JP4843882B2 - Vibration control device using inertia force installed between building layers - Google Patents

Description

【００２６】
また、ラック・ピニオン機構２２で構成される回転慣性機構は、小型軽量に構成し得ることから、建物平面利用計画上の制約を受けずに柱・梁架構内の空間に収納して設置可能であり、これ故、特に設置スペースを広く確保する必要が無く、居住スペースを減じることがない。
【００２７】
図４は本発明の他の実施形態を示す側面図である。この実施形態では制振装置における層間の動きを増幅して出力端に出力する増幅機構及び慣性機構として、揺動端に付加質量としての錘３２を取り付けたレバー機構１３８を採用した場合を例示している。即ち、第１取付部材２４と第２取付部材２６とには、これらに直角に交差するようにしてレバー３８ａ．３８ｂを一対で取り付けている。一方の第１レバー３８ａはその一端に長手方向に沿って力点部４０として形成された長穴４２が第２取付部材２６に立設された係合ピン４４に係合されるとともに、中央部が支点部４６として第１取付部材２４に立設された回動軸４８に軸支され、他端の揺動端に錘３２が付加質量として取り付けられている。他方の第２レバー３８ｂは、第１レバー３８ａとは逆に、中央部の支点部４６が第２取付部材２６の回動軸４８に軸支され、一端に力点部４０として形成された長穴４２が第１取付部材２４の係合ピン４４に係合されている。
【００２８】
そして、当該構成によれば、建物２の上下階間に生じた層間変位が、第１，第２取付部材２４，２６にそれぞれ軸方向に沿った逆方向の相対移動として伝わると、第１レバー３８ａと第２レバー３８ｂとが各々の支点部４６を中心にして揺動回転され、揺動端の錘３２が往復揺動回転して慣性力が発生し、当該慣性力が反力となって制振効果が発揮される。この場合にあっても、慣性力は錘３２の質量やその回転半径、増幅機構としてのレバー比を適宜に設定することで、慣性機構を用いていない従来の場合よりも定点での伝達率を容易に大幅に下げることが可能になり、よって大きな制振効果（減衰を上げること）が実現できる。また、このレバー機構１３８による慣性機構は、前述の実施形態と同様に、柱６と梁８とで囲まれた架構内の空間に収納して設置可能なため、特に設置スペースを広く確保する必要が無く、居住スペースを減じることがない。
【００２９】
なお、以上の各実施形態の説明にあっては、層間の動きを増幅して出力端に出力する増幅機構及び慣性機構として、ラック・ピニオン機構２２やレバー機構１３８を例示しているが、本発明はこれらに限らず、付加質量体としての錘を取り付けたボールナット機構やトグル機構も採用することができる。
【００３０】
【発明の効果】
以上、実施形態で説明したように、本発明に係る慣性力を利用した制振装置にあっては、建物上下階の層間に、該層間の動きを増幅して出力端に出力する増幅機構を設けると共に、該増幅機構の出力端に付加質量体を取り付けて慣性機構を構成し、地震や風等によって建物の上下階間に生じる層間変位を、該出力端の質量体の運動に変換して伝えて慣性力を発生させるようにしたので、当該慣性力で建物を制振することができる。また、慣性機構を用いることで、層間の変形速度に対する応答（制御力）に位相遅れが生じるのを防止でき、制振力の大幅な改善が図れる。
【００３１】
増幅機構および慣性機構を、ピニオンに付加質量体を取り付けたラック・ピニオン機構または揺動端に付加質量体を取り付けたレバー機構となして、付加質量体を往復揺動回転させて回転慣性力を発生させるようにすると、回転慣性力の大きさは回転半径の２乗に比例し、回転速度に比例したものになるので、建物の層間変位の往復直進運動をラック・ピニオン機構のギヤ比（増幅率）やレバー機構のレバー比、並びに付加質量体の回転半径及び質量をそれぞれ適宜に設定することで、所望の回転慣性力（即ち減衰力）を容易に得ることができ、しかも小さい負荷質量で大きな慣性力が得られるから、小型軽量に構成しつつ容易に固有振動数を下げることが可能となる。
【００３２】
また、ラック・ピニオン機構やレバー機構で構成される回転慣性増幅機構は、小型軽量に構成し得ることから、建物平面利用計画上の制約を受けずに柱・梁架構内の空間に収納して設置可能であり、これ故、特に設置スペースを広く確保する必要が無く、居住スペースを減じることがない。
【００３３】
更に、取付部材をダンパーを有したブレースとすることで、建物の振動減衰をより促進することができる
慣性機構と取付部材とにより共振点が形成されるが、ダンパーの減衰定数を定点理論の最適値に設定して慣性機構の大きさを調整することによって、慣性機構を用いない場合よりも定点での伝達率を大幅に下げることが可能になり、よって大きな制振効果（減衰を上げること）が実現できる。
【図面の簡単な説明】
【図１】本発明に係る制振装置の一実施形態を示す概略構成図である。
【図２】図１の制振装置を設けた建物の伝達関数を示すグラフである。
【図３】図１の制振装置を設けた建物の応答速度に対する制御力の位相関係を示すグラフである。
【図４】本発明に係る制振装置の他の実施形態を示す概略構成図である。
【図５】ブレースにダンパーを介在させた従来の制振装置の概略構成図である。
【図６】図５の従来の制振装置を設けた建物の伝達関数を示すグラフである。
【図７】図５の従来の制振装置を設けた建物の応答速度に対する制御力の位相関係を示すグラフである。
【符号の説明】
２ 建物
６ 柱
８ 梁
１０ ブレース
２０ 増幅機構
２２ ラック・ピニオン機構
２４ 第１取付部材
２６ 第２取付部材
２８ ラック
３０ ピニオン
３２ 錘（付加質量体）
３６ フライホイール（付加質量体）
１３８ レバー機構
３８ａ，３８ｂ レバー
４０ 力点部
４６ 支点部[0001]
BACKGROUND OF THE INVENTION
The present invention converts an interlayer displacement generated between upper and lower floors of a building into a motion such as rotation or swinging of a mass body, and controls the building by the inertial force. It relates to the vibration control device used.
[0002]
[Prior art]
As shown in FIG. 5, as a vibration control device 4 for a building 2, one end of a brace 10 installed in an internal space of a frame surrounded by an interlayer column 6 and a beam 8 or an intermediate member thereof is used as a mounting member. A method of absorbing vibration energy through the damper 12 is widely and generally employed.
Thus, the vibration damping effect when the damper 12 is provided between the layers via the attachment members such as the brace 10 can also be explained from the fixed point theory of the building transfer function.
[0003]
That is, according to this fixed point theory, as shown in FIG. 6, the intersection of the building transfer function when the damping constant of the damper 12 is zero and the building transfer function when the damping constant of the damper 12 is infinite is The building transfer function always passes through whatever value the damping constant of the damper 12 is set to. This point is called a fixed point of the building transfer function, and the damper 12 having an attenuation constant that makes this fixed point a peak is the optimum damper.
[0004]
[Problems to be solved by the invention]
However, the damper mounting member extending in the height direction in order to transmit the interlayer displacement between the upper layer and the lower layer of the building to the damper 12 has a limit in rigidity, and even when the brace 10 is used as the damper mounting member, In general, the rigidity of the building itself is often only about 10 to 20% of the layer rigidity. In such a case, sufficient vibration energy is not transmitted to the damper 12, and as a result, the vibration damping effect is limited to an extent that increases the damping constant of the building 2 by several percent.
[0005]
In other words, in order to obtain a sufficient damping effect, it is necessary to increase the rigidity of the mounting member of the damper 12, and for that purpose, a large member must be used or the number of installation locations of the damper 12 must be increased. As a result, the space was reduced, and the limit was imposed on the plan for using the building floor.
[0006]
Also, from the viewpoint of fixed point theory, if the natural frequency when the damping constant of the damper is 0 and the natural frequency when the damping constant is infinite, the fixed point has a high transmissibility. In this state, even if the optimum damper is used, a large damping effect cannot be expected because the fixed point itself is at a high position.
[0007]
The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a vibration damping device that can be installed without reducing a living space and that can obtain a sufficiently large vibration damping force. .
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the vibration damping device using the inertial force installed between the building layers according to the present invention is provided between the upper and lower floors of the building, and amplifies the movement between the layers to output the output terminal. A damping device using an inertial force installed between building layers , comprising an amplifying mechanism that outputs to the power source and an additional mass attached to the output end of the amplifying mechanism, and damping the building with the inertial force of the output end The amplification mechanism is a rack and pinion mechanism, and an additional mass body is attached to the pinion.
[0010]
In addition, the first mounting member that extends from the upper floor side and the first mounting member that extends from the lower floor side and is installed in parallel along the first mounting member in the frame surrounded by the pillars and beams of the building. 2 mounting members, a pair of the racks are provided on both the first mounting member and the second mounting member so as to face each other, and the pinion is engaged with and sandwiched between the pair of racks. It can also be done.
[0011]
Alternatively, an amplification mechanism that is provided between the upper and lower floors of the building, amplifies the movement between the layers and outputs the amplified output to the output end, and an additional mass attached to the output end of the amplification mechanism, A vibration damping device that uses a inertial force to suppress a building with an inertial force and is installed between building layers, wherein the amplification mechanism is a lever mechanism, and an additional mass body is attached to a swinging end of the lever mechanism. In the frame surrounded by the pillars and beams of the building, the first mounting member extending from the upper floor side and the first mounting member extending from the lower floor side and installed in parallel along the first mounting member 2 is provided, and a fulcrum portion is pivotally supported on one of the first attachment member and the second attachment member, and a force point portion is engaged with the other to provide the lever mechanism. It is characterized by.
[0013]
Furthermore, the mounting member is preferably a brace having a damper at one end thereof.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a vibration damping device using inertial force installed between building layers of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a vibration damping device according to the present invention. The vibration damping device of the present invention is basically provided between the upper and lower floors of the building 2 and amplifies the movement between the layers and outputs it to the output end, and the output end of the amplification mechanism 20 An additional mass body such as a weight 32 attached thereto is provided, and the building 2 is damped by the inertial force of the output end including the additional mass body.
[0015]
In the present embodiment, as shown in the figure, a rack and pinion mechanism 22 that takes out the horizontal relative displacement amount due to the interlayer displacement between the upper and lower floors as the rotation amount of the output side member is adopted as the amplification mechanism 20. Yes. The rack and pinion mechanism 22 is provided in a frame surrounded by the pillar 6 and the beam 8 of the building 2. In this frame, one end is fixed to the upper floor side portion of one pillar 6 and the one end is fixed to the lower floor side portion of the other pillar 6 and the first mounting member 24 extending along the diagonal line of the frame. And a second mounting member 26 extending in parallel along the first mounting member 24, and the rack members 28 a and 28 b of the rack and pinion mechanism 22 are provided on both the first mounting member 24 and the second mounting member 26. Are opposed to each other, and a pair of racks 28a and 28b are engaged with each other to pinch the pinion 30 therebetween.
[0016]
The other end of the second mounting member 26 on the extending side is provided with a damper 12 by connecting the upper mounting side beam 8 to the beam 8 on the upper floor side. The second mounting member 26 is a brace provided with the damper 12. 10 is configured to function. Here, a hydraulic type, a friction type, etc. can be adopted as the damper 12. The first mounting member 24 and the second mounting member 26 are provided with a pair of connecting members 34a and 34b for connecting them to each other and maintaining the parallelism. These connecting members 34a and 34b are fixed to one of the mounting members 24 and 26 and slidably engaged with the other. Here, the extending end side of each mounting member 24, 26 is a fixed portion, and the connecting member 34 a is fixed in the vicinity of the extending end of the first mounting member 24 so as to be slidable on the second mounting member 26. The connecting member 34b is fixed in the vicinity of the extending end of the second mounting member 26, and is slidably engaged with the first mounting member 24, so that both the mounting members 24 and 26 in the axial direction are engaged. Relative movement is allowed.
[0017]
A disk-like flywheel 36 is integrally attached to the end surface of the pinion 30 as an additional mass body, and a plurality of weights 38 as additional mass bodies are radially arranged at equal intervals on the outer peripheral surface of the flywheel 36. Are provided integrally. The additional mass flywheel 36 is attached to both ends of the pinion in the axial direction so that the flywheel 36 sandwiches both sides of the attachment members 24 and 26 to prevent the pinion 30 from falling off the racks 28a and 28b. You may make it do.
[0018]
In the vibration damping device of the present embodiment configured as described above, when the building 2 is vibrated by an earthquake or wind, and the interlayer displacement occurs on the upper and lower floors, the first and second mounting members 24 and 26 are While being kept parallel by the connecting members 34a and 34b, they move relative to each other in the opposite direction along the axial direction, and accordingly, pinions 30 meshed with the racks 28a and 28b of the first and second mounting members 24 and 26 are added. The mass flywheel 36 and the weight 32 rotate together.
[0019]
Therefore, the rotating mass body composed of the pinion 30, the flywheel 28 and the weight 32 constitutes a rotating inertia mechanism, and generates a rotating inertia force in accordance with the interlayer displacement of the building 2. Then, the building 2 can be damped by using this rotational inertia force as a reaction force. At this time, since the second mounting member 26 mainly functions as the brace 10 and receives this as a strong axial compressive force with respect to the interlayer displacement load, it can sufficiently cope with a large amount of interlayer displacement. Even when an excessive interlayer displacement occurs between the upper and lower floors of the building 2 due to a large earthquake or the like, the vibration damping function can be sufficiently secured.
[0020]
As is well known, the rotational inertia force differs depending on the rotational speed, the mass of the weight 32 and the rotational radius even if the total mass of the pinion 30 and the flywheel 36 of the additional mass body is constant. The magnitude of the rotational inertia force is proportional to the square of the radius of rotation and proportional to the rotational speed, but the reciprocal rectilinear motion of the racks 28a and 28b accompanying the interlayer displacement of the building 2 is reciprocally oscillated. By appropriately setting the gear ratio (amplification factor) of the rack and pinion mechanism that converts to rotational motion and the rotational radius and mass of the weight 32 that is an additional mass body, a desired rotational inertia force (ie, damping force) can be obtained. Can be easily obtained.
[0021]
That is, the natural frequency when the damping constant of the damper 12 is infinite is determined by the rigidity of the mounting members 24 and 26. If the rigidity cannot be changed, the natural vibration when the damping constant of the damper 12 is zero. You can devise to reduce the number. In order to reduce the natural frequency, it is sufficient to increase the inertia term in the vibration equation. As a method for this, a rack that takes out the horizontal relative displacement amount of the upper and lower floors as the rotation amount of the output side member as described above. Using the pinion mechanism 22, it is useful to assemble a rotary inertia mechanism that converts the interlayer displacement into the rotary inertia force of the mass body.
[0022]
As described above, the rotary inertia mechanism is proportional to the square of the radius of the rotary mass body by keeping the total mass of the rotary mass body the same by increasing the radius from the rotation axis to the installation position of the additional mass weight. Since a rotational inertia force can be obtained, and thus a large inertia force can be obtained with a small load mass, the natural frequency can be easily lowered while configuring a small and light weight. However, when such an inertia mechanism such as the rack and pinion mechanism 22 is used, a new resonance point is formed by the inertia mechanism and the mounting members 24 and 26, and this resonance point makes the damper 12 infinite. Appears at a frequency higher than the natural frequency. Then, when this frequency approaches the natural frequency when the damper 12 is made infinite, a new fixed point with a high transmission rate is constructed, so that the optimum value for the size of the inertia mechanism and the damping constant of the damper 12 is set. Will exist. Therefore, by adjusting these, it is possible to significantly reduce the transmission rate at a fixed point as compared with the case where the inertia mechanism is not used, and thus it is possible to realize a large damping effect (increase the damping).
[0023]
FIG. 2 shows that in the embodiment of FIG. 1, the mass of the rotary inertia mechanism of the vibration damping device in the lowermost layer is the primary vibration under the condition that the rigidity of the damper mounting members 24 and 26 is 10% of the rigidity of the building 2. The mass of the rotary inertia mechanism of the intermediate layer is adjusted for the third frequency, the mass of the rotary inertia mechanism of the uppermost layer is adjusted for the secondary frequency, and the damping of each layer The dampers of the device represent the transfer function as a result of arranging the optimum dampers of the fixed point theory for each. In this way, it is possible to achieve a greater vibration damping effect by adjusting all layers to a specific order.
[0024]
On the other hand, FIG. 6 shows an arrangement of an optimal damper 12 according to the fixed point theory in the conventional vibration damping device of FIG. 5 under the condition that the rigidity of the damper mounting member (brace 10) is 10% of the layer rigidity of the building itself. The result of the transfer function when the peak of the transfer function is lowered is shown. 3 and 7 show the same phenomenon that the vibration damping effect is improved by using the rotary inertia mechanism by the rack and pinion mechanism 22 in addition to the brace 10 having the damper 12, and the control for the response. This will be described from the physical aspect of the phase delay of the force (force applied to the brace). As shown in these drawings, the present embodiment of FIG. Since the phase of the response (control force) to the speed is 180 degrees, the phase delay as in the conventional example of FIG. 7 does not occur. Further, the table below shows a comparison of the attenuation constants of the present embodiment and the conventional example. It can also be seen from the table that the damping constant is improved by a factor of 3 or more by using the rotary inertia mechanism.
[0025]
[Table 1]

[0026]
In addition, since the rotary inertia mechanism composed of the rack and pinion mechanism 22 can be configured to be small and light, it can be stored and installed in the space in the pillar / beam frame without being restricted by the plan for using the building plane. Therefore, it is not necessary to secure a wide installation space, and the living space is not reduced.
[0027]
FIG. 4 is a side view showing another embodiment of the present invention. In this embodiment, a case where a lever mechanism 138 in which a weight 32 as an additional mass is attached to the swing end is employed as an amplification mechanism and an inertia mechanism that amplifies the movement between layers in the vibration control device and outputs the amplified motion to the output end. ing. That is, the first mounting member 24 and the second mounting member 26 are provided with levers 38a. A pair of 38b are attached. One of the first levers 38a has an elongated hole 42 formed at one end thereof as a force application point 40 along the longitudinal direction and is engaged with an engagement pin 44 erected on the second mounting member 26 , and a central portion thereof. A fulcrum portion 46 is pivotally supported on a rotating shaft 48 erected on the first attachment member 24 , and a weight 32 is attached as an additional mass to the swinging end at the other end. On the other hand, the second lever 38b has an elongated hole formed as a force point portion 40 at one end thereof, with the fulcrum portion 46 at the center portion pivotally supported by the rotation shaft 48 of the second mounting member 26 , contrary to the first lever 38a. 42 is engaged with the engaging pin 44 of the first mounting member 24 .
[0028]
And according to the said structure, if the interlayer displacement which arose between the upper and lower floors of the building 2 is transmitted to the 1st, 2nd attachment members 24 and 26 as a relative movement of the reverse direction along an axial direction, respectively, a 1st lever 38a and the second lever 38b are oscillated and rotated about the respective fulcrum portions 46, the weight 32 at the oscillating end is reciprocally oscillated and rotated to generate an inertial force, and the inertial force becomes a reaction force. Damping effect is demonstrated. Even in this case, the inertia force can be set to a fixed point transmission rate as compared with the conventional case in which the inertia mechanism is not used by appropriately setting the mass of the weight 32, its radius of rotation, and the lever ratio as an amplification mechanism. It can be easily lowered significantly, and thus a large vibration damping effect (raising damping) can be realized. Further, the inertia mechanism by the lever mechanism 138 can be housed and installed in a space surrounded by the pillar 6 and the beam 8 as in the above-described embodiment, so that it is particularly necessary to secure a wide installation space. There is no reduction in living space.
[0029]
In the description of each of the above embodiments, the rack and pinion mechanism 22 and the lever mechanism 138 are exemplified as the amplification mechanism and the inertia mechanism that amplify the motion between the layers and output to the output end. The invention is not limited to these, and a ball nut mechanism or a toggle mechanism to which a weight as an additional mass body is attached can also be employed.
[0030]
【The invention's effect】
As described above, in the vibration damping device using the inertial force according to the present invention, an amplification mechanism that amplifies the movement between the layers and outputs it to the output end is provided between the upper and lower floors of the building. At the same time, an additional mass body is attached to the output end of the amplification mechanism to form an inertia mechanism, and the displacement between the upper and lower floors of the building due to an earthquake or wind is converted into the motion of the mass body at the output end. Since the inertial force is generated through the transmission, the building can be damped by the inertial force. Further, by using the inertia mechanism, it is possible to prevent a phase lag from occurring in the response (control force) to the deformation speed between the layers, and the vibration damping force can be greatly improved.
[0031]
The amplifying mechanism and inertial mechanism are either a rack / pinion mechanism with an additional mass body attached to the pinion or a lever mechanism with an additional mass body attached to the oscillating end. When generated, the magnitude of the rotational inertia force is proportional to the square of the radius of rotation and proportional to the rotational speed. Therefore, the reciprocal rectilinear movement of the interlayer displacement of the building is increased by the gear ratio (amplification of the rack and pinion mechanism) Ratio), the lever ratio of the lever mechanism, and the rotation radius and mass of the additional mass body can be set appropriately, so that a desired rotational inertia force (ie, damping force) can be easily obtained, and with a small load mass. Since a large inertial force can be obtained, it is possible to easily reduce the natural frequency while forming a small and lightweight structure.
[0032]
In addition, since the rotary inertia amplifying mechanism composed of a rack and pinion mechanism and a lever mechanism can be made compact and lightweight, it can be stored in the space inside the column and beam frame without being restricted by the plan for using the building plane. Therefore, it is not necessary to secure a wide installation space, and the living space is not reduced.
[0033]
Furthermore, by using a brace with a damper as the mounting member, a resonance point is formed by the inertia mechanism and the mounting member that can further promote vibration damping of the building. By setting the value to adjust the size of the inertial mechanism, it becomes possible to significantly reduce the transmission rate at a fixed point compared to the case where the inertial mechanism is not used, and thus a large damping effect (raising damping). Can be realized.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a vibration damping device according to the present invention.
2 is a graph showing a transfer function of a building provided with the vibration damping device of FIG. 1;
3 is a graph showing a phase relationship of control force with respect to response speed of a building provided with the vibration damping device of FIG. 1;
FIG. 4 is a schematic configuration diagram showing another embodiment of the vibration damping device according to the present invention.
FIG. 5 is a schematic configuration diagram of a conventional vibration damping device in which a damper is interposed in a brace.
6 is a graph showing a transfer function of a building provided with the conventional vibration damping device of FIG.
7 is a graph showing the phase relationship of the control force with respect to the response speed of the building provided with the conventional vibration damping device of FIG.
[Explanation of symbols]
2 Building 6 Pillar 8 Beam 10 Brace 20 Amplifying mechanism 22 Rack and pinion mechanism 24 First mounting member 26 Second mounting member 28 Rack 30 Pinion 32 Weight (additional mass body)
36 Flywheel (additional mass)
138 Lever mechanism 38a, 38b Lever 40 Force point 46 Support point

Claims (4)

An amplification mechanism provided between the upper and lower floors of the building, which amplifies the movement between the layers and outputs the amplified movement to the output end; and an additional mass attached to the output end of the amplification mechanism, and the inertial force of the output end A vibration control device that uses the inertial force installed between building layers ,
A vibration damping device using inertial force installed between building layers, wherein the amplification mechanism is a rack and pinion mechanism, and an additional mass is attached to the pinion. A first mounting member that extends from the upper floor side and a second mounting that extends from the lower floor side and is installed in parallel along the first mounting member in a frame surrounded by pillars and beams of the building A pair of racks are provided on both the first mounting member and the second mounting member so as to face each other, and the pinion is engaged between and sandwiched between the pair of racks. The vibration damping device using inertial force installed between building layers according to claim 1 . An amplification mechanism provided between the upper and lower floors of the building, which amplifies the movement between the layers and outputs the amplified movement to the output end; and an additional mass attached to the output end of the amplification mechanism, and the inertial force of the output end A vibration control device that uses the inertial force installed between building layers,
The amplification mechanism is a lever mechanism, and an additional mass body is attached to the swing end of the lever mechanism ,
A first mounting member that extends from the upper floor side and a second mounting that extends from the lower floor side and is installed in parallel along the first mounting member in a frame surrounded by pillars and beams of the building A fulcrum is pivotally supported on one of the first attachment member and the second attachment member, and a force point is engaged on the other to provide the lever mechanism. A vibration damping device using inertia force installed between building layers. 4. The vibration damping device using inertial force installed between building layers according to claim 2, wherein the second mounting member is a brace having a damper at one end.

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