Internal-combustion engines – Two-cycle – Rear compression
Reexamination Certificate
2000-01-07
2001-02-20
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Two-cycle
Rear compression
C123S1960CP
Reexamination Certificate
active
06189496
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to breather valves used in internal combustion engines, and more particularly to an improved breather valve and breather valve arrangement intended for motorcycle engines, and to a method of replacing the breather valve in such engines with the improved breather valve.
BACKGROUND OF THE INVENTION
Rotary breather valves for motorcycle engines have been used for many years. The purpose of a breather valve is generally twofold. First, it expels air and oil from the crank case, on the down stroke of the pistons, to the gear case where the oil lubricates various gears and other parts. Second, it draws oil from the bottom of the oil separating pocket (also sometimes referred to as the “settling pocket”) in the bottom of the gear case.
Regarding the second purpose, problems arise when the engine is modified to have a larger displacement. The higher horsepower engine results in, among other things, more oil being expelled from the crank case into the gear case (and ultimately the gear case oil separating pocket). If not removed (“scavenged”) by the breather valve, this excess oil will leave the engine through the air cleaner system, which is referred to as oil carryover (sometimes also referred to as “blowby” or “puking”). Oil carryover contaminates the air filter and thereby reduces its effectiveness, undesirably enriches the fuel coming into the engine, and pollutes the environment. Excess oil in the gear case can also reduce horsepower.
It can be seen that a new breather valve is needed that improves the scavenging of oil from the oil separating pocket of the gear case.
SUMMARY OF THE INVENTION
The present invention can be practiced in a number of ways, including by replacing an existing breather valve with one for example like that described herein, by modifying the breather valve cavity (into which the breather valve is inserted) in an existing engine, or by constructing either or both the breather valve and the engine cavity, in an existing or new engine, so that the advantages of the present invention are obtained.
In one aspect of the apparatus of the present invention, a breather valve comprises a gear proximate a first end for engagement with a corresponding gear in the engine, and a generally cylindrical body fixed to and extending from the gear. The cylindrical body has an open end opposite the gear for drawing oil and air from the engine crank case into a breather valve interior. A first arcuate port in the cylindrical body is for registration with a corresponding opening in the engine to draw oil and air from the breather valve interior into the engine gear case. The first arcuate port extends substantially across the middle portion of the cylindrical body and subtends an angle between 70° and 270°. A second arcuate port in a cylindrical body is for registration with a second corresponding opening in the engine to draw oil from the gear case oil separating pocket into the breather valve interior. The second arcuate port is positioned between the first arcuate port and a second end of the breather valve, has a center offset circumferentially from the center of the first arcuate port, and subtends an angle between 20° and 150°.
In another aspect of the apparatus of the present invention, a breather valve arrangement comprises a breather valve including a gear engaging a corresponding gear in the engine, a cylindrical body having an open end opposite the gear, and a port formed in the body for drawing oil from the gear case oil separating pocket into a breather valve interior. Structure in the engine around the breather valve defines an opening for registration with the breather valve port. The breather valve and engine structure are constructed and arranged, and the breather valve port and corresponding opening are configured and sized, such that the port and corresponding opening are in at least partial registration for a total of between 30° and 135° of piston travel.
In one aspect of the method of the present invention, a method of improving the removal of oil from the gear case oil separating pocket comprises removing a first breather valve from the engine having a scavenge opening that subtends an angle of less than 20°, providing a second breather valve having a scavenge opening that subtends an angle of between 20° and 150°, and installing the second breather valve into the engine so that the second scavenge opening draws oil from the separating pocket for a longer period of time.
These and other advantages and features of novelty which characterize the invention are pointed out with particularly in the claims annexed hereto. However, for a better understanding of the invention and its advantages, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.
REFERENCES:
patent: 2111242 (1938-03-01), Harley
patent: 4142487 (1979-03-01), Somraty
patent: 4532897 (1985-06-01), Mezger
patent: 4765291 (1988-08-01), Kurio et al.
patent: 4869213 (1989-09-01), Panzica
RevTech® Adjustable Breather Valves, Crankcase Breathers,Engine, p. 10, undated catalog.
Declaration of Scott A. Sjovall, including Exhibits A-F.
Heffner Daniel J.
Sjovall Scott A.
McMahon Marguerite
Merchant & Gould P.C.
S & S Cycle, Inc.
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