OPTICAL FIBRE CONTACT ASSEMBLY

Abstract: An optic fiber contact assembly is described, which can be installed in a contact hole 14 of a connector housing (12) that was designed for holding front release electrical contacts. The assembly includes a central tube (64) which holds the end of an optical fiber (66), an outer sleeve (60) which surrounds the tube and which fits within the contact hole and is held by a front release clip (56) therein, and a coil spring (86) lying be­ tween the front ends of the tube and sleeve for biasing the tube forwardly. A guide sleeve clips onto the front of the tube, so the spring can be compressed between the rear end of the guide sleeve and a shoulder on the outer sleeve. The spring is pre-loaded by a clip which lies between the rear end of the outer sleeve and a shoulder formed on the rear end of the tube.

Description: There are many instances in which electrical conductors are replaced with optic fibers. The replacement can be facilitated by using the same connectors for connecting the ends of two optical fibers, that were previously used to connect the ends of a pair of electrical conductors, by replacing some or all of the electrical contact assemblies with optic fiber contact assemblies. Difficulties can be encountered in making such a replacement because of the difference in the way in which a pair of electrical contacts are coupled, with the way in which a pair of optic fibers are coupled. A pair of electrical contacts are often coupled by having a pin contact of one conductor enter a socket contact of the other conductor, with the socket contact having resilient arms that press against the side of the pin contact to make electrical contact therewith. In optical coupling, a pair of optic fibers are coupled by pressing their extreme tips in abutment. Such abutment must be maintained without even a minute gap between them. This requires that one of the optic fiber contacts be spring biased towards the other, to assure firm abutment of the ends even if there is slight movement due to vibration or other causes. An example of an optic fiber contact assembly is disclosed in U.S. Patent Serial No. 4,178,068. In this assembly an outer sleeve is crimped on to an optic fiber receiving tube and the optic fiber cable. The outer sleeve is slidably engaged by a retaining clip with a biasing coil spring for the optic fiber receiving tube being located between the forwardly facing end of the retaining clip and a rearwardly facing shoulder on the fiber receiving tube. The present invention, however, is concerned with the pre-loading of such biasing springs. The pre-loading of the spring can be accomplished in a specially-designed connector contact hole, by pushing a guide sleeve at the front of the contact assembly against a shoulder formed near the front of the contact hole to compress the spring. However, the presence of such a shoulder at the front of the hole would prevent front release of the contact assembly, which is often a desirable feature. Furthermore, present connector housings that are designed for holding electrical contacts, are not constructed with such a shoulder near the front. An optical fiber contact assembly which was constructed so it could fit in the contact holes of a connector housing, where the contact holes do not have an undercut forming a shoulder near the front of the hole, would facilitate conversion of existing electrical connectors to optic fiber connectors. In accordance with the present invention there is provided an optic fiber contact assembly adapted to be installed in a connector housing having contact-receiving holes devoid of undercuts at the front ends thereof and each capable alternatively to receive said contact assembly or an electrical contact, the optic fiber assembly comprising an optic fiber tube, an outer sleeve having forward and rearward ends and engageable by a retaining clip for retaining the assembly within the contact-receiving hole of the housing and a coil loading spring for the optic fiber tube, characterised in that the outer sleeve has a shaped front release contact retaining-clip engaging portion and a forwardly-facing spring abutting shoulder, in that the optic fibre tube is slidable within the outer sleeve and has a forward end portion protruding forward of the forward end of the outer sleeve, the tube having rearwardly-facing abutment means associated therewith and having a reduced diameter in the rearward section thereof to provide a forwardly facing shoulder spaced rearward of the rearwardly-facing abutment means, and in that a coil spring within the outer sleeve surrounds the tube and has a rearward end which lies adjacent to the spring-abutting shoulder of the outer sleeve and a forward end which lies adjacent to the rearwardly-facing abutment means associated with tube, further characterised in that a spring pre-loading clip is removably mounted on the tube so that it abuts the forwardly-facing shoulder of the tube and the rearward end of the outer sleeve and in that the pre-loading clip has a sufficient length to displace the tube rearwardly relative to the outer sleeve far enough to compress the coil spring along its length. The pre-loading clip may comprise a longitudinally split resilient clip. The present invention also provides a method of assembling an optic fiber contact assembly as set forth in the two preceding paragraphs in a contact-receiving hole of the connector housing, characterised by the step of sliding the tube with an optic fiber therein forwardly into the outer sleeve until the forwardly facing shoulder on the tube substantially abuts the rearward end of the outer sleeve, the tube being long enough so that the forward end portion then lies forward of the forward end of the outer sleeve and there being a rearwardly facing shoulder on the abutment means and a forwardly facing shoulder on the sleeve and located behind the rearwardly facing shoulder, characterised by the step of installing a coil spring over the forward end of the tube so that the spring is located between the rearwardly facing shoulder on the abutment means and the forwardly facing shoulder on the sleeve, characterised by the step of moving the tube rearwardly with respect to the outer sleeve by a predetermined amount that compresses the coil spring, characterised by the step of installing the spring pre-loading clip around the tube at a location between the forward-facing shoulder on the tube and the rearward-facing shoulder of the outer sleeve, the clip being long enough to keep the spring under compression, and characterised by the step of installing the outer sleeve together with the tube and optic fibre and pre-loading clip into the rear end of the contact receiving hole and deep into the contact hole until a front release retaining clip lockingly engages the outer sleeve. Figure 1 is a perspective view of a connector system of the present invention with the connectors separated. Figure 2 is a sectional view of an optic fiber contact assembly of other art. Figure 3 is a sectional view of the connector in Figure 1, showing an optic fiber contact assembly of the present invention, in a fully installed configuration. Figure 4 is a sectional view of the contact assembly in Figure 3, shown during its assembly. Figure 5 is a perspective view of the clip of the assembly of Figure 3. Figure 6 is a view taken on the line 6-6 of Figure 3, but without the mating contact. Figure 1 illustrates a connector 10 which includes a housing 12 with a plurality of contact receiving holes 14 for holdings female or socket contacts. The connector 10 can be mated with another connector 16 which has a plurality of male or pin type contacts 18 which can be plugged into the socket contacts lying in the contact holes 14. Mating of the connectors is achieved by bringing them together at a proper orientation governed by a key (not shown) and turning a threaded shell 20 so its internal threads engage the external threads on the connector 16, to draw the plug contacts 18 firmly into the socket contacts in the holes 14. The connector 10 is of the front release type which permits replacement of a socket contact by inserting a release tool into the front end 14f of a hole until the tool releases a clip deep within the hole to allow the contact to be pulled in a rearward direction R out of the housing. This type of connector has been widely used with electrical contacts wherein each socket contact had arms which received a pin contact of a shape similar to contact 18 and pressed against its outside. There are many instances where it is desirable to replace the electrical contacts with optical fiber contacts, wherein the coupling of two fiber ends is accomplished by having their tips press firmly against one another. A spring pressure must be maintained at all times to assure that the tips are constantly pressed against one another with moderate pressure. Difficulties can be experienced in trying to install an optical fiber contact assembly in a hole 14 that is designed for holding a simple electrical socket contact. Figure 2 illustrates an optic fiber contact assembly 20 which has been designed by the assignee of the present application. This contact assembly 20 has been designed for installation in a connector housing 22 that is designed especially for this contact assembly 20. In particular, each contact-receiving hole 24 has an undercut 26 which forms a rearwardly-facing shoulder 28. The contact assembly includes an outer sleeve 30 which can be pushed in a forward direction F into the hole 24 until a rear release clip 32 engages the sleeve to hold it in position. During the forward movement of the outer sleeve 30, a forwardly-facing shoulder 34 on the outer sleeve compresses a spring 36 against the rear of a guide sleeve 38. The front of the guide sleeve presses against the shoulder 28 to enable compression of the spring. The guide sleeve 38 is clipped onto the front of a tube 40 which surrounds and is bonded to an optical fiber 42. Thus, the shoulder 28 formed at the front end of the hole 24 provides a relatively simple method for compressing the spring 36 during installation of the contact assembly in the hole of the housing. The presence of the shoulder 28 prevents release of the contact assembly by a common front release tool inserted into the front of the hole 24. This can be a disadvantage in ease of replacement of a damaged socket contact. Of even greater importance in many applications, is the fact that the undercut 26 and corresponding shoulder 28 are not present in connector housings that have been used to hold electrical contacts. This would prevent retrofitting of the optic fiber contacts in such prior electrical contact connectors. Figure 3 illustrates a connector assembly 50 constructed in accordance with the present invention, which can be installed in a contact-receiving hole 14 of an insulator 52 of a housing 12. The housing 12 also includes an internal groove 54 which holds a contact retaining clip 56. In this case, the housing 12 has been previously used to hold a front release electrical contact. The contact assembly 50 can be retrofitted into the housing 12 by removing the previous electrical contact and installing the optical fiber contact assembly 50 in its place. The contact assembly 50 includes an outer sleeve 60 with a retainer-clip engaging portion 62 which can be engaged by the retaining clip 56 to hold the outer sleeve in place, in the same manner as an electrical contact is held in place. The contact assembly also includes an optic fiber tube 64 which lies within the outer sleeve 60. An optic fiber 66 lies within the tube and is bonded thereto. The optic fiber has a forward end 68 which is ground and polished flat, and which can abut the end of another optic fiber 70 of a male contact 18 to couple the two optic fibers. It may be noted that the optic fiber 68 has several layers of jacketing thereof, which lie within more rearward sections of the tube 64. A guide sleeve 72 of the connector assembly is attached to the front portion of the tube 64 and extends forwardly thereof. The front of the guide sleeve guides a pin contact 18 into alignment with the tube 64. The guide sleeve 72 forms a continuous ring at its forward portion 74, but has three slots extending along its rearward portion to form three fingers 76 that can pass around the forward end portion 78 of the tube until a rear end 80 of the arms fall into a groove or recess 82 in the tube. The rear ends 80 of the arms can then abut a rearwardly-facing shoulder or ledge 84 on the tube to hold the guide sleeve in place. A coil spring 86 lies in the clearance space between the forward portions of the outer sleeve 60 and the tube 64. The rear end of the spring can press against a forwardly-facing shoulder 88 on the outer sleeve, while the front end of the spring can press against the rear end 80 of the guide sleeve. When a pin contact 18 is pressed firmly against the tip or front end 68 of the optic fiber and tube, the spring 86 is compressed. During the time when the connectors of Figure 1 are mated, the spring is compressed. As a result, if there is vibration or the like which causes the pin contact 18 and housing 12 to separate slightly the spring will constantly force the tip 68 of the tube and fiber combination forwardly into firm contact with the tip of the pin contact 18. It is important that the coil spring 86 be maintained under at least slight compression prior to mating of the socket contact assembly 50 with the pin contact 18. Such pre-compression assures that even when the pin contact 18 is forced inward only a small distance after contacting the front end 68 of the tube and fiber combination, that the spring will be compressed to constantly push the tip of the tube forwardly. Applicant maintains such pre-compression or pre-loading of the spring by the use of a spring pre-load clip 90. The clip 90 lies between a forwardly-facing shoulder 92 on the rear portion 94 of the tube, and a rearwardly-facing shoulder 96 on the rear portion 98 of the outer sleeve. The clip has a predetermined length, which assures that the tip 68 of the tube and fiber combination will lie a predetermined distance D behind the forward face 12f of the housing of the connector, the distance D being long enough to assure that the coil spring will be partially compressed. The contact assembly 50 is assembled by first projecting an optic fiber device 100, whose forward portion has been stripped of various portions of its jacket, through a rubber grommet 102 of the connector housing. The optic fiber tube 64 may be already installed around the front of the optic fiber. As shown in Figure 4, the outer sleeve 60 is slid over the front of the tube until shoulders 96,92 on the rearward portions of the outer sleeve and tube substantially abut one another. The coil spring 86 is then slid into the clearance space 104 between the front portions of the outer sleeve and tube. The forward end 78 of the tube then lies forward enough that the tube ledge 84 is forward of the forward end of the outer sleeve. This allows the arms 76 of the guide sleeve 72 to expand around the forward end of the tube and snap behind the tube ledge 84. The tube 64 is then moved rearwardly so the spring 86 is compressed, until there is sufficient space between the shoulders 92, 96 at the rearward portions of the tube and outer sleeve to allow the clip 90 to be clipped around the tube just forward of its shoulder 92. The guide sleeve 72 is then far enough back that a bearing portion 106 on it can ride within the inside of the outer sleeve. The assembled contact assembly can then be projected through the rearward end of the insulator 52 until the assembly reaches the position shown in Figure 3, wherein the retaining clip 56 snaps into the recess 62 in the outer sleeve. The contact assembly can be replaced, when damaged, by inserting a cylindrical front release tool (not shown) into the front end of the contact hole 14, and sliding it around the outer sleeve 60 until the rear of the release tool engages the front of the retaining clip 56. Rearward pressure on the front of the clip 56 causes it to expand, and allow rearward movement of the contact assembly 50 out of the hole 14 in the housing. The contact assembly 50 can therefore be removed by a front release tool and reinstalled, all in the same manner as a front release electrical contact which can alternatively be installed in the housing 12. This allows rapid replacement of an electrical contact with an optic fiber contact assembly, during switchover between electrical to optic fiber signal-carrying conduits. Both electrical and optic fiber contacts can lie in the same connector, and Fig. 1 shows one electrical contact 11. Thus, the invention provides a retrofittable optic fiber contact assembly, which can be installed in a contact-receiving hole of a housing that can alternatively hold a common front release electrical contact. Such a hole is devoid of an undercut at its front end for use in compressing a coil spring. Applicant is able to compress the coil spring so it is pre-loaded, and so the tip of the optic fiber tube and the optic fiber therein lie a predetermined distance rearward of the front face 12f of the housing. The position of the tip 68 of the tube and fiber combination is assured by the fact that the clip 90 holds the tube shoulder 92 a predetermined distance behind the outer sleeve shoulder 96. The outer sleeve is held at a predetermined location within the housing 12. Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.

Claims: An optic fiber contact assembly adapted to be installed in a connector housing having contact-receiving holes devoid of undercuts at the front ends thereof and each capable alternatively to receive said contact assembly or an electrical contact, the optic fiber assembly comprising an optic fiber tube, an outer sleeve having forward and rearward ends and engageable by a retaining clip for retaining the assembly within the contact-receiving hole of the housing and a coil loading spring for the optic fiber tube, characterised in that the outer sleeve (60) has a shaped front release contact retaining-clip engaging portion (62) and a forwardly-facing spring abutting shoulder (88), in that the optic fibre tube (64) is slidable within the outer sleeve (60) and has a forward end portion (78) protruding forward of the forward end of the outer sleeve, the tube (64) having rearwardly-facing abutment means (80) associated therewith and having a reduced diameter in the rearward section thereof to provide a forwardly facing shoulder (92) spaced rearward of the rearwardly-facing abutment means (80), and in that a coil spring (86) within the outer sleeve surrounds the tube (64) and has a rearward end which lies adjacent to the spring-abutting shoulder (88) of the outer sleeve (60) and a forward end which lies adjacent to the rearwardly-facing abutment means (80) associated with tube (64), further characterised in that a spring pre-loading clip (90) is removably mounted on the tube (64) so that it abuts the forwardly-facing shoulder (92) of the tube and the rearward end (96) of the outer sleeve (60) and in that the pre-loading clip (90) has a sufficient length to displace the tube (64) rearwardly relative to the outer sleeve (60) far enough to compress the coil spring along its length. An optic fiber contact assembly as claimed in claim 2, characterised in that the pre-loading clip comprises a longitudinally split resilient clip (90). A method of assembling an optic fiber contact assembly as claimed in claim 1 or claim 2 in a contact-receiving hole (14) of the connector housing, characterised by the step of sliding the tube (64) with an optic fiber (66) therein forwardly into the outer sleeve (60) until the forwardly facing shoulder (92) on the tube (64) substantially abuts the rearward end (96) of the outer sleeve (60), the tube (64) being long enough so that the forward end portion (78) then lies forward of the forward end of the outer sleeve and there being a rearwardly facing shoulder on the abutment means (80) and a forwardly facing shoulder (88) on the sleeve (60) and located behind the rearwardly facing shoulder, further characterised by the step of installing a coil spring (86) over the forward end (78) of the tube (64) so that the spring is located between the rearwardly facing shoulder on the abutment means (80) and the forwardly facing shoulder (88) on the sleeve (60), further characterised by the step of moving the tube (64) rearwardly with respect to the outer sleeve (60) by a predetermined amount that compresses the coil spring (86), further characterised by the step of installing the spring pre-loading clip (90) around the tube (64) at a location between the forward-facing shoulder (92) on the tube and the rearward-facing shoulder (96) of the outer sleeve, the clip (90) being long enough to keep the spring under compression, and further characterised by the step of installing the outer sleeve (60) together with the tube (64) and optic fiber (66) and pre-loading clip (90) into the rear end of the contact receiving hole (14) and deep into the contact hole until a front release retaining clip (56) lockingly engages the outer sleeve (64).

Inventors: CORRALES, PATRICK GILBERT
Applicants: ITT INDUSTRIES INC.
Application year: 1986
Main classification: G02B6
IPC codes: G02B6