End Fitting for a Cable Bolt Assembly

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Australian Patent Application No. 2019901418 filed Apr. 26, 2019, the disclosure of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

This disclosure relates to a cable bolt assembly and a method of assembling a cable bolt assembly.

BACKGROUND ART

Roof and wall support is vital in geotechnical operations such as mining and tunnelling. Mine and tunnel walls consist of rock strata, which must be reinforced to prevent the possibility of collapse. Rock bolts are widely used for consolidating rock strata and include both cable bolts and rigid bolts.

Barrel and wedge anchors are known and used with cable bolts to facilitate the tensioning of the cable bolt after it is installed in a bore of rock strata. The barrel and wedge anchor is designed to clamp onto the cable and supports the axial tensioning of the cable bolt during installation and once the cable bolt assembly is installed. The wedges have teeth that grip into the cable, and the barrel fits over the wedges to hold them in place. In some instances, the barrel and wedge anchor can slip off the end of the cable bolt resulting in failure of the cable bolt assembly.

It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art, in Australia or any other country.

SUMMARY

In one aspect, there is disclosed a cable bolt assembly including: a cable bolt having a shaft; an end fitting disposed on the shaft and including a body extending between a leading end and a trailing end spaced apart along an axis; and mechanical interlocking provided between the body and the shaft to form a connection therebetween; the body including an exterior profiling disposed thereon and arranged to engage a further component of the end fitting to install and/or tension the cable bolt assembly in use.

In some forms, the mechanical interlocking is provided at least in part by direct connection between the body and the shaft. In some forms, at least a portion of the body is formed onto a portion of the shaft so that the body is plastically deformed about the shaft and wherein the mechanical interlocking is formed at least in part by the plastic deformation of the body about the shaft.

In some forms, the cable bolt assembly further includes one or more engagement formations provided between an internal surface of the body and the shaft, the one or more engagement formations arranged to engage the shaft and the internal surface of the body and form at least part of the mechanical interlocking between the shaft and the body. In some forms, the one or more engagement formations are embedded in at least one of the body and the shaft.

In some forms, the one or more engaging formations are provided by at least one intermediate member that is disposed between the body and the shaft. In some forms, the at least one intermediate member is in the form of a helical winding that extends around the shaft.

According to a further aspect, there is disclosed a method of assembling a cable bolt assembly including: providing an end fitting having a body extending between two ends along an axis; disposing the body onto an end portion of a shaft of a cable bolt; forming the body onto the shaft so that the body is plastically deformed about the shaft; and disposing exterior profiling on the body.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described by way of example only, with reference to the accompanying drawings in which

FIG. 1a to 1c is a side view of an embodiment of a cable bolt assembly;

FIG. 2 is a side view of an assembled component of an end fitting and a cable bolt of the cable bolt assembly of FIG. 1a to 1b;

FIG. 3 is an end view of the end fitting and cable bolt of FIG. 2;

FIG. 4 is an enlarged cross-sectional view of the end fitting and cable bolt of FIG. 3;

FIG. 5 is an exploded perspective view of a further embodiment of a cable bolt assembly;

FIG. 6 is an exploded perspective view of a further embodiment of a cable bolt assembly;

FIGS. 7a to 7d are end views of an embodiment of a crimping process of an end fitting blank used in forming a cable bolt assembly;

FIGS. 8a to 8d are end views of an embodiment of a swaging process of an end fitting blank used in forming a cable bolt assembly;

FIG. 9a a perspective view of an end fitting blank on a cable bolt shaft;

FIGS. 9b to 9d are sectional views of an embodiment of an extrusion process of an end fitting blank used in forming a cable bolt assembly;

FIG. 9e is a perspective view of an end fitting blank extruded onto a cable bolt shaft;

FIGS. 10a and 10b are cross-sectionals view of an embodiment of a method forming external profiling of an end fitting of a cable bolt assembly;

FIG. 11 is a perspective view of an embodiment of a component of an end fitting blank with various stages of external profiling applied thereto;

FIG. 12 is a sectional view of the component of FIG. 11;

FIG. 13 is an end view of an embodiment of a profiling tool;

FIG. 14 a perspective view of the tool of FIG. 13;

FIG. 15 is an end view of an further embodiment of a profiling tool;

FIG. 16 is a perspective view of the tool of FIG. 15;

FIG. 17a is a section cross section of the cable bolt assembly of FIG. 1 including an intermediate member in the form of a helical winding;

FIG. 17b is a perspective view of the helical winding shown in FIG. 17a;

FIG. 17c is a detailed view of the wire used in the helical winding of FIG. 17b; and

FIG. 17d is a detailed view of the cross section of FIG. 17a.

DETAILED DESCRIPTION

In the following detailed description, reference is made to accompanying drawings which form a part of the detailed description. The illustrative embodiments described in the detailed description, depicted in the drawings and defined in the claims, are not intended to be limiting. Other embodiments may be utilised, and other changes may be made without departing from the spirit or scope of the subject matter presented. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings can be arranged, substituted, combined, separated and designed in a wide variety of different configurations, all of which are contemplated in this disclosure.

End fittings are known on cable bolts to aid in tensioning of the bolt when installed. The end fittings are required to accommodate high tensile loading as they provide the reaction force to the tension induced in the cable. In the past these end fittings have often been retained in connection with the bolt shaft through a barrel and wedge fitting.

A swaged end fitting may be used in place of the barrel and wedge. The swaging process involves deforming the end fitting to engage with a cable bolt. The deformation process involves significant compression forces. Further swage end fittings tend to be large and bulky and sit entirely outside the bore. This means that the swaged end fitting may have a limited engagement capacity (e.g., external thread) to install and tension the cable bolt assembly. Also, mines tend to have limited space, so having an end fitting projecting from the bore further limits the available space inside the mine.

Disclosed is a cable bolt assembly comprising: a cable bolt having a shaft; an end fitting disposed on the shaft and including a body extending between a leading end and a trailing end spaced apart along an axis; and mechanical interlocking provided between the body and the shaft to form a connection therebetween; the body including an exterior profiling disposed thereon and arranged to engage a further component of the end fitting to install and/or tension the cable bolt assembly in use.

Also disclosed is a cable bolt assembly comprising a cable bolt having a shaft; and an end fitting disposed on the shaft and including a body extending between a leading end and a trailing end spaced apart along an axis. The cable bolt assembly also includes at least a portion of the body being formed onto the shaft so that the body is plastically deformed about the shaft. The body includes an exterior profiling disposed thereon and arranged to engage a further component of the end fitting for use in installing and/or tensioning the cable bolt assembly in use.

In some embodiments, the portion of the body plastically deformed about the shaft includes the exterior profiling. In some embodiments, the exterior profiling is disposed on both the portion of the body plastically deformed about the shaft and any remainder of the body. The exterior profiling is not required to extend the length of the body. The exterior profiling may extend along a portion of the body including along a portion of the portion of the body plastically deformed about the shaft and a portion of the remainder. The exterior profiling may be spaced apart and extend along the body and need not be continuous.

In some embodiments, an internal surface of the body is mechanically interlocked with the cable bolt.

The mechanical interlocking allows load transfer between the body and the cable bolt shaft and in the context of the specification relates to the formation of mechanical bonds or connections between components (either directly or indirectly through intermediate components). These bonds or connections may result from the plastic flow of material to create entanglement between two or more components and/or through the interactions between surface profiles of the components. The capacity of the resulting connection formed by the mechanical interlocking is typically measured by its ability to transmit the induced forces across the connection under tensioning of the cable bolt assembly.

In some embodiments, the cable bolt includes a plurality of wires wound about one another, and at least one of the plurality of wires is hollow. In some embodiments, the cable bolt includes a central wire, and the central wire is hollow. The cable bolt retains its shape after the body is formed onto the shaft and the mechanical interlocking is formed between the wires and the shaft. This is beneficial as the at least one hollow wire does not collapse and thus may be used for post-grouting or resin to encapsulate the cable bolt in the bore of the rock strata. In a particular form, accurate forming to allow the cable bolt shaft to retains its shape allows the compressive forces induced in forming to be carried by the outer hollow strands as they are forced into contact with one another.

A cable bolt assembly is also disclosed comprising a cable bolt having a shaft, the cable bolt includes a plurality of wires wound about one another, and at least one of the plurality of wires is hollow; an end fitting disposed on the shaft and including a body extending between a leading end and a trailing end spaced apart along an axis; and at least a portion of the body being formed onto an end portion of the shaft so that the body is plastically deformed about the shaft. In some embodiments, the cable bolt includes a central wire, and the central wire is hollow.

In some embodiments, the cable bolt assembly further comprises one or more engagement formations provided between the internal surface of the body and the shaft, the one or more engagement formations arranged to engage the shaft and the internal surface of the body to form at least part of the connection between the shaft and the body. In some embodiments, the one or more engagement formations interact with the body and the shaft to form at least part of the mechanical interlocking between the body and the shaft. In some embodiments, the one or more engagement formations are deformed during forming step to interact with both the body and the cable bolt. In some embodiments, the one or more engagement formations do not deform to form mechanical interlocking between the body and the shaft. In some embodiments, the internal surface of the body and/or the cable bolt deform about the engagement formations to form the mechanical interlocking between the components and the one or more engagement formations.

In some forms, the cable bolt shaft, end fitting body (or blank thereof), and/or engagement formations if incorporated include profiling to assist in forming mechanical interlocking of the connection. This may include cable biting that involves deforming or treating the outer profile of the cable prior to forming. Alternatively, components may be selected that already have suitable treated surface or profile, such as indented or spiral wire, which is more readily able to form the required mechanical interlocking.

In some embodiments, the body includes an exterior profiling disposed thereon and arranged to engage a further component of the end fitting for use in installing and/or tensioning the cable bolt assembly in use. In some embodiments, the portion of the body plastically deformed about the shaft includes the exterior profiling. In some embodiments the exterior profiling extends along both the formed portion of the body (incorporating the mechanical interlocking) and the remainder of the body. In some embodiments, body is of a suitable hardness or strength to allow post machining of the exterior profiling.

In some embodiments, the connection between the shaft and the portion of body plastically deformed about the shaft has a high capacity. This allows the cable bolt assembly, and in particular, the body to have a high performance. In some embodiments, the end fitting breaking load is >60% of the cable bolt uniaxial tensile strength. In some embodiments, the end fitting breaking load is >80% of the cable bolt uniaxial tensile strength.

In some embodiments, the body includes an outer diameter 1.6 times or less an outer diameter of the shaft of the cable bolt. Advantageously, having a low profile outer diameter of the body allows the cable bolt assembly to be inserted into a bore in the rock strata without or with minimal reaming of the bore.

In some embodiments, the cable bolt assembly is a high strength cable bolt having UTS (ultimate tensile strength) of greater than 40 t and in some forms, equal to or greater than 70 t. Such cables bolts, which may include hollow centre strand, have more complex geometries with multiple layers of strands and/or larger diameter strands. A challenge of designing such high strength cable bolts is in maintaining flexibility in the cable bolt to allow for adequate bending in service. In this regard, it is found that it is preferable to add cable strands rather than solely increase cable strand diameters as larger cable strands more severely reduce flexibility. The end fitting of the present disclosure and processes of forming such end fittings have been found particularly suitable for such applications where there is required to have a commensurate capacity in the connection. However, the end fittings are also applicable to lower strength cable bolts as well.

In some embodiments, the formed portion of the body extends the length between the trailing end and the leading end. In some embodiments, the formed portion of the body extends from the trailing end. In some embodiments, the formed portion of the body extends from the leading end. In some embodiments, the formed portion of the body extends one or more lengths of the body between the trailing end and the leading end.

In some embodiments, the further component of the end fitting interacts with the exterior profiling and may be arranged to be rotatable about the body to allow tensioning of the rock bolt assembly. In some forms, the further component is in the form of a nut having an interior thread with the exterior profiling being in the form of a complementary thread.

In some embodiments, the cable bolt further comprises a torque transfer arrangement that is arranged to allow a threshold torque to be applied to the shaft through the further component without inducing relative rotation between the further component and the shaft. In some embodiments, the torque transfer arrangement may be in the form of adhesive that bonds the further component to the body up to a threshold. In some embodiments, the torque transfer arrangement, may be in the form of a frangible element, such as a shear pin or plug.

In some embodiments, the forming of the body onto the shaft is by a swaging and/or extrusion process. In some embodiments the forming is by a cold working process but may include heating of the body (such as in a warm forging process or the like). In some embodiments, the forming of the body onto the shaft plastically deforms the body around the shaft without causing removal of material from the body. In other forms, some material may be removed in the forming process (such as by a subsequent machining step) and the term “forming” in the context of the specification includes such a material removal process.

In some embodiments, the external profile may be disposed on the body by a forming process or by a machining process such as milling or the like, or by a combination of forming and machining.

Also disclosed is a cable bolt assembly comprising a cable bolt having a shaft; and an end fitting disposed on the shaft of the cable bolt and including a body extending between a leading end and a trailing end spaced apart along an axis. The cable bolt assembly also includes at least a portion of the body being formed onto the body so that the body is plastically deformed about the shaft. The cable bolt assembly further comprises one or more engagement formations provided between an internal surface of the body and the shaft, the one or more engagement formations arranged to engage the shaft and the internal surface of the body to form at least part of the connection between the shaft and the body.

The engagement formations may be provided through incorporating an intermediate member between the end fitting body and the shaft.

Also disclosed is a method of assembling a cable bolt assembly having a shaft, the method comprising: providing an end fitting having a body extending between two ends along an axis; positioning at least a portion of the body onto the shaft; forming the body onto a portion of the shaft so that the body plastically deforms about the shaft; and disposing exterior profiling on the body.

In some embodiments, the exterior profiling is disposed on the formed portion of the body. The exterior profiling may be disposed on both the swaged portion of the body and the remainder of the body as discussed above. In some embodiments, wherein during forming of the body onto the shaft, the exterior profiling is established on the body. In this way, both the forming of the body on the shaft and establishing the exterior profiling may be performed at the same time or simultaneously.

In some embodiments, an internal surface of the body mechanically interlocks either directly and/or through one or more intermediate components, with the shaft.

In some embodiments, the method further comprises providing one or more engagement formations between an internal surface of the body and the end portion of the shaft, wherein the one or more engagement formations form part of the mechanical interlock between the body and the shaft. In some embodiments, during the step of forming the body on the shaft, the method also includes interacting of the one or more engagement formations to form at least part of the mechanical interlocking between the body and the cable bolt. In some embodiments, the method includes deforming the internal surface of the body and/or the shaft to mechanically interlock with one another and the one or more engagement formations. In some embodiments, during the step of forming, the method also includes deforming the one or more engagement formations to interact with both the body and the cable bolt.

In some embodiments, positioning the body onto the shaft increases the surface area of the one or more engagement formations. The one or more engagement formations may be formed on the shaft or may be discrete separate formations. The step of disposing the body onto the shaft (before forming step occurs) may facilitate the mechanical interlock of the one or more engagement formations through roughening or breaking.

A method of assembling a cable bolt assembly is also disclosed comprising providing an end fitting having a body extending between two ends along an axis; disposing the body onto an end portion of a shaft of a cable bolt, the cable bolt including a plurality of wires wound about one another and at least one of the wires is hollow; forming the body onto the shaft so that the body is plastically deformed about the shaft; and maintaining the profile of the shaft of the cable bolt during the forming process. In some embodiments the cable bolt includes a central wire, and the central wire is hollow. The benefit of the hollow wire not collapsing during forming is that it may be used for post-grouting or resin to encapsulate the cable bolt once its tensioned.

In some embodiments, the method further comprises establishing exterior profiling on the body. In some embodiments, the exterior profiling may be disposed on the swaged portion of the body. The exterior profiling may be in the form of exterior threading. In some embodiments, during the forming process, the exterior profiling is disposed on the body. In this way, both the forming of the body on the shaft and establishing the exterior profiling may be performed at the same time or simultaneously.

In some embodiments, the connection between the formed portion of body and the shaft has a high capacity. This allows the cable bolt assembly, and in particular the end fitting, to have a high performance. In some embodiments, the end fitting breaking load is >60% of the cable bolt uniaxial tensile strength. In some embodiments, the end fitting breaking load is >80% of the cable bolt uniaxial tensile strength.

A method is disclosed of assembling a cable bolt having a shaft, the method comprising: providing an end fitting having a body extending between two ends along an axis; positioning at least a portion of the body onto the shaft; forming the body onto the end portion so that the body is plastically deformed about the shaft; and providing one or more engagement formations between the internal surface and the end portion, wherein the one or more engagement formations reinforce the connection between the formed portion of the body and the shaft.

In some embodiments, an internal surface of the body mechanically interlocks with the shaft.

A method is disclosed of installing the cable bolt assembly into a bore in rock strata, the cable bolt assembly according to any one of the forms described above and the method comprising inserting the cable bolt assembly into the bore without reaming or with minimal reaming. This is enabled by the cable bolt assembly end fitting having a low profile relative to cable bolt shaft.

Referring to FIGS. 1 to 5, disclosed is an embodiment of a cable bolt assembly 10. The cable bolt assembly 10 generally includes a cable bolt shaft 14 and an end fitting 16. Cable bolt assemblies are installed in rock strata to support, and in some cases, compress the surrounding rock strata. Cable bolt shafts are typically made up of individual wires 15 wound about each other and in some cases the wires 15 are wound about a central wire 17 which may be known as a king wire. The central wire 17 may be hollow. Once the cable bolts are installed in the bore of the rock strata they may be tensioned which provides the compressive force on the surrounding rock strata. The end fitting disclosed herein provides a means for tensioning the cable bolt shaft at the time of installation.

In the illustrated embodiment, the end fitting 16 generally includes a body 18, a nut 20 and a washer 22. The body 16 is connected to the shaft through mechanical interlocking 19 (that may occur for example by entanglement between the components resulting from plastic material flow occurring from having the end fitting being swaged or extruded onto the shaft), and an exterior profiling 24 extends along a portion of the body 18 for receiving the other components of the end fitting (e.g., the nut 20, washer 22). Further, the body of the end fitting is arranged to be of a low profile so that it can locate within the bore such that the cable bolt assembly is arranged to be located in a bore formed in rock with little or no reaming of the bore and little or no tail (e.g. end of the end fitting 16 and shaft 14) protruding from the rock.

The end fitting 16 extends between a leading end 26 and a trailing end 28. The body 18 includes an internal passage 25 opening to the leading end 26. The passage 25 is defined by an internal surface 27 that may extend from the leading end 26 to the trailing end 28 or alternatively may terminate before the trailing end 28. The end portion of the shaft is disposed within the internal passage 25 of the body 18. In one form, at least a portion of the body 18 is plastically deformed about the profile of the shaft 14 to create the connection with the shaft 14 whereby the internal surface 27 of the body 18 is mechanically interlocked with the cable bolt shaft. The hollow wire of the cable does not collapse through this process, which allows it to be used for post-grouting or resin. As best shown in FIG. 3, the internal surface 27 of body 18 is deformed to a flower shape from a cross-sectional or end view. The internal surface 27 under the plastic deformation engages the cable bolt 14 and the body 18 penetrates the wires 15 of the cable bolt to engage the cable wires 15 thereby forming mechanical interlocking 19. The plastic deformation resulting from the swaging operation results in a constant loading to the cable, prevents slippage of the end fitting 16 from the cable bolt and provides the assembly 10 with a high tensile capacity. The body 18 may be formed from any suitable material that is able to plastically deform and have a high capacity, such as metals, and in particular, steel. With this arrangement, the mechanical interlocking is provided, at least in part, by direct connection between the body 18 and the shaft 14.

The connection between the body 18 and the cable bolt 14 has a high capacity. The high capacity is a result of the mechanical interlocking of the body 18 with the cable bolt 14. This allows the cable bolt assembly, and in particular, the body to have a high performance and may allow for the cable bolt to fail before the end fitting in use. The end fitting breaking load may >60% of the cable bolt uniaxial tensile strength. Further, the end fitting breaking load may be >80% of the cable bolt uniaxial tensile strength. In some forms, the end fitting breaking load is >90% of the cable bolt uniaxial tensile strength.

The body 18 has an outer diameter 1.6 times or less, e.g. 1.5 times less or 1.45 times less an outer diameter of the shaft of the cable bolt. This allows the end fitting 16 to be accommodated inside the bore of the rock strata without reaming or with minimal reaming.

Advantageously, the body 18 disclosed herein allows an arrangement where the cable bolt assembly has a high capacity and may not require the end of the bore to be reamed. In other words, the end fitting 16 has a high performance and a low profile in relation to the diameter of the cable bolt shaft diameter.

The below table illustrates the ranges of the features of the high capacity and the outer diameter of the body 18 by way of example only:

Cable bolt
Cable bolt
Maximum Swage
Minimum Swage

Outer Diameter
end area
Outer Diameter
Capacity

(mm)
(mm²)
(mm)
(tonnes)

20
314.2
32.0
20.1

25
490.9
40.0
26.4

31
754.7
49.6
33.9

36
1018
57.6
40.2

40
1256
64.0
45.2

45
1590
72.0
51.5

The formed portion of the body 18 also includes the exterior profiling 24 disposed thereon. In the illustrated embodiment, the exterior profiling 24 is in the form of external threading 24. The external threading 24 is arranged to engage a further component of the end fitting (e.g., the nut 20) to install and tension the cable bolt assembly in use. The nut 20 is threadedly engageable with the external thread 24 and rotatable about the body 18 to tension the cable in-use.

Referring now to FIG. 1a to 1b and FIG. 5, the end fitting 16 further comprises the washer 22 disposed on the body 18, distal of the nut 20. The washer 22 has a domed outer surface and is typically arranged to bear against a plate (not shown) which locates on the rock surface to accommodate the reaction load on tensioning of the cable bolt. In the illustrated form, the washer 22 is axially displaceable along the body whilst being restrained from rotating about the body. A keyway 32 can be formed between the body 18 and the washer 22 to restrain the washer from rotating about the body. In the illustrated embodiment, the keyway is a non-circular surface in the form of two opposing flat (or concave) surfaces 32. The washer 22 also includes corresponding opposing flat (or convex) surfaces 34 defined on an internal surface of the washer 22. The corresponding surfaces allow the washer to slide on the cable, but not twist. In use, restraining rotation of the washer 22 allows the cable bolt to spin with the application of torque to the nut 20 (through the torque transfer arrangement discussed below) and to resist twisting of the shaft 14 under tensioning of the cable bolt assembly 100 as mechanical engagement occurs between washer and the plate. This mechanical engagement may occur solely through frictional engagement and/or may include interlocking formations between the washer and plate.

The end fitting 16 can further comprises a needle bearing washer 23 disposed on the body 18, in-line with the washer 22, and can reduce friction during installation between the rotatable nut 20 and the non rotatable washer 22. The washer 22 can further comprise a cup wall or skirt 25 arranged to contain and protect the needle-bearing washer 23.

A torque transfer arrangement 29 is arranged to allow a threshold torque to be applied to the shaft 14 through the nut 20 without inducing relative rotation between the nut and the shaft. The torque transfer arrangement 29 comprises a frangible connection between the washer 22 and the nut 20. In some embodiments, the torque transfer arrangement 29, may be in the form of a frangible element, such as a shear pin 33 or plug (not shown).

The shear pin is shown in the embodiment of FIG. 1c. The shear pin 33 is arranged to locate through an opening 35 in the washer cup wall 25 and position within a corresponding hole disposed in a side of the nut 20. The shear pin extends between the washer and the nut. An advantage of this arrangement is that it avoids the need for the shear pin to engage directly with the cable strands which simplifies manufacture and avoids compromising the tensile strength of the cable bolt shaft 14. The shear pin maintains the washer in a fixed position relative to the nut.

The shear pin 33 is of sufficient strength to withstand the stresses applied to the bolt during normal mixing conditions where the shaft 14 is spun in the bore under drive (from the drilling rig) through the nut 20 to fracture the resin capsule mix the resin to anchor the shaft in the bore. The shear pin 33 is arranged to shear when the torque applied to the nut exceeds the shear strength of the pin, i.e. a threshold loading is applied. This occurs when the shaft is anchored within the bore by curing of the resin anchor. The shear strength of the pin is predetermined according to the design requirements of the cable bolt. Upon breaking of the shear pin, the nut is allowed to rotate independent of the washer and thus tensioning of the cable bolt shaft can occur.

The mechanical interlocking 19 between the cable bolt 14 and the body 18 and the connection between the external profiling 24 and the nut 20 are generally aligned. This feature may have the benefit of reducing failures of the cable bolt assembly 10 in use. For example, shear forces may be reduced. This also contributes to increasing the loading capacity of the cable bolt assembly 10. The tensile forces at the end portion of the cable bolt 14 are converted to shear forces across the body 18. As this shear surface area is substantially larger, this contributes to an increased loading capacity of the cable bolt assembly 10.

As shown in FIG. 4, the cable bolt assembly 10 may also include one or more engagement formations 30 provided between the internal surface 27 of the body 18 and the shaft 14. The one or more engagement formations 30 are arranged to engage the shaft 14 and the internal surface 27 of the body 18 to form at least part of the connection between the shaft 14 and the body 18. The one or more engagement formations 30 form at least part of the mechanical interlocking 19 between the shaft 14 and the body 18. In one form, they reinforce the connection between shaft 14 and body 18 formed by deforming of the body onto the shaft. In another form, they may be used in place of the direct mechanical interlocking such that the engagement formations form the primary or sole means of mechanical interlocking 19 connecting the shaft to the sleeve. In one form, the one or more engagement formations 30 increase the coefficient of friction between the cable bolt 14 and the body 18.

The one or more engagement formations 30 embed into at least one, but preferably both, the internal surface 27 of the body 18 and the cable bolt strands 15 to form the mechanical interlocking 19. The engagement formations 30 are preferably spaced along the engaging portion of the body 18 and the cable bolt 14. The engagement formations 30 increase the surface area of engagement (mechanical interlocking) between the components 14, 18. The engagement formations 30 may also deform during forming (e.g. swaging) interacting with both the body 18 and the cable bolt 14. The engagement formations 30 may deform less than the body 18. The engagement formations 30 may engage more with the body 18 than the cable bolt 14, i.e., the engagement formations 30 embed within the body 18. The engagement formations 30 may not deform during swaging. It is beneficial for the engagement formations 30 to be of similar or higher hardness than both components to enhance the mechanical interlocking 19 between the components 14, 18.

In some form, the engagement formations 30 extend along the fitting. The engagement formations may be formed from a plurality of discrete components that are included in the end fitting 16 as intermediate members disposed between the shaft 14 and body 18, or alternatively they may be incorporated as part of at least one of the components. For example, the engagement formations may be formed as part of the body which are incorporated as hardened elements in the material matrix of the body 18 or included as a co-formed process with the body 18. The one or more engagement formations may take several different forms. There may be one engagement formation, or more than one engagement formation. The engagement formations may be in the form of a series of rings spaced apart along the body. The engagement formation(s) may be of varying dimensions, shapes, materials etc. The engagement formation(s) may be in the form of scoring, indentations or a finish on the surface of the cable bolt or the internal surface of the body which creates or improves the mechanical interlocking. For example, the end of the cable bolt may include one or more engagement formations in the form of threading directly on the cable bolt or the internal surface of the body may include internal threading.

The one or more engaging formations 30 may be provided on at least one intermediate member 730 that is disposed between the body 18 and the shaft 14, as shown in the embodiment of FIGS. 17a-17d. The one intermediate member 730 is in the form of a helical winding that extends around the shaft 14 and overlayed with body 18. Alternatively, the helical winding may be pre-formed or installed on the internal surface 27 of the body. The helical winding 730 may be in the form of wires with non-circular or polygonal (e.g. triangular) cross section to assist in embedding the engaging formations into the shaft strands and body 18. The winding may remain intact after the body is formed (e.g. swaged, or extruded) onto the shaft such that the engaging formations are substantially continuous or may be arranged to fracture such that the resulting engaging formations are formed as discrete elements. The intermediate member may also assist in increasing the crushing stress of the end fitting, thereby assisting in preventing collapse of the cable under a forming process such as swaging or extruding of the end fitting.

In the embodiment shown in FIG. 17a, the cable bolt assembly 10 includes the cable bolt (i.e. shaft) 14, end fitting body 18, and the intermediate member 730 in the form of a helical winding 770, i.e. a coil that extends along the major length of the body that is both formed onto the shaft (to cause the mechanical interlocking 19 through the plastic deformation) and which is profiled on its outer surface with external thread 24.

As best shown in FIGS. 17b and 17c, the helical winding 770 is comprised of a wire 776 having a triangular cross section. In other forms not shown, the cross-section may be other polygonal shapes. In one form, the triangular cross-sectioned wire is twisted about its longitudinal axis so that edges 778 and faces 780 form a helical structure along the length of the wire so that there are localised regions that are more prone to embed in the shaft and internal surface of the body thus forming discrete regions of the mechanical interlocking 19. As best shown in FIG. 17b, the twisted wire 776 is helically wound into a coil having inner 782 and outer 784 surfaces. The twisting of the wire spaces apart the edges 778 of the wire at the surfaces 782,784 so as to form an undulating contour in the inner and outer surfaces of the coil.

The helical winding 770, in-use, can penetrate the body 18 and shaft 14 during the swaging process so that the edges 778 of the wire 778 embed into the internal surface 27 of the body and to some extent into the strands 15 of the cable bolt shaft 14.

A sealant may be disposed between the body 18 and the shaft 14. In use, the sealant seals the cable bolt against internal permeation of fluids of the plurality of wires. The sealant can be applied under and around the cable bolt wires 15, for example, at one, or both ends, of the cable head and in intermediate helical winding 770. The sealant can be further utilised for sealing the internal engagement of swage-cable against fluids introduced during grouting and water flushing, along with general groundwater once the cable is inside the rock.

A further embodiment of the cable bolt assembly is illustrated in FIG. 6. Like reference numerals are used for like features. The prefix ‘1’ is respectively used to indicate the further embodiment. The primary difference between the embodiments illustrated in FIG. 6 and the embodiment illustrated in FIGS. 1 to 5 is the structure of the anti-twist feature to inhibit the body rotating with the nut during tensioning.

Referring to FIG. 6, the cable bolt assembly 100 includes a body 118 disposed on an end portion of the cable bolt 14, the nut 20 and a washer 122. The body 118 is formed to be non-circular to facilitate gripping or to prevent twisting of the washer and body for the same reasons discussed above. In the illustrated embodiment, three slots or indentations 132 are formed on the external surface of the body 118, and the washer 122 includes a corresponding internal profile. In the illustrated embodiment, the three slots 232 are equally spaced about the circumference of the body 118.

In some forms, the end fitting 16 is fitted to the shaft by a forming process such as swaging an end fitting blank 1 on the shaft which is subsequently subjected to further processing as described in more detail below with reference to FIGS. 7a to 16.

The blank 1 may be compatible to be formed with various sizes of cable bolts. For example, the end fitting may be designed and manufactured as a one-size fits all. Alternatively, some characteristics of the blank may be varied to suit particular sizes of cable bolts, such as the material, the external diameter of the blank, the internal diameter of the passage, the length of the blank or the length of the blank which is plastically deformed onto the cable to form the formed portion of the body. The outer diameter of the blank may be sufficient to accommodate the desired external profiling disposed thereon. The internal diameter of the passage may allow for the connection between the shaft of the cable bolt and the internal surface of the body.

Further, the method of forming the body onto the shaft may define the characteristics of the body such as cold working or hot shaping. The shape of the body is changed through a forming process. In particular, the shape of the illustrated body 18 is compressed and deformed within a range of outer diameters that suit the size or the bore, the size of the cable bolt 14 while maintaining a high capacity. Embodiments of methods of assembling the cable bolt assembly 10 are discussed in more detail below as well applying the external profiling to the body of the end fitting.

Various forming processes may be performed to the blank 1 to dispose it about the shaft of the cable bolt. These include a swaging process or an extrusion process (where the body blank is drawn though a die to plastically deform the body onto the shaft) or a combination of swaging and extrusion. In the swaging embodiments disclosed like reference numerals for like features as discussed above, and the prefixes ‘3’, ‘4’ and ‘5’ indicate a different embodiment.

In general, the method disclosed with reference to FIGS. 7a to 16 for manufacturing a cable bolt assembly 10, 100, generally including the following steps:

positioning at least a portion of a body blank 1 onto an end portion of a shaft 14; and

forming the body blank 1 onto the end portion of the shaft 14 so that the body blank 1 is plastically deformed about the shaft 14.

establishing exterior profiling 24 on the body blank 1 to form the body 18. The exterior profiling 24 may include disposing the exterior profiling on the formed portion of the body 18. The exterior profiling 24 may be established at the same time or subsequent to forming the body 18.

In some embodiments, the method includes:

providing one or more engagement formations 30 between the body 18 and the end portion of the shaft 14, wherein the one or more engagement formations 30 reinforce the connection between the formed portion of the body 18 and the shaft of the cable bolt 14. The end formations may be provided by an intermediate member in the form of a helical winding between the shaft 14 and blank 1.

Turning to the embodiments disclosed with reference to FIGS. 7a to 16, prior the end fitting 16 being positioned on the cable bolt 14, the blank 1 is selected. Generally, the blank 1 is formed as a thick-walled cylinder having an internal passage 25 extending from the leading end 26, and in some embodiments, through to the trailing end 28. The outer diameter of the blank 1 prior to swaging onto the cable bolt 14 must be of a suitable dimension to accommodate the predetermined exterior profiling 24. The inner diameter of the internal passage 25 allows for the shaft of the cable bolt 14, and in some embodiments, the one or more engagement formations 30.

The next step is to position at least a portion of the blank 1 onto the end portion of the shaft of the cable bolt 14. The inner diameter of the internal passage 25 allows for the blank 1 to slide onto the shaft 14 easily. The one or more engagement formations 30 may also be provided between the internal surface of the blank 1 and the shaft of the cable bolt 14 such as by disposing the helical winding 770 over the shaft 14.

The next step is forming the body 18 onto the end portion of the shaft of the cable bolt 14. This process mechanically interlocks the internal surface of the body blank 1 with the shaft of the cable bolt, and in some embodiments, with the one of more engagement formations 30.

Advantageously, the forming process plastically deforms the body blank 1 about the shaft 14 thereby providing mechanical interlocking between the shaft and body as the body blank integrates into spacings between and around the cable bolt shaft strands 15.

The forming process may be implemented at least by the following two methods.

The first method involves using two or more dies to hammer a workpiece (e.g., the body 18) into a smaller diameter. This method may be known as “rotary swaging” or “radial forging”. This method is illustrated in FIGS. 7a to 8d.

The second method involves extruding the body blank 1, forcing it through a confining die to reduce its diameter, similar to the process of drawing wire to get desired shape. This method is illustrated in FIGS. 9a to 9e.

Forming may be a cold working process or a hot working process. In general, cold forming is better suited to a large-scale production of parts because of the cost of the required equipment and tooling as higher forces are required for deformation also heavier and more powerful equipment is required.

Some advantages of cold working in comparison to hot working may be as follows:

no heating is required;

a good surface finish is obtained;

good dimensional control is possible, and thus no secondary machining is generally needed;

products possess better reproducibility and interchangeability;

good strength, fatigue, and wear properties of material;

directional properties can be imparted; and

contamination problems are almost negligible.

The step of providing the one or more engagement formations 30 between the internal surface 27 of the body blank 1 and the end portion of the shaft 14 may occur prior to the step of swaging. Whereas, the step of establishing the exterior profiling 24 to completed forming of the body 18 may occur after the step of forming the body blank 1 onto the shaft.

Now referring specifically to FIGS. 7a to 9e, the illustrated embodiments of the methods of forming will be discussed in more detail below, namely a crimping method (which is a form of swaging), a bi-directional swaging method, and an extrusion method.

Crimping involves positioning the body 18 (or more generally referred to as a ferrule) and the shaft of the cable bolt 14 into a crimping tool 340 having multiple reciprocating dies 342. The dies 342 are positioned about the components 14, 1 and applying a compressive force to plastically deform the body blank 1 onto the shaft 14. The outer diameter of the body blank 1 is reduced as a result of the crimping, and the inner wall of internal passage 25 is caused to form around the strands 15 as a result of the compression. The sequence of crimping is shown in FIGS. 7a to 7d.

FIG. 7a illustrates positioning the blank 1 onto the shaft 14 before the swaging process. The engagement formations 30 are also provided between the blank 1 and the shaft 14.

FIG. 7b illustrates positioning the body blank 1 and the shaft 14 in between the dies 342. In the illustrated embodiment, the crimping tool 340 includes six identically shaped and sized dies 342 that are equally spaced apart about the components 14, 1. In alternative embodiments, the dies may be different dimensions, shapes etc.

FIG. 7c illustrates applying a force through the multiple dies 342 to the body blank 1 until either the dies 342 come into contact with one another or reaching a given force. The force is sufficient to cause the body blank 1 material to deform.

FIG. 7d illustrates the dies 342 withdrawn from the components 14, 1 and the body blank 1 swaged to the shaft of cable bolt 14. Advantageously, although the central wire of the cable bolt 14 is hollow, it has not collapsed through the swaging process. This is largely due to the accurate configuration, shape and dimensions of the swage machine components and the shaft strands being caused to compress against one another to resist collapsing of the cable shaft.

The bi-directional swage method involves positioning the blank 1 on the end portion of the shaft 14 and placing the components into a swaging machine 444. In the illustrated embodiment, the swage machine 444 includes two dies 446 that apply a force from opposing directions. The dies 446 respectively apply the force to the body blank 1 until either the dies 446 come into contact with one another or meeting a given force. The dies 446 apply a compressive force to again plastically deform the blank 1 to form the join between the components 14, 18. In some embodiments, the one or more engagement formations 30 may also be provided between the body blank 1 and the shaft of the cable bolt 14. The sequence of the swaging process is shown in FIGS. 8a to 8d.

FIG. 8a illustrates positioning the blank 1 onto the shaft 14 before the initiation of the swaging process. The one or more engagement formations 30 are also provided between the body blank 1 and the shaft 14.

FIG. 8b illustrates positioning the components 14, 18, 30 between the two half dies 446.

FIG. 8c illustrates applying a force through the two opposing dies 446 to the body blank 1 and the one or more engagement formations 30.

FIG. 8d illustrates the dies 446 withdrawn from the components 14, 1 with the body blank 1 swaged onto the cable bolt shaft 14. Advantageously, although the central wire of the cable bolt 14 is hollow, it has not collapsed through the swaging process. This is largely due to the accurate configuration, shape and dimensions of the swage machine components and the shaft strands being caused to compress against one another to resist collapsing of the cable shaft.

Extrusions forming involves positioning the body blank 1 and the end portion of the cable bolt 14 into a graded chamber 548, where a ram 550 applies a force to the body blank 1 to push the body blank 1 through a profile die 552. The profile die 552 gives the outer diameter of the body blank 1 cross-section. The profile die 552 is of a sufficient diameter size to apply forming forces to the body blank 1 to join the components 14, 1 with the material flow of the body between the shaft stands to form the required mechanical interlocking. In some embodiments, the one or more engagement formations are also provided between the body blank 1 and the cable bolt 14. This extrusion process is illustrated with reference to FIGS. 9a and 9d.

FIG. 9a illustrates the blank 1 positioned onto the shaft 14 before the extrusion process.

FIG. 9b illustrates positioning the components 14, 1 into the profile die 552 and positioning the ram 550 at the trailing end 28 of the body blank 1 (and the cable bolt 14).

FIG. 9c illustrates applying a force with the ram 550 to the trailing end 28 of the body blank 1 to force it through the profile die 550 to until the body blank 1 reaches an abutment surface internal the profile due 550. This step forms the body blank 1 to the shaft of the cable bolt 14.

FIG. 9d illustrates removing the ram 550 and withdrawing the profile die 552 relative to the body 18.

FIG. 9e illustrates the body 18 formed onto the shaft of the cable bolt 14.

Advantageously, although the central wire 17 of the cable bolt 14 is hollow, it has not collapsed through the extrusion process. This is largely due to the accurate configuration, shape and dimensions of the extrusion machine components and the shaft strands being caused to compress against one another to resist collapsing of the cable shaft. The hollow strand is useable for post-grouting or resin to partially or fully encapsulate the bolt.

Now referring to FIGS. 10a to 17, the next step after completion of the forming process is establishing the exterior profiling 24 on along at least a part of the formed portion of the body blank 1 to form the body 18. The thread implementation step may be done by using a thread cutting method (FIGS. 10a to 16) or by using a thread rolling method (FIG. 17). Creating the thread is performed after the forming. As a result, the body is of a suitable hardness and/or strength to allow post machining of the thread.

In the embodiment illustrated in, the exterior profiling 24 is in the form of an exterior thread 24. In alternative embodiments, the exterior profiling 24 may be in the form of a ratchet profile etc.

In general, the thread cutting method forms the exterior thread on the swaged portion of the body 18 through following two steps:

First, reducing the outer diameter of the swaged portion of the body blank 1 to a diameter close to the thread major diameter. This is completed by a tool in the form of a ‘peeling’ mechanism 654 as shown in FIGS. 13 and 14.

Second, removing the material to form the thread 24 by using a second tool in the form of a ‘cutting’ mechanism 656. The cutting mechanism 656 is shown in FIGS. 15 and 16.

It is additionally understood that peeling, pressing, or crimping of threads with or without the addition of heat are able to achieve a similar outcome.

FIG. 10a illustrates the formed body blank 1 positioned adjacent the peeling mechanism 654 which is positioned adjacent the thread cutting mechanism 656.

FIG. 10b illustrates the formed body blank 1 positioned within the peeling mechanism 654 and the cutting mechanism 656.

FIGS. 11 and 12 illustrate the formed body blank 1 partway through the exterior profiling process. The leading end 26 of the formed body blank 1 includes the incremental thread cutting 24 (thereby in the formed of the finished body 18), then the incremental peeling 664, then the un-cut formed blank body 666 towards the trailing end 28.

FIGS. 13 and 14 illustrate the peeling mechanism 654. The peeling mechanism 654 includes a larger, harder, less precise set of teeth 658 which remove material relative to the cutting mechanism 656. The peeling mechanism 654 includes slits 660 that allow material to flow out of the peeling head. The teeth 658 start at a larger aperture, and incrementally decrease to minimise stress on the teeth 658, and the body blank 1.

FIGS. 15 and 16 illustrate the cutting mechanism 656. The cutting mechanism 656 includes a more precise, continuous thread shape (i.e., thread cutters 662) relative to the peeling mechanism 654. The cutting mechanism 656 includes slits 660 which allow excess material to be flushed out. Additionally, the thread cutters 656 are aligned so that later thread cutters 662 fall into the cut of previous thread cutters 662. This allows the thread 24 to be continuous over the length of the body 18. In alternative embodiments, the thread may be cut over a portion of the length, or in sections that are spaced apart over the length.

It is understood that any suitable method of forming a thread may be implemented.

Variations and modifications may be made to the parts previously described without departing from the spirit or ambit of the disclosure.

In an alternative embodiment, embodiments of the cable bolt assembly may further include a connection on the trailing end which allows engagement with a grout or resin pumping lance. This attachment may screw over the trailing end of the body, may be integrated into the body itself; or may be slipped between the body and the shaft of the cable bolt before forming, and held in place by the forming process.

In an alternative embodiment, the exterior profiling is disposed on the body at the same time as forming the body to the end portion of the shaft. For example, the dies may be manufactured to perform both forming and machining the exterior profiling.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

End Fitting for a Cable Bolt Assembly

Information

Publication Number

Date Filed

Date Published

Inventors

Original Assignees

CPC

International Classifications

Abstract

Description

Claims

Priority Claims (1)