FRAME STRUCTURE

Abstract: The invention relates to a frame structure for an electronic appliance, particularly a telecommunications apparatus. The frame structure comprises a frame part (10) and several board units (BU) which are connected to the frame part substantially in parallel with one another and so that they are detachable from the frame part. The board units are implemented by surface-mounted components (SMC). In order to increase the capacity of the frame the board units are arranged to the frame part in such a manner that (a) a front connector (FC) of every second board unit is in the vertical direction displaced in relation to the front connector (FC) of an adjacent board unit, and (b) the front connectors (FC) of the adjacent board units (BU) partly overlap in the horizontal direction.

Description: FRAME STRUCTURE The invention relates to a frame structure for an electronic appliance particularly a frame structure for a telecommunication apparatus. The equipment bays of telecommunication apparatuses generally comprise racks in which the actual transmission apparatuses are located. The racks may contain several frames which, in turn, comprise board slots in which board units are located. The commonly used frames are 19 inches in breadth (also meaning that the installation bars of the rack are horizontally at 19 inch intervals). The board units comprise the necessary connectors for connecting external equipment to the telecommunications apparatus and for connecting the telecommunications apparatus to a telecommunications network. On account of a basic structure described above the telecommunication apparatuses are externally very alike, but their internal fittings and soft- ware determine how the apparatus operates in the network. The use of frame structures described above cause a problem of space in some usage environments; the required capacity is difficult to implement in the equipment bays available. Such a problem occurs particularly in subscriber networks, in which apparatuses have to be placed in outside cabi- nets, to which the largest permitted outside measures have been defined in nearly all countries. (A subscriber network means the part of a telecommunication network intended for the subscriber. Such a telecommunication part is often also called an access network.) For example, when a telephone network is constructed in such a manner that a two-wire line is drawn from each sub- scriber to a common subscriber multiplexer, the multiplexer equipment typically has to be placed in the outside cabinets located between subscribers and terminal exchanges. However, the capacity of the frames is difficult to increase since their back plate connectors are in accordance with standard, and set a certain minimum limit for the breadth of the board slot (i.e. for the distance between adjacent board units). An object of the present invention is to provide an improvement on the drawback presented above by finding a solution by which the capacity of current frame structures can be increased and more and more capacity can be obtained to the equipment bay, without changing its size. For example, in a subscriber network this means that more and more subscribers can easily be connected to the same outside cabinet. This objective is achieved with the frame structure according to the invention, characterized by what is described in the characterizing part of the attached claim 1. The basic idea of the invention is to implement circuit solutions with surface-mounted components, to place front connectors of adjacent board units vertically apart from one another and to arrange parallel board units so close to one another that their front connectors horizontally partly overlap. According to a primary embodiment of the invention every second board unit is arranged as an expansion board to an adjacent board unit. In other words, the expansion board is connected with an actual telecommunications equipment through its motherboard. On account of such a solution, particularly narrow board slots are not needed in the frame but the standard installation distance is enough. The capacity of a conventional frame can be doubled on account of the solution. According to an additional primary embodiment of the invention the expansion board (which is typically substantially similar to the motherboard) is upside down as to the motherboard, whereby their component sides are against each other. Thus, an electromagnetically "closed" solution is formed, the solution ensuring an efficient implementation in the EMC sense. In the following the invention and its preferred embodiments will be described in greater detail with reference to the examples of the accompanying drawings, in which Figure 1 illustrates a prior art frame structure of a telecommunication apparatus, Figure 2 illustrates a frame structure according to the invention seen from the front, Figure 3 shows a basic board/an expansion board combination according to a preferred embodiment of the invention, Figures 4a and 4b show a basic board and an expansion board ac- cording to Figure 3, Figures 5a, 5b and 5d show expansion boards comprising various connector alternatives for connecting board units of a board packet to one another, Figure 5c illustrates an inter-connection of pins of the connector in the board unit in Figure 5b, and Figure 5e illustrates an inter-connection of pins of the connector in the board unit in Figure 5d. Figure 1 illustrates a frame of a telecommunications apparatus, known as such. The frame comprises a body 10, which in this example case is composed of vertical side walls 11 and 12, four substantially horizontal cross- bars 13-16 each of which being attached from one end to a comer of a side wall and from the opposite end to the corresponding corner of the opposite side wall, and of a back plate 17 to which the electric circuits are formed (not shown) by which the board units are connected to the telecommunications apparatus to which the frame belongs. At each board slot on the back plate 17 there is a back plate connector BPC by which a board unit BU is connected to the circuits on the back plate. (For the sake of simplicity the Figure shows only one board unit and only one back plate connector.) Furthermore, the frame structure comprises installation elements by which the board units BU can detachably be attached to the frame. In the Fig- ure these elements are marked with reference mark MM. In the Figure these elements are shown in cross section substantially as U-shaped bars 18 which are attached parallel with the side walls to the upper surfaces of the lowest crossbars and to the lower surfaces of the highest crossbars. An upwards open bar 18a attached to the lowest crossbars always comprises a down- wards open corresponding bar 18b horizontally at the same place in the highest crossbars, whereby the bars corresponding to each other form a board slot into which the board unit BU is pushed. The installation elements can naturally be of various types. As to the invention, it is only essential that the frame comprises elements that allow a detachable installation of the board unit to the frame (for example by pushing the board unit into a board slot reserved for it in the frame). The board units BU which are to be installed in the frame each comprise a front connector FC by which the board unit is connected to equipment outside the frame, and a back connector BC by which the board unit is connected to the electric circuits formed on the back plate 17 of the frame. Each back connector BC is connected to a back plate connector BPC at the board slot on the back plate. As presented at the beginning the above described apparatus can be, for example, a subscriber multiplexer including several parallel subscriber connection boards known as such. The subscriber stations, such as phones, are connected to the board units through their front connectors FC and the subscriber connection boards are connected through their back connectors BC and the back plate connectors BPC to the internal bus of, for example, a multiplexer unit formed on the back plate of the frame. Figure 2 illustrates the solution of the invention by showing the frame from the front. Only two of the board units BU of the frame are shown. According to the basic idea of the invention, the front connector FC of every second board unit BU has been displaced in the vertical direction as to the front connector of the previous board unit and the front connectors of the adjacent board units partly overlap in the horizontal direction. As to the front con- nector FC the area marked with a circle A is enlarged, in order to see that for a certain distance x the front connectors of two adjacent board units overlap in the horizontal direction. Figures 3 and 4a and 4b show the solution according to the preferred embodiment of the invention. Using surface-mounted components a low structure is obtained for the board unit, the low structure enabling the structure which will be described below. Figure 3 illustrates a board packet composed of two parallel board units BU1 and BU2 and Figures 4a and 4b illustrate the board units BU1 and BU2 when the board packet is opened (as a book) in the direction of arrows AR in the Figure. The board units BU1 and BU2 are made of surface-mounted components marked by the reference mark SMC. The board units BU1 and BU2 of one board packet are similar to one another, for example, in the sense that there are surface-mounted components only on one surface of the board and the front connectors are (in vertical direction) at the same places on the end surface of the board. In the board packet a board unit BU1 is a basic board and a board unit BU2 is an expansion board. When a board packet according to Figure 3 is formed, the expansion card is first turned round its middle axis A (Figure 3) upside down in relation to the basic board, whereby surfaces 41 and 42 provided with surface-mounted components and corresponding to each other turn against each other and the front connector FC2 of the expansion board is vertically located in a different place in relation to the front connector FC1 of the basic board. The boards are connected together by a coupling unit MC (Figure 3) and only the basic board comprises a back connector BC1 by which both the basic board and expansion board are connected (through the back plate connector BPC) to the buses of the back plate. Bus interface circuits can be located on the basic board only or on both boards. The- boards are connected to one another through a coupling unit MC which is divided into a connector MC1 on the basic board and a connector MC2 on the expansion board. If the board units are, for example, subscriber connection boards, the same number of subscribers is connected through the front connector of both board units to the multiplexer unit. Cabling of the expansion board (to the front connector) preferably arrives from above (since the front connector of the expansion board is higher) and the cabling of the basic board correspondingly arrives from below. By forming a packet according to Figure 3 an efficiently protected equipment is obtained also in the EMC sense, as the components remain inside the board packet. In this sense it is preferable that the board units are galvanically connected together also in other ways than through a coupling unit MC. For this purpose metallic grounding areas GR, from which the board units are galvanically connected to one another e.g. using metallic bolts 43 or similar fixing devices, are formed into the corners of the board units. The galvanic connection formed from the corners gives in the EMC sense an efficient protection for the entire board packet. To further improve EMC protection the board slots can be provided with a metallic or a metal-coated front panel (not shown). Figures 5a...5e illustrate various types of connector alternatives for connecting board units BU1 and BU2 to one another. The Figure shows only the expansion board BU2 which in this example case comprises a male connector. The coupling unit between the boards can be, for example, a single- row connector MC (Figure 5a) which is horizontally located exactly in the mid- die of the board unit, i.e. the pins of the connector are in the horizontal plane located at the horizontal middle axis A of the board and there is an equal number of them on each side of the vertical middle axis B. Another alternative is to implement the connector as a horizontal one, but with several rows, for example, as a double-row connector MC" ac- cording to Figure 5b. Then a pair of pins composed of two overlapping pins is according to Figure 5c short circuited with each other, the connector being in practice a single-row connector (n signals can be transferred by a 2n pin). Such short circuiting between pairs of pins is performed, because when the expansion board is turned upside down as shown above the corresponding pins (signals) are still located together. A third alternative is according to Figure 5d to use a vertical con- nector MC" including one or more pin rows. In this case (a single-row connector) the pins of the connector are in the vertical plane located at the vertical middle axis B of the board and an equal number of them is located on both sides of the horizontal middle axis A of the board. In order for corresponding pins (signals) to still be located together when the expansion board is turned upside down in relation to the basic board, the highest pin is connected to the lowest pin, the second highest pin to the second lowest pin etc. (Figure 5e). When a vertical connector with several rows is used the corresponding connection has to be performed in each row. Although the invention has been described above with reference to the examples of the accompanying drawings it is obvious that the invention is not restricted thereto but can be modified within the scope of the inventive idea presented above and in the disclosed claims. For example, the basic board and expansion board solution is applicable without turning the expansion board upside down as to the basic board. The expansion board can also be different in relation to the basic board.

Claims: CLAIMS 1. A frame structure for an electronic appliance particularly for a telecommunication apparatus, the frame structure comprising a frame part (10) and several board units (BU) which are attached to the frame part substantially in parallel with one another and so that they are detachable from the frame part, which board units are implemented by surface-mounted components (SMC), characterized in that the board units are arranged to the frame part in such a manner that a front connector (FC) of every second board unit is in the vertical direction displaced in relation to a front connector (FC) of an adjacent board unit, and the front connectors of the adjacent board units (BU) partly overlap in the horizontal direction. 2. A frame as claimed in claim ^characterized in that every second board unit (BU2) is arranged as an expansion board to the adjacent board unit (BU1) functioning as a basic board, whereby the expansion board is connected to a back plate (17) ofthe frame through said adjacent board unit. 3. A frame as claimed in claim 2, characterized in that the expansion board (BU2) is turned upside down as to the basic board so that the surfaces of the boards which are provided with surface-mounted components are against each other. 4. A frame as claimed in claim 3, characterized in that the basic board and the expansion board are connected together by a horizontal connector which is substantially symmetrically arranged in relation to the mid- die axes (A, B) ofthe board unit. 5. A frame as claimed in claim 3, characterized in that the basic board and the expansion board are connected together by a vertical connector which is substantially symmetrically arranged in relation to the middle axes (A, B) ofthe board unit. 6. A frame as claimed in claim 3, characterized in that metallic grounding areas (GR) are formed on the basic and expansion board and that the grounding areas of the board units are galvanically connected together. 7. A frame as claimed in claim 6, characterized in that the metallic grounding areas (GR) are formed into the corners of the basic and expansion boards and that the boards are galvanically connected together from the corners.

Inventors: HURME HARRI, NORDSTROEM CAJ, TAKALUOMA ANTTI, HURME, HARRI, NORDSTROEM, CAJ, TAKALUOMA, ANTTI
Applicants: HURME HARRI, NOKIA TELECOMMUNICATIONS OY, NORDSTROEM CAJ, TAKALUOMA ANTTI, HURME, HARRI, NORDSTROEM, CAJ, TAKALUOMA, ANTTI
Application year: 1997
Main classification: H05K7
IPC codes: H04Q1, H05K7