CN214306245U

CN214306245U - Foldable foot seat

Info

Publication number: CN214306245U
Application number: CN202022347931.2U
Authority: CN
Inventors: 周也权; 陈光波
Original assignee: Syncmold Enterprise Corp
Current assignee: Syncmold Enterprise Corp
Priority date: 2019-11-07
Filing date: 2020-10-21
Publication date: 2021-09-28
Anticipated expiration: 2030-10-21
Also published as: CN214274958U; TWM599876U; CN213900409U; TWM608097U; CN212361423U; TWM608024U; TWM607104U; TWM603663U; TWM599369U; CN212107591U; TWM598368U; CN212203724U; TWM608107U; CN211853294U; CN212840412U; CN214093646U; TWM600822U

Abstract

The utility model relates to a foldable foot stand for bearing a supporting module. The foldable foot stand comprises a stand body, a foot stand module and a stop piece. The base is surrounded by a plurality of support legs of the support leg module, and each support leg is provided with an abutting part and a shaft connecting piece. The stop piece is arranged in the seat body and is provided with a plurality of first abutting parts, a plurality of second abutting parts and a pressing part. When any one of the support legs is located at a folding position, the abutting part abuts against the second abutting part, so that the stop piece is fixed at a second position, and the pressing part does not protrude out of the seat body.

Description

Foldable foot seat

Technical Field

The present invention relates to a foldable stand, and more particularly to a foldable stand for supporting a supporting module of an electronic device.

Background

The known folding foot rest generally has a main support and a plurality of supporting legs with the main support pin joint, pin joint department at main support and supporting legs can set up the button usually and collocation has a locking structure, after the user pressed the button, each supporting leg can be in order to fold up or expand in the main support pivot relatively, and after all supporting legs were all folded up, need further through a bolt backstop button of locking structure, let the button can't bulge the main support, in order to avoid the careless collision of user and damage the button, and then promote the security of using.

SUMMERY OF THE UTILITY MODEL

A primary object of the present invention is to provide a foldable foot stand, wherein the operating button is hidden when the supporting legs are in the fully folded state, and the operating button is exposed when the supporting legs are in the fully unfolded state, so as to be pressed.

When one of the legs of the foldable leg base is in a folded state, the pressing part of the stop member can be hidden in the base body, and the other legs are not limited by the stop member, so that the user can continue to fold the other legs easily.

Another object of the present invention is to provide a foldable foot stand, which has a plurality of pivot structures, and a pressing shaft set and a friction shaft set of the pivot structures can provide a positive force to the shaft connecting member of each supporting leg, so that the user can correspondingly adjust and rotate a hand feeling of each supporting leg by adjusting the positive force.

To achieve the above object, the present invention provides a foldable foot stand for supporting a support module. The foldable foot stand comprises a stand body, a foot stand module, a stop piece and an elastic piece. The seat body is connected with the supporting module and is provided with an accommodating space. The supporting foot module is arranged on the seat body and comprises a plurality of supporting feet, the supporting feet are mutually arranged on the seat body in a surrounding mode at intervals and can be respectively changed between an unfolding position and a folding position, and each supporting foot is respectively provided with a butting part, a shaft connecting part and a foot piece which are connected. The stop piece is arranged on the seat body, can move between a first position and a second position, and is provided with a central body, a plurality of first abutting parts and a plurality of second abutting parts, wherein one end of the central body is provided with a pressing part, and the first abutting parts and the second abutting parts respectively extend out of the central body and are respectively arranged at intervals corresponding to the support legs. The elastic piece is abutted against the seat body and the stop piece and constantly provides an elastic force for the stop piece so that the stop piece is inclined to the first position. When any one of the support legs is located at the folding position, the abutting part abuts against the second abutting part to enable the stop member to be fixed at the second position, and the pressing part is accommodated in the accommodating space and does not protrude out of the seat body.

When an external force is applied to move the stop member from the first position to the second position, each of the legs can pivot between the folded position and the unfolded position relative to the base, when the legs pivot to the unfolded position, the abutting portions are disengaged from the second abutting portions, and the stop member returns to the first position.

Each abutting part is provided with a first abutting area and a second abutting area, the first abutting area is connected between the shaft connecting piece and the second abutting area, when the supporting leg is at the unfolding position, the first abutting area can abut against the first abutting part, when the supporting leg is at the folding position, the first abutting area is far away from the first abutting part, and the second abutting area abuts against the second abutting part.

The supporting parts are respectively provided with a convex block, the convex blocks are respectively and correspondingly formed on the second supporting areas, and when any supporting leg is at the unfolding position, the corresponding convex block is supported against an inner side wall of the seat body.

The central body is also provided with a plurality of abdicating grooves, each abdicating groove is positioned at one side of each second resisting part, and when the support legs pivot relative to the base body, the convex blocks move in the abdicating grooves.

The stop member further has at least one stop block formed on the central body and extending toward the leg, wherein when the stop member is at the first position, the stop block abuts against an inner bottom wall of the seat body.

The supporting foot module can be changed between a fully-unfolded state and a fully-folded state, when the supporting foot module is in the fully-unfolded state, the supporting feet are all located at the unfolded positions, and when the supporting foot module is in the fully-folded state, the supporting feet are all located at the folded positions.

Each foot piece is provided with a connecting end and an extending end, the connecting ends are respectively connected with the shaft connecting pieces, when the foot module is in the full-unfolding state, the extending ends are far away from the supporting module, and when the foot module is in the full-folding state, the extending ends are close to the supporting module.

The base body defines a central axis, and the support legs are arranged at intervals in a circumferential direction by taking the central axis as a circle center.

The seat body is also provided with a plurality of joint parts and a plurality of containing grooves formed in the joint parts, the joint parts are arranged at intervals in the circumferential direction by taking the central axis as the center, the containing grooves are communicated with the containing space, and the shaft connecting piece is positioned in the containing grooves.

The utility model discloses but folding type foot stool still contains a plurality of pivot structures, each pivot structure has a pressurization axle group and a friction module, pressurization axle group correspondingly wear to locate this pedestal respectively friction module reaches the axle connecting piece, the axle connecting piece is with corresponding pressurization axle group rotates for this pedestal as the axle center, pressurization axle group pushes away to crowd corresponds friction module makes friction module is to corresponding the axle connecting piece provides a normal force.

Each pressurizing shaft group is provided with a first shaft piece and a second shaft piece, and the first shaft piece and the second shaft piece face each other and respectively penetrate through the base body and the shaft connecting piece to be in threaded connection with each other so as to jointly clamp the friction module and the shaft connecting piece.

The first shaft part is provided with a first head part, a first rod body and a thread groove, the first head part is connected with the first rod body, the thread groove is formed in the first rod body, the second shaft part is provided with a second head part and a second rod body, the second head part is connected with the second rod body, the friction module is provided with a first friction part and a second friction part, the first friction part is abutted between the first head part and the shaft connecting part, the first rod body penetrates through the first friction part and the shaft connecting part, the second friction part is abutted between the second head part and the shaft connecting part, and the second rod body penetrates through the second friction part and is screwed in the thread groove.

When the first head portion and the second head portion are closer to each other, the clamping force exerted by the first shaft member and the second shaft member on the friction module is stronger, the positive force exerted by the friction module on the shaft connecting member is larger, and when the shaft connecting member rotates relative to the joint portion with the pressing shaft as an axis, the friction force generated between the shaft connecting member and the friction module is larger.

Drawings

FIG. 1 is a perspective view of the foldable foot rest of the present invention in a fully unfolded state;

FIG. 2 is an exploded view of the foldable foot rest of the present invention;

FIG. 3 is an exploded view of the foldable foot stool of the present invention;

FIG. 4 is another exploded view of the foldable foot rest of the present invention;

FIG. 5 is a schematic perspective view of the foldable foot rest of the present invention in a fully folded state;

FIG. 6 is a perspective view of the stand bar of the foldable stand of the present invention;

FIG. 7 is a perspective view of the stop member of the foldable foot rest of the present invention;

FIG. 8 is another perspective view of the stop member of the foldable foot rest of the present invention;

FIG. 9 is a partial cross-sectional view of the foldable foot rest of the present invention;

FIG. 10 is a perspective partial view of the foldable foot rest of the present invention;

FIG. 11 is another partial cross-sectional view of the foldable foot rest of the present invention;

FIG. 12 is another partial cross-sectional view of the foldable foot rest of the present invention;

FIG. 13 is another perspective partial view of the foldable foot rest of the present invention;

FIG. 14 is another partially exploded view of the foldable foot rest of the present invention; and

fig. 15 is another partial cross-sectional view of the foldable foot rest of the present invention.

[ description of the main assembly symbols in the drawings ] of the embodiments of the present invention

1000 foldable foot seat

2000 support module

1 base body

11 substrate

111 inner side wall

112 inner bottom wall

113 inner ceiling wall

114 convex column

12 joint part

13 storage tank

14 space for accommodating

2 foot module

21 foot

211 shaft connecting piece

2111 outer surface

212 butting part

2121 first abutting area

2122 second abutting area

2123 bump

213 foot

2131 connecting end

2132 extending end

3 stop part

31 center body

32 first abutting part

33 second stopping part

34 groove of stepping down

35 stop block

36 pressing part

4 elastic member

5 pivot structure

51 pressurizing shaft group

511 first shaft member

5111 first head

5112A first rod

5113 thread groove

512 second shaft element

5121 second head

5122A second rod

52 Friction module

521 first friction member

522 second friction member

6 blind hole

Central axis A

C circumferential direction

P1 deployed position

P2 folding position

V1 first position

Second position of V2

Detailed Description

As shown in fig. 1 and fig. 2, the present invention provides a foldable foot stand 1000 for carrying a supporting module 2000, wherein the supporting module 2000 can be used for carrying an electronic device (not shown) such as a display, and the foldable foot stand 1000 includes a base 1, a foot module 2, a stop member 3, three elastic members 4 and three pivot structures 5.

As shown in fig. 3 and 4, the base 1 is connected to the support module 2000, defines a central axis a, and has a base 11, three joints 12, three receiving slots 13 and a receiving space 14. The base 11 has an inner sidewall 111, an inner bottom wall 112 and an inner top wall 113, the inner sidewall 111, the inner bottom wall 112 and the inner top wall 113 together define an accommodating space 14 for accommodating the stopper 3, the engaging portions 12 are arranged at intervals in a circumferential direction C with the central axis a as a center, and each accommodating groove 13 is formed on each engaging portion 12 and is communicated with the accommodating space 14.

The foot module 2 can be changed between a fully extended state (see fig. 1) and a fully collapsed state (see fig. 5). In detail, as shown in fig. 1 to 2 and 5 to 6, the leg module 2 includes three legs 21, each leg 21 has a connecting shaft 211, an abutting portion 212 and a leg 213 connected thereto. Each shaft connector 211 is located in each receiving groove 13 and has an outer surface 2111 facing the stopper 3, in this embodiment, the outer surface 2111 is an arc surface, and in other embodiments, the outer surface 2111 may also be a plane surface, an inclined surface, or a surface with other shapes. And can be pivoted with the connecting parts 12 via the pivot structures 5 (the detailed structure of the pivot structures 5 will be described in detail later), so that the legs 21 can be pivoted relative to the seat body 1 to respectively change between an unfolded position P1 (fig. 1) and a folded position P2 (fig. 5). The supporting legs 21 are disposed around the base 1 at intervals, that is, the supporting legs 21 are arranged at intervals in the circumferential direction C with the central axis a as a center, and in this embodiment, an angle between the supporting legs 21 is approximately 120 degrees. When the supporting foot module 2 is in the fully-unfolded state, the supporting foot 21 is located at the unfolding position P1, the foldable foot stand 1000 can be placed on a working surface (not shown), and when the supporting foot module 2 is in the fully-folded state, the supporting foot 21 is located at the folding position P2, so that the foldable foot stand 1000 of the utility model can be stored or carried in a smaller size.

As shown in fig. 6, each abutting portion 212 has a first abutting region 2121, a second abutting region 2122 and a protrusion 2123, the first abutting region 2121 is connected between each shaft connecting member 211 and the second abutting region 2122, and the protrusion 2123 is correspondingly formed on the second abutting region 2122. In the present embodiment, the first abutting region 2121 is a substantially flat surface, the second abutting region 2122 is an outwardly convex curved surface, and the protrusion 2123 is a corner plate, but other embodiments of the present invention can have other shapes, and the shapes of the first abutting region 2121, the second abutting region 2122 and the protrusion 2123 are not limited herein.

Each leg 213 has a connecting end 2131 and an extending end 2132, the connecting end 2131 is connected to each shaft connecting member 211, the extending ends 2132 are far away from the support module 2000 (see fig. 1) when the leg module 2 is in the fully unfolded state, and the extending ends 2132 are near the support module 2000 (see fig. 5) when the leg module 2 is in the fully folded state.

Referring to fig. 7 and 8, the stopper 3 has a central body 31, three first abutting portions 32, three second abutting portions 33, three relief grooves 34, three stoppers 35 and a pressing portion 36. The central body 31 extends along the central axis a, and the first abutting portion 32, the second abutting portion 33 and the stopper 35 extend from the central body 31 toward the shaft connectors 211 of the legs 21, and are arranged at intervals corresponding to the shaft connectors 211. The first abutting portions 32 are respectively a protrusion, each second abutting portion 33 is respectively an arc block and is located between each first abutting portion 32 and each stopper 35, in this embodiment, each second abutting portion 33 has an inward concave arc surface, and can interfere with a part of each second abutting region 2122. The indent 34 is formed on the central body 31 at an interval corresponding to the protrusion 2123 and is located at one side of the second abutting portion 33, a depth of the indent 34 is designed to be sufficient to accommodate the protrusion 2123, and the protrusion 2123 can move in the indent 34 without interference. The pressing portion 36 is formed at one end of the central body 31, is substantially an operation button, and is located below the stopper 35.

Referring to fig. 9, the elastic elements 4 are respectively sleeved on the three protruding columns 114 (as shown in fig. 4) formed on the inner top wall 113 and respectively accommodated in the three blind holes 6 (as shown in fig. 7) formed on the stopper 3, so that the elastic elements 4 are abutted against between the inner top wall 113 and the stopper 3, and provide an elastic force to the stopper 3, so that the stopper 3 is inclined to a first position V1 in the accommodating space 14 of the seat body 1.

As shown in fig. 9 and 10, when the leg module 2 is in the fully unfolded state, the legs 21 are all located at the unfolded position P1, taking the relative position relationship between one of the legs 21 and the stopper 3 as an example, the stopper 3 is disposed in the accommodating space 14 of the seat body 1 and located at the first position V1, the stopper 35 abuts against the inner bottom wall 112 of the seat body 1, the pressing portion 36 protrudes out of the seat body 1, the first abutting region 2121 abuts against the first abutting portion 32, and each corresponding protrusion 2123 abuts against the inner side wall 111 of the seat body 1, that is, the abutting portion 212 cooperates with the first abutting portion 32 and the seat body 1 to limit the pivot of the shaft connector 211, so that the legs 21 can be located at the unfolded position P1 without rotating randomly.

When an external force is applied to the stopper 3 (e.g., the pressing portion 36 is pressed by a user), so that the stopper 3 moves from the first position V1 to the second position V2 along the central axis a, as shown in fig. 11, the first abutting portion 32 and the second abutting portion 33 both rise along the central axis a and are away from the first abutting region 2121 and the second abutting region 2122.

Next, as shown in fig. 12 and fig. 13, when one of the legs 21 is pivoted relative to the seat body 1, in the process of rotating to the folding position P2, the projection 2123 moves in the relief groove 34 until the second abutting region 2122 of the abutting portion 212 abuts against the second abutting portion 33 to interfere with the second abutting portion 33, when one of the legs 21 is located at the folding position P2, the first abutting region 2121 is already away from the first abutting portion 32, and the second abutting region 2122 abuts against the second abutting portion 33 to fix the stopper 3 at the second position V2, and the pressing portion 36 does not protrude from the seat body 1 (i.e. is completely accommodated in the accommodating space 14 of the seat body 1). Since the stopper 3 is already located at the second position V2, the user can convert the foldable foot stand 1000 from the fully unfolded state to the fully folded state by continuing to rotate the other legs 21 to the folded position P2 without applying any force to the stopper 3.

It should be noted that, in the embodiment, the second abutting region 2122 is designed to be an outer convex arc surface with a non-uniform curvature to be suitable for generating a local interference with the second abutting portion 33 (as shown in fig. 12), and in other embodiments of the present invention, the curvature parameter of the second abutting region 2122 can be adjusted as required to correspondingly adjust the degree of interference with the second abutting portion 33 (for example, the contact position and the contact area with the second abutting portion 33 are changed by adjusting the curvature of the second abutting region 2122).

When the leg 21 is pivoted again to the unfolded position P1 at the folding position P2 (from the position of fig. 12 to the position of fig. 9), the second abutting region 2122 is disengaged from the second abutting portion 33, the elastic element 4 returns the stopper 3 to the first position V1, and the first abutting region 2121 abuts against the first abutting portion 32 again.

As shown in fig. 14 and 15, each pivot structure 5 has a pressing shaft set 51 and a friction module 52. Each pressing shaft set 51 has a first shaft 511 and a second shaft 512. Each first shaft 511 has a first head 5111, a first rod 5112 and a threaded groove 5113. Each first head 5111 is connected to each first rod 5112, and each thread groove 5113 is formed in each first rod 5112 (i.e., a blind hole). Each second shaft element 512 has a second head 5121 and a second rod 5122, and each second head 5121 is connected to each second rod 5122.

Each friction module 52 has a first friction member 521 and a second friction member 522, each first friction member 521 abuts between each first head 5111 and each shaft connecting member 211, each first rod 5112 correspondingly passes through each first friction member 521 and each shaft connecting member 211, each second friction member 522 correspondingly abuts between each second head 5121 and each shaft connecting member 211, each second rod 5122 is formed with an external thread, and correspondingly passes through each second friction member 522 and is correspondingly screwed in each thread groove 5113. Therefore, each pressurizing shaft group 51 is respectively and correspondingly arranged in each joint part 12, each friction module 52 and each shaft connector 211 of the seat body 1, each shaft connector 211 rotates relative to the seat body 1 by taking each pressurizing shaft group 51 as an axis, and each friction module 52 provides a positive force for each shaft connector 211 by pushing each friction module 52.

When the closer each first head 5111 and the corresponding each second head 5121 is, the stronger a clamping force is simultaneously applied to each friction module 52 by each first shaft 511 and each second shaft 512, the greater a positive force is simultaneously applied to each coupling member 211 by each friction module 52, and each coupling member 211 rotates relative to each coupling portion 12 around each pressing shaft group 51 as an axis, the greater the frictional force generated between each coupling member 211 and each friction module 52, and the heavier the hand feeling of rotating each leg 21 can be. On the contrary, if the hand feeling is heavy, the second rod body 5122 can be selectively screwed out of the corresponding thread groove 5113, that is, the portion deep into the thread groove 5113 is reduced, a clamping force applied to each friction module 52 by each first shaft 511 and each second shaft 512 is reduced, when each shaft connecting member 211 rotates relative to each joint part 12 by taking each pressing shaft group 51 as the axis, the friction force generated between each shaft connecting member 211 and each friction module 52 is reduced, and the hand feeling for rotating each support leg 21 can be lightened.

The first friction members 521 and the second friction members 522 are located at both sides of the shaft coupling members 211, so that the surfaces of the shaft coupling members 211 can be protected by the first friction members 521 and the second friction members 522 and are not easily worn directly by the pressing shaft groups 51 during rotation. Furthermore, the utility model discloses a shaft joint piece 211 is less for seeking pleasing to the eye and volume, therefore the screw gasket of known public rule is difficult to with shaft joint piece 211 matched stack, otherwise, the utility model discloses a shape, thickness and the size of first friction piece 521 and second friction piece 522 all can change according to shape, size of shaft joint piece 211, have higher adjustment degree than the screw gasket of public rule. The material of the first friction member 521 and the second friction member 522 is POM, but not limited thereto.

The above-mentioned embodiments are only intended to illustrate the embodiments of the present invention and to explain the technical features of the present invention, and are not intended to limit the scope of the present invention. All changes and equivalent arrangements which may be easily accomplished by those skilled in the art are intended to be within the scope of the present invention, which is to be determined by the appended claims.

Claims

1. A foldable foot stand for carrying a supporting module, the foldable foot stand is characterized by comprising:

a seat body connected with the support module and provided with an accommodating space;

the stand bar module is arranged on the seat body and comprises a plurality of stand bars, the stand bars are mutually arranged on the seat body in an annular mode at intervals and can be respectively changed between an unfolding position and a folding position, and each stand bar is respectively provided with a butting part, a shaft connecting part and a leg part which are connected; and

a stop member disposed on the base body and capable of moving between a first position and a second position, and having a central body, a plurality of first abutting portions and a plurality of second abutting portions, wherein a pressing portion is formed at one end of the central body, and the first abutting portions and the second abutting portions extend from the central body and are respectively arranged at intervals corresponding to the supporting legs; and

the elastic piece is abutted against the seat body and the stop piece and constantly provides an elastic force for the stop piece so that the stop piece is inclined to the first position;

when any one of the support legs is located at the folding position, the abutting part abuts against the second abutting part to enable the stop member to be fixed at the second position, and the pressing part is accommodated in the accommodating space and does not protrude out of the seat body.

2. The foldable foot rest of claim 1, wherein when an external force is applied to move the stop member from the first position to the second position, each of the legs is capable of pivoting between the folded position and the unfolded position relative to the seat body, and when the legs are pivoted to the unfolded position, the abutting portions are disengaged from the second abutting portions, and the stop member returns to the first position.

3. The foldable foot rest according to claim 2, wherein each abutting portion has a first abutting region and a second abutting region, the first abutting region is connected between the shaft connecting member and the second abutting region, when the supporting foot is in the unfolded position, the first abutting region can abut against the first abutting portion, when the supporting foot is in the folded position, the first abutting region is away from the first abutting portion, and the second abutting region abuts against the second abutting portion.

4. The foldable foot stand according to claim 3, wherein the abutting portions each have a protrusion, and the protrusions are correspondingly formed on the second abutting regions, respectively, when any one of the legs is in the unfolded position, the corresponding protrusion abuts against an inner sidewall of the seat body.

5. The foldable foot rest according to claim 4, wherein the central body further has a plurality of relief grooves formed therein, each of the relief grooves is located at one side of each of the second engaging portions, and when the foot pivots relative to the seat body, the protrusion moves in the relief groove.

6. The foldable foot rest of claim 5, wherein the stop member further comprises at least one stop formed on the central body and extending toward the foot, the stop member abutting against an inner bottom wall of the seat body when the stop member is in the first position.

7. The foldable foot rest of claim 6, wherein the foot module is changeable between a fully unfolded state and a fully folded state, the feet are in the unfolded position when the foot module is in the fully unfolded state, and the feet are in the folded position when the foot module is in the fully folded state.

8. The foldable foot rest of claim 7, wherein each foot member has a connecting end and an extending end, the connecting ends are respectively connected to the shaft connecting members, the extending ends are both far away from the supporting module when the foot module is in the fully unfolded state, and the extending ends are both adjacent to the supporting module when the foot module is in the fully folded state.

9. The foldable foot stand of claim 8, wherein the stand body defines a central axis, and the feet are arranged at intervals in a circumferential direction around the central axis.

10. The foldable foot stand of claim 9, wherein the stand body further comprises a plurality of engaging portions and a plurality of receiving slots formed on the engaging portions, the engaging portions are spaced apart from each other in the circumferential direction around the central axis, the receiving slots are communicated with the receiving space, and the shaft connecting member is located in the receiving slots.

11. The foldable foot rest according to claim 10, further comprising a plurality of pivot structures, each pivot structure having a pressing shaft set and a friction module, the pressing shaft set respectively passing through the seat body, the friction module and the shaft connecting member, the shaft connecting member rotating relative to the seat body with the corresponding pressing shaft set as an axis, the pressing shaft set pushing the corresponding friction module to make the friction module provide a positive force to the corresponding shaft connecting member.

12. The foldable foot stand of claim 11, wherein each of the pressing shaft sets has a first shaft member and a second shaft member, the first shaft member and the second shaft member facing each other and threaded through the seat body and the shaft connecting member, respectively, to clamp the friction module and the shaft connecting member together.

13. The foldable foot rest according to claim 12, wherein the first shaft has a first head, a first rod and a threaded groove, the first head is connected to the first rod, the threaded groove is formed in the first rod, the second shaft has a second head and a second rod, the second head is connected to the second rod, the friction module has a first friction member and a second friction member, the first friction member abuts against the first head and the shaft connecting member, the first rod passes through the first friction member and the shaft connecting member, the second friction member abuts against the second head and the shaft connecting member, and the second rod passes through the second friction member and is screwed into the threaded groove.

14. The foldable foot stand of claim 13, wherein the closer the first head portion and the corresponding second head portion are, the stronger a clamping force is simultaneously applied by the first shaft member and the second shaft member to the friction module, the greater a positive force is applied by the friction module to the shaft connecting member, and the greater a frictional force is generated between the shaft connecting member and the friction module when the shaft connecting member rotates about the pressing shaft with respect to the engaging portion.