Abstract:
A trailer axle assembly includes a non-rotating axle tube that extends laterally between a pair of wheel ends. Each wheel end supports a disc brake assembly that selectively generates a braking force to slow or stop rotation of the wheel ends. The disc brake assemblies include a torque plate that is mounted to the axle tube. The axle tube includes a radial location feature that holds the torque plate fixed relative to the axle tube so that rotational brake torque is transmitted directly through a solid interface. The axle tube also includes an axial location feature that positions the torque plate at a predetermined location along the axle beam and prevents relative axial movement between the axle beam and the torque plate.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The subject invention generally relates to a method and apparatus for mounting a torque plate for a disc brake assembly to a trailer axle beam. More specifically, the trailer axle beam includes radial and axial locating features that properly position and securely mount the torque plate to the axle beam.  
         [0002]     Trailer axles include a tubular axle beam that extends between a pair of wheel end assemblies. The wheel ends assemblies each include a braking mechanism for selectively braking the rotating wheel ends. Various different types of braking mechanisms can be used on the trailer axles including cam, wedge, or disc brakes, for example.  
         [0003]     Currently, disc brakes for trailer axles are bolted to a torque plate, which is welded to the axle beam. During the welding process, there is potential for distortion of the torque plate, which can affect the orientation of the brake mounting face of the toque plate. A final machining step is typically required after welding to ensure that the brake mounting face is flat and square to an axis of rotation defined by the axle beam. This extra machining step increases the overall cost and assembly time.  
         [0004]     Further, the weld interface between the axle beam and the torque plate must be strong enough to resist the high rotational brake torque values generated during braking. Any deficiencies in the weld could result in high stress cracking or fatigue wear, which could reduce the wear life of the braking component or result in a premature failure.  
         [0005]     There is a need for an improved interface between the torque plate and a trailer axle beam that eliminates the torque resistant weld and subsequent machining steps. The interface should be easily incorporated into existing beam designs and easy to assemble onto the beam, as well as overcoming the other above-mentioned deficiencies in the prior art.  
       SUMMARY OF THE INVENTION  
       [0006]     A torque plate is mounted to a non-rotating axle component by radially locating the torque plate on the axle component with a first location member to prevent relative rotation between the torque plate and the axle component and axially locating the torque plate on the axle component with a second location member to prevent relative axial movement between the torque plate and the axle component.  
         [0007]     In one disclosed embodiment, the non-rotating axle component comprises a non-rotating axle beam for a non-drive trailer axle assembly. The axle beam preferably has a generally tubular or circular cross-sectional shape. Wheel end assemblies are supported on each end of the axle beam. Each wheel end assembly includes a disc brake assembly having a rotor mounted for rotation relative to the axle beam, a pair of brake shoes, and a brake actuator and caliper for selectively moving the brake shoes into engagement with the rotating brake rotor. The disc brake assembly includes a non-rotating torque plate that is mounted to the axle beam via the first and second location members.  
         [0008]     In one disclosed embodiment the first location member is a radial location member that comprises a plurality of male members formed on one of the axle beam or torque plate and a plurality of female members formed on the other of the axle beam or torque plate. The male members are inserted at least partially into the female members to prevent rotation between the torque plate and the axle beam and to allow rotational brake torque to be directly transmitted through a solid interface. The male members could be formed as splines, teeth, pins, protrusions, or other similar members. The female members could be grooves, slots, aperture, holes, or other similar members. Further, the male and female members could be integrally formed on one of the torque plate or axle beam or could be mounted as separate components to the torque plate or axle beam.  
         [0009]     In one disclosed embodiment, the second location member is an axial location member that locates the torque plate at a predetermined location along the lateral length of the axle beam, and which prevents relative axial movement between the torque plate and the axle beam. The axial location member is preferably a ring that is mounted to the axle beam. The ring has a greater diameter than the axle beam, thus forming a circular flange. The torque plate abuts against the flange to prevent relative axial movement. Or, the axial location member could comprises a simple weld that holds the torque plate in the proper position on the axle beam, but is not subjected to high rotational brake torque forces.  
         [0010]     The subject invention eliminates the need for a weld interface between the torque plate and axle beam and provides a mounting interface that can withstand high rotational brake torque forces. Further, the subject invention eliminates the need for subsequent machining of the torque plate prior to installation of the disc brake assembly. These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a schematic view of a trailer axle and disc brake assembly showing a traditional torque plate attachment interface.  
         [0012]      FIG. 2  is a partial cross-sectional view of one example of a disc brake assembly.  
         [0013]      FIG. 3  is an exploded view, partially broken away, of one embodiment of an attachment interface between a trailer axle beam and a torque plate for a disc brake assembly incorporating the subject invention.  
         [0014]      FIG. 4  is an exploded view, partially broken away, of another embodiment of an attachment interface between a trailer axle beam and a torque plate for a disc brake assembly incorporating the subject invention.  
         [0015]      FIG. 5  is an exploded view, partially broken away, of another embodiment of an attachment interface between a trailer axle beam and a torque plate for a disc brake assembly incorporating the subject invention.  
         [0016]      FIG. 6  is an exploded view, partially broken away, of another embodiment of an attachment interface between a trailer axle beam and a torque plate for a disc brake assembly incorporating the subject invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]     A non-drive trailer axle assembly is shown generally at  10  in  FIG. 1 . The trailer axle assembly  10  includes a non-rotating axle tube or beam  12  having a generally circular cross section. While a circular-cross section is traditionally used, it should be understood that the axle beam  12  could have other cross-sectional shapes that would benefit from the subject invention. The axle beam  12  defines a lateral axis of rotation  14  about which a pair of wheel end assemblies  16  rotate. The wheel end assemblies  16  are mounted on opposing ends of the axle beam  12 .  
         [0018]     Each wheel end assembly  16  includes a disc brake assembly  18  having a torque plate  20 . Traditionally in the prior art, the torque plate  20  is welded to the axle beam  12  along a weld interface  22 . The disc brake assembly  18  is then bolted to the torque plate  20 . The torque plate  20  serves as a reaction component that resists the high rotational brake torque forces that are generated during braking.  
         [0019]     The disc brake assembly  18  further includes a rotor disc  24 , caliper  26 , and inboard and outboard brake shoes  28   a ,  28   b  positioned on opposing sides of the rotor disc  24 . The brake assembly  18  is preferably air actuated and includes an air chamber (not shown) that is coupled to a slack adjuster  30 , which cooperates with a camshaft  32  to actuate the brake assembly  18 . The camshaft  32  cooperates with a brake piston  34  and the caliper  26  to move the brake shoes  28  into engagement with the rotor disc  24 .  
         [0020]     When the braking assemblies  18  are actuated, the air chamber actuates the slack adjuster  30 , which is mounted to the camshaft  32 . The movement of the slack adjuster  20  rotates the camshaft  32 , which causes a camshaft nut  36  to slide out along the camshaft  32 . The camshaft nut  36  exerts a force against the brake piston  34 , which pushes the inboard brake shoe  28   a  against the rotor disc  24 . The force of the inboard brake shoe  28   a  exerted against the rotor disc  24  pulls the caliper  26  in along a pair of slide pins  38  (only one is shown). The slide pins  38  extend through the torque plate  20  and the brake caliper  26 . The slide pins  28  are each supported on a torque plate bushing  40  (only one is shown). The torque plate  20  provides a reaction surface for the caliper  26  that resists the high rotational brake torque forces that are generated during brake applications.  
         [0021]     Movement of the caliper  26  pulls the outboard brake shoe  28   b  into contact with the rotor disc  24 , thus generating a clamping force on both sides of the rotor disc  24 . When the brakes are released, a piston return spring  42  retracts the brake piston  34  and releases the clamping force.  
         [0022]     As discussed above, the torque plate  20  is traditionally welded directly to the axle beam  12  along a weld interface  22 . This weld interface  22  has several disadvantages. During the welding process, there is potential for distortion of the torque plate  20 , which can affect the orientation of the brake mounting face of the toque plate  20  relative to the axis of rotation  14 . A final machining step is required after welding to ensure that the brake mounting face is generally flat and square to the axis of rotation  14 . This extra machining step increases the overall cost and assembly time for installation of the brake assembly  18  on the axle  10 .  
         [0023]     Further, the weld interface  22  between the axle beam  12  and the torque plate  20  must be strong enough to resist the high rotational brake torque values generated during braking. Any deficiencies in the weld could result in premature wear or failure, which is undesirable.  
         [0024]     The subject invention provides an improved mounting interface between the torque plate  20  and the axle beam  12 . As shown in  FIG. 3 , the axle beam  12  includes a radial location feature or member, shown generally at  50 , such that the rotational brake torque can be transmitted directly through a solid interface, eliminating the need for a welded interface. The radial location feature  50  prevents relative rotation between the torque plate  20  and the axle beam  12 .  
         [0025]     In one disclosed embodiment, the radial location member  50  includes a plurality of male members located or supported on one of the torque plate  20  or axle beam  12  and a plurality of female members located or supported on the other of the torque plate or axle beam  12 . The male members are at least partially received within the female members to prevent relative rotation between the axle beam  12  and the torque plate  20 . The male and female members can be formed in various different configurations. This will be disclosed in greater detail below.  
         [0026]     The axle beam  12  also includes an axial location feature or member, shown generally at  52 , that positions the torque plate  20  at the proper predetermined position along the lateral length of axle beam  12 . The axial location feature  52  prevents relative axial movement between the torque plate  20  and the axle beam  12 .  
         [0027]      FIGS. 3 through 6  show various embodiments of the radial  50  and axial  52  location members. It should be understood that any of the radial location features  50  could be used in combination with any of the axial location features  52  and vice versa. Further,  FIGS. 3 through 6  show only one end of the axle beam  12 . It should be understood that the opposite end of the axle beam  12  includes a similar torque plate mounting interface.  
         [0028]     In the example shown in  FIG. 3 , the radial location member  50  comprises a plurality of splines or teeth  56  formed about an outer circumference of the axle beam  12 . The torque plate  20  includes a mating plurality of spline grooves or slots  58  formed on an inner circumference. The inner circumference defines an aperture  60  that receives the axle beam  12 . The splines or teeth  56 , which can be integrally formed or machined into the axle beam  12 , matingly or meshingly engage the spline grooves or slots  58  formed in the torque plate  20 . This prevents relative rotation between the torque plate  20  and the axle beam  12 . The brake assembly  18  is then bolted to the torque plate  20  via a bolted joint interface  62 .  
         [0029]     The axial location feature  52  of  FIG. 3  comprises a ring  64  that is separately mounted or integrally formed on the axle beam  12 . The separately mounted ring  64  can be welded or pressed onto the axle beam  12 . The ring  64  has a greater diameter than the axle beam  12  to form a circumferential flange  66 . The torque plate  20  engages or abuts directly against the flange  66 . Thus, the flange  66  provides an end stop that prevents axial movement between the axle beam  12  and the torque plate  20  once the brake assembly  18  is bolted into place.  
         [0030]     The radial location feature  50  of  FIG. 4  comprises a first plurality of openings or apertures  70  that are formed in one end of the axle beam  12 . The torque plate  20  includes a cuff portion  72  that includes a second plurality of holes or apertures  74 . The first and second plurality of holes  70 ,  74  are aligned with one another and a plurality of radial pins  76  are inserted into the holes  70 ,  74 . This prevents relative rotation between the axle beam  12  and the torque plate  20 . The pins  76  could be integrally formed in or pre-assembled onto one of the cuff portion  72  or axle beam  12 . Alternatively, threaded fasteners or other similar fastening elements could be used.  
         [0031]     The radial location feature  50  of  FIG. 5  comprises a plurality of pressed/semi-sheared protrusions  80  formed on an outer circumference of the axle tube  12 . A plurality of slots or grooves  82  are formed on an inner circumference of the torque plate  20 . The protrusions  80  are received within the slots  82  to prevent relative rotation between the axle beam  12  and the torque plate  20 .  
         [0032]     The axial location feature  52  of  FIG. 5  comprises a simple weld interface  84 . This weld interface solely functions to locate and hold an axial position of the torque plate  20  on the axle beam  12 . The weld interface  84  is a non-torque bearing weld and does not have any critical strength requirements.  
         [0033]     The radial location feature  50  of  FIG. 6  comprises an extruded ring  90  that is welded or press fit onto the outer diameter of the axle beam  12 . The ring  90  includes a plurality of teeth  92  formed about the outer circumference of the ring  90 . The torque plate  20  includes a plurality of mating teeth  94  formed about an inner circumference. The teeth  92 ,  94  are intermeshed to prevent relative rotation between the axle beam  12  and the torque plate  20 .  
         [0034]     By using radial  50  and axial  52  location members, the subject invention eliminates the need for a weld interface between the torque plate  20  and axle beam  12  and provides a mounting interface that can withstand high rotational brake torque forces. Also, because the weld interface is eliminated, the axle beam  12  and/or torque plate  20  can be formed from cast ductile iron, which also reduces cost. Further, the subject invention eliminates the need for subsequent machining of the torque plate  20  prior to installation of the disc brake assembly  18 . Finally, the subject invention is easily incorporated into various braking configurations including integrated brakes, and provides flexibility for clocking. Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.