WO2008124888A1

WO2008124888A1 - Differential hoist dragline rigging

Info

Publication number: WO2008124888A1
Application number: PCT/AU2008/000534
Authority: WO
Inventors: Peter Knights; Paul J. A. Lever
Original assignee: CMTE Development Ltd
Current assignee: CMTE Development Ltd
Priority date: 2007-04-16
Filing date: 2008-04-16
Publication date: 2008-10-23
Anticipated expiration: 2009-10-16

Abstract

A rigging configuration for a dragline bucket (8) uses an independently controllable first hoist rope (9) and second hoist rope (10) connected to the front of the bucket at (19) and the rear of the bucket at (18) respectively. The second hoist rope (10) passes over a pulley (17) mounted between the first hoist rope (9) and a bridle (20) extending to the front of the bucket at (19). Differential movement of the first and second hoist ropes enables accurate control of the attitude of the bucket over all modes of dragline operation while allowing the hoist ropes (9, 10) to be entrained over side by side boom point sheaves in a conventional dragline boom construction.

Description

DIFFERENTIAL HOIST DRAGLINE RIGGING

FIELD OF THE INVENTION

This invention relates to differential hoist dragline rigging and has been devised particularly though not solely for the implementation of differential hoist rigging in draglines with side by side boompoint sheaves.

The term "dragline" as used in this specification refers to a large electric dragline, typically moveable on walking feet and having a rotatable house based on a turntable platform from which is deployed a long boom. A dragline bucket is suspended from the end of the boom, typically by two hoist ropes and the bucket is moved toward or away from the house by way of a drag rope.

Draglines of this type are typically used to remove to overburden in an open cut mining situation and the dragline buckets have a large capacity, in the order of 100 to

150 tonnes.

BACKGROUND OF THE INVENTION

There have been various proposals made to improve the efficiency of the operation of a dragline by controlling the attitude (inclination in a vertical plane) of the bucket by way of differential hoist rope control. In these proposals a front hoist rope is lead from a boompoint sheave to the front of the bucket and second rear hoist rope from its boompoint sheave to the rear of the bucket. The bucket may be raised or lowered without altering the attitude of the bucket by simultaneously reeling in or paying out the front and rear hoist ropes, or the attitude of the bucket may be altered in a controlled manner by differential movement of the front and rear hoist ropes. Such control is typically necessary when moving from a carry mode to a dumping mode or to a digging mode, all of which require a different bucket attitude and for that attitude to be adjustable for efficient operation of the dragline.

One method of differential hoist rope control of a dragline bucket is found in

International Patent Application PCT/AUOO/01336 which described the use of front and rear hoist ropes entrained over boompoint sheaves which are spaced apart from one another by a distance along the boompoint tip roughly equal to the length of the bucket.

In this manner, the front and rear hoist ropes are typically kept parallel during various lateral translations of the bucket under the action of the drag rope avoiding the need for differential hoist rope movement during, for example, a carrying operation. Although this construction is effective in improving dragline operational efficiency, it is expensive to implement due to the necessity to modify the boompoint arrangement of a conventional dragline from a side by side sheave configuration to the inline sheave configuration. This is not only capital intensive, but requires considerable "downtime" in a dragline being modified to this configuration resulting in significant loss of productivity.

SUMMARY OF THE INVENTION The present invention therefore provides a dragline bucket rigging configuration utilising independently controllable first and second hoist ropes, including a front rigging arrangement connecting the first hoist rope to the forward end of the bucket, and a pulley mounted on the front rigging arrangement arranged to direct the second hoist rope which passes over the pulley before being connected directly or indirectly to the rear end of the bucket.

Preferably the front rigging arrangement includes a bridal having two lower ends fastened to the bucket adjacent the forward end of the bucket. Preferably the bridal is formed from chain.

Preferably the bridal is attached to a mount for the pulley over which the second hoist rope is entrained.

In one form of the invention the distal end of the second hoist rope is connected directly to the rear end of the bucket.

In an alternative form of the invention the distal end of the second hoist rope is connected to the rear end of the bucket by way of a bridal. Preferably the front rigging arrangement is sufficiently long to position the pulley above the rear end of the bucket when the bucket is at or near a vertical altitude in a dumping mode.

Preferably the front rigging arrangement is connected to the forward end of the bucket at a location substantially vertically above a connection point for a drag rope when the bucket is substantially horizontal in a digging mode. BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms that may fall within its scope one preferred form of the invention will now be described by way of example only with reference to the accompanying drawings in which: Fig. 1 is a side view of a dragline incorporating a rigging configuration according to the invention;

Fig. 2 is a side view to an enlarged scale of the bucket and associated bucket rigging of the dragline shown in Fig 1 ;

Fig. 3 is a front view of the dragline bucket shown in Fig. 2; Fig. 4 is a side view similar to Fig. 2 showing the dragline bucket inclined in a typical "carry" configuration.

Fig. 5 is a similar view to Fig. 2 showing the bucket in a dumping position, and

Fig. 6 is a side view of the dragline bucket incorporating a force diagram for forces acting on the pulley.

DETAILED DESCRIPTION

In the preferred form of the invention a large electric dragline 1 typically supported on, and moveable by way of, walking feet 2 has a rotatable house 3 mounted on a turntable 4. Depending outwardly from the house 3 is a dragline boom 5 typically supported by cables 6 engaged over struts 7 in order to support the boom.

The dragline has a bucket 8 suspended from hoist ropes 9 and 10 which are entrained over a pair of side by side boompoint sheaves 1 1 mounted at the distal end 12 of the boom 5. The two hoist ropes in turn are lead over portion 13 into the house 3 where each is wound onto an independent hoist drum (not shown). The hoist drums are independently rotatable by drive motors and appropriate gear boxes to enable the two hoist ropes 9 and 10 to be reeled in or paid out together, or to be independently moved to achieve differential hoist rope control in a similar manner to that described in the aforesaid International Patent Application PCT/AUOO/01336, the content of which is incorporated herein by way of cross reference. The lateral position of the bucket 8 is controlled by a drag rope 14 typically terminating in a chain portion 15 connected to the front of the bucket at 16. The drag rope 14 is also lead into the house 4 where it is wound onto a drag rope drum also driven and controlled by an electric motor in the well known manner. Turning now to Fig. 2 the rigging configuration for the bucket 8 can be more clearly seen as including a pulley or sheave 17 which has a mount supported by the front hoist rope 9. The rear hoist rope 10 is entrained around the pulley 17 so that it is diverted over portion 10a and then secured to the rear of the bucket at point 18 typically by means of a socket and wedge arrangement (not shown).

The front hoist rope 9 is connected to the forward end of the bucket at 19 by a front rigging arrangement including a chain bridal 20 which is connected in turn to the mount of the pulley 17.

Using this rigging configuration the attitude of the bucket can easily be controlled from, for example, a typical digging attitude at shown in Fig. 2 wherein the teeth 21 at the mouth of the bucket are angled downwardly to engage the overburden, to a carry position typically shown in Fig. 4 where the bucket is tilted rearwardly to retain the maximum payload, by differential movement of the front and rear hoist ropes 9 and 10. For example to move from the digging position in Fig. 2 to the carry position shown in Fig. 4 the front hoist rope 9 may be held at a constant extension while the rear hoist rope 10 is paid out to lower the rear of the bucket to the position shown in Fig. 4.

The overall height of the bucket above the ground is controlled by simultaneous movement of the front and rear hoist ropes 9 and 10 as is well known.

When it is desired to dump the contents of the bucket this can readily be achieved by moving the bucket into a dump position as shown in Fig. 5 by reeling in rear hoist rope 10 at a faster or differential rate to front hoist rope 9. If the bridal hitch points 19 are located immediately above the drag hitch points 16, the bucket can be dumped at short radius beneath the dragline boom. Otherwise dumping is typically done while the drag rope chain 15 is relatively slack. A dragline rigged in this manner has the advantage over previous proposals for differential hoist rope control of dragline bucket attitude in allowing the control to be achieved using conventional side by side boompoint sheaves 11 as can be clearly seen in Figure 1. This simplifies the conversion of a conventional dragline to a differential hoist rope configuration as the boompoint sheaves can remain in the conventional rigging arrangement with the only change needed being machine house modifications to provide independent hoist rope drums for each hoist rope.

The dragline bucket rigging configuration according to the invention has further advantages in that a particularly efficient dumping attitude is able to be obtained as shown in Fig. 5. The bucket is able to be dumped in a near vertical position by providing the bridle chains 20 sufficiently long enough to position the pulley 17 above the bucket 8 as shown in Fig. 5 allowing the bucket to dump in a near vertical position. Shorter chains could be used but have the disadvantage of positioning the pulley within the bucket envelope when forward dumping and trials of this configuration showed that forward dumping ability is compromised as the bucket will at most dump to 45 degrees. The dragline bucket rigging arrangement allows for possible application to rear dumping buckets which would overcome this limitation.

It is a further advantage of the dragline bucket rigging configuration according to the invention that a higher breakout force can be applied to the front of the bucket by the front rigging arrangement 20. This can be seen in Fig. 6 which is a force diagram for forces acting on the pulley 17. It will be seen from this force diagram that F3 (the breakout force applied via front rigging arrangement 20) is approximately equal to 1.25 times Fl which is the force applied through the front hoist rope 9. F2 is the force in the rear hoist rope 10.

Due to this resolution of forces possible in the dragline bucket rigging configuration according to the invention, 65 to 75% of combined hoist force can be applied to the front of the bucket, thus improving breakout capacity relative to the rigging configuration shown in International Patent Specification PCT/AUOO/01336. Even greater breakout forces can be achieved by reducing the length of the chains 20 but this may have a negative effect on the dumping ability as previously described above. Compared to a conventional dragline, the dragline bucket rigging configuration according to the invention provides an estimated weight reduction in the rigging of approximately 6 tonnes, a load increase in a typical dragline from 90 tonne to 96 tonne i.e. a 6.6% increase and a dig cycle time reduction of 3 seconds over a typical 55 second cycle time. These factors give an overall productivity increase in the region of 10% to 1 1%.

In this manner a significant increase in the productivity of a dragline is able to be achieved in a retrofit operation which requires modifications in the machine house to install independent hoist drums and modifications to the dragline control system but does not require modification to the dragline boom or hoist sheaves.

Claims

CLAIMS:

1. A dragline bucket rigging configuration utilising independently controllable first and second hoist ropes, including a front rigging arrangement connecting the first hoist rope to the forward end of the bucket, and a pulley mounted on the front rigging arrangement arranged to direct the second hoist rope which passes over the pulley before being connected directly or indirectly to the rear end of the bucket.

2. A dragline bucket rigging configuration as claimed in claim 1 wherein the front rigging arrangement includes a bridal having two lower ends fastened to the bucket adjacent the forward end of the bucket.

3. A dragline bucket rigging configuration as claimed in claim 2 wherein the bridal is formed from chain.

4. A dragline bucket rigging configuration as claimed in either claim 2 or claim 3 wherein the bridal is attached to a mount for the pulley over which the second hoist rope is entrained.

5. A dragline bucket rigging configuration as claimed in any one of the preceding claims wherein the distal end of the second hoist rope is connected directly to the rear end of the bucket.

6. A dragline bucket rigging configuration wherein the front rigging arrangement is sufficiently long to position the pulley above the rear end of the bucket when the bucket is at or near a vertical altitude in a dumping mode.

7. A dragline bucket rigging configuration as claimed in any one of the preceding claims wherein the front rigging arrangement is connected to the forward end of the bucket at a location substantially vertically above a connection point for a drag rope when the bucket is substantially horizontal in a digging mode.