Ejector structure of a low-pressure injection molding die

Abstract

The present invention relates to the field of injection molds, and specifically relates to an ejection structure of a low-pressure injection molding mold. The low-pressure injection molding mold includes a second male template, a second ejector plate, and a second lower fixing plate. The ejection structure includes a guiding column vertically arranged on the top of the second lower fixing plate, and a first through hole for the guiding column to pass through is arranged on the second ejector plate; and an elastic member sleeved on the guiding column, where the injection pressure < the resilience of the elastic member < the clamping force; during the compression stage, the second male template abuts against the guiding column, the second ejector plate abuts against the elastic member, and the elastic member is in a compressed state; during the injection stage, the second male template abuts against the guiding column, the second ejector plate abuts against the elastic member, and the elastic member is in a rebounding state. The ejection structure using a new type of stacked spring is applied to the mold of low-pressure injection molding, and the oil cylinder is replaced to complete the pre-press ejection action. Canceling the oil cylinder will not cause oil leakage, and there is no need for pressure holding and maintenance.

Description

Technical Field

[0001] The present invention relates to the field of injection molds, and particularly to an ejection structure of a low-pressure injection molding mold. Background Art

[0002] For products such as large-sized PC transparent parts, due to uncontrollable warping and deformation during the injection molding process of the products, and defects such as shrinkage marks, flow marks, and weld lines are likely to occur on the appearance, low-pressure injection molding needs to be adopted. Low-pressure injection molding has the following advantages compared with traditional injection molding:

[0003] 1. The number of gates is small, and the trimming cost is low;

[0004] 2. The warping and deformation of the product are small;

[0005] 3. The wall thickness of the product appearance is uniform;

[0006] 4. There is no shrinkage, no flow marks, and no weld lines on the surface of the product;

[0007] 5. The injection pressure is small, and the internal stress of the product is small.

[0008] In the prior art, the mold opening sequence of a low-pressure injection molding mold is as Figure 1 shown. From left to right, they are schematic diagrams of several steps: mold opening, mold closing, ejecting while opening, injection molding, instantaneous compression, ejecting while opening, and mold opening to pick up the part. Among them:

[0009] Mold opening means that the male and female templates of the injection molding machine are opened;

[0010] Mold closing means that the male and female templates of the injection molding machine are closed;

[0011] Ejecting while opening means that the mold ejects while the injection molding machine opens to a preset wall thickness;

[0012] Injection molding means injecting and filling the interior of the mold cavity;

[0013] Instantaneous compression means instantaneously compressing the preset wall thickness to a fixed wall thickness;

[0014] Ejecting while opening means that the mold opening and ejection are carried out simultaneously;

[0015] Mold opening to pick up the part means that the male and female molds are opened, and the part is picked up by a suction cup.

[0016] The existing layout of the oil cylinder ejection of a low-pressure injection molding mold is as Figure 2 shown. To make the ejection balanced, all the oil cylinders need to be combined into one inlet and one outlet.

[0017] Specifically, as Figure 3 and Figure 4 shown, Figure 3 is a schematic diagram of the ejection during the oil cylinder return stage of the existing low-pressure injection molding process, Figure 4It is a schematic diagram of the cylinder ejection stage of the existing low-pressure injection molding process. The principle of low-pressure injection molding is that when the mold is closed, the cavity opens a distance S, making the cavity space larger so that the melt can be quickly filled. After filling to 70% - 95%, it is then compressed and formed by the high-pressure clamping force of the injection molding machine.

[0018] Its action sequence is: cylinder ejection → driving the ejector plate and the straight ejector to eject a distance S → injection filling → when filling to 70% - 95% → high-pressure clamping compression → mold water channel cooling → mold opening → product ejection → picking → mold closing.

[0019] During the injection molding stage, it is necessary to ensure that the force for ejecting the distance S is greater than the injection pressure and less than the injection pressure to meet the conditions of low-pressure molding. Usually, it is necessary to complete the ejection by arranging multiple cylinders with balanced forces on the ejector plate. From Figure 2 it can be seen that there are many oil circuits connected to the mold, and oil leakage problems often occur during installation and production use, and the pressure-holding and maintenance cycles are very short, the cost is extremely high, and the production is unstable. Summary of the Invention

[0020] Based on this, in view of the problems of the existing technology, it is necessary to provide an ejection structure for a low-pressure injection molding mold.

[0021] To solve the problems of the existing technology, the technical solution adopted by the present invention is:

[0022] An ejection structure for a low-pressure injection molding mold, the low-pressure injection molding mold includes a second male template, a second ejector plate, and a second lower fixing plate. The ejection structure includes a guide post vertically arranged on the top of the second lower fixing plate, and the second ejector plate is provided with a first through hole through which the guide post can pass; and an elastic member sleeved on the guide post, the injection pressure < the resilience of the elastic member < the clamping force; during the compression stage, the second male template abuts against the guide post, the second ejector plate abuts against the elastic member, and the elastic member is in a compressed state; during the injection molding stage, the second male template abuts against the guide post, the second ejector plate abuts against the elastic member, and the elastic member is in a rebounding state.

[0023] Further, the top of the guide post is provided with a first annular flange protruding radially outward. When the elastic member is in a rebounding state, the two ends of the elastic member respectively abut against the first annular flange and the second lower fixing plate.

[0024] Further, the ejection structure further includes a third limit post vertically arranged at the bottom of the second male template, and the third limit post passes through the first through hole and abuts against the guide post.

[0025] Further, the second ejector plate is provided with a second annular flange extending radially inward from the inner wall of the top end of the first through hole. A second through hole is formed inside the second annular flange, and the outer diameter of the third limit post < the inner diameter of the second through hole < the outer diameter of the first annular flange.

[0026] Furthermore, the resilience of the elastic member > injection pressure × 1.5, and the clamping force > resilience of the elastic member × 1.5.

[0027] Furthermore, the elastic member includes a first cushion block, a spring, and a second cushion block. The first cushion block and the second cushion block are respectively arranged at both ends of the spring.

[0028] Furthermore, the clearance between the spring and the guide post is 0.5 - 1.0 mm.

[0029] Furthermore, the spring adopts a stacked spring.

[0030] The beneficial effects of the present application compared with the prior art are as follows:

[0031] The ejection structure with a new type of stacked spring is applied to the low-pressure injection molding die, and the oil cylinder is replaced to complete the pre-pressing and ejection action. Canceling the oil cylinder will not cause oil leakage, and there is no need for pressure holding and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the mold opening sequence diagram of the low-pressure injection molding die in the prior art;

[0033] Figure 2 is the layout diagram of the oil cylinder ejection of the existing low-pressure injection molding die;

[0034] Figure 3 is the ejection schematic diagram of the oil cylinder return stage of the existing low-pressure injection molding process;

[0035] Figure 4 is the schematic diagram of the oil cylinder ejection stage of the existing low-pressure injection molding process;

[0036] Figure 5 is the schematic diagram of the compression stage of the new ejection structure pattern of the low-pressure injection molding process in the embodiment;

[0037] Figure 6 is the schematic diagram of the injection stage of the new ejection structure pattern of the low-pressure injection molding process in the embodiment;

[0038] The reference numerals in the figure are:

[0039] 1a - first female template; 2a - first product; 3a - first wear-resistant block; 4a - first straight ejector block; 5a - first straight ejector rod; 6a - first male template; 7a - first limit post; 8a - first ejector plate; 9a - first oil cylinder; 10a - first oil cylinder connecting screw; 11a - first oil cylinder cushion block; 12a - first oil cylinder support block; 13a - first lower fixing plate;

[0040] 1b - Second female template; 2b - Second product; 3b - Second wear-resistant block; 4b - Second direct ejector block; 5b - Second direct ejector rod; 6b - Second male template; 7b - Second limit post; 8b - Third limit post; 9b - Second ejector plate; 10b - Guide post; 11b - First cushion block; 12b - Spring; 13b - Second cushion block; 14b - Second lower fixing plate

[0041] W - Wall thickness of the product; S - Distance of cavity opening Specific implementation manner

[0042] To further understand the features, technical means, specific purposes and functions achieved by the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners

[0043] As Figure 5 and Figure 6 shown

[0044] An ejection structure of a low-pressure injection molding die. The low-pressure injection molding die includes a second male template 6b, a second ejector plate 9b and a second lower fixing plate 14b. The ejection structure includes a guide post 10b vertically arranged on the top of the second lower fixing plate 14b. The second ejector plate 9b is provided with a first through hole through which the guide post 10b can pass; and an elastic member sleeved on the guide post 10b, where the injection pressure < the resilience of the elastic member < the clamping force; during the compression stage, the second male template 6b abuts against the guide post 10b, the second ejector plate 9b abuts against the elastic member, and the elastic member is in a compressed state; during the injection stage, the second male template 6b abuts against the guide post 10b, the second ejector plate 9b abuts against the elastic member, and the elastic member is in a rebounding state

[0045] Based on the above embodiment, since the second direct ejector block 4b is connected to the second ejector plate 9b through the second direct ejector rod 5b, during the injection stage, the second ejector plate 9b is acted on by the resilience of the elastic member, so that the second direct ejector block 4b is ejected from the second male template 6b. During the compression stage, under the action of the clamping force, the second female template 1b presses the second direct ejector block 4b downward, causing it to drive the second direct ejector rod 5b and the second ejector plate 9b to press the elastic member, and the elastic member is compressed. The second direct ejector block 4b returns to the inside of the second male template 6b. In these two stages, the second male template 6b does not move

[0046] Combined with Figure 1 , the action sequence of the above embodiment is: clamping → opening S distance again → the second direct ejector block 4b is ejected S distance under the action of the resilience of the elastic member → injection filling → when filling to 70% - 95% → high-pressure clamping and compression → mold waterway cooling → mold opening → the second direct ejector block 4b is ejected S distance → product ejection → part taking → clamping

[0047] Further, a first annular flange 10b1 protruding radially outward is provided at the top of the guide post 10b. When the elastic member is in the resilient state, the two ends of the elastic member respectively abut against the first annular flange 10b1 and the second lower fixing plate 14b.

[0048] Based on the above embodiment, the first elastic flange is used to limit the maximum length of the elastic member, so that the distance S ejected by the second direct ejector block 4b is controllable.

[0049] Further, the ejection structure further includes a third limit post 8b vertically arranged at the bottom of the second male template 6b. The third limit post 8b passes through the first through hole and abuts against the guide post 10b.

[0050] Based on the above embodiment, the third limit post 8b can shorten the length of the guide post 10b and reduce the difficulty of machining the guide post 10b.

[0051] Further, a second annular flange 9b1 extending radially inward from the inner wall of the top end of the first through hole is provided on the second ejector plate 9b. A second through hole is formed inside the second annular flange 9b1. The outer diameter of the third limit post 8b < the inner diameter of the second through hole < the outer diameter of the first annular flange 10b1.

[0052] Based on the above embodiment, during the compression stage, the third limit post 8b can pass through the second through hole and abut against the guide post 10b, so that the second male template 6b stops moving, while the second ejector plate 9b can continue to move downward until the second annular flange 9b1 abuts against the first annular flange 10b1; during the injection molding stage, the second female template 1b moves away from the second lower fixing plate 14b under the action of the injection molding machine, the second male template 6b stops in place, and the second ejector plate 9b moves away from the second lower fixing plate 14b under the action of the elastic member until one end of the elastic member abuts against the first annular flange 10b1. Then, the distance S that the second direct ejector block 4b moves is equal to the axial length of the first through hole minus the axial length of the first annular flange 10b1, so that the distance S is further controllable.

[0053] Further, the resilience of the elastic member > injection pressure × 1.5, and the clamping force > resilience of the elastic member × 1.5;

[0054] Based on the above embodiment, the resilience of the elastic member cannot be close to the injection pressure or the clamping force, because the resilience of the elastic member is affected by its own compression degree and temperature.

[0055] Further, the elastic member includes a first cushion block 11b, a spring 12b, and a second cushion block 13b. The first cushion block 11b and the second cushion block 13b are respectively arranged at both ends of the spring 12b.

[0056] Based on the above embodiments, in order to prevent the spring 12b from pressing and damaging the second lower fixing plate 14b or the first annular flange 10b1, the first cushion block 11b and the second cushion block 13b are needed for padding.

[0057] Furthermore, the clearance between the spring 12b and the guide post 10b is 0.5 - 1.0 mm.

[0058] Based on the above embodiments, too large a clearance between the guide post 10b and the spring 12b will affect the ejection stroke.

[0059] Furthermore, the spring 12b adopts a stacked spring.

[0060] In addition, it should be noted that the hardness of the guide post 10b, the first cushion block 11b and the second cushion block 13b all reaches 58 - 60 HRC and will not be damaged during the movement of the spring 12b.

[0061] The beneficial effects of this application compared with the prior art are as follows:

[0062] The ejection structure with a new stacked spring is applied to the mold for low-pressure injection molding, and the oil cylinder is replaced to complete the pre-pressing and ejection action. Canceling the oil cylinder will not cause oil leakage, and there is no need for pressure holding and maintenance.

[0063] The above embodiments only represent one or several implementation manners of the present invention, and the description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims

1. An ejection structure of a low-pressure injection molding die. The low-pressure injection molding die includes a second male template (6b), a second ejector plate (9b), and a second lower fixing plate (14b). Characterized in that, The ejection structure includes A guide post (10b) vertically arranged on the top of the second lower fixing plate (14b). There is a first through hole on the second ejector plate (9b) through which the guide post (10b) can pass; and An elastic member sleeved on the guide post (10b), where injection pressure < resilience of the elastic member < clamping force; During the compression stage, the second male template (6b) abuts against the guide post (10b), the second ejector plate (9b) abuts against the elastic member, and the elastic member is in a compressed state; During the injection stage, the second male template (6b) abuts against the guide post (10b), the second ejector plate (9b) abuts against the elastic member, and the elastic member is in a rebounding state; A first annular flange (10b1) protruding radially outward is provided at the top of the guide post (10b). When the elastic member is in a rebounding state, both ends of the elastic member abut against the first annular flange (10b1) and the second lower fixing plate (14b) respectively; The ejection structure further includes a third limit post (8b) vertically arranged at the bottom of the second male template (6b). The third limit post (8b) passes through the first through hole and abuts against the guide post (10b).

2. The ejection structure of a low-pressure injection molding die according to claim 1, Characterized in that, A second annular flange (9b1) extending radially inward from the inner wall of the top end of the first through hole is provided on the second ejector plate (9b). A second through hole is formed inside the second annular flange (9b1), and the outer diameter of the third limit post (8b) < the inner diameter of the second through hole < the outer diameter of the first annular flange (10b1).

3. The ejection structure of a low-pressure injection molding die according to claim 1, Characterized in that, The resilience of the elastic member > injection pressure × 1.5, and the clamping force > resilience of the elastic member × 1.

5.

4. The ejection structure of a low-pressure injection molding die according to claim 1, Characterized in that, The elastic member includes a first cushion block (11b), a spring (12b), and a second cushion block (13b). The first cushion block (11b) and the second cushion block (13b) are respectively arranged at both ends of the spring (12b).

5. The ejection structure of a low-pressure injection molding die according to claim 4, Characterized in that, The clearance between the spring (12b) and the guide post (10b) is 0.5 - 1.0 mm.

6. The ejection structure of a low-pressure injection molding die according to claim 1, Characterized in that, The spring (12b) adopts a stacked spring.

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