Pull rod with improved crack resistance

Abstract

The utility model relates to the field of injection molding machines, and discloses a pull rod with improved crack resistance, which comprises a rod body and cohesion tooth groups arranged at two ends of the rod body and used for being matched with semi-cohesion nuts, each cohesion tooth group comprises a plurality of occlusion teeth arranged at intervals along the axial direction of the rod body, each occlusion tooth comprises a tooth crest and a tooth groove, and the tooth crest of each tooth groove is close to the rod body. Each tooth groove comprises a first tooth side close to the rod body, a second tooth side away from the rod body, a transition section, a first connecting arc section between the first tooth side and the transition section and a second connecting arc section between the second tooth side and the transition section, and the cohesion tooth set comprises at least one or any combination of two or more of the following five characteristics. The five characteristics are tooth thickness, tooth height, tooth bottom diameter, groove width and tooth shape change, and the anti-cracking performance of the pull rod can be effectively improved through independent or any combination of every two or more of the five characteristics.

Description

Technical Field

[0001] The utility model relates to the field of injection molding machines, in particular to a tie rod with improved crack resistance performance. Background Art

[0002] The commonly used locking structures of the tie rods of injection molding machines include threaded type and semi-encircling type. The threaded locking structure is difficult to process, has low machining accuracy, is prone to structural failure, and has weak force transmission ability; the semi-encircling structure is simple to process, has high machining accuracy, high structural strength, is not prone to failure, and has strong force transmission ability. Therefore, the semi-encircling structure is widely used.

[0003] In the traditional semi-encircling structure, the structure of the tie rod can refer to a new type of direct-opening injection molding machine synchronous clamping device disclosed in the Chinese patent with the publication number CN212331737U, which includes a tie rod and a semi-clamping nut. The two ends of the tie rod are distributed with first protrusions and first grooves in a corrugated shape. The semi-clamping nut is provided with second grooves corresponding to the first protrusions for engagement and second protrusions for engagement with the first grooves. The sizes and shapes of the first protrusions and the second protrusions are the same, the sizes and shapes of the first grooves and the second grooves are the same, and the side walls on both sides of the first grooves and the second grooves are vertically distributed and the bottom of the grooves is arc-shaped.

[0004] In the existing tie rod, the bottom of the protrusion (tooth) and the groove (tooth groove) is transitioned by an arc. When the tie rod pulls the template, the reaction force F of the protrusion closest to the rod body is the largest, and the stress δ at a point on the arc is the largest. Based on the stress formula It can be seen that δ is proportional to F. Therefore, the existing tie rod is prone to radial cracking from the maximum stress point at the arc of the groove closest to it, and then the entire corrugated section cooperating with the semi-clamping nut breaks. Summary of the Utility Model

[0005] Aiming at the disadvantage that the sizes and structures of the teeth and tooth grooves of the existing tie rod are the same, resulting in the maximum stress on the tooth groove closest to the rod body and being prone to radial cracking of the tie rod from the connecting arc of the tooth groove and the tooth, the utility model provides a tie rod with improved crack resistance performance.

[0006] In order to solve the above technical problems, the utility model is solved by the following technical solutions:

[0007] A pull rod with improved crack resistance performance, comprising a rod body and engaging tooth groups provided at both ends of the rod body and used for cooperating with semi-engaging nuts. The engaging tooth groups include a plurality of engaging teeth arranged at intervals along the axial direction of the rod body. The engaging teeth include tooth tops and tooth grooves in the direction of the rod body near the tooth tops. The tooth grooves include a first tooth side close to the rod body, a second tooth side far from the rod body, a transition section, a first connecting arc section between the first tooth side and the transition section, and a second connecting arc section between the second tooth side and the transition section. The engaging tooth groups include at least one or any combination of two or more of the following five features:

[0008] Feature 1: The engaging tooth groups have at least two types of engaging teeth with different tooth thicknesses;

[0009] Feature 2: The engaging tooth groups have at least two types of engaging teeth with different tooth heights;

[0010] Feature 3: The engaging tooth groups have at least two types of tooth grooves with different bottom diameters;

[0011] Feature 4: The engaging tooth groups have at least two types of tooth grooves with different groove widths;

[0012] Feature 5: There is at least one deformed tooth, and the deformed tooth includes at least one or any combination of two or more of the following three changes:

[0013] Change 1: The tooth top angle changes. Based on the axis of the pull rod, the change range of the tooth top angle is -30° to 30°;

[0014] Change 2: The change range of the angle of the first tooth side is 60° to 120°, and the change range of the angle of the second tooth side is 60° to 120°;

[0015] Change 3: The transition section is a straight line or an arc section and is smoothly connected to the first connecting arc section and the second connecting arc section.

[0016] Adopting the above scheme, any one of the above five features or any combination of two or more features as the design features of the engaging tooth groups can effectively increase the crack resistance performance of the toothed part of the pull rod. The effects brought by each feature are analyzed below. Based on the stress formula K = K 1 ×K 2; where, δ is the maximum stress on the tooth groove; F is the acting force on the engaging tooth; d is the root diameter; K1 is the stress concentration coefficient, which is inversely proportional to the curvature radii of the first connecting arc segment, the second connecting arc segment, and the transition segment; K2 is the torque conversion coefficient, which is directly proportional to the tooth height; the smaller the stresses on the first connecting arc segment, the second connecting arc segment, and the transition segment, the less likely the pull rod is to crack. Therefore, the above five features are all aimed at reducing the stress at the maximum stress point between the tooth groove and the engaging tooth. Feature 1: By changing the tooth thickness of the engaging tooth closest to the pull rod (hereinafter referred to as the first tooth), the anti-deformation ability of the first tooth is reduced. After the first tooth deforms, the other teeth compensate for the force, the force proportion of the first tooth decreases, and the force proportion of the subsequent teeth increases, achieving the purpose of reducing the maximum stress at the root circular arc of the first tooth and effectively reducing the problem of cracking at the maximum stress point; Feature 2: By reducing K 2 to achieve the purpose of reducing the stress of the first tooth; Feature 3: By increasing d to achieve the purpose of reducing the stress of the first tooth; Feature 4: By reducing K 1 to achieve the purpose of reducing the stress of the first tooth; Feature 5: The forces on the tooth root mainly include the bending stress on the side of the first tooth, the tensile stress on the tooth root, and the stress on the side of the second tooth. The traditional stress concentration section is a single point. Both the first connecting arc segment and the second connecting arc segment are circular arcs with the same radius, and the first connecting arc segment, the transition segment, and the second connecting arc segment are connected to form a semi-circle. At this time, all three stresses are concentrated at one point at the bottom. It is necessary to have a sufficiently large circular arc curvature radius to achieve the purpose of reducing the tooth root stress. In the deformed tooth, modifying the point-like transition segment to a straight line has two advantages: one is to increase the root diameter and increase the tensile strength, and the other is that the straight line segment separates the three stresses that would originally be concentrated at one point, dispersing the stresses that should have been resisted by a circular arc curve with a relatively large curvature radius, and being resisted by the first connecting arc segment and the second connecting arc segment with a slightly reduced or basically unchanged curvature radius respectively, playing a role in reducing stress concentration; when the transition segment is a straight line, when changing the angles of the first tooth side, the second tooth side, and the transition segment, the maximum stress point can be moved to the first connecting arc segment or the second connecting arc segment, further reducing the stress difference between the two connecting arc segments and playing a role in reducing stress concentration.

[0017] Preferably, the transition segment is an arc segment, and the curvature radii of the first connecting arc segment, the transition segment, and the second connecting arc segment are the same or different.

[0018] Preferably, the transition segment is a straight line, the length of the transition segment accounts for 1 / 50 - 4 / 5 of the groove width, and the curvature radii of the first connecting arc segment and the second connecting arc segment are the same or different.

[0019] Preferably, the length of the transition segment accounts for 1 / 50 - 4 / 5 of the groove width.

[0020] Preferably, when the angle change range of the transition segment is -10° to 10°.

[0021] Preferably, the first connecting arc segment is a circular arc, an elliptical arc, an involute, a parabola or a hyperbola.

[0022] With the above solution, the first connecting arc segment is mainly used to connect the first tooth flank and the transition segment, so that the two are evenly transitioned to reduce the stress concentration problem caused by the sudden change in shape. Therefore, the curve selected for the first connecting arc segment needs to satisfy the characteristics of a slightly larger radius of curvature and a small change within the selected range.

[0023] Preferably, the second connecting arc segment is a circular arc, an elliptical arc, an involute, a parabola or a hyperbola.

[0024] With the above solution, the second connecting arc segment is mainly used to connect the transition segment and the second tooth flank, so that the two are evenly transitioned to enhance the bending resistance of the tooth bottom within a limited space. Therefore, the curve selected for the second connecting arc segment needs to satisfy three characteristics: the maximum radius of curvature is as large as possible, the minimum radius of curvature cannot be too small, and the radius of curvature changes rapidly.

[0025] Preferably, there are transition fillets between the tooth tip and the first tooth flank and between the tooth tip and the second tooth flank, and the fillet radius range of the transition fillets is 0.5 mm to 4 mm.

[0026] With the above solution, the transition fillet should not be too large.

[0027] Preferably, the angular change range of the first tooth flank is 60° to 120°.

[0028] Preferably, the angular change range of the second tooth flank is 60° to 120°.

[0029] Since the present utility model adopts the above technical solutions, it has remarkable technical effects: the occluding teeth in the clamping tooth group of the pull rod can be distributed by any one or a combination of two or more of the features one to five. Feature one, by changing the tooth thickness of the first tooth, reducing the stress proportion of the first tooth and increasing the stress proportion of the remaining teeth, thereby reducing the actual stress at the location of the maximum stress; Feature two, by reducing the tooth height of the first tooth, reducing the torque conversion coefficient, thereby reducing the actual stress at the location of the maximum stress; Feature three, by increasing the bottom diameter of the first tooth, thereby reducing the actual stress at the location of the maximum stress; Feature four, by increasing the radius of curvature of the first connecting arc segment and the second connecting arc segment, reducing the stress concentration coefficient K 1 , thereby reducing the actual stress at the location of the maximum stress; Feature five, by deforming the occluding teeth, dispersing the stress, adjusting the positions of the stresses, and reducing the actual stress at the location of the maximum stress. By setting the above features alone or in combination of two or more with the other four features, it is possible to reduce the actual stress at the location of the maximum stress and improve the crack resistance of the pull rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1It is a partial schematic diagram of a tension rod with improved crack resistance in Embodiment 1;

[0031] Figure 2 It is a partial schematic diagram of a tension rod with improved crack resistance in Embodiment 2;

[0032] Figure 3 It is a partial schematic diagram of a tension rod with improved crack resistance in Embodiment 3;

[0033] Figure 4 It is a partial schematic diagram of a tension rod with improved crack resistance in Embodiment 4;

[0034] Figure 5 It is a partial schematic diagram of a tension rod with improved crack resistance in Embodiment 5;

[0035] Figure 6 It is a partial schematic diagram of a tension rod with improved crack resistance in Embodiment 6;

[0036] Figure 7 It is a partial schematic diagram of a tension rod with improved crack resistance in Embodiment 7;

[0037] The names of the parts referred to by each digital label in the above drawings are as follows: 1, tooth top; 2, transition fillet; 3, first tooth side; 4, first connecting arc segment; 5, transition segment; 6, second connecting arc segment; 7, second tooth side; 8, rod body. Detailed implementation manners

[0038] The present utility model will be further described in detail below with reference to the drawings and embodiments.

[0039] Embodiment 1

[0040] A tension rod with improved crack resistance, referring to Figure 1 as shown, includes a rod body 8 and a set of engaging teeth arranged at both ends of the rod body 8 and used for cooperating with semi-engaging nuts. The set of engaging teeth includes a plurality of engaging teeth arranged at intervals along the axial direction of the rod body 8. The engaging teeth include a tooth top 1 and a tooth groove in the direction of the rod body 8 close to the tooth top 1. The tooth groove includes a first tooth side 3 close to the rod body 8, a second tooth side 7 far from the rod body 8, a first connecting arc segment 4 between the first tooth side 3 and the transition segment 5, and a second connecting arc segment 6 between the second tooth side 7 and the transition segment 5.

[0041] In this embodiment, all the engaging teeth have the same shape and are all conventional teeth. The first connecting arc segment 4, the transition segment 5, and the second connecting arc segment 6 form a semi-circular arc, and all dimensions are the same except for the tooth thickness (L).

[0042] Taking three teeth as an example, the tooth thickness (L) is L1, L2, and L3 in sequence from the one close to the rod body 8 to the one far from the rod body 8. The tooth thickness of the engaging tooth closest to the rod body 8 is the smallest and there are at least two engaging teeth with different tooth thicknesses. In this embodiment, the tooth thickness (L) of the three teeth is designed as L1 < L2 < L3. Assuming the original tooth thickness is La, 0.7La ≤ L1 < La. In this embodiment, the stress optimization effect brought by different tooth thicknesses is about 5%.

[0043] Embodiment 2

[0044] The difference between this embodiment and Embodiment 1 is that, as shown in reference to Figure 2 All the engaging teeth have the same other features except for the tooth height (h).

[0045] Taking three teeth as an example, the tooth height (h) is h1, h2, and h3 in sequence from the one close to the rod body 8 to the one far from the rod body 8. The tooth height of the engaging tooth closest to the rod body 8 is the smallest and there are at least two engaging teeth with different tooth heights. In this embodiment, the tooth height (h) of the three teeth is designed as h1 < h2 < h3. Assuming the original tooth height is ha, 0.7ha ≤ h1 < ha. Controlling the tooth height of h1 above 0.7ha can prevent the shear stress of the semi-engaging nut from being too large. In this embodiment, the stress optimization effect brought by different tooth heights is about 5%.

[0046] Embodiment 3

[0047] The difference between this embodiment and the foregoing embodiments is that, as shown in reference to Figure 3 All the engaging teeth have the same other features except for the tooth root diameter (d).

[0048] Taking three teeth as an example, the tooth root diameter (d) is d1, d2, and d3 in sequence from the one close to the rod body 8 to the one far from the rod body 8. The tooth root diameter of the engaging tooth closest to the rod body 8 is the largest and there are at least two engaging teeth with different tooth root diameters. In this embodiment, the tooth root diameter of the three teeth is designed as d1 > d2 > d3. In this embodiment, the optimization effect brought by different tooth root diameters is about 5%.

[0049] Embodiment 4

[0050] The difference between this embodiment and the foregoing embodiments is that, as shown in reference to Figure 4 All the engaging teeth have the same other features except for the groove width (W). The groove width is the distance between the first tooth side 3 and the second tooth side 7.

[0051] Taking three teeth as an example, the groove width (W) is W1, W2, and W3 in sequence from the one close to the rod body 8 to the one far from the rod body 8. The groove width of the engaging tooth closest to the rod body 8 is the largest and there are at least two engaging teeth with different groove widths. In this embodiment, the groove width of the three teeth is designed as W1 > W2 > W3. In this embodiment, the optimization effect brought by different groove widths is about 5%.

[0052] Embodiment 5

[0053] The difference between this embodiment and the foregoing embodiment lies in that, as shown in Figure 5 taking a three-tooth as an example, the shape and size are the same and they are all deformed teeth. The deformed teeth have the following three changes:

[0054] Change 1: The angle of the tooth tip 1 changes. Based on the axis of the pull rod, the angle change range of the tooth tip 1 is -30° to 30°, preferably -5° to 5°, and in this embodiment it is 0°;

[0055] Change 2: The angle change range of the first tooth flank 3 is 60° to 120°, preferably 90° to 100°, and in this embodiment it is 90°; the angle change range of the second tooth flank 7 is 60° to 120°, preferably 80° to 90°, and in this embodiment it is 90°;

[0056] Change 3:

[0057] The first connecting arc segment 4 is an involute or a circular arc, preferably an involute. In this embodiment, a circular arc is adopted. The selection criterion for the first connecting arc segment 4 is to ensure a smooth transition between the first tooth flank 3 and the transition segment 5 without mutation and reduce the stress concentration caused by the shape mutation. Therefore, it is more appropriate to adopt an involute or a circular arc with a slightly larger radius of curvature and a small change within the selected range;

[0058] The second connecting arc segment 6 is a hyperbola or an ellipse, preferably a hyperbola. In this embodiment, it is an ellipse. The selection criterion for the second connecting arc segment 6 is to ensure a smooth transition between the second tooth flank 7 and the transition segment 5 without mutation and increase the bending resistance of the transition segment 5 within a limited space. Therefore, it is more appropriate to adopt a hyperbola or an ellipse with the largest radius of curvature as large as possible, the smallest radius of curvature not too small, and a large change in the radius of curvature;

[0059] The transition segment 5 is in a straight line shape connecting with the first connecting arc segment 4 and the second connecting arc segment 6. The angle range of the transition segment 5 is 10° to 10°, preferably -5° to 5°, and in this embodiment it is 0°. The straight line should account for 1 / 50 to 1 / 5 of the overall groove width, preferably 1 / 6.

[0060] There are transition fillets 2 between the tooth tip 1 and the first tooth flank 3 and between the tooth tip 1 and the second tooth flank 7. The radius of the transition fillet 2 should not be too large, and the range is 0.5 mm to 4 mm, preferably 1 mm to 2 mm, and in this embodiment it is 1 mm.

[0061] The forces on the engaging teeth include the stress of the first connecting arc segment 4, the tensile stress of the transition segment 5, and the bending stress of the second connecting arc segment 6. In the existing bottom of the arc, the three kinds of stresses will be concentrated at one place at the bottom of the groove. Therefore, it is necessary to make the radius of curvature of the arc at the stress concentration place large enough to reduce the stress concentration problem. The deformed tooth design of this embodiment has at least the following two advantages: First, it increases the bottom diameter of the tooth and increases the tensile strength; Second, the straight segment separates the three stresses that would originally be concentrated at one place, dispersing the stresses that should originally be resisted by a curve with a relatively large radius of curvature, and the first connecting arc segment 4 and the second connecting arc segment 6 with a slightly reduced or basically unchanged radius of curvature resist respectively, reducing the stress concentration problem.

[0062] The stress optimization effect of the deformed teeth in this embodiment is about 5%.

[0063] Embodiment 6

[0064] Taking three teeth as an example, referring to Figure 6 As shown, the difference between this embodiment and Embodiment 5 is that the change in the angles of the first tooth side 3, the second tooth side 7, and the straight transition segment 5 makes the entire bottom of the groove change from a straight line to an arc segment. When the radius of curvature of the first connecting arc segment 4 increases on the basis of Embodiment 5, the angle of the straight line can be adjusted to transfer the stress to the first connecting arc segment 4, reducing the burden on the second connecting arc segment 6.

[0065] In this embodiment, the angle of the first tooth side 3 is set to 95°, the angle of the transition segment 5 is 5°, and the first connecting arc segment 4 is selected as an arc with a radius greater than 1 / 2 of the groove width. At this time, the bottom of the groove changes from a straight line to an arc. The advantage of this design is that the radius of the arc at the bottom of the groove is greater than the radius of the traditional bottom of the arc and the bottom diameter is also larger. The stress difference between the first connecting arc segment and the second connecting arc segment decreases, and the stress optimization effect is stronger than the scheme with a straight bottom. The stress optimization effect of the deformed teeth in this embodiment is about 7%.

[0066] Embodiment 7

[0067] Taking three teeth as an example, referring to Figure 7 As shown, the tooth shapes of the three teeth in this embodiment are different. Among them, from the side close to the rod body 8 to the side far from the rod body 8 are the first tooth, the second tooth, and the third tooth respectively. The first tooth is a deformed tooth, the second tooth is an elliptical tooth, and the third tooth is a traditional arc tooth. The stress optimization effect is about 10%.

[0068] The above are only the preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements should also be regarded as within the protection scope of the present invention.

Claims

1. A pull rod with improved crack resistance, comprising a rod body (8) and an engaging tooth set arranged at both ends of the rod body (8) and used to cooperate with a semi-engaging nut, the engaging tooth set comprising a plurality of engaging teeth arranged at intervals along the axial direction of the rod body (8), the engaging teeth comprising a tooth top (1) and a tooth groove in a direction of the tooth top (1) close to the rod body (8), characterized in that: The tooth groove comprises a first tooth side (3) close to the rod body (8), a second tooth side (7) away from the rod body (8), a transition section (5), a first connecting arc section (4) between the first tooth side (3) and the transition section (5), and a second connecting arc section (6) between the second tooth side (7) and the transition section (5), and the engaging tooth group comprises at least one of the following five features or any combination of two or more thereof: Feature 1: There are at least two types of teeth thickness in the meshing tooth group; Feature 2: There are at least two types of occlusal teeth with different tooth heights in the occlusal tooth group; Feature 3: There are at least two tooth grooves with different tooth bottom diameters in the meshing tooth group; Feature 4: The interlocking tooth set has at least two tooth grooves with different groove widths; Feature 5: There is at least one deformed tooth and the deformed tooth includes at least one or any combination of two or more of the following three changes: Change 1: The angle of the tooth top (1) changes. Taking the axis of the pull rod as a reference, the angle of the tooth top (1) changes within a range of -30° to 30°. Variation 2: The angle variation range of the first tooth side (3) is 60° to 120°, and the angle variation range of the second tooth side (7) is 60° to 120°; Variation 3: The transition section (5) is a straight line or an arc section, and smoothly connects with the first connecting arc section (4) and the second connecting arc section (6).

2. A pull rod with improved crack resistance according to claim 1, characterized in that: The transition section (5) is an arc section, and the curvature radii of the first connecting arc section (4), the transition section (5), and the second connecting arc section (6) are the same or different.

3. The pull rod with improved crack resistance according to claim 1, characterized in that: The transition section (5) is a straight line, and the curvature radii of the first connecting arc section (4) and the second connecting arc section (6) are the same or different.

4. A pull rod with improved crack resistance according to claim 3, characterized in that: The length of the transition section (5) accounts for 1 / 50 to 4 / 5 of the groove width.

5. The pull rod with improved crack resistance according to claim 3, characterized in that: The angle variation range of the transition section (5) is -10° to 10°.

6. The pull rod with improved crack resistance according to claim 1, characterized in that: The first connecting arc segment (4) is a circular arc, an elliptical arc, an involute, a parabola or a hyperbola.

7. The pull rod with improved crack resistance according to claim 1, characterized in that: The second connecting arc segment (6) is a circular arc, an elliptical arc, an involute, a parabola or a hyperbola.

8. The pull rod with improved crack resistance according to claim 1, characterized in that: A transition fillet (2) exists between the tooth top (1) and the first tooth side (3) and between the tooth top (1) and the second tooth side (7), and the fillet radius of the transition fillet (2) is in the range of 0.5 mm to 4 mm.

9. The pull rod with improved crack resistance according to claim 1, characterized in that: The angle variation range of the first tooth side (3) is 60° to 120°.

10. The pull rod with improved crack resistance according to claim 1, characterized in that: The angle variation range of the second tooth side (7) is 60° to 120°.

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