Abstract:
Retention of a roller follower shaft in a follower body is provided by keyed ends formed by flats on the shaft with which a follower roller forms an assembly, together with additional bearings if needed. Slots are provided extending from shaft bore openings through spaced arms of the body to distal ends of the arms. The roller follower assembly is inserted in a pocket between the arms by sliding the keyed ends of the shaft through the slots of the arms to axially align the shaft with the shaft openings. The shaft is then turned about 90 degrees in the openings in which a slight interference fit retains the shaft against lateral motion.

Description:
TECHNICAL FIELD 
     This invention relates to roller followers for engines, including cam and other eccentric followers, such as valve lifters, finger followers and rocker arms. More particularly, the invention relates to means and a method for installing and securing a roller shaft against axial or rotational movement within a follower body. 
     BACKGROUND OF THE INVENTION 
     It is known in the assembly of roller cam followers, such as for hydraulic valve lifters made in high volume, to support the follower roller on a hardened shaft secured in a transverse bore of the follower body. The shaft is selectively hardened so that the ends are sufficiently ductile to permit plastic deformation. The shaft is retained against lateral motion on the bore by deforming the shaft ends, such as by staking the shaft ends to the body after installation of the shaft therein. 
     The method works well but requires additional steps for the selective heat treatment of the shaft. Care in assembly is also required to avoid distortion of the body in the staking operation. 
     SUMMARY OF THE INVENTION 
     The present invention provides unique means and a method for installing and retaining a roller follower shaft in a follower body which simplifies manufacture and allows the use of various types of materials and configurations for a roller shaft not permitted by the previous arrangement. For example, fully hardened tool steel or ceramic materials may be utilized which cannot be deformed for use with a staking operation. In addition, the shaft diameter may be increased for direct bearing on the roller, as in use of a bronze shaft or for any desired reason, since installation of the roller and shaft assembly is through slots extending laterally from shaft bore openings rather than axially through the shaft openings themselves. 
     The invention involves keyed ends on the shaft. The keyed ends may be formed by providing flats on opposite sides of otherwise cylindrical ends. The follower body is provided with corresponding slots on inner walls of roller pocket forming arms that extend from the shaft openings laterally to distal ends of the arms. 
     In assembly, the roller is installed on the shaft together with any additional bearing materials that may be utilized. The resulting assembly is then inserted into the follower body by passing the keyed ends through the slots from the distal end of the body to the final location in alignment with the shaft openings. The shaft is then rotated approximately 90 degrees by a suitable tool or other means so that the keyed ends are misaligned with the slots and the shaft is positively retained in the shaft openings to prevent axial or further rotational motion. The shaft is preferably made to have a slight interference fit within the shaft openings so that the shaft is positively fixed in the installed position. Retention is further aided by friction created by loading of the roller against the shaft and follower body during operation of the roller follower in engine valve gear or other mechanism. 
     In particular, a roller follower for engines according to the invention includes a follower body adapted for actuating a mechanism of an engine in response to motion of a rotating eccentric. The body includes spaced arms defining an intermediate roller pocket, shaft openings through the arms and aligned on a transverse axis, and opposed parallel slots narrower than the shaft openings and formed in inner sides of the arms. The slots extend from the shaft openings to distal edges of the arms. A roller assembly includes a shaft and a follower roller. The shaft extends on a transverse axis and is supported by the roller upon engagement with an associated eccentric. The shaft includes a cylindrical central portion and ends extending axially from the central portion. The central portion mounts the roller and is received within the pocket. The ends extend into the shaft openings for retaining the roller assembly within the pocket. The ends include a tool engageable portion, and parallel flats slidably receivable within the slots for installing the roller assembly in the pocket from tree distal edges of the arms. The shaft is then rotated a quarter turn by a tool inserted in the tool engageable portion to misalign the flats and slots and engage the shaft with adjacent sides of the shaft openings for retaining the shaft in fixed position in the openings. 
     Also, according to the invention, a method for assembly and retention of a roller follower in a follower body may comprises the steps of providing a roller shaft assembly with a shaft having keyed ends; assembling the shaft assembly into aligned shaft openings in roller pocket forming arms of a follower body by sliding the keyed ends through lateral slots to the shaft openings from distal ends at edges of the arms; and rotating the shaft in the openings to misalign the keyed ends relative to the slots and fix the shaft position against removal through the slots, the shaft having an interference fit in the openings that retains the shaft in the fixed position against lateral or further rotational motion. 
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a side view of a roller hydraulic valve lifter incorporating shaft retention means according to the invention; 
     FIG. 2 is a fragmentary longitudinal cross-sectional view from the line  2 — 2  of FIG. 1 showing a first embodiment of the invention; 
     FIG. 3 is a transverse cross-sectional view from the line  3 — 3  of FIG. 2; 
     FIG. 4 is a cross-sectional view similar to FIG. 2 but showing an alternative embodiment of the invention; 
     FIG. 5 is a cross-sectional view similar to FIGS. 2 and 4 showing still another alternative embodiment; 
     FIG. 6 is a transverse cross-sectional view from the line  6 — 6  of FIG. 5; 
     FIG. 7 is a pictorial view partly broken away to show an application of the invention to a roller finger follower; and 
     FIG. 8 is a pictorial view partly broken away to show an application of the invention to an engine rocker arm. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIGS. 1-3 of the drawings in detail, numeral  10  generally indicates a roller hydraulic valve lifter engaging an associated eccentric cam  96  as an example of a roller follower in which the shaft retention means of the invention may be applied. Lifter  10  includes a follower body  12  having generally cylindrical upper and lower ends  14 ,  16 . The lower end  16  has a depending skirt  18  including oppositely disposed axially extending arms  20  which coact with the skirt  18  to form a downwardly open pocket  24  in which is received a follower roller  26 . 
     Roller  26  forms part of a roller shaft assembly  28  that further includes a plurality of needle bearings  30  rolling on an inner periphery of the roller  26  and engaging a cylindrical outer surface of a central portion  32  of a roller shaft  34 . Shaft  34  also includes keyed outer ends  36  which are formed by cutting, or otherwise forming, parallel flats  38  on opposite sides of the outer ends  36  to form the key-like shapes that characterize the ends  36 . 
     The roller shaft assembly  28  is received within the pocket  24  between inner sides  40  of the arms  20 . Thrust washers  42  are provided between the assembly and the inner sides to retain the needle bearings within the roller and prevent their rubbing against or contacting the sides  40  of the arms  20 . The outer ends  36  of the shaft are received within shaft openings  44  that extend through the arms  20  and are aligned on a common transverse axis  46 . 
     Between the openings  44  and the outer or distal ends  48  of the arms  20 , opposed parallel slots  50  are cut into the sides  40 . The slots  50  extend longitudinally, parallel to a central longitudinal axis  52  of the valve lifter  10 . Slots  50  are made with a width and depth sufficient to receive the keyed outer ends  36  of the roller shaft  34 , as will be subsequently described. The outer diameter of the roller shaft  34  is preferably sized to provide a slight interference fit of the ends  36  in the shaft openings  44  into which the shaft ends  36  extend so that the shaft is fixed by the interference fit and friction in the installed position illustrated in FIGS. 1-3. 
     To assemble the roller shaft assembly  28  into the lifter body, the shaft  34  is first inserted into the needle bearings disposed within the roller  26  and the thrust washers are positioned on either side of the roller and the associated needle bearings. The assembly is then positioned with the keyed outer ends of the shaft in alignment with the slots  50  of the follower body arms  20 . The shaft ends, with the assembly, are then slid through the slots  50  from the bottom or distal end of the lifter body. The flats  38  of the shaft slide along the sides of the slots  50  until the roller is positioned within the pocket and the shaft  34  is positioned with its axis coaxial with the longitudinal axis  46  of the shaft openings  44  into which the outer ends  36  of the shaft extend. 
     At this point, the shaft is rotated approximately 90 degrees so that the flats  38  are changed from a vertical position to a horizontal position as shown in the drawings. In this position, the outer diameter of the shaft ends  36  engages, with a slight interference fit, the inner diameters of the shaft openings  44 . The shaft is locked in place against lateral motion by reason of the interference fit in the shaft openings  44  and against longitudinal motion by the misalignment of the flats  38  with the slots  50  through which the shaft was installed. 
     Preferably, the shaft ends are provided with a tool engageable portion such as slot-like recesses  54  engageable by a tool, such as a screwdriver, to cause rotation of the shaft through the preferred 90 degree arc to lock the shaft in position within the shaft openings  44 . Other forms of tool connecting devices could, of course, be substituted and, if desired, a special tool could be provided to engage the flats  38  through the open ends of the shaft openings  44  in order to provide the rotational step required. 
     Referring now to FIG. 4 of the drawings there is shown an alternative embodiment of lifter  56  in which like numerals indicate like parts. The structure is similar to the first described embodiment except that the needle bearings  30  are replaced by a solid bearing sleeve  58  which may be of bronze or other suitable bearing material. Since the sLeeve is a solid ring, the thrust washers  42  of the first embodiment may be omitted. 
     FIGS. 5 and 6 illustrate still another embodiment of valve lifter  60  in which like numerals indicate like parts. In lifter  60 , the shaft and bearings of the earlier embodiments are replaced by a solid bronze shaft  62 . Alternatively, the shaft could be made of ceramic or any other suitable material capable of providing a bearing surface in direct contact with the roller  26 . Note that in the assembly, the bronze shaft has an outer diameter of its central portion  64  which is larger than the outer diameter of the keyed outer ends  66 . Thus, in this embodiment, the shaft can only be installed through the lower or distal end of the lifter body  12  as opposed to the conventional manner of installation in prior art assemblies wherein the shaft is inserted laterally along the axis  46  of the shaft openings  44 . 
     The other features of lifters  60  and  56 , including the flats on the shaft ends and slots in the inner sides of the arms, are similar to those of the first described embodiment so that installation of the roller shaft assembly in each case is essentially the same in the first described embodiment. Further description is thus believed unnecessary. 
     FIG. 7 of the drawings illustrates the combination of a roller shaft assembly  28  of any of the types in the previously described embodiments with a finger or roller cam follower  70  for actuating engine valve gear. Follower  70  is of conventional construction except that a pocket  72  formed between opposite sides  74  of a follower arm  75  includes shaft openings  76  with slots  78  extending from the openings  76  to distal edges  80  of the sides  74 . The slots  78  are provided to receive the keyed ends  36  of any of the roller shafts  34 ,  62  previously described, so that installation of the roller shaft assembly  28  is accomplished in the manner described in conjunction with the valve lifter. 
     FIG. 8 illustrates the combination of a roller shaft assembly  28  according to the invention with a rocker arm  82 . The rocker arm  82  includes arms  84  having inner sides  86  with slots  88  extending to shaft openings  90  to provide for installation of a roller shaft assembly  28  into the rocker arm  82  in the same manner as previously described with respect to the other embodiments shown. Thus, further description is believed unnecessary. 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted, by the language of the following claims.