Filter arrangement with baffles

The invention is concerned with an improvement in a hydraulic reservoir which comprises a tank having internally thereof filter means attached longitudinally between a first and a second generally parallel side thereof, said filter means including generally tubular filter element means extending generally longitudinally between said first and second sides of said tank and means for introducing a hydraulic fluid from an exterior of said tank to an interior of said element means from adjacent said first side of said tank. The improvement of the invention comprises a tube within said tank surrounding said element means and extending longitudinally generally the length thereof, said tube including exit means therethrough through which said hydraulic fluid passes after passage thereof from the interior to an exterior of said element means, a first end of said tube sealing adjacent said second side of said tank and a second end of said tube sealing adjacent said first side of said tank. Also a part of the improvement of the invention is baffle means within said tank arranged to receive generally all of said hydraulic fluid which passes through said exit means, said baffle means conducting said hydraulic fluid to below fluid level in said reservoir and having egress means therefrom wholly below said normal fluid level.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention is concerned with an improved filter means internal of a 
hydraulic reservoir, which filter means includes baffle means which 
directs fluid from said filter means to egress into the reservoir only 
below a normal fluid level therewithin. 
2. Prior Art 
The prior art has primarily been concerned with filter elements which are 
of the spin on or thread on type and are attachable externally of a 
hydraulic system which contains a hydraulic fluid. Generally, flow is 
provided of the hydraulic fluid through such a filter element and then 
from that filter element to a sump or other hydraulic reservoir of the 
system. A typical prior art external filter element of this nature is 
disclosed for example in U.S. Pat. No. 3,685,658. Some prior art filter 
assembly of this nature have provided bypass flow which takes over in case 
of a clogging of the filter element. U.S. Pat. No. 3,374,892 for example 
discloses such a filter assembly. Some filter elements are also used 
within hydraulic reservoirs such as those disclosed in for example U.S. 
Pat. Nos. 3,0886,072 and 3,900,400 but these are of considerably different 
structure, operation and mounting than are the structures of the present 
invention. 
It can be very desirable to place filter means for a hydraulic system 
within a hydraulic reservoir of the system so as to obtain more resistance 
to flow, protection of the filter elements from damage from external 
sources and the like. However, with such an internal filter means it has 
been found that it is necessary to ensure that excessive foaming of the 
hydraulic fluid does not occur as this fluid leaves the filter means and 
is introduced into the interior of the hydraulic reservoir. The present 
invention provides just such an internal filter means wherein foaming is 
prevented and, further, in preferred embodiments of the invention provides 
bypass valve means whereby hydraulic fluid is introduced to the reservoir 
generally via the filter means when the filter elements themselves are 
partially or completely clogged, which bypass valve directs the bypassing 
hydraulic fluid to be introduced in such a manner that foaming does not 
occur within the reservoir. These and other advantages of the invention as 
will become apparent by reading the following specification are 
accomplished as set out herein. 
SUMMARY OF THE INVENTION 
The invention relates to an improvement in a hydraulic reservoir which 
comprises a tank having internally thereof filter means attached 
longitudinally between a first and a second generally parallel side 
thereof, said filter means including generally tubular filter element 
means extending generally longitudinally between said first and second 
side of said tank and means for introducing a hydraulic fluid from an 
exterior of said tank to an interior of said element means from adjacent 
said first side of said tank. The improvement of the invention comprises a 
tube within said tank surrounding said element means and extending 
longitudinally generally the length thereof, said tube including exit 
means therethrough through which said hydraulic fluid passes after passage 
thereof from the interior to an exterior of said element means, a first 
end of said tube sealing adjacent said second side of said tank and a 
second end of said tube sealing adjacent said first side of said tank. 
Also part of the improvement of the invention is baffle means within said 
tank arranged to receive generally all of said hydraulic fluid which 
passes through said exit means, said baffle means conducting said 
hydraulic fluid to below a normal fluid level in said reservoir and having 
egress means therefrom only below said normal fluid level.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning first to FIG. 1 there is illustrated therein a hydraulic reservoir 
10 which comprises a tank 12 having internally thereof filter means 14 
attached longitudinally between a first side 16 and a second generally 
parallel side 18 of the tank 12. The filter means 14 includes generally 
tubular filter element means 20 which in the particular embodiment 
illustrated comprises four filter elements 22 which are shown most clearly 
in FIGS. 1 and 2. Hydraulic fluid introducing means 24 shown most clearly 
in FIGS. 1 and 3 provide means for introducing a hydraulic fluid from an 
exterior of the tank, generally from a hydraulic system 26 as illustrated 
schematically in FIG. 3 to an interior 28 of the filter element 20 from 
adjacent the first side 16 of the tank 12. 
The invention is particularly concerned with a tube within the tank 12 
which surrounds the filter element means 20 and extends longitudinally 
generally the length of said filter element means 20. The tube 30 includes 
exit means 32 therefrom generally from the bottom thereof through which 
the hydraulic fluid passes after passage of the hydraulic fluid from the 
interior 28 of the filter element means 20 to an exterior 34 of the filter 
element means 20. More particularly the exit means 32 leads from a chamber 
36 formed between the filter element means 20 and the tube generally to 
the inside of the hydraulic reservoir 10. The exit means 32 generally 
forms the exclusive exit from the tube 30. 
The tube 30 is compressibly sealed by compressible sealing means 38 in such 
a manner that a first end 40 of the tube 30 is held adjacent the second 
side 18 of the tank 12. The compressible sealing means of the present 
invention preferably comprises a flange 42 which extends peripherally 
outwardly from the tube 30 adjacent the first end 40 thereof and a 
compressible elastomeric gasket 44 which is compressed between the flange 
42 and the second side 18 of the tank 12. 
The improvement of the present invention preferably includes rigid 
attaching means 46 for rigidly attaching a second end 48 of the tube 30 
adjacent the first side 16 of the tank 12. Holding means 50 for the filter 
element means 20 also preferably form a part of the improvement of the 
present invention. The holding means can simply comprise a pilot 52 in a 
port closure means 54 which covers a port 56 in the first side 16 of the 
tank 12. Two of the four filter elements 22, one of which is shown in FIG. 
1, are thus rigidly held by the pilot 52. 
An opening 58 through the second side 18 of the tank 12 provides access to 
an interior 60 of the tube 30 adjacent the first end 40 thereof. The 
opening 58 is sized to allow entry of the filter element means 20 and more 
particularly of the four filter elements 22 to the interior 60 of the tube 
30. Cover means 62 is provided which is ealingly attachable, as for 
example by using a seal ring 64, over the opening 58. The cover means 62 
is attacheble longitudinally through the tube 30 to adjacent the first 
side 16 of the tank 12 and more specifically is attachable to the port 
closure means 54 as by being screwed into the port closure means 54 via an 
elongated bolt means 66. The bolt means 66 pass through the cover means 62 
and are sealed thereto by a seal ring 67. 
Compressible positioning means 68, in the embodiment illustrated a 
plurality of axially compressible resilient washers 70 which bear against 
a retaining washer 72 sreve to compressibly hold the filter element means 
20 between the first side 16 and the second side 18 of the tank 12. A 
retaining ring 74 generally serves to hold the plurality of resilient 
washers 70 and the retaining washer 72 from escaping from an extension 76 
which extends from the cover 62 towards the first side 16 of the tank 12. 
The tank 12 of the preferred embodiment includes means for disassembling it 
into a first part 78 which includes the first side 16 as part thereof and 
a second part 80 which includes the second side 18 of the tank 12 as a 
part thereof. The disassembling means for the tank generally includes the 
pair of flanges 82 and 84 extending respectively from the first part 78 
and the second part 80 of the tank 12 and a plurality of bolt-nut means 86 
fastening the first flange 82 to the second flange 84. Because of this 
disassembleability of the tank 12, the tube 30 can be readily placed 
therewithin and the port closure means 54 can be attached from the 
interior of the tank 12 when the first part 78 thereof is separated from 
the second part 80 thereof. After the tube 30 has been attached to the 
first part 78 and more particularly to the first side 16 of the tank 12, 
the gasket 44 can be put in place adjacent the flange 42 and the bolt-nut 
means 86 can be fastened in place. The filter element means 20 can be put 
in place either when the tank 12 is disassembled into the first part 78 
and the second part 80 thereof or can be put in place through the opening 
58 before or after removal of the cover 62. 
Referring now most particularly to FIGS. 4 and 5 there is illustrated 
therein baffle means 90 which extends generally downwardly from the exit 
means 32 of the tube 30. Further, the exit means 32 of the tube 30 forms 
the exclusive exit therefrom. The baffle means 90 which in the embodiment 
illustrated comprises a hollow flattened tubular member 92 serves to 
conduct fluid from the exit means 32 of the tube 30 to below a normal 
liquid level located beneath the tube 30 and generally falling between a 
fill level 94 and a full level 96 indicated on a sight gauge 97. The 
baffle means 90 includes egress means 98, generally a plurality of holes 
100, which egress means 98 is below said normal fluid level. Thus, the 
egress means 98 or more particularly the plurality of holes 100 is 
normally below the fill level 94 within the tank 12. Generally, the holes 
100 are placed in the sides 102 of the flattened tubular member 92 whereby 
fluid leaves the plurality of holes 100 generally perpendicularly to it's 
direction of flow within the flattened tubular member 92 thus leading 
generally to a smooth and even introduction of hydraulic fluid into the 
interior of the tank 12. 
Because of the spaced arrangement of the filter arrangement of the filter 
element means 20 from the interior 60 of the tube 30 the chamber 36 is 
defined therebetween. This chamber 36 serves a very important function in 
providing fluid flow into the hydraulic reservoir 10 even when the filter 
element means 20 are obstructed as by being filled with dirt or the like. 
In particular, bypass valve means 104 seen most clearly in FIGS. 1 and 6 
and shown in an alternate embodiment in FIG. 7 is provided in flow 
communication with the hydraulic system 26 from which hydraulic fluid is 
introduced via the hydraulic fluid introducing means 24 to the interior 28 
of the filter element means 20. A pressure sensed by the bypass valve 
means 104 as via a passage 106 which applies pressure to a top 108 of a 
spool 110 leads to the spool 110 being forced downwardly whereby fluid 
flow can occur about an annulus 112 and thence via a bore 114 and a 
passage 115 to the chamber 36. The fluid from the chamber 36 then flows in 
the same manner as it would have flowed through the filter element means 
20. In other words, the fluid from the chamber 36 then flows into the 
baffle means 90 and is released via the egress means 98 below the normal 
liquid level and generally below the fill level 94 of the tank 12. 
In the alternate embodiment of the bypass valve means 104 as illustrated in 
FIG. 7 a pressure is still applied in the same manner via the passage 106 
to the top 108 of the spool 110. In this embodiment, however, the fluid 
flows into a well 116 in the spool 110 and flows from the well 116 via a 
plurality of passages 118 and thence to the annulus 112. In this 
arrangement, the flow through the bypass valve means 104 is modulated by 
the plurality of passages 118. 
It is clear that in both embodiments of the bypass valve means 104 of the 
present invention the pressure sensed by the bypass valve means 104, i.e., 
the pressure in the passage 106, is proportional to a pressure of 
hydraulic fluid at the interior 28, of the filter element means 20. Thus, 
as the pressure within the interior 28 of the filter element means 20 
builds up due to clogging of the filter element means 20 as it becomes 
dirty with particulate matter brought to it from the hydraulic system 26, 
the pressure at the top 108 of the spool 110 will become sufficient to 
overcome biasing means, generally spring means such as a spring 120 which 
biases the bypass valve means 104 into a closed position. The pressure 
value within the interior 28 of the filter element means 20 which is 
sufficient to move the spool 110 of the bypass valve means 104 is thus a 
value predetermined by the strength of the spring 120 or other biasing 
means used in place thereof. The compressible positioning means 68 acts in 
concert with the bypass valve means 104 by assuring that the interior 28 
of the filter element means 20 has no other escape route to the interior 
of the tank 12. 
While the invention has been described in connection with specific 
embodiments thereof, it will be understood that it is capable of further 
modification, and this application is intended to cover any variations, 
uses or adaptations of the invention following, in general, the principles 
of the invention and including such departures from the present disclosure 
as come within known or customary practice in the art to which the 
invention pertains and as may be applied to the essential features 
hereinbefore set forth, and as fall within the scope of the invention and 
the limits of the appended claims.