Patent Application
20220186462
Not Applicable.
Not Applicable member
This invention relates to the field of draglines and power shovels. More specifically, the invention comprises a novel cable construction that allows the use of high-strength synthetic filament cables as a replacement for prior art steel constructions.
The present invention proposes to replace some of the chain and wire rope systems used in existing dragline and power shovel operations with high-strength synthetic filament cables. Synthetic filament cable are made of millions of very fine filaments. Each filament is typically smaller in diameter than a human hair. The strength-to-weight ratio of such filaments is much better than the ratio for steel wires. However, synthetic filaments are not very tough. They are quite susceptible to abrasion and cut damage. Thus, synthetic filament cables have not been commonly used in the very hostile environments found in dragline and power shovel operations (typically pit mines).
A prior art dragline bucket is shown in
In operation, the bucket is swung into position and then dropped into the material that is to be removed. The mouth of the bucket is typically given a downward pitch during the drop operation so that it digs into the material. The bucket is then dragged back toward the boom crane. As it is dragged along the bucket's mouth scoops in a load of material.
Once the bucket is full the boom crane is used to pull the bucket assembly free of the material. The boom crane then swings the bucket toward the area where the scooped material is to be deposited. When the bucket assembly reaches the deposit area, a dumping mechanism causes the bucket to pitch downward. The contents of the bucket then spill from the bucket's mouth. Once the bucket is empty, the cycle repeats.
Bucket 24 and its contents are primarily suspended by a pair of lift trunnion assemblies 22—with a trunnion assembly being located on each side of the bucket. A lower hoist chain 20 connects each trunnion to spreader bar 18. An upper hoist chain 16 connects each side of the spreader bar to yoke 48.
The term “yoke” refers to the component that connects the upper hoist chains to the tensile members used to lift the entire bucket assembly. It is also typically used to connect the chains to the dump block assembly. It can take on many shapes and forms. In the example of
The yoke may be a single large casting or it may be an assembly of several pieces. The term should be broadly construed to mean anything that connects the bucket assembly rigging to the lifting cable(s) leading to the boom on the crane.
As stated previously, the lift ropes connect the bucket assembly to the boom of the crane. Yoke 48 also provides an attachment point for dump block 28. As the name suggests, a mechanism incorporating the dump block is used to change the bucket from its scooping configuration to its dumping configuration. When this mechanism is actuated, the bucket pivots downward about the two trunnion assemblies. The mouth of the bucket pitches downward and the tail of the bucket rises. Once the bucket's contents are completely dumped, the dumping mechanism is reversed and the bucket is returned to its digging orientation.
Still referring to
The reader will note that a dump rope 26 passes from the drag socket 34, around dump block 28 and connects to the upper portion of arch 32. The dump rope is used to regulate the transition of the bucket between its digging and dumping orientations.
The bucket assembly is operated in a brutal environment. The bucket is typically dropped into an ore deposit containing rocks and other abrasive materials. Chains have traditionally been used near the bucket itself because of the extreme forces applied and the abrasive action of the material being dug. The chains shown in the assembly may be comparable in size to the anchor chains used on a large ship. For example, each link may be well in excess of 1 foot (30+ centimeters) long.
Such chains are quite heavy. They must be serviced and replaced often as well. The size and weight of the chains make them difficult and dangerous to handle. In addition, the chains rapidly elongate while in use—primarily because of link-to-link abrasion. This elongation alters the dumping geometry of the bucket assembly and reduces its performance. In addition, the elongation of the lifting chains reduces the maximum height to which the bucket assembly may be lifted. The reduction in lift height reduces the amount of material that the drag-line assembly can move. It would be advantageous to replace the chains with a lighter and less cumbersome material. It would also be advantageous to replace the chains with a tensile member that does not elongate significantly. More information regarding the structure and operation of dragline bucket assemblies is provided in my own co-pending patent application Ser. No. 15/066,162, which is hereby incorporated by reference.
Boom 120 is raised and lowered using boom ropes 134. The boom is ordinarily not raised or lowered frequently, however. Most of the digging is done by raising and lowering dip arms 122. These are raised and lowered by reeling in and paying off dipper ropes 132. In this particular example, each of the dipper ropes is attached to yoke 128 by passing a loop 136 through passage 140 and securing a dipper rope back to itself with a collar 138. Yoke 128 is connected to the bucket via a pair of trunnions 130 (one on either side).
Hoist rigging 132 is connected to the dipper via yoke 128. The hoist rigging typically comprises a pair of heavy wire ropes. Each of these wire ropes passes over a top sheave 168, and from that point travels back into cab 169. A winch mechanism in the cab reels in and pays out each of the heavy wire ropes.
Each of the wire ropes may wrap twice around its particular top sheave 168 (in a helical path).
Returning to
As those skilled in the art will know, power shovels such as depicted in
The hostile environment of mining and similar industries makes the use of light-weight flexible tensile members difficult. The advantages of using such tensile members are promising, however. Any reduction in the weight of the bucket rigging means that a larger bucket can be used (for a given crane lifting capacity) and more fill material can be carried with each scoop. Any reduction in the stretching tendency of the tensile members used means that the assembly produces a more consistent bucket fill and soil mound height, thus increasing productivity. Any reduction in metal-to-metal wear increases the lifespan of a component and reduces the frequency of component replacement. Any reduction in the use of chain reduces the safety hazards inherent in the use of chain. Thus, a new type of flexible tensile member assembly that is able to withstand the hostile environment common to mining machinery would be advantageous. A new type of flexible tensile member assembly that is able to employ modern synthetic materials would further reduce the weight of the rigging and provide an even greater advantage.
Steel chains and cables are typically used for both dragline and power shovel operations. Steel provides toughness in such a hostile environment, where dust, abrasion, and substantial impacts are common. Synthetic filament cables would provide a substantial weight savings over steel. These include cables made of DYNEEMA, SPECTRA, TECHNORA, TWARON, KEVLAR, VECTRAN, PBO, carbon fiber, and glass fiber (among many others). In general the individual filaments have a thickness that is less than that of human hair. The filaments are very strong in tension, but they are not very rigid. They also tend to have low surface friction. These facts make such synthetic filaments difficult to handle during the process of adding a termination and difficult to organize.
Hybrid cable designs are also emerging in which traditional materials are combined with high-strength synthetic materials. These present additional challenges, since the metal portions may be quite stiff while the synthetic portions will not be.
The present invention provides an armored cable construction permitting synthetic filament (and potentially hybrid) cables to be used in hostile working environments such as dragline and power shovel operations.
The present invention comprises a novel cable construction provided an armored covering over a cable containing high-strength synthetic filaments. The synthetic cable is provided with a strong and tough termination where it attaches to heavy machinery, such as mining machinery. An external armoring is then provided for a desired portion of the cable (up to the entire length of the cable). A collar is preferably provided to seal the end of the armoring portion to a cable jacket (where a cable jacket is present).
In this example each cable is terminated into a heavy steel piece (attachment fixture 144). This creates a suitable termination 142 on the end of each cable. Each attachment fixture 144 is made of steel and is quite durable. These are connected to yoke 128 using steel pins. Cable armoring 146 covers and protects the jacketed cables 150 from the point each cable emerges from its respective termination up to a collar 148.
Collar 148 provides a protective seal between the jacketed cable and its cable armoring. It prevents the ingress of dust, fine debris, liquids, and other contaminants. The collar may be of a split configuration that is clamped in place using transverse bolts.
A single potted region is shown. In reality, multiple potted connections may be made between individual filament groupings and attachment fixture 144. This type of design is described in detail in my co-pending U.S. application Ser. No. 14/693,811, which is hereby incorporated by reference.
Cable armoring 146 is added over the outside perimeter of jacketed cable 150. The cable armoring is preferably a very tough and cut-resistant material. A good example is fiber-reinforced rubber. Interlock 156 is provided between the lower end of the cable armoring and the attachment fixture. Interlock 158 is also provided between the upper end of the cable armoring and the lower end of collar 148.
Collar 148 seals around the jacketed cable. O-ring 159 is preferably provided to make a positive seal between the collar and jacketed cable 150. This prevents the ingress of dust, water, and other contaminants. Although no gap is shown between the exterior of the jacket and the interior of the cable armoring a significant gap may in fact be present in many applications. In those instances it may be necessary to connect the armoring to the attachment fixture using a split clamping ring attached by transverse bolts. A second split clamping ring may be used at the top of the cable armoring as well.
Cable armoring 146 is provided over a length of the cable in proximity to the dipper. Collar 148 seals the armoring to jacketed cable 150 at the point of termination for the cable armoring. Cable armoring 146 is likewise sealed to coupler 204 on its opposite end.
In some embodiments the cable armoring will extend from the dipper attachment up and over the top sheaves. In other instances, a separate length of cable armoring may be provide in the vicinity of the top sheaves.
Returning again to
Having provided a disclosure of the invention and some of its applications, the following additional principles should also be known:
1. The inventive methods and hardware has been described with respect to two examples of mining machinery—power shovels and dragline cranes. However, the invention is applicable to other forms of mining machinery and beyond the mining industry as well. As an example, the invention is applicable to any field where armoring of a flexible tensile member is desirable.
2. The armor layer or layers may be made removable over some or all of the tensile member's length. This may be done to facilitate inspection of the underlying synthetic core components.
3. Some “grip” engagement between the core and the armor layer will be desirable in some circumstances. As an example, the inward facing surface of the armor layer could be given a gripping texture (ribs or helical grooves) so that the armor layer does not slip with respect to the core in a region where the tensile member passes over a sheave. In such a situation surface shearing forces are preferably transmitted from the armor layer to the core layer in order to prevent the armor layer slipping like a sock. It is also possible to provide outward facing gripping surfaces on the core layer or on the jacket material surrounding the core layer.
4. Another type of gripping feature between the core and the armor layer can be cross-stitching or some form of adhesive.
5. It is desirable to provide an armor layer that indicates a breach or other significant damage to the protection it affords. As a first example the armor material may include a brightly colored layer covered by a dark layer. A gouge or a split then becomes visible as a bright portion against a dark background. For embodiments in which the armor layer is sealed to a termination at both ends of a tensile member, a brightly dyed fluid can be placed between the armor layer and the core layer. This bright fluid will seep out of any breach in the armor layer and indicate a problem.
6. An armor layer may be provided on an intermediate portion of the tensile member rather than proximate the ends. As one example, an armor layer may be provided for a region of the tensile member that passes back and forth over a top sheave.
7. An armor layer may be provided on a length of core that is passed around a spliced termination (such as a large thimble-type device) and woven back into itself. The armor layer could cover the terminated portion and the woven portion.
It is helpful to consider the application of the present inventive hardware to prior art heavy equipment.
Boom 58 is pivotally mounted to the cab. It extends for a large distance. For very large machines the boom may be as long as 100 meters. Mast 56 extends upward as shown. Multiple bridge support ropes 68 maintain the boom's position. A first group of bridge support ropes connects the top of mast 56 to the tip of boom 58. A second group of bridge support ropes 68 connect the top of mast 56 to A-frame 54 on the cab.
Bucket assembly 10 actually does the digging and scooping. The weight of the bucket (and its contents) is supported by lift rope 14 (which may be two or more ropes rigged in parallel). Lift rope 14 passes over point sheave 50 and back to hoist drum 60 within the cab. Deflection sheaves 64,66 redirect the path of the hoist rope as needed. Dragline rope 36 pulls the bucket toward the cab. It is reeled in and paid out by dragline drum 62.
Bridge support ropes 68 are conventionally thought of as “fixed” or “standing” rigging in that they are not reeled in and paid out (in this context such a tension member will be referred to generally as a “stay”). This does not mean, however, that they are not subjected to dynamic forces. As lift tope 14 is reeled in to lift the bucket, the tension on bridge support ropes 68 increases substantially. Once the scooping phase is done, the entire crane pivots to the dumping area. This swinging motion places lateral loads on the bridge support ropes. When the bucket is dumped the load on the bridge support ropes is suddenly and significantly reduced.
In these various motions the boom tends to bounce and sway. Bridge support ropes 368 undergo bouncing motions constantly. In some instances they will experience circular as well as lateral oscillations. The motions are best visualized as waves. Principles of superposition can produce violent motion in some instances. These violent motions are difficult to predict.
The fixed rigging for these types of heavy machines has traditionally been made from heavy wire rope. Wire rope is quite tough. It is also capable of repeated elastic deformation without significant damage. Wire rope also provides good damping characteristics. The steel wires making up the rope provide reasonable damping. In addition, as most wire ropes are helically laid, the layered helices themselves provide good damping characteristics by twisting and untwisting.
High-strength synthetic filaments offer potential advantages over the use of wire rope. These filaments have a much higher strength-to-weight ratio. If one can reduce the weight of the cable rigging in a large earth moving machine, the weight saving translates directly into additional payload. There is therefore a real incentive to use advanced synthetic filaments instead of steel wire in a tensile strength member in a large piece of equipment.
A tensile strength members must be connected to other components in order to be useful. For example, a cable used in a hoist generally includes a lifting hook on its free end. This lifting hook may be rigged to a load. The assembly of an end-fitting and the portion of the cable to which it is attached is generally called a “termination.”
A tough steel lifting hook is commonly attached to a wire rope to create a termination. A “spelter socket” is often used to create the termination. The “spelter socket” involves an expanding cavity within the end-fitting. A length of the wire rope is slipped into this cavity and the individual wires are splayed apart. A liquid potting compound is then introduced into the expanding cavity with the wires in place. The liquid potting compound transitions to a solid over time and thereby locks the wire rope into the cavity.
The potting compound used in a spelter socket is traditionally molten lead and—more recently—is more likely a high-strength epoxy. However, the term “potting compound” as used in this description means any substance which transitions from a liquid to a solid over time. Examples include molten lead, thermoplastics, and UV-cure or thermoset resins (such as two-part polyesters or epoxies). Other examples include plasters, ceramics, and cements. The term “solid” is by no means limited to an ordered crystalline structure such as found in most metals. In the context of this invention, the term “solid” means a state in which the material does not flow significantly under the influence of gravity. Thus, a soft but stable wax is yet another example of such a solid.
The prior art approaches to adding a termination to a cable are explained in detail in commonly-owned U.S. Pat. Nos. 7,237,336; 8,048,357; 8,236,219 and 8,371,015. These prior patents are hereby incorporated by reference. The prior art approaches are also explained in detail in commonly-owned U.S. patent application Ser. Nos. 13/678,664 and 15/710,692. These published pending applications are also hereby incorporated by reference.
Many different high-strength synthetic filaments are now known. Examples include DYNEEMA (ultra-high-molecular-weight polyethylene), SPECTRA (ultra-high-molecular-weight polyethylene), TECHNORA (aramid), TWARON (p-phenylene terephthalamide), KEVLAR (para-aramid synthetic fiber), VECTRAN (a fiber spun from liquid-crystal polymer), PBO (poly(p-phenylene-2,6-benzobisoxazole)), carbon fiber, and glass fiber (among many others). In general the individual filaments have a thickness that is less than that of human hair. The filaments are very strong in tension, but they are not very rigid and they are not very tough. They offer potential weight savings over traditional wire rope but they also require additional methodologies and hardware to allow them to survive in a hostile environment such as a pit mine.
Tensile members made predominantly from synthetic filaments are very strong in tension but weak in abrasion resistance, cut resistance, and transverse shear resistance (The word “predominantly” is used because it is known to provide hybrid cables that include both metallic components and synthetic components). This invention disclosure describes hardware and methods that are useful in adapting tensile strength members including synthetic filaments to a harsh environment. The hardware and methods are primarily directed toward synthetic cables, but the reader should bear in mind that these techniques are advantageous for traditional wire ropes in some circumstances as well.
Each bridge support rope is made primarily (if not fully) from high-strength synthetic filaments. Each of the four bridge support ropes ends in a termination 70. Each termination in this example is connected to the boom by a large transverse pin. Bend restrictors 72 provide a transition between the freely flexing portion of the rope and the portion that is rigidly locked within the termination. In this example, each bend restrictor 72 is approximately 3 meters long. The forces involved in such an assembly are tremendous.
In order to reassemble the exploded assembly depicted in
Each bolt 92 passes through a hole in one bend restrictor half and threads into a threaded receiver in the opposite bend restrictor half. The hole in each restrictor half includes a counterbore with a bearing face. The head of each bolt bears against the bearing face of a counterbore as the bolt is tightened—thereby pulling the two bend restrictor halves together.
The two bend restrictor halves are properly positioned with respect to termination 70 by that face that the bolts 92 slide through bolt receiver 86 on the termination and bolt flange 80 on jacket clamp 78. A stronger connection between the termination and the bend restrictor is preferred, however. To that end, numerous bolts are passed through mounting holes 88 in the termination and into threaded receivers 90 on the bend restrictor halves. These bolts create a very strong flange-type connection.
The two bend restrictor halves are preferably made of a very tough yet somewhat elastic material. In the embodiment shown, the two halves are made of molded urethane. While urethane is indeed a tough material, the reader should bear in mind that the tension on the cable will often be enormous and the lateral flexure loads are also quite substantial. These loads will tend to buckle and separate the two bend restrictor halves.
In order to strengthen the assembly, a series of clamp receivers 82 are provided on the exterior surface of the bend restrictor halves. Each clamp receiver is a groove having a rectangular cross section. Once the two halves are united, a band clamp 94 is opened, passed around the two halves, and secured in each clamp receiver. The example shown provides enough receivers to accommodate eight band clamps 94. Once these band clamps are tightened, the assembly becomes much stronger.
The tightened assembly is placed in service and remains in service for a defined interval. Once the interval is completed, the bend restrictor must be opened to facilitate inspection of the cable. The band clamps are removed and the two bend restrictor halves are disassembled. Inspection region 84 is thereby exposed.
The cable itself is made of several individual strands that are braided, woven, or twisted together. A braided example is shown. Termination 70 typically includes a fairly complex assembly.
The use of advanced synthetics offer significant advantages for dragline cranes and similar machinery. There are disadvantages as well, however. Wire rope is inherently tough and can be passed over the various sheaves many times without significant damage. Synthetic rope—even when contained within a jacket—is not as tough.
Lift ropes 14 in the view are made of synthetic filaments (or largely of synthetic filaments in the case of a hybrid rope). The lift ropes pass over point sheave 50. Point sheaves 50 are traditionally heavy steel structures possessing a great deal of inertia. As the lift ropes are lifted up and down by the hoist drum in the cab, they may slip of the point sheave. To address this concern the point sheave in the embodiment shown is positively driven.
Drive motor 108 drives the point sheave through reduction gear 110. Encoder 112 provides information regarding the position and rotational velocity of the point sheave. This information is fed to control unit 114, which controls the motion of drive motor 108. In one approach the motor is driven so that point sheave 50 matches the speed of the lift rope—as the lift rope is reeled in or paid off. The point sheave may also be selectively driven faster than the linear speed of the lift ropes, or slower.
A second concern with the use of synthetic ropes is the presence of heavy dust, small particulate debris, and even small stones between the lift ropes and the point sheave. These may be thrown or carried up from the region of the bucket. In the version shown a pair of spray nozzles 116 are directed toward the lift ropes. These spray high pressure water. They may be periodically activated (such as when the bucket is being lifted—or they may remain active at all times. The nozzles tend to blast dust and debris off the lift ropes before they pass over the point sheave. They also tend to cool the lift ropes.
Additional nozzles may be provided for the point sheave itself. These additional nozzles can provide cooling water for the point sheave. Temperature sensors on the sheave can be used to determine when cooling water is desirable.
In addition to the spray nozzles, the inventive embodiment can also include a mechanical cleaning element—such as brush assembly 210. Brush assembly 210 surrounds the two lift ropes. As the two lift ropes are pulled upward the brush assembly tends to remove dust and debris from the cables.
The use of synthetic ropes allows the substitution of softer and lighter materials for the various sheaves on the crane—including the point sheave. As an example, aluminum may be substituted for steel in the sheaves. The use of aluminum reduces weight and—also significantly—rotational inertia.
It is also possible to place a softer insert into the point sheave at the point of contact with the lift ropes.
The use of a tough “armoring layer” over the outside of a synthetic rope will be desirable in many applications for heavy machinery.
The material and the thickness can be varied for different regions of a cable.
Cable armoring 146 is not able to easily pass around the point sheave. In the position shown in
Likewise dragline rope 36 includes dragline junction 224. Conventional wire rope can be used around dragline drum 62 and out to dragline junction 224. Outward from the dragline junction rope made from high-strength synthetic filaments (or mostly so) is used.
Accurate inertial measurement units have now become relatively affordable. These units now incorporate MEMS instruments for linear acceleration measuring and ring-laser-gyros for attitude measuring. An internal processor then integrates the linear acceleration information and creates a full 6 degree-of-freedom “picture” of the location and orientation of the particular inertial measurement unit.
In the embodiment of
As an example, if the dragline crane moves forward into an area of soft soil the entire machine will tip forward somewhat. If only the motion at the tip were available, one might conclude that the boom had experienced a substantial load. However, with the motion of the base and the tip available, a monitoring system will “know” that the tip motion is just a result of the entire machine tipping forward somewhat and not the result of a substantially increased load on the boom.
Additional instrument units may be added along the span of the boom.
Although the preceding description contains significant detail, it should not be construed as limiting the scope of the invention but rather as providing illustrations of the preferred embodiments of the invention. Thus, the language ultimately used in the claims shall define the invention rather than the specific embodiments provided.
This non-provisional patent application claims the benefit of three earlier-filed provisional patent applications. The provisional applications were assigned Ser. Nos. 62/640,594; 62/640,595; and 62/640,730. The present invention and the three referenced provisional applications all list the same inventor.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US20/12496 | 1/7/2020 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62640595 | Mar 2018 | US | |
| 62640594 | Mar 2018 | US | |
| 62640730 | Mar 2018 | US |
