Injection cylinder structure of magnesium alloy injection molding machine

Abstract

The application discloses a structure of an injection cylinder of a magnesium alloy injection molding machine, which comprises an injection cylinder body, and the injection cylinder body comprises a cylinder main body and a front cylinder located at the front end of the cylinder main body, and the front cylinder extends backward, so that the high-pressure area formed in the injection cylinder body during injection molding work is all located in the inner cavity of the front cylinder. The structure can fundamentally eliminate the risk of material leakage and can realize accurate replacement of the wear area, thereby reducing the cost.

Description

Technical Field

[0001] This invention relates to the field of magnesium alloy injection molding equipment technology, and in particular to an injection barrel structure for a magnesium alloy injection molding machine. Background Technology

[0002] Magnesium alloy injection molding machines are precision molding devices that inject molten magnesium alloy into a mold cavity to form a product. Their injection mechanism typically includes an injection barrel J1, a screw J2 located inside the injection barrel J1, and a check valve assembly (such as a...) mounted on the head of the screw J2. Figure 1 As shown), the check valve assembly typically consists of a screw head, a check ring J3, a thrust ring J4, and a piston ring. The thrust ring J4 is fitted onto the root of the screw head as an axial positioning reference. The check ring J3 is slidably fitted onto the screw head, and the piston ring embedded on its outer circle dynamically fits against the inner wall of the barrel, together forming a one-way shut-off valve structure. In addition, the front end of the injection barrel is connected to a nozzle via a flange.

[0003] During the injection process of a magnesium alloy injection molding machine, its working principle is as follows: The screw J2 is driven forward by the injection cylinder, extruding the molten magnesium alloy material at its front end. At this time, the molten material at the front end of the check ring J3 is compressed to form a high-pressure melt. Simultaneously, the internal resistance of the mold cavity causes the melt to generate a backward thrust on the check ring J3. Under this reverse pressure, the check ring J3 is pushed backward and eventually adheres tightly to the end face of the thrust ring J4. Simultaneously, the piston ring embedded on the outer circumference of the check ring J3 is further expanded and moved backward under the action of the high-pressure melt, sealing tightly against the inner wall of the injection barrel and the check ring J3. Thus, the inside of the injection barrel is divided by this check ring assembly into independent high-pressure and low-pressure zones (e.g., Figure 1 As shown in the figure, this provides a pressure basis for stable injection and pressure holding.

[0004] To facilitate manufacturing, assembly, and maintenance, traditional magnesium alloy injection molding machines typically employ a split barrel structure, usually consisting of a front barrel J101 and a main barrel body J102 connected by screws (depending on the specific machine model, the main barrel body may also be divided into at least two sections). To suit practical applications, the interface between the front barrel J101 and the main barrel body J102 in traditional structures is generally located within the aforementioned high-pressure area. Therefore, under the harsh conditions of high temperature and high pressure in magnesium alloy molten metal, this interface is highly susceptible to melt leakage, posing a high risk of material leakage. This not only affects molding accuracy and production stability but also presents a safety hazard of high-temperature molten metal splashing. Meanwhile, during continuous injection, relative movement and frictional wear occur between the inner wall of the barrel and the piston rings. The main wear area is concentrated in the high-pressure zone, while the wear in the low-pressure zone is minimal. Therefore, when the wear in the high-pressure zone exceeds the tolerance, the entire barrel needs to be scrapped according to traditional maintenance methods. However, in reality, the part of the barrel in the low-pressure zone has not reached the end of its service life. Direct scrapping results in a large waste of usable materials and significantly increases equipment maintenance costs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an injection barrel structure for a magnesium alloy injection molding machine that can fundamentally eliminate the risk of material leakage and at the same time achieve precise replacement of worn areas.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: An injection barrel structure for a magnesium alloy injection molding machine includes an injection barrel body. The injection barrel body includes a main barrel body and a front barrel located at the front end of the main barrel body. The front barrel extends rearward, such that the high-pressure zone formed inside the injection barrel body during injection molding is entirely located within the inner cavity of the front barrel.

[0007] The length of the front barrel is set to at least cover the entire high-pressure zone, so that the inner cavity of the barrel body is completely in the low-pressure zone.

[0008] An interface is formed between the high-pressure zone and the low-pressure zone, and the joint surface between the front barrel and the barrel body is located at the interface.

[0009] The high-pressure zone is formed by a check ring on the head of the screw inside the injection barrel body, which, together with the piston ring, seals the injection barrel body during injection. This seal divides the inner cavity of the injection barrel body into a high-pressure zone and a low-pressure zone.

[0010] The aforementioned seal refers to the axial seal formed by the check ring pressing tightly against the end face of the thrust ring under the action of melt pressure, and the radial seal formed by the piston ring embedded on the outer circle of the check ring pressing tightly against the inner wall of the injection molding machine barrel body under the action of melt pressure. The axial seal and the radial seal constitute a double sealing structure.

[0011] The front barrel and the barrel body are connected by flanges, and the flanges are fastened together with screws.

[0012] Compared with the prior art, the advantages of the present invention are as follows: (1) By extending the front barrel backward, the high pressure zone formed inside the injection molding machine barrel body during injection molding is located entirely within the inner cavity of the front barrel. This structural design allows the joint surface between the front barrel and the main body of the barrel to be naturally located outside the high pressure zone, thereby completely avoiding the direct impact of the high pressure melt. In traditional barrel structures, for practical application feasibility, the mating surface is usually located within a high-pressure area. This structural layout dictates that the mating surface must withstand the continuous impact of the high-pressure molten material, and the driving force for leakage is always present. When faced with this problem, the conventional approach for those skilled in the art is to strengthen the sealing structure of the mating surface, such as adding sealing rings, improving machining accuracy, or increasing tightening force. However, these measures can only alleviate the problem but cannot fundamentally eliminate the leakage problem, because as long as the mating surface remains within the high-pressure area, the physical conditions for leakage will always exist. Therefore, this solution breaks away from conventional thinking and re-examines the position of the mating surface from the perspective of structural layout. By extending the front barrel backward, the mating surface is moved out of the high-pressure area. This improvement does not rely on any auxiliary sealing means. It completely solves the long-standing leakage problem in the industry simply through the optimization of the structural layout, significantly improving production stability and safety. (2) By confining the high-pressure area entirely within the inner cavity of the front barrel, the front barrel completely covers the entire high-pressure area, bearing all the high-pressure load and friction wear, while the main body of the barrel is completely in the low-pressure area and is almost unaffected by wear. In traditional structures, wear is primarily confined to the main barrel. This barrel contains both high-pressure and low-pressure areas. Wear on the high-pressure area requires maintenance or even renders it unusable, causing the low-pressure area, which wouldn't otherwise need replacement, to also become unusable, resulting in material waste. This solution essentially shifts the wear area from the main barrel to the front barrel. Since the front barrel only contains the high-pressure area (or, due to design, retains a small portion of the low-pressure area), it is relatively short, resulting in lower replacement costs and minimizing material waste, significantly reducing equipment maintenance costs. (3) The core improvement of extending the front barrel to make the high-pressure zone entirely located in its inner cavity simultaneously achieves two independent technical effects: solving material leakage at the joint surface and achieving precise replacement of the wear area. This improvement is not a simple adjustment to the existing split structure, but a fundamental change to the functional zoning logic of the barrel based on a deep understanding of pressure zoning and wear mechanism. The function of the front barrel is redefined from a front structural component to a complete high-pressure zone load-bearing component. This concept breaks away from the mindset of zoning by temperature or segmenting by structure that is easily formed by those skilled in the art under the inspiration of existing technology. It has outstanding substantive features, simple structure, and significant effect. Attached Figure Description

[0013] Figure 1 This is a cross-sectional view of the injection mechanism of a traditional magnesium alloy injection molding machine, where the red line represents the interface between the high-pressure zone and the low-pressure zone. Figure 2 This is a cross-sectional structural diagram of the present invention, wherein the green lines represent the joint surfaces; Figure 3 This is a cross-sectional view of the injection mechanism formed by the injection barrel body and the screw installed in this invention. The red line represents the interface between the high-pressure zone and the low-pressure zone, and the green line represents the mating surface. Detailed Implementation

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0015] As shown in the figure, an injection barrel structure of a magnesium alloy injection molding machine includes an injection barrel body 1. The injection barrel body 1 includes a barrel main body 101 and a front barrel 102 located at the front end of the barrel main body 101. The front barrel 102 extends rearward, so that the high pressure zone A formed inside the injection barrel body 1 during injection molding is entirely located in the inner cavity of the front barrel 102.

[0016] In this specific embodiment, the length of the front barrel 102 is set to at least cover the entire high-pressure zone A, so that the inner cavity of the barrel body 101 is completely within the low-pressure zone B. The spatial correspondence between the front barrel 102 and the high-pressure zone A is clearly defined. By designing the length of the front barrel 102 to at least cover the entire high-pressure zone A, it is ensured that the high-pressure zone A is completely contained within the front barrel 102, thereby allowing the barrel body 101 to be completely detached from the high-pressure zone A.

[0017] In this specific embodiment, an interface C is formed between the high-pressure zone A and the low-pressure zone B, and the mating surface D of the front barrel 102 and the barrel body 101 is located at the interface C. The position of the mating surface D is precisely defined—it is set at the interface C between the high and low pressure zones B, which is the optimal position for the mating surface D of the front barrel 102 and the barrel body 101.

[0018] It should be noted that "interface C" is explicitly defined here: When the check ring 3 forms a seal under injection pressure, the transverse section that divides the inner cavity of the injection molding machine barrel 1 into high-pressure zone A and low-pressure zone B is interface C. This section passes through the junction of the check ring 3 and the thrust ring 4, as well as the sealing line between the piston ring (not marked in the figure) and the inner wall of the barrel, and represents the theoretical boundary between high-pressure zone A and low-pressure zone B. Therefore, setting the mating surface D at this interface C has the following advantages: First, from a spatial perspective, the interface C is the boundary line of the high-pressure zone A. The joint surface D is located here, which means that it is just separated from the high-pressure zone A. This avoids the direct impact of the high-pressure melt and minimizes the length of the front barrel 102, thus balancing safety and economy. This is fundamentally different from the traditional structure described in the background art, where the joint surface is located in the high-pressure zone. Secondly, from the perspective of stress state, the pressure at interface C has dropped from high pressure to normal pressure, and the joint surface D no longer bears high pressure, greatly reducing the sealing difficulty. Even without using a complex auxiliary sealing structure, a good sealing effect can be guaranteed. In contrast, in the traditional structure, the joint surface located in the high pressure zone is always subjected to high pressure impact, making it difficult to completely solve the sealing problem. Third, from the perspective of wear distribution, the interface C serves as the boundary of the high-pressure zone A. The inner cavity of the front barrel 102 in front of it bears all the high-pressure wear, while the inner cavity of the barrel body 101 behind it does not bear any high-pressure wear. When the wear of the inner wall of the high-pressure zone exceeds the tolerance, it is only necessary to replace the front barrel 102 before the interface C. The barrel body 101 after the interface C can be used permanently. This wear distribution characteristic is in stark contrast to the traditional structure described in the background art, where the high-pressure zone spans two components, the wear is dispersed, and replacement causes waste. Fourth, from a processing perspective, using the interface C as the positioning reference for the mating surface D facilitates manufacturing and quality control. Theoretically, the optimal position is when the mating surface D completely coincides with the interface C. However, in practical engineering applications, as long as the mating surface D is located near the interface C and outside the high-pressure zone A, the purpose of this invention can be achieved. Fifth, from the perspective of overall maintenance, setting the mating surface D at the interface C between the high and low pressure zones facilitates the replacement and maintenance of the three easily damaged small parts (check ring 3, thrust ring 4, and piston ring) on ​​the screw 2. When the screw 2 is retracted to the bottom, removing the front barrel 102 allows the three small parts to be exposed outside the barrel body 101. The replacement and maintenance of the three small parts can be achieved without removing the entire barrel and the entire screw 2, effectively reducing the equipment maintenance time and thus improving production efficiency.

[0019] In this specific embodiment, high-pressure zone A is formed by the check ring 3 on the head of the screw 2 located inside the injection barrel body 1, which seals during injection. This seal divides the inner cavity of the injection barrel body 1 into high-pressure zone A and low-pressure zone B. The formation mechanism of high-pressure zone A is clarified, revealing that the boundary between high-pressure zone A and low-pressure zone B originates from the sealing effect of the check ring 3, providing a technical basis for the design of the joint surface D between the front barrel 102 and the barrel body 101. Specifically, during injection, the screw 2 pushes forward to extrude the melt, and the check ring 3, under the pressure of the melt, moves backward to tightly adhere to the end face of the thrust ring 4, simultaneously forming a radial seal with the inner wall of the barrel, thereby dividing the inner cavity of the barrel into two pressure zones—high-pressure zone A in front of the check ring 3 and low-pressure zone B behind it. This mechanism indicates that the location and extent of the high-pressure zone A are determined by the sealing position of the check ring 3. Based on this understanding, this solution extends the front barrel 102 backward to cover the entire high-pressure zone A, so that the mating surface D is naturally located outside the high-pressure zone A.

[0020] In this specific embodiment, the sealing refers to the axial seal formed by the check ring 3 pressing tightly against the end face of the thrust ring 4 under the action of melt pressure, and the radial seal formed by the piston ring embedded on the outer circle of the check ring 3 pressing tightly against the inner wall of the injection barrel body 1 under the action of melt pressure. The axial seal and the radial seal constitute a double sealing structure. A dual-seal structure is formed by axial sealing (the end face of check ring 3 fits against the end face of thrust ring 4) and radial sealing (the piston ring fits against the inner wall of the barrel), which simultaneously cuts off the leakage channels of the melt from two dimensions. The axial seal blocks the backward flow of the melt through the gap between check ring 3 and thrust ring 4, while the radial seal blocks the leakage of the melt through the gap between the outer circle of check ring 3 and the inner wall of the barrel, significantly improving the sealing reliability of the high-pressure zone. The radial seal is achieved by the piston ring embedded in the outer circle of check ring 3 being further expanded under the action of melt pressure, forming a self-reinforcing effect of the higher the pressure, the tighter the seal. The axial seal is also achieved by the melt pressure driving check ring 3 to fit backward. Both use the working pressure itself as the sealing driving force, without the need for additional external force, and the sealing response is rapid, adapting to the needs of transient pressure changes during injection. The axial seal and radial seal have a clear division of labor. The axial seal is mainly responsible for cutting off the backflow channel of the end face gap, while the radial seal is mainly responsible for cutting off the leakage channel of the circumferential gap. The two work together to make the establishment and maintenance of the high-pressure zone more stable and reliable, providing a solid pressure foundation for precision injection molding.

[0021] In this specific embodiment, the front barrel 102 is connected to the barrel body 101 via flanges (11, 12), and the flanges (11, 12) are fastened together by screws 10. This achieves a detachable connection while ensuring reliability and sealing. Specifically: First, the connection is reliable; the flange (11, 12) structure provides sufficient connection strength and rigidity to ensure that the mating surface D will not loosen under high-pressure conditions. Second, the sealing performance is good; a gasket or metal-face seal can be used between the flanges (11, 12) to further ensure the sealing performance of the mating surface D. Third, disassembly and assembly are convenient; the front barrel 102 can be quickly replaced by tightening or loosening the screws 10, facilitating daily maintenance. Fourth, it is compatible with existing equipment connection methods, facilitating upgrades and modifications to existing equipment.

Claims

1. An injection barrel structure for a magnesium alloy injection molding machine, comprising an injection barrel body, wherein the injection barrel body includes a main barrel body and a front barrel located at the front end of the main barrel body, characterized in that... The front barrel extends rearward, so that the high-pressure zone formed inside the injection molding machine barrel body during injection molding is entirely located within the inner cavity of the front barrel.

2. The injection barrel structure of a magnesium alloy injection molding machine as described in claim 1, characterized in that... The length of the front barrel is set to at least cover the entire high-pressure zone, so that the inner cavity of the barrel body is completely in the low-pressure zone.

3. The injection barrel structure of a magnesium alloy injection molding machine as described in claim 1 or 2, characterized in that... An interface is formed between the high-pressure zone and the low-pressure zone, and the joint surface between the front barrel and the barrel body is located at the interface.

4. The injection barrel structure of a magnesium alloy injection molding machine as described in claim 1, characterized in that... The high-pressure zone is formed by a check ring on the head of the screw inside the injection barrel body, which, together with the piston ring, seals the injection barrel body during injection. This seal divides the inner cavity of the injection barrel body into a high-pressure zone and a low-pressure zone.

5. The injection barrel structure of a magnesium alloy injection molding machine as described in claim 4, characterized in that... The aforementioned seal refers to the axial seal formed by the check ring pressing tightly against the end face of the thrust ring under the action of melt pressure, and the radial seal formed by the piston ring embedded on the outer circle of the check ring pressing tightly against the inner wall of the injection molding machine barrel body under the action of melt pressure. The axial seal and the radial seal constitute a double sealing structure.

6. The injection barrel structure of a magnesium alloy injection molding machine as described in claim 1, characterized in that... The front barrel and the barrel body are connected by flanges, and the flanges are fastened together with screws.

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