Seismic isolator for exhibits

A flat-type seismic isolator for exhibits includes a lower face plate installed on a foundation; an upper face plate that is installed to the lower surface of a seismic isolation object and placed above the lower face plate; an intermediate plate placed between the upper face plate and the lower face plate; and elastic restoring means and damping means provided for returning the plates to their original positions and placed in a lower area between the lower face plate and the intermediate plate and an upper area between the intermediate plate and the upper face plate, respectively. In the lower area, one lower linear guide rail is disposed in the center of the area and guide rails and rollers are disposed on opposite sides of the lower linear guide rail in parallel relation therewith for smoothly moving the intermediate plate with respect to the lower face plate in one linear direction. In the upper area, one upper linear guide rail is disposed in. the center of the area and guide rails and rollers are disposed on opposite sides of the upper linear guide rail in parallel relation therewith for smoothly moving the upper face plate with respect to the intermediate plate in one linear direction. The lower linear guide rail and the upper linear guide rail orthogonally cross each other, and the guide rails and rollers in the lower area and the upper area orthogonally cross each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a seismic isolator for exhibits that will protect exhibits at museums, art galleries, etc., from earthquakes and other vibrations.

2. Description of the Prior Art

FIG. 8 is a perspective view of a conventional seismic isolator that uses linear guide rails. A plurality of lower linear guide rails 2 are lined up in a single linear direction and fixedly attached to the upper surface of a support stand 1 , which is fixed to the top of a foundation.

A plurality of upper linear guide rails 4 are lined up in another linear direction, that is, a direction at a right angle to the lower linear guide rails 2 mentioned above, and fixedly attached to the lower surface of a pedestal carrying an exhibit, a display case, or other seismic isolation object 3 .

A coupling block 5 is placed between each of the lower linear guide rails 2 and the upper linear guide rails 4 . the lower section of the coupling block 5 is supported, through a ball, so that it can move smoothly along the lower linear guide rails 2 . The upper section of the coupling block 5 supports, through a ball and together with the upper linear guide rails 4 , the seismic isolation object 3 so that it can slide smoothly in the longitudinal direction of the upper guide rails 4 .

With this, the seismic isolation object 3 , within the length of the lower linear guide rails 2 and the upper guide rails 4 , is supported so that it can move smoothly in all horizontal directions. However, the ends of plural numbers of coiled restoring springs 6 , placed in parallel to the lower linear guide rails 2 and the upper linear guide rails 4 , are attached to the upper surface of the support stand 1 and the lower surface of the seismic isolation object 3 . They protect by restoring the seismic isolation object 3 to its original position before it moved horizontally, and by relieving vibrations in the horizontal direction.

FIG. 9 is a vertical cross sectional view of another conventional seismic isolator that uses curved faces. A plurality of support blocks 9 are installed in the lower surface of a lower face plate 7 by set screws 8 , and the lower face plate 7 is fixed to the top of a foundation that is not shown, through the support blocks 9 . Sphere support caps 10 are fixed to the upper surface of the lower face plate 7 , and spheres 11 are rotatably supported on top of the support caps 10 , through ball bearings.

An upper face plate 12 is placed above the lower face plate 7 , and a seismic isolation object, not shown, such as a pedestal carrying an exhibit or a display case, is installed on top of the upper face plate 12 .

A support plate 14 is fixedly attached to the lower surface of the upper face plate 12 , and a curved surface 1 II with a concave spherical shape is formed on the lower side of the plate 14 . The curved surface 13 is set on top of the sphere 11 , supporting the upper face plate 12 .

A bolt 15 is installed in the center of the lower surface of the upper face plate 12 . The bolt 15 is passed through a large hole 16 bored in the center of the lower face plate 7 , and a stop plate 17 is installed at the lower end. A cover 18 is installed around the periphery of the upper face plate 12 .

When the seismic isolator of FIG. 9 above is exposed to the vibrations of an earthquake, etc., the upper face plate 12 can move freely in all horizontal directions through a support plate 14 set on top of the sphere 11 . Horizontal vibrations of the upper face plate 12 are relieved by a restorative force that arises from the weight loaded onto the sphere 11 from the curved surface 13 . A seismic isolation object such as a pedestal carrying an exhibit or a display case, installed on top of the upper face plate 12 is thus protected from vibrations.

Three or more coupling blocks 5 are required with the conventional seismic isolator shown in FIG. 8 , in order to maintain horizontal the seismic isolation object 3 supported on the lower linear guide rails 2 . Supposing a displacement amplitude of 200 mm in a single direction is required, the lower linear guide rails 2 and the upper linear guide rails 4 of 200 mm each will be needed on both sides of the three or more coupling blocks 5 . Thus a problem exists in miniaturizing the seismic isolator.

Further, coupling blocks are not used in the conventional seismic isolator shown in FIG. 9 . The sphere 11 is sandwiched between the lower face plate 7 and the upper face plate 12 . Supposing a displacement amplitude of 200 mm in a single direction is required, since a displacement is provided from the vertical deviations, the curved surface 13 must have a radius of 200 mm or more. Thus problems exist in miniaturizing the seismic isolator, and in its high cost since a very large expense will be incurred in manufacturing the support plate 14 furnished with the curved surface 13 .

SUMMARY OF THE INVENTION

The object of the present invention is to solve these problems by providing a seismic isolator for exhibits that are small, that can relieve large vibrations, and that is inexpensive.

The present invention relates to a flat-type seismic isolator for exhibits comprising: a lower face plate installed on a foundation; an upper face plate that is installed to the lower surface of a seismic isolation object and placed above the lower face plate; an intermediate plate placed between the upper face plate and the lower face plate; and elastic restoring means and damping means provided for returning the plates to their original positions and placed in a lower area between the lower face plate and the intermediate plate and an upper area between the intermediate plate and the upper face plate, respectively, wherein: in the lower area, one lower linear guide rail is disposed in the center of the area and guide rails and rollers are disposed at both ends parallel to the lower linear guide rail for smoothly moving the intermediate plate with respect to the lower face plate in one linear direction; and in the upper area, one upper linear guide rail is disposed in the center of the area and guide rails and rollers are disposed at both ends parallel to the upper linear guide rail for smoothly moving the upper face plate with respect to the intermediate plate in one linear direction, the lower linear guide rail and the upper linear guide rail orthogonally crossing each other, the guide rails and the rollers in the lower area and the upper area orthogonally crossing each other. Through the guide rails and rollers, the upper face plate can move smoothly in all horizontal directions, and by the elastic restoring metals, the upper face plate is restored to its original position, and horizontal vibrations are relieved. The height of the entire device is reduced to a small size.

In a further aspect, the seismic isolator for exhibits set forth above further comprises damping means of a magnet disposed in the lower area between the lower face plate and the intermediate plate and in the upper area between the intermediate plate and the upper face plate. By use of only a magnet, vibration displacement can easily be damped.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are explained below with reference to the drawings.

FIG. 1 is a plan view showing an example embodiment. of the present invention, FIG. 2 is a front view of FIG. 1 looking from the II direction, and FIG. 3 is a side view of FIG. 1 looking from the III direction. The seismic isolator for exhibits of the present invention, as shown in FIG. 2 and FIG. 3 , comprises: a lower face plate 21 installed on a foundation 20 ; an upper face plate 22 placed above the lower face plate 21 , and installed on the lower surface of a seismic isolation object which is not shown, such as a pedestal holding an exhibit or a display case; and an intermediate plate 23 that is placed horizontally between the lower face plate 21 and the upper face plate 22 . As shown in FIG. 1 , the upper face plate 22 is a flat plate with nearly a square shape, and the intermediate plate 23 and the lower face plate 21 are also square flat plates made with the same dimensions. The similarly shaped intermediate plate 23 and the upper face plate 22 are stacked on top of the lower face plate 21 in FIG. 1 , with a space left between each.

FIG. 4 is a plan view showing an example embodiment of the lower face plate 21 . A coupling block 24 , also shown in FIG. 3 , is installed in the center of the upper surface of the lower face plate 21 , and stoppers 25 , with shock absorbing rubber affixed, are installed above and below the coupling block 24 in FIG. 4 .

In addition, roller guide rails 27 , having concave grooves 26 on its upper surface, are installed on the upper surface of the lower face plate 21 in the vicinity of the upper and lower edges and in the right-left direction of FIG. 4 . This is the vertical direction within the paper for FIG. 3 (hereafter referred to as the X-direction ). Roller stop plates 28 are fixed at both ends of the roller guide rails 27 . Rollers 29 are fit into the concave grooves 26 of the roller guide rails 27 , as shown in FIG. 2 and FIG. 3 , and roll and move along the concave grooves 26 .

For the rollers 29 , as shown in the front view of FIG. 2 as well as in the plan view of FIG. 5 , two rollers 29 are put together by a coupling plate 30 so that their axes are parallel, forming a roller unit 31 .

Restoring springs 32 and 33 , coil springs, are disposed along the roller guide rails 27 on the upper surface of the lower face plate 21 , as shown in FIG. 4 . The outer ends of the restoring springs 32 and 33 are engaged in the vicinity of the edge of the upper surface of the lower face plate 21 , while the inner ends of the restoring springs 32 and 33 are engaged on the centerline of the lower surface of the intermediate plate 23 , as shown in FIG. 1 and FIG. 3 .

The coupling block 24 , installed in the center of the upper surface of the lower face plate 21 and mentioned above, holds an X-direction guide rail 34 as the lower linear guide rail, fixedly attached to the lower surface of the intermediate plate 23 in the X-direction, through a ball, so that it can slide smoothly in the longitudinal direction of the rail 34 , as shown in FIG. 1 and FIG. 3 .

On the lower surface of the intermediate plate 23 , in addition to the fixedly-attached X-direction guide rail 34 , mentioned above, roller guide rails 27 , which have concave grooves 26 on its lower surface, (refer to FIG. 2 and FIG. 3 ), are installed in the X-direction so that they face the aforementioned roller guide rails 27 on the upper surface of the lower face plate 21 . Roller stop plates 28 are affixed to both ends of the roller guide rails 27 .

The concave grooves 26 , on the roller guide rails 27 installed on the lower surface of the intermediate plate 23 , fit onto the rollers 29 from above, as shown in FIG. 2 and 10 FIG. 3 . The intermediate plate 23 is guided by the concave grooves 26 and the X-direction guide rails 34 , and can move smoothly in the X-direction with respect to the lower face plate 21 .

When the intermediate plate 23 moves in the X-direction with respect to the lower face plate 21 , in order to stop the plate 23 from slipping and falling from the plate 21 , stoppers 35 , with shock absorbing rubber affixed, are installed on both sides of the lower surface of the intermediate plate 23 in the X-direction, facing the stoppers 25 on the upper surface of the lower face plate 21 , as shown in FIG. 1 and FIG. 3 .

Following the top to bottom direction in FIG. 1 , which is the vertical direction within the paper for FIG. 2 (hereafter referred to as the Y-direction ), a Y-direction guide rail 36 as the upper linear guide rail is attached in the center section of the upper surface of the intermediate plate 23 . In addition, roller guide rails 38 , whose upper surfaces contain concave grooves 37 , are installed in the vicinity of the edges of the Y-direction on the upper surface of the intermediate plate 23 . Roller stop plates 39 are fixed at both ends of the roller guide rails 38 , as shown in FIG. 3 . Rollers 40 (refer to FIG. 1 or FIG. 3 ) of the roller units 31 (refer to FIG. 1 ), similar to the rollers 29 explained by FIG. 5 , are fit into the grooves 37 on the roller guide rails 38 , and can roll and move along the concave grooves 37 .

Stoppers 41 , with shock absorbing rubber affixed, are installed in the vicinity of the edges in the X-direction on the upper surface of the intermediate plate 23 so that they face each other, as shown in FIG. 1 and FIG. 2 .

Restoring springs 42 and 43 , i.e. coil springs, are disposed along the roller guide rails 38 on the upper surface of the intermediate plate 23 , as shown in FIG. 1 and FIG. 2 . The outer ends of the restoring springs 42 and 43 are engaged in the vicinity of the edges in the X-direction of the upper surface of the intermediate plate 23 , while the inner ends of the restoring springs 42 and 43 are engaged on the centerline of the lower surface of the upper face plate 22 .

As shown in FIG. 1 and FIG. 2 , a coupling block 44 is installed in the center of the lower surface of the upper face plate 22 . The coupling block 44 holds the Y-direction guide rail 36 , fixedly attached to the upper surface of the intermediate plate 23 in the Y-direction, through a ball, so that it can slide smoothly in the longitudinal direction of the Y-direction guide rail 36 .

Roller guide rails 38 , whose lower surfaces contain concave grooves 37 , (refer to FIG. 2 , FIG. 3 ) are installed in the Y-direction on the lower surface of the upper face plate 22 , so that they face the aforementioned roller guide rails 38 installed on the upper surface of the intermediate plate 23 , mentioned above. Roller stop plates 39 are fixed to both ends of the roller guide rails 38 , as shown in FIG. 1 and FIG. 3 .

The concave grooves 37 , on the roller guide rails 38 installed on the lower surface of the upper face plate 22 , fit onto the rollers 40 from above, as shown in FIG. 2 and FIG. 3 . The upper face plate 22 is guided by the concave grooves 37 and the Y-direction guide rails 36 , and can move smoothly in the Y-direction with respect to the intermediate plate 23 .

When the upper face plate 22 moves in the Y-direction with respect to the intermediate plate 23 , in order to stop the plate 22 from slipping and falling from the plate 23 , stoppers 45 , with shock absorbing rubber affixed, are installed on the X-direction centerline of the lower surface of the upper face plate 22 , between the stoppers 41 on the upper surface of the intermediate plate 23 , as shown in FIG. 1 and FIG. 2 .

As a damping means, magnets 46 are installed on the lower face of the intermediate plate 23 , through rods 47 whose length can be controlled, so that the magnets face the lower face plate 21 , as shown in FIG. 1 and FIG. 3 . Further, as the damping means, magnets 48 are installed on the upper face of the intermediate plate 23 , through rods 49 whose length can be controlled, so that the magnets face the upper face plate 22 , as shown in FIG. 1 and FIG. 2 .

In order to operate the magnets 46 and 48 as damping means against motion displacement, non-magnetic plates are installed on the upper surface of the lower face plate 21 so as to face the magnets 46 , and non-magnetic plates are also installed on the lower surface of the upper face plate 22 facing the magnets 48 . Or, the lower face plate 21 and the upper face plate 22 can themselves be non-magnetic plates, and motion displacement can be damped through the over-current that is generated when the motion displacement takes place.

Next, the operation of the above mentioned seismic isolator for exhibits shown in FIGS. 1 through 3 is explained.

If the lower face plate 21 is displaced in a horizontal direction by a horizontal vibration, the upper face plate 22 , and the seismic isolation object such as a pedestal carrying an exhibit or a display case, installed on the plate 22 resist the vibration so as to maintain their positions due to inertia.

FIG. 6 is a plan view showing a vibration displacement of the lower face plate 21 at a 45 angle with respect to both the X-direction and the Y-direction, and FIG. 7 is a front view of FIG. 6 looking from the VII direction. In this case, the lower face plate 21 is displaced in the X-direction with respect to the intermediate plate 23 and the upper face plate 22 , and the intermediate plate 23 and the lower face plate 21 are displaced in the Y-direction with respect to the upper face plate 22 .

When the lower face plate 21 is displaced in the X-direction with respect to the intermediate plate 23 , the coupling block 24 installed in the center of the upper surface of the lower face plate 21 moves smoothly in the X-direction with respect to the X-direction guide rail 34 fixedly attached in the X-direction to the lower surface of the intermediate plate 23 . The roller guide rail 27 on the upper surface of the lower face plate 21 rotates the roller 29 and moves in the X-direction.

Then as shown in FIG. 7 , the restoring spring 32 contracts, the restoring spring 33 expands, generating a restoring force, while the magnets 46 generate a damping force. In addition, even if the displacement of the lower face plate 21 in the X-direction is large, the stopper 35 contacts the stopper 25 , the roller 29 contacts the roller stop plate 28 , so the intermediate plate 23 does not slip and fall off of the lower face plate 21 .

When the lower face plate 21 is displaced by vibration at a 45 angle with respect to both the X-direction and the Y-direction, and the intermediate plate 23 is displaced in the Y-direction with respect to the upper face plate 22 , the Y-direction guide rail 36 fixedly attached in the Y-direction to the upper surface of the intermediate plate 23 moves smoothly in the Y-direction with respect to the coupling block 44 fixedly attached in the center of the lower surface of the upper face plate 22 . The roller guide rail 38 on the upper surface of the intermediate plate 23 rotates the roller 40 and moves in the Y-direction.

Then the restoring spring 42 contracts, the restoring spring 43 expands, generating a restoring force, and the magnets 48 generate a damping force. In addition, even if the displacement of the intermediate plate 23 in the Y-direction is large, the stopper 41 contacts the stopper 45 , the roller 40 contacts the roller stop plate 39 , so the upper face plate 22 does not slip and fall off of the intermediate plate 23 .

The damping force from the magnets 46 and 48 can be regulated by expanding or contracting the length adjustable rods 47 and 49 so as to change the clearance between the lower face plate 21 and the magnet 46 or the upper face plate 22 and the magnet 48 .

The invention can be installed into even the narrow space within a display case, because it is a small device with a low height. Since its permissible displacement range is large, a seismic isolation object such as an exhibit in a museum, art gallery, etc., is maintained horizontal upon vibration and effectively isolated. As a further effect, since the seismic isolator can be assembled with minimized number of high cost rails by using rollers, the overall cost can be significantly reduced.

In the further aspect, the seismic isolator has the effect of being able to provide stability by quickly damping out vibration displacement through use of inexpensive magnets.