Injection molding pressure maintaining device

Abstract

The utility model discloses an injection molding pressure maintaining device which comprises a main glue injection nozzle, a main hot runner plate, a branch runner plate and a plurality of glue injection modules, each glue injection module comprises an injection nozzle, a glue storage bin, a hydraulic cylinder and a pressure maintaining limiting mechanism, the hydraulic cylinder comprises a first cylinder body, a first piston and a transmission rod, the first cylinder body has the maximum stroke, and the second cylinder body has the maximum stroke. The first piston is slidably connected into the first cylinder body and fixedly connected with the transmission rod, one end of the transmission rod extends out of the first cylinder body and is connected with a plunger, the plunger is slidably connected into the glue storage bin, the other end of the transmission rod extends out of the first cylinder body and is connected with a limiting piece, and the pressure maintaining limiting mechanism is connected with the first cylinder body and can limit movement of the limiting piece. In the pressure maintaining stage, the pressure maintaining limiting mechanism moves so that the first piston can move by a first stroke, the first stroke is smaller than the maximum stroke, and in the pressure maintaining stage, the pressure maintaining limiting mechanism moves so that the first piston can continue to move. According to the glue injection pressure maintaining device provided by the embodiment of the utility model, uniform glue feeding amount can be realized, and pressure maintaining and material supplementing can be carried out.

Description

Technical Field

[0001] The utility model relates to the technical field of injection molding, in particular to an injection pressure maintaining device. Background Art

[0002] Injection molding is a processing method used for mass-producing some parts with complex shapes. Specifically, it means injecting the heat-melted material into the mold cavity under high pressure, and after cooling and solidifying, the formed product is obtained. In the prior art, usually a structure of one mold with multiple cavities is adopted. By arranging multiple sub-runners, the colloid from the main runner is split into multiple nozzles to inject glue into multiple mold cavities, so as to improve the efficiency. However, this method is prone to uneven glue injection volume in multiple sub-runners, resulting in incomplete filling of individual products. And because the volume of the colloid will shrink after cooling, it will also cause incomplete filling of the products, and the yield is low. Content of the Utility Model

[0003] The utility model aims to at least solve one of the technical problems existing in the prior art. For this reason, the utility model provides an injection pressure maintaining device, which can achieve uniform glue injection volume and perform pressure maintaining and feeding after the colloid in the product mold cavity is cooled, thereby improving the yield.

[0004] An injection pressure maintaining device according to the utility model includes a main injection nozzle, a main hot runner plate, a sub-runner plate and a plurality of injection modules. The main injection nozzle is connected to the main hot runner plate, and a main runner communicating with the main injection nozzle is arranged in the main hot runner plate; the sub-runner plate is connected to the main hot runner plate, and a sub-runner communicating with the main runner is arranged in the sub-runner plate; each injection module includes an injection nozzle, a glue storage bin, a hydraulic cylinder and a pressure maintaining limiting mechanism. The sub-runner, the glue storage bin, the injection nozzle and the mold cavity of the product are sequentially communicated. The hydraulic cylinder includes a first cylinder body, a first piston and a transmission rod. The first cylinder body has a maximum stroke. The first piston is slidably connected in the first cylinder body and fixedly connected to the transmission rod. One end of the transmission rod extends out of the first cylinder body and is connected with a plunger. The plunger is slidably connected in the glue storage bin, and the plunger and the inner wall of the glue storage bin are in clearance fit. The other end of the transmission rod extends out of the first cylinder body and is connected with a limiting member. The pressure maintaining limiting mechanism is connected to the first cylinder body. The pressure maintaining limiting mechanism can limit the movement of the limiting member so that the first piston moves a first stroke, and the first stroke is less than the maximum stroke. In the pressure maintaining stage, the pressure maintaining limiting mechanism moves so that the first piston can continue to move.

[0005] The injection pressure maintaining device according to the above embodiments of the utility model has at least the following beneficial effects:

[0006] The injection molding holding pressure device provided by the embodiment of the present utility model is provided with a glue storage bin. The glue enters the main runner from the main injection nozzle, and then is branched to each glue storage bin through the branch runner until each glue storage bin is filled, and then is transported to the injection nozzle by the hydraulic cylinder for injection molding, thereby realizing a uniform glue injection volume. The volume of the glue storage bin is designed according to the cavity volume of the product, and the volume of the glue storage bin should be larger than the cavity volume of the product, so as to ensure that the glue in the glue storage bin can completely fill the cavity of the product and reserve a glue volume for holding pressure and feeding material, ensuring the finished product rate. The injection molding holding pressure device provided by the embodiment of the present utility model restricts the moving stroke of the limiting member through the holding pressure limiting mechanism, and further restricts the first piston from moving the maximum stroke. When the first piston moves the first stroke, the amount of glue pushed by the plunger can fill the cavity of the product. During the holding pressure stage, the glue in the cavity of the product shrinks in volume due to cooling. After a certain holding pressure time, the holding pressure limiting mechanism moves to release the restriction on the limiting member, so that the limiting member can continue to move, and further the first piston can continue to move a certain stroke, and the amount of glue pushed by the plunger can feed the missing part of the product cavity, thereby realizing holding pressure and feeding material, ensuring the complete filling of the product cavity, and improving the finished product rate.

[0007] According to some embodiments of the present utility model, the holding pressure limiting mechanism includes a second cylinder body and a second piston. The second cylinder body is connected to the side of the first cylinder body away from the plunger. The second piston is slidably connected in the second cylinder body. The axial direction of the second piston is the same as the axial direction of the first piston. The second cylinder body is provided with an oil port, and the oil port is located on the side of the second piston close to the first cylinder body. The second cylinder body has a second stroke, and the second stroke is smaller than the first stroke. A through hole is provided on the side of the second cylinder body away from the first cylinder body. One end of the transmission rod sequentially passes through the second cylinder body, the second piston and the through hole and is provided with the limiting member. The limiting member can enter the through hole and abut against the second piston.

[0008] According to some embodiments of the present utility model, a threaded column is provided in the middle of the end of the transmission rod away from the plunger. The limiting member includes a shaft sleeve and an adjusting nut. The shaft sleeve is sleeved on the threaded column and is limited by the adjusting nut.

[0009] According to some embodiments of the present utility model, a positioning hole is provided on the side of the second piston close to the shaft sleeve. The positioning hole is adapted to the shape of the shaft sleeve, and at least one gasket is provided on the bottom wall of the positioning hole.

[0010] According to some embodiments of the present utility model, the injection and holding pressure device further includes a mold body. The main injection nozzle is disposed on the mold body. The main hot runner plate is connected to the bottom of the mold body. The sub-runner plate is connected to the side of the main hot runner plate. The injection nozzle is disposed on the main hot runner plate. One end of the glue storage bin is disposed within the main hot runner plate and communicates with the injection nozzle. The other end of the glue storage bin is disposed within the sub-runner plate and communicates with the sub-runner. The first cylinder body is connected to the side of the sub-runner plate.

[0011] According to some embodiments of the present utility model, the injection nozzle is connected with a needle valve assembly. The needle valve assembly includes a piston assembly and a valve needle. The piston assembly is disposed on the mold body and is connected to a compressed air path. One end of the valve needle is connected to the piston assembly, and the other end of the valve needle extends into the injection nozzle.

[0012] According to some embodiments of the present utility model, the piston assembly includes a piston body and a fixing sleeve. The piston body is disposed within the mold body and can reciprocate within the mold body. The fixing sleeve is fixedly connected to the piston body by a thread. One end of the valve needle is connected to the fixing sleeve.

[0013] According to some embodiments of the present utility model, the needle valve assembly further includes a guiding sleeve. The guiding sleeve is disposed on the main hot runner plate. The valve needle penetrates through the guiding sleeve and is slidably connected to the guiding sleeve.

[0014] The additional aspects and advantages of the present utility model will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present utility model. Description of the Drawings

[0015] The following further describes the present utility model in conjunction with the drawings and embodiments, where:

[0016] Figure 1 is a schematic structural diagram of an injection and holding pressure device according to some embodiments of the present utility model;

[0017] Figure 2 is a schematic diagram of the first stage of an injection and holding pressure device according to some embodiments of the present utility model;

[0018] Figure 3 is a schematic diagram of the second stage of an injection and holding pressure device according to some embodiments of the present utility model;

[0019] Figure 4 is a schematic diagram of the third stage of an injection and holding pressure device according to some embodiments of the present utility model;

[0020] Figure 5 Schematic diagram of the fourth stage of the injection pressure-holding device according to some embodiments of the present utility model.

[0021] Among them, reference numerals:

[0022] Main injection nozzle 100;

[0023] Main hot runner plate 200;

[0024] Sub-runner plate 300;

[0025] Injection nozzle 400; valve needle 410; piston body 420; fixed sleeve 430; alignment sleeve 440;

[0026] Glue storage bin 500;

[0027] First cylinder block 600; first piston 610; transmission rod 620; plunger 630; threaded column 640; bushing 650; adjusting nut 660;

[0028] Second cylinder block 700; through hole 701; second piston 710; positioning hole 711;

[0029] Mold body 800;

[0030] Product 900. Detailed implementation manners

[0031] The embodiments of the present utility model will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions from beginning to end. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present utility model, and should not be construed as a limitation to the present utility model.

[0032] In the description of the present utility model, it should be understood that for the orientation description, such as the orientation or positional relationship indicated by up, down, front, back, left, right, etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present utility model.

[0033] In the description of the present utility model, the meaning of several is one or more, the meaning of multiple is two or more, greater than, less than, exceeding, etc. are understood as not including the present number, and above, below, within, etc. are understood as including the present number. If the first and second are described only for the purpose of distinguishing technical features, they should not be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence of the indicated technical features.

[0034] In the description of the present utility model, unless otherwise clearly defined, terms such as "arrangement", "installation", "connection", etc. shall be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present utility model in combination with the specific content of the technical solution. In the description of the present utility model, the description referring to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0035] Referring to Figures 1 to 5 , an injection pressure-holding device proposed according to the present utility model includes a main injection nozzle 100, a main hot runner plate 200, a sub-runner plate 300, and a plurality of injection modules. The main injection nozzle 100 is connected to the main hot runner plate 200, and a main runner communicating with the main injection nozzle 100 is provided in the main hot runner plate 200; the sub-runner plate 300 is connected to the main hot runner plate 200, and a sub-runner communicating with the main runner is provided in the sub-runner plate 300; the injection module includes an injection nozzle 400, a glue storage bin 500, a hydraulic cylinder, and a pressure-holding limiting mechanism. The sub-runner, the glue storage bin 500, the injection nozzle 400, and the cavity of the product 900 are sequentially communicated. The hydraulic cylinder includes a first cylinder body 600, a first piston 610, and a transmission rod 620. The first cylinder body 600 has a maximum stroke. The first piston 610 is slidably connected to the inside of the first cylinder body 600 and fixedly connected to the transmission rod 620. One end of the transmission rod 620 extends out of the first cylinder body 600 and is connected to a plunger 630. The plunger 630 is slidably connected to the inside of the glue storage bin 500. The plunger 630 and the inner wall of the glue storage bin 500 are in clearance fit. The other end of the transmission rod 620 extends out of the first cylinder body 600 and is connected to a limiting member. The pressure-holding limiting mechanism is connected to the first cylinder body 600. The pressure-holding limiting mechanism can limit the movement of the limiting member so that the first piston 610 moves a first stroke, and the first stroke is less than the maximum stroke. During the pressure-holding stage, the pressure-holding limiting mechanism moves so that the first piston 610 can continue to move.

[0036] It can be understood that the injection molding pressure holding device provided by the embodiment of the present utility model is provided with a glue storage bin 500. The glue enters the main runner from the main injection nozzle 100, and then is divided into each glue storage bin 500 through the sub-runners until each glue storage bin 500 is filled. Then, it is transported to the injection nozzle 400 through the hydraulic cylinder for injection, thereby realizing a uniform glue feeding amount. The volume of the glue storage bin 500 is designed according to the cavity volume of the product 900, and the volume of the glue storage bin 500 should be greater than the cavity volume of the product 900, so as to ensure that the glue in the glue storage bin 500 can completely fill the cavity of the product 900 and reserve a glue amount for pressure holding and feeding, ensuring the finished product rate. The injection molding pressure holding device provided by the embodiment of the present utility model restricts the moving stroke of the limiting member through the pressure holding limiting mechanism, and further restricts the first piston 610 from moving the maximum stroke. When the first piston 610 moves the first stroke, the amount of glue correspondingly pushed by the plunger 630 can fill the cavity of the product 900. In the pressure holding stage, the glue in the cavity of the product 900 shrinks in volume due to cooling. After a certain pressure holding time, the pressure holding limiting mechanism moves to release the restriction on the limiting member, enabling the limiting member to continue to move, and further enabling the first piston 610 to continue to move a certain stroke. The amount of glue correspondingly pushed by the plunger 630 can feed the missing part of the cavity of the product 900, thereby realizing pressure holding and feeding, ensuring the complete filling of the cavity of the product 900, and improving the finished product rate.

[0037] Further, referring to Figures 2 to 5 , according to some embodiments of the present utility model, the pressure holding limiting mechanism includes a second cylinder body and a second piston 710. The second cylinder body is connected to the side of the first cylinder body 600 away from the plunger 630. The second piston 710 is slidably connected in the second cylinder body. The axial direction of the second piston 710 is the same as that of the first piston 610. The second cylinder body is provided with an oil port, and the oil port is located on the side of the second piston 710 close to the first cylinder body 600. The second cylinder body has a second stroke, and the second stroke is smaller than the first stroke. A through hole 701 is provided on the side of the second cylinder body away from the first cylinder body 600. One end of the transmission rod 620 passes through the second cylinder body, the second piston 710, and the through hole 701 in sequence and is provided with a limiting member. The limiting member can enter the through hole 701 and abut against the second piston 710.

[0038] It can be understood that before pressure holding and feeding, pressure oil is injected into the second cylinder block through the oil port, so that the second piston 710 cannot move towards the first cylinder block 600. The first cylinder block 600 is connected to an oil circuit, and the first piston 610 is driven to move through the oil circuit to drive the plunger 630 to push the colloid in the glue storage bin 500. At the same time, the first piston 610 drives the transmission rod 620 to move, thereby driving the limiting member to move until the limiting member enters the through hole 701 and abuts against the second piston 710. Since the second piston 710 cannot move under the action of the pressure oil, the limiting member cannot continue to move, and further the first piston 610 cannot continue to move. That is to say, even if the oil circuit continues to apply pressure to the first piston 610 through oil injection, the first piston 610 still cannot complete the maximum stroke, but can only maintain the first stroke. At this time, the amount of colloid pushed by the plunger 630 corresponding to the first stroke can fill the mold cavity of the product 900. During the pressure holding stage when the first piston 610 cannot continue to move, the colloid in the mold cavity of the product 900 shrinks in volume due to cooling. After a certain pressure holding time, the second cylinder block discharges the pressure oil through the oil port, so that the second piston 710 can move. Then, since the oil circuit continuously provides pressure to the first piston 610, at this time, the first piston 610 can continue to move under the drive of the oil circuit, and drives the limiting member to push the second piston 710 to move through the transmission rod 620. The second stroke that the second piston 710 can move is the stroke that the first piston 610 can move. At this time, the amount of colloid pushed by the plunger 630 corresponding to the second stroke is the amount of colloid replenished to the mold cavity of the product 900, thereby being able to fill the space lacking material in the mold cavity of the product 900 and improving the yield rate.

[0039] It should be noted that in the embodiment of the present invention, the specific volume of the glue storage bin 500, the maximum stroke of the first cylinder block 600, the first stroke of the second piston 710 moving, and the second stroke of the second piston 710 moving are all designed according to the mold cavity volume of the actual product 900, and no specific limitation is made here.

[0040] It should be noted that in the embodiment of the present invention, the total stroke of the first piston 610 after moving the first stroke and the second stroke can be equal to the maximum stroke of the first cylinder block 600, or can be less than the maximum stroke of the first cylinder block 600, and can be designed according to the actual situation, and will not be elaborated here.

[0041] Further, referring to Figures 2 to 5 , according to some embodiments of the present invention, a threaded post 640 is provided in the middle of the end of the transmission rod 620 away from the plunger 630. The limiting member includes a bushing 650 and an adjusting nut 660. The bushing 650 is sleeved on the threaded post 640 and is limited by the adjusting nut 660.

[0042] It can be understood that when using the glue injection and pressure maintaining device to inject glue into multiple products 900 simultaneously, the amount of glue required by different products 900 or the same product 900 under different conditions before the pressure maintaining stage may vary. If the glue injection amount is still uniformly set, it is easy to result in the products 900 still being unqualified after pressure maintaining and glue replenishment. Therefore, during the actual production process, it is necessary to adjust the first stroke of the first piston 610 to adjust the amount of glue pushed by the plunger 630.

[0043] To solve the above technical problems, in the embodiment of the present utility model, a threaded post 640 is provided at one end of the transmission rod 620 away from the plunger 630. The bushing 650 is sleeved on the threaded post 640, and the position of the bushing 650 is limited by the adjusting nut 660. Thus, the moving stroke of the first piston 610 is restricted through the cooperation of the bushing 650 and the second piston 710, and the position of the bushing 650 is adjusted by adjusting the position of the adjusting nut 660, thereby adjusting the first stroke of the first piston 610, and further adjusting the amount of glue pushed by the plunger 630 corresponding to the first stroke. Specifically, when it is necessary to increase the first stroke to increase the glue injection amount, the adjusting nut 660 is screwed outward so that the adjusting nut 660 moves away from the second piston 710, enabling the bushing 650 to move along the threaded post 640. When the first piston 610 moves driven by the oil circuit, since the immovable second piston 710 will push the bushing 650 towards the adjusting nut 660, the distance between the bushing 650 and the first piston 610 increases, that is, the first stroke that the first piston 610 can move increases, thereby increasing the glue injection amount. Similarly, when it is necessary to reduce the first stroke to reduce the glue injection amount, the adjusting nut 660 is screwed inward to adjust the distance between the bushing 650 and the first piston 610. The structure is simple and the operation is convenient.

[0044] It should be noted that the adjustable range of the bushing 650 does not exceed the dimension range of the threaded post 640, and the actual dimensions can be designed according to actual production requirements, and no specific limitations are made here.

[0045] Further, referring to Figures 2 to 5 , according to some embodiments of the present utility model, a positioning hole 711 is provided on one side of the second piston 710 close to the bushing 650. The positioning hole 711 is adapted to the shape of the bushing 650, and at least one gasket is provided on the bottom wall of the positioning hole 711.

[0046] It can be understood that the provision of the positioning hole 711 helps the cooperation between the second piston 710 and the bushing 650. By providing the gasket, in addition to playing a buffering role, the distance between the bushing 650 and the second piston 710 can also be adjusted by reducing or increasing the number of gaskets, thereby adjusting the first stroke of the first piston 610.

[0047] Further, according to some embodiments of the present invention, the pressure-holding and limiting mechanism can also be of other structural forms. For example, a stop block can be used to block the movement of the limiting member, and a driving structure such as a motor is used to drive the stop block away from the limiting member so that the limiting member can continue to move. Or other structural forms can be used, which can be determined according to actual production requirements and will not be elaborated here.

[0048] Further, referring to Figure 2 and Figure 5 , according to some embodiments of the present invention, the injection pressure-holding device further includes a mold body. The main injection nozzle 100 is arranged on the mold body. The main hot runner plate 200 is connected to the bottom of the mold body. The sub-runner plate 300 is connected to the side of the main hot runner plate 200. The injection nozzle 400 is arranged on the main hot runner plate 200. One end of the glue storage bin 500 is arranged in the main hot runner plate 200 and communicates with the injection nozzle 400. The other end of the glue storage bin 500 is arranged in the sub-runner plate 300 and communicates with the sub-runner. The first cylinder body 600 is connected to the side of the sub-runner plate 300.

[0049] Further, referring to Figures 2 to 5 , according to some embodiments of the present invention, the injection nozzle 400 is connected with a needle valve assembly for conducting or blocking the injection nozzle 400. The needle valve assembly includes a piston assembly and a valve needle 410. The piston assembly is arranged on the mold body and is connected to the compressed air circuit. One end of the valve needle 410 is connected to the piston assembly, and the other end of the valve needle 410 extends into the injection nozzle 400.

[0050] Further, referring to Figures 2 to 5 , according to some embodiments of the present invention, the piston assembly includes a piston body 420 and a fixing sleeve 430. The piston body 420 is arranged in the mold body and can be driven by the compressed air circuit in the mold body to move reciprocally, thereby driving the valve needle 410 to move. The fixing sleeve 430 is fixedly connected to the piston body 420 by threads. One end of the valve needle 410 is connected to the fixing sleeve 430.

[0051] Further, referring to Figures 2 to 5 , according to some embodiments of the present invention, the needle valve assembly further includes a guiding sleeve 440 arranged on the main hot runner plate 200. The valve needle 410 penetrates through the guiding sleeve 440 and is slidably connected to the guiding sleeve 440. The guiding sleeve 440 plays a role in guiding the valve needle 410 to ensure that the valve needle 410 and the injection nozzle 400 are on the same axis, so as to accurately conduct or block the injection nozzle 400.

[0052] The working principle of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0053] As shown Figure 2 in Figure 1, it is the first stage of the working process of the glue injection and pressure maintaining device. In this first stage, the heated and melted glue is injected into the main runner through the main glue injection nozzle 100, and then into each glue storage bin 500 through the sub-runners until each glue storage bin 500 is filled. At the same time, the valve needle 410 blocks the injection nozzle 400.

[0054] It should be noted that since the valve needle 410 blocks the injection nozzle 400, after the glue storage bin 500 is filled, the glue in the glue storage bin 500 cannot be injected into the cavity of the product 900 through the injection nozzle 400, nor can it flow back to the sub-runners. With the total amount of glue determined, the glue in the sub-runners can fill each glue storage bin 500 in sequence, thus achieving a uniform glue injection volume and preventing the situation where individual products 900 are overfilled or underfilled, ensuring the yield rate.

[0055] As shown Figure 3 in Figure 2, it is the second stage of the working process of the glue injection and pressure maintaining device. In this second stage, the piston body 420 moves upward under the drive of the compressed air circuit to drive the valve needle 410 upward, thus conducting the injection nozzle 400. The first cylinder 600 drives the first piston 610 to move forward through the oil circuit, so that the plunger 630 pushes the glue forward into the injection nozzle 400, and the injection nozzle 400 injects the glue into the cavity of the product 900 until the limiting member abuts against the second piston 710. Since the second piston 710 cannot move forward under the action of the pressure oil, the limiting member cannot continue to move forward, causing the first piston 610 to be unable to continue moving forward under the drive of the oil circuit. At this time, the first piston 610 moves the first stroke, and the plunger 630 correspondingly moves the first stroke forward and pushes the corresponding glue into the injection nozzle 400, so that the injection nozzle 400 can just fill the cavity of the product 900.

[0056] As shown Figure 4 in Figure 3, it is the third stage of the working process of the glue injection and pressure maintaining device. In this third stage, the piston body 420 moves downward under the drive of the compressed air circuit to drive the valve needle 410 downward, thus blocking the injection nozzle 400 to prevent glue leakage. At the same time, the first piston 610 tends to move forward under the action of the oil pressure in the oil circuit, but is unable to continue moving forward due to the obstruction of the second piston 710 to the limiting member.

[0057] As shown Figure 5The figure shows the fourth stage of the operation of the glue injection and pressure holding device, i.e., the pressure holding stage. In this fourth stage, the colloid in the mold cavity of the product 900 gradually shrinks due to cooling. During the period when the volume of the colloid continues to shrink, the first piston 610 still has a tendency to move forward under the pressure of the oil circuit. That is, this period is the pressure holding time. After the volume of the colloid in the mold cavity of the product 900 completes shrinking, i.e., when the pressure holding time ends, the second cylinder discharges the pressure oil through the oil port, enabling the second piston 710 to move, and further enabling the first piston 610 to continue to move forward under the drive of the oil circuit. The second stroke that the second piston 710 can move is the stroke that the first piston 610 can continue to move. The amount of colloid pushed by the plunger 630 corresponding to the second stroke is the amount of colloid replenished to the mold cavity of the product 900, so as to fill the space lacking material in the mold cavity of the product 900, thus completing the pressure holding and material replenishment of the product 900. After completing the pressure holding and material replenishment, the piston body 420 moves downward under the drive of the compressed air circuit to drive the valve needle 410 to move downward, thereby blocking the injection nozzle 400.

[0058] It should be noted that in the embodiments of the present utility model, the pressure holding time can be determined according to actual production requirements and is not specifically limited herein.

[0059] The above has described the embodiments of the present utility model in detail with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments, and various changes can be made without departing from the gist of the present utility model within the knowledge scope of those of ordinary skill in the art.

Claims

1. An injection molding pressure-maintaining device, characterized in that: include: Main injection nozzle; A main hot runner plate, the main glue injection nozzle is connected to the main hot runner plate, and a main flow channel connected to the main glue injection nozzle is arranged in the main hot runner plate; A runner plate connected to the main hot runner plate, wherein a runner communicating with the main runner is disposed in the runner plate; A plurality of glue injection modules include an injection nozzle, a glue storage bin, a hydraulic cylinder and a pressure-holding and limiting mechanism. The branch channel, the glue storage bin, the injection nozzle and the mold cavity of the product are connected in sequence. The hydraulic cylinder includes a first cylinder body, a first piston and a transmission rod. The first cylinder body has a maximum stroke. The first piston is slidably connected in the first cylinder body and fixed to the transmission rod. One end of the transmission rod extends out of the first cylinder body and is connected to a plunger. The plunger is slidably connected to the glue storage bin. The plunger and the inner wall of the glue storage bin are clearance-matched. The other end of the transmission rod extends out of the first cylinder body and is connected to a limiting member. The pressure-holding and limiting mechanism is connected to the first cylinder body. The pressure-holding and limiting mechanism can limit the movement of the limiting member so that the first piston moves a first stroke. The first stroke is less than the maximum stroke. During the pressure-holding stage, the pressure-holding and limiting mechanism moves so that the first piston can continue to move.

2. The injection molding pressure-maintaining device according to claim 1, characterized in that: The pressure-maintaining and limiting mechanism includes a second cylinder body and a second piston, the second cylinder body is connected to the side of the first cylinder body away from the plunger, the second piston is slidably connected to the second cylinder body, the axial direction of the second piston is the same as the axial direction of the first piston, the second cylinder body is provided with an oil port, the oil port is located on the side of the second piston close to the first cylinder body, the second cylinder body has a second stroke, the second stroke is smaller than the first stroke, the side of the second cylinder body away from the first cylinder body is provided with a through hole, one end of the transmission rod passes through the second cylinder body, the second piston and the through hole in sequence and the limiting member is provided, the limiting member can enter the through hole and abut the second piston.

3. The injection molding pressure-maintaining device according to claim 2, characterized in that: A threaded column is arranged at the middle of one end of the transmission rod away from the plunger, and the limiting member comprises a sleeve and an adjusting nut. The sleeve is sleeved on the threaded column and is limited by the adjusting nut.

4. The injection molding pressure-maintaining device according to claim 3, characterized in that: A positioning hole is arranged on a side of the second piston close to the shaft sleeve, the positioning hole is adapted to the shape of the shaft sleeve, and at least one gasket is arranged on the bottom wall of the positioning hole.

5. The injection molding pressure-maintaining device according to claim 1, characterized in that: The injection molding pressure maintaining device also includes a mold body, the main glue injection nozzle is arranged on the mold body, the main hot runner plate is connected to the bottom of the mold body, the branch runner plate is connected to the side of the main hot runner plate, the injection nozzle is arranged on the main hot runner plate, one end of the glue storage bin is arranged in the main hot runner plate and connected to the injection nozzle, the other end of the glue storage bin is arranged in the branch runner plate and connected to the branch runner, and the first cylinder body is connected to the side of the branch runner plate.

6. The injection molding pressure-maintaining device according to claim 5, characterized in that: The injection nozzle is connected to a needle valve assembly, which includes a piston assembly and a valve needle. The piston assembly is arranged on the mold body and connected to the compressed air circuit. One end of the valve needle is connected to the piston assembly, and the other end of the valve needle extends into the injection nozzle.

7. The injection molding pressure-maintaining device according to claim 6, characterized in that: The piston assembly includes a piston body and a fixed sleeve. The piston body is arranged in the mold body and can reciprocate in the mold body. The fixed sleeve is fixedly connected to the piston body through a thread, and one end of the valve needle is connected to the fixed sleeve.

8. The injection molding pressure-maintaining device according to claim 6, characterized in that: The needle valve assembly further comprises a guide sleeve, which is arranged on the main hot runner plate, the valve needle passes through the guide sleeve, and the valve needle is slidably connected to the guide sleeve.

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