Carburetor idle jet venting device

An improved vacuum operated air valve for incorporation into the idle fuel port of an automotive carburetor. The valve includes a valve seat having an inner conically-shaped area and a surrounding planar area. The valve member includes an axially oriented stem and a flat radially-extending head, an outer end surface of which overlies the valve seat surfaces, whereby opening the valve to a very minute axial displacement opens a substantial venting area, increasing the sensitivity of the valve.

BACKGROUND OF THE INVENTION 
This invention relates to a carburetor idle port valve for internal 
combustion engines. The valve is used for controlling the air and fuel 
mixture in the carburetor during such periods as the throttle is in closed 
position, and the engine is fed fuel only through the idle port and jet. 
Devices of this general type are well known in the art, and the invention 
lies in specific constructional details which permit sensitive operation 
without need for overriding manual control, while maintaining the cost of 
manufacture at a very reasonable level. 
The idling system in a carburetor supplies a small quantity of an air and 
fuel mixture to keep the engine running when the throttle is closed or 
nearly closed. As the throttle is opened, an increased suction is applied 
to the idling system and more fuel is supplied thereby. An increased 
suction is likewise applied to the main fuel discharge nozzle as the 
throttle is opened and fuel is discharged therefrom with a gradual 
reduction in discharge from the idle system until the discharge in the 
idle system is neglible. The discharge from the idling system, when 
transferring to the main discharge system as the throttle is being opened, 
or when the throttle remains only partly open, is normally overenriched as 
the idling system is normally calibrated at one specific position. 
Overenrichment of the fuel system of a carburetor can and has brought about 
undesirable results. A simple overenrichment results in a waste of fuel 
and thus, a loss in economy of operation. More importantly, in recent 
years, the presence of unburned hydrocarbons in the exhaust gases from 
automotive engines have been found to contribute to an undesirable 
atmospheric condition more commonly called "smog". It is generally 
understood that too rich a fuel mixture may easily result in incomplete 
burning, due to lack of sufficient oxygen, which, in turn, results in the 
discharge of unburned hydrocarbons and incomplete combustion of other 
hydrocarbons to produce carbon monoxide. 
In present day automotive carburetors, the only adjustment normally 
available is the idle fuel needle screw wherein the needle adjustment is 
set to give smooth operation at curb idle. It is known to provide in the 
aftermarket, devices such as that disclosed in U.S. Pat. No. 3,348,823, to 
Roquerre and U.S. Pat. No. 3,077,341 to Schlichting which supplement 
normal needle valve adjustment with a resilient check valve which becomes 
operative during periods of high vacuum. At the present time, such devices 
are useful only in those automobiles which are equipped with carburetors, 
as distinguished from fuel injection devices. Such cars are substantially 
older, and are characterized by normal high fuel consumption and 
relatively little net worth. With the recently occurring increases in the 
cost of fuel, it becomes highly desirable to provide a device of this type 
which can be manufactured at very low cost and which is easily installed. 
SUMMARY OF THE INVENTION 
Briefly stated, the invention contemplates the provision of an improved 
vacuum operated venting means which is installed in the idle fuel supply 
which is not only relatively inexpensive to manufacture, but which 
possesses high sensitivity to the occurrence of low vacuum pressures which 
occur when the engine is above idle speed and the throttle is 
substantially closed. Such periods occur when the automobile is 
decelerating, or when the engine is used to brake the automobile when 
descending hills. As distinguished from most prior art devices which 
employ a ballcheck, the present invention contemplates the use of a valve 
member of generally nail-like configuration including an axially oriented 
stem and a flat head, the outer planar surface of which overlies a valve 
seat which is partially conical surrounded by a planar area. The normal 
contact is only upon the planar area enabling something greater than line 
contact, and permitting a substantial area of the head to overlie the 
conical portion where it is exposed to atmospheric pressure at all times. 
This construction has been found to provide unexpectedly high sensitivity 
while yet maintaining an adequate seal during periods of no vacuum 
pressure, which has been a shortcoming of devices employing a ballcheck.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENT 
In accordance with the invention, the device, generally indicated by 
reference character 10, includes an elongated hollow body 11 of machined 
brass or die cast zinc extending between first and second ends 12 and 13, 
respectively. The first end 12 is provided with a threaded tip 14 for 
engagement within the exposed idle port of the associated carburetor (not 
shown). Extending outwardly from the tip 14 is a slender medially disposed 
tubular portion 15 merging into a wider medially disposed portion 16 
through a tapered portion 17. The portion 15 includes an axially aligned 
narrow channel 18 communicating with a wider channel 19 in the portion 16. 
A washer-like valve seat 20 is frictionally retained within the channel 19, 
and is bounded by an outer cylindrical surface 21, an outer end surface 
22, and an inner end surface 23 which forms a two-part valve seat. The 
seat includes an outer annular planar surface 25 and an inner conical 
surface 26 extending to a through bore 27. 
A resiliently urged valve member 30 includes an axially oriented stem 31 
and a planar radially extending head 32, the latter being bounded by an 
inner surface 33 which bears against a compression spring 34. The outer 
surface 35 overlies the valve seat, and in closed condition contacts only 
the planar surface 25. The opposite end of the spring 34 is constrained by 
the conically shaped surface 37 which interconnects the channels 18 and 
19. The tension on the spring is adjusted by the positioning of the valve 
seat 20 with respect to the channel 19. Using a cylindrical seating tool 
(not shown) having an adjustable threaded nut on an outer surface thereon 
to determine the degree of penetration into the channel 19. 
In order to maintain the surface area of surface 25 at approximately that 
of the conical surface 26, the inner edge is slightly chamfered at 39. The 
head 32 is provided with indentations 40 to enhance the sensitivity of the 
valve when opened. 
As will be readily apparent, much of the venting action will take place 
with the valve member 30 only slightly displaced from the seat 20. This 
will occur at relatively low volume occurring when the engine is rotating 
at above idle speed with the throttle closed. The action is far superior 
to conventional ballcheck valve which presents relatively little surface 
to the incoming inducted air, and the surface below the line contact of 
the ball with the seat is the only part of the ball which is effective to 
receive contact from the air. Thus, substantially more vacuum is required 
to unseat the ballcheck valve than the valve employed in the present 
construction. 
I wish it to be understood that I do not consider the invention to be 
limited to the precise details of structure shown and set forth in this 
specification, for obvious modifications will occur to those skilled in 
the art to which the invention pertains.