Gas and liquid contact apparatus – Fluid distribution – Valved
Reexamination Certificate
2000-06-01
2001-10-16
Chiesa, Richard L. (Department: 1724)
Gas and liquid contact apparatus
Fluid distribution
Valved
C137S382000, C261SDIG003, C261SDIG008
Reexamination Certificate
active
06302384
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a carburetor with a regulating needle valve.
BACKGROUND OF THE INVENTION
In a conventional hydrocarbon liquid fuel carburetor for an internal combustion engine, a fuel regulating needle is used to control the flow of fuel or fuel and air mixture from the carburetor fuel chamber to the air intake passageway. A threaded shaft portion of a metal fuel regulating needle valve is screwed into a threaded bore formed in a metal carburetor body to project a valve tip of the needle valve from a valve chamber to an outlet passage. However, when the threaded bore is machined in the carburetor body, chips from machining in the threaded bore often remain therein and hinder a smooth screwing of the fuel regulating needle valve into the threaded bore.
In addition, due to the small size of the threads on the needle valve and in the bore of the carburetor body, it is difficult to achieve desired manufacturing tolerances. Any play in the tolerances may allow leakage between the two sets of threads. In addition, any play in the tolerance allows an undesirable axially shifting of the threaded valve needle which may change the fuel efficiency settings of the carburetor from its desired factory settings and allows undesirable evaporative emissions.
Furthermore, limiter caps mounted on the head of the fuel regulating needle valve may introduce certain complications. Limiter caps have recently been mandated in various jurisdictions to prevent the end user from easily adjusting the fuel needle valves excessively far from the manufacture's desired settings. These limiter cap; are commonly placed on the head of the fuel needle valve by a snap fit or press fit. As the caps are pressed onto the heads, axial force and radial force may displace the tip end needle from its desired position. Accordingly, accurate regulation may be hindered. The tip of the needle valve may be inclined and a lesser amount of fuel may flow from the valve chamber to the outlet passage as compared to a straight mounted tip of the needle valve. Furthermore, because of the diminutive dimension of the needle tip and the bore about the needle tip, a mere translational displacement of the needle tip from its radially central position may change the turbulence and other flow characteristics such that the flow rate may be undesirably changed from the desired setting.
Environmental efforts are also directed to minimize fuel evaporative emission which not only wastes fuel but may also have detrimental effects on air quality.
What is needed, in view of the above described problem, is a carburetor with a fuel regulating needle valve that is free from fuel leakage from the valve chamber to the exterior, or air leakage from the exterior to the valve chamber. Furthermore, what is needed is a fuel regulating needle that is firmly supported against vibrations and recovers from side and axial extended forces exerted thereon.
What is also needed is a carburetor with a fuel regulating needle that is screwed into a plastic retainer and a metal collar which are interference fitted in an unthreaded cylindrical bore in a carburetor body, thereby eliminating the need of machining the threaded bore within the carburetor body.
SUMMARY OF THE INVENTION
In accordance with the invention, a carburetor includes a carburetor body with an unthreaded cylindrical bore, a valve chamber and an outlet passage. Preferably, the cylindrical bore, valve chamber and outlet passage have a shoulder portion therebetween with the bore, valve chamber and outlet passage being axially aligned and sequentially reduced in diameter inwardly from an end wall of the carburetor to the outlet passage. A retainer and a separate collar are interference fitted into the unthreaded cylindrical bore. The fuel regulating needle valve includes a threaded shaft portion, an unthreaded stem and a valve tip. Preferably, the threaded shaft, unthreaded stem portion and valve tip are sequentially reduced in the outer diameter from a head of the fuel regulating needle valve toward a distal end of the valve tip. The threaded shaft portion is screwed into a threaded bore formed in the collar, and also screwed into an axial shaft receiving section formed in the retainer. The stem is slidably received through a distal end cylindrical portion of the retainer that has an aperture to slidably receive the unthreaded stem. The stem portion protrudes into the valve chamber, and the valve tip extends from the valve chamber into the outlet passage.
Preferably, the retainer is made from a plastic material and has an outer diameter slightly smaller than the diameter of the bore to allow the retainer to slide into the bore. The retainer has a counterbore at its outer end to receive the collar. The collar is made of metal and has an axial inner section having a diameter slightly larger than the internal diameter of the counterbore such that the collar is pressed fitted into the counterbore and expands the outer diameter of the retainer to sealingly press the retainer against the bore wall.
In one embodiment, the shaft receiving section of the retainer has a diameter substantially equal to the smaller diameter of the threaded shaft portion and is initially unthreaded to allow the threaded shaft portion to self tap its own threaded grooves into the shaft receiving section of the retainer. In another embodiment, the shoulder portion between the bore and valve chamber is frusto-conical in shape and the retainer has a complementary shaped frusto-conical section to sealingly abut thereagainst.
In the present invention, there is no need to machine a threaded bore directly in the carburetor body. Instead, a plastic retainer and the metal collar are inserted in the unthreaded cylindrical bore formed in the carburetor body. The threaded shaft portion of the fuel regulating needle valve is then screwed in an axial bore of the plastic retainer while forming thread grooves, and a tight screw fitting without axial play or leakage can be obtained. The base end cylindrical portion is enlarged to form a tight contact seal with the cylindrical bore of the carburetor. At the same time, an end wall of the plastic retainer is pressed against a conical stepped portion of the carburetor body to form a seal and the unthreaded stem portion form a sliding seal with respect to the distal end in the retainer.
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Chiesa Richard L.
Reising Ethington, Barnes, Kisselle, Learman & McCulloch, P.C.
Walbro Corporation
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