Abstract:
Systems and methods for draining fuel from a carburetor of a combustion engine can include a first control valve in communication between a fuel source and a fuel chamber of a carburetor and a second control valve in communication between the fuel chamber of the carburetor and a drain reservoir. The first and second control valves can be coupled and operable such that, upon disengagement of the engine, the first control valve can be closed to block a supply of fuel to the fuel chamber, and the second control valve can be opened to connect the drain reservoir to the fuel chamber, which can operate to draw liquid fuel from the fuel chamber into the drain reservoir. The fuel can then be moved from the drain reservoir into a fuel storage tank, where it can be stored until needed by the carburetor.

Description:
TECHNICAL FIELD 
       [0001]    The subject matter disclosed herein relates generally to fuel systems for combustion engines. More particularly, the subject matter disclosed herein relates to systems and methods for draining fuel from a carburetor. 
       BACKGROUND 
       [0002]    Many fuel system problems in mechanical equipment stem from the residual fuel that is left in the carburetor during periods of long storage. In some cases, the fuel polymerizes and forms a hard substance commonly referred to as “varnish” or “gum”. This substance can block the small passages and orifices in the carburetor that are critical to properly metering the air/fuel charge. As a result of these types of blockages, the engine can run poorly or not at all. In addition, light components of the gasoline blend can tend to evaporate, leaving behind a fuel that has a very low vapor pressure, which again can result in the engine being very difficult or impossible to start. Further still, residual fuel in the carburetor can also result in corrosion in the carburetor due to ethanol and water content in the fuel. This corrosion can have the same effect as gum or varnish, blocking or restricting important passages in the carburetor. 
         [0003]    The problem of residual fuel in the carburetor can be attributed in many cases to the fact that most single-cylinder, general-purpose gasoline engines currently use a float carburetor to meter and supply the air-fuel charge to the engine. Typically, the fuel delivery to the carburetor is regulated by a float-actuated needle valve in the carburetor, which maintains the fuel level in the carburetor during operation. When the unit is stored, this valve also continues to maintain the fuel level, supplying additional fuel from the fuel tank as fuel evaporates from the carburetor bowl. This additional supply can be stopped using some form of fuel shutoff valve, which can in some cases be linked to the engine shutoff. 
         [0004]    Even with a fuel shutoff, however, there is often a significant amount of residual fuel remaining in the carburetor when an engine is put into storage, which can lead to many fuel system problems. To address this problem, some manufacturers include a drain in the carburetor, which allows the user to drain the carburetor in preparation for storage. In typical systems, however, a screwdriver, wrench, or other implement is required to open this drain. Additionally, many small engine operators do not understand the importance of draining the fuel, and therefore they do not drain the fuel from the carburetor before storing the engine. 
         [0005]    Accordingly, it would be desirable for residual fuel remaining in the carburetor after engine shutoff to be automatically (or at least easily) drained so as to avoid the problems that can be caused by such residual fuel. 
       SUMMARY 
       [0006]    In accordance with this disclosure, systems and methods for draining fuel from a carburetor are provided. In one aspect, a control assembly for a fuel delivery and recovery system for use with a combustion engine is provided. The control assembly can comprise a first control valve in communication between a fuel source and a fuel chamber of a carburetor, a second control valve in communication between the fuel chamber of the carburetor and a drain reservoir, and an ignition control switch. The first control valve can be movable between an open position in which fuel is able to flow from the fuel source to the fuel chamber and a closed position in which fuel is prevented from flowing from the fuel source to the fuel chamber. The second control valve can be movable between an open position in which fuel is able to flow from the fuel chamber to the drain reservoir and a closed position in which fuel is prevented from flowing from the fuel chamber to the drain reservoir. The ignition control switch can be movable between an “ON” position in which the engine is engaged and an “OFF” position in which the engine is disengaged. The first control valve, the second control valve, and the ignition control switch can be coupled together, such as by mechanical linkage or any other suitable manner, such that the second control valve is in its closed position and the first control valve is in its open position when the ignition control switch is in its “ON” position, and the second control valve is in its open position and the first control valve is in its closed position when the ignition control switch is in its “OFF” position. 
         [0007]    In another aspect, a fuel delivery and recovery system for use with a combustion engine is provided. The system can comprise a fuel source, a carburetor comprising a fuel chamber in communication with the fuel source for receiving liquid fuel from the fuel source, a first control valve in communication between the fuel source and the carburetor, a drain reservoir connected to the fuel chamber, the fuel source, and a vacuum source, and a second control valve in communication between the fuel chamber of the carburetor and the drain reservoir. The first control valve and the second control valve can be coupled together such that when the first control valve is in a closed position in which fuel is prevented from flowing from the fuel source to the carburetor. Conversely the second control valve can be in a closed position in which fuel is prevented from flowing from the fuel chamber to the drain reservoir when the first control valve is in an open position in which fuel is able to flow from the fuel source to the carburetor. In addition, the vacuum source can be operable to reduce the air pressure in the drain reservoir to be less than an air pressure in the fuel chamber, whereby when the second control valve is in its open position, fuel flows from the fuel chamber to the drain reservoir. 
         [0008]    In yet another aspect, a method for recovering unused fuel in a fuel delivery system for a combustion engine is provided. The method can comprise reducing air pressure in a drain reservoir to be less than an air pressure in a fuel chamber of a carburetor during operation of the engine, and, upon disengagement of the engine, blocking a supply of fuel to the fuel chamber and connecting the drain reservoir to the fuel chamber to draw liquid fuel from the fuel chamber into the drain reservoir. 
         [0009]    Although some of the aspects of the subject matter disclosed herein have been stated hereinabove, and which are achieved in whole or in part by the presently disclosed subject matter, other aspects will become evident as the description proceeds when taken in connection with the accompanying drawings as best described hereinbelow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The features and advantages of the present subject matter will be more readily understood from the following detailed description which should be read in conjunction with the accompanying drawings that are given merely by way of explanatory and non-limiting example, and in which: 
           [0011]      FIG. 1A  is a schematic view of a fuel delivery and recovery system for use with a combustion engine in a first operating position according to an embodiment of the presently disclosed subject matter; 
           [0012]      FIGS. 1B and 1C  are schematic views of a fuel delivery and recovery system for use with a combustion engine in a second operating position according to an embodiment of the presently disclosed subject matter; and 
           [0013]      FIG. 2  is a side cutaway view of a carburetor of a combustion engine configured for connection to a fuel delivery and recovery system according to an embodiment of the presently disclosed subject matter. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    The present subject matter provides systems and methods for draining fuel from a carburetor. In one aspect shown in  FIGS. 1A through 2 , for example, the present subject matter provides a system, generally designated  100 , for draining fuel from a carburetor  102 . Carburetor  102  can be connected to a fuel source that can supply fuel to carburetor  102 . For instance, carburetor  102  can be connected to a fuel tank  120  through a fuel feed line  110 . Fuel supplied to carburetor  102  from fuel tank  120  can be introduced and stored in a fuel chamber  104  (e.g., a float chamber as shown in  FIG. 2 ) until it is supplied into the engine air stream. As noted above, the fuel delivery to carburetor  102  can be regulated by a float-actuated needle valve or by some other metering and delivery system known to those having skill in the art. 
         [0015]    Contrary to typical systems, however, when it is desired to remove residual fuel from fuel chamber  104  of carburetor  102  (e.g., after engine shutdown), the residual fuel can be drawn out of a fuel drain  106  in carburetor  102  and to a fuel return line  112  that directs the fuel back towards fuel tank  120 . Specifically, fuel return line  112  can be connected to a drain reservoir  130 . Fuel that is collected in drain reservoir  130  can subsequently be supplied back to fuel tank  120 , such as through a drain connection line  132 . In addition, a first one-way valve  134  (i.e., a check valve) can be positioned along drain connection line  132  to ensure that fuel is only able to flow from drain reservoir  130  into fuel tank  120 . 
         [0016]    To control the flow of fuel from carburetor  102  to drain reservoir  130 , the pressure within drain reservoir  130  can be controlled to be less than the pressure in fuel chamber  104  of carburetor  102 , which is usually substantially equivalent to atmospheric pressure. This pressure control can be accomplished by connecting drain reservoir  130  to a vacuum source. 
         [0017]    Specifically, drain reservoir  130  can be connected to a reduced pressure environment that can exist in portions of the engine intake tract (e.g., partial vacuum established at the carburetor outlet/engine intake manifold). As shown in  FIGS. 1A through 2 , for example, drain reservoir  130  can be connected by a pressurization line  114  to an outlet region  108  of carburetor  102  or that exhibits a reduced pressure atmosphere during operation of the engine and is thus a vacuum source. Alternatively, drain reservoir  130  can be connected to any other source of low pressure, such as an intake port or any other suitable source. 
         [0018]    The system can further include a second one-way valve  136  in parallel with a small orifice  138  along pressurization line  114 . Second one-way valve  136  can allow drain reservoir  130  to attain a lower pressure than the average value of the pulsating intake port vacuum signal. Additionally, it can retain the “negative” pressure for some time after the engine is shut off. Orifice  138  can allow drain reservoir  130  to eventually return to atmospheric pressure after the engine is shut off so that the fuel can drain back into fuel tank  120  instead of accumulating in drain reservoir  130 . 
         [0019]    In the arrangement described above and shown in  FIGS. 1A through 1C , the system  100  can operate to use the engine vacuum to “charge” drain reservoir  130  to a “negative” pressure (i.e., reduced relative to atmospheric pressure) while the engine is running. After the engine is shut down, the negative pressure in drain reservoir  130  can be used to evacuate at least some of the fuel in the fuel chamber  104  of carburetor  102 . Once removed from carburetor  102 , the fuel can eventually be drained back into fuel tank  120 . For example, drain reservoir  130  can be positioned above fuel tank  120  such that any fuel collected in drain reservoir  130  can largely be moved into fuel tank  120  by gravity alone. 
         [0020]    System  100  can be made substantially autonomous using a control assembly  140  that can couple two valves for simultaneous actuation: a first control valve  142  being positioned along fuel feed line  110  for controlling the carburetor fuel supply passage shutoff, and a second control valve  144  positioned along fuel return line  112  for controlling the fuel drain passage shutoff. The actuation of first control valve  142  and second control valve  144  can be coupled and operable such that the valves are opened in a mutually exclusive manner. In other words, the operation of first control valve  142  and second control valve  144  can be coupled such that second control valve  144  is in its open position when first control valve  142  is in its closed position, and conversely first control valve  142  is in its open position when second control valve  144  is in its closed position. 
         [0021]    Specifically, during operation of the engine, control assembly  140  can be configured as shown in  FIG. 1A  such that first control valve  142  is in an “open” position, whereby fuel is permitted to flow from fuel tank  120  through fuel feed line  110  to carburetor  102 . Concurrently, second control valve  144  can be in a “closed” position, whereby fuel is prevented from flowing from carburetor  102  through fuel return line  112  to drain reservoir  130 . Although flow along fuel return line  112  is prevented, the connection of drain reservoir  130  to outlet portion  108  of carburetor  102  can remain open, thereby reducing the pressure in drain reservoir  130 . It should be noted that because of first one-way valve  134 , the reduced pressure environment created in drain reservoir  130  prevents fuel from being drawn from fuel tank  120  into drain reservoir  130 . 
         [0022]    When the engine is stopped, control assembly  140  can be configured as shown in  FIGS. 1B and 1C  such that first control valve  142  is in a “closed” position, whereby fuel flow from fuel tank  120  to carburetor  102  is stopped, and second control valve  144  is in an “open” position, whereby fuel can flow out of fuel chamber  104  of carburetor  102  (e.g., through fuel drain  106 ) through fuel return line  112  to drain reservoir  130 . Because of the reduced pressure environment that is developed in drain reservoir  130  during the operation of the engine, fuel can be drawn from fuel chamber  104  into drain reservoir  130  as shown in  FIG. 1B , substantially emptying fuel chamber  104  of any residual fuel. 
         [0023]    Further, because operation of the engine is stopped in this arrangement, the partial vacuum developed in the engine intake tract will eventually diminish (i.e., pressure will increase back towards atmospheric pressure). As a result, the connection of drain reservoir  130  to carburetor  102  via pressurization line  114  stops acting to reduce the pressure in drain reservoir  130 . Accordingly, if a pressure release mechanism is provided, the pressure in drain reservoir  130  can equalize with the pressure in fuel tank  120 . For example, as discussed above, orifice  138  can operate to equalize the pressure in drain reservoir  130  with the pressure in outlet portion  108 . During operation of the engine, equalization of these pressures results in the air pressure in drain reservoir  130  being reduced to be at or near the partial vacuum established at outlet portion  108 . When engine operation is discontinued, however, the pressure at outlet portion  108  will tend to gradually increase towards atmospheric pressure, and thus the pressure equalization effected by orifice  138  can allow the pressure in drain reservoir  130  to likewise gradually return to atmospheric pressure. Once the pressure in drain reservoir  130  is sufficiently increased such that there is substantially no pressure differential between drain reservoir  130  and fuel tank  120 , fuel can flow through first one-way valve  134  into fuel tank  120 . 
         [0024]    In addition, the operation of first control valve  142  and second control valve  144  can further be linked to an ignition control switch  146  used to control the ignition kill. Specifically, when ignition control switch  146  is in an “ON” position (See, e.g.,  FIG. 1A ) in which the engine is engaged, first control valve  142  is in an open position and second control valve  144  is in a closed position. When ignition control switch  146  is moved to an “OFF” position (See, e.g.,  FIGS. 1B and 1C ), thereby stopping operation of the engine, first control valve  142  can be moved to a closed position and second control valve  144  can be moved to an open position. In this way, as discussed above, the flow path from fuel tank  120  to carburetor  102  can be open only during operation of the engine, and the fuel path from carburetor  102  to drain reservoir  130  can be open only upon the disengagement of the engine. As a result, control assembly  140  can operate to allow the normal supply of fuel to carburetor  102  during operation of the engine, but upon disengagement of the engine, fuel chamber  104  of carburetor  102  can be automatically drained, thereby helping to avoid the problems that can be caused by residual fuel. 
         [0025]    The present subject matter can be embodied in other forms without departure from the spirit and essential characteristics thereof. The embodiments described therefore are to be considered in all respects as illustrative and not restrictive. Although the present subject matter has been described in terms of certain preferred embodiments, other embodiments that are apparent to those of ordinary skill in the art are also within the scope of the present subject matter.