Disc brake caliper

Abstract

The present invention relates to a disc brake caliper (1) comprising a caliper body (2) arranged straddling a brake disc having a rotation axis defining an axial direction (A-A) and opposite friction surfaces, said caliper (1) comprising pads (3) accommodated in said caliper body (2) so as to slide substantially in an axial direction (A-A) with respect to the brake disc to act on said opposite friction surfaces, respectively, said caliper (1) comprising a cylinder (4), forming a cylindrical wall (5) and a bottom wall (6) transverse to the cylindrical wall (5), said caliper (1) further comprising a parking braking system (10), which comprises a rotating member (11); said rotating member (11) being rotatably accommodated in a rotation seat (12) formed in the bottom wall (6) of the cylinder (4) so that the rotating member (11) is rotatable about a rotation axis substantially parallel to the axial direction (A-A), wherein the cylinder (4) defines a first annular seat (13) made in the bottom wall (6), said first annular seat (13) extending into the bottom wall (6) in a direction transverse to the axial direction (A-A) and leading into the rotation seat (12), wherein the first annular seat (13) accommodates a first seal (15), and wherein the first seal (15) is configured to act between said rotating member (11) and said bottom wall (6) of the cylinder (4) to obtain a fluid sealing; wherein the caliper (1) is characterized in that it comprises a bushing (30) housed in the rotation seat (12) interposed, at least partially, between the rotating member (11) and bottom wall (6) of the cylinder (4).

Description

DISC BRAKE CALIPERDESCRIPTIONField of the invention

[0001] The present invention relates to a disc brake caliper, in particular for a disc brake comprising an electromechanical parking brake.Background art

[0002] In recent years, the development of electromechanical parking brakes (EPBs) has focused on increasing the parking performance thereof, both in terms of the clamping force generated and service life.

[0003] In particular, current EPB devices are required to sustain at least 300,000 load cycles.

[0004] It has been observed that a correct fluid sealing of the braking system plays a key role in increasing the service life of an EPB device, and thus the number of load cycles thereof.

[0005] Undesired brake fluid leakage and undesired air inlet from the outside cause EPB devices to deteriorate.

[0006] In fact, in the absence of correct sealing, the brake fluid can enter the gearmotor chamber of the EPB device and damage the working thereof, e.g., causing the plastic gears to swell or the motor to short-circuit.

[0007] Additionally, due to the loss of optimal sealing, the resulting seeping brake fluid generates a viciouscycle further reducing the life of EPB devices.

[0008] To address these critical issues, current EPB devices are generally provided with a seal consisting of an 0-ring coupled to an anti-extrusion ring (backup ring) configured to prevent extrusion of the O-ring rubber, which can be generated by high brake fluid pressures.

[0009] Such a known solution is not optimal because the resulting fluid sealing greatly depends on the compression of the 0-ring in the seat in which it is accommodated.

[0010] Furthermore, since the O-ring is mounted directly on the screw shaft of the EPB device, the relative sliding and heat generated during the movement of the screw cause severe wear and abrasion of the O-ring. The O-ring wear generates a significant reduction in the compression thereof, causing brake fluid leakage and a reduction in the caliper life.

[0011] A further problem caused by O-ring wear and the relative loss of compression thereof is the inlet of air during the brake actuation step without the presence of pressurized brake fluid.

[0012] In fact, actuation of the brake without the application of pressurized fluid causes the movement of the brake piston to generate negative pressure at the EPB screw.

[0013] In the presence of a worn sealing system, the negative pressure causes air to be sucked in from the outside, and a spongy feel to the pedal, reducing the braking performance.

[0014] It has been attempted to solve these critical issues and increase the sealing of the system by placing multiple O-rings side-by-side.

[0015] However, placing multiple O-rings in the same seat has not proven to be the solution because it does not solve the critical issues relating to high brake fluid pressures acting on the plurality of O-rings, which cause the seeping of brake fluid past the plurality of O-rings placed side-by-side.

[0016] US2013037357A1 describes a disc brake caliper in which a dual sealing stage is applied to a service brake translating member (the piston). One of the two sealing stages comprises a quadrangular section seal, configured to be compressed in an axial direction and easily deformable so as to ensure that the piston has a "roll- back" effect. Despite being suitable for application to a translating member, such a known solution is not adapted to ensure a correct sealing for a rotating member of a parking-braking system because the rotation of the rotating member would exacerbate the deformation of the seal, which would then be unable to effectively preventthe seeping of brake fluid.

[0017] EP2273149A1 also describes a disc brake caliper, in which a dual sealing stage is applied to a service brake translating member (i.e., the piston). One of the two sealing stages comprises a seal configured to act initially integrally with the translating member. Such a known solution is not applicable to a rotating member because adhesion to the rotating member would quickly damage the seal and the sealing capacity thereof.

[0018] Moreover, EP4169783 to the Applicant shows a disc brake caliper, in which a dual sealing stage is applied to a service brake translating member. It has been noted how, in such an embodiment, during translation, the translating member becomes worn or wears the cylinder in which it is housed and the undesired particles created in said wear ruin the seals. Furthermore, such an embodiment has been identified to be particularly complex in the assembly thereof.Solution

[0019] It is the object of the present invention to provide a disc brake caliper, comprising an improved parking- braking system, configured to solve at least some of the drawbacks of the prior art.

[0020] These and other objects are achieved by a disc brake caliper according to claim 1.

[0021] The dependent claims relate to preferred and advantageous embodiments of the present invention.Figures

[0022] In order to better understand the invention and appreciate the advantages thereof, a few non-limiting exemplary embodiments thereof will be described below with reference to the accompanying drawings, in which:

[0023] - figure 1 is a perspective view of a disc brake caliper, along an axial section according to an embodiment of the invention;

[0024] - figure 2 is a side view of the disc brake caliper shown in figure 1;

[0025] - figure 3 is a partially sectioned upper view of a disc brake caliper according to an embodiment of the invention;

[0026] - figure 4 is a detail view of a part of figure 3;

[0027] - figures 5' and 5" are two detail views of the detail indicated in figure 3 in two different section planes;

[0028] - figures 6' and 6" are two perspective views of a bushing included in the disc brake caliper according to an embodiment;

[0029] - figures 7' and 7" are two perspective views of a backup ring included in the disc brake caliper according to an embodiment of the invention, in which theycooperate with the bushing indicated in figures 6' and 6";

[0030] - figure 8 is a perspective view with separate parts of a bushing and a backup ring included in the disc brake caliper according to a further embodiment of the invention;

[0031] - figure 9 is a perspective view with separate parts of a bushing and a backup ring included in the disc brake caliper according to a further embodiment of the invention;

[0032] - figure 10 is a front view of a component of a disc brake caliper, along an axial section according to an embodiment of the invention;

[0033] - figure 11 is a front view of a component of a caliper for a disc brake along an axial section according to a further embodiment of the invention;

[0034] - figure 12 is a front view of a component of a disc brake caliper along an axial section according to a further embodiment of the invention;

[0035] - figure 13 is a front view of a component of a disc brake caliper along an axial section according to a further embodiment of the invention.Description of preferred embodiments

[0036] With reference to the figures, a disc brake caliper is generally indicated by reference numeral 1.

[0037] The disc brake caliper 1 comprises a caliper body 2 arranged straddling a brake disc having a rotation axis which defines an axial direction A-A and opposite friction surfaces.

[0038] The caliper 1 comprises pads 3 accommodated in the caliper body 2 so as to slide substantially in an axial direction A-A with respect to the brake disc to act on the opposite friction surfaces, respectively.

[0039] Furthermore, the caliper 1 comprises a cylinder 4, which forms a cylindrical wall 5 and a bottom wall 6 transverse to the cylindrical wall 5.

[0040] The caliper 1 further comprises a piston 7, which forms a side wall 8 and a thrust wall 9 substantially transverse to the side wall 8 and opposite to the bottom wall 6 of the cylinder 4.

[0041] The bottom wall 6 forms an inner surface 25 facing towards the piston 7 and an opposite outer surface 26 facing away from the piston 7.

[0042] The piston 7 is accommodated in the cylinder 4, and the side wall 8 of the piston 7 is adapted to slide in the cylindrical wall 5 of the cylinder 4.

[0043] The piston 7 is configured to be biased by a pressurized brake fluid injectable into the cylinder 4, so as to bias at least one of the pads 3 against one of the brake disc friction surfaces along a thrustdirection substantially parallel to the axial directionA-A.

[0044] The caliper 1 further comprises a parking-braking system 10 which comprises a rotating member 11.

[0045] The rotating member 11 is rotatably accommodated in a rotation seat 12 formed in the bottom wall 6 of the cylinder 4 so that the rotating member 11 is rotatable about a rotation axis substantially parallel to the axial direction A-A.

[0046] According to an embodiment, the rotating member 11 comprises an axial locking ring 35. Said axial locking ring 35 extends in a radial direction and is adapted to provide a backing engaging the outer wall 26.

[0047] According to an aspect of the invention, the cylinder 4 defines a first annular seat 13.

[0048] The first annular seat 13 extends into the bottom wall 6 in a direction transverse to the axial direction A-A and leads into the rotation seat 12.

[0049] According to an embodiment, the cylinder 4 defines a second annular seat 14 made in the bottom wall 6.

[0050] The second annular seat 14 preferably extends into the bottom wall 6 in a direction parallel to the axial direction A-A being positioned on the outer wall 26.

[0051] The second annular seat 14 is preferably distinct from said first annular seat 13 and is positioned in anopposite direction to the inner surface 25 of the bottom wall 6 with respect to the first annular seat 13.

[0052] The first annular seat 13 accommodates a first seal 15.

[0053] The first seal 15 is configured to act between said rotating member 11 and the bottom wall 6 of the cylinder 4 to obtain a fluid sealing.

[0054] The first seal 15 preferably makes a radial fluid sealing.

[0055] According to an embodiment, the second annular seal 14 accommodates a second seal 16.

[0056] The second seal 16 is configured to act between said bottom wall 6 of the cylinder 4 and the axial locking ring 35 to obtain a fluid sealing.

[0057] The second seal 16 preferably makes an axial fluid sealing.

[0058] Advantageously, the first and second seals 15, 16 ensure a high sealing and drastically reduce undesired brake fluid leakage and air inlet from the outside.

[0059] Specifically, the first seal 15, closest to the pressurized brake fluid, shields the pressure and provides most of the sealing. The second seal 16 allows stopping drops of brake fluid from seeping past the first seal 15, thus achieving a high sealing.

[0060] According to an embodiment, the parking brakingsystem 10 comprises a screw-nut system formed by a screw17 and a nut 18.

[0061] A translation of the nut 18 corresponds to a rotation of the screw 17, with respect to the caliper body 2, along a direction parallel to the axial direction A-A.

[0062] The nut 18 is configured to bias at least one of the pads 3 against one of said friction surfaces of the brake disc.

[0063] The rotating member 11 forms the screw 17.

[0064] Optionally, the screw-nut system defines a thread and said thread is of the irreversible type.

[0065] Advantageously, such a configuration drastically reduces the seeping of brake fluid past the screw 17, thus preserving the correct working of the additional components of the EPB device.

[0066] According to the invention, the caliper 1 further comprises a bushing 30 housed in the rotation seat 12 interposed, at least partially, between the rotating member 11 and the bottom wall 6 of the cylinder 4.

[0067] According to an embodiment, the bushing 30 is made of sintered bronze.

[0068] According to an embodiment, the bushing 30 comprises a transverse bushing shoulder 31 extending transversely.

[0069] The transverse bushing shoulder 31 is preferablyhoused in the first annular seat 13 interposed between the first seal 15 and the bottom wall 6 in the direction of the outer surface 26.

[0070] Furthermore, according to an embodiment, the bushing 30 comprises an axial cylinder 32 extending parallel to the axial direction A-A interposed between the rotating member 11 and the bottom wall 6 of the cylinder 4.

[0071] According to an embodiment, the first seal 15 comprises an 0-ring 19 coupled to a sealing ring, which also has a backup function and will be referred to as a backup ring 20 hereafter.

[0072] The backup ring 20 is interposed between the O-ring 19 and the rotating member 11 and is made of less deformable material than the material of the 0-ring 19.

[0073] Optionally, the backup ring 20 is made of a polymeric material, such as polytetrafluoroethylene (PTFE), or a polymeric material with PTFE filler in the polymer matrix.

[0074] According to an embodiment, the backup ring 20 is interposed between said O-ring 19 and the rotating member 11.

[0075] According to an embodiment, the backup ring 20 engages the bushing 30 with a shape coupling adapted to make a rotational coupling. In other words, the coupling between the backup ring 20 and the bushing 30 is suchthat any relative rotation between the two is prevented.

[0076] The backup ring 20 preferably comprises an axial wall 27 extending parallel to the axial direction A-A, interposed between said O-ring 19 and the rotating member 11.

[0077] Furthermore, the backup ring 20 preferably comprises a transverse ring shoulder 28 interposed between said 0- ring 19 and the bottom wall 6 in the direction of the outer surface 26.

[0078] The transverse ring shoulder 28 preferably extends in a transverse direction over a length such as to prevent contact between the O-ring 19 and the bottom wall 6 in the direction of the outer surface 26.

[0079] According to an embodiment, the transverse ring shoulder 28 extends transversely from the axial wall 27 to a retaining tooth 29 adapted to contain the O-ring 19. The O-ring 19 is preferably retained in a transverse position, on said transverse ring shoulder 28, internally radially from the axial wall 27, externally radially from the retaining tooth 29.

[0080] According to an embodiment, the transverse ring shoulder 28 of the backup ring 20 and the transverse bushing shoulder 31 of the bushing 30 extend transversely over the same length.

[0081] According to an embodiment, the transverse ringshoulder 28 of the backup ring 20 preferably engages the transverse bushing shoulder 31 of the bushing 30.

[0082] Advantageously, such a configuration of the first seal 15 prevents relative rotations between the 0-ring 19 and the screw 17, and prevents relative rotations between the 0-ring 19 and the backup ring 20. In particular, the O-ring 19 discharges a thrust action onto the bushing 30, e.g., by means of the transverse ring shoulder 28, in a direction parallel to the axial direction, thus pushing the shoulder 28 to engage with the bushing 30. Thereby, it is certain that the O-ring 19 works subjected to static and non-dynamic conditions, allowing a significant reduction in cross-section (or cord) wear of the O-ring.

[0083] According to an embodiment, the second seal 16 is a scraper.

[0084] Advantageously, a scraper ensures a high sealing against the seeping of brake fluid, dust, rust or the inlet of air from the outside, achieving a high fluid sealing in synergy with the first seal 15.

[0085] More advantageously, the scraper makes up for any wear, and consequent reduction in the sealing, of the backup ring 20 of the first seal 15, thus continuing to preserve the sealing of the entire braking system.

[0086] According to an embodiment, the second seal 16 is:

[0087] - an O-ring; or

[0088] - an X-ring; or

[0089] - a symmetrical or asymmetrical lip seal; or

[0090] - a symmetrical or asymmetrical lip seal, incorporating a reinforcing insert 23, made of metal or a polymeric material; or

[0091] - a lip seal defining three lobes 21 in a section parallel to the axial direction A-A; or

[0092] - a lip seal defining four lobes 21 in a section parallel to the axial direction A-A.

[0093] Advantageously, the scrapers thus configured make up for any deviations in geometric tolerances, due to temperature variations, for example so as to preserve the proper sealing of the braking system.

[0094] According to an embodiment, the second seal 16 is a lip seal which defines a three-lobe profile 21 in a section parallel to the axial direction A-A.

[0095] Two of the three lobes 21 are biased against the rotating member 11, preferably against the axial locking ring 35, and one of the three lobes 21 is biased against the bottom wall 6 of the cylinder 5.

[0096] Optionally, two of the three lobes 21 are pinned against the rotating member 11 preferably against the axial locking ring 35, opposite to each other along a direction parallel to the axial direction A-A.

[0097] Optionally, one of the three lobes 21 biased againstthe bottom wall 6 of the cylinder 5 is pinned against said bottom wall 6 in the direction of the inner surface 25 of the bottom wall 6.

[0098] Optionally, the second seal 16 is a lip seal which defines a four-lobe profile 21 in a section parallel to the axial direction A-A, and where two of the four lobes 21 are biased against the rotating member 11, preferably against the axial locking ring 35, and two opposite lobes 21 are biased against the bottom wall 6 of the cylinder 5.

[0099] Optionally, two of the four lobes 21 are pinned against the rotating member 11, preferably against the axial locking ring 35, opposite to each other along a direction parallel to the axial direction A-A, and two opposite lobes 21 are pinned against the bottom wall 6 opposite to each other along a direction parallel to the axial direction A-A.

[0100] According to an embodiment, the second seal 16 comprises a seal body 22 made of a polymeric material, and a reinforcing insert 23, preferably made of metal, incorporated in the seal body 22.

[0101] The reinforcing insert 23 is configured to promote the gripping of the second seal 16 to the bottom wall 6.

[0102] Optionally, the second seal 16 defines a three-lobe profile 21 in a section parallel to the axial direction A-A, and where one of the three lobes 21 is biased against the bottom wall 6 of the cylinder 5, and where the reinforcing insert 23 is incorporated in said lobe 21.

[0103] Advantageously, the reinforcing insert 23 is configured to prevent the elastic deformation of said lobe 21.

[0104] According to an embodiment, the second annular seat 14 defines a concave polygon-shaped profile in a section parallel to the axial direction A-A.

[0105] Optionally, said concave polygon has at least one concave angle of about 270°.

[0106] Optionally, the second seal 16 accommodated by the second annular seat 14 is an asymmetrical lip seal.

[0107] According to an embodiment, the bottom wall 6 of the cylinder 4 forms, at the second annular seat 14, at least one backing step 24, which results in said concave polygon-shaped profile of the second annular seat 14 in a section parallel to the axial direction A-A and along a cross-section.

[0108] The second seal 16 defines a three-lobe profile 21 or four-lobe profile 21 in a section parallel to the axial direction A-A.

[0109] At least one lobe 21 of the second seal 16 ispositioned to abut against said at least one backing step24.

[0110] According to an embodiment, the first annular seat 13 leads into said inner surface 25 of the bottom wall 6.

[0111] Optionally, the second annular seat 14 leads into said outer surface 26 of the bottom wall 6.

[0112] Advantageously, when it leads into the outer surface 26 and is free from the backing step 24, a seal incorporating a reinforcing insert can be inserted into the second annular seat 14.

[0113] Optionally, between the first annular seat 13 and said inner surface 25, along a section parallel to the axial direction A-A, the bottom wall 6 defines a first distance of between:

[0114] - 0.5 mm and 4.0 mm; or

[0115] - 1.0 mm and 3.0 mm; or

[0116] equal to 2.8 mm.

[0117] Optionally, along a section parallel to the axial direction A-A, the first annular seat 13 has a first length L1 of between:

[0118] - 3.0 mm and 4.0 mm; or

[0119] equal to 3.6 mm.

[0120] Optionally, along a section parallel to the axial direction A-A, the second annular seat 14 has asecond length L2 of between:

[0121] - 1.5 mm and 3.5mm; or

[0122] equal to 2.8 mm.

[0123] Optionally, along a section transverse to the axial direction A-A, the first annular seat 13 defines a first diameter DI with respect to the rotation axis of the rotating member 11 of between:

[0124] - 18.0 mm and 21.0 mm; or

[0125] equal to 19.6 mm.

[0126] Optionally, along a section transverse to the axial direction A-A, the second annular seat 14 defines a second diameter D2, preferably an inner diameter, with respect to the rotation axis of the rotating member 11 of between:

[0127] - 16.0 mm and 28.0 mm; or

[0128] equal to 20.0 mm.

[0129] Optionally, along a section transverse to the axial direction A-A, the second annular seat 14 defines a third diameter D3, preferably an outer diameter, with respect to the rotation axis of the rotating member 11 of between:

[0130] - 20.0 mm and 36.0 mm; or

[0131] equal to 29.0 mm.

[0132] Optionally, at the second annular seat 14, the bottom wall 6 of the cylinder 4 forms at least onebacking step 24 which defines, along a section transverse to the axial direction A-A, a step diameter Dx with respect to the rotation axis of the rotating member 11 of between:

[0133] - 18.0 mm and 34.0 mm; or

[0134] equal to 26.0 mm.

[0135] Optionally, the bottom wall 6 of the cylinder 4 forms, at the second annular seat 14, at least one backing step 24 which defines, along a section parallel to the axial direction A-A, a step length Lx of between:

[0136] - 0.5 mm and 2.0 mm; or

[0137] equal to 1.3 mm.

[0138] Optionally, along a section parallel to the axial direction A-A, the bottom wall 6 of the cylinder 4 defines a thickness W between the inner surface 25 and the outer surface 26 of between:

[0139] - 12.0 mm and 14.0 mm; or

[0140] equal to 13.5 mm.

[0141] Obviously, those skilled in the art will be able to make changes or adaptations to the present invention, however, without departing from the scope of the following claims.LIST OF REFERENCES1. Caliper2. Caliper body3. Pads4. Cylinder5. Cylindrical wall6. Bottom wall7. Piston8. Side wall9. Thrust wall10. Parking-braking system11. Rotating member12. Rotation seat13. First annular seat14. Second annular seat15. First seal16. Second seal17. Screw18. Nut screw19. O-ring20. Backup ring21. Lobes22. Seal body24. Backing step25. Inner wall26. Outer wall27. Axial wall28. Transverse ring shoulder29. Retaining tooth30. Bushing31. Transverse bushing shoulder32. Axial cylinder33. Axial Protrusion34. Axial housing35. Axial locking ringA-A. Axial directionD1. First diameterD2. Second diameterD3. Third diameterDx. Step diameter L1. First lengthL2. Second lengthLx. Step lengthW. Thickness

Claims

CLAIMS1. A disc brake caliper (1) comprising a caliper body (2) arranged straddling a brake disc having a rotation axis defining an axial direction (A-A) and opposite friction surfaces, said caliper (1) comprising pads (3) accommodated in said caliper body (2) so as to slide substantially in an axial direction (A-A) with respect to the brake disc to act on said opposite friction surfaces, respectively, said caliper (1) comprising:- a cylinder (4), forming a cylindrical wall (5) and a bottom wall (6) transverse to the cylindrical wall (5);- a piston (7), forming a side wall (8) and a thrust wall (9) substantially transverse to the side wall (8) and opposite to the bottom wall (6) of the cylinder (4); wherein said bottom wall (6) forms an inner surface (25) facing the piston (7) and an opposite outer surface (26) facing away from the piston (7); wherein the piston (7) is accommodated inside the cylinder (4), and the side wall (8) of the piston (7) is adapted to slide within the cylindrical wall (5) of the cylinder (4); wherein the piston (7) is configured to be biased by a pressurized brake fluid injectable into the cylinder (4), so as to bias at least one of said pads (3) against oneof said friction surfaces of the brake disc, along a thrust direction substantially parallel to the axial direction (A-A); said caliper (1) further comprising a parking-braking system (10) which comprises a rotating member (11); said rotating member (11) being rotatably accommodated inside a rotation seat (12) formed in the bottom wall (6) of the cylinder (4) so that the rotating member (11) is rotatable about a rotation axis substantially parallel to the axial direction (A-A); wherein the cylinder (4) defines a first annular seat (13) obtained in the bottom wall (6); said first annular seat (13) extending into the bottom wall (6) in a direction transverse to the axial direction (A-A) and leading into the rotation seat (12), wherein the first annular seat (13) accommodates a first seal (15), and the second annular seat (14) accommodates a second seal (16), wherein the first seal (15) is configured to act between said rotating member (11) and said bottom wall (6) of the cylinder (4) to obtain a fluid seal; wherein the caliper (1) is characterized in that it comprises a bushing (30) housed in the rotation seat (12) interposed, at least partially, between rotating member(11) and bottom wall (6) of the cylinder (4).

2. A caliper (1) according to claim 1, wherein the parking-braking system (10) comprises a screw-nut system formed by a screw (17) and a nut (18), wherein a rotation of the screw (17) corresponds to a translation of the nut (18), with respect to the caliper body (2), along a direction parallel to the axial direction (A-A), said nut (18) being configured to bias at least one of said pads (3) against one of said friction surfaces of the brake disc, and wherein the rotating member (11) forms said screw (17), and wherein, optionally, the screw-nut system defines a thread, and said thread is of the irreversible type.

3. A caliper (1) according to claim 1 or 2, wherein the bushing (30) comprises a transverse bushing shoulder (31), which extends transversally, housing in the first annular seat (13), interposed between the first seal (15) and the bottom wall (6) in the direction of the outer surface (26), and comprises an axial cylinder (32) which extends parallel to the axial direction (A-A) interposed between the rotating member (11) and the bottom wall (6) of the cylinder (4).

4. A caliper (1) according to any one of the preceding claims, wherein the first seal (15) comprises an O-ring(19) coupled to an anti-extrusion ring (20) wherein said anti-extrusion ring (20) is made of less deformable material than the material of the O-ring (19).

5. A caliper (1) according to claim 4, wherein the anti- extrusion ring (20) engages the bushing (30) with a shape coupling adapted to perform a rotational coupling.

6. A caliper (1) according to claim 5 and claim 3, wherein said anti-extrusion ring (20) comprises an axial wall (27), extending parallel to the axial direction (A- A) interposed between said O-ring (19) and the rotating member (11), and a transverse ring shoulder (28) interposed between said O-ring (19) and the bottom wall (6) in the direction of the outer surface (26), wherein the transverse ring shoulder (28) engages said transverse bushing shoulder (31).

7. A caliper (1) according to any one of the preceding claims, wherein the rotating member (11) comprises an axial locking ring (35) adapted to provide an axial abutment to the rotating member (11) by engaging the outer surface (26); wherein the cylinder (4) defines a second annular seat (14) obtained in the bottom wall (6), said second annular seat (14) being distinct from said first annular seat (13), extending into the bottom wall (6) in the direction parallel to the axial direction (A-A) and being positioned on the outer wall (26), and wherein the first seal (16) is configured to act between said bottom wall (6) of the cylinder (4) and the axial locking ring (33) to obtain a fluid seal.

8. A caliper (1) according to any one of the preceding claims, wherein the second seal (16) is a scraper.

9. A caliper (1) according to claim 7 or claim 8, wherein the second seal (16) is:- an O-ring; or- an X-ring; or- a symmetrical or asymmetrical lip seal; or- a symmetrical or asymmetrical lip seal embedding a reinforcing insert (23), preferably made of metal; or- a lip seal defining three lobes (21) in a section parallel to the axial direction (A-A); or- a lip seal defining four lobes (21) in a section parallel to the axial direction (A-A).

10. A caliper (1) according to any one of the preceding claims, wherein the second seal (16) is a lip seal, which defines a three-lobe profile (21) in a section parallel to the axial direction (A-A), and wherein two of the three lobes (21) are biased against the rotating member (11) and one of the three lobes (21) is biased against the bottom wall (6) of the cylinder (4)and / or wherein two of the three lobes (21) are pinned against the rotating member (11) opposite to each other along a direction parallel to the axial direction (A-A), and / or wherein one of the three lobes (21) biased against the bottom wall (6) of the cylinder (4) is pinned against said bottom wall (6) in the direction of the inner surface (25) of the bottom wall (6), and / or wherein the second seal (16) is a lip seal, which defines a four-lobe profile (21) in a section parallel to the axial direction (A-A), and wherein two of the four lobes (21) are biased against the rotating member (11) and two opposite lobes (21) are biased against the bottom wall (6) of the cylinder (4), and / or wherein two of the four lobes (21) are pinned against the rotating member (11) opposite to each other along a direction parallel to the axial direction (A-A), and two opposite lobes (21) are pinned against the bottom wall (6) opposite to each other along a direction parallel to the axial direction (A-A).

11. A caliper (1) according to any one of claims 7 to 10, wherein the second annular seat (14) defines a concave polygon-shaped profile in a section parallel to the axial direction (A-A), wherein, optionally, said concave polygon has at least one concave angle of about 270°,and wherein, optionally, the second seal (16) accommodated by the second annular seat (14) is an asymmetrical lip seal.

12. A caliper (1) according to claim 11, wherein the bottom wall (6) of the cylinder (4) forms, at the second annular seat (14), at least one backing step (24) which results in said concave polygon-shaped profile of the second annular seat (14) in a section parallel to the axial direction (A-A), wherein the second seal (16) defines a three-lobe (21) or four-lobe (21) profile in the section parallel to the axial direction (A-A), and wherein at least one lobe (21) of the second seal (16) is positioned to abut against said at least one backing step (24).

13. A caliper (1) according to any one of the preceding claims, wherein the first annular seat (13) leads into said inner surface (25) of the bottom wall (6); and / or wherein the second annular seat (14) leads into said outer surface (26) of the bottom wall (6); and / or wherein, between the first annular seat (13) and said inner surface (25), along a section parallel to the axial direction (A-A), the bottom wall (6) defines a first distance of between:0.5 mm and 4.0 mm; or- 1.0 mm and 3.0 mm; or equal to 2.8 mm, and / or wherein, along a section parallel to the axial direction (A-A), the first annular seat (13) has a first length (L1) of between:- 3.0 mm and 4.0 mm; or equal to 3.6 mm, and / or wherein, along a section parallel to the axial direction (A-A), the second annular seat (14) has a second length (L2) of between:- 1.5 mm and 3.5 mm; or equal to 2.8 mm; and / or wherein, along a section transverse to the axial direction (A-A), the first annular seat (13) defines a first diameter (DI) with respect to the rotation axis of the rotating member (11) of between:- 18.0 mm and 21.0 mm; or equal to 19.6 mm, and / or wherein, along a section transverse to the axial direction (A-A), the second annular seat (14) defines a second diameter (D2) with respect to the rotation axis of the rotating member (11) of between:- 16.0 mm and 28.0 mm; or equal to 20.0 mm; and / or wherein, along a section transverse to the axialdirection (A-A), the second annular seat (14) defines a third diameter (D3) with respect to the rotation axis of the rotating member (11) of between:- 20.0 mm and 36.0 mm; or equal to 29.0 mm; and / or wherein, at the second annular seat (14), the bottom wall (6) of the cylinder (4) forms at least one backing step (24), which defines, along a section transverse to the axial direction (A-A), a step diameter (Dx) with respect to the rotation axis of the rotating member (11) of between:- 18.0 mm and 34.0 mm; or equal to 29.0 mm; and / or wherein the bottom wall (6) of the cylinder (4) forms, at the second annular seat (14), at least one backing step (24), which defines, along a section parallel to the axial direction A-A, a step length (Lx) of between:- 0.5 mm and 2.0 mm; or equal to 1.3 mm; and / or wherein, along a section parallel to the axial direction (A-A), the bottom wall (6) of the cylinder (4) defines a thickness (W) between the inner surface (25) and the outer surface (26) of between:12.0 mm and 14.0 mm; orequal to 13.5 mm.

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