GB2427081A

GB2427081A - Backshell adpator

Info

Publication number: GB2427081A
Application number: GB0511713A
Authority: GB
Inventors: Derek Andrews; Travis Steel
Original assignee: New Chapel Electronics Ltd
Current assignee: TT Electronics Fairford Ltd
Priority date: 2005-06-09
Filing date: 2005-06-09
Publication date: 2006-12-13
Anticipated expiration: 2025-06-09
Also published as: GB2427081B; GB0511713D0

Abstract

A backshell adaptor 10 maintains electrical continuity between cable screening material (not shown) and a circular electrical connector of a connector shell. The adaptor 10 comprises a spin nut 12 for screw-threaded engagement with a circular electrical connector, a screen trap 14 which engages the screening material and which is engagable with the spin nut 12, and means for preventing or limiting unintentional rotation of the spin nut 12 when engaged with screen trap 14. The unintentional rotation means includes first and second parts 18, 46, preferably in the form of teeth 20 and recesses 44, integrally formed on the spin nut 12 and the screen trap 14, respectively, which, in use, cooperate to prevent or limit unintentional rotation of the spin nut element 12. The teeth may alternatively extend axially. Features of the unintentional rotation means on the adaptor and spin nut may be reversed.

Description

BACKSHELL ADAPTOR

The present invention relates to a backshell adaptor for use as part of a screened electrical cable assembly and, in particular, to a backshell adaptor which facilitates termination of electrical cable screening material to a circular electrical connector whilst allowing continuity to be maintained.

Backshell adaptors are well known. They typically employ an internal screw- thread on a spin nut element to allow hand tightening of the adaptor to a connector.

However, once assembled, the cable assembly as a whole is subjected to vibration, for example when located in a vehicle, such as an aeroplane. Consequently, the spin nut element of the backshell adaptor can often work loose, resulting in disengagement of the adaptor from the connector and a loss of continuity.

To overcome this, known adaptors have been provided with various arrangements to try and prevent unintentional rotation. However, these have been in the form of arcuate springs which are mounted on the adaptor and which engage the spin nut element.

The use of independent parts, such as springs, causes an installer, especially when working in extremely confined spaces, a great degree of trouble, due to the springs being relatively small. If a spring becomes separated from the adaptor, it must be located. Especially in aircraft, leaving loose or lost parts can be dangerous and is thus

not acceptable.

The present invention therefore provides a solution to this problem.

According to the present invention, there is provided a backshell adaptor for a screened electrical cable assembly and which maintains electrical continuity between screening material and a circular electrical connector of a connector shell, the adaptor comprising a spin nut element for screwthreaded engagement with a circular electrical connector, a screen trap for engagement with screening material and which is engagable with the spin nut element, and means for preventing or limiting unintentional rotation of the spin nut element when engaged with the screen trap, the unintentional rotation means including first and second parts integrally formed on the spin nut element and the screen trap respectively which, in use, cooperate to prevent or limit unintentional rotation of the spin nut element.

Preferable and/or optional features of the present invention are set forth in claims 2 to 7, inclusive.

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawing, which shows an exploded perspective view of a backshell adaptor in accordance with the present invention.

Referring to the drawing, there is shown a backshell adaptor 10 which comprises a spin nut element 12, a screen trap 14, and means for preventing or limiting unintentional rotation of the spin nut element 12 when engaged with the screen trap 14.

The adaptor 10 is formed of material which permits electrical continuity to be maintained. In the present case, the spin nut element 12 and screen trap 14 are formed from moulded plastics material which can be plated with an electrically conductive material.

Although not shown, the spin nut element 12 includes an internal screwthread formed at a first end 16 thereof for mating screw-threaded engagement with a complementary thread formed on an end of a standard or known circular electrical connector (not shown).

The spin nut element 12 also includes a first part 18 of the unintentional rotation means which takes the form of a plurality of radially inwardly projecting equi-angularly spaced first teeth 20 integrally formed at a second end 22 of the spin nut element 12 opposite the first end 16. First recesses 24 having a radially extending depth are thus formed between adjacent first teeth 20.

The first teeth 20 need not necessarily be spaced from each other.

The spin nut element 12 further includes a plurality of circumferentially spaced slots 26 which extend axially a short distance from the second end 22 of the spin nut element 12.

Flats 28 are provided on an exterior surface of the spin nut element 12 to enable the spin nut element 12 to be wound onto and off the connector by hand or by use of a

suitable tool.

The screen trap 14 comprises a screen trap body 30 and a screen trap nut 32. The screen trap body 30 includes a screw-thread 34 at a first end 36 over which, typically braided, screening material (not shown) can be pushed. The screen trap nut 32 includes an internal screw-thread 38 which can be screw-threadably engaged with the screw- thread 34 on the screen trap body 30 to trap the screening material therebetween. This arrangement is well known and thus will not be described in any further detail.

The screen trap 14 also comprises a Continuous circumferential channel 40 formed on the screen trap body 30, adjacent to a second end 42 of the screen trap body 30. The bottom surface of the channel 40 includes a plurality of equi- angularly spaced second recesses 44, forming a second part 46 of the unintentional rotation means. Due to the provision of the second recesses 44, second circumferentially spaced and integrally formed teeth 48 are inherently provided.

The circumferential channel 40 is formed on the screen trap body 30 at a position of greatest outside diameter, which is greater than the internal diameter defined by the first teeth 20 on the spin nut element 12. The screen trap body 30 is thus provided with a radially outwardly extending chamfer or frusto-conical surface 50 between the second end 42 of the screen trap body 30 and the circumferential channel 40. Due to the circumferentially spaced slots 26 allowing slight flaring of the second end 22 of the spin nut element 12, the spin nut element 12 can be pushed into snap-fit engagement with the screen trap body 30 by the first teeth 20 of the spin nut element 12 riding up the frusto- conical surface 50 of the screen trap body 30 and locating in the channel 40.

The internal diameter of the spin nut element 12, as defined by the first teeth 20 of the unintentional rotation means, is such that the first teeth 20 locate in the second recesses 44 formed in the bottom of the channel 40. The spin nut element 12 is thus unable to freely rotate when engaged with the screen trap body 30.

Opposing, circumferentially facing surfaces 52 of the first teeth 20 on the spin nut element 12 and the second recesses 44 of the channel 40 of the screen trap body 30 are sloped to allow the first teeth 20 to ride up their respective recesses 44 and relocate in an adjacent recess 44.

The surfaces 52 of the first teeth 20 and the second recesses 44 which meet when the spin nut element 12 is being screw-threadingly engaged with the connector have a shallower slope and the surfaces which meet when the spin nut element 12 is being disengaged from the connector have a more severe slope. Consequently, less torque need be applied to engage the spin nut element 12 with the connector, whilst greater torque is needed to release the spin nut element 12.

The second end 42 of the screen trap body 30 is formed with a plurality of axially extending third teeth 54 or castellations. The third teeth 54 engage with conesponding recesses formed on an end of the connector, and thus prevent rotation of the screen trap body 30 as the spin nut element 12 is being tightened to the connector.

Various modifications can obviously be made. For example, the teeth and recesses of the first and second parts of the unintentional rotation means can extend axially instead of radially.

The screen trap body can be provided with teeth which project radially from the exterior surface of the screen trap body and which locate in recesses formed in the spin nut element. In other words, the reverse of the arrangement described above.

The first and second parts of the unintentional rotation means are provided on the spin nut element and the screen trap, respectively, or vice versa.

It thus possible to provide a backshell adaptor which comprises only two main parts, being a spin nut element and a screen trap. This limits the number of small parts which can potentially come loose and be misplaced. It is also possible to provide a backshell adaptor which includes means which is integrally formed as part of the adaptor for preventing or limiting unintentional rotation of the spin nut element. By integrally forming the unintentional rotation means when manufacturing the adaptor, the production process is simplified, costs are reduced, and output is increased.

The embodiments described above are given by way of examples only, and further modifications will be apparent to persons skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims

I. A backshell adaptor for a screened electrical cable assembly and which maintains electrical continuity between screening material and a circular electrical connector of a connector shell, the adaptor comprising a spin nut element for screw-threaded engagement with a circular electrical connector, a screen trap for engagement with screening material and which is engagable with the spin nut element, and means for preventing or limiting unintentional rotation of the spin nut element when engaged with the screen trap, the unintentional rotation means including first and second parts integrally formed on the spin nut element and the screen trap respectively which, in use, cooperate to prevent or limit unintentional rotation of the spin nut element.
2. A backshell adaptor as claimed in claim 1, wherein the spin nut element is snap- fittably engagable with the screen trap.
3. A backshell adaptor as claimed in claim 2, wherein the spin nut includes one or more slots to assist snap-fit engagement with the screen trap.
4. A backshell adaptor as claimed in any one of the preceding claims, wherein the first part of the unintentional rotation means includes one or more teeth, and the second part includes one or more recesses for receiving a said tooth.
5. A backshell adaptor as claimed in claim 4, wherein the or each tooth and a depth of the or each recess extends radially.
6. A backshell adaptor as claimed in claim 4 or claim 5, wherein at least one circumferentially facing side of the or each tooth and/or the or each recess is sloped to ease rotation of the spin nut element when being engaged with the electrical connector
7. A backshell adaptor as claimed in claim 6, wherein opposing circumferentially facing sides of the or each tooth and/or the or each recess are angled differently so that less torque is required to engage the spin nut element with the electrical connector than is required for disengagement.
8. A backshell adaptor substantially as hereinbefore described with reference to the accompanying drawing.