Bar and shim for a braked aircraft wheel
The bar-shim assembly in the aircraft wheel brake design addresses rim heating and screw breakage issues by transmitting braking torque through a shim, ensuring structural integrity and reduced thermal stress.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SAFRAN LANDING SYSTEMS
- Filing Date
- 2025-11-10
- Publication Date
- 2026-05-21
AI Technical Summary
Existing aircraft wheel brake designs suffer from significant rim heating and screw breakage due to friction-generated heat and braking forces, leading to mechanical degradation and structural weakness.
A braked aircraft wheel design featuring a bar-shim assembly where a shim is placed between the rim and the bar, with a screw passing through the shim, allowing the braking torque to be transmitted without shearing the screw, and minimizing heat transfer to the rim.
The design prevents screw bending and breakage while reducing rim heating, enhancing mechanical strength and durability by minimizing thermal conduction and shear stress on the screw.
Smart Images
Figure EP2025082537_21052026_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] Title of the invention: Brake bar and wedge for aircraft wheel
[0003] The present invention relates to the field of aeronautics and, more particularly, to the braking of aircraft wheels.
[0004] BACKGROUND OF THE INVENTION
[0005] Aircraft wheels mounted on landing gear legs and equipped with a brake are known. The brake generally comprises stator discs fixed relative to the landing gear leg and arranged alternately with rotor discs, which are driven in rotation by bars attached to the inner circumference of a wheel rim. The bars are received in peripheral slots on the rotor discs in a direction substantially parallel to an axis of rotation of the wheel. Controlled pressure on all the discs generates friction between the opposing discs and thus a braking torque that slows the wheel's rotation.
[0006] Referring to Figure IA, bars B are known to be attached to the rim J of the wheel to fit over tenons T extending radially from the inner circumference of the rim J. The bars B have a U-shaped cross-section, and the tenons T, generally machined from the same material as the rim J, have a longitudinal axis extending parallel to the axis of rotation of the wheel so as to form slides allowing the rotor discs D to slide along said axis of rotation. The bars B are held in position on the tenons T by means of a screw V extending radially from the rim J. The screw V passes through the bar B and is received in a threaded hole in the corresponding tenon T.
[0007] If such an arrangement of the bars B is suitable for a braked wheel with brake discs extending fully inside the rim J, it turns out that the contact surface between said bar B and the rim J is important so that during braking, the heating of the discs generated by their friction leads to a significant heating of the rim J which can cause a degradation of its mechanical strength.
[0008] Moreover, the braking torque transmitted to the rim J via the rotor discs D causes shearing of the screw V which can lead to its breakage.
[0009] Referring to Figure IB, bars B' are also known, having at one end a cylindrical shank Q' designed to fit into an opening made in a rim of the wheel and, at the opposite end, a hole arranged to receive a screw V' of a bolt passing through an opening made on an axial extension of the rim J'. Thermally insulating shims C' are interposed between the bars B' and the rim J' to, firstly, position the bars B' in a direction parallel to the axis of rotation of the wheel and, secondly, to help limit the heat flux between the rotor discs D' and the rim J' which can be detrimental to the mechanical strength of the latter.
[0010] If the presence of the shims C' and the distance of the bars B' from the rim J' allow to limit the thermal conduction between said bars B' and said rim J', such an arrangement of the bars B' is reserved for braked wheels with brake discs extending outside the rim J'.
[0011] Furthermore, the friction between the stator discs and the rotor discs D' generates braking forces on the bars B' which tend to shear the screw V' that secures the bar B' to the rim J'. These braking forces cause the bar B' to slide on the shim C', and also cause the shim C' to slide on the rim J', which in turn causes the screw V' to bend and potentially break.
[0012] SUBJECT OF THE INVENTION
[0013] The invention aims to provide a bar-shim assembly for aircraft braked wheels that allows at least partially to overcome the aforementioned disadvantages.
[0014] SUMMARY OF THE INVENTION
[0015] To this end, the invention proposes a braked aircraft wheel comprising:
[0016] - a rim connected by a flange to a hub intended to be received by pivoting on an axle, the rim delimiting with the hub a space for receiving brake rotor discs;
[0017] - at least one bar having a cylindrical tail-shaped end fitted into an opening in the rim, and an opposite end fixed via a screw to a tenon extending projecting from an inner circumference of the rim to rotationally bind the brake rotor discs to the rim; and
[0018] - a shim placed between the rim and the bar and through which the screw passes.
[0019] According to the invention, the shim is received in the bar and fits over the tenon of the rim to define a main transmission path of a braking torque from the rotor discs to the rim passing through the shim, the bar and the tenon without constraining the screw in shear.
[0020] The shim cannot therefore slip circumferentially against the rim during braking, thus eliminating any bending of the screw. Furthermore, the shim reduces the contact area between the shim and the rim, thereby limiting rim heating caused by rotor disc friction during braking. Consequently, heat transfer between the shim and the rim is minimized.
[0021] According to a particular characteristic, the wedge is pressed into the bar.
[0022] According to another particular characteristic, the wedge has a constant and U-shaped cross-section.
[0023] In particular, the wedge comprises a base and two fins each extending from a longitudinal edge of the base, the base having an outer surface cooperating with an inner surface of the bar.
[0024] According to another particular feature, the wedge is made of titanium.
[0025] According to another particular feature, the screw includes a section received in a hole made in the bar and in the wedge, the hole having a diameter sufficiently greater than that of said section of the screw so that the rotor discs can exert a braking torque on the rim without stressing the screw.
[0026] According to another particular feature, the screw is screwed into a thread inserted into a hole made in the tenon of the rim.
[0027] According to another particular characteristic, the barrette is made of metal.
[0028] The invention also relates to a landing craft comprising at least one such braked wheel.
[0029] The invention also relates to an aircraft comprising at least one such landing gear.
[0030] BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The invention will be better understood in the light of the following description, which is purely illustrative and not limiting, and should be read in conjunction with the accompanying figures, among which: [Fig. 1A] Figure IA is an axial cross-sectional view of an aircraft braked wheel equipped with a bar according to a first embodiment of the prior art;
[0032] [Fig. IB] Figure IB is an axial cross-sectional view of an aircraft braked wheel equipped with a bar and a shim according to a second embodiment of the prior art;
[0033] [Fig. 2] Figure 2 is a front view of an aircraft including landing gear equipped with braked wheels;
[0034] [Fig. 3] Figure 3 is an axial cross-sectional view of one of the braked wheels of the aircraft illustrated in Figure 2, the rim of which is equipped with bars and shims according to a particular embodiment of the invention;
[0035] [Fig. 4A] Figure 4A is a first perspective view of the bar and the wedge illustrated in Figure 3; [Fig. 4B] Figure 4B is a second perspective view of the bar and the wedge illustrated in Figure 3; [Fig. 5A] Figure 5A is a view illustrating the shrink fitting of the bar and the wedge illustrated in Figure 4A;
[0036] [Fig. 5B] Figure 5B is a view illustrating the assembly of the bar-shim assembly illustrated in Figure 4A in the wheel illustrated in Figure 3;
[0037] [Fig. 5C] Figure 5C is a view illustrating the fixing of the bar-shim assembly illustrated in Figure 4A on the wheel illustrated in Figure 3;
[0038] [Fig. 6] Figure 6 is a detailed axial cross-sectional view of a variant of the bar-shim assembly illustrated in Figure 3.
[0039] DETAILED DESCRIPTION OF THE INVENTION
[0040] With reference to Figure 2, an aircraft 1 according to the invention comprises a structure 2 provided with two main landing gears 3. Each of the landing gears 3 comprises a leg 4 having one end articulated to the structure 2 of the aircraft 1 and an opposite end carrying an axle 5 on which wheels 10 are mounted to pivot about an axis X.
[0041] With reference to Figure 3, each of the wheels 10 comprises a main part 10.1 and an auxiliary part 10.2 attached to the main part 10.1, these main and auxiliary parts 10.1, 10.2 both being generally annular in shape and here made of aluminium.
[0042] The main part 10.1 comprises an annular rim 11 connected by a disc 12 to a hub (not shown) which is pivotally supported about the X-axis on an end portion of the axle 5 by means of bearings. The rim 11 includes a free end formed into a first flange 13.1 and, opposite it, a centering surface for the auxiliary part 10.2 of the wheel 10.
[0043] The auxiliary part 10.2 has one end formed into a second heel 13.2. In a manner known per se, the auxiliary part 10.2 is attached to the main part 10.1 after a tire (not shown) has been fitted to the rim 11. A bead 14 is interposed between the main part 10.1 and the auxiliary part 10.2 to secure said auxiliary part 10.2 to said main part 10.1.
[0044] The rim 11 extends coaxially around the hub and, together with said hub, defines an annular space having one end at least partially closed by the disc 12 and, at the opposite end, an open end. This annular space forms a receiving space for a stack of discs 20 of a brake. This stack comprises stator discs 20a fixed in rotation relative to the axle 5, and rotor discs 20b having peripheral notches 21, each receiving a bar 30 fixed to an inner circumference of the rim 11. It is understood that the rotor discs 20b are substantially fixed in rotation relative to the rim 11, such that said rotor discs 20b are driven in rotation about the X-axis by the rim 11 via the bars 30. Controlled pressure on all the discs generates friction between the facing discs 20 and therefore a braking torque that slows the rotation of the wheel 10.
[0045] With reference to Figures 4A-4B, each bar 30 comprises an elongated body 31 extending along axis X30 substantially parallel to the axis X of rotation of the wheel 10 and having a cross-section, perpendicular to axis X30, that is generally constant and U-shaped. The body 31 is here made of metal and comprises a generally flat core 32 and two wings 33, each extending from a longitudinal edge of the core 32. The core 32 and the wings 33 respectively define the base and the arms of the U-shaped cross-section.
[0046] The core 32 of the bar 30 comprises:
[0047] - a first end 32.1 provided with a cylindrical tail which is received by adjustment in an orifice 12.1 formed in the disc 12 of the wheel 10 in a direction parallel to the axis X of rotation of said wheel 10, and
[0048] - a second end 32.2 having a hole 32.3 which extends in a radial direction Y vis-à-vis the rim 11 and which is crossed by a screw 40 for fixing the bar 30 to a tenon 15 extending radially from a distal end of the inner circumference of the rim 11, opposite the veil 12.
[0049] The orifice 12.1 into which the first end 32.1 of the bar 30 is inserted is here through, and the tenon 15 is here made of material with the rim 11.
[0050] The screw 40 comprises a head 41 having a flange 41.1 bearing against an outer surface 32a of the web 32 and, opposite, a threaded end portion 42 extending through a thread 16 inserted into a bore 15.1 formed in the tenon 15 of the rim 11 along the radial direction Y. The head 41 of the screw 40 has a diameter slightly smaller than that of the hole 32.3 of the bar 30 so as to define a slight play between the screw 40 and the bar 30.
[0051] The wings 33 of the bar 30 include an outer surface 33a arranged to cooperate with a bearing face of a rider protecting the lateral sides of the peripheral notches of the rotor discs 20b. The outer surfaces 33a of the wings 33 here form a non-zero angle so that in service, they extend radially with respect to the rim 11.
[0052] A shim 50 is interposed between the bar 30 and the tenon 15 of the rim 11 to both maintain the bar 30 in position on the wheel 10 substantially parallel to the X axis of rotation of said wheel 10, form a mechanical interface between the bar 30 and the rim 11, and form a thermal barrier to the conduction of heat from the bar 30 to the rim 11.
[0053] The wedge 50 comprises a body 51, here made of titanium, having a constant cross-section and in the shape of a U. The body 51 comprises a base 52 and two fins 53 each extending from a longitudinal edge of the base 52. The base 52 and the fins 53 respectively define the base and the arms of the U-shaped cross-section.
[0054] The base 52 of the shim 50 includes a hole 52.1 receiving the head 41 of the screw 40 for fixing the bar 30 to the tenon 15 of the rim 11. The diameter of the hole 52.1 of the shim 50 is slightly larger than that of the head 41 of the screw 40 so as to define a slight play between the screw 40 and the shim 50. The diameter of the hole 52.1 of the shim 50 is here substantially equal to that of the hole 32.3 of the bar 30.
[0055] The shim 50 is shrunk into the bar 30 so that: the base 52 of the shim 50 has an outer surface 52a cooperating with an inner surface 32b of the web 32 of the bar 30, the fins 53 of the shim 50 have an outer surface 53a cooperating with an inner surface 33b of the wings 33 of the bar 30, and the hole 52.1 of the base 52 extends coaxially to the bore 15.1 of the tenon 15 of the rim 11.
[0056] The base 52 of the wedge 50 has an inner surface 52b arranged to cooperate with an upper face 15a of the tenon 15 of the rim 11, and the fins 53 of the wedge 50 have an inner surface 53b each cooperating with a lateral face of the tenon 15 of the rim 11. The wedge 50 is thus arranged to cap the tenon 15 of the rim 11.
[0057] Thus, the shrink fitting of the shim 50 in the bar 30 limits the play between the tenon 15 and the bar 30 so that the transmission of the braking torque via the bar 30 does not stress the screw 40. It is understood that the braking torque exerted by the rotor discs 20b on the rim 11 passes through the fins 53 of the shim 50 bearing against the tenon 15 of the rim 11 and not through the screw 40.
[0058] The assembly of the bar-shim assembly 30, 50 on wheel 10 will now be detailed with regard to figures 5A to 5C.
[0059] With reference to Figure 5A, the shim 50 is first inserted by force into the bar 30 so that the outer surface 52a of the base 52 of the shim 50 is in contact with the inner surface 32b of the web 32 of the bar 30, and so that the hole 52.1 of the shim 50 is coaxial with the hole 32.3 of the bar 30.
[0060] The bar-shim assembly 30, 50 is then brought close to the rim 11 so that the first end 32.1 of the bar 30 in the form of a cylindrical tail is coaxially opposite the receiving orifice 12.1 of the first end 32.1 of the bar 30, and so that the inner surface 52b of the base 52 of the shim 50 and the upper face 15a of the tenon 15 of the rim 11 extend in the same plane (figure 5B).
[0061] The bar-shim assembly 30, 50 is then translated along the longitudinal axis X30 of the bar until the first end 32.1 of the bar 30 extends inside the orifice 12.1 of the web 12, and the hole 32.3 of the bar 30 extends coaxially with the bore 15.1 of the tenon 15. It is then understood that the inner surface 52b of the base 52 of the shim 50 cooperates with the upper face 15a of the tenon 15 of the rim 11.
[0062] The screw 40 is then screwed into the thread 16 inserted into the bore 15.1 of the tenon 15 so as to hold the bar-shim assembly 30, 50 in position on the rim 11 and so that the inner surface 52b of the base 52 of the shim 50 is in contact with the upper face 15a of the tenon 15 of the rim 11 (figure 5C).
[0063] It is understood that the diameter of the hole 32.3 of the bar 30 and that of the hole 52.1 of the shim 50 are sufficiently greater than that of the head 41 of the screw 40 so that the rotor discs can exert on the rim a braking torque passing through the bar 30, the shim 50 and the tenon 15 without stressing the screw 40 in shear.
[0064] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.
[0065] Although the screw 40 extends here in a radial direction Y relative to the rim 11, it can also be inclined and thus extend in a direction Y' forming a non-zero angle with the direction Y in an axial plane of the wheel 10 so as to facilitate tightening said screw 40 (Figure 6). The tenon 15' of the rim 11 and the end of the bar 30' receiving the shim 50' are then arranged to allow such an inclination of the screw 40. The screw 40 may have a protruding head instead of a countersunk head.
[0066] Although the shim 50 is here fretted into the bar 30, it can also be received by adjustment in said bar 30.
[0067] Although the outer surfaces of the wings 33 of the bar 30 here form a non-zero angle, they can also be parallel.
[0068] Although the wheel 10 here comprises a main part 10.1 and an auxiliary part 10.2 attached to the main part 10.1, it can also comprise two half-wheels assembled together or be a single piece.
Claims
DEMANDS 1. Braked aircraft wheel (10) comprising: - a rim (11) connected by a disc (12) to a hub intended to be received by pivoting on an axle (5), the rim delimiting with the hub a space for receiving brake rotor discs (20b); - at least one bar (30) having a cylindrical tail-shaped end received by adjustment in an orifice (12.1) formed in the rim, and an opposite end fixed by means of a screw (40) to a tenon (15) extending projecting from an inner periphery of the rim to rotationally bind the brake rotor discs to the rim; and - a shim (50) interposed between the rim and the bar and through which the screw passes, characterized in that the shim (50) is received in the bar and fits over the tenon of the rim to define a main transmission path of a braking torque from the rotor discs to the rim passing through the shim, the bar and the tenon without constraining the screw in shear.
2. Wheel (10) braked according to claim 1, in which the shim (50) is pressed into the bar (30).
3. Wheel (10) braked according to any one of the preceding claims, wherein the wedge (50) has a constant cross-section and is U-shaped.
4. Wheel (10) braked according to claim 3, in which the wedge (50) comprises a base (52) and two fins (53) each extending from a longitudinal edge of the base, the base having an outer surface (52a) cooperating with an inner surface (32b) of the bar (30).
5. Wheel (10) braked according to any one of the preceding claims, wherein the shim (50) is made of titanium.
6. Wheel (10) braked according to any one of the previous claims, wherein the screw (40) comprises a section (41) received in a hole (32.3, 52.1) formed in the bar (30) and in the wedge (50), the hole having a diameter sufficiently greater than that of said section of the screw so that the rotor discs can exert a braking torque on the rim without stressing the screw.
7. Wheel (10) braked according to any one of the preceding claims, in which the screw (40) is screwed into a thread (16) inserted into a bore made in the tenon (15) of the rim (11).
8. Wheel (10) braked according to any one of the preceding claims, in which the bar (30) is made of metal.
9. Aircraft landing gear (3) comprising at least one wheel (10) braked according to any one of the preceding claims.
10. Aircraft (1) comprising at least one landing gear (3) according to claim 9.