ARRANGEMENT IN COOLING CIRCUIT BOARDS

Abstract: An arrangement in cooling circuit boards which are thrust into magzines (1) in an apparatus cabinet (3). Each magazine is assigned a regulator plate (6) having a plurality of through holes (9, 10, 11) and/or slots (12), the sizes and positions of which are selected such that the air flows adjacent different boards in a magazine (1) are adjusted to the necessary cooling need depending on the heat generation at the respective board.

Description: ARRANGEMENT IN COOLING CIRCUIT BOARDS TECHNICAL HELD The invention relates to an arrangement in cooling circuit boards that ar thrust into a magazine in an apparatus cabinet, in which air flows between th boards. BACKGROUND ART In modern telephone stations, for example, a large number of magazine containing circuit boards are used, air flowing between the boards to take awa the heat generated by the circuit board components. The air can be caused t flow by convection, a draught thus occurring as warm air rises. Forced coolin may also be used, and implemented by such as a fan, which preferabl reinforces the convection draught. A problem here is that the cooling of certai circuit boards may be insufficient, even if the total air flow through a magazin is nominally large enough. This is because the air flows passing close to all th circuit boards are substantially equally as great, whereas the boards generat different amounts of heat. The risk of components on certain boards becomin too hot, and thus being damaged, is especially large if the magazines are place in a closed apparatus cabinet. If a fan is used to increase the air flow, it mus be powerful enough to ensure that the boards generating the most heat will b sufficiently cooled. Such a fan requires energy as well as space, and can als cause troublesome noise. DISCLOSURE OF INVENTION The object of the present invention is to provide an arrangement of the kin mentioned in the introduction, with which the air flows passing along differen circuit boards in a magazine may be adjusted to the required cooling effect i response to the heat generation of the respective board. This is achieved by regulator plate assigned to each magazine, and provided with a plurality o holes or slots which, dependent on their sizes and positions, distribute th flowing air in a suitable manner. The distinguishing features of the inventio are disclosed in the claims. BRIEF DESCRIPTION OF DRAWING The invention will now be described in detail with reference to the drawing, on which Figure 1 illustrates a magazine for circuit boards, Figure 2 an apparatus cabinet in cross section and containing a plurality of magazines, one above the other, and Figure 3 illustrates an inventive regulator plate associated with the 5 respective magazine. BEST MODE FOR CARRYING OUT THE INVENTION A magazine for circuit boards is illustrated in Figure 1. The magazine is denoted by the numeral 1, and has a number of places each intended for a board. For the sake of clearness, only two boards 2 are shown, thrust into adjacent places. Such magazines are intented to be side by side and at different 10 levels above each other in such as modern telephone exchanges. The magazine is open top and bottom so that air can pass between the boards and thus lead off the heat generated by the components on the boards. In Figure 2 there is shown a number of magazines 1, seen in elevation, in an apparatus cabinet 3. The magazines are placed one above the other at their • - ■ different levels in the cabinet, in such a way that air can flow between the boards from the bottom of each magazine to its top, or vice versa. The so- called back-planes to which the circuit boards are connected are denoted by 4. The air can flow by free convection or with the aid of a fan 5. The air is supplied, e.g. via unillustrated ducts opening out at the sides of the cabinet, and 0 flows upwards in the illustrated embodiment through the magazines via special plates 6, which will be described in connection with Figure 3. The air that has flowed through a magazine is fed by sloping plates 7 to a flue 8, through which . t is led out from the cabinet. In Figure 3 there is illustrated an embodiment of a regulator plate 6, each 5 associated with its respective magazine. Each such plate is manufactured specifically for its associated magazine, taking into consideration the circuit boards included in the respective magazine. The regulator plate is thus provided with a plurality of through holes 9, 10 and 11, and a slot 12. The holes and slot form parallel rows, the mutual spacing of which agree to the spacing between 0 the boards in a magazine. The plate 6 is intended to be placed on top of a magazine, as is illustrated in Figure 2, with the holes approximately directly opposite the boards, so that the best cooling effect is attained by the flowing air. The holes in different rows have different sizes, the air flow being thus distributed so that more air passes through the larger holes than through the smaller. Different circuit boards in a magazine will thus be cooled to different - extents. Cooling will be greatest for the slot 12, and decreases with decreasing .hole size in the different rows of holes. There are no holes opposite empty places in the magazine, so that air does not flow through such places unnecessarily. The flowing air is thus utilised optimally by such regulator plates, which increases the possibility of obtaining sufficient cooling by free convection or minimizing the necessary fan power. The invention may of course be varied within the scope of the accompanying claims. For example, the holes do not need to be circular, as shown on the drawing, and they may be given any suitable configuration. Furthermore, only holes of different sizes or only slots of different sizes may be used, instead of a combination thereof. They can also be optionally arranged in patterns other than straight lines, e.g. zig-zag. It is also conceivable to place the regulato plates under, or in front of the magazines, and in these cases the air flows mus be adjusted in a corresponding way.

Claims: CLAIMS 1. Arrangement in cooling circuit boards (2) thrust into magazines CD in an apparatus cabinet (3), in which air flows between the boards (2), including a regulator plate (6) associated with its respective magazine (1), adapted trans¬ verse the air flow and provided with a plurality of air orifices (9-12), , characterized in that the air orifices constitute a plurality of hole rows {'9-11) and/or slots (12) parallel to the boards, the mutual spacing of said] orifices agreeing with those of the boards (2), and the sizes of said orifices being selected such that the air flow adjacent each circuit board is adjusted to the heat generation of the board. 2. Arrangement as claimed in claim 1, characterized in that the regulator plates (6) are placed above the magazines (1).

Inventors: OSTERMAN KARL FOLKE, OSTERMAN, KARL, FOLKE
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET L M ERICSSON
Application year: 1985
Main classification: H05K7
IPC codes: H05K7