Patent Application
20220388114
The present abrasive composition relates to tools for use in grinding and cutting.
Abrasive particles used in grinding and cutting typically include abrasive articles bonded or coated to substrates. Coated abrasive particles are generally layered articles having a backing with an adhesive to fix abrasive grains to the backing. The most common example of which is sandpaper. Bonded abrasive articles, on the other hand, are typically tools (or attachable to tools), and comprise rigid, typically monolithic, three-dimensional, abrasive composites. Abrasive composites are found in the form of wheels, discs, segments, mounted points, hones and other tool shapes. They can be mounted onto an apparatus to use with a machine adapted to rotate or reciprocate the tool carrying the abrasive composite.
Bonded abrasive tools usually have two phases including the solid abrasive grains and the solid bonding material. Certain bonded abrasive articles can have an additional “phase” in the form of “porosity,” in reference to spaces between the particles. Bonded abrasive tools can be manufactured in a variety of grades and structures that are defined according to practice in the art by the relative hardness and density of the abrasive composite (the grade) and by the volume percentage of abrasive grain, bond, and porosity within a volume of the composite (the structure).
Some bonded abrasive tools may be particularly useful in grinding and shaping certain types of work piece materials, including, for example, metals, ceramics and crystalline materials, that are used in the electronics and optics industries. In other instances, certain bonded abrasive tools may be used for shaping super-abrasive materials for use in industrial applications. Grinding and shaping certain work pieces with metal-bonded abrasive articles generally involves a significant amount of time and labor to maintain the bonded abrasive article. That is, generally, metal-bonded abrasive articles require regular truing and dressing operations to maintain the grinding capabilities of the abrasive article.
The industry continues to demand improved methods and articles capable of effective and accurate grinding, shaping and cutting.
The present abrasive composition comprises a substrate with a multiplicity of perforations. The work surface of the substrate may be generally shaped for the task for which it is intended. The work surface, including its edges and the perforations, may be curved, for example. Abrasive particles may be braised to the work surface including to its curved edges including the curved edges at the perforations. The abrasive particles may be sprinkled over the surface, including on the edges of the work surface and the perforations. Sprinkling of the abrasive particles may be sufficient to cover work surface areas.
The perforations through the work surface provide a view of the work surface for the user that helps with work quality and also reduces noise. The perforations also provide places work surface debris tends to collect and thereby provides more convenient debris removal. The shape of the substrate itself may include particular surface features intended for specific abrasion tasks, such as curved surfaces, flat surfaces, surfaces with different grades of abrasives, and rounded edges with smaller radii of curvature for use as a cutting tool.
These and other features of the present abrasive composition will be apparent to those skilled in the art from a careful reading of this detailed description, accompanied by the following drawings.
In the figures,
The invention relates to an abrasive composite for use in grinding and smoothing surfaces and for cutting into and through surfaces. The abrasive composite comprises a substrate a layer of abrasive particles [MMA1] brazed to a substrate. The substrate may be formed for particular tasks to have a suitable configuration, such as a wheel, a disk, and a block shape. Abrasive particles are braised to the surface of the substrate and may be diamond grit or may be other abrasive materials selected for the particular work piece to be abraded or cut. The substrate may be made of a metal such as copper, or made of a metal alloy such as steel, tungsten carbide alloyed with cobalt, or alloys of nickel, chromium, and iron, and may be stainless steel, or, alternatively, of a composition such as a ceramic.
Referring now to
Alternatively, the tool may be a flat, hand-held, rectangular, abrading tool 18. As shown in part in
Abrasive disk 10 has a substrate 26 that includes a multiplicity of perforations 30. Each perforation 30 is a through-hole. Perforations 30 may be circular or oval or have other shapes. Perforations 30 may have curved edges 34 on the working side of the abrasive composition rather than sharp edges. Perforations 30 may be smaller, such as 1.6 mm in diameter, or larger, such as 12.7 mm in diameter. Perforations 30, so formed, may all have the same shape or comprise perforations of different shapes, such as a combination of ovals and circles. Perforations 30 may be made in a pattern, as seen to some extent in
Perforations 30 in substrate 26 have several advantages. First, the abraded material (abrasion debris) will tend to settle on curved edges 34 of perforations 30 and thereby facilitate the removal of the abraded material. Second, perforations 30 enable the worker performing the abrasion or cutting operations on a work piece 38 can see work piece 38 through perforations 30 when abrasive disk 10 is spinning. Third, perforations 30 tend to reduce noise as less sound is reflected back to the worker and more noise is transmitted through perforations 30.
Abrasives particles 42 are braised to substrate 26. An inorganic binder [MMA2] may be added to a braze 26 to provide a temporary bond between abrasive particles 42 and substrate 26. The inorganic binder assists in keeping a suitable initial distribution of abrasive particles 42. When substrate 26 and braise 46 are heated in an oxygen-free atmosphere in a furnace, braze 46 will melt in flows and begin to form a strong bond with abrasive particles 42 as the braise cools.
Distributed abrasive particles 42 over curved edges 34 at perforations 30 of substrate 26 of abrasive disk 10 abrading tool 18 enables work piece 38 to be shaped more smoothly. Abrasive particles 42 at the curved edges 34 enables grinding the shape transitions of work piece 38 more smoothly.
Braise 46 binds abrasive particles 42 to substrate 26. Braise 46 is preferably titanium. Titanium may be added in the form of titanium hydride (to avoid self-combustion). Titanium alloys with diamond to form titanium carbide, which results in a strong bond.
Braze 26 may alternatively comprise, in combination, copper with tin or copper with silver. Both combinations bond to steel and to other metal substrates. Substrate 26 is first formed with perforations 30 before braising. Molten braise 46 is applied to substrate 26 and abrasive particles 42 are sprinkled over braise 46. “Sprinkling” means to drop abrasive particles 42 onto braise 46 to obtain a more or less complete distribution of abrasive particles 42 on substrate 26 including at perforations 30, thereby allowing abrasive particles 42 to float in the molten braise 46 and to drift before braise 46 binds to the abrasive particles 42 and solidifies with substrate 26.
It is not necessary that abrasive particles 42 touch or be separated from each other. Abrasive particles 42 will tend to float on the molten braise and to move until the braise cools whereupon it binds abrasive particles 42 to it. Abrasive particles 42, in their movement on the molten braise 46, will tend to cluster, but given the multiplicity of perforations 30 formed in substrate 26, the clustering area is limited to the area between perforations 30 and, on cooling, braise 46 on substrate 26 binds abrasive particles 42 to become effective for grinding.
Abrasive particles 42 when applied in the foregoing manner will extend above the surface of braise 46 as abrasives particles 42 float on braise 46. When braise 46 has solidified, abrasive particles 42 remain elevated above the solidified braise 46 where they are more effective for grinding. Single layers of abrasive particles 42, rather than multiple layers, promote efficient grinding action because they extend above braise 46 where they can cut more deeply into work piece 38 (
Other materials can be substituted for diamonds as abrasive particles 42, particularly when using titanium as braise 46, because all standard abrasive materials bond to a titanium braise 46. [MMA3]
Abrasive particles 42 can be provided in an amount such that the finally-formed abrasive disk 10 or a rectangular abrasive tool 18 abrasive article contains a pre-selected volume of abrasive grains. For example, the mixture can include a majority content (e.g., greater than 50 vol %) of abrasive grains/braise.
The grinding surface, as illustrated in
Another feature of the present abrasive composition is that the composite is very stiff compared to prior art products made with organic substrates. Stiffness may range upward from 1 to 30×106 psi, which is a distinct advantage because a stiffer composite is less likely to deflect during use and more firmly establishes the amount of abrasive particles being used than a less stiff substrate.
It will also be appreciated that abrasive grains of the same composition can have various mechanical properties, including for example, friability. A mixture of abrasive grain sizes and kinds can be included, having varying mechanical properties or grades. For example, the mixture can include abrasive grains of a single composition, such that the mixture includes only diamond or only cubic boron nitride, yet different grain sizes or a variety of grain sizes, and yet a different braise. For example, diamond or cubic boron nitride abrasives can include a mixture of different grades of diamond or cubic boron nitride, such that different mechanical properties exist among the abrasive grains.
It will be appreciated that variations and substitutions may be made in making an abrasive composition without departing from the spirit and scope of the present disclosure, which is defined by the appended claims.
