Patent Publication Number: US-2023150303-A1

Title: Heat shield chin ring

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to, and the benefit of, EP Patent Application No. 21461620.3, filed Nov. 17, 2021, and titled “HEAT SHIELD CHIN RING,” which is incorporated by reference herein in its entirety for all purposes. 
     FIELD 
     The present disclosure relates to a heat shield, sometimes referred to as a chin ring for use in a wheel assembly e.g. for an aircraft wheel and brake assembly. 
     BACKGROUND 
     Wheels on aircraft and other vehicles are often provided with a brake assembly comprising a stack of brake discs, comprising stators and rotors, mounted inside the wheel, within the tube well of the wheel. The brake operates by compressing the brake discs together to slow and stop rotation of the wheel. The friction between the pressed brake discs generates a large amount of heat which can cause damage to the wheel and/or tires. It is conventional to provide a heat shield between the brake assembly and the wheel rim or tube well to reduce the effects of the heat generated by braking on the wheel parts. The heat shield can also catch hot brake material that is ejected from the brake discs during braking, before it strikes the wheel. 
     The heat energy generated within the braking stators and rotors (forming a heat sink) may dissipate via conduction, radiation and convection to adjacent parts of the brake and wheel assembly including to the tire. Dissipation of heat is required to avoid overheating of the braking components but dissipation of heat to e.g. the tire and other wheel parts can cause damage to those parts. It is important to protect the tire from excessive radiant heat and to protect the heat sink from contaminants such as water, de-icing chemicals and other debris. One way to provide such protection is to provide a heat shield between the heat generating components of the braking system and the adjacent wheel assembly and brake assembly parts. 
     A chin ring can be used to perform such a function. Conventionally, a chin ring is attached to the wheel assembly so as to block the line of sight between the heat generating parts of the braking system and the tire, to reduce or prevent the radiant heat from the heat generating components reaching and causing damage to the tire. 
     Various types of heat shield are known but, typically, heat shields are in the form of metal sheets or panels provided concentric with the wheel tube well and spaced a small distance from the tube well. The heat shield can be provided as a single cylindrical piece but more typically is formed as a number of arcuate panels or sections that are attached together to form a complete cylindrical heat shield. 
     Because the heat shield blocks the convection and radiation heat from the braking components, however, the chin ring itself and the area between the wheel and the heat sink components becomes very hot and these components are crucial for wheel and brake thermal performance. 
     There is a need for an improved chin ring, from a thermal performance point of view, that also protects the wheel. 
     SUMMARY 
     According to one aspect, there is provided a chin ring heat shield for a wheel assembly, arranged to provide a shield between convection and radiation heat from braking components and a tire of the wheel assembly, the chin ring comprising a first, radially extending, flat portion extending from a first chin ring end and a second, concave portion extending generally axially away from the first portion to a second chin ring end, wherein the axial length from the first chin ring end to the second chin ring end is sufficient to block a line of sight between the braking components and the tire when the chin ring is mounted between the braking components and the tire. 
     According to another aspect, there is provided a wheel assembly including a chin ring as defined above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Examples of a chin ring arrangement according to the disclosure will be described with reference to the drawings. It should be noted that variations of the examples described are possible within the scope of the claims. 
         FIG.  1    shows a side sectional view of a chin ring according to the disclosure and for comparison with a conventional chin ring. 
         FIG.  2    shows a partial view of a wheel assembly incorporating a chin ring according to this disclosure. 
         FIG.  3    is shown to explain requirements of the geometry of a chin ring according to the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring first to  FIGS.  1  and  2   , a wheel assembly includes a wheel flange  10  onto which a tire  12  is mounted. The wheel flange  10  and tire  12  rotate around a wheel axle  14 . A braking assembly of a stack of stators and rotors  16 ,  18  is mounted around the axis A. Pistons  20  cause the stators and rotors to move into frictional engagement when a braking command is applied to the braking assembly, to apply a braking force to the wheel. 
     As described above, a chin ring (or heat shield) is provided between the braking components  16 ,  18  and the tire  12  to block radiation and convection heat from reaching the tire from the heat sink components. The axial direction, and direction of movement of the braking components into braking engagement is indicated by arrow A. The dashed lines  30  in  FIG.  1    show the shape of a conventional chin ring. The chin ring  30  is in the form of a substantially flat heat absorbent metal plate extending radially outwards from the axis defined by the axle  14 . The chin ring  30  is secured between (at  25 ) the wheel flange  10  and the heat shield  40 . Alternatively, the chin ring  30  may be attached to the opposite surface  26  of the wheel or may be secured in a different location but extends radially outwards to provide a shield in the ‘line of sight’ between the braking assembly heat sink components  16 , 18  and the tire  12 . The conventional chin ring adequately performs the function of preventing or reducing the generated heat being directed to the tire by blocking the convection heat before it reaches the tire. As mentioned above, however, this means that the chin ring  30  itself and the space  28  between the braking components and the chin ring becomes hot and retains heat which can cause damage and safety problems. 
     The present disclosure provides a modified chin ring  50 . All other parts of the wheel and braking assembly are unchanged and are as known in the art. The location of attachment of the chin ring  50  is again shown between (at  25 ) the wheel flange  10  and the heat shield  40  but the chin ring could be supported at other locations e.g. on the other surface  26  of the wheel flange. 
     As with the conventional chin ring  30 , the modified chin ring  50  extends radially outward (with respect the axle  14 ) from the wheel flange  10  at a first flat portion  501  but is then shaped to form a second curved portion  502 . The curved portion  502  extends in a substantially axial direction away from the braking components and into a curve generally in the radial direction resulting in a shield that has a concave portion  502  facing away from the tire  12 . 
     Various curves and dimensions of the first and second portions are possible provided two geometric criteria, shown in  FIG.  3   , are satisfied: The total chin ring shape must remain below the outer diameter D of the wheel flange  10  and the overall radial extent of the chin ring  50  from the first end  51  attached at the wheel flange  10  to the free, second end  52  should be sufficient to block the line of sight B between the brake components and the tire  12 , so that the radiation heat from the heat sink is prevented, by the chin ring  50  from reaching the tire  12 . 
     The curved portion  502  of the chin ring  50  directs the convection heat from the braking components away from the chin ring  50  and the intermediate space  28  to ambient. 
     The chin ring may be made of any suitable material, such as metal, ceramic or metal/ceramic composites. Stainless steel and aluminum, for example, are suitable metals. 
     The chin ring can be formed in any suitable manner for working the selected material e.g. by sintering, casting, forging, stamping, laser cutting etc. 
     To test the effectiveness of the ‘open’ chin ring  50 , temperature probes were attached to various locations of the wheel and the braking assembly in a simulation and it was observed that for heat sink components close to the chin ring area experienced a higher cooling ratio. A higher temperature drop was also observed, with the open chin ring  50  for other parts of the wheel assembly such as the piston housing, the wheel and the axle. A temperature drop compared to the conventional chin ring  30  was also observed on the surface of the tire  12  at various locations. It has been seen, therefore, that the ‘open’ chin ring design of this disclosure can provide improved thermal performance in a wheel assembly. 
     By shaping the chin ring with a curve to deflect convection heat away to ambient, but ensuring that the geometrical criteria are satisfied, the chin ring can provide improved thermal performance in a wheel assembly.