Case structure

Abstract: The present invention relates to an instrument case including two side panels (10, 11) arranged to mate with a further panel (12) to be supported substantially parallel thereby and a member (20) adapted to interlock in a plane normal thereto with both side members to brace the side members. The side panels (10, 11) the further panels and the member (20) provide a self supporting structure. The case may be completed by the addition of further panels. The case constitutes a support (52, 53) and enclosure for circuit boards, the member (20) forming a motherboard (40) which may act as a case divider. The invention solves the problem of providing a circuitboard support and mother board (40) without recourse to additional components and a card frame with its consequent weight penalty.

Description: This invention relates to case structures for instrument cases, for example for electronic instruments. Generally the practice in instrumentation is to provide a rigid carcass as an instrument case in which instrument components, for example circuit boards, are mounted. Typically such a case has internal bracing members which maintain rigidity whilst side, front, rear top and bottom panels are removable; this is wasteful in that when the case is completely assembled, such members are structurally redundant, wasting space and adding to weight. In the design of electronic instruments, for example spectrum analysers, data loggers, vibration controllers and the like there is a trend towards modularity, that is to instruments which can be configured, reconfigured and serviced by the exchange of modules. An attractive way of providing modularity is to provide a mother board which is adapted to receive and interconnect a plurality of circuit boards via plugs and sockets. This practice has led to the wide adoption of card frame structures wherein a plurality of circuit boards are supported substantially parallel by slots or rails in a free standing frame having a mother board mounted within in a plane normal to the boards. It is important that reliable connection between the boards and the mother-board is made and to this end the mother-board is generally rigidly supported upon a structural member. Typically a card frame is made in metal in channel section spars bolted together to provide a rigid free standing structure. The frame may then be cased by simply bolting side, front and rear facing panels to the structure. Card frames are ideally suited to some applications, for example static digital computers wherein a plurality of physically similar boards may be plugged into a mother-board to give a complete working arrangement, non computer components generally being arranged as separate peripherals. Another kind of card frame is disclosed in EP-A-0087349, and comprises a pair of parallel side members connected together by parallel upper and lower structural members extending perpendicularly between the side members to define a rigid rectangular frame. The four members are each moulded in one piece in plastic, but for use in an instrument case, they would still need to be cased by securing exterior facing panels to them. In the art of electronic instrumentation, there is increasing use of digital electronics and computer technology making modularity attractive. Unfortunately card frames are less than ideally suited to instrumentation since instruments usually include a number of interface components, such as displays, keyboards, printers, plotters and disk or tape drives, which are not adapted to card mounting. As previously described, the practice in instrumentation is to provide a rigid carcass, the carcass providing the instrument case, in which such components are rigidly mounted together with circuit boards. To mount a card frame within such a carcass is wasteful, in that one rigid structure is mounted inside another, inevitably leading to increased weight and loss of space, which is undesirable in a self-contained instrument, particularly a portable instrument. An additional disadvantage of a card frame in relation to electronic instruments is that it is generally not possible easily to exchange a mother-board, it being often embedded within the frame structure. It is more likely in instrumentation that there will be differences in mother-boards between models which may have differing interfaces than in for example digital computers, relying on a common processor with differing peripherals. It is an objective of the present invention to provide the modularity advantages of a card frame in a rigid instrument case adapted to receive both circuit boards and interface and other components not adapted to frame mounting, without recourse to separate internal rigid frame structure. According to the present invention an instrument case includes two side panels arranged to mate with a base panel to be supported substantially parallel to each other thereby, and a mother board support member adapted to interlock in a plane normal to the side panels and the base panel with at least both side panels to brace the side panels, said side panels, said base panel and said mother board support member providing a self supporting structure, and the mother board support member being arranged to provide a divider within the case structure, separating circuit cards in one compartment from other components in another. The case may be completed by the addition of further panels, each contributing to case rigidity. In a preferred arrangement of the present invention, the mother board support member additionally interlocks with the base panel, and with a similar top panel when fitted. Advantageously, the interlock between the mother board support member and the side panels is provided by engagement of a right angle flange projection of the member with a receptor on the side panel, such that sideways movement of the side panels in both directions is prevented. The interlock may be arranged to urge the side panels inwardly, for example by having a portion which protrudes exterior to the panel such that the panel is secured between exterior and interior portions of the member. A circuit board, when inserted, may be supported by channels moulded directly into the side panels, or alternatively by additional supporting members affixed thereto. Preferably, the mother board support member is of slotted construction so that connections may be made to both sides thereof. In a preferred form of instrument case in accordance with the present invention, at least one side panel includes an external handle for carrying the case, the handle being secured to the side panel at points on either side of the position at which the mother board support member interlocks with the side panel. In order that features and advantages of the present invention may be further appreciated, an embodiment will now be described with reference to the accompanying diagrammatic drawings, of which:- Figure 1 represents the side and base panels of case structure in accordance with the present invention; Figure 2 represents the above arrangement with a mother board support member introduced; Figure 3 shows the interlock between a support member and a side panel; Figure 4 shows the support member carrying a mother-board; Figure 5 shows case structure containing a circuit card; Figure 6 shows instrument compartments and handle; and Figure 7 shows a front panel. In a case structure for an electronic instrument (Figure 1) two side panels 10, 11 are adapted to mate with a further panel 12 in the form of a base panel. Mating occurs by virtue of engagement of an elongate tongue portion on the lower side of each side panel, for example tongue 14 of side panel 11, with a slot extending upwardly at an edge of the base panel, such as slot 15 for panel 12. Engagement of tongue and slot is sufficient to support the side panels substantially normal to the base panel, such as side panel 10. A mother-board support member 20 (Figure 2) is arranged to be introduced between side panels 10, 11 in a plane normal thereto and to interlock therewith. Interlock is provided by the entry of a right angled flange projection 30 (Figure 3) of support member 20 with a receptor portion 31 of side panel 11. As may be more clearly seen in Figure 1, receptor portion 31 is formed at substantially the level of tongue 14, hence flange 30 and receptor 31 provide a lower interlock between side panel and support member. A similar upper interlock is provided by flange 32 and receptor portion 33. It will be appreciated that the presence of the support member spanning the side panels serves to brace the side panels. It will further be appreciated that since the flange acts on a receptor in each side panel, the support member may be dimensioned to urge the side panels together. This has the desirable effect of locking the tongues of the side panels in the slots of base panel by forcing the tongue against the inner side wall of its slot, thereby removing any play. To this end flange portion 32 engages externally of receptor portion 33. Support member 20 is arranged to carry a mother-board 40 (Figure 4). Mother-board 40 bears a plurality of sockets, such as socket 41 adapted to receive complementary connectors on circuit cards. A circuit card 50 (Figure 5) has connectors, such as connector 51 arranged to mate with sockets on the mother-board 20 when the circuit board is urged horizontally towards the mother-board. Slotted extensions, such as extension 52 are mounted on the inside surface of the side panels 10, 11 respectively to provide a plurality of slots, such as slots 53, and 54 which support the circuit board 50. The slots are arranged in register with the sockets on the mother-board so that a plurality of different boards may be supported interchangeably. Support member 20 (as may be more clearly seen in Figure 2) is of slotted contruction, able to carry a mother-board on each side and permit connections therebetween. Further the support member 20 is disposed towards the middle of the side panels 10, 11 (Figure 6) to provide separate compartments 60, 61. Compartment 60 for example might be a forward compartment containing interface components such as a cathode ray tube, printer or disk drive, and compartment 61 a rearward compartment containing circuit boards. It will be appreciated that by properly arranging the support member 20, compartment 61 may be electrically screened from compartment 60. Side panel carries a hinged handle 62 which is fixed adjacent the support member position. The fixtures of the handle 62 are arranged to be on each side of the support member position to take advantage of the bracing so provided. Mother-board support member 20 is additionally provided with tongues, such as tongue 34 (Figure 3) which engage with complementary slots, such as slot 35, in base member 12. The side panels and support member may similarly engage with a top panel (not shown). Additional tongues, such as tongue 70 (Figure 7) on side panel 11, are arranged for engagement with complementary slots, such as slot 71, on a front panel 72. The front panel may be fixed into position by screws, for example a screw (not shown) passing through a hole 73 in front panel 72 to engage with a threaded portion 74 of side panel 11. A rear panel may be similarly fixed. For case structures to be subject to dusty or electrically noisy environments, the construction of the present invention lends itself to the incorporation of dust and/or electrical gaskets. For example a gasket may be laid in slot 15 (Figure 1) before the tongue 14 of side panel 11 is introduced. From the foregoing description, a number of advantages of the present invention will be apparent. Not only is a case structure with the features of a cardframe but suited to instrumentation provided, but also the front, top, (or bottom) and rear panels may be removed for access without disturbing operating integrity. The mother-board may be removed by a simple disengagement of connectors (complete removal of cards or components is not required) so that the instrument may be reconfigured. Importantly, changes may be made in one compartment without entirely dismantling the other.

Claims: An instrument case including two side panels (10, 11) arranged to mate with a base panel (12) to be supported substantially parallel to each other thereby, and a mother board support member (20) adapted to interlock in a plane normal to the side panels and the base panel with at least both side panels to brace the side panels, said side panels, said base panel and said mother board support member providing a self supporting structure, and the mother board support member being arranged to provide a divider within the case structure, separating circuit cards in one compartment (61) from other components in another (60). An instrument case as claimed in claim 1, wherein the case is completed by the addition of further panels (eg 72), each contributing to case rigidity. An instrument case as claimed in claim 1 or claim 2, wherein the mother board support member (20) additionally interlocks with the base panel (12), and with a similar top panel when fitted. An instrument case as claimed in any preceding claim, wherein interlock between the mother board support member (20) and the side panels (10, 11) is provided by engagement of a right angle flange projection (30) of the member with a receptor (31) on the side panel, such that sideways movement of the side panels in both directions is prevented. An instrument case as claimed in claim 4, wherein the interlock is arranged to urge the side panels (10, 11) inwardly. An instrument case as claimed in claim 5, wherein the interlock is arranged to urge the side panels (10, 11) inwardly by having a portion which protrudes exterior to the panel such that the panel is secured between exterior and interior portions of the member. An instrument case as claimed in any preceding claim and adapted to receive a circuit board (50) supported by channels (53, 54) moulded directly into the side panels (10, 11) or into additional supporting members (52) affixed to the side panels. An instrument case as claimed in any preceding claim, wherein the mother board support member (20) is of slotted construction so that connections may be made to both sides thereof. An instrument case as claimed in any preceding claim, wherein at least one side panel (10) includes an external handle (62) for carrying the case, the handle being secured to the side panel at points on either side of the position at which the mother board support member (20) interlocks with the side panel.

Inventors: TRELFORD A, TRELFORD A.
Applicants: SCHLUMBERGER TECHNOLOGIES LTD, SCHLUMBERGER TECHNOLOGIES LIMITED
Application year: 1989
Main classification: H05K5
IPC codes: H05K7