Gas and liquid contact apparatus – Fluid distribution – Valved
Reexamination Certificate
1999-07-23
2001-05-22
Chiesa, Richard L. (Department: 1724)
Gas and liquid contact apparatus
Fluid distribution
Valved
C261SDIG006, C261SDIG008
Reexamination Certificate
active
06234458
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a carburetor for an internal combustion engine, especially for the internal combustion engine of a portable, hand-guided working tool such as a motor chainsaw etc., wherein the carburetor comprises a carburetor housing with intake channel and with a fuel channel opening into the intake channel. The fuel channel is connected to a fuel-filled control chamber of the carburetor and has a control valve arranged therein. The control member of the control valve is adjustable by a control screw that is mounted within the housing. For limiting the adjusting range of the valve member, a cap is fixedly mounted on the control screw and has a stop, whereby a counter stop connected to the carburetor housing is positioned in the rotational path of the stop at the cap.
Such a carburetor is known from U.S. Pat. No. 3,618,906. The fuel channel opening into the intake channel has a control valve which is embodied as a needle valve and whose control screw is screwed into the carburetor housing. In order to limit the adjusting range of the needle valve, a securing cap is snapped onto the knurled head of the control screw after a pre-adjustment has been performed at the manufacture. The securing cap has an outer stop, and a counter stop at the carburetor housing projects into the rotational path of this stop. The adjusting range of the control screw is thus limited to less than one complete rotation.
For securing the rotational position of the control screw springs, friction rings etc. must be provided.
As a function of the ambient temperature as well as of the altitude, the supplied fuel amount must be adjusted by rotation of the control screw. This is performed by the user whereby, depending on the dexterity of the user, a more or less satisfactory adjustment can be achieved.
It is therefore an object of the present invention to embody a carburetor of the aforementioned kind such that even an inexperienced user can perform the required adjustment of the fuel/air mixture to the operating condition in a simple manner.
SUMMARY OF THE INVENTION
This object is inventively solved by providing a locking device between the cap-and the carburetor housing that secures the cap at the housing. The locking device has a locking member that cooperates with correlated counter locking members for securing the cap in a predetermined rotational position.
The locking device positioned between the cap and the carburetor housing provides certain rotational positions of the control screw for the user whereby the predetermined rotational positions that depending on the type of carburetor, the combustion engine and the environmental conditions to be expected are preset by physical means of the inventive design. Even an inexperienced user can perform an adaptation to the environmental conditions in a simple manner according to a reference list. For example, when the location of use is at an altitude of a thousand meters, according to the operators manual a rotation of the control screw by two preset positions can be suggested in order to provide the required altitude adjustment of the fuel/air mixture to a leaner mixture.
Due to the inventively arranged locking device further securing means such as clamping rings etc. for a rotational securing action of the control screw can be eliminated.
The counter locking member has expediently a locking depression in which the projecting nose of the locking member will engage. The counter locking member may be embodied as a locking tongue so that the counter stop secured to the housing can be used as the locking member. Preferably, the locking member is embodied as a locking rib at the housing so as to be, on the one hand, a part of the locking device and, on the other hand, a part of the rotational limitation device, i.e., it has a double function.
In an expedient further embodiment of the invention, the cap is comprised of a connecting portion, that is fixedly connected to the control screw, and a bushing portion, which is axially connected to the connecting portion and faces the carburetor housing. The bushing portion is arranged coaxial to the control screw and surrounds the control screw with radial play. The mantle of the bushing portion is preferably divided by axial slots to form locking tongues whereby the radial play relative to the control screw provides a radial spring action of the locking tongues. The locking member can thus be provided at the housing and is preferable a unitary part of the carburetor housing.
REFERENCES:
patent: 3618906 (1971-11-01), Charron
patent: 4283353 (1981-08-01), Miller
patent: 4936267 (1990-06-01), Gerhardy et al.
patent: 5236634 (1993-08-01), Hammett et al.
patent: 5252261 (1993-10-01), Gerhardy
patent: 5283013 (1994-02-01), Gerhardy
patent: 5525267 (1996-06-01), Araki
patent: 5630965 (1997-05-01), Shaw et al.
patent: 5635113 (1997-06-01), Walsh et al.
patent: 5707561 (1998-01-01), Swanson
patent: 5776379 (1998-07-01), Bowles
patent: 6059271 (2000-05-01), Gerhardy
patent: 2401803 (1974-09-01), None
patent: 0 589 405 A1 (1994-03-01), None
patent: 47-42424 (1972-10-01), None
patent: 641145 (1979-01-01), None
Andreas Stihl AG & Co.
Chiesa Richard L.
Robert W. Becker & Associates
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