in the tubular extension 69 of the 
filter housing 12, check valve 80 will be in an open condition such that 
fluid can flow through the tubular portion 36 of the diverter 30. As the 
end closure 60 is withdrawn from the housing extension 69 shutoff piston 
81 will follow the motion of the closure member through the intermediacy 
of the actuating rod 88 until the O-ring seal 82 enters the tubular 
portion 36 and creates a sealing engagement therewith. Further outward 
movement of the shutoff piston 81 is prevented by radially outwardly 
projecting flange 90 at the inner end thereof. 
Fluid flow in all of the embodiments of the invention is from the center of 
the filter element 32 to the periphery thereof and in the embodiments 
depicted in FIGS. 1 and 2 is from the inlet port 20 through the diverter 
cone 35 and the tubular portion 36 thereof, then through the filter 
element 32 to the outlet port 21. In the embodiment of the invention 
depicted in FIG. 3 however outlet port 21 is closed by means of cap 92 
secured by bolts 93 and the second port of the filter 10 is at the distal 
end of the filter housing 12. In FIG. 3 the filter 10 is mounted to an 
adaptor plate 95 in turn mounted to a wall of a fluid reservoir (not 
shown) by means of bolts passing through the apertures 96. In this return 
line type filter, head casting 11 is disposed outside the wall of the 
reservoir with the tubular housing 12 inserted therein into the fluid 
medium therein. The end closure or support 98 in this instance is a 
cup-shaped member having a similar central tubular extension 27 with a 
closed inner end wall (not shown) with circumferentially spaced apertures 
99 in the side of the cup. Thus fluid flow is into the port 20 through the 
diverter 30 into the interior of the filter element 32 and out the 
periphery thereof into the annular space within the tubular housing 12 and 
through the apertures 99 outwardly of the filter housing 12. 
In an alternative embodiment of the invention a check valve 100 is secured 
within the closure member 98. Such check valve 100 is a unidirectional 
flow pressure operated poppet type valve shown more clearly in enlarged 
form in FIG. 6. The poppet 102 thereon serves to close an aperture formed 
in the generally tubular adapter housing 104, the latter comprising a 
first annular section 105 threaded into a tubular support member 106 which 
in turn is welded in place within the cup of the end closure member 98. 
The check valve 100 comprises a snap-in type poppet assembly which can be 
readily interchanged to provide different pressure operating levels. 
Alternately, the check valve 100 could be arranged in an opposite 
disposition by means of a change of the housing section 105 to check flow 
of fluid in the reverse direction when the filter 10 is employed with the 
distal end of the filter housing 12 as the inlet port. 
When the filter is arranged with the distal end of the housing 12 as the 
inlet port, either with or without a check or shutoff valve at that 
location, a cap is placed over the inlet port 20, and the outlet port 21 
opened to act as the second port for the filter. The apertures 99 in the 
end member 98 are closed and a hole is located in the end wall of the 
tubular support member 27 so that the inlet is within the filter element 
32. Thus, fluid flow, again, is into the interior of the fluid element 32 
and through its periphery into the annular space inside the filter housing 
12, and then through the outlet port 21. The exterior conical surface of 
the diverter element, efficiently directs flow of fluid to the outlet port 
21, and it will be noted that bypass valve 33 serves, in its usual 
function, to maintain a maximum level of fluid pressure differential 
between inlet and outlet, regardless of the condition of the filter 
element 32. 
In all the embodiments of the invention a bypass valve 33 is employed to 
provide a fluid path between the inlet and outlet ports of the housing to 
prevent against a contaminated condition of the filter element 32 wherein 
such blocked filter might disrupt fluid flow or create too high a pressure 
drop. The bypass valve 33 is similar to the shutoff valve 102 depicted in 
FIG. 3 comprising a snap-in type replaceable poppet valve assembly adapted 
for quick interchange upon removal of the diverter 32 from the head 
casting 11. The poppet valve 33 is depicted in cross-section in FIG. 6 and 
is adapted to be mounted in an aperture in a flat surface formed as a 
generally transversely extending boss 108 disposed in the conical side 
wall 35 of the fluid diverter 30. The flat surface of the boss 108 lies in 
a plane generally parallel with the longitudinal axis of the filter and 
includes circumferentially spaced notches 109 about the central opening 
therein forming a part of a quick-connect arrangement and adapted to mount 
the bypass valve 33 within the hollow cone of the diverter 30 in a 
generally transverse position. 
Referring now to FIG. 6 it is seen that the valve 33 comprises a circular 
poppet 110 adapted to close upon a raised annular seat 112 in a generally 
circular poppet mount 114. The poppet is formed of nylon and the poppet 
mount 114 is preferably formed of glass filled nylon and the latter 
includes a central hub portion 115 supported by several radially extending 
legs 116, having spaces therebetween forming apertures for fluid flow 
through the mount 114. The hub 115 has a central bore for supporting a pin 
120 therein, the latter having a head at one end for retaining the poppet 
110 and a clip 121 at the either end securing a spring retainer 122 for 
guiding compression spring 124. The retaining clip 121 may be placed in 
different ones of cross holes 126 for varying the bias of the spring 124. 
The outer periphery of the poppet mount 114 is formed as a plurality of 
upstanding legs 128 each having a catch 129 thereon which is adapted to 
pass through a notch 109 in the boss 108 on the diverter 30 until 
engagement occurs between a peripheral ridge 130 on the poppet support 114 
and the lower surface of the boss 108. Partial rotation of the poppet 
assembly then will cause the catches 129 on the upstanding legs 128 to 
ride up on slight inclines on the outer face of the boss 108 until a 
slight depression is reached to secure the assembly in fluid-tight 
engagement within the boss 108. 
Referring now to FIGS. 4 and 5 there is shown the indicator element 140 of 
the invention which provides a visual indication of the fluid pressure 
differential within the filter housing 11 and thus an indication of the 
condition of the filter element 32. FIG. 4 is a view toward the inlet port 
20 of that embodiment of the invention shown in FIG. 1, the port 20 being 
a bore in the boss 142 protruding from the head casting 11. The position 
of the edge 38 of the diverter 30 is depicted in dashed lines in FIG. 4, 
the O-ring seal on such edge 38 dividing the interior of the head casting 
11 into two portions isolated from one another and which communicate 
respectively with the inlet and outlet ports of the filter 10. Lateral 
bosses 144, 146 protrude from the head casting 11 each having a port 
therein communicating with the interior of the head casting 11 on opposite 
sides of the O-ring seal on the edge 38 of the diverter 30. Thus bosses 
146 have bores therein in communication with the inlet port 20 while boss 
144 has a bore therein in communication with outlet port 21. 
The indicator 140 comprises a housing formed of identical end structures 
148 securing a glass sleeve 149 therebetween by means of bolts 150. The 
sleeve 149 and recesses in the end caps 148 form a central cylindrical 
chamber in which is disposed a piston structure consisting of back-to-back 
upper and lower cup-shaped members 152, 154 respectively secured by bolt 
155. 
A pair of diaphragms are secured at one end between the sleeve 149 and the 
end members 148 and at the other end at opposite ends of an indicator 
sleeve 160 secured between shoulders of the upper and lower cup-shaped 
piston members 152, 154. The diaphragms 158, 159 are annular rolling 
diaphragms having a fold intermediate their respective ends and are 
positioned such that there is a short axial space between the adjacent 
folds indicated generally at the arrow 162. It will be seen that as the 
piston assembly 152, 154 moves upwardly and downwardly within the 
cylindrical chamber, the viewing space 162 will maintain approximately the 
same spacing between folds but will move upwardly and downwardly with the 
piston to expose different axial segments of the indicator sleeve 160. As 
seen in FIG. 4 the indicator sleeve 160 is colored with different bands to 
provide a visual indication of the different positions of the piston 
assembly therein. 
The indicator housing 140 is mounted to the head casting 11 at the bosses 
146, 144 by means of bolts 163, with sealing being effected by O-rings 
165. Bores in the ports 146, 144 communicate with the indicator housing 
bores 166, 164 which in turn communicate respectively with the chambers 
formed above the upper diaphragm 158 and below the lower diaphragm 159. 
Thus, fluid pressure on either side of the diverter edge 38 is applied to 
the piston assembly 152, 154 to effect a differential force upon the 
piston assembly and a positioning of same in a manner well-understood in 
the art. A light compression spring 180 is mounted between a boss in the 
lower housing section 148 and the inside well of the lower piston portion 
154, thereby continuously urging the piston assembly in an upward 
direction as viewed in FIG. 5. A second spring 182 having a higher spring 
rate than that of spring 180 is coaxially mounted therewith but terminates 
at the last coil 183 thereof out of contact with the lower piston portion 
154 such that the spring 182 is not engaged until the piston assembly has 
moved to a position where indications are desired of the fluid pressure 
differential within the filter 10 housing. In this manner a different 
spring rate may be provided for fluid pressure differential indications 
while the light spring bias provided by spring 180 serves to retain the 
piston assembly fully in one position in the absence of any fluid pressure 
differential acting against the diaphragms 158, 159. A magnet 185 is 
further secured in the inner well of the upper piston element 152 and is 
adapted to create a magnetic field outside of the housing 148 for 
actuation of a reed switch or the like (not shown) to provide a remote 
indication of the piston assembly position and thus of the contaminated 
condition of the filter element 32, or even the lack of filter element in 
the filter. 
As noted in FIG. 4 the indicator sleeve 160 is divided into several axially 
spaced segments of different colors ranging from white through green and 
yellow to red, wherein white gives an indication of absence of filter 
element, green the proper operating pressure differential, and yellow and 
red indicating higher pressure differentials, demonstrating a relatively 
clogged condition of the filter element 32, and indicating the need for 
replacement thereof.