DEVICE IN COMBINATIVE YOKE MEANS

Abstract: The invention relates to a device for swinging lifting arms of combinative yoke means upwards and transfer thereof to a position inside the long sides of the yoke means, when con­ tainers and trailers are being handled, and is characterized in that the device comprises a first substantially horizontal shaft (1) for swinging the lifting arm (2) upwards from a ver­ tical to a substantially horizontal position and the other way round and a second substantially horizontal shaft (3), around which the first shaft is pivotable together with the lifting arm for swinging in and out the upwardly swung, substantially horizontal arm to a position inside and outside, respectively, the long side of the yoke means.

Description: The invention relates to a combinative yoke means, for handling containers and trailers, incorporating a device for swinging lifting arms upwards and transfer thereof to a position inside the long sides of the yoke means, said device comprising a first inclined or substantially horizontal shaft for swinging the lifting arm upwards from a vertical to a substantially horizontal position and vice versa. Such a location of the lifting arms of the combinative yoke means inside the long sides of the yoke means is of the greatest importance when using the yoke means for handling merely containers, said yoke means supporting the container in each of its four corners only by means of so-called twist locks, especially in the case when a close arrangement of containers in for example cargo terminals is desired for space reasons which has of course great economical advantages. Such a device is already known. In this device the lifting arms are first swung upwards by means of a conventional hydraulic cylinder, the piston rod of which is attached to the lifting arm and the very cylinder to an intermediate piece in which the arm is pivotably suspended, to a substantially horizontal position, after which the intermediate piece with the upwardly swung arm and the hydraulic cylinder is pulled in to a position inside the long side of the yoke means by means of another conventional hydraulic cylinder arranged on a stationary transverse beam included in the frame in which a movable beam is arranged telescopically, said intermediate piece being attached to said movable beam. A disadvantage of this known device is that the lifting arms in an upwardly swung, pulled-in position will not remain in this position due to the fact that the hydraulic cylinder always has a certain leakage of hydraulic liquid but will sink from its horizontal position. This sinking which, moreover, is accelerated by the violent movements of the yoke means in handling and of course may be different for different arms may result in the lifting arms getting in contact with one another and sometimes, moreover, hook to and lock each other and, which is very common, that the lifting arms will knock a hole in the container and the trailer which for example in a following rain may have devastating effects on the contents of the container and the trailer. Such damage to the container and the trailer must be put right immediately resulting in a stop which, consequently, involves losses of both time and money. Another disadvantage is the bad moderation of the swinging movements of the lifting arms in the longitudinal direction of the yoke means, for example due to an unevenly distributed load in the container or inexact operation of the yoke means caused by the conventional hydraulic cylinders of the lifting arms with one piston in handling which may result in a displacement of the load, damage to this in case of a fragile load and to the very yoke means, trailer and container. In this connection reference is also made to the documents US-A-4 014 447, column 2, lines 29-42, claim 1, Fig. 1-3; US-A-4 149 747, column 2, lines 18-26, Fig. 3; FR-A-2 457 832, Fig. 4 and US-E-27 905, Fig. 1, 4 which describe the prior art of this field and of which US-A-4 014 447 is considered the nearest prior art. Consequently it is the object of this invention to provide a combinative yoke means, for handling containers and trailers, incorporating a device for swinging lifting arms upwards and transfer thereof to a position inside the long sides of the yoke means, said device comprising a first inclined or substantially horizontal shaft for swinging the lifting arm upwards from a vertical to a substantially horizontal position and vice versa, and eliminating the disadvantages in the known devices described above. This object is achieved by means of the combinative yoke means incorporating a device for swinging lifting arms according to the invention which is characterized in that the device also incorporates a second inclined or substantially horizontal shaft, around which the first shaft is pivotable together with the lifting arm for swinging the upwardly swung, substantially horizontal arm in and out to positions inside and outside, respectively, the long side of the yoke means. The device is characterized in, moreover, that the first shaft and the second shaft can be arranged substantially perpendicularly to each other, that the first shaft can connect the lifting arm to an intermediate piece and that the second shaft can connect the intermediate piece with the yoke means pivotably. Furthermore, the respective second shaft can be arranged at the ends of a frame included in the yoke means or at the ends of the traverse beams of the yoke means. For swinging up the lifting arm and swinging in the intermediate piece and the lifting arm the device of the invention may comprise further a hydraulic double cylinder, one piston rod of which is connected to the intermediate piece and the other piston rod with the lifting arm and a hydraulic cylinder, respectively, connecting the intermediate piece with the yoke means. The invention is described below in greater detail in the form of an example with reference to the enclosed drawing, wherein Fig. 1 is a schematic perspective view of a combinative yoke means of the invention, for handling a trailer, incorporating a device for swinging lifting arms, Fig. 2 is a schematic perspective view of the same combinative yoke means as in Fig. 1 for handling a container, Fig. 3 is a schematic lateral view of the intermediate piece in the device of the combinative yoke means of the invention and shows how the piston rod of the hydraulic cylinder and the lifting arm are connected to this intermediate piece, and Fig. 4 is a schematic longitudinal section of the hydraulic double cylinder with its associated control circuit used in the device of the combinative yoke means of the invention. As is apparent from the drawing, especially Figs. 1 and 3, the device of the combinative yoke means of the invention comprises an intermediate piece 4 with a first substantially horisontal shaft 1 fixedly mounted therein, around which a lifting arm 2 belonging to the very combinative yoke means can be swung upwards and inwards substantially in parallel with the long side of the yoke means from a vertical to a substantially horizontal position by means of a hydraulic double cylinder 8, one upper piston rod of which is articulatedly connected to a pair of lugs 10 on the intermediate piece and the other lower piston rod with a pair of lugs 11 on the lifting arm 2. The intermediate piece comprises further a sleeve 9 in which a second substantially horizontal shaft 3 attached to the yoke means is received, around which the intermediate piece with the lifting arm in a substantially horizontal position can be swung into the position shown in Fig. 2 by means of a conventional hydraulic cylinder 7, the piston rod end of which is rotatably connected to a second pair of lugs 12 on the intermediate piece. As mentioned above, both the first shaft 1 and the second shaft 3 are substantially horizontal. It should be understood by this that the first shaft can be somewhat inclined downwards relative to the horizontal plane to the right or to the left or that the second shaft can be inclined somewhat upwards or downwards relative to the horizontal plane. Of course the two shafts 1 and 3 can also be quite horizontal, one lifting arm lying inside the other in the same horizontal plane. In order that the lifting arms 2 in an upwardly swung position might be swung in at each long side of the yoke means in a spaced relationship the second shafts 3 at one end of the yoke means, for example, can thus be mounted so that they are somewhat inclined downwards from the horizontal plane and at the other end of the yoke means so that they are inclined somewhat upwards from the horizontal plane (see Fig. 2). If the intermediate piece 4 is swung inwards to such a position that the shaft 1 is vertical there is no turning point around which the lifting arm, also at leakage of hydraulic liquid from the double cylinder, can turn and, consequently, by the device of the combinative yoke means of the invention sinking of the lifting arm and the associated damage described above in connection with the prior art are eliminated by means of the device of the invention. However, as a matter of fact the first shaft 1 is inclined in its final position, as shown in Fig. 2, somewhat inwards from the vertical plane against the yoke means and consequently the lifting arm and the intermediate piece will exert a torsional movement about the second shaft 3 in this position. However, the small torsional movement concerned here is absorbed by the hydraulic cylinder 7, the piston of which is quite retracted in this position. The above-mentioned double cylinder 8 shown in Fig. 4 is used with the device of the combinative yoke means of the invention instead of a conventional hydraulic cylinder primarily to improve damping of the tensile forces arising at the outwardly directed pivotal movements of the arms which can bring several problems as mentioned in the introductory portion of the specification. In principle the double cylinder has three positions, viz. both pistons retracted, the upper piston retracted and the lower piston pushed out and both pistons pushed out. In the present case only the two first positions are used. In the first position the lifting arm is in an upwardly swung substantially horizontal position and in the second position in its vertical lifting position (Figs. 1 and 4). Damping can be effected in the following way: at an inwardly directed pivotal motion of the lifting arm the double cylinder will be exposed to a compression force that is damped by the lower cylinder as in a usual hydraulic cylinder with a piston, while the double cylinder at an outwardly directed pivotal motion of the lifting arm, i.e. in a direction towards the end section of the yoke means, will be exposed to a tensile force that is damped by the upper cylinder. The control circuit used with the two double cylinders shown in Fig. 4 comprises the following components: two adjustable overflow valves 13, 14, a directional valve 15, a safety valve 16, a non-return valve 17, a pump 18, a tank 19 and conduits for the hydraulic liquid. The fundamental buildup of the control circuit is of course the same independently of the number of double cylinders. Thus, by using a double cylinder damping of the tensile forces at the outward motion of the lifting arms is also achieved in addition to the usual damping of the compression forces at the inward motion of the lifting arm. As everybody understands this is not without importance as the motion forces can amount to 100 000 N and more. Thus, by means of the combinative yoke means incorporating a device for swing lifting arms of the invention both a more efficient utilization of the storage surfaces of the cargo terminals and a safer handling of trailers both for humans and surroundings are obtained.

Claims: Combinative yoke means, for handling containers and trailers, incorporating a device for swinging lifting arms upwards and transfer thereof to a position inside the long sides of the yoke means, said device comprising a first inclined or substantially horizontal shaft (1) for swinging the lifting arm (2) upwards from a vertical to a substantially horizontal position and vice versa, characterized in that, a second inclined or substantially horizontal shaft (3), around which the first shaft is pivotable together with the lifting arm for swinging the upwardly swung, substantially horizontal arm in and out to positions inside and outside, respectively, the long side of the yoke means. The device of claim 1, characterized in that the first shaft and the second shaft are arranged substantially perpendicularly to each other, that the first shaft connects the lifting arm to an intermediate piece (4) and that the second shaft connects the intermediate piece with the yoke means pivotably. The device of claim 2, characterized in that the respective second shaft (3) is arranged at the ends of a frame (5) included in the yoke means. The device of claim 2, characterized in that the respective second shaft (3) is arranged at the ends of the traverse beams (6) of the yoke means. The device of claim 2, characterized in that it comprises a hydraulic cylinder (7) connecting the intermediate piece (4) with the yoke means. The device of claim 2, characterized in that it comprises a hydraulic double cylinder (8), one piston rod of which is connected to the intermediate piece (4) and its other piston rod to the lifting arm (2).

Inventors: KARLSSON, GOESTA, Karlsson, Gösta
Applicants: KARLSSON, GOESTA
Application year: 1987
Main classification: B66F9
IPC codes: B66C1