An elongated injection molded part with a flange

Abstract

This utility model belongs to the field of automotive parts technology and discloses a slender injection molded part with a flange. The injection molded part includes a main body and a flange, with a radius (R) transition between the main body and the flange. Several horizontal ribs are distributed along the length direction of the B-side of the injection molded part, extending along the width direction of the part, with a spacing of 20-25mm between adjacent horizontal ribs. This utility model can reduce the problem of easy tearing during mold opening of slender injection molded parts with flanges in the prior art.

Description

Technical Field

[0001] This utility model belongs to the field of automotive parts technology, specifically relating to a slender injection molded part with a flange. Background Technology

[0002] In the automotive parts industry, slender injection molded parts with flanges are used, such as rear trim parts for the engine compartment. These injection molded parts consist of a main body and a flange, with a rounded corner transition between the main body and the flange.

[0003] During injection molding, the A-side of the main body is located inside the front mold and faces the front mold. The A-side of the flange is also located inside the front mold and fits against the inner wall of the mold cavity of the front mold.

[0004] When the mold opens after injection molding, the front mold moves outward, and the flange A surface is the first to come into contact with the cold air from the outside. The significant temperature difference between this cold air and the inside of the mold cavity causes different shrinkage rates between flange A and B surfaces, with surface A shrinking too quickly. Furthermore, the shrinkage rates of slender injection molded parts are inherently different along their length and width. Combined with the effects of internal and external temperature differences, the direction and velocity of airflow, and the shrinkage of the radius curve, the entire flange shrinks unevenly, resulting in deformation. This causes the flange, which originally perfectly conformed to the inner wall of the mold cavity, to no longer conform well; it either sinks in or bulges outward, abutting against the inner wall. When the front mold continues to move outward, relative movement occurs between it and the flange, causing the bulging part of the flange to rub against the inner wall of the mold cavity, resulting in damage to flange A surface, affecting the product's appearance and delivery. Utility Model Content

[0005] The present invention aims to provide a slender injection molded part with a flange to reduce the problem of easy tearing of slender injection molded parts with flanges during mold opening in the prior art.

[0006] To achieve the above objectives, this utility model provides the following technical solution: a slender injection molded part with a flange, comprising a main body and a flange, with an R-angle transition between the main body and the flange, and a number of transverse ribs distributed along the length direction on the B-side of the injection molded part, the transverse ribs extending along the width direction of the injection molded part, and the interval between adjacent transverse ribs being 20-25mm.

[0007] The technical principles and effects of this technical solution are as follows:

[0008] The injection molded part is elongated, meaning the length of its longer side is much greater than the width of its wider side. The B-side of the injection molded part refers to its inner surface, which faces the inside of the mold cavity during injection molding. Several transverse ribs are distributed along the length direction, extending along the width direction of the injection molded part. This means the transverse ribs are generally parallel to the wide side and perpendicular to the long side of the injection molded part; however, due to irregular product shapes and design variations, this parallelism and perpendicularity are not absolute.

[0009] When faced with product deformation and tearing, those skilled in the art first think of directly solving the deformation problem, that is, smoothing the deformed parts or inhibiting product deformation when deformation has occurred or there is a tendency to deform. Implementing this approach requires significant modifications to the mold, such as adding an additional flattening component to hold the easily deformable parts of the product in place before mold opening. This flattening component also needs to consider its space and power, which is very complicated and costly.

[0010] The inventor also considered adding stretch marks to the product to limit the product shrinkage too quickly and thus reduce deformation. However, after experimentation, it was found that deformation could be reduced, but stress whitening would appear on the A side of the product. This was equivalent to overcoming the stretching damage, but adding another appearance problem. In fact, the problem was still not solved.

[0011] After research and experimentation, the inventors discovered that the B-side of such injection-molded parts typically features ribs to ensure product strength. However, the design of these ribs, including their width, height, and spacing, follows standard values ​​that researchers generally don't change. For example, the rib spacing is usually set at 30-40mm. But the inventors deviated from this conventional design, experimenting by altering the rib spacing to maintain strength while mitigating deformation and tearing issues, ultimately achieving good results. Finally, the inventors settled on a spacing of 20-25mm, which is the core of this solution.

[0012] The inventor analyzed the reasons and decided to shorten the rib spacing, i.e., make the ribs denser. This firstly, it wouldn't negatively impact strength. Secondly, the ribs are designed with corresponding grooves on the mold, which exert a clamping force on the flange of the injection molded part from side B. This clamping force is now stronger, limiting the shrinkage of the flange and reducing deformation, thus reducing tearing caused by deformation. However, this spacing cannot be shortened indefinitely for several reasons: First, a shorter spacing and denser ribs result in excessive clamping force from the mold grooves, making ejection difficult or even impossible. Second, denser ribs mean denser corresponding grooves, affecting mold strength. Third, denser ribs inevitably increase costs. Through research and experimentation, the inventor determined that a 20-25mm spacing is optimal.

[0013] Furthermore, the horizontal reinforcement positions include main reinforcement positions and secondary reinforcement positions. One end of the main reinforcement position extends to the long edge of the flange, and the other end extends to the long edge of the main body. One end of the secondary reinforcement position extends to the long edge of the flange, and the other end extends to the middle of the main body. The main reinforcement positions and secondary reinforcement positions are distributed in an intersecting manner.

[0014] The traditional function of horizontal ribs is to ensure product strength. However, in traditional designs, the strength is already sufficient. Therefore, making the horizontal ribs denser would be redundant in terms of strength. Increasing the number of horizontal ribs would increase material costs and make demolding more difficult. Therefore, it is better to minimize the distribution of ribs on the B-side of the injection molded part while still meeting the traditional function of ensuring strength and reducing tearing. In general, horizontal ribs are designed to run continuously along the width of the injection molded part. However, this application changes this design. The horizontal ribs include main ribs that run the width direction and secondary ribs that do not. These are distributed alternately along the length of the injection molded part in the order of main ribs, secondary ribs, main ribs, secondary ribs… The secondary ribs are mainly distributed on the flanges and radius corners, primarily because shrinkage and deformation are greater in these areas, making the requirements more stringent.

[0015] Furthermore, adjacent main reinforcement positions are connected by vertical reinforcement positions, and secondary reinforcement positions are connected to adjacent vertical reinforcement positions.

[0016] With this design, all the ribs can be connected to form a whole, making the entire injection molded part stronger.

[0017] Furthermore, the height of the main reinforcement bars is 3-4mm, and the height of the secondary reinforcement bars is 2-3mm.

[0018] Experimental studies have shown that the distribution of the main ribs at this height is sufficient to meet the strength requirements of the injection molded part. Under these circumstances, the secondary ribs only play a supplementary role in the strength of the injection molded part. Therefore, reducing their height will not have an adverse effect on the strength. On the contrary, reducing their height will facilitate the demolding of the injection molded part. The spacing of the entire horizontal ribs, combined with this height, ensures that shrinkage is limited and deformation is reduced.

[0019] Furthermore, the secondary reinforcement includes the main segment, the R segment, and the flip segment in sequence. The main segment is located on the main body, the R segment is located on the R corner, and the flip segment is located on the flip edge. The width of the R segment, the width of the flip segment, and the width of the main segment decrease in sequence.

[0020] Similarly, secondary ribs only supplement the strength of injection molded parts. Their main function is to increase the clamping force of the mold on the injection molded part, limit shrinkage, reduce deformation, and minimize the difficulty of demolding. This design meets these requirements. Experimental results show that the wider the secondary rib, the greater the clamping force and the better the shrinkage restriction effect, but the greater the difficulty of demolding. For this part, the shrinkage of the R-segment is the most obvious, and since the R-segment is directly connected to the flip-up segment, its impact on the flip-up segment is also the most direct. The flip-up segment is where tearing occurs during mold opening; therefore, shrinkage here will directly affect tearing. The main segment produces the front surface, and its A-side contacts the front surface of the front mold. When the front mold moves outward, there is no friction between it and the main segment, so tearing does not occur. In summary, setting the width of the R-segment, the flip-up segment, and the main segment to decrease sequentially allows for the optimal overall effect of strength, clamping force, and demolding.

[0021] Furthermore, the width of the R segment is 2 / 5 of the wall thickness of the injection molded part, the width of the flip segment is 1 / 3 of the wall thickness of the injection molded part, and the width of the main segment is 4 / 15 of the wall thickness of the injection molded part.

[0022] According to this design, the overall effect of strength, clamping force and demolding is relatively good. It is worth noting that if the width is set too large, it will also cause the injection molded parts to shrink severely.

[0023] Furthermore, the transitions between the sidewalls of the main segment and the R segment, and between the sidewalls of the R segment and the flip segment, are all arc-shaped.

[0024] This design facilitates demolding and also improves the product's appearance.

[0025] Furthermore, the cross-section of segment R is trapezoidal, and the length of the base of the trapezoid near one end of segment R is greater than the length of the base of the other end.

[0026] This design ensures that while maintaining sufficient clamping force, it also facilitates demolding.

[0027] Furthermore, the cross-sections of both the flip section and the main section are trapezoidal, with the length of the base of the trapezoid near the flip section or the main section being greater than the length of the base of the other end.

[0028] This design ensures sufficient clamping force for easy demolding, and when connected to the R segment, the overall integrity of the secondary rib is improved.

[0029] Furthermore, the length-to-width ratio of the injection molded part is greater than 10:1.

[0030] The above structural design works better for injection molded parts with a length-to-width ratio greater than 10:1. Attached Figure Description

[0031] Figure 1This is a schematic diagram of Embodiment 1 of the present utility model. Detailed Implementation

[0032] The following detailed description provides further details on specific implementation methods.

[0033] It should be understood that in the description of the specific embodiments, the terms "longitudinal", "lateral", "vertical", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present 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. Therefore, they should not be construed as limitations on the present invention.

[0034] The reference numerals in the accompanying drawings include: flange 1, R-angle 2, main body 3, main reinforcement position 4, vertical reinforcement position 5, secondary reinforcement position 6, flange segment 61, R segment 62, and main segment 63.

[0035] Example 1:

[0036] This embodiment provides a slender injection molded part with a flange 1. The injection molded part is slender, meaning the length of its long side is much greater than the width of its wide side. Preferably, the ratio of the length of the long side to the width of the wide side is greater than 10:1; in this embodiment, 10:1 is selected. The injection molded part of this embodiment includes a main body 3 and a flange 1, with a radius (R) 2 between the main body 3 and the flange 1 for transition. Several horizontal ribs are integrally formed on the B-side of the injection molded part. These horizontal ribs are spaced apart along the length direction of the injection molded part and extend along the width direction of the injection molded part, meaning the length direction of the horizontal ribs is consistent with the width direction of the injection molded part. The spacing between adjacent horizontal ribs is 20-25 mm; any value within this range can be used. The spacing can vary within the same product.

[0037] The aforementioned transverse ribs include main ribs 4 and secondary ribs 6, which are distributed alternately, i.e., in the order of main rib 4, secondary rib 6, main rib 4, secondary rib 6… One end of the main rib 4 extends to the long edge of the flange 1, and the other end extends to the long edge of the main body 3, meaning the main rib 4 penetrates the injection molded part in the width direction. One end of the secondary rib 6 extends to the long edge of the flange 1, and the other end extends to the middle of the main body 3, meaning the secondary rib 6 does not penetrate the injection molded part in the width direction.

[0038] Vertical ribs 5 connect adjacent main rib positions 4, and secondary rib positions 6 connect to adjacent vertical rib positions 5. Here, secondary rib positions 6 and adjacent vertical rib positions 5 refer to being located between the same two main rib positions 4. The length direction of the vertical rib positions 5 is consistent with the length direction of the injection molded part. Through this arrangement, all horizontal rib positions and vertical rib positions 5 can form a whole, making the injection molded part stronger under the same conditions.

[0039] Secondary rib 6 comprises a main section 63, an R-section 62, and a flange 61. The main section 63 is located on the main body 3, the R-section 62 is located on the R-angle 2, and the flange 61 is located on the flange 1. The widths of the R-section 62, the flange 61, and the main section 63 decrease sequentially. There are arc-shaped transitions between the sidewalls of the main section 63 and the R-section 62, and between the sidewalls of the R-section 62 and the flange 61. Furthermore, to ensure clamping force while facilitating demolding, the entire cross-section of secondary rib 6 is designed as a trapezoid, meaning the cross-sections of the R-section 62, the flange 61, and the main section 63 are all trapezoidal. The length of the base of the trapezoid near the injection molded part is greater than the length of the base at the other end, meaning the lower base of the trapezoid is located on the injection molded part. Here, the cross-section refers to the section perpendicular to the width direction of the injection molded part.

[0040] To achieve better overall performance, the heights of the main rib 4 and vertical rib 5 are both set to 3-4 mm, and the height of the secondary rib 6 is set to 2-3 mm. In this embodiment, the heights of the main rib 4 and vertical rib 5 are 3.5 mm, and the height of the secondary rib 6 is 2.8 mm. Regarding the rib width, the thickness of the injection molded part is used as a reference. In this embodiment, the thickness of the injection molded part is 2.5 mm. The middle width of segment R 62 is set to 2 / 5 of the injection molded part wall thickness, the middle width of segment 61 is set to 1 / 3 of the injection molded part wall thickness, and the middle width of main segment 63 is set to 4 / 15 of the injection molded part wall thickness. The middle width refers to the width corresponding to the median value of the height of the trapezoidal cross-section of the secondary rib 6. The widths of the main rib 4 and vertical rib 5 are both 1 / 3 of the injection molded part wall thickness. In this embodiment, the upper base of the trapezoid of the secondary rib 6 is 0.1 mm smaller than the lower base.

[0041] In this embodiment, the entire injection molded part is integrally formed. The shape and size of each rib are set by adjusting the corresponding grooves in the mold cavity. These are conventional methods for those skilled in the art, and will not be described in detail here.

[0042] For those skilled in the art, without departing from the concept of the present utility model, several modifications and improvements can be made, and these should also be considered within the scope of protection of the present utility model. These will not affect the effectiveness of the implementation of the patent or the practicality of the patent.

Claims

1. A slender injection molded part with a flange, comprising a body and a flange, wherein there is an R-angle transition between the body and the flange, characterized in that: The B-side of the injection molded part has several horizontal ribs distributed along the length direction. The horizontal ribs extend along the width direction of the injection molded part, and the interval between adjacent horizontal ribs is 20-25mm.

2. The flanged elongate injection molded member of claim 1, wherein: The horizontal reinforcement includes main reinforcement and secondary reinforcement. One end of the main reinforcement extends to the long edge of the flange, and the other end extends to the long edge of the main body. One end of the secondary reinforcement extends to the long edge of the flange, and the other end extends to the middle of the main body. The main reinforcement and secondary reinforcement are distributed in an intersecting manner.

3. The flanged elongate injection molded member of claim 2, wherein: There are vertical reinforcement bars connecting adjacent main reinforcement bars, and secondary reinforcement bars are connected to adjacent vertical reinforcement bars.

4. The flanged elongate injection molded member of claim 3, wherein: The height of the main reinforcement is 3-4mm, and the height of the secondary reinforcement is 2-3mm.

5. The flanged elongate injection molded member of claim 4, wherein: The secondary reinforcement consists of the main section, the R section, and the flip section. The main section is located on the main body, the R section is located on the R corner, and the flip section is located on the flip edge. The width of the R section, the width of the flip section, and the width of the main section decrease in that order.

6. The flanged elongate injection molded member of claim 5, wherein: The width of section R is 2 / 5 of the wall thickness of the injection molded part, the width of section Flip is 1 / 3 of the wall thickness of the injection molded part, and the width of section Main is 4 / 15 of the wall thickness of the injection molded part.

7. The elongated injection molded part with a flange according to claim 6, characterized in that: The transitions between the side walls of the main section and the R section, and between the side walls of the R section and the flip section, are all arc-shaped.

8. The flanged elongated injection molded member of claim 5, wherein: The cross-section of segment R is trapezoidal, and the length of the base of the trapezoid at one end closer to segment R is greater than the length of the base at the other end.

9. The flanged elongate injection molded member of claim 8, wherein: Both the flip section and the main section have trapezoidal cross-sections, with the length of the base of the trapezoid near the flip section or the main section being greater than the length of the base of the other end.

10. The flanged elongated injection molded member of any of claims 1-9, wherein: The length-to-width ratio of the injection molded part is greater than 10:1.

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