Spreader for container crane

Details Spreader for container crane Spreader for container crane

2002-08-23

2003-07-08

Kramer, Dean J. (Department: 3652)

Handling: hand and hoist-line implements

Spacing hoist bar or frame

Adjustable to accommodate different size loads

C294S081530

Reexamination Certificate

active

06588814

ABSTRACT:

FIELD OF THE INVENTION
DISCUSSION OF THE BACKGROUND
FIG. 1
is a schematic side elevation showing a conventional general container crane in which reference numeral
1
denotes a container ship moored at a quay
2
to and from which a container
4
is loaded and unloaded by the container crane
3
.
The container crane
3
comprises legs
6
on rails
5
for running along the quay
2
, girders
7
atop of the legs
6
and extending substantially horizontally to protrude toward the sea, traverse rails
8
extending along the girders
7
and a trolley
9
for movement in traverse direction.
The trolley
9
comprises, as shown in
FIGS. 2 and 3
, a trolley body
11
with traverse wheels
12
for rolling on the traverse rails
8
. Tied to the trolley body
11
are opposite ends of a traverse rope
13
which is wound around a traverse drum (not shown) in a machine room
10
(see
FIG. 1
) and which extends under tension longitudinally of the girders
7
. Rotation of the traverse drum in normal or reverse direction causes the trolley
9
to be moved in traverse direction.
The trolley
9
has a head block
15
suspended from the trolley
9
through hoisting ropes
14
which in turn are wound around a hoist drum (not shown) in the machine room
10
and which extend under tension longitudinally of the girder
7
. Rotation of the hoist drum in normal or reverse direction causes the head block
15
to be hoisted up or down.
Detachably interlocked with the head block
15
through twist locks
17
is a spreader
16
which grips the container
4
.
The twist lock
17
comprises a lock pin
19
adapted to be inserted into a slot on an upper surface of the suspender
18
of the spreader
16
and adapted to be twisted for example by a hydraulic cylinder for interlock of the head block
15
with the spreader
16
.
The conventional spreader
16
comprises, as shown in
FIGS. 1
,
3
and
4
, extension frames
21
and
22
which are respectively fixed by retainers
21
′ and
22
′ to respective parallel portions of an endless chain
26
which in turn extends under tension longitudinally of the stationary frame
20
. The chain
26
is driven by a drive
27
to extend or contract the lateral extension frames
21
and
22
in unison laterally or perpendicularly of the traverse direction of the trolley
9
. Such extension or contraction of the extension frames
21
and
22
allow a variety of containers
4
with different lengths to be suspended.
Each of the extension frames
21
and
22
has, at its tip, twist locks
23
constructed similarly of the twist locks
17
of the head block
15
to grip the container
4
as well as guide arms
24
for positioning the twist locks
23
for engagement with the container
4
. The guide arm
24
can be swung from an upper, turned-over open position into a position for engagement with a corner of the container
4
by actuation of a hydraulic motor
25
. This will ensure that the spreader
16
can be correctly positioned to the container
4
and that the twist locks
23
can be positively engaged with the container
4
even if there may be some deviation in lowering the spreader
16
interlocked with the head block
15
onto the container
4
for hoisting of the container
4
.
Each of the extension frames
21
and
22
of the conventional spreader
16
comprises, as shown in
FIGS. 4 and 5
, two frames each with a vertically elongated rectangular section, the two frames being spaced apart from and connected with each other widthwise of the stationary frame
20
. The extension frames
21
and
22
are supported by sliders
21
a
,
21
b
,
22
a
and
22
b
(
FIG. 5
) such that they may brush past with each other with respect to the stationary frame
20
. The extension frames
21
and
22
may be I-shaped frames other than the vertically elongated rectangular frames as shown in FIG.
5
.
Generally, the container
4
is loaded onto the container ship
1
, using the container crane
3
, by the following sequence of operations. Firstly, the spreader
16
interlocked with the head block
15
from the trolley
9
is hoisted down onto the container
4
. The rock pins
19
of the twist locks
23
are then inserted into slots on an upper surface of the container
4
and are twisted for example by a hydraulic cylinder to interlock the spreader
16
with the container
4
. In this state, the head block
15
and spreader
16
are hoisted up and the trolley
9
is moved in traverse direction to a target position above the container ship
1
. Then, the head block
15
and spreader
16
are hoisted down to place the container
4
onto the container ship
1
.
In such container crane
3
, the container
4
often has a predetermined destination. In such a case, with the destination of the container
4
being set, the trolley
9
may be automatically moved in traverse direction; and only hoisting-up and -down of the spreader
16
interlocked with the head block
15
may be manually carried out by an operator in an operation room
36
.
However, the above-mentioned conventional spreader for the container crane has following various problems.
The spreader
16
tends to be damaged since generally the spreader
16
is collided with and placed onto the container
4
when the spreader
16
interlocked with the head block
15
is to be hoisted down onto the container
4
for connection of the spreader
16
with the container
4
. More specifically, when the spreader
16
is hoisted down, only tip ends of the extension frames
21
and
22
contact the upper surface of the container
4
, resulting in cantilever relationship of the extension frames
21
and
22
to the stationary frame
20
. This means that when heavy weight (for example over 10 tons) of the head block
15
and spreader
16
acts on the extension frames
21
and
22
upon the collision, the extension frames
21
and
22
will receive extreme bending load which is, for example, 3 or 4 times as large as that received upon hoisting of the container
4
. The conventional spreader
16
, thus, tends to have damages such as bending of the extension frames
21
and
22
. Bending of the extension frames
21
and
22
requires repairing since it disables the extension frames
21
and
22
from being slidingly extended or contracted and shortens the service life of the spreader
16
.
In the conventional spreader
16
, the lateral extension frames
21
and
22
are unaligned or out of alignment in their lateral axes as shown in
FIGS. 4 and 5
so that the extension frames
21
and
22
may be twisted due to any eccentric or torsion load applied when the container
4
is hoisted by the spreader
16
.
In order to prevent such bent and/or twist of the extension frames
21
and
22
, the spreader
16
must be large in size and/or the stationary and extension frames
20
,
21
and
22
must have increased thickness. However, these will inevitably cause increase in weight of the spreader
16
, resulting in increase of electric power required for hoisting of the container crane as well as increase of operation cost.
It has been also conventionally envisaged that the stationary and extension frames
20
,
21
and
22
have box-shaped sections for enhancement of their sectional strength. However, such box-shaped sections will not allow the extension frames
21
and
22
to be brushed against with each other as shown in
FIGS. 4 and 5
; and the extension frames can be hardly extended or contracted with greater stroke depending upon variation in length of the containers. Devised out to overcome this problem were lateral extension frames in the form of two-step extendable (telescopic) structure.
However, such lateral extension frames in the form of two-step extendable structure have been proved to be impracticable since the extension frames may be greatly bent and/or bowed and fail to retain their sufficient strength when the container is hoisted.
Furthermore, in the conventional spreaders
16
, the extension frames
21
and
22
are slidably supported on the stationary frame
20
so as to be extended or contracted depending upon size of the

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