WO2018062994A1

WO2018062994A1 - Grab shell, grab and method of manufacturing a grab shell

Info

Publication number: WO2018062994A1
Application number: PCT/NL2017/050650
Authority: WO
Inventors: Leendert Gommert VAN KOEVERINGE; Michel CORBEAU
Original assignee: Nemag NV; Nemag BV
Current assignee: Nemag NV; Nemag BV
Priority date: 2016-09-30
Filing date: 2017-09-29
Publication date: 2018-04-05
Anticipated expiration: 2019-03-30
Also published as: DE112017004945T5; NL2017563B1

Abstract

Grab shell (1) comprising a bent bottom (6) of which two opposing edges are each provided with a side wall (7). The bottom and side walls include sheet metal with which a shell space is formed for holding material to be grabbed. Sheet metal of at least one side wall connects to sheet metal of the bottom via a bent edge portion in the sheet metal of the side wall.

Description

Title: Grab shell, grab and method of manufacturing a grab shell

The invention relates to a grab shell for a grab, to a grab including a grab shell and to a method of manufacturing a grab shell.

Grab shells are known per se, and are often used in grabs for handling bulk materials by grabbing.

A grab shell typically comprises a bent bottom of which two opposing edges are each provided with a side wall. The bottom and side walls include sheet metal with which a shell space is formed for holding material to be grabbed, e.g. coal, ore, biomass, minerals or rocks. A free edge of the bottom and adjoining free edges of the side walls form an entrance face, which may be provided with a cutting profile. A typical grab includes two grab shells that are movably connected to a grab body to move between a closed position in which the entrance faces of the shells abut so that the shell spaces of the grab shells form a bucket for the material to be grabbed, and an open position of the grab in which the entrance faces of the grab shells are spaced apart and form an opening there between through which material to be handled can pass in and out of the shell spaces.

Grabs are typically subjected to intensive use, and need to be extremely wear resistant. The sheet metal that is used for the grab shells is typically a wear resistant steel plate of e.g. about 8 - 15 mm thickness. This material is not easy to shape, and e.g. seaming parts to become curved in two planes easily introduces tears, cracks or stress concentrations. Grab shells have therefore traditionally been formed by welding the side walls as flat parallel plates at right angles to a bottom plate that is bent in a single plane.

A disadvantage of this configuration is that the edges of the grab shells are relatively sharp, in particular in the corners of the entrance face. This may cause damage to the hold of the bulk material. Also, the sharp edges lead to stress concentration, and due to the dynamic loading forces of the grab thus to accelerated wear. Further, the right angles can cause bulk material to stick to the grab shell at the corners, which can lead to spillage when built up material releases from the corners.

To alleviate this disadvantage, it has been proposed to provided a triangular intermediate plate in the corners of the entrance face, also known as cone plate. Although such a cone plate that is welded between the sheet metal of bottom and the side walls provides the U-shaped entrance face with less sharp corners, it causes compression of bulk material at the apex of the triangle where it meets the bottom and sidewalls, which increases wear.

The present invention aims to improve a grab shell, in particular with respect to the efficiency of the grab shell construction and/or its operational characteristics.

Thereto the invention provides for a grab shell, comprising a bent bottom of which two opposing edges are each provided with a side wall, which bottom and side walls include sheet metal with which a shell space is formed for holding material to be grabbed, and wherein sheet metal of at least one side wall connects to sheet metal of the bottom via a bent edge portion in the sheet metal of the side wall.

The bent edge portion is preferably bent in a single plane, and may in particular line bent, e.g. using a brake press. The bent edge portion may comprise a single bend, but may also include a number of successive bends. The bending radius of each bend is preferably less than 150 mm, more preferably less than 100 mm. The bending radius of each bend is preferably at least the thickness of the sheet, but is more preferably at least 4 of 5 times the thickness of the sheet.

In other words, the side wall may be provided with a bent flap that is integral with the side wall, and that can extend with a substantial transverse component to a body of the side wall to connect with the edge thereof to the edge of the bottom. The edge of the edge portion and the edge of the bottom may be welded together via a single weld line, which facilitates manufacture. The weld line may include segments that are curved in two planes. The side wall and the bottom are thus separate pieces of sheet metal that are connected, e.g. by welding. The side wall and the bottom are thus not integrally formed, but are separate pieces of sheet metal that are composed.

Within the context of this disclosure, kinks are line bends or folds in the sheet metal along a relatively sharply defined fold line, and may typically be provided using a brake press. The bending radius of a kink is within the context of this disclosure is less than 150 mm, in particular less than 100 mm. This as opposed to curves in the sheet metal, which have a more gradual bending zone that is significantly larger than 150 mm, e.g. 200 mm or more, which is obtained using a roll bending or seaming machine. The bent edge portion may comprise several successive, parallel kinks.

The side wall need not be bent along the entire length of the edge that connects to the bottom, and may e.g. only be bent in the area leading up to the entrance face. The bent edge portion is for ease of manufacturing preferably bent along a straight bending line. The bent edge portion advantageously comprises a plurality of segments that are each bent along a straight bending line. The bending lines of the successive segments may then extend at an angle to each other, in particular at a blunt angle. This way, the edge portion may follow the curve of the bottom relatively closely. The side wall may be manufactured form a single piece of sheet metal, but may also be composed of several pieces of sheet metal that are e.g. welded together to form a larger surface. The side wall may be cut from flat plate of sheet metal, which is then bent, in particular in a single plane, and preferably by line-bending.

The bottom may be bent in a single plane. This facilitates manufacture. The bottom may be bent to have a varying curvature, and may in particular be provided with a curvature that increases in an entrance area that starts from the entrance face. This facilitates grabbing the material. The bottom may be bent to a rough polygon, but preferably has a smooth curvature that is e.g. provided by roll bending. The bottom may be manufactured form a single piece of sheet metal, but may also be composed of several pieces of sheet metal that are e.g. welded together to form a larger surface. The bottom may be cut from flat plate of sheet metal, which is then bent, preferably roll bent in a single plane with a varying curvature.

During manufacture, the bent edge portions of the sidewalls are connected, in particular by welding, to opposing edges of the bent bottom so that the sidewalls extend with their main bodies in planes that are substantially perpendicular to the bottom. A free edge of the bottom and adjoining free edges of the side walls form an entrance face, and may be provided with a cutting profile.

The bent edge portions connect substantially obhquely to the bottom. In other words, the edge portions connect to the bottom with a significant transverse component in the connection path towards the bottom. The edge portion may e.g. be bent in a single bend to extend at a sharp angle with respect to the plane of the body portion of the side wall, e.g. a sharp angle in the range of 20-80°, e,g. 30°, 45° or 60°. The edge portion may itself form a flat planar flap. The bent edge portion may also include further, parallel successive bends, e.g. to stepwise increase the angle of its extension with respect to the plane of the body portion. The edge portion may then be polygonal. The bent edge portion be even be bent in a single plane to extend curvedly or substantially curvedly to the bottom.

To facilitate manufacture, the sheet metal of the edge portion may, prior to bending, be cut so that it becomes segmented and includes cutouts between side edges of the segments. The cuts may extend from the edge of the edge portion to the bending line. After bending, the side edges of the cutouts may then be connected, e.g. welded. Consecutive segments may then include a blunt angle at connected side edges. The bent edge portion of the side wall may comprise a scalloped edge, in particular at the edge of the segments. Such scalloped edge may be provided when cutting the edge of the side wall from the flat plate of sheet metal. The scalloped edge may have a varying radius, to match a varying curvature of the bottom. The opposing edges of the bottom to which the sidewalls are to be connected may, during cutting be provided with a negatively scalloped edge that matches the scallops of the bent edge portion. The data for cutting the cutting profile may be obtained through 3D CAD- CAM design software.

The invention further relates to a grab, including at least two grab shells that are movably connected to a grab body to move between a closed position in which the entrance faces of the shells abut so that the shell spaces of the grab shells form a bucket for the material to be grabbed, and an open position of the grab in which the entrance faces of the grab shells are spaced apart and form an opening there between through which material to be handled can pass in and out of the shell spaces. The grab body may include pivoting levers on which the grab shells are mounted, e.g. in case of a scissors grab, or may comprise a frame to which they are mounted via pivots, e.g. in case of a clamshell grab. The grab may in use be carried on e.g. a boom or crane via operating cables, e.g. hoisting cables and opening and closing cables or bars that are connected to the shells and/or other parts of the grab via connection points.

The invention also relates to a method of manufacturing a grab shell, in which sheet metal of a side wall for the grab shell is bent, in particular line-bent to provide it with a bent edge portion, and in which the edge of the edge portion is connected to sheet metal of a bent bottom.

Regarding the extent of this disclosure it should be noted that the technical features described above may each on its own be embodied in a grab shell or grab, i.e. isolated from the context in which it is described, separate from other features or in combination with only a number of features described in the context in which it is disclosed. Each of these features may further be combined with any other feature disclosed, in any combination.

The invention will be further elucidated on the basis of a non- limitative exemplary embodiment represented in the drawings. In the drawings:

Fig. 1 shows a schematic perspective bottom view of a first embodiment of two grab shells in accordance with the invention in a closed position;

Fig. 2 shows a schematic front view of the grab shells of fig. 1;

Fig. 3 shows a schematic side view of the grab shells of fig. 1; and Fig. 4 a schematic bottom view of the grab shells of fig. 1. It should be noted that the figures are merely schematic

representations of a preferred embodiment of the invention. In the figures, identical or corresponding parts are represented with the same reference numerals.

Referring to figs. 1 - 4, two grab shells 1 are shown that are to be movably connected to a grab body (not shown). The grab shells 1 are shown in a closed position in which entrance faces 2 of the grab shells 1 abut so that shell spaces 3 of the grab shells 1 form a bucket for the material to be grabbed. In use, the grab shells 1 may each rotate about a pivot 4 relative to a part of the grab frame so that the entrance faces 2 of the grab shells 1 move away from each other to an open position (not shown), in which the entrance faces 2 are spaced apart at the bottom, and form an opening there between through which material to be handled can pass in and out of the shell spaces 3.

The grab shells 1 shown in this example may be used for a clamshell type grab. The body is not shown in this example, but may include a frame to which the grab shells 1 are connected via pivots 4 and bar connection points 5 as is conventional for a clamshell grab. The grab shell 1 comprises a bent bottom 6. Two opposing edges 8 of the bottom 6 are each provided with a side wall 7. The bottom 6 and side walls 7 are made of sheet metal, e.g. 12 mm wear resistant steel. Sheet metal is planar, sheet like metal material that is cut and bent. The separate sheets of sheet metal of the side wall and the bottom are after cutting and bending welded together to compose the grab shell. A shell space 3 for holding material to be grabbed is formed with the bottom 6 and side walls 7. Sheet metal of at least one side wall 7 connects to sheet metal of the bottom 6 via a bent edge portion 9 in the sheet metal of the side wall 7.

The edge portion 9 is a hne-bent flap that is integral with the side wall 7, and that via a kink extends obliquely at 45° with respect to the body of the side wall to connect with its edge 10 to the edge 8 of the bottom 6. The edge 10 of the edge portion 9 and the edge 10 of the bottom 6 are welded together via a single weld line 11, which includes segments that are curved in two planes.

The kinked edge portion 9 comprises a plurality of segments 12 that are each bent along a straight bending line L. The bending lines L of the successive segments 12 extend at a blunt angle B. The side wall 7 has in this example been cut from a single flat plate of sheet metal. The sheet metal of the edge portion 9 has, prior to kinking, been cut so that it became segmented by providing cutouts between side edges 13 of the segments 12. The cuts extend from the edge 10 of the edge portion 9 to the bending line L. After kinking, the side edges 13 of the cutouts have been welded together. In the example, consecutive segments 12 include a blunt angle B at connected side edges 13.

In this example, the segments 12 have been provided with scalloped edges 14 when it was cut from the flat plate of sheet metal. The scalloped edge 14 has a varying radius, to match a varying curvature of the bottom 6. The opposing edges 8 of the bottom 6 have, during cutting, been provided with a negatively scalloped edge that matches the scallops 14 of the kinked edge portion 10.

The bottom 6 has in this example been cut form a single piece of flat sheet metal, and has been roll bent in a single plane to have a

continuous and varying curvature.

The kinked sidewalls have in this example been welded to opposing edges 8 of the bent bottom 6 so that the sidewalls 7 extend with their main bodies in planes that are substantially perpendicular to the bottom 6. A free edge 15 of the bottom 6 and adjoining free edges 16 of the side walls 7 form the entrance face, and have been provided with a cutting profile 17.

The line-bent flaps that are formed by the kinked segments of the edge portion allow the side walls of the grab shell to connect to the bottom substantially transversely over a relatively long portion of the edge as seen from the opening face, so that sharp edges may be prevented, pressure of the material to be handled may be distributed better, handling of the bulk material may be improved, and the construction has improved resistance to the dynamic loading that results from grabbing material. Due to the line- bending of the flaps the sides of the grab shell are relatively easy to manufacture and connect to the bottom, while the bottom may be bent in a single plane only, and can yet be smoothly curved. The polygonal shape of the edge portion presented by the blunt angles between subsequent kinked segments has minimal disturbance of the handling.

This is provided a grab shell, comprising a bent bottom of which two opposing edges are each provided with a side wall, which bottom and side walls include separate sheets of sheet metal with which by composition a shell space is formed for holding material to be grabbed, and wherein the sheet of sheet metal of at least one side wall connects to the sheet of sheet metal of the bottom via a bent edge portion in the sheet metal sheet of the side wall. The invention is not hmited to the exemplary embodiment represented here, but includes many vaiiations. For example, the exemplary embodiment discusses a bent portion that is kinked, but it shall be clear that other forms of bending, in particular line bending, may be used.

Further, , the grab shell may be of different shape or size than in this example, e.g. when intended for use with a scissors grab. In addition, the cooperating grab shells need not be identical, and more than two grab shells, e.g. three or four, may cooperate to form a bucket for the material to be handled. Further, the grab shell may e.g. be open at the top, closed or semi-open. Also, constructional details of the grab shell, such as any stiff eners, beams, levers, synchronizing wheels, sheaves, cable or beam connection points, pivots etc. may vary depending on the type and function of the grab. Such variations shall be clear to the skilled person and are considered to fall within the scope of the invention as defined in the appended claims.

LIST OF REFERENCE SIGNS

1. Grab shell

2. Entrance face

3. Shell space

4. Pivot

5. Connection point

6. Bottom

7. Side wall

8. Opposing edges bottom

9. Edge portion

10. Edge of edge portion

11. Weld line

12. Segments

13. Side edges of segments

14. Scalloped edge

15. Free edge bottom

16. Free edge side wall

17. Cutting profile

L Bending line

β Blunt angle

Claims

1. Grab shell, comprising a bent bottom of which two opposing edges are each provided with a side wall, which bottom and side walls include sheet metal with which a shell space is formed for holding material to be grabbed, characterized in that sheet metal of at least one side wall connects to sheet metal of the bottom via a bent edge portion in the sheet metal of the side wall.

2. Grab shell according to claim 1, in which the bent edge portion comprises one or more segments that are each bent along a straight bending hne.

3. Grab shell according to claim 2, in which the sheet metal of the edge portion includes cutouts between side edges of the segments.

4. Grab shell according to any of claims 1-3, in which the bent edge portion of the side wall comprises a scalloped edge, in particular at the edge of the segments.

5. Grab shell according to claim 4, in which the scalloped edge has a varying radius.

6. Grab shell according to any of claims 1-5, in which the bent edge portion connects obliquely to the bottom.

7. Grab shell according to any of the preceding claims, in which the edge of the edge portion of the sheet metal of the at least one side wall connects to the sheet metal of the bottom via a weld line that includes segments that are curved in two planes.

8. Grab shell according to any of the preceding claims, in which a free edge of the bottom and adjoining free edges of the side walls form an entrance face.

9. A grab, including at least two grab shells in accordance with any of the preceding claims, which grab shells are movably connected to a grab body to move between a closed position in which the entrance faces of the shells abut so that the shell spaces of the grab shells form a bucket for the material to be grabbed, and an open position of the grab in which the entrance faces of the grab shells are spaced apart and form an opening there between through which material to be handled can pass in and out of the shell spaces.

10. A method of manufacturing a grab shell, in which sheet metal of a side wall for the grab shell is bent, in particular hne-bent to provide it with a bent edge portion, and in which the edge of the edge portion is connected to a bent bottom.