A method for controlling the size of a rubber vulcanized product

Abstract

A method for controlling the dimensions of rubber vulcanized products first determines the dimensions of the rubber vulcanized product in actual use, then determines the shrinkage rate of the rubber during the manufacturing process. The size of the space in the mold where the rubber is injected is then set based on the rubber's shrinkage rate, thereby determining the dimensions of the mold for producing the rubber vulcanized product. This method accurately determines the total shrinkage rate of the rubber vulcanized product based on six factors that affect the rubber's shrinkage rate. Based on the actual dimensions of the product to be produced, the size of the space in the mold where the rubber is injected is precisely calculated using a formula. This ensures that the dimensions of the product after demolding are highly consistent with the product's designed dimensions, significantly improving the precision of the rubber vulcanized product and ensuring the performance requirements of high-precision products.

Description

Technical Field

[0001] The present invention relates to a rubber vulcanized product in the field of rail transportation, and in particular to a method for controlling the size of the rubber vulcanized product by shrinkage rate. Background Art

[0002] The vulcanization of rubber and metal is mostly completed in a mold. However, after the molten rubber is injected into the mold and cools, it shrinks, causing the actual product dimensions to be smaller than the designed dimensions. When the product requires low precision, the actual product dimensions can be slightly smaller than the designed dimensions and the product can be used. Alternatively, based on experience, the space for injecting rubber into the mold can be designed slightly larger. This will ensure that the dimensional tolerance of the vulcanized rubber product after cooling and shrinkage is not too large compared to the designed dimensions, and the product can also be used. However, for rubber-metal spherical bearings with high precision requirements, if the actual dimensions deviate significantly from the ideal designed dimensional tolerance, it will seriously affect the stiffness curve and product performance. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: how to produce a rubber vulcanized product with a size that is highly similar to that of the product design, thereby ensuring that the excellent performance of the rubber vulcanized product with high precision requirements is not affected.

[0004] In response to the above-mentioned problems, the present invention proposes a technical solution: a method for controlling the size of a rubber vulcanized product, which first determines the size of the rubber vulcanized product in actual application, then determines the shrinkage rate of the rubber during the manufacturing process, and then sets the size of the space for injecting the rubber in the mold based on the shrinkage rate of the rubber, thereby determining the size of the mold for producing the rubber vulcanized product, thereby producing a rubber vulcanized product that meets the design size requirements.

[0005] Preferably, the determination of the shrinkage rate of rubber during the manufacturing process includes the following six aspects:

[0006] A: The shrinkage rate is determined according to the temperature during vulcanization;

[0007] B: Determine the shrinkage rate based on the amount of sulfur used;

[0008] C: Determine the shrinkage rate based on the glue content;

[0009] D: Determine the shrinkage rate based on the hardness of the rubber compound;

[0010] E: Determine the shrinkage rate based on the amount of raw material injected;

[0011] F: Determine the shrinkage rate according to the type of rubber;

[0012] After the shrinkage rates of the above six aspects are determined, the total shrinkage rate is obtained by adding up these six shrinkage rates.

[0013] Preferably, the size of the rubber required after cooling in the rubber vulcanized product is determined by the formula (1) showing the relationship between the size of the rubber and the size of the space in the mold for injecting the rubber:

[0014] K=(Dg-Dz) / Dz*100% (1)

[0015] Where K is the total shrinkage of the rubber being vulcanized, Dg is the size of the space in the mold where the rubber is injected at room temperature, and Dz is the size of the rubber portion of the rubber vulcanized product at room temperature.

[0016] Formula (2) can be derived:

[0017] Dg=K*Dz+Dz (2)

[0018] From formula (2), it can be seen that when the total shrinkage rate K and the size Dz of the rubber in the rubber vulcanized product are determined, the size Dg of the space for injecting rubber in the mold can be determined, thereby designing the shape and size of the mold.

[0019] Preferably, after the shape and size of the mold are designed, the mold and the components in the rubber vulcanized product are assembled into a closed space for injecting rubber, and then molten rubber is injected into the closed space. After the rubber cools, the rubber vulcanized product is demoulded and taken out, so that the size of the produced rubber vulcanized product meets the design requirements.

[0020] Preferably, the rubber vulcanized product includes a core shaft, a rubber layer and a jacket, and the mold for producing the rubber vulcanized product includes a flap mold, a partition, an upper insert, a lower insert, an upper mold, a rubber injection cylinder, a middle mold and a lower mold; the core shaft, the jacket, the upper insert and the lower insert are together surrounded to form a closed space for injecting rubber.

[0021] Preferably, expansion grooves are formed on the lower surface of the upper insert and the upper surface of the lower insert, and the expansion grooves on the surfaces of the upper insert and the lower insert are recessed into the interior of the upper insert and the lower insert respectively; and the expansion grooves on the surfaces of the upper insert and the lower insert are arranged in a closed space for injecting rubber surrounded by the core shaft, the outer sleeve, the upper insert and the lower insert. When the molten rubber is injected into the closed space, bulges are formed at both ends of each petal-shaped rubber layer in the vertical direction. After the molten rubber cools, the rubber layer shrinks, and the bulges formed at both ends in the vertical direction gradually become flat.

[0022] Preferably, the middle mold is arranged between the upper mold and the lower mold, and a glue injection cylinder is arranged between the upper mold and the middle mold, a groove is opened at the bottom of the glue injection cylinder, and an upper insert is arranged in the groove; a through mounting hole is opened in the middle mold, and a petal mold and a partition are arranged in the mounting hole of the middle mold, the petal mold is arranged on the outside of the outer sleeve in the circumferential direction, and the partition is arranged on the outside of the core shaft in the circumferential direction, and a circular groove is opened in the lower mold, and a lower insert is arranged in the circular groove.

[0023] Preferably, the mold is assembled first, and a closed space for injecting rubber is formed in the mold. Then, molten rubber is injected into the closed space of the mold. After the rubber cools, the rubber vulcanized product is removed from the mold. The mold assembly steps include:

[0024] S1. First install the split lower insert into the lower mold, then install the mandrel onto the lower insert;

[0025] S2. Sequentially place the petal-type jacket and partitions on the upper surface of the lower panel;

[0026] S3. Close the petal mold;

[0027] S4. Assemble the split upper insert and mandrel;

[0028] S5. Assemble the middle mold and inject the rubber cylinder;

[0029] S6. Place the rubber plug and upper mold in sequence to complete the mold installation.

[0030] Preferably, the molten rubber is injected into the closed space of the mold by opening a through injection hole on the injection cylinder and the upper insert, injecting the molten rubber into the mold through the injection hole of the injection cylinder and the upper insert, so that the molten rubber is injected into the gap between the core shaft and the outer sleeve, thereby using the rubber to vulcanize the core shaft and the outer sleeve into a whole, and after cooling, a rubber vulcanized product with dimensions meeting the design requirements is formed.

[0031] The beneficial technical effects of the present invention are:

[0032] 1. Accurately determine the total shrinkage of rubber vulcanized products based on the six aspects that affect rubber shrinkage. Based on the actual size of the product to be produced, the size of the space for injecting rubber in the mold is accurately calculated through a formula, so that the size of the product after demolding can be highly close to the designed size of the product, thereby greatly improving the accuracy of rubber vulcanized products and ensuring the performance requirements of high-precision products.

[0033] 2. To address the problem of the rubber layer in split-type rubber-metal spherical bearings being large in the vertical direction and prone to forming depressions after cooling and shrinkage, expansion grooves are provided on the surfaces of the split-type upper and lower inserts. This creates protrusions at the vertical ends of the molten rubber layer. After cooling, these protrusions shrink, filling the vertical depressions, resulting in a flat vertical end of the rubber layer after cooling. This further improves the precision of the vulcanized rubber product and ensures the performance requirements of high-precision products. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a vertical cross-sectional view of the overall structure of Example 1;

[0035] Figure 2 This is a schematic diagram of the overall structure decomposition of Example 1;

[0036] Figure 3 This is a structural diagram of the glue injection cylinder of Example 1;

[0037] Figure 4 Schematic diagram of the structure of the upper insert of Example 1;

[0038] Figure 5 Schematic diagram of the structure of the lower insert of Example 1;

[0039] In the figure: upper mold 1, glue injection plug 2, glue injection cylinder 3, annular groove 31, center column 32, external glue injection hole 33, petal mold 4, outer sleeve 5, rubber layer 6, partition 7, upper insert 8, upper positioning hole 81, waist-shaped groove 82, internal glue injection hole 83, lower insert 9, outer positioning ring 91, inner positioning protrusion 92, telescopic groove 93, core shaft 10, middle mold 11, lower mold 12. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to the embodiments and accompanying drawings: Example 1

[0041] like Figure 1 and Figure 2 As shown, this embodiment uses a mold to produce a rubber metal joint bearing, and the metal joint bearing includes a core shaft 10, a rubber layer 6 and an outer sleeve 5. The mold for producing the rubber metal joint bearing includes an upper mold 1, a glue plug 2, a glue injection cylinder 3, a middle mold 11, a flap mold 4, a partition 7, an upper insert 8, a lower insert 9, and a lower mold 12. The middle mold 11 is arranged between the upper mold 1 and the lower mold 12, the glue injection cylinder 3 is arranged between the upper mold 1 and the middle mold 11, and the glue plug 2 is placed in the glue injection cylinder 3. A groove is provided at the bottom of the glue injection cylinder 3, and an upper insert 8 is provided in the groove. A split flap mold 4 and a partition 7 are provided in the mounting hole of the middle mold 11. A circular groove is provided in the lower mold 12, and a lower insert 9 is provided in the circular groove. The core shaft 10 passes through the mounting hole of the middle mold 11, and the split flap outer sleeve 5 is also arranged in the mounting hole of the middle mold 11, and the outer side of the outer sleeve 5 is tightly attached to the inner side of the flap mold 4.

[0042] like Figure 1 、 Figure 3 and Figure 4 As shown, an annular groove 31 is formed on the upper surface of the injection barrel 3, with a cylindrical center post 32 formed inside the annular groove 31. The injection plug 2 is tubular and placed in the annular groove 31, with the injection plug 2 sleeved onto the center post 32. External injection holes 33 are formed at the bottom of the annular groove 31, extending through the injection barrel 3. The external injection holes 33 are evenly distributed around the circumference of the annular groove 31. The upper mold 1 presses the injection plug 2 into the annular groove 31, blocking all the external injection holes 33.

[0043] The upper insert 8 is a split-petal insert. In this embodiment, the upper insert 8 is divided into four independent petals. A through upper positioning hole 81 is provided in the middle of the upper insert 8. A waist-shaped groove 82 is provided in the circumferential direction on the outer side of the upper positioning hole 81. Each waist-shaped groove 82 is provided with an inner glue injection hole 83 that passes through the upper insert 8 on the side close to the upper positioning hole 81. The inner glue injection hole 83 gradually decreases in diameter from top to bottom. In this embodiment, there are six inner glue injection holes 83 on the upper insert 8, and the outer sleeve 5, the petal mold 4 and the partition 7 are all three-petal. Each outer sleeve 5 is respectively surrounded by the partition 7, the core shaft 10, the upper insert 8 and the lower insert 9 to form a small closed space, and each small closed space is connected to the two inner glue injection holes 83. The molten rubber is injected into the closed space through the outer glue injection hole 33 of the glue injection cylinder 3 and the inner glue injection hole 83 of the upper insert 8. The molten rubber forms a rubber layer 6 in the closed space, that is, Figure 1 The area with oblique hatching.

[0044] like Figures 1 to 4 As shown, the lower insert 9 is a split-petal insert. In this embodiment, the lower insert 9 and the upper insert 8 are symmetrical in structure, and the lower insert 9 is also divided into four independent petals. An upwardly protruding, annular inner positioning projection 92 is provided in the middle of the upper surface of the lower insert 9. The inner positioning projection 92 is provided with a mounting hole that passes through the inner positioning projection 92 and the upper insert 8. The upper surface of the lower insert 9 is also provided with an annular outer positioning ring 91 and a strip-shaped expansion groove 93. The outer positioning ring 91 is provided on the outer side of the inner positioning projection 92, and the height of the outer positioning ring 91 is less than the height of the inner positioning projection 92. The inner side of the top and bottom of the partition 7 is provided with structures corresponding to the inner positioning projection 92 and the outer positioning ring 91 of the lower insert 9, so that the outer sides of the inner positioning projection 92 and the outer positioning ring 91 are completely in contact with the inner side of the partition 7 and limit the partition 7 in the radial direction.

[0045] The expansion slots 93 of the upper and lower inserts 8 and 9 are both located outside the outer locating ring 91, with the length of the expansion slots 93 oriented radially relative to the outer locating ring 91. The expansion slots 93 on the surfaces of the upper and lower inserts 8 and 9 are recessed into the interiors of the upper and lower inserts 8 and 9, respectively. These expansion slots 93 are located within the enclosed rubber-injected space defined by the mandrel 10, the outer sleeve 5, the upper and lower inserts 8, and the lower inserts 9. Without expansion slots 93 on the surfaces of the upper and lower inserts 8 and 9, the rubber layer 6 in the rubber-metal spherical bearing would be larger in the vertical direction, and the top and bottom of the rubber layer 6 would be more susceptible to inward depression upon cooling and shrinkage.

[0046] After the expansion grooves 93 are provided on the surfaces of the upper insert 8 and the lower insert 9, when the molten rubber is injected into the enclosed space, bulges are formed at both ends of each petal-shaped rubber layer 6 in the vertical direction. When the molten rubber cools and the rubber layer 6 contracts, the bulges formed at both ends in the vertical direction gradually become flat, so that the product has a normal shape.

[0047] In this embodiment, the rubber vulcanized product is an integral component formed by vulcanizing the core shaft 10, the rubber layer 6, and the outer sleeve 5. The integral component is the core component of the rubber metal spherical plain bearing. The specific process of producing the core component of the rubber metal spherical plain bearing by using a mold is as follows:

[0048] First, according to the vehicle's stiffness curve requirements for the rubber metal spherical bearing, the specific shape and size of the ideal rubber metal spherical bearing are designed, especially the specific shape and size of the rubber vulcanized product and the rubber layer 6, so as to determine the size of the rubber vulcanized product in actual application.

[0049] The dimensions required for a rubber vulcanized product in practical application refer to the overall dimensions of the rubber vulcanized product, which consists of the core shaft 10, rubber layer 6, and outer sleeve 5 after the rubber layer 6 vulcanizes the core shaft 10 and outer sleeve 5 together and cools. In addition to the overall dimensions of the rubber vulcanized product, the dimensions of the rubber layer 6 itself are also important. This is because the overall dimensions of the rubber vulcanized product affect its assembly dimensions. If the actual dimensions of the rubber vulcanized product are larger than the designed dimensions, the product may be too large and unsuitable for installation. If the actual dimensions of the rubber vulcanized product are smaller than the designed dimensions, the product may be too small and prone to loosening after assembly, seriously affecting its performance.

[0050] Next, the shrinkage rate of the rubber during the manufacturing process needs to be determined. In this embodiment, the determination of the shrinkage rate of the rubber during the manufacturing process includes the following six aspects:

[0051] A: The shrinkage rate is determined according to the vulcanization temperature: the higher the vulcanization temperature, the greater the rubber shrinkage rate. The shrinkage rate is determined according to the specific vulcanization temperature;

[0052] B: Determine the shrinkage rate based on the amount of sulfur used: When the sulfur amount is around 3%, the shrinkage rate of the rubber compound is about 1.5-2%; when the sulfur amount is around 15%, the shrinkage rate can reach 4%. The shrinkage rate is determined based on the actual amount of sulfur used.

[0053] C: Determine the shrinkage rate based on the glue content: the higher the glue content, the greater the shrinkage rate. The shrinkage rate is determined based on the actual glue content used.

[0054] D: Determine the shrinkage rate based on the hardness of the rubber compound: Generally, the lower the hardness, the greater the shrinkage rate; the higher the hardness, the smaller the shrinkage rate. The shrinkage rate is determined based on the actual hardness of the rubber compound measured;

[0055] E: Determine the shrinkage rate based on the raw material injection amount: Determine the shrinkage rate based on the ratio of raw material mass to finished product mass;

[0056] F: Determine the shrinkage rate based on the type of rubber: Different types of rubber have different shrinkage rates. For example, the shrinkage rate of natural rubber is 1.2% to 2.0%. In specific formulations, the empirical shrinkage rate of natural rubber is 1.6% to 2.4%. The shrinkage rate of nitrile rubber is 1.8% to 2.2%, and that of silicone rubber is 3.2% to 3.4%. The shrinkage rate is determined based on the actual type of rubber used.

[0057] After the shrinkage rates of the above six aspects are determined, the total shrinkage rate is obtained by adding up these six shrinkage rates.

[0058] Next, the size of the space for injecting rubber into the mold needs to be determined based on the rubber's shrinkage rate to design the shape and size of the mold. The specific process is as follows:

[0059] Based on the required size of the rubber in the rubber vulcanized product after cooling, the relationship between the rubber size and the size of the space in the mold where the rubber is injected is calculated using the formula (1):

[0060] K=(Dg-Dz) / Dz*100% (1)

[0061] Wherein, K is the total shrinkage of the rubber being vulcanized, Dg is the size of the space in the mold 12 for injecting the rubber at room temperature, and Dz is the size of the rubber portion of the rubber vulcanized product at room temperature;

[0062] Formula (2) can be derived:

[0063] Dg=K*Dz+Dz (2)

[0064] From formula (2), it can be seen that when the total shrinkage rate K and the size Dz of the rubber in the rubber vulcanized product are determined, the size Dg of the space for injecting rubber in the mold can be determined, thereby designing the shape and size of the mold that meets the requirements.

[0065] After the shape and size of the mold are designed, the mold and the components of the rubber vulcanized product are assembled to form a closed space for injecting rubber. Molten rubber is then injected into the closed space. After the rubber cools, the rubber vulcanized product is removed from the mold to ensure that the size of the produced rubber vulcanized product meets the design requirements. The mold assembly steps include:

[0066] S1. First, install the split lower insert 9 into the lower mold 12, and then install the mandrel 10 onto the lower insert 9;

[0067] S2. Sequentially place the petal-type jacket 5 and the partition 7 on the upper surface of the lower panel 9;

[0068] S3. The petal-type mold 4 is closed;

[0069] S4. Assemble the split-type upper insert 8 and the mandrel 10;

[0070] S5. Assemble the mold 11 and inject the plastic cartridge 3;

[0071] S6. The rubber plug 2 and the upper mold 1 are sequentially injected to complete the mold installation.

[0072] The molten rubber is injected into the mold by opening a through injection hole on the injection cylinder 3 and the upper insert 8, and injecting the molten rubber into the mold through the injection hole of the injection cylinder 3 and the upper insert 8, so that the molten rubber is injected into the gap between the core shaft 10 and the outer sleeve 5, thereby vulcanizing the core shaft 10 and the outer sleeve 5 into a whole with the rubber, and forming a product after cooling.

[0073] After the product is cooled and formed, the demoulding steps include:

[0074] S1. Remove the upper mold 1, injection plug 2, and injection cylinder 3 respectively;

[0075] S2. Pry and remove the middle mold 11;

[0076] S3. Remove the petal-type mold 4;

[0077] S4. Remove the petal-shaped upper insert 8;

[0078] S5. Take out the product and the lower insert 9 in turn to obtain a rubber vulcanized product that meets the design requirements and complete demolding.

[0079] Obviously, without departing from the principles of the present invention, several improvements or modifications should be considered as within the scope of protection of the present invention.

Claims

1. A method for controlling the size of a rubber vulcanized product, characterized in that: First, determine the size of the rubber vulcanized product in actual application, then determine the shrinkage rate of the rubber in the manufacturing process, and then set the size of the space for injecting rubber in the mold according to the shrinkage rate of the rubber, so as to determine the size of the mold for producing the rubber vulcanized product, so as to produce the rubber vulcanized product that meets the design size requirements; after designing the shape and size of the mold, assemble the mold and the components in the rubber vulcanized product into a closed space for injecting rubber, and then inject molten rubber into the closed space, and demould and take out the rubber vulcanized product after the rubber cools down, so that the size of the produced rubber vulcanized product meets the design requirements; the rubber vulcanized product includes a core shaft, a rubber layer and a jacket, and the mold for producing the rubber vulcanized product includes a flap mold, a partition, an upper insert, a lower insert, an upper mold, a glue injection cylinder, a middle mold and a lower mold; the core shaft, the jacket, the upper insert and the lower insert are together surrounded by a closed space for injecting rubber; on the bottom surface of the upper insert and the top surface of the lower insert The surfaces of the upper and lower inserts are provided with expansion grooves, and the expansion grooves on the surfaces of the upper and lower inserts are respectively recessed into the upper and lower inserts; and the expansion grooves on the surfaces of the upper and lower inserts are arranged in a closed space for injecting rubber surrounded by the core shaft, the outer sleeve, the upper and lower inserts. When the molten rubber is injected into the closed space, bulges are formed at both ends of each petal-type rubber layer in the vertical direction. After the molten rubber cools down, when the rubber layer shrinks, the bulges formed at both ends in the vertical direction will gradually become flat; the middle mold is arranged between the upper mold and the lower mold, and a glue injection cylinder is arranged between the upper mold and the middle mold, a groove is opened at the bottom of the glue injection cylinder, and the upper insert is arranged in the groove; a through mounting hole is opened in the middle mold, and a petal-type flap mold and a partition are arranged in the mounting hole of the middle mold, the flap mold is arranged on the outside of the circumferential direction of the outer sleeve, and the partition is arranged on the outside of the circumferential direction of the core shaft, and a circular groove is opened in the lower mold, and the lower insert is arranged in the circular groove.

2. The method for controlling the size of a rubber vulcanized product according to claim 1, wherein: The determination of rubber shrinkage during the manufacturing process includes the following six aspects: A: The shrinkage rate is determined according to the temperature during vulcanization; B: Determine the shrinkage rate based on the amount of sulfur used; C: Determine the shrinkage rate based on the glue content; D: Determine the shrinkage rate based on the hardness of the rubber compound; E: Determine the shrinkage rate based on the amount of raw material injected; F: Determine the shrinkage rate according to the type of rubber; After the shrinkage rates of the above six aspects are determined, the total shrinkage rate is obtained by adding up these six shrinkage rates.

3. The method for controlling the size of a rubber vulcanized product according to claim 2, wherein: Based on the required size of the rubber in the rubber vulcanized product after cooling, the relationship between the rubber size and the size of the space in the mold where the rubber is injected is given by formula (1): K=(Dg-Dz) / Dz*100% (1) Where K is the total shrinkage of the rubber being vulcanized, Dg is the size of the space in the mold where the rubber is injected at room temperature, and Dz is the size of the rubber portion of the rubber vulcanized product at room temperature. Formula (2) can be derived: Dg=K*Dz+Dz (2) From formula (2), it can be seen that when the total shrinkage rate K and the size Dz of the rubber in the rubber vulcanized product are determined, the size Dg of the space for injecting rubber in the mold can be determined, thereby designing the shape and size of the mold.

4. The method for controlling the size of a rubber vulcanized product according to claim 1, wherein: First, assemble the mold, form a closed space in the mold for injecting rubber, then inject molten rubber into the closed space of the mold, and after the rubber cools, demould and remove the rubber vulcanized product. The mold assembly steps include: S1. First install the split lower insert into the lower mold, then install the mandrel onto the lower insert; S2. Sequentially place the petal-type jacket and partitions on the upper surface of the lower panel; S3. Close the petal mold; S4. Assemble the split upper insert and mandrel; S5. Assemble the middle mold and inject the rubber cylinder; S6. Place the rubber plug and upper mold in sequence to complete the mold installation.

5. The method for controlling the size of a rubber vulcanized product according to claim 4, wherein: The molten rubber is injected into the closed space of the mold by opening a through injection hole on the injection cylinder and the upper insert, and injecting the molten rubber into the mold through the injection hole of the injection cylinder and the upper insert, so that the molten rubber is injected into the gap between the core shaft and the outer sleeve, thereby vulcanizing the core shaft and the outer sleeve into a whole with the rubber, and forming a rubber vulcanized product with dimensions meeting the design requirements after cooling.

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