Cage for rolling bearing and high-speed bearing fitted with such cage

Abstract

In a rolling bearing (3), an annular cage (1) formed by two cage halves (9, 10) connected together using a connecting element (14) comprises: male elements (15) carried by the first cage half (9) and each in the form of a substantially rigid block; a corresponding recess (16) formed in the second half cage (10) and designed to receive the male element (15); and a first annular metal insert (18) and a second annular metal insert (19) overmolded with the first and second cage halves (9, 10), respectively, and completely embedded inside their respective annular body (11).

Description

Technical Field

[0001] The invention relates to a cage for a high-speed rolling bearing and a high-speed bearing equipped with the cage. Background Art

[0002] A rolling bearing is known from DE1914884U, which comprises an outer ring, an inner ring and a plurality of rolling bodies (balls) between the outer ring and the inner ring so that they can rotate relative to each other with low friction. The rolling bodies are held in the correct position by a cage, which comprises:

[0003] a plurality of pockets or seats, each pocket or seat being defined by a respective spherical surface having a centre lying in a radial median plane coinciding with a corresponding radial median plane of the bearing in use,

[0004] - two half-cages, substantially symmetrical about the mid-plane and connected to each other, each half-cage having an annular body and a plurality of at least partially hemispherical cavities, said cavities axially opposing the hemispherical cavities of the half-cage to define cells therewith, and

[0005] - A connecting member, associated with a half-cage for connecting the two half-cages together.

[0006] In addition, for each half-cage, there are two substantially concentric and circumferentially continuous radial reliefs extending in radially opposite directions from each annular body, the first relief extending radially outward to sealingly engage a groove formed in the outer ring of the bearing, and the second relief extending radially inward to sealingly engage a groove formed in the inner ring of the bearing, the inner ring being divided into two half rings joined together.

[0007] A cage for rolling bearings made of two cage halves, which are coupled together to form a seat for the balls of the rolling bearing, is known from JP2007040383 A. The seat is formed by a simple circular hole, and the associated connecting part is a mating snap-on coupling element in the form of a dovetail joint or a snap-on coupling pin in a corresponding cylindrical seat.

[0008] Both solutions described have the disadvantage that the cage formed by coupling two polymer cage halves together may not be rigid enough to prevent the cage from elastically deforming in use due to the variations in rotational speed typically applied to the rolling bearing in use.

[0009] This disadvantage exists mainly in high-speed rolling bearings, where the possible speed variations are more pronounced and the maximum speed can be very high, potentially 3 million NDM.

[0010] In these rolling bearings, ordinary polymer cages, which are formed by snapping two cage halves together, as in JP2007040383A, can deform with increasing speed in all directions. In the radial direction, the cage expands, with the risk that the outer diameter of the cage comes into contact with the outer ring of the rolling bearing, while in the tangential direction, the seats or cells housing the rolling elements "open", with the risk of losing the holding force on the rolling elements, especially when the rolling elements are balls, which can therefore fall out. In addition, polymer cages are temperature sensitive and perform poorly at temperatures above the glass transition temperature of the material from which they are made (for material PA66, this already occurs at 70°C to 80°C). Summary of the invention

[0011] Therefore, the present invention aims to overcome the shortcomings of the prior art, and in particular to provide a cage that is capable of properly retaining the rolling elements, eliminating potential noise (especially at low speeds), and at the same time properly retaining the rolling elements at high speeds without generating undesirable contact between the cage and the outer ring of the rolling bearing, such contact will generate high friction, potentially damaging the cage, and generating excessive heat, which will further deteriorate the performance of the cage.

[0012] The present invention also aims to provide a rolling bearing for high-precision, high-speed applications using such a cage.

[0013] The present invention therefore provides a cage for retaining rolling elements in a high-speed rolling bearing and an associated rolling bearing unit as defined in the appended claims.

[0014] The cage according to the invention uses a double snap-coupling between two polymer half cages, combined with a reinforcement of the two half cages obtained using metal inserts of a specifically chosen shape, overmoulded with the half cages so as to be embedded inside the annular body of each half cage. Furthermore, according to a possible embodiment of the invention, rivets are used to obtain a more rigid connection between the two half cages. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Other features and advantages of the invention are more clearly set forth in the following description of non-limiting embodiments of the invention provided with reference to the figures in the accompanying drawings, in which:

[0016] - Figure 1 is an exploded perspective schematic diagram of a rolling bearing according to the present invention;

[0017] - Figure 2 It is in assembled state Figure 1 Schematic, enlarged, three-quarter side view of a rolling bearing in radial section,

[0018] - Figure 3 is a line cut in the radial direction from the inner part of the circumferential portion of the cage for retaining rolling elements according to the present invention, along a line perpendicular to Figure 1 and Figure 2 A schematic, highly enlarged perspective view of a cage and a rolling bearing in a partially cut-away plane of the axis of symmetry;

[0019] - Figure 4 and Figure 5 are intended to form once joined together Figure 3 A highly enlarged schematic perspective view of a detail of the connection between the two cage halves of the cage,

[0020] - Figure 6 and Figure 7 are designed to form once joined together Figure 3 A schematic three-dimensional view of the two half cages of the cage,

[0021] - Figure 8 are axially coupleable and are intended to be embedded in Figure 6 and Figure 7 A schematic perspective view of two metal inserts in the respective annular bodies of the half cages in FIG.

[0022] - Fig. 9 is a possible embodiment of the cage according to the present invention, along Figure 3 Schematic enlargement of the detail of the partial cutout in the same plane. DETAILED DESCRIPTION

[0023] exist Figures 1 to 8 In the drawing, reference numeral 1 denotes as a whole a cage for holding rolling elements 2 in a rolling bearing 3 .

[0024] The bearing 3 is a precision rolling bearing for high speed, comprising an outer ring 4, an inner ring 5, a plurality of rolling elements 2 interposed between the outer ring 4 and the inner ring 5 so that they can rotate relatively with low friction, and a cage 1 for holding the rolling elements 2 in the correct position. In the non-limiting example shown, and in any case according to a preferred embodiment of the present invention, the rolling elements 2 are balls.

[0025] In the following, "high speed" refers to a nominal rotational speed of the rolling bearing 3 of the order of 2.5 NDM to 3 NDM.

[0026] The cage 1 is designed to be interposed between the inner ring 5 and the outer ring 4 when in use, and comprises a plurality of radial through-seats or pockets 7 arranged in a row. Figure 3 ), each radial through seat or cavity is designed to seat a corresponding rolling body 2.

[0027] The radial through seats or cells 7 are each delimited by a corresponding curved surface 8 which in the embodiment shown ( Figure 3 ) is spherical and has a radial midplane P ( Figure 1 ), the radial midplane P coincides with the corresponding radial midplane of the rolling bearing 3 when in use.

[0028] The annular cage 1 includes a first cage half 9 and a second cage half 10 arranged to be opposite to each other in the axial direction.

[0029] As will be seen, the half-cages 9, 10 are rigidly connected together and each have an annular body 11 and a plurality of at least partially curved cavities 12 (at least partially spherical in this case) formed on respective opposing first front faces 13 of the annular body 11 of each half-cage 9, 10.

[0030] The cavities 12 of the half cages 9, 10 face each other. In particular, the at least partially curved cavity 12 in the first half cage 9 faces axially the corresponding at least partially curved cavity 12 in the second half cage 10, so as to define together with it a seat or cavity 7, such as Figure 3 shown.

[0031] The annular retainer 1 also includes a Figure 3 ) indicated by a mechanical connecting element, which is designed to rigidly connect the first half cage 9 and the second half cage 10 together to form the annular cage 1.

[0032] According to a first feature of the present invention, the connecting element 14 comprises a plurality of corresponding male elements 15 ( Figure 5 ) and a plurality of corresponding recesses 16, a plurality of corresponding convex elements 15 are carried by the first half cage 9 and each is in the form of a substantially rigid block protruding axially from the front face 13 of the annular body 11 of the first half cage 9, and a plurality of corresponding recesses 16 are formed in the annular body 11 of the second half cage 10 on one side of the first front face 13 of the annular body 11 of the second half cage 10.

[0033] Each recess 16 is arranged in front of a corresponding male element 15 and is designed to be rigidly coupled to a substantially rigid block 15 forming the male element.

[0034] According to one aspect of the present invention, in combination with the foregoing, the connecting element 14 further comprises ( Figure 6 , Figure 7 and Figure 8 )A first annular metal insert and a second annular metal insert are indicated by reference numerals 18 and 19 respectively.

[0035] According to one aspect of the invention, the first annular metal insert 18 is overmolded with the first half-cage 9 so as to be completely embedded inside the annular body 11 of the half-cage 9 , thereby forming an annular reinforcement frame.

[0036] Similarly, according to this aspect of the invention, the second annular metal insert 19 is overmolded with the second half-cage 10 so as to also be fully embedded inside the annular body 11 of the half-cage 10, thereby forming an annular reinforcement frame.

[0037] Reference Figure 8 The first annular metal insert 18 and the second annular metal insert 19 are each defined between an anterior front wall 20 facing the corresponding first front face 13 of each half cage 9, 10 and a posterior front wall 21 opposite the anterior front wall 20, the two walls being perpendicular to the shared symmetry axis A ( Figure 2 ) are arranged such that the first annular metal insert 18 and the second annular metal insert 19 are substantially washer-shaped.

[0038] According to an important aspect of the present invention, the first half cage 9 and the second half cage 10 are connected by circumferential couplings 22 and radial couplings 23 ( Figure 3 , Figure 4 and Figure 5 ) are combined together, the circumferential coupling portion 22 and the radial coupling portion 23 are separated from each other and are arranged in series in the axial direction, as explained in more detail below.

[0039] In particular, the substantially rigid blocks 15 project axially from corresponding axial lugs 24 of the annular body 11 of the first cage half 9 .

[0040] The lug 24 is formed on the first front face 13 of the half cage 9. Similarly, the recess 16 is preferably an axial through recess and is formed inside a corresponding axial lug 24 of the second half cage 10, which in the present case is also formed on the first front face 13 of the second half cage 10.

[0041] The axial lugs 24 of the first half-cage 9 and the second half-cage 10 also define seats or pockets 7 for the rolling elements 2 on opposite sides and are connected head-on in an abutting manner so that the substantially rigid blocks 15 are inserted into the corresponding recesses 16, so that the cage 1, once assembled by connecting the half-cages 9, 10 together, is completely symmetrical with an optimal mass distribution (this is because the mass missing from the recesses 16 is compensated by the mass of the convex elements 15), so that the center of gravity of the cage 1 according to the invention substantially coincides with the center of gravity of the rolling bearing 3, with a tolerance of approximately 0.1 mm.

[0042] According to a preferred embodiment of the present invention ( Figure 3 and Figure 4 ), the opposite radial edges of the lugs 24 are provided with chamfered or rounded concavities ( / rounded concavities) 25 ( Figure 4 ), the chamfered or rounded cavity 25 forms a channel 26 ( Figure 3 ) to allow the grease to circulate.

[0043] Each male element formed by a substantially rigid block 15 (the substantially rigid block 15 may be a solid block or provided with a through hole 27 ( Figure 5 ) block) is set with ( Figure 5) A first fastening element 28 in the form of a series of radial grooves or protrusions formed in the radial direction on opposite first side faces 29 of the block 15 oriented in the circumferential direction.

[0044] Similarly ( Figure 4 ), the recess 16 is provided with a correspondingly mating first fastening element formed by a series (a sequence of) radial protrusions or grooves 31 arranged in sequence in the axial direction (wherein the protrusion 28 corresponds to the groove 31 and vice versa) on its circumferentially oriented opposite first side faces 30 (when the half cages 9, 10 are connected, the opposite first side faces 30 are intended to face the first side faces (side faces 29) of the corresponding substantially rigid block 15).

[0045] The radial reliefs or grooves 31 of the recess 16 are designed to snap-couple with corresponding radial grooves or reliefs 28 of the substantially rigid block 15. The reliefs or grooves 28, 31 thus together form the circumferential couplings 22 described above.

[0046] According to a non-minor aspect of the invention, each substantially rigid block 15 is also provided with ( Figure 5 ) A second fastening element formed by a pair of opposing teeth 32 which project radially from opposing second side faces 33 of each substantially rigid block 15 , said side faces being arranged transversely to the first face 29 .

[0047] The first fastening elements 28 of each block or male element 15 are arranged in sequence in the axial direction and are closer to the first face 13 of the annular body 11 of the first cage half 9 than the second fastening elements formed by the teeth 32 .

[0048] Similarly ( Figure 4 ), each recess 16 of the second half-cage 10 is provided with a corresponding engagement seat 35 for the tooth 32 of the substantially rigid block 15 of the first half-cage 9 on its opposite second side 34 arranged transversely to its first side 30 .

[0049] The engagement seat 35 is arranged to engage with the opening 36 ( Figure 4 and Figure 6 ) is substantially flush, and further arranged in sequence in the axial direction with a series of radial protrusions or grooves 31 of the corresponding recess 16. In particular, a series of radial protrusions or grooves 31 of each recess 16 are arranged to be farther away from the opening 36 than the engagement seat 35.

[0050] The engagement seats 35 and the teeth 32 thus form the above-mentioned radial coupling 23 between the cage halves 9 , 10 .

[0051] According to another aspect of the present invention, the first annular metal insert 18 and the second annular metal insert 19 ( Figure 8 ) are not only embedded in the annular body 11 of each half-cage 9, 10, but are also mechanically connected together, preferably using corresponding rivets ( / rivets) 37 passing through their respective first flat circumferential stretches (flat circumferential stretches) 38.

[0052] When in use, ie when the cage 1 is assembled, the rivets 37 ( Fig. 9 ) completely penetrates the axial lug 24 at the first fastening element 28 because the rivet 37 is inserted through the hole 27 .

[0053] Fig. 9 A possible alternative embodiment 14b of the mechanical connection element 14 described above is shown.

[0054] According to this embodiment, the rivets 37 are seated in corresponding cylindrical bushings 39 which pass completely through the axial lugs 24 and which, in the present case, fit in the holes 27. This further increases the rigidity of the cage 1.

[0055] according to Fig. 9 In a possible variation of this embodiment (not shown for the sake of simplicity), the cylindrical bushing 39 may preferably be a tubular portion deep-drawn from the first and second circumferentially stretched portions 38 of the first and second annular metal inserts 18, 19. The deep-drawn portions (not shown for the sake of simplicity) are coupled together in an abutting manner and seated through the axial lugs 24 of the first and second cage halves 9, 10, taking advantage of the fact that the holes 27 and the recesses 16 are preferably through-recesses.

[0056] Preferably, each substantially rigid block 15 forming a male element is a truncated pyramid, preferably with a rectangular base, as is each corresponding recess 16, so that the connection between each substantially rigid block 15 and the corresponding recess 16 occurs via its side faces 29, 30 and 33, 34, which are arranged inclined relative to a shared symmetry axis A of the opposing half-cages 9, 10, which is also the symmetry axis of the rolling bearing 3.

[0057] According to another aspect of the present invention, the first annular metal insert 18 and the second annular metal insert 19 ( Figure 8 ) are designed to be not only rigidly connected together in the axial direction (preferably using rivets 37), but also mirror-symmetrical in the axial direction, and in addition to the plurality of aforementioned substantially flat and straight first circumferential stretching portions 38 arranged in a row, each annular metal insert also has a plurality of second curved circumferential stretching portions 40 alternating with the first flat circumferential stretching portions 38, so that each second stretching portion 40 is between a pair of adjacent first stretching portions 38, and vice versa.

[0058] The second curved circumferential stretch 40 protrudes axially from the first circumferential stretch 38 beyond the main plane containing the annular metal inserts 18, 19 defined by the flat circumferential stretch 38 and is designed to simulate the curved surface 8 ( Fig. 9 )'s circumferential profile.

[0059] In particular, taking advantage of the fact that the first annular metal insert 18 and the second annular metal insert 19 are connected together at all first circumferential stretches 38 by respective rivets 37, the circumferential stretches 40 are arranged parallel to and adjacent to the curved surface 8 to form circumferential hooping elements of the seats or cells 7 for the rolling elements 2, as shown in FIG. Fig. 9 Clearly shown in.

[0060] According to a final aspect of the invention, the annular body 11 of each first half cage 9 and second half cage 10 is composed of a second front face 41 ( Figure 3 ) definition.

[0061] This front face 41 is not flat and continuous but is defined by a plurality of radial ribs 42 forming lattice elements. The ribs 42 cross one another and are formed in a single part due to the fact that the half-cages 9, 10 are obtained by moulding synthetic plastic.

[0062] The ribs 42 can therefore impart greater radial rigidity to each half-cage 9 , 10 .

[0063] Polyamides PA66 and PA46 (preferably reinforced with 25% or 30% glass fibers) are preferred synthetic plastics for molding the half cages 9 , 10 , since they have proven to bond well with the metal (usually steel) used to make the annular inserts 18 , 19 .

[0064] Finally, in order to facilitate the snap-fit ​​connection between the elements 28 and 31 and between the elements 32, 35, at least the two sides ( / flanks) of the recess 16 of the half cage 10 are each flanked by a respective radially outer axial groove 43 and a corresponding radially inner axial groove 44 formed in the annular body 11, so that each recess 16 is formed at the axial grooves 43, 44 by elastically flexible walls ( / elastically flexible walls) 45 ( Figure 4 ) definition.

[0065] Corresponding axial grooves 43, 44 are also preferably formed in the annular body 11 of the half-cage 9 to facilitate the snap-fit ​​connection of the tooth 32 in the engagement seat 35, so that the essentially rigid block 15 of the male element forming the coupling portion 23 is only slightly elastically flexible ( / elastically flexible) at the face 33 (including due to the presence of the hole 27).

[0066] Based on the foregoing, it is obvious that the scope of the present invention also covers a rolling bearing 3, which includes an outer ring 4, an inner ring 5 and a plurality of rolling elements 2 between the inner ring and the outer ring so that they can rotate relative to each other with low friction, and is characterized in that the rolling bearing also includes an annular retaining frame 1 for retaining the rolling elements 2 between the inner ring 5 and the outer ring 4 as described above, that is, the annular retaining frame 1 is formed by connecting two annular semi-retaining frames 9, 10, and the two annular semi-retaining frames 9, 10 are reinforced / reinforced internally by metal annular inserts 18, 19, and are snap-connected together and / or connected together by rivets 37 passing through the metal inserts 18, 19.

[0067] Therefore, an important aspect of imparting the necessary rigidity is the double snap-coupling provided using the circumferential coupling portion 22 and the radial coupling portion 23 at two axial points that are adjacent but separated (thus axially connected in series).

[0068] Another important aspect is the presence of the bent-stretched portion 40, which on the one hand increases the rigidity of the semi-cages 9, 10 at the seat or cavity 7 for the rolling elements 2, preventing the "widening" of the semi-cages 9, 10 caused by the high rotational speed of the rolling bearing 3, but the bent-stretched portion 40 is also intended to act as a guide for the positioning of the metal inserts 18, 19 in the mold when an overmoulding operation is carried out to obtain the semi-cages 9, 10, and to increase the mechanical bond with the overmoulded polymer.

[0069] The entire assembled cage 1 is more rigid than similar symmetrical polymer cages of the prior art. This helps to control cage deformation caused by very high speeds (2.5 million NDM / 3 million NDM).

[0070] In this way, all the objects of the invention are achieved.

Claims

1. An annular retainer (1) for retaining rolling elements (2) in a rolling bearing (3), the retainer being configured to be mounted between a corresponding inner ring (5) and an outer ring (4) of the rolling bearing in use, and comprising a plurality of radially penetrating seats or cavities (7), the plurality of radially penetrating seats or cavities (7) being arranged in a row relative to each other and each being configured to accommodate a corresponding rolling element (2), the plurality of radially penetrating seats or cavities each being defined by a corresponding curved surface (8), the curved surface (8) having a center located in a radial midplane (P) of the retainer, the radial midplane (P) coinciding with a corresponding radial midplane of the rolling bearing in use; the annular retainer (1) comprising: (a) a first half-cage (9) and a second half-cage (10) axially opposite one another, said half-cages (9, 10) being connected to one another and each presenting an annular body (11) and a plurality of at least partially curved cavities (12), said cavities (12) being obtained on respective first opposite front faces (13) of the annular body of each half-cage facing one another, said at least partially curved cavities of the first half-cage (9) axially facing corresponding at least partially curved cavities of the second half-cage (10) so as to define with them said seat or cavity (7); and (b) a mechanical connection element (14) for rigidly connecting the first half-cage (9) and the second half-cage (10) to each other to form the annular cage (1); characterized in that, in combination, the mechanical connection element (14) comprises: (c) a plurality of corresponding male elements (15) and a plurality of corresponding female portions (16), the plurality of corresponding male elements (15) being carried by the first half cage and each being constructed as a substantially rigid block protruding axially from the first front face (13) of the annular body of the first half cage (9), the plurality of corresponding female portions (16) being formed in the annular body (11) of the second half cage (10) on one side of the first front face (13) of the annular body (11) of the second half cage (10), each female portion (16) being configured to be opposite to the male element (15) and being constructed to cooperate in an integral manner with the corresponding substantially rigid block (15) constituting the male element; and (d) a first annular metal insert (18) and a second annular metal insert (19), the first annular metal insert (18) having been overmolded with the first half-cage (9) so as to be completely embedded in the annular body (11) of the first half-cage; the second annular metal insert (19) having been overmolded with the second half-cage (10) so as to be completely embedded in the annular body (11) of the second half-cage; (e) - The first annular metal insert (18) and the second annular metal insert (19) are each defined between a front front wall (20) facing the corresponding first front face (13) of each half retainer (9, 10) and a rear front wall (21) opposite to the front front wall (20), and the two walls are arranged perpendicular to the symmetry axis (A) of the retainer (1), so that the first annular metal insert (18) and the second annular metal insert (19) are basically formed as washers.

2. The annular retainer according to claim 1, characterized in that: The first half cage (9) and the second half cage (10) are constrained to each other by means of circumferential coupling portions (22) and radial coupling portions (23) which are independent of each other and arranged in series in the axial direction.

3. The annular retainer according to claim 1 or 2, characterized in that: The substantially rigid block (15) protrudes axially from a corresponding axial lug (24) formed on the first front face (13) of the annular body of the first half cage (9); and the recess (16) is preferably an axially through recess and is formed in a corresponding axial lug (24) formed on the first front face (13) of the second half cage (10); the axial lugs (24) of the first half cage (9) and the second half cage (10) define seats or cavities (7) for the rolling elements on opposite sides and are connected to each other head-to-head so that the substantially rigid block (15) is inserted into the corresponding recess (16).

4. The annular retainer according to claim 3, characterized in that: Each of the substantially rigid blocks (15) is provided with a first fastening element (28), which is composed of a series of radial protrusions or grooves formed in the radial direction on the opposite first lateral surfaces (29) of the substantially rigid block (15); and the recess (16) is provided with a series of radial protrusions or grooves (31) arranged in sequence in the axial direction on its opposite first lateral surface (30) facing the first lateral surface (29) of the corresponding substantially rigid block (15), and the radial protrusions or grooves (31) of the recess (16) are constructed to be snap-fitted with the corresponding radial grooves or protrusions (28) of the corresponding substantially rigid block (15).

5. The annular retainer according to claim 4, characterized in that: Each of the substantially rigid blocks (15) is further provided with a second fastening element, the second fastening element comprising a pair of opposite teeth (32) projecting radially from opposite second lateral faces (33) of the substantially rigid block (15) arranged transversely to the first face (29), the first fastening elements (28) being arranged sequentially in the axial direction and closer to the first face (13) of the annular body (11) of the first half cage (9) than the second fastening elements (32); each of the recesses (16) is further provided with a second fastening element on its first lateral face (33) transversely to the first face (29) thereof. A corresponding attachment seat (35) for the tooth (32) of the substantially rigid block of the first half retainer (9) is provided on a second lateral surface (34) opposite to the configuration of the half retainer (30); the attachment seat (35) is configured to be substantially flush with the entrance opening (36) of each recess (16), and is also configured in sequence axially with the series of radial protrusions or grooves (31) of the corresponding recess (16), and the series of radial protrusions or grooves (31) of each recess (16) is configured to be farther away from the entrance opening (36) than the attachment seat (35).

6. The annular retainer according to claim 4, characterized in that: The first annular metal insert (18) and the second annular metal insert (19) are connected to each other by respective rivets (37), which pass through respective first flat circumferential stretching portions (38) of the metal inserts and through the axial lugs (24) corresponding to the first fastening element (28); the rivets (37) are received in respective cylindrical bushings (39) fitted through the axial lugs (24); the cylindrical bushings (39) are preferably composed of deep-drawn tubular portions of the first circumferential stretching portions (38) of the first annular metal insert (18) and the second annular metal insert (19), which are connected together head to head and are received through the axial lugs (24) of the first half-cage (9) and the second half-cage (10).

7. An annular cage according to any one of the preceding claims, characterized in that The first annular metal insert (18) and the second annular metal insert (19) are configured to be rigidly connected to each other in the axial direction. Preferably, the first annular metal insert (18) and the second annular metal insert (19) are configured to be rigidly connected to each other in the axial direction by rivets (37).

8. An annular cage according to any one of the preceding claims, characterized in that The first annular metal insert (18) and the second annular metal insert (19) are mirror-symmetrical in the axial direction and each include a plurality of substantially flat and straight first circumferential stretch portions (38) arranged in a row and a plurality of curved second circumferential stretch portions (40) arranged alternately with the first circumferential stretch portions (38), so that each second stretch portion (40) is between a pair of adjacent first stretch portions (38) and vice versa; the second stretch portion (40) protrudes axially from the first stretch portion (38) and is constructed so as to reproduce the circumferential contour of the curved surface (8) defining the seat or cavity (7) for the rolling element and is configured to be parallel to and adjacent to the curved surface (8) so as to constitute a circumferential hoop element of the seat or cavity (7) for the rolling element; the first annular metal insert (18) and the second annular metal insert (19) are connected to each other at all the first circumferential stretch portions (38).

9. An annular cage according to any one of the preceding claims, characterized in that The annular body (11) of each of the first half-retainer (9) and the second half-retainer (10) is bounded by a second front face (41) opposite to the first face, and the second front face (41) is defined by a plurality of radial ribs (42), and the radial ribs (42) are constructed as grid elements to impart greater radial stiffness to each of the first half-retainer (9) and the second half-retainer (10); and at least the two wings of the recess (16) of the second half-retainer (10) each have a corresponding radial outer axial groove (43) and a corresponding radial inner axial groove (44) formed in the annular body (11), so that each of the recesses (16) is defined by an elastic flexible wall (45) at the axial groove.

10. A rolling bearing (3) comprising an outer ring (4), an inner ring (5) and a plurality of rolling elements (2) interposed between the inner ring and the outer ring so that they can rotate relative to each other with low friction, characterized in that: The rolling bearing further comprises an annular retaining frame (1) for retaining rolling bodies according to any one of claims 1 to 9, wherein the retaining frame is installed between the inner ring (5) and the outer ring (4).

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