Injection mold for plastic plate

Abstract

The invention relates to the technical field of injection molds, in particular to a plastic plate injection mold which comprises a base, a lower mold shell, an electric push rod, an upper mold, a movable plate, an extrusion mechanism, a top plate and a driving mechanism, the lower mold shell is installed on the base, the electric push rod is installed below the lower mold shell, and the upper mold is located above the lower mold shell; the movable plate is installed in the lower mold shell, the extrusion mechanism is located below the movable plate, the top plate is located above the bottom of the lower mold shell, and the driving mechanism is located below the top plate. And therefore, the plastic distribution uniformity is improved, the cooling time for injecting the plastic firstly is delayed, and the injection molding quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of injection moulds, in particular to an injection mould for a plastic plate. Background Art

[0002] Injection mold refers to a mold used in the injection molding process. The plastic material is melted by heating, then injected into the mold cavity, and the desired plastic product is obtained after cooling and molding. Injection mold is the core tool for the production of plastic products, mainly used to manufacture plastic products with fixed shapes, such as plastic sheets, etc.

[0003] In the production process of processing long plastic sheets, the upper mold and the lower mold are combined to provide a space for the plastic sheet to be formed. However, during the injection molding process, if the long surface is placed horizontally, it will be difficult to inject the long surface completely, so it will be placed vertically for injection molding. However, during the injection molding process, due to the excessive length in the vertical direction, the molten plastic injected first at the bottom will carry air to the bottom of the mold, and the gas will form holes on the surface of the workpiece during the injection molding process, thereby affecting the molding quality of the workpiece; on the other hand, the molten plastic injected first will cool down quickly after contacting the bottom. At this time, when the temperature difference between the plastic injected later and the plastic is large, the two will form a quality difference, and the finished product will form stratification, affecting the molding quality of the long plastic sheet;

[0004] In order to solve the above problems, the prior art proposes a variety of solutions, such as maintaining a balanced temperature in the mold cavity so that the upper and lower temperatures can be kept consistent during molding. However, on the one hand, it does not solve the problem that the gas cannot be discharged in time due to the mold being too long. On the other hand, when the temperature needs to be lowered after the injection molding is completed, the temperature control makes it difficult to lower the temperature, thereby extending the molding time of the injection molded parts, which affects the molding quality of the injection molding of the injection molded parts.

[0005] Based on this, in order to solve the problem that bubbles are easily generated at the bottom of long plastic plates during the injection molding process due to the long injection distance, and the injection molding parts in the upper and lower positions in the injection cavity are unevenly molded, thereby affecting the injection molding quality, the present invention designs an injection mold for plastic plates. Summary of the invention

[0006] The present invention provides an injection mold for a plastic plate, which solves the problem that bubbles are easily generated at the bottom of a long plastic plate due to a long injection distance during the injection molding process, and also causes uneven molding of injection molded parts at upper and lower positions in the injection cavity, thereby affecting the injection molding quality; by changing the distance from the bottom of the mold to the injection port during the injection molding process, the molten plastic at the bottom edge is simultaneously driven to move upward, thereby improving the uniformity of plastic distribution and delaying the cooling time of the first injected plastic, thereby improving the injection molding quality.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides an injection mold for a plastic plate, comprising a base, a lower mold shell, an electric push rod, an upper mold, a movable plate, an extrusion mechanism, a top plate, and a driving mechanism, wherein the lower mold shell is installed on the base, the electric push rod is installed below the lower mold shell, the upper mold is located above the lower mold shell, the movable plate is installed in the lower mold shell, the extrusion mechanism is located below the movable plate, the top plate is located above the bottom of the lower mold shell, and the driving mechanism is located below the top plate. The electric push rod drives the movable plate to move up through the extrusion mechanism to eliminate bubbles, and when the movable plate moves up, the driving mechanism drives the top plate to move down to form a cavity to accommodate the workpiece. On the one hand, the movable plate will squeeze the molten plastic inside, thereby making the internal plastics more closely fit each other, and on the other hand, the movable plate will push the bubbles on the edge upward, thereby improving the uniformity of the distribution of the molten plastic at the bottom.

[0009] Preferably, the movable plate is annular, and a slope is provided on the top of the movable plate; the annular movable plate will push the molten plastics on the four edges upward along the four sides of the injection mold, on the one hand, transporting the molten plastic at the bottom upward, thereby moving the molten plastic at the bottom pressing the air upward, allowing the gas to flow upward, reducing the problem of pores formed by the molten plastic pressing the gas, and on the other hand, as the movable plate moves upward, the molten plastic at the bottom can be moved upward, thereby improving the uniformity of the temperature of the internal molten plastic.

[0010] Preferably, the extrusion mechanism includes a contact plate, an extrusion plate, a limit block, and a return spring, the contact plate is installed below the movable plate, the extrusion plate is installed on the contact plate and is located at the side wall of the lower mold shell, the limit block is installed on the side wall of the lower mold shell and corresponds to the longitudinal position of the extrusion plate, and the return spring is installed between the limit plate and the contact plate; the limit block intermittently extrude the extrusion plate, and the extrusion plate intermittently extrude the molten plastic, thereby gradually pushing the molten plastic above the top plate, which can, on the one hand, compress the molten plastic, thereby improving the compactness of the filling and reducing air holes, and on the other hand, when the extrusion plate reaches the top of the limit block, the limit block can limit the extrusion plate, thereby reducing the hard contact between the movable plate and the upper mold.

[0011] Preferably, the driving mechanism includes an active rack, a gear, and a driven rack, the active rack is installed below the contact plate, the gear is installed in the lower mold shell and is located below the top plate, the driven rack is connected to the top plate and meshes with the active rack through the gear; the driving mechanism here can also use multiple electric push rods, but in order to achieve step simplification and functional unification, a gear rack method is used to improve synchronization.

[0012] Preferably, the limit block is stepped, and a notch is provided at the top of the contact plate, through which it can be checked whether the molten plastic is completely filled.

[0013] Preferably, a wedge-shaped surface with the same curvature as the inclined surface is provided at the bottom end of the upper mold, and a gate is provided above the upper mold. The cooperation between the wedge-shaped surface and the inclined surface, on the one hand, improves the installation stability between the movable mold and the fixed mold (upper mold and lower mold), while avoiding the displacement of the movable mold (upper mold), and on the other hand, utilizes the inclined surface and the inclined surface to enable the internal molten plastic to move from the bottom to the top, thereby allowing the internal gas to be discharged.

[0014] Preferably, a plurality of through holes are provided on the side wall of the top plate, and a cooling component is installed under the top plate; the cooling component can be a fan driven by a motor to rotate for circulation and cooling, or it can be cooling water. The side wall of the top plate is provided with through holes, and the cooling component transfers the cold air upward and transfers it to the top plate through the through holes. As the top plate moves downward, the cooling effect of the cooling component gradually increases.

[0015] Preferably, the top plate includes an inner plate and an outer ring, the inner edge of the outer ring is provided with a limiting ring, the inner plate and the upper surface of the outer ring are fitted with each other, and the top plate is easy to disassemble through the inner plate and the outer ring.

[0016] Preferably, the movable plate is detachably connected to the contact plate, and the movable plate is made of metal; the movable plate can conduct heat, so that the molten plastic initially entering will not cool down quickly, thereby improving molding uniformity.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. The present invention proposes an injection mold for a plastic plate, which injects molten plastic into the space between the upper mold and the lower mold shell through the gate above the upper mold. At this time, the top plate will also move down to a specified position. As the top plate moves down, the internal cavity will increase, thereby reducing the entry of external gas into the bottom of the lower mold shell during the injection molding process, thereby reducing the generation of bubbles. At the same time, when the movable plate moves up, the movable plate will squeeze the internal molten plastic on the one hand, thereby making the internal plastics more closely fitted to each other, and on the other hand, the movable plate will push the bubbles on the edge upward, thereby improving the uniformity of the distribution of the bottom molten plastic; in the process of the movable plate moving up, the extrusion mechanism will gradually push the molten plastic to gather in the middle, thereby improving the uniform distribution of the molten plastic, avoiding the presence of air causing bubbles in the lower mold shell, and the squeezed gas will be pushed upward by the movable plate, and the air will be discharged upward under the action of the movable plate, thereby avoiding the problems of surface shrinkage and pores, thereby improving the molding quality of the plastic plate.

[0019] 2. The present invention proposes an injection mold for a plastic plate. During the upward movement of the movable plate, the annular movable plate will push the molten plastics on the four edges of the injection mold upwards. On the one hand, the molten plastic at the bottom is transported upwards, thereby causing the molten plastic at the bottom pressing the air to move upwards, allowing the gas to flow upwards, thereby reducing the problem of pores formed by the molten plastic pressing the gas. On the other hand, as the movable plate moves upwards, the molten plastic at the bottom can be moved upwards, thereby improving the uniformity of the temperature of the internal molten plastic.

[0020] 3. The present invention proposes an injection mold for a plastic plate, in which a cooling component transmits cold air upward and transmits it to the top plate through the through holes. As the top plate moves downward, the cooling effect of the cooling component gradually increases. At this time, the cooling temperature will be transmitted to the top plate through the through holes, and the top plate will be transmitted to the molten plastic. At the same time, the contact plate can also be cooled synchronously by the temperature transfer. As the top plate gradually descends, the temperature of the molten plastic above the top plate gradually decreases, and the cooling rate in the chamber can be controlled according to the injection amount of the molten plastic. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation mode of the present invention or the technical solution in the prior art, the drawings required for use in the specific implementation mode or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are one implementation mode of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0023] Figure 2 It is a schematic diagram of the extrusion mechanism and the driving mechanism of the present invention;

[0024] Figure 3 yes Figure 2 The enlarged view of point A in the middle;

[0025] Figure 4 yes Figure 2 The enlarged view of point B in the middle;

[0026] Figure 5 It is a schematic diagram of the wedge surface of the present invention;

[0027] Figure 6 It is an overall schematic diagram of the lower mold shell of the present invention;

[0028] Figure 7 It is a schematic diagram of the top plate of the present invention.

[0029] In the figure: 1. base; 2. lower mold shell; 3. electric push rod; 4. upper mold; 41. wedge surface; 42. gate; 5. movable plate; 51. inclined surface; 52. notch; 6. extrusion mechanism; 61. contact plate; 62. extrusion plate; 63. limit block; 64. return spring; 7. top plate; 71. through hole; 72. inner plate; 73. outer ring; 731. limit ring; 8. driving mechanism; 81. active rack; 82. gear; 83. driven rack; 9. cooling component. DETAILED DESCRIPTION

[0030] In order to better understand the above solution, the above technical solution is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0031] like Figure 1 , 2 As shown, the present invention provides an injection mold for a plastic plate, comprising a base 1, a lower mold shell 2, an electric push rod 3, an upper mold 4, a movable plate 5, an extrusion mechanism 6, a top plate 7, and a driving mechanism 8. The lower mold shell 2 is installed on the base 1, the electric push rod 3 is installed below the lower mold shell 2, the upper mold 4 is located above the lower mold shell 2, the movable plate 5 is installed in the lower mold shell 2, the extrusion mechanism 6 is located below the movable plate 5, the top plate 7 is located above the bottom of the lower mold shell 2, and the driving mechanism 8 is located below the top plate 7. The electric push rod 3 drives the movable plate 5 to move upward through the extrusion mechanism 6 to eliminate bubbles. When the movable plate 5 moves upward, the driving mechanism 8 drives the top plate 7 to move downward to form a cavity to accommodate the workpiece.

[0032] When the upper mold 4 moves to the specified position, the molten plastic is injected into the space between the upper mold 4 and the lower mold shell 2 through the gate 42 above the upper mold 4. At this time, the electric push rod 3 is synchronously driven, and the electric push rod 3 drives the movable plate 5 to reach the upper mold 4. At this time, the top plate 7 will also move down to the specified position, and then the molten plastic will be gradually injected into the lower mold shell 2. As the top plate 7 moves down, the internal cavity increases without contacting the outside world, thereby reducing the external gas from entering the bottom of the lower mold shell 2 during the injection molding process, thereby reducing the generation of bubbles. At the same time, when the movable plate 5 moves up, the movable plate 5 will squeeze the inner cavity on the one hand. On the one hand, the movable plate 5 pushes the bubbles at the edge upwards, thereby improving the uniformity of the distribution of the molten plastic at the bottom; in the process of the movable plate 5 moving upwards, the extrusion mechanism 6 gradually pushes the molten plastic to gather in the middle, thereby improving the uniform distribution of the molten plastic, avoiding the presence of air to cause bubbles to form in the lower mold shell 2, and the squeezed gas will be pushed upwards by the movable plate 5, and the air will be discharged upwards under the action of the movable plate 5, thereby avoiding the problems of surface shrinkage and pores, thereby improving the molding quality of the plastic sheet.

[0033] The driving mechanism 8 is used to synchronize the movable plate 5 and the top plate 7, so that when the movable plate 5 is just engaged with the upper mold 4, the top plate 7 drops to the lowest position, thereby achieving synchronous extension. At this time, if the materials are dropped at the same time, the speed of molten plastic injection is controlled, and then when the top plate 7 drops to the lowest, it is just filled, that is, the injection molding process is completed when the movable plate 5 is engaged with the upper mold 4, thereby reducing the situation of external gas entering the interior, and at the same time reducing the injection molding time, so that the molten plastic can be quickly injected to achieve the shaping effect; in addition, as the top plate 7 gradually descends, the top plate 7 is closer to the cooling component 9, and the cooling effect of the top plate 7 is gradually increased. In the process of the top plate 7 descending, its cooling speed will not be like the injection molded part directly falling to the bottom, directly contacting the cooling component 9, thereby delaying the cooling time of the injection molded part that falls first, thereby avoiding the excessive cooling speed below it, causing the problem of stratification, and then affecting the molding quality of the plastic sheet.

[0034] The movable plate 5 is annular, and a slope 51 is disposed on the top of the movable plate 5 .

[0035] The movable plate 5 is initially located at the lower end, and the top plate 7 is initially located at the top end. When the top plate 7 moves to below the movable plate 5, material blanking begins. During the upward movement of the movable plate 5, the annular movable plate 5 will push the molten plastics on the four edges upward along the four sides of the injection mold. On the one hand, the molten plastic at the bottom is transported upward, and the molten plastic at the bottom pressing the air is moved upward, so that the gas can flow upward, reducing the problem of pores formed by the molten plastic pressing the gas. On the other hand, the upward movement of the movable plate 5 can move the molten plastic at the bottom upward, thereby improving the uniformity of the temperature of the internal molten plastic. The inclined surface 51 can gather the molten plastic to the center on the one hand, and fit with the upper mold 4 on the other hand, thereby improving the sealing of the connection between the upper mold 4 and the lower mold shell 2, so that on the one hand, the gas will not flow in from the gap, and on the other hand, it can improve the accuracy between the movable mold and the fixed mold, thereby improving the injection molding efficiency.

[0036] like Figure 2 , 3 As shown in Figure 4, the extrusion mechanism 6 includes a contact plate 61, an extrusion plate 62, a limit block 63, and a return spring 64. The contact plate 61 is installed below the movable plate 5, the extrusion plate 62 is installed on the contact plate 61 and is located on the side wall of the lower mold shell 2, the limit block 63 is installed on the side wall of the lower mold shell 2 and corresponds to the longitudinal position of the extrusion plate 62, and the return spring 64 is installed between the limit plate and the contact plate 61.

[0037] During the upward movement of the movable plate 5, the contact plate 61 will move upward with the movable plate 5. At this time, the contact plate 61, the movable plate 5 and the top plate 7 replace the lower mold shell 2, and then form a complete chamber with the upper mold 4. When the contact plate 61 moves upward, the limit block 63 on the lower mold shell 2 will push the extrusion plate 62, and then drive the extrusion plate 62 to move inward. When the limit block 63 contacts the extrusion block, the top plate 7 is located below the extrusion block. As the movable plate 5 drives the contact plate 61 to move upward, the top plate 7 will gradually descend. During the descending process of the top plate 7, the movable plate 5 drives the contact plate 61 to rise. When the contact plate 61 rises, the limit plate will contact the extrusion plate 62, and then gradually push the extrusion block. The extrusion block will compact the molten plastic inside. During the extrusion process, gas will escape from the molten plastic, thereby reducing the generation of pores in the injection molded part. At the same time, the limit block 63 intermittently extrude the extrusion plate 62, and the extrusion plate 62 intermittently extrude the molten plastic, thereby gradually pushing the molten plastic above the top plate 7. On the one hand, it can compact the molten plastic, thereby improving the compactness of the filling and reducing pores. On the other hand, when the extrusion plate 62 reaches the top of the limit block 63, the limit block 63 limits the extrusion plate 62, thereby reducing the hard contact between the movable plate 5 and the upper mold 4, and at the same time can fix the contact plate 61, so that the lower mold composed of the contact plate 61 and the top plate 7 is stable, thereby improving the injection molding efficiency.

[0038] Since the top plate 7 and the contact plate 61 need to maintain sealing to ensure that there is no leakage of molten plastic when the top plate 7 and the contact plate 61 slide up and down, in order to improve the sealing, a sealing ring can be set on the edge of the top plate 7. The sealing ring is made of highly elastic silicone rubber and coated with lubricant to reduce friction.

[0039] The driving mechanism 8 includes an active rack 81, a gear 82, and a driven rack 83. The active rack 81 is installed below the contact plate 61, and the gear 82 is installed in the lower mold shell 2 and is located below the top plate 7. The driven rack 83 is connected to the top plate 7 and meshes with the active rack 81 through the gear 82.

[0040] Through the cooperation of the active rack 81, gear 82 and driven rack 83, when the electric push rod 3 drives the contact plate 61 and the movable plate 5 to move upward, the active rack 81, gear 82 and driven rack 83 make the contact plate 61 and the top plate 7 move in the opposite direction synchronously, and when the contact plate 61 drives the movable plate 5 to move upward and push the molten plastic, the top plate 7 will gradually move downward, and then drive the cavity above the top plate 7 to gradually become larger. When the top plate 7 passes over the limit block 63 downward, the limit block 63 will push the extrusion plate 62, and the extrusion plate 62 is pushed to move closer to each other and squeeze the molten plastic. After the molten plastic is squeezed, it drives the internal gas to flow upward, thereby improving the compactness of the filling and reducing the pores. The movable plate 5 is connected to the contact plate 61, and the contact plate 61 is connected to the active rack 81.

[0041] like Figure 5 , 6 As shown, the limit block 63 is in a stepped shape, and a notch 52 is formed at the top of the movable plate 5 .

[0042] The stopper 63 is in a multi-stage stepped shape, so that intermittent extrusion can be achieved. At the same time, when it reaches the top, it can cooperate with the extrusion plate 62. On the one hand, it can intermittently drive the extrusion plate 62 to push the molten plastic, and on the other hand, it can limit the extrusion plate 62 to avoid the stopper 63 from hard contact with the upper mold 4. The notch 52 on the movable plate 5 is used to guide the gas discharged by the internal extrusion on the one hand, and on the other hand, it can also be used as a measuring instrument for the complete filling of the container. When the internal molten plastic reaches the notch 52, after the internal filling is completed, the molten plastic will leak from the notch 52 first. At this time, the feed of the gate 42 can be closed, thereby improving the efficiency of injection molding.

[0043] A wedge-shaped surface 41 having the same curvature as the inclined surface 51 is disposed at the bottom of the upper mold 4 , and a gate 42 is disposed above the upper mold 4 .

[0044] The wedge-shaped surface 41 and the inclined surface 51 cooperate with each other, on the one hand, the installation stability between the movable mold and the fixed mold (upper mold 4 and lower mold) is improved, and the displacement of the movable mold (upper mold 4) is avoided. On the other hand, the inclined surface 51 and the inclined surface 51 enable the internal molten plastic to move from the bottom to the top, thereby allowing the internal gas to be discharged. Compared with the notch 52, the gate 42 has a larger diameter, so it is only suitable for the diameter of injecting molten plastic.

[0045] like Figure 6 , 7 As shown, a plurality of through holes 71 are opened on the side wall of the top plate 7 , and a cooling assembly 9 is installed under the top plate 7 .

[0046] The cooling component 9 here can be a motor driven fan that rotates for circulation and cooling, or it can be cooling water. A through hole 71 is opened on the side wall of the top plate 7. The cooling component 9 transfers the cold air upward and transfers it to the top plate 7 through the through hole 71. As the top plate 7 moves downward, the cooling effect of the cooling component 9 gradually increases. At this time, the cooling temperature will be transferred to the top plate 7 through the through hole 71, and the top plate 7 will be transferred to the molten plastic. At the same time, the contact plate 61 can also be cooled synchronously by the temperature transfer. As the top plate 7 gradually descends, the temperature of the molten plastic above the top plate 7 gradually decreases, and the cooling rate in the chamber can be controlled according to the injection amount of the molten plastic.

[0047] The top plate 7 includes an inner plate 72 and an outer ring 73. The inner edge of the outer ring 73 is provided with a limit ring 731. The inner plate 72 and the upper surface of the outer ring 73 are mutually attached. The movable plate 5 is detachably connected to the contact plate 61. The movable plate 5 is made of metal.

[0048] The prior art has the problem that the lower mold cannot be detached, that is, the internal paint is not completely coated, which makes it difficult to remove the workpiece, thus affecting the efficiency of secondary use. By providing a detachable movable plate 5 and a contact plate 61, and the top plate 7 is divided into an inner plate 72 and an outer ring 73, and the inner plate 72 is embedded in the outer ring 73, when the molten plastic is cooled and has strong viscosity, the movable plate 5 is removed, and then the contact plate 61 and the top plate 7 are taken out as a whole. At this time, by pushing the inner plate 72, the workpiece together with the inner plate 72 can be removed at the same time, and the inner plate 72 can be installed again to achieve secondary use.

[0049] When the plastic sheet needs to be processed, the upper mold 4 is first driven to move to the specified position and fixed, and the electric push rod 3 is driven at this time, and the electric push rod 3 drives the movable plate 5 to move toward the upper mold 4. When the movable plate 5 moves to the top of the top plate 7, the molten plastic is injected into the space between the upper mold 4 and the lower mold shell 2 through the gate 42 above the upper mold 4. At this time, the contact plate 61 connected to the movable plate 5 will also move up synchronously, and the active rack 81 below the contact plate 61 will move up accordingly, thereby driving the gear 82 to rotate, and the gear 82 will drive the driven rack 83 meshing therewith to move in the opposite direction, that is, the driven rack 83 moves downward, and the driven rack 83 drives the top plate 7 connected thereto to move downward, and then the molten plastic will be gradually injected into the lower mold shell 2. As the top plate 7 moves downward, the internal cavity increases, thereby forming the filling of the material;

[0050] As the movable plate 5 moves upward, the contact plate 61 will move upward with the movable plate 5. At this time, the limit block 63 on the lower mold shell 2 will push the extrusion plate 62 on the contact plate 61, thereby driving the extrusion plate 62 to move inward. When the limit block 63 contacts the extrusion block, the top plate 7 is located below the extrusion block. As the movable plate 5 drives the contact plate 61 to move upward, the top plate 7 will gradually descend. During the process of the top plate 7 descending, the movable plate 5 drives the contact plate 61 to rise. When the contact plate 61 rises, the limit plate will contact the extrusion plate 62, thereby gradually pushing the extrusion block. The extrusion block will compact the molten plastic inside, thereby squeezing the internal gas upward. As the top plate 7 descends, the cooling effect of the cooling component 9 on the top plate 7 becomes more obvious.

[0051] After the injection molding is completed, the upper mold 4 is pushed open (the upper mold 4 can be driven by a cylinder), and the electric push rod 3 is driven to move downward, thereby driving the movable plate 5 to descend and the top plate 7 to rise until the injection molded part is completely taken out and the next injection molding cycle is carried out.

[0052] The basic principles and beneficial effects of the present invention are shown and described above. At the same time, the present invention is not limited to the above embodiments. Without departing from the effects and scope of the present invention, the present invention may have various changes and improvements. These changes and improvements all fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. An injection mold for a plastic sheet, characterized in that: The invention comprises a base (1), a lower die shell (2), an electric push rod (3), an upper die (4), a movable plate (5), an extrusion mechanism (6), a top plate (7), and a driving mechanism (8); the lower die shell (2) is mounted on the base (1); the electric push rod (3) is mounted below the lower die shell (2); the upper die (4) is located above the lower die shell (2); the movable plate (5) is mounted inside the lower die shell (2); the extrusion mechanism (6) is located below the movable plate (5); the top plate (7) is located above the bottom of the lower die shell (2); the driving mechanism (8) is located below the top plate (7); the electric push rod (3) drives the movable plate (5) to move upwards through the extrusion mechanism (6) to eliminate bubbles; when the movable plate (5) moves upwards, the driving mechanism (8) drives the top plate (7) to move downwards to form a cavity for accommodating a workpiece.

2. The injection mold for a plastic sheet according to claim 1, characterized in that: The movable plate (5) is annular, and a slope (51) is provided on the top of the movable plate (5).

3. The injection mold for a plastic sheet according to claim 2, characterized in that: The extrusion mechanism (6) comprises a contact plate (61), an extrusion plate (62), a limit block (63), and a return spring (64); the contact plate (61) is mounted below the movable plate (5); the extrusion plate (62) is mounted on the contact plate (61) and is located on the side wall of the lower mold shell (2); the limit block (63) is mounted on the side wall of the lower mold shell (2) and corresponds to the longitudinal position of the extrusion plate (62); and the return spring (64) is mounted between the limit plate and the contact plate (61).

4. The injection mold for a plastic sheet according to claim 3, characterized in that: The driving mechanism (8) comprises an active rack (81), a gear (82), and a driven rack (83); the active rack (81) is installed below the contact plate (61); the gear (82) is installed in the lower mold shell (2) and is located below the top plate (7); the driven rack (83) is connected to the top plate (7) and meshes with the active rack (81) through the gear (82).

5. The injection mold for a plastic sheet according to claim 3, characterized in that: The limit block (63) is in a stepped shape, and a notch (52) is provided at the top of the movable plate (5).

6. The injection mold for a plastic sheet according to claim 2, characterized in that: The bottom end of the upper mold (4) is provided with a wedge-shaped surface (41) having the same curvature as the inclined surface (51), and a gate (42) is provided above the upper mold (4).

7. The injection mold for a plastic sheet according to claim 4, characterized in that: A plurality of through holes (71) are provided on the side wall of the top plate (7), and a cooling assembly (9) is installed below the top plate (7).

8. The injection mold for a plastic sheet according to claim 7, characterized in that: The top plate (7) comprises an inner plate (72) and an outer ring (73); a limiting ring (731) is provided on the inner edge of the outer ring (73); and the upper surfaces of the inner plate (72) and the outer ring (73) are in contact with each other.

9. The injection mold for a plastic sheet according to claim 5, characterized in that: The movable plate (5) and the contact plate (61) are detachably connected, and the movable plate (5) is made of metal.

Images