Note: Descriptions are shown in the official language in which they were submitted.
'7~
This invention relates to the field of apparatus and
me-thods for breaking optical fibers in such manner as to achieve
substantially perfect mirror-finish ends at the break.
In the article by Gloge, Smith, Bisbee and Chinnock
(The Bell System Technical Journal, November, 1973, pages 1579 et
se~.), it is stated (page 1580) that "The range within which per-
fectly flat and perpendicular end faces were obtained was found to
be so wide that the eventual construction of a simple hand tool
for this purpose should present no problem." Nevertheless, the
l~ hand tools subsequently created by Bell Laboratories and other
major companies have not been commercially practical or successful.
That is to say/ they have not been such that telephone repairmen,
for example, can almost always make a perfect break~- even while
in a manhole or up a telephone pole-- in a matter of-seconds if
at all r Furthermore, and very importantly, the prior art suggests
no practical correlation between the breaker and the optical con-
nectors.
Reference will now be made to some of the important
prior-art problems which the present apparatus and method have
eliminated. The following is not necessarily all inclusive, nor
are the problems necessarily listed in order of importance.
Referring first to scoring, it was conventional in the
prior art to lower a scoring blade delicately onto the fiber
(either prior to or after tensioning of the fiber). Then, as a
second operation, the blade was moved along its length suficiently
to effect scoring or nicking of the fiber. On page 1585 of the
cited article, scorer pressures ranging from 1.5 -to 7.5 grams are
suggested. It is further there stated that the smallest scores
were produced when a sharp diamond scorer was lowered onto the
fiber after application of tension. A strong preference for dia-
mond or sapphire scorers is typical of most prior art. The prior
art also employs, typically, such things as counterweights and/or
dashpots to achieve the desired delicate contact between scorer
--2--
'7~
and fiber.
Applicant has discovered that-- surprisingly-- maximum
scorer pressure on the glass may be made to be no factor whatever.
Thus, just so long as there is enough pressure -to effect scoring,
the pressure may be as high as convenient and need not be measured
at all. This discovery not only eliminates the need for counter-
weights, dashpots, measurements, etc., it makes the apparatus and
method absolutely independent of orientation (upright, inverted
or sideways) in that gravity is of no importance. Additionally,
~3 ~e~
10 ~ applicant does not ~ r~e~ (or even desire) exotic blade material
such as diamond or sapphire, having discovered that a certain type
of carbide is vastly superior.
Referring next to correlation between the breaker for
optical fibers and the connectors therefor, insofar as applicant
is aware the prior art suggests no practical means of achieving
this ma~or result. Thus, in almost all prior art the breaking
and subsequent connecting of the fibers are totally independent
operations. In only one prior-art patent is any correlation sug-
gested, and the described system is not commercially practical
since (for example) it requires adhesive mounting of fibers in a
foldable support. In accordance with the present invention, the
breaking-connecting system which not only reduces overall connec-
tion time, there being (for example) no need for adhesive, but
increases the overall ~uality of the connection.
With reference to creation of the tension in the fiber,
this has conventionally been achieved by (a) predetermined weights,
or (b) special "tensator" springs the force of which does not
change with distance, or (c) special frictional grips which are
intended to slip at a predetermined tension value, or (d) unknown
forces which require that, preferably, scoring be effected before
tensioning occurs. In the preferred forms of the present appara-
tus and method, the fiber is clamped in a nonslip manner, tension-
ing is caused by an economical spring means which is unaffected
--3--
L17~
by excessive grip pressure, and scoring is then performed. There
thu~ result major improvements in the practicality of the tool.
As but one additional example of the deficiencies of the
prior art, there is no practical means for insuring -that all types
and thicknesses of the synthetic resin coating will be removed at
regions adjacent the break-- this being important for achievement
of optimum connections. In accordance with one embodiment of the
present apparatus and method, such coating is burned off in the
critical areas with no requirement for additional manipulation of
the fiber, and with only a small reduction in ~he speed of the
operation.
In accordance with the scoring aspect-of the present
invention, the edge of a scoring blade is caused to have initial
contact with a bent, tensioned optical fiber in a downward direc-
tion and also a scoring direction, as distinguished from being
initially merely set down on such fiber. There is caused to be
sufficient force to score the fiber, but the upper limit of the
force need not be measured or known. The blade is one having an
edge sufficiently "rough" to score the fiber instantaneously, but
sufficiently smooth not to effect improper breaking or damaging
of the fiber ends. The blade is so shaped as not to interfere with
upward flexing of the fiber ends as soon as breaking occurs. In
one embodiment, the fiber is mounted in a groove and has a minimum
tendency to roll.
Stated more definitely, the edge of the scoring blade is
caused to move through an arcuate path into engagement with the
bent, tensioned fiber, the directioll of curvature of such path
being opposite to that of the Eiber surface portion engaged by the
scorer. The scorer is cemented tungsten carbide having a particle
size typically in the range of one to two microns. The hardness
of the carbide is about 92 on the Rockwell A scale.
With reference to the aspect of the invention whereby
there is a predetermined correlation to an optical connector for
--4--
connecting two opposed fiber ends, one element of the optical
connector is first quickly clamped to the fiber to be broken, at
any position. Then, such connector element is rapldly and remov-
ably mounted on the breaker at a predetermined, known position,
one characteristic of such position being that the fiber extends
beneath the path of the scorer blade. Thereafter, the fiber end
is clamped, bent, and scored so as to break at a location precisely
known, the break location being correlated in a predetermined
manner to the dimensions of the op-tical connector. Perfect break-
ing having been achieved at a predetermined location relative tothe one optical-connector element, it is only necessary to dis-
connect such one element from the breaker, repeat the operation
with a second connector element and fiber, and then mate the two
elements (and thus the fibers) with each other. -
In the fiber tensioning aspect of the present methodand apparatus, the squeezing of the handles is caused to load a
spring means to a ~orce within -the range known to create a perfect
break. Further squeezing action then releases a tensioning table
for shifting in response to such force, thus creating the requisite
tension. Very importantly, the spring rneans and release means are
so constructed and related as to nullify the effects of excessive
squeezing forces.
When the synthetic resin coating on the fiber is such
that stripping-back from the broken end does not occur automati-
cally when the break is effected, the tool is caused to be one
which has parallel, adjacent heater wires into which the fiber
firrnly nests and seats upon being tensioned. Switch rneans, res-
ponsive to handle pOSitiOII, create an electric current heating the
wires and burning off the coating just before scoring occurs.
Thus, -the ends upon being broken are not enclosed in a coating,
and will mate more perfectly in the optical connector.
These and other features and advantages of the present
invention may be understood more fully and clearly upon considera-
--5--
tion of the following specification and drawings in which:
Figure 1 is a side elevational view of an apparatus
constructed in accordance with the present inventi.on;
Figure 2 is an end elevational view thereof, as shown
frorn the right .in Figure 1, a portion being broken away and sec-
tioned in order to show a fiber-tensioning spriny;
Figure 3 is an enlarged view o~ the upper portion of
Figure 1, but showing the fiber in clamped condition;
Figure 4 is a transverse sectional view on line ~-4 of
Figure 3;
Figure 5 is a view corresponding to Figure 3 but showing
the blade in a position achieved after completion of a break;
Figure 6 is a transverse sectional view generalIy on
line 6-6 of Figure 5, and further showing in section the connector
element secured to the breaker;
Figure 7 is a greatly enlarged, partially exploded
isometric view illustrating various portions of the breaker mech-
anism, the straight dashed lines indicating parts which are either
shown in duplicate (for clarity) or are in alignment with each
other;
Figure 8 is a yreatly enlarged schematic view showing
the lower edge of the scoring blade at the instant it first con-
tacts an optical fiber;
Figure 9 is a corresponding schematic view illustratiny
the blade in a position achieved af~er cornp].etion of the break.
In both Figures 8 and 9, the diameter of the fiber .is, for clarity,
shown greatly exagyerated in cornparision to the length of the
scoring edge;
Fiyure 10 is a schematic representation of an electron-
microscope enlaryement of the edge of the scoriny blade;
Fi.gure 11 is a yreatly enlaryed verti.cal sectional view
illustrating the action of the fiber ends just after the instant
of breaking;
--6--
Figure 12 is an elevational view corresponding generally
to the upper portion of Figure 1 but illustrating the ~iber-heating
means of a second embodiment of the breaker;
Figure 13 is an enlarged isometric view illustrating
the fiber support table of such second embodiment, the table in-
corporating heating wires defining a groove in which the fiber
nests;
Figure 1~ is a further enlarged vertical sectional view
illustrating the relationship between the heating wires and fiber
1~ in the vicinity of the point of scoring;
Figure 15 is an enlarged fragmentary longitudinal sec-
tional view of the preferred optical connector;
Figures 16, 17, 18 and 19 are transverse sectional views
taken along lines 16-16, 17-17, 18-18 and 19-19, respectively, of
Figure 15; and
Figure 20 is a longitudinal sectional view showing one
of the plugs separated from the receptacle of the optical connector.
The present breaker is shown in its upright position and
is, for reasons of simplicity, described and claimed as being in
that position. It is emphasized, however, that no claim is to be
regarded as limited by this convention.
The word "cylindrical" is used, in the present specifi-
cation and claims, in its conventional sense, namely to mean a
right circular cylinder. The optical fibers presently used are
cylindrical, as shown at 133 in Figures 8, 9 and 11.
In use, the breaker is provided with a cover means which
shields most o~ the illustrated mechanism, such cover means being
nshown .
~ vertical base plate 10 has ~i~edly secured thereto, as
by screws, a forward handle 11 which may be re~erred to as the
"stationary" handle in that it is anchored to the base plate. A
rear handle 12 is pivotally mounted at its upper end to base plate
10, by means of a shoulder screw 13 and spacer sleeve 14 (Figure 7).
--7--
The handles are n~rmally held in spaced-apart position by a helical
compression spring 16 the ends of which are mounted over studs 17
and 18 on the handles.
A plug holder arm 20 i5 adjustably mounted relative to
base plate 10, being a plate-like crank which is normally generally
parallel to the base plate as shown in Figures 4 and 6. At its
lower end, plug holder arm 20 has beariny ears 21 which are
apertured to receive a large-diameter and strong shoulder screw
22. The screw 22 is horizontal and parallel to the base plate,
and is threaded into an enlarged upper end portion of the stationary
handle llo Thus, the plug holder arm can be pivotally adjusted,
through a small angle, about the axis of the shoulder screw for
purposes stated below.
As best shown in Figure 6, a plug receiver 23 is fixedly
mounted (as by a suitable adhesive) in plug holder arm 20, and
has an externally threaded fastener portion 24. The plug receiver
23 (including its portion 24) is shaped to mate in precise manner
with one component (element or portion) 13' of an optical
connector assembl~ which is adapted to achieve a precise optical
connection between two optical fibers which have been broken by
the present apparatus. In a greatly preferred example of such
a connector assembly, the component (element or portion) 13' is
a plug assembly, as described hereinafter relative to Figure 20
and other figures.
The connector portion 13' includes an internally threaded
aoupling ring 85' adapted to be threaded around portion 24 until a
tapered front shell or plug ~8l seats snuyly, in complementary
8~
manner, in plug receiver 23 as shown in Figure 6. When thus seated,
the forward (right) end of plug or shell 48' is coplanar with the
forward surface of the plug receiver 23. Connector portion 13'
further includes a clamping and aligning assembly (aescribed
below? mounted fixedly around a protective sheath 132 which encloses
the actual optical fiber 133. Such assembly effectively clamps
the optical fiber~ thus the fiber is (when plug 48' is mounted as
stated) clamped to the breaking tool.
The plug receiver 23 (Figure 6~ in the present tool is
provided with a longitudinal keyway to receive a radial key 71'
on shell 48'.
To permit the fiber 133, after the protective sheath 132
has been stripped therefrom, to-be inserted laterally into the
plug receiver 23 and associated plug holder arm 20, registered
radial slots are provided on these elements as shown at 32 in
Figures 1, 2 and 5.
A fiber support table 34 is fixedly secured to the for-
ward face of plug holder arm 20, and has an upper surface 35 which
is cylindrical about the axis of shoulder screw 22. Furthermore,
surface 35 is spaced such a distance from screw 22 that there will
be a correct degree of bend of the fiber 133 when it is tensioned
as described hereinafter. One predetermined radius of surface 35,
which i5 presently employed by applicant to achieve a correct bend,
is ].5 inches from the axis of screw 22 to the cylindrical surface
35.
Table 34 may be made, for example, of a phenolic syn--
thetic resin. Its surface 35 is registered, at the edge adjacent
9hell 48l (F:igure 6), with the axis of plug receiver 23. This
assures that there will be T10 undesired distortion of or stress
in fiber 133 during the tensioning and scoring operations described
below.
The protruding end portion of optical fiber 133 extends
not onl~ across support table 34 but across a tension table 36
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~.2~
the upper surface of which is flush with surface 35. Tension table
36 is, similarly to plug holder arm 20, a crank mounted pivotally
on screw 22. Thus, the lower end of the tension table is an aper-
tured bearing ear 37 which fits between ears 21 of the fiber
support, and likewise receives a por-tion of the shank of screw 22.
Mounted above the upper surface of table 36, in parallel
relationship thereto, is a clamp plate 3~ from which projects
downwardly and slidably into the tension table a guide pin 39
(Figures 1 and 2)~ At their regions opposite plug receiver 23,
the opposed surfaces of clamp plate 38 and table 36 are covered
with synthetic-resin friction elements adapted to achieve a desired
degree of frictional engagement with fiber 133. These friction
elements, indicated at 40, may be synthetic resin tape adhesively
- secured (or bonded) to the clamp and table surfaces. As best
shown in Figure 7, the synthetic resin tape 40 is pre~erably pro-
vided not only on the parallel surfaces of the table 36 and clamp
38, but also on the faces thereof remote from plug receiver 23.
Fiber 133 being in precise position over tables 34 and
36, and beneath plate 38, it i5 clamped by the actuating, spriny,
cam and connection mechanisms next described, in response to move-
ment of handle 12 toward handle 11. A tension rod 42 extends
downwardly from clamp plate 38 and slidably through an overhang-
ing portion of table 36, having a collar 43 provided fixedly
thereon in spaced relationship below the undersurface of the
overhanging table (reference being made to Figure 1, which shows
the tool in its "free" position with no hand pressure applied).
Collar 43 seats on the upper surface of the horizontal portion of
an L-shaped tension link ~4. The lower surface of such horizontal
portion seats on the upper end of a helical compressi.on spring 46
which is, in turn, seated on a nut 47 (Figure 3) at the lower end
of the tension rod.
The construction of spring 46 is such that, at the
instant when link 44 separates from collar 43, there is sufficient
--10--
clamping pressure between friction elements 40 to prevent any
sliding of such friction elements relative to the fiber when a
desired predetermined axial tension is applied to the fiber.
Furthermore, the force of the spring 46 is such as to supply a
substantial portion of such predetermined tension applied to the
fiber, it being pointed out that (as shown in Figures 2 and 4)
the axis of rod 42 does not intersect that of shoulder screw 22
but instead passes to the left thereof (as shown in Figure 2) so
as to create a moment about the shoulder screw axis. This torque
or moment tends to pivot tension table 36 counterclockwise as
viewed in Figure 2, thus tensioning the fiber 133. However, the
force exerted by spring 46 upon downward movement of link ~4 is not
sufficient to effect any undesired distortion or crushing of the
fiber, the relationships instead being such that the clamping and
frictional forces are only barely sufficient to prevent slippage
of the fiber between elements 40.
Tension link 44 connects pivotally (in a loose manner,
such that the tension table may pivot) to the right end of a ten-
sion arm 48, the left end of such arm being pivoted at a screw 49
to a post 50 on base plate 10. Reference is made to Figure 7,
which shows such post 50 and also shows the tension link 44 twice
for correlation of different portions of the partially exploded
view (there being, in fact, only one link 44 and one arm 48)~
Tension arm 48 operates as a cam means, in that it co-
operates with upper and lower cam followers 51 and 52 respectively
disposed above and below the arm at a location relatively adjacent
pivot screw ~9. ~t a region between cam follower 51 and tension
link 44, the upper surface of arm 48 is inclined downwardly and
then upwardly as shown at 53 and 5~ in Figures 3, 5 and 7. When
the apparatus is in its "free" or fully released position (Fiyure
1)l no squeezing pressure being applied to the handle means 11-12,
the upper cam follower 51 is spaced a short distance from the
notch formed by the inclined surfaces 53-54.
--11--
3~
When handle 12 commences to pivot counterclockwise in
response to initial squeezing action by one hand of the operator,
and against the bias of spring 16, the upper cam follower 51 moves
toward the upper portion of surface 53. ~his causes, or permits
(depending upon the position of the tool), tension arm 48 to pivot
clockwise. Thus, in response to only a very small counterclockwise
movement of handle 12, tension arm ~8 pivots clockwise to a posi-
tion close to the one shown in Figure 3, the clamp plate 38 then
having lowered until fiber 133 is in engagement with both of the
friction elements 40.
As soon as further counterclockwise pivotal movement of
handle 12 causes additional lowering of the tension arm 48, spring
46 is further compressed due to shifting of tension link 44 away
from collar 43, creating the predetermined fiber-clamping pressure
as stated above. Thus, when the parts are in the positions shown
in Figures 3 and 4, fiber 133 is properly clamped and will not
slip when tensioned. The words "further compressed" are used in
this paragraph because the spring 46 is preloaded between link 44
and nut 47, there ~eing compression of the spring even when the
tool is in the free position of Figure 1.
It is possible for handle 12 to be pivoted all the way
counterclockwise until it strikes a shoulder screw 56 which serves
as a stop (as well as performing other functions stated later in
this specification). Because of the construction of the present
mechanism, even such Eull movement of handle 12 until shoulder
screw 56 is engaged will not create excessive clamping pressure
on the fiber, or excessive tensioning of the fiber, because the
inclined surface 53 of tension arm 48 is so shaped and oriented
that tension link 44 stands substantially still at all times when
cam follower 51 is shifting between the position shown in Figure 3
and the position of such cam follower when the handle means is
fully closed against screw 56 (cam follower Sl then being rela
tively adjacent to-- but not yet at-- the region of interSeCtiOrl
-12-
of surfaces 53-54). Thus, both the clampin~ pressure and the
fiber-tensioning foxce are immune to the effects of squeezing of
the handles more than the necessary extent.
~ fter h~ndle 12 pivots counterclockwise from the free
position of Figure 1 to the initial clamping position shown in
Figure 3, lin~ 44 having just separated from shoulder 43 to pro-
vide the requisite clamping and tensioning force in rod 42, there
is still no axial tension created in the ~iber since cam and cam
follower means are provided to prevent any pivotal motion of ten-
sion table 36 until after the fiber is fully and properly clamped.As best shown in Figure 7, the cam means comprises a lowe:r cam
surface 57, an intermediate cam surface 58, and an upper cam sur-
face 59 all formed integrally on tension table 36. The lower and
upper surfaces 57 and 59 are very steeply inclined, being substan-
tially vertical as.shown in Figures 4 and 6. Intermediate surface
58, on the other hand, is gently inclined upwardly and to the left
as viewed in Figures 4 and 6 (toward back plate 10)~ A cam follow-
er roller 61 is rotatably mounted at the forward end of what may
be termed a tension actuator arm 62, the rear end of such arm
being pivoted at 63 to a screw which extends into plug holder
arm 20.
In an intermediate portion of tension actuator arm 62
there is provided a large opening 64 in which is disposed at all
times the relatively small end 65 of an arm 66 which is secured
by screws to the upper end of handle 12. The s:ize of such small
end 65 is correlated to the vertical distance between the upper
and lower walls of opening 64 in such manner that there is a pre~
determined lost-motion connection provided between the end 65 and
actuator arm 62.
Cam follower roll.er 61 prevents pivoting of tension
table 36 when the upper cam follower 51 has just reached the posi-
tion of ~igure 3 (handle 12 pivoting counterclockwise), since the
roller is then engaging the lower steep cam surface 57 as shown
-13-
7~
in Figure 4. It is emphasized ~hat the initial squeezing motion
of handle 12 toward handle 11 does not lift roller 61 off this
s-teep cam surface 57 due to the indicated lost-motion connection
at 64-65, the result being that operation of the handle to clamp
the fiber does not cause any tensioning thereof. Additional
counterclockwise motion of handle 12 causes handle arm end 65 to
engage the upper portion of actuator arm 62 and effect counter-
clockwise pivoting of such arm from the position shown in Figure
4 to a higher position (similar to that shown in Figure 6) at
which roller 61 reaches inclined portion 58 of the cam means.
Tension table 36 then, immediately, springs to the right
as viewed in Figures 4 and 6, there being pivotal motion of the
table about the axis of screw 22. If unimpeded, such pivotal
motion would continue until the upper steep cam surface 59 is en-
gaged by roller 61.- However, this does not occur since the fiber
itself prevents such extreme pivotal movement of the tension
table. Instead, the tension table only pivots a short distance
away from fiber support table 34 because only a relatively small
amount of pivoting is sufficient to create the desired tension
in fiber 133.
The tensioning motion of table 36 is effected not only
due to the torque arm described above, and the pressure of spring
46, but due to the pressure of a second helical compression spring
which is shown at 67 in Figure 2. Such spring is in a recess in
the tension tahle, and seats at its outer end on an adjustab]e
plug 68 threaded into plug holder arm 20~ The setting o plug 68,
and the size of spring 67, are caused to be such that the combined
forces oE springs 67 and ~6 create precisely the desired predeter-
mined degree of tension in the fiber 133. For a fiber 133 haviny
a diameter of 0.005 inch, this tension is preferably about 150
grams.
Because the tensioning movement of table 36 is pivotal,
not straight, the tensioned fiber conforms closely to cylindrical
-14-
surface 35 (Figure 4~ regardless o~ the position of table 34,
the position of such table being adjustable as described below.
The lost-motion opening 64 in element 62 is so wide that any
lateral motion of the handle 12-- caused by the squeezing action-
does not affect fiber tension at all.
The above-described mechanism effects the predetermined
clamping, tensioning and bending of fiber 133 in a very short
period of time/ which can be a small ~raction of a second when
the operator pivots handle 12 rapidly toward handle 11. Accord-
ingly, the fiber is ready for scoring by the precision scoringmechanism next to be described.
SCORING OF T~E FIBER
- ~s best shown in Figure 7~ the scoring mechanism com-
prises a highly rigid and stable (against lateral forces~
parallelogram linkage 69 consisting of a horizontal bottom link
71, end links (rocker arms) 72 and 73 which are pivotally mounted,
respectively, on shoulder screws 74 and 75 extending into base
plate 10, and an upper link which is formed by the base plate
itself but may be considered as extending horizontally between
the shoulder screws.
As illustrated, the bottom link 71 is strong ancl thick,
and the end links 72-73 are U-shaped and securely pivoted both to
the shoulder screws and to the bottom link. The strength and
rigidity of the parallelogram linkage 69 are for the purpose of
preventing lateral movement of a scoring blade 76 which is rbounted
substantially vertically, and in adjustable relationshipl in a
blade arm 77. Arm 77, in turn, extends above and substantially
parallel -to bottom link 71, being pivoted to such link at 78 by a
U-shaped bracket 79.
Blade 76 is, very preferably, a tungsten carbide wedge
the sharp lower edge 81 of which effects scoring of the fiber.
The elevation of scoring edge 81 above the cylindrical upper sur-
face 35 of fiber support table 34 may be adjusted in two ways:
-15-
Firstly, by loosening a set screw 82 and moving the blade upwardly
or downwardly relative to the blade arm 77, and secondly, by
turning a fine-adjustment set screw 83 which is threaded verti-
cally through arm 77.
When set screw 83 is so rotated as to move downwardly,
it bears against the upper surface of link 71 and thus effects a
slight counterclockwise pivoting of blade arm 77 about pivot 78.
This pivoting is against the bias of a helical compression spring
84 which is mounted around a screw 85 as shown in Figure 3. Such
screw extends downwardly through an oversize opening in blade arm
77 and is threaded into the horizontal link 71, so that rotation
of the screw 85 changes the spring bias.
To operate linkage 69 for achieving scoring of the fiber
by blade edge 81, a trigger 87 is provided in the form of a first
class lever. The fulcrum of the lever is the above-indicated
shoulder screw 56 treference being ~ade to Figure 7). The region
of the trigger above screw 56 extends adjacent base plate 10
(behind handle 12), terminating in a generally vertical upper end
portion 88 which fits in an opening 89 in lower link 71. To bias
trigger 87 in a counterclockwise direction, thus maintaining the
link 71 in its leftmost position (Figures 1, 3 and 7) except
dur.ing the actual scoring operation, a spring wire 90 is provided.
Such spring is best shown .in Figure 7, and has one leg seated to
the let of spacer sleeve 14, a U-shaped centra]. portion :Looped
around the stem o shoulder screw 56 beneath trigger 87, and a
lower portion which extends downwardly to the lower end of the
trigger and thence upwardly for engagement with the let side
thereo~. Excessive counterclockwi.se movement o the trigger is
prevented by sleeve 1.4 (Figure 7) which acts as a stop.
Referring to Figures 3, 5 and 7, a trigger clip or
actuator 92, in the form of a curled flat spring which provides
a cam and escapement function relative to the lower end of the
trigger, is mounted on handle 12 by means of suitable screws.
-16-
Clip 92 has an inclined upper surface 93 which extends upwardly
and to the left as viewed in Figures 3 and 5. Such surace is
adapted to engage a narrow lower "dog" portion 94 o~ the trigger
in response to counterclockwise pivotal movement of handle 12
past the position shown in Figure 3 (which Figure 3 position
achieves fiber clamping as described above).
Sufficient counterclockwise handle movement causes
lower portion 94 to ride up surface 93 and thus bend the clip
downwardly, so that an upper corner 96 of the clip moves beneath
the portion 94. The clip then springs upwardly to the position
shown in Figure 5, thereby retaining the lower tri.gger end (por-
tion 94) to the left of clip corner 96 during a substantial
portion of clockwise pivotal movement of handle 12. However,
long before the handle 12 returns (clockwise-) to its free position
of Figure 1/ the clip corner 96 escapes from behind lower trigger
portion 94 and thus frees the trigger. The shape and strength of
clip 92 are such that it will pivot trigger 87 just ~ar enough to
effect scoring, following which the trigger releases from the
clip .
Let it be assurned that handle 12 is pivoting counter-
clockwise and is in the Figure 3 position (the fiber end 133 having
been clamped, tensioned and bent as described). Continued
counterclockwise pivotal movement causes the clip to ride beneath
trigger portion 94 as stated, until the clip springs upwardly to
the Figure 5 position with corner 96 on the right side of portion
94 o~ the trigger. The operator can then, in accordance with his
wishes and characteristics, either pivot the handle 12 counter-
clockwise until shoulder screw 56 is engaged by the handle 12,
or he can ir~medi.ately release the handle so that it pivots clock-
wise i.n response to the bias of spring 16 (a clicking noise in~orms
the operator when clockwise handle movement may be started). In
either case, nothing happens until the clip corner S6 ef~ects
clockwise pivoting of trigger 87 against the bias of spring 9~,
-17-
1''7~
the upper portion 88 of the trigger then shifting link 71 to theright from the Figure 3 position to the Figure 5 position. This
causes scoring edge 81 of blades 76 to score ~iber 133, whereupon
breakage of the fiber instantly results to achieve per~ect
mirror-finish optical ends of the broken fiber portions (each
end being perpendicular to the fiber axis). Continued clockwise
movement of handle 12 causes the lower portion 94 of the trigger
to ride over the clip as stated, whereupon the trigger is released
so that spring 90 instantly pivots the trigger counterclockwise
to shift link 71 back to the position of Figure 3, blade 76 and i~s
scoring edge 81 then being out oE the way and remote from the
broken fiber end which is still projecting from shell 48' (Figure
6).
Fiyure 5 shows the parts at the instant when the clock- -
wise-moving handle 12 is about to cause release of trigger end 94
from clip 92. Thus, the blade 76 is shown in its right-most posi-
tion, the end links or rocker arms 72-73 being substantially
vertical.
It is to be noted that the end links 72 and 73 of link-
age 69 are normally (when the tool is in its free position,
Figure 1) pivoted clockwise, to the ].eft of their vertical posi-
tions, being held there by the spring 90 and by the stopping
function of sleeve 14 ~Figure 7) relative to the trigger. Thus,
link 71 and its associated blade arm 77 and blade 76 are higher
than, and to the left of, the fiber 133 ~a typical "free" eleva-
tion of the scoring edge ~1 being that shown in Figure 4). Blade
76 does not, therefore, interere in any way with mounting o the
connector portion ].3' (Figu:re 6) to the plug receiver 23 which
automatically effects positioning of the random-len~th :Eiber end
133 on table 34.
When trigger 87 is actuated clockwise, link 71 (and thus
the scoriny edge 81 of blade 76) moves downwardly and to the right
in an arcuate path, as indicated by the arcuate arrows 97 in
-18-
schematic Figures 8 and 9 (drawing sheet 1). The lengths and
positions of links 72, 73, and the adjustment of b]ade 76, are
caused to be such that the forward end of scoring edge 8i (namely,
the corner 98 shown in Figures 8 and 9) does not ever engage fiber
133. Instead, the fiber is first engaged after it is certain
that such corner 98 has passed over and beyond the fiber in the
rightward direction during the movement represented by Figure 8.
A typical first-engagement position is shown in Figure 8.
The curved downward and rightward arcuate movement
represented by arrows 97 continues until, for example, the fiber
is at approximately a central or left region of the blade. Fur
thermore, the movement is such that scoring edge 81 is substan-
tially (for example, one-quarter the diameter of the fiber~ beneath
the upper surface of the fiber. However, it is emphasized that
the fiber has broken long before the position of Figure 9 is
reached-- having instead broken when the blade has moved only a
slight distance away from the figure 8 position.
Breaking is the result of the tensioning, curvature,
and scoring which are effected in rapid sequence by the present
tool. All of the operations can be effected very quickly, with
the operator moving handle 12 just as rapidly as he desires.
With the described mechanism, no movement of the hand
of the operator can effect any side ~lateral) loading movement of
blade 76, which is an important feature relative to the precision
location of the break as described below.
One of the highly surprising and unexpected results of
the present scoring mechanism and method is that blade 76 may be
"hard mounted" instead of precis:;on loaded (as by counterweights,
fine springs, etc.) to a precise bearing pressure. In other
words, the spring 84 may be very strong, so strong that under no
conditions, except in response to the turning of set screw 83,
will there be any movement of blade arm 77 relative to link 71.
The fiber does not "know" whether or not blade 76 is associated
-i9
~ ~ J
with any spring or weight whatever. The hard mounting permits
the tool to be used in any position, which is one of its important
features.
The described motion of the blade edge 81 is along a
curved path, which path lies in a plane substantially perpendi-
cular to the axis of the fiber 133 at the region of scoring.
Furthermore, the curved path intersects the curved surface of the
fiber in the indicated plane, and the degree of intersection is
caused to be such that there will be a clean break o~ the ~iber.
As indicated by arrows 97, Figures 8 and 9, the curved path is in
an opposite direction to the curvature of the upper region of the
fiber 133, in that the indicated upper fiber region is convex
upwardly whereas the arrows 97 are convex downwardly.
It was very common in the prior art to move a scoring
blade directly downwardly (vertically) against a fiber such as
fiber 133, and with a precision amount of force (a small number
of grams). Thus, in the indicated prior-art method, the path of
the scoring blade was not what is herein called a "scoring direc-
tion", but was parallel to or-coincident with the longitudinal
diametral plane of the bent fiber. Such "longitudinal diametral
plane of the bent fiber" i5 indicated by the dashed line "P" in
Figure 8, being the vertical plane through the fiber axis along
the length of the bent fiber on the support table 34. In contrast
to such prior-art method, the initial engagement of the blade edge
fll of the present apparatus with fiber 133 is achieved by moving
the blade edge along a downward, inclined path which is at a
lar~e acute angle to the indicated "longitudinal diametral plane.
The initial engagement is such that the bent fiber is first en~
yaged on its side remote from supporting surface 35.
It will thus be seen that in accordance with a scoring
aspect of the present invention, the edge of a scoring blade is
caused to have initial contact with a bent (about a predetermined
radius)/ tensioned optical fiber in a downward direction and also
-20-
7~3~
a scoring direction, as distinguished from being merely set down
(vertically) on such fiber. There is caused to be sufficient
force to score the fiber, but the upper limit of the force need
not be measured or known.
Preferably, the scoring edge is slightly inclined, up-
wardly and to the right, as shown in Figures 8 and 9. Thus, front
corner 98 is a few thousandths of an inch higher than is the rear
corner of the blade edge.
The construction of the scoring blade (76 in the des-
cribed structure) is highly important. As above indicated, theblade 76 is formed of a carbide, very preferably tungsten carbide
as stated above. The particular tungsten carbide employed is
critically important to the achievement of the instant one-stroke
breakage. Applicant has discovered that the grain structure
should be sufficiently small that the edge 81 may be ground very
sharp. On the other hand, the grain structure should be suffi-
ciently large that-- when greatly magnified-- the edge 81 will
appear to be rough, as shown in Figure 10 which schematically
represents an electron-microscope "picture" at a 2500X magnifica-
tion.
In ~igure 10, the width of the edge 81 of blade 76 isapproximately D.0005 inch. This edge is formed by grinding (as
by a diamond grinding wheel) the opposed angled faces of the blade
to the sharp edge. Then the edge itself may be very lightly
sanded with fine sandpaper (e.g., 600 grit). The particle size
of the tungsten carbide as shown in Figure 10, is typically about
1.25 microns, and ranges generally between one and two microns.
The hardness of the tun~sten carbide is about 92 on the
Rockwell A scale (between about 91.7 and 92.2). The chemical
composition is 94% tungsten carbide, cemented together at elevated
temperature by 6% cobalt. The described cemented tungsten car-
bide may be purchased from the Carbolloy Systems Department of
General Electric, Detroit, Michiganj as "Grade 833."~
-21-
~h~
It is pointed out that if the edye of the blade is notso composed and constructed as to effect immediate scoring when
the curved, tensioned optical fiber is initially contacted in
the scoring direction, breaking will not occur immediateIy and thé
above-described great advantages of single movement and l'hard
mounting" may not be achieved. Instead, for example, the ends
may be crushed or otherwise damaged and unsatisfactory.
~ eferring next to another aspect of the scoring blader
the angle of at least the lower parts of faces 110, 111 (Figure
11), relative to each other, should be so small that they will not
be contacted in any manner damaging to the mirror faces of the
broken ends.
- In the present tool it has been found satisfactory to
~ make this angle 15 degrees, with each face 110, 111 beiny at an
angle of 7.5 degrees ~rom the ver~ical. Alternatively, the blade
~ace relatively ad3acent the optical connector (plug) element 48'
(Figure 11) may be vertical. It is emphasized that the blade
face relatively adjacent plug 48' is the most important, in that
the right section (Figure 11) of the broken fiber is discarded.
Figure 11 shows, in greatly enlarged form, how the
broken ends spring up or "pop up" from surface 35, due to the
elasticity of the glass, at the instant breaking occurs. In thus
popping up, the mirror ends tend to retract away from the faces
11~, 111 of the blade, and are not damaged by such faces. Since
the critical fiber end, the left one as shown in Figure 11 and
which protrudes from plug 48', does not rest on surface 35 except
at the instant of initial scoring, the downwardly moving blade 76
does not tend to crush or otherwise damage such fiber end, even
though the blade is hard mounted as descr:ibed. Thus, the blade
shape, blade material, and blade direction cooperate in the
achievement of single-stroke rapid fiber breaking, and without
the necessity of limiting blade pressure. The retraction shown
at the left-in Figure ll~is aided by the long length of fiber
-22-
7~3~
between the break region and the clamp portion of the optical .
connector.
METHOD A~D APPARATUS CORRELATING THE BREAKER
AND OPTICAL CONNECTOR
As previously stated, the present optical fiber breakeris not only adapted to be employed-by itself, but, additionally,
is part of an overall system including the optical connector means
referred to in connection with Figure 6 and described below
relative to Figures 15-20. In such connector, and in some other
connectors, it is highly important that there be a precisely pre-
determined amount o~ extension of the broken fiber out of the
connector plug portion (such as 48', Figure 6). In accordance
with the present apparatus and method, a random length of fiber
(as shown in Figure 6~ is inserted into the breaking tooI, but as
soon as breaking has occurred there.is a precisely predetermined
length which is (according to a major aspect of the present inven-
:~ tion) correlated accurately to the characteristics of the particu-
. lar optical connector so as to achieve an optimum optical con-:.
nection.
It has previously been described how the position of
blade 76 relative to the connector portion (for example, plug or
shell 48l, as shown in Figure 6) is critical. There will now be
described how this precise distance from.the forward face of shell
48l to the scoring edge of blade 76 may be accurately adjusted
without in any way changing the optical characteristics of the
break.
As previously set forth, the plug holder arm 20 is
pivotally mounted on shoulder screw 22 for forward and rearward
pivotal movement. Furthermore, the upper surface 35 of fiber
support table 34 is cylindrical about the axis of shoulder screw
22. In addition, the linkage 69 and the mounting of blade 76 are
such that, at all times, scorlng edge 81 lies in a plane which
contains the axis of screw 22 and also contains that radius of
surface 35 which passes through scoring edge 81. Scoring edge
81 therefore always moves in a plane perpendicular to the axis
of fiber 133 (that is to say, the axis of that portion of. the :
fiber which is directly beneath edge ~1 on table 34) to thus make
perfect breaks, causing the end faces of the broken iber sections
to be perpendicular to the fiber axes.
With the described construction, the distance from edge
81 to the front face of plug or shell element 48', Figure 6, and
accordingly the amount of protrusion of the broken-off fiber end
from element 48' after the break, may be precisely controlled by
shifting the plug receiver 23 and its associated connector ele-
me.nt relative to the blade. Such shifting is effected by turning
a screw 101 ~Figures 6 and 7) which extends through an opening
in a bracket 10~ and is threaded into base plate 10. Bracket 102
is mounted on plug holder arm 20, and a helical compression spring
103 forces it out (to the right in Figure 6) to the maximum ex-tent
permitted by screw 101.
It follows that by turnin~ screw 101 one way or the
other, plug holder arm 20 and thus the connector portion 13' and
also the table ~4, are shifted inwardly or outwardly relative to
scoring edge 81 to thereby change the distance of such edge from
the inner face of plug or shell 48'. Regardless of the ad~ust-
ment effected by turning of screw 101, the blade is perpendicular
to the exact portion of fiber 133 which is broken, and the end
faces of the break are perfectly perpendicular to the fiber axes
of the broken components. Because of the characteristics of
linkage 69 and associated components, the position of blade 76
relative to base plate 10 is fixed, even after long use of the
mechanismt there being mini.mal play or slop in a lateral direction
(to left or right in Figure 6). Thus, the amount of protrusion
of the broken fiber end from element 48' may be controlled within
close tolerances such as those on the order of one thousandth of
an inch.
-24-
7~
As above stated, the particular and greatly preferred
optical connector which is employed in conjunction with the
present tool is shown further in Figures 15-20, and described in
detail at the end part of this specification. As is there set
forth, the protective sheath 132 around fiber 133 is first strip-
ped away at an end portion of the fiber (as by a cable stripper),
following which the plug assembly 13' is mounted on the fiber.
A back shell nut 100' is turned to grip the fiber between resili-
ent pads 1~2' and 1~3', thus clamping the fiber in plug assembly
13' without damaging the fiber. Then, when the random-length
protruding end of the fiber is inserted in the breakiny tool as
described above, and ring 85' is turned to fully seat plug assembly
13' on plug receiver 23 (Figure 6).
The fiber is thus effectively clamped at a known posi-
tion relative to the breaking tool. Then, when breaking occurs at
a precisely determined position relative to the forward shell
(plug) 48', as described, the correct relationship will be present
àfter assembly 13' is unthreaded from the breaker and threaded to
a further shell portion 17' of the optical connector (Figure 15).
Due to the action of a spring 54', and the fact that
the broken fiber only projects a lirnited distance out of shell 48',
unthreading of ring 85' from the breaking tool causes the broken
end to retract completely into the plug or shell 48' so as to be
substantially immune to damage or contamination. As soon as ring
85' is threaded to element 17' of the connector (Figure 15), the
broken end again projects to just the right extent for making of
the optical connection.
The present tool has the capability of bein~ easily
changed for different diameters of optical fibers 133, and even
for different connectors, by rnaking various adjustments, changing
the plug receiver 23, etc. The tool as described above (without
making such changes or adjustments) is especially intended for use
with the described optical connector, and for breaking a particular
-25-
fiber 133 having a thin synthetic resin coating which automaticallystrips back a slight distance in response to fiber breaking. Such
fiber 133 has a two-layer high-silica glass body the outer dia-
meter of which is about 125 microns, and an acetate coating the
outer diameter of which is in the range of 132 to 138 microns.
This exemplary fiber 133 is manufactured by Corning Glass Works,
Corning, New York, under identification nurnbers S040 and 10020.
There exist types and thicknesses of plastic coatings,
on optical fibers, which do not strip back automatically from the
glass body in response to breaking, and it is an important feature
of the present tool that it is readily adapted for quickly burning
off such coatings from the break reyion.
THE SECOND EMBODIMENT - FOR BURNING OFF THE COATING
Except as specifically stated below, the second err~bodi-
ment is identical to the one described above.
Referring to Figures 12-14, inclusive, a switch is shown
at 112 and is suitably mounted to back plate 10 adjacent the upper
portion of handle 12. A spring-metal angle member 113 is mounted
on handle 12, by means of screws, being adapted to close switch
112 (which is normally open) when the handle 12 is shifted
counterclockwise to a predetermined substantially closed position.
Such predetermined position corresponds to a position of handle
12 which is somewhat counterclockwise from the position shown in
Figure 5.
It is only necessary for the operator to maintain handle
12 in the indicated substantially-closed position until the syn-
thetic resin has been burned oE~ the glass fiber 133 by the heater
wire means next described. Heating of the wire rneans, and by the
wire means, takes place during the entire period when switch 112
is thus closed-- there being a battery 114 and suitable leads
provided ~or this purpose.
Figure 13 shows a ceramic block 115 which is used in
-26-
'7~
place of block 34 as the fiber support table. Such block is
secured to plug holder arm 20 by metal brackets 116 and suitable
screws, not shown~
Two heater wires 117 and 118 are mounted in a groove
119 (Figure 14) in the upper sur~ace of block 115. The wlres may,
for example, be formed of Invar alloy. The wires are in line
contact with each other, and at their upper regions lie generally
(except for curvature described below) in a horizontal plane im-
mediately adjacent and parallel to the fiber support portion of
1~ table 115. Each wire 117, 118 may, for example, have a diameter
of 0.010 inch.
As shown in Figure 14l the optical fiber 133 nests in
and parallel to the "notch" or groove formed by upper surface
portions of wires 117 and 118. Then, when the heater circuit is
completed, the fiber is rapidly heated so that the synthetic resin
coating burns off in the region where scoring will occur.
After such burn-off, the operator merely releases handle
12 so that it is forced out by spring 16, thus instantly causing
scoring ana fiber breaking as described heretofore. The scoring
blade is so set that the heater wires are never engagea thereby.
It is emphasized that groove 119 has a bottom wall which
is curved, at a radius of about 1.5 inches r about the axis of
screw 22. rrhe wires 117, 118 therefore also curve, so the fiber
133 seated therein is tensioned and bend about a 1.5 inch radius
as described relative to the first embodiment.
Extensions of groove 119 are provided down the ~ront
and back faces of block 115, and also contain extensions of wires
117, 118. ~ helical compression spring 120 is mounted in a
recess in the front Eace, and bears outwardly against the wires
to insure that they are under tension. Thus, any change in the
lengths of the wires, caused by heating, is compensated for by
spring 120 so that the wires always lie closely against the
curved bottom wall of groove 119 at thR upper side of the block.
-27-
~2~
A screw 121, ~igure 13, connects the wires to arm 2Q,so that a "ground" circuit is completed throuyh the tool to one
side of the power source 114. A second screw 122 connects to a
lead 123 which extends to switch 112.
The notch or groove, for fiber 133, defined by the
upper surfaces of the wires is a further means of preventing
fiber 133 from starting to roll in response to the described
~otion of the scoring blade. A similar groove or notch may be
provided in the upper surface of table 34, of the first embodi-
ment, to insure against any such rolling.
SUMMARY OF METHODS AND OPERATION
- From the standpoint of a person who uses the tool in
the field or in a factory, there is no more difficulty of opera-
tion than exists relative to a typical hand tool such as a pair
of pliers, a wrench, etc. All the operator need do is ~1) mount
the connector component (plug) 13' on plug recelver 23 (Figure 6)
by threading the connector ring until it fully seats, and then
(2) squeeze and release the handles 11 and 12. The fiber is
perfectly broken, on almost all occasions, so the operator removes
the connector component 13' and then makes a connection to another
connector component in the optical system as described in the
cited patent applications and at the end of this specification~
Furthermore, it is not even necessary for the operator
to take precautions to prevent breakaye or damaye to, or contamina-
tion of, the protruding end o the fiber. This i5 because re-
lease of connector component 13' Erom threaded portion 24 of plu~
receiver 23 operates to draw the broken-off end into plug or shell
element 48' where it is fully protected. This drawing back opera~
tion is effected by expansion of the compressed spring 31, and by
associated components in the connector. It is emphasized that the
fiber 133 is tightly held ~clamped) by connector element 13'v
If the glass fiber is one which has a coating which does
-2~-
not automatically strip back in response to breaking, then theabove-indicated electrical embodiment of the tool (Figures 12-14)
is emplo~ed and the opera-tor takes a few seconds longer in making
the break. In other words, and as above stated, he holds the
handle 12 almost closed toward handle 11 for a time period suffi-
cient for the parallel wires 117, 118 to burn ofE the plastic
coating, then he quickly releases handle 12 to complete the opera-
tion.
Although the apparatus and method are so simple and
easy to perform in the field, they involve great precision, ac-
curacy, repeatability, etc. For example, the setting of blade 76
is effected by means of a microscope in order to create the op-
timum scoring action as described relative to Figures 8 and 9.
Furthermore, the setting of screw 101 to determine the extent of
protrusion of the broken-off fiber end is done with ~reat accuracy.
To summarize briefly the operation of the tool, the
first small increment of movement of handle 12 toward handle 11
causes operation of a first cam means (elements 48, 51 and 52)
to compress spring 46 to the correct extent ~or achievement of
predetermined clamping pressure between ~riction elements 40, and
also to generate a torque which urges tension table 36 away from
the fiber support table 34 for achievement of a large part of the
Eiber-tensionin~ force. However/ tensioning force is not generat-
ed in fiber 133 until there is an additional amount of movement
o handle 1~ toward handle 11, which additional movement operates
through a second cam rneans, incl~lding a lost-motion connection,
to release the tensioning table for pi~oting in response to the
bias of spring ~6 and also the precisely determined bias of spring
67 (Figure 2). This second cam means is cam surfaces 57-59 and
the associated roller 61, whereas the lost-motion connection is
between the upper and lower walls of opening 64 (Figure 4) and
the small end 65 of element 66. The relationships are such that
the excessive squeezing of the handles by the operator will not
-29-
L'7~
aEfect the tensio~ in any way~
Additional pivo-ting of handle 12 toward handle 11, and
then away therefrom, operates the linkaye 69 and the scoring blade
76 -to make a precise score of fiber 133 and thus complete the
break, the fiber having previously been clamped, tensioned and
bent as described in detail. The mechanism for achieving -this
scoring includes a third cam means (elements 92, 94, etc.) and a
parallelogram linkage 69 cooperating to create precision action
and a scoring operation which is, again, independent of handle
movement particularly in the latera~ direction which would affect
the spacing of the blade edge from the forward end of plug or
shell element 48' (Figure 6).
As described in detail above, the third cam means oper-
ates to cock itself during counterclockwise movement of handle 12,
and effect the actual operation of linkage 69 for achievement of
scoring during the reverse (clockwise) movement of handle 12
after the operator releases it. Also, during this reverse move-
ment of handle 12, in the clockwise direction, the second cam
means operates to pivot the tension table inwardly toward the
fiber support table in that element 62 is pivoted downwardly by
the end 65 of element 66, thus forcing roller 61 downwardly to
the position adjacent cam surface 57. Thus, and also due to the
operation of various springs, all parts return quickly to their
original positions (shown in Figure 1) when the handle is released.
FURTHER DESCRIPTION OF THE PREFERRED OPTICAL CONNECTOR
Reference is now made to Figures 15, 16, 17, 18, 19
and 20 in which primes are often employed in the reference
characters in order to prevent confusion with the reference
characters employed in previous portions of this specification.
The connector 10' (Figure 15) includes a central recep-
tacle to the opposîte ends of which are connected identical plug
assemblies one of which is shown in full at 13'. The other plug
assembly is only shown in part, at the left of Figure 15. These
- 30 -
'L'~
components connect optical fibers 133 and 136 to transmit light
from one to the other.
The central receptacle includes a tubular shell 17',
having a central flange 18', provided with openings 19' for
mounting to a suitable support.
Within the shell 17', as seen in Figure 15, is a lens
21' of a suitable transparent material, such as plastic or glass,
to provide a connecting system for the optical fibers. The
interior of the shell 17' includes a frustoconical surface 22'
at a shallow taper that circumscribes the right-hand portion of
the lens 21', as the connector is shown in Figure 15. The surface
22' terminates in a radially inwardly e~tending shoulder 23'.
The end 24' of the lens 21' is adjacent the shoulder 23' so that
the shoulder 23' retains the lens against movement out of the
receptacle shell toward the right-hand end.
The tapered surface 22' e~tends to the center of the
shell 17l where it joins a c~lindrical surface 26' within which
is an annular recess 27l. A split lock ring 28' fits in the
recess 27' adjacent the left-hand end 29' of the lens 21'. This
retains the lens against movement out of the receptac]e toward
the left.
The lens 21' includes a frustoconical inwardly tapering
surface 31' at its end 24' and a similar surface 32' at its end
29'. At the inner end of the surface 31' is a short cylindrical
section 33' which terminates at a radial face 34'. The other end
- 31 -
of the lens is symmetrical with a short cylindrical section 36'
and a radial inner face 37'. Cavities 38' and 39' are located
at the axis of the lens 21', extending inwardly from the surfaces
34' and 37', respectively. These cavities include frustoconical
entrance portions terminating at inner end portions which are
spherical segments. The inner ends of the cavities 38' and 39'
are spaced apart, as illustrated. An optical fluid of predeter-
mined index of refraction is located in the cavities 38' and 39'.
In the outer surface of the lens 21', extending from
the end 24' to a position adjacent the end 29', is a longitudinally
extending keyway 45'. This receives a pin 46l which extends
radially through the wall of the shell 17', thereby rotationally
positioning the lens 21' relative to the shell 17'.
As above stated, onIy the plug assembly 13' is shown
in complete detail in Figure 15, in view of the fact that the two
plug assemblies are identical. The plug assembly 13' includes a
front shell (sometimes hereinabove also called a plugj 48' and a
rear shell 49', both of which are tubular. The forward section
of the rear shell 49' fits around the rearward portion of the
front shell 48' in a telescoping relationship. As a result, the
rear shell is movable axially relative to the front shell and is
guided by the interegagement of the two shells. The forward inner
surface 50' of the rear shell 4g' is cylindrical and provided with
an annular recess 51~, which receives a split lock ring 52'. This
lock ring projects inwardly to interfere with a shoulder 53' on the
exterior of the rearward portion of the front shell ~8', which
prevents th~ rear shell 49' from sliding off the front shell 48'
when the plug is not mated with the receptacle, as in Figure 20.
A compression spring 54' circumscribes the intermediate
portion 55' of the front shell 48', with one end of the spring
engaging a rearwardly facing e~ternal radial shoulder 56' on the
front shell. The opposite end of the spring 54' bears against a
radial surface 57' just inwardly of the forward end 58' of the
-32-
rear shell 49'. This biases the rear shell 49' rearwardly rela-
tive.to the front shell 48' so that when the plug assembly 13' is
disconnected from the receptacle 11', the lock ring 52' is caused
to bear against the shoulder 53' of the front shell 48'.
The inner surface 50' of the rear shell 49' is provided
with a longitudinally extending keyway 60' which receives a key
61' projecting outwardly from the outer circumferential surface
62' of the front shell 48'. The keyway 60' and key 61' prevent
relative rotation of the front shell 48~ and the rear shell 49'.
The outer circumferent:ial surface 63' at the rearward
end of the front shell 48' is of reduced diameter, thereby provid-
ing a rearwardly facing shoulder 64' spaced inwardly of the rear-
- ward end surface 65' of the front shell. The rear shell 49' has
~ an inner circumferential surface 66' which fits around the surface
63 7 when the connector is mated, terminating at its forward end in
a radial shoulder 67'. An O-ring 68' circumscribes the front
shell 48' at the surface 63' and, when the plug assembly 13' is
attached to the receptacle, is compressed between the shoulders
64' and 67', forming a seal.
Forwardly of the shoulder 56', the external surface 69'
of the front shell 48' is dimensioned to fit closely within the
end of the recep-tacle shell 17' at the internal surface 70' of the
latter member. A key 71' projects outwardly from the surface 69'
of the front shell 48' and fits within a keyway 72l, extending
longitudinal.ly o~ the sur~ace 70' of the receptacle shell 17',
thereby indexing the plug and preventing relative rotation between
the plug 13' and receptacle 11'.
Forwardly o the circumferential surface 69', the front
shell 48' has a relatively short surface 74' of slightly reduced
30 diameter which, when the plug and receptacle are assembled, is .
engaged by an O-ring 75' to provide a seal. The O-ring 75' is
received in an annular recess 76' in the receptacle shell 17'~
Beyond the surface 74' the front shell 48' includes a
-33-
frustoconical surface 77', which is tapered at the same angle as
the surface 31' of the lens 21'. In the assembled condition, the
surface 77l of the front shell 48' engages the lens surface 31'.
Interiorly the front shell 48' includes a cylindrical
surface 79', which extends folwardly from the rearward end 65'
beyond the mid-portion of the front shell. At the inner end of
the surface 79' is a forwardly tapering frustoconical surface 80',
terminating at a cylindrical opening 81', having a relatively
small diameter.
An insert 82' fits within the cylindrical opening 79'
of the front shell 48' and is bonded in position. This insert is
solid except for a narrow slot 83', seen in Figure 18, which ex-
tends radially more-than half way through the insert 82' and is
the full length of the insert. The slot 83' is aligned rotation-
ally with the key 71'.
Circumscribing the front shell 48' is a coupling ring
85', having a knurl 86' on its exterior surface for manual rota-
tion. The forward end 86' of the coupling ring 85' is internally
threaded to mate with external threads on the right-hand end por-
tion of the receptacle shell 17'. At the rearward end of thecoupling ring 85' is a radially inwardly extending flange 87'
that fits behind a rearwardly facing shoulder 88' on the rear
shell 49'. Behind the flange 87' of the coupling ring 85' is a
split lock ring 89' that fits within an annular recess 90' in the
external surface of the rear shell 49'. The lock ring 89' and the
.. .
shoulder 88' prevent the coupling ring 85' from escaping from its
position around the plug.
At the rearward end portion of -the rear shell 49' is a
radial wall 92', having a relatively small central opening 93'.
When the plug and receptacle are assembled, as illustrated in
Figure 15, the wall 92' engages the rearward end 65' of the front
shell 48'.
Rearwardly of the wall 92' the interior of the rear shell
-3~
49' includes a relatively large diameter portion 94', beyond which
is a cylindrical surface 95' of smaller diameter. Adjacent the
rearward end, the interior of the rear shell 49' includes an
outwardly tapering frustoconical surface 96'. A key 97' extends
inwardl~ of the frustoconical surface 96', with its inner ed~e
forming an extension of the cylindrical surface 95'.
A fiber clamp 99' is located at the rearward end of the
plug assembly and is circumscribed by a back shell nut 100'. The
clamp 99', as sho~n in Figure 15, includes two flat rectangular
pads 102' and 103' of elastomeric material. These fit within
complementary recesses 104' and 105', respectively,:`in rigid
pressure members 106' and 107'. ~he latter members are of half-
round configuration and include flat radial surfaces along their
~ sides which are their mating faces. ~--
Forwardly of the recesses 10~' and 105', the members
106' and 107' include narrow, deep semicylindrical recesses 110'
and 111', which together receive a washer 112' that prevents rela-
tive longitudinal movement of the members 106' and 107'.
Forwardly of the recesses 110' and 111' the members 106'
and 107' include semicylindrical inner surfaces 113' and 114'
connecting to frustoconical surfaces 115' and 116' that diverge
to the forward.end.
Exteriorly the members 106' and 107' include outwardly
projecting flanges 117' and 118' that fit within the recess defined
by the surface 94' of the rear shell 49', preventing es.cape of the
alamp from the plug.:` Inwardly of the Elànge 118' of the member
106' is an exterior cylindrlcal surface 119' connected t.o a rear-
wardly flaring su~face 120' that is a segment of a cone~ S:imilarly,
the member 107' has a semicylindrical surface 121' and a tapered
surface 122' which is a segment of a cone~ Rearwardly of the
surfaces 120' and 122', the members 10~' and 107' have semicylin-
drical surfaces 123 t and 124', beyond which are tapered surfaces
125' and 126' which are conical sections and converge toward the
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t'7~30
rear. A keyway 127' extends axially of the member 106' at thesurfaces 120', 123', and 125'. ~ similar keyway may be formed
in the member 106' to economiæe manufacture by making the parts
106' and 107' identical.
The back shell nut 100' includes internal threads at
its forward end which are adapted to mate with external threads
on the rearward end of the rear shell 49'. The intermediate
interior portion of the back shell nut 100' defines a rearwardly
convergent tapered surface 128' which is frustoconical and at the
same angle as the surfaces 125' and 126' of the clamp members 106'
and 107'. At the rearward end, the back shell nut has a radial
wall 129', through which is an opening 130'. The exterior of the
back shell nut 100' has a knurl 131' to enable the nut to be
rotated by hand. ---
The optical fiber 133, which extends into the plug
assembly 13', has a protective sheath 132. Sheath 132 fits snugly
within the opening 130' in the back shell nut.and extends to the
rearward end of the clamping members 106' and 107'. Howeve.r, the
sheath is stripped from the fiber 133 within the plug so that the
fiber extends through the clamp and into the front shell 48'.
The fiber 133 fits closely within the opening 93' in the wall 92'
of the rear shell 49' as it enters the plug, where it passes
through the slot 83' of the insert 82'. The forward end of the
fiber extends through the open.ing 81' in the front shell, where
it is closely received, to enter the lens cavity 38l.
.:;~ Prior to attaching the plug 13' ko the receptacle 11',.
the optical fiber 133 is extended int:o the plug and the two sec
tions of the fiber clamp 99l are positioned one on either side of
the fiber. I'he forward adjacent surfaces 134' and 135' of the
clamp members 106' and 107' flare forwardly and radially outwardly~
This enables the forward portion of the fiber clamp to be com-
pressed, reducing its radial dimension at the flanges 117' and
118'~ In this way the flanges 117l and 118l can be moved through
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the end of the rear shell 49' at the circumferential surface 95'
to enter the recess at the circumferential surface 94' of larger
diameter. The flanges 117' and 118' are narrower at their side
portions, adjacent the surfaces 134' and 135', so that there is
ample clearance at those locations to pass through the opening
defined by the surface 95'.
Next, the back shell nut 100' is tightened onto the
rearward end of the rear shell 49'. This causes the tapered sur-
face 128' of the bac~ shell nut to bear against the tapered sur-
faces 125' and 126' of the clamping members 106' and 107', urging
these members forwardly and inwardly. The forward tapered sur
faces 120' and 122' of the clamping members 106' and 107' thereby
are pressed against the tapered surface 96' at the rearward end of
the rear shell 49'. The reactions of the tapered surfaces cause
the clamping members 106' and 107' to be pressed radially toward
each other to bring their mating surfaces into firm engagement.
This in turn causes the resilient pads 1~2' and 103' to bear
against and grip the fiber 133, but without damaging the fiber
because the clamping force is limited by the engagement of the
surfaces which terminate the inward movement of the members 105'and 106'. Also, the key 97', fitting in the keyway 127', prevents
rotation of the fiber clamp g9' as the fiber is gripped.
With the optical fiber thus held in the plug assembly
13', it is then attached -to the receptacle by threading the
coupling ring 85' onto the external threads of the receptacle i
shell 17'. As this occurs, -the coupling riny, through the flange
87', presses forwardly on the rear shell 49' at the shoulder 88',
sliding the rear shell forwardly over the front shell 48' until
-the wall 92' of the rear shell 49' engages the end 65' of the
front shell 48'.
The forward movement of the rear shell, reacting through
the shoulder 57', causes the spring 54' to press against the
shoulder 56' of the ~front shell 48' to bias the front shell
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forwardly. The forward frustoconical surface 77' of the frontshell 481 engages the frustoconical surface 31' of the lens 21',
however, so that the front shell does not move forwardly; but is
pressed aga;nst the lens surface 31' by the resilient force of
the spring.
As the rear shell 49 t is moved forwardly relative -to the
front shell 48', and hence relative to the lens 21', the fiber
133 also is moved forwardly. This occurs because the fiber 133
is gripped at the clamp 99' which, through the back shell nut
100', is connected to the rear shell 49'. This moves the end of
the fiber 133 into the lens cavity 38' to engage the tapered
cavity surface.~ This positions the end of the fiber adjacent the
inner cavity surface and aligns the fiber axis with the optical
axis~of the lens'',' as~'~set~~forth in th'e aforemèntioned'`pate'nt appli-
cation for Optical Fiber Connector. The optical fluid within the
cavity 38' is displaced by the fiber 133 so that it occupies the
space between the fiber end and the inner cavity surface, with
some additional fluid around the periphery of the fiber. An ex-
cess of the fluid is provided to be sure that the cavity is en-
tirely filled beyond the fiber end.
The fiber 133, forwardly of the clamp 99', is longer
than the distance between the clamp and the inner end of the lens
cavity 38', which causes the fiber to bow within the front shell
48' at the locat:ion of the tapered surface 80! and within the
slot 83' of the insert 82'. The width of the slot 83' is close
to the diameter'of the fiber 133'so that thé direction''of the bow
in the fiber is closely controlled by the direction of the slot
83'.
The second pluy assembly is identical to the plug as-
sembly 13' so that it connects to the receptacle in the same manneras does the assembly 13'. Connection of the plug assembly 13'
to the receptacle causes the light-conductive fiber 136 of the
second plug assembly to enter the cavity 39' and bear against the
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tapered surface thereof. This aligns the fiber 136 with the axisof the cavity 39' and thus wi-th the axis of the fiber 133 so that
light can be transmitted between these two fibers. Optical fluid
ln the cavity 39' fills the space between the end of the fiber
136 and the cavity surface after the fiber enters the cavity.
The components of the second plug assembly are given
the same reference numbers as the corresponding components of
the plug assembly 13', but with the suffix l'a.ll
When the second plug assembly is connected to the
central receptacle, the frustoconical surface 77a' of its front
shell 48a' is caused to bear against the tapered lens surface 32'
in a manner similar to that occurring on the opposite side of the
lens. The lens 21' has a smaller external dimension than the
dimensions of the space within the receptacle shell which it
occupies, so that it can float a limited distance within the
receptacle shell. The outer surface 137i of the lens tapers
slightly toward either end to facilitate angular as well as recti-
linear floating movement. This enables the lens 21l to be aligned
precisely with the plug assemblies by the interengagement of the
tapered surfaces of the front plug shells with the tapered lens
surfaces. This direct centering of the plugs with the lens heIps
to accurately a]ign the fibers 133 and 136 with the lens cavities
38' and 39'.
The spring of the plug that biases the front shell
ayainst the tapered lens surEace when the connector is mated also
moves the rear shell rearwardly when the plug is disconnected.
For the plug 13', as shown in Figure 20, the spring 54' shifts
the rear shell 49' rearwardly relative to the front plug 48' until
the lock ring 42' is stopped by engagement with the shoulder 53'
of the front shell 48'. This movement of the rear shell 49' causes
.
the fiber clamp 99' to move the fiber 133 also to the rear rela-
tive to the front shell. As a result, the forward end of the
fiber 133 is retracted back into the opening 81' in the front
~.
7~
shell 48'. Therefore~ the fiber 133 does not project outwardly
where it can be damaged when the plug is disconnected, instead
being inside the plug and fully protected. This is especially
advantageous for an optical fiber connector suitable for field
use, in view of the extreme vulnerability of optical fibers to
damage. Of course, the length of the fiber 133 forwardly of the
clamp 9g' must be correlated with the travel of the rear shell 49'
to assure full retraction when disconnected and enough extension
when mated to force the fiber into the lens cavity as described
above.
As previously described, the two plug assemblies are
sequentially engaged with the fiber breaker, and such breaker is
operated to form perfect mirror ends on the fiber 133 of first
plug assembly 13' and fiber 136 of thé` second p~lug assembly.
Such mirror ends, in combination with the accurate axial alignment
achieved by the present connector, create an optimum optical
coupling.
In the appended claims, the words "clean break" and
"perfect break" are sometimes used as shorthand ways of describ-
ing a break wherein the end faces are perpendicular to the fiberaxes and are mirror smooth.
The width of the scoring edge is, very preferably, less
than 0.001 inch.
The foregoiny detailed description is to be clearly
understood as yiven by way of illustration and example only, the
spirit and scope of this invention beiny limited solely by the
appended claims.
....
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