Abrading – Machine – Rotary tool
Reexamination Certificate
1998-10-09
2001-07-24
Eley, Timothy V. (Department: 3723)
Abrading
Machine
Rotary tool
C451S044000, C451S120000, C451S158000, C451S178000
Reexamination Certificate
active
06264538
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a machine for working the edge of a solid material. More specifically, the invention provides an improved machine for grinding or polishing the edge of glass or other brittle material.
DESCRIPTION OF THE RELEVANT ART
Finishing the edge of a piece of glass or similarly brittle materials presents several difficulties. For example, the hardness of the material requires advanced cutting or grinding media, such as wheels impregnated with diamonds, to perform the grinding or polishing. At the same time, the slightest vibration of the workpiece or of a grinding wheel may cause scratches or other marks in the workpiece, potentially rendering the product unsuitable for commercial use. Moreover, due to the brittle nature of glass or similar material, excessive vibrations or uncontrolled motions of either the workpiece or a grinding wheel will cause the workpiece to chip or break. A further difficulty arises because of the heat generated during the grinding or polishing of the hard material. Without cooling, the heat generated by the grinding process, in combination with the brittle nature and thermal expansion properties of the workpiece, would cause the workpiece to break. To meet this difficulty, the workpiece is typically flooded with coolant while it is being ground or polished.
The difficulties in finishing the edges of glass and other brittle materials have given rise to a variety of different approaches and machines. In some machines, the glass has been held fixed while the grinding wheels and other portions of the machine have moved. In currently preferred machines, however, the greater mass (i.e., the machine) remains stationary while the workpiece is conveyed past the grinding wheels. In some of these machines, the workpiece moves in a horizontal plane. In the more commonly used commercial edging machines, the workpiece moves in an essentially vertical plane. This essentially vertical alignment of the workpiece uses the force of gravity to hold the workpiece against a grinding reference plane, eliminating the potential need to support a large workpiece in a horizontal plane as its edges are ground or polished, and reduces the floor area required by the machine.
Because of the many challenges presented, the design of current edge finishing machines has focused on the task to be accomplished, that is, producing a commercially acceptable edge finish at reasonable production speeds. To accomplish the precise mechanical motions required to finish an edge of the workpiece, the typical machine includes scores if not hundreds of moving parts, including gears, chains, pins and bearings. Failure of any of these parts degrades the quality of the finish and decreases the speed of the machine. In many cases, failure of a single part brings production to a complete halt. In addition, many of the parts in a typical edge-finishing machine are in continual contact with the coolant required in the grinding process, which in turn causes rust or premature failure of the parts. These problems are exacerbated by the fine particles produced in the grinding process—commonly referred to as “swarf”—which quickly coat machine surfaces and work their way into the moving parts, again causing premature failure.
To appreciate the contributions of the machine of the present invention, the basic sections of a typical edge-finishing machine are described in further detail, together with the difficulties and challenges they present. These basic sections can be identified as the main conveyor section; the edge finishing section, typically comprising grinding and polishing wheels and spindles; the infeed and outfeed sections; and the coolant section.
The main conveyor section is often considered the heart of an edge-finishing machine. It must support the entire weight of the workpiece. The main conveyor section must also hold the workpiece with near-perfect alignment with the grinding or polishing wheels while at the same time conveying the workpiece past those wheels at a uniform speed. Typically, the main conveyor section includes a front conveyor belt and a back conveyor belt, with some means of moving the front and back belts toward or away from each other in order to “clamp” the workpiece with proper gripping pressure on the glass. As described above, even slight vibration or improper movement of the workpiece while it is being ground or polished will likely result in a manufacturing defect or breakage of the workpiece.
To meet these mechanical requirements, edge-finishing machines have typically employed several methods. For example, in some machines, both the front and the back conveyor belts are composed of numerous elements, generally metallic, with each element usually separately covered with an elastomeric material such as rubber to provide a pad or gripping surface. Each element in the front or back conveyor belt is linked to a similar adjoining element by means of a pin or a similar connecting device, forming a continuous chain or belt. The construction of the pads and elements of the front conveyor may differ markedly from the back conveyor, or the front and back belts may be identically constructed. The conveyor pad elements may ride against a fixed surface, with metal-to-metal sliding contact, or bearings may be used in one form or another to achieve rolling rather than sliding friction. Virtually all of the designs for the main conveyor section of edge finishing machines involve a large number of individual parts and elements, such as pins, bearings, rollers and the like, which are subject to wear and breakage and consequent problems in production efficiency or product quality.
The edge finishing section of a typical machine includes grinding or polishing wheels or spindles. These typically perform their function by spinning in contact with the workpiece while it is conveyed past them by the main conveyor. Once again many methods have been utilized in the past. In some cases each wheel is mounted directly onto the end of an electric motor. Other commercial edging machines have utilized separate spindles driven by electric motors by means of one or more rubber belts. Each of these designs, however, involves relatively complex systems to drive the polishing wheels or spindles, and therefore presents a substantial risk of failure of one of the components, especially in the hostile environment of cooling fluid and swarf.
The infeed section of the typical edge-finishing machine moves the workpiece into the main conveyor section at the proper speed and alignment. This is frequently achieved by supporting the workpiece on a belt or chain on which supporting pads are mounted. The infeed belt or padded chain is typically driven by a series of shafts and gear boxes, chains and sprockets or similar driving schemes, often powered by the same source that powers the main conveyor section. This direct mechanical coupling insures that the infeed speed of the glass sheets matches the speed of the main conveyor section. The outfeed section, which pulls the finished workpiece away from the main conveyor section, generally mirrors the infeed system, with a similar complex mechanical drive system. A main difficulty of such infeed and outfeed systems is that they contain numerous mechanical parts, such as chains, sprockets, gears and the like, any one of which can fail, particularly in the hostile environment of coolant and glass swarf. Moreover, in typical edge-finishing machines, these drive mechanisms are housed in enclosures that make them difficult to see without specifically opening, the enclosure, which may entail stopping the machine. As a consequence, inspections to avoid failures are difficult. In addition, the parts of the driving systems are often tedious to replace, prolonging machine down-time and leading to higher maintenance costs.
The coolant section of the typical edge-finishing machine includes pumps, piping, nozzles, tanks, collection systems and other components needed to direct coolant onto the grinding wheels and the workpiece. In general, c
Berry Jr. Willie
Covington & Burling
Eley Timothy V.
Industrial Tool Works, Inc.
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