Traversing hoists – Having means to prevent or dampen load oscillations – Antisway
Reexamination Certificate
2000-06-13
2002-02-05
Brahan, Thomas J. (Department: 3652)
Traversing hoists
Having means to prevent or dampen load oscillations
Antisway
C212S322000
Reexamination Certificate
active
06343702
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a crane apparatus which is used, for example, as a transfer crane of port cargo handling equipment.
2. Description of the Related Art
A conventional transfer crane has a gantry-shaped body frame, which can travel by a plurality of traveling wheels. On the top of the body frame, a trolley can move transversely. On the trolley, a rotationally drivable takeup drum is connected. A hoisting accessory is attached to the lower end of a plurality of load suspending wire ropes wound off from the takeup drum. Thus, as the trolley moves on the body frame, a suspended load held by the hoisting accessory can be traversed. When the takeup drum is rotationally driven at a predetermined stop position of the trolley to take up or pay out the plural wire ropes, the suspended load can be moved upwards or downwards.
With the above-described conventional crane apparatus, rails are provided on transverse girders placed on the body frame, and the trolley is supported on the rails. In con sideration of the weight of the rails, the weight of the trolley, or the weight of the suspended load imposed on the hoisting accessory, not only the transverse girders and the body frame, but also the entire crane apparatus must have great rigidity, inducing a large size and a heavy weight. When the trolley is moved laterally and stopped at a predetermined position, with the suspended load being held by the hoisting accessory, sway occurs in the hoisting accessory and the suspended load owing to an inertial force in the lateral direction. This sway does not settle quickly. To prevent sway of the hoisting accessory and the suspended load when the trolley stops, the trolley has to be moved at a slow speed. Since a long time is required for work, the work efficiency is low.
As a solution to the above-mentioned problem, a crane apparatus as shown, for example, in
FIG. 4
is available. It should be noted that the numbering scheme for FIG.
4
and all other figures uses the numbers (n, n′) to designate pairs of like parts disposed orthogonally to the plane of the two-dimensional figure. In this conventional crane apparatus, as shown in
FIG. 4
, a pair of left and a pair of right traverser drums
101
,
101
′ and
102
,
102
′, and a pair of left and a pair of right hoisting accessory drums
103
,
103
′ and
104
,
104
′ are rotatably supported on the top of a gantry or portal body frame via pairs of clutches
105
,
105
′ and
106
,
106
′, respectively, and are rotationally drivable by a pair of left and a pair of right drive motors
107
,
107
′ and
108
,
108
′. A first pair of right and a first pair of left traverser wire ropes
109
,
109
′ and
110
,
110
′ have first ends taken up by the traverser drums
102
,
102
′ and
101
,
101
′ and have the other ends connected to pairs of right connecting portion
114
on a traverser
113
,
113
′ via pairs of right and left sheaves
111
,
111
′ and
112
,
112
′, respectively. Second pairs of right and left traverser wire ropes
115
,
115
′ and
116
,
116
′ have an end taken up by the traverser drums
102
,
102
′ and
101
,
101
, and have other ends connected to a pair of left connecting portions
119
,
119
′ on the traverser
113
via pairs of right and left sheaves
117
,
117
′ and
118
,
118
′, respectively. Furthermore, pairs of right and left hoisting accessory wire ropes
120
,
120
′ and
121
,
121
′ have first ends taken up by the hoisting accessory drums
104
,
104
′ and
103
,
103
′ and have the other ends passed over low-position rope pulleys
126
,
126
′ and
127
,
127
′ via right and left sheaves
122
,
122
′ and
123
,
123
′ and right and left sheaves
124
,
124
′ and
125
,
125
′ of the traverser
113
, and then connected to connecting portions
128
,
128
′ and
129
,
129
′ of the traverser
113
. From the rope pulleys
126
,
126
′ and
127
,
127
′, a hoisting accessory
130
capable of holding a container C is suspended. Hence, there is no need to provide rails and a trolley on the body frame. Since the weight on the body frame is reduced, the crane apparatus can be made compact and light-weight. Besides, the traverser
113
, which supports the hoisting accessory
130
, is supported by the wire ropes
109
,
109
′,
110
,
110
′,
115
,
115
′,
116
,
116
′ at the two separated connecting portions
114
,
114
′ and
119
,
119
′. Hence, sway of the hoisting accessory
130
and the suspended load C due to their inertial force is suppressed, and the work efficiency is increased.
In the conventional crane apparatus described above, let the weight of the hoisting accessory
130
and the suspended load C be W. Then, the rope tension T of the hoisting accessory wire ropes
120
,
120
′ and
121
,
121
′ will be:
T=W/
4
The rope tensions T
1R
and T
1L
of the first traverser wire ropes
109
and
110
, and the rope tensions T
2R
and T
2L
of the second traverser wire ropes
115
and
116
will be given by:
T
1R
=(
W/
2)cos &thgr;
2
/sin(&thgr;
1
+&thgr;
2
)−
W/
8
T
1L
=(
W/
2)cos &thgr;
1
/sin(&thgr;
1
+&thgr;
2
)−
W/
8
T
2R
=T
1R
T
2L
=T
1L
where &thgr;
1
is the angle of each of the wire ropes
109
,
115
and
120
, and &thgr;
2
is the angle of each of the wire ropes
110
,
116
and
121
.
In other words, the rope tensions T
1R
and T
1L
of the first traverser wire ropes
109
,
109
′ and
110
,
110
′, and the rope tensions T
2R
and T
2L
of the second traverser wire ropes
115
,
115
′ and
116
,
116
′ vary with the angle &thgr;
1
of each of the wire ropes
109
,
109
′,
115
,
115
′ and
120
,
120
′, and the angle &thgr;
2
of each of the wire ropes
110
,
110
′,
116
,
116
′ and
121
,
121
′, namely, the traversing position of the hoisting accessory
130
. Whereas the rope tension T of each of the hoisting accessory wire ropes
120
,
120
′ and
121
,
121
′ is constant (W/4) regardless of the traversing position of the hoisting accessory
130
.
Under these situations, when the hoisting accessory
130
is traversed most rightward, the hoisting accessory
130
stops at a position at which rightward and leftward horizontal components of force from the hoisting accessory wire ropes
120
and
121
are balanced, as shown in
FIG. 5
, because the rope tension T of the hoisting accessory wire ropes
120
,
120
′ and that of the hoisting accessory wire ropes
121
,
121
′ are the same. Thus, the hoisting accessory
130
cannot be brought fully close to a crane leg
131
which supports the sheaves
122
,
122
′, etc. As a result, the traversing range of the hoisting accessory
130
narrows. A full traversing function of the crane cannot be exhibited, and the work efficiency is low. If the position of the crane leg
131
is brought outward (rightward in FIG.
5
), together with the sheaves
122
,
122
′, to enlarge the traversing range of the hoisting accessory
130
, the apparatus will be upsized.
SUMMARY OF THE INVENTION
The present invention has been accomplished to solve the above-described problems with the earlier technology. It is an object of this invention to provide a crane apparatus designed to increase the work efficiency by enlarging the traversing range of a hoisting accessory without upsizing the apparatus.
A first aspect of the present invention, as a means of attaining the above object, is a crane apparatus comprising:
traverser drums and hoisting accessory drums rotatably mounted on a support and normally and reversely rotatable by drive motors;
a traverser having a pair of right and a pair of left connecting portions, and a pair of right and a pair of left sheaves thereon;
a right pair of and a left pair of rope
Abiru Hisanori
Chikura Takashi
Hirano Tatsuya
Ichikizaki Tetsuo
Masumoto Masanori
Brahan Thomas J.
Mitsubishi Heavy Industries Ltd.
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