GB1590403A

GB1590403A - Cable connectors

Info

Publication number: GB1590403A
Application number: GB4539/77A
Authority: GB
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1977-02-03
Filing date: 1977-02-03
Publication date: 1981-06-03
Also published as: DE2804574A1; SE7801244L; FR2379918B1; IT1107059B; FR2379918A1; IT7867230A0

Description

(54) IMPROVEMENTS IN OR RELATING TO CABLE CONNECTORS (71) I, THE SECRETARY OF STATE FOR DEFENCE, London, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to cable connectors of the kind adapted to provide a releasable connection for a cable which connection can be broken on application of a predetermined tensile load to the cable.

The present invention is primarily, though not exclusively concerned with cable connectors of the above kind for use in connecting signal transmission cables at the interface between an aircraft and releasable weapons and the like (commonly called 'stores') carried by the aircraft. Such cables are required for transmitting fuze-arming signals from the aircraft to a weapon upon its release from the aircraft. Upon release of the weapon, fuze-arming signals are transmitted to it via the connecting cables only after the weapon release mechanism has successfully operated, thus ensuring that weapon remains in a safe condition should the release mechanism fail to operate. It is therefore usual to provide a length of free cable between the weapon and the aircraft so as to maintain the connection between the weapon and the aircraft for a short time after initial release, during which the fuze-arming signals are transmitted.

Conventionally a releasable two-part plugand-socket connector is provided for the connecting cable. The two connector parts are connected together when the weapon is fitted to the aircraft and are designed to be pulled apart by the tension applied to the cable as the weapon drops away from the aircraft after release.

A conventional plug-and-socket assembly designed for this purpose comprises a plug assembly which, in use, is permanently connected to the end of a cable carried by the aircraft, and a socket assembly permanently connected to one end of the cable the other end of which is permanently connected to the weapon. When the weapon is fitted to the aircraft the two parts of the connector are usually connected together either by means of a special bayonet fixing or by a shearable ball lock in which the two connector parts are held together by the engagement of a number of small steel balls in an annular detent formed in a cylindrical body of ductile material.

In use the plug assembly is suspended from the aircraft by means of a strong wire lanyard so that under the tensile loading applied to the cable by the weight of the weapon as it drops away from the aircraft after release, the steel balls shear through the ductile cylindrical sleeve to allow the connector parts to separate, the plug assembly being left dangling from the aircraft and the socket assembly falling away with the weapon.

A disadvantage of such connectors is that under the extreme environmental conditions experienced at the weapon-aircraft interface, there is a tendency after some time for the connector parts to work loose due to mechanical wear, resulting initially in an unreliable connection between the two parts of the cable, and finally in complete separation of the two parts. Furthermore, loosening of the connection between the two parts of the connector can permit ingress of water into the connector with deleterious results.

It is an object of the present invention to provide a releasable cable connection wherein at least some of the abovementioned disadvantages can be overcome or at least substantially reduced.

According to one aspect of the present invention a method of releasably connecting a piece of equipment adapted for dropping from an aircraft to said aircraft, by means of a flexible transmission cable which includes a plurality of electrical conductors, comprises: connecting and securely anchoring one end of the cable to the piece of equipment; connecting the other end of the cable within a first connector part of a two-part connector comprising contact elements in the respective parts, the second connector part thereof being securely anchored to the aircraft; each conductor being secured by crimping its bared end to a said contact element of the first connector part but the cable being otherwise substantially not anchored to the first connector part, said crimping being effective to reduce locally the tensile strength of the conductor; and positively locking the two connector parts together to effect contact between the contact elements of the two parts; whereby upon dropping the piece of equipment from the aircraft the resulting tensile load in the cable may fracture each conductor at the crimp and thereby break the cable connection between the aircraft and the piece of equipment.

In its application to providing a releasable interconnection between an aircraft and a releasable weapon carried by the aircraft, the second connector part is usually permanently mounted on the aircraft, or permanently connected and anchored thereto by means of a further length of flexible transmission cable using strain-taking devices such as cord-grips at each end. The free end of the length of transmission cable to which the fight connector part is connector part is connected and releasably anchored is then permanently connected and anchored to the releasable weapon, again using a cord-grip for example, and the two connector parts positively locked together to provide a releasable transmission connection between the aircraft and the weapon.

Thus, when the weapon is released from the aircraft, the weight of the weapon as it falls away from the aircraft causes the cable within the first conductor part to fracture at the crimps, taking that length of cable with it, and leaving behind the two connector parts on the aircraft for reuse.

Each crimped joint is preferably constituted by each conductor's bared end crimped in a hollow sleeve of the contact element, and is preferably in accordance with British Standard No. 3G178, thereby enabling a high degree of consistency in the tensile strength of the anchorage to be achieved.

According to a second aspect of the present invention a piece of equipment adapted for dropping from an aircraft and including a flexible cable for releasable connection to the aircraft, said cable including a plurality of electrical conductors, comprises: said cable having one end connected and securely anchored to said piece of equipment: a first connector part of a two-part connector comprising contact elements in the respective parts, the other end of said cable being connected within the first connector part; each cable conductor being secured by crimping its bared end to a said contact element of the first connector part but the cable being otherwise substantially not anchored to the first connector part, said crimping being effective to reduce locally the tensile strength of the conductor; whereby, prior to dropping the piece of equipment, the first connector part may be positively locked to the second connector part, which second connector part is securely anchored to the aircraft, to effect contact between the contact elements of the two parts, but upon dropping the piece of equipment from the aircraft the resulting load in the cable may fracture each conductor at the crimp and thereby break the cable connection between the aircraft and the piece of equipment.

According to a third aspect, the present invention provides, for use in a method or piece of equipment as above-defined, a first connector part of a two-part connector comprising contact elements in the respective parts which contact one another when the two parts are locked together, said first connector part comprising: a body portion having a plurality of said contact elements securely anchorable therein and having hollow ends adapted to have the conductors of a flexible cable secured thereto by crimping; and sealing means for sealing the cable entry aperture of the first connector part after withdrawal of the cable therefrom following fracture of each conductor at the crimp: said first connector part excluding means for substantially anchoring the cable to the connector part other than by said crimping.

The sealing means may comprise a body of resilient material formed with a separate entry passage for each conductor of the cable, which body, in use, is compressed into sealing contact with the conductors so that it deforms to seal the entry passages after withdrawal of the cable following said fracture.

The means for locking the two parts together may be of any suitable form, but preferably comprises a screw-ring carried by said first connector part engageable with a screw-thread formed on the second connector part, and further comprises a locknut arranged to be tightened into engagement with the screw-ring to prevent inadvertent release thereof said lock-nut also serving to compress the body of compressible material into engagement with the conductors as it is screw into engagement with the screw-ring.

A two-part electrical cable connector in accordance with the invention will now be described, by way of example only, with reference to the drawings accompanying the Provisional Specification, of which: Figure 1 is a perspective view on an enlarged scale of a socket assembly for a twopart plug-and-socket cable connector in accordance with the invention: Figure 2 is an exploded part-sectional perspective view, on an enlarged scale, of a plug assembly for a two-part plug and socket cable connector in accordance with the invention; and Figure 3 is a part-sectional side view of the socket assembly of Figure 1, and the plug assembly of Figure 2 locked together in their mated position.

Referring to the drawings, the two parts of the connector in accordance with the invention are shown separately in Figures 1 and 2, and in their mated position in Figure 3. The socket assembly shown separately in Figure 1 of the drawing is in the form of an adapter designed to provide a bridging connection between two different plug assemblies having different forms of connection to the socket assembly, one by means of a bayonet-type fixing, and the other by means of a screw fixing.

The socket assembly comprises a cylindrical metal shell 1 carrying a rectangular mounting flange 2 provided at each corner with a bolt hole 3 whereby the socket assembly can be mounted on a support.

Housed within the shell 1 is a cylindrical contact-carrying block 4 of resilient insulating material, for example rubber, formed with a plurality of through-bores 5 each individually housing a tubular female contact element 7 (Fig. 3) held captive therein by means of a locking element 8.

Each contact element 7 extends substantially the whole length of the contact-carrying block 4 and is arranged to receive male contact pins of the two different plug assemblies at opposite ends. The cylindrical shell 1 of the socket assembly is formed at one end with a screw thread 6 for attachment of one of the plug assemblies, and at the other qnd with a pair of bayonet-fixing pins 9 for the attachment of the other plug assembly.

The plug assembly adapted for attachment to the end of the socket assembly provided with the screw thread 6 is shown in exploded view in Figure 2 and comprises a main plug body 10, a screw-ring 11, and a lock-nut assembly 12. The main plug body 10 comprises a hollow cylindrical metal shell 13 formed about half-way along its length with an external annual flange 14.

On one side of the flange 14 the external surface of the cylindrical shell 13 is formed with a screw-thread 15, and on the other side of the flange with a number of circumferentially spaced lands 16 for a purpose which will become apparent later.

Housed within the cylindrical metal shell 13 of the main plug body 10 is a cylindrical contact-carrying block 17 formed with a plurality of through-bores 19 arranged in the same configuration as the bores 5 of the contact-carrying block 4 of the socket assembly shown in Figure 1. Each bore 19 individually houses a male contact element 20 only one of the which is shown in Fig.

2, comprising a pin portion 21 at one end, a hollow crimping barrel or sleeve 22 at the other end and, intermediate its two ends a neck portion 23 defining an annular shoulder 24 which is arranged to engage with a locking element 18 to prevent withdrawal of the contact element 20 after its insertion into the contact-carrying block 17.

Prior to assembly of the main plug body 10, the bared end portions of the insulationcovered conductors 26 of a multi-core electrical cable 27, which for the sake of clarity has been omitted from Fig 2 of the drawings, are each inserted into the hollow crimping sleeve 22 of a respective contact element 20 shown prior to connection to a conductor. The crimping sleeve is then squeezed tightly around the bared endportion of the associated conductor 26 so that the conductor is firmly gripped by the contact element. This crimping technique is highly critical, but if carried out in accordance with the requirements of British Standard No 3G178 relating to crimping joints for aircraft electrical cables and wires, using a precision crimping tool, which tools are commercially available for the purpose, a strong, consistent and reliable electrical and mechanical connection can be achieved.

The nature of such crimped joints, if secured properly to prevent withdrawal of the conductor from the crimping sleeve 22, are such that the tensile strength of the conductor is effectively reduced immediately adjacent the crimped joint, so that the conductor will normally fracture at this point if a sufficient tensile load is applied between the conductor 26 and the contact element 20.

Following the crimping operation, a tubular sleeve 25 of insulating material is heat-shrunk over the crimped joint and the portion of the conductor adjacent thereto to provide a support against lateral bending movements of the conductor which could otherwise stress the conductor and further weaken it at this point. The contact elements 20 are then axially inserted in their respective bores 19 of the contact-carrying block 19 to engage their shoulders 24 behind the locking element 18 and thereby captively hold the contact elements therein.

Figure 3 shows the fully assembled main plug body complete with multi-core cable 27 connected to the socket assembly at Fig 1.

As can be clearly seen in Figure 3, the dimensions of the cylindrical shell 13 are such that the leading edge of its unthreaded section can be inserted between the contact-carrying block 4 and the internal surface of the screwed threaded section of the cylindrical shell 1 of the socket assembly shown in Figure 1. The said internal surface is formed with a number of axial grooves (not shown) to receive the lands 16, the circumferential spacing of these lands 16 and the cooperating internal axial grooves being irregular so that the plug and socket assembly can be mated it only one relative angular position in which the bores 5, 19 of the respective contact-carrying blocks 4, 17 register with one another.

The two parts can be pushed together until the external annular shoulder 14 of the main plug body 10 abuts against the forward edge of the cylindrical shell 1 of the socket assembly. As this is done the pin portions 21 of the male contact elements 20 engage within respective ones of the female contact elements 7 of the socket assembly.

The screw-ring 11 of the plug assembly is formed with an internal screw thread 30 terminating at an internal annular shoulder 29. The internal dimensions of the screwring 11 are such that it can be slid axially over the cylindrical shell 13 of the main plug body 10 until its internal annular shoulder 29 abuts against the annular flange 14 of the main plug body 10, although in use a washer 28 is interposed between the two parts. The internal screw thread 30 of the screw-ring 11 then engages with the external screw thread 6 of the socket assembly shown in Figure 1, and the screwring is then tightened to firmly secure the main plug body 10 to the socket assembly in their mated position as shown in Figure 3.

The three-part lock-nut assembly 12 of the plug assembly comprises a hollow cylindrical lock-nut 32, a follower 37 and a sealing grommet 38 of resilient insulating material, eg rubber. The lock-nut 32 is formed at one end with an internal screw thread 33, adapted in use to engage the external screw thread 15 of the main plug body 10, and at its other end with an internal annular groove 35. The follower 37 which is arranged to tightly house the sealing grommet 38, is formed at one end with an annular ridge 39 which is press-fitted into the internal groove 35 of the lock-nut 32, so that the sub-assembly comprising the sealing grommet 38 and the follower 37 are axially located, but rotatable within the lock-nut 32. The external surface of the follower 37 is stepped at 40 to provide an annular gap between itself and the internal surface of the lock-nut 32 for a purpose which will be explained below.

The sealing grommet 38 is formed with a plurality of through-bores 42, arranged in the same configuration as the bores 19 in the contact-carrying block 17 of the main plug body 10. These bores 42 provide passages for the entry of the conductors 26 of the cable 27. Thus, in the assembled condition of the plug assembly, prior to its connection to the socket assembly, the screw-ring 11 is loosely retained on the threaded section of the shell 13 of the main plug body 10 by the locknut assembly 12, the screw thread 33 of which engages with the screw thread 15 of the main plug body 10. The conductors 26 of the cable 27 individually pass through respective bores 42 of the sealing grommet 38 to the contact elements 20 which are held captive within the bores 19 of the contact-carrying blocks 17.

In order to connect the plug and socket assemblies together to provide an electrical connection between the conductors 26 of the cable 27 and the contact elements 7 of the socket assembly, the free end of the main plug body 10 is axially inserted between the internal surface of the shell 1 and the contact-carrying block 4 of the socket assembly, with the spaced lands 16 aligned with the corresponding grooves (not shown) formed in the internal surface of the socket shell 1.

The screw-ring 11 is then slid forward so that its screw thread 30 engages the screw thread 6 of the socket assembly and the screw-ring is screwed tight. As this is done the main plug body is forced into the socket assembly by engagement of the internal shoulder 29 of the screw-ring 11 with the external annular flange 14 of the main plug body shell 13 via the washer 28, and the pin portions 21 of the male contact elements 20 enter the female contact elements of the sub-assembly.

Following this operation the lock-nut assembly 12 is then screwed tight against the rear edge of the screw-ring 11 to prevent any possibility of the screw-ring working loose. As the lock-nut assembly 12 is screwed up along the screw thread 15 of the main plug body 10, the forward edge of the follower 37 is forced between the internal surface of the main plug body shell 13 and the contact-carrying block 17, thereby compressing the sealing grommet 38 into engagement with the exposed surface of the contact-carrying block 17. The sealing grommet 38, being confined within the follower 37, is thus compressed tightly into sealing engagement around the conductors 26 which pass through it, thereby sealing the inside of the connector against external environmental conditions.

Thus it will be seen that in their final mating position shown in Figure 3, the two parts of the connector in accordance with the invention, ie the socket assembly of Figure 1 and the plug assembly of Figure 2, are securely locked together against separation. Furthermore, apart from the relatively small frictional retention provided by the sealing engagement between the grommet 38 and the conductors 26, the cable 27 is anchored within the connector solely by means of the crimped joints between the ends of the conductors 26 and the contact elements 20, which are themselves held firmly captive within the contact-carrying block 17.

By the nature of such crimped joints, the tensile strength of the conductors 26 is locally reduced at the point immediately adjacent to the crimp. Thus, upon application of a predetermined tensile load to the cable 27 relative to the connector, the individual conductors 26 of the cable 27 will fracture at this points allowing the cable to separate from the connector. The use of such crimped joints is preferred since they provide a high degree of consistency and so the tensile load required to cause separation of the cable 27 from the connector can be predetermined fairly accurately.

The compressed state of the sealing grommet 38 in the mated position of the connector assembly causes the bores 42 in the sealing grommet 38 to automatically seal behind the conductors 26 as they are withdrawn from the connector thus sealing the connector against external environmental conditions after separation of the cable 27.

The connector assembly shown in the drawings is designed for use in connecting transmission cables within the interface between an aircraft weapon or "store" carrier, eg a pylon mounted below the wing of the aircraft, and a weapon or store carried by the aircraft. As described earlier, such cables are required for transmitting fuze-arming signals from the aircraft to the weapon upon release thereof. The socket assembly, which is shown in the form of an adapted, is used to convert an existing connector arrangement, comprising in this example, a pull-apart bayonet connector, the two parts of which are adapted to separate upon release of the weapon, to a connector arrangement in accordance with the invention.

The socket assembly of Figure 1 is designed to replace the socket assembly of the existing arrangement, and for this purpose is provided with the bayonet-fixing pins 9 which are adapted to engage within bayonet-fixing slots (not shown) formed within a cylindrical bayonet fixing sleeve 47 rotatably carried by the existing plug assembly 44. The existing plug assembly 44 includes a plurality of male contact pins (not shown) connected to the ends of the conductors of a multi-core electric cable 49 leading from the aircraft and to which it is mechanically clamped by means of a screw clamp 51. On assembly, the bayonet plug assembly is inserted into the socket assembly of Figure 1 so that the contact pins of the bayonet plug engage within the contact elements 7. The rotatable bayonet-fixing sleeve 47 is then moved axially towards the socket assembly and partially rotated so that the bayonet-fixing slots thereof engage the pins 9 in the usual way. To ensure the existing plug assembly 44 remains firmly locked throughout the flight environments it is clamped in position by means of a pair of brackets 48.

The socket assembly of Figure 1 is then bolted to a support plate 45 supported on the aircraft carrier pylon 50 by means of pivotal couplings 46 which allows some pivotal movement of the connector assembly in use.

Having installed the adapter socket assembly in the aircraft, the weapon or store carrying the cable 27 and plug assembly of Figure 2, is fitted to the aircraft pylon and the plug assembly connected to the socket assembly by tightening up the screwring 11 and then the lock-nut assembly 12 as described above. The pivotal movement of the connector permitted by the pivotal couplings 46 simplifies the installation procedure, and reduces stresses on the cable 27 in use. The assembled connector assembly is completely sealed against environmental conditions and the screw-ring and lock-nut arrangement ensures that the two connector parts will not separate in use.

Upon successful release of the weapon from the weapon-support pylon of the aircraft, fuze-arming signals are transmitted via the connected cables 49, 27 during the short period that the slack in the cable 27 is taken up as described earlier. As the weapon drops away from the aircraft the weight of the weapon applies a tensile load to the cable 27, which tensile load is taken at the point of anchorage of the conductors 26 of the cable within the connector assembly. Because the contact elements 20, to which the ends of the conductors 26 of the cable 27 are secured, are firmly retained within the contact-carrying block 17 by the locking elements 18, the weakest point of connection lies in the crimped joints between the ends of the conductors 26 and the contact elements 20 which, as described above, effectively reduces the tensile strength of the conductors 26 at this point. Thus under the tensile load applied to the cables by the weapon as it drops away from the aircraft, the conductors 26 fracture at this point allowing the ends of the conductors 26 to be pulled out of the connector through the bores 42 in the sealing grommet 38.

Because the sealing grommet 38 is compressed around the conductors 26, by the tightening of the lock-nut 32, the bores 42 thereof sealingly close behind the conductors 26 as they are pulled out, thus autometically sealing the end of the connector against external environmental conditions.

Additional environmental protection is provided, in case the sealing means 38 fails to provide a perfect seal, by the contact elements 20 retained within the bores 19 of the contact carrying block 17.

Thus substantially the whole of the connector assembly is retained on the aircraft after release of the weapon, and can be reused. Also because the connector assembly is supported directly on the aircraft pylon, no parts of the connector are left dangling from the aircraft after release of the weapon.

Although the socket assembly of the arrangement described is in the form of an adapter, it will be appreciated that the invention also includes within its scope arrangements in which the cable 49 is directly received within the socket assembly.

It is also envisaged that connectors in accordance with the invention may be used, with suitable modification, to provide connections for multi-core cables having both electrical and fi'bre optic cores. In such cases, the fibre optic cores of the cable may similarly be anchored within the appropriate connector part by optically coupling and mechanically securing them to respective hollow optical coupling elements retained within the connector part in a similar manner to that used in the electrical connector described above.

The ends of the fibre optic cores, which may comprise a single optical fibre, or bundle of optical fibres, protected in a suitable sheathing, may be optically coupled and mechanically anchored to their respective coupling elements by a combination of adhesive and crimping, the coupling elements being formed for this purpose with a deformable crimping sleeve or barrel through which the ends of the cores are inserted. Adhesive is then applied and the crimping sleeve crimped around the core to mechanically anchor it to the coupling element and provide the necessary optical coupling. Again, as described above, the optical cores will fracture at their point of connection to the coupling elements.

Furthermore, alternative forms of positive locking means, for example mechanical latches, may be used to secure the two connector parts together WHAT I CLAIM IS: i. A method of releasably connecting a piece of equipment adapted for dropping from an aircraft to said aircraft by means of a flexible cable which includes a plurality of electrical conductors, comprising: connecting and securely anchoring one end of the cable to the piece of equipment; connecting the other end of the cable within a first conhector part of a two-part connector comprising contact elements in the respective parts, the second connector part thereof being securely anchored to the aircraft; each conductor being secured by crimping its bared end to a said contact element of the first connector part but the cable being otherwise substantially not anchored to the first connector part, said crimping being effective to reduce locally the tensile strength of the conductor; and positively locking the two connector parts together to effect contact between the contact elements of the two parts; whereby upon dropping the piece of equipment from the aircraft the resulting tensile load in the cable may fracture each conductor at the crimp and thereby break the cable connection between the aircraft and the piece of equipment.

2. A piece of equipment adapted for dropping from an aircraft and including a flexible cable for releasable connection to the aircraft, said cable including a plurality of electrical conductors, comprising: said cable having one end connected and securely anchored to said piece of equipment; a first connector part of a two-part connector comprising contact elements in the respective parts, the other end of said cable being connected within the first connector part; each cable conductor being secured by crimping its bared end to a said contact element of the first connector part but the cable being otherwise substantially not anchored to the first connector part, said crimping being effective to reduce locally the tensile strength of the conductor: whereby, prior to dropping the piece of equipment, the first connector part may be positively locked to the second connector part, which second connector part is secure

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

point allowing the ends of the conductors 26 to be pulled out of the connector through the bores 42 in the sealing grommet 38.

Because the sealing grommet 38 is compressed around the conductors 26, by the tightening of the lock-nut 32, the bores 42 thereof sealingly close behind the conductors 26 as they are pulled out, thus autometically sealing the end of the connector against external environmental conditions.

Additional environmental protection is provided, in case the sealing means 38 fails to provide a perfect seal, by the contact elements 20 retained within the bores 19 of the contact carrying block 17.

Thus substantially the whole of the connector assembly is retained on the aircraft after release of the weapon, and can be reused. Also because the connector assembly is supported directly on the aircraft pylon, no parts of the connector are left dangling from the aircraft after release of the weapon.

Although the socket assembly of the arrangement described is in the form of an adapter, it will be appreciated that the invention also includes within its scope arrangements in which the cable 49 is directly received within the socket assembly.

It is also envisaged that connectors in accordance with the invention may be used, with suitable modification, to provide connections for multi-core cables having both electrical and fi'bre optic cores. In such cases, the fibre optic cores of the cable may similarly be anchored within the appropriate connector part by optically coupling and mechanically securing them to respective hollow optical coupling elements retained within the connector part in a similar manner to that used in the electrical connector described above.

The ends of the fibre optic cores, which may comprise a single optical fibre, or bundle of optical fibres, protected in a suitable sheathing, may be optically coupled and mechanically anchored to their respective coupling elements by a combination of adhesive and crimping, the coupling elements being formed for this purpose with a deformable crimping sleeve or barrel through which the ends of the cores are inserted. Adhesive is then applied and the crimping sleeve crimped around the core to mechanically anchor it to the coupling element and provide the necessary optical coupling. Again, as described above, the optical cores will fracture at their point of connection to the coupling elements.

Furthermore, alternative forms of positive locking means, for example mechanical latches, may be used to secure the two connector parts together WHAT I CLAIM IS: i. A method of releasably connecting a piece of equipment adapted for dropping from an aircraft to said aircraft by means of a flexible cable which includes a plurality of electrical conductors, comprising: connecting and securely anchoring one end of the cable to the piece of equipment; connecting the other end of the cable within a first conhector part of a two-part connector comprising contact elements in the respective parts, the second connector part thereof being securely anchored to the aircraft; each conductor being secured by crimping its bared end to a said contact element of the first connector part but the cable being otherwise substantially not anchored to the first connector part, said crimping being effective to reduce locally the tensile strength of the conductor; and positively locking the two connector parts together to effect contact between the contact elements of the two parts; whereby upon dropping the piece of equipment from the aircraft the resulting tensile load in the cable may fracture each conductor at the crimp and thereby break the cable connection between the aircraft and the piece of equipment.
2. A piece of equipment adapted for dropping from an aircraft and including a flexible cable for releasable connection to the aircraft, said cable including a plurality of electrical conductors, comprising: said cable having one end connected and securely anchored to said piece of equipment; a first connector part of a two-part connector comprising contact elements in the respective parts, the other end of said cable being connected within the first connector part; each cable conductor being secured by crimping its bared end to a said contact element of the first connector part but the cable being otherwise substantially not anchored to the first connector part, said crimping being effective to reduce locally the tensile strength of the conductor: whereby, prior to dropping the piece of equipment, the first connector part may be positively locked to the second connector part, which second connector part is securely anchored to the aircraft, to effect contact between the contact elements of the two parts, but upon dropping the piece of equipment from the aircraft the resulting tensile load in the cable may fracture each conductor at the crimp and thereby break the cable connection between the aircraft and the piece of equipment.
3. A method or piece of equipment as claimed in claims 1 or 2 respectively wherein each crimped joint is constituted by each conductor's bared end crimped in a hollow sleeve of the contact element.
4. A method or piece of equipment as

claimed ih claim 3 wherein each crimped joint is in accordance with British Standard No. 3G178.
5. For use in a method as claimed in any of claims 1, 3 or 4 or in a piece of equipment as claimed in any of claims 2, 3 or 4, a first connector part of a two-part connector comprising contact elements in the respective parts which contact one another when the two parts are locked together, said first connector part comprising: a body portion having a plurality of said contact elements securely anchorable therein and having hollow ends adapted to have the conductors of a flexible cable secured thereto by crimping; and sealing means for sealing the cable entry aperture of the first connector part after withdrawal of the cable therefrom following fracture of each conductor at the crimp: said first connector part excluding means for substantially anchoring the cable to the connector part other than by said crimping.
6. A first connector part as claimed in claim 5 wherein the sealing means comprises a body of resilient material formed with a separate entry passage for each conductor of the cable, which body, in use, is compressed into sealing contact with the conductors so that it deforms to seal the entry passages after withdrawal of the cable following said fracture.
7. A first connector part as claimed in claim 6 comprising a screw-ring carried by said first connector part engageable with a screw-thread formed on the second connector part for locking the two parts together, and further comprising a lock-nut arranged to be tightened into engagement with the screw-ring to prevent inadvertent release thereof, said lock-nut also serving to compress the body of compressible material into engagement with the conductors as it is screwed into engagement with the screw-ring.
8. A method of releasably connecting a piece of equipment adapted for dropping from an aircraft, to said aircraft by means of a flexible cable which includes a plurality of electrical conductors as claimed in claim I and substantially as hereinbefore described with reference to the drawings accompanying the Provisional Specification.
9. A piece of equipment adapted for dropping from an aircraft including a flexible cable for releasable connection to the aircraft, said cable including a plurality of electrical conductors, as claimed in claim 2 and substantially as hereinbefore described with reference to the drawings accompanying the Provisional Specification.
10. A first connector part of a two-part connector as claimed in claim 5 and substantially as hereinbefore described with reference to the drawings accompanying the Provisional Specification.