Patent Publication Number: US-2004040796-A1

Title: Backing plate with friction material retention members and method and apparatus for manufacturing same

Description:
FIELD OF THE INVENTION  
       [0001] This invention relates to friction assemblies suitably used with brakes on vehicles, and more particularly to a backing plate and method and apparatus for manufacturing same.  
       BACKGROUND OF THE INVENTION  
       [0002] A friction assembly is a replaceable element in a brake system. In a disk brake, a friction assembly bears against a rotating disc called a rotor. The friction assembly comprises a backing plate to which a friction pad is adhered. The friction pad alone contacts the rotor of the disc brake to provide the stopping frictional force. Significant forces are involved in applying the pad to the rotor, and due to the relative movement during engagement, extreme temperature can be generated up to about 1200° F. Moreover, depending upon the size and/or the payload carried by certain vehicles, the friction assembly bears with significant pressure and vibration when stopping vehicles. It is very important that the backing plate is resistant to bending or breaking due to high pressure, temperature and vibration when stopping vehicles.  
       [0003] Typically, backing plates are modified to include bores, cavities, gouges or protuberances to receive and engage the friction material. These modifications generally improve engagement with a friction material. However, the costs associated with manufacturing backing plates with such modification can often be prohibitive.  
       [0004] It is therefore desirable to provide a backing plate having improved engagement with a friction material without involving undue manufacturing costs.  
       SUMMARY OF THE INVENTION  
       [0005] The present invention uses one or more retention members formed on a surface of a backing plate for engaging a friction material. Each retention member comprises a protrusion member with multiple spiral wings extending upwardly in a spiral orientation.  
       [0006] In accordance with an embodiment of the invention, there is provided a backing plate for a friction assembly. The backing plate comprises a body having a first surface for receiving a friction material thereon and a second surface opposed to the first surface; and at least one retention member defined on the first surface, the retention member having a depressed portion and at least one protruding portion adjacent the depressed portion, the protruding portion extending above the first surface in a spiral orientation about the depressed portion.  
       [0007] In accordance with another embodiment of the invention, there is provided a friction assembly for a brake assembly. The friction assembly comprises a body having a first surface and a second surface opposed to the first surface; at least one retention member defined on the first surface, the retention member having a depressed portion and at least one protruding portion adjacent the depressed portion, the protruding portion extending above the first surface in a spiral orientation about the depressed portion; and a friction material mounted on the first surface of the backing plate so that the friction material is engaged with the at least one retention member.  
       [0008] In accordance with another embodiment of the invention, there is provided a method for manufacturing a backing plate. The method comprises steps of forming one or more solid nipples on a first surface of a backing plate material; extruding a wall nip from each solid nipple, the wall nip having a middle depressed portion and a wall around the depressed portion; splitting the wall nip into multiple wings in a spiral orientation about the depressed portion; and flaring the wings outwardly relative to the depressed portion.  
       [0009] In accordance with another embodiment of the invention, there is provided a retention member formation apparatus for forming one or more retention members on a backing plate material. The apparatus comprises a nip forming apparatus and a nip cutting apparatus. The nip forming apparatus forms one or more wall nips on a friction material engaging surface of a backing plate material, each nip having a depressed portion and a wall surrounding the depressed portion. The nip cutting apparatus cuts the wall of each nip into multiple spiral wings in a spiral orientation about the depressed portion, and flares the multiple wings outwardly relative to the depressed portion. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010] For a better understanding of the present invention, and to, show more clearly how it may be carried into effect, reference will now be made by way of example to the accompanying drawings. The drawings show preferred embodiments of the present invention, in which:  
     [0011]FIG. 1 is a perspective view of a friction assembly in accordance with an embodiment of the present invention;  
     [0012]FIG. 2 is a perspective view of a backing plate for the friction assembly of FIG. 1;  
     [0013]FIG. 3 is a sectional view of the backing plate of FIG. 2 taken along line A-A;  
     [0014]FIG. 4 is an enlarge perspective view of a retention member for the backing plate of FIG. 2;  
     [0015]FIG. 5 is a side view of an apparatus for forming one or more retention members in backing plate in accordance with the present invention;  
     [0016]FIG. 6 is a section view of a tool assembly at a step of creating nips on a backing plate;  
     [0017]FIG. 7 is a section view of the tool assembly at a step of protruding cylindrical walls;  
     [0018]FIG. 8 is a section view of protrusions on the plate material at the die opening;  
     [0019]FIG. 9 is a side view of an apparatus for flaring retention members in the backing plate in accordance with an aspect of the present invention;  
     [0020]FIG. 10A is a partial side view of flaring tools at a die open position;  
     [0021]FIG. 10B is a partial side view of flaring tools at a die close position;  
     [0022]FIG. 11 is a schematic side view showing retention members;  
     [0023]FIG. 12 is partial enlarged views of the protruding tool;  
     [0024]FIG. 13 is partial enlarged views of the flaring and cutting tool; and  
     [0025]FIG. 14 is a schematic side view showing a retention member according to another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0026] An embodiment of the present invention provides a backing plate with one or more retention members for engaging a friction material. Each retention member comprises a protrusion member having with multi-wings extending upwardly and flared out in a spiral orientation like a propeller. The backing plate of this embodiment is intended for use with a disc brake. However, the present invention may be applied to different types of brakes with or without suitable modifications.  
     [0027]FIG. 1 generally shows a friction assembly  20  in accordance with an embodiment of the present invention. Friction assembly  20  includes a friction material  22  and a backing plate  24 . Friction material  22  is usually made of phenolic resin with iron powder, steel or carbon fibers, and/or carbon powder. Friction material  22  is mounted on backing plate  24 , e.g., molded in known manner to backing plate  24 .  
     [0028] Backing plate  24  is formed of metal, a metal composite or such other material that is suitable for the intended use of the friction assembly  20  and that may be processed in accordance with the method described below. Backing plate  24  is of a conventional shape and thickness, and may include apertures and other structural elements known in the art to permit backing plate to be incorporated within a brake assembly (not shown).  
     [0029] Referring to FIGS.  2 - 4 , backing plate  24  is further described in detail. In these figures, backing plate  24  is shown as if it is transparent for the purpose of illustration, but actual backing plate  24  is typically non-transparent.  
     [0030] Backing plate  24  has a body  26  with a planar top or first surface  28  and an opposing planar bottom or second surface  30 . First surface  28  defines one or more retention members  32  for engaging friction material  22  once it has been disposed on first surface  28 . First surface  28  preferably defines a plurality of retention members  32 .  
     [0031] Each retention member  32  comprises a depressed portion  40  and four protruding portions or wings  42 . In this embodiment, depression portion  40  is defined beneath first surface  28  of backing plate  24 , i.e., the bottom of depressed portion  40  is lower than first surface  28 . The number of the wings and the depth of the depression portion  40  may be varied as described below.  
     [0032] Protruding portions  42  extend above first surface  28 . Protruding portions  42  are integrally formed with backing plate  24  from material displaced during formation of depressed portion  40 . As best seen in FIG. 4, protruding portions  42  extend like a propeller, i.e., wings  42  extend in a spiral orientation in a clockwise or counterclockwise direction about the central axis  44  of their corresponding depressed portion  40 . Each protruding portion  42  typically extends in the spiral orientation for less than one full revolution. Each protruding portion  42  typically has a body  46  with a tip  48 . The body  46  has a bottom edge  46 a integrally attached to first surface  28 , and two generally spiral-shaped sides  46 b and  46 c merging into the tip  48 . Protruding portions  42  preferably have a height of between 0.030-0.075 inches above first surface  28  for backing plates for regular passenger vehicles. For larger vehicles, it is typically desirable to have higher protruding portions  42 . Protruding portions  42  may be as high as 0.100 inch.  
     [0033] Retention members  32  are arranged on first surface  28  of backing plate  24  in a density and pattern that provides desired retention of friction material  22  while maintaining desired structural integrity of backing plate  28 . Preferably, as shown in FIG. 2, retention members  32  are arranged in rows  52  and columns  54  on first surface  28  with retention members  32  in adjacent rows  52  being arranged in offset columns  54 . In a preferred embodiment, retention members  32  are arranged on backing plate  28  with 0.50 inches apart.  
     [0034] On second surface  30  of backing plate  28 , recessions  58  may be formed to provide material for forming retention members  32  on first surface  28 .  
     [0035] In this embodiment, each retention member  32  has four protrusion members  42 . However, in different embodiments, a retention member may have more or fewer protruding portions  42 . Typically, more protruding portions  42  on each retention member, stronger the engagement with the friction material against shearing force, as long as each protruding portion  42  is large and strong enough to exhibit the engagement effects.  
     [0036] Also, in this embodiment all retention members  32  have the same number of protruding portions  42  extending in same directions throughout the backing plate  24 . However, it is not necessary to provide all same retention members  32 . A single backing plate may have different retention members.  
     [0037] Retention members are preferably manufactured either on a blanked plate or on a strip of incoming material which is being fed into a blanking die. FIG. 5 to FIG. 13 illustrate nip forming apparatus  60  and nip cutting apparatus  100  which are suitably used for a two step operation to manufacture retention members on blanked plates or a strip of material in accordance with an embodiment of the invention.  
     [0038] The two step operation comprises:  
     [0039] Step 1: forming protrusion cylindrical wall nips  79  as shown in FIG. 8.  
     [0040] Step 2: cutting and flaring the cylindrical nips  79  into multiple wings  42  extending in a spiral orientation out of the upper surface of backing plate material  72 .  
     [0041] Nip forming apparatus  60  and the first step of forming cylindrical wall nips  79  are described referring to FIGS.  5 - 8 .  
     [0042] Nip forming apparatus  60  comprises a press die having an upper die and a bottom die. The upper die includes upper die shoe  61  which supports protrusion punches  71  through punch holder  69  and back up plate  68 . The upper die also has protrusion insert or plate  70  supported by guiding plate  63 , which is guided by four pins  64  and bushing  65 . Protrusion insert  70  has through holes  70   a,  each of which slidably receives protrusion punch  71 . Guiding plate  63  is spaced apart from punch holder  69  through gas springs  67 . Gas springs  67  are supported by upper die shoe  61  for exerting presser on protrusion insert  70  through guiding plate  63 . When no pressure exists on upper die shoe  61 , the lower punching ends of protrusion punches  71  remain within protrusion insert  70 , leaving spaces at lower ends of holes  70   a  for creation of wall nips  79  within the spaces. When upper die shoe  61  is brought down and guiding plate  63  contacts punch holder  69 , protrusion punches  71  slides down within holes  70   a  for creation of cylindrical wall nips  79 , as further described below.  
     [0043] The bottom die includes bottom die shoe  62  that supports die plates  73  and  74 . Semi-piercing punches  76  are mounted on lower die plate  74  such that the top ends extend above the upper surface of upper die plate  73 . Pressure pad  75  is provided in upper die plate  73  to surround semi-piercing punches  76 . Pressure pad  75  is urged up by pins  77  and springs  80  to facilitate separation between semi-piercing punches  76  and backing plate material  72  during the up-stroke of the press.  
     [0044] Referring to FIG. 12 protrusion punch  71  is described in greater detail. Protrusion tool  71  has cylindrical body  201  and head  200  at the upper end of body  201 . At the lower end, there are recess section  203 , tip  204  and lance  205 . On the body  201 , there are three flats  202  for oil and/or air vents. There may be more or less number of vents, and the shape of vents may not be flat. Recess section  203  has a smaller diameter than body  201 . The diameter of recess section  203  is determined depending on the diameter of hole  70   a  of protrusion insert  70  and a desired thickness of protruding portions  42 .  
     [0045] In the operation of nip forming apparatus  60 , backing plate material  72  is fed between the upper and bottom dies (FIG. 5). Backing plate material  72  may be in a form of a blanked plate or a strip of backing plate material. Backing plate material  72  is fed at a predetermined position in conjunction with the stroke cycle of the press. During the down stroke of the press, upper die shoe  61  and its components supported by upper die shoe  61  are moved down.  
     [0046] First, protrusion insert  70  is brought in contact with backing plate material  72  fed on bottom die plate  73 . Further pressure brings pressure pad  75  down, and semi-piercing punches  76  push up the sections of backing plate material  72  into hole  70   a  of protrusion insert  70  to form nipples  78  (FIG. 6). Nipples  78  are solid projections used as material for creating protruding cylindrical wall nips  79  by extrusion.  
     [0047] As the upper die continues moving down, protruding punches  71  are carried down through holes  70   a  of protrusion insert  70 . At the end of the down stroke, protruding punches  71  depress on nipples  78  to force the material to flow upward into the space between recess section  203  of protruding punches  71  and holes  70   a  of protrusion insert  70  to form cylindrical wall nips  79  (FIG. 7).  
     [0048] The upper die moves up to end the press cycle (FIG. 8). On backing plate material  72 , cylindrical wall nips  79  are formed on the upper surface and corresponding recesses  81  are formed on the lower surface. Backing plate material  72  is moved to start a new press cycle or to the next step, as desired.  
     [0049] Referring now to FIGS.  9 - 11 , described are nip cutting apparatus  100  and the second step of cutting and flaring the cylindrical nips  79  into multiple wings  42 .  
     [0050] Nip cutting apparatus  100  comprises a press die having an upper die and a bottom die. The upper die includes upper die shoe  101 , which holds cutting tools  106  in tool holder  104 . Hard plate  102  supports cutting tool  106  from its back. Tool retainer plate  103  with “O” rings  105  prevents cutting tool  106  from falling down, and also allows easy replacement of cutting tools  106 .  
     [0051] The bottom die has bottom die shoe  109  that supports die plate  107  with pins  108 . Pins  108  are used to position blank plate material  72  at a desired position for the flaring and splitting operation, by mating with recesses  81  created on the lower surface by semi-piercing punches  76  of nip forming apparatus  60 .  
     [0052] As shown in FIG. 13, cutting tool  106  has a body  310  with cutting edges  109  at the cutting and spiral multi-flutes  110 . Spiral multi-flutes  110  continues from cutting edges  109  along the circumference of body  310 , which allows splitting of cylindrical nip  79  into multi-portions  80  in a spiral orientation. Body  310  has a diameter larger than that of recess section  203  of protrusion punch  71  of nip forming apparatus  60  to flare cylindrical nip  79 . For example, when cylindrical nip  79  is formed using protrusion punch  71  with 0.158 inch-diameter recess section  203 , milling cutters  106  of a 0.375 inch-diameter with four flutes  110  may be suitably used. It is preferable that cutting tool  106  has cutting edges  109  at an angle of about 70° in respect to the tool axis. This angle is suitable to flare wall nip  79 . The cutting edges  109  are corn shaped with the back angle of  200 , which allows multi-portions  80  to flare out. In a different embodiment, the cutting edge angle may be between about 70° and about 90° and the back angle may be between about 20° and about 0°.  
     [0053] In the operation, during the down stroke of the press, baking plate material  72  with wall nips  79  is fed into the working area between the upper and bottom dies (FIG. 10A). Upper die shoe  101  with its cutting tools  106  moves down to bring cutting edges  109  in contact with protrusion cylindrical nips  79 . Further downward movement of upper die shoe  11  causes four cutting edges  109  of cutting tool  106  to split the wall of cylindrical nip  79  into four portions or wings  80 . By following the spiral flutes  110 , wings  80  are cut in a spiral orientation. As cutting edges  109  are cone shaped, wings  80  are flared out cylindrical nips  79  (FIG. 10B). Upper die shoe  101  then moves up to end the press cycle. Thus, flared protruding portions  80  are formed above the upper surface of backing plate material  72  (FIG. 11).  
     [0054] It is preferable that backing plate material  72  is fed directly from nip forming apparatus  60  to nip splitting apparatus  100  and these apparatus  60  and  100  are operated in a synchronized manner.  
     [0055] In the above embodiments, retention member  32  has depression portion  40  defined beneath first surface  28  of backing plate  24 . As shown in FIG. 14, in a different embodiment, retention member  400  may have a stem  402  extending from first surface  412  of backing plate  410 , and depression portion  420  may be defined in stem  402  above first surface  412 . In this case, protruding portions  422  extend above first surface  412  from stem  402 .  
     [0056] Also, in the above embodiments, nips  79  are described to have cylindrical walls. However, nips  79  may have different shapes.  
     [0057] It is to be understood that what has been described is embodiments to the invention. If the invention nonetheless is susceptible to certain changes and alternative embodiments fully comprehended by the spirit of the invention as described above, and the scope of the claims set out below.