GB2321789A

GB2321789A - A connector arrangement with an improved EMC seal

Info

Publication number: GB2321789A
Application number: GB9701953A
Authority: GB
Inventors: Stuart Alan Rhys Charles; Christopher Paul Satchell; Stephen George Cordes
Original assignee: Northern Telecom Ltd
Current assignee: Nortel Networks Ltd
Priority date: 1997-01-30
Filing date: 1997-01-30
Publication date: 1998-08-05
Also published as: GB9701953D0

Abstract

A connector arrangement such as a D-type, comprises male and female halves each having mounting plates 9, 10 surrounding the pins of the connector and facing each other but spaced apart when the connector halves are engaged. An electrically conductive and resilient webbing 8 is located in abutment with the plates, and has an aperture 12 to surround the housings such that a simple and inexpensive EMC seal is formed. Either connector half may comprise first and second parts each of pressed metal and having a substantially planar end section for making a butt joint with the other of the two parts. Flexible and conductive webbing 25 is conductively secured to each of said first and second parts to cover the joint whereby an EMC seal is formed.

Description

A CONNECTOR ARRANGEMENT WITH AN IMPROVED EMC SEAL Technical Fields This invention lies in the field of connector arrangements for data transmission and more particularly to electromagnetic radiation seals for such arrangements, and to computer, communications and other apparatus incorporating such arrangements.

Background to the Invention Electromagnetic compatibility (EMC) regulations specify limits on the amount of electromagnetic radiation that may be emitted by various devices.

One source of Electromagnetic (EM) radiation emissions are connecting cables, particularly where high frequency clock signals, in the order of 100MHz and above, are supported. These clock signals have a discontinuous spectrum with peaks in energy at discrete frequencies, typically the clock frequency and odd harmonics thereof. As the energy of the signal is confined to discrete frequencies, any emissions caused by such signals tend to be of a higher level than random data signals.

One prior art solution is depicted in figure 1. It comprises a single piece connector body 1 manufactured as a cast shell. The electrical contact pins 5 are enclosed within the shell. The cable is sealed against the back end of the shell and in use the front edge 40 of the shell sits flush against a face plate. A second set of electrical contact pins project from this face plate and engage pins 5. A conductive gasket arrangement 2 is located between the front edge 40 of the shell and the above mentioned face plate. The conductive gasket 2 is sufficiently resilient to compensate for disconformities between the surface of the face plate and the surface of the shell.

With this arrangement, the inter-connecting pins are completely enclosed by a conducting surface, so that an EMC seal is formed.

An alternative prior art embodiment is detailed in figure 2, which incorporates leaf spring arrangements 30 into housing 6 which supports connector pins 4. The housing 6 projects from body portion 3. The leaf springs 30 form a substantially enclosed surface at the interface between the housing 6 of the male connector half and a corresponding housing of an interconnecting female connector half.

Both these prior art arrangements suffer the disadvantage of cost. Casting is an expensive form of construction. The leaf spring arrangement is complex to manufacture and therefore more expensive than simpler arrangements.

High frequency electronic devices are becoming more accessible to consumers, as costs of integrated circuits and other components fall. A need has therefore been identified to produce a connector for devices supporting high frequency signals that may be manufactured at reduced cost over present arrangements.

Statement of Invention According to a first aspect of the present invention, a connector arrangement comprising first and second body and first and second electrical contacts located within first and second housings; said first housing projecting from said first body portion and said second housing projecting form said second body portion; said housings adapted to inter-engage whereby said electrical contacts interconnect; said arrangement further comprising an electrically conductive element located in abutment with said first and second body portions; said element comprising an aperture whereby said housings are surrounded by said conductive element such that an EMC seal is formed.

According to a second aspect the present invention provides a conductive element comprising an aperture adapted to in use, receive a housing portion of a connector half; said housing portion adapted to inter-engage with a corresponding housing portion of a corresponding connector half; each said housing containing electrical contacts adapted to interconnect when said housings interengage; said housings projecting from body portions of respective connector halves; in use the aperture of the conductive element surrounding said housing and located in abutment with said body portions.

The conducting element intermediate the body portions and enclosing the inter-engaged housings provides a simple and inexpensive electromagnetic seal surrounding the connecting pins.

Preferably resilient conducting material is located intermediate abutting surfaces of said conducting element and said first and second body portions.

Locating resilient conducting material intermediate the abutting surfaces allows disconformities between the surfaces of the body portions and the spacer to be compensated for, which improves the EM sealing characteristics of the connector.

Preferably said connectors are adapted to exert compressive force between said body portions and conducting element.

Pressure between the body portions and the conducting element assists with compensating for disconformities between these surfaces whereby the EM sealing characteristics of the connector are enhanced.

Preferably the spacing element is adapted to enclose means for forming said compressive force.

Enclosing means for forming compressive force enhances the EM sealing characteristics of the connector.

Preferably said connector means is a D-type connector.

According to a further aspect of the present invention, connector half comprising first and second parts each having a substantially planar section; said planar sections abutting whereby a join is formed in said connector; said connector half further comprising flexible and conductive webbing conductivity secured to each of said first and second parts and bridging said join whereby an EMC seal is formed.

Abutting planar surfaces within a connector often become worn with repeated use. This reduces the EM sealing properties of such a join. Locating a flexible conductive material between these surfaces allows an EM seal to be formed that compensates for wear between these two halves.

Preferably said flexible and conductive material is an adhesive tape bridging said planar components.

According To a further aspect the present invention provides electrical apparatus such as a computer, processing, communications or similar apparatus comprising a face plate and a first housing projecting from said face plate; said housing locating electrical contacts; said apparatus further comprising connector means having a body portion and a second housing projecting from said body portion; said second housing locating electrical contacts; said housings adapted to inter-engage whereby said electrical contacts inter-connect and an electrically conductive element located in abutment with said body portion and said face plate; said element comprising an aperture whereby said housings are surrounded by said conductive element such that an EMC seal is formed.

Description of the drawings Figure 1 is a prior art connector arrangement.

Figure 2 is a prior art connector arrangement.

Figure 3a and 3b are assembled connectors without EMC sealing.

Figure 4a and 4b are assembled connectors with EMC sealing.

Figure 5 is an exploded assembly view of a preferred arrangement of the present invention.

Figure 6a is a perspective view of an electrically conductive element.

Figure 6b is a perspective view of resilient and conductive webbing.

Figure 7 is a connector half containing an electromagnetic seal around a join.

Figure 8 is a perspective view of an electrically conductive element incorporating a lip.

DescriDtion of Preferred Embodiment The invention will now be described with reference to the accompanying drawings. The invention is primarily described with reference to a D-type connector. It will be readily apparent to the skilled addressee that the invention is not limited to D-type connectors and that the invention is applicable to other types of connectors.

Figures 3a and 3b depict typical D-type connectors without EMC sealing arrangements of the present invention. Figure 3a depicts a join in a cable 50 and figure 3b shows a cable 50 being connected to a face plate 35 of computer, communications or other electrical/electronic apparatus. In both figure 3a and figure 3b, housings 6 and 7 which support the electrical contacts are interengaged. In figure 3a body portions 1 and 3 of respective connector halves are separated by the inter-engaged housings 6 and 7. In figure 3b, body portion 1 and face plate 35 of the computer, communication or other electrical/electronic apparatus are separated by the interengaged housings 6 and 7.

Figures 4a and 4b depict a cable join and a connection to a face plate 35 of a piece of apparatus respectively, with a preferred form of the EMC seal of the present invention located. An electrically conductive element 8 surrounds interconnecting housings 6 and 7.

Intermediate the seal arrangement 8 and the body portions 1 and 3 or the body portion 1 and housing 35, is located resilient and conductive webbing 25.

Figure 5 is an exploded assembly drawing of a 'D-type' connector incorporating a preferred form of the EMC seal of the present invention. The connector typically comprises one set of male pins 4 projecting from body portion 3. The other half typically has one set of female pins 5 projecting from body portion 1. The male pins 4 are located within housing 6 which serves as a mechanical support. The female pins 5 are located within housing 7, which also serves as mechanical support.

The connector halves interconnect by inter-engaging housings 6 and 7. Housing 7 typically being locatable internally to housing 6.

The pins 4 and 5 being arranged within the housings 6 and 7 so as to interconnect when housings 6 and 7 inter-engage. The housings 6 and 7 provide mechanical support for the connectors when interconnected. This relieves mechanical stress from the interconnecting pins 4 and 5 which are typically of insufficient construction to support the inter-connection of the two connector halves. Without EMC sealing of the present invention, housings 6 and 7 are exposed when inter-engaged.

The present invention locates a conductive element 8 intermediate and in abutment with, face plate 9 of connector body 1 and face plate 10 of body portion 3. The conductive element 8 is provided with aperture 12. This aperture is shaped so as to receive housings 6 and 7. The conductive element 8 is of similar width to the distance between face plates 9 and 10 when housings 6 and 7 are interengaged. Figure 6a shows a conductive element 8 of a preferred arrangement.

Preferably, a conductive and resilient web 25 is located intermediate faces 15 of the conductive element 8 and each of the face plates 9 and 10. In a preferred arrangement, pressure is formed at the interfaces between web 25 and face plate 9 and 10 and conductive element 8. Such pressure operates to deform the web 25 so that it compensates for deviations in the surfaces 15 of the conductive element 8 and the surfaces of face plates 9 and 10.

Figure 6b shows webbing 25 for a D-type connector.

The conductive and resilient webbing material may be made from material trade named waveshield type 101-00R aluminium mesh, and produced by RFI Shielding Ltd, Braintree, Essex, CM7 2YW, United Kingdom This material is a composite of conductive wire mesh and a malleable substance such as rubber.

In one alternative arrangement, the webbings 25 may be conductively bonded to the conductive element 8, forming a single piece EMC seal. Such a single piece seal simplifying operation of a connector using this arrangement. In a further alternative arrangement, the conductive element 8 may be moulded or machined entirely from the above referenced webbing material, or similar material.

Alternatively a silver loaded conductive elastomer gasket may be used in place of webbing 8. A gasket of 0.6mm diameter may be used on a spacer adapted for use with a standard D-type connector arrangement. Other substances such as conductive adhesive or conductive paste may be located at the interface between the spacer and the body of the connector.

According to a preferred aspect of the present invention, aperture 12 in webbing 25 that surrounds housing 7 is arranged such that the leading edge of housing 6 abuts webbing 25. For some connector types, this may require the aperture 12 in the webbing 25 to be smaller than the aperture 12 in conductive element 8.

Figure 8 depicts an alternative arrangement whereby conductive element 8 comprises a lip 55 which is formed internal to aperture 12 and adjacent face 15. Preferably the lip extends continuously around the circumference of aperture 12. In this arrangement, lip 55 is located intermediate face plate 9 and the leading edge of housing 6 when the connector is operational. This provides for the leading edge of housing 6 to abut lip 55 which increases the number of ninety degree bends in the path of the EM radiation before leaking from the connector will occur. It is believed that this will provide improved EMC sealing. In a further arrangement, webbing 25 is provided additionally to conductive element 8 incorporating lip 55.

Alternatively, conductive element 8 incorporating lip 55 may also be constructed from the material or similar material to that used for webbing 25.

According to a preferred aspect, threaded engaging means may be located through face plate 9 or 10. These threaded means engage a co-operating means which is preferably located on corresponding face plate 10 or 9. By way of example, apertures 20 in face plate 9 or 10 may be threaded and the corresponding apertures 20 in corresponding face plates 10 or 9 may be of sufficient diameter to receive a threaded rod.

In use, the threaded engaging means are tightened to prevent the connector halves from separating. This will typically introduce compressive forces at the interfaces of face plates 9 and 10 and webbings 25 and conductive element 8. These compressive forces typically enhance the EMC sealing characteristics of the present invention. Preferably the electrically conductive element contains apertures 20 that receive these threaded engaging means. It is believed that an improved electromagnetic seal is formed with this arrangement over an arrangement that does not enclose the threaded engaging means within conductive element 8.

Alternatively, a mechanical arrangement, such as a spring clip or resilient member may locate onto the connector halves, or onto a connector half and corresponding face plate of a housing of electrical/electronic apparatus, whereby pressure is formed at the interfaces of the face plates 9 & 10, webbings 25 and conductive element 8.

Alternatively, where the electrically conductive element 8 is machined with sufficiently flat faces 15 and where the flatness of face plates 9 and 10 corresponds to the flatness of faces 15 an EMC seal may be formed without webbings 25 Figure 7 is a representation of the construction of a typical press metal connector. It comprises connector pins 5 surrounded by housing 7 projecting from face plate 9. This arrangement is mounted onto a backshell, which forms the body 1 of the connector. The backshell has a face plate 16 which abuts face plate 9 forming a seam 18 along this interface. The two face plates are typically joined by a sheet metal joint.

Tolerances for these components are usually loose, in keeping with the cost objectives of typical connectors. Accordingly, the join 18 between face plates 9 and 16 is typically insufficient to prevent leakage of electromagnetic radiation. With repeated coupling and decoupling of the connector, this interface 18 tends to wear. This wear further degrades the electromagnetic sealing capabilities interface 18.

A further aspect of the present invention locates conductive tape 17 across this join 18, so as to bridge the two connector halves, whereby an electromagnetic seal is created that is sufficient for containment of clock signals of hundreds of megahertz and above.

The conductive tape 17 is preferably adhesive on at least one side. The adhesive being sufficient to bind the tape onto the metallic surfaces of the connector bodies.

The conductive tape should be sufficiently flexible that it can be wrapped around the two face plates of join 18. By enclosing the joins an electromagnetic seal is formed. Such flexible tape being sufficient to compensate for wear between the plates of the join during use.

Such conductive tape is trade named CHO-MASK II conductive foil tape with peel off mask PT No. CMT-ST-108-0750 and is made by CHOMERIUS Inc, of Hudson NH03051 USA Other forms of conductive may also be used.

Another alternative arrangement may use a conductive adhesive. An example of such an adhesive has the trade name CON\RTV-1 and is made by Teckknit, Cranford New Jersey, USA.

Other conductive sealing means with sufficient flexibility to withstand forces encountered by the join in use may also be used.

Electrical apparatus such as computers, processing and communications devices often comprise two or more modules interlinked by cables. The cables are typically coupled to the modules using D-type connectors or similar connectors. It is believed that the present invention contains EMC emissions sufficiently so that upto approximately 32 separate connector arrangements, each carrying high frequency clock signals, may be used on such a modular system without exceeding European class A EMC standards. Where the clock signals are synchronous and in phase, then it is believed that a lower number of connectors, approximately 25 may be used within European class A standards.

For European class B standards, it is believed that approximately 10 connectors using the present invention may be used within the standards requirement and where the clock signals are synchronous and in phase approximately 6 connectors may be used within the standard.

Claims

1. A connector arrangement comprising first and second body portions and first and second electrical contacts located within first and second housings; said first housing projecting from said first body portion and said second housing projecting form said second body portion; said housings adapted to inter-engage whereby said electrical contacts interconnect; said arrangement further comprising an electrically conductive element located in abutment with said first and second body portions; said element comprising an aperture whereby said housings are surrounded by said conductive element such that an EMC seal is formed.

2. A connector arrangement as claimed in claim 1 wherein a conductive and resilient webbing is located intermediate said body portions and said conductive element.

3. A connector arrangement as claimed in claim 1 further comprising means for forming compressive force at the interfaces between said body portions and said electrically conductive element.

4. A connector arrangement wherein said connector is a Dtype connector.

5. A connector as claimed in claim 5 wherein said D-type connector is of pressed metal construction.

6. A connector as claimed in claim 1 wherein at least one of said housings and a corresponding body portion each comprises a face plate; said connector arranged whereby said face plates abut; said connector further comprising conductive and resilient webbing conductively secured to said housing and body portion and spanning said abutting face plates whereby forming an EMC seal.

7. A conductive element comprising an aperture adapted to in use, receive a housing portion of a connector half; said housing portion adapted to inter-engage with a corresponding housing portion of a corresponding connector half; each said housing containing electrical contacts adapted to interconnect when said housings inter-engage; said housings projecting from body portions of respective connector halves; in use the aperture of the conductive element surrounding said housing and located in abutment with said body portions.

8. A conductive element as claimed in claim 7 wherein conductive and resilient webbing is located at the interfaces between said spacing element and said body portions.

9. A conductive element as claimed in claim 7 wherein said webbing is electrically bonded onto said conductive element.

10. A conductive element as claimed in claim 7 further comprising a lip internal to said aperture and adjacent an edge of said aperture.

11. A conductive element as claimed in claim 10 wherein said lip extends around the circumference of said aperture.

12. A connector half comprising first and second parts each having a substantially planar section; said planar sections abutting whereby a join is formed in said connector; said connector half further comprising flexible and conductive webbing conductivity secured to each of said first and second parts and bridging said join whereby an EMC seal is formed.

13. A connector half as claimed in claim 6 wherein said conductive webbing comprises adhesive tape.

14. Electrical apparatus such as a computer, processing, communications or similar apparatus comprising a face plate and a first housing projecting from said face plate; said housing locating electrical contacts; said apparatus further comprising connector means having a body portion and a second housing projecting from said body portion; said second housing locating electrical contacts; said housings adapted to inter-engage whereby said electrical contacts inter-connect and an electrically conductive element located in abutment with said body portion and said face plate; said element comprising an aperture whereby said housings are surrounded by said conductive element such that an EMC seal is formed.

15. Electrical apparatus as claimed in claim 14 wherein said apparatus transmits high frequency clock signals across interconnecting cables.

16. Electrical apparatus as claimed in claim 14 wherein a conductive and resilient webbing is located intermediate said body portions and said conductive element.

17. Electrical apparatus as claimed in claim 14 wherein said conductive element comprises a lip internal to said aperture and adjacent an edge of said aperture.

18. Electrical apparatus as claimed in claim 17 wherein said lip extends around the circumference of said aperture.

19. Electrical apparatus as claimed in claim 14 further comprising means for forming compressive force at the interfaces between said body portions and said electrically conductive element.

20. Electrical apparatus as claimed in claim 14 wherein said connector is a D-type connector.

21. Electrical apparatus as claimed in claim 20 wherein said Dtype connector is of pressed metal construction.

22. Electrical apparatus as claimed in claim 14 wherein at least one of said housings and a corresponding body portion each comprises a face plate; said connector arranged whereby said face plates abut; said connector further comprising conductive and resilient webbing conductively secured to said housing and body portion and spanning said abutting face plates whereby forming an EMC seal.

23. Electrical apparatus as claimed in claim 14 comprising a plurality of modules interconnected by a plurality of cables supporting high frequency clock signals; said cables connected said modules using said connector arrangements.

24. Electrical apparatus as claimed in claim 23 comprising between 2 and 32 connector arrangements.