Self-lubricating ball bearing

Abstract

The invention relates to a self-lubricating ball bearing (1) comprising a ball body (2) and a ball socket (3), said ball body being rotatably mounted in said ball socket (3), characterised in that said ball socket (3) is one-piece and comprises a first stack of layers (31) consisting of a plurality of layers of a composite material comprising a self-lubricating composite, the self-lubricating composite comprises a fabric and a resin impregnating the fabric.

Description

Technical Field

[0001] The present invention relates to the technical field of self-lubricating articulations and in particular to self-lubricating rotules used in rotary guides of mechanical systems.

[0002] The invention applies more particularly to all types of ball bearings which are required to operate without grease, ie to operate self-lubricatingly, and which work under high loads in dynamic mode.

[0003] The invention is used in particular within the scope of shaft systems and transmission systems. Background Art

[0004] A ball bearing connection usually consists of a ball and a cage, the contact between the ball and the cage being spherical. It may have specific features, such as being self-lubricating or allowing more or less clearance between the ball and the cage.

[0005] One of the constraints in the manufacture of ball bearings is the mounting of the ball into the socket. It is therefore known to use a deformable socket in the form of a part with a mechanical weakness or consisting of several parts to allow the ball to be mounted in the socket. The mounting of the ball in the socket can therefore be carried out according to different known ball bearing principles as described below:

[0006] - a ball socket consisting of two parts that are screwed around the ball;

[0007] - Split ball socket, and mandatory assembly with the ball;

[0008] - a ball socket with a groove that allows the ball to enter when installed;

[0009] - A socket formed by cold working on the sphere.

[0010] Document EP1608881 describes a self-lubricating ball bearing comprising a ball and a socket, the ball being made of metal and rotatably mounted in the socket. The socket of this self-lubricating ball bearing is formed of a plurality of parts, wherein a metal inner part is crimped onto the ball, an elastomeric part is placed on the metal inner part, and an outer part is crimped onto the elastomeric part, so that the socket surrounds the ball.

[0011] The drawback of this type of self-lubricating ball bearing is that it may bring installation restrictions, which is due to the need to provide a ball socket component that can be sufficiently cold worked so that the ball socket properly surrounds the ball. This inevitably leads to low mechanical strength of the steel ball socket (due to its high deformability), and also causes difficult to control residual clearance. Such ball bearings also lead to assembly complexity, in which crimping and elastomer vulcanization operations need to be implemented to limit the clearance in the self-lubricating ball bearing thus installed. Such elastomer systems may limit the operation of the ball bearing due to their low shear strength.

[0012] Additionally, these ball bearings are composed of materials that are susceptible to corrosion, which can cause problems if the ball bearings are used in certain applications that are susceptible to corrosion. Maintenance or replacement of these ball bearings installed within a system can also result in significant costs and system downtime.

[0013] Applications WO2014169942A1 and EP 2986862B1 describe a ball bearing comprising a ball movably mounted in a socket, both elements being metal. The socket is here formed in one piece. The ball comprises a plurality of weakened areas arranged at its edge to make it deformable so that it can be accommodated in the socket.

[0014] The drawback of this type of ball bearing is that the deformability of the ball leads to mechanical fragility at the weakened area and difficult to control residual clearance. In addition, this type of ball bearing consists of a ball and a socket made of corrosive materials, which brings the risk of rapid wear of the ball bearing.

[0015] Patent application EP0969217 describes a ball bearing in which the ball and the socket are made of composite material. However, this type of ball bearing has several drawbacks. Firstly, the friction surface consists of a single layer of self-lubricating material, which therefore inevitably includes weak areas at the junction between the edges of the fabric. Moreover, the ball and the socket are made of a resin reinforced with glass filaments, a material with relatively limited mechanical strength when subjected to the stresses of operation of such a ball bearing.

[0016] Therefore, there is a need to improve the existing situation to at least partially solve the deficiencies of the prior art. Summary of the invention

[0017] The present invention relates to a self-lubricating ball bearing comprising a ball and a socket, wherein the ball is rotatably mounted in the socket, the socket being one-piece and comprising a first stack consisting of a plurality of layers of a composite material, the composite material comprising a self-lubricating compound comprising a fabric and a resin impregnated with the fabric.

[0018] A ball socket that forms a one-piece volume and comprises stacked layers of multiple layers of a composite material including a self-lubricating compound enables self-lubricating contact between the socket and the ball without having weak points or installation directions such as a specific orientation (associated with a fracture line in the case of a split ball socket in the prior art, or due to the position of the groove in the case of a grooved ball socket in the prior art), which enables improved mechanical strength relative to prior art ball bearings.

[0019] According to an aspect of at least one embodiment of the present invention, the volume of the socket can have a constant cross-section.

[0020] For this purpose, the socket has continuity over its entire volume and therefore has no interrupted areas such as grooves or gaps.

[0021] The benefit of this constant cross-sectional volume is that it provides an uninterrupted friction cross section between the socket and the ball.

[0022] Having multiple layers also makes it possible to avoid the break lines that form at the junction between two fabric ends of a single layer.

[0023] The thickness of the fabrics forming these layers may be chosen to be relatively thin in order to increase the mechanical strength of the self-lubricating composite.

[0024] Furthermore, a ball socket adapted to or mated with the ball enables a controlled gap between the ball and the socket to be obtained.

[0025] In particular, this makes it possible to obtain a self-lubricating ball bearing having a significantly lower possible clearance between ball and socket than in prior art ball bearings.

[0026] The ball socket matched with the ball also makes it possible to prevent the ball from wearing the ball socket.

[0027] Furthermore, and due to the use of composite materials, the corrosion resistance of the ball socket is improved compared to the prior art, as such materials have little or no sensitivity to corrosion.

[0028] The term "sphere" is used here to denote a component whose shape corresponds to a spherical segment (also called a sphere segment), i.e. the shape obtained after a sphere is cut by two planes which are parallel here. More particularly, here, the shape of the spherical segment is obtained after a sphere is cut by two parallel planes which are symmetrical with respect to the center of the sphere.

[0029] The socket has an inner surface which also has the shape of a spherical segment. Its outer surface may have a shape corresponding to a spherical segment obtained by cutting a sphere by two parallel planes symmetrical with respect to the center of the sphere, or a shape corresponding to a cylindrical surface.

[0030] According to certain embodiments, it is conceivable that the two planes are not parallel and symmetrical with respect to the center of the sphere.

[0031] A “volume of constant cross-section” is understood to mean that the socket has continuity over its entire volume and thus has no interruptions such as grooves or voids.

[0032] According to an aspect of at least one embodiment of the present invention, the self-lubricating composite comprises at least one strip having a thickness of 20 μm to 200 μm.

[0033] This strip of self-lubricating compound is deposited and forms a multilayer of the first stack of layers.

[0034] In this strip of self-lubricating composite, the fabric is impregnated with resin before being deposited to form the first stack of layers.

[0035] It is noted that the resin may contain fillers.

[0036] For example, the resin may contain a lubricating filler.

[0037] The use of a relatively thin strip of self-lubricating compound enables control of the amount of self-lubricating compound deposited at a given location on the socket surface, and thus better control of the thickness of the first stack at a given point.

[0038] This may, for example, enable a socket to be obtained which comprises a first stack of layers having material homogeneity due to the use of relatively thin strips.

[0039] Furthermore, due to the interweaving of the layers of the self-lubricating compound, an improved resistance to tangential friction forces can be obtained.

[0040] Thus, according to one aspect of at least one embodiment of the invention, the first stack of layers comprises croisements of strips of self-lubricating compound at angles ranging from 0° to 90°.

[0041] It is pointed out that the fabric intended to be mixed with the resin may consist of taffeta, satin, twill or canvas, without excluding other fabric configurations.

[0042] According to an aspect of at least one embodiment of the present invention, the socket includes a reinforcement shell surrounding the first stack of layers.

[0043] The reinforced shell provides protection for the socket by forming an external reinforcement and thus providing additional mechanical strength, which makes it possible to limit deformation and thermal expansion of the socket during operation of the self-lubricating ball bearing.

[0044] According to an aspect of at least one embodiment of the present invention, the reinforced shell is formed by a second stack of layers comprising a plurality of layers of at least one composite material comprising a composite comprising fibers and a resin impregnating the fibers.

[0045] According to a particular aspect of at least one embodiment of the present invention, the compound is selected from:

[0046] - composites comprising carbon fibers;

[0047] - composites containing glass fibers;

[0048] -composites containing Kevlar fibers;

[0049] - Self-lubricating compounds;

[0050] - mixtures of the above materials.

[0051] The fibers may also be a component of a fabric, ie the at least one composite material comprises a composite comprising a fabric consisting of a plurality of fibers and a resin impregnating the plurality of fibers.

[0052] Furthermore, the resin may be selected from thermosetting resins or thermoplastic resins.

[0053] The thermosetting resin may be an epoxy resin, a vinyl ester resin, a polyester resin, a phenolic resin or a polyimide resin.

[0054] The thermoplastic resin may be, for example, a polyamide (PA6), polyetherketoneketone (PEKK) or polyetheretherketone (PEEK) type resin.

[0055] According to one aspect of the present invention, there may be a certain transition thickness between the first stacked layer and the second stacked layer, in which the fabrics of the first stacked layer and the second stacked layer are alternating, which makes it possible to avoid an overly obvious interface between the two stacked layers.

[0056] According to an aspect of at least one embodiment of the present invention, the sphere is at least partially composed of a corrosion-resistant material.

[0057] A ball body composed at least partially of a corrosion resistant material helps to improve the corrosion resistance of the self-lubricating ball bearing.

[0058] According to one aspect of at least one embodiment of the present invention, the anti-corrosion material of the sphere comprises at least one material selected from the following:

[0059] -Corrosion-resistant metals;

[0060] - Corrosion resistant alloys;

[0061] -Metals treated for corrosion resistance;

[0062] - Alloys treated for corrosion resistance;

[0063] - Materials treated by salt bath nitriding;

[0064] - Composite materials.

[0065] "Alloy" refers to a solid, homogeneous mixture of a metal and one or more other substances, optionally metallic or non-metallic.

[0066] Corrosion resistant alloys and metals have a natural resistance to corrosion. Corrosion resistant treated metals and alloys do not have adequate natural corrosion resistance and therefore undergo treatment to improve their corrosion resistance.

[0067] The invention also relates to the use of a composite material for producing a plurality of layers of a first stack of layers of a socket of a self-lubricating ball bearing, the composite material comprising a self-lubricating compound comprising a fabric and a resin impregnating the fabric. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The present invention and the various advantages it brings will be more easily understood through the following description of non-limiting exemplary embodiments of the present invention and the accompanying drawings, in which:

[0069] Figure 1 A top perspective view of a self-lubricating ball bearing according to an embodiment of the present invention;

[0070] Figure 2 Based on Figure 1 A side perspective view of a self-lubricating ball bearing of an embodiment of the present invention;

[0071] Figure 3 Based on Figure 1 Another side perspective view of the self-lubricating ball bearing of the embodiment of the invention;

[0072] Figure 4a Based on Figure 1 A schematic side view of a self-lubricating ball bearing according to an embodiment of the present invention;

[0073] Figure 4b Based on Figure 4a A schematic perspective view of a self-lubricating ball bearing according to an embodiment of the present invention;

[0074] Figure 4c Based on Figure 4a A schematic front view of a self-lubricating ball bearing according to an embodiment of the present invention;

[0075] Figure 4d Based on Figure 4a A schematic side cross-sectional view of a self-lubricating ball bearing according to an embodiment of the present invention;

[0076] Figure 5a Based on Figure 1 A schematic front view of a sphere of an embodiment of the invention;

[0077] Figure 5b Based on Figure 5a A schematic side cross-sectional view of an embodiment of ;

[0078] Figure 5c Based on Figure 5a A schematic perspective view of a sphere of an embodiment of ;

[0079] Figure 6a Based on Figure 1 A schematic elevation view of a first stacked layer of an embodiment of the present invention;

[0080] Figure 6b Based on Figure 6a A schematic side cross-sectional view of a first stacked layer of an embodiment of ;

[0081] Figure 6c Based on Figure 6a A schematic perspective view of a first stacked layer of an embodiment of the present invention;

[0082] Figure 7a Based on Figure 1 A schematic front view of a reinforced shell of an embodiment of ;

[0083] Figure 7b Based on Figure 7a A schematic side cross-sectional view of a reinforced shell of an embodiment of ; and

[0084] Figure 7c Based on Figure 7a Schematic perspective view of a reinforced shell of a ball socket of an embodiment of the present invention. DETAILED DESCRIPTION

[0085] Detailed description of one embodiment of the present invention

[0086] The general principle of the invention is based on the implementation of a self-lubricating ball bearing, which comprises a socket and a ball and has improved corrosion resistance compared to the prior art because the socket has little or no sensitivity to corrosion. In addition, the principle of the invention is also based on the implementation of a self-lubricating ball bearing, which has a predetermined controlled gap between the socket and the ball.

[0087] Now refer to Figures 1 to 7c An embodiment of a self-lubricating ball bearing according to the present invention is described.

[0088] As shown in these figures, the self-lubricating ball bearing 1 comprises a ball 2 and a ball socket 3. It can be seen that the ball 2 is rotatably mounted in the ball socket 3. According to the present invention, this ball socket 3 is in one piece.

[0089] Furthermore, in this embodiment, the socket has a volume with a constant cross section. For example, the cross section of the socket (30) can be seen, for example, at Figure 4d .

[0090] In other words, the ball socket is produced in one piece and has no break areas such as recesses or recesses.

[0091] It comprises a first stack 31 consisting of a plurality of layers of composite material.

[0092] The composite material comprises a self-lubricating compound, wherein the self-lubricating compound comprises a fabric and a resin impregnating the fabric.

[0093] The invention is therefore based on the use of a composite material for producing a plurality of layers of a first stack, the composite material comprising a self-lubricating compound comprising a fabric and a resin impregnating the fabric.

[0094] The use of a composite material for this application has the benefit that the corrosion resistance of the self-lubricating ball bearing proves to be improved over the prior art, as such materials have little or no sensitivity to corrosion.

[0095] Furthermore, unlike the self-lubricating ball bearings of the prior art, this type of composite material makes it possible to obtain a self-lubricating ball bearing with a significantly reduced controlled gap between the ball and the socket due to the adaptation of the socket to the ball.

[0096] "Fabric" here means a surface made by assembling a plurality of yarns. This fabric together with its impregnated resin forms a strip of self-lubricating composite. This self-lubricating composite combines a low coefficient of friction with the ability to maintain satisfactory friction and mechanical properties when running on self-lubricating ball bearings.

[0097] The relative configuration of the constituent yarns of the fabric may be selected to form flow channels between the yarns that can be filled with resin.

[0098] Among conventional fabric configurations, a fabric of a twill 2 / 2 configuration formed by interlacing a weft yarn pair with a warp yarn pair may be used.

[0099] It is also possible to use fabrics having a taffeta configuration, which have a relatively high resistance to maximum crossing of warp and weft yarns.

[0100] In this embodiment, the fabric is a fabric made of polyester.

[0101] Strips of the self-lubricating compound are deposited and form a multilayer of the first stack 31 .

[0102] The resin may be, for example, a thermosetting or thermoplastic resin.

[0103] The thermosetting resin may be an epoxy resin, a vinyl ester resin, a polyester resin, a phenolic resin or a polyimide resin.

[0104] In this embodiment, the self-lubricating composite is in the form of a strip having a thickness of 20 μm to 200 μm.

[0105] In this embodiment, the resin used is an epoxy resin to which lubricating particles are added.

[0106] Moreover, according to various embodiments, the arrangement of the self-lubricating compound is such that the first stack of layers 31 comprises an interweaving of strips of the self-lubricating compound at an angle of 0° to 90°.

[0107] In other words, a plurality of strips of the self-lubricating compound may be superimposed, one strip forming an angle of 0° to 90° with the successive strips.

[0108] In the embodiment shown, the first stack of layers 31 comprises an interweaving of strips of self-lubricating compound at an angle greater than or equal to 5° and less than 90°.

[0109] As can be seen in the figures, the socket 3 also comprises a reinforcement shell 30 surrounding the first stack of layers 31 .

[0110] In other words, the reinforced shell forms an external reinforcement, also called sheath or armour, surrounding the first stack 31. This reinforced shell 30 is formed by a second stack comprising a plurality of layers of at least one composite material comprising a composite comprising fibres and a resin impregnating the fibres.

[0111] In this embodiment, the complex is selected from:

[0112] - composites comprising carbon fibers;

[0113] - composites containing glass fibers;

[0114] -composites containing Kevlar fibers;

[0115] - Self-lubricating compounds;

[0116] - mixtures of the above materials.

[0117] It is noted that the multilayer may at least comprise a composite material comprising a composite material comprising a fabric composed of a plurality of fibers and a resin impregnating these fibers constituting the fabric.

[0118] As regards the resin, as in the case of the ball and socket, it may be chosen, for example, from thermosetting or thermoplastic resins.

[0119] The thermosetting resin may be an epoxy resin, a vinyl ester resin, a polyester resin, a phenolic resin or a polyimide resin.

[0120] The purpose of this reinforced shell is to protect the socket when the self-lubricating ball bearing is subjected to stresses in the operating system. In other words, it forms an external reinforcement and provides additional mechanical strength, which makes it possible to limit deformations of the socket and thermal expansions during the operation of the self-lubricating ball bearing (under operating conditions, the stresses of the self-lubricating ball bearing lead to an increase in the temperature of the socket and the ball). The reinforced shell thus makes it possible to limit deformations and expansions and thus control the clearance between the socket and the ball.

[0121] In this embodiment, the ball is at least partially composed of a corrosion-resistant material to obtain a self-lubricating ball bearing with little or no sensitivity to corrosion.

[0122] The fact of having a ball body which at least partially consists of a corrosion-resistant material contributes to improving the corrosion resistance of the self-lubricating ball bearing and thus to improving the service life of the self-lubricating ball bearing.

[0123] The corrosion-resistant material comprises at least one material selected from the following:

[0124] -Corrosion-resistant metals;

[0125] - Corrosion resistant alloys;

[0126] -Metals treated for corrosion resistance;

[0127] - Alloys treated for corrosion resistance;

[0128] - material treated by salt bath nitriding; or

[0129] - Composite materials.

[0130] For example, the corrosion resistant alloy may be stainless steel.

[0131] Such a self-lubricating ball bearing having a ball made of a material subjected to an anti-corrosion treatment can be produced by a manufacturing method comprising the step of subjecting the material constituting the ball to an anti-corrosion treatment.

[0132] Such a treatment step may, for example, include a salt bath nitriding step to improve the corrosion resistance of the material.

[0133] According to an alternative, this treatment step may comprise a nitrocarburizing step.

[0134] This manufacturing method may, according to a particular embodiment, comprise testing the resistance of the obtained material to

[0135] Corrosive steps.

[0136] The manufacturing method then comprises the step of assembling the ball and the socket to form a self-lubricating ball bearing.

Claims

1. A self-lubricating ball bearing (1) comprising a sphere (2) and a spherical socket (3), wherein the sphere is rotatably mounted in the spherical socket (3). Characterized in that, the spherical socket (3) is one-piece and comprises a first stacked layer (31) consisting of a plurality of layers of a composite material, the composite material comprising a self-lubricating composite, the self-lubricating composite comprising a fabric and a resin impregnating the fabric.

2. The self-lubricating ball bearing (1) according to claim 1, Characterized in that, the self-lubricating composite comprises at least one strip having a thickness of 20 μm to 200 μm.

3. The self-lubricating ball bearing (1) according to any one of the preceding claims, Characterized in that, the first stacked layer (31) comprises an interweaving of strips of the self-lubricating composite at an angle of 0° to 90°.

4. The self-lubricating ball bearing (1) according to any one of the preceding claims, Characterized in that, the spherical socket (3) comprises a reinforcing shell (30) surrounding the first stacked layer (31).

5. The self-lubricating ball bearing (1) according to claim 4, Characterized in that, the reinforcing shell (30) is formed by a second stacked layer comprising a plurality of layers of at least one composite material, the composite material comprising a composite, the composite comprising fibers and a resin impregnating the fibers.

6. The self-lubricating ball bearing (1) according to claim 5, Characterized in that, the composite is selected from: - a composite comprising carbon fibers; - a composite comprising glass fibers; - a composite comprising Kevlar fibers; - a self-lubricating composite; - a mixture of the above materials.

7. The self-lubricating ball bearing (1) according to any one of the preceding claims, Characterized in that, the sphere (2) is at least partially composed of a corrosion-resistant material.

8. The self-lubricating ball bearing (1) according to claim 7, Characterized in that, the corrosion-resistant material of the sphere (2) comprises at least one material selected from the following: - a corrosion-resistant metal; - a corrosion-resistant alloy; - a metal treated for corrosion resistance; - an alloy treated for corrosion resistance; - a material treated by salt bath nitriding; and - a composite material.

9. Use of a composite material for producing a plurality of layers of a first stacked layer of a spherical socket of a self-lubricating ball bearing, the composite material comprising a self-lubricating composite, the self-lubricating composite comprising a fabric and a resin impregnating the fabric.

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