GB2174551A

GB2174551A - Screened rack

Info

Publication number: GB2174551A
Application number: GB08508137A
Authority: GB
Inventors: Brian Houghton
Original assignee: RAINFORD METALS Ltd
Current assignee: RAINFORD METALS Ltd
Priority date: 1985-03-28
Filing date: 1985-03-28
Publication date: 1986-11-05
Also published as: GB2174551B; GB8508137D0

Abstract

A gasket arrangement forms an electrical connection between the metal frame of a screened rack 10 and a removable or displaceable metal panel or door 56 adapted to cover an opening in the frame. The frame is provided with an elongate groove 32 extending around the opening, the groove receiving longitudinally therewithin a tubular, resilient, electrically conductive gasket 54. The groove has a cross-sectional configuration such that, when the panel or door is removed or opened relative to the opening in the frame, the gasket is held in the groove in a substantially undistorted condition by means of opposed projections 52 at the mouth of the groove and with a longitudinal peripheral portion of the gasket projecting out of the groove, and such that, when the metal panel or door 56 is brought into a closed position in abutment with the metal frame and with the gasket resiliently compressed therebetween the gasket can be accommodated further within the groove. <IMAGE>

Description

SPECIFICATION Screened rack The invention relates to a screened rack, and in particular, but not exclusively, to a rack for holding a plurality of card frames in which a plurality of printed circuit boards may be releasably held, the rack being screened against radio frequency interference.

A rack for holding card frames basically comprises a metal framework of four vertical metal posts which are interconnected by four cross pieces at their upper ends and four cross pieces at their lower ends, forming a cuboidal framework.

The six "faces" of the framework are each provided with a closure which may either be removable, e.g. a door, to allow access to the interior of the rack, or may be permanently connected, e.g. a panel, to the framework where access is not required, e.g. the base and the top.

The contact between the doors and the framework must be continuous around the whole of the perimeters of the doors, in order to achieve effective screening of the interior of the rack and to avoid unwanted effects, such as earth loops which may form in a gap between a closure and the frame. The required contact is normally provided by using a radio frequency interference gasket comprising wire mesh in the form of a tube, with a thin rubber tube inside.

When a door is closed against the gasket, the gasket deforms to provide a continuous seal around the perimeter of the door. The wire mesh is provided with a flange running along its length.

The gasket is secured to the frame by attaching Lshaped brackets to the flange by means of a screw passing through one arm of the bracket and the flange and passing into the frame. Brackets must be secured approximately every 150mm to hold the gasket in place and also to provide a stop for the door with the end of the other arm of the bracket. The securing of the gasket every 150mm is labour intensive and also expensive over the total length of frame in a rack which may amount to several metres.

It is an object of the present invention to provide a screened rack which will have substantially continuous contact around the whole perimeter of the frame of the rack but which is constructed in a much simpler and less labour intensive manner than heretofore.

In accordance with the present invention, there is provided a gasket arrangement for forming an electrical connection between two relatively dis placeable metal members when the two members are brought into abutment, wherein one of said metal members is provided with an elongate groove which receives longitudinally therewithin a tubular, resilient, electrically conductive gasket, the groove having a cross-sectional configuration such that, when said metal members are in a separated state, the gasket is held in said groove in a sub stantially undistorted condition by means of op posed projections at or adjacent the mouth of the groove and with a longitudinal peripheral portion of the gasket projecting out of the groove, and such that, when the metal members are brought into abutment with the gasket resiliently compressed therebetween, the gasket can be accommodated further within the groove.

Preferably, the groove is at least partially defined by two side walls which are inclined relative to one another and which serve to support the gasket so that it projects partially out of the groove when in said undistorted condition.

Preferably, the base of the groove is provided with a recess intermediate said two relatively inclined side walls for accommodating part of the gasket when the two metal members are in abutment with the gasket compressed therebetween.

Advantageously, the projections at or adjacent the mouth of the groove comprise integral, knifeedged lips disposed at the outer ends of said inclined side walls.

Preferably, said knife-edged lips extend along the whole length of the groove.

Preferably, said inclined side walls are mutually perpendicular.

By way of example only, a specific embodiment of the invention will now be described, with reference to the accompanying drawings, in which: Figure 1 is an exploded perspective view of a corner of a rack, formed with a gasket arrangement in accordance with the invention; Figure 2 is a cross-section through an upright member of a rack embodying the invention, with two doors fitted; Figures 2a and 2b are details of Figure 2 showing the section of the retaining grooves to a larger scale; and Figure 3 is a cross section through a horizontal member of a rack embodying the invention.

Referring to the figures, a post 10 of a rack frame is secured to two base portions 12, 14 of the frame. Only one corner of the frame is illustrated, but it will be appreciated that four posts 10 and eight portions 12, 14 are provided, and that the other seven corners are similar.

The post 10 is extruded from aluminium and comprises an exterior wall 16 and a parallel interior wall 18. A wall 20 extends normally from one edge of the wall 16 and meets a wall 22 extending parallel to wall 18. In turn, the wall 22 meets a wall 24 extending normally to, and joining, the wall 18.

Extending normally from the other edge of wall 16 is a wall 26 which joins a wall 28 at right angles thereto. Wall 28 joins wall 30 which joins, and is normal to, the wall 18.

The walls 24 and 28 are each provided with a longitudinal retaining groove 32, which are used for retaining a metal mesh sealing strip, as will be explained. The walls 18 and 30 are each provided with a groove 34, 36 respectively which assist in defining the shape of the retaining grooves 32. The wall 18 is also provided with two brackets, one 38 extending normally to the wall 18 and the 40 being an extension of the wall 18. The brackets are provided with a plurality of apertures 42 so that they may be used as mountings.

The post 10 is substantially hollow, but within the post are extruded four near-circular grooves 44. These are shaped to receive seif-tapping screws (not shown) which may be passed through holes in the base portions 12, 14 and screwed into the grooves 44 to secure the frame together, as will be explained.

Referring to the retaining grooves 32 in more detail, these comprise a flat base 46, parallel to the wall 24 or 28, two parallel opposed faces 48, per pendicular to the base 46, two faces 50 inclined at about 45 degrees to the faces 48, and two faces 52, inclined substantially perpendicularly to the faces 50. The edges of the faces 52 define two opposed, longitudinal, inwardly-facing, knife-edged lips along the two sides of the retaining groove. In use, the retaining grooves hold a flexible wire mesh tube 54 comprising a wire mesh tube with a rubber tube inside, which affords a flexible, resiliently de fordable conductor. In use, the wire mesh tube is pressed into the retaining grooves 32 and is held in the grooves by the lips 52 of the groove 32, and abuts the faces 50 of the groove 32.When in serted, the wire mesh tube 54 is substantially circular in cross-section, as in the upper groove illustrated in Figure 2, but when deformed e.g. by a door 56 as illustrated in the lower groove illustrated in Figure 2, the portion of the tube extend ing out of the groove is flattened, and the tube is deformed to fill the groove more fully, and in particular to occupy the portion of the groove between the base 46 and the two opposed faces 48.

Referring now to Figures 1 and 3, the base portions 12 and 14 comprise a horizontal portion 58, two portions 60, 62 perpendicular to the horizontal portion 58 and two flanges 64, 66, one being an extension of the horizontal portion and the other being an extension of the portion 62, parallel to the flange 64. The surface of approximately half the horizontal portion 58, indicated 68, is at a lower level than the rest of the horizontal portion. Provided on the slightly lower surface 58 is a flange 70, forming another retaining groove 32 identical to those previously described. As before, in use, a flexible wire mesh tube 54 is held in the groove.

Also provided on the surface 68 are two elongate projections 72 on either side of the flange 70, which are triangular in cross-section. The apex of each of the projections is at the same level as the higher surface of the horizontal portion 58 and the faces are inclined at 45 degrees to the surface 68.

The eight portions 12, 14 are all identical.

Referring to Figure 1, the ends of the two base portions 12, 14 are mitred at an angle of 45 degrees to form a right-angle between the two base portions. Four holes 74 are provided in the base portions 12, 14 and screws passing through these holes and into the grooves 44 secure the post to the base portions 12, 14, with the post 10 occupying the position marked with dotted lines. Since there are four posts 10, eight corners are created in this way, with the portions 12, 14 at the top of the posts 10 being inverted. In this way, a cuboidal frame is created, into the open faces of which doors may be fitted.

When the frame is complete, a retaining groove 32 extends around the whole of the periphery of the framework forming the open faces. A flexible wire mesh tube 54 is pressed into the groove 32 in each section of the frame and is held in the grooves by the lips 52 extending along substantially the whole length of the grooves. The wire mesh tube may pass into different straight sections of framework via a portion 76 which is cut out of the face 24 of the post 10. In this way, a continuous conductive connection is maintained around the whole periphery of the open face of the framework.

Referring to Figure 2, two metal doors 56 are illustrated, one in the open position and one in the closed position. The doors illustrated are hinged, but the doors may be replaced with panels which are permanently connected to the framework of the rack. When the door is open, as the upper door in Figure 2, the wire mesh tube is held in place by the lips 52 of the groove 32, and the tube assumes substantially its original shape within the groove due to the resilience of the inner rubber tube.

When the door is closed, as the lower door in Figure 2, the wire mesh tube is deformed as previously described, pressing the tube into the groove 32, and a conductive contact is provided around the whole periphery of the door. The face 24 forms a stop which the door abuts when in the closed position.

The door may be opened and closed frequently, and the wire mesh tube will still provide a continuous peripheral contact because of its resilience.

However, installing the wire mesh tube is a simple matter of pressing into a groove and requires no screwdriver and no fittings in order to secure it.

The invention is not restricted to the details of the foregoing embodiment, for example, the lips 52 of the groove 32 need not be continuous, but may comprise one or more projections extending into the groove.

Claims

1. A gasket arrangement for forming an electrical connection between two relatively displaceable metal members when the two members are brought into abutment, wherein one of said metal members is provided with an elongate groove which receives longitudinally therewithin a tubular, resilient, electrically conductive gasket, the groove having a cross-sectional configuration such that, when said metal members are in a separated state, the gasket is held in said groove in a substantially undistorted condition by means of opposed projections at or adjacent the mouth of the groove and with a longitudinal peripheral portion of the gasket projecting out of the groove, and such that, when the metal members are brought into abutment with the gasket resiliently compressed therebetween, the gasket can be accommodated further within the groove.

2. A gasket arrangement as claimed in claim 1 wherein the groove is at least partially defined by two side walls which are inclined relative to one another and which serve to support the gasket so that it projects partially out of the groove when in said undistorted condition.

3. A gasket arrangement as claimed in claim two, wherein said inclined side walls are mutually perpendicular.

4. A gasket arrangement as claimed in claim 2 or 3, wherein the base of the groove is provided with a recess intermediate said two relatively inclined side walls for accommodating part of the gasket when the two metal members are in abutment with the gasket compressed therebetween.

5. A gasket arrangement as claimed in claim 1, 2, 3, or 4 wherein the projections at or adjacent the mouth of the groove comprise integral, knifeedged lips disposed at the outermost ends of said inclined side walls.

6. A gasket arrangement as claimed in claim 5, wherein said knife-edged lips extend along the whole length of the groove.

7. A gasket arrangement as claimed in claim 5, wherein said knife-edged lips are not continuous but comprise a plurality of projections extending into the groove.

8. A gasket arrangement as claimed in any of claims 1 to 7, wherein the gasket comprises a flexible wire mesh tube having a rubber tube disposed coaxially within it.

9. A screened rack having a gasket arrangement as claimed in claim 1, disposed between a static metal rack frame and at least one removable or displaceable metal panel or door adapted to cover an opening in said rack frame, said rack frame and said panel constituting said two relatively displaceable metal members.

10. A screened rack having a gasket arrangement for forming an electrical connection between a metal frame of the rack and a removable or displaceable metal panel or door adapted to cover an opening in said frame, wherein the frame is provided with an elongate groove extending round said opening, the groove receiving longitudinally therewithin a tubular,-resilient, electrically conductive gasket, the groove having a cross-sectional configuration such that, when said metal panel or door is removed or opened relative to said opening in the frame the gasket is held in said groove in a substantially undistorted condition by means of opposed projections at or adjacent the mouth of the groove and with a longitudinal peripheral portion of the gasket projecting out of the groove, and such that, when the metal panel or door is brought into a closed position in abutment with the metal frame and with the gasket resiliently compressed therebetween, the gasket can be accommodated further within the groove.