US2965086A

US2965086A - Liquid fuel supply system

Info

Publication number: US2965086A
Application number: US842262A
Authority: US
Inventors: James B Gregory; Howard D Emerson; Charles C Moore
Original assignee: Union Oil Company of California
Current assignee: Union Oil Company of California
Priority date: 1959-09-25
Filing date: 1959-09-25
Publication date: 1960-12-20
Anticipated expiration: 1977-12-20

Description

was.

Deg 20, 1960 2,965,086

J. B. GREGORY EIAL LIQUID FUEL SUPPLY SYSTEM Filed Sept. 25, 1959 4 Sheets-Sheet l AIR CLEANER /4 F051. PUMP Fla 1 //V VEA/ 7' 0195 JAMES ls. GREGORY HOWARD 0. 5445250 CHARLES C. MOORE /liw infl v Decrzo, 1960 J. B. GREGORY ET AL 2,965,086

LIQUID FUEL SUPPLY SYSTEM I Filed Sept. 25, 1959 4 Sheets-Sheet 5 40? CA W/VER EODY 7'0 I/AIICUUM /A/I/E'/V7'0/?5 F054 PRESSURE M44455 6. 6/?5604? EEGUAATOR Han 44 0 a 5415mm 09 4/94 55 c. Mao/8 Dec. 20, 1960 J. B. GREGORY ETAL LIQUID FUEL SUPPLY SYSTEM Filed Sept. 25, 1959 4 Sheets-Sheet 4 4/): c4 EAA/ER A'Z/EL Pam/p MAME-5 5. 6%.560/9/ Han 4R0 0. s/wwsa/v #42455 c. 4/0045 United States LIQUID FUEL SUPPLY SYSTEM James B. Gregory, Howard D. Emerson, and Charles C.

Moore, Fullerton, Calif., assignors to Union Oil Company of California, Los Angeles, Calif., a corporation of California Filed Sept. 25, 1959, Ser. No. 842,262

22 Claims. (Cl. 123-136) This invention relates to the abatement of air pollu tion, and in particular concerns certain new and useful improvements in fuel systems for internal combustion engines, such as those employed for the propulsion of motor vehicles.

The operation of motor vehicles contributes markedly to the air pollution problem in large cities by the release of hydrocarbons to the atmosphere, either as unburned fuel via the exhaust system, or as evaporated fuel via the fuel supply system. A great deal of evaporated fuel originates from the motor vehicle engine carburetor both during periods of operation and non-operation. One of the major sources of these carburetor evaporation losses is from the carburetor float bowl, which is a vented reservoir of volatile fuel constantly exposed to heat from both the atmosphere and the engine. These evaporative losses are essentially a function of fuel volatility, float bowl temperature, and carburetor design.

Fuel vapors from the conventional float bowl can escape to the atmosphere along two principle routes: (1) directly to the atmosphere through external vents in the float bowl, and (2) through so-called internal vents or balancing tubes into the throat of the carburetor. When the engine is running, hydrocarbon vapors escaping through the internal vents are drawn into the combustion chamber with incoming air and subsequently combusted. However, any vapors that escape through the external vents during this operational period will contaminate the atmosphere. When the engine is turned off hydrocarbon vapors escape through both the internal and external vents to the atmosphere. However, since carburetors perform at widely varying temperatures with volatile fuels, some form of venting must be used to keep the float bowl at essentially the same pressure as the other communicating carburetor chambers when the engine is running.

One major cause of carburetor evaporation loss, only casually considered by previous investigators, is the so called carburetor hot soak which begins immediately after the engine is turned off. Heat stored by the engine while running is transmitted to the carburetor float bowl, which, depending on design, normally contains from around 80 to 200 ml. of volatile hydrocarbon fuel. As the trapped fuel in the float bowl is heated evaporation occurs through the aforementioned carburetor vents. Generally, there is a float bowl temperature rise of from about 40 to 60 F. from the bowl temperature at the time the engine is shut off to the peak temperature reached (usually in about 20 to 40 minutes) during the hot soak period. It can be generally stated that atmospheric temperatures have little effect upon the hot soak temperature of the carburetor bowl; the bowl tempera ture seems to be controlled primarily by engine coolant temperature. Carburetor design has virtually no effect on hot soak losses, except in the matter of float bowl fuel capacity. It has been found that normal losses to the atmosphere from the carburetor float bowl during the hot soak period range from to 30 percent of 2,965,086 Patented Dec. 20, 1960 n; to the fuel remaining in the float bowl at the time the engine is stopped.

It is accordingly an object of this invention to provide an improved method and apparatus for the abatement of atmospheric pollution resulting from the operation of internal combustion engines.

Another object is to provide an improved method and apparatus for effecting a substantial reduction in the gross fuel consumption of automobiles, thus resulting in more eflicient and economical operation.

A further object is to reduce substantially the evaporative fuel losses from the fuel supply system of internal combustion engines.

Other and related objects will be apparent from the detailed description of the invention, and various advantages not specifically referred to herein will be apparent to those skilled in the art on employment of the invention in practice.

We have now found that the foregoing objects and their attendant advantages can be realized in a conventional internal combustion engine, such as is used in the propulsion of motor vehicles, by providing the float bowl of a conventional carburetor with a fuel drain line which empties the fuel remaining in the carburetor float bowl to an alternate reservoir as soon as the engine is stopped. This removes the highly volatile hydrocarbons from the high temperature environment of the carburetor float bowl before any significant losses from hot soak can occur, thus eliminating a major source of air pollution.

The invention will be more readily understood by reference to the accompanying drawings which form a part of this application. Figure l is a schematic diagram of one of the simplest embodiments of this invention. Figure 2 is a schematic diagram of the apparatus of this invention in one of its preferred embodiments. Figure 3 is a further modification of the apparatus of Figure 2 wherein the tank vent is closed to the atmosphere at all times except when the float bowl is emptying. Figure 4 is a schematic diagram of another embodiment of the invention wherein the fuel tank is vented only during engine operation. Figure 5 is a modification of Figure 1 wherein the drain line includes a drain level assembly. It is to be understood that although the float bowl draining method and apparatus is broadly applicable to any internal combustion engine using a volatile fuel and a fuel induction system, it is particularly useful for gasoline-burning engines, such as those used in automobiles, trucks, buses and the like. However, it also has practical use with engines using somewhat heavier fuels such as diesel engines, jet engines, and the like.

Referring now more particularly to Figure 1, the apparatus there shown consists essentially of the fuel supply system for an internal combustion engine. The fuel supply enters fuel tank 10 via inlet conduit 36. When fuel tank 10 has an adequate supply of volatile fuel, tank cap 38 seals inlet conduit 36. Tank vent 42 communicates with the atmosphere and, as is conventional with fuel storage tanks on motor vehicles, maintains fuel tank 10 at atmospheric pressure. Fuel is supplied to carburetor float bowl 18 via line 12, fuel pump 14, and line 16. Fuel pump 14 can be any of the conventional pumps used in the fuel supply systems of internal combustion engines such as a vacuum-operated fuel pump, an electrical pump, a mechanical pump, or the like. However, fuel pump 14 is preferably electrically operated so that operation thereof can start immediately when the ignition is turned on, thus filling float bowl l8 rapidly and independently of engine operation. The fuel enters carburetor float bowl 318 at a rate controlled by the characteristics of fuel pump 14 and float valve 28 which, as it rises, restricts the outlet of line 16 into carburetor float bowl 18, thus acting as a liquid level control device to maintain a substantially constant level of fuel within carburetor float bowl 18.

The foregoing constitute conventional elements found in nearly all carburetor fuel supply systems. According to our invention, a novel fuel return system is provided in the form of a return line 30, opening from the bottom of bowl 18, and communicating in fuel delivery relationship with fuel tank 10 via drain valve 32 and line 34. Valve 32 can be located at any intermediate horizontal level between the inlet to line 30 and the outlet of line 34, but for convenience of access is preferably located immediately below the carburetor body 20.

Return lines

30 and 34 can be constructed of A: or 4 inch LD. tubing, such as is used for conventional fuel delivery lines. However, as will be more fully explained below, a suitable restriction to flow is incorporated into the fuel return system so that fuel from bowl 18 will not be returned to tank 10 at a faster rate than the supply system can deliver fuel to float bowl 18.

One method of operating the apparatus as shown in Figure 1 is to have drain valve 32 ina blocked open position. There is then a constantly open drain line from float bowl 18 to fuel tank 10, both when the engine is operating and when the engine is stopped. With drain valve 32 blocked open and the engine running, fuel is continuously pumped from fuel tank 10 via fuel pump 14 to float bowl 18. Simultaneously, fuel is constantly flowing from float bowl 18 to fuel tank 10 via line 30, blocked open drain valve 32 and line 34. Thus, there is a constantly circulating flow of fuel from fuel tank 10 to carburetor float bowl 18 and back to fuel tank 10, with an adequate reservoir level in carburetor float bowl 18 being maintained by float valve 28. The drainage capacity of the fuel return system comprising line 30, valve 32 and line 34 is such that the flow through this return system is small compared to the total capacity of the fuel supply system. Typically, the rate of gravity flow through the return system is about to /2 of the flow capacity of the fuel supply system to the carburetor.

At no time during engine operation can there be allowed an excessive float bowl drainage so that the reservoir will be depleted to an inoperable point or to a level which will detrimentally affect normal operation. This drainage or return flow can be adjusted to the desired level by manipulation of drain valve 32. Alternatively, drain valve 32 can be replaced by an appropriate orifice which will restrict return flow so as to maintain an adequate fuel supply in carburetor float bowl 18 during all conditions of engine operation. Other methods of restricting flow are also satisfactory such as the use of a capillary tube drain line or any small size line having sufficiently smaller drainage flow capacity than the delivery capacity of the fuel supply system to maintain adequate operating fuel level in float bowl 18 during engine operation. A restriction such as an orifice, the partial closing of drain valve 32, or a small diameter drain line will occasionally serve to prevent reverse surge in the drain line from the fuel tank during downhill driving or rapid stops, resulting in overfilling of carburetor bowl 18.

When the engine is stopped, fuel pump 14 no longer delivers fuel, as it is controlled by the engine operation. Carburetor float bowl 18 is then quickly emptied of fuel via line 30, drain valve 32 and line 34. Thus, with the above-described mode of operation there is little fuel loss to the atmosphere through external vent 22 of carburetor float bowl 18 since the highly volatile fuel has been removed from the float bowl within a few seconds to 3 or 4 minutes after the engine is stopped. When operation of the car is resumed fuel pump 14 quickly introduces fuel as hereinbefore described to carburetor float bowl 18, thus restoring the fuel therein to an adequate level for engine operation.

Line 34 can enter fuel tank either in th 2 space at the top of the fuel tank or, as shown in Figure 1, the drained fuel from carburetor float bowl 18 can return to the bottom of fuel tank 10. Since this drainage fuel is usually warmer than the fuel in the fuel tank because of passing through the carburetor and the engine compartment, the Figure l embodiment reduces evaporative fuel flashing by introducing said drainage fuel into the bottom of the cool body of fuel in tank 10. However, with some fuel systems it is preferred to bring fuel drain line 34 into the highest and most remote point of fuel tank 10. This introduction of the fuel drain line into a relatively permanent vapor space above the body of fuel in tank 10 prevents any possibility of reverse drainage from fuel tank 10 to float bowl 18 when the vehicle associated with the engine is stopped on a steep incline. A preferred location for the fuel return, i.e., through line 34, is into the vapor space of inlet conduit 36 which is ordinarily free of any liquid level.

Further modifications of the apparatus which have been highly successful in reducing evaporation loss, particularly during engine operation, involve the closing of external vent 22 by means of a plug or some other appropriate vapor-tight closure. We have found that if the fuel drain line of our invention is used with an internal combustion engine, then external vent 22 can be plugged with no change in the normal satisfactory operation of the engine. A large variety of conventional carburetors have been operated with plugged external vents for extended periods of time in combination with the method and apparatus of our invention with a high degree of success. Evaporation losses from the fuel system were materially reduced, with a resultant reduction in atmospheric pollution and in gross fuel consumption. It has been found that as a further means of reducing evaporate losses of volatile fuels, fuel tank 10 should be insulated to reduce the acquisition of heat, thus lowering the temperature of the fuel contained therein. By means of tank insulation there is a reduced temperature rise during motor vehicle operation, which thus reduces the vapor pressure of the fuel and effectively reduces the evaporation losses from the fuel tank itself through tank vent 42. Any conventional insulating material can be used such as glasswool, asbestos, and the like. Also, a reflective surface on the fuel tank such as a white or aluminized undercoating is useful in reducing heat acquisition from hot pavements.

A further modification of the apparatus of Figure 1 entails connecting tank vent 42 of the fuel tank 10 to external vent 22 of float bowl 18. Thus, there is communication between the vapor space of fuel tank 10 and the vapor space of float bowl 18 which, during engine operation, will permit any vapors evaporating from fuel tank 10 to pass through tank vent 42 to float bowl 18 and thence through internal vent 24 to the throat of the carburetor where these vapors are swept into the engine combustion chamber and burned. Tank vent 42 can also be returned to air cleaner 26 or to any air intake channel of carburetor 20 where fuel vapors from fuel tank 10 are carried into the combustion chamber of the internal combustion engine during engine operation. When tank vent 42 is returned to an air intake channel in the fuel induction assembly there will be occasional fuel condensation within tank vent 42. In this case, tank vent 42 should either be located and designed to drain freely or suflicient heat should be provided to vaporize any condensate formed. Because of the problems entailed in passenger car design, gravity drainage of condensate from a vent line communicating between tank vent 42 and the fuel induction assembly can be attained only by passing such a vent line up from the gas tank and just under the car roof to the front of the automobile where the vent line can then descend into the engine compartment and subsequently to the fuel induction assembly. However, if it is necessary for design considerations to construct dips or loops into the conduit system, as when run underneath the automobile body, then a heat source should be provided over the entire conduit length or at least at the low points to vaporize condensate that may occur. The vent line can be traced with an exhaust gas conducting conduit or an electrical resistance tracing to provide a heat source. Also, since the low point in many vapor conduit systems will run parallel to the exhaust gas mufller and pipes, the vent line can be run adjacent thereto and thus derive sufficient heat to stay condensate free. When the engine is stopped the same vapor path exists which maintains float bowl 18 and fuel tank 10 at substantially the same pressure thus permitting easy draining of float bowl 18.

Return lines

30 and 34 can become vapor locked under certain design conditions, i.e., when said lines are not in continuous descent to fuel tank 10, and/or do not have suflicient size to relieve themselves of the gas or vapor which occupies this line space after the carburetor bowl has drained. This vapor locking, of course, occurs only if line 34 drains into the liquid body of tank 10, and is thus eliminated when line 34 communicates with the vapor space of tank 10. To relieve this problem, we may provide one or more atmospheric vents which, when engine operation is resumed, serve to release trapped vapors, thus priming the lines for satisfactory operation. Vent line 40 is such a conduit for venting the drain-back system. As shown in Figure 1, vent 40 can be returned to the air cleaner assembly to prevent the escape of volatile fuel vapors into the atmosphere during engine operation, or it can be vented directly to the atmosphere if desired. The location of vent 40 in the fuel drain-back conduit is not critical as long as it allows gas to escape from the conduit for effective draining. The outlet of any such vents should preferably be located above the level of the fuel in float bowl 18.

An alternate method of operation of the apparatus shown in Figure 1 comprises starting the engine operation with drain valve 32 closed and carburetor float bowl 18 empty. Fuel is supplied to carburetor float bowl 18 as hereinbefore described, which fills and maintains an adequate fuel reservoir through the action of float valve 28. There is no flow of gasoline through the system comprising line 30, drain valve 32 and line 34 during engine operation. When the engine is stopped fuel pump 14 stops and therefore no longer supplies fuel via line 16 to carburetor float bowl 18. Drain valve 32 is immediately opened upon engine stoppage and float bowl 18 is drained of its fuel content via line 30, drain valve 32 and line 34 to fuel tank 10. Drain valve 32 is then closd prior to or coincident with resumption of engine operation. The opening and closing of drain valve 32 can be effected by the engine intake manifold vacuum if it is a vacuum actuated valve, or by the ignition switch if a solenoid actuated valve, or manually if a conventional mechanical valve. The opening and closing of such valves is conventional and well-known in the art and hence need not be described in detail.

Referring now more particularly to Figure 2, the apparatus here shown comprises a preferred embodiment of our fuel supply system. The volatile hydrocarbon fuel enters fuel tank 100 via inlet conduit 124. The outer surface of fuel tank 100 is covered with about one inch of glasswool insulation 160. When fuel tank 100 is filled to the desired level, tank cap 126 seals inlet conduit 124. Tank cap 126 is a conventional pressure relief cap which maintains the fuel tank under a positive pressure between about 0 and about 2 p.s.i.g. The design of these so-called pressure caps is such that when the pressure within the fuel tank falls below atmospheric, a check valve 127 in the fuel cap opens so that it is impossible for vacuum to develop within fuel tank 100. When pressures above about 2 p.s.i.g. develop, a relief valve 125 is opened to reduce the pressure to about 2 p.s.i.g. The fuel from tank 100 is supplied to carburetor float bowl 108 via line 102, fuel pump 104, fuel pressure regulator 105, and line 106. Fuel pump 104 in this preferred embodiment is an electrically operated pump which operates whenever the ignition is on and ceases operation, thus blocking the passage of fuel, when the ignition is off. Fuel pump 104, however, could be a conventional vacuum-operated fuel pump or a mechanical pump or the like. Conventional fuel pressure regulator 105 is an optional element of the fuel system whose use is dictated by the fuel pump used, the operating pressure of the fuel tank, and similar considerations. Normally these pressure regulators operate at between about 1 p.s.i.g. and about 5 p.s.i.g. fuel pressure to the carburetor. The fuel enters carburetor float bowl 108 from line 106 at a rate controlled by the pressure setting of fuel pressure regulator 105 and conventional float valve 116 which, as the fuel within float bowl 108 rises, restricts the entrance of line 106 into float bowl 108 and thus acts as a metering device to maintain a substantially constant level of fuel within carburetor float bowl 108.

The fuel drain-back system comprises line 118 opening from the bottom of float bowl 108, vacuum operated drain valve 120, and line 122 which opens into fuel tank 100. Fuel tank 100 is in communication with the atmosphere via line 128, vacuum operated vent valve 130 and conduit 132. The operation of valve 120 in the fuel drain-back system is controlled by a vacuum delay system comprising conduit 136, a small vacuum reservoir tank 138 provided with orifice 146, conduit 140, check valve 142, and vacuum supply conduit 144.

The operation of the fuel supply system of this preferred embodiment starts with the initial filling through inlet conduit 124 of fuel tank 100 until the desired fuel level is obtained. Pressure cap 126 is then secured thus sealing the end of inlet conduit 124. Prior to starting the internal combustion engine of which this fuel supply system is a part, valve 130 is open and valve 120 is open. When the engine is started the vacuum actuated valves 120 and 130close, and fuel is supplied to carburetor float bowl'108 via line 102, fuel pump 104, fuel pressure regulator 105, and line 106. Float bowl 108 is quickly filled to the operative level as controlled by float valve 116. During the period of engine operation,

valve

120 and 130 remain closed. Keeping valve 130 closed prevents the escape of fuel vapors from the tank vent line 132 to the atmosphere, which, due to the slopping of the fuel within the tank can be an appreciable source of hydrocarbon contaminant in the atmosphere. During engine operation any vapors which develop in float'bowl 108 travel via internal vent 112 in carburetor body to the other carburetor chambers and are thus swept into the combustion chambers of the engine and burned.

When the engine is shut off the conventional vacuum manifold of the internal combustion engine returns to atmospheric pressure, thus dissipating the vacuum source which was holding valves and closed, and valve 130 opens immediately allowing tank 100 to come to atmospheric pressure. The opening of valve 120, how ever, is delayed by the action of vacuum reservoir tank 138. In a fuel system as herein described, it is necessary that tank 100 be near or at the same pressure as float bowl 108 when drain valve 120 is opened. Otherwise, there could be a reverse surge of fuel into float bowl 108 which would prevent proper drainage, and might even overflow into the engine compartment resulting in excessive hydrocarbon loss to the atmosphere. When the engine vacuum manifold returns to atmospheric pressure, check valve 142 automatically closes thus allowing vacuum reservoir tank 138 to come gradually to atmospheric pressure by the entrance of air through orifice 146. The delay in opening valve 120 is thus a function of the size of orifice 146 and a vacuum reservoir tank 138. Atypical system has a time delay of about 15 seconds, and comprises a vacuum reservoir volume of about 32 cubic inches and an orifice diameter of about 0.02 inch. Obviously, however, any

other combination of orifice size and vacuum reservoir volume which would give the desired time delay could be used. Operative time delay periods of about 3 to 60 seconds are contemplated.

When the pressure in vacuum reservoir tank 138 approaches atmospheric, valve 120 opens and permits the fuel remaining in carburetor float bowl 108 to drain back to fuel tank 100 via line 118, opened drain valve 120 and line 122. Line 118 is supplied with an optional atmospheric vent 150 to air cleaner 114, which as previously discussed with respect to Figure 1, allows the escape of trapped air and vapors in the drain-back conduit system. When the engine is restarted,

valves

120 and 130 close by action of the engine vacuum source,

and the system repeats the first described mode of operation.

The fuel system as above described is not limited to the use of vacuum actuated valves.

Valves

120 and 130 can be electrical solenoid valves with appropriate circuiting, usually in conjunction with the ignition circuit. Thus,

valves

120 and 130 would be held open when the ignition is off and held closed when the ignition is turned on. Instead of the vacuum delay system used to control valve 120, we may also use a conventional mechanical or electrical delay system.

Valves

120 and 130 may also be mechanical valves operated manually.

Referring now more particularly to Figure 3, the apparatus here shown is a fragmentary view of the fuel supply system of Figure 2 with a modified fuel tank venting apparatus therein. The apparatus of Figure 3 is identical in every respect to Figure 2 with the following exceptions. The operation of valve 130 is controlled by a time delay system comprising line 134, valve 170 with its own vacuum supply line 172, line 174, vacuum reservoir 176 with orifice 178, line 180, check valve 182 and vacuum supply line 184. The operation of the apparatus of Figure 3 is identical to the operation of the apparatus of Figure 2 with the exception of the venting of fuel tank 100.

Prior to the starting of the internal combusion engine of which this fuel supply system is a part, valve 130 is closed and valve 170 is open. When the engine is started vacuum-operated valve 170 closes thereby isolating the control side of valve 130 from its vacuum source and thus maintains valve 130 closed during engine operation. When the engine is shut off, the conventional vacuum manifold of the internal combustion engine returns to atmospheric pressure thus dissipating the vacuum source which was holding valve 170 closed. Valve 170 hence opens immediately and allows valve 130 to communicate with the vacuum source represented by the vacuum reservoir tank 176. This immediately opens valve 130 and vents fuel tank 100 to the atmosphere. The closing of valve 130 is delayed, however, by the action of vacuum reservoir tank 176. In a fuel system as herein described, it is necessary that tank 100 be near or at the same pressure as float bowl 108 when drain valve 120 is open. When the engine vacuum manifold returns to atmospheric pressure, check valve 182 automatically closes thus allowing vacuum reservoir tank 176 to come gradually to atmospheric pressure by the entrance of air through orifice 178. The delay in the closing of valve 130"is thus a function of the size of orifice 178 and vacuum reservoir tank 17 6 as previously discussed in relation to the vacuum delay control system for valve 120. When the pressure in vacuum reservoir tank 176 approaches atmospheric, valve 130 closes and prevents any further vapor loss from fuel tank 100 during the engine-off period. It is necessary that the closing of valve 130 be closely coordinated with the draining of float bowl 108. The time delay should be such that float bowl 108 is completely drained before the closing of tank vent valve 130. Thus, with the modification of Figure 3, fuel tank 100 is prevented from losing vapor to the atmosphere except during the very short period of time required to drain float bowl 108. As previously discussed, the vacuum-operated valves in Figure 3 can also be mechanically or electrically operated and the time delay system controlling valve 130 can also be a conventional mechanical delay, electrical delay, or

the like.

Referring now more particularly to Figure 4, the apparatus there shown comprises another embodiment of our float bowl draining system. The volatile hydrocarbon fuel enters fuel tank 200 via inlet conduit 226. The outer surface of fuel tank 200 is covered with insulation 201 comprising two layers of heavy asbestos paper, one layer of aluminum foil and an outer layer of asbestos cloth. The entire insulation thickness is approximately /2 inch. When fuel tank 200 is filled to the desired level, tank cap 230 seals inlet conduit 226. Tank cap 230 is a conventional pressure relief cap comprising a check valve 232 which maintains the fuel tank under a positive pressure between about 0 and about 2 p.s.i.g. and a check valve 232 which opens when the pressure within the fuel tank falls below atmospheric so that it is impossible for a vacuum to develop within fuel tank 200. The fuel from tank 200 is supplied to carburetor float bowl 210 via line 202, fuel pump 204, line 205, fuel pressure regulator 206 and line 208. Fuel pump 204 in this embodiment is an electrically operated pump which functions whenever the ignition is on and ceases operation, thereby blocking the passage of fuel, when the ignition is off. Fuel pump 204 could, however, be a conventional vacuum operated fuel pump or a mechanical pump or the like. Conventional fuel pressure regulator 206 is an optional element of the fuel system identical to regulator of Figure 2, previously discussed in detail. The fuel enters carburetor float bowl 210 from line 208 at a rate controlled by the pressure setting of fuel pressure regulator 206 and conventional float valve 218 which, as the fuel within float bowl 210 rises, restricts the line 208 entry to float bowl 210 and thus acts as a metering device to maintain a substantial constant level of fuel within carbu retor float bowl 210.

In the present modification of our invention the fuel drain-back system comprises a line 220 opening from the bottom of float bowl 210, vacuum operated drain valve 221, line 222, valve 223 and line 224 which communicates with the permanent vapor space in fuel tank 200 via inlet conduit 226. Fuel tank 200 is in communication With the atmosphere via line 234, vacuum operated vent valve 236-, and conduit 238 which opens into the vapor space of float bowl 210. The latter is maintained essentially at atmospheric pressure via internal vent 214 in carburetor body 212 and air cleaner 216. The operation of valve 221 in the fuel drain-back system is controlled by a vacuum delay system comprising conduit 242, a small vacuum reservoir tank 244 provided with orifice 252, conduit 246, check valve 248 and vacuum supply conduit 250. Vacuum operated vent valve 236 is controlled by the same delay system as valve 221 and communicates therewith via line 240.

The operation of this fuel supply system entails filling fuel tank 200 through inlet conduit 226 with liquid fuel until a desired level is obtained. Pressure cap 230 is then secured to conduit 226 sealing the end thereof. Prior to starting the internal combustion engine of which this particular fuel supply system is a part,

valves

221 and 236 are closed and valve 223 is open. When the engine is started vacuum actuated

valves

221 and 236 open and valve 223 closes, and fuel is supplied to carburetor float bowl 210 via line 202, fuel pump 204, line 205, fuel pressure regulator 206 and line 208. Float bowl 210 is quickly filled to the operative level as controlled by float valve 218. During

engine operation valves

221 and 236 remain open and valve 223 remains closed. With valve 236 open, fuel vapors from tank 200 are vented to the operating engine via line 234, valve 236, line 238, the vapor space of float bowl 210 and internal vent 214'to the othercarburetor chambersyand are thus swept-into the combustion chamber'of the engine and burned. Closed valve 223 prevents any drainage from float bowl 210 to fuel tank 200*during engine operation.

When the engine is shut off the conventional vacuum manifold of the internal cornbustionengine returns to atmospheric pressure thus dissipating the vacuum source which was holding valve 223c1osed and valves 221and 236 open. Valve 223' opens immediately, but the closing of

valves

221 and 236 is delayed by the-action of vacuum reservoir tank 244. In a fuel system as herein described, it is necessary that-tank 2-00 be near or at the same pressure as float bowl 210 when drain-valve 221 is open. Otherwise, there could be a reversesurge of fuel into float bowl 210 which would prevent proper drainage and might even overflow into the engine compartment resulting inan excessive hydrocarbon loss to the atmosphere. Thus, tank vent valve 236 must remain'open as long as drain valve 221 is open. When the engine vacuum manifold returns to atmospheric pressure, check valve 248 automatically closes thus allowingvacuum reservoir tank 244 to come gradually to atmospheric pressure with the entrance of air through orifice 252. The delay in closing

valve

221 and 236 is thus a function of the size of orifice 252 and vacuum reservoir tank 244. An identical system was previously described in detail with relation to Figures 2 and 3.

When the pressure in vacuum reservoirtank 244'-ap proaches atmospheric, valves 22-1 and 236 close to seal the fuel tank from the atmosphere during the engine-off period. When the engine is restarted,

valves

221 and 236 open and valve 223 closes by action of the engine vacuum source and the system repeats the first described mode of operation. As discussed previously, thevacuum actuated valves illustarted in Figure 4*can be electric solenoid valves, or mechanical valves, or electric valves whose individual operation is controlled by the vacuum delay system shown-or'a conventional mechanical or electric delay system.

A further modification of our invention entails the use of' a leveling assembly 420, as shown in Figure 5. This leveling assembly adjusts the fuel level in the carburetor float bowl to any desired'level at the end of the drain period; Thus, fuel drains until the fuel level in float bowl 408 is at the same level as weir 422 of leveling assembly 420. A substantial portion of the fuel 'can' therefore be removed from the float bowl, but-leaving enough-to initiate and support operation until the fuel pump can start refilling float bowl 408. Theco'mp'onent parts of the apparatus of Figure 5 and their arrangement and operation are substantially identical to the corresponding parts of Figure 1 except for the added component of leveling assembly 420.

One method of operating the apparatus as shown in Figure 5 comprises starting engine operation with drain valve 426 closed and carburetor float bowl 4% partially empty, i.e.', fuel level at B--B. Fuel is supplied to carburetor float bowl 408 by fuel pump 404 via line 406 which fills and maintains an adequate fuel reservoir through the action of float valve 416. There is no flow of gasoline through the system comprising line 418, leveling assembly' 420, line 424, drain valve'426 and line 428 during engine operation. When the engine'is stopped fuel pump 404 stops and therefore no longer supplies fuel via

line

402 and 406 to carburetor float bowl 408. Drain valve 426 is immediately opened upon engine stoppage, and float bowl 408 is partially drained to fuel tank 400, via line 418, leveling assembly. 420, line 424, drain valve 426 and'line 423. The drained level of float bowl 468 is at B-B which is determined by the relative position of overflow weir 422 of drain leveling assembly 420 With respect to float bowl 408. Overflow weir 422 should be placed in level relationship with respect to the desired level of the retained body of fuel in float bowl 408. Also, to minimize drain-back from the fuel tank on steep inclines, drain level assembly-420 can be placed near fuel tank 400, e.g., within the trunk compartment of conventional automobiles. Drain valve 426 is then closed prior to or coincident with the resumption of engine operation. The opening and closing of drain valve 426 can be effected by the engine intake manifold vacuum if it is a vacuum actuated valve, or, by the ignition switch if a solenoid actuated valve, or manually if a conventional mechanical valve.

Fuel tank vent 434 and drain line vent 436 are both returned to the air intake channel of the carburetor immediately beneath where air cleaner 414 is attached to carburetor body 410. Thus, there is communication between the vapor space of fuel tank 400 and the throat of the carburetor which,- during engine operation, will permit any vapors evaporating from fuel tank 400 and drain line vent 436 to pass through tank vent 434 to the throat of the carburetor where these vapors are swept into the engine combustion chamber and burned.

Although the fuel systems shown in Figures 1, 2, 3, 4 and 5 are illustrated with a single bowl carburetor, the method and apparatus of our invention have been successfully applied to an engine having a two-bowl carburetor, and any number of carburetors or bowls may be integrated into the system.

The air pollution abatement device of this invention is rugged by virtue of its simplicity, but should any maintenance or repair work be required, this can easily be accomplished since conventional parts, fittings, and equipment are used throughout.

While in the foregoing description, we have referred mainly to carburetor fuel induction systems, the invention in its broadest aspect is not limited thereto. Other fuel induction devices, such as pressure injectors may also draw from small intermediate fuel reservoirs located in the engine compartment. ,Our invention is hence applicable to any fuel supply systems involving a storage tank relatively remote from the engine, and a secondary vented reservoir located sufficiently near the engine to absorb heat therefrom.

It will be apparent from the foregoing that the apparatus of our invention includes a new and novel carburetion device comprising a housing enclosing an air-intake and fuel evaporation throat, an integrally attached fuel reservoir chamber, a fuel inlet opening into the reservoir chamber, at least one liquid fuel transfer port traversing the housing and communicating the throat with the reservoir chamber, means for maintaining a substantially constant liquid fuel level in the reservoir chamber against a supernatant vapor space, at least one balancing tube traversing the housing and connecting the supernatant vapor space in thefuel reservoir chamber with the throat, and a drain port opening from the bottom of the reservoir chamber.

While the method and apparatus of our invention deals primarily with solving the evaporative loss problem by draining the fuel from the high temperature vented chambers associated with the internal combustion engines, there are other approaches equally useful. All vents from these fuel-containing chambers can also be shut ofi? from the atmosphere by appropriate valving during engine-off periods. This requires blocking 1) the internal vents, (2) the external vents, if any, and (3) in some cases the fuel conduit leading from the float chamber to the jet in the throat of the carburetor. The fuel supply conduit to the float chamber conventionally has a check valve in it which will prevent flow back through the fuel pump. This closing in of the float chamber or any similar vented fuel reservoir can be accomplished either by modifying existing fuel induction systems or by incorporating the requisite valves, manifolds, etc., into the design of new carburetors. The valves used can be any conventional mechanical, vacuumoperated, or electrically operated valves, but preferably would be solenoid valves whose operation is controlled by the ignition switch. This sealing of the carburetor fuel reservoir chamber can be used in combination with all of the methods and apparatus described in relation to Figures 1, 2, 3, 4 and 5 whereby pressures developed within the sealed off chambers can be relieved by transferring the fuel from the hot carburetor chamber to more remote chambers.

Since the primary purpose of the draining is to keep the fuel in engine compartment reservoirs, e.g., float chambers, cool during engine-off periods, it is contemplated that any method of removing the fuel to a cool space will accomplish the purpose of the invention, namely reduction of evaporative loss during the hot soak" period. Thus, removal to a cool space can include transfer to any secondary reservoir or to the main fuel storage tank with means provided for returning this fuel to the fuel induction system when the engine is started. Obviously, cooling of the fuel in the carburetor reservoir chambers in situ can also reduce evaporative losses, and the isolation and insulation of these carburetor fuel chambers, i.e., float chambers and the like, can greatly reduce the effect of the hot soak period. This application is a continuation-in-part of our prior co-pending application Serial No. 823,914, filed June 30, 1959.

Various other changes and modifications of this invention are apparent from the description of this invention and further modifications will be obvious to those skilled in the art. Such modifications and changes are intended to be included with the scope of this invention as defined by the following claims.

We claim:

1. In combination with an internal combustion engine, an improved liquid fuel delivery and conservation system adapted to minimize evaporative fuel losses, comprising in combination a carburetor having a fuel reservoir chamber with at least one vent to the atmosphere, a fuel storage tank, a pressure relief valve in the upper portion of said storage tank adapted to maintain a small maximum positive pressure therein, a check valve in the upper portion of said storage tank adapted to maintain at least atmospheric pressure therein, a fuel inlet port to said storage tank, a removable cap closing said fuel inlet port, a vapor conduit opening from said storage tank and communicating with the atmosphere, a vent valve in said vapor conduit, control means for actuating said vent valve, means for delivering fuel from said storage tank to said fuel reservoir chamber, a fluid drain conduit opening from said fuel reservoir chamber and communicating with the interior of said storage tank and adapted to transfer fuel from said reservoir chamber to said storage tank when said fuel delivery means is inoperative, a pressure relief vent line leading from an intermediate point in said drain conduit and communicating with the atmosphere, a first throttle valve in said drain conduit, control means for actuating said first throttle valve, a second throttle valve in said drain conduit, control means for actuating said second throttle valve, and a leveling assembly associated with said drain conduit comprising an overflow weir adapted to maintain a minimum fuel level in said fuel reservoir chamber at all times.

2. In combination with an internal combustion engine, an improved fuel delivery and conservation system adapted to minimize evaporative fuel losses, comprising in combination a fuel induction device located near said engine,

a fuel induction reservoir located near said engine and adapted to deliver fuel to said induction device, a remote fuel storage tank, means for delivering fuel from said storage tank to said induction reservoir, a vapor conduit opening from said storage tank to the vapor space in said induction reservoir, a liquid drain conduit opening from said induction reservoir to said storage tank, means responsive to engine operation for maintaining said drain conduit open for a short period following each cessation of engine operation and closed at all other times, and means responsive to engine operation for maintaining said vapor conduit open during engine operation and a short time thereafter but closed at all other times.

3. A combination as defined in claim 2 including means for confining fuel vapors within said storage tank up to a pre-determined pressure during periods when said drain conduit and vapor conduit are closed, and pressureresponsive means for exhausting fuel vapors therefrom at said pre-determined pressure.

4. In combination with an internal combustion engine, an improved liquid fuel delivery and conservation system adapted to minimize evaporative fuel losses, comprising in combination a carburetor having a fuel reservoir chamber with at least one vent to the atmosphere, a fuel storage tank, a pressure relief valve in the upper portion of said storage tank adapted to maintain a small maximum positive pressure therein, a check valve in the upper portion of said storage tank adapted to maintain at least atmospheric pressure therein, a vapor conduit opening from said storage tank leading into and communicating with the vapor space in said fuel reservoir chamber, a vent valve in said vapor conduit, means for maintaining said vent valve open when said engine is in operation and means for closing the same a short time after each cessation of engine operation, means for delivering fuel from said storage tank to said fuel reservoir chamber, a fluid drain conduit opening from said fuel reservoir chamber and communicating with the interior of said storage tank, said drain conduit being adapted to transfer fuel from said reservoir chamber to said storage tank when said fuel delivery means is inoperative, a first throttle valve in said drain conduit, control means for maintaining said first throttle valve open during operation of said engine and for closing the same a short time after each cessation of engine operation, a second throttle valve in said drain conduit and control means for maintaining said second throttle valve closed during operation of said engine and for opening the same substantially simultaneously with each cessation of engine operation.

5. A combination as defined in claim 4 including a fuel inlet port to said storage tank and a removable cap closing said inlet port, and wherein said pressure relief valve and said check valve are positioned in said removable cap.

6. A combination as defined in claim 5 wherein said drain conduit is adapted to return fuel via said fuel inlet port to said storage tank.

7. A combination as defined in claim 4 wherein said reservoir chamber is vented only to the throat of said carburetor and contains no external vents.

8. In combination with an internal combustion engine, an improved liquid fuel delivery and conservation system adapted to minimize evaporative fuel losses, comprising in combination a fuel storage tank, a pressure relief valve in the upper portion of said storage tank adapted to maintain a small maximum positive pressure therein, a check valve in the upper portion of said storage tank adapted to maintain at least atmospheric pressure therein, a vapor conduit opening directly to the atmosphere from the upper portion of said storage tank, a vent valve in said vapor conduit, means for maintaining said vent valve open for a short time after each cessation of engine operation and closed at all other times, a carburetor having a fuel reservoir chamber with at least one vent to the atmosphere, means for delivering fuel from said storage tank to said fuel reservoir chamber, a fluid drain conduit opening from said fuel reservoir chamber and communicating with the interior of said storage tank, said drain conduit being adapted to return fuel to said storage tank when said fuel delivery means is inoperative, a throttle valve in said drain conduit and control means for maintaining said throttle valve open for a short time after each cessation of engine operation and closed at all other times.

9. A combination as defined in claim 8 including a fuel inlet port to said storage tank and a removable cap closing said inlet port, and wherein said pressure relief valve and said check valve are positioned in said removable cap.

10. A combination as defined in claim 9 wherein said drain conduit is adapted to return fuel via said fuel inlet port to said storage tank.

11. A combination as defined in claim 8 wherein said reservoir chamber is vented only to the throat of said carburetor and contains no external vents.

12. In combination with an internal combustion engine, an improved liquid fuel delivery and conservation system adapted to minimize evaporative fuel losses, comprising in combination a remote fuel storage tank, a fuel induction device associated with said engine, an induction system fuel reservoir chamber located near said engine and having at least one vent to the atmosphere, fuel delivery means for delivering fuel from said storage tank to said fuel reservoir chamber, means for transferring fuel from said reservoir chamber to said fuel induction device, a fluid drain conduit opening from said fuel reservoir chamber and communicating with the interior of said storage tank, said drain conduit being adapted to return fuel to said storage tank from said reservoir chamher when said fuel delivery means is inoperative, and means for maintaining a minimum fuel level in said fuel reservoir chamber at all times.

13. A combination as defined in claim l2 wherein said means for maintaining a minimum fuel level comprises a leveling assembly associated with said drain conduit, said leveling assembly comprising an overflow weir adapted to maintain a minimum fuel level in said fuel reservoir chamber at all times.

14. A combination as defined in claim 12 wherein said fuel induction device is a carburetor, and said induction system fuel reservoir chamber is a float chamber provided with a fioat valve therein for controlling the rate of fuel delivery to maintain a constant liquid level therein.

15. A combination as defined in claim 14 wherein said fuel reservoir chamber is vented only to the throat of said carburetor and contains no external vents.

16. A combination as defined in claim 12 including a pressure relief vent line leading from an intermediate point in said drain conduit and communicating with the atmosphere,

17. A combination as defined in claim 12 including a vent communicating with the atmosphere from the vapor space in said fuel storage tank.

18. A method for reducing fuel evaporation in the fuel supply system of an internal combustion engine having a carburetor with a fuel reservoir chamber vented to the atmosphere, which method comprises emptying said chamber and returning drained fuel to the fuel storage tank immediately after stopping said engine, sealing the fuel storage tank from the atmosphere a short time after draining said fuel reservoir chamber, and venting said fuel storage tank to the atmosphere immediately upon starting said engine.

19. A method for reducing fuel evaporation in the fuel supply system of an internal combustion engine having a carburetor with a fuel reservoir chamber vented to the atmosphere, which method comprises partially draining said chamber of retained fuel to the fuel storage tank immediately after stopping said engine and maintaining at least a minimum fuel level within said fuel reservoir chamber at all times whereby the engine has fuel available for immediate starting.

20. A method for reducing fuel evaporation from the fuel supply system of an internal combustion engine having a carburetor with a fuel reservoir chamber vented to the atmosphere, which method comprises emptying said chamber by draining retained fuel to the fuel storage tank immediately after stopping said engine, venting the fuel storage tank to the atmosphere while the fuel reservoir chamber is being drained, and maintaining said fuel storage tank closed to the atmosphere at all other times.

21. A combination as defined in claim 2 wherein said vapor conduit consists essentially of an internal vent line leading from said induction reservoir to the air intake channel of said fuel induction device, and a storage tank vent line leading from said storage tank to said air intake channel, said engine-responsive means being located in said storage tank vent line.

2 A method as defined in claim 18 wherein said fuel reservoir chamber and said fuel storage tank are each vented to the atmosphere solely through an air intake channel of said carburetor.

References Cited in the file of this patent UNITED STATES PATENTS 1,909,390 Ball May 16, 1933