A mold for multi-cavity injection molding with low clamping force

Abstract

This invention provides a mold for multi-cavity injection molding with low clamping force. The hot runner mold plate has a main runner with an injection port. At least three branch runners are connected to the left and right sides of the main runner. At least two branch runners on each side are coaxially arranged with the branch runners on the other side, forming a distal runner group. The distal connection port of each distal runner group to the main runner is equidistant from the injection port. The proximal connection ports of the remaining branch runners on each side, excluding the distal runner groups, are located between the distal connection port and the injection port, and these proximal connection ports are not coaxial. The number of downward injection terminals extending from any proximal connection port does not exceed half the number of downward injection terminals extending from the distal connection port. This invention improves the synchronization of injection pressure, reduces injection pressure loss, lowers injection pressure, effectively reduces clamping force, and increases the number of injection cavities.

Description

Technical Field

[0001] This invention belongs to the field of injection mold technology, and particularly relates to a mold for multi-cavity injection molding with low clamping force. Background Technology

[0002] Two-color 5-gallon bucket lids are widely used. In traditional manufacturing, 250T to 300T injection molding machines are used to produce 16-cavity two-color lids. At this point, the clamping force is 340T, which is the limit of the 250T to 300T injection molding machine. If you want to improve the injection molding efficiency, such as to produce 20-cavity two-color lids, you generally need to use a 400T injection molding machine. This is because if you make 20 cavities according to the 16-cavity design, the clamping force exceeds 400T. However, ultra-high tonnage injection molding machines are difficult to manufacture and costly, so they cannot be widely used. As a result, the number of cavities in two-color lids cannot currently exceed 16. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a mold for multi-cavity injection molding with low clamping force, thus solving the problem that the prior art cannot use conventional 250T to 300T injection molding machines to produce 20-cavity two-color caps.

[0004] This invention provides a mold for multi-cavity injection molding with low clamping force, comprising an upper mold assembly and a lower mold assembly. The upper mold assembly includes a hot runner template with a main runner. The main runner has an injection port. At least three branch runners are connected to the left and right sides of the main runner. At least two branch runners on each side are coaxially arranged with the branch runners on the other side. The two coaxially arranged branch runners on the left and right sides form a distal runner group. The distal connection port of each distal runner group to the main runner is equidistant from the injection port. The proximal connection ports of the remaining branch runners on each side, excluding the distal runner groups, to the main runner are located between the distal connection port and the injection port. The proximal connection ports are not coaxial, and the number of downward injection ends leading from any proximal connection port does not exceed half the number of downward injection ends leading from the distal connection port.

[0005] In some embodiments, the proximal connectors are arranged equidistantly between the two distal connectors at both ends in a staggered manner.

[0006] In some embodiments, each of the distal flow channel groups is divided into a first downward injection end group and a second downward injection end group according to the left and right sides. The first downward injection end group includes A downward injection ends, and the second downward injection end group includes B downward injection ends, where A > B. The flow channel guiding direction of the proximal connection port closest to the distal flow channel group is opposite to the flow channel guiding direction of the first downward injection end group.

[0007] In some embodiments, the number of downward injection ends extending from each of the proximal connectors is C, where C ≤ B.

[0008] In some embodiments, the diameter of the branch channel connected to the first downward injection end group is 1.1 to 1.5 times the diameter of the branch channel connected to the second downward injection end group.

[0009] In some embodiments, the diameter of the branch channel connected to the second downward injection end group is not less than the diameter of the branch channel connected to the proximal connector.

[0010] In some embodiments, the diameter of the main flow channel is not less than 60% of the sum of the diameters of the two branch flow channels corresponding to the distal flow channel group.

[0011] In some embodiments, all of the downward injection ends form an N×M dot matrix, and the distance between adjacent downward injection ends is equal to the distance between adjacent connection ports.

[0012] In some embodiments, the upper module includes a first template at the bottom end, and the lower module includes a second template at the top end. The first template has a tapered limiting hole, which is coaxial with the downward injection end. The second template has a nest with a tapered limiting surface. The taper of the nest and the tapered limiting hole is 12°, and the fitting height is 15mm.

[0013] In some embodiments, the lower module includes a middle sleeve and a push rod. The middle sleeve is inserted into the inner wall of the nest, and the inner wall of the nest is provided with a first wear-resistant ring for abutting against the middle sleeve. The push rod is inserted into the inner wall of the middle sleeve, and the inner wall of the middle sleeve is provided with a second wear-resistant ring for abutting against the push rod.

[0014] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0015] By optimizing the hot runner design, a large number of downward injection ends are placed at the far end runner group furthest from the injection port, while each near end connector of different axes closer to the injection port leads out no more than half the number of downward injection ends led out by the far end connector. The position of each hot runner and downward injection end is accurately determined, the flow rate and direction of the plastic are controlled, the synchronization of injection pressure is improved, the loss of injection pressure is reduced, the injection pressure is reduced, the clamping force is reduced, and the number of injection cavities is increased. Attached Figure Description

[0016] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the hot runner design for a 16-cavity injection mold in the prior art.

[0018] Figure 2 This is a schematic diagram of the structure of a mold for multi-cavity injection molding with low clamping force, as disclosed in this invention.

[0019] Figure 3 This is a schematic diagram of the structure of a hot runner template according to one embodiment of the present invention.

[0020] Figure 4 This is an exploded structural diagram of a mold for multi-cavity injection molding with low clamping force, as disclosed in this invention. Detailed Implementation

[0021] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] In the description of this invention, when a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device. When a specific device is described as being connected to other devices, the specific device may be directly connected to the other devices without an intermediary device, or it may not be directly connected to the other devices but may have an intermediary device.

[0024] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0025] The applicant's research found that:

[0026] like Figure 1 As shown, the industry currently commonly uses 250T-300T injection molding machines for the production of 16-cavity two-color caps. Calculations show that the clamping force for a 16-cavity two-color cap reaches 340T, which is already the limit for 250T-300T injection molding machines. To improve production efficiency, manufacturers are already operating at the limit of this clamping force, posing certain safety hazards. The root cause is the excessively high cost of using 400T or higher-tonnage injection molding machines. Currently, these high-tonnage machines are mainly monopolized by foreign manufacturers, and domestic injection molding machines lack sufficient production precision, easily leading to uneven wall thickness in the caps and potential leakage. Furthermore, experiments have shown that producing a 20-cavity cap based on the 16-cavity design requires a clamping force exceeding 400T, making direct production on 250T-300T injection molding machines impossible. Therefore, there is an urgent need to design a more optimized hot runner system to fundamentally reduce injection pressure and thus lower the clamping force.

[0027] In view of this, refer to Figures 2 to 4 The embodiments of this disclosure provide a mold for multi-cavity injection molding with low clamping force, including an upper mold assembly 10 and a lower mold assembly 20. Under the control of corresponding transmission mechanisms, the upper mold assembly 10 and the lower mold assembly 20 can realize mold closing and mold opening.

[0028] The upper module 10 includes a hot runner template 11, which forms a main flow channel 12. The main flow channel 12 is provided with an inlet 13. At least three branch flow channels 14 are connected to the left and right sides of the main flow channel 12 respectively. In this embodiment, for ease of explanation, the main flow channel 12 is defined as the front-to-back flow direction. On the left and right sides of the main flow channel 12, several branch flow channels 14 are horizontally connected respectively, and the number of branch flow channels 14 on each side is the same.

[0029] At least two branch channels 14 exist on each side, each coaxially arranged with the branch channel 14 on the other side. That is, the branch channels 14 located on the left and right sides are coaxially arranged and share a distal connection port 16. The two coaxially arranged left and right branch channels 14 and their corresponding downward injection ends 18 form a distal channel group 15. Each distal channel group 15 is equidistant from the distal connection port 16 and the inlet port 13 of the main channel 12. The two distal channel groups 15 are located at the front and rear ends of the main channel 12, respectively. In each side, the proximal connection port 17 of the remaining branch channels 14 other than the distal channel group 15 and the main channel 12 is located between the distal connection port 16 and the inlet port 13, and each proximal connection port 17 has a different axis. That is, between the inlet port 13 and the distal connection port 16, the remaining branch channels 14 will be led out through the proximal connection port 17. The number of downward injection ends 18 led out by any one proximal connection port 17 does not exceed half the number of downward injection ends 18 led out by the distal connection port 16.

[0030] Since each branch flow channel 14 leads out a corresponding number of downward injection ends 18, after the plastic is injected from the inlet 13, the injection volume is distributed to each branch flow channel 14 through the main flow channel 12. Among them, since the number of downward injection ends 18 corresponding to the far-end flow channel group 15 located at both ends is the largest, it has a good space to reduce the injection pressure. Therefore, the design concept of this hot runner is to guide the plastic to flow to the downward injection ends 18 corresponding to the near-end connection ports 17 on both sides in the distance from the inlet 13 to the far-end connection port 16, filling the closer downward injection ends 18 first, and then filling the farther downward injection ends 18. By implementing zoned injection management, the injection pressure of the branch runner 14 and the downward injection end 18 corresponding to the near-end connector 17 is reduced, and the injection pressure is transferred to the more distant far-end runner group 15. When the plastic flows to the far-end runner group 15, because it has more downward injection ends 18, it can quickly absorb the injection pressure under a specific ratio of near-far downward injection ends 18, reduce the loss of injection pressure, improve the synchronization of injection pressure, effectively reduce the clamping force, and increase the number of injection cavities.

[0031] In one implementation, the proximal connection port 17 is arranged equidistantly between the two distal connection ports 16 at both ends in a staggered manner. At the same time, the inlet port 13 is located at the very center of the two distal connection ports 16 to ensure the uniformity of the flow channel distance.

[0032] Preferably, each distal flow channel group 15 is divided into a first downward injection end group 31 and a second downward injection end group 32 according to the left and right sides. The first downward injection end group 31 includes A downward injection ends 18, and the second downward injection end group 32 includes B downward injection ends 18, where A > B. The flow channel guiding direction of the proximal connection port 17 closest to the distal flow channel group 15 is opposite to the flow channel guiding direction of the first downward injection end group 31. Further, the number of downward injection ends 18 led out from each proximal connection port 17 is C, where C ≤ B.

[0033] When the plastic enters from the injection port 13, it first passes through the proximal connector 17 and then flows horizontally in the first direction to fill C downward injection ends 18. At the same time, the plastic continues to flow to the distal end and at the distal connector 16, it fills A downward injection ends 18 horizontally in the second direction and B downward injection ends 18 horizontally in the first direction. The quantity relationship is A > B ≥ C. The first direction is opposite to the second direction. By setting different numbers of downward injection ends 18 on the left and right, the injection pressure on both sides of the main channel 12 can be balanced, thereby improving the injection uniformity on both sides.

[0034] In one implementation, the diameter of the branch flow channel connected to the first downward injection end group 31 is 1.1 to 1.5 times the diameter of the branch flow channel connected to the second downward injection end group 32. That is, the diameter of the branch flow channel corresponding to the first downward injection end group 31, which has more downward injection ends 18, is 1.1 to 1.5 times larger than the diameter of the branch flow channel corresponding to the second downward injection end group 32, which has fewer coaxial downward injection ends 18, so as to complete the injection molding of more cavities.

[0035] Preferably, the diameter of the branch channels connected to the second downward injection end group 32 is not less than the diameter of the branch channels connected to the proximal connection port 17. In some possible embodiments, when B=C, the diameters of the branch channels 14 of the two are equal.

[0036] Preferably, the diameter of the main flow channel 12 is not less than 60% of the sum of the diameters of the two branch flow channels 14 corresponding to the distal flow channel group 15, to ensure that the diameter of the main flow channel 12 is large enough to transport plastic to the distal end and reduce the plastic flow rate and reduce pressure loss.

[0037] Preferably, all the downward injection ends 18 form an N×M dot matrix, and the distance between adjacent downward injection ends 18 is equal to the distance between adjacent connectors. The aforementioned adjacent connectors can be the distance between adjacent distal connectors 16 and proximal connectors 17, or the distance between adjacent proximal connectors 17.

[0038] Example 1:

[0039] Combination Figure 2In this embodiment 1, there are a total of 20 downward injection ends 18. A 20-cavity two-color cap can be produced by one injection molding. The distance between two adjacent downward injection ends 18 is 90mm and they are arranged in a 4×5 dot matrix.

[0040] The main flow channel 12 has a diameter of 18mm. On both sides of the main flow channel 12, which flows forward and backward, there are three branch channels 14, for a total of six branch channels 14. Among them, the branch channels 14 located at both ends on the left and the branch channels 14 located at both ends on the right are coaxially arranged. The coaxial branch channels 14 on the left and right sides share a remote connection port 16. The remaining two branch channels 14 are arranged equidistantly between the two remote connection ports 16, one on the left and one on the right, with a distance of 90mm between adjacent connection ports.

[0041] For the left-side branch channel 14, the diameter of the foremost branch channel 14 is 14mm, corresponding to 4 downward injection ends 18; the diameter of the middle branch channel 14 is 12mm, corresponding to 3 downward injection ends 18; and the diameter of the last branch channel 14 is 12mm, corresponding to 3 downward injection ends 18.

[0042] Regarding the right-side branch channel 14, the diameter of the foremost branch channel 14 is 12mm, corresponding to 3 downward injection ends 18; the diameter of the middle branch channel 14 is 12mm, corresponding to 3 downward injection ends 18; and the diameter of the rearmost branch channel 14 is 14mm, corresponding to 4 downward injection ends 18.

[0043] In this embodiment 1, A=4, B=3, C=3, N=4, M=5. Through a specific spacing arrangement and the diameter relationship between each branch channel and the main channel as described above, the plastic flow rate can be kept stable and the flow direction can be controlled. This allows for the synchronization of injection pressure in each injection cavity, reducing injection pressure loss and thus reducing the injection pressure and clamping force of the 20 cavities. Furthermore, it enables the clamping force of the 20-cavity two-color cap to not exceed 350T on a 250T to 300T injection molding machine.

[0044] It should be noted that the 250T to 300T injection molding machine used in this embodiment has a turntable diameter of 9.6 to 1.15 meters. Traditional manufacturing methods can only achieve 16 cavities within this turntable diameter. However, this embodiment improves the mold cavity count to 20 cavities by changing the mold arrangement and optimizing the flow channel design, thereby improving flow rate, flow volume, and distribution uniformity, under the same production environment, thus improving mold production efficiency.

[0045] Furthermore, the injection distance from the inlet 13 to the downward injection end 18 corresponding to the intermediate branch channel 14 shall not exceed 70% of the injection distance from the inlet 13 to the downward injection end 18 corresponding to the distal branch channel 14, and the injection distances of each downward injection end 18 of the intermediate branch channel 14 and the injection distances of each downward injection end 18 of the distal branch channel 14 shall be equal.

[0046] In this embodiment, the upper module 10 includes a first template 41 located at the bottom, below the hot runner template 11. The lower module 20 includes a second template 42 located at the top. Under the action of the transmission mechanism, the first template 41 and the second template 42 complete the mold closing and opening process. When the first template 41 and the second template 42 are closed, 20 mold cavities are formed. In each mold cavity, the first template 41 is provided with a conical limiting hole 43, which is coaxial with the downward injection end 18. The second template 42 is provided with a nest 44 with a conical limiting surface. In the closed state, the nest 44 and the conical limiting hole 43 achieve self-locking through the contact of the conical surface, ensuring concentricity. Because the traditional two-color cap mold has a short taper at the core mating point, it cannot play a centering role. Due to the requirements of two-color cap use, the central bursting point is very thin, only 0.11mm thick. If the concentricity is not accurate, it is easy to cause water leakage or excessive bursting force in the produced product, which will not meet the usage requirements and make the mold frequently need to be repaired. Therefore, in this embodiment, the nest 44 at the second template 42 is inserted into the tapered limiting hole 43 of the first template 41, and the taper of the nest 44 and the tapered limiting hole 43 are limited to 12° and the mating height is 15mm. This effectively controls the concentricity of the mold, making the mold production more stable and the product thickness more uniform.

[0047] In this embodiment, the lower module 20 includes a middle sleeve 45 and a push rod 46. The middle sleeve 45 is inserted into the inner wall of the nest 44, and the inner wall of the nest 44 is fitted with a first wear-resistant ring 47 for abutting against the middle sleeve 45. When the middle sleeve 45 is pushed upward, the first wear-resistant ring 47 reduces the frictional resistance between the middle sleeve 45 and the nest 44. The push rod 46 is inserted into the inner wall of the middle sleeve 45, and the inner wall of the middle sleeve 45 is fitted with a second wear-resistant ring 48 for abutting against the push rod 46. When the push rod 46 is pushed upward, the second wear-resistant ring 48 reduces the frictional resistance between the push rod 46 and the middle sleeve 45. Furthermore, both the first wear-resistant ring 47 and the second wear-resistant ring 48 are made of Teflon. By utilizing the wear resistance, heat resistance, and corrosion resistance of Teflon, the durability of the mold is improved, and the mold core will not be damaged. In traditional molds, because the mold core needs to be repeatedly ejected and reset, lubricating oil needs to be added to the mold core every few months of mold production. Otherwise, the mold core is prone to damage and sintering problems. During production, lubricating oil can easily flow out of the mold core and contaminate the product, resulting in defective products. This embodiment effectively solves the problem of needing to add lubricating oil and improves production stability and reliability.

[0048] Optionally, the upper module 10 and the lower module 20 can be reset by a cylinder, making pneumatic control more convenient and faster.

[0049] Compared with the prior art, the present invention provides a mold for multi-cavity injection molding with low clamping force. Through optimized hot runner design, a large number of downward injection ends 18 are set at the far end runner group 15 farthest from the injection port 13. Meanwhile, each proximal connection port 17 of different axes closer to the injection port 13 leads out no more than half the number of downward injection ends 18 led out by the far end connection port 16. The position of each hot runner and downward injection end 18 is accurately determined, the flow rate and direction of the plastic are controlled, the synchronization of injection pressure is improved, the loss of injection pressure is reduced, the injection pressure is reduced, the clamping force is reduced, and the number of injection cavities is increased.

[0050] Finally, it should be emphasized that the present invention is not limited to the above-described embodiments. The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A mold for multi-cavity injection molding under low clamping force, used to produce 20-cavity two-color caps, characterized in that, The system includes an upper module and a lower module. The upper module includes a hot runner template with a main channel. The main channel has an injection port. At least three branch channels are connected to the left and right sides of the main channel. At least two branch channels on each side are coaxially arranged with the branch channels on the other side. The two coaxially arranged branch channels form a distal channel group. The distal connection port of each distal channel group to the main channel is equidistant from the injection port. The proximal connection port of the remaining branch channels on each side, other than the distal channel group, to the main channel is located between the distal connection port and the injection port. The proximal connection ports are not coaxial. The number of downward injection ends led out from any proximal connection port does not exceed half the number of downward injection ends led out from the distal connection port. The proximal connectors are arranged equidistantly between the two distal connectors at both ends in a staggered manner. Each of the distal flow channel groups is divided into a first downward injection end group and a second downward injection end group according to the left and right sides. The first downward injection end group includes A downward injection ends, and the second downward injection end group includes B downward injection ends, where A > B. The flow channel guiding direction of the proximal connection port closest to the distal flow channel group is opposite to the flow channel guiding direction of the first downward injection end group. The number of downward injection terminals extending from each of the proximal connectors is C, where C ≤ B; The diameter of the branch channel connected to the first downward injection end group is 1.1 to 1.5 times the diameter of the branch channel connected to the second downward injection end group; All the downward injection ends form an N×M dot matrix, and the distance between adjacent downward injection ends is equal to the distance between adjacent connection ports.

2. The mold for multi-cavity injection molding under low clamping force as described in claim 1, characterized in that, The diameter of the branch flow channel connected to the second downward injection end group is not less than the diameter of the branch flow channel connected to the proximal connection port.

3. The mold for multi-cavity injection molding under low clamping force as described in claim 2, characterized in that, The diameter of the main flow channel is not less than 60% of the sum of the diameters of the two branch flow channels corresponding to the distal flow channel group.

4. A mold for multi-cavity injection molding with low clamping force as described in any one of claims 1 to 3, characterized in that, The upper module includes a first template at the bottom end, and the lower module includes a second template at the top end. The first template has a tapered limiting hole, which is coaxial with the downward injection end. The second template has a nest with a tapered limiting surface. The taper of the nest and the tapered limiting hole is 12°, and the fitting height is 15mm.

5. A mold for multi-cavity injection molding under low clamping force as described in claim 4, characterized in that, The lower module includes a middle sleeve and a top rod. The middle sleeve is inserted into the inner wall of the nested structure, and the inner wall of the nested structure is provided with a first wear-resistant ring for abutting against the middle sleeve. The top rod is inserted into the inner wall of the middle sleeve, and the inner wall of the middle sleeve is provided with a second wear-resistant ring for abutting against the top rod.

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