Abstract:
The invention uses structural damping to reduce noise in brake pads in lieu of the traditional method of isolation of the noise by application of a vibration insulator. The invention eliminates the problems and costs associated with applying insulators to the brake pads. The invention geometrically alters the friction back plate to move frequencies away from the resonant frequencies, increase scattering and enhance absorption. Attenuation is greater in back plates made with the invention techniques. The geometry can be changed by machining or embossing. The benefits are substantial in that the invention will reduce costs, reduce weight, reduce noise and increase wearing thickness.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a brake pad for use with disc brake systems that has an integral noise reducing structure. 
         [0003]    2. Description of the Prior Art 
         [0004]    Disc brakes were used in the U.S. on a select group of vehicles in the mid to late 1960&#39;s. They did not become main stream until the early 1970&#39;s and by the end of the decade almost all vehicles produced in the U.S. had front disc brakes. Brake noise has always been a concern over the years. A number of techniques were developed to reduce noise in disc brakes including changes to the compound used in the friction material or the addition of chamfers, rounded edges, or slots to the friction material among other changes to the friction material. 
         [0005]    An insulator consisting of a thin piece of metal and a dampening material was developed to stop noise in disc brake applications. Many configurations of insulators have been used over the years. Multiple layers consisting of rubber-steel-rubber, steel-rubber-steel, and a variety of materials have been used. Some have used further materials applied to the back plate. 
         [0006]    The insulator was first used by the original equipment manufacturers (“OEMs”) to reduce warranty claim rates from brake noise. Even though insulators did not stop all brake noise a small improvement was a big savings on vehicles covered by warranty. 
         [0007]    The aftermarket equipment manufacturers commonly refer to insulators as shims because it appears as though the insulator is placed on the back of the pad to act as a shim. 
         [0008]    Insulators have grown in popularity at the OEM level and in the aftermarket. Today almost all new cars and dealer service parts have insulators. All but a few aftermarket disc brake pads have insulators. 
         [0009]    None of the prior art brake pads are seen to teach or suggest the unique features of the present invention or to achieve the advantages of the present invention. 
       SUMMARY OF THE INVENTION 
       [0010]    The invention uses structural features that are at least in part integral to the back plate to reduce noise in brake pads in lieu of, or in combination with, the traditional method of reducing noise by application of a separate vibration insulator or cover for the back plate known in the art as a shim. The invention eliminates the problems and costs associated with applying the separate vibration insulators to the brake pads. The invention geometrically alters the back plate of the brake pad to change the resonant or natural frequency of the brake pad, thus increasing scattering and enhancing absorption. Attenuation of noise is as good or greater in back plates employing the techniques of the present invention as compared with brake pads employing the traditional methods of noise reduction. The geometry can be changed by machining or embossing. The benefits are substantial in that the invention will reduce costs, reduce weight, reduce noise and increase wearing thickness. 
         [0011]    Accordingly, it is an object of the invention to provide a brake pad having an integral noise reduction feature. 
         [0012]    It is another object of the invention to provide a brake pad that achieves adequate noise reduction at reduced cost. 
         [0013]    It is yet another object of the invention to provide a brake pad having an integral pattern of indentations or cavities on the back side of the backing plate of the brake pad. 
         [0014]    It is yet another object of the invention to provide a brake pad having an integral pattern of indentations or cavities on the back side of the backing plate of the brake pad that is simple to manufacture. 
         [0015]    These and other objects of the present invention will become apparent from the attached description and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is an environmental view showing the general configuration of a disc brake system including a pair of brake pads. 
           [0017]      FIG. 2  is an isometric view of a brake pad showing the brake lining that frictionally engages the brake rotor to slow or stop the vehicle. 
           [0018]      FIG. 3  shows a brake pad in accordance with a first embodiment of the present invention that has a crisscross pattern of grooves having a triangular cross section provided on the backside of the back plate of the brake pad. 
           [0019]      FIG. 4  shows a brake pad in accordance with a second embodiment of the present invention that has a random pattern of X-shaped indentations provided on the backside of the back plate of the brake pad. 
           [0020]      FIG. 5  shows a brake pad in accordance with a third embodiment of the present invention that has a random pattern of conical indentations provided on the backside of the back plate of the brake pad. 
           [0021]      FIG. 6  shows a brake pad in accordance with a fourth embodiment of the present invention that has a crisscross pattern of grooves having a rectangular cross section provided on the backside of the back plate of the brake pad. 
           [0022]      FIG. 7  shows a brake pad in accordance with another embodiment of the present invention that has a pattern of vertical rows of cylindrical cavities provided on the backside of the back plate of the brake pad. 
           [0023]      FIG. 8  shows a brake pad in accordance with yet another embodiment of the present invention that has a pattern of diagonal rows of cylindrical cavities provided on the backside of the back plate of the brake pad. 
           [0024]      FIG. 9  shows a brake pad in accordance with yet another embodiment of the present invention that has a random pattern of cylindrical cavities provided on the backside of the back plate of the brake pad. 
           [0025]      FIGS. 10A-10B  show a brake pad in accordance with yet another embodiment of the present invention that has a cutout extending along the outer periphery of the backside of the back plate of the brake pad. 
           [0026]      FIGS. 11A-11B  show a brake pad in accordance with yet another embodiment of the present invention that has a groove extending in proximity to the outer periphery of the backside of the back plate of the brake pad. 
           [0027]      FIG. 12  shows a brake pad in accordance with yet another embodiment of the present invention that has an annular groove provided in the backside of the back plate of the brake pad. 
           [0028]      FIG. 13  shows a brake pad in accordance with yet another embodiment of the present invention that has a pattern of horizontal rows of X-shaped cavities provided on the backside of the back plate of the brake pad. 
           [0029]      FIGS. 14A-14B  show a brake pad in accordance with yet another embodiment of the present invention that has a pattern of vertical rows of conical cavities provided on the backside of the back plate of the brake pad. 
           [0030]      FIGS. 15A-15B  show a noise reducing shim or cover used in conjunction with a brake pad in accordance with the present invention. 
           [0031]      FIG. 16  is a cutaway view illustrating noise damping material filling the cavities in the backside of the back plate of a brake pad in accordance with the present invention. 
           [0032]      FIG. 17  is a cutaway view illustrating noise damping material filling the cavity in the backside of the back plate of a brake pad as illustrated in  FIGS. 11A-11B . 
           [0033]      FIG. 18  is a cutaway view illustrating noise damping material filling the cavity in the backside of the back plate of a brake pad as illustrated in  FIGS. 10A-10B . 
           [0034]      FIG. 19  is a cutaway view illustrating noise damping material filling the cavity in the backside of the back plate of a brake pad as illustrated in  FIG. 12 . 
           [0035]      FIG. 20  is a plot of the ten data points for five of the sample brake pads tested. 
           [0036]      FIG. 21  shows a brake pad in accordance with yet another embodiment of the present invention that has a random pattern of cylindrical cavities with diameters of approximately 0.1 inch provided on the backside of the back plate of the brake pad. 
           [0037]      FIG. 22  shows a brake pad in accordance with yet another embodiment of the present invention that has a random pattern of cavities in the shape of square base parallelepipeds provided on the backside of the back plate of the brake pad. 
           [0038]      FIG. 23  shows a brake pad in accordance with yet another embodiment of the present invention that has a random pattern of cavities with hexagonal cross sections provided on the backside of the back plate of the brake pad. 
           [0039]      FIG. 24  shows a brake pad in accordance with yet another embodiment of the present invention that has a random pattern of cavities with octagonal cross sections provided on the backside of the back plate of the brake pad. 
           [0040]      FIG. 25  is a fragmentary view showing a sampling of the variety of inner end geometries that can be used with the cavities having circular or square cross sections provided in the backside of the back plate of the brake pads according to the present invention. 
           [0041]      FIG. 26  is a fragmentary view showing a sampling of the variety of inner end geometries that can be used with the cavities having hexagonal or octagonal cross sections provided in the backside of the back plate of the brake pads according to the present invention. 
           [0042]      FIG. 27  is a fragmentary view showing a sampling of the variety of cavity geometries, including cavities that extend through the entire thickness of the back plate, cavities that terminate in projections on the front side of the back plate, and cavities that extend through projections on the front side of the back plate, that can be used for the cavities provided in the back plate of the brake pads according to the present invention. 
           [0043]      FIGS. 28A-28B  show the inside and the outside of a DRT shim, respectively. 
           [0044]      FIGS. 29A-29B  show the inside and the outside of a Wolverine shim, respectively. 
           [0045]      FIGS. 30A-30D  show outboard and inboard pads and shims from OEM manufacturer. 
           [0046]      FIGS. 31A-31D  show outboard and inboard shims for OEM manufactured pads. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0047]    Referring to  FIGS. 1-20 , the present invention is directed to brake pads, such as for example brake pads  100   a - 1 , that are provided with an integral noise reduction structure. The integral noise reduction structure primarily includes indentations or cavities formed in the back surface of the back plate of the brake pad. The cavities or indentations may include one or more individual cavities or a plurality of interconnected cavities. The cavities have a top opening that is essentially coplanar with the back surface of the back plate of the brake pad. The maximum depth of the cavities or indentations is less than the thickness of the back plate of the brake pad such that the cavities or indentations do not penetrate completely through the thickness of the back plate of the brake pad. Accordingly, the cavities or indentations are closed at one end, in other words the cavities or indentations are blind, and the cavities or indentations at most extend through a portion of the thickness of the back plate of the brake pad. The patterns of the cavities are a combination of straight lines or curved lines both intersecting and not intersecting. Spacing is dependent upon the amplitude and frequency of the vibration being dampened. The deeper the cavity, the more effective the dampening of the noise will be. Proper selection of depth and configuration can increase stiffness and strength of the back plate. The depth and the pattern must be carefully chosen so as not to structurally degrade the back plate. Effective cavity depths can range from as little as 0.003 inch to 0.210 inch depending upon the thickness of the back plate. The patterns of cavities tested had cavity depths within a range from approximately 0.015 inch to approximately 0.075 inch. Some of the patterns of cavities tested had cavity widths within a range of approximately one thirty seconds ( 1/32 inch) of an inch to approximately one eighth (⅛ inch) of an inch. 
         [0048]    The brake pad  100   a  has a back plate  102   a  that has a back side  104   a  and a front side  106   a . The front side is covered in large part by the friction lining  108  as is typical for a brake pad. The brake lining  108  is made of any of the well-known materials typically employed for brake linings. Suitable material for brake linings include, but are not limited to, Aramid-containing, TWARON®-containing or other composites; however, any known material suitable for use as brake lining may be used for the brake liners in the brake pads of the present invention without departing from the scope of the present invention. The brake pads  100   a ,  100   b ,  100   c  and  100   d  are designed to be drop-in replacements for the standard brake pads of disc brake systems. 
         [0049]    The brake pad  100   a  has a crisscross pattern of grooves provided on the backside  104   a  of the back plate  102   a  of the brake pad. The grooves  110  have triangular cross sections. Grooves having rectangular or trapezoidal cross sections may also be employed in the brake pad according to the present invention. 
         [0050]    The brake pad  100   d  has a crisscross pattern of grooves provided on the backside  104   d  of the back plate  102   d  of the brake pad. The grooves  116  have rectangular cross sections. The front side  106   d  of the back plate  102   d  is covered in large part by the friction lining  108  as is typical for a brake pad. 
         [0051]    The brake pad  100   b  has a random pattern of X-shaped indentations  112  provided on the backside  104   b  of the back plate  102   b  of the brake pad. The X-shaped indentations  112  are randomly distributed on the back side of the back plate of the brake pad  100   b  and are of a variety of different sizes including different depths and different areas as seen in plan view. Each of the X-shaped indentations  112  are provided by pairs of perpendicular grooves having rectangular cross sections. The X-shaped indentations  112  may also be formed by grooves having rectangular or trapezoidal cross sections. The orientation of the X-shaped indentations  112  may also be varied. For example, the X-shaped indentations  112  may be oriented in the same way as “plus” signs or have any other angular orientation. In addition, the X-shaped indentations  112  may have randomly varying orientations. The front side  106   b  of the back plate  102   b  is covered in large part by the friction lining  108  as is typical for a brake pad. 
         [0052]    The brake pad  100   c  has a random pattern of conical indentations  114  provided on the backside  104   c  of the back plate  102   c  of the brake pad. The conical indentations  114  are randomly distributed on the back side of the backing plate of the brake pad  100   c  and are of a variety of different sizes including different depths and different areas as seen in plan view. In addition to the conical indentations illustrated, pyramidal, tetrahedral, rhomboid, spherical, cylindrical, elliptical, ogival indentations or cavities, and cavities in the shape of a rectangular parallelepiped, or any combinations of these, may be employed in a brake pad in accordance with the present invention. The front side  106   c  of the back plate  102   c  is covered in large part by the friction lining  108  as is typical for a brake pad. 
         [0053]    Referring to  FIG. 7 , a brake pad  100   e  in accordance with yet another embodiment of the present invention can be seen. The brake pad  100   e  has a pattern of vertical rows of cylindrical cavities  118  provided on the backside  104   e  of the back plate  102   e  of the brake pad  100   e.    
         [0054]    The brake pad  100   e  has the cylindrical cavities  118  provided in evenly spaced rows on the backside  104   e  of the back plate  102   e  of the brake pad. Each row of cylindrical cavities extends along a line parallel to the central plane of symmetry of the brake pad  100   e , which is perpendicular to the back plate  102   e  and passes through the middle of the brake pad and divides the brake pad into two symmetrical halves. The front side  106   e  of the back plate  102   e  is covered in large part by the friction lining  108  as is typical for a brake pad. 
         [0055]    Referring to  FIG. 8 , a brake pad  100   f  in accordance with yet another embodiment of the present invention can be seen. The brake pad  100   f  has a pattern of diagonal rows of cylindrical cavities  120  provided on the backside  104   f  of the back plate  102   f  of the brake pad  100   f.    
         [0056]    The brake pad  100   f  has the cylindrical cavities  120  provided in evenly spaced rows on the backside  104   f  of the back plate  102   f  of the brake pad. Each row of cylindrical cavities extends along a line that is at a 45° angle to the central plane of symmetry of the brake pad  100   f , which is perpendicular to the back plate  102   f  and passes through the middle of the brake pad and divides the brake pad into two symmetrical halves. The front side  106   f  of the back plate  102   f  is covered in large part by the friction lining  108  as is typical for a brake pad. 
         [0057]    Referring to  FIG. 9 , a brake pad  100   g  in accordance with yet another embodiment of the present invention can be seen. The brake pad  100   g  has a random pattern of cylindrical cavities  122  provided on the backside  104   g  of the back plate  102   g  of the brake pad  100   g.    
         [0058]    The cylindrical cavities  122  are randomly distributed on the back side of the back plate of the brake pad  100   g  and are of a variety of different sizes including different depths and different areas as seen in plan view. The front side  106   g  of the back plate  102   g  is covered in large part by the friction lining  108  as is typical for a brake pad. 
         [0059]    Referring to  FIGS. 10A-10B , a brake pad  100   h  in accordance with yet another embodiment of the present invention can be seen. The brake pad  100   h  has a cutout  124  extending along the outer periphery of the backside  104   h  of the back plate  102   h  of the brake pad  100   h.    
         [0060]    The brake pad  100   h  has the cutout  124  extending along the outer periphery of the backside  104   h  of the back plate  102   h  and to the outer perimeter of the backside  104   h  of the back plate  102   h  so as to form a step extending along at least a majority of the outer periphery of the backside  104   h  of the back plate  102   h , thus leaving a raised central platform  126  on the backside  104   h  of the back plate  102   h . Accordingly, the cutout  124  is open both at the top and on one side that is coincident with the outer perimeter of the back plate  102   h . The front side  106   h  of the back plate  102   h  is covered in large part by the friction lining  108  as is typical for a brake pad. 
         [0061]    Referring to  FIGS. 11A-11B , a brake pad  100   i  in accordance with yet another embodiment of the present invention can be seen. The brake pad  100   i  has a groove  128  extending in proximity to the outer periphery of the backside  104   i  of the back plate  102   i  of the brake pad  100   i.    
         [0062]    The brake pad  100   i  has the groove  128  extending substantially in parallel to and spaced apart from the outer perimeter of the backside  104   i  of the back plate  102   i , while being in proximity to the outer perimeter of the backside  104   i  of the back plate  102   i , for at least a majority of the outer periphery of the backside  104   i  of the back plate  102   i . In the illustrative example of  FIGS. 11A-11B , the groove  128  extends substantially in parallel to the outer perimeter of the backside  104   i  of the back plate  102   i  for essentially the entire outer periphery of the backside  104   i  of the back plate  102   i . The front side  106   i  of the back plate  102   i  is covered in large part by the friction lining  108  as is typical for a brake pad. 
         [0063]    Referring to  FIG. 12 , a brake pad  100   j  in accordance with yet another embodiment of the present invention can be seen. The brake pad  100   j  has an annular groove  130  provided in the backside  104   j  of the back plate  102   j  of the brake pad  100   j.    
         [0064]    The annular groove  130  corresponds approximately to the annular contact surface of the piston  206  in terms of its area and its inner and outer diameters. The front side  106   j  of the back plate  102   j  is covered in large part by the friction lining  108  as is typical for a brake pad. 
         [0065]    Referring to  FIG. 13 , a brake pad  100   k  in accordance with yet another embodiment of the present invention can be seen. The brake pad  100   k  has a pattern of horizontal rows of X-shaped cavities  132  provided on the backside  104   k  of the back plate  102   k  of the brake pad  100   k.    
         [0066]    The brake pad  100   k  has the X-shaped cavities  132  provided in evenly spaced rows on the backside  104   k  of the back plate  102   k  of the brake pad. Each row of X-shaped cavities  132  extends along a line perpendicular to the central plane of symmetry of the brake pad  100   k , which is perpendicular to the back plate  102   e  and passes through the middle of the brake pad and divides the brake pad into two symmetrical halves. The front side  106   k  of the back plate  102   k  is covered in large part by the friction lining  108  as is typical for a brake pad. 
         [0067]    Referring to  FIGS. 14A-14B , a brake pad  100   l  in accordance with yet another embodiment of the present invention can be seen. The brake pad  100   l  has a pattern of vertical rows of conical cavities  134  provided on the backside  104   l  of the back plate  102   l  of the brake pad  100   l.    
         [0068]    The brake pad  100   l  has the conical cavities  134  provided in evenly spaced rows on the backside  104   l  of the back plate  102   l  of the brake pad. Each row of conical cavities extends along a line parallel to the central plane of symmetry of the brake pad  100   l , which is perpendicular to the back plate  102   l  and passes through the middle of the brake pad and divides the brake pad into two symmetrical halves. The front side  106   l  of the back plate  102   l  is covered in large part by the friction lining  108  as is typical for a brake pad. 
         [0069]      FIGS. 15A-15B  show a noise reducing shim or cover  136  that can be used with any of the brake pads disclosed above to achieve additional noise reduction. The shim  136  is made of sheet metal plate  138  that covers at least a majority of the backside of the back plate of the brake pad. The plate  138  is provided with resilient claws  140  for holding the shim  136  over the backside of the back plate of the brake pad. In the illustrated example, the shim  136  is used in conjunction with the brake pad  100   l . In the illustrated example, the plate  138  is clad on both sides by layers of noise damping material  142 . Examples of noise damping material include butyl-rubber and other types of rubber and plastic. The noise damping material layer  142  may be provided on only one side of the plate  138 . 
         [0070]      FIG. 16  is a cutaway view illustrating noise damping material for filling the cavities in the backside of the back plate of brake pads made in accordance with the present invention to further enhance noise reduction. The filling  144  is for the cylindrical cavities  118  and  120 . The filling  146  is for the conical cavities  134 . The filling  148  is for the X-shaped cavities  132 . Examples of noise damping material include butyl-rubber and other types of rubber and plastic. In addition to noise damping material filling the cavities, the entire backside of the back plate of brake pads may be clad in a layer of noise damping material, which may be molded in one piece with the material filling the cavities. 
         [0071]      FIG. 17  is a cutaway view illustrating a noise damping material filling  150  for the groove  128  in the backside of the back plate of the brake pad  100   i  as illustrated in  FIGS. 11A-11B .  FIG. 18  is a cutaway view illustrating a noise damping material filling  152  for the cutout  124  in the backside of the back plate of the brake pad  100   h  as illustrated in  FIGS. 10A-10B .  FIG. 19  is a cutaway view illustrating a noise damping material filling  154  for the annular cavity  130  in the backside of the back plate of the brake pad  100   j  as illustrated in  FIG. 12 . Examples of noise damping material include butyl-rubber and other types of rubber and plastic. At present, butyl-rubber is the preferred noise damping material. 
         [0072]      FIG. 20  is a plot of the ten data points for five of the sample brake pads tested.  FIG. 20  shows that every embodiment of the invention tested showed improved performance in terms of noise reduction in comparison to standard brake pads. 
         [0073]    Other than the geometry of the indentations of cavities provided on the back sides of the brake pads, the brake pads  100   a  through  100   l  are essentially identical. The embodiments of the present invention that employ multiple individual cavities or indentations are provided with more than three cavities or indentations. In the illustrated examples of this type of noise reduction structure, the back surface of the back plate of the brake pad is provided with a dozen or more cavities or indentations. Cavities and indentations are used interchangeably in this description of the invention and in the appended claims. 
         [0074]    The cavities or indentations provided on the back side of the backing plate of the brake pads of the present invention may be formed by machining the back side of the backing plate. However, for high volume and low cost manufacture methods such as embossing, coining, stamping, rolling, and press forming would be preferred. The brake pads according to the present invention provide good noise reduction. 
         [0075]    Referring to  FIG. 1 , a disc brake system  200  using the brake pads of the present invention can be seen. The brake system  200  is of the floating caliper type. The brake pads of the present invention are equally well suited for use in disc brake systems of the fixed caliper type that employ hydraulically actuated pistons on both sides of the brake rotor  202 . The brake system  200  includes a rotor or disc  202  that fits on the wheel hub and rotates with the wheel (not shown) of a vehicle. The caliper  204  is supported near the wheel hub such that it can position a brake pad, such as brake pads  100   a  through  100   l , on either side of the rotor  202 . The caliper is supported for limited movement in the direction of the axis of rotation of the wheel hub  212 , hence the term “floating caliper.” The caliper  204  has a piston cylinder  208  that houses a hydraulically actuated piston  206  for rectilinear to and fro movement in a direction parallel to the direction of the axis of rotation of the wheel hub  212 . Hydraulic fluid under pressure is supplied to the cylinder  208  via hydraulic line  210  to effect braking. The brake pads are positioned such that their brake linings  108  frictionally engage the rotor  202  during braking. When the cylinder  208  is pressurized with hydraulic fluid, the piston  206  pushes one brake pad, e.g. the brake pad  100   a  on the right side of the caliper  204 , against one side of the rotor  202  while the caliper  204  pulls the other brake pad into engagement with the other side of the rotor  202  such that the brake pads frictionally engage the rotor  202  on both sides and thereby brake and eventually stop the wheel. 
         [0076]    The advantages of the brake pads in accordance with the present invention are as follows:
       Structural damping to reduce noise   Lighter Weight   Greater friction thickness increasing pad life   Reduced failures   Less pedal travel creating a better pedal feel   Reduced cost       
 
       Comparative Testing 
       [0083]    Samples of three standard brake pads, i.e. pads that are currently available commercially, were compared with several prototype brake pads made in accordance with the invention using the GrindoSonic™ MK4 acoustic testing apparatus using the “impulse excitation technique” in accordance with the instructions of the manufacturer of the apparatus. The test was conducted using the procedure described at the following website: 
         [0084]    http://www.kraussgmbh.de/forum/viewtopic.php?f=18&amp;t=115 
         [0085]    During the test, a small elastic and non-destructive impulse or tap is applied to one part of the sample brake pad and a probe called a piezoelectric detector, measures the vibration that has traveled through the sample. Tapping is accomplished by a small tapping device or a hammer. The operator taps the sample and a reading appears on the screen in just a few seconds. 
         [0086]    The reading on the screen of the GrindoSonic machine (“R”) is equal to twice the period of the fundamental vibration of the part being tested expressed in microseconds. The frequency in Hz of the fundamental vibration can be obtained using the formula f=2,000,000/R. The numbers listed in the table of test results are the values for R obtained for each test of a sample brake pad being tested. The values of R have been found to positively correlate with noise damping such that the higher the value of R, the higher will be the amount of noise reduction. 
         [0087]    Testing was done with the piezoelectric detector provided in the testing kit supplied with the GrindoSonic apparatus. The kit also contains various kinds of hammers for different applications. The larger the brake pads, the larger the hammer to be used for the excitation of the parts. 
       Test Results 
       [0088]    The data Table below is the result of twelve tests performed on each sample type, with the highest and lowest numbers eliminated to minimize test variance. The first column describes the brake pad type tested, i.e. briefly describes the pattern that was formed in the back surface of the back plate of the brake pad, with the parts labeled “Production” or “Standard Plate,” being the unaltered plates. Three production plates were tested to obtain an accurate average number. The graph in  FIG. 20  plots the ten data points for five of the samples. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Grindosonic ™ Evaluation - Embossed Back Plate vs. Standard Back Plate 
               
               
                 GrindoSonic Output “R” Value (Data Eliminating One High and One Low Value) 
               
             
          
           
               
                   
                 Test 
                 Test 
                 Test 
                 Test 
                 Test 
                 Test 
                 Test 
                 Test 
                 Test 
                 Test 
                   
               
               
                 Brake Pad Type 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
                 10 
                 Average 
               
               
                   
               
             
          
           
               
                 Horizontal “X” 
                 64 
                 64 
                 64 
                 64 
                 64 
                 64 
                 64 
                 64 
                 63 
                 63 
                 63.80 
               
               
                 (FIG. 13) 
               
               
                 Random “X” 
                 63 
                 63 
                 63 
                 63 
                 63 
                 63 
                 63 
                 63 
                 63 
                 63 
                 63.00 
               
               
                 (FIG. 4) 
               
               
                 Vertical “O” 
                 64 
                 65 
                 62 
                 63 
                 64 
                 63 
                 63 
                 64 
                 63 
                 64 
                 63.50 
               
               
                 (FIGS. 14A-14B) 
               
               
                 Random “O” 
                 63 
                 63 
                 63 
                 63 
                 63 
                 63 
                 63 
                 63 
                 63 
                 63 
                 63.00 
               
               
                 (FIG. 5) 
               
               
                 Diamond Cross Hatch 
                 78 
                 78 
                 78 
                 78 
                 78 
                 78 
                 78 
                 78 
                 78 
                 78 
                 78.00 
               
               
                 (FIG. 6) 
               
               
                 Production 1 
                 62 
                 62 
                 61 
                 62 
                 62 
                 61 
                 61 
                 62 
                 63 
                 61 
                 61.70 
               
               
                 Production 2 
                 62 
                 61 
                 61 
                 62 
                 62 
                 62 
                 62 
                 61 
                 61 
                 62 
                 61.60 
               
               
                 Production 3 
                 62 
                 62 
                 62 
                 61 
                 62 
                 61 
                 62 
                 62 
                 62 
                 61 
                 61.70 
               
               
                 Right Angle Circles 
                 64 
                 64 
                 64 
                 64 
                 64 
                 64 
                 64 
                 64 
                 64 
                 64 
                 64.00 
               
               
                 (FIG. 7) 
               
               
                 Random Circles 
                 67 
                 67 
                 67 
                 67 
                 67 
                 67 
                 67 
                 67 
                 67 
                 67 
                 67.00 
               
               
                 (FIG. 9) 
               
               
                 Piston Cut Out 
                 65 
                 65 
                 65 
                 65 
                 65 
                 65 
                 65 
                 65 
                 65 
                 65 
                 65.00 
               
               
                 (FIG. 12) 
               
               
                 Outer Pad Cut Out 
                 64 
                 65 
                 65 
                 64 
                 65 
                 65 
                 65 
                 65 
                 65 
                 65 
                 64.80 
               
               
                 (FIGS. 10A-10B) 
               
               
                   
               
             
          
         
       
     
         [0089]    Referring to  FIGS. 21-27 , additional embodiments of the present invention can be seen.  FIG. 21  illustrates a brake pad  100   m  in accordance with yet another embodiment of the present invention, which is a variation of the embodiment of  FIG. 9 . The brake pad  100   m  has a random pattern of cylindrical cavities  122   m  having circular cross sections provided on the backside  104   m  of the back plate  102   m  of the brake pad  100   m . The cavities  122   m  are in the form of right circular cylinders at least up to their inner end portions. 
         [0090]    The cylindrical cavities  122   m  are randomly distributed on the back side of the back plate of the brake pad  100   m  and are of an approximately uniform size, meaning that the cavities have approximately the same area in plan view and are approximately of the same depth. The front side  106   m  of the back plate  102   m  is covered in large part by the friction lining  108  as is typical for a brake pad. Referring to  FIG. 25 , a section through the back plate  102   m  shows examples of the various geometries that can be provided for the inner end portion of the cavities  122   m ,  122 ,  120 , or  118 . These example geometries include but are not limited to a planar or flat bottom  160 , a domed or hemispherical bottom  161 , a conical bottom  162 , and a bottom  163  in the shape of a truncated cone that may also be referred to as a frusto-conical bottom. In one embodiment, the diameter of the cross section of the cavities  122   n  is approximately 0.1 inch. In another embodiment, the diameter of the cross section of the cavities  122   n  is approximately 0.2 inch. Preferably, the diameter of the cross section of the cavities  122   n  is in the range of from approximately 0.05 inch to approximately 0.25 inch. More preferably, the diameter of the cross section of the cavities  122   n  is in the range of from approximately 0.08 inch to approximately 0.12 inch. 
         [0091]    The cavities in the back plates of the brake pads of the present invention can of course have cross sections other than circular. As an example, the cavities in the back plates of the brake pads of the present invention can have polygonal cross sections.  FIG. 22  illustrates a brake pad  100   n  in accordance with yet another embodiment of the present invention. The brake pad  100   n  has a random pattern of cylindrical cavities  122   n  having square cross sections provided on the backside  104   n  of the back plate  102   n  of the brake pad  100   n . Accordingly, the cavities  122   n  are in the form of parallelepipeds with square bases at least up to their inner end portions. 
         [0092]    The cavities  122   n  are randomly distributed on the back side of the back plate of the brake pad  100   n  and are of an approximately uniform size, meaning that the cavities have approximately the same area in plan view and are approximately of the same depth. The front side  106   n  of the back plate  102   n  is covered in large part by the friction lining  108  as is typical for a brake pad. Referring to  FIG. 25 , a section through the back plate  102   n  shows examples of the various geometries that can be provided for the inner end portion of the cavities  122   n . These example geometries include but are not limited to a planar or flat bottom  170 , a domed bottom  171 , a conical bottom  172 , a bottom  174  in the shape of a pyramid having a square base, a bottom  175  in the shape of a truncated pyramid having a square base, and a bottom  173  in the shape of a truncated cone that may also be referred to as a frusto-conical bottom. In one embodiment, the length of the diagonal, i.e. the longest dimension, of the cross section of the cavities  122   n  is approximately 0.1 inch. In another embodiment, the longest dimension of the cross section of the cavities  122   n  is approximately 0.2 inch. Preferably, the length of the longest dimension of the cross section of the cavities  122   n  is in the range of from approximately 0.05 inch to approximately 0.25 inch. More preferably, the length of the longest dimension of the cross section of the cavities  122   n  is in the range of from approximately 0.08 inch to approximately 0.12 inch. 
         [0093]      FIG. 23  illustrates a brake pad  100   o  in accordance with yet another embodiment of the present invention. The brake pad  100   o  has a random pattern of cylindrical cavities  122   o  having hexagonal cross sections provided on the backside  104   o  of the back plate  102   o  of the brake pad  100   o . Accordingly, the cavities  122   o  are in the form of cylinders with hexagonal bases at least up to their inner end portions. 
         [0094]    The cavities  122   o  are randomly distributed on the back side of the back plate of the brake pad  100   o  and are of an approximately uniform size, meaning that the cavities have approximately the same area in plan view and are approximately of the same depth. The front side  106   o  of the back plate  102   o  is covered in large part by the friction lining  108  as is typical for a brake pad. Referring to  FIG. 26 , a section through the back plate  102   o  shows examples of the various geometries that can be provided for the inner end portion of the cavities  122   o . These example geometries include but are not limited to a planar or flat bottom  180 , a domed bottom  181 , a conical bottom  182 , a bottom  184  in the shape of a pyramid having a hexagonal base, a bottom  185  in the shape of a truncated pyramid having a hexagonal base, and a bottom  183  in the shape of a truncated cone that may also be referred to as a frusto-conical bottom. In one embodiment, the length of the longest dimension of the cross section of the cavities  122   o  is approximately 0.1 inch. In another embodiment, the longest dimension of the cross section of the cavities  122   o  is approximately 0.2 inch. Preferably, the length of the longest dimension of the cross section of the cavities  122   o  is in the range of from approximately 0.05 inch to approximately 0.25 inch. More preferably, the length of the longest dimension of the cross section of the cavities  122   o  is in the range of from approximately 0.08 inch to approximately 0.12 inch. 
         [0095]      FIG. 24  illustrates a brake pad  100   p  in accordance with yet another embodiment of the present invention. The brake pad  100   p  has a random pattern of cylindrical cavities  122   p  having octagonal cross sections provided on the backside  104   p  of the back plate  102   p  of the brake pad  100   p . Accordingly, the cavities  122   p  are in the form of cylinders with octagonal bases at least up to their inner end portions. 
         [0096]    The cavities  122   p  are randomly distributed on the back side of the back plate of the brake pad  100   p  and are of an approximately uniform size, meaning that the cavities have approximately the same area in plan view and are approximately of the same depth. The front side  106   p  of the back plate  102   p  is covered in large part by the friction lining  108  as is typical for a brake pad. Referring to  FIG. 26 , a section through the back plate  102   p  shows examples of the various geometries that can be provided for the inner end portion of the cavities  122   p . These example geometries include but are not limited to a planar or flat bottom  190 , a domed bottom  191 , a conical bottom  192 , a bottom  194  in the shape of a pyramid having a octagonal base, a bottom  195  in the shape of a truncated pyramid having a octagonal base, and a bottom  193  in the shape of a truncated cone that may also be referred to as a frusto-conical bottom. In one embodiment, the length of the longest dimension of the cross section of the cavities  122   p  is approximately 0.1 inch. In another embodiment, the longest dimension of the cross section of the cavities  122   p  is approximately 0.2 inch. Preferably, the length of the longest dimension of the cross section of the cavities  122   p  is in the range of from approximately 0.05 inch to approximately 0.25 inch. More preferably, the length of the longest dimension of the cross section of the cavities  122   p  is in the range of from approximately 0.08 inch to approximately 0.12 inch. 
         [0097]    In some embodiments of the brake pad of the present invention, the cavities may extend through the entire thickness of the back plate of the brake pad. For example, in the embodiments of  FIGS. 4, 5, 7, 8, 9, 13, 14A, 14B, 15A, 15B, 16, and 21-27 , the cavities in the back side of the back plate of the brake pad may be extended through the entire thickness of the back plate of the brake pad without jeopardizing the integrity of the back plate of the brake pad. Referring to  FIG. 27 , examples of cavities that extend through the entire thickness of the back plate  102   m  of the brake pad can be seen. The cavity  300  is formed by a cylindrical hole that extends through at least the entire thickness of the back plate  102   m . The cavity  300  can be formed by any suitable process including those enumerated herein. The friction lining  108  covers over the opening formed by the cavity  300  in the front face  106   m  of the back plate  102   m  in areas where the front face or front side  106   m  of the back plate  102   m  is covered by the friction lining  108 . The cavity  302  is formed by a cylindrical hole that extends at least through the entire thickness of the back plate  102   m  and terminates in a raised projection  304  on the front face  106   m  of the back plate  102   m . The end of the cavity  302  proximate the front face  106   m  of the back plate  102   m  is closed such that it does not form an opening on the front face  106   m  of the back plate  102   m . The projection  304  may be formed prior to the formation of the cavity  302  by any suitable process such as, for example, embossing. The cavity  302  is then formed to extend into the projection  304  by any suitable process including those enumerated herein. Alternatively, the projection  304  may be formed during the formation of the cavity  302 . For example, the projection  304  may be pushed outward from the front face  106   m  of the back plate  102   m  by a punch, may be even in cooperation with a die, being used to form the cavity  302 . A production brake pad would be provided with a plurality of cavities  302  and corresponding projections  304  in essentially in the same manner as disclosed herein in relation to the cavities  122   m  among others. The projections  304  are covered by and embedded in the friction lining  108  in the areas of the front face  106   m  of the back plate  102   m  that are covered by the friction lining  108 . The projections  304  aid in retaining the friction lining  108  on the front face  106   m  of the back plate  102   m . Accordingly, each of the projections  304  forms a retention enhancing feature. 
         [0098]    The cavity  306  is formed by a cylindrical hole that extends at least through the entire thickness of the back plate  102   m  and terminates in a raised projection  308  on the front face  106   m  of the back plate  102   m . The end of the cavity  306  proximate the front face  106   m  of the back plate  102   m  is closed such that it does not form an opening on the front face  106   m  of the back plate  102   m . The projection  308  may be formed prior to the formation of the cavity  306  by any suitable process such as, for example, embossing. The cavity  306  is then formed to extend into the projection  308  by any suitable process including those enumerated herein. Alternatively, the projection  308  may be formed during the formation of the cavity  306  as discussed previously with respect to the cavity  302  and the projection  304 . The outward terminus or end of the projection  308  is provided with a retention enhancing feature such as the enlargement  310  illustrated in  FIG. 27 . In the illustrated embodiment, the enlargement is in the form of an enlarged head  310 . The head  310  is dimensionally enlarged in a direction transverse to the longitudinal axis of the cavity  306 . In the illustrated example, the head  310  forms a radially extending flange. A production brake pad would be provided with a plurality of cavities  306  and corresponding projections  308  in essentially in the same manner as disclosed herein in relation to the cavities  122   m  among others. The projections  308  are covered by and embedded in the friction lining  108  in the areas of the front face  106   m  of the back plate  102   m  that are covered by the friction lining  108 . The projections  308  aid in retaining the friction lining  108  on the front face  106   m  of the back plate  102   m . The enlargements  310  of the projections  308  further enhance the retention of the friction lining  108  on the front face  106   m  of the back plate  102   m.    
         [0099]    The cavity  312  is formed by a cylindrical hole that extends at least through the entire thickness of the back plate  102   m  and terminates in a raised projection  314  on the front face  106   m  of the back plate  102   m . The end of the cavity  312  proximate the front face  106   m  of the back plate  102   m  is open such that it forms an opening on the front face  106   m  of the back plate  102   m . The projection  314  may be formed prior to the formation of the cavity  312  by any suitable process such as, for example, embossing. The cavity  312  is then formed to extend into and completely through the projection  314  by any suitable process including those enumerated herein. Alternatively, the projection  314  may be formed during the formation of the cavity  312 . For example, the projection  314  may be pushed outward from the front face  106   m  of the back plate  102   m  by a punch, may be even in cooperation with a die, being used to form the cavity  312  with the punch driven completely through the projection  314  and perforating the projection  314 . A production brake pad would be provided with a plurality of cavities  312  and corresponding projections  314  in essentially the same manner as disclosed herein in relation to the cavities  122   m  among others. The projections  314  are covered by and embedded in the friction lining  108  in the areas of the front face  106   m  of the back plate  102   m  that are covered by the friction lining  108 . The projections  314  aid in retaining the friction lining  108  on the front face  106   m  of the back plate  102   m . Accordingly, each of the projections  314  forms a retention enhancing feature. The retention of the friction lining  108  on the front face  106   m  of the back plate  102   m  may be further enhanced by some material from the friction lining  108  entering and occupying at least a portion of the bore of the projection  314 . 
         [0100]    The cavity  316  is formed by a cylindrical hole that extends at least through the entire thickness of the back plate  102   m  and terminates in a raised projection  318  on the front face  106   m  of the back plate  102   m . The end of the cavity  316  proximate the front face  106   m  of the back plate  102   m  is open such that it forms an opening on the front face  106   m  of the back plate  102   m . The projection  318  may be formed prior to the formation of the cavity  316  by any suitable process such as, for example, embossing. The cavity  316  is then formed to extend into and completely through the projection  318  by any suitable process including those enumerated herein. Alternatively, the projection  318  may be formed during the formation of the cavity  316  as discussed previously with respect to the cavity  312  and the projection  314 . The outward terminus or end of the projection  318  is provided with a retention enhancing feature such as the enlargement  320  illustrated in  FIG. 27 . In the illustrated embodiment, the enlargement is in the form of an enlarged head  320 . The head  320  is dimensionally enlarged in a direction transverse to the longitudinal axis of the cavity  316 . In the illustrated example, the head  320  forms a radially extending flange. A production brake pad would be provided with a plurality of cavities  316  and corresponding projections  318  in essentially in the same manner as disclosed herein in relation to the cavities  122   m  among others. The projections  318  are covered by and embedded in the friction lining  108  in the areas of the front face  106   m  of the back plate  102   m  that are covered by the friction lining  108 . The projections  318  aid in retaining the friction lining  108  on the front face  106   m  of the back plate  102   m . The enlargements  320  of the projections  318  further enhance the retention of the friction lining  108  on the front face  106   m  of the back plate  102   m . The retention of the friction lining  108  on the front face  106   m  of the back plate  102   m  may be further enhanced by some material from the friction lining  108  entering and occupying at least a portion of the bore of the projection  318 . 
         [0101]    The enlargements  310  and  320  may be formed by upsetting the ends of projections  308  and  314 , respectively, in, for example, a coining, heading, or flaring operation. Simply driving a punch through the entire thickness of the back plate in order to perforate the back plate may cause the material of the back plate to flare out in one or more petal-like projections to form a retention-enhancing feature on the front face  106   m  of the back plate  102   m.    
         [0102]    In the embodiments of  FIGS. 4, 5, 7, 8, 9, 13, 14A, 14B, 15A, 15B, 16, and 21-26 , the depth of the cavities can range from as little as 0.003 inch to approximately 0.210 inch. More preferably, the cavities have depths within a range from approximately 0.015 inch to approximately 0.210 inch. Even more preferably, the cavities have depths within a range from approximately 0.05 inch to approximately 0.210 inch. Yet more preferably, the cavities have depths within a range from approximately 0.06 inch to approximately 0.18 inch. In some preferred embodiments, the depth of the cavities is at least approximately 0.06 inch. In other preferred embodiments, the depth of the cavities is at least approximately 0.12 inch. In yet other preferred embodiments, the depth of the cavities is at least approximately 0.18 inch. In one preferred embodiment, the depth of the cavities is approximately 0.06 inch. In another preferred embodiment, the depth of the cavities is approximately 0.12 inch. In yet another preferred embodiment, the depth of the cavities is approximately 0.18 inch. 
         [0103]    The back plates of the embodiments of  FIGS. 4, 5, 7, 8, 9, 13, 14A, 14B, 15A, 15B, 16 , and  21 - 27  are provided with at least approximately two cavities per square inch. More preferably, the back plates of these embodiments are provided with at least approximately four cavities per square inch. Even more preferably, the back plates of these embodiments are provided with at least approximately six cavities per square inch. Yet more preferably, the back plates of these embodiments are provided with at least approximately twelve cavities per square inch. Yet even more preferably, the back plates of these embodiments are provided with at least approximately twenty four cavities per square inch. Still more preferably, the back plates of these embodiments are provided with at least approximately thirty six cavities per square inch. The cavities referred to above are distributed over at least a majority of the area of the back side of the back plate of the brake pad at the given density. The thickness of the back plate as used herein does not include the height of the projections  304 ,  308 ,  314 , and  318  formed on the front side of the back plate. 
         [0104]    The various cavities and their bottom geometries can be created by any suitable means including but not limited to drilling, stamping, punching, die cutting, machining, rolling, pressing, coining, or embossing. For example, the cavities  122   m  having conical bottoms  162  can be formed by drilling as well as other suitable processes. As another example, the cavities  122   m  having flat bottoms  160  can be formed by machining with an end mill as well as other suitable processes. 
         [0105]    Vehicle and laboratory testing has been carried out to validate the effectiveness of brake pads according to present invention in reducing brake noise. During testing experimental brake pads with different back plate configurations were made using a friction material for the lining  108  that was known to produce noise. The experimental brake pads were then tested to evaluate how the different back plate configurations impacted the frequency of noisy vehicle stops. The evaluation consisted of 67 days of vehicle tests with approximately 160 miles a day. The final results showed that some brake pads with configurations according to the present invention reduced the frequency of noisy stops to 0.6% of all stops. Some brake pads according to the present invention produced less noise than all the configurations tested, including the OEM products with insulator. 
       Vehicle Testing Results 
       [0106]    Individual Test Descriptions and Discussion: 
         [0107]    1. Test number one was conducted using a standard backplate with no slots, no chamfers, and no insulator. The friction material was a material known to create an undesirable noise (NEM) and the results were that it produced noise 31% of the time. 
         [0108]    2. Test number 2 was conducted using the same material, rotor, and configuration as test number one, but with the addition of a diamond rubber shim (see  FIGS. 28A-28B ). The results were approximately the same as test Number one, with noise created 31.5% of the time. 
         [0109]    3. Test number 3 was conducted using the same configuration and friction material as in test numbers one and two, but adding a single slot to the friction lining. This resulted in a significant improvement with noise on 18.7% of the stops. 
         [0110]    4. Test number four used the same material as in tests one, two, and three, but with the addition of a chamfer on the edge of the braking face of the friction lining. This configuration created noise 28.3% of the time. 
         [0111]    5. Test number 5 was conducted using the same NEM as the previous tests. The pad had no slot, chamfer, or shim, but had circular cavities in the back side of the back plate the cavities had diameters of 0.200 inch and depths of 0.06 inch (VDS 200-60). This configuration produced noisy stops 35.9% of the time. 
         [0112]    6. Test number six was the same as test number five, except the rotors were changed and the test repeated. Noisy stops occurred 35.0% of the time. 
         [0113]    7. Test number seven was conducted the same as test number six, but with a DRT shim. The results were similar, with noise being created 36.7% of the time. 
         [0114]    8. Test number eight was conducted with no slot, no chamfer, and no shim, but the back plate had cavities with diameters of 0.100 inch and depths of 0.06 inch. The smaller diameter holes reduced the noise production by a third when compared to the larger diameter holes. Noisy stops occurred 20.4% of the time. 
         [0115]    9. Test number nine was the same as test number eight, but with the addition of the DRT shim. The results were similar with noisy stops occurring approximately 20.3% of the time, indicating that the DRT shim is not an effective noise canceling media. 
         [0116]    10. Test number ten was the same as test numbers eight and nine, but with a wolverine shim (see  FIGS. 29A-29B ). This improved the noise occurrence considerably, down to 9.7%. 
         [0117]    11. Test number eleven was the most effective of all, by producing noise only 0.6% of the time. The test was conducted with the NEM material, no slot, no chamfer, no insulator, but the back plate had cavities with diameters of 0.100 inch and depths of 0.18 inch (VDS 100-180). 
         [0118]    12. Conditions for test number twelve were the same as for test number eleven, but with new rotors, and noise was only produced 7.0% of the time. 
         [0119]    13. Conditions for test number thirteen were the same as for test numbers eleven and twelve, but with the addition of a wolverine shim. The results were favorable, and noise was only produced 1.3% of the time. 
         [0120]    14. Test number fourteen was conducted with a back plate having cavities with diameters of 0.100 inch and depths of 0.08 inch (VDS 100-80), a slot and chamfer in the friction lining, and no shim. The pad was made of a low warranty production material, and noise was produced 36.7% of the time. 
         [0121]    15. Test number fifteen was conducted in a similar manner as test number fourteen, but the back plate of the brake pad had cavities with diameters of 0.100 inch and depths of 0.12 inch (VDS 100-120). This resulted in noisy stops being produced only 15.4% of the time. 
         [0122]    16. Test number sixteen used the same setup as test number fifteen, but the back plate of the brake pad had cavities with diameters of 0.100 inch and depths of 0.18 inch (VDS 100-180). The results were that noise was produced 9.0% of the time. 
         [0123]    17. Test number seventeen was conducted using the low-warranty friction material, a slot and chamfer in the friction lining, a standard backplate, and a wolverine shim, which produced noise 1.8% of the time. 
         [0124]    18. Test number eighteen was an OEM configuration, with OEM rotors and OEM shims, and noise was produced 8% of the time. 
         [0125]    Terminology Used in the Test Descriptions Above: 
         [0126]    1. NEM: Noise Emitting Material known to produce a level 7 to 9 level noise under braking. 
         [0127]    2. FM 2: Low-warranty production material. 
         [0128]    3. DRT: Diamond Rubber shim from Advance (Meneta). 
         [0129]    4. VDS 200-60: Back plate modified with round holes of 0.200 inch diameter and 0.06 inch depth, located randomly along back plate with a density of 12 holes per square inch. 
         [0130]    5. VDS 100-80: Back plate modified with round holes of 0.100 inch diameter and 0.080 inch depth, located randomly along back plate with a density of 36 holes per square inch. 
         [0131]    6. VDS 100-120: Back plate modified with round holes of 0.100 inch diameter and 0.120 inch depth, located randomly along back plate with a density of 36 holes per square inch. 
         [0132]    7. VDS 100-180: Back plate modified with round holes of 0.100 inch diameter and 0.180 inch depth, located randomly along back plate with a density of 36 holes per square inch. 
         [0133]    8. NUCW: NuCap Shim with Wolverine Material. 
         [0134]    9. Ford OEM: Advics SLEPM9283FF ( FIGS. 30A-30D  and  FIGS. 31A-31D ). 
       Scanning Laser Vibrometer Testing 
     Objective 
       [0135]    The objective of this test was to characterize four Brake Pads for frequency response and deflection shapes using OMS Corporation&#39;s LaserScan LS01 scanning laser vibrometer. 
       Test Plan 
       [0000]    
       
         
           
             Four brake pads were used for characterization. These pads represent variations in design features and/or materials.
           Pad 1: VDS 100/080   Pad 2: Prod Unmodified   Pad 3: VDS 200/060   Pad 4: VDS 100/180   
         
             Testing was conducted on both the front and back plate of each pad. 
           
         
       
     
       Test Equipment 
       [0000]    
       
         
           
             The following equipment was used during the project: 
           
         
       
     
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                 Serial 
                 Calibration 
               
               
                 Make 
                 Model 
                 Description 
                 Number 
                 Due 
               
               
                   
               
             
             
               
                 OMS Cor- 
                 LaserScan 
                 Scanning Laser 
                 730005 
                 Jan. 5, 2016 
               
               
                 poration 
                 LS01 
                 Vibrometer 
               
               
                 Pyramid 
                 PA1000x 
                 Power 
                 N/A 
                 N/A 
               
               
                   
                   
                 Amplifier 
               
               
                 Agilent 
                 33220A 
                 Arbitrary 
                 MY43000120 
                 N/A 
               
               
                   
                   
                 Waveform 
               
               
                   
                   
                 Generator 
               
               
                 Bruel &amp; 
                 4810 
                 Shaker 
                 2716685 
                 N/A 
               
               
                 Kjaer 
               
               
                 Endevco 
                 256HX-100 
                 Accelerometer 
                 12361 
                 Reference 
               
               
                   
               
             
          
         
       
     
       Test Method 
       [0000]    
       
         
           
             The OMS LaserScan LS01 scanning laser vibrometer was used as the response transducer and data acquisition system for all measurements performed during this project. The test specimens were scanned at multiple locations sequentially. The LS01 system measured and recorded the vibration response of the pad at multiple locations as a result of the artificial excitation source. 
             An accelerometer was positioned on the corner of the brake pad as a reference signal for the closed loop operation of the scanning laser vibrometer. The weight of the accelerometer (1 oz) was less than 1% of the weight of each pad (15.9 oz) and its mass loading effects where considered negligible on the response of the pads. Frequency response measurements of the brake pad with and without accelerometer confirm the negligibility of the accelerometer mass. 
           
         
       
     
       Test Data 
       [0145]      
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Front 
               
             
          
           
               
                   
                   
                 VDS 
                 VDS 
                 VDS 
               
               
                 Frequency 
                 Unmodified 
                 100-080 
                 200-060 
                 100-180 
               
               
                   
               
             
          
           
               
                 1000 
                 2.77E−06 
                 2.04E−06 
                 4.20E−07 
                 3.92E−06 
               
               
                 2000 
                 8.71E−06 
                 1.12E−05 
                 1.13E−05 
                 1.49E−05 
               
               
                 3000 
                 1.13E−05 
                 1.87E−05 
                 1.64E−05 
                 1.53E−05 
               
               
                 4000 
                 3.70E−05 
                 2.89E−05 
                 5.01E−05 
                 1.90E−05 
               
               
                 5000 
                 3.85E−06 
                 6.26E−06 
                 6.10E−06 
                 8.61E−06 
               
               
                 6000 
                 2.32E−06 
                 6.73E−06 
                 1.14E−05 
                 2.39E−07 
               
               
                 7000 
                 2.28E−06 
                 4.97E−06 
                 2.64E−06 
                 6.76E−06 
               
               
                 8000 
                 9.17E−06 
                 1.71E−05 
                 1.17E−05 
                 8.25E−07 
               
               
                 9000 
                 5.26E−05 
                 8.86E−05 
                 3.21E−05 
                 4.09E−05 
               
               
                 10000 
                 5.16E−05 
                 2.41E−05 
                 3.71E−05 
                 1.24E−05 
               
               
                 11000 
                 1.67E−05 
                 1.84E−05 
                 9.65E−06 
                 4.60E−06 
               
               
                 12000 
                 8.91E−06 
                 7.67E−06 
                 5.63E−06 
                 8.30E−06 
               
               
                 13000 
                 4.54E−06 
                 8.07E−06 
                 1.30E−05 
                 9.25E−06 
               
               
                 14000 
                 1.81E−06 
                 8.17E−06 
                 4.11E−06 
                 1.25E−06 
               
               
                 15000 
                 1.80E−06 
                 4.51E−06 
                 2.56E−06 
                 9.24E−06 
               
               
                 16000 
                 1.64E−06 
                 4.38E−06 
                 4.77E−06 
                 7.72E−06 
               
               
                 17000 
                 3.40E−06 
                 4.82E−06 
                 1.03E−05 
                 2.47E−06 
               
               
                 18000 
                 4.07E−06 
                 5.13E−06 
                 2.30E−06 
                 2.29E−06 
               
               
                 19000 
                 8.53E−06 
                 5.83E−06 
                 8.96E−06 
                 9.43E−06 
               
               
                 20000 
                 7.08E−06 
                 9.98E−06 
                 9.42E−06 
                 1.96E−06 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Back Plate 
               
             
          
           
               
                   
                   
                 VDS 
                 VDS 
                 VDS 
               
               
                 Frequency 
                 Unmodified 
                 100-080 
                 200-060 
                 100-180 
               
               
                   
               
             
          
           
               
                 1000 
                 1.55E−06 
                 8.81E−07 
                 2.57E−06 
                 1.46E−06 
               
               
                 2000 
                 1.35E−05 
                 1.43E−05 
                 1.19E−05 
                 1.25E−05 
               
               
                 3000 
                 2.06E−05 
                 2.03E−05 
                 1.47E−05 
                 1.71E−05 
               
               
                 4000 
                 1.17E−05 
                 1.66E−05 
                 7.78E−06 
                 4.02E−06 
               
               
                 5000 
                 7.83E−06 
                 5.08E−06 
                 1.21E−05 
                 5.28E−06 
               
               
                 6000 
                 9.65E−06 
                 6.64E−07 
                 1.47E−05 
                 9.45E−06 
               
               
                 7000 
                 3.27E−05 
                 1.90E−05 
                 4.95E−05 
                 3.52E−05 
               
               
                 8000 
                 1.92E−05 
                 1.24E−05 
                 2.86E−05 
                 2.73E−05 
               
               
                 9000 
                 1.30E−05 
                 1.70E−05 
                 1.34E−05 
                 2.86E−05 
               
               
                 10000 
                 3.10E−06 
                 6.27E−06 
                 3.67E−06 
                 2.00E−06 
               
               
                 11000 
                 6.79E−06 
                 3.63E−06 
                 4.91E−06 
                 7.61E−06 
               
               
                 12000 
                 4.73E−06 
                 4.87E−06 
                 3.73E−06 
                 3.91E−06 
               
               
                 13000 
                 1.22E−06 
                 3.51E−06 
                 6.04E−06 
                 3.00E−06 
               
               
                 14000 
                 4.18E−06 
                 7.77E−06 
                 6.17E−06 
                 9.24E−07 
               
               
                 15000 
                 3.09E−06 
                 2.98E−06 
                 4.85E−06 
                 3.40E−06 
               
               
                 16000 
                 3.61E−06 
                 3.46E−06 
                 6.42E−06 
                 1.85E−06 
               
               
                 17000 
                 4.58E−06 
                 2.73E−06 
                 1.20E−06 
                 1.76E−06 
               
               
                 18000 
                 9.40E−07 
                 4.80E−06 
                 5.21E−06 
                 4.34E−06 
               
               
                 19000 
                 6.16E−06 
                 8.96E−06 
                 4.42E−06 
                 1.69E−06 
               
               
                 20000 
                 5.89E−06 
                 4.94E−06 
                 2.61E−06 
                 3.15E−06 
               
               
                   
               
             
          
         
       
     
       Summary of Vibrometer Testing 
       [0000]    
       
         
           
             Various manufacturing features of material removal from back plate shifted resonances of the brake pads. 
           
         
       
     
         [0147]    It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.