Abstract:
A valve design that enables a positive shaft seal to be obtained in an inexpensive manner by reducing the need for close tolerances heretofore required in prior art designs. This unique valve design employs a shaft seal that is adapted for transverse and/or angular movement during assembly of the valve for aligning to the shaft at an alignment position in which it is held after assembly of the valve by a holding device such as a seal nut or spring.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/921,952 filed Apr. 5, 2007 and No. 61/020,186 filed Jan. 10, 2008, which are hereby incorporated herein by reference in their entireties. 
     
    
     FIELD OF THE INVENTION  
       [0002]    The invention herein described relates generally to valves including a shaft and associated shaft seal, and more particularly to a self-aligning shaft seal for accommodating misalignment of the shaft. 
       BACKGROUND OF THE INVENTION  
       [0003]    Valves have been provided with shafts in various forms for enabling control of a valve element interiorly of a valve body by control devices located exteriorly of the valve body or sensing spool position with a sensor located exteriorly of the valve body. To prevent leakage of fluid along the shaft, various types of shaft seal arrangements have been provided. 
         [0004]      FIG. 1  illustrates a portion of a known hydraulic valve  20 . The hydraulic valve  20  has a spool  21  that is movable axially through a spool bore  22  for controlling fluid flow through the valve. A shaft  24  is fixedly attached to the spool  21  and extends outside of a valve housing  25 . A seal  26  is associated with the shaft  24  so as to prevent fluid migration out of the valve along the shaft. This sealing configuration is often referred to as a fixed seal design, wherein the seal  26  is fixed relative to an adapter  27  that is threadedly received in a threaded bore  28  in the valve housing  25 . To ensure proper alignment of the shaft  26  and seal  26  during assembly of the valve, the threads of the housing bore  28  must be aligned concentrically with the spool bore  22 . The shaft  24  also must be concentric with the spool  21  and the fixed location of the seal  26  in the adapter  27  must be concentric with the threads of the adapter so that, when the adapter is threadedly connected to the valve housing  25 , the seal  26  will be concentric with the shaft  24 . All of this alignment or concentricity requires very precise tolerance control of the valve parts. This required precision usually results in high manufacturing costs of the valve parts. When such tolerance control is not achieved, the seal  26  may not properly seal against the shaft  24  and fluid may migrate out of the valve along the shaft. 
         [0005]      FIG. 2  illustrates another prior art fixed seal design. The design shown in  FIG. 2  is similar to the design of  FIG. 1 . The difference resides in the spool  21  and shaft  26 . In the valve of  FIG. 1 , threads are used to attach the shaft  26  to the spool  21 , whereas in the valve of  FIG. 2 , a “T” slot  30  is used. The “T” slot allows the shaft  26  to shift transversely relative to the spool  21 , but the “T” slot is an expensive feature to add. Again, with the design illustrated in  FIG. 2 , precision manufacturing is required so as to provide concentricity of the valve parts. Also, in  FIG. 2 , the seal  26  is located in a defined groove in the adapter  27 . This groove is difficult to machine and requires a high precision tolerance. 
         [0006]      FIG. 3  shows yet another prior art design that is similar to the design of  FIG. 2 . In this design the “T” slot  30  is machined into the shaft  26  with the receiver machined in the spool  21 . A spring-loaded washer  32  holds the shaft seal  26  in a groove in the adapter  27  that must be machined with high precision. The concentricity issue is not alleviated with this design. The seal groove particularly must be concentric with the threads of the adapter  27  and the valve housing  25 .  FIG. 3  also shows a shaft control mechanism  33 . 
       SUMMARY OF THE INVENTION  
       [0007]    The present invention provides a valve design that enables a positive shaft seal to be obtained in an inexpensive manner by reducing the need for close tolerances heretofore required in prior art designs. This unique valve design employs a shaft seal that is adapted for transverse movement during assembly of the valve for aligning to the shaft at an alignment position in which it is held after assembly of the valve. 
         [0008]    Accordingly, the present invention provides a valve comprising a spool movable within a valve body; a shaft associated with the spool and extending out of the valve body; an adapter having a through hole for receiving the shaft; and a shaft seal for sealing against the shaft, wherein the shaft seal is adapted for transverse movement during assembly of the valve for aligning to the shaft at an alignment position and then is held in such alignment position after assembly of the valve. 
         [0009]    In a preferred embodiment, the shaft seal is supported by a seal carrier that is transversely movable relative to the shaft during assembly of the valve and then fixed relative to the shaft upon completion of assembly. 
         [0010]    The adapter may have a recess for receiving the seal carrier, and the inner transverse dimension of the of the recess may be greater than the outer transverse dimension of the seal carrier to allow for such transverse shifting of the seal carrier during assembly of the valve. 
         [0011]    The seal carrier may have a recess for retaining the shaft seal and a carrier seal located radially outwardly of the shaft seal for sealing to the adapter. 
         [0012]    The seal carrier may have in an axial end face thereof of an annular groove for retaining the carrier seal, and the carrier seal may form a face seal with an opposing axial surface of the adapter. 
         [0013]    The seal carrier may be held in position by a holding device that urges the seal carrier against the opposing axial surface of the adapter. The holding device may be a seal nut that when tightened holds the seal carrier tightly against the opposing axial surface of the adapter to prevent transverse movement of the seal carrier relative to the adapter. In another embodiment, the holding device may be a spring member that resiliently biases the seal carrier against the opposing axial face of the adapter. 
         [0014]    The seal carrier and shaft seal may be unitary, with the seal carrier extending radially outwardly from the shaft seal for being held against a surface of the adapter by a holding device. The seal carrier may be made of a sealing material for forming a face seal between opposed axial surfaces of the adapter and the holding device. 
         [0015]    In another embodiment, the seal carrier may include a ball and a split ball carrier for receiving the ball, the ball having a through hole through which the shaft extends and a recess in which the shaft seal is retained for sealing to the shaft. The split ball carrier may have axially arranged socket halves between which the ball is held, and the socket halves may be clamped between the adapter and a holding device. A seal may be interposed between at least one of the socket halves and the ball, and at least one of the socket halves may be sealed to the adapter. 
         [0016]    The invention also provides a method of assembling a valve, wherein during assembly of the valve a shaft seal is transversely moved in an adapter through which a shaft extends for aligning to the shaft at an aligned position, and then the shaft seal is held in such aligned position after assembly of the valve. Such alignment preferably is effected using a seal carrier that can be shifted transversely and then held in place by a holding device. 
         [0017]    Further features of the invention will become apparent from the following detailed description when considered in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS  
         [0018]    In the annexed drawings: 
           [0019]      FIG. 1  is a fragmentary cross-sectional view of a prior art valve; 
           [0020]      FIG. 2  is a fragmentary cross-sectional view of another prior art valve; 
           [0021]      FIG. 3  is a fragmentary cross-sectional view of still another prior art valve; 
           [0022]      FIG. 4  is an end view of a valve including an shaft seal alignment feature according to the present invention; 
           [0023]      FIG. 5  is a fragmentary cross-sectional view of the valve of  FIG. 3 ; 
           [0024]      FIG. 6  is an end view of another valve including an shaft seal alignment feature according to the present invention; 
           [0025]      FIG. 7  is a fragmentary cross-sectional view of the valve of  FIG. 6 ; 
           [0026]      FIG. 8  is an end view of still another valve including an shaft seal alignment feature according to the present invention; 
           [0027]      FIG. 9  is a fragmentary cross-sectional view of the valve of  FIG. 8 ; 
           [0028]      FIG. 10  is an end view of another valve including an shaft seal alignment feature according to the present invention; 
           [0029]      FIG. 11  is a fragmentary cross-sectional view of the valve of  FIG. 10 ; 
           [0030]      FIG. 12  is an end view of another valve including an shaft seal alignment feature according to the present invention; and 
           [0031]      FIG. 13  is a fragmentary cross-sectional view of the valve of  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION  
       [0032]    Referring now to the drawings in detail,  FIGS. 4-13  illustrate portions of valves constructed in accordance with the present invention. The valves do not require the precise manufacturing tolerances of the prior art valves. Each valve is configured to compensate for non-concentricity of valve parts so that during assembly of the valve, a proper seal is created about a spool shaft. 
         [0033]    Referring now in particular to  FIGS. 4 and 5 , an exemplary valve  40  according to the present invention comprises a spool  41  movable within a valve body  42  (such as a valve housing and the like); a shaft  44  associated with the spool  41  and extending out of the valve body  42 ; an adapter  45  having an oversized through hole  46  for receiving the shaft; and a shaft seal  47  for sealing against the shaft. As will become apparent from the following description, the shaft seal  47  is adapted for transverse movement during assembly of the valve  40  for aligning to the shaft at an alignment position and then is held in such alignment position after assembly of the valve. 
         [0034]    The spool  41 , valve body  42  and shaft  44  can be of any design known in the art presently or in the future. The adapter may be a separate component that is attached to the valve body as by means of a threaded connection, or in some embodiments the adapter may be unitary with the valve body or portion thereof. The term “shaft” is used herein to mean any elongate or axially extending member such as a shaft, rod and the like that extends from a spool or other internal member of the valve and which is movable relative to the valve body to provide a control, sensing or other valve function. The shaft, for example, may be connected externally of the valve body to a shaft control mechanism such as shown in  FIG. 3 , or have associated therewith a sensor. 
         [0035]    The shaft seal  47  is supported in a seal carrier  50 . More particularly, the seal carrier  50  has a recess  52  at its inner diameter for retaining the shaft seal, which as shown may be a wiper seal. The seal carrier also has in an axial end face  53  thereof a recess  54  for retaining an annular carrier seal  55  radially outwardly of the shaft seal for sealing to the adapter  45 . The carrier seal forms a face seal with an opposing axial surface  56  of the adapter. 
         [0036]    The seal carrier  50  has a central opening  58  through which the shaft  44  extends and an outer diameter that is smaller than an internal diameter of a recess  60  in the adapter  45 . Consequently, the seal carrier can be moved transversely relative to the adapter  45  during assembly to align the shaft seal with the shaft. That is, the seal carrier, along with the shaft seal  47 , can move radially, relative to a centerline of the adapter, to properly align the seal concentric with the shaft without requiring concentricity of the shaft and adapter. This enables looser manufacturing tolerances and makes assembly more cost efficient. 
         [0037]    After installation and alignment of the shaft seal  47  with the shaft  44 , the seal is held in position by a holding device that urges the seal carrier against the opposing axial surface of the adapter  45 . In the embodiment shown in  FIGS. 4 and 5 , the holding device is a seal nut  64  that when tightened holds the seal carrier  50  tightly against the opposing axial surface  65  of the adapter to prevent transverse and axial movement of the seal carrier relative to the adapter. To this end, the seal carrier has a radially outer annular flange portion  66  clamped between the seal nut  64  and an opposing surface of the adapter. The seal nut may be provided with a thread locking feature such as a set screw  67 , pin or similar mechanism that positively locks the seal nut in place relative to the adapter. 
         [0038]    During assembly of the valve  40 , the shaft  44  is inserted into the hole in the adapter  45 . The seal carrier  50  is then assembled onto the shaft and pressed up against the adapter. As the seal carrier is slid onto the shaft, the shaft seal will shift transversely as needed to become concentric with the shaft. The seal nut  64  is then tightened to retain the seal carrier in place between the adapter and the seal nut creating a seal between the seal carrier and the adapter and the adapter, seal carrier, and shaft. 
         [0039]      FIGS. 6 and 7  show a further embodiment of a valve indicated generally at  70 . The valve  70  is substantially the same as the valve  40  except the seal carrier  50  is located on the inside in the fluid containing area  72  of the adapter  45  (i.e., the area nearest the spool  41 ). In the valve  70 , the holding device is a spring  74  that is interposed between the spool  41  and the seal carrier  50 . As shown, one end of the spring bears against a shoulder surface  75  on the spool that surrounds the shaft  44  interiorly of the valve body. The spring  74  functions to hold the seal carrier in place. The seal nut and thread locking feature may be eliminated when using the design of  FIGS. 6 and 7 . The seal carrier will still self-align during assembly. That is, the seal carrier and thus the shaft seal  47  can shift laterally in the recess  60  (bore) in the adapter  45  during assembly and then be held in place by the spring  74 . 
         [0040]    In  FIGS. 8 and 9 , another embodiment of a valve according to the invention is indicated generally at  80 . The valve  80  employs a unitary structure  81  forming a seal carrier  82  and a shaft seal  83 . The unitary structure preferably is made of a suitable sealing material as by molding. The seal carrier  82  extends radially outwardly from the shaft seal  83  and forms a face sealing flange that is held against a surface of an adapter  84  by a seal nut  85  or other holding device. As shown, the shaft seal may be a rotary type energized seal. 
         [0041]    During assembly, the unitary seal carrier and shaft seal are slipped over the shaft and against an axial face surface of the adapter. The carrier and shaft seal will shift laterally relative to the adapter to align with the shaft. Then the seal nut is tightened to clamp the face sealing flange between an axial end of the seal nut and the axial face surface of the adapter, thereby fixing the shaft seal against radial and axial movement. 
         [0042]      FIGS. 10 and 11  show still another embodiment of a valve according to the invention. The valve  88  in these figures is substantially the same as the valve  40  shown in  FIGS. 4 and 5 , except for the configuration of some components designated by the same reference numbers. In particular, the shaft seal  47  is in the form of an O-ring. 
         [0043]    Referring now to  FIGS. 12 and 13 , yet another embodiment of a valve according to the invention is indicated at  90 . In the valve  90 , a seal carrier (or seal carrier assembly)  91  includes a ball  92  and a split ball carrier  93  for receiving the ball. The ball has a through hole  95  through which a shaft (not shown) extends and a recess  97  in which a shaft seal  98  is retained by a seal retainer  99  for sealing to the shaft. The split ball carrier has axially arranged socket halves  100  and  101  between which the ball is held, and the socket halves are clamped between the adapter  102  and a holding device. The illustrated holding device is a seal nut  103  that presses the seal carrier assembly into a counterbore (recess)  104  in the adapter  102 . A washer  105  and a clutching O-ring  106 , or similarly functioning device, may be provided to prevent the ball carrier from rotating when the seal nut is tightened. 
         [0044]    The ball carrier has a face sealing O-ring  108  that prevents oil leakage across the face  109  of the adapter to which a counterbore  104  opens. The ball carrier also holds two circumferential sealing O-rings  112  and  113  which hold the ball and prevent leakage around the outer surface of the ball. The spherical shape of the ball assembly preferably is sized to be large enough so that the O-rings will be compressed by the tightening of the seal nut to close the ball carrier. 
         [0045]    The seal carrier assembly, prior to tightening of the seal nut, allows for angular “float” during installation to allow the shaft seal to properly seal against the shaft. The seal carrier assembly also is transversely (laterally) movable in the counterbore  104  of the adapter to provide for radial alignment prior to tightening of the seal nut. Once the shaft seal has been angularly and transversely aligned with the shaft, the seal nut is tightened to hold the shaft seal in its aligned position. 
         [0046]    Although the invention has been shown and described with respect to a certain preferred 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.