Abstract:
The present invention relates to a disc brake operable to apply a clamping force to a rotatable disc. The disc brake includes a support bracket, slide pins coupled to the support bracket, inner and outer brake shoes and a caliper supported by the slide pins. The support bracket is a substantially rectangular frame defining a window. The window is adapted to accept a portion of a disc protruding therethrough. The support bracket includes a pair of spaced apart apertures extending through the frame where each aperture includes a threaded portion and a conical seat extending along an axis aligned to intersect the disc. The slide pins are threadingly engaged with a threaded portion. The slide pins do not extend through the window but protrude outwardly away from the window. Each slide pin has a tapered portion in engagement with one of the conical seats.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
       [0001]     The present invention relates to a disc brake and, more particularly, to a disc brake caliper slide pin having a tapered design.  
         [0002]     Automotive components are typically exposed to a wide variety of environmental inputs including variations in temperature and load throughout operation of a vehicle. Use of a vehicle over rough surfaces provides a road load vibrational input as well. To assure proper operation of a vehicle component, it is desirable to maintain the structural integrity of the component or assembly for an extended time period.  
         [0003]     Brake assemblies typically include a number of components interconnected to one another via threaded fasteners. To assure proper braking operation, it is desirable that the thread fasteners maintain a desired clamp load during and after exposure to the environmental and operational inputs previously discussed. Some bolted joints have experienced reduced clamp load or “backing-off” for a number of reasons. One reason relates to joint relaxation where a relatively short bolt or shaft is initially loaded to exhibit a relatively small elongation. If the bolt relaxes, the relatively small elongation is no longer present and the joint clamp load decreases. In addition, the clamping force generated by a threaded fastener may be insufficient if the surface area between any two components within the joint is insufficient to maintain the clamp load without yielding. In this case, relatively high contact stresses are generated between clamped components causing a portion of one of the clamped components to yield or flow when clamped. The yielding of the material reduces the fastener elongation and the clamp load is greatly decreased.  
         [0004]     The present invention provides a disc brake having a tapered slide pin designed to maintain a desired location during operation of the brake and the vehicle.  
         [0005]     In particular, the present invention relates to a disc brake operable to apply a clamping force to a rotatable disc. The disc brake includes a support bracket, slide pins coupled to the support bracket, inner and outer brake shoes and a caliper supported by the slide pins. The support bracket is a substantially rectangular frame defining a window. The window is adapted to accept a portion of a disc protruding therethrough. The support bracket includes a pair of spaced apart apertures extending through the frame where each aperture includes a threaded portion and a conical seat extending along an axis aligned to intersect the disc. The slide pins are threadingly engaged with a threaded portion. The slide pins do not extend through the window but protrude outwardly away from the window. Each slide pin has a tapered portion in engagement with one of the conical seats.  
         [0006]     Additionally, the present invention relates to a disc brake having a disc rotatable about a laterally extending axis, a support bracket, slide pins coupled to the support bracket and a caliper slidably supported by the slide pins. The support bracket has first and second spaced apart, substantially parallel legs as well as third and fourth spaced apart, substantially parallel legs. The first and second legs are interconnected at their ends by the third and fourth legs to define a window. The first leg has spaced apart pin apertures where each pin aperture includes a threaded portion and a tapered portion extending along an axis. Each pin aperture is substantially parallel to the disc axis of rotation and radially positioned within the outer diameter of the disc. The slide pins have a threaded end and a tapered portion adjacent the threaded end. Each threaded end engages the threaded portion of one of the pin apertures. The tapered portion of each slide pin is driven into engagement with the tapered portion of each pin aperture by rotation of the slide pin relative to the support bracket. The caliper is slidably supported by the slide pins and includes a piston cavity for moveably supporting the piston. The piston cavity has an axis extending substantially parallel to and radially inward of the slide pin axes. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0008]      FIG. 1  is an exploded perspective view of an exemplary disc brake constructed in accordance with the teachings of the present invention;  
         [0009]      FIG. 2  is a perspective view of the assembled disc brake without the disc;  
         [0010]      FIG. 3  is a perspective view of the assembled disc brake from another view;  
         [0011]      FIG. 4  is a cross-sectional view taken along line  4 - 4  as shown in  FIG. 2 ;  
         [0012]      FIG. 5  is a cross-sectional view taken along line  5 - 5  as shown in  FIG. 2 ; and  
         [0013]      FIG. 6  is a schematic depicting the radial locations of the piston bores, the slide pin apertures and the brake support apertures. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0015]     With reference to  FIGS. 1-6 , a disc brake constructed in accordance with the teachings of the present invention is identified at reference numeral  10 . Disc brake  10  is operable to selectively clamp an inboard brake shoe  12  and an outboard brake shoe  14  against a rotatable disc  16  to decelerate a vehicle (not shown). Disc brake  10  includes a support bracket  18  adapted to mount to a steering knuckle or axle component of the vehicle to support disc brake during operation. A first slide pin  20  and a second slide pin  22  are mounted to support bracket  18  in a manner to resist vibratory loosening as will be described in greater detail hereinafter. First slide pin  20  and second slide pin  22  laterally inwardly protrude from support bracket  18 . A caliper  24  is slidably supported on first slide pin  20  and second slide pin  22 . A first piston  26  and a second piston  28  are slidably supported within caliper  24 . First piston  26  and second piston  28  are moveable via hydraulic pressure being selectively supplied to caliper  24 . Inboard brake shoe  12  and outboard brake shoe  14  are positioned on opposite wear surfaces of disc  16 . Caliper  24  at least partially envelops inboard brake shoe  12  and outboard brake shoe  14  such that axial movement of first piston  26  and second piston  28  cause the brake shoes to clamp on disc  16 .  
         [0016]     More particularly, brake support bracket  18  is a one-piece frame-shaped member preferably constructed by a casting or forging process. Support bracket  18  includes a first leg  30 , a second leg  32 , a third leg  34  and a fourth leg  36 . First leg  30  is a substantially linear elongated member positioned substantially parallel to second leg  32 . Second leg  32  is arched in a radial direction in relation to a laterally extending axis  38  about which disc  16  rotates. One end of first leg  30  is interconnected to one end of second leg  32  via third leg  34 . The opposite ends of legs  30  and  32  are interconnected by fourth leg  36 . First leg  30  includes a first detent  40  and a second detent  42 .  
         [0017]     Inboard brake shoe  12  includes a lining block  43  mounted on a backing plate  44 . Backing plate  44  includes integrally formed tabs  46  and  48  protruding from each end. Detents  40  and  42  restrict inboard brake shoe  12  from radial movement but allow lateral movement of the brake shoe. Clips  50  may be inserted within detents  40  and  42  to assist in maintaining the proper position of inboard brake shoe  12  during operation. Second leg  32  includes a similar pair of detents  52  and  54 . Outboard brake shoe  14  includes a lining block  55  mounted to a backing plate  56 . Backing plate  56  includes integrally formed tabs  58  and  60  protruding from each end. Clips  62  cooperate with detents  52  and  54  to restrain tabs  58  and  60  from linear movement while allowing lateral movement parallel to axis  38 .  
         [0018]     First leg  30  includes a pair of brake mounting apertures  64  operable to receive brake fasteners to couple support bracket  18  to a knuckle or other vehicle suspension component. Caliper  24 , inboard brake shoe  12  and outboard brake shoe  14  are supported via this structural interconnection. Support bracket  18  also includes a first slide pin aperture  66  and a second slide pin aperture  68 . Slide pin aperture  66  extends laterally through first leg  30  along a first slide pin axis  69 . Slide pin aperture  66  includes an internally threaded portion  70  and a tapered portion  72 . Slide pin  20  is threadingly engaged with pin aperture  66  and protrudes laterally inboard along axis  69 .  
         [0019]     As best shown in  FIG. 4 , slide pin  20  is a substantially cylindrical member having a body portion  74  with a substantially smooth outer cylindrical surface  76 . A groove  78  is formed in body portion  74  and is in receipt of a bushing  80 . Bushing  80  functions to isolate the slide pin  20  from the caliper body to reduce caliper rattle on the slide pins. First slide pin  20  also includes a tapered portion  82  and a threaded portion  84 . Threaded portion  84  is positioned at a first end  86 . A drive recess  88  is positioned at a second opposite end  90 . First slide pin  20  is coupled to support bracket  18  by inserting a drive tool within drive recess  88  and rotating first slide pin  20  relative to support bracket  18 . First slide pin  20  is rotated until tapered portion  82  drivingly engages tapered surface  72  to form a press-type fit. An axially collapsible bellows  92  has a first end  94  coupled to first slide pin  20 . A second end  96  of bellows  92  is secured to a boss  98  formed on caliper  24 .  
         [0020]     Caliper  24  includes a pin bore  100  in receipt of first slide pin  20 . A running-class fit exists between outer cylindrical surface  76  of first slide pin  20  and pin bore  100  to allow caliper  24  to translate laterally relatively to support bracket  18  during operation. Bellows  92  is operable to axially extend and compress to account for the relative movement between caliper  24  and support bracket  18 . A cap  102  engages boss  98  and covers pin bore  100 . Cap  102  is removable to allow access to drive recess  88  should brake service and removal of first slide pin  20  be required.  
         [0021]     Caliper  24  is a generally “C” shaped member having an inboard side portion  104  and an outboard side portion  106  interconnected by a laterally extending bridge portion  108 . First side portion  104  includes boss portion  98  as well as another boss portion  109  substantially similar to boss  98 . Furthermore, first side portion  104  includes a first piston bore  110  and a second piston bore  112 . First piston  26  is slidably positioned within first piston bore  110  to move along a first piston bore axis  113 . A first piston seal  114  sealingly engages first piston  26  and first side portion  104  to protect the piston bore from ingress of contamination. Similarly, second piston  28  is slidably positioned within second piston bore  112  to move along a second piston bore axis  115 . A second piston seal  116  sealingly engages second piston  28  and first portion  104 . First piston  26  and second piston  28  are operable under hydraulic fluid pressure entering a port  118  to apply a force to backing plate  44  of inboard brake shoe  12 .  
         [0022]     Outboard side portion  106  includes a surface  120  in engagement with backing plate  56  of outboard brake shoe  14 . A pair of cut-outs  122  extend through outboard side portion  106  to allow tooling (not shown) sufficient access to form first piston bore  110  and second piston bore  112 . Outboard side portion  106  is laterally positioned between first leg  30  and second leg  32  of support bracket  18 . Because inboard brake shoe  12 , outboard brake shoe  14  and caliper  24  are laterally moveable relative to support bracket  18  and disc  16 , both inboard brake shoe  12  and outboard brake shoe  14  may clamp against disc  16 .  
         [0023]      FIG. 4  depicts the interconnection of support bracket  18  and caliper  24  via second slide pin  22 . Second slide pin  22  is substantially similar to first slide pin  20  except that a bushing is not positioned between second slide pin  22  and caliper  24 . Second slide pin  22  extends along an axis  130 . Axis  130  is substantially parallel to axis  69  and axis  38 . Second slide pin  22  includes a body portion  132  slidably positioned within a bore  134  extending through boss  109 . Second slide pin  22  includes a tapered portion  136  and a threaded portion  138 . A drive recess  140  is formed in an end of second slide pin  22  opposite the end having threaded portion  138 . Slide pin bore  68  of support bracket  18  includes a tapered portion  142  and an internally threaded portion  144 . As previously described in detail with relation to first slide pin  20 , second slide pin  22  is installed by inserting a drive tool within drive recess  140  to threadingly engage threaded portion  138  with internal thread  144 . The second slide pin  22  continues to be rotated until tapered portion  136  of second slide pin  22  drivingly engages tapered portion  132  of pin aperture  68 . The portion of second slide pin  22  between the tapered interface and the threaded portion  138  is placed in tensile loading. Because tapered portion  136  is formed at an angle of 30 degrees relative to axis  130 , tapered portion  136  is wedged into engagement with tapered portion  142  of support bracket  18 . A mechanical interconnection is formed such that a force to remove second slide pin  22  from supply bracket  18  is greater than the force used to drive tapered portion  136  into engagement with tapered portion  142  of slide pin bore  68 . In this manner, second slide pin  22  resists vibratory loosening and/or a degradation in pin elongation during operation of disc brake  10 . An end cap  146  engages boss  109  to seal bore  134  from contamination. Cap  146  may be selectively removed to allow access to drive recess  140 .  
         [0024]     With reference to  FIG. 6 , it should be appreciated that first piston bore axis  113  and second piston bore axis  115  are positioned at a first radial distance X from laterally extending axis  38 . First slide pin bore axis  69  and second slide pin bore axis  130  are positioned at a radial distance Y from disc axis of rotation  38 . Distance Y is greater than distance X such that piston bores  110  and  112  are radially inward of slide pin bores  66  and  68 . The centerline of brake mounting apertures  64  are radially positioned from axis  38  a distance Z. In the embodiment shown in  FIG. 6 , distance Y is approximately the same as distance Z. Lengths X, Y and Z need not maintain this relationship in other brake embodiments. It should also be noted that each of the piston bore axes, the slide pin bore axes and the centerlines of brake mounting apertures  64  are radially positioned within the circumference of disc  16 . This positioning provides a reduced brake envelope to assist in packaging the brake in a vehicle. Also, the arrangement provides a well balanced caliper for long term use.  
         [0025]     Furthermore, the foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations may be made therein without department from the spirit and scope of the invention as defined in the following claims.