A blow molding die

Abstract

The application discloses a blow molding die head, which comprises a die head, a die core fixedly connected in the die head, a gap between the die head and the die core forming a feeding channel, and a plurality of spiral flow channels uniformly arranged on the outer wall of the die core, characterized in that at least one coaxial circular groove is formed on the inner wall of the die head. The die head provides an opportunity for melt re-mixing, effectively reducing the difference between the melts in individual flow channels before the melts enter the final mixing stage. Different from the conventional design and adjustment on the die core, the flow channels originally exist on the die core, and further processing and design will increase the manufacturing difficulty and cost of the die core. On the contrary, the design is carried out on the die head, the structure of the inner wall of the die head is relatively simple, easy to process and manufacture, and the cost is lower.

Description

Technical Field

[0001] This invention belongs to the field of plastic machinery, and particularly relates to a blow molding die head. Background Technology

[0002] During extrusion, films are prone to developing longitudinal film marks on their surface, known as flow lines. The formation of flow lines can negatively impact film quality and reduce its longitudinal tear strength. The primary cause of flow lines is that when the molten plastic is introduced into the die head from the extruder, it enters several flow channels through the lowermost discharge holes. Before reaching the die orifice, differences in the inherent inertia or rheological properties of the melt exiting each channel result in weld marks. While attempts have been made to improve this by adjusting production process conditions or die design, significant limitations remain.

[0003] Chinese patent document CN209409296U discloses a multifunctional blow molding die with double spiral grooves, including a die head body, an adjustment ring disposed on the die head body, a die set inside the adjustment ring, and a spiral body located below the die. The spiral body has an outer spiral groove on its outer surface, and the die head body has an inner spiral groove on its inner surface. This invention increases the die head pressure by setting spiral grooves on the spiral body and the die head body respectively, improving the uniformity of material output and the consistency of film thickness, reducing film adjustment time, and thus reducing waste generation; it also balances the longitudinal and transverse stretching of the film, significantly improving the film's strength and tensile strength; it increases the die head capacity, thereby increasing output; and it can be applied to a variety of different materials, with a wide range of applications, thus reducing transformation costs.

[0004] In order to make the material output uniform, the above-mentioned patented solution sets spiral grooves on the outer wall of the mold core and the inner wall of the die respectively. Under the action of pressure, most of the melt will still be fed spirally along the spiral grooves. It cannot eliminate the original inertia or rheological differences of the melt in each spiral groove, so flow lines will still be generated. Summary of the Invention

[0005] In order to overcome the flow lines that appear on the surface of the film during the extrusion of the prior art, one object of the present invention is to provide a blow molding die head, which guides the melt in different flow channels into the groove for effective mixing by setting a groove on the inner wall of the die, thereby disrupting the original inertia of the melt flow and further reducing the presence of flow lines caused by excessive differences between the melts in different flow channels when the final mixture is made.

[0006] To achieve the above objectives, the present invention employs the following technical solution: a blow molding die head, comprising a die head; a die core, the die core being fixedly connected inside the die head; the gap between the die head and the die core forming a material conveying channel; the outer wall of the die core being formed with multiple evenly arranged spiral flow channels; and the inner wall of the die head being formed with at least one coaxially arranged circular groove.

[0007] Under pressure, the molten plastic flows out from the lower end of each of the aforementioned channels, filling each channel, feed channel, and groove. Under continuous pressure, it flows out from the upper end of the feed channel, forming a thin film. During this process, the molten material in each channel flows into the groove under pressure, causing mixing. It also flows upward synchronously with the overall flow of the melt, disrupting the original inertia of the melt flow in each channel, reducing the differences in the melt within each channel, and preventing the formation of flow lines after mixing.

[0008] Preferably, the groove has a semi-circular cross-sectional shape, so that there are no dead corners during the upward flow of the melt, thus preventing melt accumulation.

[0009] Preferably, the depths of each groove are not equal, that is, the amount of melt flowing into each groove is not equal, and each groove is mixed with a different mixing ratio to further reduce the melt differences in each groove.

[0010] Furthermore, the groove is formed with a rounded corner at the connection between it and the inner wall of the die; this ensures the smooth flow of the melt, reduces mold wear, and prevents melt accumulation.

[0011] Preferably, there are three grooves, and the distance between any two adjacent grooves is equal.

[0012] Preferably, the depth of the middle groove is greater than the depth of the other two grooves.

[0013] Preferably, the two grooves located at both ends are directly opposite the upper and lower ends of the flow channel, respectively, to facilitate the melt in the flow channel to enter the grooves for thorough mixing.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: the die head provides an opportunity for the melt to be remixed, effectively reducing the differences between individual flow channels before the melt enters the final mixing stage; unlike the conventional design and adjustment on the die core, which already has flow channels, further processing and design will increase the manufacturing difficulty and cost of the die core. On the contrary, designing on the die head results in a simpler inner wall structure, which is easier to process and manufacture, and has a lower cost. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention;

[0016] Figure 2 This is a schematic diagram of the structure of the mold core and the orifice of the present invention.

[0017] In the diagram: 10, mold core; 101, runner; 102, material distribution channel; 20, die; 201, groove. Detailed Implementation

[0018] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0019] In the description of this invention, it should be noted that the directional terms such as "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limiting the specific protection scope of this invention.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features. Thus, the use of "first" and "second" to define a feature may explicitly or implicitly include one or more of that feature, and in the description of this invention, "a number" means two or more, unless otherwise explicitly specified.

[0021] In this invention, unless otherwise explicitly specified and limited, the terms "assembly," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can also refer to a mechanical connection; they can refer to a direct connection or a connection through an intermediate medium; or they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] See Figures 1-2 As shown in the figure, the die head includes a die core 10 and a die 20. A distribution hole is formed at the center of the lower end of the die core 10; multiple evenly arranged flow channels 101 arranged along a spiral line are formed on the outer wall of the die core 10; a material distribution channel 102 is formed at the lower end of the flow channel 101 and is inclined and communicates with the top of the inner wall of the distribution hole; the material distribution channel 102 is evenly arranged in the circumferential direction; three circular grooves 201 are formed on the inner wall of the die 20.

[0023] High-temperature plastic melt is forced into the distribution hole under high pressure, and then flows evenly into the distribution channel 102. Through the distribution channel 102, it enters the lower end of the flow channel 101. As the high-temperature plastic melt continues to be injected, the melt flows upward from the lower end of the flow channel 101, filling the conveying channel, and finally outputting a cylindrical film at the top of the conveying channel. During this process, the melt flowing in the flow channel 101 also flows into the groove 201 under pressure. At the same height, the melt in each flow channel 101 simultaneously enters the groove 201, and under the influence of the upward-flowing melt, the melt in the groove 201 mixes and flows upward synchronously with the upward-flowing melt. This disrupts the original inertia of the melt flow, further reducing the presence of flow lines caused by excessive differences between the melts in different channels during the final mixing.

[0024] The above description is only a specific embodiment of the present invention, but the technical features of the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A blow molding die head, comprising a die mouth; a die core, the die core being fixedly connected inside the die mouth; a gap between the die mouth and the die core forming a material conveying channel; and a plurality of uniformly arranged spiral flow channels formed on the outer wall of the die core; characterized in that: The inner wall of the die is formed with three coaxially arranged circular grooves; the cross-sectional shape of the grooves is semi-circular; the distance between two adjacent grooves is equal; and the depth of the three grooves is unequal.

2. The die head as described in claim 1, characterized in that: The groove is formed with a rounded corner at the connection between it and the inner wall of the die.

3. The die head as described in claim 1, characterized in that: The depth of the middle groove is greater than the depth of the other two grooves.

4. The die head as described in claim 1, characterized in that: The two grooves located at both ends are directly opposite the upper and lower ends of the flow channel, respectively.

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