JP5602478B2 - Bearing structure - Google Patents

Description

  The present invention relates to a bearing structure. More specifically, the present invention relates to a support structure that supports a structure constructed between two structures.

  Various to support structures such as crossing corridors, connecting bridges, and roofs erected between two buildings (constructions), and to support bridges erected between two piers (constructions) The support structure is used.

  For example, in Patent Document 1, as shown in FIG. 12, an edge of a structure (lower structure) 101 that supports one end (movable end side) of an upper structure 100 such as a bridge constructed between two buildings is provided. Two sets of movable supports 102 that can move in all directions in the horizontal plane are arranged, and two sets of fixed supports 104 are arranged on the edge of the structure (lower structure) 103 that supports the other end (fixed end side). Is input, the movable structure 102 mainly allows the displacement of the upper structure 100 such as the bridge or prevents the upper structure 100 from being lifted.

Japanese Utility Model Publication No. 5-96208

However, in the case of the support structure as shown in FIG. 12, when a horizontal force in a direction perpendicular to the upper structure 100 is generated due to an earthquake or a storm, the horizontal force q to be borne by the fixed support 104 needs to bear a moment. Therefore, if the horizontal force of the entire upper structure 100 is Qy, the distance from the center of the fixed support 104 to the center in the axial direction of the upper structure 100 is L, and the distance between the two fixed supports 104 is W,
q = Qy × L / W
Thus, the greater the axial length of the upper structure 100, the greater the horizontal force that must be borne. Therefore, when the length of the upper structure 100 in the axial direction is increased, the fixed support is increased in size, and the mounting portion 103a of the lower structure 103 on which the fixed support is mounted must be increased in size.

  Further, since the relative displacement in the direction perpendicular to the axial direction of the upper structure 100 is absorbed by the relative sliding of the upper and lower eyelids constituting the movable bearing 102, the movable bearing 102 is orthogonal to the axial direction of the upper structure 100. There is a problem that the size in the direction to be moved increases, and the mounting portion 101a of the lower structure 101 on which the movable support is mounted must be increased in size.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a support structure capable of downsizing the support and downsizing the lower structure on which the support is mounted.

The support structure of the present invention is a support structure that supports a long structure constructed between two structures,
A first movable bearing which is disposed at one end of the structure and is rotatable in a horizontal plane;
A second movable bearing disposed at the other end of the structure and movable in the longitudinal direction of the structure ;
The first movable bearing includes a third movable bearing that is a sliding bearing that can slide freely in all directions within a horizontal plane on both sides in the width direction of the structure .

In the bearing structure of the present invention, since the relative displacement in the direction perpendicular to the longitudinal axis of the long structure can be absorbed by the rotation of the long structure, the movable end side bearing (second movable bearing) The dimension in the direction perpendicular to the longitudinal axis of the long structure can be reduced. Thereby, the dimension of the direction orthogonal to the longitudinal direction axis | shaft of a elongate structure of the mounting part (lower structure) of the building which receives the said movable end side support can also be made small. As a result, material costs and construction costs can be reduced and downsizing can be achieved.
In addition, the horizontal force in the direction perpendicular to the longitudinal axis of the long structure is a structure in which the first movable support can rotate in a horizontal plane, so there is no need to consider the moment balance, and only the shear force is considered. Therefore, it is possible to reduce the size of the support at the fixed end and the size of the mounting portion of the building that receives it.

It is preferable that the second movable bearing is composed of a pair of movable bearings disposed along the width direction of the structure.

It is preferable that the vertical load on one end side of the structure is supported only by the third movable support.
The first movable support includes a lower rod having a circular recess on the upper surface, and an upper rod having a circular protrusion that can be inserted into the recess, and the upper flange has a tip surface of the protrusion. It may be arranged so as to be separated from the bottom surface of the recess by a predetermined distance.

  The first movable support includes a lower rod having a circular recess on the upper surface, and an upper rod having a circular protrusion that can be inserted into the recess, and a tip surface of the protrusion and a bottom surface of the recess A sliding member may be disposed between the two.

  The convex portion is composed of a small-diameter portion on the base side and a large-diameter portion on the tip side, and a stopper for restricting the upward movement of the large-diameter portion disposed by being inserted into the concave portion of the lower collar is provided. It is preferable that it is provided at the opening edge of the recess of the lower collar.

  The stopper is made of an L-shaped member, and the other side of the L-shaped member is the recess of the recess so that one side of the L-shaped member protrudes from the opening edge of the recess of the lower collar toward the center of the recess. It can be fixed to the outer periphery upper end.

  An annular sliding member facing each other can be slidably provided on the inner peripheral surface of the concave portion of the lower collar and the outer peripheral surface of the convex portion of the upper collar.

  According to the support structure of the present invention, it is possible to reduce the size of the support and to reduce the size of the lower structure on which the support is placed.

(A) is side explanatory drawing of one Embodiment of the support structure of this invention, (b) is A arrow directional view, (c) is B arrow directional view. (A) is a plane explanatory view of the first movable support on the fixed end side in the support structure shown in FIG. 1, (b) is a cross-sectional explanatory view thereof. It is a figure explaining the malfunction in the case of supporting a fixed end side at three places. (A) is a plane explanatory view of the third movable support on the fixed end side in the support structure shown in FIG. 1, and (b) is a cross-sectional explanatory view thereof. (A) is a plane explanatory view of the second movable support on the movable end side in the support structure shown in FIG. 1, (b) is a cross-sectional explanatory view of the same. (A) is a figure explaining the arrangement | positioning of the upper eyelid before rotation of a support structure, (b) is a figure explaining the arrangement | positioning of a lower eyelid similarly. (A) is a figure explaining the combination arrangement | positioning of the upper collar and lower collar before rotation of a support structure, (b) is a figure explaining the displacement of the upper structure after rotation. (A) is a plane explanatory view of the other example of the 1st movable support, and (b) is the section explanatory view. (A) is plane explanatory drawing of the modification of the 1st movable bearing shown by FIG. 2, (b) is the cross-sectional explanatory drawing. (A) is plane explanatory drawing of the modification of the 1st movable bearing shown by FIG. 8, (b) is the cross-sectional explanatory drawing. (A) is plane explanatory drawing of the modification of the 2nd movable support shown by FIG. 5, (b) is the cross-sectional explanatory drawing. (A) is a plane explanatory drawing of the conventional bearing structure, (b) is the same side explanatory drawing.

Embodiments of the support structure of the present invention will be described below in detail with reference to the accompanying drawings.
(A) of FIG. 1 is a side explanatory view of an embodiment of the support structure of the present invention, (b) is a view as seen from an arrow A, and (c) is a view as seen from an arrow B.

  The support structure is to support a long upper structure (structure) U such as a passageway or a connecting bridge constructed between two buildings (constructions) B1 and B2 that are adjacent to each other at a predetermined distance. The first movable bearing 1, the second movable bearings 2a and 2b, and the third movable bearings 3a and 3b are provided.

  The first movable support 1 is disposed at one end portion (fixed end, left end portion in FIG. 1) of the upper structure U and is rotatable in a horizontal plane. The second movable supports 2a and 2b are disposed at the other end (movable end, right end in FIG. 1) of the upper structure U, and are movable in the longitudinal direction (axial direction) of the upper structure U. The third movable bearings 3a and 3b are disposed on both sides of the first movable bearing 1 in the width direction of the upper structure U (in FIG. 1 (c), the first movable bearing 1 is in the middle and below). It can move in all directions within a horizontal plane. Hereinafter, each movable bearing will be described in order.

  The first movable support 1 is disposed on the axis of the upper structure U, that is, in the center in the width direction of the upper structure U. As shown in FIG. 2, the first movable support 1 has an upper rod 4 fixed to the lower surface of the upper structure U, and a mounting portion (lower structure) 5 of the building B1 that receives a load from the upper structure U. It consists of a lower arm 6 that is fixed.

  The lower collar 6 has a rectangular shape in plan view, and has a circular recess 7 on the upper surface. The upper collar 4 is also rectangular in plan view, and has a circular convex portion 8 that can be inserted into the concave portion 7 of the lower collar 6 on its lower surface. The inner diameter of the circular concave portion 7 and the outer diameter of the circular convex portion 8 are predetermined between the outer peripheral surface of the convex portion 8 and the inner peripheral surface of the concave portion 7 when the convex portion 8 is inserted into the concave portion 7. The gap c1 is set. On the outer peripheral surface of the convex portion 8 and the inner peripheral surface of the concave portion 7, annular sliding members 10a and 10b facing each other are respectively disposed. In FIG. 2, a relatively large gap is drawn between the sliding members 10a and 10b for easy understanding, but in reality, a slight gap (for example, 1 to 3 mm in the radial direction) is provided between the sliding members 10a and 10b. Only a certain amount of gap) exists. As a result, the upper rod 4 is restricted from moving in the in-plane direction with respect to the lower rod 6, but can rotate in the horizontal plane. The sliding members 10a and 10b can be made of, for example, a synthetic resin such as PTFE, a stainless steel thin plate (polishing plate), or the like.

  In the present embodiment, the front end surface 8a of the convex portion 8 of the upper collar 4 is disposed so as to be separated from the bottom surface 7a of the concave portion 7 of the lower collar 6 by a predetermined distance t. For this reason, the load from the upper structure U is not transmitted to the mounting part 5 which is a lower structure through the 1st movable support 1. The load from the upper structure U is transmitted to the mounting portion 5 through two third movable supports 3a and 3b which will be described in detail later.

Hereinafter, the merit when not applying a vertical load to the central first movable support 1 will be described.
For example, as shown in FIG. 1B, it is assumed that the pillars P of the upper structure U are provided at four locations at four corners. When the vertical load of the upper layer and the roof from the support part in the arrow A view of FIG. 1B is Wa, and the vertical load of the same level as the support part in the arrow B view of FIG. 1C is Wb. The vertical load that each movable bearing should bear depends on the bearing arrangement indicated by the dimensions c, d, and e in FIG.
Vertical load to be borne by the first movable bearing 1 = Wb × d / (4 × e)
Vertical load to be borne by the third movable bearing 3a = Wa / 4 + Wb × (d / 4 + c) / (2 × e)
Vertical load to be borne by the third movable bearing 3b = Wa / 4 + Wb × (d / 4 + c) / (2 × e)
Thus, the calculation is complicated.

  Moreover, if three bearings are arranged on the fixed end side, the upper structure U may not be supported at all three locations due to manufacturing errors of upper and lower collars constituting the bearings and construction errors in field construction. is there. That is, as shown in FIG. 3A, when the central movable support 1 is not in contact with the upper structure U and supports the upper structure U at two positions on both sides, or in FIG. As shown in the figure, there occurs a case where the movable support 3a at the end is not in contact with the upper structure U and supports the upper structure U at the remaining two places. In these cases, there is a possibility that a vertical load higher than the above-described design value may be applied to the bearing supporting the superstructure U. Therefore, a design with a large safety factor is required to ensure safety, and material costs And so on.

On the other hand, the vertical load to be borne by each movable bearing can be easily calculated regardless of the bearing arrangement dimensions c, d and e by not causing the first movable bearing 1 at the center of the fixed end to bear a vertical load. Can do. That is,
Vertical load to be borne by the first movable bearing 1 = 0 (zero)
Vertical load to be borne by the third movable bearing 3a = (Wa + Wb) / 4
Vertical load to be borne by the third movable bearing 3b = (Wa + Wb) / 4
Thus, calculation is easy.

  The third movable bearings 3a and 3b do not generate an unexpected excessive reaction force due to an offset load, and a vertical load is applied almost as designed, so there is no need to increase the safety factor. As a result, an increase in material costs due to an excessive safety design can be suppressed.

  As shown in FIG. 4, the third movable bearings 3 a and 3 b are each composed of an upper rod 14 fixed to the lower surface of the upper structure U and a mounting portion (lower structure) that receives a load from the upper structure U. ) It consists of a lower collar 16 fixed to 5.

  The lower collar 16 has a rectangular shape in plan view, and has a circular recess 17 on the upper surface. The upper collar 14 is also rectangular in plan view. A slide plate 13 made of a stainless steel thin plate is disposed on the lower surface of the upper collar 14, and the surface of the slide plate 13 is polished to reduce frictional resistance and improve slipperiness. An elastic body 15 such as rubber, a steel material 17a made of stainless steel, and a sliding material 18 made of a thin plate made of PTFE are disposed in the recess 17 of the lower rod 16 in order from the bottom surface. The steel material 17 a is a member for holding the sliding material 18, and the slide plate 13 is slidably disposed on the upper surface of the sliding material 18. Thereby, the upper eyelid 14 can move with respect to the lower eyelid 16 in all directions within the horizontal plane.

  As shown in FIG. 5, each of the second movable supports 2 a and 2 b includes an upper rod 24 fixed to the lower surface of the upper structure U, and a mounting portion (lower structure) that receives the load from the upper structure U. ) 11 and the lower arm 26 fixed to 11.

  The lower collar 26 has a rectangular shape in a plan view, and the ridges 21 are formed on the upper surface along the longitudinal direction. The upper collar 24 is also rectangular in plan view, and a concave groove 22 is formed on the lower surface thereof along the axial direction of the upper structure U. The width w <b> 1 of the groove 22 is set to be larger than the width w <b> 2 of the ridge 21, and the ridge 21 of the lower rod 26 can be inserted into the groove 22 of the upper rod 24. When the ridge 21 of the lower rod 26 is inserted into the groove 22 of the upper rod 24, a gap c2 is formed between the side surface 21a of the ridge 21 and the side surface 22a of the groove 22.

  Ceiling surface 22b of the recessed groove 22 (the surface located above when the upper flange 24 is disposed as shown in FIG. 5. The upper flange 24 is disposed so that the open surface of the recessed groove 22 faces upward. In this case, a circular recess 23 is formed.

  A slide plate 25 made of a stainless steel thin plate is disposed on the upper surface of the ridge 21 of the lower rod 26. The surface of the slide plate 25 is polished to reduce frictional resistance and improve slipperiness. Has been. Further, an elastic body 27 such as rubber, a steel material 28 made of stainless steel, and a sliding material 29 made of a thin plate made of PTFE are disposed in the recess 23 of the upper collar 24 in order from the ceiling surface. The steel material 28 is a member for holding the sliding material 29, and the sliding material 29 is slidably disposed on the upper surface of the slide plate 25. Thereby, the upper collar 24 is movable along the longitudinal direction of the upper structure U with respect to the lower collar 26. Further, the relative rotation of the upper rod 24 and the lower rod 26 in the horizontal plane is possible by the gap c2.

Next, a mechanism for absorbing relative displacement between buildings using the above-described embodiment will be described with reference to FIGS.
FIG. 6A is a diagram for explaining the arrangement of the upper collar before the rotation of the support structure, and FIG. 6B is a diagram for similarly explaining the arrangement of the lower collar. FIG. 7A is a view for explaining the combined arrangement of the upper and lower eyelids before rotation of the support structure.

  Three movable bearings are disposed at the end of the upper structure U on the fixed end side. Specifically, the third movable bearings 3a and 3b are disposed on both sides of the central first movable bearing 1. As described above, the first movable support 1 can rotate in the horizontal plane, and the third movable supports 3a and 3b can move in all directions in the horizontal plane.

  On the other hand, two second movable supports 2a and 2b are disposed near the both ends in the width direction of the upper structure U at the end of the upper structure U on the movable end side. The second movable bearings 2a and 2b are movable in the longitudinal direction of the upper structure U as described above.

  Here, it is assumed that the two buildings B1 and B2 are relatively moved by d1 in the vertical direction and d2 in the horizontal direction in FIG. At this time, since the first movable support 1 can rotate in the horizontal plane and the third movable supports 3a and 3b can move in all directions in the horizontal plane, the vertical movement is the rotation of the upper structure U. Can be absorbed. Further, the movement in the left-right direction can be absorbed by the second movable bearings 2a, 2b that are movable in the longitudinal direction of the upper structure U.

  In the present embodiment, since the relative displacement in the direction perpendicular to the longitudinal axis of the upper structure U can be absorbed by the rotation of the upper structure U in this way, the longitudinal axis of the upper structure U of the movable end side bearing is supported. The dimension in the direction orthogonal to the direction can be reduced. Thereby, the dimension of the mounting part (lower structure) of the building which receives the said movable end side support can also be made small in the direction orthogonal to the longitudinal axis of the upper structure U. As a result, material costs and construction costs can be reduced, and space saving can be achieved.

  Further, the horizontal force in the direction perpendicular to the longitudinal axis of the upper structure U is a structure in which the first movable support 1 is rotatable in a horizontal plane, so that it is not necessary to consider the moment balance, and only the shear force is considered. Therefore, it is possible to reduce the size of the support at the fixed end and the size of the mounting portion of the building that receives it.

  (A) of FIG. 8 is a plane explanatory view of another example of the first movable bearing, and (b) is a cross-sectional explanatory view thereof. The first movable bearing 31 shown in FIG. 8 is configured to bear a vertical load from the upper structure U, unlike the first movable bearing 1 shown in FIG.

  The first movable support 31 includes an upper rod 34 fixed to the lower surface of the upper structure U, and a lower rod 36 fixed to a mounting portion (lower structure) receiving a load from the upper structure U. Yes.

  The lower rod 36 has a rectangular shape in plan view, and has a circular first recess 37a on the top surface, and has a second recess 37b having a smaller diameter than the first recess 37a on the bottom surface of the first recess 37a. ing. The upper collar 34 also has a rectangular shape in plan view, and has a circular convex portion 38 that can be inserted into the first concave portion 37a of the lower collar 36 on the lower surface thereof. The inner diameter of the circular first concave portion 37a and the outer diameter of the circular convex portion 38 are the outer peripheral surface of the convex portion 38 and the inner periphery of the first concave portion 37a when the convex portion 38 is inserted into the first concave portion 37a. A predetermined gap c3 is set between the surface and the surface. On the outer peripheral surface of the convex portion 38 and the inner peripheral surface of the first concave portion 37a, annular sliding members 40a and 40b facing each other are respectively disposed. The sliding members 40a and 40b can be made of, for example, a synthetic resin such as PTFE, a stainless steel thin plate (polishing plate), or the like.

  A slide plate 33 made of a stainless steel thin plate is disposed on the lower surface of the upper collar 34, and the surface of the slide plate 33 is polished to reduce frictional resistance and improve slipperiness. An elastic body 45 such as rubber, a steel material 47 made of stainless steel, and a sliding material 48 made of a thin plate made of PTFE are disposed in the second recess 37b of the lower rod 36 in order from the bottom surface. The steel material 47 is a member for holding the sliding material 48, and the slide plate 33 is slidably disposed on the upper surface of the sliding material 48. As a result, the upper rod 34 can rotate in the horizontal plane with respect to the lower rod 36, but the horizontal movement is restricted.

  As shown in FIG. 8, if a movable bearing that bears a vertical load is used on the fixed end side, the end of the upper structure U is supported at three places on the fixed end side. There is a problem of over-design that allows for complexity (calculation of the vertical load that the bearing should bear) and safety, but it is possible to solve these problems to some extent by improving the manufacturing accuracy and construction accuracy of the bearing. .

  FIG. 9A is a plan explanatory view of a modification of the first movable support 1 shown in FIG. 2, and FIG. 9B is a cross-sectional explanatory view thereof. The first movable support 51 according to this modification is configured to be able to support the upward force of the upper structure U.

  As shown in FIG. 9, the first movable support 51 is fixed to an upper collar 54 fixed to the lower surface of the upper structure U and a mounting portion (lower structure) of a building that receives a load from the upper structure U. It consists of a lower arm 56.

  The lower collar 56 has a rectangular shape in plan view, and has a circular recess 57 on the upper surface. The upper collar 54 is also rectangular in plan view, and has a circular convex portion 58 that can be inserted into the concave portion 57 of the lower collar 56 on the lower surface thereof. In the present modification, the convex portion 58 includes a small-diameter portion 58a on the root side and a large-diameter portion 58b on the tip side.

  The inner diameter of the circular concave portion 57 and the outer diameter of the large diameter portion 58 b are between the outer peripheral surface of the large diameter portion 58 b and the inner peripheral surface of the concave portion 57 when the large diameter portion 58 b is inserted into the concave portion 57. It is set so that a predetermined gap c4 is formed. On the outer peripheral surface of the large-diameter portion 58b and the inner peripheral surface of the concave portion 57, annular sliding members 60a and 60b facing each other are respectively disposed. Thereby, the upper collar 54 is restricted from moving in the in-plane direction with respect to the lower collar 56, but can rotate in the horizontal plane.

  In this modification, a stopper 61 is provided at the opening edge of the recess 57 of the lower collar 56 to restrict the upward movement of the large diameter portion 58b of the upper collar 54 that is inserted into the recess 57. Yes. The stopper 61 is made of a member having an L-shaped cross section, and one side 61a of the L-shaped member protrudes from the opening edge of the recessed portion 57 of the lower collar 56 toward the center of the recessed portion. The other side 61 b is fixed to the side surface 56 a of the lower collar 56 by a bolt 62. By providing the stopper 61 that can be engaged with the large-diameter portion 58b of the upper collar 54, the lifting force of the upper structure U can be supported.

Such a stopper capable of supporting the lifting force can be applied to other movable bearings.
FIG. 10 shows an example in which a stopper is applied to the first movable bearing 31 shown in FIG. Also in this example, the stopper 71 made of a member having an L-shaped cross section is arranged so that one side 71a protrudes from the opening edge of the recess 77 of the lower collar 76 toward the center of the recess. 71 b is fixed to the side surface 76 a of the lower rod 76 by a bolt 72. By providing the stopper 71 that can be engaged with the large-diameter portion 78 b of the upper collar 74, the lifting force of the upper structure U can be supported.

  FIG. 11 shows an example in which a stopper is applied to the second movable bearing 2 shown in FIG. Also in this example, the stopper 81 made of a member having an L-shaped cross section is placed on the other side of the L-shaped member such that one side 81a protrudes below the wide portion 83 at the tip of the ridge 82 of the lower collar 86. The side 81 b is fixed to the side surface 85 a of the upper collar 85 by a bolt 84. By providing the stopper 81 that can be engaged with the wide portion 83 of the lower rod 86, the upward lifting force of the upper structure U can be supported.

  In each of the above-described embodiments, by providing an elastic body or a vertical or horizontal gap, inclination (omnidirectional rotation in the vertical plane) due to bending of the upper structure U can be absorbed.

[Other variations]
The support structure of the present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, in the above-described embodiment, a member called “upper gutter” is fixed to an upper structure such as a crossing corridor, and a member called “lower gutter” is fixed to a mounting portion of a building. It is also possible to fix a member called “upper rod” to the mounting part of the building and fix a member called “lower rod” to the upper structure.
Further, the number of movable bearings to be used, their arrangement, and their dimensions can be appropriately selected according to the type and scale of the superstructure to be supported.

DESCRIPTION OF SYMBOLS 1 1st movable bearing 2a 2nd movable bearing 2b 2nd movable bearing 3a 3rd movable bearing 3b 3rd movable bearing 4 Upper rod 5 Mounting part (fixed end side)
6 Lower rod 7 Concave portion 8 Convex portion 10a Sliding material 10b Sliding material 11 Placement portion (movable end side)
13 Slide plate 14 Upper collar 15 Elastic body 16 Lower collar 18 Sliding material 21 Convex strip 22 Groove 23 Recess 24 Upper collar 25 Slide plate 26 Lower collar 27 Elastic body 29 Sliding material 31 First movable support 33 Slide plate 34 Upper collar 36 Lower collar 37a First recess 37b Second recess 38 Protrusion 40a Sliding material 40b Sliding material 45 Elastic body 48 Sliding material 61 Stopper 71 Stopper 81 Stopper B1 Building B2 Building U Superstructure

Claims (8)

A support structure for supporting a long structure erected between two structures,
A first movable bearing which is disposed at one end of the structure and is rotatable in a horizontal plane;
A second movable bearing disposed at the other end of the structure and movable in the longitudinal direction of the structure ;
3. A bearing structure comprising a first movable bearing and a third movable bearing that is a sliding bearing that is slidable in all directions in a horizontal plane on both sides in the width direction of the structure. The support structure according to claim 1, wherein the second movable support is composed of a pair of movable supports arranged along a width direction of the structure. The bearing structure according to claim 1 or 2 , wherein a vertical load on one end side of the structure is supported only by the third movable bearing. The first movable support includes a lower rod having a circular recess on the upper surface, and an upper rod having a circular protrusion that can be inserted into the recess, and the upper flange has a tip surface of the protrusion. The support structure according to claim 3 , wherein the support structure is disposed so as to be separated from the bottom surface of the recess by a predetermined distance. The first movable support includes a lower rod having a circular recess on the upper surface, and an upper rod having a circular protrusion that can be inserted into the recess, and a tip surface of the protrusion and a bottom surface of the recess The support structure according to claim 1 , wherein a sliding member is disposed between the two . The convex portion is composed of a small-diameter portion on the base side and a large-diameter portion on the tip side, and a stopper for restricting the upward movement of the large-diameter portion disposed by being inserted into the concave portion of the lower collar is provided. , support structure according to claim 4 or claim 5 is provided on the opening edge of the recess of the lower shoe. The stopper is made of an L-shaped member, and the other side of the L-shaped member is the recess of the recess so that one side of the L-shaped member protrudes from the opening edge of the recess of the lower collar toward the center of the recess. The support structure according to claim 6 , wherein the support structure is fixed to an outer peripheral upper end. And the inner peripheral surface of the recess of the lower shoe, on the outer peripheral surface of the convex portion of the upper shoe, opposing annular sliding member according to any one of claims 4-7 which is provided slidably with each other Bearing structure.

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