Apparatus for converting a carburetor for gaseous fuel

An attachment within the air cleaner housing of a liquid-fuel internal-combustion engine, the attachment having a circumferential venturi air passage and a gaseous fuel inlet slot inboard of the narrowest portion of the venturi air passage.

DESCRIPTION 
TECHNICAL FIELD 
This invention pertains to internal-combustion engines and particularly to 
providing a carburetor for an internal-combustion engine which will run 
selectively on liquid or gaseous fuel. 
BACKGROUND ART 
Internal-combustion engines have heretofore been convertible to burning 
gaseous fuel in addition to liquid fuel, generally by the replacement of 
the carburetor of the engine. That is, in addition to the normal addition 
of gaseous fuel tanks, selector valves, etc., most carburetors have been 
converted by adding a large and complicated auxiliary carburetor to the 
liquid fuel carburetor on the engine. In general, these auxiliary 
carburetors or conversion carburetors have occupied excessive space in the 
crowded engine compartment of the modern automobile and have been 
difficult to maintain. In some instances, the hood over the engine 
compartment had to be replaced or modified to accommodate the additional 
carburetion equipment. As a result, the full implementation of lower 
priced, pollution-reducing gaseous fuel has not been successful. 
DISCLOSURE OF THE INVENTION 
It is an object of this invention to provide an inexpensive carburetor 
conversion to allow the internal-combustion engine to run on either 
gaseous or liquid fuel. 
It is another object of this invention to provide a liquid and gaseous fuel 
carburetor that is confined within the existing standard liquid-fuel 
carburetor air cleaner housing so that no modifications need be made to 
the engine compartment or hood over the engine compartment. 
Basically, these objects are obtained by providing a venturi-shaped air 
passage in a gaseous fuel carburetor attachment which fits totally within 
the confines of the liquid-fuel air cleaner housing. This attachment, with 
its venturi air passage, is then fitted to the liquid-fuel carburetor 
inlet flange by one of several types of adapters which can conform to the 
various shapes of carburetor inlet flanges of modern internal-combustion 
engines. The venturi air passage is precisely joined to the gaseous fuel 
supply to obtain proper mixing of the gaseous fuel and air as it passes 
into the carburetor inlet flange. Advantageously, the air cleaner and air 
cleaner housing need not be modified when adding this attachment. 
Secondly, the parts can be inexpensively mass produced for all internal 
combustion engines with only the adapter needing to be of a variable shape 
necessary as a transition piece between the standardized parts of the 
carburetor attachment and the various shapes of carburetor inlet flanges. 
Preferably, the gaseous fuel inlet into the venturi air passage is 
precisely located along a circumferential slot or plurality of 
circumferentially spaced holes just inward of the narrowest portion of the 
neck of the venturi. Also in the preferred embodiment, the venturi air 
passage is formed of a set of spaced plates which can be adjusted relative 
to one another to that the size of the venturi air passage can be varied, 
depending on the make and model of the internal-combustion engine being 
converted.

BEST MODE FOR CARRYING OUT THE INVENTION 
As best shown in FIG. 2, a conventional carburetor for an 
internal-combustion engine includes a carburetor air cleaner housing 10 
joined in a conventional manner to a carburetor inlet flange 12. A 
standard air cleaner 14 is fitted within the air cleaner housing and a 
cover 16 is bolted to hold the air cleaner cover 16 in place by bolt 18. 
Fitted within the air cleaner inlet flange is an adapter ring 19. This ring 
will be one of various shapes, depending upon the shape and size of the 
carburetor inlet flange, which varies between different engine sizes and 
models. The upper end 19a of the ring, however, will be a standard shape, 
regardless of the shape of the bottom of the adapter ring and will thus 
allow the remainder of the parts of the attachment to be standardized for 
most models and makes of engines. 
Bolted to the upper end 19a of the carburetor adapter ring 19 is a lower 
venturi plate 20 formed of an upper half 20a and a lower half 20b. The 
lower half 20b connects to a gaseous fuel intake pipe 22 which 
communicates with a plenum chamber 24. The plenum chamber terminates in a 
circumferential slot or plurality of circumferentially spaced openings 26. 
Spaced over the lower venturi plate 20 is an upper venturi plate 28. The 
upper plate is attached to the lower plate by cap screws 30 and is spaced 
in accurately adjustable position relative to the lower plate 20 by cap 
screws 32. The lower plate 20 is preferably provided with a smooth 
horizontal wall, beginning at an outer circumferential edge that is curved 
inwardly, as at 36, to form one-half of the venturi inlet passage. The 
upper plate 28 is also provided with a smoothly converging outer edge 38 
forming the upper half of the venturi air passage. The venturi air passage 
also has a narrow neck portion 40 and a diverging section 42 inward of the 
narrow neck portion 40. Preferably, the gaseous fuel inlet opening 26 is 
located slightly inboard (approximately 0.125-0.196 inch) from the outside 
edge. This placement of the gaseous fuel inlet openings provides the 
optimum mixing of gaseous fuel with air. 
This carburetor is ideally used with natural gas as the gaseous fuel and, 
as well understood, can be used with conventional liquid fuel, as desired. 
Also, as well understood, the normal operating sequence is to stop the 
flow of liquid fuel, then to start the flow of gaseous fuel while allowing 
the liquid fuel to run completely out of the carburetor before starting 
onto the gaseous fuel. Timing of the valve sequence is provided in the 
conventional manner, with the additional use of sensors, relays, etc., to 
make any distributor adjustments and to start and stop the flows of the 
respective fuels, as is well known. 
While the preferred embodiment of the invention has been illustrated and 
described, it should be understood that variations will be apparent to one 
skilled in the art without departing from the principles herein. 
Accordingly, the invention is not to be limited to the specific embodiment 
shown in the drawings.