Bearing cage made of composite material having improved interlaminar cohesion and associated bearing unit and process

Abstract

Bearing cage made of composite material having improved interlaminar cohesion and associated bearing unit and method Bearing cage (3) having improved mechanical behavior, comprising an annular body (7) having a plurality of pockets or housings (8) for respective bearing bodies of a bearing; the annular body (7) having an axis of symmetry (A) and being made of a synthetic plastic material reinforced by fibers comprising a plurality of superimposed layers (18) of reinforcing fibers (11) embedded in a synthetic plastic material (13) and arranged with respect to the axis of symmetry (A) according to a predefined pattern; the fibers (11) of each layer (18) forming with the axis of symmetry (A) an angle (β) which differs from the angle formed with the axis of symmetry (A) by the fibers (11) of each layer (18) immediately adjacent to it by a value of approximately 15° or less, with a tolerance of ± 3°. [Figure 2]

Description

Title of the invention: Bearing cage made of composite material having improved interlaminar cohesion and associated bearing unit and method Technical field of the invention

[0001] The present invention relates to a bearing cage made of a synthetic plastic resin, and to an associated bearing unit comprising such a cage, the cage being made of a fiber-reinforced composite synthetic plastic material. The invention also relates to a method for obtaining a bearing cage made of a fiber-reinforced composite synthetic plastic material exhibiting no tendency to delamination or a greatly reduced tendency to delamination. Prior art

[0002] It is well known that a rolling bearing unit comprises a rolling bearing having an outer ring, an inner ring and a plurality of rolling bodies (for example balls) interposed between the inner and outer rings to make them relatively rotatable with low friction, and a rolling bearing cage to retain the rolling bodies in position, the cage being arranged in the radial space delimited between the inner ring and the outer ring.

[0003] A bearing housing retainer cage comprises an annular body delimited between inner and outer cylindrical lateral surfaces and a plurality of pockets or housings, each configured to house and freely retain a respective bearing body of the roller bearing. The cage body is generally made of a synthetic plastic material, for example, a phenolic resin or a polyamide or other suitable synthetic materials, and supports the pockets or housings, which are located radially through it, for example, consisting of radial through holes.

[0004] Generally, a preform consisting of a hollow tube is obtained by molding the synthetic material, then the hollow tube is radially cut into a plurality of slices, each of which constitutes a cage body. Before or after the cutting operation, pockets or recesses are drilled through the cage body.

[0005] However, to improve performance, it is also known to obtain the cage body from a fiber-reinforced synthetic material, for example phenolic resins reinforced with cotton fibers embedded in the synthetic material matrix.

[0006] In this case, the hollow tube constituting the preform can be produced by a process known as "continuous filament winding" (CFW), by tightly winding one or more filaments of composite material consisting of continuous fibers impregnated with a synthetic plastic resin onto a metal mandrel.

[0007] Here and hereafter, "plastic resin" means a synthetic material that is either thermosetting or thermoplastic, for example the impregnation of the fibers can be carried out either by a liquid thermosetting resin or by a solid thermoplastic powder.

[0008] After a predefined number of superimposed radial layers of pre-impregnated fibers have been obtained, the preform is hardened in a way known to cause the consolidation of the synthetic material impregnating the fibers into a solid matrix, in which the wound fibers remain embedded to constitute a reinforcing material.

[0009] Hardening can occur as disclosed for example in FR3053624A1.

[0010] Fiber-reinforced plastic cages, particularly when obtained by CFW, are generally adequate, but their performance can decrease very significantly depending on the humidity of the environment and / or when the bearing can be subjected to high speed and high loads, which causes the temperature of the cage, during operation, to increase until it approaches, or exceeds, the glass transition temperature of the synthetic material constituting the matrix of the cage body.

[0011] To overcome such drawbacks, a pending patent application from the same Applicant proposes to produce the cage body in a synthetic material having a glass transition temperature greater than or equal to 120 °C, for example in an epoxy resin, reinforced with high tensile strength and rigid fibers such as carbon fibers, glass fibers, Kevlar® fibers and other known fibers having equivalent performance, instead of conventional cotton fibers.

[0012] Although an epoxy resin reinforced with long carbon fibers is a composite material commonly used for tooling intended to be subjected to stresses while in a static position, it has never, until now, been used to produce bearing cages, although it can offer considerable advantages.

[0013] For example, when such a composite cage body is obtained by CFW processes, it is possible to configure the preform forming tube with a sequence of carbon fiber layers oriented at different angles to each other, both to prevent the composite preform forming tube from to exhibit a strongly anisotropic behavior and to improve its mechanical properties and, consequently, the mechanical properties of the final cage body.

[0014] However, when using such a type of composite element to produce a moving component such as a bearing cage, it has been shown that once the composite material is subjected to high centrifugal forces and the characteristic impact contact with the bearing bodies present in a bearing cage, it undergoes delamination, which causes a significant temperature increase in the application. Furthermore, it has been noted that delamination can occur between the superimposed layers of composite carbon fibers, particularly due to, or during, the machining of the preform tube following its production and curing, to obtain a plurality of cage bodies from it by radially cutting the cured preform tube and drilling pockets or recesses through it to receive the bearing bodies during use.

[0015] The problem of delamination can affect the performance when using CFW composite bearing cages and, most importantly, can produce scrap during the production cycle, thus increasing production costs. Summary of the invention

[0016] The objective of the present invention is to overcome the drawbacks of the prior art by providing a composite material bearing cage with an improved service life and preserving the mechanical properties of the cage under all operating conditions. A further objective of the invention is to provide a composite material bearing cage with improved interlaminar cohesion, in order to avoid, or at least significantly limit, delamination in CFW composite cages, first during machining and then during operation at high rotational speeds and under high loads.

[0017] An objective of the invention is also to provide a high-precision rolling bearing unit equipped with a CFW composite material cage suitable for use in applications with particularly high stresses, such as those requiring high rotational speeds and / or subjected to high loads.

[0018] An objective of the invention is finally to provide a method for obtaining a bearing cage made of a synthetic plastic material reinforced by fibers substantially free from the phenomenon of delamination.

[0019] According to the invention, a bearing cage made of composite material having improved mechanical behavior and an associated bearing unit are provided, as defined in the attached claims. Brief description of the figures

[0020] Other features and advantages of the present invention will become clear from the following description of non-limiting examples thereof, made with reference to the figures in the accompanying drawings, in which:

[0021] - Figure [1] schematically represents a rolling bearing unit equipped with a bearing body retaining cage made according to the invention;

[0022] - [Fig.2] schematically represents, at an enlarged scale, a restraint cage bearing body for a bearing housing provided according to the present invention;

[0023] - Figure 3 schematically represents a preforming tube mounted on a mandrel, tube from which the retaining cage of the [Fig.2] can be obtained;

[0024] - [Fig.4] schematically represents how the retaining cage of [Fig.2] can be produced;

[0025] - [Fig. 5] schematically represents a more detailed perspective view of the tube forming a preform of [Fig. 3] where some layers of composite material have been removed, to improve understanding; and

[0026] - [Fig. 6] represents a simple schematic top view of the tube forming preform of [Fig.3] where the winding angles of the applied reinforcing fibers are schematically represented to highlight the essence of the invention. Detailed description of the invention

[0027] With reference to Figures 1 to 6, reference number 1 indicates a rolling bearing unit ([Fig.1]) comprising a rolling bearing 2 of any known type and a rolling bearing cage 3, made of a composite material.

[0028] The bearing assembly comprises an inner ring 4, an outer ring 5 and a plurality of elements or bearing bodies 6, in the non-limiting embodiment shown, consisting of balls.

[0029] The bearing bodies 6 are arranged, in the example shown, in a ring of balls around an axis of symmetry A of the bearing housing, which is also the axis of symmetry of the cage 3. In different embodiments, not shown for reasons of simplicity, the bearing housing 2 can comprise two rings of bearing bodies arranged side by side and the bearing bodies can be, indifferently, balls, cylindrical or conical rollers, small cylinders, depending on the operating requirements.

[0030] In any case, the bearing cage 3 ([Fig.2]) comprises an annular body 7 and a plurality of pockets or housings 8, each configured to freely house, during use, a respective bearing body 6 of the bearing 2 to properly maintain the bearing bodies 6 spaced from each other by a predefined pitch.

[0031] The annular body 7 has an axis of symmetry A and a predefined axial width or length. The pockets or recesses 8 are located radially throughout the annular body 7, through respective inner and outer cylindrical lateral surfaces 9 and 10 ([Fig. 2]) of the annular body 7, substantially perpendicular to them, and, in the example shown, consist of simple radial cylindrical holes. The lateral surfaces 8 and 10 radially delimit the annular body 7 from each other.

[0032] The annular body 7 is made of a synthetic plastic material reinforced with fibers and is obtained by a process known in the art as CFW (continuous filament winding), schematically represented in a non-limiting manner in [Fig.4], solely for the purposes of illustration and for a better understanding of the invention.

[0033] With reference to [Fig. 4], in the CFW production process, a plurality of reinforcing fibers 11 are unwound in a known manner from reels 12, are impregnated in a known manner with a resin / synthetic material 13, and then the impregnated reinforcing fibers 11b are wound around a mandrel 14 at a predetermined angle with respect to the axis of symmetry Al of the mandrel 14, until a preform-forming tube 15 is obtained (Figures 3, 4, and 5). Alternatively, carefully ordered pre-preg (pre-impregnated) fibers or fiber sheets may be used.

[0034] The axis of symmetry Al of the mandrel 14 coincides with the axis of symmetry A of the cage 3 to be obtained and with the winding axis of the fibers 11 around the mandrel 14.

[0035] To obtain a plurality of annular bodies 7 from a single preform tube 15, the latter is hardened in any known and appropriate way (for example according to FR3053624A1), in order to polymerize the synthetic resin 13 to form a solid matrix, and then is cut radially into slices each consisting of an axial section 16 of the preform tube 15 cut in a radial direction in the preform tube 15, for example along the dashed lines (Figures 3 and 5), such that each axial section 16 of the preform tube 15 has the same axial width / length as a cage 3 to be obtained.

[0036] Before or after the cutting step, but generally after the hardening step, a plurality of radial holes configured to form the pockets or housings 8 are drilled through each axial section 16 of the preform forming tube 15. Alternatively, the pockets or housings 8 can be obtained, in a known manner, during the winding step as shown in [Fig.4], by properly arranging the axial position of the fibers 11b and by providing the mandrel 14 with a plurality of radially projecting pins (not shown) configured to form, each, a hole corresponding to a pocket or housing 8 in the preform forming tube 15 directly during its formation.

[0037] Consequently, as shown in [Fig.5], each section 16 comes to constitute, after the cutting step, an annular body 7.

[0038] Each annular body 7, therefore, comprises a plurality of superimposed layers 18 of reinforcing fibers 11 embedded in a synthetic plastic material 13 and arranged with respect to the axis of symmetry A / Al according to a predefined pattern.

[0039] In certain embodiments, the preforming tube 15 can be obtained either from a thermosetting resin reinforced with polymerized fibers or from a polymerized thermoplastic resin. In the latter case, the hardening step of the preforming tube 15 would no longer be necessary, since the thermoplastic powder for impregnating / coating the fibers must be melted (and therefore also polymerized) directly on the mandrel 14, for example by means of a laser beam or by means of a hot air stream.

[0040] According to a first feature of the invention, the impregnated / embedded fibers 11b of each layer 18 form with the axis of symmetry A ([Fig.6]) of the mandrel 14 an angle [3, which differs from the angle [3 formed with the axis of symmetry A by the fibers 11b of each layer 18 immediately adjacent to it by a value of about 15° or less, where "about" indicates a tolerance on the above angle value of ± 3°.

[0041] An example of the arrangement of the fibers 11b on the mandrel 14 in the various radially superimposed layers 18 is shown schematically in [Fig. 6], where a first, radially innermost layer 18b ([Fig. 5]) is formed with its impregnated fibers 11b arranged at an angle [3] of approximately 15° with respect to axis A, a second layer 18c ([Fig. 5]) immediately adjacent to this is formed with its impregnated fibers 11b arranged at an angle [3] of approximately 30° with respect to axis A, a third layer 18e ([Fig. 5]) immediately adjacent to layer 18c, radially outside of it, is formed with its impregnated fibers 11b arranged at an angle [3] of approximately 45° with respect to axis A, and so on, up to that the 11b fibers are arranged at approximately 90° with respect to axis A.

[0042] Of course, after cutting the preform tube 15 into axial sections 16, the annular body 7 of each cage 3 which will be obtained by further producing the radial holes constituting the pockets or housings 8 will be formed accordingly, according to the invention, by a plurality of radially superimposed layers 18 of fibers 11b wound around the axis of symmetry A of the resulting cage 3 with the same pattern and the same inclination of the winding [3 as those obtained for the preform tube 15.

[0043] It should be noted that the fibers 11b can be wound around the axis A in a parallel or crisscross pattern, so that the angles [3 of each layer 18 can adopt a positive and / or negative value, for example the angle [3 of each layer 18b can be +15° if the 11b fibers are arranged as in [Fig.6] or can be -15° if the 11b fibers are arranged in the opposite direction (e.g. converging in the direction of axis A, from the top of axis A in [Fig.6], instead of from the bottom of axis A, as illustrated in [Fig.6]).

[0044] According to another feature of the invention, the composite material bearing cage 3 is made using a synthetic plastic material which, after hardening, has a glass transition temperature greater than or equal to 120 °C, preferably an epoxy resin.

[0045] According to another feature of the invention, the reinforcing fibers 11 are chosen from the group consisting of: carbon fibers, glass fibers, Kevlar® fibers, any synthetic fiber similar to these in terms of tensile strength and stiffness.

[0046] In some embodiments, the reinforcing fibers may consist of mineral fibers such as basalt and quartz fibers and also of ceramic fibers, such as A12O3 or SiC fibers, and even of metallic fibers such as steel or aluminum fibers.

[0047] In some embodiments, the reinforcing fibers may consist of other organic fibers such as cotton, cellulose, flax, jute, hemp and sisal fibers.

[0048] According to a preferred embodiment, the reinforcing fibers 11b are continuous fibers 11 embedded in the synthetic resin 13 which has been made to impregnate the fibers 11.

[0049] According to a preferred embodiment, the impregnated fibers 11b are wound around the axis of symmetry Al of the mandrel 14 at predefined winding angles [3, which angles [3 are arranged such that the angle that the fibers 11b of each layer 18 form with the axis of symmetry A of the final preform forming tube 15 corresponds to the winding angle [3 with respect to it.

[0050] According to a preferred embodiment, the radially innermost layer 18b of the plurality of superimposed layers 18 presents the reinforcing fibers 11b thereof such that these form with the axis of symmetry A of the annular body 7 (i.e. formed by an axial section 16 of the preform forming tube 15) an angle [3 of about 15°, where about indicates a tolerance of ± 3°.

[0051] According to an ideal embodiment, in a radial direction from the radially innermost layer 18b, each subsequent layer 18 superimposed on it is such that its reinforcing fibers 11 / 11b have an inclination with respect to the axis of symmetry A / Al increased by up to about 15° with respect to the inclination [3 of the reinforcing fibers 11 / 11b of the layer 18 immediately adjacent to the- below this one. Such a sequence is followed until an inclination of fibers with respect to the A / Al symmetry axis of approximately 90° is reached.

[0052] The layer 18 at which the inclination of the fibers 11 / 11b with respect to the axis A of the annular body 7 is about 90° can be the outermost layer 18 or, more preferably, can be at least a first intermediate layer 18 of the annular body 7, for example located around a radial central portion 20 thereof (represented only schematically and as a dashed line in [Fig.2] for reasons of simplicity).

[0053] In the latter case, the radially superimposed layers 18 of the body 7 arranged radially on the outside of said first intermediate layer at the level of the central portion 20 have their reinforcing fibers 11 / 11b exhibiting an inclination with respect to the axis of symmetry A which decreases by up to about 15° with respect to the inclination of the reinforcing fibers 11 / 11b of the layer 18 arranged immediately adjacent below it.

[0054] According to one aspect of the invention, the bearing unit 1 of [Fig. 1] therefore comprises a bearing, for example bearing 2 or any other type of bearing having a plurality of bearing bodies 6 arranged in a defined radial space between the inner ring 4 and the outer ring 5 to make them relatively rotatable with low friction, and a bearing cage as described above for retaining the bearing bodies 6 in a spaced manner. The bearing 2 is preferably of the high-precision bearing type, characterized by high-speed and / or high-load operation.

[0055] In fact, a bearing cage 3 made according to what has been described above, taking care to place the fibers 11 / 11b of each radially superimposed layer 18 forming the body 7 so that they are arranged with respect to the axis of symmetry A at an angle which differs from the angle formed with the axis of symmetry A by the fibers 11 / 11b of each layer 18 immediately adjacent to it by a value of about 15° or less, surprisingly avoids completely or practically completely the phenomenon of delamination.

[0056] Research conducted by the Applicant's designers has shown that the nature of the delamination is caused by the angle difference between each progressive layer 18 of reinforcing fibers, for example, carbon fibers. In particular, when the angle difference between two consecutive layers 18 is greater than 15°, the cohesion between the two adjacent layers is lacking and delamination is highly probable.

[0057] It has been found that an offset of up to 15° of inclined reinforcing fibers between two consecutive layers 18 is sufficient to prevent delamination in the component (e.g., a bearing cage) even after manufacturing of a break-in procedure, where the bearing reached the expected maximum speed, which consequently validates the new cage 3 design as described in this description.

[0058] The main advantage of the present invention is to prevent the cage from delaminating even under hostile conditions, which in fact makes it possible to use epoxy resin reinforced by long carbon fibers for the production of a fiber-reinforced synthetic cage for super-precision angular contact ball bearings, which was not possible until now.

[0059] In addition, the invention reduces or even eliminates the risk of cage delamination between the different superimposed strip layers during operation, even in the case where the cage is not obtained through a CFW process but in any case has multiple layers reinforced by fibers superimposed on each other and having a parallel or interlaced fiber orientation in each superimposed layer.

[0060] Based on what has been described above, it is finally clear that the present invention also relates to a method for producing a roller bearing cage made of composite material 3 comprising an annular body 7 and a plurality of pockets or housings 8, each configured to house, during use, a respective bearing body 6 of a roller bearing 2, the annular body 7 having an axis of symmetry A and a predefined axial width, and the pockets or housings 8 being located radially throughout the annular body 7, through respective internal and external cylindrical lateral surfaces 9, 10 of the annular body 7 radially delimiting it; the method comprising the steps of:

[0061] a) Production of a preform-forming tube 15 made of fiber-reinforced synthetic plastic material by means of a continuous filament winding technique, by winding onto a mandrel (14) having an axis of symmetry (Al) coinciding with the axis of symmetry (A) of the bearing cage (3) to be obtained, at least one continuous fiber (11) of a high tensile strength and stiffness material impregnated with a synthetic resin (13) having a glass transition temperature after curing of at least 120 °C, preferably an epoxy resin, the fibers (11) being preferably selected from the group consisting of: carbon fibers, glass fibers, Kevlar® fibers, mineral fibers, such as basalt and quartz fibers, ceramic fibers, for example Al2O3 or SiC fibers, metallic fibers, for example steel or aluminum fibers, fibers organic matter including cotton fibers,cellulose, flax, jute, hemp and sisal, any synthetic, organic or inorganic fiber similar to these in terms of tensile strength and stiffness;

[0062] b) hardening of the preform forming tube (15) to polymerize the synthetic resin (13) in order to form a synthetic plastic matrix in which the reinforcing fibers (11) are embedded according to a predefined pattern and forming with an axis of symmetry (A) of the preform forming tube (15) predefined angles (|3);

[0063] c) radial cutting, in the preform tube (15), of a plurality of axial sections (16) thereof, each having an axial width identical to that of the bearing cage (3) to be obtained, each said axial section (16) of the preform tube (15) having a plurality of pockets or recesses (8) situated through it and configured to accommodate, when in use, the bearing bodies (6) of a bearing (2); the pockets or recesses (8) being obtained in step a) or being drilled in the preform tube (15) after step b); wherein:

[0064] d) in step a), at least one continuous reinforcing fiber 11 is wound around the mandrel 14 to form a plurality of radially superimposed layers 18 of impregnated reinforcing fibers 11b, the fibers 11b of each layer 18 being wound at a winding angle forming with the axis of symmetry Al of the mandrel 14 an angle [3] which differs from the angle [3] formed with the axis of symmetry Al of the mandrel 14 by the fibers 11b of each layer 18 immediately adjacent to it by a value of about 15° or less, where "about" indicates a tolerance of ±3°.

[0065] All the objectives of the invention are therefore achieved.

Claims

Demands

1. A composite material bearing cage (3) having improved mechanical behavior, comprising an annular body (7) and a plurality of pockets or housings (8), each configured to freely house, during use, a respective bearing body (6) of a bearing (2), the annular body (7) having an axis of symmetry (A) and a predefined axial width and the pockets or housings (8) being located radially throughout the annular body, through respective inner and outer cylindrical lateral surfaces (9, 10) of the annular body radially delimiting it, the annular body (7) being made of a fiber-reinforced synthetic plastic material comprising a plurality of superimposed layers (18) of reinforcing fibers (11) embedded in a synthetic plastic material (13) and arranged with respect to said axis of symmetry (A) according to a predefined pattern;characterized in that the fibers (11) of each layer form with the axis of symmetry (A) an angle (|3) which differs from the angle formed with the axis of symmetry (A) by the fibers (11) of each layer (18) immediately adjacent to it by a value of about 15° or less, where about indicates a tolerance of ± 3°.;

2. Bearing cage made of composite material according to claim 1, characterized in that the synthetic plastic material (13) has a glass transition temperature greater than or equal to 120 °C after its hardening.

3. Bearing cage made of composite material according to claim 1 or 2, characterized in that the synthetic plastic material (13) consists either of a thermosetting resin, preferably an epoxy resin, or of a thermoplastic resin.

4. A bearing cage made of composite material according to any one of the preceding claims, characterized in that the reinforcing fibers (11) are selected from the group consisting of: carbon fibers, glass fibers, Kevlar® fibers, mineral fibers, preferably basalt and quartz fibers, ceramic fibers, preferably Al2O3 or SiC fibers, metallic fibers, for example preferably steel or aluminum fibers, organic fibers including cotton, cellulose, flax, jute, hemp and sisal fibers, any fiber synthetic, organic or inorganic similar to these in terms of tensile strength and rigidity.

5. Bearing cage made of composite material according to any one of the preceding claims, characterized in that said reinforcing fibers (11) are continuous fibers embedded in a synthetic resin (13) and wound around said axis of symmetry (A) at predefined winding angles; said angle (|3) that the fibers (11) of each layer form with the axis of symmetry (A) corresponding to the winding angle with respect thereto.

6. A bearing cage made of composite material according to any one of the preceding claims, characterized in that the radially innermost layer (18b) of said plurality of superimposed layers (18) has its reinforcing fibers (11b) forming an angle of approximately 15° with said axis of symmetry (A) of the annular body (7), where approximately indicates a tolerance of ±3°.

7. Bearing cage made of composite material according to claim 6, characterized in that, from said radially innermost layer (18b), each subsequent layer (18) superimposed thereon has its reinforcing fibers (11b) having an inclination about said axis of symmetry (A) that is increased by up to about 15° with respect to the inclination of the reinforcing fibers (11b) of the layer (18) immediately adjacent below it, until at least a first intermediate layer of the annular body (7) having a fiber inclination about said axis of symmetry (A) of about 90° is reached.

8. Bearing cage made of composite material according to claim 7, characterized in that each layer (18) of said plurality of superimposed layers (18) arranged radially on the outside of said first intermediate layer (18b) has its reinforcing fibers having an inclination with respect to said axis of symmetry (A) decreased by up to about 15° with respect to the inclination of the reinforcing fibers (11b) of the layer (18) arranged immediately adjacently below it.

9. A bearing unit (1) comprising a bearing (2) comprising an outer ring (5), a ring

10. inner (4) and a plurality of bearing bodies (6) arranged in a defined radial space between the inner ring and the outer ring to make them relatively rotatable with low friction, and a bearing cage (3) according to any one of the preceding claims for retaining the bearing bodies in a spaced manner using the latter. A method for producing a roller bearing cage made of composite material (3) comprising an annular body (7) and a plurality of pockets or housings (8), each configured to house, during use, a respective bearing body (6) of a roller bearing (2), the annular body (7) having an axis of symmetry (A) and a predefined axial width, and the pockets or housings (8) being located radially throughout the annular body, through respective internal and external cylindrical lateral surfaces (9, 10) of the annular body radially delimiting it; the method comprising the steps of: (a) Production of a preform-forming tube (15) made of fiber-reinforced synthetic plastic material by means of a continuous filament winding technique, by winding onto a mandrel (14) having an axis of symmetry (Al) coinciding with the axis of symmetry (A) of the bearing cage (3) to be obtained, at least one continuous fiber (11) of a high tensile strength and stiffness material impregnated with a synthetic resin (13) having a glass transition temperature of at least 120 °C after curing, preferably an epoxy resin, the fibers (11) being preferably selected from the group consisting of: carbon fibers, glass fibers, Kevlar® fibers, mineral fibers, preferably basalt and quartz fibers, ceramic fibers, preferably Al₂O₃ or SiC fibers, metallic fibers, preferably steel or aluminum fibers, organic fibers including fibers cotton,of cellulose, flax, jute, hemp and sisal, any synthetic, organic or inorganic fiber similar to these in terms of tensile strength and stiffness; b) hardening of the preform tube (15) to polymerize the synthetic resin (13) in order to form a synthetic plastic matrix in which the reinforcing fibers (11) are embedded according to a predefined pattern and forming with an axis of symmetry (A) of the tube forming preform (15) predefined angles; (c) radial cutting, in the preform tube (15), of a plurality of axial sections (16) thereof, each having an axial width identical to that of the bearing cage (3) to be obtained, each said axial section (16) of the preform tube (15) having a plurality of pockets or recesses (8) situated through it and configured to accommodate, when in use, the bearing bodies of a roller bearing; the pockets or recesses (8) being obtained in step (a) or being drilled in the preform tube (15) after step (b); characterized in that: (d) in step (a), at least one continuous reinforcing fiber (11) is wound around said mandrel (14) to form a plurality of radially superimposed layers (18) of impregnated reinforcing fibers (11b), the fibers (11) of each layer (18) being wound at a winding angle (|3) forming with the axis of symmetry (Al) of the mandrel (14) an angle which differs from the angle formed with the axis of symmetry (Al) of the mandrel by the fibers (11) of each layer (18) immediately adjacent to it by a value of about 15° or less, where about indicates a tolerance of ± 3°.

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