Patent Application
20150128510
Although minor earthquakes are common, with thousands of smaller earthquakes occurring daily, larger magnitude seismic events can cause personal injury, death and property and environmental damage, particularly in heavily populated areas.
Two approaches have been traditionally utilized to prevent or limit damage or injury to objects or payloads due to seismic events. In the first approach, used particularly with structures themselves, the objects or payload articles are made strong enough to withstand the largest anticipated earthquake. However, in addition to the relative unpredictability of damage caused by tremors of high magnitude and long duration and of the directionality of shaking, use of this method alone can be quite expensive and is not necessarily suitable for payloads to be housed within a structure. Particularly for delicate, sensitive or easily damaged payload, this approach alone is not especially useful.
In the second approach, the objects are isolated from the vibration such that the objects fail to experience the full force and acceleration of the seismic shock waves. Various methods have been proposed for accomplishing isolation or energy dissipation of a structure or object from seismic tremors, and these methods may depend in some measure on the nature of the object to be isolated.
Thus, buildings and other structures may be isolated using, for example, passive systems, active systems, or hybrid systems. Such systems may include the use of one or more of a torsional beam device, a lead extrusion device, a flexural beam device, a flexural plate device, and a lead-rubber device; these generally involves the use of specialized connectors that deform and yield during an earthquake. The deformation is focused in specialized devices and damage to other parts of the structure are minimized; however the deformed devices often must be repaired or replaced after the seismic event, and are therefore largely suitable for only one use.
Active control systems require an energy source and computerized control actuators to operate braces or dampers located throughout the structure to be protected. Such active systems are complex, and require service or routine maintenance.
For objects other than buildings, bridges and other structures, isolation platforms or flooring systems may be preferable to such active or deformable devices. Thus, for protection of delicate or sensitive equipment such as manufacturing or processing equipment, laboratory equipment, computer servers and other hardware, optical equipment and the like an isolation system may provide a simpler, effective, and less maintenance-intensive alternative. Isolation systems are designed to decouple the objects to be protected (hereinafter the “payload”) from damage due to the seismic ground motion.
Isolators have a variety of designs. Thus, such systems have generally comprised a combination of some or all of the following features: a sliding plate, a support frame slidably mounted on the plate with low friction elements interposed therebetween, a plurality of springs and/or axial guides disposed horizontally between the support frame and the plate, a floor mounted on the support frame through vertically disposed springs, a number of dampers disposed vertically between the support frame and the floor, and/or a latch means to secure the vertical springs during normal use.
Certain disadvantages to such pre-existing systems include the fact that it is difficult to establish the minimum acceleration at which the latch means is released; it is difficult to reset the latch means after the floor has been released; it may be difficult to restore the floor to its original position after it has moved in the horizontal direction; the dissipative or damping force must be recalibrated to each load; there is a danger of rocking on the vertical springs; and since the transverse rigidity of the vertical springs cannot be ignored with regard to the horizontal springs, the establishment of the horizontal springs and an estimate of their effectiveness, are made difficult.
Ishida et al., U.S. Pat. No. 4,371,143 have proposed a sliding-type isolation floor that comprises length adjustment means for presetting the minimum acceleration required to initiate the isolation effects of the flooring in part by adjusting the length of the springs.
Yamada et al., U.S. Pat. No. 4,917,211 discloses a sliding type seismic isolator comprising a friction device having an upper friction plate and a lower friction plate, the friction plates having a characteristic of Coulomb friction, and horizontally placed springs which reduce a relative displacement and a residual displacement to under a desired value. The upper friction plate comprises a material impregnated with oil, while a lower friction plate comprises a hard chromium or nickel plate.
Stahl (U.S. Pat. No. 4,801,122) discloses a seismic isolator for protecting e.g., art objects, instruments, cases or projecting housing comprising a base plate connected to a floor and a frame. A moving pivoted lever is connected to a spring in the frame and to the base plate. The object is placed on top of the frame. Movement of the foundation and base plate relative to the frame and object causes compression of the lever and extension of the spring, which then exerts a restoring force through a cable anchored to the base plate; initial resistance to inertia is caused due to friction between the base plate and the frame.
Kondo et al., U.S. Pat. No. 4,662,133 describes a floor system for seismic isolation of objects placed thereupon comprising a floor disposed above a foundation, plurality of support members for supporting the floor in a manner that permits the movement of the floor relative to the foundation in a horizontal direction, and a number of restoring devices comprising springs disposed between the foundation and the floor member. The restoring members comprise two pair of slidable members, each pair of slidable members being movable towards and away from each other wherein each pair of slidable members is disposed at right angles from each other in the horizontal plane.
Stiles et al., U.S. Pat. No. 6,324,795 disclose a seismic isolation system between a floor and a foundation comprising a plurality of ball and socket joints disposed between a floor and a plurality of foundation pads or piers. In this isolation device, the bearing comprises a movable joint attached to a hardened elastomeric material (or a spring); the elastic material is attached on an upper surface of the ball and socket joint and thus sandwiched between the floor and the ball and socket joint; the bearing thus tilts in relation to the floor in response to vertical movement. The floor is therefore able to adjust to buckling pressure due to distortion of the ground beneath the foundation piers. However, the device disclosed is not designed to move horizontally in an acceleration-resisting manner.
Fujimoto, U.S. Pat. No. 5,816,559 discloses a seismic isolation device quite similar to that of Kondo, as well as various other devices including one in which a rolling ball is disposed within the tip of a strut projecting downward from the floor in a manner similar to that of a ball point pen.
Bakker, U.S. Pat. No. 2,014,643, is drawn to a balance block for buildings comprising opposed inner concave surfaces with a bearing ball positioned between the surfaces to support the weight of a building superstructure.
Kemeny, U.S. Pat. No. 5,599,106 discloses ball-in-cone bearings.
Kemeny, U.S. Pat. Nos. 7,784,225 and 8,104,236 discloses seismic isolation platforms containing rolling ball isolation bearings.
Hubbard and Moreno, U.S. Pat. Nos. 8,156,696 and 8,511,004 discloses apparatus and methods involving raised access flooring structure for isolation of a payload placed thereupon.
Moreno and Hubbard, U.S. Pat. No. 8,342,752 disclose isolation bearing restraint devices.
Isolation bearings are disclosed in Hubbard and Moreno, U.S. Patent Publication US 2013/0119224 filed on Sep. 25, 2012.
Moreno and Hubbard, U.S. Patent Publication No. U.S. 2011/0222800 disclose methods and compositions for isolating a payload from vibration.
Chen, U.S. Pat. No. 5,791,096 discloses a raised floor system.
Denton, U.S. Pat. No. 3,606,704 discloses an elevated floor structure suitable for missile launching installations with vertically compressible spring units to accommodate vertical displacements of the subfloor.
Naka, U.S. Pat. No. 4,922,670 is drawn to a raised double flooring structure which is resistant to deformation under load. The floor employs columnar leg members that contain a pivot mounting near the floor surface, which permits to floor to disperse a load in response to a side load.
All patents, patent applications and other publications cited in this patent application are hereby individually incorporated by reference in their entirety as part of this disclosure, regardless whether any specific citation is expressly indicated as incorporated by reference or not.
The present invention is directed in part to an improved seismic isolation system. The system may comprise isolation flooring and/or seismic isolation platforms. Although not exclusively, preferred examples of the invention may involve, or may be used in Conjunction with, a “low rise” platform or flooring system such as that disclosed in International Patent Application No. PCT/US2013/028621, filed on Mar. 1, 2013.
Isolation bearings and systems such as, without limitation, those disclosed in e.g., U.S. Pat. Nos. 5,599,106; 7,784,225; 8,104,236; 8,156,696 and 8,511,004 provide seismic isolation through the utilization of isolation bearings comprising at least one (and usually two) horizontally extending bearing plate(s) with a first generally concave surface and a second surface. A cross-sectional profile through a midline vertical axis of such a bearing plate shows that the generally concave surface comprises a shape, generally symmetrical around a central vertical axis, comprising a substantially conical shape, substantially spherical shape, or a shape, comprising a linked combination of linear and radial shapes. When the generally concave surface of the bearing plate is a top surface of the bearing plate the bearing plate shall be considered “upward” facing, whereas when this surface is the bottom surface of the bearing plate, the concave surface shall be considered “downward” facing.
Generally at least one bearing plate supports, or is supported by a rolling ball, such as a ball bearing. In preferred rolling ball isolation bearing systems a rolling ball is between opposing upward-facing and downward-facing isolation bearing plates in such a manner that when a seismic event occurs, horizontal ground movement of the floor or foundation is isolated from the payload supported by the isolation bearings. Horizontal ground movement of the lower bearing plate is attenuated by the inertia of the payload mass on the upper bearing plate so that the rolling ball, located at rest in the center of the bearing plates, is free to move out of the center of the lower plate as the plate moves under it in any direction (relative to the lower plate) opposite to the direction of lower plate movement.
A major advantage to such a bearing is that, since it is substantially equally free to move the same distance in any horizontal direction (i.e., along the x and y axes) given a constant force, the bearing does not require additional means to translate and isolate non-linear forces, or forces having both x and y components, as is necessary with isolation equipment using rollers, springs, skids or the like as the primary means of isolating the payload. Additionally, because of the use of a generally concave, generally symmetrical bearing surface, the bearing is “self-initializing”, with the rolling ball returning to the center of the bearing plate following a seismic tremor, thus restoring the bearing to its initial resting position.
However, this advantage also means that shape of the bearing plate(s) is usually circular; in this manner the rolling ball is free to travel the same distance in any direction, and thus the bearing will work equally well regardless of the direction of the seismic force. However, circular seismic bearing plates can possess practical disadvantages. Shipping, storage, manufacturing and assembly of isolation systems can all be at least somewhat made more difficult using bearing plates having a circular plan view. Such bearing plates need to be stacked horizontally for storage; when placed side-by-side, the bearing plates only touch at a single point, and this substantially storage space is wasted. Furthermore, assembly of isolation equipment using circular bearing plates often requires specialized and somewhat inflexible designing, and this customizing design requirement lends itself less than optimally to, for example, a flexible modular isolation system that can be configured in many different ways. Finally the actual assembly of circular bearings in a system is difficult, and attachment of such bearing plates to frame elements may not be as robust as desired or may be necessary.
The present invention is directed to methods and apparatus which involve improved seismic isolation bearings and systems utilizing such seismic isolation bearings, as well as methods of making and using such bearings and systems. In particular examples, the present invention involves seismic isolation systems utilizing one or more “rolling ball” isolation bearing comprising a bearing plate having a polygonal shape. That is, the isolation bearing comprises at least one payload-supporting “pan” or bearing plate having a polygonal shape in a plan view comprising a load-bearing surface having a cross-sectional profile comprising a generally conical shape, a generally spherical shape, or a shape, generally symmetrical around a central vertical axis, comprising a linked combination of linear and radial shapes.
The pan or bearing plate extends horizontally, generally radiating symmetrically about a central point, for example a central apex (or inverted apex). In the presently described examples, the pan or bearing plate is polygonal in shape when seen in plan view; for example, the plan view of the pan (and/or its frame) may comprise a triangle, a square, a pentagon, a hexagon, a heptagon, an octagon or another polygonal shape. In other examples, the bearing plate may be substantially circular in plan view and surrounded by a polygonal frame. Preferably, the polygonal shape is other than a square; preferably the polygonal shape is other than a triangle. Preferably, the polygonal shape is a hexagon or an octagon.
In preferred examples, each seismic isolation bearing comprised in a seismic flooring or platform system may comprise at least two opposing bearing plates, separated by a rigid ball, such as a metallic ball bearing. The rigid balls of two or more such bearings support the payload upon a frame, flooring element, or platform. In particularly preferred examples a seismic isolation bearing comprised in a seismic flooring or platform system comprises two bearing plates, separated by a rigid ball, such as a metallic ball bearing; in such arrangements an upper bearing plate may be joined to a frame, flooring element, or platform, while a lower bearing plate may be placed upon or affixed to a floor, foundation, or other similar support surface. A lower bearing plate may be oriented “upward”, so that when the system is at rest the rigid ball is nested at a central point on the bearing surface of the lower bearing plate. An upper bearing plate may be oriented “downward”, so that when the system is at rest the rigid ball rests within a central point on the bearing surface of the upper bearing plate.
Preferably, at least a lower beating plate comprises a polygonal outline shape in a plan view. A polygonal shape, particularly preferably (but not necessarily) an octagonal shape, can add to the stability of the seismic isolation system in at least two ways.
First, polygonal seismic isolation bearings may be assembled so that straight sides of the upper and/or lower polygonal bearing plates of at least two adjoining upper or lower isolation bearings may be joined or linked together, thereby reinforcing the stability of these bearings during a seismic event. In certain examples, a single upper or lower polygonal bearing plate may be joined to more than one adjoining bearing plate and/or to a flooring, frame, or platform element. Furthermore, when three or more isolation bearings are used in a single platform or flooring system, the frame, platform and/or flooring elements and the bearings may thus be linked together into, a single reinforced structure or network in which the entire upper and/or lower bearing element array is locked together as one.
Secondly, the polygonal shape facilitates linking the bearing plates to the frame, platform and/or flooring elements. For example, a circular isolation bearing plate has only one point (the point of tangency) at which it makes contact with a straight-edged surface. Thus, even in cases in which upper and/or lower polygonal bearing plates are not linked to each other, the joint between framing, platform, and/or flooring element and the bearing plate is made much more strong and firm when a straight edged segment of the perimeter of the bearing plate (or the bearing plate frame) is joined to a straight segment of such element.
Each of these advantages make the manufacture and assembly of seismic isolation systems comprising polygonal isolation bearings substantially easier than systems employing circular isolation bearings. Due to the straight edges of the isolation bearing plates of the present invention, seismic isolation systems can be designed to fit together more strongly and precisely than those having circular bearing plates.
Furthermore, when an isolation system employs an array of three or more, or four or more, or five or more, or six or more, isolation bearings having the same or complementary polygonal shapes, these bearings can be arranged in various ways depending on factors including, without limitation; the payload location, size, mass, and the size and/or and shape of the space in which the seismic isolation system is to be installed, in order to optimally support the load or conform with space limitations.
The polygonal bearing plates of the present invention may either be manufactured as circular bearing plates with a polygonal “frame” joined thereto by, for example, welds, appropriate fasteners (such as screws, bolts and the like). In another example, the polygonal bearing plates may be manufactured as a polygon, again, preferably surrounded by a polygonal frame.
It will be understood that the polygonal frames, bearing plates and the like may have rounded or “radiused” corners without departing from the scope of the invention. Thus the term “polygonal” or “polygon” shall be interpreted to mean “generally polygonal”; that is, comprising at least two (and preferably at least three) straight sides wherein the sum of all curves and angles totals 360°.
The use of polygonal bearing plates greatly facilitates the manufacture and assembly of seismic isolation systems. For example, connector components can be fabricated easily of, for example, metal tubing, flat plates, or angle iron with standardized placement of connection fittings such as (without limitation) screw or bolt holes, or brackets, for being joined to the polygonal bearing plate(s) and/or framing, flooring or platform elements. These connector component/bearing plate assemblies can thus be extended for the desired length or width of the isolation system, with the length of connectors and number of bearing plates being determined, at least in part, by the anticipated mass of the payload. In particular examples each of opposing sets of polygonal top and bottom bearing plates are linked by, and joined to, connector components to form top and bottom flooring or platform assemblies. Additionally, or alternatively, two or more adjacent polygonal top and/or bottom bearing plates may be joined to each other to form a strong and rigid isolation assembly.
In other possible configurations, the top and/or bottom isolation assembly may be constructed without the use of separate connector components. For example, the polygonal shape of the seismic bearing plates facilitates directly joining one bearing plate to at least one adjacent bearing plate, which is joined, in turn, to at least one additional bearing plate to form a firm, mutually stabilized structure.
One or more of the bottom bearing plates may also be directly or indirectly joined to a foundation or floor. For example, one or more bearing plate may be fastened directly to the foundation using, for example, concrete anchored fasteners or an adhesive for fastening plastics or metals to concrete, such as the 3M Scotch-Weld® brands of urethane, acrylic and epoxy adhesives.
One or more of the top bearing plates are preferably directly or indirectly fastened to a platform or flooring element. For example, a top bearing plate may be fastened directly to one or more flooring support “tile” or region using bolts, screws or other similar fasteners, or may be joined to a frame for supporting the payload, bearing plate, or tiles.
In one example, the present invention is drawn to a polygonal seismic isolation bearing plate comprising:
a) a recessed hardened load-bearing surface component; and,
b) a hardened frame component, sufficiently strong to support said load-bearing surface component during use in an isolation platform or flooring system during an earthquake, said frame component being directly or indirectly joined to said load bearing surface component;
wherein, in top view, the frame component comprises a polygonal shape, and wherein said frame component is structured to be joined along at least one straight edge to at least one other component of said isolation platform or flooring system.
In such a system the load-bearing surface component may be welded or otherwise securely joined to a circumferential ring (for this purpose considered part of the load bearing surface), which can then be joined to a frame component, or may be joined directly to the frame component. The frame component is preferably polygonal in shape, and is structured to be joined to other bearing plate assemblies, or to other components of the isolation flooring or platform assembly. In a particularly preferred embodiment the polygonal shape is not a square, or not a rectangle.
In another example, the invention is drawn to a polygonal seismic isolation bearing assembly comprising:
a) a hardened ball disposed between
b) a top isolation bearing plate, and
c) a bottom isolation bearing plate;
wherein each said top and bottom isolation bearing plates comprise:
i) a recessed hardened load-bearing surface component; and,
ii) a hardened frame component, sufficiently strong to support said load-bearing surface component during use in an isolation platform or flooring system during an earthquake, said frame component being directly or indirectly joined to said load bearing surface component;
wherein, in top view, the frame component comprises a polygonal shape, and wherein said frame component is structured to be joined along at least one straight edge to at least one other component of said isolation platform or flooring system.
Preferably the frame element of one or both of the top bearing plate or the bottom bearing plate is welded or otherwise joined to its respective load-bearing surface component. As above, the frame component is preferably polygonal in shape, and is structured to be joined to other bearing plate assemblies, or to other components of the isolation flooring or platform assembly. In a particularly preferred embodiment the polygonal shape is not a square, or not a rectangle.
Additionally, either or both the top and bottom isolation bearing plates may be directly or indirectly joined to one or more other isolation bearing plate in substantially the same plane. An example of indirect joining is by each bearing plate in substantially the same plane being joined to the same connector component. Another example of indirect joining is by each bearing plate in substantially the same plane being joined to a common flooring or platform component.
In another example, the present invention is directed to a seismic isolation floor or platform assembly comprising a plurality of polygonal isolation bearing assemblies, each such bearing assembly comprising:
a) a hardened ball disposed between
b) a top isolation bearing plate, and
c) a bottom isolation bearing plate;
wherein each said top and bottom isolation bearing plates comprise:
i) a recessed hardened load-bearing surface component; and,
ii) a hardened frame component, sufficiently strong to support said load-bearing surface component during use in an isolation platform or flooring system during an earthquake, said frame component being directly or indirectly joined to said load bearing surface component;
wherein, in top view, the frame component comprises a polygonal shape, and wherein said frame component is structured to be joined along at least one straight edge to at least one other component of said isolation platform or flooring system.
In the seismic isolation floor or platform assembly at least two of said plurality of polygonal isolation bearing assemblies may be joined in a manner selected from the group consisting of:
i) said top isolation bearing plates are directly or indirectly joined together, or
ii) said bottom isolation bearing plates are directly or indirectly joined together, or
iii) both said top isolation bearing plates are directly or indirectly joined together and said bottom isolation bearing plates are directly or indirectly joined together.
The inventions shall now be described by detailing specific, non-limiting examples.
The following examples provide details concerning various arrangements of polygonal bearing plates, isolation bearing assemblies and configurations of such bearings in a platform or flooring arrangement. It will be understood that the invention is limited only by the claims at the end of this specification.
Referring now to the drawings,
The assembly shown in
Although the foregoing invention has been exemplified and otherwise described in detail for purposes of clarity of understanding, it will be clear that modifications, substitutions, and rearrangements to the explicit descriptions may be practiced within the scope of the appended claims. For example, the inventions described in this specification can be practiced within elements of, or in combination with, other any features, elements, methods or structures described herein. Additionally, features illustrated herein as being present in a particular example are intended, in other aspects of the present invention, to to be explicitly lacking from the invention, or combinable with features described elsewhere in this patent application, in a manner not otherwise illustrated in this patent application or present in that particular example. Solely the language of the claims shall define the invention. All publications and patent documents cited herein are hereby incorporated by reference in their entirety for all purposes to the same extent as if each were so individually denoted.
This application claims the benefit of U.S. Provisional Patent Application No. 61/902,420, filed Nov. 11, 2013, the disclosure of which is hereby incorporated by reference in its entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61902420 | Nov 2013 | US |
