Abstract:
A manual override for a hydraulic control valve spool includes a rotatable shaft having a threaded hole; a lever pin having a first end connected for movement with a hydraulic control valve spool and a second end having an external thread that is threadably received in the threaded hole; and the threaded hole and external thread include a mechanical antirotation element.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/986,198 filed Apr. 30, 2014, which is hereby incorporated herein by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates generally to a fluid control valve, and more particularly to a hydraulic control valve having a manual override for moving the main control spool of the valve. 
       BACKGROUND 
       [0003]    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. 
         [0004]    Hydraulic fluid control valves may include a housing having internal fluid passages, external ports, and spool bores with valve spools slidably disposed within each spool bore. The spool bores may include a main control valve spool bore in which a main directional control valve spool is slidably disposed to control hydraulic fluid flow between a hydraulic pump and a hydraulic motor. As used herein, the term “hydraulic motor” means any rotary or linear hydraulic device that is actuated by hydraulic fluid under pressure, such as, for example, a hydraulic cylinder or rotary actuator or gerotor motor or other hydraulic motor. 
         [0005]    In such valves, the main valve control spool may be moved by a fluid pilot actuator or by an electric actuator or by other type of actuators. To operate the main valve control spool in the event the fluid pilot actuator or electric actuator or other actuator malfunctions or is otherwise not available, a manual override may be provided. Such manual overrides may include a manual override lever pin having spaced-apart end regions. One of the end regions may be secured to a rotatable manual override shaft, and the other end region may be connected to the control spool. When the manual override shaft is rotated, the manual override lever pin rotates about a lateral axis with the manual override shaft and moves the main valve control spool. 
       SUMMARY OF INVENTION 
       [0006]    Conventional hydraulic control valve manual overrides of this type typically connect the manual override lever pin to the manual override shaft with a threaded connection. To secure the threaded connection, a thread locking compound such as that sold under the trademark Loctite may be applied to the threads during assembly. To improve this threaded connection, exemplary embodiments provide a mechanical antirotation element such as an interference locking thread profile, e.g., the profile identified by the trademark Spiralock®. 
         [0007]    According to one aspect of the invention, a manual override for a hydraulic control valve spool includes a rotatable shaft having a threaded hole; a lever pin having a first end connected for movement with a hydraulic control valve spool and a second end having an external thread that is threadably received in the threaded hole; and the threaded hole and external thread include a mechanical antirotation element. 
         [0008]    Optionally, the mechanical antirotation element includes an interference threaded connection. 
         [0009]    Optionally, the threaded hole includes an interference thread form. 
         [0010]    Optionally, the threaded hole includes a Spiralock® thread form. 
         [0011]    According to another aspect, a hydraulic control valve includes a valve body; a hydraulic control valve spool bore; a hydraulic control valve spool bore disposed in the bore; a rotatable shaft having a threaded hole; and a lever pin rotatable with the rotatable shaft, the lever pin having a first end connected for movement with the hydraulic control valve spool and a second end having an external thread that is threadably received in the threaded hole of the rotatable shaft. The threaded hole and external thread provide an interference threaded connection. 
         [0012]    Optionally, the threaded hole includes an interference thread form. 
         [0013]    Optionally, the threaded hole includes a Spiralock® thread form. 
         [0014]    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 
         [0015]      FIG. 1  is a lateral cross sectional view of a preferred embodiment of a manual override for a main control valve spool according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Referring now to the drawings in greater detail,  FIG. 1  illustrates a hydraulic control valve  10  that includes a cast and machined metal housing  11 . The housing  11  includes a longitudinally extending main control valve spool bore  12 , and a main control valve spool  13  is slidably disposed in the bore  12 . The main control valve spool is movable between various positions, such as, for example between a center or off position to block hydraulic fluid flow to work ports (not shown) and actuated displaced positions to control hydraulic fluid flow to the work ports. This movement of main valve control spool  13  may be controlled by a conventional actuator such as, for example, a hydraulic pilot actuator or an electric actuator or other suitable actuator. 
         [0017]    The valve  10  also includes a manual override  14  that operates to control movement of the main valve control spool  13  in the event the actuator malfunctions or is otherwise unavailable. The override  14  includes a rotary shaft  15  that is rotatably journaled in the housing  11  and a lever  16  that may be grasped to manually rotate shaft  15 . A generally cylindrical lever pin  17  has one end  17   a  secured to the main valve control spool  13  in a suitable manner such as, for example, by a ball and socket connection with the ball being integrally formed on the one end  17   a  and the socket (not shown) being formed on the control valve spool  13 . The other end  17   b  of the lever pin  17  is threaded and is threadably connected to a threaded lateral hole  18  in rotary shaft  15 . 
         [0018]    If after assembly and during operation the lever pin  17  were to rotate about its longitudinal axis relative to shaft  15  and begin to unthread its threaded end  17   b  from threaded hole  18 , the lever pin  17  may jam relative to the main valve control spool  13  and interfere with or prevent movement of main valve control spool  13 . To prevent this, an interference thread is provide for the threaded hole  18  of shaft  15 . The interference thread may preferably be a thread form identified by the trademark Spiralock® for the threaded hole  18 , which provides a female thread form with a 30 degree ramp on its major diameter and gives a free running assembly until it is torqued and the major diameter of the threaded end  17   b  engages this ramp and provides a secure lock. To assure proper plastic deformation of the thread form of the threaded hole  18  as the lever pin  17  is torqued into threaded hole  18 , manual override lever pin  17  is significantly harder than the shaft  15 . In the preferred embodiment, the lever pin  17  is a medium carbon steel such as cold drawn AISI 1141 steel with a hardness in the range of about 48-52 Rockwell C, while the shaft  15  is a non-heat treated as drawn AISI 316 stainless steel. 
         [0019]    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.