A demolding mechanism for whole-circle back-drafting of small inner diameter products
Patent Information
- Application Number
- CN202610843266.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-11
- Publication Date
- 2026-09-11
AI Technical Summary
[0003]对于内径尺寸较小且内壁具有整圈连续倒扣结构的塑料产品，其脱模机构的设计尤为困难，现有技术中常用的解决方案，例如利用软胶型芯依靠弹性强制脱模，极易导致产品损伤且型芯寿命短，对倒扣尺寸限制严苛；而采用多个细小滑块拼合的爆炸型芯结构，虽能实现脱模，但在狭小的内径空间内，这些滑块因尺寸被迫微型化而变得结构单薄、刚性严重不足，在注塑机持续的高压注射和顶出循环中，极易发生断裂、变形或过早磨损，从而导致机构使用寿命短、维修频繁、生产成本高且生产效率低下
1、该用于小内径产品整圈倒扣的脱模机构，通过由多个内缩滑块共同围合构成环状型芯，并采用中心对称的A、B两组交错压合安装方式，巧妙地解决了小内径空间的限制问题，同时极大地增强了整个组合型芯的径向刚性和结构稳定性，使得整个脱模机构在注塑高压下能有效抵抗变形。
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Figure CN122723947A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of injection molds, and in particular to a demolding mechanism for small inner diameter products with full-circle undercut. Background Technology
[0002] Injection molds are crucial molding equipment in the injection molding process. They are precision combination tools, typically consisting of two main parts: a moving mold and a fixed mold. After the two molds are closed, they form a cavity and gating system that match the shape and size of the desired plastic product. During injection molding, molten plastic raw material is injected into the mold cavity under high pressure from the injection molding machine. After cooling and solidification, the moving mold and fixed mold separate, allowing the molded plastic product to be removed from the mold. Injection molds can efficiently, accurately, and in large quantities produce various plastic parts with complex shapes and high dimensional accuracy requirements, and are widely used in many industries such as automobiles, electronics, home appliances, and daily necessities.
[0003] For plastic products with small inner diameters and continuous undercut structures on the inner wall, the design of their demolding mechanisms is particularly difficult. Commonly used solutions in existing technologies, such as using soft rubber cores to force demolding through elasticity, are prone to product damage and have short core lifespans, and impose strict limitations on the undercut dimensions. While using an explosive core structure composed of multiple small sliders can achieve demolding, these sliders become structurally thin and lack rigidity due to their forced miniaturization within the confined inner diameter space. Under the continuous high-pressure injection and ejection cycles of the injection molding machine, they are prone to breakage, deformation, or premature wear, resulting in short service life, frequent maintenance, high production costs, and low production efficiency. Summary of the Invention
[0004] To achieve the above objectives, the present invention provides the following technical solution: a demolding mechanism for undercutting small inner diameter products around the entire circle, which is set in the moving mold part of the injection mold, including an inward core-pulling rod as the core driving component, wherein the middle or effective working section is a truncated cone or inclined plane structure. The first connecting rod is located inside the retractable core-pulling rod, and one end of the first connecting rod extends to the left side of the retractable core-pulling rod; The second connecting rod is located on the side of the retractable core-pulling rod away from the first connecting rod, and one end of the second connecting rod extends to the right side of the retractable core-pulling rod; The first insert is located on the outside of the inward-retracting core puller; The pin passes through the first insert, the inward-retracting core rod, and the first connecting rod; The number of the six inward sliding blocks is six, and the six inward sliding blocks together form a ring structure to form the inner wall molding surface of the injection molded product. The second insert is located on the outside of the first connecting rod.
[0005] Preferably, the inner core-pulling rod has an internal mounting groove that matches the first connecting rod, the right side of the inner core-pulling rod has a T-shaped groove, and the left end of the second connecting rod is a T-shaped block that matches the T-shaped groove.
[0006] Preferably, the inner core rod has a clearance hole adapted to the movement trajectory of the pin, the first connecting rod has a first through hole adapted to the pin, and the first insert has a second through hole adapted to the pin.
[0007] Preferably, the inner walls of the six retractable sliders are all in contact with the conical or inclined surface of the retractable core-pulling rod. The right side of the six retractable sliders is in contact with the surface of the first insert and the left side is in contact with the surface of the second insert. The six retractable sliders are divided into two groups, A and B, with equal numbers and centrally symmetrical distribution. The retractable sliders in group A are directly attached to the outside of the retractable core-pulling rod, and the retractable sliders in group B are attached to the outside of the retractable core-pulling rod and pressed against the outside of the retractable sliders in group A.
[0008] Preferably, the right side of the first insert has a movable groove that matches the movement trajectory of the retractable core-pulling rod, the end of the first connecting rod extending to the left side of the retractable core-pulling rod has an external thread, and the interior of the second insert has an internal thread that matches the external thread.
[0009] Preferably, the entire demolding mechanism has two working states: a closed state and an open state. When in the closed state, the conical or inclined surface of the inner core-pulling rod forces the six circumferentially distributed inner sliding blocks to expand outward to the forming position, together forming a complete product inner cavity core. When in the open state, the second connecting rod pulls the inner core-pulling rod to the right, and the inner sliding blocks synchronously retract radially inward towards the central axis under the guidance of the conical or inclined surface of the inner core-pulling rod.
[0010] Preferably, in the closed state, the pin is located at the rightmost end of the clearance hole on the retractable core rod, and the first insert provides radial restraint to the retractable core rod through the pin.
[0011] Preferably, during the open state process, the second connecting rod drives the retractable core-pulling rod to move to the right until the pin is located at the leftmost end of the clearance hole on the retractable core-pulling rod, and the first insert provides radial restraint to the retractable core-pulling rod through the pin.
[0012] Preferably, the second connecting rod is connected to the moving mold fixing part of the injection mold, and is used to provide a driving force for pulling the inner core-pulling rod when the closed state is switched.
[0013] In summary, the present invention provides a demolding mechanism for full-circle undercutting of small inner diameter products, which has the following beneficial effects: 1. This demolding mechanism for small inner diameter products with full-circle undercutting is formed by multiple inward sliding blocks forming a ring-shaped core. It adopts a centrally symmetrical A and B sets of staggered pressing installation method, which cleverly solves the problem of limited space in small inner diameter products. At the same time, it greatly enhances the radial rigidity and structural stability of the entire combined core, so that the entire demolding mechanism can effectively resist deformation under injection high pressure.
[0014] 2. This demolding mechanism for small inner diameter products with full-circle undercutting uses the conical or inclined surface of the inner core-pulling rod to precisely match the inner sidewall of all the inner sliding blocks. With the single linear drive of the second connecting rod, the axial motion can be efficiently and synchronously converted into the radial inward movement of all the inner sliding blocks. Through the coordinated work of the inclined surface drive and synchronous inward movement, the demolding action is reliable.
[0015] 3. The demolding mechanism for small inner diameter products with full-circle undercutting is driven directly by the natural relative movement between the mold plates when the mold opens and closes. It does not rely on additional complex hydraulic or electrical systems. This not only simplifies the overall structure of the mold and reduces manufacturing costs, but also ensures strict synchronization between the driving force and the main movement of the mold. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the internal structure of the present invention; Figure 3 This is a schematic diagram of the exploded structure of the present invention; Figure 4 This is a schematic diagram of the structure at the inward-retracting core-pulling rod of the present invention; Figure 5 This is a schematic diagram of the structure at the connection between the retractable core-pulling rod and the retractable slider of the present invention. Figure 6 This is a schematic diagram of the structure of the present invention in the closed state; Figure 7 This is a schematic diagram of the structure of the present invention in the open state.
[0017] Explanation of reference numerals in the attached figures: 1. Retractable core-pulling rod; 2. First connecting rod; 3. Second connecting rod; 4. First inlay; 5. Pins; 6. Retractable slider; 7. Second inlay. Detailed Implementation
[0018] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Example
[0019] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown, a demolding mechanism for undercutting small inner diameter products is provided in the moving mold part of the injection mold, including an inward core-pulling rod 1 as the core driving component, the middle or effective working section of which is a truncated cone or inclined plane structure. The first connecting rod 2 is located inside the retractable core-pulling rod 1, and one end of the first connecting rod 2 extends to the left side of the retractable core-pulling rod 1; The second connecting rod 3 is located on the side of the retractable core-pulling rod 1 away from the first connecting rod 2, and one end of the second connecting rod 3 extends to the right side of the retractable core-pulling rod 1; The first insert 4 is located on the outside of the inward-retracting core-pulling rod 1; Pin 5 passes through the first insert 4, the inward-retracting core rod 1, and the first connecting rod 2; There are six retractable sliders 6. The six retractable sliders 6 together form a ring structure, which is used to form the inner wall molding surface of the injection molded product. The second insert 7 is disposed on the outside of the first connecting rod 2.
[0020] like Figure 2 , Figure 4 and Figure 5 As shown, the inner core-pulling rod 1 has an installation groove that matches the first connecting rod 2 inside, and a T-shaped groove is provided on the right side of the inner core-pulling rod 1. The left end of the second connecting rod 3 is a T-shaped block that matches the T-shaped groove.
[0021] By setting the mounting slot, it is ensured that the first connecting rod 2 can be stably installed inside the retractable core-pulling rod 1. By opening a T-shaped groove on the right side of the retractable core-pulling rod 1 and cooperating with the T-shaped block at the left end of the second connecting rod 3, a reliable drive connection is formed, which allows the retractable core-pulling rod 1 to be precisely driven by the second connecting rod 3, while allowing the retractable core-pulling rod 1 to move relative to the first connecting rod 2 in the axial direction. like Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, the inner core rod 1 has a clearance hole that matches the movement trajectory of the pin 5, the first connecting rod 2 has a first through hole that matches the pin 5, and the first insert 4 has a second through hole that matches the pin 5.
[0022] The three core components, namely the inner retractable core-pulling rod 1, the first connecting rod 2, and the first insert 4, can be connected in series to form a movable connection through the pin 5. The cooperation between the pin 5 and the clearance hole on the inner retractable core-pulling rod 1 limits the movement stroke and trajectory of the inner retractable core-pulling rod 1 relative to the pin 5, ensuring that the inner retractable core-pulling rod 1 makes precise linear movement within a specific range and transmits the movement to the inner retractable slider 6.
[0023] like Figure 1 , Figure 2 , Figure 3 , Figure 5 , Figure 6 and Figure 7 As shown, the inner walls of the six retractable sliders 6 are all in contact with the conical or inclined surfaces of the retractable core-pulling rod 1. The right side of the six retractable sliders 6 is in contact with the surface of the first insert 4 and the left side is in contact with the surface of the second insert 7. The six retractable sliders 6 are divided into two groups, A and B, with equal numbers and centrally symmetrical distribution. The group A retractable sliders 6 are directly attached to the outside of the retractable core-pulling rod 1, while the group B retractable sliders 6 are attached to the outside of the retractable core-pulling rod 1 and pressed against the outside of the group A retractable sliders 6.
[0024] First, by forming a ring with multiple inward-shrinking sliders 6, the problem of designing a single large slider in a small inner diameter space is solved. Second, the staggered pressing design of the two sets of inward-shrinking sliders 6 (A and B) greatly enhances the radial rigidity and structural stability of the entire annular core. Under high injection pressure, it can effectively prevent the inward-shrinking sliders 6 from radially deforming or shifting, ensuring the accuracy of the inner wall dimensions of the injection-molded product and the accurate forming of the undercut shape.
[0025] like Figure 2 As shown, the right side of the first insert 4 has an active groove that matches the movement trajectory of the retractable core-pulling rod 1, the end of the first connecting rod 2 extending to the left side of the retractable core-pulling rod 1 has an external thread, and the interior of the second insert 7 has an internal thread that matches the external thread.
[0026] The movable groove on the first insert 4 provides precise axial guidance for the movement of the inner retracting core-pulling rod 1, limiting its unnecessary wobble and ensuring the smoothness of the movement. The threaded connection between the first connecting rod 2 and the second insert 7 allows for easy adjustment of the initial position of the first connecting rod 2, thereby fine-tuning the forming position or demolding endpoint position of the inner retracting slider 6, enhancing the assembly flexibility and process adaptability of the mechanism.
[0027] like Figure 6 and Figure 7As shown, the entire demolding mechanism has two working states: closed and open. When in the closed state, the conical or inclined surface of the inner core-pulling rod 1 forces the six circumferentially distributed inner sliding blocks 6 to expand outward to the forming position, together forming a complete product inner cavity core. When in the open state, the second connecting rod 3 pulls the inner core-pulling rod 1 to the right, and the inner sliding blocks 6 synchronously retract radially inward towards the central axis under the guidance of the conical or inclined surface of the inner core-pulling rod 1.
[0028] In the closed state, the inner retracting core-pulling rod 1 drives the inner retracting slider 6 to expand outward for molding; in the open state, the second connecting rod 3 pulls the inner retracting core-pulling rod 1 to move, and by utilizing the conversion between the axial and radial movements of the inclined plane, the inner retracting slider 6 is driven to retract and demold; through the single linear pulling action of the second connecting rod 3, all six inner retracting sliders 6 can be driven simultaneously to complete precise radial retraction, thereby efficiently freeing up the undercut space of the injection molded product, realizing automated and non-destructive demolding of complex undercut structures under small inner diameter constraints.
[0029] like Figure 6 As shown, in the closed state, the pin 5 is located at the rightmost end of the clearance hole on the retractable core rod 1, and the first insert 4 provides radial restraint to the retractable core rod 1 through the pin 5.
[0030] This state limiting mechanism ensures that the final position of the entire core system is determined and locked during the injection and holding pressure stages. The inner core-pulling rod 1 cannot continue to move to the right, thus ensuring that its inclined surface pushes out the inner slider 6 and maintains it in the maximum outward expansion position. The molding surface dimensions are stable, and it prevents the entire mechanism from accidentally retracting under injection pressure, which could lead to defects in the injection molded product.
[0031] like Figure 7 As shown, during the opening process, the second connecting rod 3 drives the inner retractable core-pulling rod 1 to move to the right until the pin 5 is located at the leftmost end of the clearance hole on the inner retractable core-pulling rod 1, and the first insert 4 provides radial limit to the inner retractable core-pulling rod 1 through the pin 5.
[0032] When pin 5 reaches the leftmost end of the clearance hole, it means that the rightward movement of the inner core-pulling rod 1 and the inward movement of the inner slider 6 have both reached the design maximum value. The undercut space is completely cleared, and the limiting function of the first insert 4 prevents the entire mechanism from moving excessively, causing interference or damage to the parts, and ensures the integrity and repeatability of the demolding action.
[0033] like Figure 1 , Figure 2 , Figure 3 , Figure 6 and Figure 7 As shown, the second connecting rod 3 is connected to the moving mold fixing part of the injection mold, and is used to provide the driving force to pull the inner core-pulling rod 1 when the closed state is switched.
[0034] The driving source of the second connecting rod 3 is specifically designed as a fixed part of the mold, providing a stable driving force source. The tension or thrust is naturally generated by the relative movement between the mold plates when the mold is opened, without the need for additional complex hydraulic or electric devices. This reduces costs while ensuring the synchronization of the driving force with the mold opening and closing actions.
[0035] In use, the entire mechanism is connected to the moving mold fixed part of the mold via the second connecting rod 3 to ensure a stable power source. Initial position fine-tuning is completed via the threaded connection between the first connecting rod 2 and the second insert 7. When the mold begins to close, under the action of external power or the locking mechanism, the second connecting rod 3 pushes the retractable core-pulling rod 1 to the left until it reaches the designed closed position. During this process, the conical or inclined surface of the retractable core-pulling rod 1 begins to contact the inner walls of the six retractable sliders 6 and applies a radially outward thrust. Since the two sets of retractable sliders 6, A and B, are centrally symmetrical... Furthermore, they are staggered and pressed together, and receive axial support under the clamping of the first insert 4 and the second insert 7. They can smoothly and synchronously expand outward. When the inner core-pulling rod 1 moves to its limit position, the pin 5 also moves to the rightmost end relative to the clearance hole on the inner core-pulling rod 1. At this time, the first insert 4 forms a rigid radial limit on the inner core-pulling rod 1 through the pin 5, preventing any retraction. At the same time, the six inner sliding blocks 6 are completely pushed out to the maximum outward expansion position. They together form a complete annular core with a robust structure and precise dimensions. Its outer surface is the inner wall of the injection molded product. After the mold is fully closed, molten plastic is injected into the cavity and molded under high pressure. After holding pressure and cooling, the mold enters the mold opening and demolding stage. At this time, as the moving mold part begins to retract, the second connecting rod 3 generates a rightward pulling force under the traction of the fixed part of the moving mold. Through the cooperation of the T-slot and the T-block, it directly acts on the inner retracting core-pulling rod 1, causing it to begin to move to the right. As the inner retracting core-pulling rod 1 moves to the right, the position of its conical surface or inclined surface changes, and the radial support effect on the inner retracting slider 6 weakens. The six inner retracting sliders 6 are inclined on their inner sides. Guided by the surface, it begins to radially retract synchronously and smoothly towards the central axis of the mechanism, gradually making room for the undercut on the inner wall of the product. When the retracting core-pulling rod 1 is pulled to the end of its stroke, the pin 5 reaches the leftmost end of its clearance hole and is again limited by the first insert 4. At this time, the retracting slider 6 has also completed the retraction of the entire designed stroke, and its outer contour is completely separated from the undercut area of the product. Finally, the undercut constraint on the inner wall of the injection molded product is completely released, and the mold opening action can smoothly pull the entire shrunken core assembly out of the injection molded product, thus completing one demolding cycle.
[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A stripper mechanism for whole-circle undercuts of small inner diameter products, provided in the movable mold part of an injection mold, characterized in that: Including the inward core-pulling rod (1), as the core driving component, the middle or effective working section of which is a truncated cone or inclined plane structure; The first connecting rod (2) is located inside the retractable core-pulling rod (1), and one end of the first connecting rod (2) extends to the left side of the retractable core-pulling rod (1); The second connecting rod (3) is located on the side of the retractable core-pulling rod (1) away from the first connecting rod (2), and one end of the second connecting rod (3) extends to the right side of the retractable core-pulling rod (1). The first insert (4) is set on the outside of the inward-retracting core-pulling rod (1); The pin (5) passes through the first insert (4), the inward-retracting core rod (1), and the first connecting rod (2); The number of the six inner sliding blocks (6) is six, and the six inner sliding blocks (6) together form a ring structure to form the inner wall forming surface of the injection molded product; The second insert (7) is located on the outside of the first connecting rod (2).
2. The demolding mechanism for full-circle undercutting of small inner diameter products according to claim 1, characterized in that: The inner core-pulling rod (1) has an installation groove that matches the first connecting rod (2) inside. The inner core-pulling rod (1) has a T-shaped groove on its right side. The left end of the second connecting rod (3) is a T-shaped block that matches the T-shaped groove.
3. The demolding mechanism for full-circle undercutting of small inner diameter products according to claim 1, characterized in that: The inner core-pulling rod (1) has a clearance hole that matches the movement trajectory of the pin (5), the first connecting rod (2) has a first through hole that matches the pin (5), and the first insert (4) has a second through hole that matches the pin (5).
4. A demolding mechanism for full-circle undercutting of small inner diameter products according to claim 1, characterized in that: The inner walls of the six retractable sliders (6) are all in contact with the conical or inclined surface of the retractable core-pulling rod (1). The right side of the six retractable sliders (6) is in contact with the surface of the first insert (4) and the left side is in contact with the surface of the second insert (7). The six retractable sliders (6) are divided into two groups, A and B, with equal numbers and centrally symmetrical distribution. The retractable sliders (6) of group A are directly attached to the outside of the retractable core-pulling rod (1). The retractable sliders (6) of group B are attached to the outside of the retractable core-pulling rod (1) and pressed against the outside of the retractable sliders (6) of group A.
5. A demolding mechanism for full-circle undercutting of small inner diameter products according to claim 1, characterized in that: The right side of the first insert (4) is provided with a movable groove that matches the movement trajectory of the retractable core-pulling rod (1). The first connecting rod (2) extends to the left side of the retractable core-pulling rod (1) and is provided with an external thread. The interior of the second insert (7) is provided with an internal thread that matches the external thread.
6. A demolding mechanism for full-circle undercutting of small inner diameter products according to claim 3, characterized in that: The entire demolding mechanism has two working states: closed and open. When it is in the closed state, the conical or inclined surface of the inner core-pulling rod (1) forces the six circumferentially distributed inner sliding blocks (6) to expand outward to the forming position, together forming a complete product inner cavity core. When it is in the open state, the second connecting rod (3) pulls the inner core-pulling rod (1) to the right, and the inner sliding blocks (6) synchronously retract radially inward towards the central axis under the guidance of the conical or inclined surface of the inner core-pulling rod (1).
7. A demolding mechanism for full-circle undercutting of small inner diameter products according to claim 6, characterized in that: In the closed state, the pin (5) is located at the rightmost end of the clearance hole on the retractable core rod (1), and the first insert (4) provides radial restraint to the retractable core rod (1) through the pin (5).
8. A demolding mechanism for full-circle undercutting of small inner diameter products according to claim 6, characterized in that: During the opening process, the second connecting rod (3) drives the inner retractable core pull rod (1) to move to the right until the pin (5) is located at the leftmost end of the clearance hole on the inner retractable core pull rod (1), and the first insert (4) provides radial limit to the inner retractable core pull rod (1) through the pin (5).
9. A demolding mechanism for full-circle undercutting of small inner diameter products according to claim 6, characterized in that: The second connecting rod (3) is connected to the moving mold fixing part of the injection mold and is used to provide the driving force to pull the inner core-pulling rod (1) when the closed state is switched.