GB2262390A - Rack for accommodating circuit boards - Google Patents

Description

2262390 ENCLOSURE FOR CIRCUIT BOARDS This invention relates to cabinets,

cases and other enclosures in which electrical and/or electronic apparatus is mounted on racks. trays or other supports housed in the enclosure. The invention is particularly concerned with enclosures of this kind in which circuit boards are accommodated in racks which are housed in the enclosure and which generally comprise a plurality of mutually spaced pairs of opposed guide rails into any pair of which opposed edges of a circuit board can be slid from the front of the rack, as the circuit board is slid fully home one or more than one edge connector mounted on the circuit board at or near its rear edge effecting electrical connection with a connector or connectors directly or indirectly carried by a backplane at the rear of the enclosure.

With a view to facilitating insertion of a circuit board into, and withdrawal of a circuit board from, a pair of opposed guide rails of the rack, it is the general practice to secure to the front edge of the circuit board, i.e. the trailing edge of the board as it is slid into the rails, a substantially rectangular flat plate, hereinafter referred to as the front plate, which serves as a handle. Neighbouring edges of the front plates of adjacent circuit board when slid fully home in their pairs of guide rails will lie close together so that when circuit boards are accommodated in all the pairs of guide rails of the rack, the front plates of the boards together present a substantially flat surface at the front of the enclosure.

2.

When a circuit board has been slid fully home in its pair of guide rails, it is also the general practice to detachably secure the board in position and this is usually effected by means of fixing screws which pass through opposite ends of the front plate of the board and screw into tapped holes in opposed elongate members which extend transversely across the front of the enclosure adjacent the front ends of the pairs of guide rails. Each elongate member is customarily an extrudate of metal or metal alloy and, for reasons of ease of manufacture and cost, generally the tapped holes for reception of the fixing screws of the front plates of the circuit boards are formed in and mutually spaced along the length of a strip of metal or metal alloy which is separately formed with respect to each extrudate and which is removably housed in a pair of opposed grooves in said extrudate.

Where, as is usually the custom, the front plate of each circuit board is of metal or metal alloy, in some circumstances it is required for the front plates of adjacent circuit boards to be electrically interconnected after each board has been slid fully home, thereby to ensure that the front plate of each board will be effectively connected to earth. For this purpose,, it has been proposed to provide alongside one longer edge of the front plate of each circuit board at least one resilient electrical contact which will effect electrical connection with the front plate of -the 3. adjacent circuit board when one of said adjacent circuit boards is already accommodated in the enclosure and the other of said adjacent circuits boards is slid fully home in its pair of guide rails. Whilst this arrangement ensures that a satisfactory electrical connection is achieved between the front plates of adjacent circuit boards. as said other of the adjacent circuit boards is slid fully home there is a tendency for the resilient contact or contacts to urge the board transversely with respect to its direction of sliding motion to such an extent as to render difficult the effecting of electrical connection between the or each edge connector at the rear edge of the board and the connector or connectors of the backplane.

With a view to preventing or at least limiting the extent of transverse movement of the board caused by said resilient contact or contacts, it has been proposed to provide near each end of and protruding from the rear face of the front plate of each circuit board at least one substantially rigid pin, hereinafter referred to as a locating pin, which will engage in an associated hole in one of said opposed elongate members transversely extending across the front of the enclosure to locate the front plate positively with respect to the elongate member as the circuit board is being slid fully home. In a first such arrangement that has been proposed, the front plate of each circuit board has near each end of and protruding from its rear face two transversely 4. spaced locating pins which will engage in associated holes mutually spaced along and between the tapped holes in the separately formed strip removably housed in the associated extrudate extending transversely across the front of the enclosure. Preferably, the or each locating pin is of such a length having regard to the distance between the front face of the extrudate which the front plate will abut and the associated hole in the strip that said undesirable transverse movement of a circuit board is prevented or limited before the or each edge connector at the rear edge of the board initially engages the connector or connectors of the backplane. In a second such arrangement that has been proposed, a second strip separately formed with respect to the extrudate extending transversely across the front of the enclosure is removably housed in a pair of opposed grooves in the extrudate at a position intermediate of the strip having the tapped holes and the front face of the extrudate against which the front plates of circuit boards will abut, which second strip has along its length mutually spaced holes for receiving locating pins protruding from the rear faces of the front plates of circuit boards. As a consequence of the position of the second strip, the locating pins of the front plates of circuit boards in this second arrangement are substantially shorter in length than the locating pins of circuit boards of the first arrangement. Whilst each of these arrangements is wholly satisfactory in 5. itself, each arrangement has the disadvantage that one of its front plates cannot be satisfactorily employed with the extrudate and strip of locating holes of the other arrangement. From the point of view of the user of an enclosure, this is a wholly unsatisfactory situation since he cannot employ in his enclosures circuit boards with front plates obtained from more than one source.

It is an object of the present invention to provide, for removably housing in an extrudate extending transversely across the front of a rack adapted to accommodate a plurality of circuit boards, an improved elongate member having mutually spaced along its length guides for reception of locating pins protruding from the rear faces of front plates of circuit boards when accommodated in said rack.

According to the invention, the improved elongate member is of substantially T-shaped transverse crosssection, opposite ends of the head of the T-shaped elongate member being adapted to be removably housed in oppositely disposed grooves in said extrudate and said mutually spaced guides are disposed in at least the limb of the T-shaped elongate member, each guide being of such a depth that it will accommodate a locating pin having any length within a limited range of lengths of locating pin.

6.

The improved elongate member of substantially Tshaped transverse crosssection may be an extrudate of metal or metal alloy or of plastics material and, in this case, each guide may be a hole extending throughout the length of the limb and the thickness of the head of the T-shaped elongate member or the limb of the T-shaped elongate member may have a plurality of castellations mutually spaced throughout the length of the elongate member and each guide comprise in part a gap between two adjacent castellations and in part a hole extending throughout the thickness of the head of the T-shaped elongate member.

Preferably, however, for reasons both of ease of manufacture and cost, the improved elongate member comprises a substantially flat strip of metal or metal alloy which has a line of holes mutually spaced throughout its length and which has been so folded that the member is of substantially T-shaped transverse cross-section with said holes mutually spaced along the length of the end face of the limb of the T-shaped elongate member, said holes and the parts of the strip defining opposite side walls of castellations formed therebetween constituting said mutually spaced guides. Each of the holes in the strip may be of elongate shape and extend at least in part along that part of the strip defining one or each of the opposite side walls of the limb of the T-shaped elongate member.

g 0 If desired, the substantially flat strip from which the improved elongate member of T-shaped transverse cross-section is formed may have transversely spaced from said line of mutually spaced holes a second line of holes mutually spaced along the length of the strip, the strip having been so folded that said second line of mutually spaced holes lies in a part of the strip defining a side wall of the head of the T-shaped elongate member with the mutually spaced holes in said side wall in substantially axial alignment with the mutually spaced holes in the end face of the limb of the T-shaped elongate member.

In all cases, the elongate member may also have mutually spaced throughout its length and between the locating pin guides, holes for reception of fixing screws for temporarily securing the front plates of circuit boards to the rack. Where the improved elongate member is an extrudate, the holes for the fixing screws may be tapped holes; where the improved elongate member is made of a folded metal strip, the holes for the fixing screws may be tapped holes or they may be plain holes in which self-tapping fixing screws can be accommodated.

Preferably, however, the improved elongate member does not include holes for the reception of the fixing screws of the front plates of the circuit boards and the circuit boards are temporarily secured in the rack by 8. the circuit board injector/ejector device described and claimed in the specification of co-pending Patent Application No: present application.

filed on the same day as the The invention also includes a rack for accommodating a plurality of circuit boards and for housing in an enclosure, which rack comprises a plurality of mutually spaced pairs of opposed guide rails and, extending alongside the front of each row of guide rails of said pairs of opposed guide rails, an extrudate having removably housed therein an elongate member having mutually spaced along its length guides for reception of locating pins protruding from the rear faces of front plates of circuit boards when accommodated in the opposed guide rails of said rack, wherein each elongate member is of substantially Tshaped transverse cross-section, opposite ends of the head of the T-shaped elongate member being removably housed in oppositely disposed grooves in said extrudate and wherein said mutually spaced guides are disposed in at least the limb of the T-shaped elongate member, each guide being of such a depth that it will accommodate a locating pin having any length within a limited range of lengths of locating pin.

The invention is further illustrated by a description, by way of example, of three preferred forms of elongate member for removably housing in an extrudate extending transversely across the front of a rack adapted to accommodate a plurality of circuit boards, with reference to the accompanying drawings, in which:

Figures 1 and 2, respectively, are fragmental plan and side views of a first preferred elongate member; Figure 3 is a fragmental perspective view of a second preferred elongate member; Figure 4 is a fragmental perspective view of a third preferred elongate member; Figure 5 is a perspective view of a rack for accommodating circuit boards and for housing in an enclosure; Figure 6 is a perspective view of a circuit board for accommodating in the rack shown in Figure 5; Figure 7 is a fragmental view from above of the circuit board shown in Figure 6, and Figures 8 to 10 are fragmental side views, partly in section and partly in elevation, of one end of the front plate of the circuit board shown in Figures 6 and 7 with a circuit board injector/ejector device mounted thereon, Figure 8 showing use of the device to provide the force necessary to effect a multiplicity of pin and socket connections at the rear of the circuit board, Figure 9 showing locking of the device to prevent withdrawal of the circuit board and Figure 10 showing use of the device to provide the force necessary to disconnect the multiplicity of pin and socket connections at the rear of the circuit board.

10.

Referring to Figures 1 and 2, the first preferred form of elongate member is an extrudate 7 of T-shaped transverse cross-section having formed in the limb of the T-shaped elongate member a plurality of castellations 21 mutually spaced throughout the length of the elongate member and defining between adjacent castellations a plurality of gaps 23. The head of the Tshaped member 7 has throughout the length of the member a plurality of mutually spaced holes 22, each in axial alignment with a gap 23 between two adjacent castellations 21. Axially aligned gaps 23 and holes 22 constitute guides 10 for reception of locating pins protruding from the rear faces of front plates of circuit boards. Each of the holes 22 is tapped and so can serve either as a part of a guide 10 for reception of a locating pin or, where a front plate of a circuit board is to be secured to T-shaped elongate member 7 by fixing screws, can serve for reception of a fixing screw.

The second preferred form of elongate member shown in Figure 3 is an extrudate 47 of metal or metal alloy which is of T-shaped transverse cross-section and which has mutually spaced throughout its length a plurality of holes 48 each extending throughout the length of the limb and the thickness of the head of the T-shaped elongate member. The holes 48 constitute guides 10 for reception of locating pins protruding from the rear faces of the front plates of circuit boards.

The third preferred form of elongate member shown in Figure 4 is formed from a flat strip 57 of metal or metal alloy which has a line of holes 58 mutually spaced throughout its length. The strip 57 has been so folded that the elongate member formed therefrom is of T-shaped transverse crosssection with the holes 58 mutually spaced along the length of the limb of the T-shaped elongate member. The holes 58 and the parts 59 of the strip defining opposite side walls of castellations 60 formed therebetween constitute mutually spaced guides 10 for reception of locating pins protruding from the rear faces of front plates of circuit boards.

The guides 10 of each of the elongate member illustrated in Figures 1 and 2, Figure 3 and Figure 4 are of such a depth that they will accommodate locating pins having any length within a limited range of lengths of locating pin.

Referring to Figures 5 to 7, the rack 1 comprises a plurality of mutually spaced pairs.of opposed horizontal guide rails 2 into any pair of which opposed upper and lower edges of a circuit board 11 can be slid from the front of the rack. In the rear of an enclosure in which the rack is housed would be disposed a plurality of connectors (not shown) directly or indirectly carried by a backplane, each of which connectors has in its front face a multiplicity of sockets. Extending transversely across the front of the 12.--- rack 1 along each of its upper and lower edges is an extrudate 5 of metal alloy having throughout its length a pair of opposed grooves 6 (Figures 8 to 10) in which an elongate metal member 7, as illustrated in Figures I and 2, is removably housed. The extrudate 5 has throughout its length a flange 8 which extends forwardly from the front face of the rack 1 and in which a channel 9 extends throughout the length of the flange.

A circuit board 11 for accommodating in the rack 1 has mounted on the board at or near its rear edge an edge connector 12 from which protrudes a multiplicity of pins for effecting pin and socket connections with the multiplicity of sockets of a connector at the rear of the aforesaid enclosure. Secured to the front edge of the circuit board 11 by brackets 13 is a rectangular front plate 14 which is of a composite form comprising two flat panels secured face-to-face, the rear or inner panel 15 being of electrically conductive metal or metal alloy and the front or outer panel 16 being of electrically insulating material. The inner panel 15 of the composite front plate 14 has extending along a major part of the length of each of its side edges a flange 17 which is integral with and extends rearwardly from the panel. Electrically connected to the outer face of one of the flanges 17 is a resilient electrical contact 18 which will effect electrical connection with a flange of the inner panel 15 of the composite front plate 14 of 13. the adjacent circuit board 11 when one of the adjacent circuit boards is already accommodated in the rack 1 and the other of the adjacent circuit boards is slid fully home into its pair of guide rails 2. To prevent any tendency for the resilient contact 18 to urge the circuit board 11 transversely to its direction of sliding motion to such an extent as to render difficult the effecting of the multiplicity of pin and socket connections at the rear of the enclosure in which the rack is housed. the composite front plate 14 has protruding rearwardly from each of its upper and lower ends a pair of transversely spaced rigid pins 19 which are adapted to engage in guides 10 of the elongate metal member 7 to locate the composite front plate positively with respect to the extrudate 5 as the circuit board 11 is slid fully home in a pair of opposed guide rails 2.

As will be seen on referring to Figure 8 to 10, at or near each end of the composite front plate 14 is a preferred circuit board injector/ejector device 31 comprising a body 32 which is fixedly secured to the composite front plate and a lever 33 which is pivotally mounted on the body about a horizontal pivotal axis 34. The lever 33 has a tongue 35 which, when the lever is pivoted in a direction towards the front face of the composite front face of the composite front plate 14, will protrude beyond the body 32 so that a rounded surface 36 on the tongue will bear against an inclined 14. side face 37 of the channel 9 in the flange 8 of the associated extrudate 5, which inclined side face constitutes the "push-in" surface of the extrudate. lever 33 also has a fixing screw 38 which is so screw threaded in a tapped hole 39 in the lever that the fixing screw cannot be readily removed therefrom and which is adapted to screw into a tapped hole 40 in the body 32. Projecting from the outer end of the lever 33 is a finger 41 having a rounded end 42 which, when the lever is pivoted in a direction away from the front face of the composite front plate 14, will bear against the front end face 43 of the flange 8 of the associated extrudate 5, which front end face constitutes the "pushout" surface of the extrudate. A leaf spring 44 accommodated in the device urges the pivotally mounted lever 33 in a direction away from the front face of the composite front plate 14.

Referring specifically to Figures 8 to 10, when the circuit board 11 is to be accommodated in the rack 1 housed in an enclosure, the leading ends of the upper and lower edges of the circuit board 11 are introduced into a pair of opposed guide rails 2 and the circuit board is slid between the guide rails until the locating pins 19 protruding rearwardly from the composite front plate 14 initially engage in guides 10 of the T-shaped elongate members 7. The levers 33 at the ends of the composite front plate 14 are then pivoted in a direction 15. towards the front face of the composite front plate against the action of the leaf springs 44 so that the rounded surfaces 36 of the tongues 35 protruding beyond the bodies 32 bear against and co-operate with the "Push-in" surfaces constituted by the inclined side faces 37 of the channels 9 in the flanges 8 of the extrudates 5 to assist in providing the force necessary to effect the multiplicity of pin and socket connections between the edge connector 12 at the rear of the circuit board 11 and a connector at the rear of an enclosure in which the rack 1 is housed. When the circuit board 11 has been slid fully home and the multiplicity of pin and socket connections has been effected, the rounded surfaces 36 of the tongues 35 bearing against the inclined side faces 37 of the channels 9 prevent withdrawal of the circuit board 11 from the enclosure. The fixing screws 38 are then screwed into the tapped holes 40 in the bodies 32 to prevent pivotal movement of the levers 33.

When the circuit board 11 is to be withdrawn from the rack 1. the fixing screws 38 are unscrewed from the tapped holes 40 in the bodies 32 and the levers 33 are pivoted in a direction away from the front face of the composite front plate 14 so that the rounded ends 42 of the fingers 41 bear against and co-operate with the "Push-out" surfaces constituted by the front end faces 43 of the flanges 8 of the extrudates 5 to assist in 16. providing the force necessary to effect disconnection of the multiplicity of pin and socket connections at the rear of the circuit board and, since the tongues 35 are no longer engaged in the channels 9, the circuit board can then be readily slid outwardly from the rack 1.

17.

Claims (1)

1. CLAIMS 1. An elongate member for removably housing in an extrudate

   extending transversely across the front of a rack adapted to accommodate a plurality of circuit boards, which elongate member has mutually spaced along its length guides for reception of locating pins protruding from the rear faces of front plates of circuit boards when accommodated in said rack, wherein the elongate member is of substantially T-shaped transverse cross-section, opposite ends of the head of the T-shaped elongate member being adapted to be removably housed in oppositely disposed grooves in said extrudate and wherein said mutually spaced guides are disposed in at least the limb of the T-shaped elongate member, each guide being of such a depth that it will accommodate a locating pin having any length within a limited range of lengths of locating pin. 2. An elongate member as claimed in Claim 1, wherein the T-shaped elongate member is an extrudate of metal or metal alloy or of plastics material and each guide is a hole extending throughout the length of the limb and the thickness of the head of the T-shaped elongate member. 3. An elongate member as claimed in Claim 1, wherein the T-shaped elongate member is an extrudate of metal or metal alloy or of plastics material and wherein the limb of the T-shaped elongate member has a plurality of castellations mutually spaced throughout the length of

   18. the elongate member, each guide comprising in part a gap between two adjacent castellations and in part a hole extending throughout the thickness of the head of the T-shaped elongate member. 4. An elongate member as claimed in Claim 2 or 3, wherein each of said holes in the elongate member is tapped so that it is suitable for reception of a fixing screw for temporarily securing a front plate of a circuit board to the rack. 5. An elongate member as claimed in Claim 1, wherein the elongate member comprises a substantially flat strip of metal or metal alloy which has a line of holes mutually spaced throughout its length and which has been so folded that the member is of substantially T-shaped transverse cross-section with said holes mutually spaced along the length of the end face of the limb of the Tshaped elongate member, said holes and the parts of the strip defining opposite side walls of castellations formed therebetween constituting said mutually spaced guides. 6. An elongate member as claimed in Claim 5, wherein each of the holes in the strip is of elongate shape and extends at least in part along that part of the strip defining one or each of the opposite side walls of the limb of the T-shaped elongate member. 7. An elongate member as claimed in Claim 5 or 6, wherein the substantially flat strip from which the T- 1 19. shaped elongate member is formed has transversely spaced from said line of mutually spaced holes a second line of holes mutually spaced along the length of the strip, the strip having been so folded that said second line of mutually spaced holes lies in a part of the strip defining a side wall of the head of the T-shaped elongate member with the mutually spaced holes in said side wall in substantially axial alignment with the mutually spaced holes in the end face of the limb of the T-shaped elongate member. 8. An elongate member as claimed in any one of Claims 1 to 3 and 5 to 7, wherein the elongate member also has mutually spaced throughout its length and between said mutually spaced guides, holes for reception of fixing screws for temporarily securing the front plates of circuit boards to the rack. 9. An elongate member as claimed in Claim 8, wherein the holes for reception of fixing screws are tapped holes. 10. A rack for accommodating a plurality of circuit boards and for housing in an enclosure, which rack comprises a plurality of mutually spaced pairs of opposed guide rails and, extending alongside the front of each row of guide rails of said pairs of opposed guide rails, an extrudate having removably housed therein an elongate member having mutually spaced along its length guides for reception of locating pins 20. protruding from the rear faces of front plates of circuit boards when accommodated in the opposed guide rails of said rack, wherein each elongate member is of substantially T-shaped transverse cross-section, opposite ends of the head of the T-shaped elongate member being removably housed in oppositely disposed grooves in said extrudate and wherein said mutually spaced guides are disposed in at least the limb of the T-shaped elongate member, each guide being of such a depth that it will accommodate a locating pin having any length within a limited range of lengths of locating pin. 11. An elongate member for removably housing in an extrudate extending transversely across the front of a rack housed in an enclosure and adapted to accommodate a plurality of circuit boards substantially as hereinbefore described with reference to and as shown in Figures 1 and 2 or Figure 3 or Figure 4 of the accompanying drawings. 12. A rack for accommodating a plurality of circuit boards and for housing in an enclosure substantially as hereinbefore described with reference to and as shown in Figures 5 and 8 to 10 of the accompanying drawings.

   -c