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CN-122008483-A - Pre-molding mechanism with pressure maintaining function and injection molding machine

CN122008483ACN 122008483 ACN122008483 ACN 122008483ACN-122008483-A

Abstract

The invention relates to the technical field of injection molding, in particular to a pre-molding mechanism with a pressure maintaining function and an injection molding machine, comprising an injection molding frame, an injection molding head, a rotary valve element and a reverse pushing assembly, wherein a rotary valve element is arranged in an injection molding pipeline to divide the pipeline cavity into an injection molding cavity and a feeding cavity, the pressure driving assembly is used for sensing the pressure change of the feeding cavity, when the pressure exceeds a threshold value, a rotary valve element is automatically driven to rotate to enable a fixed valve channel to be communicated with a rotary valve channel so as to realize controllable on-off of a melt, and meanwhile, the reverse pushing assembly is arranged, when a spiral push rod is reset, the spiral push rod is in transmission connection with the rotary valve element to drive the rotary valve element in a closed state to move towards the injection molding cavity, and the melt in the injection molding cavity is extruded, so that after the screw rod is retracted, the pressure compensation is actively applied to the cavity, and the problems of shrinkage cavity, dent and other quality defects of products caused by the backflow of the melt and incapacity of active pressure compensation when the screw rod in the existing pre-molding mechanism are solved.

Inventors

  • YU XUEFENG

Assignees

  • 伯恩智能装备(宁波)有限公司

Dates

Publication Date
20260512
Application Date
20260413

Claims (10)

  1. 1. A pre-molding mechanism with dwell function, characterized by comprising: The injection molding machine comprises an injection molding machine frame, wherein one side of the injection molding machine frame is provided with an injection molding pipeline, the other side of the injection molding machine frame is provided with a pushing cylinder, a sliding frame is further arranged in the injection molding machine frame and connected with an output rod of the pushing cylinder, a motor is arranged on the sliding frame, a spiral push rod is arranged in the injection molding pipeline, and the spiral push rod is in transmission connection with an output shaft of the motor; the injection molding head is arranged at the outlet of the injection molding pipeline; The rotary valve member is arranged in the injection molding pipeline in a sliding manner along the axial direction of the injection molding pipeline and divides the inner cavity of the injection molding pipeline into an injection molding cavity communicated with the cavity and a feeding cavity communicated with a space where the spiral push rod is arranged, and comprises a fixed valve core and a rotary valve core which are coaxially arranged, and a pressure driving component for driving the rotary valve core to rotate relative to the fixed valve core; The reverse pushing assembly is arranged in the injection molding pipeline, is in transmission connection with the spiral pushing rod and the rotary valve element, and is used for driving the rotary valve element in a closed state to extrude the injection molding cavity when the spiral pushing rod is reset.
  2. 2. The pre-molding mechanism with the pressure maintaining function according to claim 1, wherein the rotary valve member further comprises a sliding cylinder coaxially and slidably arranged in the injection molding pipeline, the fixed valve core is coaxially arranged at one end of the sliding cylinder facing the injection molding cavity, and the rotary valve core is rotatably arranged in the sliding cylinder and is abutted against one side of the fixed valve core facing the feeding cavity.
  3. 3. The mechanism according to claim 2, wherein a driven cylinder is provided at an end of the rotary spool facing the feed chamber, a disposition chamber is formed between an inner periphery of the sliding cylinder and an outer periphery of the driven cylinder, an arc-shaped groove is provided at the outer periphery of the driven cylinder, and the pressure driving assembly comprises: A pressure ring coaxially and slidably arranged in the placement cavity and in spline connection with the inner periphery of the sliding cylinder, wherein a driving block sliding with the arc-shaped groove is arranged on the inner periphery of the pressure ring; And the elastic element is arranged in the arranging cavity and is abutted against the pressure ring.
  4. 4. The pre-molding mechanism with pressure maintaining function according to claim 3, wherein a limiting boss is arranged at one end of the periphery of the driven cylinder towards the feeding cavity, and the pressure ring is elastically abutted to one end of the limiting boss.
  5. 5. The pressure maintaining mechanism as claimed in any one of claims 2 to 4, wherein a connecting shaft is provided at one end of the rotary valve core, the connecting shaft penetrates through the fixed valve core and is rotatably connected with the fixed valve core, and a snap ring is provided at one end of the connecting shaft extending to the injection cavity.
  6. 6. The pressure maintaining mechanism as set forth in any one of claims 1 to 4, wherein an outer chamber and an inner chamber are coaxially disposed in the opening of the injection molding pipe, a connection hole is formed between the outer chamber and the inner chamber, and the reverse pushing assembly includes: One end of the inner pushing cylinder is coaxially connected with the rotary valve element, the other end of the inner pushing cylinder extends into the inner cavity and forms an inner piston end, an inner pressure cavity is formed by surrounding the outer periphery of the inner pushing cylinder and the inner wall of the inner cavity, and the inner pressure cavity is communicated with the connecting hole; one end of the push rod is connected with the head of the spiral push rod, the other end of the push rod extends into the outer cavity to form an outer piston end, an outer pressure cavity is formed by enclosing between the outer piston end and the inner wall of the outer cavity, and the outer pressure cavity is communicated with the connecting hole; The inner pressure cavity and the outer pressure cavity are filled with hydraulic oil.
  7. 7. The pre-molding mechanism with pressure maintaining function according to claim 6, wherein the reverse pushing assembly further comprises a connecting rod penetrating through the head of the spiral push rod along the radial direction, and two ends of the connecting rod are fixedly connected with the push cylinder.
  8. 8. The pressure maintaining mechanism as set forth in claim 6, wherein the inner periphery of the injection molding pipe is provided with a limit groove extending in an axial direction thereof, and the outer side of the rotary valve member is provided with a stopper extending into the limit groove and slidably fitted therewith.
  9. 9. The pre-molding mechanism with dwell function of claim 6, wherein said reverse pushing assembly further comprises: the fixed cylinder is coaxially arranged in the injection molding pipeline; The separating cylinder is coaxially arranged in the fixed cylinder, an outer cavity is formed between the outer periphery of the separating cylinder and the inner periphery of the fixed cylinder, a positioning cylinder is arranged at one end of the separating cylinder, which faces the feeding cavity, an inner cavity is formed between the outer periphery of the positioning cylinder and the inner periphery of the separating cylinder, and the connecting holes are axially distributed on the separating cylinder.
  10. 10. An injection molding machine with a pressure maintaining function, characterized by comprising a pre-molding mechanism with a pressure maintaining function as set forth in any one of claims 1 to 4.

Description

Pre-molding mechanism with pressure maintaining function and injection molding machine Technical Field The invention relates to the technical field of injection molding, in particular to a pre-molding mechanism with a pressure maintaining function and an injection molding machine. Background In the injection molding process, the pre-molding mechanism is responsible for melting and conveying solid plastic particles to the front end of an injection molding pipeline, and after the melt reaches a preset amount, the melt is pushed by a screw rod to be injected into a mold cavity, so that the product molding is completed. To ensure product compactness and dimensional stability, the injection molding process usually needs to enter a pressure maintaining stage after injection is finished so as to supplement the volume vacancy generated by melt cooling shrinkage. However, existing pre-molding mechanisms have significant drawbacks in practical applications. Since the injection action of the injection molding machine requires a certain margin, typically only about 98% of the melt is injected into the mold cavity, after which the screw stops rotating and is retracted. In the screw rod rollback process, residual melt in the injection nozzle easily flows back to the feeding cavity under the action of pressure difference, and does not continuously enter the cavity to fill the shrinkage space. Even if a part of the melt can flow into the cavity, the flow and pressure thereof are difficult to control, and a stable and effective pressure maintaining effect cannot be formed. This leads to quality defects such as shrinkage cavities, dents and the like in the product, and on the other hand, leads to an extended molding cycle and reduced process stability. To solve the above problems, a scheme of providing a check valve in the nozzle, which prevents the backflow of melt through the check valve, has been proposed in the prior art. However, the scheme has the defects that the opening and closing of the check valve depend on the flow direction of melt, the response is delayed, the pressure compensation cannot be actively applied to the cavity after the screw rod is retracted, the axial movement of the valve core can change the valve cavity volume to cause pressure fluctuation, the check structure is in the form of a ball valve or a cone valve, the sealing reliability is limited, and the high requirement of precise injection molding is difficult to meet. Therefore, developing a pre-molding mechanism that can automatically close the flow channel after the screw rod is retracted, prevent backflow, and actively apply pressure compensation to the cavity is a technical problem to be solved in the art. Disclosure of Invention The injection molding machine comprises a rotary valve, a rotary valve core, a rotary valve and a rotary pushing assembly, wherein the rotary valve is arranged in an injection molding pipeline, the rotary valve is arranged in the injection molding pipeline, the pipeline is divided into an injection molding cavity and a feeding cavity, the pressure of the feeding cavity is sensed by a pressure driving assembly, when the pressure exceeds a threshold value, the rotary valve core is automatically driven to rotate so as to enable a fixed valve channel to be communicated with the rotary valve channel, and controllable on-off of a melt is realized. The invention provides a pre-molding mechanism with a pressure maintaining function, which comprises an injection molding machine frame, wherein an injection molding pipeline is arranged on one side of the injection molding machine frame, a pushing cylinder is arranged on the other side of the injection molding machine frame, a sliding frame is further arranged in the injection molding machine frame and connected with an output rod of the pushing cylinder, a motor is arranged on the sliding frame, a spiral push rod is arranged in the injection molding pipeline and is in transmission connection with an output shaft of the motor, an injection molding head is arranged at an outlet of the injection molding pipeline, a rotary valve member is arranged in the injection molding pipeline in a sliding mode along the axial direction of the injection molding pipeline and divides an inner cavity of the injection molding pipeline into an injection molding cavity communicated with the cavity and a feeding cavity communicated with a space where the spiral push rod is arranged, the rotary valve member comprises a fixed valve element and a rotary valve element which are coaxially arranged, and a pressure driving component for driving the rotary valve element to rotate relative to the fixed valve element, a rotary valve channel is arranged on the fixed valve element, when the pressure driving component is arranged at the preset position, the rotary valve element is in a reset state of being in which the rotary valve element is in a rotary valve driving mode of being in which the rotary valve elemen