Patent Publication Number: US-8991422-B2

Title: Return diffuser for hydraulic tank

Description:
BACKGROUND 
     1. Technical Field 
     This disclosure relates generally to hydraulic systems and, more specifically, to return or inlet lines to a hydraulic tank or reservoir that are equipped with diffusers. The diffusers are used to control the delivery of high velocity hydraulic fluid that is returned to the tank. 
     2. Description of the Related Art 
     Fixed and/or variable positive displacement hydraulic pumps have numerous applications in many fields, including automotive, aerospace, industrial, agricultural, heavy equipment and the like for performing work. In a typical hydraulic system, return fluid is simply returned into the pump reservoir where it dwells for time period before being drawn in by the inlet to the pump for recirculation. Under conditions of high load and high flow rate, such hydraulic systems may be unable to keep up with the fluid demand of the pump, leading to cavitation and unacceptable levels of noise. Another inherent disadvantage with such systems is that the kinetic energy of the incoming fluid to the reservoir is lost and not utilized to feed the inlet to the pump, leading to relatively low efficiencies. 
     Specifically, hydraulic fluid or oil in such a system is moving at a high velocity when it is returned to the tank. The high velocity flow rates result in considerable amounts of turbulence. The turbulence has many undesirable effects, such as causing cavitation in the hydraulic circuit. Another undesirable effect is that the turbulence causes fluid to be lost through the reservoir air vent. This results in permanent loss of the fluid and causes the fluid to coat the exterior of the equipment, creating safety and cleanliness problems. 
     In the past, hydraulic tanks have been provided with baffles and the direction of discharge has been varied in an attempt to correct the above problems. However, baffles are not preferable because they consume space in the tank and limit the design possibilities for the tank. More recently, the inlet lines to hydraulic tanks had been equipped with a diffuser for reducing the velocity and turbulence of the hydraulic fluid being returned to the tank. The use of a diffuser may also eliminate the need for one or more baffles. 
     The use of a diffuser for hydraulic high-speed return lines to slow down the fluid entering the tank is shown, for example, in U.S. Pat. No. 4,127,143, which discloses a frustoconically shaped diffuser having an internal diameter that expands as it enters the tank. However, the &#39;143 patent also relies upon a baffle between the tank inlet and the outlet. Many currently available diffusers are essentially screen-like axial extensions to the inlet and the screen may deaerate the fluid as well as reduce the velocity of the fluid thereby reducing turbulence and foaming. Currently available diffusers may also trap particles that are present in the returning fluid which may help protect the downstream components, such as the pump. 
     However, currently available return diffusers for hydraulic tanks are subject to damage when the pressure of the returning fluid spikes. This problem is particularly prevalent in high velocity/high-pressure applications. Therefore, there is a need for improved return lines and diffusers for hydraulic tanks that effectively reduce the velocity of the returning fluid, deaerate the fluid, reduce the turbulence and foaming of the fluid as well as remove particulate matter from the fluid, but which are less prone to damage resulting from fluid flow or pressure spikes. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect, a diffuser assembly for a hydraulic reservoir is disclosed. The diffuser assembly may include an inlet tube having a proximal end for receiving hydraulic fluid and a closed distal end with a middle portion disposed between the proximal and distal ends. The inlet tube may also include an inlet axis. The middle portion of the inlet tube may be connected to first and second diffusers for communicating fluid from the inlet tube to the reservoir. The first and second diffusers may each include a conduit having a proximal end connected to the middle portion of the inlet tube and a closed distal end with a plurality of openings disposed between the proximal and distal ends. The first and second diffusers may each further include first and second diffuser axes respectively. The first and second diffuser axes may be disposed at angles relative to the inlet axis ranging from about 60° to about 120°. 
     In another aspect, a hydraulic fluid reservoir is disclosed. The disclosed hydraulic fluid reservoir may include a chamber for containing hydraulic fluid. The reservoir may also include an outlet and an inlet. The inlet may be connected to a proximal end of an inlet tube. The inlet tube may include a closed distal end with a middle portion disposed between the proximal and distal ends. The inlet tube may also include an inlet axis. The middle portion of the inlet tube may be connected to first and second diffusers for communicating fluid from the inlet tube to the internal chamber. The first and second diffusers may each include a conduit having a proximal end connected to the middle portion of the inlet tube and a closed distal end with a plurality of openings disposed between the proximal and distal ends. The first and second diffusers may each further include first and second diffuser axes respectively. The first and second diffuser axes may be disposed at angles relative to the inlet axis ranging from about 60° to about 120°. 
     In yet another aspect, a hydraulic system is disclosed. The disclosed hydraulic system may include a reservoir that may include a chamber for containing hydraulic fluid. The reservoir may also include an inlet and an outlet. The inlet may be in communication with a proximal end of an inlet tube. The inlet may also be in communication with a work implement. The outlet may be in communication with a pump. The pump may be in communication with the work implement. The inlet tube may also include a closed distal end with the middle portion disposed between the proximal and distal ends of the inlet tube. The middle portion of the inlet tube may be connected to first and second diffusers for communicating fluid from the inlet tube to the internal chamber. The first and second diffusers may each include a conduit having a proximal end connected to the middle portion of the inlet tube and a closed distal end with a plurality of openings disposed between the proximal and distal ends of the conduits. The first and second diffusers may each further include first and second diffuser axes respectively. The first and second diffuser axes may be disposed at angles relative to the inlet axis ranging from about 60° to about 120°. 
     Finally, in yet another aspect, a method of circulating hydraulic fluid through a hydraulic system is disclosed. The disclosed method may include providing a hydraulic system as discussed above, pumping hydraulic fluid from the reservoir chamber through the pump and through the work implement to the inlet tube, and flowing the hydraulic fluid from the inlet tube through the first and second diffusers to the chamber. 
     In any one or more of the embodiments described above, the first and second diffusers may be spaced apart from each other. 
     In any one or more of the embodiments described above, the first and second diffusers may be disposed at least substantially parallel to one another. 
     In any one or more of the embodiments described above, the first and second diffuser axes are at least substantially perpendicular to the inlet axis. 
     In any one or more of the embodiments described above, the reservoir chamber may be free of baffles. 
     Regarding the disclosed method, the method may further include trapping particles entrained in the at least one of the first and second diffusers as the hydraulic fluid flows from the inlet tube through the first and second diffusers to the chamber. 
     Other advantages and features will be apparent from the following detailed description when read in conjunction with the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 . is a schematic illustration of a hydraulic circuit that incorporates the disclosed diffuser assembly. 
         FIG. 2  is a plan view of the disclosed diffuser assembly. 
         FIG. 3  is an end view of the diffuser assembly shown in  FIG. 2 . 
         FIG. 4  is a plan view of one of the diffuser conduits of the diffusers of the diffuser assembly shown in  FIG. 2 . 
         FIG. 5  is a sectional view taken substantially along line  5 - 5  of  FIG. 4 . 
         FIG. 6  is a sectional view taken substantially along line  6 - 6  of  FIG. 4   
         FIG. 7  is a sectional view taken substantially along line  7 - 7  of  FIG. 4 . 
         FIG. 8  is a top plan view of the inlet tube of the diffuser assembly shown in  FIG. 2 . 
         FIG. 9  is a side plan view of the inlet tube shown in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
     Turning first to  FIG. 1 , a hydraulic circuit  10  is disclosed which may include a tank or reservoir  11  that may include an interior chamber  12  for containing hydraulic fluid or oil. The reservoir  11  may also include an inlet  13  and an outlet  14 . The outlet  14  may optionally include a filtering element (not shown) and may be in communication with a pump  15 . The pump  15 , in turn, may be in communication with a work implement  16 . The work implement  16  may then be in communication with the inlet  13  where hydraulic fluid is returned to the chamber  12  through the diffuser assembly  20 . The diffuser assembly  20  may include an inlet tube  21  having a proximal end  23  coupled to the reservoir inlet  13  and a closed distal end  22 . The inlet tube may be coupled to a plurality of diffusers  24 , which are shown in greater detail in connection with  FIGS. 2-4 . While only two diffusers  24  are shown in  FIGS. 1-2 , more than two diffusers  24  may be utilized. The number of diffusers  24  may depend upon the desired flow characteristics, flow attenuation, sound reduction, etc. as will be discussed below in connection with  FIG. 2 . 
     Turning to  FIG. 2 , the distal end  22  of the inlet tube  21  may be closed using a plate  25  while the proximal end  23  may be coupled to the inlet  13  using the bracket  30  as shown in  FIG. 3 .  FIG. 2  also illustrates the connection between the inlet tube  21  and the diffusers  24 . In the example shown in  FIG. 2 , the diffusers  24  are disposed perpendicular to the inlet tube  21  or perpendicular to the inlet axis  26 . More specifically, the diffusers  24  may each include a diffuser axis  27 . In the example shown in  FIG. 2 , the diffuser axes  27  are perpendicular to the inlet axis  26  and parallel to each other. However, the relative angles between the axes  27  and the axis  26  may vary and may range from about 60° to about 120°. As explained below, the axes  27  may also have a non-parallel relationship with respect to each other. As shown in  FIGS. 2 and 4 , each diffuser  24  includes a conduit  28 . Each conduit  28  includes a proximal end  29  and a distal end  31 . The proximal ends  29  are curved so that they may be welded to holes or apertures drilled into the inlet tube  21  as shown in  FIG. 2 . The distal ends  31  of the conduits  28  may also be enclosed by a plate  32  which optionally may be equipped with a pressure release valve  33 . 
     The conduits  28  may be screens or perforated tubes as shown in  FIGS. 2-4 . In the example shown, the diffuser conduits  28  include a plurality of holes  35 . As shown in the sectional views of  FIGS. 5-7 , the holes  35  are arranged in columns and staggered rows as each row of holes  35  includes four holes  35 . Each conduit  28  may also include a slot  36  ( FIG. 4 ) for accommodating a plate  37  that contributes to the reduction in the velocity of the hydraulic fluid flowing through the diffusers  24 . In addition to reducing the velocity of the hydraulic fluid flowing through the holes  35  of the conduits  28 , the holes  35  may also act as a filter by trapping particles entrained in the returning hydraulic fluid which may help protect downstream components such as the pump  15  or work implement  16  from damage. 
     Returning to  FIG. 2 , the axes  27  of the diffusers  24  are shown in a parallel relationship with respect to each other. However, because the diffuser conduits  28  may vary in terms of the configurations, positions and number of the holes  35 , the effect the diffusers  24  have on the fluid flowing into the reservoir  11  can vary widely and therefore other orientations of the diffusers  24  are possible. Thus, the diffusers  24  may be positioned in a non-parallel relationship to one another. Further,  FIG. 2  also shows the axes  27  of the diffusers  24  in a perpendicular relationship to the axis  26  of the inlet tube  21 . Again, because the design of the diffusers  24  may vary widely, which will affect the flow characteristics, sound and flow attenuation properties, the diffusers  24  may be disposed in a non-perpendicular relationship to the axis  26  as discussed above. 
     Further, the  FIG. 2  shows the diffusers  24  disposed towards the distal end  22  of the inlet tube  21 , which creates a volume chamber  40  between the diffusers  24  and the proximal end  23  of the inlet tube  21 . In addition to variations in the design of the diffusers  24 , the size of the volume chamber  40  may also affect the volume of the sound created by fluid flowing through the diffusers  24 , the attenuation of the fluid flowing through the diffuser assembly  20  as well as the flow characteristics of the fluid flowing through the diffuser assembly  20 . Thus, moving the diffusers  24  towards or away from the proximal end  23  is one way in which the diffuser assembly  20  can be “tuned” to achieve the desired effects on the fluid flowing through the diffuser assembly  20 . Again, in addition to the spacing of the diffusers  24  along the inlet tube  21 , the angular relationships between the diffuser axes  27  and between the diffuser axes  27  and the axis  26  of the inlet tube  21  may also be used to tune the diffuser assembly  20  to achieve the desired effects on the fluid flowing through the diffuser assembly  20 . 
       FIGS. 8 and 9  illustrate the inlet tube  21  which may include a pair of holes  39  that receive the proximal ends  29  of the diffuser conduits  28  as explained above. Again, the spacing of the holes  39  along the inlet tube  21  may be varied in the position of the holes  39  with respect to each other may be varied so that the axes  27  are not necessarily parallel. In summary, while the parallel relationship between the axes  27  and the perpendicular relationships between the axes  27  and the axis  26  provide good flow attenuation, good reduction in the fluid flow velocity through the diffusers  24 , good reduction in turbulence, reduced noise, etc., the parallel and perpendicular relationships shown in the drawings may be altered, particularly if the design of the diffuser conduits  28  is changed. 
     INDUSTRIAL APPLICABILITY 
     Currently available prior art return diffusers typically include a single screen cylinder or tube that is coaxial with the reservoir inlet. However, this common arrangement is subject to damage when the amount of hydraulic fluid being returned to the reservoir or tank spikes. This, of course, is problematic as the hydraulic circuit must be shut down and the inlet and diffuser must be removed for repairs. To overcome this problem, a diffuser assembly is disclosed wherein an inlet tube is provided that is coaxial with the inlet of the reservoir. A plurality of diffusers, such as a pair of diffusers are spaced apart along the inlet tube and are disposed at an angle with respect to the axis of the inlet tube. Preferably, the diffusers are disposed at angles ranging from about 60° to about 120° with respect to the axis of the inlet tube. One convenient arrangement is to attach the diffusers to the inlet tube at right angles to the inlet tube axis. However, other angles within the stated range may be employed. Surprisingly, by increasing the diffusers from a single diffuser to a plurality of diffusers and by positioning the diffusers at an angle that is not coaxial with the inlet to the reservoir, damage to the diffusers from fluid flow spikes is avoided. Further, the disclosed diffuser assembly does not require a separate baffle within the reservoir, although one or more baffles may be employed. Thus, the elimination of the need for baffles is obtained by the disclosed diffuser assembly and the disclosed diffuser assembly is more durable and less prone to damage from fluid flow spikes.