WO1997029623A1

WO1997029623A1 - Electronic device enclosure

Info

Publication number: WO1997029623A1
Application number: PCT/GB1997/000360
Authority: WO
Inventors: Bruce Fryers
Original assignee: 3Com Ireland
Priority date: 1996-02-09
Filing date: 1997-02-10
Publication date: 1997-08-14
Also published as: GB9602692D0; AU1613897A; GB2310086A

Abstract

An enclosure for electronic circuitry, for instance in a Local Area Network, has a domed cover defining an aperture at the upper edge of one side wall. In conjunction with further apertures in the base of the enclosure connection currents are caused to flow through the enclosure to carry away heat generated by components within the enclosure.

Description

Electronic Device Enclosure

The present invention relates to the design of an enclosure for an electronics device, in particular an enclosure which provides venting for the dispersion of heat generated by the electronic device.

It is known to provide electronics devices in enclosures, such enclosures providing protection for the electronic circuitry within, convenient locations for the connections of inputs and outputs and the required external appearance for the device. It is also known that electronic circuit components generate heat during their operation and therefore that, unless steps are taken to avoid it, the temperature within an enclosure of an electronics device can rise to unacceptable levels. It is unacceptable for temperatures to rise too much, because this may impair the operation of the device or require the components of the device to be manufactured to a higher temperature specification, thus increasing their cost.

For these reasons it is known to take steps in the design of the enclosure to provide for the circulation of air within the enclosure in order to cool the circuitry inside. This can take the form simply of apertures in the base and top of the enclosure which permit convection currents to pass upwards through the enclosure to cool the circuitry.

It is also known to provide forced air circulation by providing a fan in conjunction wim the venting apertures in the enclosure.

The provision of apertures in the upper surface of the enclosure of an electronic device is disadvantageous in that it may permit dust to collect in the device, and also, where a number of devices are arranged in a stack, the heat from one device simply passes into the underside of the device above thereby reducing the effectiveness of the cooling in that device.

It is also desired where possible to avoid the use of fans. This is because the requirement to supply a fan increases the power consumption and cost of the overall device as well as increasing the noise generated by the device in operation.

The present invention provides an enclosure for an electronics device which is designed to cool its interior by natural convection currents. The underside, and possibly the side faces, of the enclosure are provided with apertures by way of which air may enter the enclosure. The upper surface of the enclosure is inclined upwards towards one of its edges, preferably the rear edge. An exit vent is provided beneath the raised edge of the upper surface through which the convection current caused by heat generated within the enclosure can pass. In this invention it is not necessary to provide apertures in the upper surface of the enclosure, thereby avoiding the disadvantages mentioned above, and particularly facilitating the stacking of such enclosures, as the heat generated within the enclosures is not directed upwards out of the enclosures but is directed out from a side of the enclosure. It has been found that this arrangement provides sufficient cooling so that in some circumstances it is unnecessary to provide a fan where previously it has been necessary to do so.

The upper surface of the cover may simply be planar and inclined upwards from the front to the rear to provide the rearwards facing vent at the top of the rear wall. However, preferably the upper surface is additionally inclined from the sidewalls providing a doming of the cover towards the rear to provide a curved shape vent.

This invention will be better understood from the following description of a preferred embodiment which is made in conjunction with the accompanying drawings in which:

Figure 1 shows a top and front perspective view of the preferred embodiment of the invention;

Figure 2 shows a top and rear perspective view of the device shown in Figure 1 ; Figure 3 shows a rear underside perspective view of the device shown in Figure 1; and

Figure 4 is a schematic side view of a stack of enclosures as shown in Figure 1. The illustrated embodiment of this invention is an enclosure for an electronics device known as a repeater for use in Local Area Networks (LANs). The accompanying figures illustrate the device according to the preferred embodiment in a number of different views and the parts of the device are designated by the same reference numerals throughout the figures. The enclosure according to the preferred embodiment is a flat generally rectangular box shape comprising two principal components, base section 10 and cover 20.

The base section 10 is formed in a well known manner from sheet metal and comprises lower surface 11, rear wall 12, two sides (not shown) and a front (not shown). In the rear wall 12 are provided a number of apertures for the mounting of various connection devices in a manner well known which provide for the attachment of cables connecting other network devices to the repeater circuitry within the enclosure.

In the base section 11 are provided a plurality of apertures 13 and further apertures may be provided in the side walls. The cover 20 of the enclosure is a plastics moulding having an upper surface 21, a front surface 22 and sides 23. Cover 20 fits over base section 10 such that the front 22 and sides 23 cover the front and sides respectively of the base section 10 and are moulded to provide the desired appearance for the enclosure. Sides 23 may be provided with apertures arranged to align with apertures provided within the side walls of base section 10.

The upper surface 21 of the cover 20 is moulded to provide a vent 24 at the rear of the enclosure. In particular the upper surface is increasingly domed towards the rear of the enclosure. This doming permits the heat generated bv electronic circuitrv within the enclosure to rise but directs convection currents caused thereby to and out of the rear of the device via vent 24, thereby drawing air into the enclosure via apertures 13 in the base of the device and the apertures, if any, provided in the side walls of the device.

The physical positioning of the electronic components within the enclosure, in particular those generating significant amounts of heat, may be designed in conjunction with the shape of the cover and position of the inlet apertures to optimise the air flow through the enclosure, and hence the cooling effect.

No apertures are provided in the upper surface 21 of cover 20 and no fan need be provided to assist in providing additional air circulation. The air circulation caused by the convection current drawn through vent 24 is sufficient to cool the electronics of the repeater circuitry within the enclosure.

In the illustrated enclosure, electromagnetic (EM) screening for the electronics inside is provided on five sides by the formation of the base section 10. EM screening is provided beneath the upper surface 21 by a sheet of metal positioned parallel with lower surface 11 level with the top edges of front surface 22 and sides 23. The doming of the upper surface thus defines a volume above this sheet and vent 24 is also above this level. Apertures are formed in the sheet which are shaped and sized so as not to interfere with the screening properties of the sheet but to permit convection currents to rise into said volume and out of vent 24.

While the base is described above as formed of metal and the cover of plastic, either part may be formed of the other material, or either or both parts may be formed of any other suitable material, with EM screening being provided as required.

The directing of the convention current outwards from vent 24 directs the heat carried away from the underside of a further enclosure positioned immediately above thereby avoiding or minimising reducing the cooling achieved in that device. This is illustrated in Figure 4 which is a schematic side view of two enclosures as shown in Figures 1-3 stacked one above the other. The enclosures are mounted one above the other by way of four risers 30 which clip into position on the enclosures as shown, two on each side. This view clearly illustrates the dorning of upper surfaces 21 as described above which provides vent 24 at the rear side of each enclosure.

The arrows in Figure 4 illustrate in general terms the convection currents caused by heat generated within the enclosure. This heat causes air to rise into the volume defined by the doming of the upper surface as shown by the broken line arrows and then to pass out of the enclosure to the rear as shown by arrows B. Air is drawn into the underside of the upper enclosure via apertures 13, and because of the dorning in the upper surface 21 of the lower enclosure this air is drawn at least mainly from in front of the stack of enclosures as shown already by arrows A. Thus air which is drawn into an enclosure is not warm air which has been expelled from another enclosure and thus the cooling effect of the circulating air is maximised.

As is illustrated in Figure 4, the dorning of the upper surface 21 of the enclosure begins approximately halfway from the front to the rear of the device. This allows, in the stacked arrangement, for easy access for the air being drawn into the underside of the device. In the stacked arrangement the upper surface of an enclosure having another enclosure positioned above can be considered to have a dual function. It acts both to guide warm air within the enclosure in a rearwards direction and out of vent 24 and also to guide the air drawn in from the front of the stack into the apertures 13 in the enclosure above. This arrangement provides effective cooling of electronics components within the enclosures and does not require the use of a fan to force the convection currents.

It will of course be appreciated that more than two enclosures may be stacked together in the manner illustrated in Figure 4. The preferred embodiment of this invention may be implemented as an enclosure 220mm wide, the front of which having a height of 38mm and having an overall front to rear length of 180mm. As shown in the drawings a section of the upper surface is raised and this is approximately a 5mm rise in the above mentioned implementation. The doming of the upper surface provides the rear facing vent which has a vertical opening of 12mm at its highest point. The risers which are used to stack the enclosures together provide a vertical gap of 20mm between the side walls of adjacent enclosures.

A smaller enclosure has an identical width but has a height of 21mm, a front to rear length of 130mm and a maximum vertical vent opening of 10mm. Because this enclosure has the same width it can be incorporated into stacks with the larger enclosure as well as stacking with others of the same size.

With a maximum ambient temperature of 40°C the larger enclosure described above can dissipated 1 lw of heat and the small enclose can dissipate 7w while mamtaining an internal temperature of not more than 70°C.

Claims

CLAIMS:

1. An enclosure for electronics circuitry, the enclosure comprising a base, a plurality of side walls upstanding from said base and a cover, the base having at least one aperture therein providing communication between the interior and exterior of the enclosure and the cover having at least a portion inclined upwards towards one of said side walls, said one of said side walls having a vent provided adjacent to its upper edge.

2. An enclosure according to Claim 1 in which said cover is increasingly domed towards said one of said sidewalls.

3. An enclosure according to Claim 1 or 2 in which apertures are provided in at least one of the others of said side walls.

4. An enclosure for electronics circuitry generating heat, the enclosure comprising a base, a plurality of side walls upstanding from said base and a cover, the base having at least one aperture therein and the cover being shaped to rise towards and define a vent at the top of one of said side walls whereby convection currents caused by said heat pass out of said vent with at least a horizontal direction component.

5. A plurality of enclosures according to any of the preceding claims arranged in a stack one above another.

6. An enclosure for electronics circuitry substantially as herembefore described with reference to the accompanying drawings.