Easy-to-demould mould for variable cross-section long pipe

Abstract

A mold easy to demold for a variable cross-section long pipe comprises a first mold body, a second mold body, a first mold core and a second mold core, the first mold core is installed on the first mold body, the second mold core is installed on the second mold body, and a positioning plate is arranged on the face, close to the first mold body, of the second mold body. A positioning groove is formed in the face, close to the first mold body, of the second mold body and can contain the positioning plate. A mold core hole is formed in the positioning plate, and the second mold core penetrates through the mold core hole. And the positioning plate is fixed on the second die body through a bolt. A second positioning table is arranged on the second mold core, and the diameter of the second positioning table is larger than that of the mold core hole; the left side of the second positioning table is positioned by the positioning plate, and the right side of the second positioning table is positioned by the second mold body.

Description

Technical Field

[0001] This invention relates to an easy-to-demold mold, and more particularly to an easy-to-demold mold for a long tube with a variable cross-section. Background Technology

[0002] In the pen manufacturing industry, pen tubes are produced using injection molding, which requires injection molds. The mold consists of a moving mold and a stationary mold. Both the moving and stationary molds are composed of a main body and a core. The core can be divided into an inner core and an outer core. The inner core forms the inner cavity of the pen tube, and the outer core forms the outer wall. The core fits precisely to the main body, generally using a clearance fit, but the clearance value is very small, or a transition fit. For pen tubes with a single cross-section, this is easy to process. However, in practice, many pen tubes are composed of a relatively long section of pen tube with a uniform cross-section (containing the pen refill or ink, and held by the hand), and a section connected to this uniform cross-section pen tube with a gradually decreasing cross-section, creating a variable cross-section pen tube that is larger at one end and smaller at the other. The cross-section of this variable cross-section pen tube can be circular, rectangular, elliptical, triangular, etc.

[0003] Due to limitations in manufacturing technology, the mold cores used to produce these variable cross-section pen tubes currently consist of two parts: a longer, uniform cross-section mold core and a shorter, variable cross-section mold core. After processing, the two mold core parts are installed separately onto the main body of the mold, and the two main bodies are then joined together and secured with screws. During operation, these two main mold bodies function as a single unit. That is, only during processing are the main body and the mold core separate parts; however, during operation, they form an inseparable whole.

[0004] When installing the mold core onto the main body, the installation direction is from the mating surface. In this way, when the main body is put together, the mating surface positions the mold core, keeping the mold core stationary.

[0005] During normal injection molding, a dozen or even dozens of pen tubes are injected simultaneously. The normal demolding process is as follows: the moving mold drives the inner mold core to move, the inner mold core drives the pen tube to move and leave the stationary mold, and the pen tube detaches from the inner mold core and enters the material channel. In the above process, the movement of the pen tube is mainly driven by the friction between the inner mold core and the inner wall of the pen tube. This presents the first problem: there is also friction between the outer wall of the pen tube and the outer mold core, and since the inner and outer mold cores are made of the same material and have a basically the same contact area, sometimes the inner mold core cannot drive the pen tube to move, causing the pen tube to remain inside the mold. The consequence of this is that the next injection molding process will continue to inject raw material, and the amount of raw material injected in each injection molding process is the same. Since one or even several pen tubes remain in the mold, the excess raw material will be distributed in the other pen tubes. This requires a larger clamping force to compress more raw material, which will damage the machine and also reduce product quality.

[0006] One method to solve this problem is to create grooves on the inner mold core, which will form ribs on the pen tube that match the grooves. The pen tube can then be moved by the interaction of the grooves and ribs. However, this brings at least two problems: first, creating grooves incurs additional processing costs; second, the ribs on the pen tube will create stress and result in uneven gloss, affecting the pen tube's appearance. Summary of the Invention

[0007] To address the technical problem of unsuccessful demolding in the prior art, this invention provides an easy-to-demold mold for long tubes with variable cross-sections.

[0008] A mold for easy demolding of a long tube with variable cross-section includes a first mold body, a second mold body, a first mold core, and a second mold core. The first mold core is installed on the first mold body, and the second mold core is installed on the second mold body. The second mold body has a positioning plate on the surface close to the first mold body.

[0009] The second mold body has a positioning groove on the surface close to the first mold body, and the positioning groove can accommodate the positioning plate.

[0010] The positioning plate is provided with a mold core hole, and the second mold core passes through the mold core hole.

[0011] The positioning plate is fixed to the second mold body by bolts.

[0012] The second mold core is provided with a second positioning platform, the diameter of which is larger than the diameter of the mold core hole; the left side of the second positioning platform is positioned by the positioning plate, and the right side is positioned by the second mold body.

[0013] After the first mold body and the second mold body are pressed together, the first mold core and the second mold core are also in a tightly joined state.

[0014] A first positioning platform is provided on the left side of the first mold core. The first mold core is inserted into the first mold body from the surface of the first mold body that is away from the mating surface of the first mold body and the second mold body. The left side of the first positioning platform is positioned by the sprue plate, and the right side is positioned by the first mold body.

[0015] A spring is provided between the first mold body and the second mold body. When the spring is in a free state, it ensures that the first mold body and the second mold body are in a separated state.

[0016] The first mold body and the second mold body are provided with spring grooves at their mating surfaces.

[0017] The first mold body is provided with a first mold core hole, the first positioning platform is provided with a first positioning notch, the first mold core hole is provided with a first mold core hole notch, and the first positioning notch cooperates with the first mold core notch to keep the first mold core in a unique position.

[0018] The second mold body is provided with a second mold core hole, the second positioning platform is provided with a second positioning notch, the second mold core hole is provided with a second mold core hole notch, and the second positioning notch cooperates with the second mold core notch to keep the second mold core in a unique position. Attached Figure Description

[0019] Figure 1 This is a cross-sectional view of the exploded view of the present invention.

[0020] Figure 2 This is a perspective view of the exploded view of the present invention.

[0021] Figure 3 This is a view from one direction after the first mold body is assembled and the second mold body is assembled.

[0022] Figure 4 This is a view from another direction after the first mold body is assembled and the second mold body is assembled.

[0023] Figure 5 , 6 This is a schematic diagram of the structure of the first mold core and the second mold core.

[0024] In the figure: 1-First mold body, 2-Second mold body, 3-Second mold core, 4-Positioning plate, 5-Positioning groove, 6-Mold core hole, 7-First mold core, 8-Grate plate, 9-Second positioning platform, 10-First positioning platform, 11-First mold core hole, 12-Second mold core hole, 13-First positioning notch, 14-First mold core notch, 15-Second positioning notch, 16-Second mold core notch, 17-Spring. Detailed Implementation

[0025] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The scope of protection of the present invention is not limited to the specific embodiments described below. Conventional modifications and substitutions made by those skilled in the art based on the technical solutions of the present invention are all within the scope of protection of the present invention.

[0026] The easy-to-demold mold for variable cross-section long tubes described in this invention is mainly used in the injection molding production of variable cross-section pen tubes in the pen manufacturing industry. It can also be adapted to the injection molding of other variable cross-section long tubes in the field of small pipe fittings. Through the structural design of precise positioning of split mold core and step-by-step mold opening assisted by spring, it solves the technical problems of pen tubes being easily stuck during demolding of traditional molds and the need to open grooves, which leads to a decline in product quality. At the same time, it realizes convenient mold disassembly and quick mold core replacement.

[0027] Combination Figures 1-6 The mold includes a first mold body 1, a second mold body 2, a first mold core 7, a second mold core 3, a positioning plate 4, a sprue plate 8, and a spring 17. The first mold core 7 is a uniform cross-section mold core adapted to a uniform cross-section segment of the pen tube, and the second mold core 3 is a variable cross-section mold core adapted to a variable cross-section segment of the pen tube. After the two are joined together, they form a complete pen tube inner cavity forming mold core, which is adapted and installed with the first mold body 1 and the second mold body 2 respectively, and together completes the injection molding of the variable cross-section pen tube.

[0028] I. Assembly Structure and Positioning Method of Each Component (a) Assembly and positioning of the second mold body and the second mold core 1. The second mold body 2 has a positioning groove 5 at the mating surface near the first mold body 1. The size of the positioning groove 5 is adapted to the positioning plate 4 and can fully accommodate the positioning plate 4, so that the positioning plate 4 is flush with the mating surface of the second mold body 2 after installation, avoiding interference when the mold is closed. The positioning plate 4 has a mold core hole 6, and the second mold core 3 passes through the mold core hole 6. The positioning plate 4 is fixed in the positioning groove 5 of the second mold body 2 by at least two sets of bolts. The bolts are symmetrically distributed to ensure the flatness and stability of the positioning plate 4 during installation.

[0029] 2. The second positioning platform 9 is integrally formed in the middle of the second mold core 3. The outer diameter of the second positioning platform 9 is larger than the diameter of the mold core hole 6 on the positioning plate 4, and the outer diameter of the second positioning platform 9 and the diameter of the second mold core hole 12 opened in the second mold body 2 are precisely clearance-fitted (fitting clearance 0.005-0.02mm). After the second mold core 3 is inserted into the second mold core hole 12, the left end face of the second positioning platform 9 is tightly fitted with the right end face of the positioning plate 4, and the right end face is tightly fitted with the stepped surface of the second mold core hole 12. Through the bidirectional limiting of the positioning plate 4 and the second mold body 2, the axial positioning of the second mold core 3 is realized, preventing the mold core from axially moving during the injection molding process.

[0030] 3. The outer wall of the second positioning platform 9 is provided with a second positioning notch 15, and the inner wall of the second mold core hole 12 is provided with a corresponding second mold core notch 16. After the two are fitted together, a circumferential anti-rotation structure is formed, so that the second mold core 3 maintains a unique circumferential position in the second mold body 2, avoiding the product cross-section forming deviation caused by the rotation of the mold core during injection molding, and ensuring the forming accuracy of the variable cross-section pen tube.

[0031] (ii) Assembly and positioning of the first mold body and the first mold core 1. A first mold core hole 11 is provided in the first mold body 1. The first mold core 7 is inserted into the first mold core hole 11 from the outer end face of the first mold body 1 away from the joint surface of the first and second mold bodies. Its assembly direction is different from the traditional mold core installation method from the joint surface, so as to avoid interference of the joint surface in positioning the mold core when the mold is closed and improve the convenience of mold core installation.

[0032] 2. The left end of the first mold core 7 is integrally formed with a first positioning platform 10. The outer diameter of the first positioning platform 10 and the diameter of the first mold core hole 11 are precisely clearance-fitted (fitting clearance 0.005-0.02mm). After the first mold core 7 is installed, the right end face of the first positioning platform 10 is tightly fitted with the stepped surface of the first mold core hole 11, and the left end face is tightly fitted with the right end face of the sprue plate 8. The axial positioning of the first mold core 7 is achieved through the bidirectional limiting of the first mold body 1 and the sprue plate 8. The sprue plate 8 is fixedly connected to the first mold body 1 and provides installation support for the injection sprue, so that the injection molding material is evenly injected into the mold cavity through the sprue.

[0033] 3. The outer wall of the first positioning platform 10 is provided with a first positioning notch 13, and the inner wall of the first mold core hole 11 is provided with a corresponding first mold core notch 14. Its structure is the same as that of the second positioning notch 15 and the second mold core notch 16. When the two are combined, the first mold core 7 is prevented from rotating circumferentially, ensuring the coaxiality (coaxiality error ≤ 0.01mm) when the first mold core 7 and the second mold core 3 are docked.

[0034] (iii) Mold core mating and mold body fitting 1. The right end face of the first mold core 7 and the left end face of the second mold core 3 are both precision-polished flat mating surfaces. When the first mold body 1 and the second mold body 2 are closed and pressed together under the action of external force, the mating surfaces of the first mold core 7 and the second mold core 3 are tightly joined without gaps, which prevents the raw material from overflowing from the mating surface during injection molding and forming flash, thus ensuring the molding quality of the inner cavity of the pen tube.

[0035] 2. Spring grooves are symmetrically provided at the joint surfaces of the first mold body 1 and the second mold body 2. Spring 17 is embedded in the spring grooves, and the two ends of spring 17 are in close contact with the bottom surfaces of the spring grooves of the first mold body 1 and the second mold body 2, respectively. Spring 17 is a compression spring. In the free state, its elastic restoring force can push the first mold body 1 and the second mold body 2 to separate from each other, so that the two maintain a preset separation distance, providing power for the step-by-step mold opening during demolding. When the mold is closed by external force, spring 17 is completely compressed in the spring groove, which does not affect the specific mold closing and fitting of the first and second molds.

[0036] II. Mold Injection and Demolding Process The core innovation of this invention's mold is the spring-assisted step-by-step mold opening method. By changing the traditional overall mold opening form, the friction between the pen tube and the outer mold core is reduced during demolding, ensuring that the friction between the inner mold core and the inner wall of the pen tube is always greater than the friction between the inner and outer walls, thus achieving smooth demolding of the pen tube. The specific workflow is as follows: (a) Mold closing and injection molding stage 1. Under the action of external force (mold closing force of injection molding machine), the first mold body 1 moves to the second mold body 2, and the spring 17 is compressed in the spring groove until the mating surfaces of the first and second mold bodies are tightly fitted, and the mold closing is completed; at this time, the first mold core 7 and the second mold core 3 are tightly connected to form a complete inner mold core, which cooperates with the outer mold core of the mold to form the injection cavity of the pen tube.

[0037] 2. The injection molding material is injected into the injection cavity through the sprue on the sprue plate 8. After the material cools and solidifies, it forms a variable cross-section pen tube that matches the shape of the cavity. The inner wall of the pen tube is tightly fitted with the outer wall of the first and second mold cores, and the outer wall is tightly fitted with the inner wall of the outer mold core.

[0038] (II) Step-by-step mold opening and demolding stage 1. First step: Spring-driven initial mold opening reduces friction on the outer wall of the pen tube. After the clamping force of the injection molding machine is removed, the spring 17 pushes the first mold body 1 and the second mold body 2 to separate from each other along the mating surface, forming an initial mold opening gap (the gap is 5-10mm, determined by the spring stroke); during this process, part of the outer mold core of the mold separates synchronously with the first and second mold bodies, and the friction of this part no longer exists after separation.

[0039] 2. Second step: The moving mold drives the inner mold core to move, thus demolding the pen tube. After the initial mold opening, the moving mold of the injection molding machine drives the first mold body 1 and the first mold core 7 to continue moving away from the second mold body 2. At this time, the static friction between the first mold core 7 and the inner wall of the pen tube does not change and is greater than the dynamic friction between the outer wall of the pen tube and the outer mold core. Driven by the first mold core 7, the pen tube moves together with the inner mold core, breaks free from the constraints of the second mold core 3 and the outer mold core, and finally separates from the inner mold core, enters the material channel, and completes the demolding.

[0040] (III) Reset Phase After demolding, the clamping force of the injection molding machine acts on the first mold body 1 again, pushing it to move towards the second mold body 2. The spring 17 is compressed again until the first and second mold bodies are closed and fitted together. The mold returns to its initial state before mold closing and injection molding, ready for the next injection molding operation.

[0041] III. Beneficial Effects of the Invention Through the above-described structural design and operating method, this invention has the following significant advantages compared to traditional variable cross-section pen tube injection molds: 1. Achieve smooth demolding without grooves: By using a spring-assisted step-by-step mold opening method, the friction between the outer wall of the pen tube and the outer mold core is reduced during demolding. This allows the inner mold core to drive the pen tube to demold by relying on the friction between it and the inner wall of the pen tube. There is no need to open grooves on the inner mold core, which avoids stress concentration and uneven gloss caused by the formation of ribs on the pen tube, thus improving the product's aesthetics and quality.

[0042] 2. Avoid pen tube sticking in the mold: The step-by-step mold opening method effectively solves the problem of pen tube sticking during demolding in traditional molds, avoiding material waste, increased mold closing force and machine damage caused by pen tube sticking, extending the service life of injection molding machines and molds, and reducing production losses.

[0043] The above-described specific embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent modifications and substitutions made based on the technical solutions of the present invention should be included in the scope of protection of the present invention.

Claims

1. A mold for easy demolding of a long tube with variable cross-section, characterized in that: The mold includes a first mold body, a second mold body, a first mold core, and a second mold core. The first mold core is installed on the first mold body, and the second mold core is installed on the second mold body. The second mold body has a positioning plate on the surface near the first mold body. The second mold body has a positioning groove on the surface near the first mold body, and the positioning groove can accommodate the positioning plate.

2. A mold for easy demolding of a long tube with variable cross-section, characterized in that: The positioning plate is provided with a mold core hole, and the second mold core passes through the mold core hole.

3. A mold for easy demolding of a long tube with variable cross-section, characterized in that: The positioning plate is fixed to the second mold body by bolts.

4. A mold for easy demolding of a long tube with variable cross-section, characterized in that: The second mold core is provided with a second positioning platform, the diameter of which is larger than the diameter of the mold core hole; the left side of the second positioning platform is positioned by the positioning plate, and the right side is positioned by the second mold body.

5. A mold for easy demolding of a long tube with variable cross-section, characterized in that: After the first mold body and the second mold body are pressed together, the first mold core and the second mold core are also in a tightly joined state.

6. A mold for easy demolding of a long tube with variable cross-section, characterized in that: A first positioning platform is provided on the left side of the first mold core. The first mold core is inserted into the first mold body from the surface of the first mold body that is away from the mating surface of the first mold body and the second mold body. The left side of the first positioning platform is positioned by the sprue plate, and the right side is positioned by the first mold body.

7. A mold for easy demolding of a long tube with variable cross-section, characterized in that: A spring is provided between the first mold body and the second mold body. When the spring is in a free state, it ensures that the first mold body and the second mold body are in a separated state.

8. A mold for easy demolding of a long tube with variable cross-section, characterized in that: The first mold body and the second mold body are provided with spring grooves at their mating surfaces.

9. A mold for easy demolding of a long tube with variable cross-section, characterized in that: The first mold body is provided with a first mold core hole, the first positioning platform is provided with a first positioning notch, the first mold core hole is provided with a first mold core hole notch, and the first positioning notch cooperates with the first mold core notch to keep the first mold core in a unique position.

10. A mold for easy demolding of a long tube with variable cross-section, characterized in that: The second mold body is provided with a second mold core hole, the second positioning platform is provided with a second positioning notch, the second mold core hole is provided with a second mold core hole notch, and the second positioning notch cooperates with the second mold core notch to keep the second mold core in a unique position.

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