GB2305300A

GB2305300A - Modular electronic assembly

Info

Publication number: GB2305300A
Application number: GB9518829A
Authority: GB
Inventors: Neil Richard Butler
Original assignee: GEN DATACOMM ADV RES
Current assignee: GEN DATACOMM ADV RES
Priority date: 1995-09-14
Filing date: 1995-09-14
Publication date: 1997-04-02
Anticipated expiration: 2015-09-14
Also published as: GB2305300A8; GB9518829D0; GB2305300B

Abstract

A modular electronic assembly has a mounting frame provided with slots for slidingly receiving electronic sub-assemblies 1, each sub-assembly 1 being engageable with a respective electrical connector 3 on the mounting frame, an electrical drive 5,7,6 being provided between each sub-assembly 1 and the respective slot in the mounting frame, whereby the sub-assembly may be selectively drawn into and ejected from its slot by operation of the drive.

Description

Modular Electronic Assembly Field of the Invention This invention relates to a modular electronic assembly comprising a mounting frame and a plurality of electronic sub-assemblies mounted therein.

Background to the Invention Typically in such assemblies, for example card racks mounting printed cir- cuit boards, there is a need to be able to remove and replace individual subassemblies. Manual ejection and insertion of the sub-assemblies is becoming ever more difficult as the sizes of the boards increase, and the number of edge connectors on the boards also increases. Lever arrangements are used to facilitate ejection and insertion, but such arrangements often leave gaps in panels, providing undesirable areas of leakage for RFI (radiofrequency interference?). Many modular systems require a positive location and alignment set-up to prevent damage to the edge connectors or pins. Lever systems tend to generate forces in such a way as to make the accurate alignment difficult to maintain.

Summary of the Invention According to the invention, there is provided a modular electronic assembly, comprising a mounting frame provided with a plurality of slots for slidingly receiving a plurality of electronic sub-assemblies, each sub-assembly being engageable with a respective electrical connector on the mounting frame to provide a plurality of electrical connections between the sub-assembly and electrical circuits on the mounting frame, and electrical drive means being provided between each subassembly and the respective slot in the mounting frame, whereby the sub-assembly may be selectively drawn into and ejected from its slot by operation of the drive means.

Preferably the drive means comprise an electric motor mounted on the subassembly, driving a screw-threaded shaft engageable with a correspondingly threaded socket in the slot. The socket is preferably spring mounted to facilitate engagement between the shaft and the socket when the sub-assembly is located manually in the slot. The power for the motor is suitably provided by contacts on the mounting frame connecting with corresponding contacts on the sub-assembly, so that loosely sliding the sub-assembly into the slot makes the motor power contacts to commence the driving of the sub-assembly towards its fully-seated position in which the plurality of contacts are correctly made.A limit switch in the slot can switch off the power to the motor when the correct position is reached, or means can be provided to sense an over-current in the motor and to break the circuit in response thereto.

Ejection can be effected by means of an external switch or under control of software running in the electronic circuits of the sub-assembly, for example. The polarity of the electrical supply to the motor is simply reversed to reverse the motor to cause ejection, the circuit being broken when the motor power contacts separate at the limit of travel of the screw drive.

The screw drive can be arranged to be operated manually in the event of drive failure, by extending the threaded shaft through to the front of the assembly and providing on the free end a handle or a configuration engageable by an external tool. The shaft may be extended by means of a flexible drive shaft if it is necessary to avoid obstacles.

The drive may be located so as to ensure an evenly-balanced driving force on the sub-assembly, minimising the risk of distortion. For a very large subassembly, more than one drive means may be provided, the drive means being spaced apart to ensure that the forces are balanced. Separate motors may be provided, or more than one screw can be driven from a single motor.

It will be appreciated that, although it may be convenient to mount the drive motor on the sub-assembly, in some circumstances the reverse arrangement may be more convenient, with the drive motor mounted in the slot. equally, the motor may drive a threaded socket engaging on a fixed, or spring-mounted threaded shaft.

Brief Description of the Drawings In the drawings, which illustrate an exemplary embodiment of an electronic sub-assembly mounted in a card rack: Figure 1 is a perspective view; Figure 2 is an enlarged part-sectioned view of the mounting drive means; and Figures 3, 4 and 5 are views corresponding to that of Figure 2, but omitting the motor and gearing, illustrating successive stages in operation of the screw drive.

Detailed Description of the Illustrated Embodiment Referring to Figure 1, the sub-assembly 1 has a printed circuit board signal connector 2 which is received in a backplane connector 3 on the slot in the card rack 4. The board 1 also mounts an electric motor 5 which drives a finely screwthreaded spindle 6, via a reduction gearbox 7. The spindle 6 has a flexible drive extension 8 which extends to the front panel of the sub-assembly 1 to permit manual rotation, using a suitable tool, of the threaded spindle in the event of a drive failure. An earth stud 9 extends from the rear of the sub-assembly 1 to be received in a mating earth receptor 10 as the first point of contact between the sub-assembly and the backplane of the rack as the sub-assembly is inserted into its slot. The backplane of the slot also mounts a sprung power receptor 11.

As may be seen from Figures 2 to 5, the power receptor contains a screwthreaded nut 12 slidable therein and biased towards the front of the receptor by a helical compression spring 13. The mouth 14 of the receptor is tapered inwardly to guide the spindle 6 into the nut 12. The power receptor also serves to provide electrical power to the motor 5, via the spindle 6, the earth stud 9 providing the return path of the motor power circuit.

In use, the sub-assembly is inserted into its slot by hand and pushed rearwardly until the earth stud 9 contacts the earth receptor 10 and the spindle 6 contacts the nut 12 and pushes it inwardly of the power receptor 11 against the force of the spring 13, as shown in Figure 4. This serves two purposes. Firstly, the motor power circuit is closed, causing the motor to turn the spindle 6. Secondly, the nut is urged into contact with the spindle, ensuring that the threads engage and that the rotation of the spindle draws the sub-assembly into its contact position in which the signal connector 2 is firmly engaged with the backplane connector 3 to ensure satisfactory electrical contacts are made therebetween. At this point, shown in Figure 5, further rotation of the motor is impossible, and an overcurrent condition is generated in the motor. A motor control circuit (not shown) detects this condition, opens the motor power circuit and at the same time reverses the polarity of the supply to the motor so that, when the circuit is closed again, the mo- tor will reverse to eject the sub-assembly by the reverse action to that hereinbefore described.

Motor control in the case of ejection may be achieved by a combination of software and hardware tailored to particular applications. In its simplest form, an eject button could be provided on the front panel of the sub-assembly.

Claims

1. A modular electronic assembly, comprising a mounting frame provided with a plurality of slots for slidingly receiving a plurality of electronic subassemblies, each sub-assembly being engageable with a respective electrical connector on the mounting frame to provide a plurality of electrical connections between the sub-assembly and electrical circuits on the mounting frame, and electrical drive means being provided between each sub-assembly and the respective slot in the mounting frame, whereby the sub-assembly may be selectively drawn into and ejected from its slot by operation of the drive means.

2. A modular electronic assembly according to Claim 1, wherein the drive means comprise an electric motor mounted on the sub-assembly, driving a screw-threaded shaft engageable with a correspondingly-threaded socket in the slot.

3. A modular electronic assembly according to Claim 2, wherein the socket is spring-mounted.

4. A modular electronic assembly according to Claim 2 or 3, wherein power for the motor is provided by contacts on the mounting frame connecting with corresponding contacts on the sub-assembly.

5. A modular electronic assembly according to Claim 2, 3 or 4, comprising a limit switch in the slot to switch off the power to the motor when the correct position is reached.

6. A modular electronic assembly according to Claim 2, 3 or 4, comprising means for sensing an over-current in the motor and for breaking the motor power circuit in response thereto.

7. A modular electronic assembly according to any preceding claim, comprising an electric switch for causing the drive means to operate to eject the sub-assembly from the slot.

8. A modular electronic assembly according to any preceding claim, comprising manually-operable drive means to permit insertion or ejection of the sub-assembly in the event of failure of the electrical drive means.

9. A modular electronic assembly, substantially as described with refer ence to, or as shown in, the drawings.

9. A modular electronic assembly according to Claim 8, wherein the manually-operable drive means comprises a flexible drive shaft.

10. A modular electronic assembly, substantially as described with reference to, or as shown in, the drawings.

Amendments to the claims have been filed as follows

1. A modular electronic assembly, comprising a mounting frame provided with a plurality of slots for slidingly receiving a plurality of electronic subassemblies, each sub-assembly being engageable with a respective electrical connector on the mounting frame to provide a plurality of electrical connections between the sub-assembly and electrical circuits on the mounting frame, and electrical drive means being provided between each sub-assembly and the respective slot in the mounting frame, whereby the sub-assembly may be selectively drawn into and ejected from its slot by operation of the drive means, wherein the drive means comprise an electric motor mounted on the sub-assembly, driving a screw-threaded shaft engageable with a correspondingly-threaded socket in the slot.

2. A modular electronic assembly according to Claim 1, wherein the socket is spring-mounted.

3. A modular electronic assembly according to Claim 2, wherein power for the motor is provided by contacts on the mounting frame connecting with corresponding contacts on the sub-assembly.

4. A modular electronic assembly according to Claim 2 or 3, comprising a limit switch in the slot to switch off the power to the motor when the correct position is reached.

5. A modular electronic assembly according to Claim 2 or 3, comprising means for sensing an over-current in the motor and for breaking the motor power circuit in response thereto.

6. A modular electronic assembly according to any preceding daim, comprising an electric switch for causing the drive means to operate to eject the sub-assembly from the slot.

7. A modular electronic assembly according to any preceding claim, comprising manually-operable drive means to permit inSertion or ejection of the sub-assembly in the event of failure of the electrical drive means.

8. A modular electronic assembly according to Claim 7, wherein the manually-operable drive means comprises a flexible drive shaft.