US 4,178,894 AGranted

Nonpolluting liquid fuel system for engines

AssigneeBriggs & Stratton Corporation

InventorPaul R. Nau

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Abstract

Inside the fuel tank of a small engine liquid fuel system is a buffer chamber that has its interior communicated with the rest of the tank interior only through a small upper air vent and a restricted bottom fuel port. During fueling, fuel enters the buffer chamber slowly and continues to enter it after the tank is apparently full, lowering the fuel level sufficiently to prevent seepage through the tank cap. The engine crankcase is vented to the carburetor air induction passage through a breather check valve in the carburetor body. A first valve, responsive to pressure differences between the atmosphere and the tank interior, vents overpressures in the tank to the crankcase. A second valve, responsive to the difference between tank pressure and subatmospheric cranckcase pressure, admits air to the tank when the engine is running.

Claims9

Dependent claims

In a fuel system for a cyclically operating internal combustion engine that has a crankcase in which there is a subatmospheric pressure during at least a portion of each engine cycle when the engine is operating, and which system comprises a tank that holds a liquid fuel supply for the engine and wherein a substantially constant atmospheric pressure is to be maintained:

A. an imperforate removable closure for an opening in the tank through which fuel is filled thereinto, said closure, when in place, providing a substantially vapor-proof seal for the tank;
B. means defining a suction chamber which is at all times communicated with the interior of the crankcase and which is communicable with the atmosphere through a breather passage;
C. a check valve in said breather passage arranged to normally close the same but to open when pressure in the suction chamber exceeds atmospheric pressure;
D. means defining a fuel tank pressure relief passage communicated at one end with the interior of the fuel tank and communicated at its other end with the interior of the crankcase;
E. pressure responsive outlet valve means operatively associated with said pressure relief passage, comprising a movable element having opposite surfaces that are respectively exposed to the atmosphere and to the interior of the tank, at the top thereof, said outlet valve means being normally closed to prevent flow through said pressure relief passage but being arranged to be opened by pressure in the tank that exceeds atmospheric pressure;
F. means defining a fuel tank suction relief passage communicated at one end with the interior of the tank and communicated at its other end with the atmosphere;
and
G. pressure responsive valve means operatively associated with said suction relief passage, comprising a movable element having opposite surfaces that are respectively exposed to the interior of the tank, at the top thereof, and to the interior of the suction chamber, said inlet valve means being normally closed to prevent flow through said suction relief passage but being arranged to be opened by subatmospheric pressure in said suction chamber.

5 more elements

In combination with a cyclically operating internal combustion engine that has a crankcase in which a subatmospheric crankcase pressure obtains during at least a portion of each engine cycle and has a carburetor with a body wherein there is an air induction passage through which combustion air is drawn into the engine, a liquid fuel system for the engine in which a supply of fuel is maintained under substantially atmospheric pressure but from which substantially no unburned fuel vapors are vented to the atmosphere, said fuel system being characterized by:

A. means defining a tank for liquid fuel having
(1) a filler opening through which fuel can be filled into the tank,
(2) a pressure relief outlet, and
(3) a suction relief inlet;
B. an imperforate removable closure for said filler opening;
C. means for communicating the interior of the crankcase with the air induction passage through a valve seat;
D. a check valve cooperating with said valve seat to prevent flow in the direction from the air induction passage to the crankcase but arranged to permit flow in the opposite direction;
E. means defining a pressure relief passage for communicating said pressure relief outlet with the interior of the crankcase;
F. pressure responsive valve means normally closing said pressure relief passage and comprising a pressure responsive valve element having opposite surfaces that are respectively subjected to atmospheric pressure and to pressure in the interior of the tank, said valve element being arranged to open the pressure relief passage when pressure in the tank exceeds atmospheric pressure;
G. means defining a suction relief passage for communicating said suction relief inlet with atmospheric air;
and
H. other pressure responsive valve means normally closing said suction relief passage and comprising a second pressure responsive valve element having opposite surfaces that are respectively subjected to atmospheric pressure and to crankcase pressure, said second pressure responsive to valve element being arranged to open the suction relief passage when atmospheric pressure exceeds crankcase pressure.

9 more elements

A liquid fuel system for a small cyclically operating internal combustion engine that has a crankcase in which there is a subatmospheric pressure during at least a portion of each engine cycle, said liquid fuel system being of the type comprising a fuel tank having a top wall in which there is a filler opening, a carburetor body overlying the fuel tank top wall and wherein there is an induction air passage into which air is drawn through a filter and from which the air flows to the engine for combustion, and a resiliently flexible membrane confined between opposing surfaces on the underside of the carburetor body and on the top wall of the fuel tank, said fuel system being characterized by:

A. the top wall of the fuel tank being formed with a substantially deep depression that is spaced from the filler opening and extends down to near the bottom of the tank to define a buffer chamber in the tank interior,
(1) said buffer chamber being closed at its top by a portion of said membrane that comprises a first diaphragm, and
(2) the interior of the buffer chamber being communicated with the remainder of the tank interior only through
(a) restricted port means at the bottom of the buffer chamber through which fuel enters the buffer chamber substantially more slowly than it can be filled into the tank through the filler opening, thus frustrating filling of the tank to a level at which fuel can be easily expelled therefrom through the filler opening, and
(b) restricted vent means downwardly adjacent to the membrane by which pressure in the buffer chamber is equalized with that in the remainder of the tank interior;
B. the carburetor body having means defining
(1) a nipple,
(2) a breather passage that opens at one end through said nipple and opens at its other end to the induction air passage, and
(3) a check valve seat in said breather passage, so located that a portion of the breather passage extends between its said one end and the check valve seat;
C. a duct communicated at one end with the interior of the crankcase and connected at its other end with said nipple, to constantly maintain crankcase pressure in said portion of the breather passage;
D. a check valve element cooperating with said check valve seat to normally prevent communication between the induction air passage and said portion of the breather passage but arranged to be opened by crankcase pressures that exceed pressure in the induction air passage;
E. the carburetor body further having a first tank vent passage which communicates with said portion of the breather passage and opens to the underside of the carburetor body at a hole in the membrane that is spaced from said first diaphragm;
F. the top wall of the fuel tank having a first groove in its upper surface that
(1) has one end portion spaced a small distance from the top of the buffer chamber and
(2) extends from its said end portion to said hole in the membrane;
G. the underside of the carburetor having a first well therein which defines a pressure chamber and which
(1) is communicated with the atmosphere,
(2) opens downwardly over the buffer chamber and said one end portion of said first groove, and
(3) is closed at its bottom by said first diaphragm, which normally cooperates with a tank top wall upper surface portion that is between the buffer chamber and said first groove to prevent communication between the tank interior and said first groove, but which rises away from said surface portion, to permit such communication, in response to pressures in the tank interior that exceed atmospheric pressure;
H. the carburetor body further having a second tank vent passage which communicates with the induction air passage and opens to the underside of the carburetor body at another hole in said membrane that is spaced from the first mentioned hole therein and from said first diaphragm;
I. the top wall of the fuel tank further having
(1) a vent hole therethrough which is spaced from the buffer chamber and from said first groove, and
(2) a second groove in its upper surface, spaced from the buffer chamber and said first groove, said second groove having one end spaced a small distance from said vent hole and its other end portion communicated with the second tank vent passage through said other hole in the membrane;
and
J. the underside of the carburetor body also having a second well therein which defines a suction chamber and which
(1) is communicated with said portion of the breather passage,
(2) opens downwardly towards the portion of the top wall of the tank that has said vent hole and said second groove therein, and
(3) is closed at its bottom by a portion of the membrane that provides a second diaphragm which normally cooperates with an area of the tank top wall upper surface to prevent communication between said vent hole and said second groove but rises away from that surface area to permit such communication when pressure in the suction chamber is substantially lower than pressure in the interior of the tank.

25 more elements

Dependencies are inferred from the claim text.

Facts

Application: 05/887,476Filed 17 Mar 1978
Granted: 18 Dec 1979
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

F02M 37/0023
Constructional details; Manufacturing or assembly of elements of fuel systems; Materials therefor: valves in the fuel supply and return system
F02M 17/48
Carburettors characterised by draught direction and not otherwise provided for , e.g. for model aeroplanes: with up- draught and float draught,…
F02M 25/06
Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture:…
F02M 25/0836
Adding fuel vapours drawn from engine fuel reservoir: arrangement of valves controlling the admission of fuel vapour to an engine, e.g. valve…