Abstract:
A method of securing a mounting bracket on a wall of a structural member comprises inserting lugs of the mounting bracket through slots through a wall of the member and securing the lugs to an inside surface of the wall. The mounting bracket is used for mounting the structural member within a cabinet by sliding the member in snug fit within a cabinet, the internal securing of the lugs avoiding interference with the snug fitting relationship.

Description:
This is a divisional application of application Ser. No. 09/005,454, filed Jan. 12, 1998 now U.S. Pat. No. 6,055,195 on Dec. 21, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to equipment mounting structures, and particularly to such structures including cabinets, racks, frames and the like for removably housing circuit board packages used for telecommunications purposes. 
     In telecommunication networks, changes are constantly occurring, both in the subscribers connected to the network and to the services provided to the various subscribers. For accommodating rapid changes, the recent practice has been to terminate subscriber communication lines, e.g., metal wires and optical fibers, on circuit board packages removably housed within equipment shelves. The shelves, in turn, are mounted on various mounting structures, referred to as racks or frames and the like, which, in turn, can be mounted within enclosed cabinets. The circuit board packages include various electrical and/or optical components for processing signals arriving at the circuit board packages, and the mounting structures provide means for housing the circuit board packages and include cables for routing signals and electrical power to, between and from the various circuit boards. Changes in the network are readily achieved by replacing various circuit board packages or changing the signal routing therebetween. 
     For greatest flexibility of use, design standards have been established whereby different circuit board package receiving shelves can be interchanged with one another in the same and different mounting structures located in a common telephone control office or different central offices. A problem caused is that the design standards are often so complete and detailed that desired changes in the various components of the mounting structures, arising from experience with use of the mounting structures or in the design of replacement structures, are difficult to make within the existing standards. 
     The present invention addresses this problem primarily in the context of providing improved components for use in existing mounting structures or, owing to advantages provided by the new components, for use in new mounting structures made according to new standards. 
     SUMMARY OF THE INVENTION 
     In general, mounting structures for which components are provided according to the present invention comprise a frame formed from a grid of support members, spaced apart shelf-assemblies mounted on the frame for receipt of circuit board packages, and various cables more or less fixed in place for conveying signals and power throughout the frame and any cabinet in which the frame is disposed. 
     In accordance with this invention, a mounting method makes use of a bracket comprising an elongated metal strip including spaced apart mounting lugs projecting transversely (e.g., at right angles) from the strip. The lugs include screw threaded openings. In the mounting method, the lugs are inserted through slots in side walls of the shelf-assemblies and screwed in place against an interior surface of the side walls by means of flat-headed screws passing through counter-bored openings through the side walls. The elongated metal strips project laterally outwardly from the side walls for the securing of the shelf-assemblies to the supporting framework. The internal securing of the lugs to the side walls avoids increases in the maximum allowed widths of the shelf-assemblies. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Some of the drawings are schematic and the various drawings are not to the same scale. 
     FIG. 1 is an exploded view, in perspective, of an electrical equipment mounting structure made in accordance with this invention, the structure including a rigid framework, shelf assemblies fixedly secured within the framework, and front and rear cabinet doors; 
     FIG. 2 is a perspective view of one of the shelf assemblies shown in FIG.  1  and showing certain structural elements in accordance with this invention; 
     FIG. 3 is an exploded view, in perspective, of the framework shown in FIG.  1  and two shelf assemblies mounted therein; 
     FIGS. 4-9 are figures relating to cable retaining clips wherein: 
     FIG. 4 is a view in perspective of one clip; 
     FIG. 5 is a side elevation of the clip shown in FIG. 3; 
     FIGS. 6 and 7 are partial sectional views of the sub-assembly shown in FIG. 2 showing the clip shown in FIGS. 4 and 5 mounted in place. FIG. 5 shows the clip ready for use, and FIG. 6 shows optical fibers and a power cable retained by the clip; and 
     FIGS. 8 and 9 are similar to FIGS. 4 and 5, respectively, but showing another clip; 
     FIGS. 10-12 are figures relating to a recessed handle for a shelf-assembly member wherein: 
     FIG. 10 is a rear elevation of a cover plate for the shelf assemblies shown in FIG. 1; 
     FIG. 11 is a view, in perspective, of a portion of a frontwardly facing surface of the cover plate shown in FIG. 10; and 
     FIG. 12 is a section taken along the line  12 — 12  of FIG. 10; 
     FIGS. 13 and 14 are perspective views of two shelf-assembly mounting brackets shown in FIGS. 1-3; and 
     FIG. 15 is a front view of a shelf-assembly mounted within a framework of a mounting structure different from the one shown in FIGS. 1-3 and showing the use of the bracket shown in FIG. 14 in an orientation different from the orientation of the bracket as shown in FIGS.  1  and  3 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Electrical equipment mounting structures of the type which are in the present invention are known, and an example of one such structure is shown in U.S. Pat. 5,150,277 (Sep. 22, 1992), the subject matter of which is incorporated herein by reference. 
     FIG. 1 herein shows an example of an electrical equipment mounting structure of known type but of a recent design taking advantage of experience gained with the use of known mounting structures and containing various structural features taking pre-existing design standards into consideration. The mounting structure includes a basic framework  10  comprising strong and rigidly secured together horizontal and vertical struts  12 . Two shelf-assemblies  16  are shown mounted on the framework  10  with each shelf-assembly  16  being provided with a rear cover plate  18 . The framework  10  is part of a cabinet i.e., an enclosed structure including front  21  and rear doors  22  mounted on the framework. 
     One of the shelf-assemblies  16  shown in FIG. 1 is shown by itself in FIG.  2 . Also shown in FIG. 2 are four circuit board packages  23  of known type removably received within the shelf-assembly  16 . 
     As shown in FIGS. 1 and 3, the shelf-assemblies  16  are secured to the framework  10  by mounting brackets. Pairs of cooperating brackets are used. FIG. 2 shows one bracket  24  (including lugs  25 , hereinafter further described) of each of two pairs of brackets mounted on each wall  26  of each shelf-assembly  16 . In FIG. 1, only the lugs  25  of the brackets  24  are visible, but FIG. 1 clearly shows the other bracket  28  of two of the bracket pairs present. How the brackets  24  and  28  are used for mounting the sub-assemblies  16  within the framework  10  is shown in FIG.  3 . Further discussion of the design and use of the brackets  24  and  28  is provided hereinafter. 
     FIG. 2 additionally shows examples of cables typically routed within the shelf assemblies to and from circuit board packages  22  mounted thereon. Two types of cables are shown; one being cables  38  comprising a plurality of individual optic fibers  40 , and the other being a power feeder  42  for conveying power to electrical and/or optical components (not shown) mounted on the circuit board packages and to power supplies (not shown) mounted within the electrical equipment cabinets. 
     Various improvements of structural elements used in the structures shown in FIGS. 1-3 are now described. 
     Clips 
     As mentioned, electrical and/or optical components mounted on the circuit packs are interconnected to various other components within or external to the equipment mounting structures by means of cables of electrical wires and/or optical fibers. Some of the cables are more or less permanently fixed in place whereas others of the cables must be periodically re-routed. Retainer means are used for fixing the cables in place at various locations on the mounting structures and, particularly with non-permanent cables, a need exists for a simple retaining means whereby a cable being routed can be quickly and firmly secured in place at various spaced apart positions on the mounting structure and just as simply be detached from the retaining means. 
     A cable retainer clip  100  satisfying these requirements is shown in FIGS. 4-7. The clip  100  is shown by itself in FIGS. 4 and 5, at several locations on the shelf assembly  16  shown in FIG. 2, and at a single location ready for use, and in use, respectively, in FIGS. 6 and 7. 
     The clip  100  is designed to be resiliently bent with relatively great displacements and many times without breakage or loss of strength. To this end, the clip is preferably of “spring tempered” stainless steel, e.g., of a steel commonly used in coil and leaf springs. Other materials can be used, e.g., copper alloys or plastics, and, by way of generalization, all such materials are referred to as “spring tempered” materials for indicating suitability for the function of the clip  100  shortly to be described. 
     The clip  100  can be mounted in any number of orientations but, for convenience of description, it is assumed to be so oriented that the terms “horizontal” and “vertical” can be used for descriptive purposes. 
     The clip  100  (FIGS. 4 and 5) has a generally strip-like shape, i.e., it is relatively narrow and long along an axis  102  (FIG. 5) of elongation. Other length to width shapes are possible but, as to be described, the clip functions as a leaf spring and the strip-like shape is generally preferred. With the clip axis  102  horizontally oriented, the clip can be described as including three successive steps  104 ,  106  and  108  with the steps succeeding one another both horizontally and vertically. Thus, a first step  104  having first and second oppositely disposed ends  110  and  112  extends horizontally with the second step end  112  connected by a first vertical plate  114  to a first end  116  of a second step  106 . A second end  118  of the second step  106  is connected, in turn, by a second vertical plate  120  to a first end  122  of a third step  108 . 
     Dependent from the first end  110  (FIG. 5) of the first step  104  is a first cam member  124 , and a second cam member  126  is dependent from the second end  128  of the third step  108 . Each cam member  124  and  126  is semicircular in cross-section. Of importance, but being a matter of selection dependent upon the expected use of the clip  100 , is the spacing of the bottom surfaces of the cams  124  and  126  relative to the second step  106 . In this embodiment, the first cam  124  is secured directly to the first end  110  of the first step  104  and is of such size that the bottom surface  130  of the first cam  124  extends (in the clip unmounted condition shown in FIGS. 4 and 5) slightly below the bottom surface  132  of the second step  106 . 
     The second cam  126  is disposed at some distance below the third step  108  and is connected to the second end  128  thereof by a vertical plate  134 . The bottom surface  136  of the second cam  126  thus extends well below the bottom surface  130  of the first cam  124 . 
     A feature of the clip  100  is that, in a preferred use, the clip is mounted at a corner  140  (FIGS. 2 and 6) of a shelf brace member  142  and is effective for removably securing spaced apart cables against (FIG. 6) transverse upper ( 146 ) and side ( 144 ) surfaces of the member. 
     To this purpose, the clip second step  106  (FIG. 4) is conveniently provided with an opening  150  by means of which the clip can be firmly attached to the upper surface  146  by means of a single machine screw  152  (FIG.  6 ). As shown, the clip  100  is positioned adjacent to the member corner  140  such that while the second step  106  extends along the upper surface  146  of the member  142 , the portion of the clip  100  from the second end  118  of the second step  106  to the second cam  126  connected to the clip third step  108  is disposed along the member side surface  144 . The vertical plate  120  (FIG. 5) between the second step  106  and the third step  108  extends generally parallel to the side surface  144  of the member  142 . Contact between the clip vertical plate  120  and the side surface  144  prevents rotation of the clip around the single screw  152  used to secure the clip  100  to the member  142 . 
     As previously mentioned, the bottom surface  130  of the cam  124  extends, in the unmounted (FIG. 5) and non-flexed condition of the clip, below the bottom surface  132  of the second step  106 . However, when the clip  100  is mounted on the member  142  with the upper surface  146  of the member extending parallel to the second step  106 , the firm fastening of the second step  106  to the surface  146  causes a slight upward tilting of the first step  104  relative to the second step  106 . FIG. 6 shows the clip  100  securely mounted on the structural member  142 , but the degree of tilting of the first step  104  is so small that the first step  104  appears parallel to the surface  146 . The slight tilting which does occur, i.e., a flexure of the first step  104 , provides a spring force pressing the cam member  124  against the surface  146 . This is discussed further hereinafter. 
     The location of the clip cam  126  relative to the side surface  144  of the structural member  142  is also shown in FIG.  6 . In this instance, the cam  126  is spaced from the surface  144  by, essentially, the length of the third step  108 . 
     A preferred use of the clip  100  is now described. The clip  100  is first mounted on the member  142 , as shown in FIG. 6, and various cables and the like are thereafter disposed between the clip  100  and the member two surfaces  144  and  146 , as shown in FIG.  7 . (Alternatively, but not typically, cables can be first placed against one or both member surfaces and then clamped in place as the clip is mounted in place.) 
     Preferably, however, with the clip fixedly in place, a plurality of relatively small diameter light guide fibers  40  (FIG. 7) are forced inwardly of the clip  100  by disposing one or more cables on the member upper surface  146  and extending perpendicular to the axis  102  of the clip  100  and urging the fiber(s), e.g., by hand, against the curved outer surface of the cam  124 . The cam  124  is thus lifted above the surface  146  allowing the fiber(s)  40  to pass underneath the cam and into the space encompassed by the first step  104 . The upward movement of the cam  124  further tilts and flexes the step  104  and, upon passage of the fiber inwardly of the cam  124 , pressure of the flexed leaf spring clip forces the cam  124  back into contact with the member surface  146 . The small optical fibers are thus retained within the clip  100 . Similarly, because of the circular shape of the surface of the cam  124  facing inwardly of the clip, optical fibers otherwise securely retained within the clip can easily be removed, e.g., again by hand, by forcing the fibers laterally against the inner surface of the cam for lifting the cam for removal of the fibers. 
     Of importance, owing to the relatively small diameter of optical fibers, the amount of flexure of the clip necessary for the passage of the fibers beneath the cam  124  is relatively small. Accordingly, the pressure applied against the fibers is sufficiently small for avoiding damage of the fibers. 
     The other end of the clip containing the cam  126  serves, in this embodiment, a slightly different purpose in that, instead of retaining delicate and small diameter optical fibers, it is intended to retain a relatively large and quite rugged power cable  42 . In this instance, owing to the rather large size of the cable, it is preferable that the cam  126  be spaced from the member side surface  144 , as shown in FIG. 6, to provide an opening for initial receipt of the power cable partially inwardly of the clip. However, the dimensions of the clip relative to the power cable are such that a relatively large force is then required to force the cable fully inwardly of the space defined by the clip vertical plate  134 , the third step  108  and the structural member surface  144 . Although the cam  126  does not thereafter close the space containing the cable, the spring pressure extended by the flexed clip retains the power cable  42  in place in reliance upon friction between the typically rough surface of the power cable and the clip and structural member retaining surfaces. 
     While the power cable  42  is thus readily inserted into the clip space and firmly retained thereon, the cable is similarly quite easily removed from the clip. 
     Another embodiment of a retainer clip  160  is shown in FIGS. 8 and 9. Here, three steps  162 ,  164  and  166  are present, but the first  162  and third  166  steps are at equal levels above (FIG. 9) the second step  164 . The first  162  and third  166  steps terminate in dependent cams  168 , the bottom surfaces  170  of which are spaced below the bottom surface  172  of the second step  164 . 
     In use, as shown in FIG. 2, the second step  164  is secured to a continuous flat vertical surface  176  relative to which both clip steps  162  and  166  (FIG. 9) are slightly flexed by contact by the two cams  168  against the surface  176 . Each step  162  and  166  and its attendant cam  168  functions for retaining optical fibers as previously described in connection with the cam  124  of the clip  100  (FIGS.  6  and  7 ). 
     Handle 
     As previously noted, in connection with the mounting structure shown in FIG. 1, separate removable shelf-assemblies  16  are included within the frame  10 . Typically, the shelf-assemblies are assembled while separate from the frame and closed with rear covers  18 . The covers are relatively large and awkward to handle and an improvement in the covers is that they be provided with handles on the rear facing surfaces thereof. Owing to various design standards, however, nothing can be placed on the covers which projects rearwardly of the cover rearwardly facing surface. Accordingly, quite simple but strong handles are provided recessed within the rearwardly facing surfaces of the rear covers. 
     FIG. 10 shows a typical rear cover  18  in accordance with existing design standards and including a pair of recessed handles on the rearwardly facing surface  202  of the cover  18 . FIG. 10 shows the rearwardly facing surface  202 , and FIGS. 11 and 12 show a portion of the opposite (frontwardly facing) surface  204  of the cover. 
     The cover  18  is basically a flat plate of metal having a thickness, in one typical cabinet, of 1.54 mm, a length of 715 mm and a width of 499 mm. The plate weighs around 2 kg and, because of its relatively large size, includes four right-angled stiffening braces  208 , portions of two of which are shown in FIGS. 11 and 12. The braces  208  run the entire length of the cover plate (as indicated in FIG.  10 ), are mounted on the frontwardly facing surface  204  of the plate, and have a projecting height from the plate surface  204  of 14 mm. 
     For providing two recessed handles on the rear surface  202  of the cover plate, two circular depressions  210  are formed by known sheet metal forming processes, e.g., deep drawing, and comprise a portion of a sphere having a radius of 72 mm and an inside depth of 20 mm. Adding the thickness of the cover plate, the depressions  210  project about 21.5 mm inwardly of the plate rear surface  202 . The depressions  210  thus have a projecting height relative to the front surface  204  of the cover plate of 18.5 mm, which is greater than the height of the braces  208 . However, the amount of space provided between the inside surface of the cover and components within the shelf-assembly is adequately large to accommodate the space taken-up by the depressions. 
     Each depression  210  has a generally continuous spherical wall except for (FIG. 12) a pair of oppositely disposed circular holes  214  (of 5 mm diameter) entirely through the depression wall and spaced (centers of the holes) 4 mm from the rear surface  202  of the cover plate. A stainless steel rod  216 , e.g., of 3.9 mm diameter, extends between and through each hole, thus spanning the depression and spaced from the depression inner bottom surface by a distance of around 17 mm and having a length, between the depression wall holes  214 , of around 95 mm. 
     The depression and rod dimensions are selected for use of the rods  216  as hand graspable handles. The depths of the depressions  210  and the spacing of the rods  216  from the depression bottoms admit entry of a handler&#39;s fingers inwardly of the depressions and “forwardly” of the rods. Of significance, the rods  216  are fully recessed inwardly of the rear surface  202  of the cover so as not to increase the rearwardly extending dimensions of the cover. Additionally, the depressions do not weaken the cover plate and, being substantially continuous (the two rods  216  substantially filling and closing the depression wall holes  214 ), there is little impairment of the enclosing function of the cover  18 . 
     For firmly securing the rods  216  in place, bores  220  (FIG. 11) are cut into the braces. Each bore  220  extends entirely through the brace vertical wall  221  and continues as a groove  220   a  along the surface  224  of the brace horizontal wall  226 . At each depression  210 , the axes  228  of the brace bores  220  on opposite sides of the depression are precisely aligned and bisect the depression. Accordingly, a handle rod  216  can be threaded along each pair of aligned bores  220  with the rod ends being snap-fitted and firmly locked in place within the brace grooves  220   a.    
     Mounting Brackets 
     As shown in FIGS. 1-3, the shelf-assemblies  16  are mounted in the cabinet framework  10  by means of various mounting brackets. Of interest herein are the two previously referred to brackets  24  and  28 . The brackets  24  are secured (FIG. 2) directly to side walls  26  of the shelf-assemblies  16 ; the brackets  28  are secured (FIG. 1) directly to the framework  10 ; and the brackets  24  are secured (FIG. 3) to the brackets  28  for securing the shelf assemblies to the framework  10 . Preferably, all the various securings are by means of standard nuts and screws. 
     A bracket  24  is shown by itself, in perspective, in FIG.  13 . The bracket  24  comprises an elongated strip  300  of metal having two screw receiving holes  302  therethrough, and a pair of (the aforementioned) mounting lugs  25  disposed at opposite ends of the strip  300  and extending at right angles to the strip. Each lug  25  has a hole  306  therethrough including an internal screw thread. Most simply, a threaded nut (also identified by numeral  306 ) is secured in place, as being press fitted into a circular opening through the lug. 
     The bracket  24  is secured to a shelf-assembly  16  as shown most clearly in FIG.  2 . The bracket lugs  25  are passed through slots (not visible) in the side walls  26  of the assemblies and are secured to the inside surfaces of the walls  26  by means of flat-headed screws  306   a  passing through counter-bored screw openings through the side walls  26 . The screws  306   a  are tightly screwed into the nuts  306  mounted on the bracket lugs  25 . In FIG. 2, the shanks of four screws  306   a  are visible on the inside surface of the left-hand side wall  26  of the assembly. 
     When the brackets  24  are so screwed in place, the elongated strips  300  of the brackets project laterally away from the assembly side walls  26  and can be screwed (FIG. 3) to the brackets  28  secured to the framework  10 . One bracket  28  is shown, in perspective, by itself in FIG.  14 . The bracket  28  is a right-angled metal member including a first elongated strip  320  having a “peaked” side edge  322  joined, along a common edge  323 , to a second elongated strip  324  having a straight edge  326 . By “peaked” is meant that spaced along otherwise straight portions of the edge  322  are a number of spaced apart projections  322   a.  The purpose of the spaced apart projections is described hereinafter. The projections  322   a  are quite rigid and strong extensions of the strip  320  which, in effect, has a greater width at the locations of the projections  322   a  than at the locations at the gaps between the projections. 
     As mentioned, the right angle brackets  28  are mounted on the framework  10 . This is shown in FIG. 3 where the bracket  28  straight edged second strips  324  are shown to be secured to inwardly facing surfaces  12   a  of vertical struts  12  of the framework. The bracket  28  elongated strips  320  are also clearly visible in FIG. 1 except that the projections  322   a  (FIG. 14) on the brackets  28  are hidden by the front edges  26   a  of the shelf-assembly side walls  26 . Also hidden in FIG. 1 are the elongated strips  300  (FIG. 13) of the brackets  24  secured directly to the shelf-assembly side walls  26 . (In FIG. 1, the lugs  25  of the brackets  24  are visible). 
     As previously mentioned, portions of the mounting structure shown in FIG. 1 are different from previously made structures but are so designed that, for example, the shelf-assemblies  16  can be used in the earlier made mounting structures. In such use, the design standards are such that, except for a very narrow portion of the front end of the shelf-assembly side walls  26 , nothing can be mounted on the side walls  26  which increases, to the smallest extent, the width of the shelf-assemblies. The design of the brackets  24  takes this restriction into account. Thus, the lugs  25  of the brackets  24  are not screwed to external surfaces of the walls  26 , but extend through the aforementioned slots through the walls. The flat-headed screws  306   a,  used for securing the lugs  25  to the walls  26 , are either completely recessed inwardly of the exterior surfaces of the walls  26  or, at worst, flush therewith. Thus, except for the laterally extending strips  300  of the brackets  24 , which are disposed forwardly of the framework of the previously made mounting structures, the mounting of the brackets  24  on the shelf assembly side walls  26  in no way increases the width of the shelf-assemblies. 
     A feature of the brackets  28  is that they are multi-functional for use, in different orientations, in different mounting structures. As shown in FIGS. 1 and 3, for example, the straight edge strip  324  of the brackets  28  is secured to a strut  12  of the framework  10 , and the projections  322   a  are secured to the elongated strips  300  of the brackets  24  secured to the shelf-assemblies  16 . In this application, the full width of the peaked strip  322  of the bracket is used. 
     In another application, as shown in FIG. 15, the orientation of the bracket  28  is changed such that the bracket straight edged strip  324  is secured directly to a shelf-assembly and the peaked strip  320  secured directly to a strut  12  of a framework  10   a.  In this application, the full width of the bracket peaked strip  320  is not used, but rather the bracket strip  320  is secured to the strut by means of screws  334  passing through openings  330  (FIG. 14) through the bracket strip  320  inwardly of the strip edge  322  and spaced from the projections  322   a.  The projections  322   a  thus project beyond the strut  12  and into spaces on respective sides of the struts  12 . Therein lies a problem. As indicated in FIG. 15, a vertically extended channel  13  beyond each strut  12  (e.g., between it and a forwardly projecting side wall  13   a  of the mounting structure shown) is used for the passage of various cables  40  some of which exit the space for routing forwardly around the struts for extension to the shelf-assembly  16 . For preventing blocking of the exits for the cables by the unused (in this application) width of the bracket, gaps are provided between the projections  322   a  along the bracket edge  322 . Thus, while the projections  322   a  can be provided on the bracket  28  for providing it with the necessary dimensions for the application shown in FIGS. 1-3, the gaps between the otherwise unused projections  322   a  of the brackets  28  permit use of the brackets  28  in the FIG. 15 application. Provided the gaps between the projections  322   a  are wide and deep enough to permit passage of exiting cables between adjacent projections  322   a,  and provided the projections  322   a  are adequately strong for their mounting (FIGS. 1-3) function, the projections  322   a  can have other shapes than the preferred shapes shown.