The present invention refers generally to lifting devices for standardized goods containers, and more closely to a lifting yoke or a lifting frame for handling such containers .

Thus, the present invention refers, for example, to the type of lifting yokes described in Swedish published specification 7407425-3 and comprising a central frame unit which is supported, for example, by a crane or other lifting device, generally by the aid of cables. Extending from the central frame unit are two pairs of substantilly parallel beams , one pair in either direction. The outer ends of the . corresponding beam pairs are mutually connected ty cross-bars.

The beams extending from the central frame unit are adapted to be extended and retracted in relation thereto for adjusting the mutual spacing between the cross-bars to enable the lifting yoke to be adapted to various container sizes.

At their ends the cross-bars are provided with downwardly extending rotary blocks adapted to be inserted into the upper corner boxes of the containers and locked therein to enable the containers to be lifted. At the outer edges of the cross bars there are normally upwardly and downwardly swingable feeler arms guiding the lifting yoke into correct position during lowering towards the containers and thus, causing the rotary blocks correctly to meet the openings of the corner boxes in question.

For various reasons however, it sometimes happens that the containers are deformed and that the rotary blocks encounter difficulties to meet the holes of all the four corner boxes. The adjustment of the lifting yoke is so exact that already displacements amounting to some few milimetres between the four corner boxes may cause the lifting blocks to meet only two or thr-ee of the openings of the corner boxes. In such cases the lifting yoke is blocked so that a lifting cannot be performed. Accordingly, it is desirable that the yoke is slightly flexible in order to be able to compensate for deviations in the spacing between the corner boxes of a container.

It is neither unusual that lifting yokes during operation start swingning and might strike against, for example, ship sides or

other objects. If in particular the cross-bars strike against some object there will be a heavy impact stress on the operating mechanism for the adjustment of the lifting yoke and there will also be some risk of a deformation of the yoke itself. Accordingly, it is desirable that the effect of such impacts can be . all eviated and that a compensation for any deformation may be obtained to enable the yoke to be used for continued operation without repair.

An attempt to solve the problem is constituted by resilient transmissions between the operating arms and the cross-bars. However, it has shown to involve some drawbacks to have the operating arms resiliently connected to the cross-bars, i.a. due to the cinetic energy of the operating arms unresiliently actuating the mounting of the operating arms to the operating chain. There have also been some difficulties with regard to the adjustment of the syncronizing of the cross-bars. The known structure is neither useful in connection with other embodiments of lifting yokes than in which there is a special operating arm. Hence, the cpeirating arm or arms constitute sometimes also the arms or bars which support the cross bars and if these then are resiliently mounted the structure would be too flexible in order to operate satisfactory.

The object of the present invention is to remove the above problems and this object has been reached by a device of the type referred to in the claims from which also what- is especially characterizing the invention is clear.

The invention is closer described in the following with reference to the attached drawings in which

Fig. 1 is a schematic upper plane view of a lifting yoke constructed according to the invention,

Fig. 2 is a schematic view, partially in section, through the lifting yoke shown in Fig. 1 showing a preferred embodiment of the invention, and

Fig. 3 is a broken, partially sectioned view showing a detail of the invention.

The lifting yoke 1 shown in Fig. 1 comprises a central frame unit 2 having pairs of side beams 3 , 4 adapted to be extended and retracted in relation to the frame unit 2. At the outer ends said cairs

of side beams 3 , 4 are connected by cross-bars 5 , 6 which at their outer ends support devices 7 including lifting blocks and feeler arms.

The outward and inward shifting of the pairs of side beams 3, 4 is performed with the aid of specific operating arms 8, 9- These are guided in the central frame unit 2 and attached substantially centrally of the cross-bars 5 , 6. The operation is performed by the aid of a motor 18 driving one 9 of the operating arms and this movement being transferred to the other operating arm 8 by su i means as chains. Feeler means (not shown) mark the various adjusting positions of the lifting yoke which thereby is ad justed to a length corresponding to the length of the container in question.

In Fig. 2 there is schematically shown an arrangement of the resilient mounting. From the cross-bars 5 and 6 there extend operating arms 8, 9 towards and above each other in the same way as in connection with the lifting yoke in acorrdance with Fig. 1. A resilient mounting 20 between a looped chain 21 and each operating arm 8, 9 is at the ends of the operating arms. The chain 21 runs around two opposite sprocket wheels 22 , 23 one at each end of the central frame unit. One of said sprocket wheels 22 , 23 is driven for the movement of the chain 21 and accordingly for the adjustment of the yoke.

The resilient mounting 20 is clear from Fig. 3. At the end of the operating arm e.g. 8 there is a cross-piece 24 secured by welding. Said cross-piece 24 extends from the qperating arm in the direction towards the chain 21 and is in the extending portion provided with a thorough opening 25. A rod 26 extends through said opening 25 and each end thereof is connected to the ch-ain 21. The rod 26 is threaded and two pairs of nuts 27, 28 are screwed onto the rod one pair on each side of the cross-piece 24. Between the cross-piece 24 and each pair of nuts 27, 28 there is a set of spring washers 29, 30.

By tightening the pairs of nuts 27, 28 towards the cross-piece 24 the sets of spring washers 29, 30 are biased. Between the connection of the chain 21 with one end of the rod 26 and just the resilient part of the mounting there is a stretching screw 31 by the aid of which the stress of the chain can be altered .

By this structure there is obtained a resilient transmission between the chain 21 and the operating arms 8, 9. In connection with the adjustment operations heavy weights are brought into movement .and are stopped and this fact gives rise to great stresses on the machinery as well as on the chain. By the present structure said stresses are reduced essentially and this structure can also absorb chocks of the type previously mentioned so that said chocks are not transferred to machinery and chain.

The structures shown in Figs. 2 and 3 may be used separately in the lifting yoke or in combination with any known structure. The embodiment in accordance with Figs. 2 and 3 is also of the advantage that it is easy to mount in connection with repair or altering of a prior yoke.

If the distances between the c-penings in the corner boxes of a container do not exactly corresponds to the adjusted position of the lifting yoke the lifting block still can penetrate into the openings of the corner boxes under the action of the weight of the yoke. As the inserting ends of the lifting blocks are slightly conical the insertion into the corner boxes in contact with the walls of the openings will produce a tendency towards a shifting of the cross-bars 5, 6 outwardly or inwardly in the longitudinal direction of the yoke. With spring action in the attachments 20 such a limited moment in the plane of the yoke enables also deformed containers to be lifted without specific rreasures.

For the experts on this field it is quite clear that from the point of view of adaptation it may be sufficient to provide only one resilient attachment but the provision of two or more such attachments increases the adaptability of the yoke. Other resilient means than spring washers 15 may also be used such as pynthetic or natural rubber.

If the lifting yoke starts swinging during operation and strikes any of the cross-bars 5, 6 against some object, such as the side of the ship, this impact will be damped by the resilient transmission. This will considerably reduce the stresses imparted to the operating machinery in consequence of such impacts and also the risks for deformation of the yoke will be reduced due to this damping

effect.

While the invention has been described with reference to a lifting yoke having parallel pairs of shiftable beams which at their ends support the cross-bars on which the lifting blocks are mounted it will be appreciated that it is equally useful in connection with lifting yokes having a dif frent number of beams for supporting the cross-bars and also in connection with lifting yokes in which only one beam is used for carrying the cross-bars, such beam in this case forming both the operating and the supporting beam.