AU732116B2 - A plug-in panel for circuit boards - Google Patents

Description

A PLUG-IN PANEL FOR CIRCUIT BOARDS Technical Field of the Invention The invention concerns a front panel for circuit boards which are intended to be mounted into housings which are protected against radio frequency interference.

Description of related art 233 507 describes a modular unit, for insertion into radio frequency interference protected housings for electronic equipment, which comprises a circuit board, a front plate having a U-shaped cross-section which is provided with a longitudinal web on one side of its sides and on its other side with a parallel longitudinal strip having an insertion slope. Metal spring elements are provided on the longitudinal web which, when the object is inserted into the housing, form an electrically conductive strip between the front plate and the adjacent front plate.

20 A problem with this construction is that the metal spring causes difficulties during 00 mounting and removal of the circuit board, because the spring tends to snag the adjacent card, especially if there are component parts which extend out from its rear side. The spring or components can thereby be easily damaged, and there is also a risk of injuring the person fitting or removing the card. The sealing spring S 25 is furthermore cumbersome to mount.

ooo* Furthermore it is important that the cooling air flow through such housings is properly distributed so that all the electronic equipment receive sufficient cooling.

It is therefore important that there are no unwanted openings in the housing which could effect the air flow and therefore the gaps between the front panels need to be airtight. This is difficult to achieve reliably with such (difficult to fit) springs.

A further problem with these front panels is the mounting of the circuit board to the panel. This is achieved by holding blocks being mounted on the inside of the front panel and the board being attached by screws to these blocks. This is timeconsuming both to manufacture and to use, since the blocks must be accurately fitted at predetermined positions on the panel.

Summary An object of the invention is to provide a front panel which can be easily mounted without risk of damage to the fitter or adjacent equipment and which provides adequate radio frequency interference protection.

It is a further object of preferred embodiments of the invention to provide an easily constructed front panel.

According to the invention there is provided a plug-in panel, for a modular unit, including a front panel and circuit board mounting means wherein said front panel 0.0 9 includes an elongated substantially planar part with a front surface, a rear surface, two long sides and two short sides wherein at least one of said long sides is provided with integral means for receiving a flexible, resilient sealing l leo means made of a material with electrical shielding properties, and wherein said circuit board mounting means is an integral part of said planar part and projects out from said rear surface.

999999 9_ 25 Preferably, these objects are achieved by means of a front panel comprising .ogo integrated circuit board mounting means and a flexible textile or polymer sealing means. The front panel is preferably made of an extrusion which is pre-formed with the mounting means for the circuit board and for the sealing means.

Brief description of the drawings Figure 1 shows schematically an electrically shielded housing which is part of a radio base station for a cellular telephone network.

Figure 2 shows a perspective view of a front panel and associated circuit board according to one embodiment of the invention.

Figure 3 shows an exploded view from behind of a front panel according to the invention.

Detailed description of the embodiments Figure 1 shows schematically, a radio interference protected (electrically shielded) housing 1 which is, for example, part of a radio base station for a cellular telephone network. This housing contains circuit boards and transceivers which are mounted on the rear side of substantially flat front panels 3 which have first and second long sides 5, 7 and two transverse short sides 8. The front panels 3 are mounted with their long sides 5, 7 vertical on a user accessible side of the housing 1. These circuit boards and transceivers have components which generate heat during use and the housing is provided with, for example, an 20 extraction fan 9 and air outlets 11 on top of the housing and air inlets 13 at the base of the housing 1. It is important that the air flow from the inlets 13 to the extractor fan 9 is properly distributed so that all the boards and transceivers receive sufficient cooing. It is therefore important that there are no unwanted openings in the housing 1 which could effect the air flow and therefore the gaps 25 between the front panels 3 need to be air-tight. This is ensured by sealing means *ogo 15 mounted on one long side 5 of a front panel 3 and which seal against the second side 7 on an adjacent front panel 3 or against the edge of the housing 1.

Front panels 3 can be mounted in housing 1 by being slid straight in the housing and sealing is ensured by the elastic force between sealing means 15 and adjacent surfaces such as an adjacent front panel 3 or the edge of the housing 1.

Figure 2 shows schematically a perspective view of a front panel 3, with a front surface 4, and associated circuit board 17 according to one embodiment of the invention. Sealing means 15 in the form of an elongated sealing strip is shown mounted on long side In figure 3 the embodiment of the front panel is shown exploded and from behind.

The rear surface 6 of panel 3 has integrated mounting means 19 for the circuit board. In this embodiment the mounting means 19 are shown positioned near to side 7 of the front panel 3 however they can alternatively be positioned in any other suitable position, for example near side 5 or near the centre of the rear surface 6. The mounting means can consist of lugs 19 which project out substantially perpendicular to the plane of the front panel 3. These lugs 19 are provided with holes 21 intended to received fastening means 23 which co-operate with holes 21 in the circuit board 17 in order to hold the circuit board 17 onto the front panel 3. The mounting means 19 can be any means which are suitable for attaching a circuit board to, for example, projections with grooves adapted to the thickness of a circuit board. Fastening means 23, shown here as self-tapping screws, can be any suitable fastening means such as rivets, nut and bolt, snap- 2" fastening clips or the like, or holes 21 could be provided with a thread for cooperating with a threaded fastener. The thread could be provided by tapping, attaching a captive nut or rivnut or the like. Adhesives or other fastening means such as soldering can also conceivably be used.

Side 5 of the front panel 3 is provided with receiving means 25, for example a S. 25 groove for receiving and retaining a sealing means 15 in the form of an elongated sealing strip 15. Sealing strip 15 is preferably made of a flexible, resilient material with shielding properties. The material could be made of any suitable textile or polymer or rubber material containing conducting material or combinations of such materials. Sealing strip 15 can be retained by means of its own elasticity or by an adhesive in receiving means 25 or receiving means 25 can be provided with appropriate retaining means such as gripping teeth or a tapered groove cross-section (not shown).

In the preferred embodiment shown the front panel 3 is made of extruded metal and the mounting 19 and receiving means 25 are formed as part of the extrusion.

Mounting means 19 can for example be formed as an integral projecting rib on the rear surface 6 of the front panel 3 and, in order to save weight, the rib can be subsequently machined to form spaced apart mounting brackets. In this way the number of loose parts and mounting operations can be reduced. In this preferred embodiment, for use in dry environments the sealing means is made of a soft textile material with shielding properties, for use in moist or wet environments it is preferable to use a water-resistant/water-tight polymer or rubber material.

It is naturally possible that the front panel can be equipped with sealing means on long side 7 instead of, or in addition to, side 5. It is also possible to provide sealing means (shown by a dotted line in figure 3) on the short sides 8 of front panel 3.

While the invention has been illustrated with examples relating to front panels for 20 a radio base station for a cellular telephone network the invention can also be used in other situations where there is a need for electrical shielding and/or airtight sealing.

The invention is not limited to the embodiments described above but is also able 25 to modified within the scope of the claims.

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Claims (9)

1. A plug-in panel, for a modular unit, including a front panel and circuit board mounting means wherein said front panel includes an elongated substantially planar part with a front s'urface, a rear surface, two long sides and two short sides wherein at least one of said long sides is provided with integral means for receiving a flexible, resilient sealing means made of a material with electrical shielding properties, and wherein said circuit board mounting means is an integral part of said planar part and projects out from said rear surface.

2. A plug-in panel according to claim 1 wherein said front panel is made of extruded metal.

3. A plug-in panel according to any one of the previous claims wherein both of said long sides are provided with means for receiving a sealing means.

4. A plug-in panel according to any one of the previous claims wherein said S°mounting means includes lugs provided with holes for receiving fastening go: means.

5. A plug-in panel according to any one of the previous claims wherein said mounting means extend substantially perpendicular to the plane of said planar part. S 25

6. A plug-in panel according to any one of the previous claims including sealing oooo means on one or both of said short sides.

7. A plug-in panel according to any one of the previous claims wherein said sealing means includes a textiles material.

8. A plug-in panel according to any one of the previous claims wherein said sealing means includes a rubber material.

9. A plug-in panel according to any one of the previous claims wherein said sealing means includes a polymer material. plug-in panel substantially as herein described with reference to the invention illustrated in the accompanying drawings. DATED this 19th day of January 2001 TELEFONAKTIEBOLAGET L.M. ERICSSON .o °o *go ooo o*