Patent Application
20160222625
The present disclosure relates to dragline mining machines and particularly to a configuration of boom chord and lacing for dragline machines used in mining.
Dragline machines use a large bucket suspended from a boom to move a payload, such as earth or ore, at a worksite. The boom for the dragline may be more than 400 feet long and has numerous weld joints that need routine inspection and periodically need repairs. The boom may be constructed of chords running the length of the boom and lacings that connect the chords with a series of geometric patterns, such as triangles, that provide support for the bucket and payload, as well as the boom itself.
Tubular booms use round steel pipes for chords and lacings with the chords diameter being larger than the lacing diameter. Some lacings are perpendicular to the chords and some are at an angle. In both cases, the end of the lacing must be formed to match the round contour of the mating surface on the chord using a coping cut on the end of the lacing. Further, because the lacings often terminate in the same spot, the weld joints overlap.
The closed interior of the chord pipe makes it difficult to inspect the back side of the weld joint. Further, overlapping weld joints at a particular attachment point on a chord make it difficult to inspect for damage to a weld or lacing. Overlapping weld joints also make repairs costly and time consuming because multiple lacings are affected each time one lacing is repaired or replaced.
G.B. 523,571A (the '571 patent), titled “Improvements in or relating to construction of Buildings” teaches the use of a formed metal plate in a truss with lacing supports that avoids coping cuts for lacing attachments. The '571 patent uses formed metal across one entire side of the triangle-shaped structure. This adds weight and cost that would be unacceptable if applied to a boom structure.
In one aspect of the disclosure, a boom for a dragline machine includes a plurality of chords, each chord having a first mounting surface and a second mounting surface, the first and second mounting surfaces being planar and forming a reflex angle and the respective inside surfaces for the first and second mounting surfaces being planar and forming an obtuse angle. Each chord may be arranged so that at least one of the first and second mounting surfaces are facing and generally parallel with one mounting surface of another of the plurality of chords. A plurality of lacings may be used to couple respective facing mounting surfaces of the plurality of chords.
In another aspect of the disclosure, a method of making a boom includes forming a metal plate into a chord having outside surfaces at a reflex angle and inside surfaces at an obtuse angle. The method includes forming additional chords from additional metal plates. The additional chords may have an identical cross section to the chord or may have a different shape from the chord. The chord and the additional chords may be coupled with lacing so that one outside surface of each chord faces a respective outside surface of one other chord.
In yet another aspect of the disclosure, a boom for a dragline machine may include three chords, each chord made from a metal plate formed into three planar surfaces, each chord having at least one obtuse angle between adjacent planar surfaces. The boom may also include a plurality of inter-chord lacings made of pipes, each end of each inter-chord lacing lying in a single plane, wherein each lacing is attached between facing surfaces of two chords.
The chords 110, 112, 114 are connected using inter-chord lacings. For example, lacing 116 and lacing 120 are perpendicular inter-chord lacings. Inter-chord lacings 118 and 118a are oblique inter-chord lacings. Internal lacings 122, 124, 126 are connected in whole or in part to other lacings. In the illustrated embodiment, each internal lacing 122, 124, 126 is coupled at one end to one of the chords 110, 112, 114 and at the other end to another lacing 120.
Supports 128 and 130 are disposed along inside surfaces of the chords 110 and 112, 114 respectively and are formed to match the interior regions of their respective chords 110 and 114, as shown in more detail in
In another embodiment, the inter-chord lacing 120A may be formed from a metal plate and may have a U-shaped profile or an asymmetric profile with two sides perpendicular for mounting internal lacings 122A, 124A, and 126A. For example, the inter-chord lacing 120A may have a profile the same or similar to that of the chord 114 illustrated in
For both the top chord 110 and the side chord 114, the supports 128 and 130 are coupled to the inside surfaces of the chords. The supports 128 and 130 help prevent the chords 110 and 114 from deflecting due to lacing forces, that is, those forces occurring during both at rest due to gravity and also by movement of the boom when material is loaded and unloaded. The supports 128 and 130 also limit twist and buckling of the chord 110 and 114.
Similarly, an inter-chord lacing 120 will be perpendicular to both mounting surfaces 152 and 162 of the side chords 112 and 114. A lacing 164 connecting mounting surfaces 144 and 160 will also be perpendicular to the plane defined by those mounting surfaces 144, 160. The end of each of these lacings lies in a single plane and can be cut with a single cut of, for example, a circular saw, band saw, or cutoff saw to form a planar end cut. The complex coping cuts required for round lacing attachment to round chords of prior boom implementations are avoided. As can be seen in
Further, the open frustum shape of the chords 110, 112, 114 allows visual inspection of both sides of weld joints that attached the lacings to the chords 110, 112, 114. This improves the quality of an inspection because both sides of a chord can be easily viewed so that cracks and imperfections can be identified.
At block 204, additional chords 112, 114 may be formed from additional metal plates; the shape of the additional chords may be the same or different as the chord formed at block 202.
At block 206, lacings may be formed with a planar end profile. That is, lacings made of round pipe may have ends that form a single plane, either perpendicular to a longitudinal axis of the pipe or oblique to the longitudinal axis. For example, the chord-end of any lacing may be cut with a band saw, a cutoff saw, or a circular saw.
At block 208, the chord 110 and the additional chords 112, 114 may be coupled with lacing so that one outside surface 142, 144 of a first chord 110 faces a respective outside surface 150, 160 of one other chord 112, 114. Coupling the chord 110 and the additional chords 112, 114 with lacing may also include attaching each end of a lacing 116 to the outside surfaces 142, 150 of two facing chords 110, 114. Coupling the chord 110 and the additional chords 112, 114 with lacing may also include attaching each end of the lacing so that no lacing, e.g., lacing 116, is in contact with another lacing, e.g., lacing 118a. The lacings are typically attached with welds, but in the case where other materials or composites may be used for the chords, the chords and lacings may have different attachments, such as rivets, bolts, or epoxies.
At block 210, a support 128, 130 may be disposed between the inside surfaces of the chord. The support 128130 may be a formed plate that is attached perpendicular to a length of a chord 110, 112, 114 and in contact with the inside surfaces 141, 143, 145 and 151, 153, 158 of respective chords 110, 114. Chord 112 may be a mirror image of chord 114 and has similar inside surfaces that contact similar supports. The supports 128, 130 may be disposed opposite points where a lacing is attached or may be disposed mid-span between lacings.
The use of formed chords rather than tubular pipe chords has the advantage of allowing both sides of a weld joint to be inspected and repaired. The separation of lacing attachment points allows a lacing and its welds to be individually inspected and, if needed, repaired without impacting other lacings. Dragline machine booms 106 are typically inspected every month. Since a boom 106 of a dragline machine 100 may be over 400 feet long and have hundreds, if not thousands, of lacings and welds, any improvement in the inspection and repair processes may have a considerable impact on machine up-time. However, the advantages of the chord and lacing techniques disclosed herein are not limited to dragline machines 100. Any chord-based support structure may benefit from the formed chord and offset lacings discussed in this disclosure, including, but not limited to, portable cranes, overhead cranes, conveyor system supports, antenna towers, etc.
