Anti-backlash automatic locking connector coupling mechanism

A coupling mechanism (11) comprising a receptacle (13) having an open cavity (31) therein, a plug (15) receivable in the cavity (31), and a rotatable coupling member (17) drivingly coupled to the plug (15) and coupling the plug (15) to the receptacle (13). A locking member (19) is mounted on the coupling member (17) for rotation with the coupling member (17) and for translation relative to the coupling member (17). A spring (21) acts between the locking member (19) and the coupling member (17) and urges the locking member (19) to translate with the coupling member (17). Translation of the locking member (19) is limited so that the spring (21) is compressed to store energy. A cam track (33) and a cam follower (105) have interlocking members which are driven into interlocking relationship by the stored energy in the spring (21) when the locking member (19) and the receptacle (13 ) are in a predetermined angular position relative to each other. The interlocking members retain the locking member (19) rotation relative to the receptacle (13).

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an automatic locking connector coupling mechanism 
of the type which is particularly adapted, but not limited to, the 
coupling of optical fibers. 
2. Description of Related Art 
It is often necessary to couple electrical conductors or optical fibers. 
This can be accomplished, for example, by utilizing a plug and a 
receptacle and a coupling member to couple the plug to the receptacle. The 
plug and receptacle carry aligned electrical conductors or optical fibers 
so that the coupling mechanism can electrically or optically couple the 
conductors or fibers, as the case may be. 
In an effort to prevent decoupling, it is common practice to provide a lock 
or detent to inhibit unlocking motion of the coupling member. For example, 
one optical fiber coupling mechanism uses a lock wire to maintain mating 
integrity of the coupling mechanism. This is undesirable because of the 
time required to lock and release the coupling mechanism using the lock 
wire. 
Other coupling mechanisms use a bayonet arrangement and a spring. This type 
of coupling mechanism allows separation of the coupling mechanism 
interface when a force greater than that generated by the spring is 
applied. While this may be permissible for some electrical coupling 
mechanisms, it cannot be tolerated in an optical fiber coupling mechanism 
because of the signal change that is produced as a result of interface 
separation. 
Friction devices have also been used in an effort to prevent accidental 
decoupling of the coupling mechanism. However, friction devices tend to 
wear relatively fast. 
SUMMARY 
This invention provides a coupling mechanism which generally overcomes 
these disadvantages. The coupling mechanism of this invention positively 
locks the coupling mechanism against interface separation, and 
consequently, axial tensile forces acting on the coupling mechanism will 
not result in interface separation. Furthermore, the coupling mechanism of 
this invention locks automatically and can be unlocked by predetermined 
sequential movements so that the coupling mechanism is easy to use. 
This invention uses energy stored in a spring to lock the coupling 
mechanism against decoupling. The energy is stored in the spring as a 
result of manipulating the components of the coupling mechanism to couple 
a plug and receptacle. After the coupling mechanism is locked, axial 
forces alone cannot bring about separation of the interface of the 
coupling mechanism. 
This invention can be embodied in a coupling mechanism which includes a 
receptacle or receptacle element having an open cavity and a plug or plug 
element receivable in the cavity. A rotatable coupling member is drivingly 
coupled to the plug and receptacle, and the coupling member couples the 
plug to the receptacle in response to rotation of the coupling member. 
The unique features of the invention relate primarily to means for locking 
the coupling member against motion that would bring about decoupling of 
the plug and the receptacle. This can be implemented by utilizing a 
locking member mounted for rotation with the coupling member and for 
translation relative to the coupling member. A resilient member acts 
between the locking member and the coupling member and urges the locking 
member to translate with the coupling member. Cooperating means on the 
locking member and the receptacle limit the translation of the locking 
member so that the resilient member is deflected by the rotation of the 
coupling member and the locking member. Accordingly, the cooperating means 
and the rotation of the coupling member and the locking member combine to 
deflect the resilient member so that energy is stored in the resilient 
member. 
The cooperating means also includes interlocking means on the locking 
member and one of the plug and the receptacle. The interlocking means 
automatically interlocks in response to the stored energy in the resilient 
member and the locking member and such one of the plug and receptacle 
being in a predetermined relative angular position. This interlocking 
retains the locking member and coupling member against rotation relative 
to such one of the plug and the receptacle so that the coupling mechanism 
cannot be unintentionally decoupled. 
With this construction, axial tensile forces on the plug and receptacle 
cannot bring about separation of the interface. Rather, to decouple the 
coupling mechanism, it is necessary to first apply an axial retraction 
force to the locking member sufficient to overcome the force of the 
resilient member and, with the locking member axially retracted, rotate 
the locking member and coupling member in the proper direction to bring 
about a loosening of the coupling member. Accordingly, unless this 
unlocking combination is employed, the coupling mechanism will not 
decouple. 
Another feature of this invention is that the stored energy in the spring 
is used to impart additional tightening rotation to the locking member and 
coupling member in response to the interlocking of the locking means. This 
automatically applies a preloading force to the optical fibers, conductors 
or other members carried by the plug and receptacle. This preloading force 
helps prevent separation of the interface by shock, vibration or thermal 
cycling. This preload generates a separating force at the interface of the 
coupling mechanism that must be restrained by the coupling mechanism. 
Although the resilient member can be compressed in different ways, this can 
advantageously be brought about by employing a cam track and a cam 
follower which are urged together by the resilient member. One of the cam 
track and the cam follower is on the locking member, and the other of the 
cam follower and the cam track is on either the plug or the receptacle. 
The cam track has a resilient member deflection section which is 
configured to bring about deflection of the resilient member as the 
coupling member and locking member are rotated. More particularly, this 
resilient member deflection section inhibits, to some desired degree, the 
translation of the locking member with the coupling member to bring about 
deflection of the resilient member and the consequent storing of energy. 
Preferably, the cam track and cam follower are also configured to provide 
the interlocking means. In a preferred construction, the interlocking 
means includes at least one recess on the cam track and at least one 
projection on the cam follower, and by urging the projection into the 
recess at a predetermined angular position, the locking member and the 
coupling member are locked against rotational movement at least in a 
direction which would allow decoupling of the plug and receptacle. The 
additional tightening rotation of the coupling member can also be provided 
by appropriately configuring the projection and the recess to include, for 
example, an inclined cam surface partly defining the recess. 
The invention, together with additional features and advantages thereof, 
may best be understood by reference to the following description taken in 
connection with the accompanying illustrative drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings in more detail, FIGS. 1 and 2 show a coupling 
mechanism 11 which comprises a receptacle or receptacle element 13, a plug 
or plug element 15, a coupling member 17, a locking member 19, and a 
resilient member in the form of a coil compression spring 21. Although the 
receptacle 13 can be of various different constructions, in this 
embodiment, it includes a base or mounting plate 23 having mounting holes 
25 for mounting the base 23 on external structure (not shown), a sleeve 27 
having external screw threads 29 and defining an open-ended cavity 31 and 
an annular cam track 33 mounted on, or integral with, the base 23 and 
extending around the inner end of the sleeve. Circumferentially spaced 
ribs 35 on the inner wall of the sleeve 27 define circumferentially spaced 
axially extending slots 37 in the cavity 31. 
The receptacle 13 has an externally threaded socket 39 (FIGS. 1 and 2) 
coaxial with the sleeve 27 and separated from the sleeve by a transverse 
wall 41 (FIG. 2). The transverse wall 41 has one or more passages 43 for 
receiving and retaining various members, such as pin terminus assemblies 
44, or which may be left open for the passage of, for example, a fluid. 
The pin terminus assemblies 44 may be conventional, and each of them 
includes a pin 45 projecting from the wall 41. Optical fibers 46 are 
coupled to the assemblies 44 in a known manner and project in the other 
direction from the wall 41. 
The cam track 33 as shown in FIGS. 1 and 3 comprises resilient member 
deflection sections 47, 49 and 51 separated circumferentially by recesses 
53, 55 and 57. Although various constructions are possible, in this 
embodiment, the sections 47, 49 and 51 are coplanar, lie in a radial plane 
and represent raised portions of the cam track 33. 
The cam track 33 has three axial surfaces 59 which define, respectively, 
one end of the recesses 53, 55 and 57. An axial surface 61 defines the 
other end of the recess 53. The other ends of the recesses 55 and 57 are 
defined by inclined cam surfaces 63. The cam track 33 defines projections 
65, 67 and 69 between adjacent recesses 53, 55 and 57. 
The plug 15 has an externally threaded socket 71 (FIGS. 1 and 2) and a 
transverse wall 73 (FIG. 2) with one or more passages 75 for receiving and 
retaining conventional identical socket terminus assemblies 76, or which 
may be left open for the passage of fluid. Each of the socket terminus 
assemblies 76 includes a socket 77 for receiving the pin 45 and is 
attached to an optical fiber 78. A series of short splines 79 is arranged 
on the exterior of the plug 15 in circumferentially spaced relationship. 
The plug 15 is sized, and the splines 79 are sized and arranged so that 
the plug can be received within the cavity 31 of the receptacle 13, with 
the splines 79 being received, respectively, in the slots 37. To assure 
that the angular relationship between the receptacle 13 and the plug 15 is 
correct, one of the slots 37' (FIG. 6) and one of the splines 79' are 
wider circumferentially than the other slots and splines. Accordingly, the 
spline 79' must be received in the slot 37', and this assures correct 
"clocking" of the plug 15 in the receptacle 13. With the plug 15 received 
in the receptacle 13 as shown in FIGS. 2 and 6, the passages 43 are in 
axial alignment with the passages 75, respectively, and the pins 45 are 
received in the sockets 77, respectively, to thereby provide accurate 
alignment and optical coupling of the optical fibers 46 and 78. 
The coupling member 17 performs a number of important functions, including 
the important function of coupling the plug 15 to the receptacle 13. The 
coupling member 17 (FIGS. 1 and 2) is annular and has an essentially 
cylindrical peripheral wall 81 with a series of circumferentially spaced, 
external splines 83 on the outer surface of the peripheral wall, internal 
threads 85 on the peripheral wall and an annular flange 87 at one end of 
the peripheral wall. 
The coupling member 17 is mounted on the plug 15 for relative rotational 
movement. Although this can be accomplished in various ways, in this 
embodiment, a radially inwardly projecting portion of the flange 87 is 
received between a shoulder 89 of the plug 15 and a retaining ring 91 as 
shown in FIG. 2. The other end of the coupling member 17 is attachable to 
the receptacle 13 by virtue of the cooperation between the threads 29 and 
85. Accordingly, by tightening of the threads 29 and 85, the coupling 
member 17 can tightly couple the plug 15 to the receptacle 13 with the 
passages 43 and 75 in axial alignment, respectively. Of course, the 
threads 29 and 85 can be replaced with various other means, such as a pin 
and slot or lugs and grooves, which are responsive to relative rotation 
between the coupling member 17 and the receptacle 13 for translating the 
coupling member on the receptacle and coupling the plug 15 to the 
receptacle. Proper axial alignment of the passages 43 and 75, 
respectively, can be further assured by the use of guide pins 93 carried 
by the transverse wall 41 being received in guide bushings 95, 
respectively, carried by the transverse wall 73. Of course, the coupling 
member 17 can be rotatably mounted on the receptacle 13 and threadedly 
attached to the plug 15, if desired. 
If the coupling member 17 were to counterrotate, it would loosen the 
coupling of the receptacle 13 to the plug 15 and tend to separate the 
interface 97 where the transverse walls 41 and 73 meet and where the pins 
45 are held in engagement with the sockets 77. To prevent this, the 
locking member 19, the spring 21 and the cam track 33 are provided. The 
locking member 19 is a tubular member having a peripheral wall 99, with a 
passage 101 extending through it, and the coupling member 17 is received 
in the passage 101, with the spring 21 lying between the locking member 
and the coupling member. The peripheral wall 99 has internal 
circumferentially spaced, axially extending slots 103 for slidably 
receiving the splines 83, respectively, as shown in FIG. 6. to thereby 
couple the locking member to the coupling member for rotation together and 
for relative translation, which in this embodiment, is relative axial 
movement. One of the slots 103' and the associated spline 83' are slightly 
larger circumferentially to thereby angularly orient the locking member 19 
and the coupling member 17. 
As shown in FIG. 2, the locking member 19 has an end portion which extends 
beyond the coupling member 17 and terminates in a cam follower 105 at an 
end of the locking member. The configuration of the cam follower 105 is 
shown laid out flat in FIG. 3, and it comprises projections 107, 109, and 
111 separated circumferentially by recesses 113, 115 and 117. Each of the 
projections 107 has a cam follower surface 119 which lies in a radial 
plane. An axial surface 121 defines the opposite ends of the projection 
107 and one end of the projections 109 and 111. The opposite ends of the 
projections 109 and 111 are defined by an inclined cam follower surface 
123. 
The spring 21 acts between the locking member 19 and the coupling member 17 
and urges the locking member to translate with the coupling member. In 
this embodiment, the spring 21 engages a radially outwardly projecting 
portion of the flange 87 of the coupling member 17 and an internal annular 
shoulder 125 (FIG. 2) of the locking member. 
Although the spring 21 could have various different cross sections, 
preferably it is constructed of flat wire having a plurality of windings 
127, 129 and 131 of progressively increasing diameter so that, when 
compressed, each of the windings can be at least partially received within 
an adjacent winding. In this embodiment, when fully compressed, the spring 
21 is in a spiral configuration with all of the windings being in radial 
alignment. A spring of this type allows for greater compression for a 
given unstressed length of the spring and, therefore, contributes to 
compactness. 
The end of the locking member 19 opposite the cam follower 105 carries a 
retaining ring 133 (FIGS. 1 and 2). This retaining ring 113 limits 
expansion of the spring 21 in the position of FIG. 4. 
With the components of the coupling mechanism 11 assembled as shown in FIG. 
2, the spring 21 acts between the coupling member 19 and the locking 
member 17 to resiliently bias the locking member to the left as viewed in 
FIG. 2 so that the cam follower 105 is urged against the cam track 33. 
More specifically, the cam follower surfaces 119 slide along the sections 
47, 49 and 51 of the cam track 33 as the locking member 19 and the 
coupling member 17 are rotated as a unit. As rotation of the members 17 
and 19 continues, the threads 29 and 85 cooperate to draw the plug 15 more 
tightly into the receptacle 13. Rotation of the members 17 and 19 also 
translates the coupling member 17 axially along the plug 15, but 
translation of the locking member 19 is prevented by virtue of the sliding 
contact between the cam follower surfaces 119 and the sections 47, 49 and 
51 of the cam track 33. Accordingly, the spring 21 is deflected, and in 
this embodiment, is compressed by rotation of the coupling member 17 and 
the locking member 19 to store energy in the spring 21. More specifically, 
the sections 47, 49 and 51 of the cam track 33 are configured to bring 
about compression of the spring 21 by virtue of, in this embodiment, not 
allowing the locking member 19 to translate with the coupling member 17. 
When the members 17 and 19 are rotated in the direction of the arrow in 
FIG. 3 slightly beyond the position shown in FIG. 3, the projections 107, 
109 and 111 are axially aligned with the recesses 53, 55 and 57, 
respectively, and can be urged into these recesses by the energy stored in 
the spring 21. This automatically locks the locking member 19 and the 
coupling member 17 against counterrotational movements that would decouple 
the coupling mechanism 11. The projections 107, 109 and 111 and the 
corresponding recesses 53, 55 and 57 comprise interlocking means which are 
responsive to the stored energy in the spring 21 and to the locking member 
19 and the receptacle 13 being in a predetermined relative angular 
position to interlock to retain the locking member 19 and, hence, the 
coupling member 17 against rotation relative to the receptacle 13. 
Similarly, the projections 65, 67 and 69 and the associated recesses 113, 
115 and 117 also form part of the interlocking means. Of course, the 
threads 29 and 85, the angular orientation of the locking member 19 and 
coupling member 17, and the cam track 33 and the cam follower 105 are 
constructed and arranged so that the threads 29 and 85 are tight, and the 
plug 15 is tightly held in the cavity 31 as shown in FIG. 2 when the 
projections 107, 109 and 111 enter their respective recesses. 
As shown in FIGS. 5 and 7, the projection 107 is circumferentially shorter 
than the associated recess 53, but the projections 109 and 111 fit 
relatively snugly within the associated recesses 55 and 57. Similarly, the 
projection 65 fits loosely within the recess 113, and the projections 67 
and 69 fit more snugly within the associated recesses 117 and 115. 
Another feature of the invention is that the cam surfaces 63 cooperate with 
the inclined follower surfaces 123 to impart additional rotation to the 
locking member 19 relative to the receptacle 13 in a direction that will 
tighten the coupling member 17 on the receptacle. This added bit of 
rotation of the coupling member 17 in a tightening direction preloads the 
walls 41 and 73 against each other and holds the pins 45 tightly in the 
sockets 77. This additional rotation occurs in response to the initiation 
of the interlocking of the interlocking means. The looseness of the 
projections 107 and 65 in their associated recesses allows this additional 
rotation to occur without interference that might be caused by tolerances. 
With the projections 107, 109 and 111 received in the recesses 53, 55 and 
57, respectively, the spring 21 expands somewhat from the position shown 
in FIG. 2. However, the spring 21 continues to strongly bias the 
projections 107, 109 and 111 into their associated recesses. The retaining 
ring 133 serves as a stop for the locking member 19 and limits the 
expansion of the spring 21 after the projections 107, 109 and 111 are 
pushed into their associated recesses in the cam track 33. 
With the coupling mechanism 11 in the position shown in FIG. 4, axial 
tension forces exerted on the receptacle 13 and the plug 15 are resisted 
by the threads 29 and 85, and so the coupling mechanism 11 cannot separate 
at the interface 97. Furthermore, even if the axial tension force is 
applied to the receptacle 13 and the locking member 19 and even if the 
tensile force is greater than the spring force 21, the only effect will be 
to withdraw the locking member 19 axially to the right as viewed in FIG. 
4. If the force exists for a sufficient time, this may withdraw the 
projections 107, 109 and 111 from the associated recesses, but even this 
will not separate the coupling mechanism 11 at the interface 97 because 
the threads 29 and 85 prevent this. 
To decouple the coupling mechanism 11, it is necessary to retract the 
locking member 19 against the biasing force of the spring 21 sufficiently 
to withdraw the projections 107, 109 and 111 from their associated 
recesses in the cam track 33. With the locking member 19 withdrawn in this 
manner, a rotational force is then applied to the locking member 19 in a 
direction to unscrew the threads 29 and 85. The receptacle 13 and the plug 
15 can then be completely decoupled by completely unthreading the coupling 
member 17 from the receptacle 13. 
FIG. 8 shows a coupling mechanism 11a which is identical to the coupling 
mechanism 11 in all respects not shown or described herein. Portions of 
the coupling mechanism lla corresponding to portions of the coupling 
mechanism 11 are designated by corresponding reference numerals followed 
by the letter "a." 
The primary difference between the coupling mechanisms 11 and 11a is that 
the latter is adapted to couple electrical conductors 46a and 78a rather 
than the optical fibers 46 and 78. For this purpose, the transverse walls 
41 and 73 of the coupling mechanism 11 are replaced by dielectric inserts 
151 and 153, respectively, with these inserts being retained against 
shoulders 155 and 157 by threaded retaining rings 159. Annular seals 161, 
which may be O-rings, provide moisture protection at the interface 97a. 
The inserts 151 and 153 carry the pin contact assemblies 44a and socket 
contact assemblies 76a in a conventional manner, and an electrically 
conductive coupling is provided between the conductors at or adjacent the 
interface 97. 
Although exemplary embodiments of the invention have been shown and 
described, many changes, modifications and substitutions may be made by 
one having ordinary skill in the art without necessarily departing from 
the spirit and scope of this invention.