Wind resistant device

Abstract

To provide a wind resistant device which can restrain relative displacement between an upper structure and a lower structure with a small scale structure.SOLUTION: A wind resistant device is provided with a seismic isolator in a base isolation layer 13 between a lower structure 11 and an upper structure 12 and includes: a ball screw 2 which is attached to the upper structure 12, restrained from rotating around an axis; a ball nut 3 which is attached to the lower structure 11, allowed to rotate around the axis and which is configured to be threaded engaged with the ball screw 2; a brake 6 which may restrain rotational movement of the ball nut 3; and a brake control unit 7 which controls the brake 6 according to wind external force acting on the upper structure 12.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a wind-resistant device.

Background Art

[0002] In the intermediate floor seismic isolation structure, the upper structure is provided via a seismic isolation layer on the lower structure built on the ground. When the seismic isolation layer is provided on a high floor and the lower structure has a natural period of several seconds, by appropriately synchronizing the natural period of the upper structure including the seismic isolation layer with the natural period of the lower structure, it becomes possible to realize a TMD (tuned mass damper) having a large mass ratio. On the other hand, when the structure of the intermediate floor seismic isolation structure is subjected to strong winds, depending on the scale of the structure, the external force is large, and the time when the strong wind acts is generally longer than that of an earthquake. Therefore, in addition to the seismic isolation device, a wind-resistant device for suppressing the vibration of the upper structure during strong winds may be provided. The wind-resistant device disclosed in Patent Document 1 is provided with shear pins that fix the upper structure and the lower structure and shear-fracture under a predetermined load in the seismic isolation layer between the upper structure (building) and the lower structure (building foundation). This wind-resistant device suppresses the vibration of the upper structure because the shear pins fix the upper structure and the lower structure against relatively small external forces such as assumed wind external forces. Against large external forces such as a major earthquake, the shear pins shear-fracture and the fixation between the upper structure and the lower structure is released, and it is configured so that the seismic isolation effect of the seismic isolation layer can be exhibited. The seismic isolation system disclosed in Patent Document 2 is provided with a friction brake that restrains the relative displacement between the upper structure and the lower structure, and is configured to control the friction brake according to the wind speed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the building is large in scale and the wind external force is also large, a large force is required to restrain the relative displacement between the superstructure and the substructure, so a large-scale wind-resistant device is required. When installing a large-scale wind-resistant device, there may be problems in the design of the building side that bears the reaction force.

[0005] Therefore, an object of the present invention is to provide a wind-resistant device that can restrain the relative displacement between the superstructure and the substructure with a small-scale configuration.

Means for Solving the Problems

[0006] To achieve the above object, the wind-resistant device according to the present invention is provided together with a seismic isolation device in a seismic isolation layer between a substructure and a superstructure, and is attached to one of the substructure and the superstructure in a state where rotation around an axis is restrained. A ball screw, a ball nut attached to the other structure of the substructure and the superstructure in a state where rotation around an axis is allowed and screwed onto the ball screw, a brake capable of restraining the rotational movement of the ball nut, and a brake control unit for controlling the brake according to the wind external force acting on the superstructure.

[0007] In the present invention, the relative displacement (translation motion) in the axial direction between the substructure and the superstructure is converted into a rotational motion by the ball screw and the ball nut, and this rotational motion is restrained by a brake according to the wind external force acting on the superstructure, thereby restraining the relative displacement in the axial direction between the substructure and the superstructure. For example, the brake control unit turns off the brake when the predicted or measured wind external force acting on the superstructure is equal to or less than a predetermined value, or less than the predetermined value, and turns on the brake when the predicted or measured wind external force acting on the superstructure is equal to or greater than a predetermined value, or is determined to exceed the predetermined value. The force required to restrain the rotational motion converted from the translational motion between the lower structure and the upper structure is smaller than the force required to directly restrain the translational motion between the lower structure and the upper structure. Therefore, in the present invention, compared with the case of directly restraining the translational motion, the relative displacement between the lower structure and the upper structure can be restrained with a smaller force. As a result, the wind-resistant device can be configured on a small scale.

[0008] In the wind-resistant device according to the present invention, the brake control unit may turn off the brake when the wind external force acting on the upper structure is equal to or less than a predetermined value, or less than the predetermined value, and turn on the brake when it is determined that the wind external force acting on the upper structure is equal to or greater than the predetermined value, or exceeds the predetermined value.

[0009] With such a configuration, when the wind external force acting on the upper structure is equal to or greater than a predetermined value, or exceeds the predetermined value, that is, during strong winds, the displacement of the upper structure relative to the lower structure is fixed, and when the wind external force acting on the upper structure is equal to or less than a predetermined value, or less than the predetermined value, that is, when there is no strong wind, the displacement of the upper structure relative to the lower structure is allowed, and the seismic isolation effect of the seismic isolation device can be exerted.

[0010] In the wind-resistant device according to the present invention, the ball screw may be rotatably attached around a vertical axis passing through the attachment position to the one structure, and around a horizontal axis passing through the attachment position to the one structure and orthogonal to the axis, and the ball nut may be rotatably attached around a vertical axis passing through the attachment position to the other structure, and around a horizontal axis passing through the attachment position to the other structure and orthogonal to the axis.

[0011] With such a configuration, the ball screw and the ball nut can be installed in a posture corresponding to the horizontal relative displacement between the lower structure and the upper structure. For example, even when the seismic isolation device is a laminated rubber bearing and the distance between the lower structure and the upper structure becomes smaller than the initial state due to the creep deformation of the laminated rubber of the laminated rubber bearing, the ball screw and the ball nut can be installed in a posture corresponding to the distance between the lower structure 11 and the upper structure 12.

[0012] In the wind-resistant device according to the present invention, a rotating member is fixed to the ball nut, protrudes from the outer periphery of the ball nut, and rotates around the axis together with the ball nut, and the brake may be capable of restraining the rotational movement of the rotating member.

[0013] By adopting such a configuration, by fixing a rotating member having a shape adapted to the arrangement of the brake and the ball nut and the form of the brake to the ball nut, the restrictions on the arrangement of the brake and the ball nut and the form of the brake can be reduced.

[0014] In the wind-resistant device according to the present invention, the brake may be a disk brake or a drum brake that restrains the rotational movement of the rotating member.

[0015] The frictional force required to restrain the rotational movement of the rotating member with a disk brake or a drum brake is smaller than the frictional force required to directly restrain the translational movement between the upper structure and the lower structure. Therefore, the present invention can restrain the relative displacement between the lower structure and the upper structure with a small frictional force. As a result, the brake can be configured on a small scale.

Advantages of the Invention

[0016] According to the present invention, the relative displacement between the upper structure and the lower structure can be restrained with a small-scale configuration.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0018] Hereinafter, the wind-resistant device according to the embodiment of the present invention will be described with reference to FIGS. 1 to 7. As shown in FIGS. 1 and 2, the wind-resistant device 1 according to this embodiment is installed in the seismic isolation layer 13 of a building 14 in which a seismic isolation layer 13 is provided between a foundation 11 and a superstructure 12 above the foundation 11, together with a seismic isolation device 15. A plurality of wind-resistant devices 1 are provided in the building 14. The arrangement of the plurality of wind-resistant devices 1 will be described later. Hereinafter, the foundation 11 will be referred to as the substructure 11, and the superstructure 12 above the foundation 11 will be referred to as the superstructure 12. The seismic isolation device 15 is a seismic isolation bearing such as a laminated rubber bearing or a sliding bearing. The wind-resistant device 1 allows relative displacement between the substructure 11 and the superstructure 12 when the wind external force acting on the superstructure 12 is equal to or less than a predetermined value, or less than the predetermined value, and restrains the relative displacement between the substructure 11 and the superstructure 12 when the wind external force acting on the superstructure 12 is equal to or greater than a predetermined value, or exceeds the predetermined value.

[0019] As shown in FIGS. 3 and 4, the wind-resistant device 1 includes a ball screw 2, a ball nut 3, a bearing 4, a rotating member 5, a brake 6, and a brake control unit 7. The ball screw 2 and the ball nut 3 are screwed together. A large number of balls are provided between the screw portions of the ball nut 3 and the ball screw 2. The direction in which the axes of the ball screw 2 and the ball nut 3 extend is referred to as the axial direction. The axial direction extends horizontally in the initial state.

[0020] The ball screw 2 has one end in the axial direction (the first end 2a, see Fig. 4) attached to the upper structure 12. The rotation of the ball screw 2 around its axis is restricted. In this embodiment, the first end 2a of the ball screw 2 is connected to the spline shaft 221 of the ball spline 22, and the spline shaft 221 is attached to the upper structure 12. The first end 2a side of the ball screw 2 and the spline shaft 221 are inserted into a holder 223 connected to the outer cylinder 222 of the ball spline 22. The ball screw 2 is restricted from rotating around its axis by the ball spline 22 and is guided to move in the axial direction.

[0021] As shown in Figs. 4 and 5, the bearing 4 is fixed to the lower structure 11 and supports the ball screw 2 so as to be movable in the axial direction. The bearing 4 has a hole 43 into which the ball screw 2 is inserted. A holder 223 (see Fig. 4) is connected to one side of the bearing 4 in the axial direction. The interior of the holder 223 is connected to the hole 43 of the bearing 4. On the other side of the bearing 4 in the axial direction, a ball nut 3 is rotatably attached around the axis. The ball nut 3 and the bearing 4 do not undergo relative displacement in the horizontal direction. That is, the ball nut 3 does not undergo relative displacement in the horizontal direction with respect to the lower structure 11. The ball screw 2 is inserted into the ball nut 3. As shown in Fig. 4, the other end (the second end 2b) side of the ball screw 2 in the axial direction protrudes from the ball nut 3 to the other side in the axial direction.

[0022] As shown in Figs. 4 and 6, the rotating member 5 is coaxially fixed to the ball nut 3. The rotating member 5 rotates together with the ball nut 3. The brake 6 can restrict the rotational movement of the rotating member 5. The brake control unit 7 controls the brake 6 according to the wind external force acting on the building 14 (see Figs. 1 and 2).

[0023] When the lower structure 11 and the upper structure 12 are displaced relative to each other in the axial direction, and when the ball screw 2 and the ball nut 3 are displaced relative to each other in the axial direction, since the rotation around the axis of the ball screw 2 is restricted, the ball nut 3 rotates around the axis along the thread portion of the ball screw 2. The ball screw 2 and the ball nut 3 convert the relative displacement (linear motion) in the axial direction between the lower structure 11 and the upper structure 12 into rotational motion.

[0024] The rotating member 5 is formed in a disk shape. The rotating member 5 is coaxially attached to the outer peripheral surface of the ball nut 3. The rotating member 5 protrudes radially outward from the outer peripheral surface of the ball nut 3. As described above, the rotating member 5 rotates together with the ball nut 3. Therefore, when the lower structure 11 and the upper structure 12 are displaced relative to each other in the horizontal direction, the rotating member 5 rotates around the axis of the ball screw 2 together with the ball nut 3.

[0025] The brake 6 can restrict the rotational motion of the rotating member 5 with respect to the ball screw 2. The brake 6 is a disk brake, a drum brake, or the like that can restrict the rotational motion of the rotating member 5 by frictional force by pressing the rotating rotating member 5. When the brake 6 is turned ON and the rotation of the rotating member 5 is restricted, the rotation of the ball nut 3 with respect to the ball screw 2 is restricted, and the relative displacement in the horizontal direction between the ball screw 2 and the ball nut 3, that is, the relative displacement in the horizontal direction between the lower structure 11 and the upper structure 12 is restricted.

[0026] The brake control unit 7 switches the ON / OFF of the brake 6 according to the magnitude of the predicted or measured wind external force. The brake control unit 7 may be configured such that an administrator manually switches the ON / OFF of the brake 6, or may be automatically controlled to switch the ON / OFF of the brake 6.

[0027] When the manager manually controls the brake control unit 7, the brake 6 is turned OFF when it is determined that the wind external force acting on the superstructure 12, which is predicted or actually measured, is equal to or less than a predetermined value, or less than the predetermined value, and the brake 6 is turned ON when it is determined that the wind external force acting on the superstructure 12, which is predicted or actually measured, is equal to or greater than a predetermined value, or exceeds the predetermined value.

[0028] When the brake control unit 7 is automatically controlled, either or both of a prediction unit that predicts the wind external force acting on the superstructure 12 and a measurement unit that measures the wind external force acting on the superstructure 12 are provided. The brake control unit 7 switches the ON / OFF of the brake 6 based on the wind external force acting on the superstructure 12 received from either or both of the prediction unit and the measurement unit. The brake control unit 7 turns OFF the brake 6 when it is determined that the wind external force acting on the superstructure 12 received from either or both of the prediction unit and the measurement unit is equal to or less than a predetermined value, or less than the predetermined value, and turns ON the brake 6 when it is determined that the wind external force received from either or both of the prediction unit and the measurement unit is equal to or greater than a predetermined value, or exceeds the predetermined value.

[0029] Note that even when the brake 6 is in the ON state, when a seismic force equal to or greater than a predetermined value acts on the building 14, the brake 6 is turned OFF, the horizontal relative displacement between the lower structure 11 and the superstructure 12 is allowed, and control is performed so that the seismic isolation effect by the seismic isolation device 15 is exhibited.

[0030] When the brake 6 is OFF, the relative displacement in the axial direction between the ball screw 2 and the ball nut 3 is allowed, and the relative displacement between the lower structure 11 and the superstructure 12 is allowed. When the brake 6 is ON, the relative displacement in the axial direction between the ball screw 2 and the ball nut 3 is restricted, and the relative displacement between the lower structure 11 and the superstructure 12 is restricted.

[0031] Assuming that the force exerted by the brake 6 on the friction surface of the rotating member 5 is N and the coefficient of friction of the friction surface is μ, the braking force of the brake mechanism is μN. Assuming that the distance in the radial direction of the rotating member 5 from the position where the frictional force acts (approximately the radius of the rotating member 5) is R, the moment for fixing the ball nut 3 is μNR. On the other hand, assuming that the external force for linearly moving the ball screw 2 is F and the lead of the ball screw 2 (the linear movement distance for rotating the ball nut once, the pitch of the ball screw 2) is Ld, the relationship between the linear movement distance X and the rotation amount θ of the rotating member 5 is shown by the following formula (1). X = Ldθ / (2π) ···(1) When equating the work FX done when the external force F for linearly moving the ball screw 2 is displaced by the linear movement distance X against the moment to the work done when the moment acts and rotates by θ, the following formula (2) is obtained. F = (2πμR / Ld)N ···(2) For example, if the coefficient of friction of the friction surface μ = 0.3, the distance R in the radial direction of the rotating member 5 from the position where the frictional force acts = 500 mm, and the lead Ld of the ball screw 2 = 50 mm, then F = 18.8 N. It can be seen that the pressing force N of the friction surface required for the brake 6 can be much smaller than the force F required for fixing the upper structure 12.

[0032] As shown in FIGS. 3 and 7, in the present embodiment, the spline shaft 221 connected to the ball screw 2 is attached to the upper structure 12 via the ball joint 21. Thereby, the ball screw 2 can rotate in the horizontal direction and the vertical direction with respect to the upper structure 12 around the attachment position to the upper structure 12, that is, the position 211 where the ball joint 21 is provided. As shown in FIGS. 3, 4, and 7, the bearing 4 has a first trunnion mechanism 41 rotatable about a vertical axis 411 with respect to the lower structure 11 and a second trunnion mechanism 42 rotatable about a horizontal axis 421. Thereby, the bearing 4 is rotatable about the intersection of the vertical axis 411 of the first trunnion mechanism 41 and the horizontal axis 421 of the second trunnion mechanism 42 while the position of the bearing 4 with respect to the lower structure 11 is fixed. The intersection of the vertical axis 411 of the first trunnion mechanism 41 and the horizontal axis 421 of the second trunnion mechanism 42 is disposed on the axis of the ball screw 2.

[0033] Due to these, even when the lower structure 11 and the upper structure 12 are displaced relative to each other in the horizontal direction other than the axial direction or in the vertical direction in the initial state, the ball screw 2 and the ball nut 3 assume a posture following the relative displacement between the lower structure 11 and the upper structure 12, and are displaced relative to each other in the axial direction, and can convert the relative displacement between the lower structure 11 and the upper structure 12 into a rotational motion. Further, for example, even when the seismic isolation device 15 is a laminated rubber bearing and the distance between the lower structure 11 and the upper structure 12 becomes smaller than the initial state due to the creep deformation of the laminated rubber of the laminated rubber bearing, the ball screw 2 and the ball nut 3 can be installed in a posture corresponding to the distance between the lower structure 11 and the upper structure 12.

[0034] As shown in FIG. 1, a plurality of wind-resistant devices 1 are provided in the building 14. It is preferable that each of the plurality of wind-resistant devices 1 includes at least two wind-resistant devices 1 whose axial directions in the initial state extend in one horizontal direction (X direction) and at least two wind-resistant devices 1 whose axial directions in the initial state extend in another horizontal direction (Y direction) orthogonal to the one horizontal direction. By doing so, relative rotation of the lower structure 11 and the upper structure 12 about the vertical axis can be prevented. In the present embodiment, two wind-resistant devices 1 whose axial directions in the initial state extend in the X direction are arranged at intervals in the Y direction, and two wind-resistant devices 1 whose axial directions in the initial state extend in the Y direction are arranged at intervals in the X direction. When a plurality of wind-resistant devices 1 are provided in the building 14, the number and respective orientations may be set as appropriate.

[0035] Next, the operation and effects of the wind-resistant device according to this embodiment will be described. In the wind-resistant device 1, the axial relative displacement (translation motion) between the lower structure 11 and the upper structure 12 is converted into a rotational motion by the ball screw 2 and the ball nut 3, and this rotational motion is restrained by the brake 6 according to the wind external force acting on the upper structure 12, thereby restraining the axial relative displacement between the lower structure 11 and the upper structure 12. Since the force required to restrain the rotational motion into which the translational motion between the lower structure 11 and the upper structure 12 is converted is smaller than the force required to directly restrain the translational motion between the lower structure 11 and the upper structure 12, in the wind-resistant device 1 according to this embodiment, the relative displacement between the lower structure 11 and the upper structure 12 can be restrained with a smaller force compared to the case of directly restraining the translational motion. As a result, the wind-resistant device 1 can be configured on a small scale.

[0036] In this embodiment, the brake control unit 7 turns off the brake 6 when the predicted or measured wind external force acting on the upper structure is equal to or less than a predetermined value, or less than the predetermined value, and turns on the brake 6 when it is determined that the predicted or measured wind external force acting on the upper structure is equal to or greater than the predetermined value, or exceeds the predetermined value. With such a configuration, when the wind external force acting on the upper structure 12 is equal to or greater than the predetermined value, or exceeds the predetermined value, that is, during strong winds, the displacement of the upper structure 12 relative to the lower structure 11 is fixed, and when the wind external force acting on the upper structure 12 is equal to or less than the predetermined value, or less than the predetermined value, that is, when there is no strong wind, the displacement of the upper structure 12 relative to the lower structure 11 is allowed, and the seismic isolation effect of the seismic isolation device 15 can be exerted.

[0037] The ball screw 2 is attached to the upper structure 12 via a ball joint 21. The bearing 4 that supports the ball nut 3 has a first trunnion mechanism 41 and a second trunnion mechanism 42. With such a configuration, the ball screw 2 and the ball nut 3 can be installed in a posture corresponding to the horizontal relative displacement between the lower structure 11 and the upper structure 12. For example, when the seismic isolation device 15 is a laminated rubber bearing and the distance between the lower structure 11 and the upper structure 12 becomes smaller than the initial state due to the creep deformation of the laminated rubber of the laminated rubber bearing, the ball screw 2 and the ball nut 3 can be installed in a posture corresponding to the distance between the lower structure 11 and the upper structure 12. The brake 6 restrains the rotational movement of the rotating member 5 protruding from the outer periphery of the ball nut 3. With such a configuration, by fixing the rotating member 5 having a shape adapted to the arrangement of the brake 6 and the ball nut 3 and the form of the brake 6 to the ball nut 3, the restrictions on the arrangement of the brake 6 and the ball nut 3 and the form of the brake 6 can be reduced.

[0038] The brake 6 is a disk brake or a drum brake that restrains the rotational movement of the rotating member 5 fixed coaxially to the ball nut 3. Since the frictional force required to restrain the rotational movement of the rotating member 5 by the disk brake or the drum brake of the brake 6 is smaller than the frictional force required to directly restrain the translational movement between the upper structure and the lower structure, the present invention can restrain the relative displacement between the lower structure and the upper structure with a small frictional force. Thereby, the brake 6 can be configured in a small scale.

[0039] As described above, the embodiments of the wind-resistant device according to the present invention have been described, but the present invention is not limited to the above embodiments, and can be appropriately changed without departing from the gist thereof. For example, in the above embodiment, the ball screw 2 is attached to the upper structure 12 and the ball nut 3 is attached to the lower structure 11 via the bearing 4, but the ball screw 2 may be attached to the lower structure 11 and the ball nut 3 may be attached to the upper structure 12.

[0040] The ball screw 2 is rotatably attached to the upper structure 12 about the first end 2a via a ball joint 21, and the ball nut 3 is rotatably attached to the lower structure 11 about the mounting position by a bearing 4 having a first trunnion mechanism 41 and a second trunnion mechanism 42. The ball screw 2 may be rotatably attached to the upper structure 12 about a vertical axis passing through the first end 2a, and the bearing 4 may have only the first trunnion mechanism 41. The ball screw 2 is attached to the upper structure 12 via a ball spline 22, but may be attached to the upper structure 12 without providing the ball spline 22.

[0041] In the above embodiment, the brake 6 may be other than a disk brake or a drum brake. In the above embodiment, the rotating member 5 is disk-shaped, but the shape of the rotating member 5 may be other than disk-shaped. The brake 6 restricts the rotation of the rotating member 5 fixed to the ball nut 3, but the rotating member 5 may not be fixed to the ball nut 3 and may be configured to restrict the rotation of the ball nut 3.

[0042] In the above embodiment, the brake control unit 7 turns off the brake 6 when the predicted or measured wind external force acting on the upper structure is equal to or less than a predetermined value, or less than the predetermined value, and turns on the brake 6 when it is determined that the predicted or measured wind external force acting on the upper structure is equal to or greater than the predetermined value, or exceeds the predetermined value. The control of the brake 6 by the brake control unit 7 may be set as appropriate.

[0043] There are 17 international goals adopted at the United Nations Summit in September 2015, namely the "Sustainable Development Goals (SDGs)". The wind-resistant device according to this embodiment can contribute to the achievement of, for example, the goal of "11. Sustainable cities and communities" among the 17 goals of the SDGs.

Explanation of reference numerals

[0044] 1 Wind-resistant device 2 Ball screw 3 Ball nut 4 Bearing 5 Rotating member 6 Brake 7 Brake control unit 11 Lower structure 12 Upper structure 13 Seismic isolation layer 14 Building 15 Seismic isolation device 21 Ball joint 41 First trunnion mechanism 42 Second trunnion mechanism 411 Vertical axis 421 Horizontal axis

Claims

1. It is provided together with a seismic isolation device in a seismic isolation layer between a lower structure and an upper structure, a ball screw attached to one of the lower structure and the upper structure in a state where rotation around an axis is restricted, a ball nut attached to the other of the lower structure and the upper structure in a state where rotation around an axis is allowed and screwed onto the ball screw, a brake capable of restricting the rotational movement of the ball nut, and a brake control unit that controls the brake according to the wind external force acting on the upper structure. A wind-resistant device having these components.

2. The brake control unit turns off the brake when the wind external force acting on the upper structure is less than or equal to a predetermined value, or less than the predetermined value, and turns on the brake when it is determined that the wind external force acting on the upper structure is greater than or equal to the predetermined value, or exceeds the predetermined value. The wind-resistant device according to Claim 1.

3. The ball screw is rotatably attached around a vertical axis passing through the attachment position to the one structure and around a horizontal axis passing through the attachment position to the one structure and perpendicular to the axis, The ball nut is rotatably attached around a vertical axis passing through the attachment position to the other structure and around a horizontal axis passing through the attachment position to the other structure and perpendicular to the axis. The wind-resistant device according to Claim 1 or 2.

4. It has a rotating member fixed to the ball nut, protruding from the outer circumference of the ball nut, and rotating around the axis together with the ball nut, The brake can restrict the rotational movement of the rotating member. The wind-resistant device according to Claim 1 or 2.

5. The brake is a disk brake or a drum brake that restricts the rotational movement of the rotating member. The wind-resistant device according to Claim 4.

Images