Fuel Supply System For An Internal Combustion Engine

Abstract

Fires in the fuel supply system for an internal combustion engine operating in a confined space are prevented by enclosing the carburetor of the engine in a vaportight housing and enveloping the fuel tube leading into the housing in an outer tubular casing. Air of combustion is drawn into the housing through a check valve during the intake stroke of the engine.

Description

This invention relates to fuel supply systems for internal combustion engines, and particularly to a fuel supply system for an engine operating under conditions of high fire or explosion hazard.

The invention will be described hereinafter with reference to a small auxiliary engine for a sailboat but other applications will readily come to mind. It is convenient to equip a sailboat with a small inboard motor and a propeller to facilitate maneuvers in restricted harbor spaces and to provide propelling power when the weather is calm. The engine is normally installed in a small compartment below deck, and boat fires are caused relatively frequently when fuel, fuel vapors, or fuel mixture accidentally released from the fuel supply system are ignited on hot engine parts in the poorly ventilated engine compartment.

A primary object of the invention is the provision of a fuel supply system which permits an internal combustion engine to be used in a confined space or under other conditions in which a relatively minor amount of fuel released from the fuel supply system may cause a fire or an explosion.

With this object and others in view, the invention provides a housing which encloses a cavity substantially sealed from the ambient atmosphere under normal conditions. A check valve mounted on the housing admits air to the cavity when the pressure of the ambient air exceeds the fluid pressure in the cavity by a certain amount.

The cavity holds a carburetor or other mixing device for mixing the admitted air with a liquid fuel. A supply conduit which passes through the housing communicates with the carburetor for supplying the same with the fuel. A fuel mixture conduit passes through the housing and communicates with the carburetor for transferring the fuel mixture to an associated internal combustion engine.

Other features, additional objects, and many of the attendant advantages of this invention will readily be appreciated as the same becomes better understood by reference to the following detailed description of preferred embodiments when considered in connection with the appended drawing in which:

FIG. 1 shows a fuel supply system of the invention and portions of an associated internal combustion engine in side-elevational section;

FIGS. 2 and 3 illustrate the fuel supply system of FIG. 1 in respective sections on the lines II--II and III--III;

FIG. 4 is a top plan view of the fuel system of FIG. 1;

FIG. 5 illustrates a part of the system of FIG. 1 in front elevational section;

FIG. 6 shows a modification of the fuel supply system of FIG. 1 in a corresponding view; and

FIG. 7 shows a further modification of the apparatus of FIG. 6 in fragmentary side elevation.

Referring now to the drawing in detail, and initially to FIGS. 1 to 5, there is seen the single, air-cooled cylinder 17 and the piston 18 of an internal combustion engine, not otherwise illustrated. The apertured bottom of an approximately cup-shaped portion 3 of a carburetor housing is directly attached to the intake port of the cylinder 17 by mounting screws 17', the opening in the bottom of the portion 3 being sealed by the discharge portion of a carburetor 12 mounted in the housing cavity and conventional in itself.

In the illustrated condition of the apparatus, the housing cavity is substantially sealed by a cover portion 4 of the housing and an annular gasket 5 between the two housing portions which are held in engagement by a U-shaped wire strap 21. As is best seen in FIG. 4, the ends of the strap are pivoted on the housing portion 3, and the center portion of the strap is received in a shallow groove in the outer wall of the cover portion 4.

A drain pan 11 is integral with the cover portion 4 and reaches into the housing portion 3 to catch any liquid dripping from the carburetor 12. The pan 11 slopes downwardly toward sump 10 bounded by the cover portion 4 in the lowermost part of the housing cavity. A partition 14 integral with the cover portion 4 partly divides the housing cavity into two compartments, the sump 10, pan 11, and carburetor 12 being located in the compartment nearer the cylinder 17.

A bottom wall of the other compartment in the cover portion 4 is formed with a relatively large circular aperture and provides a valve seat in the cavity for a check valve 1 whose valve disc is guided toward and away from the seat by a stem movably received in a spider in the aperture. The valve 1 is biased toward the closed position by its own weight and by a helical compression spring 22 interposed between the valve stem and the spider. An annular groove 13 in the bottom wall is open toward the housing cavity and slopes slightly toward horizontal openings 15 in the partition 14. The partition partly bounds the sump 10, and the groove 13 thus communicates through the openings 15 with the sump for gravity flow of liquid from the groove into the sump.

Fuel is supplied to the carburetor 12 through a fuel line best seen in FIG. 2. A nipple 9 is threadedly mounted in the housing portion 3. An outer pipe 8 is sealed to the nipple 9 to form therewith a protective casing for a fuel tube 7 approximately coaxially mounted in the pipe 8 and the nipple 9. The effective flow section of the annular gap between the nipple 9 and the tube 7 is only a small fraction of the flow section of the valve 1 when the latter is opened by the pressure of the ambient air during the intake stroke of the piston 18.

The throttle in the carburetor 12 is controlled in a conventional manner by a Bowden wire 20 which enters the housing cavity through an opening in the housing portion 3 and a seal assembly 6. The latter mainly consists of a resilient plastic cap 19 which grips the outer sleeve 23 of the carburetor operating wire 20 and envelops the screw 24 which permits the effective length of the wire to be adjusted in a known manner.

Access to the carburetor 12 may be had by swinging the strap 21 from the illustrated position and thereafter removing the cover portion 4. The screw on the carburetor which controls the idling speed is accessible through an opening in the fixed housing portion 3 normally sealed by a threaded plug or cover member 16 as is seen in FIG. 5. Additional openings and sealing plugs may be provided for routine adjustments.

The fuel tube 7 is connected with a nonillustrated fuel tank in a well-ventilated portion of the boat and is covered by the pipe 8 over its entire length. The annular gap between the tube 7 and the pipe 8 may be open to the atmosphere at a point remote from the housing 3, 4 without significantly affecting the operation of the valve 1 because of the small effective flow section of the gap. If the tank is located above the illustrated devices, and fuel flows by gravity to the carburetor 12, fuel leaking from the tube 7 runs into the housing cavity along the tube, drips from the nipple 9 into the pan 11, and is ultimately collected in the sump 10. Fuel droplets sprayed into the housing cavity from the air intake of the carburetor 12 are directed largely toward the partition 14, and flow along the partition into the sump. Any droplets which find their way into the valve compartment in the cover portion 4 flow into the groove 13 and also find their way into the sump.

The collected fuel may be removed from time to time by releasing the cover portion 4 from the fixed housing portion 3, and pouring the liquid back into the fuel tank. The carburetor controls, the fuel line, and the conduit transferring fuel mixture from the carburetor 12 to the cylinder 17 need not be disturbed during this operation.

The fuel supply system illustrated in FIG. 6 differs from that described above by the configuration of the housing cover 4' and by elements associated therewith. The cover 4' is a flat dish of approximately cylindrical shape about a horizontal axis. A pocket in the sidewall of the dish provides the sump 10, and a drain pan 11 integral with the cover 4' extends under the carburetor 12 and the fuel supply nipple 9 in the fixed housing portion 3, as described above.

The upright radial wall of the cover 4' has a relatively large opening in its top portion upwardly remote from the sump 10. The opening is normally closed by a check valve 2 mainly consisting of a resilient valve flap 26 and a valve seat 25. During the intake stroke of the piston 18, the pressure of the ambient air is sufficient to deflect the flap 26 against its own resilient force inwardly of the housing cavity away from the seat 25, as is shown in FIG. 6. When the pressure differential across the valve 2 is insufficient to overcome the restraint of the flap 26, which is attached to the cover 4', the flap engages the seat 25 and seals the housing cavity from the ambient atmosphere. No significant amounts of fuel or fuel vapors can escape from the housing 3, 4'.

When it is desired to empty the sump 10, a wire strap 21' journaled in a boss of the cover 4' is swung out of engagement of its nonillustrated, hook-shaped ends with projections on the fixed housing portion 3, and the fuel is poured back from the sump 10 into the nonillustrated fuel tank.

If fuel tends to collect relatively fast in the sump 10 by condensation or otherwise, it may be inconvenient to release the cover portions 4, 4' from the fixed housing portion 3 for recovering the fuel, and the sump may be emptied by means of a suction pump which is operated intermittently by hand. An automatic suction arrangement which prevents the accumulation of fuel in the sump, and thereby further improves the safety of the apparatus of FIG. 6 is shown in FIG. 7 from which many elements of FIG. 6, not themselves relevant to the suction arrangement, have been omitted.

The cover 4" seen in FIG. 7 differs from the aforedescribed cover 4' solely by a narrow radial bore in the lowermost wall of the sump 10. A suction tube 30 leads from the bore to the fuel mixture conduit 31 which connects the carburetor, not itself seen in FIG. 7, to the intake port of the cylinder 17, and more specifically to a ring 32 clamped between the housing portion 3 and the cylinder 17 by mounting screws 17" which also attach the housing portion 3 to the cylinder.

The axial opening of the ring 32 converges and diverges in the manner of a venturi, and a radial bore leading into the narrow throat of the ring is connected to the suction tube 30. During each intake stroke of the piston, fuel is drawn from the sump 10 into the ring 32. It is atomized and enriches the fuel mixture transferred from the carburetor to the engine.

Claims

It should be understood, of course, that the foregoing disclosure relates only to preferred embodiments of the invention, and that it is intended to cover all modifications and variations of the examples of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention as set forth in the appended claims.

1. A fuel supply system for an internal combustion engine comprising, in combination:

a. a housing enclosing a cavity normally substantially sealed from the ambient atmosphere;

b. a check valve mounted on said housing for admitting air to said cavity when the pressure of said air exceeds the fluid pressure in said cavity by a predetermined amount;

c. mixing means in said cavity for mixing the admitted air with a liquid fuel;

d. a supply conduit passing through said housing and communicating with said mixing means for supplying fuel to said mixing means;

e. a fuel mixture conduit passing through said housing and communicating with said mixing means for transferring the mixture of air and fuel to an associated internal combustion engine; and

f. an elongated tubular casing sealed to said housing and spacedly enclosing a portion of said supply conduit outside said cavity.

2. A system as set forth in claim 1, wherein said housing includes two housing portions and releasable sealing means for normally holding said portions in sealing engagement about said cavity, the system further comprising mounting means for mounting one of said portions in fixed spatial relationship to said engine, at least one of said conduits extending in said one portion.

3. A system as set forth in claim 2, further comprising control means for controlling the operation of said mixing means, said control means including a control member, said one portion being formed with an opening, and said control member movably passing through said opening in sealing relationship with said one portion and being operatively connected to said mixing means.

4. A system as set forth in claim 2, wherein said one portion defines an aperture normally covered by the other portion of said housing, said aperture being dimensioned and located to give access to said mixing means.

5. A system as set forth in claim 2, wherein said one portion is formed with an aperture dimensioned and located to give access to said mixing means, the system further comprising a cover member releasably received in said aperture and normally sealing the same.

6. A system as set forth in claim 2, wherein the other portion of said housing is formed with an aperture, said check valve being mounted on said other portion and normally sealing the aperture of the same.

7. A system as set forth in claim 1, wherein said casing and said supply conduit define therebetween a gap having an effective flow section much smaller than the effective flow section of said check valve in the open condition of the latter.

8. A fuel supply system for an internal combustion engine comprising, in combination:

a. a housing enclosing a cavity normally substantially sealed from the ambient atmosphere,

1. said housing including two housing portions and releasable sealing means for normally holding said portions in sealing engagement about said cavity;

b. mounting means for mounting one of said portions in a predetermined spatial position, a part of the other portion of said housing bounding a sump in the lowermost portion of said cavity in said predetermined position of said one portion:

c. a check valve mounted on said housing for admitting air to said cavity when the pressure of said air exceeds the fluid pressure in said cavity by a predetermined amount;

d. mixing means in said cavity for mixing the admitted air with a liquid fuel;

e. a drain pan located under said mixing means in said cavity and sloping toward said sump in said position of said one portion;

f. a supply conduit passing through said housing and communicating with said mixing means for supplying fuel to said mixing means; and

g. a fuel mixture conduit passing through said housing and communicating with said mixing means for transferring the mixture of air and fuel to an associated internal combustion engine.

9. A system as set forth in claim 8, wherein said other portion of said housing is formed with an aperture and a groove spacedly adjacent said aperture and open toward said cavity, said check valve being mounted on said other portion and normally sealing said aperture, said groove communicating with said sump.

10. A system as set forth in claim 9, further comprising a partition in said cavity interposed between said aperture and said mixing means and partly dividing said cavity, said partition being formed with an opening therethrough communicating with said groove and with said sump for flow of liquid from said groove to said sump in said position of said one portion.

11. A fuel supply system for an internal combustion engine comprising, in combination:

a. a housing enclosing a cavity normally substantially sealed from the ambient atmosphere;

1. said housing including two housing portions and releasable sealing means for normally holding said portions in sealing engagement about said cavity;

b. mounting means for mounting one of said portions in a predetermined spatial position, a part of the other portion of said housing bounding a sump in the lowermost portion of said cavity in said predetermined position of said one portion;

c. a check valve mounted on said housing for admitting air to said cavity when the pressure of said air exceeds the fluid pressure in said cavity by a predetermined amount;

d. mixing means in said cavity for mixing the admitted air with a liquid fuel;

e. suction means communicating with said sump for withdrawing liquid from the same;

f. a supply conduit passing through said housing and communicating with said mixing means for supplying fuel to said mixing means; and

g. a fuel mixture conduit passing through said housing and communicating with said mixing means for transferring the mixture of air and fuel to an associated internal combustion engine.

12. A system as set forth in claim 11, wherein said suction means include a suction conduit connecting said sump with said fuel mixture conduit.