Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-12-13
2001-09-11
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S087000, C494S016000, C494S085000, C494S900000
Reexamination Certificate
active
06287404
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to bubble removal in uncured liquid adhesives and more particularly to the removal of bubbles or voids formed in the uncured liquid adhesive injected in a fiber optic termination or connector during the adhesive injection process.
2. Description of the Related Art
Most fiber optic assemblies are fabricated by bonding a connector or termination to an optical fiber with an adhesive. Bubbles and voids are introduced into the adhesive and the termination during adhesive mixing, adhesive applicator filling, and termination filler processes. Bubbles and voids in uncured adhesives can be responsible for optical fiber cracks developed during curing processes. In such an instance, the bubbles or voids expand as heat is applied. This can force out an excessive amount of adhesive at the termination end. Too much adhesive surrounding a protruding optical fiber at the termination end can cause some fibers to break during a subsequent heat curing process. It has been found that bubbles and voids in the cured adhesive are strongly correlated with subsequent fiber breakage in the termination, particular after the assembly is exposed to temperature cycling. As a result, product yield is reduced and manufacturing time and cost increased due to scrapped parts and retermination efforts.
Bubbles are generally removed from an uncured adhesive after it is mixed or after an applicator is filled with the mixed adhesive. There are two known techniques for removing bubbles or gas from uncured adhesives, namely: the centrifuge method and the vacuum chamber method. The centrifuge method involves placing the applicator or sealed mixing package containing uncured liquid adhesive in a centrifuge and subjecting it to a spin cycle. Currently there are no known techniques for removing bubbles from a connector or termination using a centrifuge after the liquid adhesive is injected into it. In the vacuum chamber method, the elements are subjected to a vacuum of a predetermined magnitude and duration to draw out the bubbles.
The use of a vacuum to remove bubbles or gas from an uncured adhesive may also be accompanied by the removal of volatile components or solvents from the adhesive. In some instances, the removal of such components may adversely affect the chemistry of the adhesive and thus change it or make it unreliable. Some of the adhesive properties that can change or degrade are: pot life, hardness, glass transition temperature and bond strength. Vacuum chambers are also cumbersome, inefficient, time consuming to use and costly.
Fiber cracking problems are also sometimes caused by the fabrication process sequence, where an optical fiber is bonded to a connector or termination using a shrinkable tube. The shrinkable tube or some other component is applied to the assembly before the liquid adhesive is heat cured. Unfortunately, the processes which use these shrinkable tubes or other components to hold the termination on the optical fiber prior to adhesive curing merely end up forcing the liquid adhesive out the other side from the end of the termination. Bubbles or voids present in the adhesive expand when heated. If not allowed to escape or be vented from the assembly, they also force the adhesive out of the end of the termination. As noted above, too much adhesive surrounding a protruding optical fiber at the termination end can also cause the fiber to break during the heat curing process. Accordingly, the removal of bubbles must be carried out prior to curing, i.e. being subjected to the application of heat.
SUMMARY
Accordingly, it is an object of the present invention to provide a method and apparatus for removing bubbles of voids from the liquid adhesive injected into a fiber optical termination or connector, where the bubbles or voids are introduced into the termination or connector during the adhesive injection process.
It is another object of the invention to provide an assembly used in connection with a centrifuge for holding a fiber optic termination or connector containing uncured adhesive.
It is a further object of the invention to remove bubbles and voids from a fiber optic termination or connector containing uncured liquid adhesive using a centrifuge without letting the liquid adhesive escape or run out during a spin cycle of the centrifuge.
The foregoing and other objects are achieved by a fixture used in connection with a centrifuge for removing a bubble or void in the adhesive present in a fiber optic termination or connector prior to the bonding of an optical fiber thereto, comprising: a transparent elongated body member having a first or upper end portion for receiving a ferrule/body portion of a fiber optic termination or connector and providing a seat thereat for the termination or connector; a piston and sealing unit sized for insertion into a second or lower end portion of said body member and having an end member for abutting a tip of the ferrule portion of a termination or connector and closing off an axial bore therein; and an elongated end cap member having a first end or lower portion sized so as to fit over the first or upper end portion of said body member for exerting pressure on the piston and sealing unit at least in the region of the termination or connector and a second or upper end portion for receiving a body portion of the termination or connector including an open ended chamber containing adhesive, said second or upper end portion of the end cap additionally having an aperture for venting any bubble or void in the adhesive from the end cap during removal thereof.
The invention is also directed to a method of removing bubbles or voids from fiber optic adhesive located in a fiber optic termination or connector prior to the bonding of an optical fiber thereto, and comprising the steps of: placing a fiber optic termination or connector including a ferrule end portion and an adhesive entry end portion containing liquid adhesive on an outer end portion of a generally tubular body member, with the ferrule end portion protruding into the tubular body member; placing a generally tubular end cap member over the entry end portion of the termination or connector and the outer end portion of the body member, causing a pressure to be extended on the body member to thereby seal the ferrule end portion of the termination or connector against the body member; inserting a generally tubular piston and sealing unit in a lower end portion of the tubular body member until contact is made with the ferrule end portion of the termination or connector for temporarily sealing an axial bore in the end portion of the ferrule which ultimately receives an optical fiber and forming a composite fixture from these elements; placing the fixture in a centrifuge; operating the centrifuge for a predetermined time period, so as to vent any bubble from the liquid adhesive through the end cap member; and removing the fixture therein from the centrifuge now having a bubble free termination or connector.
Further scope of the applicability of the present invention will become apparent from the detailed description provided hereinafter. However, it should be understood, that the detailed description and specific examples disclosing the preferred embodiments of the invention are given by way of illustration only since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from a reading of this detailed description.
REFERENCES:
patent: 4087043 (1978-05-01), Anderson et al.
patent: 4235367 (1980-11-01), Davidson
patent: 4290550 (1981-09-01), Chulay et al.
patent: 4451250 (1984-05-01), Romanauskas
patent: 4552278 (1985-11-01), Romanauskas
patent: 5236409 (1993-08-01), Romanauskas
patent: 5399144 (1995-03-01), Romanauskas et al.
Aftergut Jeff H.
Dixon Keith L.
The United States of America as represented by the Administrator
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