US1973162A - Carburetor - Google Patents

Description

Sept. 11, 1934.

s. F. BRIGGS CARBURE'I'OR Filed Sept. 21, 1932 2 Sheets-Sheet 1 Sept. 11, 1934.

S. F. BRIGGS CARBURETQR 2 Sheets-Sheet 2 Filed Sept. 21, 1932 5/55/75/7 flP/ S Patented Sept. 11, 1934 UNITED STATES PATENT OFFICE Briggs & Stratton Corporation, Milwaukee,

Wis a corporation of Delaware Application September 21, 1932, Serial No. 634,126

14 Claims.

This invention relates to improvements in carburetors and has as an object to provide a carburetor having novel means to facilitate starting of an internal combustion engine with which the carburetor is used.

Heretofore, various means have been employed to facilitate starting of a cold engine. The conventional choke valve wasthe most commonly used, but this method was open to many well known objections.

made in the past to obviate the necessity for a choke valve or to provide automatic means for its control.

The present invention contemplates an improvement in carburetors whereby the choke valve is entirely obviated and wherein during the initial starting of the cold engine a substantial charge of fuel is quickly drawn into the mixing chamber and thereafter until a predetermined to time at which the engine has attained a desired running temperature, a smaller quantity of auxiliary fuel is drawn into the carburetor mixing chamber.

With the above and other objects in view which will appear as the description proceeds, the invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the herein disclosed invention may be made as come within the scope of the claims.

In the accompanying drawings, several com plete examples of the physical embodiment of this invention is illustrated constructed according to the best modes so far devised for the practical application of the principles thereof, andin which:

' Figure 1 is a fragmentary illustration of a .40 carburetor of conventional design with portions.

thereof broken away and in section to illustrate the application of this invention thereto; and

Figures 2 and 3 illustrate slightly modified con,- structions.

Referring now more particularly to the accompanying drawings, the numeral 5 represents the body of a conventional carburetor having a venturi 6 and a mixing chamber 7. The particular carburetor illustrated is of the down draft type with the mixing chamber and the throttle valve 8 therein at the lower end, the main air inlet being at the upper end of the carburetor.

A fuel jet 9 is mounted within the mixing chambar with its outlet orifice 10 positioned at the throat of the venturi and slightly above. the fuel Hence, efforts have been a supply line 13 and its level in the float chamber is maintained in the customary manner by the actuation of a float 14.

Formed either as an integral part of the float chamber or as a separate unit, is a fuel reservoir 15. This fuel reservoiris communicated with the float chamber through an inlet port 16 in the partition wall 17 and as the reservoir is vented in any suitable manner as by the provision of a vent opening 18 in its upper wall, the fuel fills the reservoir 15 to the level determined by the float. An outlet orifice 19 is formed in the bottom wall of the reservoir and a duct 20 connected there-.

with and debouching into the mixing chamber '7 directly adjacent the throttle valve affords a communication from the reservoir to the mixing chamber. This communication is controlled by a valve 21 which in the present instance is in the form of a needle valve seating in the orifice 19.

The valve 21 has a stem 22 extending upwardly through the reservoir to mount an armature 23 at its upper end. The armature 23 is arranged to be attracted to a'solenoid 24 upon energization thereof. The armature 23 together with the weight of the valve 21 and its stem normally maintains the valve in its closed position, but when the solenoid 24 is energized, the attraction of the armature thereto opens the valve and establishes communication from the reservoir to the mixing chamber.

The energization of the solenoid 24 is effected by the closing of a circuit diagrammatically illustrated and which comprisesa battery 25, a manually operable switch 26 and a thermostatically operable switch 2'7 all connected in series withthe solenoid through conductors 28 and 29. The .manually operable switch 26 may be either the ignition switch of the internal combustion engine or some other switch operated in conjunction I therewith, and the thermally operable switch 27 consists merely of a bi-metallic strip 30 positioned adjacent a portion of the exhaust manifold 31.

The bi-metallic strip 30 is so arranged that at ambient temperatures it holds the switch 27 closed, but upon the manifold 31 becoming heated by the normal operation of the engine, it flexes and opens the valve 2'7.

It is well known that in colder weather the difficulty of starting is increased. Hence, it may be desirable to provide means for co-ordinating the functioning of the priming device with the 'metallic member 37 is engageable.

\that a maximum rate of flow ambient temperature. For this purpose, it has been found efiective to regulate the rate of flow of fuel fromthe reservoir 15 into the mixing chamber. and also to regulate the degree of communication betwen the reservoir and the float chamber. Figures 2 and 3 illustrate two practical embodiments of this feature. In Figure 2, the opening 16' which affords a communication between the float chamber 11 and the reservoir 15, is controlled by a valve 33 carried at the outer free end of the bi-metallic strip 34 rigidly secured to the wall 17, as at 35. The bi-metallic strip 34 is so arranged that a greater degree of opening is effected during colder temperatures than under warm conditions.

Also, in the structure shown in Figure 2, the valve stem 22 is provided with a series of stepped notches 36 with which the free end of a bent bi- The opposite end of the bi-metallic member 37 is fixed to the wall 17, as at 38. This member is so formed that in cold weather a maximum opening is permitted but at warmer temperatures the degree of opening of the valve 21 is limited.

Coordination of the rate of flow of fuel from the float chamber into the reservoir with the ambient temperature may be also obtained by providing a second and larger orifice 39 in the wall 17 to communicate the float chamber and reservoir, which orifice is controlled by a valve 40 mounted on a bi-metallic strip 41 similar to the strip 34. This valve 40 opens upon the temperature dropping below a predetermined point so is obtained during colder temperatures.

It is observed that in the embodiment'of the invention illustrated in Figure ,2, the duct 20 leading from the reservoir to the mixing chamber of the carburetor debouches into the carburetor outwardly of the throttle valve, whereas in the disclosure of Figure 1, it is shown as entering the mixing chamber at a point above the throttle valve. The exact location of this point. of communication may vary under different conditions but at all times is maintained close to the edge of the throttle valve in its normal substantially closed position.

' v Operation Assuming that the engine is at rest and cold, the thermal valve 27 will be in its normal closed position, but the switch 26 will be open. Consequently the solenoid 24 will be deenergized and the valve 21 closed so that the reservoir 15 will be filled with fuel to the level determined by the float 14.

When the engine is started the switch 26 will be closed. This closes the circuit of the solenoid 24 to open the valve 21, whereupon the supplyof fuel contained within the reservoir will flow into the mixing chamber by gravity in the event the carburetor is of the down draft type illustrated, or if it is the conventional up draft type the suction within the mixingv chamber adjacent the throttle valve will draw the fuel up into the mixing chamber.

A rich mixture will thus be conducted to the engine and as the outlet orifice 19'is substantially twice the size of the inlet 16, the fuel within the reservoir will be discharged into the mixing chamber faster than it will flow from the fioat chamber into the reservoir. As a result all of the accumulated fuel within the reservoir will be discharged into the mixing chamber during the initial starting period and thereafter auxil-= iary fuel willcontinue to flow into the mixing chamber through the duct 20, but the volume thereof will be restricted to the amount determined by the area of the inlet orifice 16.

This condition will obtain until the engine has reached its normal operating temperature at which the bi-metallic strip 30 of the thermal switch 27 will be actuated by the heat radiated from the manifold 31. When this occurs the cir- Figure 2 is obviously substantially the same as has been described, with the exception that the rate of flow of the fuel from the reservoir to the carburetor mixing chamber is controlled thermostatically.

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in the art to which an invention of the character described appertains, that this invention affords a simple and eflicient means for discharging auxiliary fuel into the mixing chamber of a carburetor to obtain the desired rich mixture, without the necessity for the conventional choke valve.

- What I claim as my invention is:

1. In a carburetor having 'a mixing chamber, a fuel reservoir, means to supply fuel to the reservoir at a predetermined rate of flow, means to discharge fuel from the reservoir to the mixing chamber at a rate of flow greater than that of the supply to the reservoir, and avalve to control the discharge from the reservoir to the mixing chamber, whereby the reservoir fills with' fuel when the valve is closed and empties when the valve is open at a rate determined by the area of the discharge and thereafter supplies fuel to the mixing chamber at a rate determined by the inlet.

2. In a. carburetor having a mixing chamber with a throttle valve therein, means to supply fuel directly to the mixing chamber adjacent the throttle valve comprising, a fuel reservoir having an inlet and an outlet, the inlet being connected with a source of fuel supply and being of smaller area than the outlet whereby fuel discharges from the reservoir at a faster rate than it flows into the reservoir, means to connect the discharge of the reservoir with the mixing chamber, and a valve to control the discharge, the reservoir filling with fuel when the valve is closed and emptying upon opening of the valve to supply fuel to the mixing chamber at a rate of flow determined by the area of the outlet until the reservoir is emptied and thereafter supplying fuel to the mixing chamber at a rate of fiow determined by the area of the inlet.

3. In a carburetor having a mixing chamber with a throttle valve operating therein, means to supply fuel to the mixing chamber at a point adjacent the throttle valve comprising, a reservoir having an inlet for communicating the reservoir with a fuel supply and an outlet of greater area than the inlet whereby fuel can discharge from the reservoir at a rate faster than it can to open the valve, the contents of the reservoir discharging into the mixing chamber upon opening of the valve at a rate of flow determined by the area" ofthe outlet and thereafter the fuel entering the reservoir through its inlet discharging into the mixing chamber, whereby the volume of fuel discharged into the mixing chamber is reduced after the contents of the reservoir are emptied, and said thermostatically controlled means operating after a predetermined time to close the valve.

4. In a carburetor having a mixing chamber provided with a throttle valve, a fuel reservoir having an inlet through which fuel enters the reservoir and an outlet of greater area than the inlet so that the contents of the reservoir may be drained at a rate greater than said contents can be replenished, a duct connecting the outlet with the mixing chamber adjacent the throttle valve, a valve for closing the outlet of the reservoir, electromagnetic means to control the position of the valve, an electric circuit adapted when closed to energize the electromagnetic means and open the valve to enable the contents of the reservoir to be discharged into the mixing chamber and thereafter to enable fuel to pass into the mixing chamber from the supply through the reservoir and the duct at a rate of fiow determined by the area of the inlet, and thermal means operable to open the circuit and effect closing of the valve.

5. In a carburetor having a float chamber and a mixing chamber provided with a throttle valve, means to supply fuel directly to the mixing chamber adjacent the throttle valve comprising, a reservoir communicated with the float chamber through an inlet opening, said reservoir having an outlet opening of greater area than the inlet opening whereby the contents of the reservoir may be discharged at a rate faster than it can be replenished through the inlet opening, a duct leading from the outlet opening to the mixing chamber adjacent the throttle valve, a valve to close the outlet opening, electromagnetic means to open the valve and permit the contents of the reservoir to be discharged into the mixing chamber to supply fuel to the mixing chamber at a rate determined by the area of the discharge and then to supply fuel to the mixing chamber at a lesser rate determined by the area of the inlet opening, and thermally responsive means to control the electromagnetic means, said thermally responsive means operating within a predetermined period after the opening of the valve to close the valve.

6. In combination with the carburetor and a part of an internal combustion engine susceptible to becoming heated during normal operation thereof, the carburetor having a mixing chamber provided with a throttle valve, means to supply fuel directly to the mixing chamber adjacent the throttle valve during starting of the internal combustion engine, comprising a fuel reservoir having an inlet through which fuel enters at a predetermined rate of fiow and an outlet through which fuel discharges at a greater rate of flow, a duct connecting the outlet with the mixing chamber, a valve for the outlet, electromagnetic means to control the valve, an electric circuit adapted to be closed upon starting of the internal combustion engine to energize the electromagnetic means and open the valvewhereby the contents of the reservoir discharges into the mixing chamber at the rate of flow determined bythe area of the discharge opening and thereafter fuel is discharged into the mixing chamber at the rate of flow determined by the inlet, and thermal means operable upon the attainment of a predetermined temperature at said part of the internal combustion engine susceptible to be heated to open the circuit and deenergize the electromagnetic means to enable the valve to close.

7. In a carburetor having a mixing chamber, means to supply auxiliary fuel to the mixing chamber comprising, a fuel passage debouching into the mixing chamber, said fuel passage having a restricted inlet through which fuel enters and a metering orifice spaced from the restricted inlet and larger than said inlet, the space in the fuel passage between the inlet and metering orifice affording a reservoir, and a valve to close the metering orifice, whereby a supply of fuel is retained in the reservoir between the inlet and metering orifice when the valve is closed and whereby fuel is conducted to the mixing chamber by said passage when the valve is opened first in a large volume and thereafter in a smaller volume.

, 8. In a carburetor having a mixing chamber, an auxiliary fuel passage debouching into the mixing chamber, said fuel passage having a restricted inlet through which fuel enters and a metering orifice spaced from the restricted inlet and larger than said inlet, the space between the restricted inlet and the metering orifice being enlarged to afford a fuel reservoir, a valve to close the metering orifice and cause'the reservoir to fill with fuel, and automatic means to open the valve and release the supply of fuel from the reservoir for passage to the mixing chamber whereby auxiliary fuel passes to the mixing chamber at a rate of flow determined by the area of the metering orifice until the reservoir is emptied and thereafter at a rate of flow determined by the area of the restricted inlet.

9. In a carburetor having a mixing chamber and a throttle valve therein, a fuel reservoir, a thermostatically controlled communication leading from the reservoir to the mixing chamber adjacent the throttle valve to conduct fuel from the reservoir to said mixing chamber, and thermostatically responsive means to control the rate of flow of fuel from the reservoir to the mixing chamber.

10. In a carburetor having a mixing chamber and a throttle valve therein, a fuel reservoir, a communication between the reservoir and the mixing chamber, means to supply fuel to the reservoir to pass from the reservoir through said communication to said mixing chamber, thermostatically responsive means to control, the fuel supply to the reservoir, a valve to close said communication, and thermostatically responsive means to control the position of said valve.

11. In a carburetor having a mixing chamber and a throttle valve therein, a fuel reservoir, a communication between the reservoir and the mixing chamber, means to supply fuel to the reservoir to pass from the reservoir through said communication to said mixing chamber, thermostatically responsive means to control the fuel supply to the reservoir, a valve to close said comber, the reservoir filling with fuel when the valve is closed and emptying when the valve is open at a rate determined by the area of the discharge and thereafter supplying fuel to the mixing chamber at a rate determined by the supply of fuel to the reservoir.

13-. In a carburetor having a mixing chamber, a fuel reservoir, means to supply fuel to the reservoir, thermostatic means to control the rate of fuel supply to the reservoir, means to discharge fuel from the reservoir to the mixing chamber, a valve to control the discharge of fuel from the reservoir to the mixing chamber, whereby the reservoir fills'with fuel when the valve is closed and empties when the valve is open, the rate of flow of the fuel from the reservoir to the mixing chamber being determined by the area of the discharge until the reservoir is empty and thereafter by the rate of flow into the reservoir, and thermostatic means to control the valve.

14:. In a carburetor having a mixing chamber, a fuel reservoir, means to supply fuel to the reservoir, thermostatic means to control the rate of fuel supply to the reservoir, means to discharge fuel from the reservoir to the mixing chamber, a valve to control the discharge of fuel from the reservoir to the mixing chamber, whereby the reservoir fills with fuel when the valve is closed and. empties when the valve is open, the rate of flow of the fuel from the reservoir to the mixing chamber being determined by the area of the discharge until the reservoir is empty and thereafter by the rate of flow into the reservoir, means to open said valve, and thermostatic means to control the degree of opening of the valve.

STEPI-EN F. BRIGGS.

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