US3841688A

US3841688A - Lifting device for bales

Info

Publication number: US3841688A
Application number: US00394828A
Authority: US
Inventors: S Karlsson
Original assignee: ASEA AB
Current assignee: ABB Norden Holding AB
Priority date: 1973-09-06
Filing date: 1973-09-06
Publication date: 1974-10-15
Anticipated expiration: 1991-10-15

Abstract

A lifting device for bales which bales are secured by bands extending around the bale and forming a lifting loop of magnetic material secured to the band at both sides of the bale includes magnets for catching and lifting up the lifting loop and two grab members for gripping under the lifted loop. The grab members are movable in the lifting device by means of swinging brackets mounted in frames and movable in the longitudinal direction of the lifting device. The swinging brackets are mounted on one side of the frame and the frames at the other side are provided with locking devices to lock the free ends of the swinging brackets and keep them in position during lifting.

Description

nited States ateitt [191 Karisson LIFTING DEVICE FOR BALES [75] Inventor: Signar Karlsson, Sorberge, Sweden [73] Assignee: Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden [22] Filed: Sept. 6, 1973 [21] Appl. No.: 394,828

[52] US. Cl. 294/67 R, 294/74, 294/81 R [51] Int. Cl. B66c 11/10 [58] Field of Search 294/67 R, 67 B, 67 BB,

294/67 BC, 67 DA, 67 DB, 65, 65.5, 74, 81 R, 81 SF, 88, 106; 214/114 [56] References Cited UNITED STATES PATENTS 3,413,027 11/1968 Bohlin et a1 294/81 R 3,493,259 2/1970 Morgan 294/74 3,610,673

10/1971 Strombeck et al 294/81 R X 1 3,727,965 4/1973 Cranston et al 294/67 R Primary Examiner-Even C. Blunk Assistant Examiner.lohnny D. Cherry [5 7 ABSTRACT A lifting device for bales which bales are secured by bands extending around the bale and forming a lifting loop of magnetic material secured to the band at both sides of the bale includes magnets for catching and lifting up the lifting loop and two grab members for gripping under the lifted loop. The grab members are movable in the lifting device by means of swinging brackets mounted in frames and movable in the longitudinal direction of the lifting device. The swinging brackets are mounted on one side of the frame and the frames at the other side are provided with locking devices to lock the free ends of the swinging brackets and keep them in position during lifting.

4 Claims, 6 Drawing Figures PATENIED OCT 1 51974 SHEET 20F 3 m\ mm 6, mm k\ 1 Q m QM PNENIED GET '1 1 74 SHEET LIFTING DEVICE FOR BALES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lifting device for lifting bales of the type which is secured by a strap surrounding the bale and is provided with a lifting loop or handle of a magnetic material, preferably the same material as the strap, said lifting loop being attached to the strap on both sides of the bale.

2. The Prior Art This type of bale, for example for paper pulp, is nowadays generally being used and is the subject of statutory rules in some countries with regard to loading and unloading in ports.

Lifting devices for such bales consist, on the one hand, of a magnet to lift up the loop and, on the other hand, of grab members with grip under the loop and raise the bale.

It is important in this connection that the lifting loop is not overloaded, and it should be pointed out that if the lifting forces are exerted in the middle of the lifting loop so that the loop forms a triangle over the bale, the tensile force in each of the two loop parts will exceed the total weight of the bale, unless the lifting loop is unreasonably long.

SUMMARY OF THE INVENTION According to the invention the tensile force in the lifting loop is limited to a minimum, which is to say half of the weight of the bale, since the lifting loop lifts in two parts. This is achieved because the lifting device comprises two grab members, mutually displaceable, which, when they have gripped under the strap, are pushed away from each other until the distance between them is the same as the width of the bale. In this way, the bale is lifted in by two vertical loop parts, which divide the load equally between them, and the middle of the lifting loop extends between the two grab members, parallel to the upper side of the bale and with the same tensile load as the vertical'parts, i.e., half of the bale weight. I

The lifting device according to the invention has a construction which includes a magnet for catching and lifting up the lifting loop of magnetic material and grab members for gripping under the lifted loop to raise the whole bale. The guide members are movably mounted in the lifting device, and include swinging brackets mounted in the frames and movable with respect to each other in the longitudinal direction of the device. The swinging brackets are mounted in one side of the frames and the frames at the other side are provided with locking devices to grip the free ends of the swinging brackets and keep them in position during lifting.

BRIEF DESCRIPTION OF THE DRAWINGS guiding means. FIG. 6 is a diagram showing the balance of force in the device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the lifting device seen from the side and with the side cover removed. The device comprises a chassis or housing 1 and is suspended from yoke 2, the stem of which is able to move downwards and upwards in the housing because the stem or stems is/are provided with a groove 3 sliding on a pin 4 in the housing, whereas the lower end of the stem is provided with another pin 5 sliding in a groove 6 at the side of the housing. At the lower end of the yoke shaft other yokes 7 are positioned, said yokes influencing two link connections 8 of the pantographic link connection type.

Said link connections aresuspended at their inner, upper ends to fixed pins 9 in the housing 1, whereas the lower ends slide in grooves 11 at the side of the housing by means of pins 10 with rollers. At the outer end of the link connections 8 there are frames 12 which are provided at their upper ends with fixed pins 13 for one leg of the link connection, the other leg sliding in grooves 15 at the sides of the frames by means of pins 14 with rollers.

Thus it is clear that, when yokes 2 are lifted the yokes 7 will press the link connections 8 together from below and upwards, the link connections then expanding laterally and pressing the frames 12 outwards.

As is clear from the following, the motion of the frames is not supposed to be conveyed by the lifting force. The purpose of this is only to counterbalance the forces from the lifting loop of the bale when the lifting device has been made ready for lifting (see FIGS. 2 and 3).

FIGS. 2 and 3 show longitudinal sections at approximately the centre of the lifting device and show operating members for moving the frames out of and into the housingrThese operating devices consist of hydraulic cylinders or preferably air cylinders 16, pivotably journalled in the housing and having piston-rods 17 which push against the link connections 8, thus forcing these out or in.

FIGS. 2 and 3 also show a number of magnets 18 secured to a frame 19 with suspension loops 20. These loops are suspended at the lower ends of swinging brackets 21 which are able to pivot around fixed pins 22 in the housing 1. The swinging brackets 21 are drawn upwards by tension springs 23. The upper ends of the brackets 21 are provided with rollers 24 influenced by guide rails 25 on the frames 12.

This means that, when the frames 12 are pushed against each other as in FIG. 2, the rollers 24 are pressed upwards and inwards, the lower ends of the brackets 21 being pressed downwards. The frame 19 with the magnets 18 slides downwards on a level with the lower side of the lifting device so that the magnets can easily grip the magnetic lifting loop 26 on .the strap 27 which holds the bale 28 in position. Then when the frames 12 are swung apart the rollers 24 are released and the springs 23 lift the swinging brackets 21 and also the frame 19 with the magnets 18 holding the lifting loop 26 which then becomes easily accessible. The movement of the frame 19 upwards and downwards is intensified by the shape of the loops 20. When the lift ing loop 26 is then stretched out as explained below, the lifting loop 26 is drawn away from the magnets.

The lifting loop 26 is gripped by swinging brackets 29 attached to the lower end of shafts (not shown) in the frames 12. These shafts are provided at their upper ends with a crank arm 30 with a crank pin 31 sliding in a guiding means 32 at the roof of the housing 1. This guiding means is most clearly illustrated in FIG. 5, showing a part of the device seen from below, and it is seen that when the frames 12 are in their innermost position the swinging brackets 29 lie parallel to the side of the housing 1. When the frames 12 move outwards, the crank pin 3 very soon engages with the guiding means 32, and the crank arm 30 is swung outwards whereas the swinging brackets 29 are swung inwards, in under the lifting loop 26 which just before this has been lifted'up by the magnets 18. The design of the frames 12 is best apparent from FIG. 4. As the lifting loop 26 lies over the swinging brackets 29 (see FIG. 3), these have to be secured in their swung-out position, which is done by means of a lock gripping the free end of the swinging bracket when the bracket has swung out to its perpendicular position.

The lock consists of a turnable locking wedge 33, which is seen in FIGS. 2 and 3. Said locking wedge is mounted on a pin which is able to turn in the frame 12 and at the other end of which, i.e, the end pointing towards the inside of the housing 1, a guide wedge 34 is attached (see FIG. I). This guide wedge is operated by a guide rail 35 which is-positioned at the inside of the housing 1 approximately opposite the innermost position of the frame 12, so that the guide wedge rests on the rail in this position. The locking wedge 33 is lifted and the arm 29 is free. At the left-hand side of FIG. 2 the lock is shown in its released position, and in FIG. 3 the lock is engaged and secures the free end of the arm 29, see the right-hand side.

The locking wedge 33 and the guide wedge 34 are suitably spring loaded in the direction towards locked position. It is also clear that the guiding means 30-32 and 33-35 must be well adjusted with respect to each other so that locking and disengaging of the free ends of the swinging brackets can be made unimpededly while the frames are moved outwards and inwards.

In the description of FIGS. 1 and 3 and of the lifting force over the yokes 7 towards the lower, inner end of the link connections 8, it was mentioned that this force tends to stretch out the link connections, and this stretching force is to counterbalance the tendency of the tension in the lifting loop 26 to press the link connections 8 together.

How to achieve this is most clearly illustrated in FIG. 6 showing a theoretical sketch of the principle of suspending a bale. FIG. 6 shows the bale 28 strapped by the band 27 and suspended in the lifting loop 26 by means ofa pair of linking arms 36. From a purely practically point of view, such a suspension can be achieved by arranging a pair of link arms on either side of the bale and joining the free ends of these arms by means of round bars 37 on which the lifting loop 26 rests. The suspension force is applied at the joints 38 of the link arms.

It is now seen that if the link arms 36 are so long in relation to the width of the bale 28 that the angle between them is acute, the stress in the lifting loop 26 will pull the bars 37 towards each other. In this way the angle between the different parts of the lifting loop increases, and the stress in the lifting loop also increases.

If, on the other hand, the link arms 36 are so short that they form an obtuse angle, the lifting force will press the bars 37 away from each other, the angle between the parts of the lifting loop thus decreasing. This also increases the stress in the loop 26. To this is also added a force which attempts to break the connection between the lifting loop 26 and the strap 27.

A complete balance is obtained, however, if the link arms are so adapted to the bale width that the angle between the link arms is The link arms then halve the angles between the parts of the lifting loop, and these angles also become 90. The two supporting parts of the lifting loop become vertical and the stress in the lifting loop is exactly half of the weight of the bale. If the bars 37 in this case are connected by a stiff link, this link will be completely unloaded and it is of no significance whether the connection 38 between the link arms 36 is stiff or movable.

It is clear from FIGS. 1 and 3 that the balance between the lifting force and the stress in the lifting loop, in the case of vertical, supporting parts, is achieved when the legs of the link connections 8 are perpendicular to each other. If the bales were always available in standard sizes it would be relatively easy to adjust the dimensions of the lifting device so that the link connection arms would be almost perpendicular to each other in extended position. However, even when the lifting device is made with good fitting and well lubricated it must be assumed that such frictional forces occur in the lifting device that reasonable variations in the dimensions can be tolerated without disturbing the balance.

The operation of the device prior to and after the lifting, is performed, as mentioned, by means of the working cylinders 16 which are adapted for remote control operation. These cylinders and their working pressure should be so adjusted that the link connections 8 are stretched to such an extent that'the lifting loop 26 is extended to substantially the same width as the bale 28. The supporting parts of the lifting loop will be vertical corresponding to minimum stress in the lifting loop which is equal to half the bale weight. As mentioned the frictional forces in the link. connections will keep them in the stretched-out position.

I claim:

1. Lifting device for lifting a bale (28), which bale is secured by a band (27) surrounding the bale and forming a lifting loop (26) of a magnetic material secured to the band at both sides of the bale, the device comprising a magnet (18) to catch and lift up said lifting loop and two grab members to grip under the lifted loop and raise the whole bale, said grab members being movable in the lifting device, in which said grab members comprise swinging brackets (29) mounted in frames (12) and being mutually movable in the longitudinal direction of the lifting device, the swinging brackets being mounted in one side of the frames and the frames at the other side being provided with locking devices (33) to grab the free end of each swinging bracket and keep it in position during lifting.

2. Lifting device according to claim 1, in which guiding means (30,32 and 34,35) are provided in the lifting device for guiding the swinging of the swinging brackets (29) and the operation of said locking devices (33), said guiding means including means which come into operation when said frames (12) are in the area closest to each other.

ances the tractive force in the lifting loop 26).

4. Lifting device according to claim 1, in which said magnet 18) is movable in the vertical direction and its lowest position is approximately on a level with the lower side of the lifting device when said frames (12) are closest to each other, while the magnet is raised when the frames are separated.

Claims

3. Lifting device according to claim 1, in which there are particular mechanical operating members (16) to move said frames (12) and swinging brackets (29) towards and away from each other when the lifting device is unloaded and the lifting device is provided with a suspension device (7) which is connected to said frames (12) by way of link connections (8) in such a way that the frames are pressed apart by the weight from the bale (28) with a force which substantially counterbalances the tractive force in the lifting loop (26).

4. Lifting device according to claim 1, in which said magnet (18) is movable in the vertical direction and its lowest position is approximately on a level with the lower side of the lifting device when said frames (12) are closest to each other, while the magnet is raised when the frames are separated.