Brakes – Internal-resistance motion retarder – Using viscosity of fluid medium
Reexamination Certificate
1999-02-09
2001-06-26
Oberleitner, Robert J. (Department: 3613)
Brakes
Internal-resistance motion retarder
Using viscosity of fluid medium
C267S136000
Reexamination Certificate
active
06250441
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a damper which is interposed between structures adapted to undergo relative movement and which functions as a stopper for preventing a sudden displacement of the structure. More particularly, the present invention concerns a so-called viscous shear-type damper which makes use of viscous shear occurring between fixed and movable resistance plates which are arranged in parallel with very small gaps therebetween, and are adapted to undergo relative movement via a viscous material filled in the gaps.
2. Description of the Related Art
In Japanese Utility Model Application Publication No. 43262/1979 (hereafter referred to as the prior art), the present assignees earlier proposed a viscous shear-type damper of this type as an “apparatus for causing damping action.”
Namely, the apparatus for causing damping action according to the aforementioned prior art is characterized by the following. Fixed resistance plates formed of rectangular thin plates and moving resistance plates or movable resistance plates formed of thin plates whose length is shorter than that of the fixed resistance plates and whose transverse width is wider than that of the fixed resistance plates are arranged alternately with very small gaps therebetween. The moving resistance plates have mutually opposing cutout portions at their transverse end portions, and engaging blocks are engaged in the cutout portions. A viscous material is filled between the resistance plates thus assembled, and the entire assembly is accommodated in a casing. The fixed resistance plates at their longitudinal end portions abut against casing walls, whereas the moving resistance plates engaged by the engaging blocks have spaces with respect to the casing walls in their transverse end portions. The engaging blocks and the casing are respectively fixed to mutually opposing structural members.
As such, the above-described apparatus in accordance with the prior art has the following features:
(1) Fluid pressure does not take place in the apparatus, and leakage of a fluid does not occur, so that it is unnecessary to adopt a hermetically sealed structure for the apparatus.
(2) Since the apparatus does not have fitting and sliding portions similar to those of a piston cylinder-type damper, a high level of processing accuracy is not required.
(3) Even if the engaging blocks have slight inclinations, parallel positional relationships are maintained between the fixed resistance plates and the movable resistance plates, and a factor of resilient instability of the moving resistance plates in the principal moving direction, in particular, is decreased appreciably.
However, in the above-described prior art, bubbling due to entrainment of air occurs in the viscous material during the operation, i.e., during a sudden displacement of the moving resistance plates. At times, there are cases where overflow can occur, making it impossible to allow stable viscous-shear resisting force to be demonstrated sufficiently.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been devised to overcome the above-described problem of the prior art, and its object is to obtain a viscous shear-type damper which makes it possible to obtain the viscous-shear resisting force stably.
Thus, in the present invention, an attempt is made to overcome the above-described drawback by the dissipation of excessive pressure on the basis of the knowledge that the entrainment of air in the viscous material and the overflow thereof in the prior art cause the excessive pressure in the viscous material due to the sudden displacement of the movable resistance plates and the engaging blocks.
The viscous shear-type damper in accordance with the present invention specifically adopts the following arrangement. Namely, in accordance with one aspect of the present invention, there is provided a viscous shear-type damper comprising: a casing including an upper cover which is horizontally movable and a container portion having a rectangular parallelepiped-shaped accommodating space which is covered by the upper cover; an engaging member provided in the accommodating space in such a manner as to be suspended from a lower surface of the upper cover; a plurality of movable resistance plates which are arranged horizontally one above another in the accommodating space of the container portion while maintaining fixed intervals therebetween and engaging with the engaging member; a fixed resistance plate which is arranged horizontally and fixed to the casing and which is interposed between adjacent ones of the movable resistance plates while maintaining a very small gap therewith; a viscous material filled in the accommodating space of the container portion to fill the gap between adjacent ones of the movable resistance plates and the fixed resistance plate; and a rectifying section disposed at an end portion of the fixed resistance plate to allow the viscous material to flow.
In a preferred example in the present invention, each of the rectifying sections is arranged such that partition plates each having a through hole for allowing the viscous material to flow therethrough are arrayed at intervals.
In accordance with another aspect of the present invention, there is provided a viscous shear-type damper comprising: a casing having a rectangular parallelepiped-shaped accommodating space and serving as a container portion; an engaging member provided in the accommodating space of the container portion and including at least a pair of leg portions arranged parallel to wall surfaces of the accommodating space and a beam spanning upper ends of the leg portions; a plurality of movable resistance plates which are arranged horizontally one above another in the accommodating space of the container portion while maintaining fixed intervals therebetween and engaging with the leg portions of the engaging member; a fixed resistance plate which is arranged horizontally and fixed to the casing and which is interposed between adjacent ones of the movable resistance plates while maintaining a very small gap therewith; a viscous material filled in the accommodating space of the container portion to fill the gap between adjacent ones of the movable resistance plates and the fixed resistance plate; and a rectifying section disposed at an end portion of the fixed resistance plate to allow the viscous material to flow.
In the viscous shear-type damper of the present invention, with respect to the slow displacement of an upper structure accompanying a temperature change, its displacement moves the engaging member through the upper cover, and further displaces the movable resistance plates engaged with the engaging member. In this case, the movement of the movable resistance plates is slow, the viscous-shear resisting force does not occur between the movable resistance plate and the fixed resistance plate, and this displacement is allowed.
With respect to a sudden displacement of the upper structure accompanying an earthquake, its displacement suddenly moves the movable resistance plates through the upper cover and the engaging member, and causes the movable resistance plates to undergo large relative movement with respect to the fixed resistance plate. Due to this relative displacement, the viscous-shear resisting force occurs in a relevant portion of the viscous material interposed between both resistance plates. This viscous-shear resisting force constitutes a large resisting force against the sudden displacement during earthquake motion. The earthquake motion is periodical, and the aforementioned viscous-shear resisting force accompanying the same acts alternately in mutually opposite directions, with the result that a high damping characteristic is exhibited and the vibration of the upper structure is absorbed quickly.
In this operation, the rectifying section of the present invention performs the following operation.
Due to the sudden movement of the engaging blocks and the movable resistance plates, the viscous material is subje
Nguyen Xuan Lan
Nixon & Vanderhye
Oberleitner Robert J.
Oiles Corporation
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