Patent Document

BACKGROUND 
       [0001]    This invention relates to a hydraulic fluid cooling and filtering assembly and a method of cooling and filtering fluid in a hydraulic system. 
         [0002]    Hydraulic systems are used in many different applications including in vehicles such as trucks and trailers. In order to maintain a hydraulic system operating efficiently the hydraulic fluid must be maintained cool and free of particulates. There is a continual need for improved systems and methods of conditioning hydraulic fluid in hydraulic circuits. 
       SUMMARY 
       [0003]    One aspect of the invention features a hydraulic fluid cooling and filtering assembly. The assembly includes an inlet tank in hydraulic communication with an assembly inlet, an outlet tank in hydraulic communication with an assembly outlet, and a heat exchanger. The heat exchanger includes multiple fluid channels forming separate flow paths between respective fluid channel inlets at the inlet tank and respective fluid channel outlets at the outlet tank where the fluid channel outlets are spaced apart along a length of the outlet tank over a flow outlet span and cross-flow air channels are formed between the fluid channels. A filter element is disposed within the outlet tank. The filter element includes an internal cavity in hydraulic communication with the assembly outlet and porous filtering material separating the internal cavity from the heat exchanger fluid channel outlets. The filter element is elongated and has an outer filtering surface extending along at least most of the flow outlet span of the heat exchanger, and the outer filtering surface is directly exposed to the fluid channel outlets such that straight lines are defined by the respective inlets and outlets of each fluid channel of the heat exchanger that intersect the outer filtering surface, the lines passing only through fluid within the outlet tank. 
         [0004]    In some cases, the outlet tank includes one or more ports configured to receive a fluid monitoring device. In some cases, the inlet tank includes one or more ports configured to receive a fluid monitoring device. In some examples, the heat exchanger is constructed of brazed aluminum bar-plate. In some cases, the filtering element is a self-supporting filtering element. 
         [0005]    In some implementations the assembly is connected in a hydraulic circuit that includes a pump to motivate fluid from the assembly inlet of the inlet tank to the assembly outlet of the outlet tank through fluid flow from the assembly inlet of the inlet tank, into the inlet tank, through the multiple fluid channels, out of the heat exchanger fluid channel outlets, through the porous filtering material of the filter element, and into the internal cavity defined by the filtering element and in hydraulic communication with the assembly outlet. 
         [0006]    In some implementations the assembly includes a bypass path in hydraulic communication with the inlet tank and with the assembly outlet and a bypass valve disposed within the bypass path to allow fluid flow from the inlet tank, through the bypass path, around the heat exchanger and the filter, and out of the assembly outlet when the bypass valve is in an open position. In some implementations the bypass valve is an electrically operated valve set to open at a threshold fluid pressure between the inlet tank and the assembly outlet. 
         [0007]    In some implementations, the assembly includes a cover removably coupled to the outlet tank and a filter bypass valve in hydraulic communication with the outlet tank and the internal cavity defined by the filter element where the bypass valve is coupled to the cover such that removing the cover from the outlet tank removes the bypass valve. The filter bypass valve permits fluid to flow from the heat exchanger fluid channel outlets, around the porous filtering material of the filter element, and into the internal cavity defined by the filter element when the bypass valve is in an open position. 
         [0008]    Another aspect of the invention features a hydraulic fluid cooling and filtering assembly including an inlet tank in hydraulic communication with an assembly inlet, an outlet tank in hydraulic communication with an assembly outlet, a cover removably coupled to the outlet tank, a heat exchanger, a filter element disposed within the outlet tank, and a filter bypass valve. The heat exchanger includes multiple fluid channels forming separate flow paths between respective fluid channel inlets at the inlet tank and respective fluid channel outlets at the outlet tank where the fluid channel outlets are spaced apart along a length of the outlet tank over a flow outlet span and cross-flow air channels are formed between the fluid channels. The filter element includes an internal cavity in hydraulic communication with the assembly outlet and porous filtering material separating the internal cavity from the heat exchanger fluid channel outlets. The filter bypass valve is in hydraulic communication with the outlet tank and the internal cavity defined by the filter element and the bypass valve is coupled to the cover such that removing the cover from the outlet tank removes the bypass valve. The filter bypass valve permits fluid to flow from the heat exchanger fluid channel outlets, around the porous filtering material of the filter element, and into the internal cavity defined by the filter element when the bypass valve is in an open position. 
         [0009]    Yet another aspect of the invention features a method of cooling and filtering fluid in a hydraulic circuit including: providing a circuit having a pump and a hydraulic fluid cooling and filtering assembly with an inlet tank in hydraulic communication with an assembly inlet, an outlet tank in hydraulic communication with an assembly outlet a heat exchanger, and a filter element disposed within the outlet tank; operating the pump to move a fluid within the circuit; cooling the fluid through the heat exchanger; and filtering the cooled fluid through the filter element. The heat exchanger includes multiple fluid channels forming separate flow paths between respective fluid channel inlets at the inlet tank and respective fluid channel outlets at the outlet tank where the fluid channel outlets are spaced apart along a length of the outlet tank over a flow outlet span and cross-flow air channels are formed between the fluid channels. The filter element includes an internal cavity in hydraulic communication with the assembly outlet and porous filtering material separating the internal cavity from the heat exchanger fluid channel outlets. The filter element is elongated and has an outer filtering surface extending along at least most of the flow outlet span of the heat exchanger, such that straight lines are defined by the respective inlets and outlets of each fluid channel of the heat exchanger that intersect the outer filtering surface where the outer filtering surface is exposed to the fluid channel outlets. 
         [0010]    In some cases the circuit also includes a hydraulic fluid reservoir and the hydraulic fluid cooling and filtering assembly is located remote from the hydraulic fluid reservoir in the circuit. 
         [0011]    The concepts described herein may provide several advantages over cooling and filtering systems. For example, implementations of the invention may reduce the number of individual components required in hydraulic systems, enable more space-efficient hydraulic system designs, simplify hydraulic system maintenance, reduce wear and/or increase the lifespan of hydraulic system components, in certain circumstances. Implementations of the invention may be of a compact design allowing for more convenient placement of the invention in space restricted environments. 
         [0012]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  illustrates an exemplary system incorporating an integrated hydraulic cooling and filtering assembly. 
           [0014]      FIGS. 2A and 2B  are perspective views of an exemplary integrated hydraulic cooling and filtering assembly. 
           [0015]      FIG. 3  is a sectional view of an exemplary integrated hydraulic cooling and filtering assembly. 
           [0016]      FIG. 4  shows an exploded view of the example outlet tank and filter bypass valve. 
       
    
    
       [0017]    Like reference symbols in the various drawings indicate like elements 
       DETAILED DESCRIPTION 
       [0018]      FIG. 1  illustrates an exemplary system  100  incorporating an integrated hydraulic cooling and filtering assembly  102 . The system  100  is mounted on a work truck  112  and includes the integrated hydraulic cooling and filtering assembly  102 , a reservoir  104 , a pump  106 , a hydraulic load  108 , and hydraulic lines  110 . The integrated hydraulic cooling and filtering assembly  102  is a pressurized assembly including both a heat exchanger for cooling the hydraulic fluid and a filter for removing particulates from the fluid. The integrated hydraulic cooling and filtering assembly  102  is described in more detail below. The reservoir  104  stores hydraulic fluid for the system  100  and supplies the hydraulic fluid to the pump  104 . The reservoir  104  may include a breather cap to prevent pump cavitation. The pump  106  moves hydraulic fluid through the system  100  and withstands the pressure needed to overcome the hydraulic load  108 . 
         [0019]    The system  100  operates by either supplying pressurized hydraulic fluid to the hydraulic load  108  or venting the pressurized fluid from the hydraulic load  108  to the integrated hydraulic cooling and filtering assembly  102  to operate the hydraulic load  108 . For example, the hydraulic load  108  may be hydraulic motor used to run a conveyor belt on a feed body truck  112 . The components in system  100  may be rearranged in any suitable configuration and other components not illustrated may be included. For example, additional components may include hydraulic motors, hydraulic cylinders, control valves, actuators, or accumulators. 
         [0020]    Although a work truck is illustrated in system  100  the hydraulic system and integrated hydraulic cooling and filtering assembly  102  may be used in various other suitable applications related to vehicles, heavy equipment, vessels (i.e., ships and boats), and other suitable hydraulic systems. 
         [0021]      FIGS. 2A and 2B  are perspective views of an exemplary integrated hydraulic cooling and filtering assembly  102  and  FIG. 3  is a sectional view of an exemplary integrated hydraulic cooling and filtering assembly  102 . Referring to  FIGS. 2A and 2B , the integrated hydraulic cooling and filtering assembly  102  includes an inlet tank  12 , an outlet tank  14 , and a heat exchanger  16 . The inlet  12  and outlet  14  tanks are pressurized tanks connected (i.e., welded) at opposite ends of the heat exchanger  16 . The inlet tank  12  includes an assembly inlet  18  and is in hydraulic communication with one end of the heat exchanger  16 . The outlet tank  14  includes an assembly outlet manifold  19  with one or more assembly outlets  20  and is in hydraulic communication with the opposite end of the heat exchanger  16 . Plugs  30  are inserted into some of the assembly outlets  20  when they are not in use. Additionally, the assembly outlets  20  can be used as alternate return ports to bypass the cooler and filter, if desired. The plugs  30  may be threaded plugs, as shown, or other suitable types. Together with the heat exchanger  16 , inlet tank  12 , and outlet tank  14  form a integrated pressurized assembly. The heat exchanger  16 , inlet tank  12 , and outlet tank  14  are constructed of aluminum, though other suitable materials may be used, for example steel or other alloys or metals. 
         [0022]    The heat exchanger  16  is a brazed aluminum bar-plate construction including a plurality of fluid channels  22  configured to allow hydraulic fluid to flow from the inlet tank  12  through the fluid channels  22  and into the outlet tank  14 . The heat exchanger  16  may be constructed of other appropriate metals or alloys, in some implementations. As shown in  FIG. 3  and described in more detail below, the inlet tank  12  is connected to respective fluid channel inlets  23  and the outlet tank  14  is connected to respective fluid channel outlets  24 . The fluid channel inlets  23  and outlets  24  terminate at respective openings defined within inboard walls of the inlet  12  and outlet  14  tanks. The channels  22  are composed of a thermally conductive material (e.g., aluminum) such that hydraulic fluid is cooled as it passes through the channels  22 . The spacing between the fluid channels  22  define cross-flow air channels  26  to conduct heat away from the hydraulic fluid within the channels  22  to air in the cross-flow air channels  26 . In some implementations, the heat exchanger  16  may include a fan to force air through the cross-flow air channels  26  and improve the cooling efficiency of the heat exchanger  16 . In addition, the heat exchanger  16  may include a fan shroud  28  for attaching the fan to the heat exchanger  16  to increase thermal transfer efficiency. 
         [0023]    In addition, the outlet tank includes a removable tank cover  46  to access a filter element (element  36  of  FIGS. 3 and 4 ) disposed within the outlet tank  14 . Two or more swing bolts  56  attached to the outlet tank  14  retain the tank cover  46  in place, although other appropriate fasteners may be used, for example a threaded tank cap. 
         [0024]    In some implementations, the heat exchanger  16  may be constructed as a tube and fin heat exchanger. In such an implementation, a plurality of fluid tubes may define the fluid channels  22  with a plurality of metal fins interspersed between the tubes within the cross-flow air channels  26  and in thermal contact and mechanical contact with the tubes. 
         [0025]    The heat exchanger  16  may be air cooled, as shown, or in some implementations, may be liquid cooled, for example, using water, a liquid refrigerant, or other appropriate coolant. In such an implementation the cross-flow air channels  26  may be replaced with coolant channels in thermal contact with the fluid channels  22 . 
         [0026]    In addition, the inlet  12  and outlet  14  tanks include at least one port  34  configured to receive a fluid monitoring device such as a pressure gauge, transducer, or a thermocouple. The fluid monitoring device may be used to control a fan, provide indication of the condition of a filter element  36 , or control one or more valves, for example. In some implementations, as shown in  FIG. 2A , the integrated hydraulic cooling and filtering assembly  102  may be directly mounted to a reservoir  104  to which one of the assembly outlets  20  is connected. 
         [0027]    Referring to  FIG. 3 , the outlet tank  14  houses a filter element  36 . The filter element  36  includes a cylinder of porous, generally pleated, filtering material  38  defining an internal cavity  40  and openings  42  at either end. The filter is placed in the outlet tank  14  with a nipple  43  on the assembly outlet manifold  19  at the bottom of the outlet tank  14  fits into an opening  42  at the lower end of the filter element  36  forming a seal between the bottom of the outlet tank  14  and the filter element  36 . In addition, the nipple  43  provides a flow path to the assembly outlet manifold  19  and the assembly outlets  20  aids in properly positioning the filter element  36  within the outlet tank  14 . The upper end of the filter element  36  forms a seal against a lower flange (element  66  in  FIG. 4 ) of the filter bypass valve  44  (described in more detail below with reference to  FIG. 4 ) which is attached to the tank cover  46 . The seals created between the filter element  36  and the bottom of the outlet tank  14  and the bypass valve  44  prevent fluid flow around the filtering material  38  and into the internal cavity  40  of the filter element  36 . Thus, the filtering material  38  forms a fluid separation between the internal cavity  40  and the fluid channel outlets  24 . A tube sheet formed by the fluid channel outlets  24  defines a flow outlet span  48  from which all of the fluid exiting the heat exchanger  16  fluid channels  22  enters the outlet tank  14  and is distributed across an outer surface of the filter element  36  defined by the filtering material  38 . The filter element  36  is disposed within the outlet tank  14  such that the filtering material  38  extends along the flow outlet span  48  of the heat exchanger  16  as defined by the fluid channel outlets  24 . The respective inlets  23  and outlets  24  of each fluid channel  22  define straight lines  49  that intersect the outer filtering surface of the filter element  36 . Positioning the filter element  36  within the outlet tank  14  as described reduces the average distance that incoming fluid must flow through the outlet tank before passing through the filter element, which may help to equalize flow distribution through the filter material, thereby prolonging filter life by distributing filtered sediment. This arrangement may also help to prevent accumulation of sediment falling out of suspension due to flow direction changes between the outlets and the filter surface. 
         [0028]    Although it is not required that the outer surface of the filtering material  38  extend along the entire heat exchanger  16  flow outlet span  48 , the filtering material  38  should extend along a substantial portion of the flow outlet span  48 . Likewise, it is not necessary that the flow outlet span  48  extend along the entire length or diameter of the filtering element  36  (i.e., either vertically or horizontally). For example, the flow outlet span  48  may encompass an area either larger or smaller than that defined by the filter element  36 . Although the filter element  36  is preferably aligned with the channel outlets  24  and the outlet span  48 , the filter element  36  may be offset vertically or horizontally from the flow outlet span  48 . Thus disposed within the outlet tank  14 , the filtering material  38  forms a fluid separation between the internal cavity  40  and the fluid channel outlets  24 . 
         [0029]    Furthermore, the filter element  36  is disposed directly within the outlet tank  14  without the additional support of a separate filter chamber or filter screen. Such a design improves the flow capacity through the filter element  36  and the outlet tank  14  by exposing the outer filtering surface of the filter element  36  directly to the fluid channel outlets  24  and thus avoiding any restrictions or impediments to the oil flow caused by either a separate filter chamber or screen itself or by build-up of foreign material in openings of such a separate filter chamber or screen. For example, the filter element  36  of the described design may be considered to be a self-supporting filter in that the filter element  36  does not require additional structural support or an additional pre-filtering/screening element. In addition, the described design reduces the maintenance required to maintain a hydraulic system by eliminating the need to clean or flush openings of such separate filter chambers or screens and by making the filter element  36  easily accessible and replaceable. 
         [0030]    In addition, the inlet  12  and outlet  14  tanks are hydraulically connected to each other via a heat exchanger bypass path  32  (e.g., bypass pipe). One end of the bypass path connects to a bottom portion of the inlet tank  12  while the other end connects to the assembly outlet manifold  19  of the outlet tank  14 . The bypass path  32  provides an alternate flow path around both the heat exchanger  16  and the outlet tank  14 . A bypass valve  50  is disposed between the inlet tank  12  and the bypass path  32  to prevent fluid flow through the bypass path  32  during normal operation of the integrated hydraulic cooling and filtering assembly  102 . The bypass valve  50  may be a manual bypass valve, a mechanically pressure operated valve, an electrically operated cartridge valve, or a hybrid mechanical/electrical valve. For example, a pressure operated valve may be used to protect both the heat exchanger  16  and the filter element  36  from high differential pressure caused by buildup in the fluid channels  22  or pressure surges within a hydraulic system. An electrically operated bypass valve may configure to open and shut based on either temperature or pressure. For example, an electrically operated valve may be connected to temperature sensors in ports  34  in the inlet and/or outlet tanks  12 ,  14  and configured throttle flow through the bypass path  32  to maintain system temperature within a specified range. Whereas, a hybrid valve may be an electrically operated valve that also includes a means for opening mechanically, either manually or based on differential pressure. 
         [0031]      FIG. 4  shows an exploded view of the example outlet tank  14  and filter bypass valve  44 . In more detail, the outlet tank  14  includes an assembly outlet manifold  19 , welded to a bottom portion of an outlet tank body  52 , a cover alignment element  54  welded, or otherwise coupled, to a top portion of the outlet tank body  52 , the filter bypass valve  44 , the tank cover  46 , and swing bolts  56  to fasten the tank cover  46  to the cover alignment element  54 . The outlet tank body  52  includes an opening  58  for receiving a tube sheet that defines the heat exchanger  16  fluid channel outlets  24  which is welded, or otherwise coupled, in connection with the body  52 . Internal corners within the outlet tank body  52  may be rounded to promote efficient fluid flow within the outlet tank  14 . In addition, a seal (e.g., an gasket or O-ring) may be positioned between the tank cover  46  and the cover alignment element  54 . 
         [0032]    The tank cover  46  is removable to allow easy access to the filter element  36  and the filter bypass valve  44 . The cover alignment element  54  have small protrusions which align with corresponding pockets on the inside surface of the tank cover  46  ensure proper alignment of the cover  46 . The tank cover  46  is then retained in place by the swing bolts  56 . In addition, the filter bypass valve  44  is coupled to the inside surface of the tank cover  46  such that when the tank cover  46  is removed the filter bypass valve  44  will be withdrawn from the filter element  36  and removed from the outlet tank  14  as well. Thus configured, the bypass valve  44  is easily removable for service or replacement without requiring disassembly of either the outlet tank  14  or the integrated hydraulic cooling and filtering assembly  102 . 
         [0033]    The filter bypass valve  44  includes a body  60  defining at least one cross-flow port  62  and including a upper portion  63  with an upper flange  64 , a lower flange  66 , a nipple portion  68 , a bypass disc  70 , and a captured spring  72 . The upper flange  64  of the filter bypass valve  44  rests in a recess  74  of the tank cover  46  and is retained by fasteners (e.g., screws). When the tank cover  46  is in place on the outlet tank  14 , the lower flange  66  and nipple portion  68  of the filter bypass valve  44  form a seal with one of the openings  42  of the filter element  36 ; the nipple portion  68  extending slightly into the filter element&#39;s  36  internal cavity  40 . The captured spring  72  extends along a guide rod  73  and is retained at one end by a fastener  76  (e.g., a nut or a snap ring) and applies pressure to a bottom surface of the bypass disc  70  at the other end. The guide rod  73  extends through the filter bypass valve body  60  and attaches to the upper portion  63  of the filter bypass valve body  60 . When positioned within the outlet tank  14 , the guide rod  73  and captured spring  72  assembly extends into the internal cavity  40  of the filter element  36  as shown in  FIG. 3 . 
         [0034]    In operation, fluid flows through the filter bypass valve body  60  via the cross-flow ports  62 . The bypass disc  70  is forced against the nipple portion  68  by the captured spring  72  forming a seal and preventing the fluid from entering the filter element&#39;s  36  internal cavity  40  via the filter bypass valve  44 . The captured spring  72  maintains the filter bypass valve  44  in a closed position until the differential pressure across the filtering material  38  becomes sufficient to force the bypass disc  70  away from the filter bypass valve body  60  against spring pressure (e.g., 25 psid). The nipple portion  68  defines an opening in the filter bypass valve body  60  that permits fluid flow around the filtering material  38  and into the filter element&#39;s  36  internal cavity  40  when the valve is in an open position. 
         [0035]    Referring again to  FIG. 3 , during normal operation of the integrated hydraulic cooling and filtering assembly  102 , hydraulic fluid flows from the hydraulic system into the inlet tank  12  through the assembly inlet  18 . The fluid fills the inlet tank  12  and flows into the heat exchanger  16  fluid channels  22  through fluid channel inlets  23 . Heat is removed from the fluid as the fluid passes through the fluid channels  22  and transferred through the fluid channel  22  walls to air that is passed through the cross-flow air channels  26 . The fluid then exits the fluid channels  22  through fluid channel outlets  24  entering the outlet tank  14  in an even distribution across the filter element  36 . The fluid then flows through the porous filtering material  38  and into the filter element&#39;s  36  internal cavity  40 . The fluid flows axially inside the internal cavity  40  and exits the internal cavity  40  through the nipple  43  on the assembly outlet manifold  19 . Finally, the fluid exits the integrated hydraulic cooling and filtering assembly through one or more of the assembly outlets  20 . 
         [0036]    Hydraulic fluid can be cooled and filtered by a method including providing a hydraulic circuit with an integrated hydraulic cooling and filtering assembly and a hydraulic pump; and operating the pump to move a fluid within the circuit such that the fluid is cooled through the heat exchanger  16  and the cooled fluid filtered through the filter element  36 . The hydraulic circuit includes an integrated hydraulic cooling and filtering assembly  102  (as described above) with an inlet tank  12 , a heat exchanger  16 , and an outlet tank and a hydraulic pump. A suction end of the hydraulic pump is connected in hydraulic communication with an assembly outlet  20  of the integrated hydraulic cooling and filtering assembly  102  and a discharge of the hydraulic pump connected in hydraulic communication with an assembly inlet  18  of the integrated hydraulic cooling and filtering assembly  102 . Additional hydraulic system components (e.g., a reservoir, valves, hydraulic loads, etc.) may be connected between either the assembly outlet  20  and the pump suction or between the pump discharge and the assembly inlet. The outlet tank  14  includes a filter element  36  as described above. The circuit also may include additional components connected in hydraulic communication between the pump discharge and the integrated hydraulic cooling and filtering assembly inlet  18  or between the integrated hydraulic cooling and filtering assembly outlet  20  and the pump suction or between both locations. For example, such additional components may include reservoirs, hydraulic motors, hydraulic cylinders, control valves, actuators, accumulators, or additional pumps or integrated hydraulic cooling and filtering assemblies  102 . They integrated hydraulic cooling and filtering assembly  102  is of a compact design and therefore may be located remote from other hydraulic system components, such as a hydraulic fluid reservoir. For example, in a space restricted environment, such as work trucks, the integrated hydraulic cooling and filtering assembly may be installed remote from a larger hydraulic reservoir, thereby allowing for more efficient use of space in the truck design. 
         [0037]    While a number of examples have been described for illustration purposes, the foregoing description is not intended to limit the scope of the invention, which is defined by the scope of the appended claims. There are and will be other examples and modifications within the scope of the following claims.

Technology Category: 2