GB2303939A

GB2303939A - Fibre optic connector on circuit board having jacking members on opposite edges

Info

Publication number: GB2303939A
Application number: GB9614629A
Authority: GB
Inventors: Brian Shepherd
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 1995-07-29
Filing date: 1996-07-11
Publication date: 1997-03-05
Anticipated expiration: 2016-07-11
Also published as: GB2303939B; GB9515607D0; GB9614629D0

Abstract

A circuit board 30 has a fibre optic connector 35 mounted along its rear end arranged to mate with a cooperating fibre optic connector on a backplane 20. Two jacking members 42 extend from the rear end to the forward end of the board along opposite edges of the board. Electrical contacts 37, 57 and fluid couplings 38, 58 for coolant are shown. A housing contains several circuit board assemblies 30 each having a fibre-optic connector 35 and two jackscrews 42 extending along opposite edges of each board. The jackscrews engage cooperating connectors (22, Fig 1) mounted in a floating manner on a backplane 20 so that the cooperating connectors can move relative to the backplane and to each other. The housing (1, Fig 1) has parallel channels (3, Fig 1) the edges of the boards and the jackscrews 42 are received; the jackscrews may carry wedge locks to force the boards into contact with the channels. The backplane has projecting lugs 24 along each side that engage in the channels 3. The board connectors 32 may have polarizing formations 46 concentric of the jackscrews 42.

Description

CONNECTORS AND ASSEMBLIES This invention relates to connectors and assemblies.

The invention is more particularly concerned with fibre-optic connectors and with assemblies including such connectors.

Aircraft avionics electrical circuit boards commonly have an electrical connector at one end mated with a cooperating connector. The cooperating connector is mounted on a backplane extending at the rear of equipment casing or in a rack. Where there are a large number of electrical contacts, the force necessary to mate the connectors can be high. Because of the limited space available, where there are a large number of contacts, their size must be correspondingly reduced. This leads to difficulties of alignment and makes the contacts more delicate. The forces necessary to mate the two parts of an electrical connector arise from friction between the contacts and their housings and, once the two parts are mated, there is no force tending to separate the two parts of the connector.The initial force necessary to achieve mating can be applied by means of cam latches attached to the front end of the circuit board, which engage with the casing in which the boards are mounted.

Where the connector includes fibre-optic contacts, there can be additional problems.

Fibre-optic contacts of the kind that make a butt engagement with one another usually have a spring that urges one or both contacts together. The spring accommodates any tolerances along the axis of the contacts. This means that the resilient force exerted by the springs must be overcome during insertion and that there is a continuous force exerted by the springs tending to separate the two halves of the connector after mating. If each connector has a large number of contacts, this force is correspondingly multiplied. Where the backplane supports several connectors, the force exerted on the backplane is further multiplied. This can make secure mounting and retention of circuit boards with fibre-optic contacts very difficult.

It is an object of the present invention to provide a connector and assembly that can be used to facilitate mounting and retention.

According to one aspect of the present invention there is provided an assembly of the kind comprising a circuit board and fibre-optic connector mounted along the rear end of the board and arranged to mate with a cooperating fibre-optic connector mounted on a backplane, the assembly including two jacking members extending from the rear end to the forward end of the board along opposite edges of the board such that the forward end of the jacking members is accessible at the forward end of the board, the rear end of the jacking members being arranged to engage said cooperating connector such that the two connectors can be drawn together and retained together by operation of the jacking members from the forward end of the assembly.

The jacking members are preferably jackscrews. The cooperating fibre-optic connector is preferably mounted on the backplane in a floating manner such that it is free to move relative to the backplane to a limited extent. The connectors may include electrical contacts and fluid connectors. The connectors may have cooperating polarizing formations concentrically of thejacking members.

According to another aspect of the present invention there is provided a system of the kind comprising a housing, a circuit board assembly mounted in the housing with opposite edges located in respective channels extending in the housing from its forward to its rear end, the circuit board assembly including a fibre-optic connector mounted along the rear end of a circuit board and arranged to mate with a cooperating fibre-optic connector mounted on a backplane extending within the rear of the housing, the circuit board assembly including two jacking members extending from the rear end to the forward end of the board along opposite edges of the board within said channels such that the forward end of the jacking members is accessible at the forward end of the board, the rear end of the jacking member being arranged to engage said cooperating connector such that the two connectors can be drawn together and retained together by operation of the jacking member from the forward end of the assembly.

The jacking members are preferably jackscrews and may carry wedge locks operable to engage the channels and clamp the board in the channels. The housing may have a plurality of parallel channels, the system having a plurality of circuit board assemblies having opposite edges located in respective channels, and a plurality of cooperating fibre-optic connectors mounted on the backplane. The cooperating fibre-optic connectors are preferably mounted on the backplane in a floating fashion such that the cooperating connectors can move relative to one another to a limited extent. The backplane may comprise a support member with lugs projecting at each side that engage in the channels, the lugs having holes therethrough within which the cooperating connectors are mounted on the backplane.

According to a further aspect of the present invention there is provided a system including an assembly comprising a circuit board and a first fibre-optic connector mounted along the rear end of the board, and a backplane assembly comprising a second fibre-optic connector and a support assembly for the second connector, the support assembly including a first member and a floating bush securing the second connector with the first member such that the second connector can float relative to the first member.

A system including several circuit boards and fibre-optic connectors will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic side elevation of the system including several circuit board assemblies; Figure 2 is a plan view of a circuit board assembly mounted to the backplane; Figure 3 is a side elevation view of the board of Figure 2 along the arrow III; Figure 4 is a perspective view of a part of the backplane assembly; Figure 5 is a partly sectional side elevation of a part of the backplane assembly;.

Figure 6 is a perspective view of the mating connectors; Figure 7 is a plan view of an alternative circuit board assembly; Figure 8 is a sectional view of a multi-way insert for the assembly of Figure 7; Figure 9 is a partly cut-away view of the insert in Figure 8; and Figure 10 is a perspective view of the connectors of the assembly shown in Figure 7.

With reference first to Figure 1, the system includes an outer housing I supporting a vertically-oriented backplane assembly 20 and several horizontal circuit board assemblies 30 (only one of which is shown) mated with the backplane assembly. The housing 1 may be an instrument casing, a rack or the like having two vertical side walls 2 provided with horizontal channels 3 receiving and supporting opposite edges of the board assemblies 30.

With reference now also to Figures 2, 3 and 6, the circuit board assemblies 30 comprise a circuit board or substrate 31 and a connector assembly 32 mounted at the rear end of the board and extending across its entire width. The connector assembly 32 has an outer housing 33 of generally rectangular shape and made of a rigid plastic or metal. Apertures 34 extending along the length of the housing 33 each contain a fibre-optic contact 35 of a conventional butt type or a mechanical transfer type. A spring, or other resilient means, (not shown) located in the aperture urges the contact 35 rearwardly. Optical fibres 36 coupled with the contacts 35 extend from the forward end ofthe apertures and are connected to circuit components 4 on the board 31.The connector assembly 32 also includes one or more electrical contacts 37 and two fluid couplings 38 through which coolant can be supplied to and from the board assembly. It will be appreciated that any combination of optical, electrical and fluid contacts and couplings could be used.

The connector assembly 32 also includes two elongate metal jackscrews 41 and 42 at the extreme opposite sides of the housing 33. The jackscrews 41 and 42 extend through apertures 43 in the housing 33 and are rotatably retained in the aperture by a locking nut 44 on the forward side of the aperture and a locating collar 45 on the rear side. The locating collar 45 has a polarizing extension 46 projecting rearwardly alongside the rear end of the jackscrew. The rear end of each jackscrew 41 and 42 is threaded and projects rearwardly beyond the rear of the housing 33. The forward end ofeachjackscrew 41 and 42 extends forwardly close to the edges of the board 31 and is terminated by a knob 47 (Figure 1) or screw head etc by which the jackscrew can be screwed and unscrewed.The jaclcscrews 41 and 42 extend above the upper surface of the board 31, within the channels 3 in the side walls 2 of the housing 1, and are spaced from the surface of the board by a small clearance distance.

The jackscrews 41 and 42 may carry wedge locks (not shown) or similar devices, within the channels 3, which expand in height when the jackscrew is rotated, so as to exert a clamping force on the upper surface of the board 31 causing it to be held down firmly against the lower surface of the channel. One form of suitable clamping device is described in GB 2163210.

This helps improve the mechanical retention of the boards and can improve heat dissipation from the boards to the side wall of the housing.

With reference now also to Figures 4 and 5, the backplane assembly 20 includes a vertical support assembly 21 and connectors 22 located to mate with the connector assemblies 32 on the board assemblies 30. The support assembly 21 is made up of two vertical, rigid, metal rails 23 of L-shape in section and formed with a series of square, projecting lugs 24, one for each of the connectors 22. The lugs 24 are of the same shape and separation as the channels 3 and are located in the rear end of the channels to support the backplane assembly.

The rails 23 are joined to a bent, sheet-metal cage 25 of U-shape in section, which serves to protect and guide fibres and wires emerging from the rear side of the connectors 22 and within which other optical components may be mounted. The connectors 22 are supported on the support assembly 21 by means of floating bush assemblies 50 at opposite ends of the connectors, which locate in holes 51 in the lugs 24. The diameter of the holes 51 is sufficient to enable the bush assemblies to float, thereby allowing limited movement of the connectors 22 relative to the support assembly 21. The floating bush assemblies 50 also accommodate downward movement of the connector assembly 32 produced by the clamping action of the jackscrews 41 and 42 on the upper surface of the board 31.

The connectors 22 have a housing 52 of the same material as the housing 33 of the connector assemblies 32. Each connector 22 is shaped to mate with a corresponding one of connector assemblies 32 and has a rectangular central recess 53 on its forward face in which the rear end of the board connectors is inserted. The housing 52 has apertures 54 containing fibre-optic contacts 55 located to engage the contacts 35 in the mating connector. The contacts 55 are resiliently mounted, in the same way as the contacts 35 and, in their natural state (before mating), they project forwardly from the forward face of the connector.

The backplane connector 22 has a centrally located electrical contact 57 arranged to engage the electrical contact 37 on the mating connector, and two fluid couplings 58 located to connect with the fluid couplings 38. At the extreme right and left-hand ends of the connector 22, its housing 52 has a screw-threaded recess 59 in which the externally-threaded rear end of the jack screws are retained. The recesses 59 also both have a polarising slot 60, which receives the polarising extensions 46 on the locating collars 45. The slot 60 in the right-hand recess 59 is located on its left-hand side, when viewed in plan; the slot in the lefthand recess is located on the right-hand side. This ensures that the two parts of the connector can only be mated in one orientation.By orientating the polarising extensions 46 differently on different connectors 32, they can be given a unique key so that the board assemblies 30 cannot be connected at the wrong locations in the housing 1.

The housing 52 of the connector 22 has, on its rear face, two rearwardly-projecting studs 61 at opposite ends, positioned in alignment with the axis of the recesses 59 and the holes 51 in the lugs 24 of the support assembly 21. The studs 61 are externally threaded and carry the floating bush assemblies 50, most clearly shown in Figure 5. The bush assembly 50 comprises a metal disc 70 against the housing 52 and a metal bush 53 with a flange 54 at its forward end defining an annular recess 55 with the disc. A resilient annular liner 56 of Ushape in section is retained in the recess 55. The bush 53 and disc 70 are clamped firmly against the housing 52 by a nut 71 and washer 72. The dimensions of the recess 55, its liner 56 and the holes 51 are such that the bush can float resiliently to a limited extent both in the plane of the rails and along an axis normal to this plane.

The backplane assembly 20 is retained in the housing 1 by location of the lugs 24 in the channels 3, which prevents movement of the assembly in the plane of the rails, and by several retaining screws (not shown) which hold the support assembly 21 against the rear wall of the housing. The retaining screws can easily be removed from the front of the housing to enable the entire backplane assembly 20 to be slid forwards along the channels and removed for maintenance or replacement.

A circuit board assembly 30 is installed in the system by locating its edges in the channels 3 and pushing it rearwardly until the rear of the connector 32 on the board 31 enters the recess 53 in the front face of the backplane connector 32 and the tip of the jackscrews 41 and 42 enter the forward part of the recesses 59. Further rearward movement of the board assembly 30 is accomplished by screwing the two jackscrews 41 and 42 into the recesses 59 by twisting the knobs 47 at the forward end of the jackscrews; this pulls the connector 32 and board 31 rearwardly. As the board connector 32 is displaced further, its fibre-optic contacts 35 abut the contacts 55 in the backplane connector 22 and push these rearwardly against the resilience of their spring mounting.The force necessary to overcome the cumulative effect of the resilience of all the springs is readily produced by the mechanical advantage of the jackscrews 41 and 42. When the jackscrews 41 and 42 have been fully tightened, the faces of the connectors 32 and 22 will be in contact with one another, ensuring full contact of the electrical and optical contacts. The fluid couplings 38 and 58 on the two connectors will also be engaged with one another. Fluid connection to the fluid coupling 58 on the backplane connector is made via holes 26 along the rails 23.

The firm retention between the mating connectors 22 and 32 produced by the engagement ofthejackscrews 41 and 42 in the recesses 59 eliminates relative movement between the connectors caused by vibration or shock. This eliminates interfacial fretting at the faces of the contacts 35 and 55, which can otherwise be a severe problem in optical devices. Contact bounce and wear is also eliminated or reduced. Because the connector halves are retained together individually, there is no cumulative force on the backplane 20 of the kind that would be produced if the connectors were held together by clamping the forward end of the board to the housing 31. This enables a relatively lightweight structure to be used in the backplane.Because the backplane connectors 22 are able to float at the bush assemblies 50, when the jackscrews 41 and 42 are tightened, the backplane connectors are supported by th hoard 31 and its connector assembly 32, which is opposite to the way in which conventional printed circuit boards are mounted, where the boards are supported by the connectors. The secure, reliable retention produced by this arrangement still enables the boards to be individually removed from the front of the housing 1. The backplane assembly 20 with its optical interconnections is also removable from the front of the housing 1.

The functions of aligning the connectors, polarizing, jacking and thermal clamping are carried out within a single coaxial system, namely the jackscrews 41 and 42, which are controlled from the front of the housing 1. This enables a very compact configuration to be achieved.

With reference now to Figures 7 to 10, there is shown an alternative system having a board assembly 130 and a backplane assembly 120, which has a connector 122 with four inserts 100, each including a group of four fibre-optic contacts 135 connected to the end of respective cables 136. The contacts 135 are ofthe mechanical transfer type and are each urged forwardly by two helical springs 137 so that they make resilient contact with cooperating contacts in the mating connector 132. These types of insert enable a high density of contacts.

Claims

1. An assembly of the kind comprising a circuit board and fibre-optic connector mounted along the rear end of the board and arranged to mate with a cooperating fibre-optic connector mounted on a backplane, wherein the assembly includes two jacking members extending from the rear end to the forward end of the board along opposite edges of the board such that the forward end ofthejacking members is accessible at the forward end of the board, and wherein the rear end of the jacking members is arranged to engage said cooperating connector such that the two connectors can be drawn together and retained together by operation of the jacking members from the forward end of the assembly.

2. An assembly according to Claim 1, wherein the jacking members are jackscrews.

3. An assembly according to Claim 1 or 2, wherein the cooperating fibre-optic connector is mounted on the backplane in a floating manner such that it is free to move relative to the backplane to a limited extent.

4. An assembly according to any one of the preceding claims, wherein the connectors include mating electrical contacts.

5. An assembly according to any one of the preceding claims, wherein the connectors include mating fluid connectors.

6. An assembly according to any one of the preceding claims, wherein the connectors have cooperating polarizing formations concentrically of the jacking members.

7. A system of the kind comprising a housing, a circuit board assembly mounted in the housing with opposite edges located in respective channels extending in the housing from its forward to its rear end, wherein the circuit board assembly includes a fibre optic connector mounted along the rear end of a circuit board and arranged to mate with a cooperating fibre-optic connector mounted on a backplane extending within the rear of the housing, wherein the circuit board assembly includes two jacking members extending from the rear end to the forward end of the board along opposite edges of the board within said channels such that the forward end of the jacking members is accessible at the forward end of the board, and wheren the rear end of the jacking member is arranged to engage said cooperating connector such that the two connectors can be drawn together and retained together by operation of the jacking member from the forward end of the assembly.

8. An assembly according to Claim 7, wherein the jacking members are jackscrews.

9. An assembly according to Claim 7 or 8, wherein the jacking members carry wedge locks operable to engage the channels and clamp the board in the channels.

10. A system according to any one of Claims 7 to 9, wherein the housing has a plurality of parallel channels, wherein the system has a plurality of circuit board assemblies having opposite edges located in respective channels, and a plurality of cooperating fibre-optic connectors mounted on said backplane.

11. A system according to Claim 10, wherein the cooperating fibre-optic connectors are mounted on said backplane in a floating fashion such that the cooperating connectors can move relative to one another to a limited extent.

12. An assembly according to any one of Claims 7 to 11, wherein the backplane comprises a support member with lugs projecting at each side that engage in said channels, and wherein said lugs have holes therethrough within which the cooperating connectors are mounted on said backplane.

13. A system including an assembly comprising a circuit board and a first fibre-optic connector mounted along the rear end of the board, and a backplane assembly comprising a second fibre-optic connector and a support assembly for the second connector, wherein the support assembly includes a first member and a floating bush securing the second connector with the first member such that the second connector can float relative to the first member.

14. A circuit board assembly substantially as hereinbefore described with reference to Figures 1 to 6 of the accompanying drawings.

15. A circuit board assembly substantially as hereinbefore described with reference to Figures 1 to 6, as modified by Figures 7 to 10 of the accompanying drawings.

16. A fibre-optic connector system substantially as hereinbefore described with reference to Figures 1 to 6 of the accompanying drawings.

17. A fibre-optic connector system substantially as hereinbefore described with reference to Figures 1 to 6, as modified by Figures 7 to 10 of the accompanying drawings.

18. Any novel feature or combination of features as hereinbefore described.