A preform rubber mold

Abstract

The utility model belongs to rubber product forming die technical field, concretely relates to a kind of preforming rubber mould, including rubber sleeve mould, and rubber sleeve mould includes male die and female die, is provided with several convex moulds on male die, and mould is same with workpiece specification, and several inner concave mould cavities matched with mould are formed on female die, and mould and mould cavity are one-to-one correspondence, corresponding positioning hole is provided on male die and female die, and the positioning of male die and female die is realized by positioning column assembly to positioning hole, after male die and female die are matched, mould is placed in mould cavity, and clearance layer is between the outer surface of mould and mould cavity inner wall, and clearance layer constitutes the forming cavity of rubber sleeve. Utilize rubber sleeve mould, and rubber sleeve is independently formed, then rubber sleeve is wrapped to workpiece, avoid the problem of excessive glue gathering, extrusion damage workpiece in the process of forming rubber sleeve by directly carrying out flat plate vulcanization to workpiece. Overcome the problem of uneven thickness of rubber sleeve, workpiece eccentricity etc.

Description

Technical Field

[0001] This utility model belongs to the field of rubber product molding mold technology, specifically relating to a pre-formed rubber mold. Background Technology

[0002] Vulcanization is the final step in rubber processing. After vulcanization, rubber is shaped into practical rubber products. Vulcanization is a process in which a chemical reaction occurs between the raw rubber and the vulcanizing agent under pressure, heat, or radiation. This reaction transforms linear macromolecules into three-dimensional network macromolecules, fundamentally altering their physical, mechanical, and other properties. For product shaping during vulcanization, mold compression molding is commonly used. However, in processing certain specialized workpieces, conventional flat-plate vulcanization molding is insufficient, such as for marine sensors and radar systems. These require forming a vulcanized rubber layer on the workpiece surface. The vulcanization process necessitates mating the rubber with the workpiece. However, due to the ceramic spherical structure on the top of the workpiece, mold compression molding makes it difficult to control the accumulation of rubber within the mold. Under pressure, the accumulated rubber can easily damage the ceramic spheres, causing workpiece damage. Summary of the Invention

[0003] In view of the defects of the prior art, the purpose of this utility model is to provide a pre-formed rubber mold for the flat vulcanization of rubber on the surface of vulnerable workpieces. By pre-forming the rubber layer and then cooperating with the workpiece vulcanization, the pressure of the flat vulcanization process is reduced and the workpiece is avoided from being damaged.

[0004] To achieve the above objectives, the technical solution adopted by this utility model is as follows: a pre-formed rubber mold, including a rubber sleeve mold, the rubber sleeve mold including a male mold and a female mold, the male mold having a plurality of protruding molds, the molds having the same specifications as the workpiece, the female mold having a plurality of concave cavities matching the molds, the molds and cavities corresponding one-to-one, the male mold and the female mold having corresponding positioning holes, the positioning and assembly of the male mold and the female mold being achieved by assembling the positioning pins into the positioning holes, after the male mold and the female mold are assembled, the mold is placed in the cavity, there is a gap layer between the outer surface of the mold and the inner wall of the cavity, the gap layer forming the forming cavity of the rubber sleeve.

[0005] Furthermore, a mold release groove is provided at the edge of the opposite side surface of the male mold and / or female mold.

[0006] Furthermore, the male mold and the female mold are each provided with three corresponding positioning holes, which form a triangular structure.

[0007] Furthermore, the gap distance at each position of the gap layer is 0.2-5mm, that is, the thickness of the rubber sleeve formed by the gap layer is 0.2-5mm.

[0008] Furthermore, the workpiece is a symmetrical structure composed of two symmetrical units, the mold is consistent with a single symmetrical unit, and the interface between the mold and the male mold is the symmetrical plane of the single symmetrical unit; the gap layer constitutes the molding cavity of the semi-rubber sleeve, and the two semi-rubber sleeves are used in pairs to wrap around the outer surface of the workpiece.

[0009] Furthermore, the workpiece is a ceramic ball with a connecting rod, and the ceramic ball is located at one end of the connecting rod; the rubber sleeve is wrapped around the workpiece.

[0010] Furthermore, the mold includes a hemispherical protrusion and a semi-cylindrical protrusion. The hemispherical protrusion is located at one end of the semi-cylindrical protrusion. The hemispherical protrusion has the same specifications as the ceramic ball, and the semi-cylindrical protrusion has the same specifications as the connecting rod. The male mold is provided with multiple molds, with adjacent molds arranged in opposite directions, and the hemispherical protrusions of the multiple molds are staggered.

[0011] Preferably, the diameter of the hemispherical protrusion of the mold is 30 mm, and the diameter of the semi-cylindrical protrusion is 8 mm; the diameter of the hemispherical cavity of the cavity is 33 mm, and the diameter of the semi-cylindrical cavity is 11 mm; the end of the semi-cylindrical protrusion away from the hemispherical protrusion is flush with the side surface of the male mold, the end of the semi-cylindrical cavity away from the hemispherical cavity is connected to a limiting cavity, the axis of the limiting cavity coincides with that of the semi-cylindrical cavity, the limiting cavity extends to the side surface of the female mold, the limiting cavity and the semi-cylindrical cavity have a stepped transition, and the diameter of the limiting cavity is 8 mm; six molds are provided on the male mold.

[0012] Preferably, the diameter of the hemispherical protrusion of the mold is 33 mm, and the diameter of the semi-cylindrical protrusion is 11 mm; the diameter of the hemispherical cavity of the cavity is 38 mm, and the diameter of the semi-cylindrical cavity is 19 mm; the end of the semi-cylindrical protrusion away from the hemispherical protrusion is flush with the side surface of the male mold; the end of the semi-cylindrical cavity away from the hemispherical cavity is sequentially connected to a coaxial transition cavity and a limiting cavity; the transition cavity includes a tapered part with a gradually increasing outer diameter and a cylindrical part connecting the large end of the tapered part; the limiting cavity transitions to the cylindrical part in a stepped manner; the limiting cavity extends to the side surface of the female mold; the diameter of the limiting cavity is 11 mm; six molds are provided on the male mold.

[0013] Furthermore, the preformed rubber mold also includes a molding mold, which includes an upper mold and a lower mold. The upper mold is positioned above the lower mold, and the upper and lower molds together form a mold cavity that can contain a workpiece and a rubber sleeve. The workpiece, which encloses the rubber sleeve, is placed inside the mold cavity. The mold cavity includes an upper mold cavity formed on the lower surface of the upper mold and a lower mold cavity formed on the upper surface of the lower mold, and the upper and lower mold cavities are symmetrically arranged. The upper and lower molds are provided with corresponding molding mold positioning holes, and the positioning and assembly of the upper and lower molds are achieved by assembling molding mold positioning pins into the molding mold positioning holes. A molding mold release groove is provided at the edge of one of the opposite surfaces of the upper mold and / or the lower mold.

[0014] Beneficial effects: This utility model utilizes a rubber sleeve mold to independently form the rubber sleeve, which is then wrapped around the workpiece. This avoids the problems of excessive rubber material accumulation and workpiece damage that occur during the direct flat vulcanization process of forming the rubber sleeve on the workpiece. It also reduces the pressure during the flat vulcanization process and prevents workpiece damage. Furthermore, it overcomes problems such as uneven rubber sleeve thickness and workpiece eccentricity. Attached Figure Description

[0015] Figure 1 This is a three-dimensional view of the male mold of the rubber sleeve mold in Example 1; Figure 2 This is a top view of the male mold of the rubber sleeve mold in Example 1; Figure 3 This is a rear view of the male mold of the rubber sleeve mold in Example 1; Figure 4 for Figure 2 AA section view; Figure 5 This is a perspective view of the female mold of the rubber sleeve mold in Example 1; Figure 6 This is a top view of the female mold of the rubber sleeve mold in Example 1; Figure 7 This is a rear view of the female mold of the rubber sleeve mold in Example 1; Figure 8 for Figure 6 AA section view; Figure 9 This is a three-dimensional view of the male mold of the rubber sleeve mold in Example 2; Figure 10 This is a top view of the male mold of the rubber sleeve mold in Example 2; Figure 11 This is a rear view of the male mold of the rubber sleeve mold in Example 2; Figure 12 for Figure 10 AA section view; Figure 13 This is a perspective view of the female mold of the rubber sleeve mold in Example 2; Figure 14 This is a top view of the female mold of the rubber sleeve mold in Example 2; Figure 15 This is a rear view of the female mold of the rubber sleeve mold in Example 2; Figure 16 for Figure 14 AA section view; Figure 17 This is a schematic diagram of the molding die; Figure 18 This is a schematic diagram of the parting surface between the upper and lower molds in a molding die; In the diagram: 1. Male mold; 2. Molding mold; 201. Hemispherical protrusion; 202. Semi-cylindrical protrusion; 3. Female mold; 4. Cavity; 401. Hemispherical cavity; 402. Semi-cylindrical cavity; 403. Limiting cavity; 404. Transition cavity; 5. Positioning hole; 6. Demolding groove. 01. Upper mold, 02. Lower mold, 03. Mold cavity, 04. Molding mold positioning hole, 05. Molding mold release groove. Detailed Implementation

[0016] To make the above-mentioned objects, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a full understanding of this utility model. However, this utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed below.

[0017] Example 1 See appendix Figure 1-8 A pre-formed rubber mold includes a rubber sleeve mold, which is vulcanized using a flat vulcanization process to form a rubber sleeve for wrapping a workpiece. The workpiece is a ceramic ball with a connecting rod, and the ceramic ball is located at one end of the connecting rod. The rubber sleeve mold includes a male mold 1 and a female mold 3. The male mold 1 is provided with a plurality of protruding molds 2, which are the same size as the workpiece. The female mold 3 is formed with a plurality of concave cavities 4 that match the molds. The molds 2 and cavities 4 correspond one-to-one. The male mold 1 and the female mold 3 are provided with corresponding positioning holes 5. Positioning and assembly of the male mold 1 and the female mold 3 are achieved by assembling positioning pins into the positioning holes. After the male mold 1 and the female mold 3 are assembled, the molds 2 are placed in the cavities 4. There is a gap layer between the outer surface of the mold 2 and the inner wall of the cavity 4. The gap layer constitutes the forming cavity of the half rubber sleeve. Two half rubber sleeves are used in pairs to wrap the outer surface of the workpiece.

[0018] To facilitate demolding and separation of the male mold 1 and female mold 3, a demolding groove 6 is provided at the edge of the opposite side surface of the male mold 1 and / or female mold 3.

[0019] To ensure accurate positioning when the male mold 1 and female mold 3 are joined, three corresponding positioning holes 5 are provided on each of the male mold 1 and female mold 3. The three positioning holes 5 form an isosceles triangle structure and are distributed on the two long sides of the male mold 1 or female mold 3. Two positioning holes are located at the two ends of one long side, and the other positioning hole is located on the other long side. The positioning post is designed as a stepped structure with one end larger than the other.

[0020] It should be noted that the above workpiece is a symmetrical structure composed of two symmetrical units. The mold is consistent with a single symmetrical unit, and the interface between the mold 2 and the male mold 1 is the symmetrical surface of a single symmetrical unit.

[0021] The mold 2 includes a hemispherical protrusion 201 and a semi-cylindrical protrusion 202. The hemispherical protrusion 201 is located at one end of the semi-cylindrical protrusion 202. The hemispherical protrusion 201 has the same specifications as the ceramic ball, and the semi-cylindrical protrusion 202 has the same specifications as the connecting rod. The male mold 1 is provided with six molds, with adjacent molds arranged in opposite directions. The hemispherical protrusions of the multiple molds are staggered, which can effectively save space in the mold. The diameter of the hemispherical protrusion 201 of the mold is 30mm, and the diameter of the semi-cylindrical protrusion 202 is 8mm. The diameter of the hemispherical cavity 401 of the cavity is 33mm, the diameter of the semi-cylindrical cavity 402 is 11mm, the height of the gap layer is 1.5mm, and the thickness of the formed semi-rubber sleeve is 1.5mm. The end of the semi-cylindrical protrusion 202 away from the hemispherical protrusion 201 is flush with the side surface of the male mold. 02 The end away from the hemispherical cavity is connected to the limiting cavity 403. The limiting cavity 403 and the semi-cylindrical cavity 402 have the same axis. The limiting cavity 403 extends to the side surface of the female mold. The limiting cavity 403 and the semi-cylindrical cavity 402 have a stepped transition. The diameter of the limiting cavity 403 is 8mm. The diameter of the limiting cavity 403 is the same as the diameter of the semi-cylindrical protrusion 202. After assembly, they fit perfectly and can stop the glue material to avoid the glue material from overflowing the template.

[0022] After the semi-rubber sleeves are vulcanized, the workpiece is wrapped with two semi-rubber sleeves, and the rubber sleeves and the workpiece are placed together into a molding die. The molding die includes an upper die 01 and a lower die 02. The upper die 01 is positioned above the lower die 02. The upper die 01 and the lower die 02 enclose a mold cavity 03 that can contain the workpiece and the rubber sleeves. The workpiece wrapped with the rubber sleeves is placed inside the mold cavity 03. The mold cavity 03 includes an upper mold cavity formed on the lower surface of the upper die and a lower mold cavity formed on the upper surface of the lower die. The upper mold cavity and the lower mold cavity are symmetrically arranged. The workpiece wrapped with the rubber sleeves is vulcanized again through the molding die, and the two semi-rubber sleeves are fused together and attached to the outer surface of the workpiece.

[0023] To ensure accurate positioning of the upper mold 01 and lower mold 02 during mold closing, corresponding molding mold positioning holes 04 are provided on the upper mold 01 and lower mold 02. The upper mold 01 and lower mold 02 are positioned and assembled by assembling molding mold positioning pins into the molding mold positioning holes 04. To facilitate mold release and separation of the upper mold 01 and lower mold 02, molding mold release grooves 05 are provided at the edges of the opposite side surfaces of the upper mold and / or lower mold.

[0024] This embodiment changes the original method of directly molding the rubber sleeve on the workpiece surface in one step. It adopts a two-stage vulcanization process. The first vulcanization pre-forms the rubber sleeve, and the second vulcanization bonds the rubber sleeve to the workpiece. This avoids problems such as rubber material accumulation, uneven pressure, and easy damage to the ceramic balls of the workpiece, and effectively improves product quality.

[0025] Example 2 The technical solution of Example 2 is basically the same as that of Example 1, except that the specifications and dimensions of the workpiece and rubber sleeve and the end structure of the female mold cavity are different.

[0026] For details, please see the appendix. Figure 9-16 The diameter of the hemispherical protrusion 201 in the mold is 33 mm, and the diameter of the semi-cylindrical protrusion 202 is 11 mm; the diameter of the hemispherical cavity 401 in the cavity is 38 mm, and the diameter of the semi-cylindrical cavity 402 is 19 mm; the height of the gap layer in the spherical part is 2.5 mm, and the height of the gap layer in the cylindrical part is 3.5 mm, that is, the thickness of the rubber sleeve covering the ceramic ball is 2.5 mm, and the thickness of the rubber sleeve covering the connecting rod is 3.5 mm; the semi-cylindrical protrusion 202 is away from the hemispherical protrusion 201. The end of 1 is flush with the side surface of the male mold 1. The end of the semi-cylindrical cavity 402 away from the hemispherical cavity 401 is connected to a coaxial transition cavity 404 and a limiting cavity 403 in sequence. The transition cavity 404 includes a tapered part with a gradually increasing outer diameter and a cylindrical part connecting the large end of the tapered part. The limiting cavity 403 transitions to the cylindrical part in a stepped manner. The limiting cavity 403 extends to the side surface of the female mold 2. The diameter of the limiting cavity 403 is 11mm. The transition cavity 404 can form a thicker rubber sleeve to improve the grip.

[0027] After the semi-rubber sleeves are vulcanized, the workpiece is encased in two semi-rubber sleeves, and the rubber sleeves and workpiece are placed together into the molding die. (See attached mold for details.) Figure 17-18 The molding die includes an upper die 01 and a lower die 02. The upper die 01 is positioned above the lower die 02. The upper die 01 and the lower die 02 enclose a mold cavity 03 that can contain a workpiece and a rubber sleeve. The workpiece wrapped in the rubber sleeve is placed inside the mold cavity 03. The mold cavity 03 includes an upper mold cavity formed on the lower surface of the upper die and a lower mold cavity formed on the upper surface of the lower die. The upper mold cavity and the lower mold cavity are symmetrically arranged. The workpiece wrapped in the rubber sleeve is vulcanized again by the molding die, and the two half rubber sleeves are fused together and attached to the outer surface of the workpiece.

[0028] To ensure accurate positioning of the upper mold 01 and lower mold 02 during mold closing, corresponding molding mold positioning holes 04 are provided on the upper mold 01 and lower mold 02. The upper mold 01 and lower mold 02 are positioned and assembled by assembling molding mold positioning pins into the molding mold positioning holes 04. To facilitate mold release and separation of the upper mold 01 and lower mold 02, molding mold release grooves 05 are provided at the edges of the opposite side surfaces of the upper mold and / or lower mold.

[0029] This embodiment changes the original method of directly molding the rubber sleeve on the workpiece surface in one step. It adopts a two-stage vulcanization process. The first vulcanization pre-forms the rubber sleeve, and the second vulcanization bonds the rubber sleeve to the workpiece. This avoids problems such as rubber material accumulation, uneven pressure, and easy damage to the ceramic balls of the workpiece, and effectively improves product quality.

[0030] Based on the above two embodiments, it should be noted that this utility model provides a workpiece style and a mold structure for processing the workpiece. However, the mold and flat molding method of this utility model are not limited to processing the workpiece in this embodiment, but can also be used for the surface rubber molding process of other vulnerable parts. Furthermore, the mold structure of this utility model is not limited to processing the workpiece size in the embodiments. Any applicability improvements made by those skilled in the art to the dimensions of the mold and cavity based on the workpiece size are all within the protection scope of this utility model.

[0031] It should be noted that the parts of this utility model not described in detail are existing technologies.

[0032] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0033] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0034] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0035] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0036] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0037] The above-listed embodiments are merely preferred embodiments of this utility model. Obviously, this utility model is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this utility model should be considered within the protection scope of this utility model.

Claims

1. A pre-formed rubber mold, characterized in that: The system includes a rubber sleeve mold, comprising a male mold and a female mold. The male mold has several raised cavities that are the same size as the workpiece. The female mold has several recessed cavities that match the raised cavities. The raised cavities and the molds correspond one-to-one. The male mold and the female mold have corresponding positioning holes. Positioning and assembly of the male mold and the female mold are achieved by assembling positioning pins into the positioning holes. After the male mold and the female mold are assembled, the raised cavities are placed in the cavities. There is a gap layer between the outer surface of the raised cavities and the inner wall of the cavities. The gap layer constitutes the forming cavity of the rubber sleeve.

2. The preformed rubber mold according to claim 1, characterized in that: A mold release groove is provided at the edge of the opposite side surface of the male mold and / or female mold.

3. The preformed rubber mold according to claim 1, characterized in that: The male mold and female mold are each provided with three corresponding positioning holes, which form a triangular structure.

4. A pre-formed rubber mold according to claim 1, characterized in that: The gap distance at each location of the gap layer is 0.2-5mm.

5. A pre-formed rubber mold according to claim 1, characterized in that: The workpiece is a symmetrical structure composed of two symmetrical units. The mold is consistent with a single symmetrical unit, and the interface between the mold and the male mold is the symmetrical plane of the single symmetrical unit. The gap layer forms the molding cavity of the semi-rubber sleeve, and the two semi-rubber sleeves are used in pairs to wrap around the outer surface of the workpiece.

6. A pre-formed rubber mold according to any one of claims 1-5, characterized in that: The workpiece is a ceramic ball with a connecting rod, and the ceramic ball is located at one end of the connecting rod; the rubber sleeve is wrapped around the workpiece.

7. A preformed rubber mold according to claim 6, characterized in that: The mold includes a hemispherical protrusion and a semi-cylindrical protrusion. The hemispherical protrusion is located at one end of the semi-cylindrical protrusion. The hemispherical protrusion has the same specifications as the ceramic ball, and the semi-cylindrical protrusion has the same specifications as the connecting rod. The male mold is provided with multiple molds. Two adjacent molds are arranged in opposite directions, and the hemispherical protrusions of the multiple molds are staggered.

8. A preformed rubber mold according to claim 7, characterized in that: The diameter of the hemispherical protrusion of the mold is 30 mm, and the diameter of the semi-cylindrical protrusion is 8 mm; the diameter of the hemispherical cavity of the cavity is 33 mm, and the diameter of the semi-cylindrical cavity is 11 mm; the end of the semi-cylindrical protrusion away from the hemispherical protrusion is flush with the side surface of the male mold, and the end of the semi-cylindrical cavity away from the hemispherical cavity is connected to a limiting cavity, the axis of the limiting cavity coincides with that of the semi-cylindrical cavity, the limiting cavity extends to the side surface of the female mold, the limiting cavity and the semi-cylindrical cavity have a stepped transition, and the diameter of the limiting cavity is 8 mm; six molds are provided on the male mold.

9. A preformed rubber mold according to claim 7, characterized in that: The diameter of the hemispherical protrusion of the mold is 33 mm, and the diameter of the semi-cylindrical protrusion is 11 mm; the diameter of the hemispherical cavity of the mold cavity is 38 mm, and the diameter of the semi-cylindrical cavity is 19 mm; the end of the semi-cylindrical protrusion away from the hemispherical protrusion is flush with the side surface of the male mold; the end of the semi-cylindrical cavity away from the hemispherical cavity is connected in sequence to a coaxial transition cavity and a limiting cavity; the transition cavity includes a tapered part with a gradually increasing outer diameter and a cylindrical part connecting the large end of the tapered part; the limiting cavity transitions to the cylindrical part in a stepped manner and extends to the side surface of the female mold; the limiting cavity has a diameter of 11 mm; six molds are provided on the male mold.

10. A preformed rubber mold according to claim 6, characterized in that: It also includes a molding die, which includes an upper die and a lower die. The upper die is positioned above the lower die, and the upper die and the lower die together form a mold cavity that can contain a workpiece and a rubber sleeve. The workpiece, which is wrapped in a rubber sleeve, is placed inside the mold cavity. The mold cavity includes an upper mold cavity formed on the lower surface of the upper die and a lower mold cavity formed on the upper surface of the lower die. The upper mold cavity and the lower mold cavity are symmetrically arranged. The upper die and the lower die are provided with corresponding molding die positioning holes. The upper die and the lower die are positioned and assembled by assembling molding die positioning pins into the molding die positioning holes. A molding die release groove is provided at the edge of the opposite side surface of the upper die and / or the lower die.

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