Not Applicable.
Not Applicable
This invention relates to the field of tensile strength members used in the field of heavy lifting and digging equipment.
The present invention is particularly suited to heavy lifting and digging equipment. It will benefit the reader's understanding to consider some exemplary machines in this field.
Boom 14 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 16 extends upward as shown. Multiple bridge support ropes 36 maintain the boom's position. A first group of bridge support ropes connects the top of mast 16 to the tip of boom 14. A second group of bridge support ropes 36 connect the top of mast 16 to A-frame 36 on the cab.
Bucket 18 actually does the digging and scooping. The weight of the bucket (and its contents) is supported by hoist rope 20. Hoist rope 20 passes over point sheave 22 and back to hoist drum 28 within the cab. Deflection sheaves 24, 26 redirect the path of the hoist rope as needed. Dragline rope pulls the bucket toward the cab. It is reeled in and paid out by hoist drum 28.
Bridge support ropes 36 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 hoist rope 20 is reeled in to lift the bucket, the tension on bridge support ropes 36 increases substantially. Once the scooping phase id own, 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 36 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.
Hoist ropes 20 pass over point sheave 22 and back to a drum in the cab. The hoist ropes are attached to yoke 48. The yoke lifts the forward portion of dipper 42 during each loading cycle. A pair of dipper arms 46 also support dipper 42. Each dipper arm 46 is attached to boom 45 by a pinion assembly 52. As those skilled in the art will know, pinion assembly 52 creates a rack-and-pinion engagement between each dipper arm and the boom (as opposed to a simple pivot joint). When the dipper is lifted, the rack-and-pinion engagement propels the dipper forward. The result is a combined motion where the digging teeth on the bottom lip of the dipper move forward and upward. In more recent designs the forward motion may be produced by a large hydraulic cylinder rather than a rack-and-pinion engagement.
As for the dragline crane, the fixed rigging on the power shovel is not really fixed. The stays 50 bounce and move as the machine operates. There are some problems unique to power shovels. The reader will note how the rear extreme of each dipper arm 46 passes close to a stay 50. The stays may move in a lateral wave and may also move in a circular wave (a jump rope-type motion). In extreme cases the rear of a dipper arm can collide with a stay.
Another problem known for power shovels is the fact that the dipper arms can sometimes lift the boom. This is sometimes referred to as “boom jacking.” If the dipper lodges in a resistant piece of earth and stops the momentum of the stroke may pull the dipper arms forward and pivot the boom upward (with the dipper becoming a temporary fulcrum). This motion temporarily unloads stays 50. Shortly after the stays go slack the dipper will break free and the boom will fall downward until the stays are tight again. The result is a tremendous shock load. This shock load produces extreme cyclic motion in the stays. The motion will dampen over time but damage is possible in the interim.
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.
The present invention comprises a method and hardware for damping and controlling unwanted motion in the fixed rigging of large machines. In a first approach large clamp blocks are added to multi-cable rigging systems. These blocks use a first cable to damp the motion of an adjacent cable. The invention also encompasses adding armored sections to synthetic cables to enhance their abrasion resistance and cut resistance.
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 54. Each termination in this example is connected to the boom by a large transverse pin. Bend restrictors 56 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 56 is approximately 3 meters long. The forces involved in such an assembly are tremendous.
In order to reassemble the exploded assembly depicted in
The two bend restrictor halves are properly positioned with respect to termination 54 by that face that the bolts 114 slide through bolt receiver 126 on the termination and bolt flange 118 on jacket clamp 104. A stronger connection between the termination and the bend restrictor is preferred, however. To that end, numerous bolts are passed through mounting holes 108 in the termination and into threaded receivers 110 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 112 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 120 is opened, passed around the two halves, and secured in each clamp receiver. The example shown provides enough receivers to accommodate eight band clamps 120. 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 116 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 54 includes a fairly complex assembly.
The lateral or circular wave motion of each particular bridge support rope 36 will be transmitted to the adjoining bridge support rope and this will tend to prove rope-to-rope damping (Even though the motion of neighboring ropes may be similar, it will not tend to be in phase).
Intermediate clamp block 132 is a similar structure to end clamp block 130, but it is placed at some intermediate point of the rope. Intermediate clamp block 132 is shown near the boom tip in
Pillow 134 is a cushion of material added between the cable and the boom itself. As an example, a thick block of HDPE may be added in this location to cushion the “slap” caused by the bridge support topes going slack for a brief interval.
Cables used on heavy machinery must endure a very hostile environment. Flying rock and gravel tends to hit the cables. Such debris can often be pinched between the cable and the sheaves. In order to increase the working life of synthetic cables in such an environment, it is desirable to add an armoring layer.
The synthetic cables used for the inventive embodiments will preferably:
1. Utilize high modulus synthetics (such as DYNEEMA and VECTRAN) or medium modulus synthetics (such as NYLON, polyester, and KURALON).
2. Utilize helically wound, woven, r braided construction to maximize compliance for shock loading. This type of construction is also bend resistant. A good example is a high helix 12 strand braid.
3. Utilize coatings to provide lubrication and/or further seal the rope against harmful debris.
4. Use jackets around each of the individual strands (sub-ropes).
5. Cover the cable as a whole with a single or multi-layer jacket that allows staged visual indication of wear.
For demanding application—such as a pit mine—armoring is desirable in the contact regions. For something like a dragline crane, armoring will be needed in the regions near the bucket. The armoring material is preferably field replaceable as a wear component. The replacement could be done as a result of damage or as an ordinary wear item. The armoring may be free to rotate with respect to the rope, or it may be fixed to the rope.
Looking again at the example of
A second armoring example would be a tightly woven synthetic sleeve (such as KEVLAR). In this example frictional engagement alone could suffice to hold the armoring over the desired section of the cable. The armoring could also be a solid tube or a series of tube/bead bumper structured that are designed to roll as an external object (such as the dipper arms of a power shovel) impacts the cable.
A single cable might also include two separate lengths of armoring with a gap in between. The armoring could even be a two piece assembly that is clamped over the cable.
The use of position and/or motion sensors along the length of each rope could provide information needed by a control system. The control system would then analyze the motion present and control one or more active dampers to reduce and control the unwanted motion. The use of such sensors is disclosed in detail in commonly owned application Ser. No. 16/255,913. This pending application is hereby incorporated by reference.
A first transverse clamp block 150 is attached from the first stay to the third stay. This first transverse clamp block in this example is made of two halves which are clamped vertically in place. This first transverse clamp block is configured to damp motion between the first and third stays. A second transverse clamp block 150 is attached between the second stay and the fourth stay. The second transverse clamp block 150 is configured to damp motion between the second and fourth stays.
Transverse dampers can also be added.
Additional combinations and modifications will occur to those skilled in the art. Additional examples include:
1. The use of dampers 146 that are transversely-mounted (as shown in
2. The combination of transversely mounted clamp blocks (as shown in
3. The use of diagonally-mounted clamp blocks and/or dampers. In the example of
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. Those skilled in the art will be able to devise many other embodiments that carry out the present invention. Thus, the language used in the claims shall define the invention rather than the specific embodiments provided.
This non-provisional patent application is a continuation-in-part of U.S. patent application Ser. No. 16/296,284. The present application lists the same inventor as the parent application.
Number | Name | Date | Kind |
---|---|---|---|
1529397 | Burke | Mar 1925 | A |
1933472 | De Vou | Oct 1933 | A |
2462747 | Jacobs | Feb 1949 | A |
2657814 | Smith | Nov 1953 | A |
2832485 | Schneider | Apr 1958 | A |
3035646 | Johansson | May 1962 | A |
3690483 | Kraschnewski | Sep 1972 | A |
4085854 | Baron | Apr 1978 | A |
4090538 | Kotcharian | May 1978 | A |
5427469 | Galarnyk | Jun 1995 | A |
6007256 | Asada | Dec 1999 | A |
6113039 | Riffle | Sep 2000 | A |
20130110460 | Taylor | May 2013 | A1 |
20130195595 | Hottmann | Aug 2013 | A1 |
20150345105 | Gross | Dec 2015 | A1 |
20170233979 | Stalker | Aug 2017 | A1 |
20170350196 | Hoyvik | Dec 2017 | A1 |
Number | Date | Country | |
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20220298746 A1 | Sep 2022 | US |
Number | Date | Country | |
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62640242 | Mar 2018 | US |
Number | Date | Country | |
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Parent | 16296284 | Mar 2019 | US |
Child | 17833974 | US |