Ventilating unit for carburetor

Details Ventilating unit for carburetor Ventilating unit for carburetor

1998-12-21

2001-03-20

Miller, Carl S. (Department: 3747)

Internal-combustion engines

Charge forming device

Fuel flow regulation between the pump and the charge-forming...

C123S517000

Reexamination Certificate

active

06202631

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a ventilating unit for a carburetor attached to an internal combustion engine. More particularly, to main air paths having their lower ends open to a space above a surface of fuel in a float chamber of the carburetor. A plurality of branches communicate with upper ends of the main air paths via upper ends thereof and are open to the atmosphere via lower ends thereof.
2. Description of Background Art
Japanese Patent Laid-Open No. Hei 7-166961 exemplifies a ventilating unit for a carburetor which includes two branches.
FIG. 6
shows an example of existing ventilating units for a carburetor. In
FIG. 6
, a carburetor body
1
includes a float chamber
3
provided under the carburetor body
1
. A space
3
a
positioned above a surface of fuel in the float chamber
3
opens to the atmosphere via a pair of ventilating units. Each ventilating unit includes a passage
30
in the shape of letter T. In the passage
30
, a portion
30
1
serves as a main air path
12
, and extends from an end on the ceiling to a merging point
30
a
. A portion
30
2
extends laterally from the merging point
30
a
and then vertically downwardly to the carburetor body, and is coupled to a first ventilating tube
16
, thereby forming a first branch
13
. A portion
30
3
extends upwardly from the merging point
30
a
and connects to a second ventilating tube
18
in the shape of an inverted letter U, thereby forming a second branch
14
.
Even if a motorcycle including the foregoing ventilating system runs on a rough road, extensive rippling occurs on the surface of the fuel f in the float chamber
3
and fuel f partially intrudes into the main air paths
12
and the first branches
13
and the second branches
14
allow atmospheric pressure to act on the main air paths
12
and the first branches
13
. In such a case, the fuel intruding into the main air paths
12
and the first branches
13
is separated, so that a part thereof is returned to the float chamber
3
via the main air paths
12
while the remaining fuel will be quickly dispersed into the atmosphere via the first branches
13
. Therefore, it is possible to minimize a period during which fuel stays in the ventilating unit
10
and to maintain the float chamber
3
at atmospheric pressure.
In the related art, each merging point
30
a
where the main air path
12
and the first and second branches
13
and
14
communicate with one another has a cross-sectional area that is substantially equal to those of the passage
12
and the branches
13
and
14
. If a relatively large amount of fuel f gushes into the main air paths
12
from the float chamber
3
, it also enters into the first and second branches
13
and
14
at the same time, as shown in FIG.
7
. In such a case, it is difficult for atmospheric pressure to act on the merging point
30
a
, which delays the flow of fuel f to the float chamber
3
and the atmosphere. In this state, the float chamber
3
is isolated from the atmosphere. As a result, a fuel nozzle communicating with the float chamber
3
under the upper surface of fuel f may infect fuel with reduced efficiency, which may adversely affect ease of riding.
SUMMARY AND OBJECTS OF THE INVENTION
This invention is aimed at overcoming the foregoing problems of the related art, and provides a ventilating unit for a carburetor in order to prevent fuel from intruding into all of the branches even when a relatively large amount of fuel gushes into main air paths from a float chamber, enabling such intruding fuel to flow down to the float chamber and to be dispersed into the atmosphere, and stabilizing fuel injection by a fuel nozzle.
In order to accomplish the object, a first feature of the invention is to provide a ventilating system for a carburetor, in which main air paths have lower ends opening to a space above a surface of the fuel in a float chamber of the carburetor, upper ends communicating with upper ends of a plurality of branches, and the branches open to the atmosphere via lower ends. The upper ends of the main air paths and the upper ends of the branches communicate with one another via the expansion chambers that are positioned above the float chamber and have larger cross-sectional areas than cross-sectional areas of the main air paths of the branches.
According to the first feature, even when a relatively large amount of fuel gushes into the main air paths, it is attenuated in the expansion chambers having large cross-sectional areas. There is sufficient room around fuel in the expansion chambers, so that all of such fuel does not simultaneously enter into the branches.
Therefore, since the expansion chambers are continuously supplied with atmospheric pressure via a part of the branch which is free from the intruding fuel, the fuel attenuated by the expansion chamber flows down via the main air paths to return to the float chamber.
In a second feature, the branches open on the bottom and ceiling of the expansion chambers, in addition to the first feature.
It is possible to maximize distances between the upper ends of a plurality of branches according to the second feature, and to reliably prevent fuel from simultaneously entering into the branches from the expansion chambers.
According to a third feature, the upper ends opening on the bottom of the expansion chambers and the upper ends opening on the ceiling of the expansion chambers are arranged with extension axes thereof mutually displaced in addition to the first or second features.
In accordance with the third feature, fuel that gushes into the main air paths toward the ceiling of the expansion chambers can be effectively prevented from entering into the branches because of the displaced extension axes of the main air paths and branches. Therefore, the expansion chambers can be reliably maintained at atmospheric pressure by the branches.
According to a fourth feature, the upper ends of the main air paths and the upper end of at least one of the branches open on the bottom of the expansion chambers, and the upper ends of the main air paths are positioned above the upper ends of the branches, in addition to the first, second or third features.
In the fourth feature, fuel gushing into the expansion chambers can quickly flow down separately via the main air paths and the branches. When the top surface of fuel in the expansion chambers is at a lever lower than the upper ends of the main air paths, fuel is no longer returned to the main air paths. This is effective in reducing a time period during which fuel stays in the main air paths. Therefore, fuel remaining in the expansion chambers flows downwardly only through the branches, and will be discharged outwardly therefrom.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description


REFERENCES:
patent: 2965086 (1960-12-01), Gregory
patent: 3460522 (1969-08-01), Kittler
patent: 4577607 (1986-03-01), Nishio
patent: 5732686 (1998-03-01), Yokoyama
patent: 0041724 (1977-03-01), None
patent: 6-185414 (1994-05-01), None
patent: 7-166961 (1995-06-01), None

Affiliated with

Also associated with

Rating

Ventilating unit for carburetor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Ventilating unit for carburetor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ventilating unit for carburetor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2463405