Abstract:
A float arm assembly and method of construction therefore has a float arm with a free end and another end arranged for operable communication with a float arm position sensor. A float is molded to the float arm to provide a unitary and rigid float arm assembly.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to fuel systems and more particularly to fuel level senders for use in a fuel tank.  
       BACKGROUND OF THE INVENTION  
       [0002]     Vehicles having internal combustion engines typically have fuel tanks for maintaining liquid fuel therein. Generally, the fuel tank has a fuel level sender therein to provide an indication to a user, such as on a fuel level gauge, as to the amount of fuel within the tank. Commonly, the fuel level sender incorporates a float arm assembly having a float arm extending through a float to facilitate attaching the float on the float arm. Further, it is known to use at least one or more washers received adjacent opposite ends of the float in combination with a fastener, such as a self locking Tinnerman® style washer or threaded nut to maintain the float fastened to the float arm.  
         [0003]     By securing a float to a float arm through the use of fasteners, typically performed in a secondary operation, variances result from one float arm assembly to another as a result of the stack up tolerances between the various components. The resulting variances affect the performance of the float arm, and thus, affect the accuracy of the fuel level reading indicated to a user. As a result, the user receives a potentially misleading value as to the quantity of fuel remaining in the fuel tank. Additionally, the fasteners used in securing the float to the float arm add additional weight to the assembly, thereby impacting the buoyancy of the float within the fuel, and thus, affecting its performance. Further, the secondary operations performed in using fasteners to secure the float to the float arm complicate the assembly process, and thus, increase the costs associated with assembling of the float arm assembly.  
       SUMMARY OF THE INVENTION  
       [0004]     A float arm assembly for use in a fuel tank has a float arm with a free end and another end arranged for operable communication with a float arm position sensor. The assembly has a float molded to the float arm to provide a unitary and rigid float arm assembly.  
         [0005]     Another aspect of the invention includes a method of constructing a float arm assembly for use in a fuel tank. The steps include providing a float arm having a free end and another end arranged for operable communication with a float arm position sensor. Further, molding a float to the float arm to provide a unitary and rigid float arm assembly.  
         [0006]     The float arm assembly and method of manufacture therefore provides a float arm assembly that is moveable within a fuel tank in response to a continuously varying fuel level within the fuel tank to provide accurate readings of the fuel level within the fuel tank. With the float being molded to the float arm, the stack up tolerances resulting between the float and the float arm are kept to a minimum, thereby reducing the potential for variances from one float arm assembly to another, and further, improving the accuracy of the fuel level readings. Additionally, the method of construction of the float arm assembly eliminates the need for secondary operations to assemble the float arm to the float, thereby enhancing the manufacturing efficiencies and reducing the costs generally associated with secondary operations, such as labor, capital equipment, floor space and component costs, for example.  
         [0007]     Some of the objects, features and advantages included in at least some of the disclosed embodiments of the invention include providing a float arm assembly for use in a fuel tank that has a reduced number of component parts, provides a float arm assembly facilitating repeatable and reliable fuel level readings, reduces potential stack up tolerance variations in assembly and problems associated therewith in use, minimizes the weight of a float arm assembly, maximizes the buoyancy of a float on a float arm assembly, improves the manufacturing efficiencies for a float arm assembly, maximizes the potential volume for a float on a float arm assembly, allows optimization of the geometry of a float on a float arm assembly, allows optimal design of a float arm to improve the buoyancy of a float attached thereto, is of relatively simple design and provides for a long and useful life in use. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     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 accompanying drawings, in which:  
         [0009]      FIG. 1  is a perspective view of a fuel level sender having a float arm assembly constructed according to one embodiment of the invention;  
         [0010]      FIG. 2  is a partial cross-sectional view of a fuel tank with the fuel level sender of  FIG. 1  shown received within the fuel tank;  
         [0011]      FIG. 3  is a partial cross-sectional view of the float arm assembly of  FIG. 1  having a float arm with a float molded thereto;  
         [0012]      FIG. 4  is a partial cross-sectional view of a float arm assembly constructed according to another embodiment of the invention having a float arm with a float molded thereto;  
         [0013]      FIG. 5  is a partial cross-sectional view of a float arm assembly constructed according to yet another embodiment of the invention having a float arm with a float molded thereto;  
         [0014]      FIG. 6  is a partial cross-sectional view of a float arm assembly constructed according to yet another embodiment of the invention having a float arm with a float molded thereto; and  
         [0015]      FIG. 7  is a partial cross-sectional view of a float arm constructed according to yet another embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     Referring in more detail to the drawings,  FIGS. 1 and 2  illustrate a float arm assembly  10  constructed according to one embodiment of the invention. The float arm assembly  10  is constructed for use within a fuel tank  12  ( FIG. 2 ), such as a fuel tank on a motorcycle, recreational vehicle or an automobile, for example. The assembly  10  has a float  14  molded onto or over at least a portion of a float arm  16 , such that the float  14  is carried by the float arm  16  and may be fixed thereto to eliminate or reduce slop or play between the float  14  and the float arm  16 . As a result, the float arm assembly  10  is responsive to a change in the fuel level within the fuel tank  12  preferably with little, and more preferably without any relative movement between the float  14  and the float arm  16 , thereby facilitating a relatively accurate determination of the level of fuel in the fuel tank.  
         [0017]     The float arm assembly  10  is generally constructed for use as a component of an electromechanical fuel level sender  18 , although it can be used with substantially any type of fuel level sender or indicator including, without limitation, mechanical level indicators. In use, the float arm  16  moves between a first position corresponding to a position in which the fuel tank  12  is generally empty ( FIG. 2 ), and a second position corresponding to a position in which the fuel tank  12  is generally full of liquid fuel ( FIG. 1 ). The float arm  16  moves in response to the movement of the float  14  which is buoyant in liquid fuel, and hence, is responsive to changes in the level of fuel in the fuel tank. As the float arm  16  moves between its first and second positions, an electrical sensor  20  detects the position of the float arm  16 , such as through a change in a voltage reading, for example, and communicates this position through an electrical signal via a wire harness  22  to a control circuit or fuel tank control unit (not shown). The electrical signal received by the control circuit, for example, is generally processed through a preprogrammed algorithm that determines the level of fuel within the fuel tank  12  as a function of the electrical signal. Accordingly, the accuracy of the fuel level signal sent by the electrical sensor  20  plays a role in the accuracy of the fuel level indicated to a user.  
         [0018]     The fuel level sender  18  is shown here as being attached to a bracket  24  adjacent one end  26  of the bracket  24 , wherein the bracket  24  has another end  28  attached to a mount flange  30 . The mount flange  30  is shown in  FIG. 2  fastened within an opening  32  of the fuel tank  12  to position the float arm assembly  10 , as desired, within the fuel tank  12 . The mount flange  30  is secured within the opening  32  using any suitable attachment mechanism, such as a snap ring or c-clip  34  to maintain the mount flange  30 , and thus, float arm assembly  10  in its desired position within the fuel tank  12 . The mount flange  30  has a generally cylindrical sidewall  31  with one or more grooves to receive one or more seals  33  between the flange  30  and the fuel tank or an insert  35  carried by the fuel tank. The fuel tank  12  is represented here by example as a saddle-type motorcycle fuel tank, though it should be recognized that the float arm assembly  10  is intended for use in any fuel tank application, such as in automobiles or recreational vehicles, and can be employed with any suitable mount or otherwise supported or carried as desired, by way of examples and without limitation.  
         [0019]     The float arm  16  is desirably constructed from an elongate rod having one end  36  arranged for operable attachment to the electrical sensor  20  and a free end  38  ( FIG. 3 ). The float arm  16  may be constructed having any suitable outer geometry, such as cylindrical, rectangular, or otherwise, as desired. Desirably, the float arm  16  is formed to its desired finished size and shape, depending on the application envelope, and thereafter is positioned at least in part within a mold cavity of an injection mold or blow mold so that the float  14  may be molded onto or over the end  38  of the float arm  16 . It should be recognized that additional operations may be performed on the float arm  16  after molding the float  14  to the float arm  16 , and that the float arm  16  need not be in its final state or form prior to molding the float  14  to the float arm  16 .  
         [0020]     The float arm  16  is preferably constructed from a metallic material, such as stainless steel or galvanized music wire, for example, or, as represented in an alternate embodiment in  FIG. 7 , a float arm  17  may be formed as an extruded or molded polymeric material. To avoid degradation to the float arm  16  while molding the float  14  thereto, if a polymeric material is used in constructing the float arm  16 , the polymeric material can be chosen to have a higher melt point than the material used in constructing the float  14 . Some types of polymeric materials that may be used, by example and without limitation, include an acetal having a melt temperature of about 320-375° F. (Delrin® or Celcon, for example), a polyamide having a melt temperature of about 350-510° F. (Nylon, for example) or a polyphthalimide having a melt temperature of about 590° F. (Amodel®, for example).  
         [0021]     The float arm  16  preferably has an attachment feature to retain the float  14  on the float arm  16 . As shown in  FIG. 3 , the attachment feature or features of the float arm  16  includes one or more voids such as cavities or grooves  42  extending radially inwardly from an outer surface  40  of the float arm  16 . Desirably, the grooves  42  span circumferentially about the float arm  16 , and are shown here as being axially spaced from one another. It should be understood that the grooves  42  may take on any geometric pattern, such as a helical configuration commonly used for threads, or may be discontinuous about the circumference of the float arm  16 , such as in the formation of slots or other void configurations. In addition, the geometry of the grooves  42  may be generally square-shaped, v-shaped, or otherwise configured, as desired.  
         [0022]     The float  14  is constructed from any suitable float material having the desired density properties required to provide a desired buoyancy for the float  14  in use. Some types of materials that may be used, by example and without limitation, include a foamed-nylon having a mold temperature of about 175-210° F., Nitrophyl having a mold temperature of about 375° F. or an acetal having a mold temperature of about 175-210° F.  
         [0023]     As shown in  FIG. 3 , the float  14  is preferably molded on the float arm  16  so that the float material extends at least partially into the grooves  42  to form a discontinuous passage  45  within the float  14 , and desirably substantially fills the grooves  42  in the float arm  16  during the molding process. As such, the float  14  is preferably rigidly attached to the float arm  16 . Desirably, the float  14  extends axially beyond the end  38  of the float arm  16  such that at least a portion (P) of the float  14  is devoid of the float arm  16  in lateral cross section such that the discontinuous passage  45  is formed as an enclosed cavity within the float  14  and so that the free end  38  of the float arm  16  is encapsulated by the float  14 . Accordingly, the length of the float arm  16  can be minimized, thereby minimizing the weight of the float arm  16 . By minimizing the length and weight of the float arm  16 , the envelope required to house the float arm assembly can be reduced, and the buoyancy of the float  14  can be maximized. Furthermore, the number and types of useful applications for which the float arm assembly  10  may be incorporated are enhanced by allowing for varying configurations of the float  14 , as best meets the specific application needs.  
         [0024]     As shown in  FIG. 4 , another embodiment of a float arm assembly  110  is shown wherein a float arm  116  has a float  114  molded thereto. The float arm  116  has an outer surface  140  terminating at a free end  138  with at least one and shown here as a plurality of attachment features or protrusions  144  extending radially outwardly from the outer surface  140  generally adjacent the free end  138 . The protrusions  144  define at least in part the attachment feature and are shown being axially spaced from one another to define annular channels  146  between adjacent protrusions  144 . The protrusions  144  are represented here as extending circumferentially and radially about the float arm  116 , though it should be recognized that the protrusions  144  may extend at any orientation including radially, may be discontinuous about the circumference of the float arm  116  to provide outwardly extending tabs or fingers, and also can take on the construction of a helical thread pattern, by way of example and without limitation.  
         [0025]     The float  114  is preferably molded to the float arm  116  such that the free end  138  of the float arm  116  is preferably encapsulated by the float  114 . The float  114  desirably extends at least partially and preferably substantially occupies the channels  146  between the protrusions  144  during the molding process, thereby forming a discontinuous passage  145  within the float  114 . Otherwise, the float  114  may be constructed generally the same as the float  14  in the previous embodiment, and thus, is not discussed further.  
         [0026]     As shown in  FIG. 5 , another embodiment of a float arm assembly  210  is shown wherein a float arm  216  has a float  214  molded thereto. The float arm  216  has a longitudinal axis  217  with at least a portion (X) of the float arm  216  adjacent a free end  238  of the float arm  216  being inclined or bent relative to the longitudinal axis  217  to define the attachment feature retaining the float  214  on the float arm  216 .  
         [0027]     The float  214  is preferably molded to the float arm  216  such that the free end  238  of the float arm  216  is preferably encapsulated by the float  214 . With the float arm  216  being bent or inclined within the material of the float  214 , the float  214  is formed having a discontinuous passage  245  with at least one bend therein to further assure that the float  214  is positively retained on and generally rigidly fixed to the float arm  216 . The inclined portion (X) resists removal of the float  214  from the float arm  216 , particularly along the direction of the longitudinal axis  217 . Otherwise, the float  214  may be constructed generally the same as described in the previous embodiments, and thus, is not discussed further.  
         [0028]     As shown in  FIG. 6 , another embodiment of a float arm assembly  310  is shown wherein a float arm  316  has a float  314  molded thereto. The float arm  316  terminates at a free end  338  and has an attachment feature including an opening extending into the float arm  316 , and preferably a through hole  321  extending through the float arm  316  generally adjacent the free end  338 .  
         [0029]     The float  314  is molded to the float arm  316  such that the free end  338  of the float arm  316  is preferably encapsulated by the float  314 . The material of the float  314  desirably flows at least partially and preferably substantially within the through hole  321  during the molding process to retain the float  314  on the float arm  316  in use. Accordingly, the float  314  has a discontinuous passage  345  resulting from the material of the float  314  entering the through hole  321 . It should be recognized that although only one through hole is shown, a plurality of through holes could be formed in the float arm  316 . Otherwise, the float  314  may be constructed the same as described in the previous embodiments, and thus is not discussed further.  
         [0030]     It should be recognized that the embodiments of the float arm assembly discussed above are intended to be illustrative of some presently preferred embodiments of the invention, and not limiting. Various modifications within the spirit and scope of the invention will be readily apparent to those skilled in the art. For example, without limitation, the float arms in the embodiments above may have a portion of the float arm exposed external to the float molded thereto, and further, any of the features of the float arm embodiments above may be combined with one another, as desired. Additionally, the float does not have to be perfectly rigidly attached to the float arm, some play or movement of the float relative to the float arm may occur. Even if initially rigidly attached to the float arm, dimensional changes of the float or float arm may introduce some play or movement between them. Further, while several examples of floats with discontinuous passages have been shown and described other float configurations having passages (blind or through bores or passages), that are not right cylindrical passages with generally smooth and continuous surfaces, can be employed. The invention is defined by the claims that follow.