Measuring and testing – Specimen stress or strain – or testing by stress or strain... – Specimen clamp – holder – or support
Reexamination Certificate
1999-11-10
2001-10-16
Noori, Max (Department: 2855)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
Specimen clamp, holder, or support
Reexamination Certificate
active
06301972
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to load applying devices for applying a low friction load to one or more captured members and, more particularly, to a normal or radial load applying apparatus for testing specimens or components, such as optoelectronic devices and fiber optic connectors.
BACKGROUND OF THE INVENTION
Most mechanical force applying devices that apply a load to a captured member do not provide a purely normal force. Frictional effects influence the force vector, such that the load that is applied usually travels with the surface of the member. Therefore, the load deviates from an ideal normal condition.
The present invention seeks to provide an apparatus for applying a pure normal or radial load. This is accomplished by applying a frictionless, normal or radial force through a fluid (liquid or air) bearing interface disposed at one end of a biasing cylinder and preferably spherically or cylindrically shaped. The bearing interface resembles a ball and socket arrangement in the preferred embodiment. A table fixture comprises four of the biased cylinders. Each cylinder is disposed ninety degrees apart, within a 360 degree radius. The fixture provides a force that simulates a pull force, often applied in a field test to a specimen (e.g., one or more fiber optic cables, a photo detector, or other component or components to be tested).
The specimen is clamped inside the fixture. A load is applied by extending each cylinder, in turn, in serial fashion, while the other cylinders remain retracted about the 360 degree radius of the fixture. No torsional force can be applied by this fixture, owing to the frictionless condition provided by the bearings. The bearings also allow the specimen to deflect in a vertical plane (parallel to the longitudinal axis of rotation).
DISCUSSION OF RELATIVE ART
In U.S. Pat. No. 5,379,647, issued to Sherwin on Jan. 10, 1995 for HOLE ELONGATION TESTING SYSTEM, a device is shown in which a shim is used to reduce friction between two opposing plates.
In U.S. Pat. No. 5,763,772, issued to Bywalez et al on Jun. 9, 1998 for PROCESS FOR DETERMINING THE INITIAL STRESS OF ANTIFRICTION BEARINGS WHICH ARE PRELOADED AGAINST EACH OTHER OR INSTALLED WITH AN INITIAL STRESS, the testing of the deformation of preloaded, anti-friction bearings is illustrated.
In U.S. Pat. No. 5,633,467, issued on May 27, 1997 to Paulson for APPARATUS AND METHOD FOR NON-DESTRUCTIVE TESTING OF STRUCTURES, a low friction support is shown for a probe for testing load bearing of a specimen. The apparatus comprises circumferentially spaced races or bushings.
In U.S. Pat. No. 5,033,308, issued on Jul. 23, 1991 to Le Compagnon et al for METHOD AND APPARATUS FOR TESTING CHARACTERISTICS OF EXTRUDED ELASTOMERIC WEATHERSTRIPS, a frictionless, vertical slide plate is depicted that translates force to a load.
In U.S. Pat. No. 4,790,805, issued to Slobodkin on Dec. 13, 1988 for CONSTRAINT PRESSURE IN LINE-WEB CRUSH-SCORING, a frictionless plunger is shown that applies force to a knife blade.
In U.S. Pat. No. 4,852,605, issued on Aug. 1, 1989 to Gouhier for VALVE OPERATING WITHOUT FRICTION, a frictionless fluid valve is illustrated that uses a membrane deformable by fluid pressure to unseat a valve ball.
In “Pneumatic Pull Tester” by D. G. Pittwood, IBM Technical Disclosure Bulletin, Vol. 13, No. 3 August 1970, pp. 717-718, a pneumatic pull tester is shown with a frictionless piston that can be preloaded.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided an apparatus for applying a normal or radial force to a captured member, with a minimum amount of friction. In one embodiment thereof, the apparatus comprises a fixed fluid bearing and a preloading, axially movable fluid bearing spaced apart from the fixed fluid bearing. A spherical/cylindrical captured member is positioned between the fixed fluid bearing and the movable fluid bearing. A biasing member, disposed adjacent the movable fluid bearing member, biases the movable fluid bearing member against the captured member. The fixed and movable bearings each have oppositely adjacent end surfaces that define a recess for capturing the tested member therebetween. The recess surfaces conform to the shape of the captured member, wherein a normal or radial force is applied thereto with a minimum of frictional force. Each of the recess surfaces can comprise a spherical or cylindrical shape or any other regular or irregular shape.
In a second embodiment of the invention, four movably biased fluid bearings, as described above, can be radially positioned at right angles with respect to each other. The four fluid bearings are radially disposed upon a fixture table, defining 360 degrees of arc. The specimen is placed inside a collar disposed in the center of the fixture table. The collar supports the conforming surface of each of the fluid bearings and captures the specimen between the radially disposed surfaces. A normal or radial force is applied to the specimen by a fluid bearing of the fixture table at a given time. The force is applied with a minimum of frictional force, while the other fluid bearings remain movably inactive. Each fluid bearing can apply a normal or radial force to the specimen in a given sequence.
It is an object of this invention to provide a frictionless fluid bearing apparatus for applying a normal or radial force to a machine member.
It is another object of the invention to provide an improved fixture for applying a series of frictionless normal or radial forces to a specimen to be tested.
REFERENCES:
patent: 2525345 (1950-10-01), Getchell
patent: 3335603 (1967-08-01), Gram
patent: 3975950 (1976-08-01), Erdei
patent: 4537080 (1985-08-01), Christiansen
patent: 4790805 (1988-12-01), Slobodkin
patent: 4852605 (1989-08-01), Gouhier
patent: 5033308 (1991-07-01), Le Compagnon et al.
patent: 5379647 (1995-01-01), Sherwin
patent: 5581040 (1996-12-01), Lin
patent: 5633467 (1997-05-01), Paulson
patent: 5763772 (1998-06-01), Bywalez et al.
patent: 5948994 (1999-09-01), Jen et al.
Hall Richard R.
Tiberia Candido C.
Fraley Lawrence R.
International Business Machines - Corporation
Noori Max
Salzman & Levy
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