METHOD FOR PRODUCE A COATED SUPPORT ELEMENT MADE OF ELASTOMER MATERIAL

Description

[0001] The present invention relates to a method for manufacturing a bearing element made of elastomeric material and coated with a coating, particularly for vehicles, preferably for rail vehicles. The bearing element can, in particular, be a spring element, and the coating of the bearing element can, in particular, be a fire-retardant coating. A further aspect of the invention relates to such a bearing element made of elastomeric material.

[0002] To improve the fire protection properties of rail vehicles, the elastomer springs used in them are to be coated with a fire-resistant coating that meets specified fire protection standards. However, manufacturing the coating and applying it to the actual spring body is difficult for several reasons. In particular, it is challenging to bond the different rubber compounds of the spring body and the coating and to ensure defined layer thicknesses in order to achieve a reproducible manufacturing process.

[0003] For example, EP 2196492 A1 relates to an elastomeric body with an elastic, flame-retardant coating.

[0004] The JP 2005007608 A manufacture of rubber bearings for front stabilizers by two-component injection molding of vulcanizable elastomers, wherein first the outer layer is injected and after drawing a tool core the inner part of the bearing is injected.

[0005] WO 9846930 A1 discloses a spring formed from two components, wherein the inner block may be injection-molded. The inner block is fully cross-linked. Afterwards, the inner block is coated with a sheath.

[0006] Overall, the production of a composite body made up of several components is extremely complex from a process engineering perspective, as the first component produced needs to be cooled, meaning the production device must have a cooling function, which makes the design and manufacture of the production device complicated and expensive.

[0007] Therefore, the object of the present invention is to provide a method that overcomes the difficulties mentioned above.

[0008] This problem is solved by a method for manufacturing a coated support element made of elastomeric material according to claim 1. Advantageous embodiments are defined in the dependent claims.

[0009] The process comprises, in particular, the following steps: First, an injection molding device with several molded parts that are movable relative to each other is provided. In a closed position, the molded parts together enclose a cavity. The cavity preferably corresponds to the shape of the support element to be manufactured.

[0010] A mold core is then inserted into the cavity. The mold core preferably corresponds to the shape of the support element to be manufactured, minus a coating. A gap remains between the molded parts and the mold core, which preferably corresponds to the shape of the coating on the support element to be manufactured.

[0011] A first mixture, in particular an elastomeric mixture, is then inserted into the gap. The first mixture is preferably plasticized by closing the molded parts and fills the gap, preferably completely. In this way, the first mixture forms a shell that has the shape of the coating.

[0012] The shell is then partially vulcanized before cooling. This means the vulcanization process is started but not yet completed, so that at least the surface of the shell is hardened. This allows the shell to be separated from the mold components and the mold core.

[0013] Then the mold core is removed from the shell. Removing the mold core can also be facilitated by designing it as a breakable core that can be disassembled into small pieces that are easier to remove.

[0014] The outer shell is then removed from the cavity for cooling. To do this, the molded parts are opened, the core is removed first, and then the outer shell. Depending on the design of the molded parts and the core, it is also possible to remove the shell together with the core or after the core. This allows the shell to cool outside the injection molding machine, eliminating the need for the molded parts to have a built-in cooling system.

[0015] The shell is then cooled until its stiffness is increased and its dimensional stability is achieved. That is, the shell is cooled, preferably below its glass transition temperature, until its stiffness is increased to such an extent that it remains dimensionally stable after the core is removed and does not collapse.

[0016] After cooling, the shell is reinserted into the cavity. In this way, the shell is supported from the outside by the mold components, allowing the mold core to be removed and the second mixture injected without stretching the shell or altering its shape.

[0017] Subsequently, preferably under pressure and with the molded parts in the closed position, a second mixture, in particular an elastomeric mixture different from the first mixture, is injected into the cavity. The injection preferably takes place through one or more openings in the molded parts. The second mixture is preferably plasticized and forms a support body that rests against the inside of the shell. Preferably, this support body completely occupies the portion of the cavity freed up by removing the mold core. Alternatively, however, the support body can also be partially or completely hollow.

[0018] The support body can contain or be connected to other components besides the second mixture, such as metal parts. For example, metal plates, which serve as load introduction elements, can be provided on the top and / or bottom of the support body. These plates are connected, for example, by bonding, to the second mixture or the elastomer material of the support body. Such metal plates can be inserted into the cavity before and / or after the second mixture is injected, with the cavity being shaped to accommodate the metal plates. The coating is preferably applied only to those surfaces of the support body that are not covered by metal plates.

[0019] Alternatively or additionally to the metal plates, the support body can be reinforced with metal sheets. These metal sheets can be placed in the cavity before the second compound is injected, so that the second compound is injected around them. In this way, a support body can be formed from an elastomer-metal composite material.

[0020] Finally, the bearing body and the shell are vulcanized together in the cavity. During this process, the bearing body and the shell are fused together, so that the shell forms the coating of the bearing body. The vulcanization time should be sufficient to heat the cooled shell to vulcanization temperature.

[0021] The finished coated support element, i.e., the support body with the coating, is then removed from the cavity.

[0022] In this way, a coated support element of high quality can be manufactured in an efficient and easily reproducible manufacturing process.

[0023] The casing is preferably cooled in a cooling chamber or by blowing on it with cooled gas. Both are simple and efficient cooling methods to which the removed casing can easily be subjected.

[0024] In a preferred embodiment, the coating is a fire-retardant coating, preferably made of a fire-resistant elastomer material that is not, or only very slowly, destroyed by fire or very high temperatures. In particular, the first mixture is a fire-resistant rubber compound. In this way, the elastomer material of the support body can be protected to maintain its function.

[0025] In a further preferred embodiment, the support element is designed as an emergency spring element for air springs of rail vehicles or as a primary spring element (within the bogie between the wheelset and the bogie frame) for rail vehicles. The air springs are, in particular, the secondary springs provided between the car body and the bogie, while the primary spring elements are provided, in particular, within the bogie between the wheelset and the bogie frame. Alternatively, the support element can also be provided for other vehicles, such as motor vehicles.

[0026] The support element produced according to the invention, made of elastomeric material, can be used for vehicles, in particular rail vehicles, coated with a fire-resistant coating, especially one made of a fire-resistant elastomeric material different from that of the support body. The features and effects described in connection with the method apply accordingly to the present support element.

[0027] A preferred embodiment of the method according to the invention is explained in more detail below with reference to a drawing. The drawing shows in Fig. 1 a schematic cross-sectional view of an injection molding device during a first step of the process in which the shell is produced, and Fig. 2 a schematic cross-sectional view of an injection molding device during a second step of the process in which the support body is injected onto the shell from the inside.

[0028] Figs. 1 and 2Figure 1 illustrates the production of a support element 3 made of elastomeric material coated with a coating 1 according to an embodiment of the method according to the invention. In this embodiment, the support element 3 is designed as a spring element for rail vehicles, namely either as a primary spring element or as an emergency spring element for air springs of rail vehicles, and the coating 1 of the support element 3 is a fire-resistant coating.

[0029] In the method, an injection molding device 5 is first provided with several mold parts 7a, 7b, 7c that are movable relative to each other, comprising a stationary mold lower part 7a, several horizontally movable mold side parts 7b and a vertically movable mold upper part 7c, as shown in Figs. 1 and 2The injection molding device 5 is designed such that the molded parts 7a, 7b, 7c together enclose a cavity 9 in a closed position. The cavity 9 corresponds to the shape of the support element 3 to be produced.

[0030] A mold core 11 is now inserted into the cavity 9, as shown in Fig. 1 The mold core 11 corresponds to the shape of the support element 3 to be produced, minus the coating 1. A gap 13 remains between the mold parts 7a, 7b, 7c and the mold core 11, which corresponds to the shape of the coating 1 of the support element 3 to be produced.

[0031] Then, as in Fig. 1As shown, a first mixture 15 in the form of an elastomeric mixture is inserted into the gap. In the present embodiment, the first mixture 15 is a fire-resistant rubber mixture for producing a fire-resistant elastomeric material that is not, or only very slowly, destroyed by fire or very high temperatures. Subsequently, the molded parts 7a, 7b, 7c are closed, whereby the first mixture 15 becomes plasticized and completely fills the gap 13. In this way, the first mixture 15 forms a shell 17, which has the shape of the coating 1.

[0032] The shell 17 is then vulcanized until at least the surface of the shell 17 is hardened, so that the shell 17 can be separated from the mold parts 7a, 7b, 7c and the mold core 11.

[0033] The shell 17 is then removed from the cavity 9 for cooling. For this purpose, the mold parts 7a, 7b, 7c are moved into the open position, the mold core 11 is removed, and then the shell 17 is removed. The mold core 11 may be formed as a break-up core, which can be broken down into small pieces that are easier to remove.

[0034] Subsequently, the shell 17 is cooled below its glass transition temperature to increase its stiffness, until the required dimensional stability is achieved and it no longer collapses after the removal of the mold core 11. Cooling of the shell 17 takes place in a cooling chamber or by blowing on it with cooled gas.

[0035] After cooling, the shell 17 is reinserted into the cavity 9, so that the shell 17 is supported from the outside by the molded parts 7a, 7b, 7c for the subsequent injection process.

[0036] Then, as in Fig. 2As shown, with the mold parts 7a, 7b, 7c in the closed position, a second mixture 19 in the form of an elastomeric mixture is injected under pressure into the cavity 9. The injection takes place through an opening 21 in the upper part of the mold 7c. The second mixture 19 is plasticized and forms a support body 23, which rests against the inside of the shell 17. In addition to the second mixture 19, the support body 23 also contains two metal plates 25, which are provided on the top and bottom of the support body 23 and are connected to the second mixture 19 and the elastomeric material of the support body 23, respectively. The metal plates 25 are inserted into the cavity 9 before and after the injection of the second mixture 19, respectively. The cavity 9 conforms to the shape of the metal plates 25, and the upper metal plate has a bore 27 aligned with the opening 21 for the injection of the second mixture 19.The coating 1 covers only the side surfaces of the support body 23 that are not covered by metal plates 25.

[0037] Finally, the support body 23 is vulcanized together with the shell 17 in the cavity 9. In this process, the support body 23 and the shell 17 are joined together, so that the shell 17 forms the coating 1 of the support body 23.

[0038] Subsequently, the molded parts 7a, 7b, 7c are opened and the finished coated support element 3, i.e. the support body 23 provided with the coating 1, is removed from the cavity 9.

[0039] Using such a method, a high-quality support element 3 coated with a fire-resistant coating can be manufactured in an efficient and easily reproducible manufacturing process.

Claims

1. Process for producing a support element (3) made of elastomer material and coated with a coating (1) comprising the steps of - provision of an injection press apparatus (5) comprising a plurality of mould parts (7a, 7b, 7c) movable relative to one another which in the closed position together encompass a cavity (9) corresponding to the shape of the support element (3) to be produced, - insertion into the cavity (9) of a mould core (11) which corresponds to the shape of the support element (3) to be produced minus the coating (1) with the result that a gap (13) remains between the mould parts (7a, 7b, 7c) and the mould core (11) which corresponds to the shape of the coating (1) of the support element (3) to be produced, - introduction of a first mixture (15) into the gap (13) so that the first mixture (15) fills the gap (13) and thus forms a shell (17) having the shape of the coating (1), - part-vulcanization of the shell (17), - removal of the mould core (11), - removal of the shell (17) from the cavity (9) for cooling, - cooling of the shell (17) until the stiffness thereof is increased and dimensional stability thereof is achieved, - introduction of the shell (17) into the cavity (9), - injection of a second mixture (19) into the cavity (9) so that this forms a support body (23) contacting the inside of the shell (17), - full-vulcanization of the support body (23) together with the shell (17) so that these are joined to one another and the shell (17) forms the coating (1) of the support body (23).

2. Process according to Claim 1, wherein the cooling of the shell (17) is carried out in a cooling chamber or by blowing with cooled gas.

3. Process according to Claims 1 to 2, wherein the coating (1) is a fire protection coating.

4. Process according to any of Claims 1 to 3, wherein the support element (3) is in the form of an emergency spring element for air springs of rail vehicles or as a primary spring element for rail vehicles.