CA1198803A

CA1198803A - Equipment cabinet

Info

Publication number: CA1198803A
Application number: CA000445817A
Authority: CA
Inventors: Frederick T. Cogan
Original assignee: Frederick T. Cogan; Mitel Corporation
Current assignee: Microsemi Semiconductor ULC
Priority date: 1984-01-23
Filing date: 1984-01-23
Publication date: 1985-12-31
Also published as: US4707764A; GB8424791D0; JPS60154700A; IT1221754B; DE3445576C2; FR2558678A1; GB2153153B; DE3445576A1; GB2153153A; IT8423065A0

Abstract

ABSTRACT

An expandable moulded cabinet for housing printed circuit boards, which is modular and uses only two kinds of parts. Instead of printed circuit board retainers and a backplane being fastened to a cabinet frame, which would require careful attention to tolerances, the retainers are held by the cabinet in approximately correct positions, and the backplane is supported by and is fixed directly to the retainers alone, and not the cabinet. Thus the only precision tolerances required are to the locations on the backplane where the printed circuit board retainers are supported. An inexpensive and versatile cabinet results.

Description

01 'Fhis invention relates to cabinets, and 02 particularly to an electronic equipment cabinet such 03 as a ~ABX cabinet which carries a plurality of 04 printed circuits boards.
05 Electronic equipment cabinets for housing 06 computer main frames, electronic PABXs, etc, 07 typically have several common features. A plurality 08 of wired or printed circuit boards are usually 09 vertically disposed in parallel, and are plugged into a backplane or motherboard. A backplane is 11 u~ually formed of a printed circuit board which is 12 placed behind and orthogonal to the parallel printed 13 circuit boards, and provides interconnection between 1~ them. The backplane is often i-tself a printed circuit board, but sometimes caxries wire wrap posts 16 for automated wiring between points. Usually the 17 backplane carries a plurality of connectors into 18 which the printed circuit boards are removably 19 connected.
The cabinet therefore is usually formed of 21 pairs of printed circuit board frames or retainers 22 which hold the printed circuit boards in parallel 23 relationship, and allow the printed circuit boards 24 to be sl.id within guides to the backplane connectors.
26 The structure of the cabinet often is in a 27 form of a rack, with a ~osmetic housing. The rack is 28 usually formed of strong and rigid materials, since 29 it forms at least the base or the frame of the cabinet. The frames for the print~d circuit boar~s 31 and the backplane are screwed to the rack. The 32 tolerance of the rack structure is important, as 33 are the positions of the screw holes for fastening 34 the printed circuit board frames and the backplane.
This importance is emphasi~ed not only in order -to 36 have the cabinet fit together, but most 01 importantly because the printed circuit boards must 02 slide toward and fit precisely into the connectors 03 of the backplane.
04 Consequen-tly during manuEacture, due to 05 additive tolerances or the like, adjustments must be 06 made to avoid bending stress on the prin~ed circuit 07 boards once they are in place and connected to the 08 connectors, which could result in cracking of the 09 printed wiring, and thus ultimate failure of the apparatus.
11 In addition, such cabinets are often 12 subjected to stress during transportation to the 13 ultimate ins~allation site due to dropping, l~ bouncing, etc, which can distort the cabinet an amount virtually invisible to the eye, but still 16 to a signiEican-t extent, sufficient such that the 17 printed circuit board alignment with the connectors 18 would be adversely afEected. Indeed, this could l9 cause damage to the printed circuit boards if they are shipped from the factory in operating position 21 in the cabinet. Yet it is highly desirable to ship 22 a completely operative piece of equipment from the 23 factory without the requirement for insertion of the 24 printed circuit boards and retesting at the ultimate site, to save significant cost.
The present invention is an equipment 27 cabinet which virtually eliminates the tolerance

2~ problem encountered with the aEorenoted type of 2g cabinet. Indeed, the critical alignments are completely divorced from the cabinet structure 31 itself. Yet a rack structure is not utilized.
32 Consequently tolerance problems in manufacturing the 33 cabinet can be to a substantial extent disregarded

3~ with respect to the prin~ed circuit board-backplane alignment probleml Therefore adjustments in 3~ positioning of a large number of elements in the 01 cabinet in a final adjustment procedure can be 02 eliminated. Furthermore, the entire appara-tus can be 03 assembled at the factory and shipped with all printed 04 circuit boards in place with a high degree o~
05 confidence in the reliabili~y o~ operation when the 06 apparatus is set up at the :~inal site, since 07 transportation bending stresses on the cabinet are to 0~ a substantial extent not transmitted to the backplane, 09 prin-ted circuit board retainer, and printed circui-t boards.
11 In addition, a modular cabinet has been 12 invented having a central section or sections which 13 can interconnect with end sections and a-ttach thereto 14 in a simple manner. The end sections are iden-tical, and means is provided whereby additional inner or 16 central sections can be cascaded, all of the center 17 sections being identical. The result is a cabinet 18 which is formed of modular sections which can be 19 expanded to any desired size, using only two kinds of parts, an inner section and an end section.
21 The cabinet sections are preferably formed 22 of plastic, such as a rigid ~oamed type of plastic 23 such as *STYRON or any other suitable plastic. The 24 sections can be held together by glue.
~5 Each o~ the inner sections and the outer 26 sections contain spaced guides for defining the 27 approximate postions of, and retaining the printed 28 circuit board retainers. A backplane is attached 29 directly, and only, to the printed circuit board retainers through a precision location structure. As 31 a result, the printed circuit board retainers are 3~ spaced precisely relative to each other and to the 33 backplane, whereby the printed circuit boards can be 34 held in precise location rela~ive to the backplane.
However since ~le backplane is not attached to the 3~ cabinet itself, bendirlg stresses on the cabinet do not 37 ef~ect the backplane. Furthermore, since the 39 * trade mark 01 printed circuit board retainers are held with only 02 low tolerance requirements to approximate positions, 03 bending stresses on the cabinet substantially do not 04 afEect them~ Consequently the cabinet molds need 05 not be made to the precision otherwise required to 06 exactly locate the relative positions of the printed 07 circuit boards and backplane.
08 It should be noted that the application of 09 the present invention as described in the detailed description below is directed to the printed circuit 11 board-backplane location problem noted above.
12 However the principles of the structure described 13 could be applied to other applications as such needs 14 arise.
In general, the preferred embodiment of 16 the invention is an equipment cabinet or retaining 17 circuit boards, comprising pairs of spaced guides 18 fixed on opposite inside surEaces of the cabine~, a 1~ first circuit board retainer retained between the guides, and a circuit backplane fixed directly to an 21 end of the retainer.
22 More particularly, an embodiment of the 23 invention is an equipment cabinet for printed 24 circuit boards comprising apparatus for retaining a plurality o~ circuit board guides in approximate 26 parallel spaced positions relative to each other, 27 apparatus precisely positioning one of the ends of 23 each of the retaining apparatus relative to the 29 others and fixing the ends to a backplane, whereby the backplane is held in the cabinet only by being 31 fixed to the guides.
32 A further embodiment of the invention is 33 an equipment cabinet comprising at least one inner 3~ cabinet section, including a wall separating two open side portions, a pair of end cabinet sections, 36 the end sections being identical in form, apparatus 37 for connecting the end sections to the inner 3~ ~

01 sec~ion, to close the open side portions anc~ thereby 02 form a shell divided by the wall, and pairs of 03 spaced guides fixed on each wall of the inner 0~ sec~ion and opposite inner walls oE the end 05 sections, the guides being in alignment with each 06 other, whereby a plurality of equipmen~ bases such 07 as printed circuit board retainers can be held in 03 approximate predefined positions thereby in each 09 divided portion of the shell.
The equipment bases can form circuit board 11 retaining apparatus, to ~hich a backplane can be 12 fixed spacing them relative to each other and to the 13 backplane with precision. The backplane is only 1~ fixed to the circui~ board retainers.
A better understanding of the invention 16 will be obtained by reference to the detailed 17 description below, with reference to the following 18 drawin~s, in which:
19 Figure 1 is a perspective view of the cabinet, Erom an upper rear portion, with the 21 exterior o~ the cabinet shown in phantom, 22 Figùre 2 is a front elevation oE a section 23 of the invention along the plane defined by section 24 lines A-A-A, Figure 3 shows a side view of the interior 26 of one section of the cabinet restricted to the 27 circuit board retainers and backplane, 28 Figure 4 is a perspective view of a 2g preferred form of circuit board retainer.
Turning flrst to Figures 1 and 2, an outer 31 housing or shell 1 is shown in phantom. The housing 32 is formed of an inner cabinet section 2 and two end 33 sections 3. The only difference between the two end 34 sections as shown in the Figure is that one has been tu~ned 180 about a mutual center axis and has also 36 been turned 180 about a vertical axis. Therefore 37 what would be the bottom of one end section appears il8~3 01 at the top, facing the top of the other end 02 section. The parting line between sections is shown 03 as reference numeral 4.
04 The portions of the end sec-tions which are 05 shown are formed of top and bottom surfaces and an 06 end panel, thus generally forming a pair of facing 07 "U" shapes. Both oÆ the sides are preferably left 0~ open to accommodate the insertion of apparatus to be 09 retained from either the front or rear. Of course the completed cabinet can be closed by a door to 11 seal it from view or tamperiny.
12 The inner section is generally in the 13 shapP of an elongated "I" beam, with a central 14 separator wall 5, across the top and bottom of which are cabinet top and bottom panels which extend to 16 the parting lines 4, and are coextensive with the 17 top and bottom panels of the end sections 3.
18 Means is provided for connecting the inner 19 section and end sectio~s together, with proper alignment. These preferably take the forrn of 21 rectangular tubes 6 and 6A. These tubes extend 22 across the tops and bottoms of the inner section and 23 end sections orthogonal to the parting line ~.
24 Tubes 6A are dimensioned such that they fit within tubes 6. Consequently tubes 6A should 26 extend past the ends of the tops and bottoms o the 27 inner and end sections, whereby when they are fitted 28 within tubes 6, the inner and end sections come 29 together forming par~ing lines 4. Indeed element 6A
need not be actually formed in a tube shape, but 31 can be an ex-tension of the walls of the sections to 32 fit within tube 6, allowing the outside surfaces of 33 the resulting cabinet to be coextended. Indeed, the 34 extension 7 of tube 6A should he dropped slightly from its immediate adjacent surface to accommodate 36 the wall thickness of tube 6.

0] Clearly other alignment means could be 02 used to fit the sections together. However it is ~3 preferred that whatever means are used, the end 04 sections should be identical such that the fewest 05 number of parts would be necessary.
06 In respect of the preferred embodiment 07 described above, it should be noted that each of the 0~ end sections contains a tube ~ along the top or 09 bottom thereof, and a tube 6A along the opposite top or bottom. Inner section 2 has a tube ~ extending 11 along a to~ or bottom on one side, and a tube 6A
12 extending along the same top or bottom on the 13 opposite side. On the opposite end, on -the same 14 side as tube 6, a tube 6A is provided, and on the same side as tube 6A, a tube 6 is provided.
16 In assembling the cabinet, end sections 3 17 merely have their tubes 6 and 6A aligned with tubes 1~ 6A and 6 respectivel~ of the inner section. The end 19 sections are compressed towards each other, closing the cabinet as a clam shell. ~oth open sides (front 21 and rear~ can be identical, 22 It is p~eferred that the cabinet sections 23 should be formed of a plastic material, such as 2~ STYRON, or other protective material. Thus a glue can be used to permanently secure the cabinet 26 sections together.
27 Since the inner and end sections are 28 preferably plastic molded, it may be seen that this 29 assembly ~orms a very inexpensive cabinetO This form of cabinet would, for use in the prior art, not 31 be satisfactory, however, since it typically has 32 substantial flexibility and relatively poor 33 dimensional tolerance. However the unique interior 3~ structure to be described below eliminates what would otherwise be its deficiencies with respect to 3~ interior equipment alignment ~olerances.
37 It should be noted that the cabinet can be 3~ 7 01 expanded in a modular manner simply by replacing one 02 of the end sections by one or a sequence of inner 03 sections, the last inner section being completed by 04 fitting an end section to its open region.
05 Therefore the inner sections can be cascaded with 06 identical units, in which the rectangular tubes 6A
07 are fitted into rectangular tubes 6.
08 The result is a modular cabinet which can 09 define two inner portions separated by wall 5 and the end walls of the end sections (and of course the 11 associated ~Op5 and bottoms), or a plurality of 1~ inner regions bounded by walls S, with end interior 13 regions bounded by walls S and the end walls of the 14 end sections.
An inexpensive, modular, expandable 16 cabinet thus results, which has only two kinds of 17 parts, inner and end sections.
18 A plurality of pairs of spaced guides 8 1~ extend inwardly orthogonal to the sides of the end sections and wall 5. Preferable the guides 8 are in 21 the form of lips or lands which are centrally 22 located along vertical axis and extend horizontally 23 outwardly from the associated walls. The lip 24 dimensions should be such that printed circuit board retainers ~eference 9 can be slid between them, yet 26 they should not interfere with printed circuit 27 boards retained by the retainers.
28 In order to increase the structural 29 rigidity of the sections, it is preferred that a rigid beam 10 should extend from top to bottom along 31 the end sections and along the walls 5. Indeed, the 32 beams 10 and tubes 6 and 6A can be coextensive, each 33 forming a wall rigidizing support. It has been 34 found that the guides 8 usefully can be extended around beams 10, whereby the printed circui~ board 36 retainers are held between guides 8, and between 37 beams 10.
3~ 8 01 In the embodiment shown, only one pair of 02 guides 8 support a single printed circuit board 03 retainer on each side. However it will be clear to 04 a person understanding this invention that more than 05 one set of guides can be used to horizontally 06 support the printed ci~cuit board retainers.
~7 ~he posi-tions of guides 8 define the 08 parallel separation of printed circuit board 09 retainers 9. As shown in Figure 2, but not shown in 1~ Figure 1, the printed circuit retainers 9 contain 11 slots 11 Erom front to rear (or close to their 12 rear). Printed circuit boards 12, again shown only 13 in Figure 2, are slid from the front of the 14 retainers 9 along the slots toward the rear of the retainers. Since the retainers 9 have slots 11 in 16 both top and bottom surfaces, t~e printed circuit 17 boards are retained therebetween once they have been 18 inserted>
19 Figure 4 is a perspective view of the preferred form of a printed ci~cuit board retainer 21 9. The slots 11 which are sho~n, preferably are 22 located both in the top and bottom surfaces of the 23 retainer, which is shown here in the form of a 24 base. However it ls clear that the retainer can be in the form of a stiff frame, with slots or other ~6 structures which could hold the printed ci~cuit 27 boards in position.
28 The inserted ends of the printed circuit 29 hoard retainers are each fastened to a backplane 13. Thus all of the retainers in each of the 31 housing regions is fi~ed to a backplane associated 32 with that region. Typically the backplane is formed 33 o~ a large printed circuit board, on which are 34 disposed conductors as required.
Figure 3 should now be referred to in 36 con~unction with ~igures 1 and 2. Figure 3 shows 37 the printed circuit board retainers 9 in spaced 3~ 9 01 relationship as determined by the guides 8 (not shown 02 in this Figure). Howeve.r the rear ends are maintained 03 in precisely spaced relationship by being faskened to 04 backplane 13. The positioning can be provided by 05 holes 14 in the backplane, the positions of which can 06 be very precisely controlled, and which substantially 07 do not change with external stress on the cabine-t 08 outer housing 1.
09 Preferably the rear end of the retainers 9 are formed into standoffs 15, which locate the 11 distance that the adjacent side of backplane 13 12 maintains frvm the rear of retainers 9. Also 13 preferably the standoffs have cylindrical threaded 14 extensions 16 which pass through holes 14. With retainers 9 positioned with their extension 16 through 16 holes 14 of backplane 13, their rear ends are 17 precisely located with respect to the backplane 13.
18 Screws 17 can be screwed into the threaded extension 19 16, fastening the printed circuit board retainers in place.
21 Printed circuit board connectors 18 are 22 fixed to backplane 13 on its side between retainers 9, 23 in a well known manner, and its terminals soldered to 24 the backplane 13 also in a well known manner.
1`hus when printed circuit boards 12 are 26 slid via slots 11 toward the backplane, their end 27 connector terminals can be inserted into connectors 28 18, since the~ have been precisely located due to the 29 precision of the location of the rear end of retainers 9 with respect to the backplane 13, and thus -to the 31 connectors 18.
32 As may be seen in Figure 4, the front of 33 retainer 9 is Eormed into a lip 19 which extends 3~ across the ront of each retainer. The lip 19 contains slots 20, each of which e~tends in front o a 36 slot 11. ~his provides leverage poi.nts or 01 printed circuit board extractors or locks 21, which 02 facilitates firm insertion and extraction of the 03 printed circuit boards from connectors 18, in a well 04 known manner.
05 As noted earlier, it is preferred that 06 printed circuit board retainers 9 should con~ain 07 elongated slots 11 from front to rear, on both sides 08 thereof as shown in Figures 2 and 3.
09 It will be noted that if backplanes 13 were merely fixed to printed circuit board retainers 11 9 which are held within guides 8, the entire 12 assembly would be moveable front and rearwardly.
13 This of course would not be desirable.
14 According to the preferred embodiment of the present invention, the top edges of retainers 9 16 contain cut-outs 22 which extend along the edges 17 from the rear end toward the front. The ends 23 of 18 the cut-outs 22 bear against the guides 8, providing 19 a stop in one direc-tion.
Backplane stops 24 extend inwardly from 21 the walls of the cabinet 5, provide surfaces against 22 which the backplane bears. Consequently when the 23 retainers 9 are fastened to backplanes 13, they are 24 securely held between cut-out ends 23 and backplane stops 2~. They can also serve as printed circuit 26 board retainer supports.
27 Of course o~her means for providing s~ops 28 can be used, such as L brackets attached to the side 29 edges of the printed circuit board retainers which would bear against guides 8, and L brackets 31 extending inwardly of the walls of the cablnet to 32 provide stops for the backplanes 13.
33 It should be noted that cut-outs 22 also 34 provide means for physically polarizing the printed circuit board retainers 9, in order that they could 36 only be inserted in one direction if desired. In 37 Figure 2 it will be noted that one of each of the 3~

01 guides of each pair is shown longer than -the other.
02 The short guide ~its into cut-out 22, while the long 03 guide e~tends over the retainer a distance farther 04 than ~he width of cut-out 22. The distance between 05 each guide in the pair is the distance between the 0~ inner surface of the cut-out 22 and the opposite 07 surEace of retainer 9. As a result if retainer 9 is 08 attempted to be inserted up-side-down, it is 09 prohibited by the longer guide not fi-tting into cut-out 22. Polarization of the orientation o~ the 11 printed circuit board retainers sometimes would be 12 desirable, for example, in the event the printed 13 circuit board e~tractors or locks require slots 22 14 or other mechanisms which are not identical on the top or bottom o~ the retainers. Thus in some 16 structures it may be desirable to predetermine the 17 direction that the printed circuit board retainers 18 ace.
19 lt is thus clear that the only support ~or the backplane is the printed circuit board retainers 21 and stops; the backplanes are not structurally fixed 22 to the cabinet by other means. The printed circuit 23 board retainers to which the backplanes are fixed 24 with precision, are the~lselves only approximately positioned by the cabinet. Therefc,re relatively 26 poor tolerance manufacture of the cabinet will not 27 affect the position of the printed circuit boards 2~3 relative to the backplane connectors, as had been 29 common in the prior art.
It should be noted that there are various 31 sets of guide pairs utilized along a vertical axis, 32 i~ order to ~acilitate the use of a plurality of 33 printed circuit board guides. These can of course 34 be spaced as desired, and, lndeed, redundant pairs o~ guides could be used to ~acilitate the use of 36 various ~izes of printed circuit boards, as deined 37 by the distance between the printed circuit board 01 retainers. The cabinet can thus be made as an 02 universal cabinet wh,ich could accommodate different 03 sizes of boards according to -the applica-tionl 04 without the necessity for producing new cabinets for OS different applications.
06 It is preferred that the guides 8, tubes 6 07 and 6A and the walls of a section should be molded 08 in one piece. Alternatively, if desired the guides 09 8 can be formed as separate clamping or fastened items, which are preferably fastened to beams 10.
11 The pres~nt invention has proved to 12 provide a substantially reduced cost cabinet, of 13 modular and easy to assemble construction, which 14 provides improved ease of assembly and ease of ensuring precision of location of the parts which 16 are required to be precisely located. At the same 17 time the precision can be maintained even in the 18 presence of external stresses placed on the cabinet 19 housing itselE, A person understanding this invention may 21 now conceive of alternative embodiments using the 22 principles described herein. All are considered to 23 be wlthin the sphere of the invention as defined in 2~ claims appended hereto.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An equipment cabinet for retaining circuit boards comprising:
(a) one or more pairs of spaced guides fixed on opposite inside surfaces of the cabinet, (b) a first circuit board retainer retained between the guides, (c) a circuit backplane for receiving and retaining said circuit boards in conjunction with said retainer, and (d) means for fixing said backplane in a predetermined orientation relative to said retainer, and remotely of the cabinet surfaces such that alignment of the retainer and backplane is independent of the structure of said cabinet.

2. A cabinet as defined in claim 1, including:
(i) further pairs of spaced guides fixed on opposite inside surfaces of the cabinet, a predetermined distance from the former pairs of spaced guides, (ii) a second circuit board retainer retained between the guides, having an end fixed directly to the backplane, and (iii) at least one printed circuit board retained between the circuit board retainers, in circuit communication with the backplane.

3. A cabinet as defined in claim 2, in which said guides include interacting key and slot means for defining the facing direction of each surface of the circuit board retainer.

4. A cabinet as defined in claim 2 or 3, in which the circuit board guides contain oppositely located slots extending from the other end of guides to at least adjacent said one end thereof, for retaining said printed circuit board.

5. A cabinet as defined in claim 1, 2 or 3, further including means for fixing the lateral positions of the retainer and backplane within the cabinet.

6. An equipment cabinet for retaining printed circuit boards comprising:
(a) means for retaining circuit boards in parallel relationship to each other, (b) a backplane for circuit communication with said circuit boards fixed to the retaining means, (c) means in said cabinet for defining the approximate position, and holding the retaining means in said position, and (d) means for fixing the precise position of the retaining means relative to the backplane, whereby said backplane is retained only by said retaining means and not by said cabinet.

7. A cabinet as defined in claim 6, in which the fixing means is comprised of spaced holes in the backplane, and threaded standoffs extending from the edges of the retaining means for passing through said holes and retention thereat by screws.

8. A cabinet as defined in claim 6, in which the retaining means is comprised of a frame containing precise board guides extending from a front to a rear edge, said fixing means being comprised of precisely located spaced holes in the backplane, standoffs extending from the rear edge of the retaining means for passing through said holes, and means for holding the backplane to the retaining means.

9. A cabinet as defined in claim 2, 3 or 6, in which the circuit board retainers contains one or more slots across the front thereof for facilitating insertion of a circuit board extraction lever or lock therein.

10. A cabinet as defined in claim 8, in which the position defining means is comprised of pairs of spaced guides located on opposite inside surfaces of the cabinet, for supporting the retaining means in an approximate position as it is inserted into the cabinet and after being fixed to the backplane, and stops for bearing against the backplane and the retaining means, fixing their lateral positions within the cabinet.

11. An equipment cabinet for printed circuit boards comprising:
(a) guides for retaining a plurality of circuit board retaining means in approximate parallel spaced positions relative to each other, (b) means precisely positioning one of the ends of each of the retaining means relative to the others and fixing the precise position of said ends relative to a backplane, and (c) locating means for fixing the lateral position of the backplane and the retaining means within the cabinet, whereby said backplane is held in said cabinet only by being fixed to said retaining means, and bearing against the locating means.

12. A cabinet as defined in claim 11, in which the backplane is retained orthogonally to the retaining means, further including a plurality of circuit board connectors fixed to the backplane adjacent the retaining means, in circuit communication with circuitry disposed on the backplane.

13. A cabinet as defined in claim 12, in which the circuit board retaining means include flat bases having slots extending from an end thereof toward the backplane, the slots being of widths slightly greater than the thickness of a circuit board, the slots in opposite retaining means being directly opposite each other.

14. A cabinet as defined in claim 13, in which the bases contain said slots in both sides thereof.

15. A cabinet as defined in claim 12, in which the guides are disposed in pairs on opposite sides of the cabinet for supporting the circuit board retaining means, the pairs of supporting guides being spaced slightly more than the width of the circuit board retaining means, whereby the circuit board retaining means can be slid therebetween.

16. An equipment cabinet comprising:
(a) at least one inner cabinet section including a wall separating two open side portions, (b) a pair of end cabinet sections, the end sections being identical in form, (c) means for connecting the end sections to the inner section, to close the open side portions, and thereby form a shell divided by the wall, (d) pairs of spaced guides fixed on each wall of the inner section, and opposite inner walls of the end sections, the guides being in alignment with each other, (e) a first circuit board retainer retained between the guides, (f) a circuit backplane for receiving and retaining said circuit boards in conjunction with said retainer, (g) means for fixing said backplane in a predetermined orientation relative to said retainer, and remotely of the cabinet surfaces, whereby a plurality of said retainers can be held in approximate predefined positions thereby in each divided portion of the shell, and alignment of said retainer and backplane is independent of the structure of said cabinet.

17. A cabinet as defined in claim 16, in which the connecting means is comprised of alignment tubes fixed to one of the inner cabinet sections and end sections for fitting into a corresponding tube slightly larger or smaller in size fixed to an adjacent one of the inner cabinet section and end section, and means for locking the sections together.

18. A cabinet as defined in claim 16 or 17, in which the sections are formed of a molded plastic material.

19. A cabinet as defined in claim 16 or 17, further including additional one or more inner cabinet sections identical to said one cabinet section, including means for connecting said inner cabinet sections laterally to each other whereby a pair of open side portions are formed and one or more enclosed regions, and said end sections to close the side portions, whereby a cabinet having multiple enclosed regions are formed with a plurality of pairs of spaced guides on opposite sides of each enclosed region.

20. A cabinet as defined in claim 16 or 17, including stop means for fixing the lateral positions of the retainers and backplane, and a plurality of circuit board connections fixed to the backplane between the retainers.

21. A cabinet as defined in claim 16 or 17, including a slot extending partway along at least one side of the retainers for accommodating at least one of the guides, whereby a stop is formed to inhibit extension of the retainers into the cabinet more than a predetermined distance.