Abstract:
A method for retaining lubrication in a splined joint comprises the steps of forming a seal between an inward surface of a grease seal cup and a first component, forming another seal between an outward surface of the grease seal cup and a sealing member extending from a second component, and engaging an end portion of the grease seal cup with an end portion of the first component, so that the end portion of the grease seal cup resists axial displacement of the grease seal cup during engagement of the first component with the second component. The grease seal cup of the method has a cylindrical portion integral with the end portion. The cylindrical portion has a tapered annular wall with the inward and outward surfaces. The end portion of the grease seal cup extends radially and inwardly from the cylindrical portion, so that the tapered annular wall is squeezed between the first component and the sealing member. The pre-fabricated light weight grease seal cup can be used in existing splined joints without adversely affecting the weight balance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional application of Ser. No. 11/103,973 filed Apr. 12, 2005. 
     
    
     GOVERNMENT INTERESTS 
       [0002]    The invention was made with Government support under contract number F33657-91-C-0006 awarded by Boeing Military Aircraft and is subject to the provisions of that contract. The Government has certain rights in this invention. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    The present invention generally relates to splined joints and, more particularly, to grease seal cups to retain lubrication for life extension in existing splined joints. 
         [0004]    Splined joints are used in many devices for transmitting torque between two components, such as a motor drive shaft and compressor shaft. Generally, a splined joint includes a series of internal splines formed on one of the components engaging a series of external splines formed on the other of the two components. Typically, a splined joint is assembled by positioning the two components end-to-end lengthwise so that the internal splines are circumferentially aligned with the spaces between the external splines and then sliding the components axially into overlapping engagement so that the two sets of splines become enmeshed with one another. 
         [0005]    A lubricating material, such as grease, may be provided at the interface of the internal and external splines to reduce component wear. During component operation, the lubricating material tends to be removed from the spline interface due to centrifugal force. Additionally, some splined joints are exposed to materials, such as hot hydraulic fluid, which also tend to remove the grease that is intended to lubricate the splines. Without lubrication, the splines wear out prematurely and limit the component service life. For some applications, the loss of spline joint lubrication has limited component service life to ¼-life. 
         [0006]    U.S. Pat. No. 4,281,942 provides a lubrication system for a spline connection. The described system comprises a split ring at one end of the spline connection and a supply of oil at the other end. During operation, centrifugal force pushes the two halves of the split ring apart, allowing the oil to flow through the spline connection and out through the split ring. A quad o-ring around the circumference of the split ring pulls the two halves together when the shaft is stationary, closing off the oil path. Although the disclosed system may provide lubrication for a spline connection, the added weight of the heavy metal split ring may not be suitable for some existing applications. For example, applications including a Scotch yoke design require the weight balance to be maintained and the incorporation of the heavy split ring may necessitate a total redesign. Additionally, this lubrication system does not sufficiently reduce lubrication loss due to hot hydraulic fluid exposure. 
         [0007]    Japanese Patent No. JP11180259 provides a grease cup for a connecting shaft. The cup comprises a rigid washer positioned between a shaft and a rotary lever. The rigid washer is bent upward during assembly to suppress the outflow of grease from the area between the shaft and the lever and to prevent the inflow of water. Although the described grease cup may be used to reduce grease loss from the joint between a shaft and a lever, it may not have the symmetry necessary for use in a splined joint between two high-speed rotating shafts. Additionally, because the described cup is formed during installation by bending the washer, it may not be useful for applications requiring an easy to install pre-fabricated component. 
         [0008]    As can be seen, there is a need for improved mechanisms to retain splined joint lubrication. A lightweight apparatus that can maintain the weight balance of an existing system is needed. Additionally, an apparatus is needed that is pre-fabricated and easy to install. 
       SUMMARY OF THE INVENTION 
       [0009]    In one aspect of the present invention, an apparatus for a splined joint formed between a first component and a second component comprises a cylindrical portion having an inner diameter adapted to receive the first component; and an end portion radially inward from and integral to the cylindrical portion, the end portion having an opening adapted to receive the second component. 
         [0010]    In another aspect of the present invention, an apparatus for a splined joint formed between a drive shaft and a driven shaft comprises a polymer cup-shaped structure having a cylindrical portion and an opening; and a seal cup cavity radially inward from the cylindrical portion. 
         [0011]    In still another aspect of the present invention, an apparatus for a splined joint of a compressor comprises a cylindrical portion positioned radially outward from the splined joint and radially inward from a spanner nut of the compressor such that the splined joint is sealed. 
         [0012]    In yet another aspect of the present invention, an assembly comprises a driven shaft having a plurality of external splines; a drive shaft having a plurality of internal splines in engagement with the external splines; and a grease seal cup positioned such that a cylindrical portion of the grease seal cup is radially outward from the drive shaft and radially inward from a sealing member of the driven shaft, said cylindrical portion forming a first seal with the drive shaft and forming a second seal with the sealing member. 
         [0013]    In another aspect of the present invention, an apparatus for a splined joint formed between a hydraulic motor shaft and a compressor shaft comprises a cylindrical portion having an inner diameter adapted to receive the hydraulic motor shaft and having a tapered outward surface, the cylindrical portion having an axial length of between about 0.273 inches and about 0.283 inches, the cylindrical portion comprising polytetrafluoroethylene, the cylindrical portion adapted to form a first seal with the hydraulic motor shaft and to form a second seal with a spanner nut of the compressor shaft; and an end portion radially inward from and integral to the cylindrical portion, the end portion having an opening adapted to receive the compressor shaft, the end portion having a thickness of between about 0.025 inches and about 0.031 inches. 
         [0014]    In a further aspect of the present invention, a method of joining a drive shaft and a driven shaft comprises the steps of applying a lubricant to the external splines of the driven shaft; passing the driven shaft through the opening of a grease seal cup to position the external splines within the seal cup cavity of the grease seal cup; and axially urging the drive shaft toward the driven shaft such that a splined joint is formed. 
         [0015]    In yet another aspect of the present invention, a method of preventing loss of spline joint lubrication comprises the steps of forming a first seal between a grease seal cup and a first component of the spline joint; and forming a second seal between the grease seal cup and a sealing member of a second component of the splined joint. 
         [0016]    These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0017]      FIG. 1  is a partial cross section of a grease seal cup installation according to one embodiment of the present invention; 
           [0018]      FIG. 2   a  is a top view of a grease seal cup according to one embodiment of the present invention; 
           [0019]      FIG. 2   b  is a cross-section view through line  2   b  of  FIG. 2   a;    
           [0020]      FIG. 3  is an exploded view of the grease seal cup installation of  FIG. 1 ; 
           [0021]      FIG. 4   a  is a cross-section view of a grease seal cup according to one embodiment of the present invention; 
           [0022]      FIG. 4   b  is a cross-section view of a grease seal cup according to another embodiment of the present invention; 
           [0023]      FIG. 4   c  is a cross-section view of a grease seal cup according to another embodiment of the present invention; 
           [0024]      FIG. 4   d  is a cross-section view of a grease seal cup according to another embodiment of the present invention; 
           [0025]      FIG. 5  is a flow chart of a method for joining a drive shaft and a driven shaft according one embodiment of the present invention; and 
           [0026]      FIG. 6  is a flow chart of a method for preventing loss of spline joint lubrication according one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]    The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
         [0028]    Broadly, the present invention provides grease seal cups to retain lubrication for life extension in existing splined joints and methods for producing the same. The grease seal cups according to the present invention may find beneficial use in many industries including aerospace, watercraft, automotive, and electricity generation. The present invention may be beneficial in applications including power transmission for automobiles, aircraft and ships. This invention may be useful in any splined joint application. 
         [0029]    In one embodiment, the present invention provides a grease seal cup for a splined joint that connects a first shaft to a second shaft. The first shaft, such as a hydraulic motor shaft, may have a plurality of internal splines. The second shaft, such as a compressor shaft, may have a plurality of external splines. Unlike the prior art, the grease seal cup may comprise a flexible polymer, such as Teflon®. The second shaft may be positioned through an opening in the bottom of the grease seal cup and the first shaft may be urged into engagement through the top of the grease seal cup. During the installation of the first shaft, the cylindrical portion of the grease seal cup may be squeezed between the outer surface of the first shaft and a component of the second shaft, such as a spanner nut, to seal the splined joint. The present invention may comprise a pre-fabricated cup-shaped apparatus that can be easily installed on the second shaft. This is unlike the prior art that requires washer bending during installation. Because the present invention may comprise a light weight polymer cup-shaped structure, it can be used in existing splined joints without adversely effecting the weight balance, which is also unlike the prior art. 
         [0030]    A grease seal cup installation of the present invention is depicted in  FIG. 1 . A grease seal cup  40  may be positioned radially outward from a splined joint  44 . The splined joint  44  may include a series of internal splines  47  (see  FIG. 3 ) formed on a first component  45  engaging a series of external splines  48  (see  FIG. 3 ) formed on a second component  46 . The grease seal cup  40  may form a first seal  60   a  with the first component  45  and form a second seal  60   b  with a sealing member  58 . The sealing member  58  may be a structure of the second component  46  that is radially outward from the splined joint  44 , such as a spanner nut. 
         [0031]    An embodiment of the grease seal cup  40  is depicted in  FIGS. 2   a  and  2   b . The grease seal cup  40  may comprise a cylindrical portion  41  and an end portion  42 . The end portion  42  may comprise an annular shaped member having an opening  43  there through. The cylindrical portion  41  may be adapted to receive the first component  45 . The opening  43  of an end portion  42  may be adapted such that the second component  46  may be passed through the opening  43  for grease seal cup installation. The end portion  42  may be radially inward from and integral to the cylindrical portion  41  such that the circumference of the end portion  42  is in contact with the cylindrical portion  41 . Radially inward may be defined with reference to a longitudinal centerline  57  through the grease seal cup  40 . The cylindrical portion  41  and the end portion  42  may define a seal cup cavity  49  for receiving the splined joint  44 . 
         [0032]    A diameter  51   a  of the opening  43 , depicted in  FIGS. 2   a  and  2   b , may be adapted to receive the second component  46 . In other words, the diameter  51   a  of the opening  43  may be such that at least a portion of the second component  46  may be passed through the opening  43  to position the external splines  48  within the seal cup cavity  49 . The diameter  51   a  may vary with application and may depend on factors including the dimensions of the second component  46 . For example, for some splined joint applications, the diameter  51   a  of the opening  43  may be between about 0.395 inches and about 0.405 inches. A diameter  51   b  of the end portion  42 , depicted in  FIG. 2   b , may be such that the circumference of the end portion  42  is in contact with the cylindrical portion  41 . A thickness  52  of the end portion  42  may vary with application and may depend on factors including the composition of the end portion  42 . For some splined joint applications, the thickness  52  may be between about 0.025 inches and about 0.031 inches. 
         [0033]    The cylindrical portion  41  may have a top end  55  and a bottom end  56 , as depicted in  FIG. 2   b . The bottom end  56  may be integral to the end portion  42 . The cylindrical portion  41  may extend axially from the bottom end  56  to the top end  55 . An axial length  68  of the cylindrical portion  41  may vary with application and may depend on factors including the dimensions of the splined joint  44 . For some applications, the axial length  68  of the cylindrical portion  41  may be about equal to the axial length of the splined joint  44 . For some splined joint applications, the axial length  68  may be between about 0.273 inches and about 0.283 inches. 
         [0034]    An inner diameter  50  of the cylindrical portion  41  may be adapted to receive the first component  45 . The inner diameter  50  of the cylindrical portion  41  may be about equal to a first component outer diameter  53 , as depicted in  FIG. 3 . For some splined joint applications, the inner diameter  50  of the cylindrical portion  41  may be between about 0.565 inches and about 0.575 inches. 
         [0035]    As illustrated in  FIG. 3 , the cylindrical portion  41  of the grease seal cup  40  may have an inward surface  61  and an outward surface  54 . The inward surface  61  may conform to an outer diameter surface  59  of the first component  45  (see  FIG. 3 ). The outward surface  54  of the cylindrical portion  41  may be adapted such that the grease seal cup  40  may form the first seal  60   a  with the first component  45  and form the second seal  60   b  with the sealing member  58 , as depicted in  FIG. 1 . The sealing member  58  may be a structure of the second component  46  that is radially outward from the splined joint  44 , such as a spanner nut. The sealing member  58  may vary with application. For some applications, the sealing member  58  may comprise a spanner nut to retain the shaft seal and ball bearing in place. 
         [0036]    The outward surface  54  may be adapted such that the cylindrical portion  41  may be deformed during installation of the grease seal cup  40  to form the seals  60   a,b  (See  FIG. 3 ). In one embodiment, the outward surface  54  may be at an angle  62  to provide a tapered shape wherein an outer diameter  63   a  of the cylindrical portion  41  towards the top end  55  is greater than an outer diameter  63   b  of the cylindrical portion  41  towards the bottom end  56 , as depicted in  FIG. 4   a . In other words, the outward surface  54  may be tapered outward from the end portion  42 . In an alternate embodiment, the outward surface  54  may comprise a flange  66  positioned towards the top end  55 , as depicted in  FIG. 4   b . In other alternate embodiments, the outward surface  54  may comprise at least one radially extending projection. For example, a plurality of ridges  64  or ribs  65  may be positioned on the outward surface  54 , as depicted in  FIGS. 4   c  and  4   d.    
         [0037]    The outward surface  54  may comprise any outward surface that is tightly squeezed during the installation of the grease seal cup  40  to provide the seals  60   a,b.  The seals  60   a,b  may physically prevent materials from entering or exiting the splined joint  44 . The seals  60   a,b  may prevent materials, such as hot hydraulic oil, from entering the splined joint  44 . The seals  60   a,b  may prevent spline joint lubrication from being removed by centrifugal force during shaft operation. 
         [0038]    The grease seal cup  40  may be installed by passing the second component  46  through the opening  43  to position the external splines  48  within the seal cup cavity  49 . The first component  45  may be urged axially toward the second component  46  such that the splined joint  44  is formed. A chamfer  67  may be provided at the top end  55  of the inward surface  61  of the cylindrical portion  41  for ease of installation. The axial urging of the first component  45  may squeeze the cylindrical portion  41  between the outer circumference surface  59  of the first component  45  and the sealing member  58 . The flexible deformation of the cylindrical portion  41  may provide the seals  60   a,b.    
         [0039]    The grease seal cup  40  may comprise a flexible polymer material. Useful flexible polymer materials may include polyamides, polyimides, elastomers, fluorocarbons, nylons, silicones, and polyvinyl and poly olefin compounds. Useful flurocarbons may include polytetrafluoroethylene (Teflon®). Polytetrafluoroethylene may be an inert polymer that may be useful for applications exposed to high temperatures and high pressures. Useful elastomers may include poly(vinylidine fluoridehexafluoropropylene) copolymer (Viton®). The grease seal cup  40  may be formed by conventional methods, such as machine cutting or moulding techniques. For grease seal cups  40  comprising more than one material, convention composite moulding techniques may be useful. 
         [0040]    The first component  45  may comprise any shaft having internal splines  47 . For example, the first component may comprise a drive shaft, such as a hydraulic motor drive shaft. The second component  46  may comprise any shaft having external splines  48 . For example, the second component  46  may comprise a driven shaft, such as a compressor shaft. 
         [0041]    A method  100  of joining a drive shaft and a driven shaft is depicted in  FIG. 5 . The method  100  may comprise a step  110  of applying a lubricant to the external splines of the driven shaft and a step  120  of passing the driven shaft through the opening of a grease seal cup to position the external splines within the seal cup cavity of the grease seal cup. The method  100  may comprise a step  130  of axially urging the drive shaft toward the driven shaft such that a splined joint is formed. The step  110  of applying a lubricant may comprise providing a grease to the surface of the external splines. The step  130  of axially urging may comprise squeezing the grease seal cup between an outer surface of the drive shaft and a spanner nut of the driven shaft. 
         [0042]    A method  200  of preventing loss of spline joint lubrication is depicted in  FIG. 6 . The method  200  may comprise a step  210  of forming a first seal between a grease seal cup and a first component of the spline joint, and a step  220  of forming a second seal between the grease seal cup and a sealing member of a second component of the splined joint. The step  210  of forming the first seal may comprise squeezing the cylindrical portion of the grease seal cup such that the inward surface of the grease seal cup contacts the outer circumference surface of the first component. The step  220  of forming the second seal may comprise squeezing the cylindrical portion of the grease seal cup such that the outward surface of the grease seal cup contacts a sealing member of the second component. 
         [0043]    As can be appreciated by those skilled in the art, the present invention provides grease seal cups to retain lubrication in existing splined joints. The provided grease seal cups may comprise flexible polymer cups that may be easy to install. The grease seal cups may be used in existing applications having a Scotch yoke design without adversely affecting the weight balance. 
         [0044]    It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.