Patent Document

REFERENCE TO COPENDING APPLICATION  
       [0001]    This application is a continuation of copending application Ser. No. 09/538,123 filed Mar. 29, 2000. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to a carburetor valve rotational setting retainer assembly, and more particularly to a rotational setting retainer assembly for low and high-speed needle valves of a carburetor for a combustion engine.  
         BACKGROUND OF THE INVENTION  
         [0003]    Government agencies of an increasing number of countries are imposing exhaust emission control regulations to protect the environment. These regulations are being applied to all combustion engines including portable or two cycle engines used in common equipment such as chain saws, lawn mowers and hedge trimmers. One means of limiting excessive exhaust emissions in a small engine is to restrict the maximum amount of fuel delivered to the combustion chamber. This maximum fuel amount is preset on each individual engine by the engine manufacturer with the understanding that the end user requires some adjustment capability to meet changing work conditions and environmental factors such as altitude. The higher the altitude, the lower the air density, and the lower the fuel amount necessary to operate the engine. The user of the engine must therefore be able to adjust the fuel to air mixture ratios and may do so via low and high-speed needle valves protruding from the carburetor.  
           [0004]    Not only is it desirable to limit the richness of the fuel to air mixture because of exhaust emission regulatory concerns, but the engine manufacturer of a portable combustion engine product also wants to restrict minimum amounts of fuel, or the leanness of the fuel to air mixture. Often a user will desire more power from a small engine and will attempt to operate the engine in an ultra-lean state. This will deprive an engine of proper cooling and will lead to warranty concerns. Therefore, limiter caps are designed not only to restrict the carburetor to a maximum amount of fuel, but also to restrict the carburetor to a minimum amount of fuel.  
           [0005]    Not only is it desirable to limit the maximum and minimum amounts of fuel, but it is also desirable to hold steady the fuel flow in a running engine. Any rotation of the needle of the needle valve, possibly caused by the vibration of a running engine would alter the fuel flow. Therefore, it is desirable to restrain the rotation of the needle of the needle valves thereby preventing any unintended changes to the fuel flow setting. Traditionally, compressed springs are disposed concentrically about the needle and axially between the carburetor body and the head of the needle valve. The spring induced axial force produces increased frictional forces amongst the threads between the carburetor body and the needle, thus resisting needle rotation and alteration of the fuel flow setting.  
           [0006]    Unfortunately, engine vibration is not the only source of unintentionally altered fuel flow. Lateral wobble and axial shifting of the needle tip, disposed within an orifice of the carburetor fuel feed channel, can cause fuel flow changes resulting in a rough running engine. Furthermore, the factory prescribed setting of the low and high-speed needle valves can be rotatably and axially altered when the limiter caps are applied to the heads of each needle. For further background information on needle tip wobble, U.S. patent application Ser. No. 09/584,970 is incorporated by reference herein.  
         SUMMARY OF THE INVENTION  
         [0007]    A retaining assembly maintains the factory pre-set fuel flow settings during the later attachment of a limiter cap to a fuel needle valve of a carburetor. A retainer disposed outward from the carburetor body laterally biases the fuel needle valve which increases frictional forces between the adjustment threads of the needle and carburetor body. The retainer also provides rotation resistant friction between the valve and the retainer itself. Preferably, the carburetor has a pair of spaced-apart and generally parallel low and high-speed needle valves. However, the carburetor may have a single fuel needle valve and a parallel rod cooperating with the retainer to inhibit rotation of the single valve.  
           [0008]    Each valve has a needle which adjustably threads to the carburetor body. A shank of the needle protrudes from the carburetor body and engages concentrically a radially enlarged head at the distal end. Restraining rotation of the needle by exerting an axial force is a spring compressed concentrically between the head of the needle and the carburetor body. Restraining rotation of both needles by exerting a lateral force is a retainer aligned generally axially between the carburetor body and the heads of the needles, and preferably disposed radially outward from the springs of the low and high-speed needle valves.  
           [0009]    Preferably, the needles have a needle tip which resides within a fuel flow orifice of the carburetor body. Both axial and lateral movement of the tip relative to the orifice respectively changes fuel flow into the throttling bore or mixture chamber. The retainer produces bending stresses and strains within the needles of both valves which propagate longitudinally down the needle to the tip. The tip is thereby biased laterally toward a side of the orifice.  
           [0010]    Objects, features and advantages of this invention include the elimination of needle tip wobble which adversely effects fuel flow, providing a simple and inexpensive means to restrain rotation of the low and high speed needle valves, and facilitating and preserving final fuel flow adjustment of the carburetor. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    These and other objects, features and advantages of this invention will be apparent from the following detailed description of the preferred embodiments and best mode, appended claims and accompany drawings in which;  
         [0012]    [0012]FIG. 1 is an exploded perspective view of a carburetor valve rotational setting retainer assembly having a low and high speed needle valve of this invention;  
         [0013]    [0013]FIG. 2 is a bottom view of a carburetor illustrating the retainer assembly laterally biasing a low-speed needle and a high-speed needle valve toward each other;  
         [0014]    [0014]FIG. 3 is a side view of the carburetor;  
         [0015]    [0015]FIG. 4 is a perspective view of a first embodiment of the retainer being a clip retainer;  
         [0016]    [0016]FIG. 5 is a side view of the carburetor illustrating a second embodiment of the retainer being a wedge retainer;  
         [0017]    [0017]FIG. 6 is a perspective view of the wedge retainer;  
         [0018]    [0018]FIG. 7 is a partial side view of the carburetor illustrating a third embodiment of the retainer being a band retainer;  
         [0019]    [0019]FIG. 8 is a perspective view of the band retainer;  
         [0020]    [0020]FIG. 9 is a partial side view of the carburetor illustrating a fourth embodiment of the retainer being a triangular band retainer having a pin;  
         [0021]    [0021]FIG. 10 is a perspective view of the triangular band retainer;  
         [0022]    [0022]FIG. 11 is a partial side view of the carburetor illustrating a fifth embodiment of the retainer being a ring retainer;  
         [0023]    [0023]FIG. 12 is a perspective view of the ring retainer;  
         [0024]    [0024]FIG. 13 is a partial side view of the carburetor illustrating a sixth embodiment of the retainer being a block retainer;  
         [0025]    [0025]FIG. 14 is a cross section view of the block retainer having two angled bores taken along line  14 - 14  of FIG. 13;  
         [0026]    [0026]FIG. 15 is the cross section view of the block retainer of FIG. 14 with one of the angled bores replaced with a pilot hole; and  
         [0027]    [0027]FIG. 16 is an exploded perspective view of a carburetor valve rotational setting retainer assembly illustrating a seventh embodiment having a single fuel needle valve and a pin. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]    Referring in more detail to the drawings, FIGS.  1 - 4  show a low and high speed needle valve assembly  20  having a biasing retainer  22 , embodying the present invention. Mounting threadably to a carburetor body  24  are low and high-speed needle valves  26 ,  28  which move longitudinally, via rotation, in and out of respective threaded ports  30  defined by the carburetor body  24 . Air flowing through a throttling bore  31  extending through the carburetor body  24  mixes with a prescribed fuel quantity, or flow rate, controlled by the low and high speed needle valves  26 ,  28 . The fuel flow rate within the carburetor body  24  is adjusted by threadably rotating the needle  32  within the respective port  30  either inward to reduce the fuel flow or outward from the carburetor body  24  to increase the fuel flow.  
         [0029]    The low and high-speed needle valves  26 ,  28  each have a spring  34  and a shank or needle  32 . The spring  34  provides resistance against unintentional rotation of the needle  32 . The spring  34  concentrically encircles the needle  32  and is compressed axially between a radially extended head  36  of the needle  32  and the carburetor body  24 , the spring  34  engaging an inward facing annular surface  38  defined by the radially expanded head  36 . The axial constant force produced by the compression of the spring  34  provides the resistance which restrains rotation of the needle  32  by creating friction between the threads of the carburetor body  24  and the needle  32  within the port  30 .  
         [0030]    Customarily, the low and high-speed needle valves  26 ,  28  of each carburetor are adjusted and set at the factory by the engine manufacturer after the carburetor body  24  is mounted to a running combustion engine, not shown. If the fuel and air mixture is too lean, the running engine may over heat causing warranty concerns. If the fuel and air mixture is too rich, government regulatory emission requirements may be exceeded or violated. Therefore, limiting adjustment capability by the end user of the engine of the low and high-speed needle valves  26 ,  28  within an acceptable range is desirable. The engagement of known limiter caps  40  to the valves  26 ,  28  establishes the end user adjustment range for fuel flow within the carburetor (i.e. neither too rich nor too lean). The limiter caps  40  are press fitted over the heads  36  of the low and high-speed needle valves  26 ,  28  in the factory after the proper fuel flow settings are made.  
         [0031]    Without the retainer assembly and after factory adjustment by the engine manufacturer, the press fitting of the limiter caps  40  to the heads  36  of either one or both of the needles  32  may unintentionally rotate, wobble or laterally shift the needles causing the factory setting and prescribed adjustment range of the needles  32  to be altered or changed. To feasibly solve this problem, the single retainer  22  of the present invention engages and laterally biases a shank  46  of each needle  32  which protrudes outward from the carburetor body  24 . Preferably, the retainer  22  is axially aligned and disposed radially outward from the respective springs  34 . The lateral force exerted by the retainer  22  against the springs  34  causes the springs  34  to exert a lateral force against the shanks  46  of the needles  32 . The needles  32 , therefore, are skewed against, or tend to favor one side, of the respective ports  30 . The resultant friction between the springs  34  and the shanks  46  along with the increased friction between the threads of the needles  32  and ports  30  will assist the springs  34  to further resist any rotation of the needles  32 . That is, the axial force produced by the springs  34  is compounded by the lateral force produced by the retainer  22 . Furthermore, the necessity of utilizing the spring  34  to resist rotation can be eliminated with a sufficiently strong or appropriately sized retainer  22 . In such an embodiment, the force produced by the retainer  22  is exerted directly on the shanks  46  of the low and high speed needle valves  26 ,  28 .  
         [0032]    Another feature of the retainer  22  is the elimination or reduction of needle tip  48  wobble within an orifice of the fuel flow channel of the carburetor body  24 , not shown. The wobble action of the tip  48  of the needle  32  is caused by machining tolerance limitations of the carburetor body  24  threads contained within port  30  and the mating threads of needle  32 . The resultant wobble can affect fuel flow causing a rough running combustion engine. The exertion of a lateral bias or force upon the shanks  46  of the needles  32  by the retainer  22  will produce a longitudinal stress and strain along the needle  32 . This causes the needle  32  to favor or even bear on one side of the orifice and thereby eliminates some or all of the adverse wobble effects.  
         [0033]    Referring to FIGS.  2 - 4 , a first embodiment of the retainer  22  is illustrated as a clip retainer  50  which laterally engages both springs  34  of the respective low and high-speed needle valves  26 ,  28  to laterally bias the projecting portions of the shanks  46  toward one another. An angled first leg  52  of the clip retainer  50  engages the spring  34  and thereby interconnects with a longitudinal outward surface  56  of the shank  46  of the low speed needle valve  26 , which faces outward with respect to the high-speed needle valve  28 . An angled second leg  54  of the clip retainer  50  engages the other spring  34  and interconnects with a longitudinal outward face  56  of the shank  46  of the high-speed needle valve  28 , which faces outward with respect to the shank  46  of the low-speed needle valve  26 . The clip retainer  50  laterally snap fits or is interference fitted about both the low and high-speed needle valves  26 ,  28 . To assist in the snap fit, the distal ends  60 ,  62  of the respective first and second legs  52 ,  54  bend substantially radially outward with respect to the shank  46  of the respective low and high-speed needle valves  26 ,  28 .  
         [0034]    Referring to FIGS. 1, 5 and  6 , a second embodiment of the retainer  22  is shown as a wedge retainer  64 . The wedge retainer  64  may take the form of a variety of shapes including an L-shape, an I-shape and preferably a T-shape. The wedge retainer  64  has a substantially planar primary member  66  which is wedged, via a snap fit, between and thereby engages the springs  34  of the low and high-speed needle valves  26 ,  28 . The wedging effect causes the projecting portions of the shanks  46  to laterally bias outward from one another. Providing the snap fit is an enlarged distal end  68  of the primary member  66 . The thickness of the distal end  68  is appreciably larger than the distance between the low and high speed needle valves  26 ,  28  in the assembled state. The primary member  66  also has an enlarged base end  70  ensuring, when coupled with the enlarged distal end  68 , that the wedge retainer  64  has minimal lateral movement and remains wedged between the springs  34  or shanks  46  during end user adjustment rotation of the low or high-speed needle valves  26 ,  28 . The primary member  66  with the enlarged distal and base ends  68 ,  70  form the I-shape referred to above.  
         [0035]    The primary member  66  of the wedge retainer  64  engages the springs  34  on one side between the distal and base ends  68 ,  70  and thereby interconnects with a longitudinal inward face  71  of the shank  46  of the low-speed needle valve  26  which radially faces generally toward the shank  46  of the high-speed needle valve  28 . Likewise, the primary member  66  engages the other spring  34  on the other side and thereby interconnects with the longitudinal inward surface  71  of the shank  46  of the high speed needle valve  28  which faces substantially toward the shank  46  of the low-speed needle valve  26 .  
         [0036]    The wedge retainer  64  has a substantially planar first base member  72  extending substantially perpendicularly from the primary member  66  along the base end  70 . Base member  72  is disposed generally tangentially with respect to the shank  46  of the low-speed needle valve  26 . The primary member  66  coupled with the first base member  72  form the L-shape referred to above. Preferably, the wedge retainer  64  also has a substantially planar second base member  74  extending from the primary member  66  along the base end  70 , but in an opposite direction with respect to the first base member  72 . The second base member  74  lies generally tangentially to the shank  46  of the high-speed needle valve  28 . The first and second base members  72 ,  74  lie substantially within the same imaginary plane and thereby compose an enlarged surface  76  upon which a force can be exerted to snap fit the wedge retainer  64  between the low-and high-speed needle valves  26 ,  28 . The primary, first base and second base members  64 ,  72 ,  74  form the T-shape referred to above.  
         [0037]    Referring to FIGS. 1, 7 and  8 , a third embodiment of the present invention is shown wherein the retainer  22  is a band retainer  78 . Like the clip retainer  50 , the band retainer  78  laterally bands or biases together the projecting portions of the shanks  46  of the respective low and high-speed needle valves  26 ,  28 . The band retainer  78  encircles both the shanks  46  of the low and high-speed needle valves  26 ,  28  and may be made of an elastic or plastic material which may also have a shrinking capability upon the application of heat.  
         [0038]    Referring to FIGS. 1, 9 and  10  a fourth embodiment of the retainer  22  is shown as being a triangular band retainer  79  having a slightly larger diameter or circumference than the band retainer  78 . The larger diameter enables the band retainer  79  to encircle not only the shanks  46  but also a pin  80  which rigidly protrudes outward from the carburetor body  24 . The pin  80  is preferably and substantially disposed at an equal distance from the low and high-speed needle valves  26 ,  28 . As with band retainer  78  above, the triangular band retainer  79  can be made of the same material as the band retainer  78 .  
         [0039]    Referring to FIGS. 1, 11 and  12 , a fifth embodiment of the retainer  22  is shown as being a ring retainer  82  preferably made of a plastic material. The ring retainer  82  biases the projecting portions of the shanks  46  of the low and high-speed needle valves  26 ,  28  similar to the wedge retainer  64 . The ring retainer  82  is concentrically disposed about the spring  34  and the shank  46  of either the low or high-speed needle valves  26 ,  28 . The thickness of the ring retainer  82  wall is slightly larger than the distance between the needle valves  26 ,  28  and is defined by a circumferential inward surface  84  and a circumferential outward surface  86 . Because the radial distance between the inward surface  84  and the outward surface  86  is larger than the distance between the springs  34 , the ring retainer  82  laterally biases the projecting portions of the shanks  46  outward or away from one another.  
         [0040]    Referring to FIGS.  1 ,  13 - 15 , a sixth embodiment of the retainer  22  is shown as being a block retainer  88 . The block retainer  88  laterally displaces either one of the shanks  46  of the low and high-speed needle valves  26 ,  28 . The block retainer  88  has a continuous curved surface  90  defining an angled bore  91  and extended between an inward perimeter  92  and an outward perimeter  94 . The inward perimeter  92  is centered about a centerline  96  of the respective hole  30 . The outward perimeter  94  is radially misaligned to the centerline  96  of the hole  30 . This mis-alignment forces the low or high-speed needle valves  26 ,  28  to become laterally displaced. The non-displaced needle valve inserts within a pilot hole  98  (shown in FIG. 15) of the block retainer  88  which is centered about the centerline  96  of the other hole  30 .  
         [0041]    Referring to FIG. 14, block retainer  88 ′ is shown wherein lateral displacement of both the low and high-speed needle valves  26 ,  28  is achieved by replacement of the pilot hole  98  with another angled bore  91 . The bores  91  are preferably angled toward or away from one another and are preferably not parallel to one another. The opposing angles will help avoid misalignment of the block retainer  88  to the carburetor body  24  during assembly. Also during assembly, an indexing feature  100  of the block retainer  88  mates with a mating indexing feature  102  (shown in FIG. 16) on the carburetor body  24 . Preferably, the indexing feature  100  is an inward extended pin and the mating indexing feature  102  of the carburetor body  24  is an orifice or receptacle.  
         [0042]    When the block retainer  88  is utilized with the low and high-speed needle valves  26 ,  28  a threaded fastener  104  secures the block retainer  88  to the carburetor body  24 . Preferably, the threaded fastener is a screw or bolt, counter sunk into the block retainer  88  and threaded into the carburetor body  24 .  
         [0043]    Referring to FIG. 16, yet another embodiment of the retainer assembly  20 ′ is shown wherein either the low or high-speed needle valve  26 ,  28  is a fuel needle valve  106  and the remaining valve is eliminated and replaced with a dummy needle valve or shaft  108  which projects rigidly outward from the carburetor body  24 ′. The retainer  22  engages the fuel-air mixture needle valve  106  and the shaft  108  as it does with the low and high-speed needle valves  26 ,  28  shown in FIG. 1. When utilizing the block retainer  88  embodiment of the retainer  22 , the shaft  108  is press fitted into the pilot hole  98 . This press fit eliminates the need for the threaded fastener  104 . The preferable material for the block retainer  88  is plastic.  
         [0044]    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 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.

Technology Category: 4