Abstract:
A novel composite brake drum with a shell and a drum liner that includes one or more mid-positioned squealer bands that are roughly in line with the ribs of the brake shoes. This places the most rigid part of the brake drum and the location of greatest heat sink over the most rigid portion of the brake shoes, which is also the position of greatest heat input. The axial cooling fins radiating from the squealer band aid in dissipating the heat from friction generated during the braking cycle.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The present invention is related to brake drums, and more particularly, brake drums for heavy-duty commercial vehicles having reduced weight without the loss of required braking performance and drum integrity. 
         [0003]    2. Description Of The Related Art 
         [0004]    Like most components for heavy-duty commercial vehicles such as truck as buses, the user desires the lowest amount of weight in the vehicle while obtaining the highest amount of performance. A standard full cast brake drum weigh approximately 112 pounds, while prior composite brake drums weigh approximately 92 pounds. Brake drums can only be lightened so much before performance suffers caused by lack of structural strength, heat absorption, and thermal fatigue from the friction of the brake lining. 
         [0005]    One example of prior art attempts to lighten brake drums includes composite brake drums that contain a steel shell with gray iron centrifugally cast into the steel shell. The steel shell provides the structural strength to prevent cracking, and the gray iron liner provides the wear surface for the brake lining and heat absorption from the friction of the brake lining due to braking of the vehicle. The current shape of the composite brake drum is similar to conventional brake drum with the “squealer band” near the open end of the brake drum. Another prior art example is the “Gunite Gold” brake drum at 94 pounds. This brake drum uses high molybdenum content (&gt;0.60%) and other alloys to provide strength at high braking temperatures. However, dynamometer tests show longer brake drum life at the expense of a higher tendency of brake fade with much lower deceleration at or above 60 miles per hour. 
         [0006]    The purpose of a brake drum is to absorb the kinetic energy and potential energy of the vehicle into heat energy in the brake drum, resist the forces exerted by the brake shoes in stopping a vehicle, and transmit the braking torque to the wheels and tires of the vehicle. It is also the goal to accomplish this with components as light and cost effective as possible while maintaining the safe and effective operation of the braking system. 
         [0007]    It is the intent of the invention to improve the absorption of heat energy and resist the forces exerted by the brake shoes in a more efficient manner by moving the squealer band over the center of the brake shoes, which is the point of maximum force and maximum heat input. It is a further goal to minimize metal fatigue and brake fade based on the temperature of the brake drum while in use. 
       SUMMARY 
       [0008]    For purposes of summarizing the invention, certain aspects, advantages, and novel features of the invention have been described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any one particular embodiment of the invention. Thus, the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein. 
         [0009]    Therefore, the present invention is primarily directed to a composite brake drum with a centerline squealer band. The inventive brake drum obtains improved performance by positioning the squealer band generally in line with the ribs of the brake shoes. This places the most rigid part of the brake drum and the location of greatest heat sink over the most rigid portion of the brake shoes, which is also the position of greatest heat input. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. 
           [0011]      FIG. 1  is an outboard perspective view of a composite brake drum with a squealer band located at a middle position along the width of the brake drum, which is also over the ribs of the brake shoe; 
           [0012]      FIG. 2  is a section view of a composite brake drum showing a single squealer band located in line with the ribs of the brake shoe; 
           [0013]      FIG. 3  is a section view along line A-A of  FIG. 1  of an exemplary composite brake drum showing a single band located along the width of the brake drum to be generally in line with the ribs of the brake shoe; 
           [0014]      FIG. 4  is a section view of a brake drum showing a plurality of squealer bands located over each of a plurality of ribs of the brake shoe; and 
           [0015]      FIG. 5  is a outboard view of a brake drum. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The various embodiments of the inventive brake drum and their advantages are best understood by referring to  FIGS. 1 through 4  of the drawings. The elements of the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. 
         [0017]    The drawings represent and illustrate examples of the various embodiments of the brake drum, and not a limitation thereof. It will be apparent to those skilled in the art that various modifications and variations can be made in the brake drum described below without departing from the scope and spirit of the invention as described herein. For instance, features illustrated or described as part of one embodiment can be included in another embodiment to yield a still further embodiment. Moreover, variations in selection of materials and/or characteristics may be practiced to satisfy particular desired user criteria. Thus, it is intended that the present invention covers such modifications as come within the scope of the features and their equivalents. 
         [0018]    Furthermore, reference in the specification to “an embodiment,” “one embodiment,” “various embodiments,” or any variant thereof means that a particular feature or aspect of the invention described in conjunction with the particular embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases “in one embodiment,” “in another embodiment,” or variations thereof in various places throughout the specification are not necessarily all referring to its respective embodiment. Finally, as used in this description, terms such as “inboard” and “outboard” are to be understood as they relate to a vehicle on which the brake drum is mounted. 
         [0019]    An exemplary brake drum embodying the principles of the present invention, is generally characterized by a shell  14  made from steel or other suitable, lightweight, durable material, which houses a circumferential drum liner  15  which is formed from cast iron or other suitable friction- or wear-resistant material, a mounting plate  12  at the brake drum&#39;s outboard end with mounting holes  16  for mounting the drum to the hub of a vehicle axle, a wraparound, or shoulder portion  13 , and one or more squealer bands  11  circumscribing the brake drum. A brake drum is typically used with a brake shoe  21 , an exemplary version of which consists of a brake lining  17  that is mounted on a brake shoe table  18 . The brake shoe table  18  has one or more ribs  19  extending radially inwardly with respect to the brake drum from the table toward the interior of the drum to provide rigid support for the brake shoe table  18  and support for attachment points for a brake strut (not shown). In operation, the shoe  21  and brake lining  17  is selectively applied to the braking surface of the brake drum  10  through actuation of the brake through the rib or ribs  19  of the brake shoe  21 . Brake drum  10  converts kinetic energy and potential energy of the vehicle into heat energy by providing a friction surface for the brake linings  17  thereby transmitting brake torque to the wheels and tires of the vehicle. 
         [0020]    The main body of the brake drum  10  includes a squealer band  11  that circumscribes the brake drum positioned along the width  22  of the drum body such that when mounted on a vehicle, it is roughly in line with a brake shoe rib  19  of the brake shoe table  18 . For example, with reference to  FIG. 3 , brake drum  10  is configured so that squealer band  11  is roughly in line with the midpoint between the two brake shoe ribs  19   a, b . On either side of the squealer band  11  are a plurality of axial fins or ribs  14 . In still another embodiment, depicted in  FIG. 4 , each of a plurality of squealer bands  11   a, b  is positioned roughly in line with each of the respective brake shoe ribs  19   a, b.    
         [0021]    Typically, when a squealer band is used on a brake drum, it is positioned near the inboard, open end of the brake drum. One reason for a squealer band at the open end of the brake drum is to prevent cracks that may start at the open end and to provide rigidity at the open end of the brake drum. A squealer band located midway along the width of the drum body goes against this concept. While the heat generated by the friction of the brake lining is suppose to be evenly distributed along the braking surface of a brake drum, the heat input to a brake drum is greatest at the most rigid portion of the brake shoe, i.e., opposite the brake shoe rib  19 , where the lining contact pressure is greatest. Positioning the squealer band  11  at the location of the greatest heat input provides the most efficient use of the brake drum material for a heat sink during the braking operation. Additionally, positioning the squealer band  11  in line with the brake shoe ribs  19  sets the most rigid part of the brake drum to receive the most force from the brake shoe, and, therefore, provides the most efficient use of structure to resist the forces exerted by the brake shoes when they are applied to the braking surface. 
         [0022]    As described above and shown in the associated drawings, the present invention comprises a lightweight brake drum with middle position squealer band. While particular embodiments of the invention have been described, it will be understood, however, that the invention is not limited thereto, since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. It is, therefore, contemplated by the following claims to cover any such modifications that incorporate those features or those improvements that embody the spirit and scope of the present invention.