Dragline excavating systems are commonly employed in mining and earth moving operations. Examples of dragline excavating systems are disclosed in U.S. Pat. No. 4,791,738 to Briscoe, U.S. Pat. No. 5,084,990 to Briscoe, and U.S. Pat. No. 5,992,061 to Fleck, et al. In general, a dragline excavating system includes a dragline bucket that engages the ground and collects dirt, rocks, and other debris from the ground. A pair of hoist chains are secured to opposite sides of the dragline bucket and extend upward to join with hoist ropes that effectively support the dragline bucket and control the vertical position of the bucket. A pair of dump ropes are also secured to the dragline bucket to control the orientation (i.e., tilt or angle) of the dragline bucket in relation to the ground. In addition, a pair of drag chains are secured to a front of the dragline bucket and are joined with drag ropes to control a horizontal, dragging movement of the bucket.
As the dragline excavating system is utilized, the dirt, rocks, and other debris may abrade the dragline bucket and the rigging as they contact or slide against the ground. Connections between the various elements may also experience wear in areas where surfaces of the elements bear against each other and are subjected to tensile, compressive, abrasive, or various other forces Following a period of use, therefore, portions of the dragline excavating system are subjected to maintenance to permit worn or otherwise damaged elements to be inspected, repaired, or replaced.
Connections between some of the elements of the dragline excavating system are pinned connections that permit two joined elements to rotate relative to each other. In general, a pinned connection includes a pin that extends through two connection elements (i.e., the elements that are joined by the pin) to effectively join the connection elements together. Many pinned connections incorporate bushings that extend around and contact surfaces of the pin. In order to install the bushings, apertures that receive the bushings are commonly heated to expand the inner diameters of the apertures, while the bushings are cooled (e.g., with dry ice) to contract the outer diameters of the bushings. The bushings are then pressed into the apertures. The bushings may alternatively be welded in the aperture to secure the bushings. Following installation of the bushings, the pin is inserted into the connection to set within the bushings. With floating pins, plates or other elements are welded over the outer ends of the apertures to prevent the pin from being removed or ejected from the joined elements. Fixed pins would include a head and a nut or other securing means to hold the pin in the connection.
Mining and earth moving machines are halted during periods of maintenance, which has a limiting effect upon the overall efficiency of the machine. In order to inspect, repair, or replace pinned connections, it is common for the welded plates to be removed to provide access to the pin and bushings, which involves cutting at least one of the plates with a welding torch. In addition, maintenance may include separating the pin and/or bushings from the joined elements, which involves cutting the bushings with the welding torch. During use of a dragline excavating system, fines (i.e., relatively small particles or dust) from the dirt, rocks, and other debris may become compacted or otherwise lodged into the pinned connections, which hinders separation of the pin and bushings after the plates are removed. Furthermore, misalignment within the pinned connection that results from installation or wear during use may also hinder separation of the pin and bushings. Given the presence of these fines and the potential misalignment, hammering may be used to separate the pin and bushings from the joined elements. In addition to the time consumed by both the installation and maintenance processes, repeatedly welding, cutting, and hammering may pose risks to personnel and degrade or otherwise damage the joined elements. Accordingly, elements of the dragline excavating system that may be quickly maintained (i.e., inspected, disassembled, and repaired) without welding and hammering operations may enhance the overall efficiency of the dragline excavating system.
USPTO Backgrounds
USPTO Backgrounds