GB2280281A

GB2280281A - Lockable connector

Info

Publication number: GB2280281A
Application number: GB9412854A
Authority: GB
Inventors: Simon Charles Tristan Benton; Matthew John Polaine
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-06-26
Filing date: 1994-06-27
Publication date: 1995-01-25
Anticipated expiration: 2014-06-27
Also published as: GB2280281B; GB9412854D0

Abstract

A connector for connecting optical fibre cables to terminal fittings on a patchboard has a lock which prevents unauthorised connection or disconnection of the cable from or to the patch board. The lock 11, 12, 13 is coaxial with the cable on which the connector is to operate, and has a cover 1 which is locked over a terminal fitting but which can be moved axially to a position in which it is connected to the terminal fitting so that the fitting can be rotated by gripping and turning the cover. <IMAGE>

Description

LOCKABLE CONNECTOR The invention relates to lockable connectors and particularly to optical fibre cable connectors including a security device for preventing unauthorised disconnection of the connector. The invention may also be applied to copper cables which need to be tamper-proof connected.

Optical fibre cable is being increasingly used for telecommunications and data transmissions. The core of the fibre acts as a wave guide transmission media for optical signals. Hitherto the power level of the signals have been relatively low. However with increasing power levels and particularly with communication systems in which the information is transmitted in bursts there is a serious risk of eye damage if a connector can be readily removed and pointed towards the face.

Additionally although it is difficult to make an unauthorised tap into optical fibre, it is less difficult and not so easily detectable to tap into copper cable.

Therefore a need has arisen for a security device for maintaining connections against unauthorised disconnection.

One of the problems encountered with optical fibre cable connectors is signal transmission losses.

Optical fibre cable is flexible however if it is bent below a predetermined radius dependant upon the type of fibre and transmission frequency, the fibre no longer acts as an effective wave guide and attenuation losses become excessive so that the power of the transmitted signal is dramatically reduced. It is therefore necessary to limit the degree of bending of the optical fibre cable particularly adjacent to the connection point.

The present invention seeks to provide a lockable connector, particularly for an optical fibre cable connector arrangement.

According to the present invention there is provided a lockable connector for connecting an optical fibre cable to a terminal fitting, the connector comprising a connection portion, a shroud surrounding the connection portion, at least part of the shroud being held by a lock in a position where it is freely rotatable around the connection portion and being movable, when the lock is unlocked, to a position where it is connected to the connection portion, for rotation therewith.

Preferably the actuator enables both rotational and axial movement necessary to release a bayonet fitting connection.

However the actuator may be arranged to provide only rotational movement if the connector fitting is a screw fitting. A bend limiter, for an optical fibre connector may be provided between the security lock device and the connector fitting whether it is of the screw or bayonet type of fitting so that the access provided to the actuator is spaced further from the connector fitting at the mating end of the connector so as to enable a number of similar cable connectors to be mounted on a patch board in close proximity.

The security lock device may comprise a set of combination wheels or a snap-fitting key and lock device which may, in use, be covered with a tamper tell-tale sheath extending over the connector for at least the bend limitation section.

If necessary, the tail of the fibre entering the connector may be fitted with a strain relief tail. In such an arrangement the security lock device has an integral strain relief tail, which, when used in conjunction with the bend limiter gives initial bend restraint until greater loads are applied and the action of the bend limiter comes into effect.

The invention will now be further described, by way of example, with reference to the accompanying drawing in which: Figure 1 shows an exploded view of the lockable connector; Figure 2 shows the assembled connector and a mating bulkhead uniter connector; Figure 3 shows a lockable connector including bend limiter; and Figure 4 shows an alternative form of security lock device for the lockable connector as shown in figures 1 to 3.

Figure 1 shows a lockable connector for an optical fibre cable. The connector has a bayonet fitting 2 for connection to a separate terminal fitting 30 fixed in a panel 32 (Figure 2). A fibre cable 34 to be connected passes through the connector.

The bayonet fitting 2 is attached to an actuating sleeve 4.

The sleeve 4 surrounds the cable 34 and extends away from the terminal end of the connector. Rotation of the bayonet fitting 2 or of the sleeve 4 connects or disconnects the connector.

When the connector is locked, both the bayonet fitting itself and the actuating sleeve are hidden inside a shroud.

In this condition, the shroud is freely rotatable around the bayonet fitting/actuating sleeve without producing rotation of either of these parts. The shroud is also prevented from moving axially relative to the sleeve. The connector cannot therefore be connected to or disconnected from a terminal fitting.

When the connector is unlocked, part of the shroud can move axially relative to the sleeve, so that an internal formation on the movable shroud part engages with a radial projection on the sleeve. Once this engagement is made, rotation of the shroud part rotates the actuating sleeve which allows connection/disconnection of the connector and a terminal fitting.

The shroud comprises an end cap 1 and a locking whiptail 9 with a lock 10, all of locating on a body 7. The actuating sleeve has an integral boss 6.

The end cap 1 is shown in cross section to illustrate how its bore 14 cooperates with the body 7. During assembly of the connector, the end cap 1 is pushed onto the body 7 and the O-ring 5 sits down the tapered shoulder 7a. However, if an attempt is made to remove the end cap 1 then the O-ring rides up the tapered shoulder 7a and wedges against the bore 14 making it very much harder to remove the end cap 1. It has been found that the force required to remove the end cap may be at least 4 times greater than the force required for assembly. In addition to the O-ring arrangement the end cap 1 is provided with a slot 17 which, during assembly, cooperates with lugs 16 on the body 7 which enables the end cap 1 to be snapped into position so that the lugs 16 engage in the slot 17 in the end cap 1. The end cap is therefore free to move around the axis of the body 7, but is prevented from moving axially relative to the body.

A combination security lock device comprises a first lock member 15 which forms part of the bsdy 7 but is free to rotate relative to the actuator sleeve 4 and a second lock member 11 which forms part of the whiptail 9 which itself is part of the shroud. The lock is assembled by placing combination rings 12 over the first lock member on which the rings are free to rotate but locked axially. In one particular rotational position (the lock 'unlocked' position), a castellated section on the second member 11 of the lock can be pushed into the first section. Spinning the rings to any other position results in the second member being held axially to the first.

The actuating sleeve 4 is secured to the bayonet fitting 2 so that turning the sleeve enables the connector to be engaged and locked into a mating optical terminal 32 of the type shown in Figure 2. The bayonet fitting 2 is a proprietary item having a spigot guide 18 which enables the bayonet female fitting 19 to be lined-up and engaged with the male spigot of the bayonet fitting as illustrated in the terminal arrangement shown in Figure 2.

Within the body 7 there is located a cup shaped boss 6, attached to the actuating sleeve 4. The boss 6 encompasses a chamber with two portions 6a and 6b. The body 7 is shown partly in cross section to illustrate how the cup shaped boss 6 is located and can freely rotate.

When the second lock member 11 is fully inserted and locked in the body 7, a dog 8 at the inner end of the member 11 lies in the chamber 6a of the boss 6 within which it can rotate freely. However when the lock is unlocked and the lock member is able to move axially, the dog 8 comes to lie in the chamber portion 6b where the dog is received in a recess which ensures that rotation of the second lock member produces rotation of the boss 6 and of the actuating sleeve 4 to allow disconnection of the bayonet fitting 2. This allows a fibre guide 20 on the bayonet fitting 2 to be withdrawn from the mating section on the patchboard terminal arrangement.

The lockable connector is particularly useful for connecting optical fibre cable into a multi position patchboard. In such patchboards the terminal arrangements are located in close proximity which may make access to the actuator 4 for disconnection and connection difficult.

The bayonet fitting 2 may be a proprietary bayonet fitting of the bayonet or screw fitting type and is generally made of diecast metal or similar rigid material such as acetal.

The guide 19 carries a ceramic ferrule with a micro hole through which the stripped optical fibre is threaded. The end of the fibre may be cleaved and is polished flush with the end face of the guide 19. The guide 19 is accurately located in a zirconia sleeve in the mating uniter connector, shown in Figure 3, so that the mating optical fibres are aligned. Although the material for the lockable connector may be chosen according to a particular application, in the preferred embodiment the actuating sleeve 4 is preferably nylon or polytetrafluoroethylene (PTFE). The O-ring 5 may be a synthetic rubber, such as Neoprene. The combination rings 12 and the second lock member 11 may be glass filled nylon (GFN). The locking whiptail 9 and the bend limiter which will now be described in more detail with reference to Figure 3 may be a hard flexible material such as a hybrid nylon/polypropylene mixture.

Referring now to Figure 3 in which the components of Figures 1 and 2 have been given the same reference numerals, the lockable connector shown there additionally includes a bend limiter section 21 which may be similar in form to that described in European Patent 0 260 774. It may be necessary to include an extension section in the form of a bend limiter section 21 in the lockable connector firstly to space the locking/unlocking function of the actuator from the free end of the lockable connector and secondly to ensure that the fibre is not bent beyond a critical radius at which transmission losses become excessive. The lockable connector at Figure 3 is particularly suitable for use with patchboards having a large number of mating terminal arrangements (not shown) into each of which a lockable connector as shown in Figure 3 is inserted. This enables the whiptail end of the lockable connector to be displaced relative to adjacent connectors and unlocked so that it can be slid back along the cable to make a rotation-locked connection with the actuating sleeve 4. The connector is then operated in the same manner as previously described for the embodiment of Figures 1 and 2.

The combination lock device may be replaced by a mechanical key actuated lock as shown in Figure 4. A mechanical lock can act in the same way as the combination lock already described in preventing, when locked, relative axial movement between the body 7 and the actuating sleeve 4 whilst allowing relative rotation and in allowing, when unlocked, sufficient relative axial movement to produce engagement between a dog on either the body or the sleeve to ensure that the two parts thereafter rotate together.

Equivalent mechanical engagement systems could alternatively be employed.

Referring now to Figure 4 the locking device consists of a key 22 having tines 23 and 24 which may be entered in keyways 25 and 26 respectively in lock plate 27 set adjacent to the castellated section 11 which engage with the castellated section 11 to bend the section away from the fixed cooperating faces of the lock beneath the lock plate 27. Insertion of the key 22 in the keyways 25 and 26 unlocks section 11 to permit the actuator 4 to be exposed so that a bayonet or screw fitting may be disengaged by rotation and if necessary longitudinal motion of the actuator 4. The shapes of the tines 23 and 24 and the keyways 25 and 26 may be varied as known by locksmiths to create a unique set of keys. It will be appreciated that with the three ring combination shown in Figures 1 to 3 there are up to 216 combinations. If further combinations are required further rings may be added to the combination set. As shown in Figure 4 the locking device may be mounted so that the combination rings or the lock plate 27, which are integral with the whiptail 9, are separated from the section 11 by operation of the key 22 or the combination.

By means of the present invention the connector may be securely locked in position on a patchboard or into a mating uniter connector mounted on a bulk head so that it cannot be removed except by an authorised person having the combination or key. If necessary tamper tell-tale tape can be secured over the combination rings and the bend limiter section may be sheathed in synthetic rubber.

It will be appreciated that the end cap 1 is sufficiently rigid to prevent the transmission of stress, for example when applied by pliers, so that the bayonet fitting 2 cannot be removed from the mating optical terminal 32 except through manipulation of the actuator 4.

Claims

1. A lockable connector for connecting an optical fibre cable to a terminal fitting, the connector comprising a connection portion, a shroud surrounding the connection portion, at least part of the shroud being held by a lock in a position where it is freely rotatable around the connection portion and being movable, when the lock is unlocked, to a position where it is connected to the connection portion, for rotation therewith.

2. A connector as claimed in Claim 1, wherein the shroud is in two parts, one part being permanently freely rotatable relative to the connection portion and the other part being either rotatable or non-rotatable relative to the connection portion, depending on the state of the lock.

3. A connector as claimed in Claim 1 or Claim 2, wherein the connection portion comprises a terminal fitting and an actuating sleeve secured to the terminal fitting and providing a passage for an optical fibre cable.

4. A connector as claimed in Claim 3, wherein the sleeve includes a boss attached thereto, the boss having a recess for engagement with a feature on the shroud when the lock is unlocked, to hold the shroud and the boss together for rotation together.

5. A connector as claimed in any preceding claim, wherein the lock is a combination lock.

6. A connector as claimed in Claim 5, wherein the combination lock has rotatable indexable wheels mounted coaxially with the connector.

7. A connector as claimed in any preceding claim, wherein the lock portion includes a key-operated lock, and the key is inserted in a direction radially of the connector.

8. A lockable connector for connecting an optical fibre cable to a terminal fitting substantially as herein described with reference to the accompanying drawings.