Liquid purification or separation – Filter – Movable medium
Reexamination Certificate
1999-09-22
2003-06-03
Popovics, Robert (Department: 1723)
Liquid purification or separation
Filter
Movable medium
C210S396000, C210S400000, C210S402000, C210S433100, C210S526000, C210S167150
Reexamination Certificate
active
06571959
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to systems for removing particulate matter suspended in a fluid, and more particularly to systems for removing fine particles from fluid utilized in conjunction with the machining of metal or non-metals.
BACKGROUND
There are many applications in which it is necessary for environmental reasons, or for the reclamation and recycling of resources, to separate particulate matter suspended in a liquid from the liquid itself. One example of such an application is the need to remove particulate matter from water used by an industrial floor cleaning machine, or a street sweeping machine, prior to disposing of the water in an environmentally safe manner. Another example of such an application is the removal of waste material from coolant used with cut-off saws or grinding machines. Yet another example of such an application is the necessity to separate chips and fine particles of waste material from coolants used with machine tools to facilitate the machining of metal or non-metallic materials.
The process of machining a workpiece into a finished part on a machine tool requires that a cutter of some sort be forced into the workpiece to carve away waste material portions of the workpiece and achieve the desired shape of the finished part. The action of the cutter against the workpiece generates both a large volume of chips or fine particles of waste material, and a substantial amount of heat in the cutter and workpiece. These chips or particles of waste material, and the heat generated, must be transported away from the cutter and workpiece during the machining process, in order to achieve dimensional accuracy of the finished part, and in order to allow the cutter to operate at the high speeds necessary to effectively and efficiently shape the finished part without overheating.
In order to remove the chips or particles, and the heat generated in the machining process, machine tools generally incorporate some sort of cooling and flushing system for directing a flow of a liquid coolant or oil at the workpiece and cutter during the machining process, to absorb the heat generated at the interface of the cutter and the workpiece, and to transport both the heat and chips or particles away from the cutter and workpiece. After flowing over the cutter and workpiece, the coolant fluid, with the chips or particles entrained, is collected and drained from the machine tool.
Modern machining processes are carried out at very high speeds, requiring a large flow of coolant fluid for effective removal of the chips and heat. Depending upon the machining process involved, a continuous flow of coolant is required during the machining process at flow rates in the range of 10 to 400 gallons a minute. This flow of coolant is typically supplied to the machine tool by a coolant fluid circulating and cleaning system which includes mechanisms for separating the chips and particles from the flow of coolant so that the coolant may be continuously re-circulated.
For larger sized chips or particles of waste material, the primary mechanism for separating the waste material from the cooling fluid involves utilizing the force of gravity. In some coolant cleaning systems utilizing scraper type conveyors, the coolant fluid drained from the machine tool is directed into a dirty fluid reservoir of the coolant cleaning system where the chips and particles are allowed to settle in the bottom of the reservoir. A conveyor mechanism then scrapes across the bottom of the reservoir to pick up the settled chips and particles and transports them to a chip collection bin or container. The coolant above the bottom of the tank is then drawn off by a pump and re-circulated to the machine tool. In other coolant cleaning systems, the coolant with entrained chips and particles is directed onto a screen, or a hinge belt conveyor system, as the fluid enters the dirty fluid reservoir, so that the fluid can run through the screen or hinge belt into the bottom of the reservoir, with the larger sized chips and particles being screened out and separated from the coolant fluid by the screen or hinge belt. The cleaned coolant below the screen or belt is then re-circulated to the machine tool. U.S. Pat. No. 5,858,218 to Setlock et al; U.S. Pat. No. 5,849,183 to Ota et al; U.S. Pat. No. 5,603,846 to Uchiyama et al; U.S. Pat. No. 5,167,839 to Widmer II et al; and U.S. Pat. No. 4,992,167 to Uchiyama; are illustrative of these approaches utilizing the force of gravity to separate the chips and particulate matter from the fluid. U.S. Pat. No. 4,895,647 is also illustrative of these approaches, and includes a permanent magnet disposed on the bottom wall of the reservoir to supplement the force of gravity with magnetic attraction of ferrous chips and particles.
Although these coolant cleaning systems utilizing the force of gravity work reasonably well for larger sized chips and particles, there are several inherent problems involved in the practical application of such systems which have led the designers of such systems to also include additional filtration devices in their systems.
For coolant systems relying on the force of gravity to cause the chips and particles of waste material to settle out on the bottom of the dirty fluid reservoir, one inherent problem is that the flow rates of coolant demanded by modern machining processes do not allow the fluid to remain stagnant in the dirty fluid reservoir long enough for smaller chips and fine particles of waste material to settle out in the bottom of the tank. While it would seem at first glance that theoretically all particles of waste material would eventually settle to the bottom of the tank, given enough time, practical considerations such as limitations on floor space prevent system designers from providing dirty fluid reservoirs large enough for this to happen. For example, a coolant system required to provide 400 gallons per minute of coolant to a machine tool would need to have a dirty fluid reservoir capable of holding 2000 gallons of coolant in order to allow the coolant to remain in the reservoir for a period of five minutes before being re-circulated to the machine tool. In practice, a reservoir this large simply takes up too much floor space for most applications, and as a compromise, the dirty fluid reservoir capacity of many coolant cleaning systems is designed to hold only enough coolant for the coolant to remain in the reservoir a minute, or a minute and one half at the most, before being re-circulated. This means that the coolant in the reservoir is never really stagnant, but is actually flowing through the reservoir at a rate high enough to keep some finer particles suspended in the fluid. Swirling and churning of the fluid in the tank, caused by draw down of the circulation pump and the action of conveyors, hinge belts, and the like moving through the reservoir, increase the percentage of finer particles that remain suspended in the coolant.
Even if the coolant in the dirty fluid reservoir could remain relatively stagnant, other factors such as viscosity and surface tension of the coolant would cause a certain percentage of fine particles to remain suspended in the fluid rather than settling out. This is particularly true for finer particle of light metals such as aluminum or magnesium. For the tight tolerances required in some machining operations, even this small percentage of suspended fine particles must be removed by some sort of filtration beyond that provided by the force of gravity.
Coolant cleaning systems that utilize a hinge belt or inlet screen to catch and convey away the chips and particles of waste material as the fluid enters the reservoir, rather than allowing them to settle to the bottom for removal by a conveyor, also must deal with the problem of removing the finer particles suspended in the fluid. All of the factors described above in relation to coolant cleaning systems relying on settlement of waste material in the bottom of the dirty fluid reservoir that cause finer particles to remain suspended in the fluid, such as s
Dambek David M.
Moore Robin C.
Crowe Lawrence E.
Popovics Robert
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