Internal-combustion engines – Lubricators – Crankcase – pressure control
Reexamination Certificate
2000-02-28
2002-02-26
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Lubricators
Crankcase, pressure control
C123S1960CP
Reexamination Certificate
active
06349693
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to the art of methods and apparatuses for filtering particles from a fluid, and more specifically to methods and apparatuses for oil filter enhancements and for filtering magnetically attractable particles and other suspended particles in an engine lubricant using magnets or other filter media.
BACKGROUND OF THE INVENTION
Much of the fine abrasive particles produced inside an internal combustion engine at the site of friction is carried immediately away by the flow of lubricating fluid. A major part of an engine wear is due to the destructive nature of small ferrous abrasive particles being recycled continuously to the friction bearing surfaces by the engine's lubrication system. This is due to the limited ability of the normally provided oil filter medium to arrest such abrasive particles. By design, the filter has to allow for a relatively unrestricted normal oil flow, this can only happen with relatively large pore sizes. Most filter media are designed to stop particles of about 20 microns cross-sectional dimension. A lot of magnetic particles in the range of sub-micronic to 20 microns cross-sectional dimension are produced and generally not arrested by the media, or even dangerously bypassed during cold engine starts and/or partially clogged and saturated filter media conditions. Therefore, if these particles are not removed, they continue to produce ever more metal shavings in an increasing and uncontrolled avalanche effect that may lead, according to many experts, to substantial engine wear. To further complicate this scenario, current engines and like machinery are designed with tighter tolerances, higher running temperatures, continuously increasing performance demands, extended service intervals, longer powertrain warranties, and more stringent smog specifications. This wear scenario eventually results in a degradation of close tolerances at critical locations between rotating parts, causing a loss of performance, more frequent maintenance repairs, and eventually catastrophic engine failure. It is therefore of great interest that a convenient, non-intrusive method and apparatus be introduced to address at least one of the major causes of engine performance decay, premature engine wear, and premature disposal of the lubricating oil.
Attempts to enhance the filtration capabilities of filters have been tried by means of creating a magnetic field in order to attract magnetic particles to the internal wall of the common disposable spin on filter. This is generally attempted by placing magnets in different arrangements around the outside surface of a spin on filter. However these previous known structures provide limited, incomplete, weak, statistically insignificant, expensive, hard to remove, bulky, and generally their effectiveness is limited to very small areas of the canister filter inside wall. Even with the approach of U.S. Pat. No. 5,647,993 issued to Karp, suggesting a helical arrangement to capture the magnetic field around the outside wall of the filter, the net effect on the internal wall of the filter becomes negligible to effectively arrest magnetic particles. When fast lubricant flow, turbulence, magnetic particle cluster separation, low statistical contact of same volume in proximity to weakly magnetized areas are considered, this approach sounds effective but the results have proven generally unsatisfactory.
The art of placing magnets on the external wall of a filter is inherently flawed for two mutually exclusive reasons: weak magnets can only exert weak attractive fields on the internal surface of the spin-on filter, and are therefore largely ineffective to attract and retain magnetic particles. This is due to fluid turbulence, weak magnetic influence, fast flow, localized eddy currents, magnetic leakage, and limited enhanced area. On the other hand, as magnet size, number, and strength increases, other problems arise such as more expensive, bulky, and hard to remove.
Other problems involve the choice of materials to withstand the high temperatures associated with the working lubricant, which may reach up to 300 degrees Farenheit in rare occasions. For example U.S. Pat. No. 5,441,647, issued to Wascher, discusses a material having a higher melting point than the operating fluid, or the similar approach of a suction cup with magnet as shown in U.S. Pat. No. 5,571,411, issued to Butler et al.
Other problems of magnets attached to the canister filter include the difficulty of removal of the magnets, the limited clearance in the radial direction from the canister once the filter is installed, the variability in the canister filter diameter, the discipline required every time to remove and place on the new filter canister. In some cases, as suggested in U.S. Pat. No. 5,282,963, issued to Hull et al., a tool is needed to remove the apparatus. In addition, the use of magnetic material clamps tend to weaken the already weak effect through the canister wall of the magnets it intends to hold. In some vibration environments, the devices may detach themselves, causing immediate possible damage due to sudden cluster separation inside the filter upon loss of retaining magnetic field, resulting in the sudden and concentrated release of all collected particle clusters.
Yet another problem, demonstrating the lack of commercial success of the current art, is the cost and discipline in removing and replacing, which may not justify in terms of quantifiable evidence, the economic benefit of using them. Therefore, any cost and inconvenience factor must be minimized or eliminated to overcome this problem.
In some prior art, such as U.S. Pat. No. 4,450,075 issued to Krow, the magnets are in direct contact with the lubricating fluid. This is an improvement over the magnets attached to the walls, because all the surface area and magnetic strength of the magnets are exposed directly to the fluid. However, placing the magnets in the highly turbulent and fast flow areas of the oil canister center, or other similar locations, pose an additional risk of clogging the flow. In some situations, due to the reduction of flow area, this create areas of higher than normal turbulence and velocity, according to flow and mass continuity theory equations. These conditions result in an even higher risk, not only to counteract the attraction and retention of the particles, but an easier dislodging of already built particulate clusters, if any.
In some situations, a complicated arrangement such as an external bypass oil filter and adapter arrangement may be used to remove magnetic and non-magnetic particulate. These obviously complement the filtering function of the normal full flow filter, but at the expense of high cost and space sacrifice in an already cramped engine bay. In addition, as much as 10% of oil flow may be diverted away from the intended regions for oil protection, and in some high temperature operating cases, this may mean heat stress through oil cooling reduction flow to bearing surfaces. Such a system is shown in U.S. Pat. No. 4,406,784 issued to Cochran, which requires extensive external hardware and installation cost.
Many patents teach different and incomplete ways about the removal of magnetic particles from a fast flowing lubricating fluid, and in some cases from the lubricant at rest, such as in the case of magnetic bolts shown in U.S. Pat. No. 5,465,078 issued to Jones. Approaches to removing magnetic particles from the flow of internal combustion engine lubricant tend to be of the following descriptors: external magnets using the magnetic external wall of the filter, immersed in the path of turbulent and fast oil flow, different means of installing and removing from canister, complicated and expensive to install apparatus, helical configurations for magnetic fields, external by-pass filtration, elaborate and expensive filters, etc. From those descriptors the following US Patents are examples of this prior art: U.S. Pat. Nos. 4,026,805, Fowler; 4,051,036, Conrad et al.; 4,052,312, King; 4,053,409, Kuhfuss; 4,218,320, Liaw;
Jason Benton
McMahon Marguerite
LandOfFree
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