Dragline bucket

Abstract

The invention provides for the design of a dragline bucket of the type where there are separate front and rear hoist ropes attached to front mounting points and rear mounting points respectively. The front and rear hoist ropes can be independently operated to vary the horizontal attitude of the bucket. The bucket design methodology seeks to equalize the loads in the front and rear hoist ropes during the major phases of the operating cycle such as digging, hoisting and dumping, and this is typically achieved by providing a bucket with comparatively shallow side walls compared with the overall length of the bucket and the positions at which the front and rear hoist ropes ultimately join onto the bucket. The bucket typically has a flat floor and relatively shallow side walls which may in some embodiments taper downwardly from the rear section to the front section.

Description

FIELD OF THE INVENTION This invention relates to a new type of bucket for a rigged dragline assembly. [0001] Draglines are large excavating machines designed to fill, carry and dump loads of material, typically earth. Draglines are often used in open cut coal mines to remove waste overburden covering a shallow coal seam. BACKGROUND OF THE INVENTION [0002]FIG. 1 illustrates a typical large electric dragline in accordance with the prior art. A conventional dragline includes a rotatable support 1 mounted on a stationary base 2. An outwardly projecting boom assembly 3 is mounted pivotally to the rotatable support. Winches 6,9 are mounted on the support for retrieving or releasing cables or ropes. Normally there are two main sets of ropes or cables, hereinafter referred to as hoist ropes 4 and drag ropes 5. Hoist ropes 4 extend from the hoist winch 6 mounted on the support, up and outwardly along the boom, over pulleys or sheaves 7 mounted at the most distant point of the boom, down to ...

AI Technical Summary

Benefits of technology

[0059] The bucket of the present invention has generally shallow sides which may be tapered from rear to front. This means that when the bucket carries a payload, the centre of gravity of the combined payload and bucket is shifted further towards the rear of the bucket than in a conventional bucket design. This advantageously tends to equalise the load carried by the front and rear hoist ropes. This effect is illustrated in more detail below in the Example and Comparative Example.

[0061] A further advantage of the bucket of the present invention is that it has a short height dimension relative to its length dimension and, preferably, its width dimension. Preferably, the length dimension is at least twice the height dimension, more preferably at least, or about, three times the height dimension. This flat bucket geometry minimises the amount of bucket steel required to constrain the payload and thus increases the efficiency of the carrying operation, i.e. maximum payload for minimum steel.

[0064] The attachment means may be, for example, hooks or openings in the bucket. Preferably, the attachment means for the rear hoist rope comprise a single rope and / or chain attached to a central point at the rear of the bucket, or a dual attachment to multiple rear points via an intermediate “bridal” or “yoke” chain or rope. The dual arrangement minimises the chance of the bucket twisting or uncontrollably rotating in situations where the bucket is hanging almost exclusively by the rear hoist rope, e.g. during dumping or “chopping”. Preferably, the attachment means for the front hoist rope comprises a pair of flanges having a plurality of openings therein, each flange extending upwards from respective side walls forming the length of the bucket. Preferably, the attachment means for the drag rope comprises a pair of flanges having a plurality of openings therein, each flange extending in a forward direction from respective side walls forming the length of the bucket.

[0065] Preferably, the bucket does not include an arch. As shown in FIG. 2, traditional dragline buckets include an arch 22. The incorporation of the arch 22 has the effect of shifting the centre of gravity of the bucket towards the front part. The absence of an arch, in this preferred embodiment of the present invention, contributes to shifting the centre of gravity more towards the rear of the bucket. In addition, the elimination of the arch reduces the total bucket weight and thus increases the total payload that may be carried without exceeding the machine's RSL.

[0066] Preferably, the bucket of the present invention is substantially cuboid- or trapezoid-shaped, having an open top and an open front section. Preferably, the side walls forming the length of the bucket are flared outwards from the base, which increases the volume of the bucket and helps to retain material in the bucket.

[0075] Preferably, the front and rear hoist ropes are adjusted independently to control the carry angle of the bucket, thereby controlling the combined centre of gravity of the payload and bucket. Thus, in addition to the bucket design being used to distribute evenly the load between the front and rear hoist ropes, the carry angle may also be used to facilitate even weight distribution. A large carry angle will tend to shift the centre of gravity towards the front hoist rope due to the extra payload being carried on the front payload face, whereas a small carry angle will tend to shift the centre of gravity towards the rear hoist rope due to the loss of payload from the front payload face.

Problems solved by technology

There are a number of limitations that conventional rigging designs place on operating a dragline:

This adds to cycle time, increases wear and reduces hoisting efficiency.

There are dynamic methods for dumping just inside and outside of boom point radius, however these methods are not recommended by the manufacturers.

However, the payload is inevitably not distributed evenly between the two hoist ropes.

Hence, in a dragline assembly having separate front and rear hoist ropes, there is typically a large difference in lifetime between the front and rear hoist ropes, since each rope has differing maximum cyclic stress.

Hoist ropes having unequal lifetimes are highly undesirable from a maintenance point of view.

Replacement of a hoist rope is a costly exercise, because it involves lengthy downtime of the dragline assembly.

However, if one hoist rope fatigues quicker than the other, replacement of both ropes at the same time is inefficient since one rope, having useful remaining lifetime, is unnecessarily replaced.

Images