Screws, screwdrivers and combinations of screws and screwdrivers

Abstract

A screw, a screwdriver and a combination of the screw and the screwdriver. The screw includes a screw post and a screw head. The screw head is formed with a guide hole and includes a plurality of first holding portions. The screwdriver is used to be inserted into the screw and includes a handle and a plurality of holding arms. Each holding arm includes a connecting arm body and a second holding portion. The connecting arm body is used to be inserted into the guide hole and the second holding portion is used to be held in the corresponding first holding portion. The holding arms can be operated to be transformed between a closed state and an unfolded state. When the holding arms are in the closed state, the second holding portions are close to each other so that the second holding portions can be inserted into the guide hole. When the holding arms are in the unfolded state, the second holding portions are away from each other so that the second holding portions can be held in the first holding portions respectively. Thus, the screw can play a good anti-theft effect.

Description

TECHNICAL FIELD

[0001] The present invention relates to a screw, a screwdriver and a combination of the screw and the screwdriver, and in particular, to a screw, a screwdriver and a combination of the screw and the screwdriver with a theft-proof function. BACKGROUND

[0002] The conventional screw with a theft-proof function usually has a special-shaped groove recessed on the end face of the screw head. A screwdriver with a shape corresponding to the groove is inserted into the groove to drive the screw to rotate to screw in or out.

[0003] Since the groove is recessed from the top face along the axial direction of the screw, a person with knowledge can still generate a force point to rotate the screw by inserting a screwdriver or a tool with a similar shape into the groove. Therefore, the screw cannot achieve a good theft-proof effect. SUMMARY

[0004] Therefore, one of the purposes of the present invention is to provide a screw that can overcome at least one of the disadvantages of the prior art.

[0005] The present invention is achieved by the following technical solutions. The screw according to the present invention comprises a stud and a screw head. The screw head is arranged at one end of the stud and defines an axis together with the stud. The screw head comprises an end face at the end opposite to the stud and a plurality of retaining portions. The screw head forms a guide hole recessed from the end face toward the stud and extending along the axis. The retaining portions are arranged around the guide hole and spaced apart around the axis. Each of the retaining portions is spaced apart from the end face along the axis. Each of the retaining portions extends along a head radial direction perpendicular to the axis.

[0006] Each of the retaining portions of the screw according to the present invention has a clamping groove extending outward from the outer periphery of the guide hole along the head radial direction and communicating with the guide hole.

[0007] Each of the retaining portions of the screw according to the present invention further has two retaining faces located at opposite sides of the clamping groove. The retaining faces are spaced apart along another head radial direction perpendicular to the head radial direction and parallel to each other.

[0008] Each of the retaining portions of the screw according to the present invention has two retaining faces spaced apart along another head radial direction perpendicular to the head radial direction and parallel to each other.

[0009] The screw according to the present invention further comprises a stop face between the stud and the retaining portions and facing the retaining portions, and a pushing protrusion protruding from the stop face and located in the guide hole.

[0010] The screw of the present application, the pushing protrusion has a spherical surface, and a peripheral surface connected between the stop surface and the spherical surface.

[0011] The screw of the present application, the end surface is circular.

[0012] The screw of the present application, the guide hole has a plurality of alignment groove portions angularly spaced around the axis and respectively aligned with the holding portions.

[0013] The screw of the present application, the screw head further comprises a plurality of arc-shaped chamfer surfaces angularly spaced around the axis, each of the arc-shaped chamfer surfaces being located between a corresponding holding portion and a corresponding alignment groove portion.

[0014] Another object of the present application is to provide a screwdriver capable of overcoming at least one of the drawbacks of the prior art.

[0015] The screwdriver of the present application comprises a handle and a plurality of holding arms, the handle extends along an axis, the holding arms are disposed on the handle and angularly spaced around the axis and arranged in a ring shape, each of the holding arms comprises a connecting arm body movably connected to the handle and partially exposed outside the handle, and a holding portion protruding outside the connecting arm body and located outside the handle, the holding arms can be operated to change between a closed state and an unfolded state, when the holding arms are in the closed state, the holding portions of the holding arms are close to each other, when the holding arms are in the unfolded state, the holding portions of the holding arms are away from each other.

[0016] The screwdriver of the present application, the connecting arm body has an outer surface, and a head end located outside the handle, the holding portion is a clamping block protruding from the outer surface and adjacent to the head end.

[0017] The screwdriver of the present application, the outer surface is arc-shaped, the holding portion protrudes outwardly from the outer surface along an arm diameter, the holding portion has two force applying surfaces, the force applying surfaces are spaced apart and parallel to each other along another arm diameter perpendicular to the arm diameter.

[0018] The screwdriver of the present application, the holding portion further has a first outer arc-shaped chamfer surface located at one end opposite to the handle, and a second outer arc-shaped chamfer surface opposite to the first outer arc-shaped chamfer surface.

[0019] The screwdriver of the present application, the connecting arm body has an inner arc-shaped chamfer surface located inside the holding portion.

[0020] The screwdriver of the present application, the connecting arm body is formed with a receiving groove inside the holding portion, and the connecting arm body further has two abutting edges respectively located on opposite sides of the receiving groove.

[0021] The screwdriver of the present application, the connecting arm body of each holding arm is rotatably pivoted to the handle, and the screwdriver further comprises a resilient ring sleeved on the connecting arm body of the holding arm to apply a resilient contraction force thereto.

[0022] The screwdriver of the present application, the handle comprises a housing and a limiting bead arranged in the housing, and the connecting arm body of each holding arm is rotatably pivoted between the housing and the limiting bead and can rotate around the limiting bead.

[0023] The screwdriver of the present application, the housing is formed with a receiving space and a plurality of pivot portions angularly spaced around the axis and located on the periphery of the receiving space, each pivot portion has a pivot groove extending radially outward along the housing and communicating with the receiving space, the connecting arm body has an arm portion partially received in the receiving space and a pivot plate portion, the arm portion has a tail end located in the receiving space and a recessed arc surface adjacent to the tail end and abutting against the limiting bead, the portion of the arm portion adjacent to the tail end is outwardly spread apart by the limiting bead to maintain a proper spacing, and the pivot plate portion protrudes radially outward along the arm from a side of the arm opposite to the recessed arc surface, is adjacent to the tail end, and is rotatably pivoted to the corresponding pivot groove.

[0024] The screwdriver of the present application, each pivot portion further has two pressure surfaces respectively located on opposite sides of the pivot groove, the pressure surfaces are spaced apart and parallel to each other along another housing radial direction perpendicular to the housing radial direction, and the pivot plate portion has two pressure receiving surfaces respectively facing the corresponding pressure surfaces, the pressure receiving surfaces are spaced apart and parallel to each other along another arm radial direction perpendicular to the arm radial direction.

[0025] Another object of the present application is to provide a screw and screwdriver combination capable of overcoming at least one disadvantage of the background art.

[0026] The screw and screwdriver combination of the present application, each of the first retaining portions has a clamping slot extending outwardly along the head radial direction from the periphery of the guide hole and communicating with the guide hole, the connecting arm body has an outer surface and a head end located outside the handle, and the second retaining portion is a clamping block protruding from the outer surface and adjacent to the head end for clamping in the clamping slot of the corresponding first retaining portion.

[0027] The screw and screwdriver combination of the present application, each of the first retaining portions has a clamping slot extending outwardly along the head radial direction from the periphery of the guide hole and communicating with the guide hole, the connecting arm body has an outer surface and a head end located outside the handle, and the second retaining portion is a clamping block protruding from the outer surface and adjacent to the head end for clamping in the clamping slot of the corresponding first retaining portion.

[0028] The screw and screwdriver combination of the present application, each of the first retaining portions has a clamping slot extending outwardly along the head radial direction from the periphery of the guide hole and communicating with the guide hole, the connecting arm body has an outer surface and a head end located outside the handle, and the second retaining portion is a clamping block protruding from the outer surface and adjacent to the head end for clamping in the clamping slot of the corresponding first retaining portion.

[0029] The screw and screwdriver combination of the present invention, the screw head further comprises a stop surface between the shank and the first retaining portion and facing the first retaining portion, and a pushing protrusion protruding from the stop surface and located in the guide hole, the stop surface is used to stop the retaining arm, and the pushing protrusion is used to push the retaining arm to change the retaining arm from the closed state to the unfolded state.

[0030] The screw and screwdriver combination of the present invention, the pushing protrusion has a hemispherical surface, and the connecting arm body has an inner arc chamfer surface inside the second retaining portion for the hemispherical surface to push.

[0031] The screw and screwdriver combination of the present invention, the connecting arm body is formed with an accommodation groove inside the second retaining portion for a part of the pushing protrusion to accommodate, the pushing protrusion further has an outer peripheral surface connected between the stop surface and the hemispherical surface, and the connecting arm body further has two abutting edges located on opposite sides of the accommodation groove, each of the abutting edges can abut and slide on the outer peripheral surface in a line contact manner.

[0032] The screw and screwdriver combination of the present invention, the screw head further comprises a pushing protrusion located in the guide hole, the pushing protrusion is used to push the retaining arm to change the retaining arm from the closed state to the unfolded state, the connecting arm body of each of the retaining arms is rotatably pivoted to the handle, and the screwdriver further comprises a resilient ring sleeved on the connecting arm body of the retaining arm to apply a resilient contraction force to the connecting arm body.

[0033] The screw and screwdriver combination of the present invention, the handle comprises a housing and a limiting bead arranged in the housing, the connecting arm body of each of the retaining arms is rotatably pivoted between the housing and the limiting bead and can rotate around the limiting bead.

[0034] The screw and screwdriver combination of the present invention, the housing is formed with an accommodation space and a plurality of pivot portions angularly spaced around the second axis and located outside the accommodation space, each of the pivot portions has a pivot groove extending radially outward along the housing and communicating with the accommodation space, the connecting arm body has an arm portion partially accommodated in the accommodation space and a pivot plate portion, the arm portion has a tail end located in the accommodation space and a recessed arc surface adjacent to the tail end and abutting against the limiting bead, the arm portion of the retaining arm is kept at a proper distance by the limiting bead outwardly expanding the part adjacent to the tail end, and the pivot plate portion protrudes radially outward along the arm from a side opposite to the recessed arc surface of the arm portion, is adjacent to the tail end, and is rotatably pivoted to the corresponding pivot groove.

[0035] The screw and screwdriver combination of the present application, each of the pivot connection portions further has two pressing surfaces respectively located at opposite sides of the pivot connection groove, the pressing surfaces are spaced apart and parallel to each other along another shell radial direction perpendicular to the shell radial direction, the pivot plate portion has two pressed surfaces respectively facing the corresponding pressing surfaces, the pressed surfaces are spaced apart and parallel to each other along another arm radial direction perpendicular to the arm radial direction.

[0036] The screw and screwdriver combination of the present application, the end surface is annular.

[0037] The screw and screwdriver combination of the present application, the guide hole has a plurality of alignment groove portions angularly spaced around the first axis and respectively aligned with the first holding portion positions, the alignment groove portions are respectively used for inserting a part of the second holding portion, the end surface has a plurality of inner end edges respectively located at outer peripheries of the alignment groove portions, the second holding portion further has a first outer arc-shaped chamfer surface, the first outer arc-shaped chamfer surface is arranged to slide on the corresponding inner end edge to guide the insertion direction when the second holding portion is inserted into the corresponding alignment groove portion of the guide hole and contacts the corresponding inner end edge.

[0038] The screw and screwdriver combination of the present application, the screw head further includes a plurality of arc-shaped chamfer surfaces angularly spaced around the first axis, each of the arc-shaped chamfer surfaces is located between the corresponding first holding portion and the corresponding alignment groove portion, the second holding portion further has a second outer arc-shaped chamfer surface opposite to the first outer arc-shaped chamfer surface, the second outer arc-shaped chamfer surface is arranged to slide on the corresponding arc-shaped chamfer surface to guide the extraction direction when the second holding portion is extracted from the guide hole and contacts the corresponding arc-shaped chamfer surface.

[0039] The screw and screwdriver combination of the present application has the beneficial effect that the first holding portion of the screw head is designed to enable the screw to achieve good anti-theft effect. In addition, the screw must be used with the screwdriver to perform tightening or loosening operation, so it can be applied in special use occasions to meet special use requirements. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a perspective exploded view of an embodiment of the screw and screwdriver combination of the present application, illustrating the assembly relationship between a screw and a screwdriver;

[0041] Figure 2 is an incomplete perspective exploded view of the embodiment;

[0042] Figure 3 is an incomplete cross-sectional exploded view of the embodiment;

[0043] Figure 4 is a rear view of the screw of the embodiment;

[0044] Figure 5 is an incomplete perspective exploded view of the screwdriver of the embodiment, showing the assembly relationship between a handle, holding arms and a resilient ring;

[0045] Figure 6 is a cross-sectional view taken along line VI-VI in Figure 1 ;

[0046] Figure 7 is a front view of the screwdriver of the embodiment;

[0047] Figure 8 is a cross-sectional view of the embodiment, showing the holding arms in a closed state;

[0048] Figure 9 is an incomplete cross-sectional view of the embodiment;

[0049] Figure 10 is an incomplete cross-sectional view of the embodiment, showing the holding arms in an unfolded state;

[0050] Figure 11 is a cross-sectional view of the embodiment, showing the holding arms in the unfolded state, and the second holding portions respectively holding the first holding portions. DETAILED DESCRIPTION

[0051] The present application will be described in detail below with reference to the accompanying drawings and embodiments.

[0052] Referring to Figure 1 , an embodiment of the combination of the screw and the screwdriver comprises a screw 1 and a screwdriver 2.

[0053] Referring to Figure 2 , Figure 3 and Figure 4The screw 1 comprises a shank 11 and a screw head 12. The screw head 12 is disposed at one end of the shank 11 and cooperates with the shank 11 to define a first axis A1. The screw head 12 includes a connecting wall 13, a surrounding wall 14, and a pushing boss 15. The connecting wall 13 is connected to the shank 11 and has a stop surface 131 at an end opposite to the shank 11. The surrounding wall 14 protrudes from the stop surface 131 of the connecting wall 13 away from the shank 11 and surrounds the first axis A1. The surrounding wall 14 has an annular end surface 140 at an end opposite to the shank 11, an inner peripheral surface 141 connected between the end surface 140 and the stop surface 131, an outer peripheral surface 142 connected between the end surface 140 and the stop surface 131 and opposite to the inner peripheral surface 141, and a plurality of first retaining portions 143 facing the stop surface 131. The surrounding wall 14 forms a guide hole 144 recessed from the end surface 140 to the stop surface 131 along the first axis A1 and defined by the inner peripheral surface 141. The first retaining portions 143 are located around the guide hole 144 and are disposed at equal angles around the first axis A1. Each of the first retaining portions 143 is spaced apart from the end surface 140 along the first axis A1 by a distance D, and each of the first retaining portions 143 extends along a head radial direction R1, R1' perpendicular to the first axis A1.

[0054] In the present embodiment, each of the first retaining portions 143 has a clamping groove 145 extending outwardly from around the guide hole 144 along the head radial direction R1, R1' and communicating with the guide hole 144, and two retaining surfaces 146 located at opposite sides of the clamping groove 145. Specifically, the number of the first retaining portions 143 in the present embodiment is four, but is not limited thereto, and the number of the first retaining portions 143 can be designed to be two, three, or more than four according to requirements. The clamping grooves 145 of two opposite first retaining portions 143 extend along the head radial direction R1, and the retaining surfaces 146 of each of the first retaining portions 143 are spaced apart from and parallel to each other along another head radial direction R1' perpendicular to the head radial direction R1. The clamping grooves 145 of the other two opposite first retaining portions 143 extend along the head radial direction R1', and the retaining surfaces 146 of each of the first retaining portions 143 are spaced apart from and parallel to each other along another head radial direction R1 perpendicular to the head radial direction R1'.

[0055] It is to be noted that each of the card slots 145 in the present embodiment extends to the outer circumferential surface 142 so that the card slots 145 penetrate through the surrounding wall 14. Therefore, the screw 1 is applicable to the case where the screw head 12 can be countersunk. That is, after the screw 1 is inserted into a through hole (not shown) of an article to be fastened, the through hole can accommodate the screw head 12 so that the article to be fastened can cover the card slots 145 of the screw head 12 and only the end surface 140 and the guide hole 144 are exposed. In another implementation of the present embodiment, each of the card slots 145 can not extend to the outer circumferential surface 142 so that the card slots 145 do not penetrate through the surrounding wall 14. At this time, the screw 1 is applicable to the case where the screw head 12 can be completely exposed from the surface of the article to be fastened without being countersunk.

[0056] In the present embodiment, the guide hole 144 has a plurality of alignment groove portions 147 which are equally angularly spaced around the first axis Al, the alignment groove portions 147 are respectively aligned with the first retaining portions 143 and are respectively communicated with the card slots 145. The end surface 140 has a plurality of inner end edges 148 which are respectively located around the periphery of the alignment groove portions 147. The surrounding wall 14 further has a plurality of arc-shaped chamfer surfaces 149 which are equally angularly spaced around the first axis Al. Each of the arc-shaped chamfer surfaces 149 is located between a corresponding first retaining portion 143 and a corresponding alignment groove portion 147, and each of the arc-shaped chamfer surfaces 149 is connected between the inner circumferential surface 141 and a retaining surface 146 of the corresponding first retaining portion 143.

[0057] The push protrusion 15 protrudes along the first axis Al from the stop surface 131 and is located in the guide hole 144. The push protrusion 15 is a cylinder and has a hemispherical surface 151 at an end opposite to the stop surface 131, and an outer circumferential surface 152 connected between the stop surface 131 and the hemispherical surface 151. The push protrusion 15 extends along the first axis Al to a length which is less than the length of each of the first retaining portions 143 extending along the first axis Al.

[0058] Referring to Figure 2 , Figure 3 , Figure 5 and Figure 6, the screwdriver 2 is used to insert the screw 1 and includes a handle 3, a plurality of holding arms 4, and a resilient ring 5. The handle 3 includes a housing 31 and a limiting bead 32 arranged in the housing 31. The housing 31 extends along a second axis A2 for a user to hold. The housing 31 has two oppositely arranged and abutted half shells 310 which are locked together by, for example, screw locking. The half shells 310 of the housing 31 jointly define a head end 311, an opposite tail end 312 (as shown in Figure 1 FIG. 1), a receiving space 313 recessed from the head end 311 toward the tail end 312, a plurality of pivot joints 314 equiangularly spaced around the second axis A2 and located at the outer periphery of the receiving space 313, and an annular groove 315 communicated with the receiving space 313 and located between the head end 311 and the pivot joints 314. The annular groove 315 is used to accommodate a part of the resilient ring 5.

[0059] In the present embodiment, each of the pivot joints 314 has a pivot slot 316 extending outward from the outer periphery of the receiving space 313 along a shell radial direction R2, R2' perpendicular to the second axis A2 and communicated with the receiving space 313, and two pressing surfaces 317 respectively located at opposite sides of the pivot slot 316. Specifically, the number of the pivot joints 314 of the present embodiment is exemplified by four, but is not limited thereto. The pivot slots 316 of two opposite pivot joints 314 extend along the shell radial direction R2, and the pressing surfaces 317 of each of the aforementioned pivot joints 314 are spaced apart and parallel to each other along another shell radial direction R2' perpendicular to the shell radial direction R2. The pivot slots 316 of the other two opposite pivot joints 314 extend along the shell radial direction R2', and the pressing surfaces 317 of each of the aforementioned pivot joints 314 are spaced apart and parallel to each other along another shell radial direction R2 perpendicular to the shell radial direction R2'.

[0060] Referring to Figure 3 , Figure 5 , Figure 6 and Figure 7 , the holding arms 4 are arranged on the handle 3 and equiangularly spaced around the second axis A2 and arranged in a ring shape. The number of the holding arms 4 of the present embodiment is exemplified by four, but is not limited thereto. Each holding arm 4 includes a connecting arm body 41 movably connected to the handle 3 and partially exposed outside the handle 3, and a second holding portion 42 protruding outward from the connecting arm body 41 and located outside the handle 3 to hold a corresponding first holding portion 143.

[0061] The connecting arm body 41 has an arm portion 410 and a pivot plate portion 411. The arm portion 410 extends along the second axis A2 and is partially accommodated in the accommodating space 313 and partially protrudes out of the head end 311 for being inserted into the guide hole 144. The arm portion 410 has a head end 412 outside the housing 31, an opposite tail end 413, and an outer surface 414 connecting the head end 412 and the tail end 413 in an arc shape. The inner side of the arm portion 410 opposite to the outer surface 414 is recessed to form an accommodating groove 415 adjacent to the head end 412 for accommodating a part of the push protrusion 15. The arm portion 410 has a recessed arc surface 416 adjacent to the tail end 413 and matching the shape of the limiting bead 32, which abuts against the outer surface of the limiting bead 32 by surface contact and can rotate on the outer surface of the limiting bead 32. The outer surface 414 of the arm portion 410 is recessed to form a groove 417 adjacent to the recessed arc surface 416 for accommodating a part of the elastic ring 5.

[0062] The arm portion 410 also has an inner arc chamfer surface 418 inside the outer surface 414 and connected to the head end 412, and two abutting edges 419 respectively connected to the opposite sides of the inner arc chamfer surface 418. The inner arc chamfer surface 418 is used to contact and be pushed by the spherical surface 151 of the push protrusion 15. The abutting edges 419 are respectively located on the opposite sides of the accommodating groove 415, and each of the abutting edges 419 can abut against and slide on the outer peripheral surface 152 of the push protrusion 15 by line contact.

[0063] The pivot plate portion 411 is outwardly protruded from the outer surface 414 of the arm portion 410 along an arm radial direction R3, R3' perpendicular to the second axis A2 and adjacent to the tail end 413. The pivot plate portion 411 is shaped to fit into and pivotably coupled to the corresponding pivot slot 316. The pivot plate portion 411 has two pressure receiving surfaces 420 respectively facing the corresponding pressure applying surfaces 317. The pivot plate portion 411 of two opposite holding arms 4 is protruded along the arm radial direction R3, and the pressure receiving surfaces 420 of each of the pivot plate portion 411 are spaced apart and parallel to each other along another arm radial direction R3' perpendicular to the arm radial direction R3. The pivot plate portion 411 of the other two opposite holding arms 4 is protruded along the arm radial direction R3', and the pressure receiving surfaces 420 of each of the pivot plate portion 411 are spaced apart and parallel to each other along another arm radial direction R3 perpendicular to the arm radial direction R3'. Each of the pressure applying surfaces 317 of the handle 3 is used to apply pressure to the corresponding pressure receiving surface 420 to drive the corresponding holding arm 4 to rotate around the second axis A2.

[0064] Referring to Figure 3 , Figure 5 and Figure 7 , the second holding portion 42 is a clamping block outwardly protruded from the outer surface 414 of the arm portion 410 along the arm radial direction R3, R3' and adjacent to the head end 412 outside the accommodating slot 415, the inner arc-shaped chamfered surface 418 and the abutting edge 419 for clamping in the clamping slot 145 of the corresponding first holding portion 143. The second holding portion 42 has two force applying surfaces 421 respectively used to abut against the corresponding holding surface 146. The second holding portion 42 of two opposite holding arms 4 is protruded along the arm radial direction R3, and the force applying surfaces 421 of each of the second holding portion 42 are spaced apart and parallel to each other along another arm radial direction R3' perpendicular to the arm radial direction R3. The second holding portion 42 of the other two opposite holding arms 4 is protruded along the arm radial direction R3', and the force applying surfaces 421 of each of the second holding portion 42 are spaced apart and parallel to each other along another arm radial direction R3 perpendicular to the arm radial direction R3'.

[0065] The second holding portion 42 further has a first outer arc-shaped chamfer surface 422 connected between the force applying surfaces 421 and adjacent to the head end 412, and a second outer arc-shaped chamfer surface 423 connected between the force applying surfaces 421 and opposite to the first outer arc-shaped chamfer surface 422. The first outer arc-shaped chamfer surface 422 is arranged to slide on the corresponding inner end edge 148 to be guided by the inner end edge 148 in the insertion direction when the second holding portion 42 is inserted into the corresponding alignment slot portion 147 of the guide hole 144. The second outer arc-shaped chamfer surface 423 is arranged to slide on the corresponding arc-shaped chamfer surface 149 to be guided by the arc-shaped chamfer surface 149 in the extraction direction when the second holding portion 42 is extracted from the guide hole 144.

[0066] Referring to Figure 3 , Figure 6 and Figure 7 , the pivot plate portions 411 of the holding arms 4 are respectively pivoted in the pivot slots 316 of the housing 31, so that each of the holding arms 4 can rotate relative to the housing 31. The pivot slots 316 can respectively limit the pivot plate portions 411 to prevent the holding arms 4 from rotating about the second axis A2. The recessed arc surfaces 416 of the arm portions 410 of the holding arms 4 abut the outer surface of the limiting bead 32, so that the arm portions 410 can hold the limiting bead 32. The limiting bead 32 outwardly expands and limits the portion of the arm portions 410 adjacent to the tail end 413, so that the portion of the arm portions 410 adjacent to the tail end 413 does not contact each other to maintain appropriate spacing, and can stably position the pivot plate portions 411 of each of the holding arms 4 in the corresponding pivot slots 316. In this way, each of the holding arms 4 can rotate about the limiting bead 32 with the limiting bead 32 as the rotation center.

[0067] The housing 31 and the limiting bead 32 are pivoted with the holding arms 4 in such a way that the limiting bead 32 can serve as the rotation center of the holding arms 4. In this way, the number of pivot members required for pivoting the holding arms 4 to the housing 31 can be greatly reduced, thereby reducing the complexity of the structure and assembly of the screwdriver 2 and reducing the manufacturing cost of the screwdriver 2.

[0068] The connecting arm bodies 41 of the holding arms 4 are rotatably pivoted between the housing 31 and the limiting bead 32 and can rotate about the limiting bead 32, so that the holding arms 4 can be operated to be in a closed state (as shown in Figure 3 , Figure 7 and an unfolded state (as shown in Figure 10、 Figure 11 When the holding arms 4 are in the closed state, the second holding portions 42 of the holding arms 4 are close to each other, and the arm portions 410 adjacent to the head ends 412 are abutted together, so that the second holding portions 42 can be inserted into the guide holes 144. When the holding arms 4 are in the unfolded state, the second holding portions 42 of the holding arms 4 are away from each other, and the arm portions 410 adjacent to the head ends 412 are separated from each other, so that the second holding portions 42 can be respectively clamped in the clamping grooves 145 to respectively hold the first holding portions 143.

[0069] It is to be noted that in the present embodiment, the number of the holding arms 4 is designed according to the number of the first holding portions 143 of the screw 1. When the number of the first holding portions 143 is designed to be two, three or more than four, the number of the holding arms 4 is correspondingly designed to be two, three or more than four according to the number of the first holding portions 143.

[0070] The elastic ring 5 is sleeved on the arm portions 410 of the holding arms 4 and accommodated in the grooves 417 and the annular grooves 315, so as to apply elastic contraction force to the holding arms 4 to make the holding arms 4 always remain in the closed state. The elastic ring 5 of the present embodiment is made of a material with elasticity, such as silica gel or rubber. By accommodating the elastic ring 5 in the grooves 417 and the annular grooves 315, the elastic ring 5 can be prevented from sliding on the arm portions 410 along the second axis A2, and the elastic ring 5 can be prevented from being easily disassembled by being exposed outside the handle 3. Of course, in other embodiments of the present embodiment, the elastic ring 5 can be sleeved on the arm portions 410 and adjacent to the second holding portions 42, without being limited to the manner disclosed in the present embodiment.

[0071] Referring to Figure 3 、 Figure 8 and Figure 9 , in order to insert the screwdriver 2 into the screw 1, first, the second holding portions 42 of the holding arms 4 are respectively aligned with the alignment groove portions 147 of the guide holes 144. Then, the screwdriver 2 is moved along an insertion direction D1 towards the screw head 12, so that the second holding portions 42 are respectively inserted into the alignment groove portions 147. During the movement of the screwdriver 2 along the insertion direction D1, the head diameters R1, R1' (as shown in FIG. 1) of the screwdriver 2 are respectively aligned with the head diameters R2, R2' (as shown in FIG. 1) of the screw head 12, and the screwdriver 2 is inserted into the screw 1. Figure 4When the second holding portion 42 is inserted into the alignment slot portion 147 with positional deviation (as shown), the force exerted by the inner end edge 148 on the first outer arc chamfer surface 422 of the second holding portion 42 will cause the first outer arc chamfer surface 422 to slide on the inner end edge 148 towards the corresponding alignment slot portion 147, thereby guiding the insertion direction of the second holding portion 42 to be coaxial with the first axis Al. In this way, the positional deviation of the screwdriver 2 during insertion can be absorbed to ensure that the screwdriver 2 can still insert the second holding portion 42 into the alignment slot portion 147 even under positional deviation.

[0072] By the design of the alignment slot portion 147 of the guide hole 144, the user can know the position of the first holding portion 143 and the insertion position of the second holding portion 42 during insertion of the screwdriver 2 by viewing the alignment slot portion 147. In this way, the convenience of the user during insertion operation can be improved.

[0073] Referring to Figure 9 , Figure 10 and Figure 11 When the holding arm 4 moves to the position where the inner arc chamfer surface 418 contacts the hemispherical surface 151 of the pushing protrusion 15, the inner arc chamfer surface 418 will be blocked by the hemispherical surface 151. The force exerted by the hemispherical surface 151 on the inner arc chamfer surface 418 will simultaneously push the inner arc chamfer surface 418 to outwardly expand the portion of the arm portion 410 adjacent to the head end 412 and cause the holding arm 4 to rotate around the limiting bead 32 in a first rotation direction T1, respectively. By simultaneously pushing the inner arc chamfer surface 418 through the hemispherical surface 151, the pushing protrusion 15 can reduce the complexity of the structure of the pushing protrusion 15, increase the contact area between the pushing protrusion 15 and the inner arc chamfer surface 418, and allow the pushing protrusion 15 to smoothly push the inner arc chamfer surface 418, thereby allowing the holding arm 4 to smoothly rotate around the limiting bead 32.

[0074] During rotation of the holding arm 4, the arm portion 410 will drive the second holding portion 42 to extend into the clamping slot 145 of the first holding portion 143, respectively, and the arm portion 410 will outwardly expand the elastic ring 5 to deform and accumulate restoring force.

[0075] When the holding arms 4 are moved to a position where the inner arc chamfer surfaces 418 are separated from the hemispherical surfaces 151, the holding arms 4 will not rotate any more. At this time, the second holding portions 42 are respectively clamped in the clamping grooves 145, and the force applying surfaces 421 of each of the second holding portions 42 respectively abut against the holding surfaces 146. Subsequently, the abutment edges 419 of each of the holding arms 4 abut against and slide on the outer peripheral surface 152 of the pushing protrusion 15 in a line contact manner, thereby reducing the friction between the arm portions 410 of the holding arms 4 and the pushing protrusion 15, so that the holding arms 4 can move smoothly relative to the pushing protrusion 15.

[0076] When the head ends 412 of the holding arms 4 and the second holding portions 42 abut against and are blocked by the stop surfaces 131 of the connecting wall 13, the screwdriver 2 cannot be moved any more in the insertion direction D1, and the pushing protrusion 15 penetrates and is accommodated in the accommodation groove 415 of the arm portion 410. The arm portion 410 is supported by the pushing protrusion 15, so that the holding arms 4 can be stably kept in the unfolded state, thereby enabling each of the second holding portions 42 to be stably positioned in a clamping position (as shown in Figure 11 at which the second holding portion 42 is clamped in the corresponding clamping groove 145. At this time, the operation of inserting and holding the screwdriver 2 in the screw 1 is completed.

[0077] Referring to Figure 6 , Figure 7 and Figure 11 , after the screwdriver 2 is inserted and held in the screw 1, the screwdriver 2 can be rotated in a first rotation direction S1 to rotate the screw 1 to perform a screwing operation, and the screwdriver 2 can be rotated in a second rotation direction S2 opposite to the first rotation direction S1 to rotate the screw 1 to perform an unscrewing operation. Since the pressure receiving surfaces 420 of each of the holding arms 4 are spaced apart from and parallel to each other along the arm diameters R3, R3', and the pressure applying surfaces 317 of each of the pivot connecting portions 314 of the housing 31 are spaced apart from and parallel to each other along the housing diameters R2, R2', therefore, an acting force applied by each of the pressure applying surfaces 317 on the corresponding pressure receiving surface 420 is perpendicular to a force arm formed by the arm portion 410 of the corresponding connecting arm body 41, the pivot plate portion 411 and the limiting bead 32, so that a torque value generated by the acting force multiplied by the force arm is large. Therefore, after a user applies a force to the housing 31, the screwdriver 2 can be rotated smoothly about the second axis A2.

[0078] Referring to Figure 4 , Figure 7 and Figure 11Furthermore, since the retaining surfaces 146 of each of the first retaining portions 143 of the screw head 12 are spaced apart and parallel to each other along the head radial direction R1, R1', and the force-applying surfaces 421 of each of the second retaining portions 42 of the retaining arm 4 are spaced apart and parallel to each other along the arm radial direction R3, R3', the force applied by each force-applying surface 421 to the corresponding retaining surface 146 is perpendicular to the corresponding retaining surface 146 and the first axis A1. This allows the torque generated after the force is applied to the screw head 12 to smoothly drive the screw 1 to rotate around the first axis A1. In this way, the screwdriver 2 can smoothly drive the screw 1 to rotate along the first rotation direction S1 or the second rotation direction S2.

[0079] See Figure 3 and Figure 9 To remove the screwdriver 2 from the screw 1, pull the screwdriver 2 in a pulling direction D2 opposite to the insertion direction D1, causing the second holding portion 42 of the holding arm 4 to move away from the stop surface 131, and the abutting edge 419 of each holding arm 4 to slide on the outer peripheral surface 152. When the abutting edge 419 moves away from the outer peripheral surface 152 and the inner arc-shaped chamfered surface 418 corresponds to the position of the hemispherical surface 151, the reset elastic force accumulated by the elastic ring 5 will drive the holding arms 4 to move in a direction opposite to the first rotation direction T1 (e.g., ...). Figure 10 The second rotation direction T2 (as shown) rotates around the limiting bead 32, causing the portion of the arm 410 adjacent to the head end 412 to contract and move closer, and the inner arc-shaped chamfered surface 418 to abut against the hemispherical surface 151.

[0080] The retaining arm 4 continues to rotate along the second rotation direction T2 as the screwdriver 2 moves, causing the arm 410 to gradually move the second retaining part 42 away from the slot 145. When the screwdriver 2 moves to Figure 9 When the screwdriver 2 continues to move along the withdrawal direction D2, the second holding part 42 of the holding arm 4 can be moved away from the screw head 12 via the alignment groove 147.

[0081] During the process of the screwdriver 2 moving along the withdrawal direction D2, the radial directions R1 and R1' of the head (e.g., ...) Figure 4When the second holding portion 42 is misaligned (as shown) and the second outer arc chamfer surface 423 of one of the second holding portions 42 contacts the corresponding arc chamfer surface 149, the force exerted by the arc chamfer surface 149 on the second outer arc chamfer surface 423 will cause the second outer arc chamfer surface 423 to slide on the arc chamfer surface 149 towards the corresponding alignment slot portion 147, thereby guiding the disengagement direction of the second holding portion 42 to coaxial the second axis A2 with the first axis Al. In this way, the misalignment of the screwdriver 2 during disengagement can be absorbed to ensure that the screwdriver 2 can still pass the second holding portion 42 into the alignment slot portion 147 and then move away from the screw head 12 via the alignment slot portion 147 even under misalignment.

[0082] Referring to Figure 3 , Figure 10 and Figure 11 , since the first holding portions 143 of the screw head 12 are arranged around the first axis Al and located outside the periphery of the guide hole 144, and each of the first holding portions 143 is spaced apart from the end face 140 along the first axis Al by the distance D and extends along the head diameters R1, R1', the holding arm 4 of the screwdriver 2 needs to pass through the guide hole 144 in the closed state and then be pushed by the push protrusion 15 of the screw 1 to change the holding arm 4 from the closed state to the unfolded state, so that the second holding portion 42 of the holding arm 4 can hold the first holding portion 143 to perform the screwing or unscrewing operation of the screw 1. Therefore, a person with knowledge can not directly interfere with the first holding portion 143 by inserting the screwdriver or tool into the guide hole 144 of the screw 1 on the market, so that the screwdriver or tool cannot rotate the screw 1. In addition, since the end face 140 of the screw head 12 is annular and spaced apart from the first holding portion 143 along the first axis Al by the distance D, the end face 140 can block the screwdriver or tool to prevent it from interfering with the first holding portion 143. Furthermore, the push protrusion 15 of the screw 1 can block the screwdriver or tool on the first axis Al, thereby limiting the depth of insertion of the screwdriver or tool to prevent the screwdriver or tool from trying to interfere with the first holding portion 143 by rotating the angle. In this way, the screw 1 can achieve good anti-theft effect.

[0083] On the other hand, by integrally forming the pushing protrusion 15 on the stop surface 131, the pushing structure for pushing the holding arms 4 from the closed state to the unfolded state is simple in design, which can reduce the design complexity and manufacturing cost. Since the screw 1 must be used with the screwdriver 2 to tighten or loosen, the anti-theft effect is improved and the screw 1 can be applied to special use occasions.

[0084] It should be noted that the screw 1 and the screwdriver 2 of the present embodiment can also have the following different variations according to requirements:

[0085] One of the variations is that each first holding portion 143 can be a clamping block formed inside the surrounding wall 14, and each second holding portion 42 can form a clamping groove for the clamping block.

[0086] Another variation is that the connecting arm body 41 of each holding arm 4 can be connected to the handle 3 by sliding connection.

[0087] Another variation is that the screw 1 omits the pushing protrusion 15, and the screwdriver 2 pushes the holding arms 4 by a pushing rod that is arranged between the holding arms 4 and can move up and down, so that the holding arms 4 can be switched between the closed state and the unfolded state.

[0088] Another variation is that the screw 1 omits the pushing protrusion 15, and the screwdriver 2 drives each holding arm 4 to rotate by an electric motor, so that the holding arms 4 can be switched between the closed state and the unfolded state.

[0089] In summary, the screw 1 of the present embodiment, by the design of the first holding portion 143 of the screw head 12, the screw 1 can achieve good anti-theft effect. In addition, the screw 1 must be used with the screwdriver 2 to tighten or loosen, so it can be applied to special use occasions to meet special use requirements, and indeed achieve the purpose of the present application.

Claims

1. A screw, characterized in that: the screw comprises a shank and a head, the head is disposed at one end of the shank and jointly defines an axis with the shank, the head includes an end face at the end opposite to the shank, and a plurality of retaining portions, the head is formed with a guide hole recessed from the end face toward the shank and extending along the axis, the retaining portions are located around the periphery of the guide hole and are disposed at intervals around the axis, each of the retaining portions is spaced apart from the end face along the axis, and each of the retaining portions extends along a head radial direction perpendicular to the axis.

2. The screw of claim 1, wherein: Each of the retaining portions has a clamping groove extending outward from the periphery of the guide hole along the head radial direction and communicating with the guide hole.

3. The screw of claim 2, wherein: Each of the retaining portions further has two retaining faces located at opposite sides of the clamping groove, the retaining faces are spaced apart along another head radial direction perpendicular to the head radial direction and are parallel to each other.

4. The screw of claim 1, wherein: Each of the retaining portions has two retaining faces, the retaining faces are spaced apart along another head radial direction perpendicular to the head radial direction and are parallel to each other.

5. The screw of any one of claims 1-4, wherein: The head further includes a stop face between the shank and the retaining portions and facing the retaining portions, and a pushing boss protruding from the stop face and located in the guide hole.

6. The screw of claim 5, wherein: The pushing boss has a semispherical face, and an outer peripheral face connected between the stop face and the semispherical face.

7. The screw of any one of claims 1-4, wherein: The end face is annular.

8. The screw of any one of claims 1-4, wherein: The guide hole has a plurality of alignment groove portions angularly spaced apart around the axis and respectively aligned with the retaining portions.

9. The screw of claim 8, wherein: The head further includes a plurality of arc-shaped chamfer faces angularly spaced apart around the axis, each of the arc-shaped chamfer faces is located between a corresponding retaining portion and a corresponding alignment groove portion.

10. A screwdriver, characterized in that: the screwdriver comprises a handle and a plurality of retaining arms, the handle extends along an axis, the retaining arms are disposed on the handle and angularly spaced apart around the axis and arranged in an annular shape, each of the retaining arms includes a connecting arm body movably connected to the handle and partially externally exposed from the handle, and a retaining portion protruding from an outer side of the connecting arm body and located outside the handle, the retaining arms can be operated to be transformed between a closed state and an unfolded state, when the retaining arms are in the closed state, the retaining portions of the retaining arms are close to each other, and when the retaining arms are in the unfolded state, the retaining portions of the retaining arms are away from each other.

11. A screwdriver according to claim 10, characterized in that: The connecting arm body has an outer surface and a head end located outside the handle, and the retaining portion is a clamping block protruding from the outer surface and adjacent to the head end.

12. The screwdriver according to claim 11, characterized in that: The outer surface is arc-shaped, the retaining portion protrudes outward from the outer surface along an arm radial direction, and the retaining portion has two force applying faces spaced apart along another arm radial direction perpendicular to the arm radial direction and parallel to each other.

13. The screwdriver according to claim 11, wherein: The retaining portion further has a first outer arc-shaped chamfer face at one end opposite to the handle, and a second outer arc-shaped chamfer face opposite to the first outer arc-shaped chamfer face.

14. The screwdriver according to claim 10, wherein: The connecting arm body has an inner arc-shaped chamfer face located inside the retaining portion.

15. A screwdriver according to claim 14, characterized in that: The connecting arm body is formed with a receiving groove inside the holding portion, and has two abutting edges respectively located at opposite sides of the receiving groove.

16. A screwdriver according to any one of claims 10 to 15, wherein: The connecting arm body of each holding arm is rotatably pivoted to the handle, and the screwdriver further comprises a resilient ring sleeved on the connecting arm body of the holding arm to apply elastic contraction force to the connecting arm body.

17. A screwdriver according to claim 16, wherein: The handle comprises a housing and a limiting bead arranged in the housing, and the connecting arm body of each holding arm is rotatably pivoted between the housing and the limiting bead and can rotate around the limiting bead.

18. The screwdriver according to claim 17, characterized in that: The housing is formed with a receiving space and a plurality of pivoting portions angularly spaced around the axis and located outside the receiving space, each pivoting portion has a pivoting groove extending along the housing radial direction outward and communicating with the receiving space, the connecting arm body has an arm portion partially received in the receiving space and a pivoting plate portion, the arm portion has a tail end located in the receiving space and a recessed arc surface adjacent to the tail end and abutting against the limiting bead, the part of the arm portion adjacent to the tail end is outwardly spread by the limiting bead to maintain proper spacing, and the pivoting plate portion protrudes outward along the arm radial direction from the side of the arm portion opposite to the recessed arc surface, is adjacent to the tail end and is rotatably pivoted to the corresponding pivoting groove.

19. The screwdriver according to claim 18, characterized in that: Each pivoting portion further has two pressure surfaces respectively located at opposite sides of the pivoting groove, the pressure surfaces are spaced apart and parallel to each other along another housing radial direction perpendicular to the housing radial direction, and the pivoting plate portion has two pressure receiving surfaces respectively facing the corresponding pressure surfaces, the pressure receiving surfaces are spaced apart and parallel to each other along another arm radial direction perpendicular to the arm radial direction.

20. A combination of a screw and a screwdriver, characterized in that: The combination comprises a screw and a screwdriver, the screw comprises a shank and a head, the head is disposed at one end of the shank and jointly defines a first axis with the shank, the head includes an end face at the end opposite to the shank, and a plurality of first retaining portions, the head is formed with a guide hole recessed from the end face toward the shank and extending along the first axis, the first retaining portions are disposed at the periphery of the guide hole and spaced around the first axis, each of the first retaining portions is spaced from the end face along the first axis, each of the first retaining portions extends along a head diameter perpendicular to the first axis, the screwdriver is inserted into the screw and comprises a handle and a plurality of retaining arms, the handle extends along a second axis, the retaining arms are disposed on the handle and angularly spaced around the second axis and arranged in a ring shape, each of the retaining arms includes a connecting arm body movably connected to the handle and partially exposed outside the handle, and a second retaining portion protruding outside the connecting arm body and located outside the handle, the connecting arm body is inserted into the guide hole, and the second retaining portion is retained in the corresponding first retaining portion, the retaining arms are operable to be transformed between a closed state and an unfolded state, when the retaining arms are in the closed state, the second retaining portions of the retaining arms are close to each other, so that the second retaining portions are inserted into the guide hole, when the retaining arms are in the unfolded state, the second retaining portions of the retaining arms are away from each other, so that the second retaining portions are respectively retained in the first retaining portions.

21. The screw and screwdriver combination of claim 20, wherein: Each of the first retaining portions has a clamping groove extending radially outward from the periphery of the guide hole along the head diameter and communicating with the guide hole, the connecting arm body has an outer surface and a head end located outside the handle, and the second retaining portion is a clamping block protruding from the outer surface and adjacent to the head end to be clamped in the clamping groove of the corresponding first retaining portion.

22. The screw and screwdriver combination of claim 21, wherein: Each of the first retaining portions further has two retaining faces respectively located at opposite sides of the clamping groove, the retaining faces are spaced apart along another head diameter perpendicular to the head diameter and parallel to each other, the outer surface is arc-shaped, the second retaining portion protrudes outward along an arm diameter from the outer surface, and the second retaining portion has two force applying faces respectively abutting against the retaining faces, the force applying faces are spaced apart along another arm diameter perpendicular to the arm diameter and parallel to each other.

23. The screw and screwdriver combination of any one of claims 20-22, wherein: The head further includes a stop face between the shank and the first retaining portions and facing the first retaining portions, and a pushing protrusion protruding from the stop face and located in the guide hole, the stop face is used to stop the retaining arms, and the pushing protrusion is used to push the retaining arms to transform the retaining arms from the closed state to the unfolded state.

24. The screw and screwdriver combination of claim 23, wherein: The pushing protrusion has a hemispherical surface, and the connecting arm body has an inner arc-shaped chamfer surface inside the second retaining portion for the hemispherical surface to push.

25. The screw and screwdriver combination of claim 24, wherein: The connecting arm body is formed with an accommodation groove inside the second holding part for accommodating a part of the pushing protrusion, the pushing protrusion further has an outer peripheral surface connected between the stop surface and the semispherical surface, and the connecting arm body further has two abutting edges respectively located on opposite sides of the accommodation groove, each of the abutting edges being capable of abutting and sliding on the outer peripheral surface by line contact.

26. The screw and screwdriver combination of any one of claims 20-22, wherein: The screwdriver further comprises a pushing protrusion located in the guide hole, the pushing protrusion being used to push the holding arms so as to change the holding arms from the closed state to the unfolded state, the connecting arm body of each of the holding arms is rotatably pivoted to the handle, and the screwdriver further comprises a resilient ring sleeved on the connecting arm body of the holding arm to apply elastic contraction force to the connecting arm body.

27. The screw and screwdriver combination of claim 26, wherein: The handle comprises a shell and a limiting bead arranged in the shell, the connecting arm body of each of the holding arms is rotatably pivoted between the shell and the limiting bead and is capable of rotating around the limiting bead.

28. The screw and screwdriver combination of claim 27, wherein: The shell is formed with an accommodation space and a plurality of pivoting parts angularly spaced around the second axis and located outside the accommodation space, each of the pivoting parts has a pivoting groove extending radially outward along the shell and communicating with the accommodation space, the connecting arm body has an arm part accommodated in the accommodation space and a pivoting plate part, the arm part has a tail end located in the accommodation space and a recessed arc surface adjacent to the tail end and abutting against the limiting bead, the part of the arm part adjacent to the tail end is kept at a proper distance by the limiting bead, and the pivoting plate part protrudes radially outward along the arm from a side of the arm opposite to the recessed arc surface, is adjacent to the tail end, and is rotatably pivoted to the corresponding pivoting groove.

29. The screw and screwdriver combination of claim 28, wherein: Each of the pivoting parts further has two pressure surfaces respectively located on opposite sides of the pivoting groove, the pressure surfaces are spaced apart and parallel to each other along another shell radial direction perpendicular to the shell radial direction, the pivoting plate part has two pressure receiving surfaces respectively facing the corresponding pressure surfaces, and the pressure receiving surfaces are spaced apart and parallel to each other along another arm radial direction perpendicular to the arm radial direction.

30. The screw and screwdriver combination of any one of claims 20-22, wherein: The end surface is annular.

31. The screw and screwdriver combination of any one of claims 20-22, wherein: The guide hole has a plurality of alignment groove parts angularly spaced around the first axis and respectively aligned with the first holding parts in position, the alignment groove parts are respectively used for inserting a part of the second holding part, the end surface has a plurality of inner end edges respectively located outside the alignment groove parts in peripheral direction, and the second holding part further has a first outer arc-shaped chamfer surface arranged to slide on the corresponding inner end edge to be guided in the insertion direction when the second holding part is inserted into the corresponding alignment groove part of the guide hole to contact the corresponding inner end edge.

32. The screw and screwdriver combination of claim 31, wherein: The screw head further comprises a plurality of arc-shaped chamfer surfaces angularly surrounding the first axis, each of the arc-shaped chamfer surfaces being located between a corresponding first retaining portion and a corresponding alignment slot portion, the second retaining portion further having a second outer arc-shaped chamfer surface opposite to the first outer arc-shaped chamfer surface, the second outer arc-shaped chamfer surface being arranged to slide on the corresponding arc-shaped chamfer surface to be guided in the direction of withdrawal when the second retaining portion is withdrawn from the guide hole and contacts the corresponding arc-shaped chamfer surface.

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