Dragline dump position control

#This invention relates to dragline dump position control and has been devised particularly though not solely to control the dumping position for a dragline that uses a differential hoist rope control for carry angle alteration.

#When operating a dragline of the type described in international patent application PCT/AU00/01336, the content of which is incorporated herein by way of cross reference, there is a problem if an attempt is made by the operator to dump a payload within the bucket close in to the drag fairleads for the drag rope in that the bucket may not be able to reach its target dump angle due to the tension in the drag rope. In extreme cases, the angle reached may be insufficient to empty the bucket and this results in excessive slack in the front hoist rope which may become fouled and/or damaged. (Throughout this specification the term “front hoist rope” is used to refer to the hoist rope attached to the front of the bucket i.e. adjacent the attachment point of the drag rope, and the term “rear hoist rope” used to refer to the rope attached to the other or rear end of the bucket). In addition, when the slack is retrieved, excessive peak loads may be imparted to the hoist system components.

#In a dragline using differential hoist rope control, it is highly desirable for the relative movements of the hoist ropes and the drag rope to be computer coordinated, and therefore also desirable to be able to control the dump position of the bucket by way of the computer control in order to ensure that any attempt to dump in an excessively close position is avoided.

#Not withstanding 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 diagrammatic side view of a dragline using differential hoist rope control with the bucket position ready to dump, close to the drag fairleads;

#FIG. 2 is a similar view to FIG. 1 showing an attempt to dump the bucket without reaching the target dump angle;

#A dragline 1 of the type typically used in large scale mining operations has a house 2 rotatably mounted on a platform base 3 which normally comprises shoes enabling the dragline to walk backward to achieve the desired position for the operation of the bucket 4.

#In draglines of the type using differential hoist rope control to alter the carry angle 5 of the bucket 4, the bucket is supported from the boom 6 by way of a front hoist rope 7 and a rear hoist rope 8 entrained around sheaves 9 and 10 respectively. The bucket is further controlled by a drag rope 11.

#When a dragline of this type is operated with the bucket close in to the drag rope fairleads 12 as shown in FIG. 1, and an attempt is made to dump the payload by paying out or releasing tension on the front hoist rope 7, the bucket may not be able to reach its target dump angle, typically negative 70 degrees, due to the tension in the drag rope 11.