GB2163210A

GB2163210A - Clamping arrangement for electronic modules

Info

Publication number: GB2163210A
Application number: GB08519174A
Authority: GB
Inventors: Derek Anthony Rush
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 1984-08-17
Filing date: 1985-07-30
Publication date: 1986-02-19
Also published as: GB2163210B; GB8519174D0

Abstract

Heat dissipation from electronic modules 20 is improved by clamping their edges against heat- conducting fins in a housing 2 by means of two expanding jackscrews 40. Each jackscrew 40 has a shaft 41 mounted in bearings 45 and 46 in the module 20 and carries a row of alternate closed rings 50 and split rings 51. The closed rings 50 are smaller in diameter than the split rings 51 and have a circular section. The split rings 51 are of tubular shape, having ends of circular section which engage the closed rings. The forward end of the shah 41 is screw-threaded to engage a fixed nut 44 in the housing 2. When the shaft 41 is screwed into the fixed nut 44 it pulls a connector 30 on the module 20 into engagement with a cooperating connector in the housing. At the same time, the closed rings 50 are forced against the split rings 51 causing them to expand radially and exerting a clamping force against the edges of the modules forcing them into thermal contact with the fins 5 on the housing 2. <IMAGE>

Description

SPECIFICATION Clamping means, and modules and units including clamping means This invention relates to clamping means, and to modules and units including clamping means.

Various arrangements are used to dissipate the heat produced by electronic modules mounted in a housing. In one such arrangement the modules include a heat-conducting frame, such as of metal, which is in good thermal contact with the heat-generating components in the module. The housing is provided with heat-dissipating walls which may be actively cooled by a coolant fluid, or by an air blower, or may simply have a large thermal capacity. The frame of the module is clamped in good thermal contact with the heat-dissipating walls so that heat generated by the module is conducted away through the frame to the walls of the housing.

One arrangement for achieving this clamping uses two jackscrews on opposite sides of the module which are screwed into the housing to retain the module in position. Each jackscrew carries two wedges with opposed inclined surfaces that are urged laterally away from one another when the jackscrew is tightened, such as to force the frame of the module into contact with the wall of the housing.

Such clamping arrangements suffer from the disadvantage that the clamping effect is relatively localised and good thermal contact is not achieved along the entire length of the module.

It is an object of the present invention to provide clamping means by which the thermal contact can be improved.

According to one aspect of the present invention there is provided clamping means for clamping one member relative to another member, the clamping means comprising an elongate shaft that extends parallel to a surface of the one member, a plurality of inexpansible ring members that embrace and are spaced apart along the shaft, and a plurality of radially-expansible ring members interposed between the inexpansible ring members, the clamping means including means for urging said ring members together along the length of the shaft, and said inexpansible ring members and said expansible ring members being arranged such that urging said inexpansible ring members towards said expansible ring members causes said expensible ring members to expand radially around their circumference so as to engage said one member and clamp it relative to said other member.

In this way, a clamping force is exerted by each expansible ring member so that the force can be equally distributed along the length of the one member.

The expansible ring members may be of a rigid material, the expansible ring members being split to allow for radial expansion thereof, and the expansible and inexpansible ring members being provided with cooperating surfaces arranged such that said expansible ring members expand radially outwards on axial displacement of the inexpansible ring members. Preferably the cooperating surfaces have circular shapes. The expansible ring members may be of steel or of a compliant resilient material. The inexpansible ring members may be circular in section, and the expansible ring members may be of tubular shape with each expansible ring member being of substantially the same length. The ring members may be free to rotate about the shaft.The shaft is preferably provided with screw means, that is arranged to engage cooperating screw means, such that rotation of the shaft causes axial displacement of the shaft and thereby causes axial displacement of said ring members towards one another. The shaft may be provided with a knurled knob by which the shaft can be rotated.

According to another aspect of the present invention there is provided an electronics module including electronic circuit elements mounted on a frame and clamping means according to the said one aspect of the present invention, the clamping means being arranged for clamping said electronics module in a housing.

The module preferably includes two clamping means that extend along opposite sides of the module. The module may include an edge member extending along the length of the or each clamping means, and the or each clamping means may be arranged to urge the said edge member into thermal contact with a heat-conducting member. The or each said clamping means may extend through bearings on said module that permit rotational and axial displacement of said shaft. The module may include connector means at one end of the module, clamping means being arrange to effect displacement of the module along the length of the clamping means such as to urge the connector means into engagement with cooperating conector means.

According to a further aspect of the present invention there is provided an electronics unit including a housing and a plurality of electronics modules according to the said other aspect of the present invention, the clamping means being arranged for clamping each module in the housing.

The housing may include a plurality of channels which are adapted to receive edges of the modules, the clamping means being arranged to clamp the edges of the modules in the channels.

An electronics unit including several electronic modules with clamping means, in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic perspective view of the unit; Figure 2 is a plan view of the top of one module; Figure 3 is a partly cut-away enlarged plan view of a part of the module, showing the clamping means; Figure 4 s a cross-sectional end elevation of the module showing the clamping means; and Figures 5A to 5C are cross-sectional side elevation view along the length of the clamping means showing its operation at different positions.

With reference to Fig. 1, the electronics unit comprises a housing 2 in which are supported several electronics modules 20.

The housing 2, which is only illustrated schematically, has side walls 3 which serve to dissipate heat produced by the modules 20.

In this respect, the walls 3 may be cooled, such as by means of a cooling# fluid, flowing through them. Each module 20 is supported at opposite edges 21 and 22 in channels 4 in the walls 3, the channels being defined between parallel fins 5 which are in intimate thermal contact with the edges of the modules. The fins 5 are of metal or another heatconducting material and serve to conduct heat away from the modules 20 to the walls 3 of the housing 2.

With reference now also to Fig. 2, each module 20 comprises a rectangular printed circuit board 23 on which are mounted various electronic circuit elements 24. The printed circuit board 23 is supported on a cast aluminium alloy frame 27 and is protected by sheet aluminium cover plates 28 on both sides. The frame 27 projects beyond the board 23 and supports, at its forward edge 29 a connector 30 which is electrically connected to the circuit elements 24 on the board, and which is arranged to mate with a cooperating backplane connector (not shown) mounted in the housing 2. The mounting of the connector 30 on the frame 27 preferably allows the connector to float freely to a limited extent relative to the frame, so as to allow for displacement of the module while it is being secured in the housing 2.The forward edge 29 of the module 20 is also provided with keying pins 31 which ensure correct orientation of the module and which can be used to give each module a unique key so that it cannot be inserted into the wrong location in the housing.

The edges 21 and 22 of the module 20 are formed by projecting edges of the frame 27, towards the upper surface of the module 20.

Beneath each edge 21 and 22 the module 20 carries a clamping device or expanding jackscrew 40, as shown in more detail in Figs. 3 and 4. Each jackscrew 40 has a stainless steel shaft 41 that extends the length of the module 20 parallel to the surface of the edge 21 or 22. At its rear end, the shaft 41 has a knurled knob 42, which may also be provided with a screwdriver slot, and by which the shaft may be rotated about its axis. At its forward end, the shaft 41 has a screwthreaded portion 43 which engages a fixed nut 44 in the housing 2. The forward and rear ends of the shaft 41 extend through respective bearings 45 and 46 at the forward and rear end of the frame 27. The bearing 45 and 46 allow both rotation of the shaft 41 about its axis, and displacement of the shaft along its axis.Intermediate the two bearings 45 and 46, the shaft 41 supports a series of alternate closed rings 50 and split rings or tubes 51, typically, there may be twenty-one closed rings and twenty open rings. The rings 50 and 51 are free to be displaced along and around the shaft 41. At its rear end, adjacent the last closed ring 50, the shaft 41 carries a thrust bush 52 which is fixed with the shaft 41 for rotation and axial displacement with the shaft.

With reference now also to Figs. 5A to 5C, each closed ring 50 is circular in shape and circular in section, having an internal diameter d of about 6.5 mm, substantially equal to the outside diameter of the shaft 41, and a thickness t of 0.3 mm. The rings 50 are preferably of a steel or other hard metal. The split rings 51 are of a spring metal such as stainless steel, and have the same internal diameter, in their natural state, as the closed rings 50. The split rings 51 are thicker than the closed rings, having a thickness T of 0.5 mm, and are elongated axially, being 5.5mm long. Opposite ends of the rings 51 are of semicircular section, with a radius of 0.25 mm, the middle part of each ring being of cylindrical shape.

Each ring 51 has a narrow slot 53 extending along its length, as shown in Fig. 3, to enable the ring to be expanded radially, the slot 53 being opened as the ring is expanded.

The two jackscrews 40 extend within the channels 4, between a fin 5 of the housing wall 3 and an edge 21 or 22 of the frame 27 of the module 20. The external diameter (d + 2T) of the split rings 51 in their natural state is such as to allow free movement of the module 20 into or out of the housing 2.

In operation, the forward end of the module 20 is pushed gently into the housing 2, with the edges 21 and 22 of the module supported in opposite channels 4 in the housing, until the keying pins 31 engage appropriate keyways in the housing. The module 20 is then pushed fully in, as far as possible, so that the connector 30 on the module makes initial engagement with the connector in the housing 2. Full engagement is prevented by the projecting, forward end of the jackscrews 40 coming into contact with the rear of the housing. The jackscrews 40 are then turned by their knurled knobs 42, so that the screw threads 43 at their forward ends engage and are screwed into the nuts 44 in the housing, thereby pulling the module 20 forward and the connector 30 into full engagement.Further rotation of the jackscrews 40 causes them to effect a clamping action, urging the edges 21 and 22 of the module 20 upwards into good thermal contact with the fins 5 of the housing, along the length of the module.

This is achieved because rotation of the jackscrew 40 causes the thrust bush 52 to exert axial compression on the row of rings 50 and 51, causing radial expansion of the split rings 51. As the closed rings 50 are urged against the adjacent, respective split rings 51, they exert a force producing a reaction F directed between the centres of curvature of the contacting surfaces of the closed and split rings.

This reaction F has a component directed radially, resisting expansion of the split rings 51. As the jackscrews 40 are screwed in further, the split rings 51 are expanded further by opening the slot 53, against the resilience of the split ring, as shown in Fig.

5B. As the split rings 51 expand, their upper surfaces engage the lower surface of the edge 21 or 22 of the module, whilst their lower surfaces engage the upper surface of the fin 5, below the edges of the module, thereby urging the upper surface of the module edges upwards into good thermal contact with the fins 5.

Expansion of the jackscrew 40 is limited by the width of the channels 4 and the thickness of the edges 21 and 22 of the modules. The maximum expansion of the jackscrew 40 is shown in Fig. 5C, when the split rings 51 contact one another outside the closed rings 50. The external diameter of the jackscrew 40 thereby can be adjusted from a minimum of 7.5mm (that is, the diameter (d + 2T) of the split rings 51 before expansion) to a maximum of 7.925mm when the split rings contact one another.

When the jackscrew 40 is unscrewed, the resilience of the split rings 51 cause them to contract back about the shaft 41, thereby urging the closed rings 50 rearwardly along the shaft.

It will be appreciated that, because several split rings 51 are used along the length of the jackscrew 40, the clamping force exerted on the edge of the module 20 will be applied at several points along the length of the module such as to ensure good thermal contact all along the edge of the module.

The length of the split rings 51 can vary from that described. They could no longer than that shown, so that they are more tubular in shape, or shorter, so that they are circular in section. Rings of different length could be used on the same jackscrew.

Where the expansible rings are of a hard metal, the contacting surfaces of the inexpansible and expansible rings must be shaped to cooperate and produce a radial force on the expansible ring, such as is provided by the surfaces of circular section described above (although other shape surfaces are possible).

The expansible ring could, however, be of a compliant resilient material, such as of a rubber or elastomer, so that an axial force exerted on the expansible ring, compresses it axially, thereby producing a radial expansion.

Instead of using a fixed nut 44 in the housing 2 and a screw threaded portion 43 on the shaft 41 to produce an axial displacement of the shaft, other arrangements are possible. For example, one or both of the bearings 45 or 46 on the module 20 itself could be replaced with a screw-threaded bore that receives a screw-threaded portion of the shaft. In this way, rotation of the shaft in one sense produces axial displacement of the shaft and urges the series of rings 50 and 51 closer together to cause a clamping action.

It will be appreciated that clamping means in accordance with the present invention could be used to exert a clamping effect on articles other than the electronic module described.

Claims

1. Clamping means for clamping one member relative to another member, wherein the clamping means comprises an elongate shaft that extends parallel to a surface of the one member, a plurality of inexpansible ring members that embrace and are spaced apart along the shaft, and a plurality of radiallyexpansible ring members interposed between the inexpansible ring members, wherein the clamping means includes means for urging said ring members together along the length of the shaft, and wherein said inexpansible ring members and said expansible ring members are arranged such that urging said inexpansible ring members towards said expansible ring members causes said expansible ring members to expand radially around their circumference so as to engage radially around their circumference so as to engage said one member and clamp it relative to said other member.

2. Clamping means according to Claim 1, wherein the said expansible ring members are of a rigid material, wherein the expansible ring members are split to allow radial expansion thereof, and wherein the expansible and inexpansible ring members are provided with cooperating surfaces arranged such that said expansible ring members expand radially outwards on axial displacement of the inexpansible ring members.

3. Clamping means according to Claim 2, wherein the said cooperating surfaces have circular shapes.

4. Clamping means according to any one of the preceding claims, wherein the said expansible ring members are of steel.

5. Clamping means according to Claim 1, wherein the said expansible ring members are of a compliant resilient material.

6. Clamping means according to any one of the preceding claims, wherein the said inexpansible ring members are circular in section.

7. Clamping means according to any one of the preceding claims, wherein the said expansible ring members are of tubular shape.

8. Clamping means according to Claim 7, wherein each said expansible ring member is of substantially the same length.

9. Clamping means according to any one of the preceding claims, wherein the said ring members are free to rotate about the said shaft.

10. Clamping means according to any one of the preceding claims, wherein said shaft is provided with screw means that is arranged to engage cooperating screw means, such that rotation of the shaft causes axial displacement of the shaft and thereby causes axial displacement of said ring members towards one another.

11. Clamping means according to any one of the preceding claims, wherein said shaft is provided with a knurled knob by which the shaft can be rotated.

12. Clamping means substantially as hereinbefore described with reference to the accompanying drawings.

13. An electronics module including electronic circuit elements mounted on a frame and clamping means according to any one of the preceding claims, wherein said clamping means is arranged for clamping said electronics module in a housing.

14. An electronic module according to Claim 13 including two said clamping means that extend along opposite sides of said module.

15. An electronics module according to Claim 13 or 14 including an edge member extending along the length of the or each clamping means, and wherein the or each clamping means is arranged to urge the said edge member into thermal contact with a heat-conducting member.

16. An electronics module according to any one of Claims 13 to 15, wherein the or each said clamping means extends through bearings on said module that permit rotational and axial displacement of said shaft.

17. An electronics module according to anyone of Claims 13 to 16, including connector means at one end of said module, wherein said clamping means is arranged to effect displacement of the module along the length of the clamping means such as to urge said connector means into engagement with cooperating connector means.

18. An electronics module substantially as herein before described with reference to the accompanying drawings.

19. An electronics unit including a housing and a plurality of electronics modules according to anyone of Claims 13 to 18, wherein said clamping means is arranged for clamping each said module in said housing.

20. An electronics unit according to Claim 19, wherein the housing includes a plurality of channels which are adapted to receive edges of said modules, and wherein said clamping means are arranged to clamp the edges of the modules in said channels.

21. An electronics unit substantially as hereinbefore described with reference to the accompanying drawings.

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