Injection molding apparatus and method for forcing melt material to flow into the die cavity of the injection molding apparatus

Injection molding device and method for forcing melt to flow into the cavity of the injection molding deviceTechnical field

[0001] The present invention generally relates to an injection molding device, and more specifically, to a metering device for a hot runner nozzle that can inject a predetermined amount of melt into a mold cavity.

Background technique

[0002] In an injection molding device, a manifold receives a high-pressure melt flow from a machine nozzle. The manifold distributes the melt flow into multiple nozzles, and the melt is forced through the nozzles into multiple mold cavities. The melt then cools in the mold cavity, releasing the molded product so that another cycle can begin.

[0003] The amount of melt delivered to each nozzle may vary due to effects such as flow imbalance caused by shear in the manifold. In order to compensate for this effect and ensure that a sufficient amount of melt is delivered to each cavity, the pressure exerted by the machine nozzle on the melt flow must be very high. For applications such as injection molding of thin-walled containers and micro-molded products, even higher nozzle pressures are required to produce molded products of acceptable quality. As a result, the machine nozzle must be very large in order to generate enough pressure to correctly distribute the melt in the mold cavity. However, in many cases, it is not practical to increase the size of the machine nozzle. Therefore, there is a need for alternative solutions for increasing the pressure generated in each individual nozzle.

[0004] For thin-walled molded products and micro-molded products, it is also very important to accurately measure the melt volume delivered in each injection. This poses a special challenge especially when dealing with micro-molded products that usually weigh only a fraction of a gram. Several prior art devices have been developed to control the volume of melt injected into the mold cavity. These devices are usually used when injecting more than one material into a mold cavity, and are relatively complex and costly to manufacture.

[0005] US Patent No. 5112212 to Akselrud et al. discloses a shooting pod, which can be used as a metering device and used in a co-injection device. The injection groove is arranged at a position far away from the hot runner nozzle, and is used to control the volume of one of the two molten materials injected into the mold cavity. The injection trough includes a piston that can move axially in the cylinder to force the molten material from the cylinder into the nozzle leading to the mold cavity. The cylinder includes an inlet, which can transfer the melt from the melt source to a storage tank located at the lower end of the piston. The piston can be rotated so that the tank does not communicate with the inlet but seals it, so that when the piston descends, a known volume of melt can be forced into the mold cavity.

[0006] US Patent No. 4863369 to Schad et al. discloses an injection molding device that uses a shot trough to deliver an accurately measured amount of melt into a mold cavity. A valve is provided in the conduit between the melt source and each nozzle. Once the injection trough and nozzle are filled with melt, the valve closes and the mold gate opens. The plunger of the injection trough pushes forward until it touches the bottom of the cylinder, thereby delivering a precise amount of melt into the mold cavity.

[0007] The disadvantage of a shot chute that is located away from the nozzle and the mold cavity is that the known or measured melt volume will change from one injection cycle to the next injection cycle. The reason for this is that there is a large volume of melt between the injection tank and the mold cavity, that is, the melt in the nozzle, the melt in the manifold channel and the melt in the injection tank. This larger volume of melt introduces multiple variables. For example, a small difference in temperature or pressure can cause a significant change in this known volume. The large distance between the injection trough and the mold cavity also causes the melt to stay outside the nozzle for a longer time between the injection of one product to the next. This results in the molded product not having the best quality, because the temperature of the melt from the shot trough is under or overheated.

[0008] Therefore, the object of the present invention is to provide a metering device for the nozzle of an injection molding device, which can avoid or reduce

Light at least one of the above shortcomings.

Summary of the invention

[0009] According to one aspect of the present invention, there is provided an injection molding device, including:

[0010] A manifold having a manifold channel for receiving a melt flow of a moldable material under pressure, the manifold channel having an outlet in the nozzle channel for conveying the melt flow to the nozzle;

[0011] A cavity for receiving the melt flow from the nozzle, and the nozzle channel communicates with the cavity through the mold gate;

[0012] A gate mechanism for selectively closing the gate of the mold;

[0013] A piston extending through the nozzle channel of the nozzle and slidable therein, the outer wall of the piston rests on the inner wall of the nozzle channel, and the piston can move from the retracted position to the extended position, thereby pressing the melt toward the mold cavity;

[0014] A valve provided at the front end of the piston, which can be selectively moved to block the communication between the groove provided in the outer wall of the piston and adjacent to the valve and the melt chamber of the nozzle channel, the valve being in the retracted position of the piston Open at time to allow the melt to flow from the manifold channel to the groove and into the melt cavity of the nozzle channel;

[0015] Wherein, the movement of the piston toward the extended position forces the melt in the melt cavity of the nozzle channel to flow into the mold cavity.

[0016] According to another aspect of the present invention, there is provided a method for forcing melt to flow into a mold cavity of an injection molding device, the method comprising:

[0017] Close the mold gate of the mold cavity in order to prevent the melt flow from flowing into the mold cavity from the nozzle channel of the nozzle;

[0018] The piston provided in the nozzle channel is maintained in the retracted position, wherein the valve provided at the front end of the piston is opened to allow the melt flow from the manifold channel of the manifold to flow in through the groove provided near the front end of the piston Into the melt cavity of the nozzle channel, so as to fill the nozzle channel with melt;

[0019] Close the valve to prevent the flow of melt flow between the groove and the melt cavity of the nozzle channel;

[0020] Opening the mold gate; and

[0021] The piston is moved toward the extended position, thereby forcing the melt in the melt cavity of the nozzle channel to flow into the mold cavity.

[0022] According to another aspect of the present invention, there is provided a piston for a nozzle of an injection molding device, which includes:

[0023] A valve provided at the front end of the piston, which can be selectively closed to block the communication between the groove provided in the outer wall of the piston and adjacent to the valve and the melt cavity of the nozzle channel; and

[0024] The valve opens when the piston is in the retracted position to allow melt to flow through the valve from the groove, and closes when the piston moves toward the extended position to force the melt to flow into the mold cavity.

[0025] According to another aspect of the present invention, an injection molding device is provided, which includes:

[0026] A manifold having a manifold channel for receiving a melt flow of a moldable material under pressure, the manifold channel having an outlet in the nozzle channel for conveying the melt flow to the nozzle;

[0027] A mold cavity for receiving a melt flow from a nozzle channel, which communicates with the mold cavity through a mold gate;

[0028] A gate mechanism for selectively closing the gate of the mold;

[0029] A melt cavity provided in the nozzle channel and adjacent to the mold gate, which has a predetermined volume;

[0030] A valve provided between the outlet of the manifold channel and the melt chamber, the valve being selectively movable to control the flow of melt from the manifold channel to the melt chamber; and

[0031] Wherein, the predetermined volume of melt is injected into the mold cavity in one injection.

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[0032] According to another embodiment of the present invention, there is provided a method for injecting a predetermined volume of molten material into a mold cavity, including:

[0033] a) The molten material is injected into the valve gate type hot runner nozzle through the hot runner manifold, the hot runner nozzle includes a movable valve needle, the valve needle is in the closed position engaged with the mold gate;

[0034] b) Open the mold gate;

[0035] c) The molten material is injected into the mold cavity through the mold gate by moving the injection piston at least partly provided in the nozzle, so as to transfer a predetermined volume of the molten material from the hot runner nozzle to the mold cavity;

[0036] d) Close the communication between the hot runner nozzle and the mold cavity by moving the valve needle to engage with the mold gate.

[0037] According to another embodiment of the present invention, there is provided a method for injecting a predetermined volume of molten material into a mold cavity, which includes:

[0038] a) The molten material is injected into the valve gate type hot runner nozzle through the hot runner manifold, the hot runner nozzle includes a movable valve needle, the valve needle is in a closed position engaged with the mold gate;

[0039] b) Blocking the communication between the hot runner manifold and the hot runner nozzle;

[0040] c) Open the mold gate;

[0041] d) Move the injection piston, which is at least partially provided in the nozzle, toward the mold gate, so as to transfer a predetermined volume of molten material from the hot runner nozzle to the mold cavity;

[0042] e) Close the communication between the nozzle and the mold cavity by moving the valve needle to engage with the mold gate.

[0043] The present invention provides the advantage of stably delivering a metered amount of melt into the mold cavity.

Description of the drawings

[0044] The embodiments of the present invention will be described more completely with reference to the accompanying drawings, in which:

[0045] FIG. 1 is a side sectional view of the injection molding apparatus of the present invention;

[0046] FIG. 2 is a side sectional view of the valve of the piston shown in FIG. 1;

[0047] FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2;

[0048] FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. 3;

[0049] FIGS. 5 to 9 are schematic side views of the part shown in FIG. 1 in different stages of the injection cycle;

[0050] FIG. 10 is a schematic side cross-sectional view of another embodiment of the injection molding apparatus of the present invention.

Detailed ways

[0051] Referring to FIG. 1, a part of an injection molding apparatus is shown with reference numeral 10 in the figure. The injection molding apparatus 10 includes a manifold 12 having a manifold melt channel 14 for receiving a melt flow of moldable material under pressure from a manifold bushing 16. The manifold bushing 16 communicates with a machine nozzle (not shown). A hole 20 extends through the manifold 12 at the end of the manifold melt channel 14. The hole 20 communicates with the melt channel 14 and extends substantially orthogonal thereto.

[0052] A hot runner nozzle 18 is connected to the lower surface of the manifold 12. The nozzle channel 22 of each nozzle 18 is aligned with the corresponding hole 20 in order to receive a melt flow of moldable material from the manifold 12. The mold gate 24 is provided near the tip of each nozzle 18. The mold gate 24 can be opened to allow the melt flow to be transferred into the corresponding mold cavity 26. Any number of nozzles 18 can be used to feed one or more mold cavities 26. The cavity 26 may have the same size and shape, or may have different sizes and shapes. A manifold heater (not shown) and nozzle heater 32 maintain the melt flow at a desired temperature, and cooling channels (not shown) can promote cooling of the mold cavity 26.

[0053] A metering device in the form of a hot runner injection piston 40 can slide within the hole 20 of the manifold 12 and the nozzle 18. The valve needle 28 extends through the central hole 42 of the injection piston 40 and can slide therein to open and close the mold gate 24. The injection piston 40 and the valve needle 28 can be driven independently and move with each other. The valve needle 28 can be pneumatically driven by the valve piston 30 sliding in the cylinder 34. The injection piston 40 can be pneumatically driven by the second piston 44 sliding in the second cylinder 46. The injection piston 40 and the valve needle 28 are not limited to being driven pneumatically, they can be driven hydraulically, or driven by any other suitable devices including electric motors and electromagnetic motors. In addition, the valve needle 28 may be replaced by other types of gate mechanisms.

[0054] The injection piston 40 also includes a piston body 50 that protrudes outward from the second piston 44. The piston body 50 is connected to the second piston 44 ±o by a fastener (not shown). Alternatively, the piston body 50 may be integrated with the piston 44. The piston body 50 includes an outer surface 51 that can block the communication between the manifold channel 14 and the nozzle channel 22 during the movement of the piston body 50 toward the mold cavity 26. An annular groove 48 is provided in the outer surface 51 of the piston body 50. It can be understood that the annular groove 48 need not extend around the entire circumference of the outer surface 51. A valve 52 is provided adjacent to the groove 48 at the front end of the piston body 50. The valve 52 can be opened to establish communication between the groove 48 and the melt cavity 54 of the nozzle channel 22. The melt cavity 54 of the nozzle channel 22 is provided between the mold gate 24 and the valve 52. When the injection piston 40 is in the retracted position and the valve needle 28 is in the closed position, the melt volume in the melt chamber 54 of the nozzle 18 is known. This known volume of melt in the melt cavity 54 corresponds to the volume of melt that will be injected into each mold cavity 26. The close proximity of the melt to be injected and the known volume of the cavity 26 reduces the amount of change experienced in prior art devices.

[0055] See Figures 2-4, where the valve 52 is better shown. The valve includes a flange 56 which extends outwardly from the lower end of the piston body 50. As shown in Figure 3, the flange 56 includes a set of cuts 58 spaced around its circumference. The disk 66 can move axially relative to the flange 56. The disc 66 includes a second set of cuts 72 spaced around its circumference. The disc 66 is oriented such that the second set of cuts 72 are angularly offset from the set of cuts 58 of the flange 56. The disc 66 and the flange 56 have the same outer diameter. This arrangement ensures that when the disc 66 is resting on the flange 56, no melt can flow through the valve 52 in any direction, so that the required amount of melt in the melt cavity 54 can be injected into the mold cavity. 26 in.

[0056] The disc 66 also includes a rod 68 extending outwardly therefrom and an enlarged head 70 mounted on the end of the rod 68. A central chamber 60 is provided in the lower end of the piston body 50, which is used to accommodate the enlarged head 70 and limit its stroke. When the valve 52 is in the fully open position, the enlarged head 70 rests on the shoulder 62 of the central chamber 60. The rod 68 can move axially through the square hole 64 so as to reciprocate the disk 66 to engage and disengage the flange 56. A square shape is used to prevent the disk 66 from rotating relative to the flange 56. It is understood that the rod 68 may have any shape or configuration that can prevent the disk 66 from rotating. For example, the rod 68 may be a circular shape with a groove for accommodating a pipe pin. Due to the force exerted on it by the melt in the nozzle channel, the disk 66 can move together with the piston body 50 or independently of its movement. The retreat of the injection piston 40 opens the valve 52 by forming a gap 80 between the flange 56 and the disk 66, and the extension of the injection piston 40 closes the valve 52 by eliminating the gap 80. Other settings can be used to provide a valve capable of performing the same function.

[0057] In operation, the high-pressure melt flow flows through the manifold bushing 16 to the manifold channel 14 of the manifold 12. Referring to FIG. 5, the cycle starts when the mold gate 24 is in the closed position, where the valve needle 28 is engaged with the mold gate 24, and the injection piston 40 is in the retracted position. In the retracted position, the groove 48 is aligned with the manifold channel 14 to receive melt therefrom. The melt flows from the manifold 12 into the groove 48, which forces the valve 52 into a fully open position, thereby allowing the nozzle channel 22 to be filled. Once the nozzle 18 is filled with melt, the injection piston 40 moves toward the extended position as indicated by the arrow 82 in FIG. 6. The forward movement of the injection piston 40 causes the disk 66 to be forced to move towards the flange 56, thereby closing the valve 52. At the same time, the outer surface 51 of the piston body 50 cuts off the communication between the manifold channel 14 and the nozzle channel 22. In this position, no other melt can enter the melt cavity 54. See Figure 7, once the melt cavity 54 has been isolated from the rest of the nozzle channel 22, the mold is poured

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The port 24 is opened by retracting the valve needle 28 as indicated by the arrow 84. As shown in FIG. 8, the forward stroke of the injection piston 40 as indicated by the arrow 86 forces the melt in the melt cavity 54 of the nozzle channel 22 into the mold cavity 26. Then, the mold gate 24 is closed by extending the valve needle 28 as shown by the arrow 88 in FIG. 9, and the injection piston 40 returns to the retracted position as shown by the arrow 90. This returns the injection piston 40 and valve needle 28 to the position shown in FIG. 5 so that the cycle can be repeated. It can be understood that this arrangement ensures that the volume of the melt injected into the cavity 26 is equal for each cavity 26 and is constant for each cycle.

[0058] Referring to FIG. 10, another embodiment of the injection molding device 110 is shown in the figure. For the parts corresponding to the parts already introduced, the number used in the introduction of Figure 1 plus 100 is used to indicate. The injection molding device 110 is similar to the injection molding device 10 shown in FIG. 1, but it adds pressure sensors 200, 202, and 204, which are provided in the mold cavity 126, the nozzle channel 122, and the manifold channel 114, respectively. The pressure sensors 200, 202, and 204 send information to the hot runner and mold controller 206 for controlling the timing and sequence of the movement of the injection piston 140 and the valve needle 128. It can be understood that it is not necessary to use all three pressure sensors 200, 202, and 204. If necessary, only one or two of the pressure sensors 200, 202, and 204 may be used.

[0059] Temperature sensors 208 and 210 are provided to measure the temperature of the melt in the mold cavity 126 and the nozzle 118, respectively. Additional sensors (not shown) may be provided in the manifold 112. Similar to the pressure sensors 200, 202, and 204, the temperature sensors 208, 210 also send information to the controller 206 for controlling the timing and sequence of the movement of the injection piston 140 and the valve needle 128. The controller 206 may communicate with the motion drive device 216, and the motion drive device 216 may communicate with the position sensors 212 and 214. The position sensors 212 and 214 are used to control the position and movement of the injection piston 140 and the valve needle 128, respectively. The sensor can be any type of sensor, such as an optical sensor or an inductive sensor. In some cases, only the position sensors 212 and 214 are used to simplify the injection molding apparatus 110.

[0060] This arrangement is particularly useful in an injection molding apparatus 110 in which all mold cavities have the same size. The sensors 200, 202, and 204 can be used to ensure that the pressures in the cavities 126 are approximately equal, and that the pressures are also equal between different batches of molded products. The sensors 200, 202, and 204 can also be used in a kit mold, where the pressure in each mold cavity 126 is different and corresponds to a predetermined value.

[0061] Since the manifold usually supports more than one nozzle, those skilled in the art can understand that the movement of the individual pistons of each nozzle can be staggered so that the pressure from the machine nozzle can be kept stable.

[0062] In another embodiment, the mold cavity 26 has a different size. In order to fill each mold cavity 26 correctly, the melt cavity 54 of each nozzle 18 must be sized to accommodate the correct volume of melt. The nozzle 18 associated with each mold cavity 26 is the same, but each injection piston 40 must be made to have a corresponding size.

[0063] Although the preferred embodiments of the present invention have been introduced, those skilled in the art can understand that changes and improvements can be made to the present invention without departing from the spirit and scope defined by the appended claims.