Static structures (e.g. – buildings) – Means compensating earth-transmitted force
Reexamination Certificate
1999-11-12
2001-12-04
Stephan, Beth A. (Department: 3635)
Static structures (e.g., buildings)
Means compensating earth-transmitted force
C052S167200, C052S167500, C052S001000
Reexamination Certificate
active
06324794
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a fluid spring for protecting a structural element from the potential effects of a cyclic event.
In U.S. Pat. Nos. 5,526,609 and 5,765,313 to Lee et al. there is disclosed both method and apparatus for a real time structural parameter modification (RSPM) in which a mechanical spring is engaged and disengaged with a structural element by means of a hydraulic switch. When engaged, the spring acts to stiffen the structural element and store energy when the structure experiences a potentially harmful cyclic event. The stored energy is released from the system by disengaging the spring from the structural element. After the stored energy is released, the structural element is once again engaged by the spring and the cycle is repeated.
In the RSPM system the mechanical spring and the hydraulic switch are separate elements. The size of the apparatus, and in particular the spring, are relatively large and thus occupy a good deal of space. The reaction time needed to engage and disengage the spring is also relatively long diminishing the ability of the system to react to high shock loads. Any delay in responding to high shock loads can result in unacceptable G-loads.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to improve apparatus used to protect structures from the potentially harmful effects caused by a cyclic event.
It is a further object of the present invention to reduce the size of apparatus used to protect a structural object during a cyclic event such as an earthquake or a high wind storm.
It is a still further object of the present invention to increase the response time of apparatus designed to protect a structure from a cyclic event and, in particular, against the harmful effect of high external shock loads.
Another object of the present invention is to eliminate the need for a mechanical spring in apparatus for protecting a structural object from the harmful effects of a cyclic event.
Still another object of the present invention is to combine a fluid spring and a fluid damper within a common cavity and regulate the exchange of fluid between the two devices and an accumulator to protect a structure against the potentially harmful effects of a cyclic event.
These and further objects of the present invention are attained by means of apparatus for protecting a structural object from the harmful effects of a cyclic event and includes a fluid spring in which the fluid spring chamber is housed within a manifold and a piston is slidably contained within the chamber. A piston rod is secured at one end to the piston and passes out of the chamber through one side of the manifold. The other end of the rod is connected to a second structural member and the manifold is connected to a first structural member. The spring chamber is filled with a compressible fluid and is placed in fluid flow communication with an accumulator chamber by means of a flow circuit whereby fluid is exchanged between the spring chamber and the accumulator chamber when the structure experiences a cyclic load. In the preferred embodiment of the invention, a flow circuit under the control of a microprocessor controls the exchange of fluid between the fluid spring and the accumulator. Initially, when the structure experiences a cyclic event, the fluid in the spring chamber stores energy and the pressure in the chamber rises. A sensor monitors a system characteristic that is indicative of the pressure in the spring chamber and, through the microprocessor, causes a control valve to be cycled allowing high pressure fluid in the spring chamber to move to the accumulator where it is dissipated as heat. A check valve in the flow circuit is arranged to open when the accumulator pressure exceeds the spring chamber pressure thus refilling the spring chamber when the load on the structure is reduced. A relief valve is also contained in the flow circuit which is adapted to open automatically when the structure experiences a dangerously high shock load permitting fluid in the spring chamber to rapidly move into the accumulator which, in effect, releases the structure from the fluid spring.
In another form of the invention a damper chamber is placed in back to back relationship with the spring chamber within a common cavity and is separated from the spring chamber by the piston. A second flow circuit connects the damper chamber to the accumulator to control the rate of return of the piston and absorb energy from the system as the structure is recovering from a cyclic load thereby providing the capability to remove kinetic energy from the system during the return mode of the piston. A check valve in the flow circuit is arranged to open when the accumulator pressure exceeds the damper chamber pressure thus refilling the damper chamber. A relief valve is provided in the flow circuit which opens automatically when the pressure in the damper chamber reaches a value indicating that the structure is again experiencing a load which is higher than desirable, whereupon the fluid in the damper chamber is permitted to rapidly move into the accumulator chamber.
In still another embodiment of the invention, a pair of fluid spring chambers are placed in a back to back relationship within a common cavity and, are separated by a piston. Each spring chamber communicates with the accumulator as described above through separate but identical flow circuits so that cyclic loads acting on either side of the piston can be absorbed by the unit.
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patent: 5491938 (1996-02-01), Niwa et al.
patent: 5526609 (1996-06-01), Lee et al.
patent: 5540522 (1996-07-01), Launaro et al.
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patent: 5765313 (1998-06-01), Lee et al.
Clinard R. Leon
Houghton Benjamin T.
Taylor Scott
Tomita Ken-ichi
Enidine Inc.
Glessner Brian E.
Stephan Beth A.
Wall Marjama & Bilinski
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