Abrading – Combined tool
Reexamination Certificate
1999-07-12
2001-02-27
Eley, Timothy V. (Department: 3723)
Abrading
Combined tool
C451S527000, C451S547000
Reexamination Certificate
active
06193593
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to abrasive tools, and more particularly to grinding wheels and methods adapted to remove material from the surface of bimetallic engine blocks.
2. Background Information
As automakers push to reduce the weight of automobiles, the engine block remains one of the heaviest single components. Manufacturing the engine blocks in a bimetallic manner, such as by fabricating the blocks from aluminum and placing cast iron sleeves into the cylinder bores can substantially reduce the weight of the engine block relative to conventional cast iron engine blocks. An important aspect of the engine block manufacturing process, however, is to provide the block with a flat or planarized upper surface or fire deck for mating with the cylinder head. Machining of conventional unimetallic engine blocks (i.e. cast iron) is generally accomplished by common machining processes such as fly cutting or high speed milling utilizing hardened ceramic inserts, such as silicon nitride, tungsten carbide or polycrystalline diamond (PCD), on the milling head. This process using PCD inserts has also now been adopted for use in machining bimetallic blocks. Although satisfactory when utilized for unimetallic blocks, this approach tends to produce undesirable results when used with blocks fabricated from two materials, one of which is soft, i.e., aluminum, and the other of which is brittle, i.e., cast iron. When utilized to mill bimetallic parts, the relatively expensive PCD inserts tend to wear rapidly. Moreover, to insure a smooth and flat surface, multiple passes with the milling inserts are typically utilized, although score lines may still be seen. Waviness also sometimes occurs in the surface of the fire deck. These problems may be associated with, or exacerbated by, the differences in optimal milling tool configuration for soft versus brittle materials. For example, most high-speed milling cutters made for softer materials, such as aluminum, operate most efficiently at substantially greater rake angles than those used for harder materials such as cast iron. Clearance angles, or the angle between the land and a tangent to the cutter from the tip of the tooth, also depend on the various work materials. Cast iron typically requires values of 4 to 7 degrees, whereas soft materials such as magnesium, aluminum, and brass are cut efficiently with clearance angles of 10 to 12 degrees. (See, e.g., B. H. Amstead et al.
Manufacturing Processes,
1977, pp. 555-556).
One solution to this problem has been to countersink the cast iron sleeves to the depth to which the aluminum is to be removed. Once countersunk, the aluminum block may then be milled in a conventional manner to bring the aluminum to the predetermined height and flatness. While this approach has been used successfully to planarize fire decks of bimetallic engine blocks, the step of countersinking the cast iron sleeves disadvantageously adds an extra machining step, an extra tool change and an extra tool set up which tends to increase the time and expense of engine block fabrication. It is thus desirable to devise a tool and/or process able to planarize the fire deck of a bimetallic engine block in a single pass or process step.
Another technique commonly utilized for metal removal involves use of conventional grinding wheels, typically face grinding wheel or surface grinding wheel comprising alumina grain in resin bond. While this technique tends to be effective on cast iron workpieces, aluminum is relatively soft, gummy and abrasive, and thus difficult to grind.
Thus, a need exists for an improved tool and/or method for machining fire decks of bimetallic engine blocks in a single process step.
A significant reason for the difficulty associated with milling bimetallic work pieces is that during the milling operation, each blade or insert of the milling head is maintained in relatively interrupted contact with the bimetallic block, in which the insert repeatedly takes relatively large cuts across the boundary between the soft aluminum and the brittle cast iron as the milling head rotates. The relatively large number of cutting points provided by each abrasive grain of a grinding wheel provides a more continuous contact with the workpiece and take smaller cuts or bites as they cross the boundary between materials.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention a grinding cup wheel adapted for grinding material from a fire deck of an engine block has an axis of rotation and a first annular grinding element removably disposed in concentric orientation with the wheel. The first annular grinding element includes a first abrasive component chosen from the group consisting of metal brazed single layer abrasive components and abrasive components comprising grain bonded in a porous matrix having about 55 to 80 volume percent interconnected porosity.
According to a second aspect of the present invention, a grinding cup wheel adapted for grinding a fire deck of a bimetallic engine block has a first annular grinding element disposed concentrically therewith. The grinding cup wheel also has a second annular grinding element disposed concentrically with and radially inward of the first annular grinding element. The second annular grinding element is disposed at a predetermined height in the axial direction closer to the bimetallic surface than the first annular grinding element. The second annular grinding element removes material from the bimetallic surface after the first annular grinding element.
According to a further aspect of the present invention, the grinding wheel is adapted for surface grinding a bimetallic workpiece and includes a first annular grinding element disposed concentrically with an axis of rotation of the wheel. A second annular grinding element is disposed concentrically with and radially inward of the first annular grinding element, each of the first and second annular grinding elements having grinding surfaces adapted to engage the workpiece, the grinding surface of the second annular grinding element being disposed at a predetermined height in the axial direction closer to the engine block than that of the first annular grinding element. The first annular grinding element and the second annular grinding element each include an abrasive component chosen from the group consisting of metal brazed single layer abrasive components and abrasive components bonded in porous matrix having about 55 to 80 volume percent interconnected porosity. The grinding cup wheel is adapted for orientation of the axis of rotation at a predetermined angle alpha relative the fire deck and for being translated towards the engine block along a tool path parallel to the fire deck. The first annular grinding element is adapted to engage and abrasively grind material from the block and said second annular grinding element is adapted to remove material from the fire deck after said first annular grinding ring, so that the second annular grinding ring is adapted to apply a surface finish to the fire deck.
The grinding apparatus also may be adapted for use in finishing other similar bimetallic components of vehicles, machines and the like.
The above and other features and advantages of this invention will be more readily apparent from a reading of the following detailed description of various aspects of the invention taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4018576 (1977-04-01), Lowder et al.
patent: 4896638 (1990-01-01), Shepley
patent: 4934351 (1990-06-01), Shepley
patent: 4993891 (1991-02-01), Kaminiski et al.
patent: 5009676 (1991-04-01), Rue et al.
patent: 5035723 (1991-07-01), Kalinowski et al.
patent: 5129919 (1992-07-01), Kalinowski et al.
patent: 5203886 (1993-04-01), Sheldon et al.
patent: 5221294 (1993-06-01), Carman et al.
patent: 5244477 (1993-09-01), Rue et al.
patent: 5486131 (1996-01-01), Cesna et al.
patent: 5842912 (1998-12-01), Holzapfel et al.
patent: 5938506 (1999-08-01), Fruitman et al.
E. Lenz, “Negative Rake Cutting T
Buckley Richard F.
Duarte David M.
Hagan John
Miller Bradley J.
Wu Mianxue
Eley Timothy V.
Sampson & Associates P.C.
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