Abstract:
A rotor having a disc and a hub assembly, in which the disc may be easily removed from the hub. The assembly has driving pins to connect the disc with the hub. The driving pins take up the tolerance between the disc and hub connection and absorb the torque applied to the rotor, preventing stress and therefore fatigue on the disc and hub.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to a rotor and more particularly to a two-piece rotor with characteristics that make the rotor more convenient and efficient to replace. 
   BACKGROUND OF THE INVENTION 
   A braking system is the most important system in a vehicle. The braking system can exert thousands of pounds of pressure on the brakes. In the braking system are disc brakes. The disc brakes use a clamping action to produce friction between a rotor and brake pads mounted in a caliper attached to a suspension member. The vehicle slows down due to the friction between the pads and the rotor. 
   A rotor is a round metal disc which rotates with a wheel of a vehicle and, in order to generate braking power, force is applied to the rotor from the brake pads. The friction force against the rotor stops the wheel from spinning and, therefore, stops the vehicle. Conventionally, a brake disc is one combined piece and very laborious to replace. 
   In today&#39;s commercial vehicle market, there are many problems with rotors having a short life span that wear out regularly due to the tremendous amount of force applied to the rotor when the vehicle is braking, especially the amount of force a commercial vehicle applies on the rotor. Therefore, the rotor needs to be replaced frequently. 
   Conventionally, a rotor is a one-piece design for a more simple and inexpensive method of manufacturing. However, replacing a rotor, which becomes necessary after the contact surfaces exhibit too much wear from the pads, includes complete disassembly of the wheel hub and disc brake assembly. The rotor for a commercial truck is extremely heavy and usually takes more than one person or machine to remove and replace, which is very time consuming and inefficient. 
   In U.S. Pat. No. 5,864,935, a two piece rotor is disclosed in order to conveniently replace the brake disc after wear on to a wheel hub. However, this design creates multiple pieces and requires multiple fasteners, which in turn requires more assembly and disassembly steps. The prior art rotor also requires that the entire rotor be removed from the wheel hub to replace the disc. 
   Accordingly, it is beneficial to have a rotor that will be replaced less frequently, in a more simplified manner, with less assembly and disassembly without removing the wheel hub, and with less parts. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a rotor for a vehicle brake system having a disc with an outside and an inside perimeter. The rotor also includes a hub which is a separate piece from the disc and connected to the disc. 
   Further, the present invention contemplates a method of assembling a rotor on to a wheel hub of a vehicle. The first step of the assembling method is connecting a hub to a wheel hub of a vehicle. The second step is connecting a disc to the hub. A further step is inserting drive mechanisms into the connected hub and disc for minimizing the tolerance between the hub and the disc and for absorbing the torque placed on the rotor. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a perspective front view of an assembled splined rotor. 
       FIG. 2  shows a perspective back view of an assembled splined rotor. 
       FIG. 3  shows a perspective cross-sectional view to illustrate the holes for driving pins. 
       FIG. 4A  shows a perspective view of a disc which is a part of the splined rotor. 
       FIG. 4B  shows a perspective cross-sectional view to illustrate the cooling passages for the disc. 
       FIG. 5  shows a perspective view of a hub which is a part of the splined rotor. 
       FIG. 6  shows a perspective cross-sectional view of the hub. 
       FIG. 7  shows a perspective view of a retaining ring. 
       FIG. 8  shows a perspective view of a spiral drive pin. 
       FIG. 9  is an enlarged view of the retaining ring and groove of  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As will be described, the preferred embodiment of the present invention overcomes the problem created by the present day necessity of replacing a worn out rotor on a disc brake system by providing a two-piece rotor design with features including a separate disc, a separate hub, and a retaining groove and pin holes for locking the two-pieces together. 
   In addition, the present invention overcomes the problem of a rotor in a disc brake system overheating and creating fractures through-out the rotor by providing cooling pockets. This feature reduces the likelihood that the rotor will reach an excessively high temperature therefore fracturing and weakening the braking system. 
   The present invention of a two piece rotor or splined rotor is designed to simplify replacement after wear or failure of the disc portion of the rotor. The rotor is secured from moving radially and axially to prevent a wheel from being unbalanced. 
   The invention will now be described with reference to the drawings. As shown in  FIG. 1 , the invention is a two-piece rotor  10  with a disc portion  20  and a hub portion  30 . 
   As shown in  FIGS. 4A and 4B , the disc  20  is ring-like with an outside perimeter  22  and an inside perimeter  24 . The disc  20  has a beveled circumferential groove  23  around the inside perimeter, illustrated in  FIG. 9 . The inside perimeter  24  outlines an opening  25  at the center of the disc  20 . Two opposing drive tangs  26  extend from the inside perimeter  24  into the opening  25  of disc  20 . 
   At both ends of the drive tangs  26  is a semi-circular cavity  27 . Openings or cooling pockets  40 , preferably six, extend from the inside perimeter  24  to the outside perimeter  22  to allow air to flow through the disc  20 . Exit openings  41  from the cooling pockets  40  are at the inside perimeter  24  where the drive tangs  26  are located. It is preferred to have three cooling pockets  40  within each drive tang  26 . The pockets are sized for maximum cooling of the rotor to prevent the disc portion from getting heat line fractures in the face of the disc. The amount of material between the pockets is also a factor because this allows for proper filling and venting of the casting when being poured at the foundry. The pockets are a must to prevent the rotor from cracking. 
   The drive tangs  26  cover about half of the inside perimeter  24  of the disc  20 . The other half of the inside perimeter  24  contains cooling slots  42  (similar to the cooling pockets  40 ) that extend from the inside perimeter  24  to the outside perimeter  22 , to allow air to flow through the disc  20 . Preferably half of the perimeters are used to allow for even distribution of the air flow thru the rotor to cool the rotor and prevent from cracking. If these pockets were to be eliminated the rotor would have hot spots and have cracking issues. 
   As shown in  FIGS. 5 and 6 , the hub  30  is generally cylindrical with a first end  32  and a second end  34 . The first end  32  has two drive tangs  33  similar to the drive tangs of the disc  20 . At the ends of each drive tang  33  is a semi-circular cavity  27 . The drive tangs  33  include openings or cooling pockets  40  that extend from the inside perimeter  36  of the hub  30  to the outside perimeter  38  of the hub  30 , similar to the cooling pockets  40  of the disc  20 . The exit openings  41  of the cooling pockets  40  are at the inside perimeter  36  of the hub  30 . The drive tangs  26  oppose each other on the first end  32  of the hub  30 . 
   The drive tangs  33  of the hub  30  take up half of the first end  32 . The other half of the first end  32  has two opposing ledges  39  located between the drive tangs  33  formed by the thickness of the hub  30 . 
   The second end  34  of the hub  30  is flanged for connecting to a wheel hub (not shown). The flanged portion  34  extends around the entire outside perimeter  38  of the hub  30  and contains multiple holes  50  and a series of scallops or curved segments  52  for attachment to a wheel hub. 
   As shown in  FIGS. 1 and 2 , the disc  20  and hub  30  are connected to each other to form the rotor  10 . The disc  20  is attached to the hub  30  by the drive tangs  26  at the first end  32  of the hub  30 . The drive tangs  26  of the disc  20  are placed on the ledges  39  of the hub  30  having the drive tangs  26  of the disc  20  and the drive tangs  33  of the hub  30  are side by side. 
   As shown in  FIG. 1 , the semi-circular cavities  27  at the end of each drive tang  26 ,  33  are adjacent and form four circular cavities to house a drive mechanism, preferably a coiled spring pin  60  shown in  FIG. 8 . The coiled spring pin  60  is used as a radial clamp force to make the disc  20  and hub  30  integral and take up any tolerances or loose gaps, as shown in  FIG. 3 , between the two pieces. A solid drive pin may also be used only if the tolerances are maintained to take-up all clearances from the mating parts. 
   As shown in  FIG. 8 , the coiled spring pin  60  is wound around an axis and is able to be compressed and is able to flex after compression. For insertion into the adjacent semi-circular cavities  27 , the coiled spring pin  60  is compressed before being inserted into the part. After insertion, the coiled spring pin  60  expands to form to the size of the part it is housed in and is able to tighten the connection of the disc  20  and the hub  30  by filling the loose gaps. When assembled, at least two of the cavities to house the drive mechanisms are used. 
   A beveled retaining ring  70 , as shown in  FIG. 7 , is used to take up axial tolerances between the disc  20  and the hub  30 . The retaining ring  20  partially fits in groove  23  on the inside perimeter  24  of the disc  20 . As shown in  FIG. 3 , the retaining ring  20  extends out from groove  23  and rests on top of the drive tangs  26 ,  33  covering and locking in the drive mechanism or coiled spring pins  60 . The retaining ring  70  prevents axial movement between the disc  20  and the hub  30 . 
   After assembly of the rotor  10 , the cooling pockets  40  of the hub  30  are aligned with the cooling slots  42  of the disc  20 . This allows air to flow throw the disc  20  and through the hub  30  to cool the center of the hub  30  and prevent high temperatures from cracking the hub  30  when the rotor  10  is in operation. 
   During operation of the rotor  10 , a high amount of torque is applied to the rotor. The torque is applied to the coiled spring pins  60 . The coiled spring pins  60  can take approximately a maximum of 212,000 psi before shearing. 
   After shearing of the drive pins, replacement coiled spring pins  60  would need to be installed in the assembly. With the two piece design, installing the replacement drive pins is more convenient and less labor intensive. The disc  20  is the only part that would need to be removed from the wheel hub. The hub  30  of the rotor will remain attached to the wheel hub. The rotor  10  with the disc  20  and hub  30  connected is very heavy for a commercial vehicle. By only having to remove the disc  20 , which weighs less than the hub  30 , for maintenance and repairs, allows for more efficiency by the mechanic. The drive pins are used as alignment devices which allows the rotor to be replaced without specialized removal of the hub from the vehicle. 
   Although the invention has been described in detail with reference to certain preferred embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiment contained herein.