BACKGROUND OF THE INVENTION

This invention relates to a polishing tool component.

Polishing pads are used extensively in industry for fine finishing or polishing various workpieces, which are typically stone or ceramic in nature. Such polishing pads consist of a carrier having a layer of abrasive particles suitably secured to a surface thereof. The abrasive particles may be secured to the surface of the carrier by means of metal or resin binders.

French Patent No. 2532875 discloses a grinding wheel comprising a plurality of abrasive pads mounted on a support. The abrasive pads comprise a mass of discrete abrasive particles uniformly dispersed in a bonding matrix. The pads are in the form of strips.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a polishing tool component, comprising a carrier and a plurality of spaced abrasive elements located in the carrier, each abrasive element presenting an abrasive working surface having a perimeter which is circular, polygonal or like non-elongate shape and comprising a mass of abrasive particles uniformly dispersed in a bonding matrix, the abrasive working surfaces of the elements together defining a working surface for the component.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of an embodiment of a polishing pad of the invention;

Figure 2 is a section along the line 2-2 of Figure 1;

Figure 3 is a perspective view of a carrier of a second embodiment of the invention; and

Figure 4 is a section along the line 4-4 of Figure 3.

DESCRIPTION OF EMBODIMENTS

The polishing tool component of the invention may be one suitable for various polishing tools such as revolving tools, revolving pendulum action tools and planetary polishing tools. The shape of the component may be any known in the art such as rectangular, as is generally used with revolving and revolving pendulum action tools, or disc-shaped, as is generally used with planetary polishing tools.

The carrier will generally present a surface in which the abrasive elements are located. The working surfaces of the elements may be located in this surface or they may project beyond this surface. When the working surfaces project beyond the carrier surface in which they are located, they may include at least one peak. This peak may provide a sharp point, e.g. it may be cone-shaped. Such peaks, when provided, will generally each have the same height from the carrier surface in which the elements are located.

The perimeter of the working surfaces may be circular, square or rectangular. The working surface may cover the entire area within the perimeter or may cover a portion of the area only, e.g. be ring-shaped.

The abrasive working surfaces of the elements together define an abrasive working or polishing surface for the component. To achieve this it is preferable that the abrasive elements are uniformly distributed across the carrier. The elements may, for example, be arranged in rows such that the working surfaces of the elements in one row are staggered relative to the working surfaces of the elements in an adjacent row. Alternatively, the elements may be arranged in rows such that the working surfaces of the elements in one row are in register with the working surfaces of the elements in an adjacent row.

The abrasive particles will preferably be ultra-hard abrasive particles such as diamond or cubic boron nitride. These particles will typically have a particle size of up to 500 microns and be present in an amount of up to 30 percent by volume.

The bonding matrix may be metal, ceramic or resin. When it is resin it is preferably a non-porous thermoplastic polymer, which may contain fibrous or particulate filling materials. Examples of suitable thermoplastic polymers are:

Poly etheretherketone (PEEK) and polyetherketone (PEK) such as that marketed by ICI under the trade name NICTREX ^® .

Polyaryletherketone such as that marketed by BASF under the trade name ULTRAPEK ^® .

Poly (amide-imide) such as that marketed by Amoco under the trade name TORLOΝ ^® .

Polyphenyl sulphide (PPS) such as that marketed by Phillips under the trade name RYTOΝ ^® .

Liquid Crystal Polymer (LCP) such as that marketed by Hoechst under the trade name NECTRA ^® .

Examples of suitable metal bonding matrices are bronze and cobalt- bronze.

The carrier may be rigid or flexible. It may be made of a metal such as steel or a polymer which may be thermosetting or thermoplastic. Examples of suitable thermosetting polymers are phenolic and polyurethane. Examples of suitable thermoplastic polymers are acrylonitrile/butadiene/styrene and polypropylene.

Two embodiments of the invention will now be described with reference to the accompanying drawings. Referring first to Figures 1 and 2, there is shown a polishing pad comprising a carrier 10 having a major curved

surface 12 and an opposite major flat surface 14. The two major surfaces 12, 14 are joined by sides 16. The carrier is joined to a base 18 along its lower major surface 14. The base 18 and carrier 10 are held joined to each other by means of pins 20 protruding upwardly from the surface 22 of base 18 and which engage complemental recesses 24 formed in the surface 14. The base 18 is shaped for mounting on a suitable polishing head. The base 18 and the carrier 10 may constitute an integral unit for mounting on to a suitable polishing head.

The polishing pad has a plurality of abrasive elements 26 located in it. The elements 26 are discrete and spaced from one another. The elements 26 extend from the curved surface 12 into the carrier. Each element comprises a ring 28 consisting of a mass of abrasive particles uniformly dispersed in a bonding matrix. Each ring 28 has a truncated cone shape tapering from a base 30 to a polishing surface 32. The polishing surface 32 of each element is located in the curved surface 12 of the carrier. The polishing surfaces 32 together form an abrasive polishing surface for the pad. It will be noted that the elements are located in the carrier in a series of rows wherein the elements of one row are staggered relative to the elements in an adjacent row. This arrangement ensures that the polishing surfaces 32 together define a polishing surface for the pad which effectively covers the curved surface 12 of the carrier.

It will be noted that the abrasive rings 28 are circular in cross-section. They can have other shapes in cross-section such as square, rectangular, triangular, pyramidal, oval or elliptical.

The cone-shape of the abrasive elements has the advantage that the tendency for the abrasive elements to be pulled out of the carrier in use is minimised.

In one preferred form of the invention, the abrasive rings comprise a mass of diamond particles dispersed in a bonding matrix. The carrier 12 is manufactured by placing the abrasive rings in a desired pattern on a surface of a mould and thereafter introducing a resin into the mould. The resin will flow around the elements and into the hollow in each ring. On setting of the resin, the component is produced. The resin may be injected into the mould.

In an alternative embodiment (not illustrated) instead of the pin/recess means of joining the carrier to the base, a countersunk screw can be provided in one of the components which engages a threaded hole in the other component.

A second embodiment of the invention is illustrated by Figures 3 and 4. Referring to these figures, a carrier 40 for a polishing pad has a major curved surface 42 and an opposite major flat surface 44. The two major surfaces 42, 44 are joined by sides 46. The carrier 40 may be joined to a base (not shown) in a similar manner to that of the embodiment of Figures 1 and 2.

The polishing pad 40 has a plurality of abrasive elements 48 located in it. The elements 48 are located in recesses 50 formed in the curved surface 42 of carrier 40. Each element 48 consists of a mass of abrasive particles uniformly dispersed in a bonding matrix. The elements are

right-circular cylindrical in shape and have a cone-shaped working surface 52 which projects beyond the curved surface 42 of the carrier. The apex 54 of each cone provides a point. The height of the apices 54 from the curved surface 42 is the same. It will be noted that in this embodiment the elements 48 are located in the carrier in a series of rows wherein the elements 48 of one row are in register with the elements 48 in an adjacent row.

In this embodiment the cone-shaped working surfaces 52 together define a polishing surface for the pad. In use, it is the peaks or apices 54 which first contact the workpiece. The points will wear quickly, thus allowing effective contact between the workpiece and the remainder of the cone- shaped abrasive working surfaces. Any mis-alignment in the polishing pad is thus quickly accommodated facilitating early bedding in of the abrasive elements. Efficient and rapid polishing occurs.

It has been found the cone-shaped working surfaces 52 which have an included angle in the apices of greater than 90° achieve excellent polishing ificiencies.