[0001] The present invention relates to a method and an arrangement pertaining to side-lift
yokes for handling mutually stacked empty containers from the sides thereof.
[0002] With the object of rationalizing the handling of empty containers, it has become
usual to transport two containers at a time, with one container stacked on the other.
All corners of this type of container are provided with elongated openings by means
of which the containers can be handled with the aid of hooks or with the aid of so-called
twist-locks that form part of a lifting yoke. The side-lift yokes used to handle two
mutually stacked containers comprise, in principle, a horizontal frame which includes
vertical carrier beams at respective ends thereof. Mounted centrally of the frame
is a truck-lift coupling that can be lengthened or shortened in accordance with the
container length. Respective carrier beams include support surfaces which are brought
into engagement with the container sides, and a top-mounted locking hook for insertion
into the upper locking opening of the bottom container. The two containers can thus
be lifted and transported with the add of a truck-lift through the medium of the side-lift
yokes.
[0003] The safety rules governing the handling of two mutually stacked containers have become
more stringent with time, and it is now no longer permitted to transport stacked containers
with the upper container stacked loosely on the lower container. Different types of
locking devices have therefore been proposed, in an endeavour to meet these requirements.
In addition to guiding the upper container on the lower container with the aid of
guide flanges mounted on the tops of the containers, the side-lift yoke and carrier
beams respectively have been provided wish two superposed locking hooks, of which
the bottom hook is intended to lock in the upper locking opening of the container
and the top hook is intended to lock in the bottom locking opening of the top container,
the intention being to hold the top container firmly to the bottom container. One
problem in this regard is that when stacking containers, the upper container will
not always be positioned in correct alignment with the lower container. This will
cause the locking openings to be offset in relation to one another, meaning that in
the case of carrier beams that are provided with twin locking hooks it is not possible
to insert one of these locking hooks into one of the locking openings. As a result,
it is necessary to bring the upper container into correct alignment with the lower
container before this type of side-lift yoke can be made ready for lifting the containers,
which is a time-consuming task.
[0004] An object of the present invention is to facilitate the handling of two mutually
stacked empty containers and to shorten container handling times. This object is achieved
by means of the present invention, which has the characteristic features set forth
in the following Claims.
[0005] The invention will now be described in more detail with reference to an exemplifying
embodiment thereof and also with reference to the accompanying drawings, in which
Fig. 1 illustrates a known side-lift yoke which includes an inventive arrangement;
Fig.
2 is a side view of the side-lift yoke;
Fig.
3 is a more detailed view of the inventive arrangement and shows the arrangement in
a movement phase;
Fig.
4 illustrates the inventive arrangement in another movement phase; and
Fig.
5 illustrates the twist-lock principle by way of explanation only.
[0006] Fig. 1 thus illustrates a known side-lift yoke comprised of a horizontal frame 1
and a lifting device 2 which is located in the centre of the frame and which is used
to couple the yoke to an automotive vehicle, such as a truck or the like. The yoke
further comprises vertical carrier beams 4 which are mounted on the ends of beams
3, these beams being telescopically movable in the frame 1. Each carrier beam 4 includes
a respective upper and lower support surface 5 which are intended to abut the longitudinal
sides of the container when locking the side-lift yoke. The side-lift yoke is also
provided with a locking device 6 at the top of each carrier beam 3, this locking device
being described below in more detail with reference to the actual invention. The side-lift
yoke as such is known to the art and will include a suitable hydraulic system among
things, and will not therefore be described in more detail here.
[0007] The inventive locking device is shown in more detail in Figs. 3 and 4. The reference
numeral 7 in Figs. 3 and 4 identifies the upper corner of a corner-reinforced lower
container and the bottom corner of a corner-reinforced upper container which rests
or the lower container The inventive locking device comprises two mutually independent
and horizontally movable cylindrical locking bolts 8, each having a head 9 which is
elongated when seen in cross-section or the bolt. Respective locking bolts 8 are moved
horizontally by means of a hydraulic cylinder 10, which is connected to the locking
bolt 8 with the aid of a piston and piston rod 11. Respective locking bolts 8 can
also be twisted through 90° with the aid of a hydraulic cylinder which includes a
piston and piston rod, together referenced 12. This piston rod is mounted excentrically
at the inner end of the locking bolt 8, and functions to twist the bolt through 90°
as aforementioned. The hydraulic cylinder 12 is connected to a bracket 13 which is
connected to the locking bolt 8 and which together with the hydraulic cylinder 12
is operative in moving the bolt 8 when said bolt is manoeuvered by the hydraulic cylinder
10. By way of explanation, it can be mentioned that the locking bolt 8 with its undercut,
elongated head 9 forms what is generally known in the art as a "twist-lock".
[0008] The corner reinforcements at respective corners of each container include elongated
locking openings 14 on each upper side of each container. In this connection, reference
is made to Fig. 5 which illustrates one such locking opening in a container 7 schematically
and shows a locking bolt 8 and its head 9 inserted in the opening. The elongated head
and its opening-adapted shape enables the head to be inserted into the locking opening
14. When the locking bolt is twisted, the head will grip behind the defining edges
of the locking opening 14 and therewith lock the bolt to the container, and in the
illustrated case lock the container to the side-lift yoke.
[0009] The invention functions in the following manner. Fig. 3 shows a lower container 7
and an upper container 7 which rests on top of the lower container 7 and which when
stacking the containers has been placed out of longitudinal alignment and, although
not evident from the drawing, may have also been placed out of lateral alignment with
the lower container. The vertical carrier beams 4 of the side-lift yoke have been
placed against the bottom container 7, the two locking bolts 8 being fully retracted
inwardly of the side surface 5 during this operation. With the aid of the hydraulics
10, 11, the truck driver handling the side-lift yoke is able to move the upper locking
bolts 8 outwardly of the support surface 5 and into the bottom locking openings 14
of the upper container 7, whereafter the bolts 8 are twisted through 90° so as to
lock the upper container to the side-lift yoke. The truck driver is now able to move
the upper container 7 both laterally and longitudinally with the aid of the side-lift
yoke, so as to bring the upper container into full alignment with the lower container,
as shown in Fig. 4. When the truck driver has positioned the upper container 7 correctly
on the lower container with the aid of the upper pair of locking bolts 8, the lower
pair of locking bolts 8 are moved outwardly of the support surface 8 with the aid
of the hydraulics (10, 11) and twisted through 90°, therewith locking the lower container
7 to the side-lift yoke. Both containers 7 are herewith locked to the side-lift yoke
and can be lifted and transported safely with the support surfaces 5 of the carrier
beams in abutment with the sides of the container.
[0010] The invention thus enables the upper container to be brought into correct alignment
with the lower container and the containers thereafter locked together, with the aid
of the side-lift yoke. This has not earlier been possible, and it has previously been
necessary either to ensure that the containers are stacked while in precise alignment
with one another or to bring the upper container into alignment with the lower container
in some way or another. The invention thus provides for simple and speedy handling
of mutually stacked empty containers.
[0011] Although the invention has been described with reference to a "twist-lock", it will
be understood that other types of extendable and retractable locking devices can be
used.
1. A method of handling two mutually stacked containers from a respective side thereof
with the aid of a side-lift yoke, characterized in that the side-lift yoke is locked to the two lower corners of the upper container
on a respective side thereof and, when necessary, the upper container is brought into
alignment with the lower container with the aid of the side-lift yoke, whereafter
the side-lift yoke is locked at the two upper corners of the lower container on said
side while continuing to lock the side-lift yoke to the upper container.
2. A side-lift yoke arrangement for handling two mutually stacked containers from a respective
side thereof, characterized in that the side-lift yoke includes a first upper pair of locking devices (8) which
are intended to engage with locking openings (14) in the bottom corners or the upper
container (7) on said respective side, and a second pair of lower locking devices
(8) which are intended to engage with locking openings (4) in upper corners of the
lower container (7) on said respective side, wherein the upper pair of locking devices
and the lower pair of locking devices can be withdrawn from the plane extending through
support surfaces (5) on the side-lift yoke that coact with the lower container (7),
independently of the other pair.
3. An arrangement according to Claim 2, characterized in that each of the locking devices includes a cylindrical bolt (8) which has an
undercut head (9) of elongated shape in cross-section, wherein the head (9) is intended
for insertion into a locking opening (14) of a container (7), and wherein each cylindrical
bolt (8) is movable axially towards and away from respective container sides and can
be twisted through 90° for engagement of the head in the locking opening.
