Railway rolling stock – Trucks – Overhead crane
Reexamination Certificate
1999-12-23
2002-04-09
Stormer, Russell D. (Department: 3617)
Railway rolling stock
Trucks
Overhead crane
C052S167700, C052S167100, C052S167800, C212S299000, C212S253000, C248S638000
Reexamination Certificate
active
06367390
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
1. Field of the Invention
The present invention relates to a seismic isolation system for a crane, which prevents derailment and the like of a large crane caused by an earthquake.
2. Description of Related Art
A “Overhead Traveling Crane” disclosed in Japanese Patent Publication No. 63-356 (No. 356/1988) is well known as a crane equipped with a seismic isolation system.
This “Overhead Traveling Crane” is, as shown in
FIGS. 24 and 25
, configured so that horizontal shafts
152
are mounted on saddles
151
on both sides of a narrow girder-shaped crane body
150
, a track
154
having two traveling wheels
153
which travel on a rail
157
is provided on the horizontal shafts
152
so as to be slidable, and there is provided a vibration damping mechanism consisting of compression springs
155
and dampers
156
, which are disposed between the opposed faces of the inside face of the saddle
151
and the track
154
so as to be parallel with the horizontal shafts
152
.
On the crane of this type having the girder-shaped crane body
150
, if an earthquake occurs, the crane body
150
is mainly subjected to only an excitation force perpendicular to the crane traveling direction as a dangerous external force, and the excitation force in this direction is damped by the action of the compression springs
155
and the dampers
156
to prevent the wheels from being damaged or derailed.
On a large container crane, an unloader, and the like provided on the ground, a crane body
1
is generally formed into a portal type as shown in
FIGS. 17 and 18
. These figures show a general construction of a container crane. This portal crane body
1
has traveling means
2
at four corners.
The traveling crane having such a portal crane body is subjected to a transverse excitation force R perpendicular to the travel direction, a transverse overturning moment M, a torsional load S (rotary load) from the travel direction to the right and left, and an impulsive axial load A by vibrations at the time of an earthquake.
Also, on the traveling crane having a large portal crane body, the height of the position of the center of gravity is very high, and therefore the natural period is long as compared with the overhead traveling crane, so that the transverse displacement of the portal crane body also increases. Therefore, even if the conventional vibration damping mechanism shown in
FIG. 25
is applied to the portal crane body, a stroke necessary for damping the transverse excitation force R cannot be provided, and also damping action against the overturning moment M and the torsional load S cannot be provided.
OBJECT AND SUMMARY OF THE INVENTION
The present invention has been made in view of the above situation, and accordingly an object thereof is to provide a seismic isolation system for a crane, which is effective even for a traveling crane having a portal crane body.
To achieve the above object, the present invention provides a seismic isolation system for a crane, provided between a crane body and traveling means having a plurality of wheels for running the crane body along a rail, comprising: a connecting mechanism which allows relative movement of the crane body and the traveling means while the crane body and the traveling means are connected to each other when an earthquake occurs; a restraining mechanism which keeps a steady relative positional relationship between the crane body and the traveling means at the normal time and allows a relative movement of the crane body and the traveling means when the relationship is broken off by a seismic force; energy absorbing means for restraining an increase in relative movement of the crane body and the traveling means caused by the occurrence of an earthquake; and a restoring mechanism for restoring the positional relationship between the crane body and the traveling means to the steady relationship.
In the above-described seismic isolation system for a crane in accordance with the present invention, the steady positional relationship between the crane body and the traveling means is kept by the restraining mechanism at the normal time. When an earthquake occurs, however, the traveling means is displaced transversely, and the crane body attempts to remain at the original position by the inertia force, so that the restraining mechanism is released by the seismic force. Therefore, a relative movement of the crane body and the traveling means occurs, and the energy caused by the relative movement is absorbed by the energy absorbing means. The relative movement of the crane body and the traveling means is relaxed properly by a damper mounted between the crane body and the traveling means. Thus, the seismic isolation function is fulfilled safely and properly.
Also, the present invention provides a seismic isolation system for a crane, provided between a crane body and traveling means having a plurality of wheels for running the crane body along a rail, comprising a swing bearing ring consisting of a lower ring installed horizontally on the side of the traveling means and an upper ring engaging concentrically with the lower ring so as to be rotatable relatively, and further comprising a vertical shaft supporting swing bearing provided at an eccentric position on the upper ring of the swing bearing ring; a crane load supporting block having a lower vertical shaft supported on the swing bearing; saddles installed at the lower part of the crane body so as to pivotally support the block by using a horizontal transverse shaft; a horizontal lever whose proximal end is pivotally supported on the upper ring of the swing bearing ring through the horizontal transverse shaft; and a horizontal lever swing restoring mechanism which automatically restores the horizontal lever to the neutral position while supporting the distal end of the horizontal lever so as to be rotatable around the vertical centerline of the swing bearing ring.
In the above-described seismic isolation system for a crane in accordance with the present invention, the load of the crane body is transmitted from the saddles installed on the crane body to the traveling means through the crane load supporting block, the swing bearing, and the swing bearing ring.
An axial load, a overturning moment load, and a radial load applied to the crane body by an earthquake during the operation of the crane are supported by the swing bearing ring and the swing bearing on the traveling means.
Also, an excitation force applied in the radial direction perpendicular to the travel direction of the traveling means acts on the lower ring of the swing bearing ring on the traveling means so as to turn the swing bearing, which is erected at an eccentric position from the center of the swing bearing ring, around the vertical centerline of the swing bearing ring together with the horizontal lever. This turning force is automatically restrained by the horizontal lever swing restoring mechanism provided between the horizontal lever and the traveling means, whereby a damping operation against the excitation force is performed.
In the seismic isolation system for a crane in accordance with the present invention, the horizontal lever swing restoring mechanism comprises a roller which is provided at the distal end of the horizontal lever so as to be rotatable freely along the swing direction, and a guide rail provided on the traveling means so as to be inclined downward toward the middle position of the rail, which is the neutral position.
When the guide rail for guiding the roller (or a wheel) at the distal end of the horizontal lever mounted on the swing bearing ring is provided so as to be inclined downward from both sides thereof toward the rail middle position, which is the neutral position, as described above, the operation in which the horizontal lever having been swung by seismic vibrations is automatically restored to the neutral position is performed properly when the roller having been pushed against the guide rail by the gravity of the crane body is automatically restored
Harada Hideaki
Ikeda Hiroshi
Okubo Yoshiaki
Alston & Bird LLP
Mitsubishi Heavy Industries Inc.
Olson Lars A.
Stormer Russell D.
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