FIELD OF THE INVENTION The present invention broadly relates to a method of producing or repairing a cutting blade. The present invention relates particularly, though not exclusively, to a method of producing or repairing a cutting blade for a "diamond" saw of the type being used for cutting rock or hard earth.

BACKGROUND OF THE INVENTION Various devices for cutting, grinding and fracturing hard earth formations and rock during excavations (e.g. trimming or planing floor faces, rock side faces, trenching and general building footing detailing) are known in the prior art. Such devices can be mounted on the free end of an articulated arm of a tracked or conventionally wheeled excavator or the like. For cutting such hard earth or rock formations, usually large cutting blades are used which typically have a diameter of more than 1 metre. Such cutting blades may comprise a steel disc having an edge from which a large number of cutting tips project radially. In case of a diamond saw each ti'p is composed of a very hard steel which has a large number of industrial diamond particles embedded in its matrix. Each of these "diamond tips" are soldered onto the disc using silver solder. Welding of the diamond tips onto the disc is not possible as the heat associated with the welding process would be detrimental to the hardness of the diamond tips. Unfortunately, the strength of the bondings between the diamond tips and the disc is not satisfactory. For example, a small movement of the cutting blade in an axial direction of the blade which pushes side portions of the diamond tips against the rock often is sufficient to break off the diamond tips. Repair of the cutting blades usually is very expensive as (i) the cutting process is interrupted typically for a significant time and (ii) a specialist is required, typically on site, to repair the cutting blade. Consequently, there is a need for an alternative technical solution.

SUMMARY OF THE INVENTION

The present invention provides in a first aspect a method of producing a cutting blade, the cutting blade having a blade body and a plurality of cutting tips projecting from the blade body, the method comprising the steps of : attaching the cutting tips to intermediate members and attaching the intermediate members with the cutting tips to the blade body in a manner such that the cutting tips project from the blade body.

The present invention provides in a second aspect a method of repairing a cutting blade, the cutting blade having a blade body and a plurality of cutting tips projecting from the blade body, the method comprising the steps of : attaching the cutting tips to intermediate members and attaching the intermediate member with cutting tips to the blade body in a manner such that the cutting tips project from the blade body. In the first and second aspect of the present invention the blade body typically is a disc and the cutting tips typically project from an edge portion of the disc. The method according to the first and second aspect of the present invention has significant advantages. The cutting tips, such as diamond tips, can be attached to the intermediate members when the intermediate members are not attached to the blade body. For example, each cutting tip may be bonded to a respective intermediate member using solder such as silver solder. Typically, a pressure is applied to effect diffusion of the solder into bonding surfaces of each intermediate member and each cutting tip to provide a strong bonding between respective intermediate members and cutting tips. As the intermediate members and the cutting tips may be bonded together when the intermediate members are not connected to the blade body, it is possible to apply a relatively large pressure. For example, this may be conducted in a workshop off site using a mechanical press. The pressure that can be applied in this case is significantly larger than the pressure that may be applied for bonding each cutting tip directly to the blade body such as commonly done when repairing cutting blades on site. Consequently, the bonding strengths between each cutting tip and the respective intermediate member that may be achieved using the methods of the first and second aspects of the present invention can be significantly larger than the bonding strengths achievable with prior art methods. In the methods according to the first and second aspects of the present invention the intermediate members with cutting tips typically are directly attached to the blade body. The step of attaching the intermediate members with the cutting tips to the blade body according to the first and second aspects of the present invention typically comprises welding the intermediate members to the blade body. For example, when a cutting blade needs to be repaired, the intermediate members with cutting tips may be welded onto the blade body on site. This welding process typically is relatively simple and may not require / specialised staff. The attaching of the cutting tips to the respective intermediate members may be conducted off site. Consequently, it may not be necessary to have specialised staff on site to repair the cutting blade. If a cutting blade needs to be repaired because some of the diamond tips are broken off, the respective intermediate member may be cut off and new or recycled intermediate member with cutting tip may be welded onto the blade body on-site.

The present invention provides in a third aspect a cutting blade produced by the method according to the first aspect of the present invention.

The present invention provides in a fourth aspect a cutting blade repaired by the method according to the second aspect of the present invention.

The present invention provides in a fifth aspect a cutting blade for cutting rock or hard earth formations, the cutting blade comprising: a disc arranged to be driven by a drive, a plurality of intermediate members welded to the disc and projecting from an edge of the disc in a radial manner and a plurality of cutting tips, each cutting tip being bonded to a respective intermediate member.

The cutting tips may take any suitable form, but typically are diamonds tips. Each diamond tip typically is bonded to a respective intermediate member.

The present invention provides in a sixth aspect a cutting tip assembly for a cutting blade for cutting rock or hard earth formations, the cutting blade assembly comprising: an intermediate member and a cutting tip being attached to the intermediate member, wherein the intermediate member is arranged for welding to a blade body in a manner such that the cutting tip projects from the blade body.

The intermediate member typically is arranged so that the cutting tip experiences less heat, when the intermediate member with cutting tip is welded onto the blade body, than for direct welding of the cutting tip onto the blade. The cutting tip typically is a diamonds tip.

The invention will be more fully understood from the following description of specific embodiments of the invention. The description is provided with reference to the accompanying drawings.

Brief Description of the Drawings Figure 1 shows a diagram illustrating a method of producing or repairing a cutting blade according to .a specific embodiment of the present invention, and Figure 2 shows a cutting blade according to a specific embodiment of the present invention.

Detailed Description of Specific Embodiments Referring to Figures 1 and 2 methods of producing and repairing a cutting blade according to specific embodiments of the present invention are now described. Figure 1 shows (a) a diamond tip 10, (b) a intermediate member 12, (c) the diamond tip 10 and the intermediate member 12 bonded to each other and (d) the diamond tip 10 and the intermediate member 12 bonded to each other and the intermediate members 12 welded onto a blade body such as disc 14 of a cutting blade 16. The diamond tips 10 are composed of a very hard steel having industrial diamonds embedded in its matrix. The intermediate members 12 and the disc 14 are composed of a steel conventionally used for toolmaking. Figure 2 shows a cutting blade 18 according to a specific embodiment of the present invention. In the embodiment shown in Figure 2 the cutting blade 17 is mounted to a drive 19 and comprises diamond tips 10 bonded to intermediate members 12 which are welded on disc 18. In this embodiment the disc 18 has gullets 21 between intermediate members 12 but it is to be appreciated that disc 18 may not necessarily comprise gullets 21. For producing or repairing a cutting blade, such as cutting blade 17 or cutting blade 16, diamond tips 10 are bonded to respective intermediate members 12. For this bonding process respective bonding surfaces are initially cleaned with a wire brush. Soldering flux is then applied to the bonding surfaces. The diamond tips 10 and the intermediate members 12 are then carefully heated. Silver solder is then applied to the respective bonding surfaces separately. Although it is possible to heat the intermediate member 12 many times, it is preferred to heat each diamond tip 10 only once in order to ensure that the hardness of the material is not compromised. The silver solder coated and heated bonding surfaces of the respective diamond tips 10 and intermediate members 12 are then joined and a pressure, typically of the order of more than lOOpsi, is applied to press the intermediate members 12 and the respective diamonds tips 10 together. This relatively large pressure effects the diffusion of solder into the matrix of the porous steel material of the diamond tips 10 and the intermediate member 12 so that the silver solder may have an anchoring function. The intermediate members 12 with diamond tips 10 are then welded on to a disc such as disc 14 or 18 to form the cutting blade. For repairing a cutting blade such as a cutting blade 16 or 18 the intermediate members 12 associated with defective of broken diamond tips 10 are cut off the disc 14 or 17 respectively. A new or recycled intermediate member with cutting tip bonded to it may then be welded onto the disc 14 or 18 so as to repair the cutting blade. Spares of cutting tips bonded to intermediate members may be present on site and used to repair the blade when required without the need for specialised staff. Although the invention has been described with reference to particular examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. For example, it is to be appreciated that the cutting tips may not necessarily be diamond tips. The cutting tips may be composed of any suitable materials other than hard steel with embedded diamond particles. Further, the intermediate members may have any suitable shape. For example, the intermediate members may be of a substantially L-shaped cross-section and the diamond tips may be received by the intermediate members so that the intermediate members are bonded to two sides of the diamond tips. The intermediate members may also be of a substantially U-shaped cross-section arranged to receive the diamond tips at three side portions. The diamond tips may not necessarily have the shape of a rectangular prism but may be of any suitable shape such as a pyramidal shape. Further, bonding between the diamond tips and the intermediate members may not necessarily be effected by silver soldering. Any other suitable solder may be used for effecting the bond. Further, other bonding methods which not necessarily involve soldering may be used. Examples of alternative bonding methods include fusion bonding or chemical bonding. In addition, it is to be appreciated that each diamond tip with intermediate member may not be directly bond to the disc, but me be indirectly bonded to the disc for example via an additional intermediate member. Further, it is to be appreciated that the cutting tips may be attached to the intermediate members and/or the intermediate members may be attached to the disc by interference fits.