A packing shrinkage compensation mechanism for injection mold

Abstract

The application provides a pressure-maintaining shrinkage compensation mechanism of an injection mold, and belongs to the technical field of molds. The mechanism solves the problem of insufficient product forming quality when the existing injection mold produces products with a long length. In the pressure-maintaining shrinkage compensation mechanism of the injection mold, the injection mold comprises a movable mold plate and a fixed mold plate, and a long strip-shaped cavity is formed between the movable mold plate and the fixed mold plate after the two are combined. The fixed mold plate is provided with a nozzle capable of injecting melt into the cavity. The compensation mechanism comprises a compensation storage cavity which is arranged on the fixed mold plate and is in communication with the cavity. The fixed mold plate is further provided with a pushing piece capable of pushing the melt in the compensation storage cavity into the cavity. The outlet position of the nozzle and the position of the compensation hole are respectively located at the two ends of the cavity. The application can avoid the generation of shrink marks at the end of the product, thereby reducing the optical performance of the light guide body, and ensure that each part of the product has high forming precision, thereby greatly improving the forming quality of the product.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of mold, and relates to a pressure maintaining and shrinkage compensation mechanism of an injection mold. BACKGROUND

[0002] In the automobile, lighting and electronic industries, the application of light guides is more and more. Because the wall thickness of the light guide product is thick, the forming cycle is long, therefore, the production of the light guide has high requirements on injection molding. Generally, the light guide is formed by using transparent resin such as PMMA, PC, etc. In order to ensure the excellent appearance of the product, the melt flow is molded by low temperature, high pressure and ultra-low injection speed process, so that the melt is kept in a laminar flow state. However, due to the low injection speed, and the light guide is usually long, it is not conducive to the pressure maintaining at the end of product filling, and often causes the insufficient forming quality of the product, mainly reflected in the shrinkage mark at the end of the product, which makes the optical performance of the light guide decline, or the uneven shrinkage of different parts of the product, which causes large internal stress of the product, product warping deformation, and the deformation of shape not only affects the optical performance but also affects the assembly size.

[0003] At present, in order to solve the above problems, the number of nozzles of the gating system is usually increased or the structure of multi-channel is used, such as a single-gate multi-channel injection mold disclosed in Chinese patent document (application number: 201520811860.3), which makes the melt at different positions in the cavity including the end of the product have enough melt, and then the pressure maintaining and cooling time is prolonged to compensate the volume caused by the shrinkage of the product. SUMMARY

[0004] The purpose of the present application is to solve the above problems existing in the prior art, and a pressure maintaining and shrinkage compensation mechanism of an injection mold is provided. The present application solves the problem of insufficient product forming quality when the existing injection mold produces a product with a long length.

[0005] The purpose of the present application can be realized by the following technical scheme: a pressure maintaining and shrinkage compensation mechanism of an injection mold, the injection mold comprising a movable mold plate and a fixed mold plate, the movable mold plate and the fixed mold plate form a long strip-shaped cavity after the mold is closed, the fixed mold plate is provided with a nozzle capable of injecting melt into the cavity, characterized in that the pressure maintaining and shrinkage compensation mechanism comprises a compensation storage cavity which is provided on the fixed mold plate and is in communication with the cavity, the fixed mold plate is further provided with a pushing piece capable of pushing the melt in the compensation storage cavity into the cavity, and the outlet position of the nozzle and the position of the feeding hole are respectively located at the two ends of the cavity.

[0006] When the fixed mold plate and the movable mold plate are closed, the injection molding filling is started, the nozzle injects the melt into the cavity, at this time, since the compensation storage cavity is communicated with the cavity, part of the melt entering the cavity will also flow into the compensation storage cavity. After the injection molding filling is completed, the pressure maintaining process is started, at the same time, the pushing member pushes the melt in the compensation storage cavity to the cavity in the reverse direction, so as to realize the shrinkage compensation of the product. The present pressure maintaining and shrinkage compensation mechanism is mainly suitable for the production of long strip-shaped plastic products such as light guides, therefore, a long strip-shaped cavity is adopted, and the position of the outlet of the nozzle is located at the first end of the cavity, so that the first end of the cavity has sufficient melt to enter, and the position of the compensation hole is arranged at the end of the cavity, so that the problem that the melt at the nozzle is difficult to effectively fill the end of the cavity is solved, so that the end of the cavity also has sufficient melt, which is beneficial to the filling and pressure maintaining of the end of the product, avoids the generation of shrink marks at the end of the product, and reduces the optical performance of the light guide, and at the same time, ensures that each part of the product has high molding precision, and the molding quality of the product is greatly improved.

[0007] In the pressure maintaining and shrinkage compensation mechanism of the injection mold, the fixed mold plate is located on the upper side of the movable mold plate, the bottom of the fixed mold plate has an upper cavity surface, the top of the movable mold plate has a lower cavity surface, and the upper cavity surface and the lower cavity surface enclose the cavity. The present injection mold is a vertical injection mold, which is matched with the auxiliary pressure maintaining structure, so that the melt in the cavity is more uniformly filled, and the phenomenon that the mold plates cannot be opened and closed due to the front falling caused by the gravity of the mold in the similar horizontal machine does not occur, so that the precision of the machine and the mold is durably ensured.

[0008] In the pressure maintaining and shrinkage compensation mechanism of the injection mold, the upper cavity surface is provided with a vertically arranged compensation hole, the pushing member has a pushing part in the form of a rod and extending downward into the compensation hole, and the outer peripheral wall of the pushing part and the inner wall of the compensation hole form a seal. The pressure maintaining and shrinkage compensation mechanism further comprises a driving member capable of driving the pushing member to move vertically up and down. After the pushing part moves upward with the pushing member, the lower end of the compensation hole and the lower end surface of the pushing part form the compensation storage cavity. In this structure, the size of the compensation storage cavity is determined by the up-and-down position of the pushing part, therefore, the technician can adjust the size of the compensation storage cavity by controlling the initial upper limit position of the pushing part according to the actual production requirements, so as to adjust the size of the melt compensation amount, and improve the molding quality of the product. The outer peripheral wall of the pushing part and the inner wall of the compensation hole form a seal, so as to avoid the leakage of the melt in the compensation storage cavity, ensure that the pushing part can effectively push the melt in the compensation storage cavity into the cavity, avoid the error between the actual compensation amount and the calculated compensation amount of the melt, and ensure the good molding quality of the product.

[0009] In the aforementioned pressure-holding shrinkage compensation mechanism for injection molds, a moving mold fixing plate is provided on the upper side of the fixed mold plate. A vertically arranged mounting hole is provided on the fixed mold plate above the material filling hole. The ejector component also includes a push rod body connected to the upper end of the ejector section. The push rod body is slidably disposed within the mounting hole, and the driving component is connected to the push rod body. Through the guiding fit between the push rod body and the mounting hole, the ejector component moves stably, thereby improving the operational stability of this pressure-holding mechanism.

[0010] In the aforementioned pressure-holding shrinkage compensation mechanism for injection molds, the mounting hole includes a first stepped hole on the top surface of the fixed mold plate and a second stepped hole at the bottom of the first stepped hole. The upper end of the material replenishment hole is located at the bottom of the second stepped hole. The diameter of the second stepped hole is smaller than the diameter of the first stepped hole but larger than the diameter of the material replenishment hole. The ejector body includes a first guide portion that slides with the inner wall of the first stepped hole and a second guide portion connected to the lower end of the first guide portion and sliding with the inner wall of the second stepped hole. The mounting hole is located on the top surface of the fixed mold plate, and the drive component is mounted on the moving mold fixing plate, making production more convenient and reducing manufacturing costs. However, this structure results in the drive component being far from the cavity, leading to a relatively long ejector component. The diameter of the material replenishment hole and the outer diameter of the ejector component are relatively small, typically in the millimeter range. Furthermore, the driving force needs to be relatively large to ensure smooth entry of the material into the cavity from the compensation storage cavity. This raises the question of how to prevent the ejector component from deforming during torque transmission. The above structure, with its successively decreasing diameters of the first step hole, second step hole, and feeding hole, creates a multi-stage decreasing outer diameter structure for the first guide section, second guide section, and feeding section of the push rod body. This avoids stress concentration, shortens the length of the feeding section, and prevents deformation of the thinner feeding section. Furthermore, because the outer diameter of the second guide section is smaller than that of the first guide section, the sliding friction between the second guide section and the second step hole is also less than the sliding friction between the first guide section and the first step hole. Therefore, this structure can also shorten the length of the first guide section, reducing the sliding friction of the feeding component while preventing deformation of the feeding component. This ensures smooth operation of the feeding component, guarantees the moving accuracy of the feeding component, avoids errors between the actual and calculated compensation amounts of the molten material, and ensures good product molding quality.

[0011] In the aforementioned pressure-holding shrinkage compensation mechanism of the injection mold, the lower cavity surface of the moving platen has a recessed portion formed by downward indentation at the end away from the nozzle. The material replenishment hole is located above the recessed portion, and the moving platen is also equipped with ejector pins that can extend into the recessed portion. The recessed portion corresponds to the thicker part of the product wall. The cavity at the recessed portion has more molten material compared to the non-recessed portion. When the material replenishment component extrudes the molten material into the recessed portion, it also compresses the molten material within the recessed portion, thereby distributing the molten material in the recessed portion and the molten material in the compensation storage cavity to the required locations. The sufficient amount of molten material available for distribution improves the molten material compensation effect, ensuring high molding accuracy in all parts of the product and improving the product molding quality. The ejector pins on the moving platen that can extend into the recessed portion to push the product out ensure that the product can be separated from the mold more smoothly.

[0012] In the aforementioned pressure-holding shrinkage compensation mechanism for injection molds, the first step hole, the second step hole, and the material replenishment hole are concentrically arranged. The driving component is a hydraulic cylinder or a pneumatic cylinder, and the piston rod of the driving component is vertically downward and connected to the push rod body. Preferably, the driving component is a hydraulic cylinder.

[0013] In the aforementioned pressure-holding shrinkage compensation mechanism of the injection mold, an annular groove surrounding the first step hole is formed on the top surface of the fixed platen. A heating coil is disposed within the annular groove, and the ejector is made of metal. The metal ejector has high thermal conductivity, high structural strength, and is not easily deformed. The heat generated by the heating coil is transferred to the ejector, giving it a relatively high temperature. This, in turn, ensures that the ejector section of the ejector also has a high temperature, thus maintaining the temperature of the molten material in the compensation storage cavity and ensuring that the molten material in the compensation storage cavity always has good fluidity. Furthermore, the heating coil is located on the outer periphery of the first step hole, far from the cavity, preventing the heat generated by the heating coil from affecting or interfering with the temperature of the molten material in the cavity. This ensures precise temperature control of the molten material in the cavity and improves the molding quality of the product.

[0014] Compared with existing technologies, the pressure holding shrinkage compensation mechanism of this injection mold has the following advantages:

[0015] 1. Compared with existing technologies that compensate for product shrinkage by increasing the number of nozzles in the gating system or by using a multi-channel structure, this pressure-holding shrinkage compensation mechanism does not require increasing the number of nozzles or opening multiple channels, thus controlling the cost of the mold's hot runner. Therefore, this pressure-holding shrinkage compensation mechanism also has the advantages of being easy to manufacture and cost-saving.

[0016] 2. This invention can solve the problem that the molten material at the nozzle is difficult to effectively fill the end of the cavity, so that the end of the cavity also has sufficient molten material, which is beneficial for the product to fill the end and maintain pressure, avoids shrinkage marks at the end of the product that would reduce the optical performance of the light guide, and at the same time ensures that all parts of the product have high molding accuracy, greatly improving the molding quality of the product. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the injection mold before injection filling.

[0018] Figure 2 This is a schematic diagram of the structure after injection molding and filling of this injection mold.

[0019] Figure 3 yes Figure 2 Enlarged view of point A in the middle.

[0020] Figure 4 This is a schematic diagram of the structure after the pusher pushes the molten material in the compensation storage cavity into the mold cavity.

[0021] Figure 5 This is a schematic diagram of the structure of Embodiment 2 of this injection mold.

[0022] In the figure, 1. Moving mold plate; 1a. Lower cavity surface; 1a1. Recessed part; 2. Fixed mold plate; 2a. Upper cavity surface; 3. Cavity; 4. Nozzle; 5. Material filling hole; 51. Compensating storage cavity; 6. Pushing component; 61. Pushing part; 62. Push rod body; 621. First guide part; 622. Second guide part; 7. Driving component; 71. Piston rod; 8. Moving mold fixing plate; 9. Mounting hole; 91. First step hole; 92. Second step hole; 10. Ejector pin; 11. Annular groove; 12. Heating coil. Detailed Implementation

[0023] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0024] Example 1

[0025] like Figures 1 to 3As shown, the injection mold includes a moving mold plate 1 and a fixed mold plate 2. After the moving mold plate 1 and the fixed mold plate 2 are closed, a long cavity 3 is formed between them. The fixed mold plate 2 is provided with a nozzle 4 that can inject molten material into the cavity 3. The pressure holding shrinkage compensation mechanism includes a compensation storage cavity 51 opened on the fixed mold plate 2 and connected to the cavity 3. The fixed mold plate 2 is also provided with a pusher 6 that can push the molten material in the compensation storage cavity 51 into the cavity 3. The outlet of the nozzle 4 and the position of the filling hole 5 are respectively located at both ends of the cavity 3. Specifically, this injection mold is a vertical injection mold. The fixed mold plate 2 is located on the upper side of the moving mold plate 1. The bottom of the fixed mold plate 2 has an upper cavity surface 2a, and the top of the moving mold plate 1 has a lower cavity surface 1a. The upper cavity surface 2a and the lower cavity surface 1a enclose the cavity 3.

[0026] like Figure 2 and Figure 3 As shown, after the moving mold plate 1 and the fixed mold plate 2 close, injection molding begins. The nozzle 4 injects molten material into the cavity 3. At this time, since the compensation storage cavity 51 is connected to the cavity 3, some of the molten material entering the cavity 3 will also flow into the compensation storage cavity 51. After the injection molding process is completed, the holding pressure process is then initiated. Simultaneously, as... Figure 4 As shown, the pusher 6 pushes the molten material in the compensation storage cavity 51 in the reverse direction into the cavity 3 to achieve product shrinkage compensation.

[0027] like Figures 1 to 3 As shown, a moving mold fixing plate 8 is provided on the upper side of the fixed mold plate 2, and a driving component 7 is provided on the moving mold fixing plate 8. The driving component 7 is a hydraulic cylinder, but it can also be a pneumatic cylinder. A vertically arranged feeding hole 5 is provided on the upper cavity surface 2a. The pusher 6 has a rod-shaped pushing part 61 that extends downward into the feeding hole 5. The outer peripheral wall of the pushing part 61 forms a seal with the inner wall of the feeding hole 5. The fixed mold plate 2 is provided with a driving component 7 that can drive the pusher 6 to move vertically up and down. After the pushing part 61 moves upward with the pusher 6, a compensation storage cavity 51 is formed between the lower end of the feeding hole 5 and the lower end face of the pushing part 61. A vertically arranged mounting hole 9 is provided on the fixed mold plate 2 located above the feeding hole 5. The pusher 6 also includes a push rod body 62 connected to the upper end of the pushing part 61. The piston rod 71 is arranged vertically downward and connected to the push rod body 62. The push rod body 62 is slidably disposed in the mounting hole 9, and the driving component 7 is connected to the push rod body 62 and can drive the push rod body 62 to move up and down.

[0028] like Figure 1 and Figure 2As shown, the mounting hole 9 includes a first stepped hole 91 formed on the top surface of the fixed template 2 and a second stepped hole 92 formed at the bottom of the first stepped hole 91. The upper end of the feeding hole 5 is located at the bottom of the second stepped hole 92. The first stepped hole 91, the second stepped hole 92, and the feeding hole 5 are concentrically arranged. The diameter of the second stepped hole 92 is smaller than the diameter of the first stepped hole 91 but larger than the diameter of the feeding hole 5. The push rod body 62 includes a first guide part 621 that slides with the inner wall of the first stepped hole 91 and a second guide part 622 connected to the lower end of the first guide part 621 and sliding with the inner wall of the second stepped hole 92. Because the diameters of the first stepped hole 91, the second stepped hole 92, and the feeding hole 5 decrease sequentially, the outer diameters of the first guide part 621, the second guide part 622, and the pushing part 61 of the push rod body 62 form a multi-stage decreasing structure. This avoids stress concentration, shortens the length of the pushing part 61, and prevents deformation of the thinner pushing part 61.

[0029] like Figure 2 and Figure 3 As shown, the lower cavity surface 1a of the moving template 1 has a recessed portion 1a1 formed by downward indentation at one end away from the nozzle 4. The feeding hole 5 is located on the upper side of the recessed portion 1a1. The moving template 1 is also provided with an ejector pin 10 that can extend into the recessed portion 1a1 to push the product out.

[0030] Example 2

[0031] This embodiment is basically the same as embodiment one in structure and principle, except that: Figure 5 As shown, an annular groove 11 is formed on the top surface of the fixed template 2, surrounding the first step hole 91. A heating coil 12 is installed inside the annular groove 11, and the pusher 6 is made of metal. The pusher 6, made of metal, has high thermal conductivity and high structural strength, making it resistant to deformation. The heat generated by the heating coil 12 can be transferred to the pusher 6, giving it a relatively high temperature. This, in turn, ensures that the pusher part 61 of the pusher 6 also has a high temperature, which can keep the molten material in the compensation storage cavity 51 warm, ensuring that the molten material in the compensation storage cavity 51 always has good fluidity. In addition, the heating coil 12 is located on the outer periphery of the first step hole 91 and is far from the cavity 3, preventing the heat generated by the heating coil 12 from affecting or interfering with the temperature of the molten material in the cavity 3. This ensures precise temperature control of the molten material in the cavity 3 and improves the molding quality of the product.

[0032] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

[0033] Although this document frequently uses terms such as 1. moving mold plate; 1a. lower cavity surface; 1a1. recessed portion; 2. fixed mold plate; 2a. upper cavity surface; 3. cavity; 4. nozzle; 5. material filling hole; 51. compensation storage cavity; 6. pusher component; 61. pusher part; 62. pusher rod body; 621. first guide part; 622. second guide part; 7. driving component; 71. piston rod; 8. moving mold fixing plate; 9. mounting hole; 91. first step hole; 92. second step hole; 10. ejector pin; 11. annular groove; 12. heating coil, etc., the possibility of using other terms is not excluded. The use of these terms is merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A packing shrinkage compensation mechanism of an injection mold, the injection mold comprising a movable mold plate (1) and a fixed mold plate (2), a long strip-shaped cavity (3) being formed between the movable mold plate (1) and the fixed mold plate (2) after the two plates are closed, the bottom of the fixed mold plate (2) being provided with an upper cavity surface (2a), a vertically arranged feeding hole (5) being formed in the upper cavity surface (2a), and a nozzle (4) being arranged on the fixed mold plate (2) and capable of injecting melt into the cavity (3), characterized in that, The holding pressure shrinkage compensation mechanism comprises a compensation storage cavity (51) which is opened on the fixed mold plate (2) and communicates with the mold cavity (3), the fixed mold plate (2) is further provided with a pushing member (6) which can push the melt in the compensation storage cavity (51) into the mold cavity (3), the positions of the outlet of the nozzle (4) and the feeding hole (5) are respectively located at both ends of the mold cavity (3); the holding pressure shrinkage compensation mechanism further comprises a driving member (7) which can drive the pushing member (6) to vertically move up and down, the pushing member (6) has a pushing part (61) which is in the shape of a rod and extends downward into the feeding hole (5), after the pushing part (61) moves upward with the pushing member (6), the lower end of the feeding hole (5) and the lower end face of the pushing part (61) form the above-mentioned compensation storage cavity (51); the fixed mold plate (2) is provided with a vertically arranged mounting hole (9) which is located on the upper side of the feeding hole (5), the mounting hole (9) comprises a first stepped hole (91) which is opened on the top surface of the fixed mold plate (2) and a second stepped hole (92) which is opened on the hole bottom of the first stepped hole (91), the pushing member (6) further comprises a push rod main body (62) which is connected to the upper end of the pushing part (61), the push rod main body (62) comprises a first guide part (621) which is in sliding fit with the inner wall of the first stepped hole (91) and a second guide part (622) which is connected to the lower end of the first guide part (621) and is in sliding fit with the inner wall of the second stepped hole (92), the outer diameters of the first guide part (621), the second guide part (622) of the push rod main body (62) and the pushing part (61) form a multi-stage decreasing structure, the top surface of the fixed mold plate (2) is provided with an annular groove (11) which is arranged around the first stepped hole (91), and a heating ring (12) is inserted into the annular groove (11).

2. The packer shrinkage compensation mechanism of the injection mold according to claim 1, characterized in that, The fixed mold plate (2) is located on the upper side of the movable mold plate (1), the top of the movable mold plate (1) has a lower mold cavity surface (1a), and the upper mold cavity surface (2a) and the lower mold cavity surface (1a) enclose the above-mentioned mold cavity (3).

3. The packer shrinkage compensation mechanism of the injection mold according to claim 2, characterized in that, The outer peripheral wall of the pushing part (61) is in sealing fit with the inner wall of the feeding hole (5).

4. The packer shrinkage compensation mechanism of the injection mold according to claim 1, characterized by, The upper side of the fixed mold plate (2) is provided with a movable mold fixing plate (8), the driving member (7) is arranged on the movable mold fixing plate (8), and the driving member (7) is connected with the push rod main body (62).

5. The packer shrinkage compensation mechanism of an injection mold according to claim 2 or 3, characterized in that, The end of the lower mold cavity surface (1a) of the movable mold plate (1) which is away from the nozzle (4) has a downward recessed lower recess (1a1), the feeding hole (5) is located on the upper side of the lower recess (1a1), and the movable mold plate (1) is further provided with a ejector pin (10) which can extend into the lower recess (1a1).

6. The packing shrinkage compensation mechanism of an injection mold according to any one of claims 1 to 4, characterized in that, The first stepped hole (91), the second stepped hole (92) and the feeding hole (5) are concentrically arranged, the driving member (7) is a hydraulic cylinder or a pneumatic cylinder, the piston rod (71) of the driving member (7) is vertically arranged downward and is connected with the push rod main body (62).

7. The packing shrinkage compensation mechanism of an injection mold according to any one of claims 1 to 4, characterized by, The pushing member (6) is made of metal material.

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