Assembly including an optical fiber secured in a wall

In order to simply attach an optical fiber in a wall, the end porton of the fiber is enclosed by a tubular envelope. The envelope is accommodated in a holder which projects through an opening in the wall. The holder is rotatable about its longitudinal axis. The outer cylinder surface of the holder is provided with a circumferential groove. In two diametrically opposed portions, the depth of this circumferential groove is greater than the thickness of the wall of the holder so that two elongate openings are formed in the wall of the holder. The outer surface of the tubular envelope is also provided with a circumferential groove whose axial position coincides with that of the circumferential groove in the holder. A U-shaped spring is attached to the wall so that its legs are situated in the circumferential groove in the holder at the area of the elongate openings. The spring force presses the legs through these openings into the circumferential groove in the envelope so that the envelope is retained in the holder.

BACKGROUND OF THE INVENTION 
The invention relates to an optical fiber connector assembly. The assembly 
includes a wall in which an end portion of an optical fiber, which is 
enclosed by a tubular envelope, is secured. 
The wall may form part of, for example, a housing of a connector for 
connecting the optical fiber to other optical elements or another device. 
It is desirable that the tubular envelope can be mounted in the wall in a 
simple manner. In many cases it is also important that the assembly can be 
simply removed again, for example, when maintenance, modifications or 
repairs are required after some time. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide a detachable optical fiber 
connector in which the envelope can be secured in the wall and removed 
therefrom in a very easy manner. 
To achieve this, in the assembly according to the invention the tubular 
envelope is accommodated with a clearance in a holder which is shaped as a 
hollow cylinder. The holder projects through an opening in the wall, is 
rotatable about its longitudinal axis, and is provided with a 
circumferential groove on its outer cylinder surface. The depth of the 
groove at two diametrically opposed portions is greater than the wall 
thickness of the holder so that two elongate openings are formed in the 
wall of the holder. The openings extend in the circumferential direction. 
The outer surface of the tubular envelope is also provided with a 
circumferential groove whose axial position coincides with that of the 
circumferential groove in the holder. An essentially U-shaped spring is 
attached to the wall so that its legs are situated in the circumferential 
groove of the holder at the area of the elongate openings. The spring 
force then presses the legs into the circumferential groove in the 
envelope through the openings in the holder. 
The legs of the spring retain the envelope in the holder. When the holder 
is rotated 90.degree. about its axis, the legs will be situated in 
portions of the circumferential groove of the holder which have not been 
recessed so far that they form openings. As a result, the legs are lifted 
out of the circumferential groove in the envelope so that the envelope can 
be simply pulled out of the holder. 
In order to facilitate rotation of the holder, in a preferred embodiment of 
the assembly according to the invention the holder is provided with a 
non-round portion which projects from the wall. For example, the non-round 
portion may be provided with a profile which can be engaged by a tool or 
with a protrusion which can be turned by hand. 
BRIEF DESCRIPTION OF THE DRAWING 
FIG. 1 is a partly longitudinal sectional view and a partly side 
elevational view of a first embodiment of an assembly according to the 
invention; 
FIG. 2 is a partly side elevational view and a partly longitudinal 
sectional view, taken along the line II--II in FIG. 1, of a part of the 
assembly shown in FIG. 1; 
FIG. 3 is a cross-sectional view taken along the line III--III in FIG. 2; 
FIG. 4 is a cross-sectional view, corresponding to that shown in FIG. 3, of 
a second embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a portion of a wall 1 which forms part of a housing, for 
example a connector housing. In the wall 1 there is formed a round opening 
3 through which a holder 5 projects. The holder 5 is a hollow cylinder and 
is rotatable about its longitudinal axis in the opening 3. The holder 5 
accommodates a tubular envelope 7 with some clearance. An end portion of 
an optical fiber 9 is secured in the envelope. 
On the outer cylindrical surface of the holder 5 there is provided a 
circumferential groove 11. The depth of groove 11 at two diametrically 
opposed portions is greater than the wall thickness of the holder 5. 
Consequently, these portions form two elongate openings 13 in the wall of 
the holder 5. These openings extend in the circumferential direction (See, 
FIGS. 2 and 3.) 
The outer surface of the tubular envelope 7 of the optical fiber 9 is also 
provided with a circumferential groove 15. The envelope 7 is arranged in 
the holder 5 so that the axial positions of the circumferential grooves 11 
and 15 coincide. 
To the wall 1 there is also attached an essentially U-shaped spring 17. 
Spring 17 is attached to wall 1, for example, by a pin 19 which projects 
from the wall 1. The legs of the spring 17 are arranged in the 
circumferential groove 11 of the holder 5, that is to say at the area of 
the elongate openings 13. The spring 17 is proportioned so that when they 
are not in tension, the distance between the legs is smaller than the 
diameter of the tubular envelope 7 at the area of the circumferential 
groove 15 provided therein. 
Consequently, the spring force presses the legs into the circumferential 
groove 15 of the envelope 7 through the openings 13. The spring 17 thus 
retains the envelope 7 in the holder 5. Because the legs of the spring 17 
are also arranged in the circumferential groove 11 of the holder 5, the 
holder 5 is also retained in the axial direction by the spring 17. 
The holder 5 is also inserted through two rings 21 and 22 which are 
accommodated in a chamber 23 recessed in the wall 1. Between the rings 21 
and 22 there is arranged a conical, resilient ring 25 so that the spring 
17, the holder 5 and the envelope 7 have some freedom of movement in the 
axial direction. This is important, for example in connectors, in order to 
compensate for tolerances. 
The spring 17 of the embodiment shown in the FIGS. 1 to 3 is substantially 
truly U-shaped. In order to avoid excessive rigidity of the legs, the 
spring must be comparatively long. When a spring having a smaller length 
is preferred, another spring construction can be chosen, for example as 
shown in FIG. 4. 
The spring 27 shown in FIG. 4 is again essentially U-shaped, but at the 
area of the transition between the base and the legs it is bent through an 
angle of 270.degree. instead of 90.degree. as in the case of the spring 
17. Thus, equally flexible legs are obtained even though the length of the 
spring is smaller. The width, however, is slightly larger and the 
thickness (the dimension in the axial direction) is doubled. The spring 27 
can be secured to the wall 1, for example, by pressing the straight 
portion 29 of the base into a groove in the wall (not shown). 
When the holder 5 is rotated approximately 90.degree. about its 
longitudinal axis, the legs of the spring 17 or 27 engage the bottom of 
the groove 11 because the openings 13 are turned away, and because the 
spring cannot rotate together with the holder because it is secured to the 
wall 1 near its base. The legs of the spring 17 or 27 are thus pressed 
apart as shown in FIG. 4. Consequently, the legs are lifted out of the 
circumferential groove 15 in the tubular envelope 7 of the optical fiber 
9. As a result, the envelope will be loosely disposed in the holder 5 so 
that it can be easily pulled out of the holder. 
When the envelope 7 is to be mounted in the holder 5, the holder 5 is first 
moved to the position in which it has been rotated through 90.degree. as 
shown in FIG. 4. After this, the envelope 7 is slid into the holder 5 so 
far that the axial position of its circumferential groove 15 coincides 
with that of the circumferential groove 11 of the holder. Subsequently, 
the holder 5 is rotated through 90.degree. again so that the legs of the 
spring 17 or 27 are forced into the circumferential groove 15 of the 
envelope 7 via the openings 13. 
It is alternatively possible to slide the envelope 7 into the holder 5 so 
far that its circumferential groove 15 is situated beyond the 
circumferential groove 11 of the holder. After rotation of the holder 5, 
the legs of the spring 17 or 27 will then rest on the outer surface of the 
envelope 7. When the envelope 7 is subsequently pulled back slightly, the 
legs of the spring 17 or 21 will be automatically forced into the 
circumferential groove 15. 
In order to facilitate rotation of the holder 5, the holder is preferably 
provided with a non-round portion 31 which projects from the wall 1. As 
shown in FIG. 3, this portion may be provided with a protrusion 33 for 
rotating the holder 5 by hand. Alternatively the non-round portion 31 may 
have a profile which can be engaged by a tool (for example, a wrench). 
Such a profile may consist of, for example, two opposite, parallel 
surfaces 35 (see FIG. 4).