Abstract:
An adjustment screw assembly ( 10 ) having an adjustment screw ( 11 ) engaged to a rocker arm ( 14 ) of a combustion engine ( 12 ) is disclosed. The adjustment screw ( 11 ) comprises a lower member ( 26 ) and a vertical member ( 28 ) wherein the vertical member ( 28 ) threads to the rocker arm ( 14 ) and the lower member ( 26 ) secures pivotally and rotatably to the vertical member ( 28 ) forming a pivotal connection ( 31 ). The pivotal connection ( 31 ) has a male connector ( 38 ) which snap fits through an engagement lip portion ( 46 ) of a female socket ( 35 ) and is thereby held together for combustion engine assembly purposes. Once the adjustment screw ( 11 ) is assembled and placed within the combustion engine ( 12 ), internal springs ( 24 ) of the engine ( 12 ) resiliently hold and secure the lower member ( 26 ) to the vertical member ( 28 ).

Description:
TECHNICAL FIELD 
     This invention relates to an adjustment screw and more particularly to an adjustment screw assembly having rocker arms for a combustion engine. 
     BACKGROUND OF THE INVENTION 
     Adjustment screws are commonly utilized in combustion engine applications to provide a pivotal linkage and fine tune the interconnection between rocker arms, valves and fuel injector followers. For diesel engine applications, the adjustment screw is also utilized as the pivotal linkage between the rocker arm and a fuel injector follower. The adjustment screw must be adjustable to manage clearance, and therefore clatter, between the adjustment screw and valves or fuel injector follower. Furthermore, when the adjustment screw is used for fuel injector follower applications oil lubrication is required between the follower and the adjustment screw. This oil is supplied internally through the rocker arm. 
     The adjustment screw has a lower button and a vertical member. The vertical member engages adjustably to the rocker arm and the lower button engages pivotally to the vertical member. A resilient clip device is typically used to connect the lower button to the vertical member. The clip assures that the lower button does not fall away from the vertical member during assembly of the combustion engine. After assembly, the clip serves no further function because a spring of the combustion engine provides an upward force which holds the lower button against the end of the vertical member. In addition, clearances are such that it does not allow the button to come out. Although the clip is required only during assembly, the clip is not readily removable from the adjustment screw and therefore remains installed throughout the useful life of the combustion engine. Unfortunately, the clip is a latent concern, with a possibility to fragment during prolonged operation of the combustion engine. Any fragments have a possibility to become lodged within the engine block or entrained within the lubricating oil, thereby creating an engine operation and warranty concern. 
     SUMMARY OF THE INVENTION 
     The invention provides an adjustment screw assembly having a pivoting rocker arm for a combustion engine. The adjustment screw has a vertical member having an upper end threaded adjustably to the rocker arm and a lower end. An upper end of a lower member is pivotally connected to the lower end of the vertical member forming a pivotal connection. The pivoting action of the rocker arm causes the adjustment screw to oscillate which in turn causes a linear up and down movement of an actuator through contact of a bottom surface of the lower member to a top surface of the actuator. Because the contact is continuous and the bottom surface remains parallel to the top surface, the bottom surface slides back and forth transversely across the actuator&#39;s top surface as the actuator moves up and down. Preferably, the actuator is either valves or a fuel injector follower for a diesel engine. 
     The pivotal connection comprises a male connector snap fitted inside a female socket. The female socket has an engagement lip portion having an inner edge centering about a female socket centerline. The male connector has an outer perimeter centering about a male connector centerline. A male connector diameter of the outer perimeter is slightly larger than an inner edge diameter, thereby forming the snap fit as the outer perimeter of the male connector is forced past the inner edge of the female socket. Preferably, to accomplish the snap fit, the female socket centerline is offset to the male connector centerline at a prescribed angle during the snapping action. The female socket may either be the upper end of the lower member or the lower end of the vertical member, and vice-versa for the male connector. 
     By use of this snap fit lower member, it is possible to eliminate the clip once used to secure the lower member to the vertical member thereby rendering a reduction of parts used to construct the adjustment screw. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference is now made to the accompanying drawings, in which: 
     FIG. 1 is a cross-sectional view of two adjustment screws viewed within a rocker-arm assembly environment in accordance with the invention; 
     FIG. 2 is a partial perspective view of a combustion engine viewing downward with a rocker arm cover removed in order to view internal detail; 
     FIG. 3 is a plan view of the adjustment screw; 
     FIG. 4 is an exploded cross-sectional view of the adjustment screw; 
     FIG. 5 is a perspective view of a leading surface of a lower member of the adjustment screw; 
     FIG. 6 is a cross-sectional view of the adjustment screw; 
     FIG. 7 is a cross-sectional view of the adjustment screw wherein a lower member centerline is offset from a vertical member centerline by a prescribed angle for assembly purposes; and 
     FIG. 8 is a cross-sectional view of a second embodiment of the adjustment screw. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1 of the drawings, two adjustment screw assemblies  10  are shown within a combustion engine environment, preferably a diesel engine  12 . Each adjustment screw assembly  10  has an adjustment screw  11  engaging a pivoting rocker arm  14  at a radially extended rocker arm end  16 . Although movement of the rocker arm  14  is pivotal about a shaft  18 , movement at the extended rocker arm end  16  is substantially vertical, with some rotational pivoting movement present. Each rocker arm  14  connects perpendicular to a common shaft  18 . Disposed beneath each adjustment screw  11  is an actuator  19  which can either be a valve or a fuel injector follower  22 . The longitudinal axes of the adjustment screw  11  and the actuator  19  are substantially co-linear and vertical. The adjustment screw  11  is generally perpendicular to the rocker arm  14 . The actuator  19  is biased upward against the adjustment screw  11  at all times by installed springs  24 . Springs  24  are therefore compressed at all times and positioned concentrically about the actuator  19 . 
     Referring to FIGS. 1 and 2, the adjustment screw  11  has a lower member  26  and a vertical member  28 . The lower member  26  attaches pivotally to a lower end  29  of the vertical member  28 . Lower member  26  has a bottom surface  48  in continuous contact with a top surface  23  of the actuator  19 . The top surface  23  substantially moves in an up and down linear direction while the bottom surface  48  of the lower member  26  moves accordingly in the vertical direction. Because of the oscillating or pivoting action of the rocker arm end  16 , the lower member  26  moves slightly in the transverse direction to the vertical movement of the actuator  19 . This transverse movement causes the bottom surface  48  of the lower member  26  to slightly slide across the lubricated top surface  23  of the actuator  19 . 
     The vertical member  28  threadably connects within the rocker arm end  16 . An upper end  27  of the vertical member  28  has outer diameter threads  30  engaging inner diameter threads  32  of the rocker arm  14 . The height of adjustment screw  11  is adjustable via rotation between threads  30 ,  32  through a hexagonal shaped recess  34  exposed concentrically at the upper end  27  which protrudes through the rocker arm  14 , also shown in FIG.  3 . Adjustment is required to assure continuous contact between the top surface  23  of the actuator  19  and the bottom surface  48  of the lower member  26 . Once adjusted, a locking nut  36  screws downward over threads  30 , until the locking nut  36  tightens against a top surface  33  of the rocker arm end  16 . 
     Referring to FIG. 2, each cylinder of the combustion engine, typically utilizes five adjustment screws  11 . Four are applied to the exhaust and air intake valves  20  and one to the fuel injector follower  22 . When the adjustment screw  11  is utilized for the fuel injector follower  22 , additional oil lubrication is required between the lower member  26  and the fuel injector follower  22  as a form of cooling and lubrication. The rocker arm shaft  18  is hollow and thereby supplies oil through internal ports of the rocker arm  14  to the adjustment screw  11 . 
     Referring to FIG. 4, the lower member  26  has an upper end  25  which snap fits to the lower end  29  of the vertical member  28 , thereby providing a rotational and pivotal connection  31 . The upper end  25  and the mating lower end  29  take the form of a female socket  35  and a male connector  38 . As shown, the upper end  25  is the female socket  35  and the lower end  29  is the male connector  38 . However, this relationship can be reversed as shown in FIG. 8 as a second embodiment. The female socket  35  houses the male connector  38  having a male connector centerline  54 . Centering about the male connector centerline  54  is a leading surface  52  which curves and substantially conforms to a hemisphere, expanding radially in the trailing axial direction (away from the pivotal connection). 
     The female socket  35  has a mid portion  42  connecting rigidly between a trailing portion  44  and an engagement lip portion  46 . The mid, trailing, and engagement lip portions are each disposed about a female socket centerline  40 . Centering about the female socket centerline  40  is a leading surface  50  of the trailing portion  44 . Leading surface  50  is concave and semi-spherical in shape to pivotally and rotationally mate with the leading surface  52  of the male connector  38 . The leading surface  50  conforms to the leading surface  52  forming the rotateable pivotal connection  31 . 
     Referring to FIGS. 4 and 5, the mid portion  42  has an inner wall  56 , and the engagement lip portion  46  has an inner edge  58 , both centering about the female socket centerline  40 . The leading surface  52  of the male connector  38  has an outer perimeter  60  having a male connector diameter  62  which is larger than an edge diameter  64  of the inner edge  58  yet smaller than a wall diameter  66  of the inner wall  56 . The difference in length between the male connector diameter  62  and the edge diameter  64  is substantially small so that the male connector  38  can snap into the female socket  35  without causing permanent deformation, yet large enough so that the female socket  35  does not easily separate from the male connector  38 . In assembly, the outer perimeter  60  aligns radially inward of the inner wall  56 . 
     Sharing outer perimeter  60  with the leading surface  52  is a trailing surface  53 . Trailing surface  53  centers about the male connector centerline  54  and generally tapers radially inward from the outer perimeter  60  in the trailing axial direction. In assembly, the engagement lip portion  46  of the female socket  35  is axially aligned to and disposed radially outward from the trailing surface  53 . 
     The leading surface  50  of trailing portion  44  of female socket  35  has a perimeter  68  having a perimeter diameter  70  which is smaller than the outer perimeter  60  of the male connector  38 . In other words, the leading surface  50  is generally smaller than the leading surface  52  of male connector  38 . Regardless of the adjustment screw  11  pivoting action, or misalignment of the female socket centerline  40  to the male connector centerline  54 , the outer perimeter  60  is always disposed radially outward of the perimeter  68  of leading surface  50 . This will prevent binding between leading surface  50  and the leading surface  52 . 
     The perimeter  68  of leading surface  50  and the inner wall  56  of mid portion  42  respectively define the inner and outer perimeters of a leading annular surface  72  of the trailing portion  44 . Leading annular surface  72  extends radially, centers about female socket centerline  40 , and is substantially perpendicular to the inner wall  56 . A lower comer  74  formed by leading annular surface  72  and inner wall  56  is slightly curved. In axial opposition to the leading annular surface  72  of trailing portion  44  is a trailing annular surface  76  of the engagement lip portion  46 . Likewise, the trailing annular surface  76  extends radially between the inner edge  58  and the inner wall  56 , centers about female socket centerline  40  and is substantially perpendicular to the inner wall. The inner wall  56  and the trailing annular surface  76  form a slightly curved upper comer  78 . The outer perimeter  60  of male connector  38  is disposed axially between the leading annular surface  72  of trailing portion  44  and the trailing annular surface  76  of the engagement lip portion  46 . 
     As stated previously, the interface between the fuel injector follower  22  and the adjustment screw  11  must have additional lubrication. Additional lubrication flows through the shaft  18  which is hollow and through the rocker arm  14  as shown in FIG.  1 . From the rocker arm  14 , the oil flows into a circumferential groove  80  extending around the vertical member  28  of the adjustment screw  11 . From the circumferential groove  80 , the oil flows into a communicating radial port  82 . Communicating generally with the longitudinal center of the radial port  82  is an axial port  84 . Axial port  84  is concentric to and extends longitudinally along the vertical member centerline  54  from the radial port  82  through the lower end  29  of the vertical member  28 . 
     Referring to FIG. 6, the oil flows from the lower end  29  of vertical member  28  into a cavity  88 . The cavity is defined between a radially extending and flat surface  86  of the leading surface  52  of the male connector  38  and the leading surface  50  of the trailing portion  44 . Flat surface  86  centers about the male connector centerline  54 . 
     Substantially concentric to and extending axially through the lower member  26  is an aperture  90 . Aperture  90  communicates with cavity  88  and the top surface  23  of the fuel injector follower  22 . Oil thereby flows from the axial port  84  into the cavity  88  and through the aperture  90  to provide lubrication at the fuel injector follower  22  interface. The cavity  88  assures communication and oil passage between the aperture  90  and the axial port  84  when the adjustment screw  11  is pivoting between the lower member  26  and the vertical member  28 , respectively. 
     Referring to FIG. 7, assembly of lower member  26  to the vertical member  28  is a snap fit. Snap fitting requires orientation of the male connector centerline  54  at a prescribed angle θ to the female socket centerline  40 . An intersection  92  located along the male connector centerline  54  and aligned axially to the outer perimeter  60  is first aligned to the female socket centerline  40 . The male connector centerline  54  is then offset to the prescribed angle θ from the female socket centerline  40  While maintaining the prescribed angle θ, the intersection  92  is moved along the female socket centerline  40  toward the female socket  35  until the male connector  38  snap fits into the female socket  35 . The pivotal connection  31  is thereby formed and lower member  26  is pivotally and rotationally engaged to vertical member  28 . 
     Preferably, the male connector diameter  62  is generally “12.65 millimeters, ” the edge diameter  64  is generally “12.56 millimeters, ” and the prescribed angle θ is approximately twenty degrees. The maximum installation load required to snap fit the female socket  35  to the male connector  38  must not exceed one hundred and thirty pounds at the twenty-degree prescribed angle θ. The minimum pull apart load shall not be lower than fifty pounds also at the twenty-degree prescribed angle θ. The load direction measures along the female socket centerline  40 . The material of lower member  26  and vertical member  28  is steel, and the lower member  26  is heat treated. 
     Referring to FIGS. 1-7, the first embodiment of the invention is shown where the upper end  25  of the lower member  26  is the female socket  35 . The aperture  90  centers about the female socket centerline  40 . And, the lower end  29  of the vertical member  28  is the male connector  38 . The axial port  84  centers about the male connector centerline  54 . 
     Referring to FIG. 8, a second embodiment of an adjustment screw  11 ′ is shown where the upper end  25 ′ of the lower member  26 ′ is the male connector  38 . The aperture  90 ′ centers about the male connector centerline  54 . The lower end  29 ′ of the vertical member  28 ′ is the female socket  35 . The axial port  84 ′ centers about the female socket centerline  40 . 
     Although the preferred embodiments of the present invention have been disclosed, various changes and modifications may be made thereto by one skilled in the art without departing from the scope and spirit of the invention as set forth in the appended claims