US2662758A - Carburetor - Google Patents

Description

Dec. l5, 1953 R. ANDERSON ETAL 2,662,758

CARBURETOR Filed Nov. 5, 1949 Patented Dec. l5, 1953 UNITED STATES PATENT OFFICE CARBURETOR Application November 5, 1949, Serial No. 125,768

. 4 Claims. 1

Our invention relates to carburetors and :ls more particularly concerned with a type of carburetor which can be operated in any position.

In modern aircraft practice it is common to utilize carburetors which 4will operate in any position. Such carburetors however are intricate, expensive, and cumbersome, and are entirely unsuitable for use with small power tools.

A primary object of our invention is to provide a compact, simple, inexpensive, yet efficient carburetor especially adapted for small tools and similar uses and capable of operating effectively in all positions, r

Another object of our invention is to provide means for overcoming the difference in the effect of gravity on the operating parts when the carburetor is in upright and inverted positions and in all positions therebetween.

Our invention is an improvement on that disclosed and claimed in the application of Robert F. Bracke, Serial No. 125,265, filed November 3, 1949 having common ownership with applicants assignee.

In the drawing the single figure is an elevational view in section of a preferred form of our invention.

Referring to the drawing it will be seen that our carburetor comprises a body 2 having an air inlet 4 leading to a choke bore 6 provided with any usual choke valve 8. The choke bore t in turn communicates with a Venturi shaped air passage lil discharging into the throttle bore l2. A throttle valve I4 which may be of any usual construction is located in the throttle bore l2. A small vent t6 is provided to prevent floodi ing of the carburetor under any conditions of operation.

A high speed fuel jet I8 is located in the Venturi shaped passage Ill. It is to be noted that this jet, preferably but not necessarily, coincides with the central axis of the passage in the direction of flow of air therethrough and is formed in the wall of a tubular part 20 which bisects the Venturi shaped passage Ill. A11 idle jet 22 is also provided. For some purposes a third jet 26 may be provided. This fuel jet 26 is for the purpose of enriching the mixture at speeds very slightly above idle and is particularly advantageous where the carburetor is to be utilized on a four-cycle engine. This jet 26 however is not essential and may be dispensed with if desired. f

The carburetor is adapted to be connected to any suitable source of fuel supply by means of a pipe 2a.threadedlyv attached to a tapered fuel inlet 30 provided in the lower part of the body 2, This inlet communicates with a chamber 32 formed between a valve seat member 34 and a plug 36. The member 34 has a valve seat 38 adapted to be engaged by the tapered surface of a main fuel valve t6 which is urged toward its seat by a spring 42. A float 43 of cork or other suitable material or construction is attached to the `downwardly projecting stem 45 of the fuel valve 4U and is designed to balance the pull of gravity on the fuel valve and its associated stems so that the force with which the spring d2 urges the fuel valve toward its seat is not affected by changes in the position of the carburetor.

The fuel valve 40 has an upwardly projecting stem 44 whose upper end is spaced slightly from the lower end of an operating rod 48 when the parts are in rest position, as shown in the drawing. This operating rod has a flange 48 resting on a spring 50 of just suflicient strength to overcome the weight of rod 46 and any frictional resistance to movement thereof so that this rod is returned to the position shown independently of the main fuel Valve 40 and offers no resistance to closing movement of this valve.

The operating rod 46 passes through the tube 20 and its upper end slides freely in the wall 52 just beneath a diaphragm chamber 54 whose lower part is formed in the upper end of the body 2. The upper part of the diaphragm chamber 54 is formed by a cover 56 attached to the body 2 by screws 58 or in any other suitable manner, A diaphragm of flexible material impervious to gasoline and oil has its edge confined between the body 2 and cap 56 and forms a. seal therebetween. The central portion of the diaphragm 60 is provided with metal plates 62 held in place by a rivet 64. The lower face of this rivet is positioned to engage the upper end of the actuating rod |26 and move it downwardly under the iniiuence of the diaphragm 68 in a manner hereinafter more fully described.

The main fuel valve 48 controls communication between the chamber 32 and radial passages 66 leading to an annular chamber 68. A duct il) connects the annular chamber 63 with a high speed orifice I2 controlled by the high speed needle valve 13 which is adjustable to vary the effective size of the orice 12. Fuel fiowing past the orifice 12 travels by way of ducts 14 and 16, chamber 18, and passageway 89 to the main fuel jet I8. Passage also continues past the main fuel jet and Vconnects with duct 82 leadingkto idle orifice 84 which is adjustably controlled by 3 the idling needle valve 86 to regulate the discharge of fuel through idle jet 22. In carburetors also equipped with the jet 26, this jet receives its fuel from chamber 18 by way of ducts 88 and 90.

A passage 92 connects the lower side of the diaphragm chamber with the fuel duct 10 leading to high speed orifice l2 so that the suction available to move the central portion of the diaphragm 60 downwardly is the suction existing in thevpassage between the main fuel valve and the high speed orifice. This passage 92 also removes from the diaphragm chamber any fuel which may leak thereinto around the upper end of the rod 46 and maintains the diaphragm chamber free of fuel so that the diaphragm can accurately and immediately reflect changes in the forces acting thereon.

inv

A small duct .94 connects the lower part of the..

diaphragm chamber with the choke bore 6 and permits a small quantity of air to bleed into the diaphragm chamber. This air in turn is sucked out of the diaphragm chamber through duct 92 and mixes with fuel supplied to the several fuel jets. The small quantity of air entering the diaphragm chamber through duct 94 assists in maintaining the diaphragm chamber perfectly dry and is too small in volume t have any appreciable effect on the supply of fuel to the several jets.

To facilitate starting, particularly in cold weather, we provide what is commonly known as a tickler. This tickler comprises a plunger 96 having an enlarged lower end normally positioned immediately above the diaphragm rivet 6&3. The upper end of the plunger is attached to a cap 98 resting on a spring |90 which serves to hold the plunger in elevated position. The lower end of the spring i rests upon a sleeve l0?. screwed into the upwardly projecting tubular extension |94 of the cover 55. The cap 98 may be pressed downwardly by the fingers to open the fuel valve during a starting operation.

In operation our novel carburetor is attached to the intake manifold of an engine and to a source of fuel such as a fuel supply tank located slightly above the carburetor. Both needle valve:J are open such for example as one-half to threefourths of a turn, the choke is closed or partly closed, and if the motor is cold the tickler may be pressed downwardly while the engine is cranked. As soon as the engine starts the tickler is released and the choke is immediately or gradually returned to the open position shown as determined by temperature and other starting conditions.

Air entering the carburetor and flowing through the Venturi shaped passage lil creates a suction at the high speed jet i8 proportional to engine demand. This suction is communicated to the diaphragm chamber through passage 8U, chamber 18, ducts 'i6 and "it, orifice l2 and ducts 79 and 92.

The upper side of the diaphragm 6D is subjected to atmospheric pressure through the clearance around the plunger 95 of the tickler, and the kerf l on the lower end of the sleeve i02 and the difference in pressure on the opposite sides of the diaphragm causes the diaphragm to ilex downwardly and hold the main fuel valve 40 open. If the suction in the diaphragm chamber is increased, as it is at higher engine demand, the diaphragm is flexed to a greater extent and the main fuel valve opens to a correspondingly greater degree.

When the carburetor is in the position shown in the drawing the force of gravity acting on the fuel valve 4% and its associated stems 44 and 45 tends to open this valve but this force is exactly counter-acted by the buoyancy of the oat 33. If the carburetor is inverted the force of gravity acting on the valve 4b and its associated stems would tend to close this valve but is counteracted by the buoyancy of the float i3 vIf the carburetor is placed in a position with the fuel valve 4G and its stems 44 and 45 in a horizontal plane, the force of gravity will have no tendency to either open or close the valve. Likewise the buoyancy of the float 43 will have no tendency to open or close the valve 4B so that in this position also the spring 42 has no function except to urge the valve toward closed position. It therefore will be apparent that our novel construction has the advantage of neutralizing any force exerted by gravity tending to open or close the main fuel valve, so that opening and closing movements of this valve depend solely on the springs i2 and 50 and the suction produced in the diaphragm chamber.

The duct Sui allows a small amount of air at atmospheric pressure to bleed into the diaphragm chamber but this inflow of air is not sucient to affect the operation of the diaphragm. The purpose of this air bleed is to keep the diaphragm chamber dry so that the movement of the diaphragm can instantaneously respond to quick changes of the throttle Valve and quick changes in engine demand. For some purposes it may be advantageous to eliminate passage 92 and connect the lower side of the diaphragm chamber with the junction of fuel passages 8i) and 82 by providing a substantial clearance between the wall 52 and upper end of the actuating rod 4G.

It is to be understood that our invention is not limited to the particular details shown and described but may assume numerous forms and includes all variations, modifications, and equivalents coming within the scope of the appended claims.

We claim:

l. A carburetor of the class described the combination of a body providing an air passage therethrough, jet means for supplying fuel to air flowing through said passage, said body having a fuel inlet, a fuel passage connecting said inlet with said jet means, a valve in said passage for controlling flow of fuel to said jet means, a spring for closing said valve, means responsive to engine operation for opening said valve, and means for overcoming the effect of gravity on said valve for all positions of said carburetor, said means including a fuel chamber, a float in said chamber, said float being lighter than a corresponding volume of said fuel, and means attaching said oat to said valve.

2. In a carburetor of the class described the combination of means providing a passage therethrough, jet means for supplying fuel to air flowing through said passage, said first-named means having a fuel inlet and providing a conduit connesting said inlet with said jet means, a valve in said conduit for regulating ilow of fuel to said jet means, means responsive to engine operation for opening said valve, othei` means for closing said valve, said conduit including a chamber between said inlet and valve and a float in said chamber for overcoming any action of gravity tending to open or close said valve, said float being lighter than a corresponding volume of said fuel.

3. In acarburetor of the class described the combination of a body providing an air passage therethrough, jet means for supplying fuel to air flowing through said passage, said body having a fuel inlet and a fuel passage connecting said inlet with said jet means, a valve in said conduit controlling flow of fuel to said jet means, automatic means for opening said valve, a second means for closing said valve, and float means balancing the tendency of gravity to open and close said valve, said oat being lighter than a corresponding volume of said fuel.

4. In a carburetor of the class described the combination of a body having an air passage therethrough, jet means for supplying fuel to air flowing through said passage, said body providing an inlet and a fuel passage connecting said inlet with said jet means, a valve in said fuel conduit for regulating flow of fuel to said jet means, said valve having oppositely extending stems, a cork float attached to one of said stems, said oat being located in a part of said fuel passage, a spring acting on said stem to close said valve, diaphragm means operating on the other stem to open said valve, and means responsive to engine demand for creating a pressure differential across said diaphragm.

ROBERT ANDERSON. ROBERT F. BRACKE.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,933,379 Mock Oct. 31, 1933 2,084,377 Barbarou June 22, 1937 2,390,658 Mock Dec. 11, 1945

Images