Measuring and testing – By abrasion – milling – rubbing – or scuffing
Reexamination Certificate
2000-09-25
2003-04-15
Larkin, Daniel S. (Department: 2856)
Measuring and testing
By abrasion, milling, rubbing, or scuffing
C073S010000
Reexamination Certificate
active
06546782
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an apparatus and method for testing lubricating properties of fluids and wear resistance of materials
BACKGROUND OF THE INVENTION
Fuel system components employed in some modern ground and aviation equipment rely on the fuel passing through them for lubrication of sliding contacts. Some of these components experience extreme temperature and pressure conditions in operating engines. One such component is the fuel injector used in diesel engines.
One way to examine the efficacy of fuel compositions as lubricants and the resistance of materials to the wear mechanisms experienced in fuel injectors would be to construct full scale working units and run them in test engines, examining them afterwards for wear. This approach is both costly and time consuming. It is of great utility in the transportation industry to predict the efficacy of fuel compositions in providing lubrication and the wear resistance of various materials of construction without having to construct and operate full scale equipment under conditions duplicating the operating conditions to which the equipment would be subject when in use.
To reduce time and cost, the properties of lubricating compositions are often tested using a testing jig. Typical equipment used for this purpose uses a mechanism to impart motion between two samples of material with the lubricant of interest interposed between the samples. The lubricating ability of the lubricant under study is determined either by studying the rate of wear of standard sample materials with different lubricants under the same conditions of load and motion, or to measure the amount of torque transmitted between a driving mechanism holding one sample and a driven mechanism holding the other sample when a given lubricant is interposed between the driving and driven samples. Both schemes have been employed to model components in operating equipment. The scheme utilizing the study of wear rates in sample materials has the added benefit that along with studying the lubricating ability of different lubricant compositions, the same equipment can be used to study the effect on wear of different combinations of materials or different surface finishes when they are examined with standard lubricating compositions.
Both schemes have been employed in bench top scale equipment and attempts have been made to correlate the results thus obtained with the results obtained from employing full scale equipment in an operating engine.
The wear rate in a component subjected to sliding contact is dependant upon many factors. Some of these factors are: materials of construction; surface finish; contact load; the relative rate of motion of the surfaces; and the nature of the lubricant and its film thickness. The environment in which a component is employed can also contribute to performance of a lubricant. Factors such as temperature and fluids present in addition to the lubricating composition employed must also be considered when constructing equipment that approximates conditions in operating engines. Numerous schemes for attempting to accomplish this end have appeared in the prior art.
U.S. Pat. No. 3,166,927 to Sonntag et. al. discloses an apparatus for measuring resistance to relative motion of two annular test surfaces having angular movement relative to one another. The apparatus disclosed is capable of imparting either rotary motion between two surfaces or oscillating motion (via an arm and eccentric) between the test surfaces. One of the two rods is a driving rod. One end of the driving rod is fastened to a motor, the other end is fitted with a mechanism for holding a test sample and a mechanism for contacting one surface of that test sample under controlled load against one surface of a second test sample. The end of the driving rod bearing the sample holder, the sample holder itself, and any sample contained in the sample holder resides in a lubricant sample well capable of containing a quantity of the lubricant composition under test.
The other rod of the pair is a driven rod. One end of the driven rod also resides in the sample well with the driving rod. The end of the driven rod within the lubricant sample well is also fitted with a mechanism by which a sample can be mounted on the end of the driven rod. The driven rod is supported so that when the driving rod sample is contacted against the sample fastened to the driven rod it is not displaced by the force of the contacting load. The end of the driven rod that is not within the sample well is fastened to a dynamometer and torque tube arrangement for measuring torque transmitted from the driving sample to the driven sample.
A scheme is disclosed wherein the sample lubricant and the testing surfaces are contained in a controlled temperature and atmosphere chamber for varying the testing conditions with respect to temperature and pressure. This arrangement is believed by the inventors to counteract the inaccuracies inherent in friction testing machines due to test sample axis misalignment and non-uniform wear of test sample surfaces during a testing procedure.
U.S. Pat. Nos. 3,302,447 and 4,228,674 to Mertwoy discloses an apparatus directed solely at testing the lubrication properties of hydraulic fluids under the conditions of temperature and pressure such fluids typically encounter in use U.S. Pat. No. 3,302,447 discloses the basic device, a set of chucks holding balls made of suitable material in rotatable contact, with provision for heating the hydraulic fluid under test, and applying pressure to the working faces of the balls used in the tests, subjecting the hydraulic fluid to loading conditions. U.S. Pat. No. 4,228,674 improves upon the former design, inverting the testing jig to counteract buoyancy of the testing samples in the hydraulic fluid under test, and providing for the ability to employ a fluid in the chuck driving mechanism having a different viscosity than the fluid under test, eliminating testing inaccuracies arising from fluids of different viscosity effecting the ability of the drive mechanism to rotate the chuck containing the test balls. A further improvement disclosed in the '674 patent is the use of a spring and tensioning mechanism to preload the test balls, substituting for lead weights employed for this purpose in the device disclosed in the '447 patent.
U.S. Pat. No. 3,913,337 to Lindeman discloses an apparatus for testing the lubricating properties of various fluids and the wear properties of various materials. In the disclosed apparatus, one of two motors, chosen for high speed operation or low speed operation, rotate a disk of test material between two stationary samples of test material. The stationary samples are in the form of a rod or block. One face of each stationary sample is held in contact with the faces of the disk by a caliper mechanism. Said caliper mechanism permits operator adjustment of the force applied to the faces of the disk of test material by the stationary samples. The test disk is arranged so that while rotating it passes through a bath containing the lubricating fluid under test. The entire mechanism except for the motors is contained in a sealed box, and provisions are made for heating and pressurizing the fluid under test. The disk is analyzed for wear at the end of an operator selected period during which the disk is rotated at an operator selected rotational rate while the stationary calipers impinge the stationary samples against the disk under an operator selected load. The apparatus provides for transducers which can measure the drag exerted against the rotational effort of the motor whereby the lubricating properties of the test fluid can be evaluated.
U.S. Pat. No. 4,253,326 to Munnich, et. al discloses an apparatus which may be employed to measure film thickness and moment of friction simultaneously. Additionally, it may be used to evaluate the wear properties of materials. The apparatus consists of two sample holders, the driving sample holder is mounted on a rotating shaft, the driven sample holder is mo
De La Cruz Jose
Lacey Paul
Garber C D
Larkin Daniel S.
Paula D. Morris & Associates P.C.
Southwest Research Institute
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