Abstract:
A working valve section for a sectional fluid control valve comprising a valve section housing having a substantially planar surface for being attached to an adjacent valve section housing; a main control spool bore ( 43 ) extending into the housing substantially parallel to the planar surface; a compensator spool bore ( 46 ) extending into the housing substantially parallel to the planar surface, the compensator spool bore being spaced from the main control spool bore; a first relief slot ( 49   a ) extending across the planar surface substantially coextensive with the main control spool bore; and a second relief slot ( 49   b ) extending across the planar surface substantially coextensive with the compensator spool bore.

Description:
RELATED APPLICATIONS 
     This application is a national phase of International Application No. PCT/US2015/028452 filed Apr. 30, 2015 and published in the English language, which claims priority to U.S. Provisional Patent Application No. 61/986,183 filed Apr. 30, 2014, which are hereby incorporated herein by reference in their entirety. 
    
    
     FIELD OF INVENTION 
     The present invention relates generally to a fluid control valve, and more particularly to a hydraulic sectional control valve having relief slots for relieving stress on spool bores. 
     BACKGROUND 
     Fluid control valves are used in a wide variety of applications for causing and controlling motion of various components. Hydraulic fluid control valves and systems are used in such applications when relatively large forces are to be transmitted and controlled through such components. 
     One type of hydraulic fluid control valve is a sectional valve. A sectional valve may typically include a plurality of separate cast and machined metal working valve sections. Each valve section may include internal fluid passages, external ports, and spool bores with valve spools slidably disposed within the spool bores. The spool bores may include main control valve spool bores in which main control valve spools are slidably disposed, and compensator spool bores in which compensator spools are slidably disposed to maintain predetermined pressure drops across the main control spools or to otherwise control fluid pressure. The spool bores and the spools are precisely machined, so that the spools slide freely in the bores with minimal clearance and minimal fluid leakage between the spool and the bore. 
     The valve sections typically include precisely machined substantially planar or flat surfaces, and the valve sections are assembled together with the flat surfaces of adjacent sections contacting one another. Tie rod holes extend through the sections, and tie rods extend through the holes. A torque is applied to the tie rods to assemble the sections tightly together without fluid leakage between the sections. This assembly torque establishes a compressive load within the sections of the valve, and this compressive load may cause a distortion within the sections. This distortion may be particularly troublesome when the distortion occurs around a spool bore, because the diametrical clearance between the bore internal diameter and the spool outer diameter tends to be very small, for example in the range of 0.0002 of an inch. Excessive spool bore distortion can cause the spool to bind within the bore, which is detrimental to the operation of the hydraulic sectional valve. Because the diametrical clearance needs to be small to keep leakage around the spool to an acceptable level, increasing the diametrical clearance to allow for increased spool bore distortion may not always provide a valid solution to compensate for spool bore distortion that results from tie rod assembly torque. 
     SUMMARY OF INVENTION 
     Therefore, presented herein are exemplary embodiments to reduce the amount of spool bore distortion by providing a first relief slot extending along the axis of the main control spool bore, and a second relief slot extending along the axis of the compensator spool bore. Preferred embodiments also provides additional features and advantages described below. 
     According to one aspect of the invention, a working valve section for a sectional fluid control valve includes a valve section housing having a substantially planar surface for being attached to an adjacent valve section housing; a main control spool bore extending into the housing substantially parallel to the planar surface; a compensator spool bore extending into the housing substantially parallel to the planar surface, the compensator spool bore being spaced from the main control spool bore; a first relief slot extending across the planar surface substantially coextensive with the main control spool bore; and a second relief slot extending across the planar surface substantially coextensive with the compensator spool bore. 
     Optionally, the first and second relief slots are each elongated and are each substantially perpendicular to the other. 
     Optionally, the first and second relief slots are spaced from one another. 
     Optionally, the valve section includes a second valve section, the second valve section includes a second housing having a second substantially planar surface, and the second substantially planar surface is attached to the first mentioned substantially planar surface. 
     Optionally, the main control spool bore is substantially perpendicular to the compensator spool bore. 
     Optionally, the relief slots are approximately 0.0005-0.002 inches deep. 
     Optionally, the first relief slot is 10-50% wider than the spool bore. 
     Optionally, the first relief slot is 10-25% wider than the spool bore. 
     Optionally, the first relief slot is 20-50% wider than the spool bore. 
     Optionally, the second relief slot includes rounded corners. 
     According to another aspect, a working valve section for a sectional fluid control valve includes a valve section housing having a substantially planar surface for being attached to an adjacent valve section housing; a main control spool bore extending into the housing substantially parallel to the planar surface; a compensator spool bore extending into the housing substantially parallel to the planar surface, the compensator spool bore being spaced from the main control spool bore; and a relief area extending across the planar surface substantially coextensive with the main control spool bore and the compensator spool bore. The substantially planar surface includes an area positioned between the main control spool bore and the compensator spool bore that protrudes above the relief area. 
     Optionally, the relief area includes first and second relief slots that are each elongated and are each substantially perpendicular to the other. 
     Optionally, the first and second relief slots are spaced from one another. 
     Optionally, the working valve section includes a second valve section, the second valve section includes a second housing having a second substantially planar surface, and the second substantially planar surface is attached to the first mentioned substantially planar surface. 
     Optionally, the main control spool bore is substantially perpendicular to the compensator spool bore. 
     Optionally, the relief slots are approximately 0.0005-0.002 inches deep. 
     Optionally, the first relief slot is 10-50% wider than the spool bore. 
     Optionally, the first relief slot is 10-25% wider than the spool bore. 
     Optionally, the first relief slot is 20-50% wider than the spool bore. 
     Optionally, the second relief slot includes rounded corners. 
     The foregoing and other features of the invention are hereinafter described in greater detail with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation view of a prior art valve section, in which shims are used to minimize spool bore distortion; 
         FIG. 2  is a side elevation view of another prior art valve section, in which a single relief slot is used to minimize spool bore distortion; 
         FIG. 3 a    is a side elevation view of a valve section according to a first preferred embodiment of the present invention; 
         FIG. 3 b    is a top view of the valve section illustrated in  FIG. 3   a;    
         FIG. 3 c    is an end view of the valve section illustrated in  FIG. 3 a   ; and 
         FIG. 4  is side elevation view of a second embodiment of the invention, which is similar to the valve section illustrated in  FIG. 3 a    but with modifications. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings in greater detail,  FIG. 1  illustrates a prior art hydraulic valve section  10 . The valve section  10  is one section of a complete sectional hydraulic valve (not shown) that includes multiple sections secured together by tie rods (not shown). The valve section  10  includes a cast and machined metal housing  11  having a longitudinal axis  12 . A main control valve spool bore  13  extends along the longitudinal axis  12  from side to side through the housing  11  and is closed by threaded end caps  14   a . The housing  11  also has a vertical axis  15 , and a compensator spool blind bore  16  extends along the vertical axis  15  and is closed by threaded end cap  14   b . A main control valve spool (not shown) is slidably disposed in the main control valve spool bore  13 , and a compensator spool (not shown) is slidably disposed in the compensator spool bore  16 . The housing  11  also includes a machined substantially planar surface  17 , and a plurality of tie rod holes  18  extend from the surface  17  completely through the housing  11  in a direction substantially perpendicular to the planar surface  17 . 
     To minimize distortion of the spool bores  13  and  16  of the valve section  10  when the valve section  10  is assembled with other valve sections (not shown) to provide a complete multi-function hydraulic sectional valve (not shown), flat annular washer shaped shims  19  are provided at the location of each hole  18 . A tie rod (not shown) extends through each hole  18  and through its associated shim  19 . The shims  19  are placed onto the tie rods during the assembly process, and the tie rods are torqued to secure the valve sections together under stress in a fluid tight manner. The thickness of the shims  19  creates a small gap between the valve sections, and this prevents or minimizes stress being applied to the housing  11  at the location of the spool bores  13  and  15  to prevent or minimize distortion of the spool bores  13  and  15 . The disadvantage of the shims  19  is that it may be difficult to control the assembly process, since the shims need to be very thin (for example, on the order of 0.001 inch) and it is difficult to assure that just one shim or other prescribed number of shims gets assembled at a time. This is especially true when assembling in the presence of hydraulic oils since the oil may tend to cause the shims to stick together and since the shims are very thin. 
     Another way in which spool bore distortion is minimized in prior art hydraulic sectional valves is illustrated in  FIG. 2 .  FIG. 2  illustrates a prior art hydraulic valve section  20 . The valve section  20  is one section of a complete sectional hydraulic valve (not shown) that includes multiple sections secured together by tie rods (not shown). The valve section  20  includes a cast and machined metal housing  21  having a longitudinal axis  22 . A main control valve spool bore  23  extends along the longitudinal axis  22  from side to side through the housing  21  and is closed by threaded end caps (not shown). The housing  21  also has a vertical axis  25 , and a compensator spool blind bore (not shown) extends parallel to the axis  25  and is closed by a threaded end cap (not shown). A main control valve spool (not shown) is slidably disposed in the main control valve spool bore  23 , and a compensator spool (not shown) is slidably disposed in the compensator spool bore. The housing  21  also includes a machined substantially planar assembly surface  27 , and a plurality of tie rod holes  28  extend from the surface  27  completely through the housing  21  in a direction substantially perpendicular to the planar surface  27 . 
     To minimize distortion of the spool bores of the valve section  20  when the valve section  20  is assembled with other valve sections (not shown) to provide a complete multi-function hydraulic sectional valve (not shown), a single relief slot  29  is provided. The relief slot  29  extends longitudinally across the surface  27  of the valve section  20 , and the relief slot  29  has a depth (into the plane of the surface  27 ) that is very shallow and on the order of magnitude of the thickness of one or more of the shims described above in connection with  FIG. 1 . The vertical width of the slot  29  is substantially greater than the diameter of the main spool bore  23 . The disadvantage with the single relief slot  29  is that the amount of bearing area on the section  20  seal area gets smaller as the area of the slot  29  gets larger. This may reduce the life of the section  20  since the pre-load that is created within the valve sections when they are torqued together may not get applied to an area of the valve section  20  that is under high pressure during operation. The small gap that is created may allow for distortion of the section  20  when under pressure thus creating higher stresses in that part of the section  20 , than if the small gap were not there. 
     A third way to minimize distortion in valve spool bores is by honing the hydraulic sectional main control valve spool bore as a complete assembly. The spool bore gets manufactured to its final size after the individual valve sections of the hydraulic sectional valve have been assembled with the tie rods and torqued. This guarantees that any spool bore distortion that occurred during assembly doesn&#39;t adversely affect the spool to spool bore fit. The disadvantage of this method is that it may be more difficult and/or more costly in comparison with the above described shims and single slot. 
     As illustrated in  FIGS. 3 a -3 c   , a first preferred embodiment of the present invention provides a hydraulic valve section  30 . The valve section  30  is one section of a complete sectional hydraulic valve (not shown) that includes multiple sections secured together by tie rods (not shown). The valve section  30  includes a cast and machined metal housing  31  having a longitudinal axis  32 . A main control valve spool bore (not shown) extends along the longitudinal axis  32  from side to side through the housing  31  and is closed by threaded end caps (not shown). The housing  31  also has a vertical axis  35 , and a compensator spool blind bore (not shown) extends along or parallel to the axis  35 . A main control valve spool (not shown) is slidably disposed in the main control valve spool bore  33 , and a compensator spool (not shown) is slidably disposed in the compensator spool bore. The housing  31  also includes a machined substantially planar surface  37 , and a plurality of tie rod holes  38  extend from the surface  37  completely through the housing  31  in a direction substantially perpendicular to the planar surface  37 . 
     To minimize distortion of the spool bores of the valve section  30  when the valve section  30  is assembled with other valve sections (not shown) to provide a complete multi-function hydraulic sectional valve (not shown), first and second relief slots  39   a  and  39   b  are provided. The first relief slot  39   a  extends longitudinally from side to side across surface  37  of the valve section  30 , and the relief slot  39   a  has a depth in a direction perpendicular to the surface  37  that is very shallow and on an order of magnitude of the thickness of one or more of the shims described above in connection with  FIG. 1 . The second relief slot  39   b  extends vertically from the top of the valve section  30  substantially perpendicular to the direction of the first relief slot  39   a , and the relief slot  39   b  preferably does not extend vertically to the bottom of the valve section  30 . The second relief slot  39   b  also has a depth that is very shallow and on the order of magnitude of the thickness of one or more of the shims described above in connection with  FIG. 1 , and the depth of the second relief slot  39   b  is preferably substantially equal to the depth of the first relief slot  39   a . In particular, a preferable depth for this slot in relatively high pressure settings is between 0.0005 inches and 0.002 inches. In low pressure settings, this depth may be increased which makes manufacturing easier. The second relief slot  39   b  preferably terminates a distance from the first relief slot  39   a . By providing separate relief slots for the main control valve spool bore and for the compensator spool bore, the areas of the relief slots can be minimized while distortion stress on the spool bores is also minimized. In particular, the width of the relief slots is preferably between 10% and 50% wider than the width of the respective spool bores. In some embodiments, the relief slots are 10-20% wider, and in other embodiments, relief slots are 20-50% wider. In any case, a portion of surface  37  is positioned between the two spool bores so as to prevent localized distortion. 
       FIG. 4  is a view similar to  FIG. 3 a   , but illustrating a second embodiment of the invention which is similar to the first embodiment valve section with minor modifications. The valve section  40  is one section of a complete sectional hydraulic valve (not shown) that includes multiple sections secured together by tie rods (not shown). The valve section  40  includes a cast and machined metal housing  41  having a longitudinal axis  42 . A main control valve spool bore  43  extends along the longitudinal axis  42  from side to side through the housing  41  and is closed by threaded end caps (not shown). The housing  41  also has a vertical axis  45 , and a compensator spool blind bore  46  extends along the vertical axis  45 . A main control valve spool (not shown) is slidably disposed in the main control valve spool bore  43 , and a compensator spool (not shown) is slidably disposed in the compensator spool bore  46 . The housing  41  also includes a machined substantially planar surface  47 , and a plurality of tie rod holes  48  extend from the surface  47  completely through the housing  41  in a direction substantially perpendicular to the planar surface  47 . 
     To minimize distortion of the spool bores of the valve section  40  when the valve section  40  is assembled with other valve sections (not shown) to provide a complete multi-function hydraulic sectional valve (not shown), first and second relief slots  49   a  and  49   b  are provided. The first relief slot  49   a  extends longitudinally from side to side across surface  47  of the valve section  40 , and the relief slot  49   a  has a depth in a direction perpendicular to the surface  47  that is very shallow and on an order of magnitude of the thickness of one or more of the shims described above in connection with  FIG. 1 . The second relief slot  49   b  extends vertically from the top of the valve section  40  substantially perpendicular to the direction of the first relief slot  49   a , and the relief slot  49   b  preferably does not extend vertically to the bottom of the valve section  40 . The second relief slot  49   b  also has a depth that is very shallow and on an order of magnitude of the thickness of one or more of the shims described above in connection with  FIG. 1 , and the depth of the second relief slot  49   b  is preferably substantially equal to the depth of the first relief slot  49   a . In particular, a preferable depth for this slot in relatively high pressure settings is between 0.0005 inches and 0.002 inches. In low pressure settings, this depth may be increased which makes manufacturing easier. The second relief slot  49   b  preferably terminates a distance from the first relief slot  49   a . By providing separate relief slots for the main control valve spool bore and for the compensator spool bore, the areas of the relief slots can be minimized while distortion stress on the spool bores is also minimized. In particular, the width of the relief slots is preferably between 10% and 50% wider than the width of the respective spool bores. In some embodiments, the relief slots are 10-20% wider, and in other embodiments, relief slots are 20-50% wider. In any case, a portion of surface  37  is positioned between the two spool bores so as to prevent localized distortion. This embodiment also depicts rounded corners at the terminal end of slot  49   b . These rounded corners are a product of machining the slot with a surface rotary milling bit. 
     Although the invention has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.