Gas separation – Plural serial basically diverse separating media – Plural stages in unitary casing
Reexamination Certificate
2000-04-13
2001-09-25
Simmons, David A. (Department: 1724)
Gas separation
Plural serial basically diverse separating media
Plural stages in unitary casing
C055S385300, C055S497000, C055S502000, C055SDIG002, C123S19800E
Reexamination Certificate
active
06293981
ABSTRACT:
BACKGROUND OF THE INVENTION
An arrangement of an air filter and a membrane carburetor is disclosed in German patent publication 4,419,084. Here, an air filter is mounted forward of the membrane carburetor to clean the combustion air. The air filter lies essentially above the carburetor on the side of the compensation chamber thereof. The intake channel section is formed in the carburetor housing and is connected to the clean space of the air filter via an intake stub configured about at right angles. An assembly-friendly insert connection of the compensation channel is not possible because of the closeness of the clean space to the compensation chamber. For this reason, a simple sealing collar is suggested which is intended to bridge the small distance between a connecting opening in the air filter housing and the connecting opening to the compensation chamber. Such a configuration of a compensation connection, however, presents the problem of dirt entry which can lead to a plugging of the compensation channel. This can cause operational disturbances of the engine driven by the membrane carburetor.
Furthermore, the known arrangement is very large whereby problems result because of the tight spaces in the housings of portable handheld work apparatus such as motor-driven chain saws, cutoff machines, brushcutters or the like. The filter surface is small because of the minimum component space which can lead to increased flow speeds. These can operate disadvantageously on the necessary compensation of the membrane carburetor.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an arrangement of an air filter and a membrane carburetor which is so improved that an operationally reliable compensation of the level of contamination of the air filter is possible even where there are constraints as to space.
The arrangement of the invention includes an air filter unit and a membrane carburetor. The arrangement also includes: a membrane carburetor having a carburetor housing defining an air intake channel through which air can be drawn; the carburetor housing further defining an interior space; a control membrane mounted in the interior space so as to partition the interior space into a fuel-filled control chamber and a compensation chamber; channel means provided in the carburetor housing for conducting fuel into the intake channel from the control chamber; the carburetor housing having an end whereat the compensation chamber is located; an air filter unit having an air filter housing engaging over the carburetor housing on the end thereof; the air filter housing defining a clean air space disposed above the compensation chamber; the air filter unit including an air filter mounted in the air filter housing for passing air into the clean air space; a flow space disposed downstream of the air filter and upstream of the air intake channel; the intake channel communicating with the flow space so as to permit air to flow from the flow space into the intake channel; a connecting stub having a pregiven volume and extending between the clean air space and the flow space for facilitating the flow of filtered air from the clean air space to the flow space; the flow space having a volume greater than the pregiven volume of the connecting stub; and, a structure defining a compensation channel branching off from the flow space and connecting the compensation chamber to the flow space.
The combustion air, which is made available to the engine, is quieted because of the flow space upstream of the intake channel so that the high flow velocities (occurring because of the tight construction) have no influence on the power capacity of the engine. The flow space is configured with crevices in such a manner that space sections are provided in the shadow of the flow wherein essentially the static pressure at the clean air side of the air filter is present. The compensation channel therefore branches away from the flow space and preferably out of the space regions lying in the flow shadow.
Preferably, the flow space is configured to have an L shape when viewed in cross section. The longer leg essentially serves to provide the flow connection between the clean chamber of the air filter and the intake channel section; whereas, the shorter leg advantageously lies close to the compensation chamber and is provided for connecting to the compensation channel.
According to another feature of the invention, the connection of the compensation channel with the flow space is configured as an insert connection. The air filter housing has a wall which includes the connecting opening. This wall lies approximately at right angles to the control membrane of the carburetor. The wall of the air filter housing having the connecting opening is provided approximately parallel to the assembly wall of the air filter housing in order to ensure a simple assembly. In this way, the flow connections between the compensation chamber and the flow space as well as between the intake channel section and the flow space are simultaneously established when seating the air filter housing on the carburetor. The assembly wall exhibits a connecting opening between the flow space and the intake channel section.
REFERENCES:
patent: 3796027 (1974-03-01), Gumtow
patent: 4425145 (1984-01-01), Reese
patent: 5429776 (1995-07-01), Edlund
patent: 5706777 (1998-01-01), Schlessmann et al.
patent: 4419084 (1994-12-01), None
Denner Horst
Holderle Hans
Knödler Bernd
Kummermehr Stefan
Menzel Johannes
Andreas Shihl AG & Co.
Hopkins Robert A.
Ottesen Walter
Simmons David A.
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