Internal-combustion engines – Two-cycle – Whirl through piston-controlled ports
Reexamination Certificate
1999-11-10
2001-04-10
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Two-cycle
Whirl through piston-controlled ports
Reexamination Certificate
active
06213065
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
Two-cycle engine accessories
2. Description of the Prior Art
Occasionally a descriptive term in this application may be shortened so as to recite only a part rather than the entirety thereof as a matter of convenience or to avoid needless redundancy. In instances in which that is done, applicant intends that the same meaning be afforded each manner of expression. Thus, the term gas pressurizing control cylinder (
4
) might be used in one instance but in another, if meaning is otherwise clear from context, expression might be shortened to control cylinder (
4
) or merely cylinder (
4
). Any of those forms is intended to convey the same meaning. The term attach or fasten or any of their forms when so used means that the juncture is of a more or less permanent nature, such as might be accomplished by bolts, welds or adhesives. Thus it is stated herein that the pneumatic exhaust control piston (
40
), where interthreading is employed as the means of connection, is attached to the combustion cylinder (
200
). A connection in which one object is easily removed from another is described by the word emplace, as where it is stated herein that the sliding tongue (
2
) is partially emplaced within the exhaust port (
203
) during a particular phase of operation. Employment of the words connect or join or any of their forms is intended to include the meaning of both in a more general way.
The term rigid emplacement denotes a connection other than by attachment which, nevertheless, permits separation only with considerable difficulty. It is accordingly stated herein that the connection of the spring (
3
) to the spring seating bolt head (
32
) at the spring abutment zone (
31
) is one of rigid emplacement
The word comprise may be construed in either of two ways herein. A generic term used to describe a given one of a number of specific elements is said to comprise it, thereby characterizing the specific element with equivalency in meaning for the generic term. Thus, means (
300
) to emplace the sliding tongue (
2
) within the exhaust port (
203
) may be said to comprise the spring (
3
), meaning that in the particular case, the means (
300
) is that particular object (
3
) as opposed to some other, such as an operably manipulated cable or a servo-mechanism of some sort. However, the word comprise may also be used to describe a feature which is part of the structure or composition of a given element. Thus, a shock absorbing gas pressurizing control cylinder (
4
) may be said to comprise a pneumatic chamber (
44
), meaning that the structure of the cylinder (
4
) is such as to have the pneumatic chamber (
44
) as a feature of its structure. The meaning in the respective cases is clear from context, however. Accordingly, modifying words to clarify which of the two uses is the intended one seem unnecessary.
Terms relating to physical orientation such as , up, down, higher and lower refer to the positioning of an engine part in the manner in which it is typically mounted in a vehicle and consistent with the manner the subjects of this application are shown in the drawings. Thus, the exhaust port (
203
) is frequently spoken of as being disposed proximate the top of the combustion cylinder (
200
) and the intake port as being disposed at the bottom thereof (
200
). Consistent with this is the reference, supra, to “raising” the exhaust port (
203
) as a design remedy.
The term effectually open and effectually closed, is used herein with reference to the degree of obstruction of the sliding tongue (
2
). The tongue (
2
) is stated herein to effectually open and effectually close the exhaust port (
203
). The use of such terminology acknowledges the fact that even when the tongue (
2
) is brought to its maximum interference point within the port (
203
), a substantial opening necessary to allow the flow of sufficient exhaust for engine idling remains. Although the tongue's (
2
) closure may not, therefore, be complete, it may correctly be said to be effectually so. Conversely, although the tongue (
2
) may have not been withdrawn completely from the port (
203
) during high RPM operation, maximum airflow may have, nevertheless, have been attained. At that height, the tongue (
2
) is stated herein to be effectually open.
The two-cycle engine known to prior art has widespread application including several varieties of lawn mowers, snow throwers, snowmobiles, water craft and other sports vehicles. Such an engine enjoys economy in production in that several valves and other moving parts are eliminated therefrom. The body of the piston (
201
) itself conveniently blocks and unblocks ductwork communicating with the combustion cylinder (
200
) as it (
201
) reciprocates in advance and withdrawal within the cylinder (
200
). It is universally recognized that at high powered operation involving numerous revolutions per minute (RPM), maximum power may be attained—or at least approached—if the end products of combustion, or exhaust, are expeditiously removed from the engine. An engine built to accommodate that result, however, encounters difficulty at low RPM, where the enlargement of the exhaust port (
203
) diminishes air velocity much in the same manner experienced with the slower ejection rate of water from a substituted garden hose of greater diameter than that otherwise employed. Differences in air velocity are associated with what is commonly regarded as “throttle response” or “quickness” At low RPM, advantage is gained by reserving at least a portion of the exhaust to interfere with the combustion process. Accordingly, compromises have had to be made in manufacture to attain acceptable performance at what might be considered either end of the spectrum.
An engine dedicated to acceptably smooth performance at low RPM, therefore, necessarily loses something at high RPM. Where high RPM performance is a priority, efforts undertaken to recover what is otherwise foregone entail, for example, “raising the ports”—that is, enlarging the top parameter of the exhaust port (
203
) so that it (
203
) becomes and remains at least partially unblocked by the combustion piston (
201
) during a longer portion of the combustion cycle. Thus, in terms of a 360 degree combustion piston (
201
) stroke, approximately as much as 25 degrees may be added. The matter is also frequently addressed in terms relating to the “timing” of the cycle or “pulse activation” and, not surprisingly, efforts have been undertaken to address the low RPM end of the spectrum by spoiling, as it were, the precise timing of the engine otherwise demonstrated at high RPM.
Novel devices have been introduced over recent decades to interfere mechanically with the otherwise efficient discharge of exhaust at low RPM and to enhance it mechanically at high RPM. The most promising appears to comprise a device attached to the combustion cylinder (
200
) which regulates power by moving a mechanical obstructor into—or conversely out of—the exhaust path. Because of its configuration and manner of operation, such a device has occasionally been referred to as a “guillotine”.
The airflow comprises a cycle in which the fuel, air and oil mixture passes through the combustion cylinder's intake port (
207
), becomes pressurizing gas (
202
) as a result of the combustion piston's (
201
) operation and ultimately emerging as spent gas through the exhaust port (
203
). When the obstructing device is emplaced for maximum blockage of the exhaust port (
203
), the increase in air velocity enhances carburetor efficiency.
The transition between maximum blockage at low RPM and an effectually open position at high in many of the prior art devices is too abrupt for the carburetor to keep up with, however. A properly configured system should be capable of producing smoother transition between the two extremes to maximize carburetor performance.
Early developments produced a manually controlled cable which operably manipulated the obstructing device for the effect desired. It was eventually discovered that electro-se
Huynh Hai
Loyd W. Bonneville Attorney
Wolfe Willis R.
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