Machine element or mechanism – Elements – Cams
Reexamination Certificate
1999-09-20
2001-09-18
Luong, Vinh T. (Department: 3682)
Machine element or mechanism
Elements
Cams
C123S090500, C123S090160
Reexamination Certificate
active
06289765
ABSTRACT:
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.
REFERENCES:
patent: 4793295 (1988-12-01), Downing
patent: 5239951 (1993-08-01), Rao et al.
patent: 5273005 (1993-12-01), Philo et al.
patent: 5361733 (1994-11-01), Spath et al.
patent: 5385124 (1995-01-01), Hillebrand et al.
patent: 5775275 (1998-07-01), Philo
patent: 5931133 (1999-08-01), Giannone et al.
Delphi Technologies Inc.
Luong Vinh T.
VanOphem John A.
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