Joints and connections – Member deformed in situ – Separating element between strands of member
Reexamination Certificate
1998-02-26
2002-08-13
Browne, Lynne H. (Department: 3629)
Joints and connections
Member deformed in situ
Separating element between strands of member
C439S585000, C385S087000, C174S073100
Reexamination Certificate
active
06431783
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to connecting members such as those used in optical connectors which are located between optical fiber transmission lines for switching, connecting or disconnecting the transmission lines and those directly fitted to ferrules, as well as to optical fiber connecting structures.
Presently, detachable optical connectors are used for connecting optical fiber cables and optical fiber cords intended for short-distance applications such as in-building wiring and wiring to equipment. Optical fibers are so thin and flexible that they are usually secured using ferrules. An optical connector is constructed of a plug incorporating a ferrule and an adaptor incorporating a sleeve.
FIG. 6
shows a cross section of an optical connector employing a conventional crimp ring. As shown in
FIG. 6
, a ferrule
101
in which an optical fiber
201
is inserted and fixed has a flange
102
, and a stopper
104
is fitted behind a rear end portion of the ferrule
101
in the back of the flange
102
with a compression spring
103
, which is mounted on the outer periphery of the rear end portion of the ferrule
101
, placed in between. This means that the ferrule
101
is fitted in such a way that it can move relative to the stopper
104
in its axial direction with the aid of the compression spring
103
. A coated optical fiber
202
is inserted into the compression spring
103
and the stopper
104
with a tensile strength member
204
of an optical fiber cable
203
located at the rear end of the stopper
104
, and the tensile strength member
204
is secured around the outer periphery of a rear end portion of the stopper
104
by crimping a crimp ring
105
.
The crimp ring
105
is formed of a first cylindrical portion
111
whose inside diameter fits the outer periphery of the rear end portion of the stopper
104
, a second cylindrical portion
112
which fits on the outer periphery of the optical fiber cable
203
, and a connecting part
113
interconnecting the first and second cylindrical portion
111
,
113
, as shown in FIG.
7
. The first cylindrical portion
111
is crimped to secure the tensile strength member
204
between an inside curved surface
111
a
of the first cylindrical portion
111
and the stopper
104
and, then, the second cylindrical portion
112
is crimped to firmly hold the optical fiber cable
203
in position with a compressive effect provided by an inside curved surface
112
a
of the second cylindrical portion
112
.
Since the optical fiber cable
203
is held in position with compressive and frictional forces exerted by the inside curved surface
112
a
of the second cylindrical portion
112
of the crimp ring
105
as described above, its total securing force varies as a result of changes in the outside diameter of the optical fiber cable
203
. It is therefore necessary to design the crimp ring
105
with varying inside diameters of the second cylindrical portion
112
to cater for such changes in the outside diameter of the optical fiber cable
203
. In addition, the outside diameter of the second cylindrical portion
112
should be made suitable for diameter rating of a crimping tool to be used. Thus, one problem is that the crimp ring
105
is remarkably expensive, because it is conventionally produced by cutting an aluminum material, for instance. Another problem is that the second cylindrical portion
112
becomes relatively thick as a result of a relationship between the outside diameter of the optical fiber cable
203
and the diameter rating of the crimping tool, thereby requiring a great force in crimping operation.
This invention is intended to solve the foregoing problems in the conventional art; and has as an object the provision of clamp rings which are easy to crimp and manufacture.
Also known in the prior art are structures for terminating optical fiber ends by directly fitting a ferrule to each end of an optical fiber cord. An example of such structures is shown in
FIGS. 8A-8B
. As shown in
FIGS. 8A-8B
, after inserting a coated optical fiber into a ferrule, a tensile strength member
204
of an optical fiber cable
203
is placed around the periphery
302
of a rear end portion of the ferrule
301
, a ring member
303
is fitted, and both ends of the ring member
303
is fixed in position by an adhesive
304
to thereby secure the individual components in integral form.
Such conventional structure has such a problem that a sufficient tensile strength (about 10 kgf) can not be achieved since the tensile strength member
204
is fixed by using the adhesive
304
.
Another problem of this conventional structure is that it increases the chance of fiber breakage. This is because the adhesive
304
is sucked into the tensile strength member
204
and that portion of the tensile strength member
204
where the adhesive
304
has been sucked looses flexibility.
The structure has yet another problem in that it requires a good deal of man hours for assembly work, because the adhesive
304
needs a long time to cure.
The invention aims at solving these problems. Accordingly, it is also an object of the invention to provide a structure which makes it possible to directly secure an optical fiber cable to a ferrule without using an adhesive, as well as an optical fiber terminating structure which provides a sufficient tensile strength without causing a loss of optical fiber cable flexibility, yet permitting ease of production.
SUMMARY OF THE INVENTION
In a first mode of carrying out the invention, a connecting member is provided for connecting a tensile strength member to the periphery of a rear end portion of a ferrule retaining part for holding a ferrule in which an optical fiber of an optical fiber cable incorporating a coated optical fiber and the tensile strength member surrounding the coated optical fiber is inserted and fixed with an outer covering of the optical fiber cable stripped off from its terminal portion. The connecting member comprises a first annular portion which fits on the periphery of the rear end portion of the ferrule retaining part, a second annular portion located in the back of the first annular portion, the second annular portion having a smaller diameter than the first annular portion, a step portion interconnecting the second annular portion and the first annular portion, and a clamping portion extending inward from the rear end of the second annular portion in such a way that the extreme end of the clamping portion secures the periphery of the optical fiber cable. The first annular portion, the second annular portion, the step portion and the clamping portion are formed as a single piece of metal having approximately the same wall thickness.
The connecting member of the invention preferably comprises a clamping ring and is formed by press-forming operation, for example.
In a second mode of carrying out the invention, an optical fiber connecting structure for connecting a tensile strength member to the periphery of a rear end portion of a ferrule, in which an optical fiber of an optical fiber cable incorporating a coated optical fiber and the tensile strength member surrounding the coated optical fiber is inserted and fixed with an outer covering of the optical fiber cable stripped off from its terminal portion, is characterized in that the tensile strength member is connected to the periphery of a rear end portion of the ferrule by crimping a connecting member with its one end fitted on the periphery of the rear end portion of the ferrule and the other end fitted on the periphery of the optical fiber cable.
In this structure, the connecting member preferably comprises a first annular portion which fits on the periphery of the rear end portion of the ferrule, a second annular portion located in the back of the first annular portion, the second annular portion having a smaller diameter than the first annular portion, a step portion interconnecting the second annular portion and the first annular portion, and a clamping portion extending inward from the rear end of the second
Koshigoe Tatsuo
Minami Kouji
Nakajima Masahiro
Suzuki Nobuo
Taira Junji
Adams & Wilks
Bochna David E.
Browne Lynne H.
Seiko Instruments Inc.
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