Carburetor having a concentric tube fuel supply

Disclosed herein is a carburetor including a housing having a throat, means for supplying fuel to the throat intermediate its opposite ends, the fuel supplying means including a tube extending into the throat and including a plurality of fuel supply openings spaced along its length. A pivotable throttle member is positioned in the throat intermediate its opposite ends and is pivotable between a fluid flow restricting position and an open position. The pivotable throttle member includes a cam surface. The carburetor is also constructed such that an increased number of the openings supply fuel to the throat as the throttle member pivots from a fluid flow restricting position to an open position and the openings are closed as the throttle member pivots from an open position to a fluid flow restricting position. This is accomplished by a sleeve surrounding the tube and supported for slidable movement on the tube, and a cam follower engaging the cam surface, the cam follower carrying the sleeve whereby the sleeve is slideable on the tube in response to movement of the cam surface with respect to the cam follower.

FIELD OF THE INVENTION 
The invention relates to carburetors and more particularly to a carburetor 
which includes a fuel supply tube extending into the carburetor throat, 
the fuel supply tube including a plurality of spaced apart fuel supply 
apertures and means responsive to movement of a throttle valve for 
controlling the number of fuel supply apertures which are open to thereby 
control the quantity of fuel supplied to the carburetor throat. 
BACKGROUND PRIOR ART 
An example of a prior art carburetor, employing means for varying the fuel 
supplied in proportion to movement of a throttle plate upstream of the 
fuel supply means, is illustrated in the U.S. Arff Pat. No. 2,047,661, 
issued July 14, 1936. Another prior art carburetor employing a tube 
extending into the carburetor throat wherein the tube includes a plurality 
of apertures for supplying fuel to the carburetor throat is shown in the 
U.S. Purvis et al. Pat. No. 1,688,285, issued Oct. 16, 1928. 
Attention is also directed to the U.S. Hill Pat. No. 3,182,974, issued May 
11, 1965; the U.S. Baribeau et al. Pat. No. 3,800,770, issued Apr. 2, 
1974; and the U.S. Baribeau et al. Pat. No. 3,834,679, issued Sept. 10, 
1974. 
SUMMARY OF THE INVENTION 
The invention includes a carburetor comprising a housing having a throat, 
and means for supplying fuel to the throat intermediate its opposite ends, 
the fuel supplying means including a tube extending into the throat, the 
tube including a plurality of fuel supply openings therein and spaced 
along its length. The carburetor also includes a pivotable throttle member 
positioned in the throat intermediate its opposite ends and pivotable 
between a fluid flow restricting position and an open position, the 
pivotable throttle member including a cam surface. Means are also provided 
for causing an increased number of the openings to supply fuel to the 
throat as the throttle member pivots from a fluid flow restricting 
position to an open position and for closing an increasing number of the 
openings as the throttle member pivots from an open position to a fluid 
flow restricting position. The closing means includes a sleeve surrounding 
the tube and supported for slideable movement on the tube, and a cam 
follower engaging the cam surface, the cam follower carrying the sleeve 
whereby the sleeve is slideable on the tube in response to movement of the 
cam surface with respect to the cam follower. 
The invention also includes a carburetor comprising a housing including a 
throat and a pivotable throttle member positioned in the throat and 
pivotable between a fluid flow restricting position and an open position. 
The pivotable throttle member includes a cam surface. The carburetor also 
includes a tube extending into the throat intermediate its opposite ends, 
the tube including a plurality of fuel metering orifices spaced along its 
length, means for supplying fuel to the tube, and means for selectively 
preventing fuel flow through selected ones of the orifices. The carburetor 
further includes means for selectively causing movement of one of the tube 
and the fuel flow preventing means, such movement varying the fuel flow 
into the throat. The movement causing means includes a cam follower 
supported by the cam surface and connected to one of the tube and the fuel 
flow preventing means, and for causing its movement to open the orifices 
when the throttle member moves from the flow restricting position to the 
open position. 
Various features and advantages of the invention are set forth in the 
following description of a preferred embodiment, in the drawings and in 
the claims.

Before explaining at least one embodiment of the invention in detail, it is 
to be understood that the invention is not limited in its application to 
the details of construction and to the arrangement of the components set 
forth in the following description or illustrated in the drawings. The 
invention is capable of other embodiments and of being practiced and 
carried out in various ways. Also, it is to be understood that the 
phraseology and terminology employed herein is for the purpose of 
description and should not be regarded as limiting. 
DESCRIPTION OF A PREFERRED EMBODIMENT 
Illustrated in FIG. 1 is a side draft type carburetor 10 including a body 
12 having a throttle bore 14. The carburetor also includes a throttle 
valve or throttle member 16 supported in the throat area 18 of the 
throttle bore 14 and for movement so as to control the air flow volume 
through the throat 18, the throttle valve 16 being pivotable about an axis 
20 illustrated in FIG. 2 and between an idle position wherein the fluid 
flow through the carburetor throat 18 is restricted as shown in phantom 
lines in FIG. 2 and a position as shown in solid lines in FIG. 2 wherein 
the throttle valve 16 permits free flow of fluid through the carburetor 
throat, the airflow through the carburetor 10 being from left to right 
when viewed as in FIG. 2. 
While the throttle valve 16 can have various constructions, in the 
particular arrangement illustrated, the throttle valve includes a 
generally planar face 22 and is supported for pivotal movement by support 
lugs 24 about axis 20, the support lugs 24 being located such that the 
axis 20 generally lies in the plane of the face 22 of the throttle valve 
and extends horizontally and perpendicularly to the direction of air flow 
through the carburetor throat 18. It will be noted that the axis of 
rotation 20 is adjacent an upper portion of the carburetor throat and that 
the housing 12 of the carburetor includes a housing portion 26 defining a 
recessed chamber 28 which is above the carburetor throat and above the 
axis of rotation 20 of the throttle valve 16 so as to house the throttle 
valve 16 when the throttle valve is rotated to an open position as 
illustrated in solid lines in FIG. 2. When the throttle valve 16 is in 
this position, the planar face 22 of the throttle valve 16 forms an upper 
wall of a portion of the throttle bore 14 and this upper wall portion is 
continuous with the remainder of the upper wall of the throttle bore 14. 
The rearward surface 30 of the throttle valve 16, i.e. that surface portion 
of the throttle valve 16 facing in the direction of air flow through the 
throttle bore 16 when the throttle valve is in the closed position, 
includes an upper portion 32 which is rounded so as to generally conform 
with the rounded contour of the recess 28 and to permit rotation of the 
throttle valve. The throttle valve 16 also includes a central vertical 
groove 34 in its rear surface 30, the groove 34 generally bisecting the 
rearward and lower portions of the throttle valve and extending 
perpendicularly to the axis of rotation 20 of the throttle valve. As 
illustrated in FIG. 1, the throttle valve 16 also includes a semi-circular 
bore 35 formed in the lower portion of the throttle valve, as seen in FIG. 
1, and extending from the lower face 22 and intersecting the central 
groove 34. The semi-circular bore 35 provides for a predetermined minimum 
air flow through the carburetor when the throttle valve is in the fully 
closed position. 
The extent of the relative movement of the throttle valve 16 is illustrated 
in FIG. 2. The throttle valve is shown in solid lines as being in the 
fully open position wherein the throttle valve is housed in the recess 28 
and does not restrict air flow through the throat. The phantom lines 
indicate the throttle valve 16 in an idle position wherein air flow 
through the carburetor bore is limited to that flowing through the 
semi-cylindrical bore 35 in the lower portion of the throttle valve 16. 
Means are also provided for supplying fuel to the carburetor throat 18 and 
for controlling the quantity of fuel supplied such that it is a function 
of the position of the throttle valve and the amount of air permitted to 
flow through the carburetor throat. In the illustrated construction, the 
means for supplying fuel to the carburetor throat includes a tube or 
conduit 40 which extends into the carburetor throat, the lower end of the 
tube 40 extending downwardly into a float bowl 42 adapted to contain 
liquid fuel. The tube 40 is housed in the groove 34 in the rear surface of 
the throttle valve 16 and generally bisects the carburetor throat and has 
a longitudinal axis extending generally perpendicular to the axis of 
rotation 20 of the throttle valve 16 as well as perpendicular to the 
direction of air flow through the carburetor. The end of the tube 40 which 
extends into the carburetor throat includes a plurality of small orifices 
44 in its rearward surface, the small orifices facing in the direction of 
fluid flow through the carburetor. The tube 40 also includes a plurality 
of air inlet holes 46 in that portion of the tube which faces the up 
stream portion of the carburetor throat. 
While various means can be provided for supplying liquid fuel to the tube 
40, in the illustrated construction, the lower end of the tube extends 
into the float bowl 42. The lower end of the tube 40 is closed by a 
transverse wall 48, the transverse wall 48 having a small metering orifice 
50 therethrough, the metering orifice 50 permitting fuel flow upwardly 
from the float bowl into the tube. A predetermined fuel level is 
maintained in the float bowl 42 by any conventional means such as a float 
52 adapted to control a fuel supply valve (not shown). 
In operation of the carburetor, air flow through the carburetor will result 
in a low pressure area being formed on the downstream side of the tube 40 
and adjacent the discharge holes 44 of the tube thereby causing liquid 
fuel in the lower end of the tube 40 to be drawn upwardly and to be 
discharged through the discharge holes 44. The air inlet holes 46 function 
to permit air flow into the tube 40 causing emulsification of the liquid 
fuel with air and such that fine particles of liquid fuel are disbursed in 
the air and discharged through the discharge holes 44. 
Additional means are also provided for supplying additional air to the tube 
40 to control the quantity or rate of fuel flow into the tube, the air 
supplying means including means for adjusting the air flow volume into the 
tube. As illustrated in FIG. 2, this means includes an aperture 56 in the 
lower end of the tube 40 and above the level of the fuel in the float 
chamber 42. The aperture 56 communicates with air passages 58, 60 which 
are in turn connected with an air inlet 62 shown in FIG. 1. The air flow 
through the air passages 58 and 60 is controlled by a needle valve 64 
operated by a screw 66. As the needle valve 64 is opened, thereby 
permitting an increased air flow through the passages 58 and 60 and into 
the tube 40, the amount of fuel drawn by the low pressure adjacent the 
discharge holes 44 of the tube 40 will decrease, thereby leaning the fuel 
mixture. 
Means are also provided for controlling or varying the number of orifices 
44 and 46 which are open as a function of the angular position of the 
throttle member 16, that controlling means functioning to close an 
increasing number of the air inlet holes 46 and fuel discharge orifices 44 
as the throttle member 16 moves toward a flow restricting position and to 
open an increasing number of the air inlet holes 46 and discharge orifices 
44 as the throttle member 16 moves from a flow restricting position to an 
open position. In the illustrated construction, such means comprises a 
sleeve or slider 70 which surrounds in coaxial relation the tube 40 and 
which is adapted to be slideably movable along the length of the tube 40 
in response to movement of the throttle member 16. As best shown in FIG. 
3, the upper end of the sleeve 70 includes a pair of outwardly extending 
cam followers 72 which are adapted to be slideably supported on the spaced 
apart cam surfaces 74 on the opposite sides of the central groove 34 in 
the rear surface of the throttle valve. The shape of the cam surfaces 74 
is such that, as the throttle valve 16 is rotated from the closed position 
to an open position, the cam followers 72 and the sleeve 70, rigidly 
attached thereto, will be moved slideably upwardly on the tube 40. Such 
upward movement of the sleeve 70 causes an increasing number of the 
discharge holes 44 to be opened. The means for varying the number of 
orifices 44 which are open also includes a compression spring 76 which 
surrounds the upper end of the tube 40 and which is maintained in 
compression between an upper surface 78 of the housing portion 26 and the 
cam followers 72. The compression spring 76 is a light pressure return 
spring adapted to maintain the slider or sleeve in contact with the 
contour of the cam surface 74 to insure proper function of the slider or 
sleeve 70. 
One of the advantages of the invention is that the amount of movement of 
the slider 70 is a function of the rotation of the throttle member 16, and 
the ratio of the fuel flow into the carburetor and the air flow through 
the carburetor can be controlled or selected by varying the contour of the 
cam surfaces 74. The discharge of fuel can also be accurately controlled 
as desired by variation of the size of the fuel outlet orifices 44 and 
their spacing as well as by the relative size and spacing of the air inlet 
holes 46. Fuel discharge at idle speeds can also be readily controlled by 
adjustment of the air bleed valve. 
Various features of the invention are set forth in the following claims.