Abstract:
An improved brake drum and method for balancing a brake drum are provided. A section of the raised squealer band of the brake drum is removed to correct the imbalance. Preferably, a cutting machine is used to make a continually varying depth cut along a section of the squealer band to correct the imbalance.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to brake drums and, in particular, to improved balanced brake drums and a method of balancing such brake drums.  
         [0002]     Most brake drums for trucks and similar heavy duty vehicles are comprised of a cast iron brake drum that is subsequently machined to near final tolerances. Typically, the machine brake drum has a slight imbalance that needs to be corrected. Accordingly, the brake drum is subjected to a balancing operation. Such balancing can comprise welding correcting weights to an outer surface of the drum or removing part of the brake drum.  
         [0003]     In particular, brake drums that have an integral raised squealer band extending from near an open end of the brake drum can be balanced by removing a portion of the squealer band. Such balancing by removing a portion of the squealer band to a constant or substantially constant depth is shown in U.S. Pat. No. 5,483,855. Another method of balancing is shown in U.S. Pat. No. 4,986,149, which utilizes a complex mechanism for measuring the imbalance and removing a crescent or wedge of material from the integral squealer band by the use of a lathe in a complex turning process.  
       SUMMARY OF THE INVENTION  
       [0004]     It is an object of the present invention to provide an improved balanced brake drum having a section of the integral raised squealer band removed.  
         [0005]     It is another object of the present invention to provide an improved method of balancing a brake drum by removing a portion of the integral raised squealer band.  
         [0006]     It is another object of the present invention to provide an improved method of balancing a brake drum by removing a portion of the integral raised squealer band leaving a portion of the squealer band with a continually varying thickness.  
         [0007]     The improved method for balancing a brake drum in accordance with the present invention utilizes a cutting or milling machine to remove a portion of the squealer band along a predetermined length and at a constantly varying depth into the squealer band. The entry cut is at a very small angle with regard to the circumferential edge of the squealer band so as to avoid stress concentrations at the point of entry. Typically, the cut can be one of several variations, all of which are included in the requirement that the cut result in a constantly varying depth of squealer band. For example, if the cut were at an extremely large radius of curvature, to the point that the cut is a straight line, the cut would form a chord across and into the squealer band. If the cut were at a lesser radius of curvature, but still greater radius of curvature than that of the squealer band itself, the cut would form a convex shape along its length. It is also possible that the cut could comprise to two straight sections, one entering the squealer band to a predetermined depth and then exiting the squealer band to form two separate areas of the cut. Each such section could be straight or curved, either to form a generally convex cut or even a generally concave cut. The removed section could also itself form a concave curved section into the squealer band. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a perspective view of a brake drum and accordance with the present invention;  
         [0009]      FIG. 2  is an end view of the hub end of the brake drum in accordance with the present invention;  
         [0010]      FIG. 3  is an end view of the open end of the brake drum in accordance with the present invention;  
         [0011]      FIG. 4  is an end view of the open end of the brake drum showing a first embodiment of the squealer band balancing in accordance with the present invention;  
         [0012]      FIG. 5  is an end view of the open end of the brake drum showing a second embodiment of the squealer band balancing in accordance with the present invention;  
         [0013]      FIG. 6  is an end view of the open end of the brake drum in accordance with the present invention showing a third embodiment of the squealer band balancing;  
         [0014]      FIG. 7  is an end view of the open end of the brake drum in accordance with the present invention showing a fourth embodiment of the squealer band balancing,  
         [0015]     And  FIG. 8  is an end view of the open end of the brake drum in accordance with the present invention showing a fifth embodiment of the squealer band balancing. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     Referring to  FIGS. 1-3  of the drawings, a brake drum in accordance with an embodiment of the present invention is shown generally at  10 . It is seen that brake drum  10  is a generally cylindrical structure, having a circular open end  12  and a nearly cylindrical braking section  14  extending from open end  12  to hub end  16 . Hub end  16  is seen to comprise a generally flat inner surface  21  that terminates by forming circular hub opening  20 . A plurality of wheel lug openings  22  are spaced around inner surface  21  of hub end  16 .  
         [0017]     Transition section  18  is seen to extend from braking section  14  to inner surface  21  of hub end  16 . Braking section  14  itself is a generally cylindrical section extending at a nearly normal relation to open end  12 . However, it is also understood that a preferred embodiment of the present invention could have the outer surface of braking section  14  extending at a slightly less than normal angle to open end  12 .  
         [0018]     It should be understood that brake drum  10  is typically made of cast iron in a foundry operation. Accordingly, finishing machining operations are necessary prior to the final balancing of brake drum  10 . Such machining would include the finishing of an inner surface  25  of braking section  14  to assure a nearly perfect inner cylindrical surface. Such surfaces necessary to accommodate the brake pads from the braking structure that brake drum  10  would surround. Further, the edges of open end  12  and squealer band  24  are machined.  
         [0019]     Brake drum  10  is then final balanced using the method of the present invention.  
         [0020]     Referring to  FIGS. 1-3 , it is seen that a section of squealer band  24  has been removed at  30 , extending from entry location  32  to exit location  34 . This section is removed by use of a milling machine which is set up to avoid any plunge-type entry or exit cuts, but rather the machine removes the section of squealer band  24  in a manner to create a continuously varying depth of squealer band  24  below removed section  30 .  
         [0021]     Referring now to  FIG. 4 , the squealer band  24  is shown in an exaggerated thickness, as is brake drum  10  viewed from open end  12 . Removed section  30  is seen to be a chord or straight line from entry point  32  to exit point  34 . It is readily seen that the depth of the cut or removed section  30  is of a nature to cause squealer band  24  to be of a continually varying thickness below removed section  30 .  
         [0022]     Referring now to  FIG. 5 , brake drum  10  with open end  12  is again depicted with the thickness of squealer band  24  shown in an exaggerated manner to show the details of the removed section. In this embodiment of the present invention, the milling machine is set up to enter squealer band end  38 , cut material along a straight line  42  to a center point  43  and then continue along straight line  44  to exit point  40 . It is seen that the depth of the removed squealer band  24  beneath the removed areas  42  and  44  is of a continually varying nature. It should also be understood that point  43  is not necessarily an abrupt junction between straight sections  42  and  44 , but could rather be an arcuate section.  
         [0023]     Referring now to  FIG. 6  of the drawings, brake drum  10  is viewed from open end  12  with the thickness of squealer band  24  exaggerated to depict the removed section in the balancing operation in accordance with the present invention. The milling machine is set up to begin its cut into squealer band  24  at  50  and exit at  52 , with an arcuate, concave section formed along  54 . It is seen that the thickness of squealer band  24  beneath arcuate removed section  54  is continually varying.  
         [0024]     Referring now to  FIG. 7  of the drawings, brake drum  10  is viewed from open end  12 , with the thickness of squealer band  24  exaggerated to show the details of the section removed in the balancing operation. Here the milling machine is seen to enter at  60  removing material from squealer band  24  along straight line  64  downwardly to a point  65 , and then outwardly at an angle along the straight line  66  exiting at  62 . Here it is seen that the removed section that the thickness of squealer band  24  beneath the removed section  64  and  66  is of a continually varying depth. It should also be understood that point  65  is not necessarily an abrupt junction between straight section  64  and  66  but rather may be somewhat of an arcuate section.  
         [0025]     Referring now to  FIG. 8  of the drawings, another embodiment of a balanced brake drum in accordance with the present invention is shown. Here brake drum  10  is shown from open end  12  with the thickness of squealer band  24  exaggerated to depict the present invention. Here the balancing operation is formed with the milling machine beginning its cut into squealer band  24  at  70 , extending along an arcuate section of a radius greater than the radius of the outer circumference of squealer band  24  and exiting squealer band  24  at  72 . Accordingly, it is seen that the thickness of squealer band beneath removed section  71  is of a continually varying thickness.