Abstract:
A carburetor throttle valve actuation assembly for a combustion engine is readily adapted for use as a remote control actuator, a local control throttle actuator, or both together providing an optional choice for the end user. The carburetor has a throttle valve having a shaft journaled to a body for movement about a rotation axis. A slave lever connects rigidly to a distal end of the shaft projecting outward from the body. A connection spaced radially outward from the axis engages the slave lever to a radially projecting swivel member of a local, manually operated, throttle valve actuation assembly. The swivel member rotates in unison with the slave lever about the axis, is spaced axially outward from the shaft and is journaled to a bracket engaged rigidly to the body. Preferably, the connection has a hole in the slave lever. If the remote throttle control actuator is used, a Bowden wire engages to a pin projecting axially outward from the slave lever at the hole. If the local throttle control actuator is used either a cylindrical void carried by the swivel member mates to the pin, or a peg projecting outward from the swivel member and toward the body is inserted into the hole forming the connection that permits axial movement of the slave lever with respect to the swivel member.

Description:
REFERENCE TO RELATED APPLICATION 
     Applicants claim priority of Japanese Application No. 2005-013570, filed Jan. 21, 2005. 
     TECHNICAL FIELD 
     The present invention relates to a throttle valve arrangement for a carburetor and more particularly to a remote and local dual actuating throttle valve arrangement. 
     BACKGROUND OF THE INVENTION 
     In a conventional carburetor, a mixing passage through a body of the carburetor mixes and flows a controlled mixture of fuel-and-air into a combustion engine. For controlling the speed of the engine, a rotating throttle valve of a rotary or butterfly type intersects the mixing passage to restrict the volume of fuel-and-air flow to the engine. 
     A rotary throttle valve is generally a cylinder that seats rotatably and is movable axially, within a cylindrical cavity that intersects the mixing passage. The rotary throttle valve has a through-bore that adjustably aligns with the mixing passage to control flow. A needle of the cylinder projects downward into the through-bore and axially movably into an opposing fuel feed tube of the body to adjustably obstruct an orifice in a wall of the tube that flows liquid fuel into the through-bore. As the rotary throttle valve rotates toward an open position, the through-bore aligns to the mixing passage to increase flow, and simultaneously, the cylinder lifts axially to partially retract the needle from the tube exposing more of the orifice to the through-bore and thus increasing fuel flow. 
     The butterfly-type throttle valve is generally a pivoting plate disposed in and conforming to the contour of the mixing passage. Like the rotary throttle valve, the butterfly throttle valve controls the amount of fuel-and-air mixture flowing to the engine. Unlike the rotary throttle valve, the butterfly valve does not directly control the amount of liquid fuel entering the air stream. 
     Both the rotary and butterfly throttle valves, however, have a rotating shaft that projects out of the carburetor body. For some engine applications a lever is attached to this shaft and connected to a Bowden wire or other linkage for a user to remotely rotate the throttle valve. For other applications a lever or knob attached to this shaft is manually grasped and rotated to locally actuate the throttle valve. For instance, a leaf blower utilizing a small two stroke engine may only require local actuation of a throttle valve, and a lawn mower application may require remote actuation. 
     The cost of manufacturing a wide array of differing parts dependent upon whether an otherwise identical carburetor is remotely or locally actuated and the cost of two subsequent carburetor assembly lines is expensive and time consuming. Yet further, in some applications, it would be advantageous to have the ability to both remotely and locally actuate a carburetor throttle valve that positively and reliably sets the pre-specified engine speeds. 
     SUMMARY OF THE INVENTION 
     A throttle valve actuation assembly for a combustion engine carburetor is readily adapted for optional assembly as a remote control throttle actuator or a local control throttle actuator, or for combined assembly and operator optional use as both a remote and local control throttle actuator. The carburetor has a throttle valve having a shaft journaled to a body for movement about a rotation axis between idle and wide open positions. A slave lever connects rigidly to a distal end of the shaft projecting outward from the body. A connection spaced radially outward from the rotation axis connects the slave lever to a radially projecting swivel member of a local, manually operated, throttle valve actuator. The swivel member rotates about the axis, is spaced axially outward from the end of the shaft and is journaled to a bracket fixed to the body. Preferably, the connection has a hole in the slave lever. If the remote throttle control actuator is used with or without use of the local actuator, a Bowden wire engages to a slotted pin projecting axially outward from the slave lever at the hole. If the local throttle control actuator is used, either the pin mates to a cylindrical void carried by the swivel member, or a peg projecting outward from the swivel member and toward the body is inserted into the hole forming the connection. 
     Preferably, a circumferential positioning interface is carried between the swivel member and the stationary bracket. A detent follower of the circumferential positioning interface is orientated axially adjacent to the stationary bracket and attaches to the swivel member for unitary rotation. When the local throttle valve actuator is operated, the user positively places the throttle valve in pre-established positions via the circumferential positioning interface without concern for the throttle valve wandering due to engine vibration or unintentional bumping of the local throttle valve actuator. 
     Objects, features, and advantages of this invention include a versatile carburetor capable of being easily and inexpensively interchangeable between a remote and locally actuated throttle valve applications, a base carburetor design requiring fewer parts to meet varying engine applications, a throttle valve that reliably stays in a desired set position without intentional user intervention, and the ability to assemble varying carburetors on the same assembly line with less likelihood of assembly error. Moreover, the throttle valve arrangement is simple in design, robust, allows for easy calibration of rotary-type throttle valves, is durable, rugged and in service has a long and useful life. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a top plan view of a combustion engine carburetor with a throttle valve arrangement embodying the present invention; 
         FIG. 2  is a cross section of the carburetor taken along line  2 — 2  of  FIG. 1 ; 
         FIG. 3  is a perspective view of a local throttle valve actuator of the throttle valve arrangement; 
         FIG. 4  is an exploded perspective view of a slave lever connected to a Bowden wire for remote actuation of a throttle valve of the throttle valve arrangement; 
         FIG. 5  is an exploded perspective view of a modified local throttle valve actuator connected to a slave lever that is also connected to the Bowden wire for both local and remote actuation of the throttle valve of the throttle valve arrangement; 
         FIG. 6  is a top plan view of the carburetor with the throttle valve in a idle position and illustrating a detent follower that provides resistance against rotation for holding the throttle valve in an idle position; 
         FIG. 7  is a top plan view of the carburetor of  FIG. 6  except illustrating the throttle valve in a partially open position; 
         FIG. 8  is a top plan view of the carburetor of  FIG. 6  except illustrating the throttle valve in a wide open throttle position; 
         FIG. 9  is a cross section of the detent follower taken along line  9 — 9  of  FIG. 6 ; 
         FIG. 10  is a top plan view of the carburetor illustrating a modified detent follower that provides resistance against rotation of the throttle valve and showing the throttle valve in the wide open throttle position; and 
         FIG. 11  is a cross section of the detent follower taken along line  11 — 11  of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 and 2  illustrate a combustion engine carburetor  20  with a throttle valve arrangement  22  of the present invention. A throttle valve  23  of the throttle valve arrangement  22  is preferably a rotary-type commonly used with smaller two stroke engine applications, such as hedge trimmers and leaf blowers that typically require only a closed throttle position  24  ( FIG. 6 ), designating an engine shut-off or slow idle position, and a wide open throttle position  26  ( FIG. 8 ), designating maximum engine speed or power. One skilled in the art, however, could apply any type of throttle valve to the throttle valve arrangement  22  including the known butterfly-type which typically has a valve plate in the mixing passage  34  attached to a rotatable shaft extending transverse across the mixing passage. The carburetor  20  can also be applied to four stroke engines and applications having intermediate throttle valve position(s)  28  ( FIG. 7 ) for adjusting engine speed and power output. 
     The throttle valve  23  has a generally cylindrical throttle  30  (see  FIG. 2 ) rotatably received in a cylindrical cavity  32  of a body  33  that intersects a fuel-and-air mixing passage  34  through the body  33 . The rotary throttle  30  rotates about an axis  36  and is operatively moveable axially or vertically within the cylindrical cavity  32  as it moves between the closed or idle position  24  and the wide open throttle position  26 . A throttling bore  38  extends transversely through the rotary throttle  30  and communicates operatively with the fuel-and-air mixing passage  34 . The throttling bore  38  is substantially perpendicular to the axis  36  and aligns so that when the carburetor  20  is in the wide open throttle position  26  the throttling bore  38  is in substantially full communication with the fuel-and-air mixing passage  34 . 
     During assembly, the rotary throttle  30  preferably is inserted into the cylindrical cavity  32  from above, then a retaining cover  40  is secured and sealed to the body over the cavity  32 . The rotary throttle  30  moves vertically to control the amount of liquid fuel entering the throttling bore  38  and the fuel-and-air mixing passage  34  from a side orifice  42  of a fuel feed tube  44 . The feed tube  44  is located concentrically to the axis  36  and projects upward from a fuel supply and metering system  46  of the carburetor  20 . A downward projecting needle  48  of the rotary throttle valve  23  is attached to the rotary throttle  30  and moves vertically within the fuel feed tube  44  to adjustably obstruct the orifice  42  and thus adjust fuel flow. At wide open throttle position  26 , the distal end of the needle  48  typically is located above the orifice  42  and generally does not obstruct fuel flow into the throttling bore  38 . At the closed position  24 , preferably the needle  48  is fully inserted into the feed tube  44  and obstructs all, or nearly all, fuel flow through the orifice  42 , thus preferably acting as an engine shut down feature for at least small engine applications. For other engine applications at the idle position  24  the needle  48  greatly reduces the fuel flow rate to that needed for proper idling of the operating engine. 
     A cam relationship  50  between a substantially annular bottom face of the rotary throttle  30  and a substantially annular bottom of the cylindrical cavity  32  causes the rotary throttle  30  and needle  48  to move vertically when it rotates about the axis  36 . The annular bottom forms a cam follower carried by the body  33  and the annular bottom face of the rotary throttle  30  is a cam surface. Since the rotary throttle  30  moves axially, the axial length of the cylindrical cavity  32  is generally greater than the axial length of the rotary throttle  30 . Preferably, when the rotary throttle valve  23  is in the closed position  24 , the rotary throttle  30  is vertically furthest away from the cover  40 , and conversely, when in the wide open throttle position  26  it is closest to the cover. Preferably, a coiled spring  52  disposed substantially concentrically to the axis  36  is compressed between the cover  40  and the rotary throttle  30  in the cylindrical cavity  32 . The spring force yieldably biases the rotary throttle  30  and needle  48  toward the cavity bottom and may cause rotation toward the closed position  24 . 
     A shaft  54  of the rotary throttle valve  23  projects concentrically axially upward from the rotary throttle  30  and through the body cover  40  to a distal end  56 . A slave lever  58  projects radially outward from the distal end  56  to engage a cam  60  of a starter device  62  having a cylindrical body  61  with a rotational centerline  64  oriented substantially perpendicular to the rotation axis  36  of the throttle valve  23 . A support bracket  66  of the cover  40  projects substantially unitarily upward to rotatably carry the body  61  of the starter device  62 . A coiled return spring  68  rotatably yieldably urges the body  61  and cam  60  to an initial inoperative position. The cam  60  underlies an engagement claw  70  bent from a substantially planar portion  72  of the slave lever  58  so that the claw  70  is engaged and moved by the cam body  61  of the starter  62  as the cam body  61  rotates about the centerline  64  away from its initial position. 
     The engagement claw  70  and cam  60  are axially (with respect to axis  36 ) or vertically separated from each other so that they will not engage each other by the rotational movement of the slave lever  58  during normal use. However, when the slave lever  58  is at the fully closed position  24 , and by rotating the starter body  61  through a certain angle, the cam  60  lifts the slave lever  58  by a prescribed axial distance via the engagement claw  70 . When the starter body  61  is rotated all the way to a prescribed limit determined by a stopper (not shown), the slave lever  58 , that is in the lifted state, is turned in the valve opening direction by a prescribed rotational amount or degree. Thereby, the amount of fuel supply and the amount of valve opening area are both increased to provide the proper ratio and quantity of fuel-and-air mixture for cold starting an engine. 
     In addition to the rotary throttle valve  23 , the slave lever  58 , and the starter device  62 , the throttle valve arrangement  22  preferably has a local throttle valve actuator  74 . Like the throttle valve  23  and the slave lever  58 , the throttle valve actuator  74  generally operates by rotation about the rotation axis  36  of the throttle valve  23 . Unlike the rotary throttle valve  23  and the slave lever  58 , the local throttle valve actuator  74  does not move axially with respect to the body  33  and cover  40  of the carburetor  20 . 
     The local throttle valve actuator  74  has a bracket  76  secured preferably to the body cover  40  by two threaded fasteners  78  generally at opposite legs  80  of the bracket  76 . A bridging segment  82  of the bracket  76  extends between the legs  80  and spans over the distal end  56  of the shaft  54  and the slave lever  58 . The legs  80  are sufficiently spaced apart from one-another so as not to obstruct free rotational movement of the slave lever  58 . Journaled to the bridging segment  82  and extending rotatably through a hole  84  in the bridging segment  82  is a swivel member  86  having a radially projecting lower end  88  located below the bridging segment  82  and an opposite radially projecting upper end  90  projecting axially above the bridging segment  82 . A coupling  92 , connects the lower end  88  of the swivel member  86  to the planar portion  72  of the slave lever  58  and preferably accommodates axial movement of the slave lever  58 . 
     As best illustrated in  FIGS. 2 and 3 , the planar portion  72  of the slave lever  58  is located in an imaginary plane orientated substantially perpendicular to the rotation axis  36 . A hole  94  of the lost motion coupling  92  is in the planar portion  72  and is located appreciably radially outward from the rotation axis  36  and distal end  56 . For carburetor applications not requiring a Bowden cable for remote throttle valve actuation, the lost motion coupling  92  has a peg  96  that projects preferably unitarily downward from the lower end  88  of the swivel member  86  and through the hole  94  for rotational sequencing or co-rotation between the slave lever  58  and the local throttle valve actuator  74 . Because the slave lever  58  moves axially, up and down, a prescribed distance, the axial clearance generally between the slave lever  58  and the lower end  88  of the swivel member  86  must be equal to or greater than the prescribed distance. Similarly, the axial length of the peg  96  must be greater than the prescribed distance so that the peg  96  does not release from the slave lever  58  when the rotary throttle valve  23  rotates and lowers axially to the closed position  24 . 
     Preferably, the swivel member  86  has a tube or hollow cylinder  98  that has the lower and upper ends  88 ,  90  and substantially midway is journaled for rotation to the bridging segment  82 . The cylinder  98  carries an axially extending access bore  99  for insertion of a tool (not shown) to threadably adjust the needle  48  with respect to the orifice  42 . The cylinder  98  is preferably metallic for strength. Preferably, press fitted on the upper end  90  of the hollow cylinder  98  is a radially projecting handle  100  for manual rotation of the throttle valve  23  which is preferably made of injection molded plastic. For receipt of the needle adjustment tool, the handle  100  has a bore  101  communicating co-axially with the access bore  99 . 
     Engaged to and projecting radially outward from the lower end  88  of the cylinder  98  is a bent leg  102  that has the peg  96 . Ideally, the lower end  88  has a diameter slightly greater than the upper end  90  and thus has an upward facing annular shoulder  104  (as best shown in  FIG. 9 ). For smooth rotation and to prevent wear, a metallic washer  106  of the local throttle valve actuator  74  is located between the bridging segment  82  and the annular shoulder  104 . Also located concentrically to the axis  36  and located axially between the bridging segment  82  and the handle  100  is a spacer or collar  108 . A C-clip  110  resiliently snap fits to the cylinder  98  for axial retention of the collar  108 . A frictional resistance produced between the collar  108 , washer  106  and bracket  76  can retain the handle  100  at a desired angular position and against the smaller biasing force of the compression spring  52 . 
     As best illustrated in  FIG. 5 , an optional and interchangeable arrangement replaces the peg  96  of the lost motion coupling  92  with an inverted cylindrical void  96 ′ carried by the swivel member  86 ′ or leg  102 ′ that axially receives an upward projecting, cylindrical, pin  112  having a downward projecting pin  114  ( FIG. 4 ) extending through the hole  94  of the lost motion coupling  92 ′. The pin  114  preferably carries a continuous groove  116  for receipt of a C-clip  118  for reliably retaining the pin  112  on the slave lever  58 . Alternatively, the pin  112  could be snap fitted into the hole  94  without use of the C-clip  118 . The depth of the cylindrical void  96 ′ is greater than the upward projecting distance of the pin  112 . This allows the common slave lever  58  to axially rise with respect to the swivel member  86 ′ as the throttle valve  23  moves in the opening direction thereby accommodating axial movement of the slave lever. 
     In applications not necessarily requiring the local throttle valve actuator  74 ′, the pin  112  also has a diametrically extending slot  120  for receipt of a distal end  122  of a Bowden wire  124  for remote actuation and having an enlarged head  126  as typically known in the art. Preferably, the pin  112  is snap locked rotatably in the hole  94  so that when the Bowden wire  124  is pulled and the throttle valve  23  rotates in the open direction against the biasing force of the coiled compression spring  52 , the pin  112  will also rotate slightly in the hole  94  to prevent kinking or binding of the cable  124 , thus the coupling  92 ′ accommodates both rotational and axial motion. Preferably, the depth of the slot  120  is greater than the axial movement of the throttle valve  23  allowing for connecting of both the local throttle valve actuator  74 ′ and the Bowden wire  124  for remote actuation. 
     As best illustrated in  FIGS. 6–9 , a circumferential positioning interface  127  of the throttle valve arrangement  22  is generally carried between the swivel member  86  and the bridging segment  82  of the bracket  76 . The interface  127  is preferably added to throttle valve arrangement  22  of the carburetor  20  to assist or replace the frictional resistance between the collar  108 , washer  106  and bracket  76  that generally resists the closure biasing force of the spring  52 . The circumferential positioning interface  127  has a generally pie shaped detent follower or steel spring plate engaged  128  engaged to the swivel member  86  for unitary rotation about the axis  36 . The detent follower  128  carries a plurality of holes, indents or recesses that are strategically spaced circumferentially about the axis  36  to designate desired operating speeds of the engine when they selectively receive a cam surface  142  of the carried preferably by a ball or ball bearing  138  of the interface  127  generally trapped in a socket  140  of the bridging segment  82 . As illustrated in  FIGS. 6–9 , a first recess  132  designates wide open throttle position  26  and thus an engine running at maximum speed or power, a second recess  134  designates a partially open throttle valve position  28  and thus an engine running at partial and a possibly quieter speed or partial power, and a third recess  136  designates the closed throttle valve position  24  thus engine shut-down. 
     When, for instance, an engine of a leaf blower is operating at maximum power, the ball bearing  138  of the circumferential positioning interface  127  of the local throttle valve actuator  74  projects in-part into the third recess  132 . Regardless of the biasing force of the compression spring  52 , vibrational forces of the running engine or other extenuating forces, the throttle valve  23  will remain in the wide open position  26  until the operator manually applies a greater force to the handle  100  that causes the follower or spring plate  128  to rotate and resiliently flex outward or upward causing disengagement of the ball  138  from the third recess  132 . Continued rotation of the handle  100  causes the ball  138  to slide across the follower  128  of the interface  127  until the next recess  134  is encountered positively placing the throttle valve  23  into the adjacent or intermediate pre-specified position. When the ball  138  is placed in the first recess  136  designating the closed position  24  of the throttle valve  23 , the engine will reliably shut-down without concern that the throttle valve would be slightly open unintentionally, which would prevent or pro-long engine shut-down. 
     Although the detent follower  128  is illustrated having recesses  130  that communicate generally through the follower  128 , other detent followers can be applied to the local throttle valve actuator that would provide the desired positive placement of the throttle valve in pre-specified positions. One such detent follower is disclosed in U.S. Pat. No. 6,561,496 that is incorporated herein by reference in its entirety. Another detent follower is illustrated in  FIGS. 10 and 11  wherein like elements have like numerals except for the addition of a subsequent double prime symbol. As modified, a circumferential positioning interface  127 ″ has a cam follower  128 ″ that does not utilize a steel spring plate or ball bearing to carry a convex cam surface. Instead, the cam follower  128 ″ is preferably molded as one unitary piece with the swivel member  86 ″. This one piece is preferably made of injection molded plastic or similar economical material providing the cam follower  128 ″ with a resilient flexibility that yieldably biases the cam follower into predefined circumferential positions with respect to the axis  36 ″. A convex cam surface  142 ″ carried by the cam follower  128 ″ faces downward and generally replaces the ball bearing  138  as previously illustrated in  FIGS. 6–9 , thus greatly reducing the number of required parts during assembly. Accordingly, three recesses or holes  130 ″ are circumferentially spaced about the axis  36 ″ and opened upward or outward in the bridging segment  82 ″ to selectively receive the cam surface  142 ″. A recess  132 ″ of the recesses  130 ″ is orientated for the wide open throttle position, a recess  134 ″ is orientated for an intermediate throttle valve position and a recess  136 ″ is orientated for an throttle valve idle position. 
     While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It is not intended herein to mention all the possible equivalent forms, modifications or ramifications 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 as defined by the following claims.