Self-bottom-expanding expansion piece

Abstract

The invention discloses a self-bottom-expanding expansion piece which is used in cooperation with a screw with a conical head, the front section of the self-bottom-expanding expansion piece is an expansion section, and the rear section of the self-bottom-expanding expansion piece is a supporting section. The expansion section comprises two arc-shaped expansion pieces, and the head parts of the expansion pieces are provided with bottom expansion tool bits used for cutting in a base material; the base part of the expansion sheet is connected with the head part and the supporting section, and notches extending in the circumferential direction are formed in the two sides of the base part, so that the base part is in a necking shape relative to the head part and the supporting section; under the expansion action of the conical head, the base part of the expansion section deforms, so that the head part rotates outwards around the necking part, meanwhile, the two wings of the head part deform outwards, and the radian of the head part is gradually increased to be matched with the radian of the periphery of the conical head. According to the self-bottom-expanding expansion piece, the two-section type expansion piece design is adopted, the necking-down base part and the notch structure are combined, the problems that in the prior art, an expansion piece is prone to breakage, difficult to expand and high in cost are solved, and the self-bottom-expanding expansion piece has the advantages of being high in strength, easy to expand and low in cost.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical anchor bolts, in particular to a self-expanding bottom expansion piece. Background Art

[0002] Mechanical anchor bolts are a type of building fastener that is anchored mechanically, including expansion anchor bolts and self-expanding bottom anchor bolts.

[0003] Expansion anchor bolt: By applying torque or knocking force, the expansion piece expands and squeezes the hole wall, using the friction force generated by the friction effect as the main anchoring force; Self-expanding anchor bolts: The expansion blade must be equipped with a hard blade capable of cutting the substrate. This allows the expansion blade to be mechanically locked into the substrate during installation, through the rotational expansion and insertion of the expansion blade. This mechanical engagement provides the primary anchoring force. The expansion blade must be sufficiently strong to withstand the impact of the stall torque applied during expansion; otherwise, it will be torn apart by the stall torque, resulting in failure of expansion.

[0004] It is difficult to embed hard blades on conventional expansion pieces with more than four petals. The reason is that when the expansion pieces with more than four petals are expanding, they are not enough to overcome the stall torque caused by the base material (usually the hard objects and steel bars in the concrete), which can easily cause the expansion pieces with more than four petals to be torn off, and then the anchoring fails.

[0005] Existing technology increases the strength of the expansion piece by increasing the wall thickness of the expansion sleeve and expansion piece. However, this significantly increases the complexity of the production process for self-expanding bottom anchors and significantly increases their cost. The cost is dozens, even hundreds, of times higher than that of traditional expansion anchors. As a result, self-expanding bottom anchors, which offer excellent anchoring performance, are excluded from general structural engineering projects. Furthermore, general structural engineering prohibits the use of expansion anchors (JGT160-2017 Mechanical Anchors for Concrete). This has left the application of self-expanding bottom anchors in a difficult position. Summary of the Invention

[0006] The purpose of the present invention is to provide a self-expanding bottom expansion piece, which is composed of a cylindrical support section and an expansion piece. The expansion piece adopts a two-petal expansion piece design, combined with a necked base and a notch structure, to solve the problems of easy breakage, difficult expansion and high cost of the expansion piece in the prior art, and has the advantages of high strength, easy expansion and low cost.

[0007] To achieve the above-mentioned purpose, the solution of the present invention is: a self-expanding bottom expansion piece, which is a cylindrical structure and is used in conjunction with a screw with a tapered head; The front section of the self-expanding bottom expansion piece is the expansion section, and the rear section is the support section; The expansion section includes two arc-shaped expansion pieces, and the heads of the expansion pieces are provided with bottom expansion cutter heads for cutting into the substrate; The base of the expansion piece connects the head and the support section, and circumferentially extending notches are formed on both sides of the base, so that the base is in a necked shape relative to the head and the support section; When the expansion piece moves axially on the cone head under the action of external force, its base is deformed, causing the head to rotate outward around the neck. At the same time, the two wings of the head are deformed outward, causing the curvature of the head to gradually increase to match the curvature of the outer periphery of the cone head.

[0008] Furthermore, the self-expanding bottom expansion piece is an axisymmetric structure.

[0009] Furthermore, in the expansion piece, the arc length of the base is 1 / 5 to 1 / 2 of the arc length of the head.

[0010] Furthermore, in the expansion piece, the height of the base is 1 / 5 to 1 / 2 of the height of the head.

[0011] Furthermore, the inner diameter of the front end of the expansion section is d, the maximum outer diameter of the cone head is D, and before the expansion piece is expanded to the bottom, d<D; after the expansion piece is expanded to the bottom, d=D.

[0012] Furthermore, before the expansion piece is expanded, the orthographic projection main view of the expansion piece head is rectangular, and after the expansion piece is expanded, it is trapezoidal.

[0013] Furthermore, the orthographic projection main view of the notch is a rectangle.

[0014] Furthermore, on the expansion section, the gap between the heads of the two expansion pieces in the circumferential direction is 0-5 mm.

[0015] Furthermore, the wall thickness δ of the expansion piece is 2-5 mm.

[0016] Furthermore, the bottom expanding cutter head is made of cemented carbide or diamond.

[0017] After adopting the above solution, the beneficial effects of the self-expanding bottom expander with a two-petal expansion structure of the present invention are: 1. The expansion piece has high bending strength along the chord length direction to ensure the stability of the expansion bottom: Made of the same material, the two-flap expander blade of the present invention is significantly stronger than conventional four-flap expanders or larger. During bottom hole enlargement, its bending strength is four times that of a four-flap expander blade, fully ensuring the required torque. This solves the long-standing problem of insufficient strength of expanders with hard blades during bottom enlargement, effectively preventing the expander blade from tearing due to insufficient strength.

[0018] 2. Easy to expand: The fewer the expansion blades, the longer the arc length of each blade, making expansion more difficult. However, the present invention provides notches on either side of the base of the expansion blade, creating a constricted shape relative to the head and sleeve body. The constricted neck facilitates outward rotation and expansion of the head, while the notches free the two sides of the expansion blade's head relative to the sleeve body. This allows the two wings of the head to expand freely under load, unrestricted by the sleeve body.

[0019] During installation, the expansion of the cone head causes the necking structure to preferentially deform elastically at the base. The combined effects of axial thrust and rotational torque force the head to rotate outward around the necking. Simultaneously, under the combined effects of the cone head's thrust and the substrate's reaction force, the head's two wings deform outward, gradually increasing their radius of curvature to match the cone head's outer curvature, forming a trumpet-shaped, expanded base structure. This makes the entire expansion process smoother and more efficient.

[0020] 3. Low production cost: The production cost of the self-expanding bottom expander of the present invention is very close to that of the sleeve of a conventional expansion anchor, and far lower than the cost of increasing the wall thickness. This overcomes the limitation of conventional expansion anchor sleeves, which require increasing the wall thickness to increase strength. This lower price creates favorable conditions for the widespread adoption of the excellent anchoring performance of the self-expanding bottom expander. When this highly safe and reliable product can be brought to market at a lower cost, its safety performance will benefit more fields and users, fully demonstrating its significant social value.

[0021] 4. High versatility: The self-expanding bottom expander of the present invention can be adapted to the screw of a conventional expansion anchor bolt. This feature allows the self-expanding bottom expander to be easily integrated into the existing building anchoring system without requiring large-scale modification of existing installation equipment and processes, making it easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is an assembly diagram of a self-expanding bottom expansion member and a screw rod according to an embodiment of the present invention; Figure 2 This is a structural diagram of a self-expanding bottom expansion member and a screw rod according to an embodiment of the present invention; Figure 3 This is a front view of a self-expanding bottom expander according to an embodiment of the present invention; Figure 4 is a top view of a self-expanding bottom expander according to an embodiment of the present invention; Figure 5 yes Figure 4 A-direction view; Figure 6 yes Figure 4 BB surface cross-sectional view; Figure 73D diagram of a self-expanding expansion member before and after bottom expansion according to an embodiment of the present invention; Figure 8 1 is a side view of a self-expanding expansion member before and after bottom expansion according to an embodiment of the present invention; Figure 9 This is a schematic diagram of the bottom expansion process of a self-expanding bottom expansion member according to an embodiment of the present invention; Figure 10 The figure is a schematic diagram of a self-expanding bottom expansion piece formed by pressing a steel plate according to an embodiment of the present invention.

[0023] Description of labels: 1. Self-expanding bottom expansion piece; 2. expansion section; 21. expansion piece; 211. head; 212. base; 213. notch; 214. notch; 215. gap; 22. bottom expansion cutter head; 3. Support section; 4. Screw; 41. Cone head; 5. Base material; 51. Straight hole. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] The present invention provides a self-expanding bottom expansion member 1, such as Figures 1 to 10 As shown, the self-expanding bottom expander 1 is used in conjunction with a screw 4 with a cone head 41 commonly found on the market to achieve self-expanding bottom and expansion effects. The self-expanding bottom expander 1 has an axisymmetric structure and is evenly stressed during installation and use, effectively avoiding deformation or damage caused by uneven stress.

[0026] About hole expansion: like Figure 2 As shown, the front section of the self-expanding bottom expander 1 is the expansion section 2, which is used to expand the hole of the substrate 5. The expansion section 2 can smoothly form a hole that meets the requirements on the substrate 5 during the installation process. The rear section of the self-expanding bottom expander 1 is the support section 3, which is used to provide support for the rod portion of the screw 4.

[0027] The expansion section 2 has a two-lobed structure, comprising two arcuate expansion blades 21. Each expansion blade 21 consists of a head 211 and a base 212 connecting the head 211 and the support section 3. The head 211 is equipped with a bottom expansion blade 22, which is used to cut into the substrate 5 and provide the critical cutting force for the hole expansion operation.

[0028] On the expansion section 2, the circumferential gap 215 between the heads 211 of the two expansion pieces 21 is 0-5 mm. Even with a gap 215 of 0 mm, the expansion action can be achieved even if the two expansion pieces 21 are not integral. If the gap 215 is too large, the arc length of the expansion pieces 21 will be reduced, lowering their bending strength and resulting in a decrease in anchoring performance. Therefore, the gap 215 should be as small as possible.

[0029] The self-expanding bottom expander 1 of this invention can be manufactured from the same base tubing used in the sleeves of conventional expansion anchors, without increasing consumables or production costs. Therefore, the wall thickness of its expansion section 2 can be within the same range as that of the sleeves of conventional expansion anchors, typically 2 to 5 mm.

[0030] The two-petal design of the present invention can significantly reduce production costs compared to the existing design of increasing the sleeve wall thickness while maintaining the same bending strength, as shown in Table 1.

[0031]

[0032] The sleeve in a conventional self-expanding anchor bolt must increase its wall thickness (4.5 mm) to achieve the required bending strength for bottom expansion, which inevitably increases manufacturing costs. However, the solution of the present invention allows the expansion element to easily achieve the same bending strength standard as conventional self-expanding anchor bolts without increasing the wall thickness, and without increasing the cost. From a manufacturing perspective, the difference between conventional self-expanding anchor bolts and the anchor bolts of the present invention may not be very significant. However, in actual application, for example, a nuclear power plant requires approximately 200,000 anchor bolts. In this case, the difference in consumable costs between conventional self-expanding anchor bolts and the anchor bolts of the present invention becomes extremely significant.

[0033] It should be noted that a complete anchor bolt consists of a sleeve (the expander in this case) and a screw, and is sold as a set. Therefore, the prices in Table 1 are calculated based on a complete anchor bolt. However, since the self-expanding bottom expander of the present invention can be adapted to conventional screws with a tapered head, in actual production and sales, the self-expanding bottom expander of the present invention can be sold separately.

[0034]

[0035] Note: Non-structural: connection parts that do not bear the main load-bearing function of the structure; Structural type: connection parts in buildings or structures that bear important structural load-bearing functions; Structural seismic fortification: Based on structural applications, it further considers the special and strong dynamic load impact of earthquakes.

[0036] like Figure 9 As shown, the anchor bolt is placed in the straight hole 51 of the substrate 5. When the expansion piece rotates to expand the bottom, the expansion cutter head 22 can cut the substrate 5 to form an expanded hole. At the same time, the expansion piece is embedded in the expanded hole to form a lock key structure. This type of anchor bolt, which uses mechanical meshing force as the main anchoring force, has extremely high anchoring stability. When the anchor bolt is subjected to load, due to the powerful bite of the mechanical lock key, the anchor bolt will not be displaced and can always maintain a stable anchoring state, which is incomparable to traditional expansion anchor bolts. Traditional expansion anchor bolts mainly rely on expansion force to achieve anchoring. After being subjected to large loads or long-term use, problems such as expansion force attenuation and anchor bolt loosening are prone to occur, thereby affecting the anchoring effect and structural safety.

[0037] A pull-out test is performed on the installed expansion anchor bolts and the anchor bolts using the self-expanding bottom expansion piece of the present application.

[0038] The self-expanding anchor bolt of the present application provides a strong anchoring force due to the mechanical engagement of the mechanical locking key, so that the screw 4 is broken by being pulled apart when subjected to tension. This indicates that the anchoring force between the self-expanding bottom expansion member 1 and the substrate 5 has reached a high level, capable of withstanding large tensile forces without causing the entire anchor bolt to fail.

[0039] When traditional expansion anchor bolts are pulled out, since their anchoring method mainly relies on expansion force, taking M12×100 as an example, when the pulling force reaches 10KN, the screw begins to move. When the pulling force reaches 20KN, it will be pulled out as a whole, causing anchor failure.

[0040] About extensions: like Figures 2 to 5 As shown, in the two-petal expansion section 2 structure, the arc length of a single expansion piece 21 is relatively long, close to half the circumference, and is greatly constrained by the sleeve body, making it difficult to deform, that is, difficult to rotate and expand into a trumpet shape. Therefore, this design forms circumferentially extending notches 213 on both sides of the base 212, so that the base 212 is necked relative to the head 211 and the support section 3. This case does not limit the shape of the notch 213. This specification provides a shape, such as Figure 3 As shown, the notch 213 is a rectangle in the orthographic projection main view.

[0041] The neck-shaped structure facilitates the rotation of the head 211. Figure 7 As shown, when the self-expanding bottom expander 1 is subjected to external force, undergoes axial displacement and contacts the cone head 41, the necking structure causes the base 212 to deform first. Under the combined action of axial thrust and rotational torque, the head 211 is forced to rotate outward around the necking. Figure 8 a.

[0042] like Figure 7As shown, the presence of the notch 213 allows both sides of the head 211 of the expansion piece 21 to be free relative to the sleeve body, that is, the two wings of the head 211 can be freely unfolded when subjected to force without being constrained or restricted by the sleeve body. Figure 8 As shown, under the combined action of the thrust of the cone head 41 and the reaction force of the substrate 5, the two wings of the head 211 deform outwards. As the deformation progresses, the curvature radius gradually increases. Figure 8 The number 211' in b changes to the number 211, eventually forming a trumpet-shaped expanded bottom structure. At the same time, the curvature of the head 211 will gradually decrease to perfectly match the outer peripheral curvature of the cone head 41, thereby achieving a tight fit and ensuring the stability and reliability of the expanded bottom effect.

[0043] It can also be understood as Figure 6 As shown, the central angle α1 of the base 212 is smaller than the central angle α2 of the head 211 (not shown in the figure), which facilitates the expansion of the two wings and enables the expansion member to move toward the end face of the screw 4 when expanding the bottom hole. Figure 7 As shown, the inner diameter of the front end of the expansion section 2 is denoted by d, and the maximum outer diameter of the conical head 41 is denoted by D. Before the expansion piece is expanded, d < D; after the expansion piece is expanded, d = D. Before the expansion piece is expanded, the orthographic projection of the head 211 of the expansion piece 21 is rectangular. After the expansion piece is expanded, the orthographic projection is trapezoidal because the deformation of the front end is greater than that of the rear end.

[0044] The arc length of the base portion 212 of the expansion piece 21 is 1 / 5 to 1 / 2 of the arc length of the head portion 211, and the height of the base portion 212 is 1 / 5 to 1 / 2 of the height of the head portion 211. This ratio design ensures that the expansion piece 21 has high bending strength while also achieving good expansion and hole expansion.

[0045] Comparing the present invention with the sleeve of a conventional expansion anchor bolt can more clearly highlight the advantages of the present design.

[0046] The sleeve of a traditional expansion anchor bolt has at least three expansion pieces 21, usually four expansion pieces 21. Since the arc length of a single expansion piece 21 is relatively short, less than a quarter of the circumference, its degree of enclosure around the cone head 41 is relatively small. During the expansion process, the arc of the expansion piece 21 with a shorter arc length basically does not change, nor does it need to change. As long as the expansion piece 21 is simply rotated outward, a certain degree of expansion effect can be achieved. However, the present invention adopts a two-petal design, which has a higher degree of enclosure around the cone head 41. For the specific expansion process, please refer to Figure 9 During the expansion process, if the curvature of the head 211 of the expansion piece 21 does not change, due to the high degree of enclosure, it will be subject to greater space restrictions. Figure 8, it is difficult to further achieve expansion and bottom expansion, and cannot meet the requirements for effective anchoring and stability in actual engineering. This well explains the necessity of the above-mentioned notch 213 and necking.

[0047] There are many ways to shape the bottom expansion blade 22. The method used in this application is to cut a notch 214 in the middle of the head 211 of the expansion piece 21. Figure 3 As shown, the bottom expanding blade 22 is then welded into the notch 214. The front end of the bottom expanding blade 22 must protrude beyond the front end of the expansion blade 21 to achieve cutting of the substrate 5. Alternatively, the bottom expanding blade 22 can be integrally welded to the head 211 of the expansion blade 21, which will not be described in detail in this case. The bottom expanding blade 22 can be made of any material that can fit the substrate 5, such as cemented carbide, diamond, etc. Different materials of bottom expanding blades 22 are suitable for different types of substrates 5 and bottom expanding requirements.

[0048] The self-expanding bottom expansion piece 1 of the present invention is cut and formed by a seamless steel pipe. Figures 3 to 5 , can also be formed by pressing steel plates, refer to Figure 10 . To further illustrate various embodiments, the present invention is provided with accompanying drawings. These drawings form part of the present disclosure and are primarily used to illustrate the embodiments and, in conjunction with the relevant description in the specification, to explain the operating principles of the embodiments. By referring to these drawings, one of ordinary skill in the art will understand other possible embodiments and the advantages of the present invention. The components in the figures are not drawn to scale, and similar reference numerals are generally used to represent similar components.

[0049] At the same time, the directions such as front, back, left, and right involved in this embodiment are only used as a reference for directions and do not represent directions in actual use. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the design of this case. Any equivalent changes made based on the key design of this case shall fall within the scope of protection of this case.

Claims

1. A self-expanding bottom expander, characterized in that: The self-expanding bottom expansion piece is a cylindrical structure and is used in conjunction with a screw with a conical head; The front section of the self-expanding bottom expansion piece is the expansion section, and the rear section is the support section; The expansion section includes two arc-shaped expansion pieces, and the heads of the expansion pieces are provided with bottom expansion cutter heads for cutting into the substrate; The base of the expansion piece connects the head and the support section, and circumferentially extending notches are formed on both sides of the base, so that the base is in a necked shape relative to the head and the support section; When the expansion piece moves axially on the cone head under the action of external force, its base is deformed, causing the head to rotate outward around the neck. At the same time, the two wings of the head are deformed outward, causing the curvature of the head to gradually increase to match the curvature of the outer periphery of the cone head.

2. The self-expanding bottom expansion piece according to claim 1, characterized in that: The self-expanding bottom expansion piece is an axisymmetric structure.

3. The self-expanding bottom expansion piece according to claim 1, characterized in that: In the expansion piece, the arc length of the base is 1 / 5 to 1 / 2 of the arc length of the head.

4. The self-expanding bottom expander according to claim 1, wherein: In the expansion piece, the height of the base is 1 / 5 to 1 / 2 of the height of the head.

5. The self-expanding bottom expansion piece according to claim 1, characterized in that: The inner diameter of the front end of the expansion section is d, the maximum outer diameter of the cone head is D, and before the expansion piece expands to the bottom, d<D; after the expansion piece expands to the bottom, d=D.

6. The self-expanding bottom expansion piece according to claim 1, characterized in that: Before the expansion piece is expanded, the orthographic projection main view of the expansion piece head is rectangular, and after the expansion piece is expanded, it is trapezoidal.

7. The self-expanding bottom expansion piece according to claim 1, characterized in that: The orthographic projection main view of the notch is a rectangle.

8. The self-expanding bottom expander according to claim 1, characterized in that: On the expansion section, the gap between the heads of the two expansion pieces in the circumferential direction is 0-5 mm.

9. The self-expanding bottom expander according to claim 1, wherein: The wall thickness δ of the expansion piece is 2-5 mm.

10. The self-expanding bottom expansion piece according to claim 1, characterized in that: The bottom expanding cutter head is made of hard alloy or diamond.

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