Abstract:
A hydraulic storage tank is provided. The hydraulic storage tank includes a storage tank, a return flow filtration chamber, a contaminant containment chamber (CCC) and a tube connecting the return flow filtration chamber with the CCC. The storage tank defines a reservoir for storing hydraulic fluid. The return flow filtration chamber is configured to house a return flow filter. The CCC includes a boundary wall bounding a cavity and a CCC outlet fluidly communicating the cavity with the reservoir. The CCC outlet is radially inward from the boundary wall. The tube defines a discharge passage fluidly connecting the filtration chamber with the cavity of the CCC and includes an inlet in fluid communication with the filtration chamber and an outlet in fluid communication with the CCC. The outlet of the tube directs fluid in angular direction about an axis defined by the contaminant containment chamber outlet.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This patent application claims the benefit of U.S. Provisional Patent Application No. 61/093,014, filed Aug. 29, 2008, the disclosure and teachings of which are incorporated herein, in their entireties, by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention generally relates to hydraulic fluid storage tanks and particularly hydraulic fluid storage tanks for hydraulic fluid that is drawn from the tank, circulated through a hydraulic system and then deposited back into the storage tank. 
       BACKGROUND OF THE INVENTION 
       [0003]    Typical hydraulic systems have a hydraulic reservoir (i.e. a hydraulic fluid storage tank) that stores excess hydraulic fluid that is used by the system. The hydraulic fluid is a working fluid that is typically used to drive hydraulic cylinders, pumps, hydraulic motors or other devices for performing desired operations. Typically, the hydraulic systems will include a hydraulic pump to pressurize the fluid as it passes through the system to provide adequate power to drive the devices of the system. Additionally, hydraulic systems typically reuse the hydraulic fluid such that the hydraulic fluid is drawn from the storage tank passed through the system and then deposited back into the storage tank where it is held until it is reused by the system again. 
         [0004]    To prevent debris or impurities from repeatedly passing through the system, prior art storage tanks  10 , such as illustrated in  FIG. 1 , typically include a return flow filter  12  that may be either internal to the tank (as shown) or external to the tank (not shown) that filters the return fluid (illustrated as arrows  14 ) prior to the fluid being mixed with the rest of the clean fluid  16  being stored in the fluid tank  10 . Unfortunately, when a device within the system fails, debris created due to the failure of the failed component enters the hydraulic system and is transferred back to the storage tank  10 . 
         [0005]    To prevent the system from running dry of fluid or from creating a back pressure on the system, many systems include a bypass valve  17  (either within the filter  12  itself or the reservoir  18  in which the filter  12  is housed, as shown in  FIG. 1 ) that allows fluid  20  to bypass the filter  12 , or at least the filter media of the filter  12 , when the return flow filter  12  becomes spent. Unfortunately, when the bypass valve  17  opens, this permits the large debris  21  from any component failure to pass into the clean fluid storage area  22  of the storage tank  10 . This debris  21  then has the opportunity to reenter the hydraulic system, which can result in further damage to the hydraulic system. 
         [0006]    To prevent this debris  21  from again passing through the system, the storage tank  12  typically includes a baffle  24  that impedes the debris from reaching fluid outlet  26  (also known as a suction port). Additionally, the fluid outlet  26  or suction port is typically protected by a strainer  28 , which is basically a coarse screen. Unfortunately, the baffle plate  24  and strainer  28  can be expensive and when the strainer  28  becomes clogged, pumps within the hydraulic system begin to run dry from fluid or are not otherwise sufficiently supplied with fluid such that the pumps begin to cavitate or otherwise degrade. 
         [0007]    The present invention relates to improvements over the current state of hydraulic storage tanks that incorporate a fluid bypass that allows fluid to bypass the return flow filter. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The present invention provides a new and improved hydraulic fluid storage tank. More particularly, the present invention provides a new and improved hydraulic fluid storage tank that prevents the need of screen or filtration device proximate an outlet or suction port of the storage tank reservoir. Further yet, the present invention provides a new and improved hydraulic fluid storage tank that need not be entirely drained to clean contaminants that pass through a bypass valve in a return flow filtration assembly due to filter clogging. 
         [0009]    In that respect, in one embodiment, a hydraulic storage tank is provided. The hydraulic storage tank includes a storage tank, a return flow filtration chamber, a contaminant containment chamber (CCC) and a tube connecting the return flow filtration chamber with the CCC. The storage tank defines a reservoir for storing hydraulic fluid. The return flow filtration chamber is configured to house a return flow filter. The CCC includes a boundary wall bounding a cavity and a CCC outlet fluidly communicating the cavity with the reservoir. The CCC outlet is radially inward from the boundary wall. The tube defines a discharge passage fluidly connecting the filtration chamber or other source of return fluid with the cavity of the CCC and includes an inlet in fluid communication with the filtration chamber and an outlet in fluid communication with the CCC. The outlet of the tube directs fluid in angular direction about an axis defined by the contaminant containment chamber outlet. 
         [0010]    In a preferred embodiment, the discharge passage flows through the boundary wall of the CCC, rather than down through the outlet of the CCC. The outlet of the discharge passage is thus aligned non-radially such that the outlet flow of the discharge passage generates a swirling or angular motion of the fluid about a central axis defined by the outlet of the CCC. This motion causes heavier particulates to flow radially outward such that as the fluid flows through the CCC, the particulates are trapped within the CCC and prevented from the flowing back into the reservoir. 
         [0011]    In a further embodiment, an entire hydraulic system is provided. The hydraulic system includes a storage tank, a return flow filtration chamber, a contaminant containment chamber (CCC), a tube connecting the return flow filtration chamber with the CCC and a pump. The storage tank defines a reservoir for storing hydraulic fluid. The return flow filtration chamber is configured to house a return flow filter. The CCC includes a boundary wall bounding a cavity and a CCC outlet fluidly communicating the cavity with the reservoir. The CCC outlet is radially inward from the boundary wall. The tube defines a discharge passage fluidly connecting the filtration chamber with the cavity of the CCC and includes an inlet in fluid communication with the filtration chamber and an outlet in fluid communication with the CCC. The outlet of the tube directs fluid in angular direction about an axis defined by the contaminant containment chamber outlet. The pump operably coupled to the storage tank circulates fluid through the system from the storage tank and back into the storage tank. 
         [0012]    Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
           [0014]      FIG. 1  is a simplified schematic representation of a hydraulic storage tank of the prior art; 
           [0015]      FIG. 2  is a simplified schematic representation of an embodiment of a hydraulic storage tank according to teachings of the present invention; 
           [0016]      FIG. 3  is first cross-sectional illustration of a storage tank according to an embodiment of the present invention; 
           [0017]      FIG. 4  is a further cross-sectional illustration of the storage tank of  FIG. 3 ; 
           [0018]      FIG. 5  is a further cross-sectional illustration of the storage tank of  FIG. 3 ; and 
           [0019]      FIG. 6  is an enlarged schematic representation of the flow path of the fluid within the contaminant containment chamber of the storage tank of  FIG. 3 . 
       
    
    
       [0020]    While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Turning now to  FIG. 2 , a simplified schematic representation of a hydraulic storage tank  100  according to the teachings of the present invention. The storage tank  100  stores hydraulic fluid  102  within reservoir  104  formed by the storage tank  100 . The storage tank  100  forms part of a larger hydraulic system (not shown), which draws the hydraulic fluid from the storage tank  100 , uses the fluid to power other devices, and then returns the fluid back to the storage tank  100 . 
         [0022]    The hydraulic storage tank  100  generally includes a return flow filter assembly  106 . The return flow filter assembly  106  includes a filtration chamber  108  which is generally positioned within reservoir  104  that houses a return flow filter  110 . The return flow filter assembly includes a bypass valve  112  that forms part of the return flow filter  110  that opens due to an increase in pressure within the filtration chamber  108  when the return flow filter  110  becomes clogged or spent. The bypass valve  112  could be located external to and form no part of the return flow filter  110 . 
         [0023]    The filtration chamber  108  further includes a discharge passage  114  that allows fluid to exit the filtration chamber  108 . In the illustrated embodiment, fluid can only pass through the discharge passage  114  by passing through the return flow filter  110 . However, this fluid may or may not be filtered depending on whether or not the fluid passes through the filter media of the return flow filter  110  (i.e. when the return flow filter  110  is not spent) or through the bypass valve  112  (i.e. when the return flow filter  110  is spent). 
         [0024]    Unlike the prior art tank  10  described above, the discharge passage does not dispense the fluid directly into reservoir  104 . Thus, any particulate that may pass through the bypass valve  112  upon component failure is not immediately dispensed into the reservoir  104 , and the rest of the clean fluid  102 , like the prior art tank  10 . 
         [0025]    Instead, according to an embodiment of the present invention, the discharge passage  114  dispenses into a contaminant containment chamber  116 . This contaminant containment chamber  116  is configured to trap large particulate debris  117  prior to the fluid returning to reservoir  114 . 
         [0026]    The contaminant containment chamber  116  acts on centrifugal fluid motion to separate the large particulate debris  117  from the fluid. The discharge passage  114  includes an arrangement of one or more apertures that forms outlet  118  that is configured to direct the return fluid in a circular flow within contaminant containment chamber  116 . In the illustrated embodiment, the return fluid is directed in a circular flow about an axis  120  defined by the centerline of discharge passage  114 . More particularly, the fluid exits outlet  118  generally angularly relative to axis  120  and generally tangent to the circular cross-section of the tube/pipe forming discharge passage  114 . It should be noted that the tube/pipe forming discharge passage  114  is generally closed at the end  119  that is positioned within contaminant containment chamber  116 . 
         [0027]    This circular motion causes the larger particulates to move to the outer portion of the circular flow and proximate annular boundary wall  121  of the contaminant containment chamber  116 . 
         [0028]    The contaminant containment chamber  116  includes an outlet  122  that is positioned radially inward of the annular boundary wall  121  such that only fluid free of the large particulates  117  is permitted to exit into reservoir  104 . In the illustrated embodiment, outlet  122  is an aperture formed in a top wall  124  of the contaminant containment chamber  116  that is generally perpendicular to annular boundary wall  121 . The outlet  122  has an inner diameter that is larger than an outer diameter of the pipe or tube that forms discharge passage  114  and the outlet circumscribes discharge passage  114 . 
         [0029]    The contaminant containment chamber  116  further includes a purge port  126  that includes a plug  128  that can be opened to clean the contaminant containment chamber  116 . One benefit of this embodiment of the present invention is that all of the large contaminant  117  is stored within the contaminant containment chamber  116  and when the purge port  126  is opened for maintenance all of the fluid within the reservoir  104  need not be removed to clean the contaminant containment chamber  116 . Instead, only the amount of fluid within reservoir  104  that is within the annular boundary wall  121  will be drained from reservoir  104 . In the past, the entire tank  10  would need to be drained to remove contaminants  21  (See  FIG. 1 ). 
         [0030]    To maximize the amount of fluid  102  that remains in reservoir  104  when draining contaminant containment chamber  116 , it is desirous to have opening  122  as close to the top  130  of the storage tank  130  as possible. 
         [0031]    To generate the circular fluid motion within contaminant containment chamber  116 , outlet  118  of the discharge passage  114  includes a louver  132  that directs fluid exiting the tube/pipe forming the discharge passage  114  angularly about central axis  120 . In a preferred embodiment, the louver  132  is directly machined from the sidewall of the tube/pipe forming the discharge passage  114 . Alternatively, a secondary piece can be mounted to the discharge passage  114  to effectuate angularly directing the flow of fluid out of outlet  118 . 
         [0032]    The outlet  118  of the discharge passage  114  may actually be formed from a plurality of outlets that are angularly spaced apart about axis  120 , however, the plurality of outlets can be referred to in the singular for simplicity as they combine to generally form an outlet out of discharge passage  114 . 
         [0033]    By utilizing a contaminant containment chamber  116  according to the teachings of the present invention, the outlet  140  of the storage tank  100 , i.e. the suction port, from which fluid stored within reservoir  104  exits tank  100  can be free of any strainers or screens. Further, the additional baffle plate is not necessary. Further, in some embodiments, the amount of material required to form the baffle plate in the prior art is more than or about equal to the amount of material required to from the contaminant containment chamber  116 . 
         [0034]    In alternative embodiment, the discharge passage  114  need not be aligned with the central axis  120  defined by opening  122  and contaminant containment cavity  116 , but could extend perpendicular to the illustrated arrangement such that the discharge passage passes through boundary wall  121 . In this arrangement, the flow of the fluid through the discharge passage  114  at the outlet thereof could be directly aligned with the tangent of the desired circular motion within the contaminant containment chamber  116 . 
         [0035]      FIG. 3  is a cross-sectional illustration of an alternative embodiment of the a hydraulic storage tank  200  that utilizes this alternative discharge passage arrangement. 
         [0036]    The hydraulic storage tank  200  generally includes a return flow filter assembly  206 . The return flow filter assembly  206  includes a filtration chamber  208  which is generally positioned within reservoir  204  that houses filter  210 . 
         [0037]    A discharge passage  214  fluidly connects the filtration chamber  208  to contaminant containment chamber  216 . The output of discharge passage  214  is dispensed into contaminant containment chamber  216 . The orientation of the discharge passage  214  relative to the contaminant containment chamber  216  is such that the fluid flow, illustrated as arrow  219 , swirls within contaminant containment chamber  216 , as discussed previously, to cause particulates  217  entrapped in fluid flow  219  to be deposited along boundary wall  221 . 
         [0038]    In this arrangement, the outlet  232  of the discharge passage passes through annular boundary wall  221  rather than down through a top wall  224  of the contaminant containment chamber  216  (see  FIG. 3 ). As illustrated in  FIG. 4 , the flow path of the fluid flow  219  as it exits outlet  232  is offset from the radius of boundary wall  221 . Thus, the fluid flow does not pass through the central axis  220  of the contaminant containment chamber  216 . Instead, the flow path is substantially tangent to the annular boundary wall  221  such that the flow is directed in the swirling motion as illustrated in  FIG. 4 . 
         [0039]    The outlet  232  need not be perfectly tangent, but is desired that the angle α between the radius and flow path, as illustrated in  FIG. 6 , is greater than 30 degrees and more preferably greater than 45 degrees and even more preferably greater than 60 degrees. The closer angle α approaches 90 degrees the better swirling action and reduced amount of deleterious turbulence that is generate in the fluid within the contaminant containment chamber  216 . While angle α may be used to describe the orientation of the outlet  232  relative to the rest of the contaminant containment chamber  216 , angle β may also be used. Angle β is the angle between the flow path and the tangent of the boundary wall  221 . This angle is preferably between zero and sixty degrees. Using angle β can be beneficial in the event that the boundary wall  221  is not perfectly circular. 
         [0040]    The contaminant containment chamber  216  includes an outlet  222  that is proximate the center of the contaminant containment chamber  216  defined by annular boundary wall  221 . This outlet  222  allows the fluid to exit the contaminant containment chamber  216  but traps the heavier particles  217  within the contaminant containment chamber  216  because, due to the swirling action, they are prevented from reaching the center point of the chamber  216 . 
         [0041]    In one embodiment, a further filter  270  (see  FIG. 3 ) is attached to the outlet  222 . This filter  270  is typically a course filter used typically only to prevent contaminants from passing though outlet  222  during start-up of the fluid system. At this transient time, the swirling effect has not been established and may cause turbulence in the contaminant containment chamber  216  that will mix the previously separated contaminant particulates into the fluid flow such that they will pass through outlet  222 . However, for systems that will remain in a constant flow position or steady state configuration without repeated startups this course startup filter may not be required. 
         [0042]    By not having the discharge passage pass through the center of the contaminant containment chamber  216 , such as illustrated in the embodiment of  FIG. 2 , this arrangement is more conducive to the inclusion of a filter element  270  coupled to outlet  222 . In one embodiment, outlet  222  is formed by a pipe or other conduit extending upward from top wall  224 . This pipe type outlet  222  may have a U-shaped bend such that it discharges cleaned fluid in a downward direction, and typically below top wall  224  (see generally  FIG. 5 ). This U-shaped arrangement can also work to prevent fluid from being drawn from the storage tank  200  when the contaminant containment chamber  216  is drained to remove particles  217  or to replace the filter element contained therein. 
         [0043]    While only a single discharge passage  214  is illustrated in the embodiment of  FIGS. 3-4 , a pair of discharge passages  214  may be used. These passages would typically be oriented at 180 degree orientations from one another so that the fluid discharge therefrom does not interfere with one another, but promotes the swirling action in a common or coordinated angular direction. 
         [0044]    All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
         [0045]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
         [0046]    Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.