Abstract:
A wheel mandrel tool includes an alignment section, a thread forming section including a first set of grooves, a gripping section including a second set of grooves, and a shank section. The thread forming section forms threads in a wheel bore by a swaging process and the gripping section holds the wheel during a rotary trimming process.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to tools used in performance tuning of toy car wheels, and more particularly to tools that provide swage threading of a wheel bore, and to tools that enable the removal of wheel tread imperfections. 
         [0003]    2. Background of the Invention 
         [0004]    Toy cars are used in a wide variety of games and activities. In some toy car competitions, the toy cars are raced down a sloped track, using only gravity to provide their kinetic energy. Examples of toy cars include Boy Scouts of America Pinewood Derby and PineCar Racer toy cars. The present invention is not limited to use on these cars, but can be applied generally to toy cars. To enhance the performance of toy cars, it is common practice to remove imperfections from the treads of the wheels using a process known as rotary trimming. In the rotary trimming process, the toy car wheel is held using an apparatus known as a mandrel, placing the mandrel into a drill or similar tool, and pressing a blade or similar flat object against the tread surface of the spinning wheel to remove any high-spots or other imperfections. 
         [0005]    Prior art wheel mandrel tools are of two piece construction: a threaded screw and threaded mandrel base. The threaded screw is inserted through the wheel bore (i.e. the opening in the wheel through which the axle is placed) and then screwed into the threaded mandrel base. The screw holds the wheel on the mandrel in a concentric arrangement. The mandrel base is placed into the chuck of a drill or similar tool, and the chuck is tightened to hold the mandrel. To remove imperfections from the wheel tread, the drill is turned on to spin the wheel, and a blade, sandpaper, or other tools are pressed against the spinning wheel. Buffing of the wheel tread is also possible using this process by application of buffing compound to the spinning wheel. 
         [0006]    Prior art wheel mandrels have several shortcomings. First, prior art wheel mandrels function only to hold a wheel, allowing the wheel to be attached to, and spun by, a drill, in order to remove tread imperfections as described above. Prior art wheel mandrels do not change the inside surface of the wheel bore. Furthermore, because the threaded screw portions of these tools have a smaller diameter than the wheel bore, they may not fit tightly enough to ensure that the wheel tread is concentric to the drill axis. Thus, the wheel tread and the wheel bore may not be concentric after trimming the wheel tread. To minimize this issue, some prior-art wheel mandrels provide a conical centering portion on the head of the threaded screw. This conical section centers the wheel on the tool ensuring concentricity of wheel bore to the circumference of the wheel. 
         [0007]    The present invention provides a wheel mandrel that overcomes the weaknesses of prior-art tools, providing a dual function mandrel having particular utility for swage threading and holding a work piece for rotary trimming. 
       SUMMARY 
       [0008]    In one embodiment, a wheel mandrel tool comprises a work piece alignment section, a thread forming section including a first set of grooves, the first set of grooves having a first inner diameter and a first outer diameter, a work piece gripping section including a second set of grooves, the second set of grooves having a second inner diameter and second outer diameter, and a shank section. The present invention advantageously provides dual functions of swage threading the wheel bore and holding the wheel during rotary trimming. The wheel mandrel is preferably made of one piece construction, 
         [0009]    These and other features of the present invention will be readily apparent to persons of ordinary skill in the art upon reading the entirety of this disclosure, which includes the accompanying drawings and claims. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  shows a schematic cross-section a prior-art toy car wheel that may be improved by application of the present invention. 
           [0011]      FIG. 2  shows a cross-section schematically illustrating of one embodiment of the present invention. 
           [0012]      FIG. 3  shows an enlarged cross-section of one portion of the embodiment of the present invention shown in  FIG. 2 . 
       
    
    
       [0013]    The use of the same reference label in different drawings indicates the same or like components. The drawings are not necessarily drawn to scale. 
       DETAILED DESCRIPTION 
       [0014]      FIG. 1  shows a schematic cross-section of a prior-art toy car wheel  300 . Wheel  300  includes a wheel bore  303  (i.e. the hole through which a toy car axle is placed). The wheel bore has an initial wheel bore diameter  301  and a wheel bore length  302 . 
         [0015]      FIG. 2  shows a schematic cross-section of one embodiment of the present invention. Wheel mandrel  100  includes an alignment section  102 , a thread forming section  103 , a gripping section  104 , and a shank section  106 . Unlike some prior-art wheel mandrels, the present invention is preferably made of one piece construction. In other words, sections  102 ,  103 ,  104 , and  106  are not easily separated from each other, and are all preferably formed from the same piece of material. 
         [0016]    Shank section  106  has a diameter that is substantially constant throughout its length. The length of shank section  106  should be sufficient to be held in the spinning tool chuck, and should protrude well beyond the chuck to prevent injury during the wheel trimming process. 
         [0017]    To use wheel mandrel  100  for enhancing the performance of toy car wheel  300 , shank section  106  is placed into the chuck of a spinning tool (e.g. a drill). Prior to threading wheel  300  onto tool  100 , a lubricant may optionally be placed on tool  100  to minimize the risk of thread tear out prior to thread formation. While tool  100  is spinning, the wheel  300  is placed on alignment section  102 , which centers wheel  300  onto tool  100 . Wheel  300  is pressed against thread forming section  103  such that thread forming section  103  begins to cut threads into wheel bore  303 . This threading process also pulls wheel  300  further onto tool  100 . As wheel  300  travels across thread forming section  103  to gripping section  104 , the entire length of wheel bore  303  becomes threaded by a thread swaging process. A shoulder stop  105  prevents the wheel from traveling onto shank section  106 . Shoulder stop  105  is preferably substantially perpendicular to the tool axis, and preferably has a smooth finish. In another embodiment, shoulder stop  105  may be chamfered. 
         [0018]    Gripping section  104  serves to hold wheel  300  securely and concentrically on wheel mandrel  100  during the subsequent wheel tread trimming process. The length of gripping section  104  is preferably as long as, or longer than, the wheel bore length  302 , such that the gripping area between the wheel and gripping section  104  is maximized. The shank section  106  remains in the chuck of the drill and the drill spins the wheel while a blade, sandpaper, or other tool is pressed against the spinning wheel to remove imperfections from the tread of the wheel. Buffing of the wheel tread is also possible by application of buffing compound to the spinning wheel. After the wheel tread trimming process is completed, wheel  300  may be prevented from spinning while the spinning direction of the drill is reversed, such that wheel  300  is unscrewed from tool  100  for easy removal. 
         [0019]      FIG. 3  shows a schematic cross-section of an enlarged area of the tool of  FIG. 2  to illustrate additional features of the present invention. Thread forming section  103  includes a first set of grooves  211 , which have a first inner diameter  203 . The outer diameter of grooves  211  varies with lateral position, with a minimum outer diameter  201  near alignment section  102  and a maximum outer diameter  202  near gripping section  104 . The length of thread forming section  103  will influence the gripping force required to thread the wheel bore. Increasing the length decreases the gripping force required on the wheel during thread formation. In a preferred embodiment, the length of thread forming section  103  is in the range of ⅛ inch to ¼ inch. Thread forming section  103  can be configured for lobed swage thread forming, or to swage threads without lobes. 
         [0020]    Outer diameter  202  is a critical dimension for thread swaging. Outer diameter  202  should be greater than initial wheel bore diameter  301 . If outer diameter  202  is too small, then threads are not completely formed inside wheel bore  303 . However, if outer diameter  202  is too large, then the threads may be damaged during the thread formation process. The correct diameter should allow displaced wheel material (e.g. plastic) to substantially fill grooves  212 . Swaged threads are preferred to cut threads because the swaging process reduces wheel bore diameter from initial wheel bore diameter  301  to a final wheel bore diameter. The final wheel bore diameter is preferably just slightly larger than the diameter of a wheel axle that is used to hold the wheel onto the toy car. 
         [0021]    Alignment section  102  has a diameter that preferably similar to the wheel bore diameter  301  (see  FIG. 1 ). Making the diameter of alignment section  102  the same or only slightly smaller than the wheel bore diameter ensures that the wheel is positioned concentrically on the tool before the wheel contacts grooves  211  in thread forming section  103 . The length of alignment section  102  is preferably similar to wheel bore length  302  (see  FIG. 1 ) in wheel  300 . Alignment section  102  may have a chamfered edge, as shown in  FIG. 2 . In the embodiment of  FIG. 3 , alignment section  102  has a set of grooves  213 . Grooves in the alignment section may prevent damage to the threaded wheel bore when the wheel is removed from the wheel mandrel upon completion of the operation. The inner diameter  203  of grooves  213  is preferably the same as the inner diameter  203  of grooves  211 . 
         [0022]    Gripping section  104  has a set of grooves  212  with an inside diameter  203  that is preferably the same as inside diameter  211 , and an outside diameter  202  that is substantially the same as the largest outside diameter of grooves  211 . Grooves  212  should fit tightly into the threads that are cut into wheel bore  303  by threading section  103  of tool  100 . 
         [0023]    In a preferred embodiment, grooves  212 , grooves  211 , and grooves  213  are continuous across gripping section  104 , threading section  103 , and alignment section  102 . The inner diameter  203  is consistent across grooves  212 ,  211 , and  213 . The outer diameter  202  of gripping section  104  is larger than the outer diameter  201  of alignment section  102 , and the outer diameter of grooves  211  vary from outer diameter  202  to outer diameter  201 . In another embodiment, alignment section  102  may have a smooth surface (i.e. a uniform diameter with no grooves). In a preferred embodiment, grooves  211 ,  212 , and  213  are formed as a standard machine screw thread. 
         [0024]    An improved wheel mandrel has been disclosed. While specific embodiments of the present invention have been provided, it is to be understood that these embodiments are for illustration purposes and not limiting. Many additional embodiments will be apparent to persons of ordinary skill in the art reading this disclosure.