Internal-combustion engines – Poppet valve operating mechanism – Tappet
Patent
1979-10-19
1982-06-22
Lazarus, Ronald H.
Internal-combustion engines
Poppet valve operating mechanism
Tappet
123 9048, 123 9049, F01L 110
Patent
active
043356850
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
LIFTER ASSEMBLY
1 Technical Field
This invention relates to a lifter assembly for a fuel pump plunger and to a method of manufacturing the assembly and an individual part thereof.
2 Background Art
Generally, lifter assemblies for fuel pumps include a support structure formed from a casting or a piece of barstock or the like by a series of machining operations. A roller is included as a part of such a lifter assembly to engage an engine-driven camshaft. The ends of the roller may have smaller diameters than the center portion thereof, and only the center portion serves for bearing engagement with the camshaft. The reduced diameter pin ends are rotatably mounted in bores formed in the support structure.
Alternatively, the roller may be rotatably mounted on a pin having its ends fixedly mounted on the support structure. In either case, the support structure must be relatively thick, and the roller or pin ends must be relatively long to bear the loads to which they are subjected. The length of the bearing surface of the roller which engages the camshaft is thereby reduced by the necessity of having the roller supported by the relatively massive support structure.
There is considerable stress at the point of contact of the roller with the camshaft. Thus, it is important that the roller be of at least some minimum width if such stress is to be kept at an acceptable level. In order to attain the necessary minimum width for the roller, adjacent prior art roller followers have had to be placed a sufficiently spaced distance from one another to allow mounting of the pin ends to the support structure. This has often created spacing problems in the engine structure.
One attempt to solve some of the problems are discussed above is set out in U.S. Pat. 3,822,683, issued July 9, 1974 to Jerry A. Clouse. In this patent, a roller follower is described which utilizes a cylindrical member in which a roller bearing is rotatably mounted. A clip fits in opposed slots in the cylindrical member with foot portions of the clip being in position to retain the ends of the roller bearing. In the apparatus of this patent, the roller does not have a reduced diameter pin end and can extend generally the entire distance from one foot portion to the other of the clip. However, the walls defining the slots in which the clip sits protrude significantly outwardly from the ends of the roller. Thus, sufficient overall saving in roller follower size is not attained. Also, the slots must be mechined into the cylindrical member or must otherwise be provided therein. Further, the cylindrical member is relatively heavy since it extends from the roller over the entire length of the roller follower. Thus, inertial changes are relatively great on reversal of the direction of movement of the roller follower. Still further, due to the solid construction of the cylindrical member, a window cannot readily be formed therein for entry of a rack to rotate a fuel pump plunger. Indeed, in the patent disclosing the just discussed roller follower, the rack motivates the fuel pump plunger a spaced distance above the roller follower.
Even if one has enough space in an engine to place the roller followers well apart, there is still a significant problem of cost and time in preparing the aforementioned support structures. That is, such machining operations as have been alluded to clearly add significantly to the cost of the overall roller follower.
DISCLOSURE OF INVENTION
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention, a lifter assembly is disclosed for a fuel pump plunger. The assembly comprises a sleeve having a lateral window therethrough; a roller holder fitting within said sleeve from a first end thereof, said holder having a semi-cylindrical cavity therein orthogonal to the axis of said sleeve and opening generally at said sleeve first end; and a roller rotatingly mounted in said cavity with the ends thereof within the sleeve.
One embodiment of the inventi
REFERENCES:
patent: 1565223 (1925-12-01), Church
patent: 1802330 (1931-04-01), Boland
patent: 3523459 (1970-08-01), Mowbray
patent: 3822683 (1974-07-01), Clouse
patent: 4089234 (1978-05-01), Henson
Caterpillar Tractor Co.
Lazarus Ronald H.
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