FIELD

The invention relates to the field of degradation tools and methods of manufacturing degradation tools.

BACKGROUND

Degradation tools are used for breaking, boring into or otherwise degrading structures or bodies, such as rock, asphalt, coal or concrete and may be used in applications such as mining, construction and road reconditioning. For example, in road reconditioning operations, a plurality of degradation tools may be mounted on a rotatable drum and caused to break up road asphalt as the drum is rotated. A similar approach may be used to break up rock formations in applications such as coal mining. Soft rock mining applications, such as mining potash or gypsum, use similar systems. Similarly, tunnel advancement may be performed using degradation tools. Examples of degradation tools include pick tools and percussive inserts.

Some degradation tools may comprise a strike tip comprising superhard material such as polycrystalline diamond (PCD) or polycrystalline cubic boron nitride (PCBN), which has a better abrasion resistance than working tips formed of cemented tungsten carbide material. Unlike degradation tools that have a cemented carbide strike tip, a superhard strike tip is typically not configured to rotate during operation. A superhard strike tip is usually bonded to a cemented carbide support body, and the cemented carbide support body is in turn attached to a steel holder body by inserting it into a bore in the steel holder body and fixing it using a technique such as shrink fitting, press fitting, or an interference fit.

The type of arrangement described above can lead to problems during operation where loads arising from striking a formation is not efficiently transferred from the support body to the steel body. This puts excessive localised stresses on the support body, steel holder body and even the strike tip, which can lead to early failure of the degradation tool.

Figure 1 illustrates schematically in a side cross section view a first example arrangement in which the load is not effectively transferred. In this example the degradation tool 101 includes a steel support body 102, a cemented carbide support body 103 that has a strike tip 104 at its working end. The steel body has a bore 105 into which the support body 103 is inserted. The base 106 of the bore 105 is not planar, but has a substantially conical shape. In order to maximise the contact between the base of the support body 103 and the base 106 of the bore, a load transferring entity 107 (sometimes referred to as a shim) is provided between the base of the support body 103 and the base of the bore 105. However, when the shim deforms as the support body 103 is inserted into the bore 105, it still leaves a void 108 around a central axis of the bore. During operation, load cannot be transferred from the support body 103 to the steel body 102 at the void 108, and so stresses build up in the support body as load has to be transferred to the steel body in directions at an angle to the main direction of the load. This can shorten the life of the degradation tool 101 .

Figure 2 illustrates schematically in a side cross section view a second example arrangement in which the load is not effectively transferred. In this example, the degradation tool 201 . Again, a steel holder body 202 is provided along with a cemented carbide support body 203, which has a strike tip 204. In this example, the cemented carbide support body 203 is inserted into a bore 205. The cemented carbide support body has an overhang portion 206 that abuts a surface 207 of the steel holder 202 that is adjacent to an opening of the bore. In order to effectively transfer load during operation, the overhang portion must by in contact with the surface 207 adjacent to the opening of the bore 205, and the base of the support body 203 must be in contact with the base of the bore. However, if the tolerances are not sufficiently accurate, the overhang portion 206 can sit above the surface 207 adjacent to the bore, leading to a gap 208 between the overhang portion 206 and the surface 207 adjacent to the bore. Again, this causes unwanted stress in the support body 203, which can lead to early failure of the degradation tool.

SUMMARY

It is an object to mitigate the problems caused by inadequate load transfer from a support body to a steel holder during operation of a degradation tool.

According to a first aspect, there is provided a method of manufacturing a degradation tool. The method comprises providing a holder body, the holder body have a bore arranged to receive a support body, the bore having side walls and a base. A load transferring entity is provided at the base of the bore, the load transferring entity having a maximum effective thickness. A support body is inserted into the bore, the support body comprising a strike tip at a first end and a support body base at a second, opposite end. The insertion of the support body causes deformation of the load transferring entity to reduce the maximum effective thickness of the load transferring entity to a lower, second maximum effective thickness, allowing the load transferring entity to form a load transferring bridge between the support body base and the base of the bore.

As an option, the method comprises causing irreversible deformation of the load transferring entity on insertion of the support body.

As an option, the load transferring entity is provided as a plurality of particles. As a further option, the plurality of particles is provided in a flexible container. The average particle size of the particles is optionally multi-modal, which allows better packing of the particles. A lubricant is optionally provided at a surface of the particles.

As an option, the load transferring entity is provided as a porous body.

As an option, the load transferring entity is provided as a hollow body.

As an option, the load transferring entity is provided as a substantially spherical body. As an option, the load transferring entity is provided as a plurality of substantially spherical bodies.

As an option, the load transferring entity is provided as a spring. Various materials may be used for the load transferring entity. Optional examples of suitable materials include copper, aluminium, nickel, iron, tin, lead, silver, titanium, and alloys thereof.

The support body optionally comprises a cemented metal carbide.

As an option, the bore base is non-planar.

The support body optionally further comprises a shoulder arranged to abut a surface of the holder body adjacent to an opening of the bore. As a further option, there is provided a second load-transferring entity between the shoulder of the support body and the surface of the holder body adjacent to the opening of the bore. The irreversible deformation of the load transferring entity is optionally plastic, although other types of irreversible deformation may be envisaged.

As an option, the method further comprises reducing the maximum effective thickness of the load transferring entity to a lower, second maximum effective thickness by an amount selected from any of greater than 5%, greater than 10%, greater than 15% and greater than 20%.

According to a second aspect, there is provided a degradation tool comprising a holder body and a cemented carbide support body, the cemented carbide support body further comprising a strike tip at a first end and a support body base at a second, opposite end. The holder body has a bore arranged to receive the cemented carbide support body, the bore having side walls and a base. A deformed load transferring entity is disposed between the base of the bore and the support body base such that the load transferring entity provides a load transferring bridge between the support body base and the base of the bore at a central axis of the bore.

As an option, the load transferring entity comprises a material selected from any one of copper, aluminium, nickel, iron, tin, lead, silver, titanium, and alloys thereof.

The support body optionally comprises a cemented metal carbide.

As an option, the bore base is non-planar. The support body optionally further comprises a shoulder arranged to abut a surface of the holder body adjacent to an opening of the bore. As a further option, the degradation tool comprises a second load-transferring entity between the shoulder of the support body and the surface of the holder body adjacent to the opening of the bore.

The bore optionally further comprises a tapered portion at the entrance to the bore such that the width of the bore at the entrance is greater than the width of the bore at the base.

The strike tip optionally comprises any of polycrystalline diamond and polycrystalline cubic boron nitride. As an option, the deformed load transferring entity is irreversibly deformed.

As an alternative option, the deformed load transferring entity is a spring. The degradation tool is optionally used for any of road milling or mining.

According to a third aspect, there is provided an assembly comprising a holder assembly and at least one degradation tool as described above in the second aspect, the holder assembly comprising any of a drum and an oscillating disc.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates schematically a side elevation cross section of a first exemplary known degradation tool arrangement; Figure 2 illustrates schematically a side elevation cross section of a second exemplary known degradation tool arrangement;

Figure 3A illustrates schematically a side elevation cross section of a first exemplary degradation tool arrangement before insertion of a support body;

Figure 3B illustrates schematically a side elevation cross section of the first exemplary degradation tool arrangement after insertion of the support body;

Figure 4A illustrates schematically a side elevation cross section of a second exemplary degradation tool arrangement before insertion of a support body;

Figure 4B illustrates schematically a side elevation cross section of the second exemplary degradation tool arrangement after insertion of the support body; Figure 5 illustrates schematically a side elevation cross section of a third exemplary degradation tool arrangement before insertion of a support body;

Figure 6 illustrates schematically a side elevation cross section of a fourth exemplary degradation tool arrangement before insertion of a support body;

Figure 7 illustrates schematically a side elevation cross section of a fifth exemplary degradation tool arrangement before insertion of a support body; Figure 8 illustrates schematically a side elevation cross section of a sixth exemplary degradation tool arrangement before insertion of a support body; Figure 9 illustrates schematically a side elevation cross section of a seventh exemplary degradation tool arrangement before insertion of a support body; and

Figure 10 is a flow diagram showing exemplary steps for manufacturing a degradation tool.

DETAILED DESCRIPTION

Referring to Figure 3A, there is illustrated schematically a side elevation cross section view of a first exemplary degradation tool 301 before assembly. The degradation tool 301 comprises a steel holder body 302 and a cemented carbide support body 303. The steel holder body 302 has a bore 304 into which the support body 303 will be inserted. The base 305 of the bore 304 is non-planar, and has a substantially inverted conical shape (this shape arises from the way in which the bore is machined out of the steel holder body 302). A solid ball of a malleable material is located at the base 305 of the bore 304. In this example, copper is used, but any suitable malleable material may be used. Examples include copper, aluminium, nickel, iron, tin, lead, silver, titanium and alloys thereof.

Referring now to Figure 3B, there is illustrated schematically a side elevation cross section view of the second exemplary degradation tool 301 after assembly. The support body has been forced into the bore 304. As it is forced down, it plastically deforms the malleable material 306 such that the malleable material fills the void between the base of the bore 304 and the support body 303 to form a load transferring entity 307. The type of void 108 shown in Figure 1 is not apparent because the initial maximum effective thickness of the malleable material 306 before deformation is greater than the maximum effective thickness of the deformed load transferring entity 307. The material therefore deforms to fill the void. This ensures that during operation, load is transferred from the base of the support body 303 to the steel holder body 302 along a main axis of the bore 304, and so ensures that stresses during operation are in predictable locations. This prolongs the tool life of the degradation tool 301 .

Referring to Figure 4A, there is illustrated schematically a side elevation cross section view of a second exemplary degradation tool 401 before assembly. In this example, a steel holder body 402 is provided along with a support body 403. The steel holder body 402 is provided with a bore 404 into which the support body 403 will be inserted. The support body 403 is provided with an overhang portion 405 that is arranged to abut a surface 406 of the steel holder body 401 adjacent to an opening to the bore 404. A malleable material 407 in the form of a copper ribbon, washer or wire is disposed on the surface 406 of the steel holder body 402 adjacent to the opening to the bore 404.

Referring to Figure 4B, when the support body 403 is inserted into the bore 404, the malleable material plastically deforms to form a load bearing entity 408 disposed between the overhang portion 405 of the support body 403 and the surface 406 of the steel holder body 402 adjacent to an opening to the bore 404. The base of the support body makes full contact with the substantially planar base of the bore 404. This ensure that during operation, load is transferred from the support body 403 to the steel holder body 402 both at the base of the support body 403 and at the overhang portion 405 of the support body. Again, this minimises unwanted or unpredictable stresses on the support body 403, thereby prolonging the life of the degradation tool 401 .

Note that the features of the first exemplary degradation tool and the second exemplary degradation tool may be used together; two load bearing entities can be provided, one at the base of the bore and the other adjacent to an opening of the bore to transfer load from an overhang portion to the steel body.

For the two example above to work, it is not necessary to provide a malleable material; merely one that can be deformed in such a way that it will fill voids allowing for a complete transfer of load from the support body to steel holder body. Figure 5 shows a third exemplary embodiment in which a plurality of deformable balls 501 are provided. The deformable balls 501 are located at the base of a bore 502 in the steel holder 503. When the support body 504 is inserted, the deformable balls 501 initially flow within the void and spread out, before plastically deforming to fill the void. Most, if not all of the deformable balls 501 plastically deform during insertion; however some will only deform during subsequent use of the deformation tool. This very much depends on their location within the void. The deformable balls 501 have a maximum effective thickness of ti , shown from the base of the bore to the top of the plurality of balls 501 . After compaction, the maximum thickness of the resultant load bearing entity is lower than ti . In order to improve compaction of these balls, they may have a lubricated surface. Alternatively or additionally, the balls may be provided with a multimodal size distribution to ensure that the balls compact more efficiently. In order to ensure a precise number (or volume) of balls is added, they may be provided in a flexible container such as a polymer bag or netting (not shown).

Figure 6 shows a fourth exemplary embodiment in which a powder of deformable particles 601 is provided. The deformable particles 601 are located at the base of a bore 602 in the steel holder 603. When the support body 604 is inserted into the bore 602, the particles 601 plastically deform to fill the void. The deformable particles 601 have a maximum effective thickness of ti , shown from the base of the bore to the top of the power 601 . After compaction, the maximum thickness of the resultant load bearing entity is lower than ti . In order to improve compaction of the particles 601 , they may have a lubricated surface. Alternatively or additionally, the particles 601 may be provided with a multimodal size distribution to ensure that the particles compact more efficiently. In order to ensure a precise weight or volume of powder is added, the powder may be provided in a flexible container such as a polymer bag.

Figure 7 shows a fifth exemplary embodiment in which a porous copper disc 702 is provided. The porous copper disc 701 is located at the base of a bore 702 in the steel holder 703. When a support body 704 is inserted into the bore 702, the copper disc 701 plastically deforms to fill the void. The disc 701 has a maximum effective thickness of ti . After compaction, the maximum thickness of the resultant load bearing entity is lower than ti .

Figure 8 shows a sixth exemplary embodiment in which a metal foam disc 801 is provided. The metal foam disc 801 is located at the base of a bore 802 in the steel holder 803. When a support body 804 is inserted into the bore 802, the metal foam disc 801 partly crushes and partly plastically deforms to fill the void as a load bearing entity. The foam disc 801 has a maximum effective thickness of ti . After compaction, the maximum thickness of the resultant load bearing entity is lower than ti . Figure 9 shows a seventh exemplary embodiment in which a spring 901 is provided. The spring 901 is located at the base of a bore 902 in the steel holder 903. When a support body 904 is inserted into the bore 902, the spring 901 compresses and acts as a load bearing entity to transmit load from the support body 904 to the steel holder 903. The spring 901 has a maximum effective thickness of ti . After compression, the maximum thickness of the spring is lower than ti . Note that many different types of spring may be used. In the example of Figure 9, a Belleville washer is used as a spring. However, it will be appreciated that any type of spring may be used, for example a leaf spring, a coil spring, a hollow or porous material frilled with a further material having a significant elastic modulus, and so on. A spring may not be as efficient at transferring load from the support body 904 to the steel body 903 as a solid body, but it will have a damping effect that could reduce localised stresses on the support body 904 and steel body 903 during operation.

Note that the embodiments described above may be used in any combination. For example, the first exemplary embodiment is shown with a non-planar base 305 of the bore 304. It will be appreciated that this embodiment would also work with a planar bore base. It will be appreciated that the first exemplary embodiment is also compatible with the type of support body 403 shown in Figure 4, which has an overhand portion 405.

A key feature of all the above embodiments is that the load bearing entity, prior to insertion of the support body, has a maximum thickness higher than its maximum thickness after insertion of the support body, and the load bearing entity is irreversibly deformed. The method of manufacture is illustrated in Figure 10, with the following numbering corresponding to that of Figure 10: S1 . A holder body is provided with a bore arranged to receive a support body, the bore having side walls and a base;

52. A load transferring entity is provided at the base of the bore, the load transferring entity having a maximum effective thickness;

53. The support body is inserted into the bore. The support body comprises a strike tip at a first end and a support body base at a second, opposite end. Insertion of the support body causes deformation of the load transferring entity to reduce the maximum effective thickness of the load transferring entity to a lower, second maximum effective thickness. The deformation and thickness reduction of the load transferring entity ensures that any voids between the support body and the base of the bore are filled, and the load transferring entity forms a load transferring bridge between the support body base and the base of the bore. This in turn ensures that unwanted stresses are reduced on the support body during use.

As used herein, a "super hard material" is a material having a Vickers hardness of at least about 28 GPa. Diamond and cubic boron nitride (cBN) material are examples of super hard materials. As used herein, PCD refers to polycrystalline diamond, which comprises grains of inter-grown diamond that may include other material such as cobalt dispersed between the diamond grains. PCBN material refers to a type of super hard material comprising grains of cubic boron nitride (cBN) dispersed within a matrix comprising metal or ceramic. A multi-modal size distribution of a mass of particles is understood to mean that the particles have a size distribution with more than one peak, each peak corresponding to a respective "mode".

As used herein, the term "effective thickness" is used to refer to the distance between the lowest point of the load transferring entity and the highest point of the load transferring entity with respect to a main axis through the bore, and includes thickness that is taken up by pores or interstices. The following non-exhaustive list of exemplary arrangements all have an effective thickness of 2mm:

• a solid sphere having a diameter of 2mm;

· a hollow or porous sphere having an external diameter of 2mm;

• a mass of small spheres or powder particles reaching a maximum thickness of 2mm; and

• a disc of porous metal foam with a thickness of 2 mm.

While this invention has been particularly shown and described with reference to embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as defined by the appended claims. For example, degradation tools with superhard strike tips are described. However, the same principles may be applied to degredation tools with cemented metal carbide strike tips or other types of strike tips.