Hollow nut and expansion bolt assembly

Abstract

The utility model relates to the technical field of connecting pieces, and discloses a hollow nut and an expansion bolt assembly. The hollow nut comprises a nut body and a conical head which are integrally connected, an inner hole penetrating through the nut body and the conical head is formed in the hollow nut, and threads are arranged on the hole wall of the inner hole. The conical head is provided with a first end and a second end which are oppositely arranged, the first end is connected to the nut body, and the outer diameter of the first end is larger than that of the second end. According to the hollow nut and the expansion bolt assembly, by designing and improving the structure of the hollow nut, the technical problem that an expansion bolt component cannot be repeatedly used in the related technology is solved.

Description

Technical Field

[0001] The present application relates to the technical field of connectors, and in particular to a hollow nut and expansion bolt assembly. Background Art

[0002] An expansion bolt is a bolt used to fix objects. It provides additional support and fixing force by expanding the expansion sleeve in the hole to achieve building structure connection, pipe bracket fixation, etc.

[0003] The basic structure of the existing expansion bolts includes a bolt (or screw) and an expansion sleeve. When in use, the bolt and the expansion sleeve need to be inserted into the hole, and the bolt is rotated to expand and fill the hole. However, this expansion bolt is difficult to disassemble, and the bolt head left outside the hole needs to be cut off after assembly, resulting in the bolt component cannot be reused. Utility Model Content

[0004] The purpose of the present application is to provide a hollow nut and expansion bolt assembly, which is used to solve the technical problem that the expansion bolt components in the related art cannot be reused.

[0005] In the first aspect, the present application provides a hollow nut, which includes a nut body and a conical head that are integrally connected, an inner hole that passes through the nut body and the conical head is provided in the hollow nut, and a thread is provided on the hole wall of the inner hole; the conical head has a first end and a second end that are relatively arranged, the first end is connected to the nut body, and the outer diameter of the first end is larger than the outer diameter of the second end.

[0006] In one embodiment, the hollow nut further includes an anchoring structure, and the anchoring structure is protrudingly provided on the outer wall of the nut body.

[0007] In one embodiment, the anchoring structure includes a first annular protrusion and a second annular protrusion spaced apart along the axial direction of the nut body.

[0008] In one embodiment, the first annular protrusion is disposed at an end of the nut body away from the conical head; along the axial direction of the nut body, the thickness of the first annular protrusion is greater than the thickness of the second annular protrusion.

[0009] In one embodiment, along the axial direction of the nut body, the thickness of the first annular protrusion is 17 mm-23 mm, and the thickness of the second annular protrusion is 12 mm-18 mm.

[0010] In one embodiment, the conical head includes a cylindrical portion and a conical head portion, the cylindrical portion is connected to the nut body, and anti-slip grooves are arranged on the outer wall of the conical head portion.

[0011] In one embodiment, the anti-slip pattern includes a plurality of strip-shaped protrusions arranged at intervals.

[0012] In one embodiment, along the radial direction of the nut body, the cylindrical portion is 12 mm-18 mm higher than the surface of the nut body.

[0013] In one embodiment, a transition connection structure is provided between the cylindrical portion and the nut body.

[0014] The hollow nut provided in the present application includes a nut body and a conical head which are integrally arranged. An inner hole which passes through the nut body and the conical head is arranged in the hollow nut, and a thread is arranged on the hole wall of the inner hole. In this way, the inner hole of the hollow nut can allow a bolt to pass through and be threadedly connected with the bolt. Driven by the bolt, the hollow nut can move and its conical head can replace the traditional bolt to expand the expandable casing. The above-mentioned hollow nut can be detachably connected to the bolt, so that the bolt can be flexibly arranged to realize the reuse of the bolt.

[0015] In the second aspect, the present application provides an expansion bolt assembly, comprising an expandable casing, a bolt and a hollow nut as described in the first aspect, wherein the expandable casing and the hollow nut are arranged successively along the axial direction of the hollow nut, and the bolt is detachably arranged in the expandable casing and the hollow nut, one end of the bolt extends into the inner hole of the hollow nut and is threadedly connected to the hollow nut, and the other end extends out of the expandable casing and is used to drive the hollow nut to move.

[0016] The expansion sleeve assembly provided by the present application provides a hollow nut with a conical head, and uses the hollow nut to replace the traditional bolt member. The bolt and the hollow nut are detachably connected and the bolt can drive the hollow nut to move, so that the expansion sleeve is realized by expanding the conical head of the hollow nut, so that the bolt can be completely disassembled after installation, thereby realizing the reusability of the bolt. In addition, the bolt is easy to disassemble, and the installation wall and the parts to be fixed will not be damaged during the disassembly process, which can reduce construction waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A schematic diagram of the structure of a hollow nut provided in an embodiment of the present application;

[0019] Figure 2A schematic diagram of the structure of the expansion bolt assembly provided in an embodiment of the present application in an unexpanded state;

[0020] Figure 3 A schematic diagram of the structure of the expansion bolt assembly provided in an embodiment of the present application in an expanded state;

[0021] Figure 4 for Figure 2 The structural schematic diagram of the expansion bolt assembly shown is assembled on the wall;

[0022] Figure 5 for Figure 3 The schematic diagram of the structure of the expansion bolt assembly assembled on the wall is shown.

[0023] Description of main component symbols:

[0024] 100, hollow nut; 1, nut body; 11, anchoring structure; 110, first annular protrusion; 120, second annular protrusion; 2, conical head; 21, cylindrical part; 22, conical head; 221, anti-slip pattern; 23, transition connection structure;

[0025] 200, expandable casing;

[0026] 300, bolt; 301, screw; 302, head;

[0027] 400, parts to be connected;

[0028] 500, wall;

[0029] 600. Mounting hole. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0031] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it may be directly or indirectly disposed on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the accompanying drawings and is only for the convenience of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the patent. The terms "first" and "second" are only used for the convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0032] References to "one embodiment", "some embodiments" or "an embodiment" described in the specification of this application mean that a particular feature, structure or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. Thus, the phrases "in one embodiment", "in some other embodiments", "in some other embodiments", etc., which appear at different places in this specification, do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. In addition, in one or more embodiments, particular features, structures or characteristics may be combined in any suitable manner.

[0033] On the first aspect, an embodiment of the present application provides a hollow nut, which is applied in the field of building installation and can be used as a component of an expansion bolt assembly and used together with an expandable casing and a bolt.

[0034] like Figure 1 As shown, the hollow nut 100 comprises a nut body 1 and a conical head 2 connected in one piece, and an inner hole penetrating the nut body 1 and the conical head 2 is provided in the hollow nut 100, and a thread is provided on the hole wall of the inner hole. The conical head 2 has a first end (such as Figure 1 end shown in a) and the second end (as shown in Figure 1 The first end is connected to the nut body 1, and the outer diameter of the first end is greater than the outer diameter of the second end.

[0035] The hollow nut 100 is hollow inside and forms an inner hole extending along its axial direction. Figure 2 and Figure 3 As shown, the inner hole is used for the bolt 300 to pass through and be threadedly connected with the bolt 300, so that the hollow nut 100 is connected to other components or transmits axial force.

[0036] The hole wall of the inner hole is provided with a thread, and the thread can be provided on the entire hole wall along the axial direction of the inner hole, or only provided on one section of the hole wall. The thread is a standard thread specification, so as to be used in conjunction with the bolt 300 and other standard parts.

[0037] The conical head 2 includes a large end and a small end, the large end is defined as a first end, and the small end is defined as a second end. The first end is used to connect the nut body 1, and the second end is used as a free end for docking with components such as the expandable casing 200.

[0038] The hollow nut 100 can be used together with the expandable casing 200 and the bolt 300. The expandable casing 200 refers to an expandable hollow casing. A slit is provided at one end of the expandable casing 200. When the conical head 2 of the hollow nut 100 is inserted into the casing, the outer diameter of the casing becomes larger. The bolt 300 includes a screw rod 301 and a head 302 connected thereto. The inner hole of the hollow nut 100 can be threadedly connected to the screw rod 301.

[0039] In some embodiments, the specific usage is as follows:

[0040] S1. Place the hollow nut 100 and the expandable casing 200 into the drilled installation hole 600.

[0041] like Figure 4 As shown, the mounting hole 600 is a hole provided on the to-be-connected member 400 and the wall 500. The outer diameters of the hollow nut 100 and the expandable sleeve 200 are adapted to the hole diameter of the mounting hole 600 to ensure that the hollow nut 100 and the expandable sleeve 200 can be smoothly installed in the mounting hole 600.

[0042] The hollow nut 100 and the expandable casing 200 are sequentially arranged along the axial direction of the mounting hole 600, the expandable casing 200 is arranged on one side close to the opening of the mounting hole 600, and the conical head 2 of the hollow nut 100 is docked or inserted into the end of the expandable casing 200 away from the opening of the mounting hole 600. Figure 2 and Figure 3 As shown, the screw rod 301 of the bolt 300 extends into the inner hole of the hollow nut 100 and the inside of the expandable casing 200, and the head 302 of the bolt 300 remains outside the mounting hole 600. The size of the head 302 of the bolt 300 is larger than the aperture of the mounting hole 600. The head 302 of the bolt 300 abuts against the hole mouth or against the part 400 to be connected at the hole mouth, or the end of the screw rod 301 abuts against the bottom of the mounting hole 600.

[0043] S2. Twist the bolt 300 in a first direction to move the hollow nut 100 in an axial direction toward the opening of the mounting hole 600.

[0044] The thread on the wall of the inner hole can be designed as a left-hand thread or a right-hand thread, and correspondingly, the first direction can be a counterclockwise direction or a clockwise direction.

[0045] The screw rod 301 of the bolt 300 is threadedly engaged with the thread on the wall of the inner hole, so that the rotational motion of the bolt 300 can be transmitted to the linear motion of the hollow nut 100 along its axial direction.

[0046] like Figure 3 and Figure 5 As shown, when the hollow nut 100 moves toward the direction close to the opening of the mounting hole 600, its conical head 2 can be inserted into the expandable casing 200, and as the hollow nut 100 continues to move forward, the conical head 2 abuts against the end of the expandable casing 200 and expands its end, so that the expandable casing 200 fills the mounting hole 600. At this time, the hollow nut 100 and the expandable casing 200 are fixed to each other, and the expandable casing 200 can fix the part to be connected 400 and the wall 500 to each other.

[0047] It should be noted that the axial directions of the hollow nut 100 and the expandable casing 200 are consistent. Figure 2 The radial direction of the hollow nut 100 is Figure 2 The direction shown in Y.

[0048] S3, after the hollow nut 100 is moved into position, the bolt 300 is twisted along the second direction to separate the bolt 300 from the hollow nut 100, and the bolt 300 is taken out from the mounting hole 600.

[0049] Specifically, after the end of the expandable casing 200 is expanded to the position, the expandable casing 200 fills the installation hole 600, and the expandable casing 200 and the hollow nut 100 can achieve a fixed connection. At this time, the bolt 300 can be rotated in the opposite direction to release the connection between the bolt 300 and the hollow nut 100 and the expandable casing 200, and the bolt 300 can be taken out. The bolt 300 after being taken out is structurally intact and can be reused with a new hollow nut 100 and the expandable casing 200.

[0050] It can be understood that the second direction is opposite to the first direction.

[0051] The hollow nut 100 provided in the present application includes an integrally arranged nut body 1 and a conical head 2. An inner hole penetrating the nut body 1 and the conical head 2 is provided in the hollow nut 100, and a thread is provided on the hole wall of the inner hole. In this way, the inner hole of the hollow nut 100 can allow the bolt 300 to pass through and be threadedly connected with the bolt 300. Driven by the bolt 300, the hollow nut 100 can move and its conical head 2 can replace the traditional bolt to expand the expandable casing 200. The above-mentioned hollow nut 100 can be detachably connected to the bolt 300, so that the bolt 300 can be flexibly arranged to achieve the reuse of the bolt 300.

[0052] The hollow nut 100 provided in the present application can be made of metal or plastic according to the use requirements and application scenarios. The surface of the hollow nut 100 can be galvanized, chrome-plated or heat-treated to improve the corrosion resistance, wear resistance and aesthetics of the hollow nut 100.

[0053] The hollow nut 100 provided in the present application is as follows: Figure 1 As shown, it also includes an anchoring structure 11 , which is protruding from the outer wall of the nut body 1 .

[0054] like Figure 1 and Figure 4 As shown, the anchoring structure 11 protrudes from the surface of the nut body 1 and can be used to resist the hole wall of the mounting hole 600, thereby increasing the anchoring effect between the hollow nut 100 and the mounting wall 500, and improving the connection strength and rigidity of the hollow nut 100 and the expansion bolt assembly using the hollow nut 100.

[0055] In the embodiments provided in the present application, the structure of the anchoring structure 11 is not unique.

[0056] In some embodiments, Figure 1 As shown, the anchoring structure 11 includes a first annular protrusion 110 and a second annular protrusion 120 which are arranged at intervals along the axial direction of the nut body 1 .

[0057] On the one hand, the annular protrusion has a reasonable structure, which is conducive to improving the uniformity of force on the hollow nut 100 in the circumferential direction; on the other hand, the first annular protrusion 110 and the second annular protrusion 120 are arranged at intervals along the axial direction, which is conducive to improving the uniformity of force on the hollow nut 100 in the axial direction.

[0058] Furthermore, in some embodiments, the first annular protrusion 110 is disposed at one end of the nut body 1 away from the conical head 2 , and along the axial direction of the nut body 1 , the thickness of the first annular protrusion 110 is greater than the thickness of the second annular protrusion 120 .

[0059] At the end away from the conical head 2, the hollow nut 100 is less affected by the expandable casing 200, so that the first annular protrusion 110 can better resist the hole wall of the mounting hole 600. By thickening the first annular protrusion 110, it is helpful to improve the anchoring effect between the hollow nut 100 and the mounting wall 500.

[0060] In addition, a groove structure is formed between the first annular protrusion 110 and the second annular protrusion 120, and between the second annular protrusion 120 and the conical head 2, so that the weight of the single hollow nut 100 is reduced, the consumables are reduced, and the manufacturing cost is lower.

[0061] Furthermore, in some embodiments, along the axial direction of the nut body 1, the thickness of the first annular protrusion 110 (eg Figure 1 D1 in FIG. 1 ) is 17 mm to 23 mm, and the thickness of the second annular protrusion 120 (as shown in FIG. Figure 1 (shown as D2 in the figure) is 12mm-18mm.

[0062] Optionally, in one embodiment, the thickness of the first annular protrusion 110 is 20 mm, and the thickness of the second annular protrusion 120 is 15 mm.

[0063] The first annular protrusion 110 and the second annular protrusion 120 have reasonable structures and can play a good anchoring role.

[0064] Furthermore, in some embodiments, along the radial direction of the nut body 1, the outer diameter of the anchoring structure 11 is the same as the outer diameter of a conventional nut, and the anchoring structure 11 is made of the same material as the nut body 1 and the conical head 2 and can be manufactured by integral molding.

[0065] In one embodiment, the height of the first annular protrusion 110 and the second annular protrusion 120 above the surface of the nut body 1 is equal to the height of the first end of the conical head 2 protruding from the surface of the nut body 1, so as to further improve the structural rationality of the hollow nut 100 and improve the anchoring effect of the anchoring structure 11.

[0066] The structure of the anchoring structure 11 is not limited thereto, as long as it can play a good anchoring role. Optionally, in some embodiments, the anchoring structure 11 may also include a protrusion disposed on the outer wall of the nut body 1, and a plurality of protrusions are evenly distributed along the axial direction and circumferential direction of the nut body 1, and the height of the protrusion protruding from the surface of the nut body 1 is equal to the height of the first protruding end of the conical head 2 protruding from the surface of the nut body 1.

[0067] In one embodiment, the outer surface of the conical head 2 is provided with anti-slip grooves 221 .

[0068] Optionally, the anti-slip pattern 221 includes a plurality of strip-shaped protrusions distributed along the circumference of the conical head 2 .

[0069] The anti-slip pattern 221 is used to increase the friction resistance between the conical head 2 and the expandable casing 200 to avoid slipping between the conical head 2 and the expandable casing 200 during the rotation of the bolt 300, which causes the hollow nut 100 to rotate with the bolt 300 and cause adjustment failure.

[0070] It can be understood that in some embodiments, in order to improve the anti-slip performance of the hollow nut 100, small protrusions or depressions can be set on the surface of the conical head 2, or a coating with good friction properties can be coated on the surface of the conical head 2. The specific design can be carried out according to actual conditions.

[0071] In one embodiment, the conical head 2 includes a cylindrical portion 21 and a conical head 22. The cylindrical portion 21 is connected to the nut body 1. The conical head 22 is arranged at one end of the cylindrical portion 21 away from the nut body 1. Anti-slip grooves 221 are arranged on the outer wall of the conical head 22.

[0072] The cylindrical portion 21 is used to abut against the hole wall of the installation hole 600 to enhance the anchoring effect between the hollow nut 100 and the installation wall 500 ; the conical head 2 is used to interact with the expandable casing 200 to expand the end of the expandable casing 200 .

[0073] The hollow nut 100 provided in the present application has a cylindrical portion 21 that is 12 mm to 18 mm higher than the surface of the nut body 1 along the radial direction of the nut body 1 (e.g. Figure 1 (shown in H).

[0074] Optionally, in one embodiment, the cylindrical portion 21 is 15 mm higher than the surface of the nut body 1 .

[0075] The above-mentioned conical head 2 has a reasonable structure and can achieve a good expansion effect.

[0076] The hollow nut 100 provided in the present application has a conical head 22 whose length along the axial direction of the nut body 1 can be designed according to actual conditions, for example, according to the expansion requirements of the expandable casing 200, and no sole limitation is made here.

[0077] The hollow nut 100 provided in the present application has a transition connection structure 23 between the cylindrical portion 21 and the nut body 1 .

[0078] like Figure 1 As shown, an inclined connecting slope is formed between the cylindrical portion 21 and the outer surface of the nut body 1 , and the outer diameter of the transition connection structure 23 decreases continuously along the direction of the conical head 2 pointing toward the nut body 1 .

[0079] The transition connection design between the conical head 2 and the nut body 1 is beneficial to improving the strength of the hollow nut 100, thereby reducing the risk of the hollow nut 100 being twisted off during use.

[0080] In summary, the hollow nut 100 provided by the present application can replace the traditional bolt member to expand the expandable casing 200, so that the bolt 300 can be flexibly set, realize the detachable structural design of the bolt 300, and realize the repeated use of the bolt 300. When the hollow nut 100 is used together with the expandable casing 200 and the bolt 300, the bolt 300 is easy to disassemble, and can keep itself intact during the disassembly process, and will not damage the installation wall 500 and the to-be-fixed member 400. In addition, the hollow nut 100 has a simple structure and is easy to manufacture.

[0081] In the second aspect, the present application provides an expansion bolt assembly, comprising an expandable casing 200, a bolt 300 and the hollow nut 100 in the first aspect, the expandable casing 200 and the hollow nut 100 are arranged successively along the axial direction of the hollow nut 100, the bolt 300 is detachably arranged in the expandable casing 200 and the hollow nut 100, one end of the bolt 300 extends into the inner hole of the hollow nut 100 and is threadedly connected to the hollow nut 100, and the other end extends out of the expandable casing 200 and is used to drive the hollow nut 100 to move.

[0082] The expandable sleeve is used to expand during the installation process to fill the installation hole 600 to provide additional support and fixing force for the wall 500 and the part to be fixed 400. The expandable sleeve 200 includes a hollow sleeve, and the outer diameter of the hollow sleeve matches the aperture of the installation hole 600. The end of the expandable sleeve 200 is designed with a groove, a crack and other structures, which are used to expand and expand to fill the installation hole 600 during installation.

[0083] The bolt 300 includes a screw rod 301 and a head 302. The screw rod 301 extends into the inner hole of the hollow nut 100 and the interior of the expandable casing 200. The screw rod 301 is also threadedly connected with the thread on the inner hole wall of the hollow nut 100. The head 302 of the bolt 300 remains outside the expandable casing 200 and is used to support the part to be fixed 400 or connect equipment such as a wrench.

[0084] The structure of the hollow nut 100 and the usage of the expansion bolt assembly are the same as those described in the first aspect and will not be described in detail here.

[0085] The expansion sleeve assembly provided by the present application provides a hollow nut 100 with a conical head 2, and uses the hollow nut 100 to replace the traditional bolt member. The bolt 300 is detachably connected to the hollow nut 100 and the bolt 300 can drive the hollow nut 100 to move, so that the expandable sleeve 200 is expanded by using the conical head 2 of the hollow nut 100 so that the bolt 300 can be completely disassembled after installation, thereby realizing the reusability of the bolt 300. In addition, the bolt 300 is easy to disassemble, and the installation wall 500 and the part to be fixed 400 will not be damaged during the disassembly process, which can reduce construction waste.

[0086] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A hollow nut, characterized in that: The hollow nut comprises a nut body and a conical head which are integrally connected. An inner hole which passes through the nut body and the conical head is provided in the hollow nut, and a thread is provided on the hole wall of the inner hole. The conical head comprises a first end and a second end which are arranged opposite to each other. The first end is connected to the nut body, and an outer diameter of the first end is larger than an outer diameter of the second end.

2. The hollow nut according to claim 1, characterized in that: The hollow nut further comprises an anchoring structure, and the anchoring structure is protruded on the outer wall of the nut body.

3. The hollow nut according to claim 2, characterized in that: The anchoring structure includes a first annular protrusion and a second annular protrusion spaced apart in the axial direction of the nut body.

4. The hollow nut according to claim 3, characterized in that: The first annular protrusion is arranged at one end of the nut body away from the conical head; along the axial direction of the nut body, the thickness of the first annular protrusion is greater than the thickness of the second annular protrusion.

5. The hollow nut according to claim 4, characterized in that: Along the axial direction of the nut body, the thickness of the first annular protrusion is 17 mm-23 mm, and the thickness of the second annular protrusion is 12 mm-18 mm.

6. The hollow nut according to any one of claims 1 to 5, characterized in that: The conical head comprises a cylindrical portion and a conical head portion, the cylindrical portion is connected to the nut body, and anti-slip grooves are arranged on the outer wall of the conical head portion.

7. The hollow nut according to claim 6, characterized in that: The anti-slip pattern includes a plurality of strip-shaped protrusions arranged at intervals.

8. The hollow nut according to claim 6, characterized in that: Along the radial direction of the nut body, the cylindrical portion is 12 mm to 18 mm higher than the surface of the nut body.

9. The hollow nut according to claim 6, characterized in that: A transition connection structure is provided between the cylindrical portion and the nut body.

10. An expansion bolt assembly, characterized in that: It comprises an expandable casing, a bolt and a hollow nut as described in any one of claims 1 to 9, wherein the expandable casing and the hollow nut are arranged successively along the axial direction of the hollow nut, the bolt is detachably arranged in the expandable casing and the hollow nut, one end of the bolt extends into the inner hole of the hollow nut and is threadedly connected to the hollow nut, and the other end extends out of the expandable casing and is used to drive the hollow nut to move.

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