Design method of a vibration isolation spherical steel support containing metal rubber and the support

Abstract

The application provides a design method and a support of a vibration isolation spherical steel support containing metal rubber, and the design method comprises the following steps: S1, determining the vertical design bearing capacity N of the vibration isolation spherical steel support S ; S2, determining the number n1 of metal rubber components according to the elastic load interval (N b , N c ); S3, calculating the vertical stiffness K1 of the metal rubber vibration isolation assembly according to the number n1 by using a formula; S4, calculating the vertical stiffness K and the basic frequency f of the vibration isolation spherical steel support; S5, judging whether the basic frequency f is less than or equal to f1 / (2^0.5), wherein f1 is the lower limit of the frequency of the dominant frequency band interval corresponding to the peak value of the reaction force of the vibration isolation spherical steel support caused by vehicle-induced vibration, if yes, the design is completed, and if no, the metal rubber component is redesigned, and the step S2 is returned until the condition of the step S5 is met. The application realizes the normal function of the support while making it have the vertical vibration isolation function, increases the bearing capacity by only changing the number of standard metal rubber components, and breaks through the design bottleneck of the bearing capacity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bridge structure, in particular to a design method of a metal-rubber-containing vibration isolation spherical steel support and the support. BACKGROUND

[0002] With the increasing number of urban infrastructure construction projects, more and more bridges shuttle in densely populated cities, and the vibration and noise pollution caused by the bridges seriously affect the surrounding environment and the quality of life. In engineering, the vibration and noise of the surrounding environment are usually controlled by using a vibration isolation support, and this type of support has gradually become a future development trend. At present, the vibration isolation support is mainly divided into two categories: one is a rubber vibration isolation support, which is limited by material and processing technology, and is mainly used in medium and small span bridges and has durability problems; the other is a vibration isolation spherical steel support, which usually adds one or more elastic materials with damping properties or adds a wedge, a lever, a magnetorheological material, etc. outside the support body structure, and is suitable for large-span space structures and large-span bridges, etc., and has the advantages of high bearing capacity, flexible rotation, good durability, long service life, etc.

[0003] Metal rubber is made of metal wire as raw material and does not contain any ordinary rubber, but has the same elasticity and porosity as rubber, and is particularly suitable for solving difficult problems such as damping vibration, filtering, sealing, throttling, and noise reduction in high and low temperature, large temperature difference, high pressure, high vacuum, strong radiation, and severe vibration environments. For example, the Chinese patent with publication number CN207277177U discloses a highway bridge support which uses metal rubber to replace traditional rubber to solve the durability problems such as aging and creep of traditional rubber supports; and the Chinese patent with publication number CN108442241A discloses a plate-type metal rubber support and a construction method thereof, which sets multiple steel plate layers in the metal rubber to make the metal rubber and the steel plate layers integrated, thereby solving the above-mentioned problems of traditional rubber and making the support have vibration isolation function. How to use metal rubber to achieve vibration isolation effect on the spherical steel support, especially the vertical vibration isolation function, needs further research.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The problem solved by the present application is that the prior art usually increases the size of the component to improve the vertical bearing capacity, which is limited by material manufacturing process, performance, etc. and results in limited bearing capacity.

[0006] To solve the above problems, the present application provides a design method of a metal-rubber-containing vibration isolation spherical steel support, comprising:

[0007] Step S1, determining the vertical design bearing capacity N of the vibration isolation spherical steel support S ;

[0008] Step S2, the number n1 of metal rubber components is determined according to the elastic load interval (N b ,N c ), and N S ×λ / N c ≤n1≤δ×N h / (N b ×λ), wherein N h is the dead load of the vibration isolation spherical steel support, and both δ and λ are safety factors; wherein δ is less than 1.0 and λ is greater than 1.0.

[0009] Step S3, the vertical stiffness K1 of the metal rubber vibration isolation assembly is calculated according to the number n1 by using the formula K1=k×n1 / n2, wherein n2 is the number of layers of the metal rubber, and k is the vertical stiffness of a single metal rubber component;

[0010] Step S4, the vertical stiffness K and the fundamental frequency f of the vibration isolation spherical steel support are calculated, and K=(K1×K2) / (K1+K2), f=(K / m)^0.5 / (2π), wherein K2 is the comprehensive vertical stiffness of the components of the vibration isolation spherical steel support except the metal rubber vibration isolation assembly, and m is the mass of the superstructure of the vibration isolation spherical steel support.

[0011] Step S5, it is judged whether the fundamental frequency f is less than f1 / (2^0.5), wherein f1 is the lower limit of the frequency of the dominant frequency band interval corresponding to the peak value of the reaction force of the vibration isolation spherical steel support caused by train-induced vibration, if yes, the design is completed, and if no, the metal rubber component is redesigned, and the step S2 is returned until the condition of the step S5 is met.

[0012] The present application avoids the dominant frequency band of the train vibration system by increasing the metal rubber vibration isolation layer and optimizing the vertical stiffness of the vibration isolation spherical steel support, so that the fundamental frequency of the mass-spring system formed by the vibration isolation spherical steel support and the superstructure is avoided, the sensitivity of the lower structure of the support and the surrounding environment to train vibration is reduced, and the environmental vibration hazard is managed.

[0013] The redesigned metal rubber component can be the adjustment of the elastic load interval, the vertical stiffness and the number of the metal rubber component. The design method of the present application is suitable for longitudinal, multidirectional and spherical steel supports, and can also be transverse and fixed spherical steel supports.

[0014] Preferably, the elastic load interval (N b ,N c ) in the step S2 is determined according to the vertical compression load N- deformation Δ curve of the metal rubber component. The vertical compression load N- deformation Δ curve of the cylindrical metal rubber component is as follows: Figure 1As shown, the loading characteristics of the entire process can be roughly divided into four stages: segment oa, segment ab, segment bc, and segment cd. Among them, segment bc is an approximately straight line segment, and the corresponding loads are the lower limit of the elastic load N of a single standard metal-rubber component. b and upper limit N c Then the service load range of a single metal-rubber component is (N) b1 N c1 ), where N b1 =δ×N h / n1、N c1 =N S / n1.

[0015] The present invention also provides a vibration-damping spherical steel bearing containing metal rubber, comprising an upper bearing plate, a middle bearing plate, and a lower bearing plate. An upper cover plate is disposed between the middle bearing plate and the upper bearing plate. A metal rubber vibration isolation assembly is disposed between the middle bearing plate and the upper cover plate, or between the middle bearing plate and the lower bearing plate, or between the upper cover plate and the upper bearing plate. The metal rubber vibration isolation assembly comprises metal rubber components evenly arranged on a circumference concentric with the middle bearing plate, and the metal rubber components are cylindrical.

[0016] The above arrangement ensures uniform stress distribution on individual metal-rubber components, resulting in high reliability. The metal-rubber components can also be annular or cylindrical, and their arrangement can be rectangular or a combination of other forms.

[0017] Preferably, the metal-rubber vibration isolation assembly further includes a substrate, with the metal-rubber components distributed on the upper and lower sides of the substrate. By setting the metal-rubber vibration isolation layer, the overall stiffness and fundamental frequency of the support can be changed, thereby avoiding the dominant frequency band where the support reaction force peaks when a train passes, effectively reducing the vibration hazards generated when a train passes, and achieving the control of environmental vibration hazards.

[0018] Preferably, the metal-rubber component is located between the middle seat plate and the upper cover plate.

[0019] Preferably, the top of the middle seat plate is provided with a groove for accommodating the metal rubber component; the metal rubber component is set higher than the groove and the diameter of the metal rubber component is smaller than the diameter of the groove, and the top of the metal rubber component abuts against the upper cover plate.

[0020] The metal-rubber component placed in the groove at the top of the middle seat plate needs to be exposed to a certain height so that the metal-rubber component can fully play its role in vibration isolation. At the same time, there is a certain circumferential gap between the metal-rubber component and the upper cavity of the middle seat plate, which facilitates the radial deformation of the metal-rubber component when it bears vertical load. The lower surface of the upper cover plate is in close contact with the upper surface of the vibration isolation layer composed of several metal-rubber components. There is a certain vertical gap between the upper cover plate and the middle seat plate in the circumferential direction, which facilitates the normal vertical displacement of the upper cover plate.

[0021] Preferably, a planar stainless steel sliding plate and a planar non-metallic sliding plate are arranged in abutment connection between the upper cover plate and the upper seat plate, and the planar stainless steel sliding plate is located above the planar non-metallic sliding plate. The planar stainless steel sliding plate and the planar non-metallic sliding plate form a planar friction pair to transmit a vertical load and ensure smooth horizontal sliding of the support.

[0022] Preferably, a spherical stainless steel sliding plate and a spherical non-metallic sliding plate are arranged in abutment connection between the lower seat plate and the middle seat plate, and the spherical stainless steel sliding plate is located above the spherical non-metallic sliding plate. The spherical stainless steel sliding plate and the spherical non-metallic sliding plate together form a spherical friction pair to ensure normal rotation function of the support.

[0023] Preferably, a guide friction pair composed of a guide stainless steel sliding plate and a guide non-metallic sliding plate is arranged between the upper seat plate and the lower seat plate. The guide friction pair can transmit a horizontal load of the support.

[0024] Compared with the prior art, the design method of the vibration isolation spherical steel support containing metal rubber and the support have the following beneficial effects: 1) the normal function of the support is realized while the vertical vibration isolation function is achieved, which provides a basis for the design of the vertical vibration isolation support; 2) the bearing capacity can be increased only by increasing the number of standard metal rubber components, which is simple and convenient and breaks through the design bottleneck of the bearing capacity of the support; 3) the overall height of the vibration isolation spherical steel support is low, the size of the components is small, and the weight is light, which can effectively reduce the cost of the support; 4) the standard metal rubber components in the metal rubber vibration isolation layer are uniformly arranged, the vertical stress is uniform, the vibration hazard caused by the train can be effectively reduced, and good social benefits can be achieved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 FIG. 1 is a structural schematic view of the vibration isolation spherical steel support according to Embodiment 1 of the present application;

[0026] Figure 2 FIG. 2 is another view of the vibration isolation spherical steel support according to Embodiment 1 of the present application;

[0027] Figure 3 FIG. 3 is a structural schematic view of the metal rubber component according to Embodiment 1 of the present application;

[0028] Figure 4 FIG. 4 is a planar arrangement view of the metal rubber component according to Embodiment 1 of the present application;

[0029] Figure 5 FIG. 5 is a vertical compression load N-deformation curve of the cylindrical metal rubber component according to Embodiment 1 of the present application;

[0030] Figure 6This is a schematic diagram of the vibration isolation spherical steel support described in Embodiment 2 of the present invention in the longitudinal direction of the bridge.

[0031] Figure 7 This is a schematic diagram of the vibration isolation spherical steel support in the transverse direction of the bridge as described in Embodiment 2 of the present invention.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1-Upper seat plate; 2-Flat stainless steel sliding plate; 3-Flat non-metallic sliding plate; 4-Upper cover plate; 5-Metal rubber component; 6-Middle seat plate; 7-Spherical stainless steel sliding plate; 8-Spherical non-metallic sliding plate; 9-Lower seat plate; 10-Guide stainless steel sliding plate; 11-Guide non-metallic sliding plate; 12-Base plate. Detailed Implementation

[0034] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, without conflict, the technical features of the various embodiments of the present invention can be combined with each other.

[0035] Example 1

[0036] like Figures 1-5 As shown, a design method and a bearing for a unidirectional movable spherical steel vibration isolation bearing containing metal rubber are disclosed. The vibration isolation spherical steel bearing includes an upper bearing plate 1, a middle bearing plate 6, and a lower bearing plate 9. An upper cover plate 4 is provided between the middle bearing plate 6 and the upper bearing plate 1. A metal rubber vibration isolation assembly is provided between the middle bearing plate 6 and the upper cover plate 4, or between the middle bearing plate 6 and the lower bearing plate 9, or between the upper cover plate 4 and the upper bearing plate 1. The metal rubber vibration isolation assembly includes metal rubber components 5 evenly arranged on a circumference concentric with the middle bearing plate 6. The metal rubber components 5 are cylindrical.

[0037] The metal rubber component 5 is located between the middle seat plate 6 and the upper cover plate 4. The top of the middle seat plate 6 is provided with a groove for accommodating the metal rubber component 5. The metal rubber component 5 is higher than the groove and the diameter of the metal rubber component 5 is smaller than the diameter of the groove. The top of the metal rubber component 5 abuts against the upper cover plate 4.

[0038] A planar friction pair consisting of a planar stainless steel sliding plate 2 and a planar non-metallic sliding plate 3 is provided between the upper cover plate 4 and the upper seat plate 1. A spherical friction pair consisting of a spherical stainless steel sliding plate 7 and a spherical non-metallic sliding plate 8 is provided between the lower seat plate 9 and the middle seat plate 6. A guide friction pair consisting of a guide stainless steel sliding plate 10 and a guide non-metallic sliding plate 11 is provided between the upper seat plate 1 and the lower seat plate 9.

[0039] The design method includes:

[0040] Step S1: Determine the vertical design bearing capacity N of the vibration isolation spherical steel support. S =5000kN and parameters such as horizontal load Nv, horizontal displacement D, and rotation angle θ;

[0041] Step S2, based on the elastic load range (N) b N c To determine the number n1 of the metal-rubber components, and N S ×λ / N c ≤n1≤δ×N h / (N b ×λ), the N h The dead load of the vibration-isolated spherical steel support is 3000kN, and δ and λ are safety factors, with values ​​of 0.6 and 1.3 respectively; according to Figure 5 The vertical compressive load N-deformation Δ curve of the metal-rubber component can be roughly divided into four stages: segment oa, segment ab, segment bc, and segment cd. Among them, segment bc is an approximately straight line segment, and the corresponding loads are the lower limit of the elastic load N of a single standard metal-rubber component. b =60kN and upper limit N c =320kN, where n1 takes values ​​from 21 to 23.

[0042] Step S3: Calculate the vertical stiffness K1 of the metal-rubber vibration isolation component using the formula K1 = k × n1 / n2, based on the quantity n1, where n2 is the number of metal-rubber layers and k is the vertical stiffness of a single metal-rubber component. Figure 5 The vertical compressive load N-deformation Δ curve of the metal-rubber structure is determined and taken as 186kN / mm; if n1 is 21, then the vertical stiffness of the metal-rubber vibration isolation component K1=k×n1 / n2=186×21 / 1=3906kN / mm.

[0043] Step S4: Calculate the vertical stiffness K and fundamental frequency f of the vibration isolation spherical steel support, where K = (K1 × K2) / (K1 + K2), f = (K / m)^0.5 / (2π), where K2 is the comprehensive vertical stiffness of the components of the vibration isolation spherical steel support excluding the metal rubber vibration isolation assembly, which is 5000 kN / mm, and m is the mass of the upper structure of the vibration isolation spherical steel support, which is 300000 kg. Thus, K = 2193 kN / mm and f = 13.6 Hz.

[0044] Step S5: Determine whether the fundamental frequency f ≤ f1 / (2^0.5), where f1 is the lower limit of the dominant frequency band corresponding to the peak value of the reaction force of the vibration isolation spherical steel support caused by vehicle vibration, which is 20Hz. Obviously, f=13.6≤20 / (2^0.5)=14.1Hz, which meets the design requirements.

[0045] Example 2

[0046] As shown in Figures 6-7 , a design method of a multi-directional active metal rubber vibration isolation spherical steel support and the support, the vibration isolation spherical steel support comprises an upper seat plate 1, a middle seat plate 6, and a lower seat plate 9, an upper cover plate 4 is arranged between the middle seat plate 6 and the upper seat plate 1, a metal rubber vibration isolation assembly is arranged between the middle seat plate 6 and the upper cover plate 4 or between the middle seat plate 6 and the lower seat plate 9 or between the upper cover plate 4 and the upper seat plate 1, the metal rubber vibration isolation assembly comprises metal rubber members 5 which are uniformly arranged on the circumference of the middle seat plate 6 and are in a cylindrical shape.

[0047] The metal rubber vibration isolation assembly further comprises a base plate 12, and the metal rubber members 5 have two sides and are respectively located on the upper and lower sides of the base plate 12. Preferably, the metal rubber members 5 need to be aligned in the vertical and horizontal directions. The metal rubber vibration isolation assembly is located between the middle seat plate 6 and the upper cover plate 4, a groove is arranged at the top of the middle seat plate 6 for accommodating the metal rubber members 5, the metal rubber members 5 are higher than the groove, and the diameter of the metal rubber members 5 is smaller than the diameter of the groove, and the top of the metal rubber members 5 abuts against the upper cover plate 4.

[0048] A planar friction pair composed of a planar stainless steel sliding plate 2 and a planar non-metallic sliding plate 3 is arranged between the upper cover plate 4 and the upper seat plate 1, a spherical friction pair composed of a spherical stainless steel sliding plate 7 and a spherical non-metallic sliding plate 8 is arranged between the lower seat plate 9 and the middle seat plate 6, and a guide friction pair composed of a guide stainless steel sliding plate 10 and a guide non-metallic sliding plate 11 is arranged between the upper seat plate 1 and the lower seat plate 9.

[0049] The design method comprises:

[0050] Step S1, determining the vertical design bearing capacity N of the vibration isolation spherical steel support and parameters such as horizontal load Nv, horizontal displacement D, and rotation angle θ, wherein N = 4500 kN. S

[0051] Step S2, determining the number n1 of the metal rubber members according to the elastic load interval (N b ,N c ), wherein N S ×λ / N c ≤n1≤δ×N h / (N b ×λ), N h is the dead load of the vibration isolation spherical steel support, which is 3000 kN, δ and λ are safety factors, and the values of δ and λ are 0.55 and 1.4 respectively. Figure 4 ​The metal rubber structure vertical compression load N-deformation Δ curve can be roughly divided into four stages: o-a section, a-b section, b-c section and c-d section, wherein the b-c section is an approximate straight line section, and the corresponding loads are the lower limit N b = 50 kN and the upper limit N c = 340 kN, wherein the value of n1 is 19-21.

[0052] Step S3, the vertical stiffness K1 of the metal rubber vibration isolation assembly is calculated according to the number n1 by using the formula K1 = k x n1 / n2, wherein n2 is the number of layers of the metal rubber, and k is the vertical stiffness of a single metal rubber component, which is determined according to the formula k = (N Figure 4 The vertical compression load N-deformation Δ curve of the metal rubber structure is determined to be 210 kN / mm; if n1 is 20, then the vertical stiffness K1 of the metal rubber vibration isolation assembly is K1 = k x n1 / n2 = 210 x 20 / 2 = 2100 kN / mm.

[0053] Step S4, the vertical stiffness K and the fundamental frequency f of the vibration isolation spherical steel support are calculated, and K = (K1 x K2) / (K1+K2), f = (K / m)^0.5 / (2π), wherein K2 is the comprehensive vertical stiffness of the components in the vibration isolation spherical steel support except the metal rubber vibration isolation assembly, which is 4500 kN / mm, and m is the mass of the upper structure of the vibration isolation spherical steel support, which is 270000 kg, so that K = 1432 kN / mm and f = 11.6 Hz.

[0054] Step S5, it is judged whether the fundamental frequency f is less than or equal to f1 / (2^0.5), wherein f1 is the lower limit of the frequency of the dominant frequency band interval corresponding to the peak value of the reaction force of the vibration isolation spherical steel support caused by train-induced vibration, which is 17 Hz, and obviously f = 11.6 ≤ 17 / (2^0.5) = 12.0 Hz, which meets the design requirements.

[0055] The support obtained by the above design method not only can realize the normal function of the support, but also has a vertical vibration isolation function, which can effectively reduce the vibration hazards caused by trains and realize the management of environmental vibration hazards. Meanwhile, the standard metal rubber components in the metal rubber vibration isolation layer are uniformly arranged and have uniform stress and good reliability. In the design of the previous vibration isolation support, the vertical bearing capacity is mainly improved by increasing the size of the components, but it is restricted by the manufacturing process, performance and other aspects of the components, and it is difficult to break through higher bearing capacity. However, in the present application, the bearing capacity can be increased by only increasing the number of standard metal rubber components, which is simple and convenient and breaks through the design bottleneck of the bearing capacity of the support.

[0056] Although the present application has been disclosed with reference to the above embodiments, the application is not limited to the above embodiments. It will be apparent to those skilled in the art that various modifications and changes can be made thereto without departing from the spirit and scope of the application. The scope of the application should be limited only by the appended claims.

Claims

1. A design method of a metal rubber-containing isolated spherical steel bearing, characterized by, Comprising: Step S1, determining the vertical design bearing capacity N of the vibration isolation spherical steel support S ; Step S2, based on the elastic load range (N) b N c The number n1 of the metal-rubber component (5) is determined by N. S ×λ / N c ≤n1≤δ×N h / (N b ×λ), the N h For the dead load of the vibration isolation spherical steel support, δ and λ are both safety factors; Step S3, according to the number n1, the formula is used to calculate the vertical stiffness K1=k×n1 / n2 of the metal rubber vibration isolation assembly, wherein n2 is the number of layers of the metal rubber component (5), and k is the vertical stiffness of a single metal rubber component (5); Step S4, the vertical stiffness K and the fundamental frequency f of the vibration isolation spherical steel support are calculated, and K=(K1×K2) / (K1+K2), f=(K / m)^0.5 / (2π) Wherein K2 is the comprehensive vertical stiffness of the parts of the vibration isolation spherical steel support except the metal rubber vibration isolation assembly, and m is the mass of the superstructure of the vibration isolation spherical steel support; Step S5, judge whether the fundamental frequency f is less than or equal to f1 / (2^0.5), wherein f1 is the lower limit of the frequency of the dominant frequency band interval corresponding to the peak value of the reaction force of the vibration isolation spherical steel support caused by vehicle-induced vibration, if yes, the design is completed, if not, the metal rubber component is redesigned, and the step S2 is returned until the step S5 condition is met.

2. The design method of the metal rubber-containing seismic isolation spherical steel bearing according to claim 1, characterized by, The elastic load range (N b ,N c ) is determined from the vertical compression load N—deformation Δ curve of the metal rubber member (5).

3. The design method of the metal rubber-containing seismic isolation spherical steel bearing according to claim 1, characterized by, The vibration isolation spherical steel support containing metal rubber comprises an upper seat plate (1), a middle seat plate (6) and a lower seat plate (9), an upper cover plate (4) is arranged between the middle seat plate (6) and the upper seat plate (1), a metal rubber vibration isolation assembly is arranged between the middle seat plate (6) and the upper cover plate (4) or between the middle seat plate (6) and the lower seat plate (9) or between the upper cover plate (4) and the upper seat plate (1), the metal rubber vibration isolation assembly comprises metal rubber components (5) arranged uniformly in a circle on the circumference of the middle seat plate (6), and the metal rubber components (5) are arranged in a cylindrical shape.

4. The design method of the metal rubber-containing seismic isolation spherical steel bearing according to claim 3, characterized by The metal rubber vibration isolation assembly further comprises a base plate (12), and the metal rubber components (5) are distributed on both sides of the base plate (12).

5. The design method of the metal rubber-containing seismic isolation spherical steel bearing according to claim 4, characterized by The metal rubber components (5) are located between the middle seat plate (6) and the upper cover plate (4).

6. The design method of the metal rubber-containing seismic isolation spherical steel bearing according to claim 5, characterized by A groove is arranged on the top of the middle seat plate (6) for accommodating the metal rubber components (5), the metal rubber components (5) are higher than the groove, the diameter of the metal rubber components (5) is smaller than the diameter of the groove, and the top of the metal rubber components (5) abuts against the upper cover plate (4).

7. The design method of the metal rubber contained seismic isolation spherical steel bearing according to claim 3, characterized in that, A planar stainless steel sliding plate (2) and a planar non-metallic sliding plate (3) are arranged between the upper cover plate (4) and the upper seat plate (1) and are connected in abutment, and the planar stainless steel sliding plate (2) is located above the planar non-metallic sliding plate (3).

8. The design method of the metal rubber-containing seismic isolation spherical steel bearing according to claim 7, characterized by, A spherical stainless steel sliding plate (7) and a spherical non-metallic sliding plate (8) are arranged between the lower seat plate (9) and the middle seat plate (6) and are connected in abutment, and the spherical stainless steel sliding plate (7) is located above the spherical non-metallic sliding plate (8).

9. The design method of the metal rubber-containing seismic isolation spherical steel bearing according to claim 8, characterized by, A guide friction pair composed of a guide stainless steel sliding plate (10) and a guide non-metallic sliding plate (11) is arranged between the upper seat plate (1) and the lower seat plate (9).

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