Abstract:
A carburetor with a manual priming pump having an integrated fuel drain which provides both the engine manufacturer and end user with an easy way to drain fuel from a fuel chamber of the carburetor. The priming pump has a pump chamber defined by a resilient priming bulb. The pump chamber generally communicates between the fuel chamber and a fuel-and-air mixing passage of the carburetor body and is preferably positioned above the fuel chamber. The dual function of the manual priming pump, prime or drain, is switched by a valve with a rotatable selector member received between a seat and the resilient priming bulb of the pump. The selector member moves between a drain position and a priming position thus enabling draining of the fuel chamber or priming of the carburetor via successive manual depressions of the priming bulb.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to a carburetor for a combustion engine and more particularly to a carburetor having a priming pump with an integral fuel bowl drain.  
         BACKGROUND OF THE INVENTION  
         [0002]    Carburetors, especially those found on small engines such as garden equipment, small outboard motors and utility engines commonly have a primer, which is used to supply fuel from the carburetor to the engine prior to starting the engine, and a bowl drain which is a valve or tube used to drain the fuel from the carburetor bowl. The bowl drain is independent or separate from the primer and is required to drain the bowl of fuel for shipping, maintenance, and engine storage purposes. Two common primer types are a liquid fuel primer and an air pressure primer. The liquid fuel primer injects or pumps a quantity of liquid fuel from the carburetor bowl into the engine intake manifold. The air pressure primer pumps a quantity of air into the space existing above the level of fuel within the carburetor bowl. This air momentarily pressurizes the air space thus forcing some of the liquid fuel from the bowl through the carburetor main nozzle and into the engine intake manifold.  
           [0003]    The liquid fuel primer is more expensive than the air pressure primer however it is preferable for larger engines, cold weather applications, and more experienced operators. Directly injecting liquid fuel requires less actuations of the priming bulb for a given quantity of fuel than the air primer. Also with direct fuel injection, the fuel can be placed more accurately into a given area of the carburetor or engine intake. The less expensive air pressure primer has a greater margin of error on the number of depressions or primes, but it still works well on small engines used primarily in warm weather, such as a walk behind lawn mower.  
           [0004]    One common type of bowl drain has a fitting normally attached near the top of the carburetor that is connected to a tube extending to the bottom of the carburetor bowl and is normally used by the engine or equipment manufacturer to evacuate the fuel from the bowl of the carburetor after initial testing of the engine at the factory prior to shipment. This is accomplished by putting a suction hose on the fitting and drawing the fuel from the bowl. The fitting is then sealed to prevent contaminants from entering the bowl. This type of bowl drain is ideal for a manufacturing environment having an adequate suction source, because the bowl can be drained in a few seconds as opposed to the much slower gravity drain. Unfortunately, this type of tube bowl drain is of little use to the end user for draining the bowl since the end user seldom has the right size hose and a vacuum source suitable for drawing gasoline from the bowl. A second typical bowl drain has a manually operated valve at or near the bottom of the carburetor bowl which when opened allows the fuel to drain via gravity from the bowl. This second or valve-type of bowl drain is much better suited to the end user of the equipment, but can be inadvertently left open resulting in fuel spill and the inability to start the engine until the valve is manually closed. Moreover, the valve-type of bowl drain requires extra parts leading to higher manufacturing costs.  
         SUMMARY OF THE INVENTION  
         [0005]    This invention provides a carburetor with a manual priming pump having an integrated carburetor fuel drain which provides both the engine manufacturer and end user with an easy way to drain fuel from a fuel chamber of the carburetor. The priming pump has a pump chamber defined by a resilient priming bulb. The pump chamber generally communicates between the fuel chamber and a fuel-and-air mixing passage of the carburetor body and is preferably positioned above the fuel chamber. The dual function of the manual priming pump, prime or drain, is switched by a valve with a rotating member engaged sealably between a seat and the resilient priming bulb of the pump. The member moves between a drain position and a priming position thus enabling draining of the fuel chamber or priming of the carburetor via successive manual depressions of the priming bulb.  
           [0006]    The member is preferably a rotating disk having a drain fuel-in orifice and a drain fuel-out orifice which when the member is in the drain position align respectively to a fuel draw passage and a fuel drain passage both preferably defined in-part by the carburetor body. The fuel draw passage communicates with the fuel chamber and the fuel drain passage communicates with the environment external to the carburetor. Both passages communicate with the pump chamber when the member is in the drain position, but only the fuel draw passage communicates with the pump chamber when the member is in the priming position. The priming pump may be of either the liquid fuel direct injection or the air pressure type. Either type can be mounted directly on the carburetor body or remotely, such as on an air filter or an engine housing.  
           [0007]    Objects, features and advantages of this invention include providing a carburetor priming pump which is also capable of draining the carburetor fuel bowl. The novel priming pump simplifies draining of the fuel bowl for the end user. The invention provides an extremely compact construction and arrangement, a relatively simple design, extremely low cost when mass produced and is rugged, durable, reliable, requires little to no maintenance and in service has a long useful life. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    These and other objects, features and advantages of this invention will be apparent from the following detailed description, appended claims and accompanying drawings in which:  
         [0009]    [0009]FIG. 1 is a perspective view of a carburetor having a fuel priming pump of the present invention;  
         [0010]    [0010]FIG. 2 is an exploded perspective view of the fuel priming pump;  
         [0011]    [0011]FIG. 3 is an end view of the carburetor taken in the direction of arrow  3  of FIG. 1 with parts broken away and in a section to show internal detail;  
         [0012]    [0012]FIG. 4 is a perspective view of the carburetor with parts broken away in a section taken generally along line  4 - 4  of FIG. 1 to show internal detail;  
         [0013]    [0013]FIG. 5 is a perspective view of the carburetor taken in the direction of arrow  5  of FIG. 1 with parts broken away and in section to show internal detail;  
         [0014]    [0014]FIG. 6 is a fragmentary side view of the carburetor with parts removed and showing a selector disc in a priming position;  
         [0015]    [0015]FIG. 7 is a fragmentary side view of the carburetor of FIG. 6 showing the selector disc in a drain position;  
         [0016]    [0016]FIG. 8 is a perspective view with portions broken away and in section of a second embodiment of a carburetor of the present invention;  
         [0017]    [0017]FIG. 9 is a fragmentary perspective view of the second embodiment of the carburetor showing a selector disc in a priming position and with parts of the priming pump removed to show internal detail;  
         [0018]    [0018]FIG. 10 is a fragmentary perspective view of the carburetor of the second embodiment showing the selector disc in a drain position;  
         [0019]    [0019]FIG. 11 is an enlarged perspective view with portions broken away and in section of a vent check taken from FIG. 8;  
         [0020]    [0020]FIG. 12 is an enlarged perspective view with portions broken axially and in section of a modified check valve; and  
         [0021]    [0021]FIG. 13 is an exploded perspective view of a modification of the carburetor showing a priming pump mounted on an air cleaner. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    Referring in more detail to the drawings, FIGS. 1, 2 and  3  illustrate a carburetor  10  for a combustion engine (not shown) embodying this invention. In operation, air enters an inlet  22  of a fuel-and-air mixing passage  14  defined by a carburetor body  16  of the carburetor  10 . Fuel enters the fuel-and-air mixing passage  14  via a main fuel feed passage  18  having a nozzle disposed in the region of a venturi  20  within the passage  14 . The fuel mixes with the air and exits the carburetor  10  at an outlet  12  of the fuel-and-air mixing passage  14  where the mixture then flows into an engine combustion chamber (not shown). Fuel enters the main fuel feed passage  18  from a fuel chamber  26  of the carburetor  10  defined by a fuel bowl  24  engaged sealably to the underside of the carburetor body  16 , and preferably with a sealing gasket there-between. During normal running conditions of the combustion engine, the fuel-and-air mixing passage is at sub-atmospheric pressure and the fuel chamber  26  is near atmospheric pressure. Fuel is thus forced to flow up through the nozzle of the main fuel feed passage  18  and into the fuel-and-air mixing passage  14 . When the engine is not running, for example, before attempting to start the engine, a vacuum does not exist within the fuel-and-air mixing passage  14  and an alternative means must be provided to supply fuel to the combustion chamber. A manual priming pump  28  is one such alternative means and is engaged to the carburetor body  16  via a plurality of threaded fasteners  30 .  
         [0023]    The priming pump  28  has a resilient priming bulb  32  which defines a pump chamber  34 . In preparation for starting of the engine, manual operation of the priming pump  28  is achieved by depressing the priming bulb  32  with a force greater than its own resilience. Release of the bulb  32  will cause it to return, or unflex, to its natural state, causing fuel and/or air to flow through a series of passages and check valves. This flow assures that necessary fuel enters the fuel-and-air mixing passage  14  for starting of the engine. To induce flow, a sub-atmospheric pressure or suction is applied to these passages via the bulb  32  which is leak tight relative to the carburetor body  16 , as best shown in FIG. 3. To accomplish this seal, a circumferential lip  36  of the bulb  32  substantially projects laterally outward along the bulb&#39;s perimeter or distal edge, and is sealably press fitted into a circumferential groove  37  of an encasement  38  which engages the carburetor body  16 . The groove  37  is defined by the encasement  38  and communicates radially inward toward the pump chamber  34 . The encasement  38  is secured to the carburetor body  16  by the threaded fasteners or bolts  30 .  
         [0024]    Referring to FIG. 2, integrated into the priming pump  28  is the ability to drain the fuel bowl  24  of fuel without the utilization of a local gravity drain valve or the use of external siphoning equipment. Sandwiched between the encasement  28  and the carburetor body  16  is a planar member or selector disc  40 . Disc  40  has a tab  42  which projects through a slot  44  defined by the encasement  38 . The disc  40  is moved rotatably, or positioned, via manually grasping the protruding tab  42 . A series of orifices communicating axially through the disc  40  align or mis-align with various passages depending on the position of the disc  40 . One such passage and orifice alignment will function to prime the carburetor  10  for engine starting when bulb  32  is repeatably depressed and is identified as the prime position  48 , as best shown in FIG. 6. And, another passage and orifice alignment will function to drain the fuel chamber  26  by depressing the same bulb  32  and is identified as the drain position  46 , as best shown in FIG. 7. Referring to FIG. 1, when tab  42  is in the lower position, or nearest the fuel bowl  24 , the disk  40  is in the drain position  46 , and when the tab  42  is positioned upward, it is in the prime position  48 .  
         [0025]    The encasement  38  has a substantially planar midsection  50  disposed parallel to an exterior mating surface or seat  52  of the priming pump  28  and defined by the carburetor body  16 . The planar member or disc  40  is substantially of a consistent thickness and is disposed between the seat  52  of the priming pump  28  and the planar midsection  50  of the encasement  38 . Projecting axially inward from the midsection  50  of the encasement  38  is a cylindrical or circumferential wall  54  which has a distal edge  56  that engages the perimeter of the seat  52  defined by the carburetor body  16 . Projecting axially outwardly is a second cylindrical or circumferential wall  58  wherein the groove  37  which receives the lip  36  of the priming bulb  32  is formed. The pump chamber  34  is ultimately defined by the priming bulb  32 , the second circumferential wall  58  and an outward surface of the planar midsection  50 .  
         [0026]    To stabilize or enhance rotation of the disc  40 , a pin or shaft  62  concentrically extends through and unitarily engages the disc  40 . The shaft  62  rotatably fits within a bore  64  defined by the seat  52  or the carburetor body  16  at one end, and a bore  66  defined by the encasement  38  on the outward side of the disc  40  at the other end. The disc  40  has an inward side  68  and an opposite outward side  70 . The inward side  68  slideably and sealably engages against an inward gasket  72  disposed between the seat  52  and the disc  40 . Likewise, an outward gasket  74  reduces friction and seals between the outward side  70  of the disc  40  and the encasement  38 . The inward and outward gaskets  72 ,  74  are disposed radially inward from the circumferential wall  54  of the encasement  38 . The inward and outward gaskets  72 ,  74  are substantially identical to one-another, both being annular in shape and having a pattern of holes  75  which align with various passages communicating through the seat  52  defined by the carburetor  16 . Likewise, the planar midsection  50  of the encasement  38  will have the same pattern of holes  75 . As the disc  40  rotates relative to the adjacent gaskets  72 ,  74 , a series of orifices  77 , axially penetrating the disc  40 , will align or misalign with the designated holes  75  thereby allowing the associated passages to communicate with the pump chamber  34  or be obstructed from doing so.  
         [0027]    Referring to FIGS. 2, 4 and  7 , when disc  40  is rotated to the drain position  46 , a drain fuel-in orifice  76 , extending axially through the disc  40 , aligns with a fuel draw passage  78  defined by the carburetor body  16 . The fuel draw passage  78  extends from a lower portion  80  of the fuel chamber  26  to and through the seat  52 . Similarly, a drain fuel-out orifice  82  through the disc  40  communicates with a drain passage  84  defined by the carburetor body  16  which extends between a tube or nozzle  86  disposed externally to the carburetor body  16  and through the seat  52 . When operating the priming pump  28  in drain position  46 , the resilient priming bulb  32  is manually depressed or flexed, causing fuel to flow through a check valve  87  disposed in the drain passage  84  and located near or flush with the seat  52  of the carburetor body  16 . The fuel then flows out of the carburetor  10  through the external tube  86 . When the priming bulb  32  is released, the resilience of the bulb  32  causes it to return outwardly, or unflex, to a natural or preformed state, thereby producing a vacuum within the pump chamber  34  causing fuel to flow through the fuel draw passage  78  and through a check valve  88  disposed therein. This manual process must be repeated until the fuel bowl  24  is completely drained of fuel unless the tube  86  extends below the lower portion  80  of the fuel chamber  26 . If tube  86  does so extend below the bottom  80 , a desirable siphoning action will be created by the initial depression(s) of bulb  32  causing the fuel to drain continuously until depleted.  
         [0028]    Referring to FIG. 6, when the priming pump  28  is in the priming position  48 , the drain fuel-in orifice  76  and the drain fuel-out orifice  82  in the disc  40  are misaligned to the respective fuel draw passage  78  and drain passage  84 . Consequently, the drain passage  84  is cut-off, obstructed, or isolated from the pump chamber  34  by the disk  40 . However, the fuel draw passage  78  is not obstructed when the priming pump  28  is in the priming position  18  because a second or prime fuel-in orifice  90 , communicating axially through the disc  40 , becomes aligned with the fuel draw passage  78 . Likewise, a fuel prime orifice  92  in the disc  40  is aligned with a fuel prime passage  94  defined by the carburetor body  16 .  
         [0029]    Referring to FIG. 4, the fuel prime passage  94  is in communication with the fuel-and-air mixing passage  14  via a port  97  disposed substantially near the venturi  20  and between the inlet  12  and venturi  20 . So that fuel may only flow from the pump chamber  34  to the fuel-and-air mixing passage  14 , a spring loaded check valve  96  is disposed within the fuel prime passage  94  substantially flush to the seat  52 . Depressing the bulb  32  will cause fuel located within the pump chamber  34  to flow out past the check valve  96  through the fuel prime passage  94  and into the fuel-and-air mixing passage  14 , thereby priming the carburetor  10 . Release of the bulb  32  will cause the bulb to expand, or unflex, and return to its preformed shape creating a vacuum which causes fuel to flow from the fuel chamber  26 , through the fuel draw passage  78 , and into the pump chamber  34 .  
         [0030]    Referring to FIGS.  8 - 11 , a second embodiment of the carburetor  10 ′ of the present invention is shown. In this embodiment, the disc  40 ′ has a drain position  46 ′ oriented similarly to the first embodiment, however, a priming position  48 ′ has an orientation different than the first embodiment. In the second embodiment, when the disc  40 ′ is in the priming position  48 ′, fuel no longer flows through the fuel passage  94  of the first embodiment, instead, the fuel flows through a main feed passage  18 ′, as best shown in FIG. 5, by pressurizing an upper air dome portion  100  of the fuel chamber  26 ′.  
         [0031]    Under normal running conditions, the fuel chamber  26 ′ is under near atmospheric pressure conditions via a vent passage  102  which extends from the upper air dome portion  100  of the fuel chamber  26 ′ to a biased normally closed vent check valve  104  disposed near the inlet  22 ′ of the fuel-and-air mixing passage  14 ′. During running conditions of the engine, fuel flows out of the fuel chamber  26 ′ via the main feed passage  18 ′. Also, when the engine is running, the vibration or shaking forces produced by the operating engine cause a ball  109  of the vent check valve  104  to dance or move in a counterbore  114  and away from a ball seat  110  against a biasing force of coil spring  112  so that the passage  102  communicates with the atmosphere through the orifice  117 . The ball seat  110  is slideably received in the open end of a tubular body  113  with a closed end  116  having a port  115  communicating with the vent passage  102 . Preferably the body  113  is press fit in a counterbore  114  in the carburetor body at the end of the vent passage  102 . The bore  114  of the tubular body has a larger inside diameter than the outside diameter of the ball to permit fluid to pass between them. The ball seat  110  is press fit in the body  13  and has a vent orifice  117 . When the vent check valve ball  109  moves away from the seat  110  within the bore  114 , the spring  112  compresses axially against the end  116 . When the engine is not running, the ball  109  of the vent check valve  104  is forced back against the ball seat  110  by the spring  112 , thereby closing or blocking off the vent orifice  117 .  
         [0032]    An air prime passage  106  communicates between the vent passage  102  and the pump chamber  34 ′, and through the seat  52 ′. When the disc  40 ′ is in the priming position  48 ′, as best shown in FIG. 9, an air prime orifice  108  of the disc  40 ′ aligns with the air prime passage  106 , and amounts to the only communication from the pump chamber  34 ′ through the disc  40 ′ when in the priming position  48 ′. In operation, depressing the bulb  32 ′ will cause air to flow through the air prime passage  106  and into the vent passage  102  with all of the air flowing into the upper air dome portion  100  of the fuel chamber  26 ′ because the vent check valve  104  is closed. This creates a sufficient pressure surge, within the fuel chamber  26 ′ so that fuel flows upward through the fuel feed passage  18 ′ and into the fuel-and-air mixing passage  14 ′, as best shown in FIG. 5. If the cross section of the vent orifice  117  is substantially smaller than the flow cross section of the vent passage  102  and smaller than the flow cross section of the air prime passage  106 , the ball  109  and the spring  112  of the vent check valve  104  are not absolutely necessary for the priming pump  28 ′ to work. This is so because only a small amount of air will escape through the vent orifice  117  while the majority enters and pressurizes the air dome portion  100  of the fuel chamber  26 ′.  
         [0033]    [0033]FIG. 12 illustrates an alternative check valve  104 ′ which may be used in lieu of check valve  104 . The ball  109  of the check valve  104 ′ is freely movable between the seat  110  and the end wall  116 ′ of its body  113 ′ and the end wall has a plurality of radially and circumferentially spaced-apart ports  115 ′ which communicate with the vent passage  102  when the body  113 ′ is press fit therein. The clearance between the bore  114 ′ and the ball  109  and the mass of the ball is sized and calibrated so that regardless of the orientation of the check valve  104 ′, the pressure pulses produced in the passage  102  by pressing the pump bulb  32  force the ball  109  onto its seat  110  to close the vent passage  117  and the sub-atmospheric pressure produced by release of the bulb  32  produces an in-rush of air through the orifice  117  which unseats the ball  109  so that incoming air flows around the ball and into the passage  102 . When the engine starts, the vibration or shaking forces produced by the operating engine cause the ball  109  to dance or move in the bore  114 ′ away from the seat  110  so that the passage  102  communicates with the atmosphere through the orifice  117 . The construction of check valve  104 ′ eliminates the need for any compression spring  112  and ensures that the ball  109  will be unseated so that the vent passage  102  communicates with the atmosphere while the engine is operating.  
         [0034]    The clearance between the ball  109  and the bore  114 , and the mass or weight of the ball can be readily designed so that even if the valve assembly  104 ′ is oriented with its axis extending vertically and the seat  110  is at the upper end, the ball  109  will be moved upward and bear on its seat  110  due to the force of air acting on and moving past the ball produced by depressing the pump bulb  32 . Conversely, even if the valve assembly  104 ′ is oriented with its axis extending vertically and the seat  110  at the lower end with the ball resting thereon, the ball will be moved upward away from the seat to open the valve by the force of incoming air through the vent  117  produced by release of the pump bulb  32 . In all orientations, when the engine is running, the vibration or shaking forces of the engine will keep the ball  109  unseated so that it will not inhibit communication of the passage  102  with the external atmosphere and the normal function of the bowl drain. Preferably, the valve assembly  104 ′ is oriented so that in the normal resting orientation of the carburetor, when the engine is not operating, the ball  109  will bear on the seat  110  to further reduce diurnal vapor emission.  
         [0035]    As best shown in FIG. 13, a modification of the present invention has the priming pump  28 ″ mounted, remote from the carburetor body  16 ″, and onto an air cleaner housing  120 . Depending upon the engine application, this orientation may be preferred if the carburetor body  16 ″ is not readily accessible to the end user. A series of tubes  122  are supported between the air cleaner housing  120  and a flange  124  which fasten to the carburetor body  16 ″. The seat  52 ″ (not shown) is not defined by the carburetor body  16 ″ as it is for the first and second embodiments. Instead, the seat  52 ″ is defined by the air cleaner housing  120  or an additional section of the encasement  38 ″.  
         [0036]    While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. For instance, the carburetor body  16  may include all the features of the first and second embodiments. That is, a carburetor body can include the air prime passage  106  specific to the second embodiment and the fuel prime passage  94  specific to the first embodiment. The priming pump  28 ′ can be provided as a kit assembly wherein the disc  40  of the first embodiment and the disc  40 ′ of the second embodiment along with the associated gaskets are both provided within the kit. The choice of an air priming pump  28 ′ or a fuel priming pump  28  is then left to the end carburetor assembler who is supplied with the generic carburetor body and the kit.  
         [0037]    Alternatively, the end carburetor assembler may be supplied with the generic carburetor body, and either the disc  40  or  40 ′ depending on the desired end use of the carburetor. It is not intended herein to mention all the possible equivalent forms or ramification of the invention. It is understood that terms used herein are merely descriptive, rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.