A pre-embedded anchor bolt for concrete

Abstract

The utility model relates to building structure connecting piece technical field especially relates to a pre -buried anchor bolt for concrete, including screw rod, the expansion cone of setting in screw rod one end, with screw rod screw thread connection and located expansion cone outside internal thread expansion sleeve, and the nut of tightening in screw rod other end, the barrel wall of internal thread expansion sleeve is set up with at least one through -hole, the pre -buried anchor bolt still includes the mechanical self -locking unit of setting in the through -hole, the inner side of mechanical self -locking unit is the guide inclined plane of adapting with expansion cone taper face, mechanical self -locking unit is configured as: in the process that expansion cone is pulled and is extruded into internal thread expansion sleeve, can be pushed and at least partially radial stretch out through -hole along guide inclined plane, the utility model discloses setting up the mechanical self -locking unit with guide inclined plane on internal thread expansion sleeve, forms the composite anchoring structure that combines with the friction and mechanical embedding, promotes the performance that the anchor bolt is resistant to vibration, resistant to fatigue and adapts concrete cracking.

Description

Technical Field

[0001] This utility model relates to the field of building structure connectors, and in particular to a pre-embedded anchor bolt for concrete. Background Technology

[0002] In the field of building and mechanical installation, pre-embedded anchors are key components for achieving a reliable connection between the superstructure and the concrete foundation. Among them, internally threaded expansion anchors are widely used due to their convenient installation and strong anchoring force. These anchors typically include a screw, an expansion cone, an internally threaded expansion sleeve, and a nut. During installation, tightening the nut pulls the screw, causing the expansion cone to be squeezed into the expansion sleeve, which forces the expansion sleeve to expand radially, thereby generating a huge static friction force between it and the concrete hole wall, achieving anchoring.

[0003] However, the anchoring force of this traditional expansion friction anchor relies almost entirely on the static friction between the expansion sleeve and the concrete hole wall. Under conditions of long-term exposure to strong vibration, impact loads, or microcracks in the concrete matrix due to shrinkage or load, this friction connection interface is prone to loosening or slippage, leading to a decrease in preload, a significant reduction in anchoring performance, and even the failure mode of the anchor being pulled out entirely, posing a serious safety hazard.

[0004] Therefore, to address the above problems, a pre-embedded anchor bolt for concrete is proposed. By setting a mechanical self-locking unit with a guiding bevel on the internal thread expansion sleeve, a composite anchoring structure combining friction and mechanical embedding is formed, which improves the anchor bolt's resistance to vibration, fatigue, and adaptability to concrete cracking. Utility Model Content

[0005] In order to overcome the problem that when traditional drill pipe retrieval devices are used in daily life, the retrieval cone has to withstand a great pulling torque when the broken rod is blocked, which can easily cause the brittle tap wire to break again.

[0006] The technical solution of this utility model is: a pre-embedded anchor for concrete, including a screw rod, an expansion cone sleeved on one end of the screw rod, an internally threaded expansion sleeve threaded to the screw rod and located outside the expansion cone, and a nut tightened on the other end of the screw rod, wherein at least one through hole is provided on the cylinder wall of the internally threaded expansion sleeve. The pre-embedded anchor bolt also includes a mechanical self-locking unit disposed in the through hole; The inner surface of the mechanical self-locking unit is a guide slope that is adapted to the conical surface of the expansion cone; The mechanical self-locking unit is configured to be pushed along the guide ramp and extend at least partially radially out of the through hole during the process of the expansion cone being pulled into the internal thread expansion sleeve.

[0007] Preferably, when the nut is tightened, the screw drives the expansion cone to move axially. The cone surface of the expansion cone contacts the guide slope of the mechanical self-locking unit and generates an interaction force. This force can be decomposed into a radial component. Driven by this component, the mechanical self-locking unit overcomes the friction with the through hole wall and moves radially outward. Its outer surface protrudes from the outer contour of the expansion sleeve. This process is synchronized with the radial expansion of the expansion sleeve body. An initial static friction is generated between the expansion sleeve body and the concrete hole wall, while the extended mechanical self-locking unit is forcefully pressed into and embedded in the relatively soft concrete material, forming one or more discrete, directional mechanical embedding points. This mechanical embedding effect is not sensitive to micro-cracks in the concrete, and when subjected to pull-out loads, its load-bearing capacity hardly decreases due to the embedding reaction force of the concrete on the mechanical self-locking unit, thereby improving the overall reliability of the anchor bolt. Especially when subjected to alternating loads and impact loads, it can effectively suppress the relaxation of the preload and the slippage of the anchor bolt.

[0008] Preferably, the outer surface of the mechanical self-locking unit is provided with an engagement portion, which is configured to be able to embed into the concrete hole wall when the mechanical self-locking unit extends radially.

[0009] Preferably, the engagement portion consists of a plurality of continuous or discontinuous sawtooth protrusions linearly distributed along the inclined direction of the internal inclined surface of the internal threaded expansion sleeve.

[0010] Preferably, the serrated protrusions are inclined toward the side where the nut is located.

[0011] Preferably, the mechanical self-locking unit is a wedge-shaped block, and the through hole is a rectangular or trapezoidal hole that matches the shape of the wedge-shaped block.

[0012] Preferably, there are multiple through holes and mechanical self-locking units, which are evenly distributed along the circumference of the internal thread expansion sleeve.

[0013] Preferably, the internal threaded expansion sleeve is provided with a limiting structure at the positions corresponding to the two ends of the through hole to restrict the axial movement of the mechanical self-locking unit.

[0014] The beneficial effects of this utility model are: This invention transforms the anchoring mechanism of an anchor bolt into a composite structure combining surface friction and point locking by incorporating a mechanical self-locking unit with a guiding bevel on the internally threaded expansion sleeve. During installation, the single action of tightening the nut simultaneously drives the expansion sleeve body to expand radially, generating frictional force and simultaneously pushing the mechanical self-locking unit to extend radially. Its interlocking portion embeds into the concrete hole wall, forming a mechanical interlock. This allows the force to be transmitted simultaneously through two paths—the friction surface and the mechanical locking point—when the anchor bolt is under load, reducing the risk of failure of a single force transmission path. This anchor bolt is particularly suitable for mechanical equipment foundations, bridge bearings, seismic structures, and applications where concrete micro-cracks may exist. It effectively resists preload relaxation caused by vibration and fatigue loads, providing safety redundancy and long-term reliability. Attached Figure Description

[0015] Figure 1 The diagram shown is a first three-dimensional structural schematic of the pre-embedded anchor bolt for concrete according to this utility model. Figure 2 The diagram shown is a two-dimensional structural schematic of the pre-embedded anchor bolt for concrete according to this utility model. Figure 3 The diagram shown is a partial three-dimensional structural schematic of the pre-embedded anchor bolt for concrete according to this utility model. Figure 4 The diagram shown is a first cross-sectional view of the pre-embedded anchor bolt for concrete according to this utility model. Figure 5 The diagram shown is a partial cross-sectional view of the pre-embedded anchor bolt for concrete according to this utility model. Figure 6 The diagram shown is a second cross-sectional view of the pre-embedded anchor bolt for concrete according to this utility model. Figure 7 The diagram shown is a third cross-sectional view of the pre-embedded anchor bolt for concrete according to this utility model. Explanation of reference numerals in the attached drawings: 1. Screw; 2. Expansion cone; 3. Internal thread expansion sleeve; 4. Nut; 31. Through hole; 5. Mechanical self-locking unit; 51. Guide slope; 52. Engaging part. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Example 1 Please see Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7This utility model provides an embodiment: a pre-embedded anchor for concrete, including a screw 1, an expansion cone 2 sleeved on one end of the screw 1, an internally threaded expansion sleeve 3 threaded to the screw 1 and located outside the expansion cone 2, and a nut 4 tightened on the other end of the screw 1. The internally threaded expansion sleeve 3 has at least one through hole 31 on its sleeve wall. The pre-embedded anchor bolt also includes a mechanical self-locking unit 5 installed in the through hole 31; The inner surface of the mechanical self-locking unit 5 is a guide slope 51 that is adapted to the cone surface of the expansion cone 2; The mechanical self-locking unit 5 is configured to be pushed along the guide slope 51 and extend at least partially radially out of the through hole 31 during the process of the expansion cone 2 being pulled into the internal thread expansion sleeve 3.

[0018] When the nut 4 is tightened, the screw 1 drives the expansion cone 2 to move axially. The cone surface of the expansion cone 2 contacts the guide slope 51 of the mechanical self-locking unit 5 and generates an interaction force. This force can be decomposed into a radial component. Driven by this component, the mechanical self-locking unit 5 overcomes the friction with the wall of the through hole 31 and moves radially outward. Its outer surface protrudes from the outer contour of the expansion sleeve. This process is synchronized with the radial expansion of the expansion sleeve body. An initial static friction is generated between the expansion sleeve body and the concrete hole wall, while the extended mechanical self-locking unit 5 is forcefully pressed into and embedded in the relatively soft concrete material, forming one or more discrete, directional mechanical embedding points. This mechanical embedding effect is not sensitive to micro-cracks in the concrete, and when subjected to pull-out loads, its load-bearing capacity hardly decreases due to the embedding reaction force of the concrete on the mechanical self-locking unit 5, thereby improving the overall reliability of the anchor bolt. Especially when subjected to alternating loads and impact loads, it can effectively suppress the relaxation of the preload and the slippage of the anchor bolt.

[0019] Example 2 Optionally, based on Embodiment 1, this utility model provides another embodiment, which provides a pre-embedded anchor for concrete, including a screw 1, an expansion cone 2, an internally threaded expansion sleeve 3, a nut 4, and a mechanical self-locking unit 5.

[0020] Four rectangular through holes 31 are opened on the expansion end of the sleeve. These through holes 31 are evenly distributed along the circumference of the sleeve. A wedge block is embedded in each through hole 31 as a mechanical self-locking unit 5. The inner side of the wedge block is machined into a guide slope 51 that matches the taper of the expansion cone 2, and the outer side of the wedge block remains flat.

[0021] During installation, firstly, mounting holes matching the anchor bolt specifications are drilled in the concrete substrate; the assembled anchor bolt is placed into the mounting holes; the nut 4 is tightened using a torque wrench, and the nut 4 applies pressure to the end of the sleeve through the washer; under the pressure of the nut 4, the screw 1 is subjected to axial tension, which drives the expansion cone 2 to move into the sleeve; the conical surface of the expansion cone 2 contacts the guide slope 51 of the mechanical self-locking unit 5, generating a radial component force, which pushes the four wedge blocks to move radially outward synchronously; the wedge block part extends out of the through hole 31, and its outer surface is in close contact with the concrete hole wall, forming the initial mechanical locking.

[0022] This embodiment adds discrete mechanical support points to the traditional friction expansion by using a wedge block structure; when the anchor bolt is subjected to external force, the load is transmitted through the friction surface and the mechanical support points, which improves the reliability of the anchoring system.

[0023] Example 3 Optionally, based on Embodiment 2, the present invention further optimizes the structure of the mechanical self-locking unit 5.

[0024] In Example 2, reverse serrations are machined on the outer surface of the wedge block as the biting part 5252; the tooth direction of the serrations is inclined towards the side where the nut 4 is located, and the mechanical self-locking unit 5 is made of alloy steel with a hardness of HRC 55-60 to ensure that the serrations have sufficient strength and wear resistance.

[0025] During the process of the expansion cone 2 being squeezed into the sleeve, when the wedge block is pushed out and comes into contact with the concrete hole wall, the sharp serrated edge is pressed into the relatively soft concrete material under radial pressure. Since the serration direction is towards the root of the anchor bolt, when the anchor bolt is subjected to a force F in the pull-out direction, the reaction force F_r of the concrete on the serrated inclined surface can be decomposed into a radial component F_n and a tangential component F_t. The direction of F_t causes the wedge block to tend to further wedge into the concrete, forming a self-locking effect.

[0026] The self-locking condition is satisfied: F_t × μ>F_n, where μ is the friction coefficient between concrete and metal; by reasonably designing the sawtooth angle, the self-locking requirement can be ensured under any load conditions.

[0027] In this embodiment, the reverse sawtooth structure transforms the traditional surface contact into multi-point line contact, significantly increasing the pressure on the contact surface. Under stress, the interlocking of the sawtooth with the concrete creates an irreversible mechanical interlock, effectively resisting loosening caused by vibration and impact loads.

[0028] Example 4 Optionally, this embodiment adds a limiting structure to prevent the mechanical self-locking unit 5 from falling off, based on embodiment 2.

[0029] The difference from Embodiment 2 is that, on the inner wall of the internal thread expansion sleeve 33, corresponding to the axial ends of each through hole 31, a groove is formed by machining downward along the edge of the through hole 31 as a limiting structure. The size of the groove is slightly smaller than the size of the two end faces of the wedge block. The edges of the two end faces of the wedge block are machined with flange structures that are compatible with the groove structure. The wedge block and the through hole 31 adopt a trapezoidal cross section. The trapezoidal wedge block and the trapezoidal through hole 31 form a sliding fit to ensure that the wedge block can only move radially and cannot move axially.

[0030] Before the anchor bolt is transported and installed, the limiting flange and groove structure prevent the wedge block from falling out of the through hole 31, ensuring the integrity of the product. During installation, the expansion cone 2 pushes the wedge block, which extends smoothly along the preset radial trajectory. The limiting structure ensures that the extension of all wedge blocks is consistent, keeping the anchor bolt centered in the concrete hole and avoiding skewing. The limiting structure not only solves the problem of small parts being easily lost, but also ensures that the movement trajectory of the mechanical self-locking unit 5 is precisely controllable, ensuring that each wedge block moves synchronously, so that the anchor bolt is subjected to uniform force, improving the consistency and reliability of the installation quality.

[0031] Furthermore, there are multiple through holes 31 and mechanical self-locking units 5, which are evenly distributed along the circumference of the internal thread expansion sleeve 3. The multiple mechanical self-locking units 5 evenly distributed in the circumference enable the anchor bolt to have corresponding mechanical self-locking units 5 working when it is subjected to loads from any direction, providing balanced mechanical anchoring force; avoiding deflection or stress concentration of the anchor bolt in the hole due to unilateral force, and ensuring the stability and reliability of the connection.

[0032] Through the above steps, by using a mechanical self-locking unit 5 with a guide slope 51 on the internally threaded expansion sleeve 3, the anchoring mechanism of the anchor bolt is transformed into a composite structure combining surface friction and point locking. During installation, the single action of tightening the nut 4 synchronously drives the expansion sleeve body to expand radially, generating frictional force, and simultaneously pushes the mechanical self-locking unit 5 to extend radially, with its biting part 52 embedding into the concrete hole wall to form a mechanical interlock. This allows the force flow to be transmitted simultaneously through two paths, the friction surface and the mechanical locking point, when the anchor bolt is under load, reducing the risk of failure of a single force transmission path. This anchor bolt is particularly suitable for mechanical equipment foundations, bridge bearings, seismic structures, and situations where there may be micro-cracks in the concrete. It can effectively resist the relaxation of preload caused by vibration and fatigue load, providing safety redundancy and long-term reliability.

[0033] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A pre-embedded anchor for concrete, comprising a screw rod (1), an expansion cone (2) sleeved on one end of the screw rod (1), an internally threaded expansion sleeve (3) threaded to the screw rod (1) and located outside the expansion cone (2), and a nut (4) tightened on the other end of the screw rod (1), characterized in that: At least one through hole (31) is provided on the cylinder wall of the internal thread expansion sleeve (3). The pre-embedded anchor also includes a mechanical self-locking unit (5) disposed in the through hole (31); The inner surface of the mechanical self-locking unit (5) is a guide slope (51) that is adapted to the cone surface of the expansion cone (2). The mechanical self-locking unit (5) is configured to be pushed along the guide slope (51) and extend at least partially radially out of the through hole (31) during the process of the expansion cone (2) being pulled into the internal thread expansion sleeve (3).

2. The pre-embedded anchor bolt for concrete according to claim 1, characterized in that: The outer side of the mechanical self-locking unit (5) is provided with an engagement part (52), which is configured to be able to embed into the concrete hole wall when the mechanical self-locking unit (5) extends radially.

3. A pre-embedded anchor bolt for concrete according to claim 2, characterized in that: The engagement portion (52) consists of a plurality of continuous or discontinuous sawtooth protrusions linearly distributed along the inclined direction of the internal inclined surface of the internal thread expansion sleeve (3).

4. A pre-embedded anchor for concrete according to claim 3, characterized in that: The serrated protrusions are inclined toward the side where the nut (4) is located.

5. A pre-embedded anchor bolt for concrete according to claim 1, characterized in that: The mechanical self-locking unit (5) is a wedge-shaped block, and the through hole (31) is a rectangular hole or trapezoidal hole that matches the shape of the wedge-shaped block.

6. A pre-embedded anchor for concrete according to claim 1, characterized in that: The number of the through holes (31) and the mechanical self-locking units (5) is multiple, and they are evenly distributed along the circumference of the internal thread expansion sleeve (3).

7. A pre-embedded anchor bolt for concrete according to claim 1, characterized in that: The internal thread expansion sleeve (3) is provided with a limiting structure at the positions corresponding to the two ends of the through hole (31) to restrict the axial movement of the mechanical self-locking unit (5).

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