Injection mold and method for overmolding a rolling bearing

Abstract

Injection mold (1) for overmolding an outer circumferential surface of an outer ring (3) of a rolling bearing (2) with a plastic layer, wherein the rolling bearing (2) has an inner ring (4), the outer ring (3) and a plurality of rolling elements (5) arranged between the inner ring (4) and the outer ring (3), comprising a pre-centering device and a fine centering device, wherein the pre-centering device is formed via a central mandrel (6) of a main mold body (7) on which the inner ring (4) of the rolling bearing (2) can be axially guided, and wherein the fine centering device is formed via at least three radial centering projections (8) of a mold insert (9) distributed circumferentially with respect to an outer diameter of the outer ring (3), and a method for overmolding an outer circumferential surface of an outer ring (3) of a rolling bearing (2) using such an injection mold (1).

Description

[0001] The invention relates to an injection molding tool for overmolding an outer circumferential surface of an outer ring of a rolling bearing with a plastic layer, wherein the rolling bearing has an inner ring, an outer ring and a plurality of rolling elements arranged between the inner ring and the outer ring, and to a method for overmolding an outer circumferential surface of an outer ring of such a rolling bearing with a plastic layer, using such an injection molding tool. State of the art

[0002] Rolling bearings are essential components in a wide variety of mechanical systems, enabling low-friction rotary motion. To improve the performance and longevity of these bearings, it is advantageous to encase the outer ring with a plastic material.

[0003] Overmolding the outer ring of a rolling bearing offers several technical advantages. The plastic coating can act as a protective layer, shielding the bearing from environmental influences such as moisture and corrosion. Furthermore, the plastic can incorporate additional structural elements that facilitate the assembly and use of the bearing in various applications. This results in improved functionality and a longer bearing lifespan.

[0004] A key element of an injection molding process for overmolding, particularly the outer ring of a rolling bearing, is the precise centering of the bearing within the injection mold. Accurate positioning of the bearing ensures that the plastic is distributed evenly around the outer ring, thus preventing deformations and irregularities.

[0005] Document DE 298 05 581 U1 describes, for example, a roller bearing onto which a roller housing is formed around the outer ring of a ball bearing in a molding tool. The ball bearing is precisely centered in the molding tool by means of a projection. When the molding tool is closed, a housing of the outer ring, a bore surface of an inner ring of the ball bearing, and an outer contour of an axle journal to be attached form complementary mold surfaces that later perform the function of fastening and positioning the individual parts relative to each other.

[0006] Document DE 11 38 988 A describes, for example, a radial rolling bearing injection-molded in plastic, an injection mold for overmolding a radial rolling bearing, and a method for overmolding a radial rolling bearing. The injection mold has a bolt engaging in the mold cavities to center and hold the rolling bearing, and disc-spring-like washers on both sides of the rolling bearing that cover the space between the inner and outer rings of the rolling bearing. Bolts are provided to compress the washers so that they cannot yield to the injection pressure.

[0007] The object of the invention is to provide an injection molding tool for overmolding an outer ring of a rolling bearing, which allows for simple and reliable centering of the rolling bearing in the injection molding tool.

[0008] Furthermore, the invention aims to provide an improved method for overmolding an outer ring of a rolling bearing. Description of the invention

[0009] The problem is solved by an injection molding tool with the features according to claim 1.

[0010] Furthermore, the problem is solved by a method for overmolding an outer circumferential surface of an outer ring of a rolling bearing with the features according to claim 7.

[0011] The injection molding tool according to the invention serves to overmold an outer circumferential surface of an outer ring of a rolling bearing with a plastic layer, wherein the rolling bearing has an inner ring, an outer ring and a plurality of rolling elements arranged between the inner ring and the outer ring.

[0012] According to the invention, the injection mold comprises a pre-centering device and a fine centering device.

[0013] According to the invention, the pre-centering device is designed via a central mandrel of a main tool body, on which the inner ring of the rolling bearing can be guided axially.

[0014] The direction specification "axial" describes a direction along or parallel to a central longitudinal axis of the tool body. The direction specification "radial" describes a direction perpendicular to the central longitudinal axis of the tool body.

[0015] According to the invention, the fine centering device is formed by means of at least three radial centering projections of a tool insert which are uniformly distributed circumferentially with respect to an outer diameter of the outer ring.

[0016] In a preferred embodiment of the present invention, the injection mold has an axially movable mold insert, wherein the mold insert is designed to move the rolling bearing axially along the central mandrel from a pre-centering position to a fine centering position and to form a casting cavity between the outer ring of the rolling bearing, the mold insert and the mold insert.

[0017] Preferably, the mold insert has an intermediate gate component that is fluidly connected to the casting cavity and can be fluidly connected to a hot runner nozzle. The intermediate gate component can be formed directly in the mold insert or by a separate component that can be inserted into a corresponding opening in the mold insert.

[0018] The tool insert is preferably detachably connected to the main tool body. This allows for maximum flexibility in the design of the overmolding and enables easy adaptation of the injection mold to different rolling bearing dimensions.

[0019] The tool insert is preferably designed in a ring shape and arranged on the main tool body in such a way that a cavity for receiving the rolling bearing is formed between the central mandrel of the main tool body and the tool insert, wherein the centering projections of the tool insert extend radially in the direction of the central mandrel of the main tool body.

[0020] Preferably, the centering projections are partially formed over an axial extent of the tool insert.

[0021] The term "partial" refers to a partial formation of the respective centering projection along the axial extent of the tool insert.

[0022] The inventive design of the injection mold enables the simple and cost-effective production of a fully overmolded rolling bearing. The rolling bearing can be overmolded in its fully assembled state, eliminating the need for complex post-processing. Furthermore, the inventive design of the injection mold allows for very high coaxiality accuracy of the overmolding relative to the bearing raceway on the inner ring of the rolling bearing.

[0023] These centering devices, namely the pre-centering device and the fine centering device, are therefore designed to ensure high accuracy and repeatability, resulting in a consistently high quality of the overmolded rolling bearings.

[0024] Using the method according to the invention, an outer circumferential surface of an outer ring of a rolling bearing can be overmolded with a plastic layer. The method utilizes the injection molding device according to the invention for this purpose.

[0025] According to the present invention, the method comprises at least the following steps: - Pre-centering of the rolling bearing via an inner ring of the rolling bearing by axially sliding the rolling bearing onto a central mandrel of a tool main body, - Axial displacement of the rolling bearing along the central mandrel from a pre-centering position to a fine centering position via a tool mold insert and simultaneous - Forming a casting cavity between an outer ring of the rolling bearing, a tool insert and the tool mold insert via the tool mold insert, - Feeding a plastic into the casting cavity by conveying plastic via a hot runner nozzle into an intermediate gate component formed or arranged in the mold insert, wherein the intermediate gate component is fluidly connected to the casting cavity and the plastic is forced from the hot runner nozzle through the intermediate gate component into the casting cavity, - Cooling the plastic to a demolding temperature, - Axial lifting of the tool mold insert and - Axial demolding of the rolling bearing via an ejector.

[0026] The term "demolition temperature" refers to the temperature at which the "overmolded" rolling bearing can be removed from the mold or tool without deformation or damage to the plastic.

[0027] This process offers an innovative solution for manufacturing overmolded rolling bearings. The precise centering of the bearing within the mold ensures that the injection molding process is efficient and reliable, resulting in high-quality end products. Description of the characters Fig. Figure 1 shows a sectional view of an injection mold.

[0028] In Fig. Figure 1 shows a schematic sectional view of an injection molding tool 1 according to the present invention.

[0029] The injection mold 1 is multi-part and comprises a main mold body 7, a mold insert 9, a mold insert 10 with an intermediate gate component 12 and an ejector 14.

[0030] The injection mold 1 is used to overmold an outer circumferential surface of an outer ring 3 of a rolling bearing 2 with a plastic layer.

[0031] The rolling bearing 2 has an inner ring 4, an outer ring 3 and a plurality of rolling elements 5 arranged between the inner ring 4 and the outer ring 3.

[0032] The injection molding tool 1 includes a pre-centering device for pre-centering the rolling bearing 2 and a fine-centering device for fine-centering the rolling bearing 2.

[0033] The pre-centering device is formed by a central mandrel 6 of a tool main body 7, on which the inner ring 4 of the rolling bearing 2 can be axially guided. This means that the pre-centering of the rolling bearing 2 is carried out via the inner ring 4 of the rolling bearing 2.

[0034] The direction specification “axial” describes a direction along or parallel to a central longitudinal axis 15 of the tool body 7. The direction specification “radial” describes a direction perpendicular to the central longitudinal axis 15 of the tool body 7.

[0035] The fine centering device is formed by six radial centering projections 8 of the tool insert 9, which are uniformly distributed around the circumference of the outer diameter of the outer ring 3 of the rolling bearing 2. The number of centering projections 8 can vary depending on the application. The tool insert 9 is ring-shaped and detachably arranged on the main tool body 7 such that a cavity for receiving the rolling bearing 2 is formed between the central mandrel 6 of the main tool body 7 and the tool insert 9. The rolling bearing 2 is located in its fine centering position within this cavity. The centering projections 8 of the tool insert 9 extend radially into this cavity towards the central mandrel 6 of the main tool body 7.

[0036] The centering projections are partially formed over an axial extent of the tool insert 9.

[0037] The term "partial" refers to a partial formation of the respective centering projection 8 along the axial extent of the tool insert 9.

[0038] The tool insert 10 is designed to be axially movable in order to move the rolling bearing 2, which is placed on the central mandrel 6, axially along the central mandrel 6 from a pre-centering position to a fine-centering position. The fine-centering position corresponds to a final position of the rolling bearing, as shown in Fig. Figure 1 shows that in the fine centering position, the rolling bearing 2 is finely centered by the engagement of the centering projections 8 of the tool insert 9 with the outer ring 3 of the rolling bearing.

[0039] Furthermore, a casting cavity 11 is formed between the outer ring 3 of the rolling bearing 2 and the tool insert 9 via the tool form insert 10, the outer ring 3 of the rolling bearing 2 in the fine centering position and the tool insert 9.

[0040] The mold insert 10 includes the intermediate gate component 12. In this case, the intermediate gate component 12 is designed as a separate component, arranged in a corresponding opening of the mold insert. The intermediate gate component 12 has six axial nozzles, each of which is fluidly connected to the casting cavity 11. However, the number of nozzles can vary depending on the application.

[0041] Furthermore, the intermediate gate component 12 can be fluid-connected to a hot runner nozzle 13.

[0042] The injection mold 1 can be used to overmold a rolling bearing 2, specifically an outer circumferential surface of the outer ring 3, with a plastic. The rolling bearing 2 is pre-centered via its inner ring 4 by axially sliding it onto the central mandrel 6 of the main mold body 7. Subsequently, the rolling bearing 2 is axially displaced along the central mandrel 6 from the pre-centering position to the fine-centering position via the mold insert 10. Simultaneously, the casting cavity 11 is formed between the outer ring 3 of the rolling bearing 2, the mold insert 9, and the mold insert 10. The plastic for overmolding the outer circumferential surface of the outer ring 3 of the rolling bearing is injected through the hot runner nozzle 13 into the intermediate gate component 12 located in the mold insert 10.Through the fluid connection between the intermediate gate component 12 and the casting cavity 11, the plastic is forced from the hot runner nozzle 13 through the intermediate gate component 12 into the casting cavity 11. After the casting cavity 11 is filled and the plastic has cured, the mold insert 10 is axially lifted and the rolling bearing 2 is axially demolded via an ejector 14. Reference sign 1 injection mold 2 rolling bearings 3 Outer ring 4 inner ring 5 rolling elements 6 Central Spindle 7 Tool main body 8 Centering projection 9 Tool insert 10 Tool mold insert 11 Casting cavity 12 Intermediate gate component 13 Hot runner nozzle 14 ejectors

Claims

Injection mold (1) for overmolding an outer circumferential surface of an outer ring (3) of a rolling bearing (2) with a plastic layer, wherein the rolling bearing (2) has an inner ring (4), the outer ring (3) and a plurality of rolling elements (5) arranged between the inner ring (4) and the outer ring (3), comprising a pre-centering device and a fine centering device, wherein the pre-centering device is formed via a central mandrel (6) of a main tool body (7) on which the inner ring (4) of the rolling bearing (2) can be axially guided, and wherein the fine centering device is formed via at least three radial centering projections (8) of a tool insert (9) distributed circumferentially with respect to an outer diameter of the outer ring (3). Injection mold (1) according to claim 1, characterized in that the injection mold (1) has an axially movable mold insert (10), wherein the mold insert (10) is designed to move the rolling bearing (2) axially along the central mandrel (6) from a pre-centering position to a fine centering position and to form a casting cavity (11) between the outer ring (3) of the rolling bearing (2), the mold insert (9) and the mold insert (10). Injection molding tool (1) according to claim 2, characterized in that the mold insert (10) has an intermediate gate component (12) which is fluidly connected to the casting cavity (11) and can be fluidly connected to a hot runner nozzle (13). Injection molding tool (1) according to claim 1, 2 or 3, characterized in that the tool insert (9) is detachably connectable to the tool main body (7). Injection mold (1) according to one of claims 1 to 4, characterized in that the mold insert (9) is designed in an annular shape and is arranged on the mold body (7) such that a cavity for receiving the rolling bearing (2) is formed between the central mandrel (6) of the mold body (7) and the mold insert (9), wherein the centering projections (8) of the mold insert (9) extend radially in the direction of the central mandrel (6) of the mold body (7). Injection mold (1) according to one of claims 1 to 5, characterized in that the centering projections (8) are partially formed over an axial extension of the mold insert (9). A method for overmolding an outer circumferential surface of an outer ring (3) of a rolling bearing (2) with a plastic layer using an injection mold (1) according to any one of claims 1 to 6, comprising at least the following steps: - Pre-centering the rolling bearing (2) via an inner ring (4) of the rolling bearing (2) by axially sliding the rolling bearing (2) onto a central mandrel (6) of a main mold body (7), - Axial displacement of the rolling bearing (2) along the central mandrel (6) from a pre-centering position to a fine centering position via a mold insert (10) and simultaneously - Forming a casting cavity (11) between an outer ring (3) of the rolling bearing (2), a mold insert (9) and the mold insert (10) via the mold insert (10), - Feeding a plastic into the casting cavity (11),by conveying plastic via a hot runner nozzle (13) into an intermediate gate component (12) formed or arranged in the mold insert (10), wherein the intermediate gate component (12) is fluidly connected to the casting cavity (11) and the plastic is forced from the hot runner nozzle (13) via the intermediate gate component (12) into the casting cavity (11), - cooling of the plastic to a demolding temperature, - axial lifting of the mold insert (10) and - axial demolding of the rolling bearing (2) via an ejector (14).

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