Patent Application
20080135000
1. Field of the Invention
The present invention relates to a poppet valve operating system having a rocker shaft with slidably mountable rocker arms which are indexed upon the rocker shaft by means of reliefs formed in the outer cylindrical surface of the rocker shaft.
2. Disclosure Information
Many overhead valve engines utilize rocker arms for actuating cylinder poppet valves. Such rocker arms are generally either pedestal mounted or shaft mounted. Shaft mounted arms are usually slidably installed upon a cylindrical rocker shaft. Once the arms have been installed, they must be maintained in a precise axial location along the shaft to assure that proper contact is made with the valve and other actuating mechanisms such as a camshaft or push rod. Designers have devised a number of schemes for maintaining rocker arms in a desired position on a rocker shaft. These schemes usually include the use of custom spacers which are interposed between the rocker arms and the mounting pedestals. The spacers are sometimes supplemented by compression springs or other devices. Needless to say, all the devices add weight, complexity and expense. Also, the need for different spacers may lead to misbuilds of the engine cylinder heads.
It would be desirable to provide a rocker arm retention system for use with rocker shaft mounted arms which positively retains rocker arms, but nevertheless permits their disassembly for servicing.
A poppet valve operating system for an internal combustion engine includes a number of poppet valves which are urged into a closed position by compression springs. At least one rocker shaft is adapted for mounting to a cylinder head of an engine. The rocker shaft has a cylindrical outer surface. A number of indexing reliefs are formed in the outer cylindrical surface of the rocker shaft. Rocker arms for actuating poppet valves are mounted to the rocker shaft. Each rocker arm includes a rocker arm body having a circular bore corresponding to the outer cylindrical surface of the rocker shaft and a resiliently biased telescoping pin housed in the rocker arm body. The telescoping pin has an inner end projecting into the circular bore of the rocker arm body. The telescoping pin extends into one of the indexing reliefs formed in the rocker shaft.
According to another aspect of the present invention, each indexing reliefs formed in the other cylindrical surface of the rocker shaft extends about at least a portion of the periphery of the outer cylindrical surface. The indexing reliefs extend for a distance sufficient to accommodate a rotational arc traversed by each of the rocker arms as rocker arms actuate the poppet valves. The telescoping pins and indexing reliefs cooperate to prevent the rocker arms from moving axially upon the rocker shaft.
According to another aspect of the present invention, a method for utilizing an internal combustion engine poppet valve rocker arm upon a rocker shaft includes the steps of axially engaging a circular bore formed in a rocker arm body with an end portion of a rocker shaft, so as to drive a resiliently biased telescoping pin, having a normal position projecting from the wall of the bore, into a retracted position in which the pin abuts an outer cylindrical surface of the rocker shaft. The rocker arm body is moved along the rocker shaft until a predetermined valve actuation location has been reached and then, the rocker arm body is rotated to allow the resiliently biased pin to extend from the circular bore into an indexing relief formed in the outer cylindrical surface of the rocker shaft. Thereafter, the rocker arm may be removed from the rocker shaft by rotating the rocker arm body with respect to the rocker shaft sufficiently to slidingly engage telescoping pin with a ramp leading from a lower portion of the indexing relief to the outer cylindrical surface of the rocker shaft, thereby compressing the telescoping pin into its retracted position. Then, the rocker arm body including the retractive telescoping pin may be moved along the rocker shaft until it slides free of the rocker shaft.
It is an advantage of a poppet valve operating system according to the present invention that rocker arms are retained upon a rocker shaft without the need for any additional fasteners, spacers or springs. This helps to prevent improper or incorrect installation of rocker arms in an engine.
It is a further advantage of a valve operating system according to the present invention that excess weight is minimized because of the ability to eliminate additional fasteners, spacers and springs.
It is yet another advantage of a valve operating system according to the present invention that rocker arms may be easily removed or installed from a rocker shaft, so as to permit repair of various components in the valve operating system.
Other advantages, as well as features and objects of the present invention will become apparent to the reader of this specification.
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Removal and reinstallation of rocker arms upon a rocker shaft according to the present method permits easy servicing of the valve actuation system, without the need for special tools, because rocker arms 38 need only be rotated upon rocker shafts 22 to allow their disengagement from the rocker shaft and followed by axial movement of the rocker arms off the rocker shaft. This operation is facilitated because the rocker arm body need only be rotated by a small amount exceeding the rotational arc traversed by the rocker arm when the poppet valves are operated.
While particular embodiments of the invention have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.
